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Persistent activation of IGF1R/mTOR signaling pathway plays crucial role in the development of hepatocellular carcinoma (HCC). Therefore, our goal was to elucidate microRNAs (miRNAs) targeting IGF1R/mTOR and the therapeutic potential of single or dual miRNA on HCC development. In this study, we found that miR-497 and miR-99a that target the 3'-UTR of both IGF1R and mTOR were down-regulated in HCC human tissues and cell lines. Functional assay revealed that ectopic expression of miR-497 or miR-99a in HCC cells resulted in a significant inhibition on tumor growth and invasiveness in vitro and tumor development in vivo via repressing the expression of IGF1R and mTOR. Such inhibitory effect on tumor growth is reversed by application of IGF1 ((IGF1R ligand) or MHY1485 (mTOR agonist) in vitro. Furthermore, we found that simultaneous over-expression of both miR-497 and miR-99a exhibited much stronger inhibitory effects on tumor growth than their individual effect, which is still correlated with significantly stronger repression of IGF1R and mTOR. Overall, our results suggest that miR-497 and miR-99a both function as tumor-suppressive miRNAs by suppressing IGF1R/mTOR signaling pathway. The synergistic actions of these two miRNAs partly correlated with IGF1R and mTOR levels, which may represent new strategies for the molecular treatment of HCC.

EGFR-mutated non-small cell lung cancer patients experience relapse within 1-2 years of treatment with EGFR-inhibitors, such as erlotinib. Multiple resistance mechanisms have been identified including secondary EGFR-mutations, MET-amplification, and epithelial-mesenchymal transition (EMT). Previous studies have indicated a role of Insulin-like growth factor 1 receptor (IGF1R) in acquired resistance to EGFR-directed drugs as well as in EMT. In the present study, we have investigated the involvement of IGF1R in acquired high-dose erlotinib resistance in the EGFR-mutated lung adenocarcinoma cell line HCC827. We observed that IGF1R was upregulated in the immediate response to erlotinib and hyperactivated in erlotinib resistant HCC827 cells. Resistant cells additionally acquired features of EMT, whereas MET-amplification and secondary EGFR-mutations were absent. Using CRISPR/Cas9, we generated a HCC827(IGFR1-/-) cell line and subsequently investigated resistance development in response to high-dose erlotinib. Interestingly, HCC827(IGFR1-/-) cells were now observed to specifically amplify the MET gene. Additionally, we observed a reduced level of mesenchymal markers in HCC827(IGFR1-/-) indicating an intrinsic enhanced epithelial signature compared to HCC827 cells. In conclusion, our data show that IGF1R have an important role in defining selected resistance mechanisms in response to high doses of erlotinib.

Exportin-1 mediates nuclear export of multiple tumor suppressor and growth regulatory proteins. Aberrant expression of exportin-1 is noted in human malignancies, resulting in cytoplasmic mislocalization of its target proteins. We investigated the efficacy of selinexor against liposarcoma cells both in vitro and in vivo. Exportin-1 was highly expressed in liposarcoma samples and cell lines as determined by immunohistochemistry, western blot, and immunofluorescence assay. Knockdown of endogenous exportin-1 inhibited proliferation of liposarcoma cells. Selinexor also significantly decreased cell proliferation as well as induced cell cycle arrest and apoptosis of liposarcoma cells. The drug also significantly decreased tumor volumes and weights of liposarcoma xenografts. Importantly, selinexor inhibited insulin-like growth factor 1 (IGF1) activation of IGF-1R/AKT pathway through upregulation of insulin-like growth factor binding protein 5 (IGFBP5). Further, overexpression and knockdown experiments showed that IGFBP5 acts as a tumor suppressor and its expression was restored upon selinexor treatment of liposarcoma cells. Selinexor decreased aurora kinase A and B levels in these cells and inhibitors of these kinases suppressed the growth of the liposarcoma cells. Overall, our study showed that selinexor treatment restored tumor suppressive function of IGFBP5 and inhibited aurora kinase A and B in liposarcoma cells supporting the usefulness of selinexor as a potential therapeutic strategy for the treatment of this cancer.

The insulin-like growth factor (IGF) signaling system plays key roles in the establishment and progression of different types of cancer. In agreement with this idea, substantial evidence has shown that the type I IGF receptor (IGF-IR) and its primary ligand IGF-I are important for maintaining the survival of malignant cells of hematopoietic origin. In this review, we discuss current understanding of the role of IGF-IR signaling in cancer with a focus on the hematological neoplasms. We also address the emergence of IGF-IR as a potential therapeutic target for the treatment of different types of cancer including plasma cell myeloma, leukemia, and lymphoma.

The molecular and cellular mechanisms behind the involvement of inflammation in melanoma have not been fully elucidated. In this study, knockdown of Hmgb1 expression increased apoptosis, reduced invasion and p-NF-κB expression, but increased Klotho protein level in melanoma tumor cells. The effect of Hmgb1 knockdown was overcome by LPS. Introduction of exogenous Hmgb1 significantly decreased apoptosis, increased invasion, elevated p-NF-κB, but lowered Klotho protein level in melanoma cells. The effect of exogenous Hmgb1 was agonized by NF-κB inhibitor CAPE. Hmgb1 knockdown activated, but exogenous Hmgb1 inactivated, p-IGF1R/p-PI3K p-85/p-Akt/p-mTOR signaling. Knockdown of Klotho gene expression significantly decreased apoptosis, increased invasion in melanoma cells, and inhibited xenograft A375 tumor growth. A significantly high percentage of cells stained positive for p-NF-κB, but negative for Klotho, in melanoma tissues compared to normal and benign skin tissues. The positive p-NF-κB and negative Klotho protein expression correlated with poor prognosis in melanoma patients. Multivariate analysis revealed an independent association between p-NF-κB / Klotho protein level and overall survival. In conclusion, Hmgb1 can inhibit Klotho gene expression and malignant phenotype in melanoma cells through activation of NF-κB signaling.

Serum carcinoembryonic antigen (CEA) is the most commonly used tumor marker in a variety of cancers including colorectal cancer (CRC) for tumor diagnosis and monitoring. Recent studies have shown that colonic crypt cells expressing little or no CEA may enrich for stem cells. Numerous studies have clearly shown that there exist CRC patients with normal serum CEA levels during tumor progression or even tumor relapse, although CEA itself is considered to promote metastasis and block cell differentiation. These seemingly contradictory observations prompted us to investigate, herein, the biological properties as well as tumorigenic and metastatic capacity of CRC cells that express high (CEA+) versus low CEA (CEA-/lo) levels of CEA. Our findings show that the abundance of CEA-/lo cells correlate with poor differentiation and poor prognosis, and moreover, CEA-/lo cells form more spheres in vitro, generate more tumors and exhibit a higher potential in developing liver and lung metastases than corresponding CEA+ cells. Applying RNAi-mediated approach, we found that IGF1R mediated tumorigenic and capacity of CEA-/lo cells but did not mediate those of CEA+ cells. Notably, our data demonstrated that CEA molecule was capable of protecting CEA-/lo cells from anoikis, implying that CEA+ cells, although themselves possessing less tumorigenic and metastatic capacity, may promote metastasis of CEA-/lo cells via secreting CEA molecule. Our observations suggest that, besides targeting CEA molecule, CEA-/lo cells may represent a critical source of tumor progression and metastasis, and should therefore be the target of future therapies.

CD99 is a cell surface molecule that has emerged as a novel target for Ewing sarcoma (EWS), an aggressive pediatric bone cancer. This report provides the first evidence of methuosis in EWS, a non-apoptotic form of cell death induced by an antibody directed against the CD99 molecule. Upon mAb triggering, CD99 induces an IGF-1R/RAS/Rac1 complex, which is internalized into RAB5-positive endocytic vacuoles. This complex is then dissociated, with the IGF-1R recycling to the cell membrane while CD99 and RAS/Rac1 are sorted into immature LAMP-1-positive vacuoles, whose excessive accumulation provokes methuosis. This process, which is not detected in CD99-expressing normal mesenchymal cells, is inhibited by disruption of the IGF-1R signaling, whereas enhanced by IGF-1 stimulation. Induction of IGF-1R/RAS/Rac1 was also observed in the EWS xenografts that respond to anti-CD99 mAb, further supporting the role of the IGF/RAS/Rac1 axis in the hyperstimulation of macropinocytosis and selective death of EWS cells. Thus, we describe a vulnerability of EWS cells, including those resistant to standard chemotherapy, to a treatment with anti-CD99 mAb, which requires IGF-1R/RAS signaling but bypasses the need for their direct targeting. Overall, we propose CD99 targeting as new opportunity to treat EWS patients resistant to canonical apoptosis-inducing agents.

Activation of receptor tyrosine kinases (RTKs) is associated with carcinogenesis, but its contribution to smoking-associated lung carcinogenesis is poorly understood. Here we show that a tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced insulin-like growth factor 1 receptor (IGF-1R) activation via β-adrenergic receptor (β-AR) is crucial for smoking-associated lung carcinogenesis. Treatment with NNK stimulated the IGF-1R signaling pathway in a time- and dose-dependent manner, which was suppressed by pharmacological or genomic blockade of β-AR and the downstream signaling including a Gβγ subunit of β-AR and phospholipase C (PLC). Consistently, β-AR agonists led to increased IGF-1R phosphorylation. The increase in IGF2 transcription via β-AR, signal transducer and activator of transcription 3 (STAT3), and nuclear factor-kappa B (NF-κB) was associated with NNK-induced IGF-1R activation. Finally, treatment with β-AR antagonists suppressed the acquisition of transformed phenotypes in lung epithelial cells and lung tumor formation in mice. These results suggest that blocking β-AR-mediated IGF-1R activation can be an effective strategy for lung cancer prevention in smokers.

Breast Cancer (BC) is a highly prevalent disease. A woman living in the United States has a 12.3% lifetime risk of being diagnosed with breast cancer [1]. It is the most common female cancer and the second most common cause of cancer death in women [2]. Of note, amplification or overexpression of Human Epidermal Receptor 2 (HER2) oncogene is present in approximately 18 to 20% of primary invasive breast cancers, and until personalized therapy became available for this specific BC subtype, the worst rates of Overall Survival (OS) and Recurrence-Free Survival (RFS) were observed in the HER2+ BC cohort, compared to all other types, including triple negative BC (TNBC) [3].HER2 is a member of the epidermal growth factor receptor (EGFR) family. Other family members include EGFR or HER1, HER3 and HER4. HER2 can form heterodimers with any of the other three receptors, and is considered to be the preferred dimerization partner of the other HER or ErbB receptors [4]. Phosphorylation of tyrosine residues within the cytoplasmic domain is the result of receptor dimerization and culminates into initiation of a variety of signalling pathways involved in cellular proliferation, transcription, motility and apoptosis inhibition [5].In addition to being an important prognostic factor in women diagnosed with BC, HER2 overexpression also identifies those patients who benefit from treatment with agents that target HER2, such as trastuzumab, pertuzumab, trastuzumab emtansine (T-DM1) and small molecules tyrosine kinase inhibitors of HER2 [6, 11, 127].In fact, trastuzumab altered the natural history of patients diagnosed with HER2+ BC, both in early and metastatic disease setting, in a major way [8-10]. Nevertheless, there are many women that will eventually develop metastatic disease, despite being treated with anti-HER2 therapy in the early disease setting. Moreover, advanced tumors may reach a point where no anti-HER2 treatment will achieve disease control, including recently approved drugs, such as T-DM1.This review paper will concentrate on major biological pathways that ultimately lead to resistance to anti-HER2 therapies in BC, summarizing their mechanisms. Strategies to overcome this resistance, and the rationale involved in each tactics to revert this scenario will be presented to the reader.

The metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is frequently over-expressed and serves as a prognostic marker in human cancers. However, little is known about the role of MALAT1 in gastric cancer. Here, we reported that the tissue and plasma MALAT1 levels were significantly higher in gastric cancer patients with distant metastasis (P<0.01) than patients without distant metastasis and the healthy controls. In addition, high levels of plasma MALAT1 independently correlated to a poor prognosis for gastric cancer patients (hazard ratio, 0.242; 95% CI, 0.154-0.836; P=0.036; Cox regression analysis). Functional studies revealed that knockdown of MALAT1 could inhibit cell proliferation, cell cycle progression, migration and invasion, and promote apoptosis in gastric cancer cells. Furthermore, the miR-122-IGF-1R signaling correlated with the dysregulated MALAT1 expression in gastric cancer. These data suggest that MALAT1 could function as an oncogene in gastric cancer, and high MALAT1 level could serve as a potential biomarker for the distant metastasis of gastric cancer., Competing Interests: The authors declare no competing financial interests.

The complexity of the IGF-1 signalling axis is clearly a roadblock in targeting this receptor in cancer therapy. Here, we sought to identify mediators of resistance, and potential co-targets for IGF-1R inhibition. By using an siRNA functional screen with the IGF-1R tyrosine kinase inhibitor (TKI) BMS-754807 in MCF-7 cells we identified several genes encoding components of the DNA damage response (DDR) pathways as mediators of resistance to IGF-1R kinase inhibition. These included ATM and Ataxia Telangiectasia and RAD3-related kinase (ATR). We also observed a clear induction of DDR in cells that were exposed to IGF-1R TKIs (BMS-754807 and OSI-906) as indicated by accumulation of γ-H2AX, and phosphorylated Chk1. Combination of the IGF-1R/IR TKIs with an ATR kinase inhibitor VE-821 resulted in additive to synergistic cytotoxicity compared to either drug alone. In MCF-7 cells with stably acquired resistance to the IGF-1R TKI (MCF-7-R), DNA damage was also observed, and again, dual inhibition of the ATR kinase and IGF-1R/IR kinase resulted in synergistic cytotoxicity. Interestingly, dual inhibition of ATR and IGF-1R was more effective in MCF-7-R cells than parental cells. IGF-1R TKIs also potentiated the effects of cisplatin in a panel of breast cancer cell lines. Overall, our findings identify induction of DDR by IGF-1R kinase inhibition as a rationale for co-targeting the IGF-1R with ATR kinase inhibitors or cisplatin, particularly in cells with acquired resistance to TKIs., Competing Interests: Nuala McCabe and Richard Kennedy are both employees of Almac Diagnostics. The authors do not have any conflict of interest in relation to this manuscript.

MicroRNAs (miRNAs) are attractive therapeutic targets for various therapy-resistant tumors. However, the association between miRNA and BRAF inhibitor resistance in melanoma remains to be elucidated. We used microarray analysis to comprehensively study the miRNA expression profiling of vemurafenib resistant (VemR) A375 melanoma cells in relation to parental A375 melanoma cells. MicroRNA-7 (miR-7) was identified to be the most significantly down-regulated miRNA in VemR A375 melanoma cells. We also found that miR-7 was down-regulated in Mel-CVR cells (vemurafenib resistant Mel-CV melanoma cells). Reestablishment of miR-7 expression could reverse the resistance of both cells to vemurafenib. We showed that epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor (IGF-1R) and CRAF were over-expressed in VemR A375 melanoma cells. Introduction of miR-7 mimics could markedly decrease the expressions of EGFR, IGF-1R and CRAF and further suppressed the activation of MAPK and PI3K/AKT pathway in VemR A375 melanoma cells. Furthermore, tumor growth was inhibited in an in vivo murine VemR A375 melanoma tumor model transfected with miR-7 mimics. Collectively, our study demonstrated that miR-7 could reverse the resistance to BRAF inhibitors in certain vemurafenib resistant melanoma cell lines. It could advance the field and provide the basis for further studies in BRAF inhibitor resistance in melanoma., Competing Interests: The authors state no conflict of interest.

Icaritin (IT) is a flavonoid isolated from Herba Epimedii. In this study, we evaluated the anti-melanoma activities of IT, and determined its cytotoxic mechanism. We found that IT exerted cytotoxicity to melanoma cells. Furthermore, IT induced melanoma cell apoptosis, which was accompanied with PARP cleavage. Mechanistically, IT suppressed p-STAT3 (tyr705) level in parallel with increases of p-STAT3 (ser727), p-ERK and p-AKT. IT significantly inhibited STAT3 nuclear translocation and reduced the levels of STAT3 -targeted genes. IT also inhibited IGF-1-induced STAT3 activation through down-regulation of total IGF-1R level. No dramatic changes in IGF-1R mRNA levels were observed in IT-treated cells, suggesting that IT acted primarily at a post-transcriptional level. Using molecular docking analysis, IT was identified as a novel fatty acid synthase (FASN) inhibitor. We found that IT reduced the level of total IGF-1R via FASN inhibition. In summary, we reported that IT exerted anti-melanoma activities, and these effects were partially due to inhibition of FASN/IGF-1R/STAT3 signaling., Competing Interests: The authors declare no conflicts of interest.

Multiple myeloma (MM) is a highly heterogeneous plasma cell malignancy. The MM cells reside in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, proliferation, and drug resistance. As in most cancers, the insulin-like growth factor (IGF) system has been demonstrated to play a key role in the pathogenesis of MM. The IGF system consists of IGF ligands, IGF receptors, IGF binding proteins (IGFBPs), and IGFBP proteases and contributes not only to the survival, proliferation, and homing of MM cells, but also MM-associated angiogenesis and osteolysis. Furthermore, increased IGF-I receptor (IGF-IR) expression on MM cells correlates with a poor prognosis in MM patients. Despite the prominent role of the IGF system in MM, strategies targeting the IGF-IR using blocking antibodies or small molecule inhibitors have failed to translate into the clinic. However, increasing preclinical evidence indicates that IGF-I is also involved in the development of drug resistance against current standard-of-care agents against MM, including proteasome inhibitors, immunomodulatory agents, and corticoids. IGF-IR targeting has been able to overcome or revert this drug resistance in animal models, enhancing the efficacy of standard-of-care agents. This finding has generated renewed interest in the therapeutic potential of IGF-I targeting in MM. The present review provides an update of the impact of the different IGF system components in MM and discusses the diagnostic and therapeutic potentials., Competing Interests: The authors declare no potential conflict of interest.

Ewing sarcoma is driven by characteristic chromosomal translocations between the EWSR1 gene with genes encoding ETS family transcription factors (EWS-ETS), most commonly FLI1. However, direct pharmacological inhibition of transcription factors like EWS-FLI1 remains largely unsuccessful. Active gene transcription requires orchestrated actions of many epigenetic regulators, such as the bromodomain and extra-terminal domain (BET) family proteins. Emerging BET bromodomain inhibitors have exhibited promising antineoplastic activities via suppression of oncogenic transcription factors in various cancers. We reasoned that EWS-FLI1-mediated transcription activation might be susceptible to BET inhibition. In this study, we demonstrated that small molecule BET bromodomain inhibitors repressed EWS-FLI1-driven gene signatures and downregulated important target genes. However, expression of EWS-FLI1 was not significantly affected. Repression of autocrine IGF1 by BET inhibitors led to significant inhibition of the IGF1R/AKT pathway critical to Ewing sarcoma cell proliferation and survival. Consistently, BET inhibitors impaired viability and clonogenic survival of Ewing sarcoma cell lines and blocked EWS-FLI1-induced transformation of mouse NIH3T3 fibroblast cells. Selective depletion of individual BET genes partially phenocopied the actions of BET inhibitors. Finally, the prototypical BET inhibitor, JQ1, significantly repressed Ewing sarcoma xenograft tumor growth. These findings suggest therapeutic potential of BET inhibitors in Ewing sarcoma and highlight an emerging paradigm of using epigenetic agents to treat cancers driven by fusion transcription factors., Competing Interests: The authors have declared that no conflicts of interest exists.

The insulin-like growth factor-1 receptor (IGF-1R) is a receptor tyrosine kinase that has crucial roles in cell proliferation and protection from apoptosis. It is therefore not surprising that IGF-1R is often found overexpressed in many types of tumors. This has made IGF-1R a prominent target molecule for pharmacological companies to develop new anti-cancer agents. However, several clinical trials during the last 5 years using IGF-1R specific antibodies have shown disappointing results. We have previously shown that upon IGF-1 stimulation, the receptor becomes SUMOylated and translocates into the nucleus of cancer cells to act as a transcription co-factor. Soon after our original study, several others have reported nuclear IGF-1R (nIGF-1R) as well, and some of them have demonstrated a prognostic value of nIGF-1R expression in cancer. In the current study we demonstrate that nIGF-1R binds to and phosphorylates histone H3 at tyrosine 41 (H3Y41) in HeLa cells. Furthermore, our results suggest that phosphorylation of H3Y41 by nIGF-1R, stabilizes the binding of Brg1 chromatin remodeling protein to Histone H3. Our findings suggest that phosphorylated nIGF-1R, rather than total nIGF-1R, plays a superior role in these contexts. We identified SNAI2 oncogene as a target gene for nIGF-1R and its expression was decreased upon mutation of H3Y41 or by Brg1 knockdown. Furthermore, we demonstrate that both IGF-1R and Brg1 binds to the SNAI2 promoter. As SNAI2 protein is implicated in e.g. cancer invasion and metastasis, the nIGF-1R-mediated effects shown in this study may influence such important tumor phenotypic actions., Competing Interests: The authors declare no conflict of interest.

Diabetic cardiomyopathy (DCM) is characterized by structural alterations such as cardiomyocyte hypertrophy, necrosis and focal fibrosis. Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear enzyme which can be activated by DNA damage and plays a critical role in various diseases. We hypothesized that PARP-1 may play an important role in DCM and that its inhibition may protect cardiomyocytes from inflammation and apoptosis in DCM. H9c2 cardiomyocytes were treated with normal glucose, mannitol or high glucose (HG). Male C57BL/6 mice or PARP-1-/- mice were treated with streptozotocin (STZ) by intraperitoneal injection for 5 consecutive days to induce diabetes. In vitro, HG stimulation induced oxidative stress and DNA damage and increased PARP-1 expression and activity. Compared with the control, pretreatment with PARP-1 siRNA significantly reduced HG-induced inflammatory response, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 secretion, and intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS) expression. PARP-1 inhibition reduced HG-induced cardiomyocyte apoptosis through downregulation of cleaved caspases and activation of IGF-1R/Akt pathway. In vivo, hyperglycemia increased the protein expression of nitrotyrosine and PARP-1 as well as PARP-1 activity. PARP-1 gene deletion significantly improved cardiac dysfunction and reduced inflammatory response and apoptosis. This work demonstrated the critical role of PARP-1 in diabetic heart injury, and suggested that PARP-1 inhibition may be a feasible strategy for the treatment of DCM., Competing Interests: No conflict of interest for all authors.

Ovarian cancer (OC) is highly resistant to current treatment strategies based on a combination of surgery, chemotherapy and radiation therapy. We have recently demonstrated the anti-neoplastic effect of Amla extract (Emblica officinalis, AE) on OC cells in vitro and in vivo. We hypothesized that AE attenuates growth of OC through microRNA (miR)-regulated mechanism(s). The inhibitory effect of AE on proliferation, migration and invasiveness (P≤0.001) of SKOV3 cells and >90% attenuation of tumor growth in a xenograft mouse model suggested multiple targets. RT-qPCR analysis of microRNAs associated with OC showed a >2,000-fold increase in the expression of miR-375 in AE-treated SKOV3 cells that was blocked by an exogenous miR-375 inhibitor (P≤0.001). AE also decreased the gene and protein expression of IGF1R, a target of miR-375 (P≤0.001), and SNAIL1 (P≤0.002), an EMT-associated transcription factor that represses E-cadherin expression (P≤0.003). AE increased E-cadherin expression (P≤0.001). Treatment of SKOV3 cells with AE resulted in increased miR-375 in exosomes in the medium (P≤0.01). Finally, AE significantly decreased the expression of IGF1R and SNAIL1 proteins during attenuation of SKOV3-derived xenograft tumor. Together, these results show that AE modulates cancer cells and the tumor microenvironment via activation of miR-375 and by targeting IGF1R and SNAIL1 in OC cells., Competing Interests: The authors have no conflict of interest to declare regarding the contents of the manuscript. The contents of this article are those of authors and do not necessarily reflect the position and policy of the Department of Veterans Affairs or the United States Government.

Mutant-selective, 3rd-generation EGFR-TKIs were recently developed to control lung cancer cells harboring T790M-mediated resistance. However, the development of resistance to these novel drugs seems inevitable. Thus, we investigated the mechanism of acquired resistance to the mutant-selective EGFR-TKI WZ4002. We established five WZ4002-resistant cells, derived from cells harboring both EGFR and T790M mutations by long-term exposure to increasing doses of WZ4002. Compared with the parental cells, all resistant cells showed 10-100-folds higher resistance to WZ4002, as well as cross-resistance to other mutant-selective inhibitors. Among them, three resistant cells (HCC827/WR, PC-9/WR and H1975/WR) showed dependency on EGFR signaling, but two other cells (PC-9/GR/WR and PC-9/ER/WR) were not. Notably, insulin-like growth factor-1 receptor (IGF1R) was aberrantly activated in PC-9/GR/WR cells in phospho-receptor tyrosine kinase array, consistently accompanied by loss of IGF binding protein-3 (IGFBP3). Down-regulation of IGF1R by shRNA, as well as inhibition of IGF1R activity either by AG-1024 (a small molecule IGF1R inhibitor) or BI 836845 (a monoclonal anti-IGF1/2 blocking antibody), restored the sensitivity to WZ4002 both in vitro and xenograft. Taken together, these results suggest that activation of the IGF1R pathway associated with IGFBP3 loss can induce an acquired resistance to the mutant-selective EGFR-TKI, WZ4002. Therefore, a combined therapy of IGF1R inhibitors and mutant-selective EGFR-TKIs might be a viable treatment strategy for overcoming acquired resistance., Competing Interests: None to declare.

The underlying mechanisms for acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) in about 30%-40% of non-small cell lung cancer (NSCLC) patients remain elusive. Recent studies have suggested that activation of epithelial-mesenchymal transition (EMT) and type 1 insulin-like growth factor receptor (IGF1R) is associated with acquired EGFR-TKIs resistance in NSCLC. Our study aims to further explore the mechanism of EMT and IGF1R in acquired EGFR-TKIs resistance in NSCLC cell lines with mutant (PC-9) or wild-type EGFR (H460). Compared to parental cells, EGFR-TKIs-resistant PC-9/GR and H460/ER cells displayed an EMT phenotype and showed overexpression of IGF1R. SiIGF1R in PC-9/GR and H460/ER cells reversed EMT-related morphologies and reversed their resistance to EGFR-TKIs. Exogenous IGF-1 alone induced EMT in EGFR-TKIs-naïve PC-9 and H460 cells and increased their resistance against EGFR-TKIs. Inducing EMT by TGF-β1 in PC-9 and H460 cells decreased their sensitivity to EGFR-TKIs, whereas reversing EMT by E-cadherin overexpression in PC-9/GR and H460/ER cells restored their sensitivity to EGFR-TKIs. These data suggest that IGF1R plays an important role in acquired drug resistance against EGFR-TKIs by inducing EMT. Targeting IGF1R and EMT may be a potential therapeutic strategy for advanced NSCLC with acquired EGFR-TKIs resistance.

Pregnancy-associated plasma protein-A (PAPP-A) stimulates insulin-like growth factor (IGF) action through proteolysis of IGF-binding protein (IGFBP)-4. In experimental animals, PAPP-A accelerates ovarian tumor growth by this mechanism. To investigate the effect of PAPP-A in humans, we compared serum and ascites from 22 women with ovarian carcinoma. We found that ascites contained 46-fold higher PAPP-A levels as compared to serum (P < 0.001). The majority (80%) of PAPP-A was enzymatically active. This is supported by the finding that ascites contained more cleaved than intact IGFBP-4 (P < 0.03). Ascites was more potent than serum in activating the IGF-I receptor (IGF-IR) in vitro (+31%, P < 0.05); in 8 of 22 patients by more than two-fold. In contrast, ascites contained similar levels of immunoreactive IGF-I, and lower levels of IGF-II (P < 0.001). Immunohistochemistry demonstrated the presence of IGF-IR in all but one tumor, whereas all tumors expressed PAPP-A, IGFBP-4, IGF-I and IGF-II. Addition of recombinant PAPP-A to ascites increased the cleavage of IGFBP-4 and enhanced IGF-IR activation (P < 0.05). In conclusion, human ovarian tumors express PAPP-A, IGFBP-4 and IGFs and these proteins are also present in ascites. We suggest that both soluble PAPP-A in ascites and tissue-associated PAPP-A serve to increase IGF bioactivity and, thereby, to stimulate IGF-IR-mediated tumor growth.

The insulin-like growth factor-I receptor (IGF-IR), plays a key role in regulating mammalian development and growth, and is frequently deregulated in cancer contributing to tumor initiation and progression. Discoidin domain receptor 1 (DDR1), a collagen receptor tyrosine-kinase, is as well frequently overexpressed in cancer and implicated in cancer progression. Thus, we investigated whether a functional cross-talk between the IGF-IR and DDR1 exists and plays any role in cancer progression.Using human breast cancer cells we found that DDR1 constitutively associated with the IGF-IR. However, this interaction was enhanced by IGF-I stimulation, which promoted rapid DDR1 tyrosine-phosphorylation and co-internalization with the IGF-IR. Significantly, DDR1 was critical for IGF-IR endocytosis and trafficking into early endosomes, IGF-IR protein expression and IGF-I intracellular signaling and biological effects, including cell proliferation, migration and colony formation. These biological responses were inhibited by DDR1 silencing and enhanced by DDR1 overexpression.Experiments in mouse fibroblasts co-transfected with the human IGF-IR and DDR1 gave similar results and indicated that, in the absence of IGF-IR, collagen-dependent phosphorylation of DDR1 is impaired.These results demonstrate a critical role of DDR1 in the regulation of IGF-IR action, and identify DDR1 as a novel important target for breast cancers that overexpress IGF-IR.

Transmembrane 4 L six family member 4 (TM4SF4) is a member of the tetraspanin L6 domain family. Other members of this family, TM4SF1 (also known as L6-Ag) and TM4SF5, have been shown to be upregulated in multiple tumors and involved in epithelial-to-mesenchymal transition and cell migration. However, unlike its homologs, little is known about TM4SF4. Here, we show that TM4SF4 was highly expressed in radiation-resistant lung adenocarcinoma cells, such as A549 and Calu-3 cells, and its expression activated cell growth, migration, and invasion. Overexpression of TM4SF4 in A549 cells increased the activation of PI3K, AKT, and NF-kappaB and the expression of PTEN. IGF1R was clearly activated by overexpression of TM4SF4, although EGFR was also slightly activated. TM4SF4 expression was correlated with the increased expression of IGF1, consequently resulting in IGF1R activation. Tumorigenic activity of TM4SF4 in lung adenocarcinoma cells was also demonstrated by xenograft assay; however, this activity was almost completely suppressed by treatment with anti-TM4SF4 antibody. Our results suggest that TM4SF4 overexpression in lung carcinoma cells results in resistance to radiotherapy via IGF1-induced IGF1R activation and blocking the activity of TM4SF4 using specific antibody can be a promising therapeutics against TM4SF4-overexpressing lung adenocarcinoma.

Picropodophyllin (PPP) is an anticancer drug undergoing clinical development in NSCLC. PPP has been shown to suppress IGF-1R signaling and to induce a G2/M cell cycle phase arrest but the exact mechanisms remain to be elucidated. The present study identified an IGF-1-independent mechanism of PPP leading to pro-metaphase arrest. The mitotic block was induced in human cancer cell lines and in an A549 xenograft mouse but did not occur in normal hepatocytes/mouse tissues. Cell cycle arrest by PPP occurred in vitro and in vivo accompanied by prominent CDK1 activation, and was IGF-1R-independent since it occurred also in IGF-1R-depleted and null cells. The tumor cells were not arrested in G2/M but in mitosis. Centrosome separation was prevented during mitotic entry, resulting in a monopolar mitotic spindle with subsequent prometaphase-arrest, independent of Plk1/Aurora A or Eg5, and leading to cell features of mitotic catastrophe. PPP also increased soluble tubulin and decreased spindle-associated tubulin within minutes, indicating that it interfered with microtubule dynamics. These results provide a novel IGF-1R-independent mechanism of antitumor effects of PPP.

The insulin-like growth factor (IGF) signaling pathway is involved in certain human cancers, and the feasibility of directly targeting the IGF receptor has been actively investigated. However, recent evidence from clinical trials suggests that this approach can be problematic. We have developed an alternative strategy to indirectly inhibit the IGF signaling by targeting the metalloproteinase, pregnancy-associated plasma protein-A (PAPP-A). PAPP-A associated with the cell surface cleaves IGF binding protein-4 (IGFBP-4), when IGF is bound to IGFBP-4, and thereby increases IGF bioavailability for receptor activation in an autocrine/paracrine manner. We hypothesized that inhibition of PAPP-A would suppress excessive local IGF signaling in tissues where this is caused by increased PAPP-A proteolytic activity. To test this hypothesis, we developed an inhibitory monoclonal antibody, mAb 1/41, which targets a unique substrate-binding exosite of PAPP-A. This inhibitor selectively and specifically inhibits proteolytic cleavage of IGFBP-4 with an inhibitory constant (Ki) of 135 pM. In addition, it inhibited intracellular signaling of the IGF receptor (AKT phosphorylation) in monolayers of A549 cells, an IGF-responsive lung cancer-derived cell line found to express high levels of PAPP-A. We further showed that mAb 1/41 is effective towards PAPP-A bound to cell surfaces, and that it is capable of inhibiting PAPP-A activity in vivo. Using a murine xenograft model of A549 cells, we demonstrated that mAb 1/41 administered intraperitoneally significantly inhibited tumor growth. Analysis of xenograft tumor tissue recovered from treated mice showed penetration of mAb 1/41, reduced IGFBP-4 proteolysis, and reduced AKT phosphorylation. Our study provides proof of concept that IGF signaling can be selectively reduced by targeting a regulatory proteinase that functions extracellularly, upstream of the IGF receptor. PAPP-A targeting thus represents an alternative therapeutic strategy for inhibiting IGF receptor signaling.