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Background HER2-positive patients with advanced gastric cancer have a poor prognosis, and trastuzumab-resistant patients lack effective treatment. Case presentation We report a 72-year-old male with HER2-positive gastric cancer. The patient had metastatic tumor during adjuvant chemotherapy after surgery, followed by second-line chemotherapy, and achieved a progression-free survival (PFS) of 4.5 months. Subsequent third-line chemotherapy treatment also failed. Fortunately, the patient had a significant tumor response and 8.5 months of PFS on trastuzumab combined with chemotherapy. After trastuzumab resistance, the patient was treated with programmed cell death protein-1 inhibitor combined with apatinib, which selectively inhibited VEGFR2, but the effect was not satisfactory. Finally, the patient was treated with capecitabine combined with pyrotinib, an irreversible TKI, acting on HER2. The tumor shrank significantly after this treatment. Conclusion The mechanism and countermeasures of trastuzumab resistance were discussed in this case. For patients with HER2-positive advanced gastric cancer, pyrotinib can achieve good results after trastuzumab resistance.

It is difficult to define patients with primary trastuzumab resistance (PTR) after (neo)adjuvant trastuzumab with minimal data and understanding of the actual prevalence, prognosis, and potential treatment strategies in the real-world setting.The medical records of 1096 patients with human epidermal growth factor receptor 2-positive early-stage breast cancer who had received (neo)adjuvant trastuzumab-containing treatment from 2010 to 2016 in the Cancer Hospital and Chinese Academy of Medical Sciences were reviewed. PTR was defined as recurrence during adjuvant trastuzumab or within 12 months from their last (neo)adjuvant trastuzumab dosage. The cutoff date for data collection was September 1, 2018, with a median follow-up time of 46 months.A total of 126 recurrences were observed, and 75 (6.8%; 75/1096) of them were categorized as PTR; the remaining were non-PTR. The prognosis of patients in the PTR group was much inferior to those in the non-PTR group (27 months vs. not reached; P .01). As expected, patients with PTR did possess a much lower response rate to first-line trastuzumab-containing therapy (27.3% vs. 61.9%; P = .02). Subgroup analyses indicated that patients in the PTR group seemed to get little survival benefit from the reuse of trastuzumab compared with those without trastuzumab (26 months vs. 28 months; P = .80). However, in the non-PTR group, re-treatment with trastuzumab in the metastatic setting prolonged the survival of patients compared to those without trastuzumab (not reached vs. 34 months; P = .04).This study verified the rationality of present definition of PTR after (neo)adjuvant trastuzumab. Patients with PTR did have a poor prognosis. Further research and clinical trials are required to establish the best treatment patterns for these patients.

Gastric cancer is one of the most prevalent human cancers with poor prognosis. Trastuzumab is a well-used targeted drug for gastric cancer with HER2 amplification. Trastuzumab resistance restrains the clinical use of trastuzumab. In this study, we reported human Gse1 coiled-coil protein (GSE1) promoted trastuzumab resistance in HER2-positive gastric cancer cells. Acquired trastuzumab-resistant gastric cancer cells overexpressed GSE1, and depletion of GSE1 decreased the trastuzumab resistance of trastuzumab-resistant gastric cancer cells. BCL-2 was a downstream gene positively regulated by GSE1 and also performed promoting the role of trastuzumab resistance in HER2-positive gastric cancer cells. A high level of GSE1 was associated with a high risk of tumor lymph node metastasis and higher clinical stage in HER2-positive gastric cancer patients. GSE1 was a potential target that could be used for HER2-positive gastric cancer therapy.

The efficacy of trastuzumab, a treatment for HER2+ breast cancer, can be limited by the development of resistance. Cyclin E (CCNE) overexpression has been implicated in trastuzumab resistance. We sought to uncover a potential mechanism for this trastuzumab resistance and focused on a model of CCNE overexpressing HER2+ breast cancer and noncanonical phosphorylation of the TGF-β signaling protein, SMAD3. Network analysis of transcriptional activity in a HER2+, CCNE overexpressing, trastuzumab-resistant cell line (BT474R2) identified decreased SMAD3 activity was associated with treatment resistance. Immunoblotting showed SMAD3 expression was significantly downregulated in BT474R2 cells (p

Background We explored the therapeutic and prognostic effect of YAP/TAZ intensityinHER2-positive breast cancer patients. We also investigated the relationship between YAP/TAZ expression and Trastuzumab-resistance. Methods We collected clinicopathological information from 397 cases. We evaluated therapeutic and prognostic effect of YAP/TAZ and other variables. We also cultivated Trastuzumab-resistance cell lines and explored relationship between YAP/TAZ and Trastuzumab-resistance. Results Over-expression of YAP/TAZ was remarkable in Trastuzumab-resistant cells, and so did HER3 and HER2/HER3 heterodimer. Inhibition of YAP/TAZ expression reversed Trastuzumab-resistance.YAP/TAZ deficiency contributed to favorable therapeutic response, and so did hormone receptor insufficiency and chemotherapy dosage inferiority. Deficient YAP/TAZ intensity and abundant hormone receptor intensity contributed to better survival. Over-expression of YAP/TAZ was obvious in recurrent cases in comparison with their matching primary lesions. Prognostic superiority of insufficient YAP/TAZ intensity was more outstanding in hormone receptor negative cases. Over-expression of YAP/TAZ and HER3 was generally synchronous. Absence of HER3 expression in residual lesions might correlate with better breast cancer-free survival. Conclusions Over-expression of YAP/TAZ as well as HER-3 and HER2/HER3 heterodimer was synchronously remarkable in Trastuzumab-resistant cell lines. Inhibition of YAP/TAZ expression reversed Trastuzumab resistance. Deficient YAP/TAZ intensity as well as insufficient hormone receptor intensity and high chemotherapy dosage contributed to favorable therapeutic response. Deficient YAP/TAZ intensity and abundant hormone receptor intensity contributed to better survival, and so did absence of HER3expression in residual lesions. Prognostic superiority of YAP/TAZ expression depended on hormone receptor status. Cases with synchronous over-expression of YAP/TAZ and HER3 suffered poor survival, which revealed the potential effect of YAP/TAZ-HER2/HER3 crosstalk in prognosis of HER2-positive patients.

Background:Prognosis of patients affected by metastatic esophageal–gastric junction (EGJ) or gastric cancer (GC) remains dismal. Trastuzumab, an anti-HER2 monoclonal antibody, is the only targeted agent approved for the first-line treatment of patients with HER2-overexpressing advanced EGJ or GC in combination with chemotherapy. However, patients invariably become resistant during this treatment. We recently identified the overexpression of fibroblast growth factor (FGF) receptor 3 (FGFR3) as a molecular mechanism responsible for trastuzumab resistance in GC models, providing the rationale for the inhibition of this receptor as a potential second-line strategy in this disease. Pemigatinib is a selective, potent, oral inhibitor of FGFR1, 2, and 3.Methods:The FiGhTeR trial is a phase II, single-arm, open-label study to assess safety and activity of the FGFR inhibitor pemigatinib as second-line treatment strategy in metastatic EGJ/GC patients progressing under trastuzumab-containing therapies. The primary endpoint is the 12-week progression-free survival rate. Plasma and tumor tissue samples will be collected for translational research analyses at baseline, during treatment, and at progression on pemigatinib.Discussion:Co-alterations in genes coding for different tyrosine-kinase receptors are emerging as relevant mechanisms of acquired resistance to anti-HER2 therapeutic strategies in GC. In particular, our group has recently identified that in GC models the overexpression of FGFR3 sustains the acquired resistance to trastuzumab. This trial aims to assess the safety, tolerability and activity of the FGFR inhibitor pemigatinib as a second-line treatment in metastatic EGJ/GC patients refractory to first-line trastuzumab-containing therapies. Furthermore, this study offers the opportunity to prospectively study mechanisms and pathways involved in trastuzumab resistance.Protocol number:CRC2017_02EudraCT Number:2017-004522-14

Background/Aims: Resistance to trastuzumab remains a common challenge to HER-2 positive breast cancer. Up until now, the underlying mechanism of trastuzumab resistance is still unclear. tRNA-derived small non-coding RNAs, a new class of small non-coding RNA (sncRNAs), have been observed to play an important role in cancer progression. However, the relationship between tRNA-derived fragments and trastuzumab resistance is still unknown. Methods: We detected the levels of tRNA-derived fragments expression in normal breast epithelial cell lines, trastuzumab-sensitive and -resistant breast cancer cell lines using high-throughput sequencing. qRT-PCR was conducted to validate the differentially expressed fragments in serums from trastuzumab-sensitive and -resistant patients. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the power of specific tRNA-derived fragments. Progression-free survival (PFS) was analyzed using Cox-regression. Results: Our sequence results showed that tRNA-derived fragments were differentially expressed in the HBL-100, SKBR3, and JIMT-1 cell lines. tRF-30-JZOYJE22RR33 and tRF-27-ZDXPHO53KSN were found significantly upregulated in trastuzumab-resistant patients compared to sensitive individuals, and the ROC analysis showed that tRF-30-JZOYJE22RR33 and tRF-27-ZDXPHO53KSN were correlated with trastuzumab resistance. In a multivariate analysis, higher levels of tRF-30-JZOYJE22RR33 and tRF-27-ZDXPHO53KSN expression were associated with significantly shorter PFS in patients with metastatic HER-2 positive breast cancer. Conclusion: Our results suggest that tRF-30-JZOYJE22RR33 and tRF-27-ZDXPHO53KSN play important roles in trastuzumab resistance. Patients with high levels of tRF-30-JZOYJE22RR33 and tRF-27-ZDXPHO53KSN expression benefitted less from trastuzumab-based therapy than those that express lower-levels of these molecules. tRF-30-JZOYJE22RR33 and tRF-27-ZDXPHO53KSN may be potential biomarkers and intervention targets in the clinical treatment of trastuzumab-resistant breast cancer.

After the publication of this work [1] errors were found in Figs. 1a and 5d.

To monitor trastuzumab resistance and determine the underlying mechanisms for the limited response rate and rapid emergence of resistance of HER2+ metastatic gastric cancer (mGC).Targeted sequencing of 416 clinically relevant genes was performed in 78 paired plasma and tissue biopsy samples to determine plasma-tissue concordance. Then, we performed longitudinal analyses of 97 serial plasma samples collected from 24 patients who were HER2+ to track the resistance during trastuzumab treatment and validated the identified candidate resistance genes.The results from targeted sequencing-based detection of somatic copy number alterations (SCNA) ofLongitudinal circulating tumour DNA sequencing provides novel insights into gene alterations underlying trastuzumab resistance in HER2+mGC.

// Lingfei Wang 1, 2, * , Xiaojie Yu 2, * , Chao Wang 2, * , Shujun Pan 3, * , Beibei Liang 1 , Yajun Zhang 2 , Xiaodan Chong 2 , Yanchun Meng 4 , Jian Dong 5 , Yirong Zhao 2 , Yang Yang 2 , Huajing Wang 2 , Jie Gao 6 , Huafeng Wei 1, 2 , Jian Zhao 1, 2 , Hao Wang 2 , Chaohua Hu 7 , Wenze Xiao 8 and Bohua Li 1, 2 1 Shanghai Key Laboratory for Molecular Imaging, Shanghai University of Medicine and Health Sciences, Shanghai 201318, China 2 International Joint Cancer Institute, Second Military Medical University, Shanghai 200433, China 3 Hangzhou Sanatorium of People’s Liberation Army, Hangzhou 310007, China 4 Department of Medical Oncology, Fudan University Shanghai Cancer Center, Shanghai Medical College of Fudan University, Shanghai 200032, China 5 Department of Vascular Surgery, Changhai Hospital, Second Military Medical University, Shanghai, 200433, China 6 Department of Pharmaceutical Sciences, Second Military Medical University, Shanghai 200433, China 7 Department of General Surgery, Xiaogan Central Hospital Affiliated to Wuhan University of Science and Technology, Wuhan 432000, China 8 Department of Rheumatology, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai 201399, China * These authors contributed equally to this work Correspondence to: Chaohua Hu, email: huchaohua2006@126.com Wenze Xiao, email: wenzexiao@yahoo.com Bohua Li, email: bohuali1020@163.com Keywords: trastuzumab resistance, GDC-0941, anti-ErbB2 antibody, programmed cell death, breast cancer Received: March 07, 2017 Accepted: May 05, 2017 Published: May 16, 2017 ABSTRACT Trastuzumab, an anti-ErbB2 humanized antibody, brings benefit to patients with ErbB2-amplified metastatic breast cancers. However, the resistance to trastuzumab is common. Our previously reported H2-18, an anti-ErbB2 antibody, potently induced programmed cell death in trastuzumab-resistant breast cancer cells. Here, we aim to investigate the antitumor efficacy of H2-18 in combination with the pan-PI3K inhibitor GDC-0941 in trastuzumab-resistant breast cancer cell lines. The results showed that H2-18 and GDC-0941 synergistically inhibited the in vitro proliferation of BT-474, SKBR-3, HCC-1954 and HCC-1419 breast cancer cells. H2-18 plus GDC-0941 showed significantly enhanced programmed cell death-inducing activity compared with each drug used alone. The combination of H2-18 and GDC-0941 did not increase the effect of single agent on ROS production, cell cycle and ErbB2 signaling. Importantly, the in vivo antitumor efficacy of H2-18 plus GDC-0941 was superior to that of single agent. Thus, the enhanced in vivo antitumor efficacy of H2-18 plus GDC-0941 may mainly be attributable to its increased programmed cell death-inducing activity. Collectively, H2-18 plus GDC-0941 could effectively inhibit tumor growth, suggesting the potential to be translated into clinic as an efficient strategy for ErbB2-overexpressing breast cancers.

Trastuzumab is an antibody-based therapy drug targeting HER2-overexpressing tumors. While it has been proven to be very successful initially, most patients eventually develop resistance to trastuzumab. The mechanism of drug resistance is not well understood. Identifying pathways that mediate trastuzumab resistance will improve our understanding of the underlying mechanism and is crucial for the development of therapeutic strategies to overcome resistance. Here we report a quantitative proteomics profiling of a trastuzumab-sensitive (T-S) gastric cancer cell line NCI N87 and a trastuzumab-resistant NCI N87 (T-R) subline generated by low-dose, continuous trastuzumab treatment. By identifying proteins differentially expressed in these two cell lines, we show that multiple pathways including mTOR, Wnt, DNA damage response and metabolic pathways are significantly altered. We further confirm by western blotting that protein levels of multiple components of the mTOR pathway, including mTOR, AKT and RPS6KB1, are increased, whereas AKT1S1 is decreased, suggesting the activation of mTOR pathway. Importantly, treatment of AZD8055, an mTOR inhibitor, leads to the decreased phosphorylation levels of mTOR downstream molecules RPS6KB1 at Thr421/Ser424 and AKT at Ser473. Furthermore, AZD8055 also preferentially reduces viability, and inhibits migration and invasion abilities of the T-R cells. Together, our findings indicate that mTOR pathway is among multiple signaling pathways that mediate trastuzumab resistance in NCI N87 T-R cells, and that mTOR inhibitors may be used to treat trastuzumab resistant, HER2-positive gastric cancer tumors.

Background/Aims: Trastuzumab is an important treatment used for patients with Her-2-positive breast cancer, but an increasing incidence of trastuzumab resistance has been observed clinically during the past decade. Aberrant microRNA (miR) expression levels are correlated with prognosis and response to trastuzumab in breast cancer. MiR-129-5p is downregulated in trastuzumab-resistant human breast cancer cells (JIMT-1), but its potential function and underlying mechanism remain unclear. Methods: Quantitative RT-PCR (qRT-PCR) was used to determine the expression levels of miR-129-5p and its potential target genes. The effects of miR-129-5p on cell responses to trastuzumab were analyzed by CCK-8 and flow cytometry assays in Her-2-positive breast cancer cells (SKBR-3 and JIMT-1). Bio-informatics analyses were performed to predict target genes of miR-129-5p, and luciferase assays were carried out to confirm the binding of miR-129-5p and rpS6. Results: MiR-129-5p, which was downregulated and predicted to target rpS6 in trastuzumab-resistant breast cancer cells, enhanced the sensitivity of breast cancer cells to trastuzumab by reducing the expression of rpS6. Moreover, the overexpression of rpS6 reversed the sensitivity of cells to trastuzumab induced by miR-129-5p. Conclusions: MiR-129-5p sensitized Her-2-positive breast cancer to trastuzumab by downregulating rpS6. These findings provide novel insights into the common role of rpS6 and its related molecular mechanisms in mediating trastuzumab-resistance in Her-2-positive breast cancers.

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer (BC) comprises around 20-30% of all BC subtypes and is correlated with poor prognosis. For many years, trastuzumab, a monoclonal antibody, has been used to inhibit the HER2 activity. Though, the main resistance to trastuzumab has challenged the use of this drug in the management of HER2-positive BC. Therefore, the determination of resistance mechanisms and the incorporation of new agents may lead to the development of a better blockade of the HER family receptor signaling. During the last few years, some therapeutic drugs have been developed for treating patients with trastuzumab-resistant HER2-positive BC that have more effective influences in the management of this condition. In this regard, the present study aimed at reviewing the mechanisms of trastuzumab resistance and the innovative therapies that have been investigated in trastuzumab-resistant HER2-positive BC subjects.

Trastuzumab is an effective therapeutic treatment for Her2-like breast cancer; despite this most of these tumors develop resistance to therapy due to specific gene mutations or alterations in gene expression. Understanding the mechanisms of resistance to Trastuzumab could be a useful tool in order to identify combinations of drugs that elude resistance and allow a better response for the treated patients. Twelve primary biopsies of Her2+/hormone receptor negative (ER-/PgR-) breast cancer patients were selected based on the specific response to neoadjuvant therapy with Trastuzumab and their whole exome was sequenced leading to the identification of 18 informative gene mutations that discriminate patients selectively based on response to treatment. Among these genes, we focused on the study of the ANKRD44 gene to understand its role in the mechanism of resistance to Trastuzumab. The ANKRD44 gene was silenced in Her2-like breast cancer cell line (BT474), obtaining a partially Trastuzumab-resistant breast cancer cell line that constitutively activates the NF-kb protein via the TAK1/AKT pathway. Following this activation an increase in the level of glycolysis in resistant cells is promoted, also confirmed by the up-regulation of the LDHB protein and by an increased TROP2 protein expression, found generally associated with aggressive tumors. These results allow us to consider the ANKRD44 gene as a potential gene involved in Trastuzumab resistance.

Trastuzumab represents the predominant therapy to target breast cancer subtype marked by HER2 amplification. It has been in use for two decades and its continued importance is underlined by recent FDA approvals of its biosimilar and conjugated versions. Progression to an aggressive disease with acquisition of resistance to trastuzumab remains a major clinical concern. In addition to a number of cellular signaling pathways being investigated, focus in recent years has also shifted to epigenetic and non-coding RNA basis of acquired resistance against trastuzumab. This article provides a succinct discussion on the most recent advances in our understanding of such factors.

[Background]: An important proportion of HER2-positive metastatic breast cancer patients do not respond to trastuzumab. The combination of dasatinib and trastuzumab has shown to be synergistic in preclinical models., [Methods]: We conducted a phase II trial combining dasatinib 100 mg once daily with trastuzumab 2 mg/kg and paclitaxel 80 mg/m2 weekly. Primary objective was objective response rate (ORR) and secondary included safety, other efficacy parameters and pharmacodynamics in tumour tissue, blood samples and skin biopsies., [Results]: From June 2013 to December 2015, 29 patients were included. Median number of cycles was 12 (1–49). Only 6 patients discontinued due to adverse events. ORR was 79.3% (95% CI 60.3–92), clinical benefit rate 82.8% (95% CI 64.2–94.2). Median time to progression 23.9 months (95% CI 14.9–not reached [NR]), median progression-free survival 23.9 months (95% CI 10.3–NR). No grade 4 toxicity was seen. Grade 3 toxicities included: ejection fraction decrease, neutropenia, hyponatremia, fatigue and sensory neuropathy and one left ventricular systolic dysfunction. Phosphorylated (p)-SRC was reduced in peripheral blood mononuclear cells. Phosphorylated SRC, ERK and AKT were also reduced in epidermal keratinocytes., [Conclusions]: Dasatinib can be safely combined with trastuzumab and paclitaxel. The combination is active with an ORR of almost 80%. Trial registration: NCT01306942, EudraCT 2010-023304-27., The study was financially supported by Bristol-Myers Squibb which also supplied the dasatinib.

Trastuzumab, the first antibody widely used in anti-HER2 targeted therapy, dramatically improved the overall outcome of HER2 positive breast cancer patients. However, trastuzumab resistance emerged as a major problem in its clinical application. In order to explore mechanisms underlying trastuzumab resistance, we performed RNA-Seq to analyze the gene expression variation in trastuzumab resistant breast cancer cell line. The sequencing result was then combined with the relevant data in TCGA database to conduct a co-expression analysis. We found a series of differentially expressed genes with potential contributions to trastuzumab resistance. Among them, KLK10 was verified to be a potential therapeutic target for reversing trastuzumab resistance. In summary, this study provides a new clue to screen molecular targets and predictive biomarkers for trastuzumab resistance.

// Lichao Sun 1, 2, * , Joseph Burnett 1, * , Mari Gasparyan 1 , Fangying Xu 1 , Hui Jiang 3 , Chang-Ching Lin 1 , Ila Myers 1 , Hasan Korkaya 4 , Yajing Liu 5 , Jamie Connarn 1 , Huining He 6 , Ning Zhang 6 , Max S. Wicha 5 , Duxin Sun 1 1 Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI, 48109, USA 2 State Key Laboratory of Molecular Oncology, Cancer Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, 100021, China 3 Department of Biostatistics, University of Michigan, Ann Arbor, MI, 48109, USA 4 Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, 30912, USA 5 Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48109, USA 6 College of Pharmacy and Tianjin Cancer Institute and Hospital, National Clinical Research Center of Cancer, Research Center of Basic Medical Sciences, Tianjin Medical University, Tianjin, 300070, China * These authors have contributed equally to this work Correspondence to: Duxin Sun, email: duxins@umich.edu Keywords: trastuzumab resistance, EMT, cancer stem cells, MEOX1, HER2+ breast cancer Received: January 11, 2016 Accepted: May 22, 2016 Published: June 06, 2016 ABSTRACT Continued use of trastuzumab in PTEN-deficient HER2+ breast cancer induces the epithelial-to-mesenchymal transition (EMT), transforms HER2+ to triple negative breast cancer, and expands breast cancer stem cells (BCSCs). Using cancer cell lines with two distinct states, epithelial and mesenchymal, we identified novel targets during EMT in PTEN-deficient trastuzumab-resistant breast cancer. Differential gene expression and distinct responses to a small molecule in BT474 (HER2+ trastuzumab-sensitive) and the PTEN-deficient trastuzumab-resistant derivative (BT474-PTEN-LTT) provided the selection tools to identify targets during EMT. siRNA knockdown and small molecule inhibition confirmed MEOX1 as one of the critical molecular targets to regulate both BCSCs and mesenchymal-like cell proliferation. MEOX1 was associated with poor survival, lymph node metastasis, and stage of breast cancer patients. These findings suggest that MEOX1 is a clinically relevant novel target in BCSCs and mesenchymal-like cancer cells in PTEN-deficient trastuzumab resistant breast cancer and may serve as target for future drug development.

HER2-positive advanced gastric cancer patients frequently develop resistance to trastuzumab through mechanisms still poorly understood. In breast cancer, other members of the HER-family are known to be involved in trastuzumab-resistance, as is overexpression of the scaffold protein IQGAP1. In the present work, we investigated acquired resistance to trastuzumab in gastric cancer experimental models. Trastuzumab-resistant (HR) subclones derived from 3 HER2-overexpressing gastric cancer cells were generated and characterized for alterations in HER2-signaling mechanisms by next-generation sequencing, immunohistochemical, western blot and qRT-PCR techniques, and molecular modeling analysis. All subclones showed a reduced growth rate with respect to parental cell lines but each had a different resistance mechanism. In NCI N87 HR cells, characterized by a marked increase in HER2-signaling pathways with respect to the parental cell line, trastuzumab sensitivity was restored when IQGAP1 expression was silenced. AKG HR subclone showed higher HER3 protein expression than the parental line. High nuclear HER4 levels were observed in KKP HR cells. In conclusion, our study revealed that high IQGAP1 expression leads to resistance to trastuzumab in gastric cancer. Furthermore, 2 new mutations of the HER2 gene that may be involved in acquired resistance were identified in AKG HR and KKP HR subclones.

HER2 is overexpressed in about 20% of breast cancers and contributes to poor prognosis. Unfortunately, a large fraction of patients have primary or acquired resistance to the HER2-targeted therapy trastuzumab, thus a multi-drug combination is utilized in the clinic, putting significant burden on patients. We systematically identified an optimal HER2 siRNA from 76 potential sequences and demonstrated its utility in overcoming intrinsic and acquired resistance to trastuzumab and lapatinib in 18 HER2-positive cancer cell lines. We provided evidence that the drug-resistant cancer maintains dependence on HER2 for survival. Importantly, cell lines did not readily develop resistance following extended treatment with HER2 siRNA. Using our recently developed nanoparticle platform, systemic delivery of HER2 siRNA to trastuzumab-resistant tumors resulted in significant growth inhibition. Moreover, the optimal HER2 siRNA could also silence an exon 16 skipped HER2 splice variant reported to be highly oncogenic and linked to trastuzumab resistance.

e13006 Background: Approximately 20% of breast cancers are HER2-positive. Trastuzumab has improved patient outcomes significantly for these cancers. However, acquired resistance occurs in almost all patients with metastatic breast cancer. Therefore, identifying molecular changes that are associated with trastuzumab resistance is worthwhile. STAT6 is a transcription factor that regulates a variety of genes involved in cell cycle regulation, growth inhibition, and apoptosis. STAT6 expression is lost in approximately 3% of breast cancers, but little work has been done in the context of trastuzumab resistance in breast cancer. Methods: In isogenic cell line pairs, we observed that trastuzumab-resistant cells expressed significantly lower levels of STAT6 compared to trastuzumab-sensitive cells. Therefore, in order to study the consequences of STAT6 loss in HER2+ breast cancer, we knocked out both alleles of the STAT6 gene using somatic cell gene targeting. Results: We observed that loss of STAT6 resulted in resistance to trastuzumab treatment in HER2-over-expressing cells. Additionally, loss of STAT6 resulted in anchorage-independent growth and changed expression of several genes involved in epithelial to mesenchymal transition. Functional studies revealed that STAT6 loss caused a non-tumorigenic human breast cell line to form tumors in mice. Conclusions: Loss of STAT6 in breast cells results in enhanced growth properties and resistance to trastuzumab. This study suggests that STAT6 may play a role in the pathophysiology of HER2+ human breast cancer. Disclaimer: The work herein was completed while AMA was a faculty member at Rush University. AMA is currently an employee with the U.S. Food and Drug Administration. The views and data in this publication do not reflect the opinions of the U.S. Government or The U.S. Food and Drug Administration.

Trastuzumab, a monoclonal antibody to human epidermal growth factor receptor 2 (HER2), has improved survival in patients with HER2-positive advanced gastric or gastroesophageal junction cancer (AGC). The inevitable development of resistance to trastuzumab remains a problem, however, with several treatment strategies that have proven effective in breast cancer having failed to show clinical benefit in AGC. In this review, we summarize the mechanisms underlying resistance to HER2-targeted therapy and outline past and current challenges in the treatment of HER2-positive AGC refractory to trastuzumab. We further describe novel agents such as HER2 antibody–drug conjugates that are under development and have shown promising antitumor activity in early studies.

Aim: In this study, we aim to use bioinformatics approach to identify paclitaxel-targeted modulators potentially involved in the process of reversing the trastuzumab resistance. Materials & methods: We extracted data from GSE77346 to identify potential trastuzumab resistance-related genes, used bioinformatics analysis and functional/activity network approach to find genes involved in trastuzumab resistance reversal. Results: We identified hub differentially expressed genes related to trastuzumab resistance, trastuzumab targeting and paclitaxel targeting, respectively. We then found C-Jun may be critical in trastuzumab resistance reversal. This process may involve transcriptional activation of DUSP1 by JUN, which lead to regulation of DUSP1-related signaling pathways. Conclusion: The present study revealed paclitaxel may reverse the trastuzumab resistance by JUN, which possibly in turn regulated DUSP1 and DUSP1-related signaling pathways.

Background: Somatic mutations in the ERBB genes (epidermal growth factor receptor: EGFR, ERBB2, ERBB3, ERBB4) promote oncogenesis and lapatinib resistance in metastatic HER2+ (human epidermal growth factor-like receptor 2) breast cancer in vitro. Our study aimed to determine the frequency of mutations in four genes: EGFR, ERBB2, ERBB3 and ERBB4 and to investigate whether these mutations affect cellular behaviour and therapy response in vitro and outcomes after adjuvant trastuzumab-based therapy in clinical samples. Methods: We performed Agena MassArray analysis of 227 HER2+ breast cancer samples to identify the type and frequency of ERBB family mutations. Of these, two mutations, the somatic mutations ERBB4-V721I and ERBB4-S303F, were stably transfected into HCC1954 (PIK3CA mutant), HCC1569 (PIK3CA wildtype) and BT474 (PIK3CA mutant, ER positive) HER2+ breast cancer cell lines for functional in vitro experiments. Results: A total of 12 somatic, likely deleterious mutations in the kinase and furin-like domains of the ERBB genes (3 EGFR, 1 ERBB2, 3 ERBB3, 5 ERBB4) were identified in 7% of HER2+ breast cancers, with ERBB4 the most frequently mutated gene. The ERBB4-V721I kinase domain mutation significantly increased 3D-colony formation in 3/3 cell lines, whereas ERBB4-S303F did not increase growth rate or 3D colony formation in vitro. ERBB4-V721I sensitized HCC1569 cells (PIK3CA wildtype) to the pan class I PI3K inhibitor copanlisib but increased resistance to the pan-HER family inhibitor afatinib. The combinations of copanlisib with trastuzumab, lapatinib, or afatinib remained synergistic regardless of ERBB4-V721I or ERBB4-S303F mutation status. Conclusions: ERBB gene family mutations, which are present in 7% of our HER2+ breast cancer cohort, may have the potential to alter cellular behaviour and the efficacy of HER- and PI3K-inhibition.

Introduction: Although targeting human epidermal growth factor receptor 2 (HER2) is a meaningful treatment in HER2-positive breast cancer, ultimately resistance develops. Androgen receptor (AR) expression and immune cell infiltration are thought to be involved in trastuzumab response and may, therefore, be of interest as additional targets for therapy in HER2-positive breast cancer.Aim: To improve insights into the presence among AR expression, immune cell infiltration and HER2, we analysed HER2-positive breast tumours.Methods: Primary tumours of 221 patients treated with trastuzumab for metastatic disease were selected. HER2 status was centrally confirmed. AR, T-cells (CD3 and CD8), programmed cell death protein 1 (PD-1) and PD-1 ligand 1 immunohistochemical staining and M2 tumour-associated macrophages (TAMs; CD68 and CD163) immunofluorescence were performed. Tumour-infiltrating lymphocytes were evaluated by haematoxylin and eosin staining.Results: Sufficient tumour material was available for 150 patients. Oestrogen receptor was expressed in 51.3% of the tumours andARin 81.3% of the tumours. AR expression was inversely correlated with M2 TAM (Pearson's r = -0.361, P Conclusion: AR expression inversely correlates with immune cell infiltration in HER2-positive breast cancer. (C) 2018 Elsevier Ltd. All rights reserved.

Trastuzumab, the first targeted antibody against human epidermal growth factor receptor 2 (HER2), has been used to treat gastric cancer patients with HER2 overexpression. However, trastuzumab resistance often occurs following an initial period of benefits, and the underlying mechanisms remain largely unclear. The present study revealed that collagen type IV α1 chain (COL4A1), whose expression is upregulated in gastric cancer tissues and trastuzumab‑resistant gastric cancer cells, may potentially confer trastuzumab resistance in gastric cancer. By performing bioinformatics analysis of 2 microarray datasets, the present study initially identified COL4A1, overexpressed in gastric cancer tissues and trastuzumab‑resistant gastric cancer cells, as a potential candidate for inducing trastuzumab resistance. The drug resistance function of COL4A1 in gastric cancer was then validated by performing protein/gene interactions and biological process annotation analyses, and further validated by analyzing the functionality of microRNAs that target COL4A1 mRNA. Collectively, these data indicated that COL4A1 may confer trastuzumab resistance in gastric cancer.

SRC tyrosine kinase is frequently overexpressed and activated in late-stage, poor prognosis ovarian tumours, and preclinical studies have supported the use of targeted SRC inhibitors in the treatment of this disease. The SAPPROC trial investigated the addition of the SRC inhibitor saracatinib (AZD0530) to weekly paclitaxel for the treatment of platinum resistant ovarian cancer; however, this drug combination did not provide any benefit to progression free survival (PFS) of women with platinum resistant disease. In this study we aimed to identify mechanisms of resistance to SRC inhibitors in ovarian cancer cells. Using two complementary strategies; a targeted tumour suppressor gene siRNA screen, and a phospho-receptor tyrosine kinase array, we demonstrate that activation of MAPK signalling, via a reduction in NF1 (neurofibromin) expression or overexpression of HER2 and the insulin receptor, can drive resistance to AZD0530. Knockdown of NF1 in two ovarian cancer cell lines resulted in resistance to AZD0530, and was accompanied with activated MEK and ERK signalling. We also show that silencing of HER2 and the insulin receptor can partially resensitize AZD0530 resistant cells, which was associated with decreased phosphorylation of MEK and ERK. Furthermore, we demonstrate a synergistic effect of combining SRC and MEK inhibitors in both AZD0530 sensitive and resistant cells, and that MEK inhibition is sufficient to completely resensitize AZD0530 resistant cells. This work provides a preclinical rationale for the combination of SRC and MEK inhibitors in the treatment of ovarian cancer, and also highlights the need for biomarker driven patient selection for clinical trials.

Although Trastuzumab, an anti-HER2 antibody, benefits certain patients with HER2-overexpressing breast cancer, de novo or acquired trastuzumab resistance remains a haunting issue. EGFRvIII, co-expressing with HER2 in some breast tumors, indicates a poor clinical prognosis. However, the role of EGFRvIII in the function of trastuzumab is not clear. Here, we demonstrated that EGFRvIII overexpression contributed to de novo trastuzumab resistance and the feedback activation of STAT3 caused by trastuzumab also resulted in acquired resistance in EGFRvIII(+)HER2(+) breast cancers. CH12, a highly effective anti-EGFRvIII monoclonal antibody that preferentially binds to EGFRvIII, significantly suppressed the growth of EGFRvIII+HER2(+) breast cancer cells in vitro and in vivo. Importantly, CH12 in combination with trastuzumab had a synergistic inhibitory effect on EGFRvIII(+)HER2(+) breast cancers in vitro and in vivo via attenuating the phosphorylation of EGFR and HER2 and their downstream signal pathways more effectively and reversing STAT3 feedback activation. Moreover, the combination therapy suppressed angiogenesis and induced cell apoptosis significantly. Together, these results suggested a synergistic efficacy of the combination of trastuzumab with CH12 against EGFRvIII(+)HER2(+) breast cancers, which might be a potential clinical application in the future.

The therapy for patients with breast cancer has developed markedly in the past ten years. Our understanding of the molecular biology of tumours and the characteristics of the patients has shaped the recent advances. In this review we present the latest knowledge about the therapy for breast cancer. There are new tests and options not only in the field of anti-HER2 therapy but also in the management of triple negative and hormone receptor-positive patients. Comprehension of prognosis and therapeutic response to chemotherapies is little by little helping to define patient groups who will not respond to chemotherapy or who do not need treatment because their prognosis is extremely good. In the field of anti-HER2 therapy, work is continuing on the development of drugs suitable for and able to overcome trastuzumab resistance. For hormone receptor-positive cancers, we now have a better understanding of which therapy groups will benefit from which anti-endocrine drugs, and which will be able to overcome a possible resistance (treatment of the PI3K pathways, inhibition of the cell cycle). Molecular tests are still being evaluated with regard to the clinical situations in which they may have the greatest relevance for therapeutic decision-making; however, evidence is also increasing as to the fields in which good predictions for the prognosis can be obtained. On the whole, more work is needed to promote our understanding of the new developments in diagnostics and therapy and to involve both physicians and patients equally in the procedures.Die Therapie von Patientinnen mit Mammakarzinom hat sich in den letzten 10 Jahren deutlich weiterentwickelt. Das Verständnis um die molekulare Biologie der Tumoren und Patientinneneigenschaften haben die jüngsten Entwicklungen geprägt. In diesem Review werden die neuesten Erkenntnisse zur Therapie des Mammakarzinoms dargestellt. Hierbei gibt es sowohl auf dem Gebiet der Anti-HER2-Therapie als auch bei der Behandlung von triple-negativen und hormonrezeptorpositiven Patientinnen neue Tests und Therapien. Das Verständnis um Prognose und Therapieansprechen auf Chemotherapien definiert nach und nach Patientinnengruppen, die nicht auf eine Chemotherapie ansprechen oder die keine Therapie benötigen, weil die Prognose außerordentlich gut ist. Auf dem Gebiet der Anti-HER2-Therapie wird weiterhin an Medikamenten gearbeitet, die bei einer Trastuzumab-Resistenz geeignet sind, diese zu überwinden. Für hormonrezeptorpositive Karzinome wird besser verstanden, welche Therapiegruppen von welchen antiendokrinen Medikamenten profitieren, und welche eine eventuelle Resistenz überwinden können (Behandlung des PI3K-Pathways, Inhibition des Zellzyklus). Molekulare Tests befinden sich weiterhin in der Evaluation, in welchen klinischen Situationen sie den größten Nutzen für Therapieentscheidungen bringen können, jedoch wächst die Evidenz, in welchen Bereichen eine gute Aussage über die Prognose gewonnen werden kann. Insgesamt muss daran gearbeitet werden, das Verständnis für die neuen Entwicklungen in Diagnostik und Therapie zu fördern und Ärzte und Patientinnen gleichermaßen in die Ausbildung mit einzubeziehen.

Sandra Jernström,1,2 Vesa Hongisto,3 Suvi-Katri Leivonen,1,2 Eldri Undlien Due,1 Dagim Shiferaw Tadele,1 Henrik Edgren,4,5 Olli Kallioniemi,4 Merja Perälä,6 Gunhild Mari Mælandsmo,2,7,8 Kristine Kleivi Sahlberg,1,9 1Department of Cancer Genetics, Institute for Cancer Research, Oslo University Hospital, 2KG Jebsen Centre for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway; 3Misvik Biology Oy, Turku, 4Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, 5Medisapiens, Helsinki, Finland, 6VTT Technical Research Centre of Finland, Turku, Finland; 7Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway; 8Institute of Pharmacy, Faculty of Health Sciences, University of Tromsø, Tromsø, 9Department of Research, Vestre Viken Hospital Trust, Drammen,Norway Background: Approximately 15%–20% of all diagnosed breast cancers are characterized by amplified and overexpressed HER2 (= ErbB2). These breast cancers are aggressive and have a poor prognosis. Although improvements in treatment have been achieved after the introduction of trastuzumab and lapatinib, many patients do not benefit from these drugs. Therefore, in-depth understanding of the mechanisms behind the treatment responses is essential to find alternative therapeutic strategies. Materials and methods: Thirteen HER2 positive breast cancer cell lines were screened with 22 commercially available compounds, mainly targeting proteins in the ErbB2-signaling pathway, and molecular mechanisms related to treatment sensitivity were sought. Cell viability was measured, and treatment responses between the cell lines were compared. To search for response predictors and genomic and transcriptomic profiling, PIK3CA mutations and PTEN status were explored and molecular features associated with drug sensitivity sought. Results: The cell lines were divided into three groups according to the growth-retarding effect induced by trastuzumab and lapatinib. Interestingly, two cell lines insensitive to trastuzumab (KPL4 and SUM190PT) showed sensitivity to an Akt1/2 kinase inhibitor. These cell lines had mutation in PIK3CA and loss of PTEN, suggesting an activated and druggable Akt-signaling pathway. Expression levels of five genes (CDC42, MAPK8, PLCG1, PTK6, and PAK6) were suggested as predictors for the Akt1/2 kinase-inhibitor response. Conclusion: Targeting the Akt-signaling pathway shows promise in cell lines that do not respond to trastuzumab. In addition, our results indicate that several molecular features determine the growth-retarding effects induced by the drugs, suggesting that parameters other than HER2 amplification/expression should be included as markers for therapy decisions. Keywords: ErbB2, drug screening, gene expression, pharmacogenomics, predictors

// Alberto Ocana 1 , Marta Gil-Martin 2 , Miguel Martin 3 , Federico Rojo 4 , Silvia Antolin 5 , Angel Guerrero 6 , Jose Manuel Trigo 7 , Montse Munoz 8 , Atanasio Pandiella 9 , Nuria Gonzalo Diego 10 , Susana Bezares 11 , Rosalia Caballero 12 , Eva Carrasco 11 and Ander Urruticoechea 13 1 Department of Medical Oncology, Complejo Hospitalario Universitario de Albacete, Albacete, Spain 2 Department of Medical Oncology, Institut Catala d’Oncologia-IDIBELL, L’Hospitalet, Barcelona, Spain 3 Department of Medical Oncology, Instituto de Investigacion Sanitaria Gregorio Maranon, Universidad Complutense, Madrid, Spain 4 Fundacion Jimenez Diaz, Madrid, Spain 5 Department of Medical Oncology, Complejo Hospitalario Universitario A Coruna, La Coruna, Spain 6 Department of Medical Oncology, Instituto Valenciano de Oncologia, Valencia, Spain 7 Department of Medical Oncology, Hospital Clinico Universitario Virgen de la Victoria, Malaga, Spain 8 Department of Medical Oncology, Hospital Clinic i Provincial de Barcelona, Barcelona, Spain 9 Centro de Investigacion del Cancer and CIBERONC, CSIC-Universidad de Salamanca, Salamanca, Spain 10 Pharmacokinetics Laboratory, Farmacia ICO Metropolitana, IDIBELL, Instituto Catalan de Oncologia, Hospital Duran i Reynals, Barcelona, Spain 11 Scientific Department, GEICAM Spanish Breast Cancer Group, Spain 12 Translational Department, GEICAM Spanish Breast Cancer Group, Spain 13 Department of Medical Oncology, Fundacion Onkologikoa, Donostia, Gipuzkoa, Spain Correspondence to: Alberto Ocana, email: // Keywords : HER2 positive breast cancer, dasatinib, SRC kinase, trastuzumab resistance, metastatic breast cancer Received : March 04, 2017 Accepted : April 04, 2017 Published : April 14, 2017 Abstract The anti-HER2 antibody trastuzumab have shown clinical activity in combination with chemotherapy in different breast cancer settings. However, most of patients treated with this antibody progress after a period of treatment. Activation of the kinase SRC has been linked with resistance to trastuzumab in several preclinical studies. We designed a phase I clinical study to explore the activity of weekly trastuzumab (2 mg/kg) plus paclitaxel (80 mg/m 2 ) in combination with the anti-SRC kinase inhibitor Dasatinib in the first line treatment of HER2 metastatic breast cancer. The primary objective was to determine the maximum tolerated dose (MTD) and recommended phase II dose (RP2D); secondary objectives included efficacy, objective response rate (ORR), pharmacokinetics and pharmacodynamics. A “3+3” design guided dose escalation with two oral dose levels of dasatinib: 100mg (DL1) and 140 mg (DL2). 10 patients were included in the phase I part. Dasatinib 100 mg q.d. was established as the recommended RP2D. The median number of administered cycles was 12 (range, 1 to 18). Grade 3 treatment-related AEs at DL1 were diarrhea ( n = 2), hyponatremia ( n = 1), fatigue ( n = 1), and AST/ALT elevation ( n = 1). A significant reduction in p-SRC expression on epidermal keratinocytes on sequential skin biopsies was observed. In conclusion, we describe the feasibility of the combination of dasatinib, trastuzumab and paclitaxel, and its effect on proteins involved in trastuzumab resistance. The phase II part of this study is currently evaluating efficacy.

Resistance to trastuzumab is frequently observed during the treatment of patients with human epidermal growth factor 2 (HER2)-positive metastatic breast cancers. The aim of the present study was to determine if the phosphorylated proline-rich Akt substrate of 40 kDa (phospho-PRAS40Thr246), a novel biomarker for phosphoinositol-3 kinase (PI3K) pathway activation, could predict the response of HER2-positive metastatic breast cancers to treatment with trastuzumab. Formalin-fixed, paraffin-embedded tumor tissue samples were retrospectively collected from 55 trastuzumab-treated patients. Next, the expression of phospho-PRAS40Thr246 and phosphatase and tensin homolog (PTEN) was assessed by immunohistochemistry. In total, five common phosphoinositol-3 kinase α catalytic subunit mutations, namely E542K, E545K, E545D, H1047R and H1047L, were identified by the amplification-refractory mutation system, using the allele-specific polymerase chain reaction. The activation of the PI3K pathway, as determined by low PTEN expression or the presence of oncogenic PIK3CA mutations, was observed in 49.1% (27 cases) of the 55 HER2-positive metastatic breast cancer tissues. In total, 40% of the tumors were defined as being phospho-PRAS40Thr246-positive. Furthermore, the results revealed that phospho-PRAS40Thr246 expression was associated with the PI3K pathway activation status and an increased risk of tumor progression in HER2-positive metastatic breast cancer patients who had received trastuzumab-based therapy. Therefore, phospho-PRAS40Thr246 expression levels may reflect the PI3K pathway activation status and act as a biomarker for HER2-amplified breast cancer patients who are unlikely to respond to trastuzumab-based therapy.

HER2-overexpressing breast cancers are characterized by frequent distant metastasis and often develop resistance after short-term effective treatment with the monoclonal antibody drug, trastuzumab. Here, we found that the oncogenic miRNA, miR-221, inhibited apoptosis, induced trastuzumab resistance and promoted metastasis of HER2-positive breast cancers. The tumor suppressor PTEN was identified as a miR-221 target; overexpression of PTEN abrogated the aforementioned miR-221-induced malignant phenotypes of the cells. These findings indicate that miR-221 may promote trastuzumab resistance and metastasis of HER2-positive breast cancers by targeting PTEN, suggesting its role as a potential biomarker for progression and poor prognosis, and as a novel target for trastuzumab-combined treatment of breast cancers. [BMB Reports 2014; 47(5): 268-273].

e12006 Background: Trastuzumab, an effective treatment for HER2+ breast cancer, can be limited by development of resistance. Cyclin E (CCNE) overexpression was implicated in trastuzumab resistance, though the association is not well understood. We sought to explore a potential mechanism focusing on altered phosphorylation of the TGFβ signaling protein, SMAD3, in CCNE overexpressing HER2+ breast cancer cells, leading to trastuzumab resistance. Methods: A transcriptional activity cell array (TRACER) was used to examine the relationship between specific transcription factors and trastuzumab resistance in BT474 HER2+ human breast cancer cells. Immunoblotting examined phosphorylation patterns of SMAD3 in trastuzumab sensitive and resistant conditions. Effects of blocking CCNE overexpression with a CDK2 inhibitor were measured. To test the relative influence of SMAD3 and SMAD3 linker region phosphorylation on cell proliferation, BT474R2 cell lines were created overexpressing SMAD3 (BT474R2-SMAD3), a mutant construct blocking CCNE-mediated SMAD3 linker region phosphorylation (BT474R2-5M), and a control (BT474R2-Blank). In vitro and in vivo studies measured response to trastuzumab. Results: Resistance to trastuzumab was confirmed for BT474R2 cells, showing a markedly increased resistance to treatment when compared to the parental line. Network analysis of TRACER data identified decreased SMAD3 activity was central to resistance. Immunoblotting showed SMAD3 expression was significantly downregulated in BT474R2 cells (p < 0.01). Noncanonical phosphorylation of SMAD3 was increased in CCNE-overexpressing cells. Blocking CCNE mediated noncanonical phosphorylation of SMAD3 with CDK2 inhibition resulted in decreased proliferation of BT474R2 cells. In vitro studies examining response to trastuzumab showed an increased sensitivity for BT474R2-5M cells. Findings were validated in NSG mice inoculated with BT474R2-5M cells that developed significantly lower tumor volumes (p < 0.001) when treated with trastuzumab. Conclusions: These results identified a mechanism of CCNE-mediated trastuzumab resistance, regulated through noncanonical SMAD3 phosphorylation, which may be effectively treated with CDK2 inhibition to help enhance the efficacy of trastuzumab for patients with HER2+ breast cancer.

The American Society of Clinical Oncology 2013 Annual Meeting took place from May 31 until June 4 2013 in Chicago (IL, USA). Highlights within the area of gynecological oncology and breast cancer included two studies in cervical cancer addressing screening as well as treatment of advanced disease. In breast cancer, the presented studies covered a wide range of topics from local therapy to targeted therapy in the advanced setting. They were not practice changing but rather for the most part confirmatory of earlier findings. Last but not least, a positive Phase III study, BOLERO III, proved the hypothesis that trastuzumab resistance can be overcome by intracellular signal transduction using the mTOR inhibitor everolimus.

Production and approval of trastuzumab (Herceptin®) for the treatment of metastatic breast cancer (MBC) was a millstone in a ntibody-based targeted therapy in the cancer treatment. However, despite t he early success in the clinical trials, trastuzumab failed to appreciate the initia l attraction due to development of resistance to the drug. Majority of patients who be nefit from the drug acquire resistance to it and experience tumor recurrence wi thin 1 year. Several molecular and cellular mechanisms underlying the resistance t o trastuzumab have been proposed. In this review, first, we provide a brief history leading to production of trastuzumab. Also we consider the cellular and mole cular antitumor effects of trastuzumab and then, we discuss the mechanisms underlying trastuzumab resistance in four levels.

// Qing-Yun Chong 1 , Ming-Liang You 1, 2 , Vijay Pandey 1 , Arindam Banerjee 1 , Yi-Jun Chen 1, 2 , Han-Ming Poh 1, 2 , Mengyi Zhang 1, 2 , Lan Ma 3 , Tao Zhu 4, 5 , Salundi Basappa 6 , Liang Liu 7, 8 and Peter E. Lobie 1, 2, 3, 9 1 Cancer Science Institute of Singapore, National University of Singapore, Singapore 2 Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 3 Tsinghua Berkeley Shenzhen Institute, Tsinghua University Graduate School at Shenzhen, Shenzhen, China 4 Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China 5 The CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China 6 Laboratory of Chemical Biology, Department of Chemistry, Bangalore University, Central College Campus, Bangalore, India 7 Department of Oncology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China 8 Department of Radiology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China 9 National University Cancer Institute, Singapore Correspondence to: Peter E. Lobie, email: csipel@nus.edu.sg Liang Liu, email: liuliangfudan@163.com Keywords: trefoil factor 3, breast cancer, HER2, trastuzumab resistance, estrogen receptor Received: November 17, 2016 Accepted: May 10, 2017 Published: June 09, 2017 ABSTRACT HER2+/ER+ breast cancer, a subset of the luminal B subtype, makes up approximately 10% of all breast cancers. The bidirectional crosstalk between HER2 and estrogen receptor (ER) in HER2+/ER+ breast cancer contributes to resistance towards both anti-estrogens and HER2-targeted therapies. TFF3 promotes breast cancer progression and has been implicated in anti-estrogen resistance in breast cancer. Herein, we investigated the cross-regulation between HER2 and estrogen-responsive TFF3, and the role of TFF3 in mediating trastuzumab resistance in HER2+/ER+ breast cancer. TFF3 expression was decreased by HER2 activation, and increased by inhibition of HER2 with trastuzumab in HER2+/ER+ breast cancer cells, partially in an ERα-independent manner. In contrast, the forced expression of TFF3 activated the entire HER family of receptor tyrosine kinases (HER1-4). Hence, HER2 negatively regulates its own signalling through the transcriptional repression of TFF3, while trastuzumab inhibition of HER2 results in increased TFF3 expression to compensate for the loss of HER2 signalling. In HER2+/ER+ breast cancer cells with acquired trastuzumab resistance, TFF3 expression was markedly upregulated and associated with a corresponding decrease in HER signalling. siRNA mediated depletion or small molecule inhibition of TFF3 decreased the survival and growth advantage of the trastuzumab resistant cells without re-sensitization to trastuzumab. Furthermore, TFF3 inhibition abrogated the enhanced cancer stem cell-like behaviour in trastuzumab resistant HER2+/ER+ breast cancer cells. Collectively, TFF3 may function as a potential biomarker and therapeutic target in trastuzumab resistant HER2+/ER+ breast cancer.

Cancer is a growing problem worldwide. The cause of death in cancer patients is often due to treatment-resistant metastatic disease. Many molecularly targeted anticancer drugs have been developed against 'oncogenic driver' pathways. However, these treatments are usually only effective in properly selected patients. Resistance to molecularly targeted drugs through selective pressure on acquired mutations or molecular rewiring can hinder their effectiveness. This review summarizes how molecular imaging techniques can potentially facilitate the optimal implementation of targeted agents. Using the human epidermal growth factor receptor (HER) family as a model in (pre)clinical studies, we illustrate how molecular imaging may be employed to characterize whole body target expression as well as monitor drug effectiveness and the emergence of tumor resistance. We further discuss how an integrative omics discovery platform could guide the selection of 'effect sensors' - new molecular imaging targets - which are dynamic markers that indicate treatment effectiveness or resistance.

// Qiong Lu 1, * , Lingfei Wang 1, * , Yajun Zhang 1, * , Xiaojie Yu 1, * , Chao Wang 1 , Huajing Wang 1 , Yang Yang 1 , Xiaodan Chong 1 , Tian Xia 1 , Yanchun Meng 2 , Yuxiao Wang 4 , Cuihua Lu 3 , Lijun Zhou 4 , Bohua Li 1 1 International Joint Cancer Institute, The Second Military Medical University, Shanghai, People’s Republic of China 2 School of Medicine, Nankai University, Tianjin, People’s Republic of China 3 Department of Gastroenterology, The Affiliated Hospital of Nantong University, Nantong, Jiangsu, People’s Republic of China 4 Central Laboratory, Navy General Hospital, Beijing People’s Republic of China * These authors have contributed equally to this work Correspondence to: Bohua Li, email: bohuali1020@163.com Lijun Zhou, email: zhoulj63@163.com Cuihua Lu, email: lch670608@sina.com Keywords: ErbB2, programmed cell death, trastuzumab resistance, domain I- specific antibody, breast cancer Received: May 09, 2016 Accepted: August 11, 2016 Published: August 24, 2016 ABSTRACT Trastuzumab, an anti-HER2/ErbB2 humanized antibody, has shown great clinical benefits in ErbB2-positive breast cancer treatment. Despite of its effectiveness, response rate to trastuzumab is limited and resistance is common. Here, we developed a new anti-ErbB2 antibody, denoted as H2-18, which was isolated from a phage display human antibody library. Previous studies have demonstrated that trastuzumab recognizes the juxtamembrane region of domain IV, and pertuzumab, another humanized ErbB2-specific antibody, binds to ErbB2 near the center of domain II. Our crystallographic analysis showed that the epitope recognized by H2-18 is within domain I of the ErbB2 molecule. H2-18 potently induced programmed cell death (PCD) in both trastuzumab-sensitive and -resistant breast cancer cell lines, while trastuzumab and pertuzumab, either used alone or in combination, only exhibits very weak PCD-inducing activity. More importantly, H2-18 could inhibit the growth of trastuzumab-resistant breast cancer cells far more effectively than trastuzumab plus pertuzumab, both in vitro and in vivo . In conclusion, H2-18 shows a unique ability to overcome trastuzumab resistance, suggesting that it has the great potential to be translated to the clinic.

Resistance to the HER2-targeted antibody trastuzumab is a major clinical concern in the treatment of HER2-overexpressing metastatic breast cancer. Increased expression or signaling of the insulin-like growth factor-I receptor (IGF-IR) has been reported in a subset of cell lines and clinical samples derived from trastuzumab-resistant breast cancers. Genetic and pharmacologic inhibition of IGF-IR signaling has been shown to improve response to trastuzumab in trastuzumab-naïve and trastuzumab-resistant models. In this paper, we will discuss the role of IGF-IR signaling in trastuzumab resistance. Further, we will discuss cotargeting IGF-IR and HER2 as a potential therapeutic strategy for HER2-over-expressing breast cancers that have progressed on trastuzumab treatment.

Purpose: Resistance to anti-HER2 monoclonal antibody trastuzumab is a relevant issue in breast cancer patients. Among the mechanisms implicated in trastuzumab resistance, increasing evidence supports a role of tumor microenvironment. We previously found that a novel toll-like receptor 9 agonist, referred to as immune modulatory oligonucleotide (IMO) and currently under clinical investigation, acts through epidermal growth factor receptor (EGFR) and shows direct antiangiogenic effects by cooperating with anti-EGFR or anti-VEGF drugs, thus interfering with cancer cells and microenvironment.Experimental Design: In this study, we used KPL-4 and JIMT-1 trastuzumab-resistant breast cancer cells to evaluate the combination IMO plus trastuzumab as a therapeutic option for trastuzumab-resistant breast cancers.Results: IMO inhibits KPL-4 and JIMT-1 xenografts growth and potentiates trastuzumab antitumor effect, with complete suppression of tumor growth, potent enhancement of trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity, and strong inhibition of EGFR/HER2-related signaling. In KPL-4 xenografts, IMO alone interferes with HER signal transduction, whereas trastuzumab is ineffective. IMO induces an HER-dependent signal inhibition also in vitro by modulating a functional interaction between toll-like receptor 9 and HER receptors occurring at membrane level. Finally, IMO plus trastuzumab produces a cooperative antiangiogenic effect related to suppression of endothelial HER-related signaling.Conclusions: We showed a cooperative effect of IMO plus trastuzumab in trastuzumab-resistant breast cancers due to IMO direct antitumor and antiangiogenic activity and antibody-dependent cell-mediated cytotoxicity enhancement. Moreover, we provided first evidence of a toll-like receptor 9/HER interaction at membrane level as novel mechanism of action. Altogether, we propose IMO plus trastuzumab as an effective strategy in trastuzumab-resistant breast cancers. (Clin Cancer Res 2009;15(22):692130)

Background: The likelihood of recurrence in patients with breast cancer who have HER2-positive tumors is relatively high, although trastuzumab is a remarkably effective drug in this setting. Signal transducer and activator of transcription 3 protein (STAT3), a transcription factor that is persistently tyrosine-705 phosphorylated (pSTAT3) in response to numerous oncogenic signaling pathways, activates downstream proliferative and anti-apoptotic pathways. We hypothesized that pSTAT3 expression in HER2-positive breast cancer will confer trastuzumab resistance. Methods: We integrated reverse phase protein array (RPPA) and gene expression data from patients with HER2-positive breast cancer treated with trastuzumab in the adjuvant setting. Results: We show that a pSTAT3-associated gene signature (pSTAT3-GS) is able to predict pSTAT3 status in an independent dataset (TCGA; AUC = 0.77, P = 0.02). This suggests that STAT3 induces a characteristic set of gene expression changes in HER2-positive cancers. Tumors characterized as high pSTAT3-GS were associated with trastuzumab resistance (log rank P = 0.049). These results were confirmed using data from the prospective, randomized controlled FinHer study, where the effect was especially prominent in HER2-positive estrogen receptor (ER)-negative tumors (interaction test P = 0.02). Of interest, constitutively activated pSTAT3 tumors were associated with loss of PTEN, elevated IL6, and stromal reactivation. Conclusions: This study provides compelling evidence for a link between pSTAT3 and trastuzumab resistance in HER2-positive primary breast cancers. Our results suggest that it may be valuable to add agents targeting the STAT3 pathway to trastuzumab for treatment of HER2-positive breast cancer., SCOPUS: ar.j, info:eu-repo/semantics/published

// Sheng-Jia Shi 1, * , Li-Juan Wang 2, * , Bo Yu 1 , Yun-Hui Li 1 , Yong Jin 1 , Xiao-Zhong Bai 1 1 Department of Administration and Department of Aristogenesis, No. 202 Hospital of PLA, No. 5, Shenyang, 110003, Liaoning Province, P.R. China 2 Department of Oncology, the First Affiliated Hospital of Medical College of Xi’an Jiaotong University, Xi’an, 710061, Shaanxi Province, P.R. China * These authors have contributed equally to this work Correspondence to: Xiao-Zhong Bai, e-mail: baixz2015@163.com Keywords: lnc-ATB, trastuzumab resistance, EMT, TGF-β, breast cancer Received: February 05, 2015 Accepted: February 25, 2015 Published: March 23, 2015 ABSTRACT Trastuzumab resistance is leading cause of mortality in HER2-positive breast cancers, and the role of TGF-β-induced epithelial-mesenchymal transition (EMT) in trastuzumab resistance is well established, but the involvement of lncRNAs in trastuzumab resistance is still unknown. Here, we generated trastuzumab-resistant breast cancer cells with increased invasiveness compared with parental cells, and observed robust epithelial–mesenchymal transition (EMT) and consistently elevated TGF-β signaling in these cells. We identified long noncoding RNA activated by TGF-β (lnc-ATB) was the most remarkably upregulated lncRNA in TR SKBR-3 cells and the tissues of TR breast cancer patients. We found that lnc-ATB could promote trastuzumab resistance and invasion-metastasis cascade in breast cancer by competitively biding miR-200c, up-regulating ZEB1 and ZNF-217, and then inducing EMT. In addition, we also found that the high level of lnc-ATB was correlated with trastuzumab resistance of breast cancer patients. Thus, these findings suggest that lncRNA-ATB, a mediator of TGF-β signaling, could predispose breast cancer patients to EMT and trastuzumab resistance.

Background Subsets of high grade endometrial cancer (EnCa) over-express HER2 (ERBB2), yet clinical trials have failed to demonstrate any anti-tumor activity utilizing trastuzumab, an approved platform for HER2 positive breast cancer (BrCa). A truncated p95HER2 variant lacking the trastuzumab binding site may confer resistance. The objective of this investigation was to characterize the expression of the p95HER2 truncated variant in EnCa. Materials and methods With institutional approval, 86 high grade EnCa tumors were identified with tumor specimens from surgeries performed between 2000 and 2011. Clinical data were collected and all specimens underwent tumor genotyping, HER2 immunohistochemistry (IHC, HercepTest®), HER2 fluorescent in situ hybridization (FISH), along with total HER2 (H2T) and p95HER2 assessment with VeraTag® testing. Regression models were used to compare a cohort of 86 breast tumors selected for equivalent HER2 protein expression. Results We identified 44 high grade endometrioid and 42 uterine serous carcinomas (USC). IHC identified high HER2 expression (2+ or 3+) in 59% of the tumors. HER2 gene amplification was observed in 16 tumors (12 USC, 4 endometrioid). Both HER2 gene amplification and protein expression correlated with H2T values. High p95HER2 expression above 2.8RF/mm 2 was observed in 53% ( n =54) with significant correlation with H2T levels. When matched to a cohort of 107 breast tumors based on HercepTest HER2 expression, high grade EnCa presented with higher p95 levels ( p Conclusions These data demonstrate that compared to BrCa, high grade EnCa expresses higher levels of p95HER2 possibly providing rationale for the trastuzumab resistance observed in EnCa.

While approval of trastuzumab, a recombinant monoclonal antibody directed against HER2, along with a diagnostic kit to detect breast cancers which are positive for HER2 overexpression, has advanced a new era of stratified and personalized medicine, it also created several challenges to our scientific and clinical practice. These problems include trastuzumab resistance and trastuzumab-induced cardiotoxicity. In this review, we will summarize data from the literature regarding mechanisms of trastuzumab resistance and trastuzumab-induced cardiotoxicity and present some promising model systems that may advance our understanding of these mechanisms. Our discussion will include development of circulating tumor cells and circulating tumor DNA for monitoring tumor burden, of patient-derived xenograft models for preclinical testing of novel therapies, and of novel therapeutic strategies for trastuzumab-resistance and possible integration of these strategies in the design of co-clinical studies for testing in relevant patient subpopulations.

Trastuzumab is a remarkably effective therapy for patients with human epidermal growth factor receptor 2 (HER2) - positive breast cancer (BC). However, not all women with high levels of HER2 benefit from trastuzumab. By integrating mRNA and protein expression data from Reverse-Phase Protein Array Analysis (RPPA) in HER2-positive BC, we developed gene expression metagenes that reflect pathway activation levels. Next we assessed the ability of these metagenes to predict resistance to adjuvant trastuzumab using gene expression data from two independent datasets. 10 metagenes passed external validation (false discovery rate [fdr] < 0.05) and showed biological relevance with their pathway of origin. These metagenes were further screened for their association with trastuzumab resistance. An association with trastuzumab resistance was observed and validated only for the AnnexinA1 metagene (ANXA1). In the randomised phase III Fin-her study, tumours with low levels of the ANXA1 metagene showed a benefit from trastuzumab (multivariate: hazard ratio [HR] for distant recurrence = 0.16[95%CI 0.05-0.5]; p = 0.002; fdr = 0.03), while high expression levels of the ANXA1 metagene were associated with a lack of benefit to trastuzmab (HR = 1.29[95%CI 0.55-3.02]; p = 0.56). The association of ANXA1 with trastuzumab resistance was successfully validated in an independent series of subjects who had received trastuzumab with chemotherapy (Log Rank; p = 0.01). In conclusion, in HER2-positive BC, some proteins are associated with distinct gene expression profiles. Our findings identify the ANXA1metagene as a novel biomarker for trastuzumab resistance., SCOPUS: ar.j, info:eu-repo/semantics/published