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Graft verus host disease (GVHD) following Liver transplantation is rare life threatening complication with very high mortality rate around 85%. Due to increased recognition of this condition management approach is rapidly evolving due to newer diagnostic methods and drugs. Etiology, risk factors, pathogenesis, preventive strategies, management approach and newer drugs are discussed. We present our experience of 2 cases from a large cohort of 1052 Liver transplant operations over a decade.

Biological importance of Gab1 in HNSCC cells

Preclinical and clinical studies have evidenced that effective targeted therapy treatment designed against receptor tyrosine kinases (RTKs) in different solid tumor paradigms is predicated on simultaneous inhibition of both the PI3K and MEK intracellular signaling pathways. Indeed, reactivation of either pathway results in resistance to these therapies. Recently, oncogenic phosphatase SHP2 inhibitors have been developed with some now reaching clinical trials. To expand on possible indications for SHP099, we screened over 800 cancer cell lines covering over 25 subsets of cancer. We found head and neck squamous cell carcinoma (HNSCC) was the most sensitive adult subtype of cancer to SHP099. We found that, in addition to the MEK pathway, SHP2 inhibition blocks the PI3K pathway in sensitive HNSCCs, resulting in downregulation of mTORC signaling and antitumor effects across several HNSCC mouse models, including an human papillomavirus (HPV+) patient-derived xenograft. Importantly, we found low levels of the RTK ligand epiregulin identified HNSCCs that were sensitive to SHP2 inhibitor, and, adding exogenous epiregulin mitigated SHP099 efficacy. Mechanistically, epiregulin maintained SHP2–GAB1 complexes in the presence of SHP2 inhibition, preventing downregulation of the MEK and PI3K pathways. In the presence of SHP2 inhibitor, HNSCCs are highly dependent on GAB1 for their survival and knockdown of GAB1 is sufficient to block the ability of epiregulin to rescue MEK and PI3K signaling. These data connect the sensitivity of HNSCC to SHP2 inhibitors and to a broad reliance on GAB1-SHP2, revealing an important and druggable signaling axis. Overall, SHP2 inhibitors are being heavily developed and may have activity in HNSCCs, and in particular those with low levels of epiregulin.Significance:This work identifies a novel role of SHP2 inhibitor by dual downregulation of PI3K and MEK pathways, through loss of GAB1 activation and disruption of GAB1 complexes in low-epiregulin HNSCC.

Cell line information and SHP099 screen data

GSK-J4 inhibits histone demethylation of EWS-FLI1 target genes

Supplemental Figure 3. Chemotherapy and venetoclax combination cell viability assays. Cell viability assays were performed for 72h treatment of cyclophosphamide and topotecan, venetoclax, or combination at indicated concentrations, with bliss synergy scores in (A) MYCN-amplified, and (B) MYCN-wild-type cell lines. (C) Plot of Bliss sum of cell lines in A-B, calculated by the summation of the bliss synergy scores across the doses presented.

Supplemental Figure 2. PDX ex vivo model demonstrated cleavage of PARP with corresponding NOXA upregulation (A) Western blot of COG-N-561 ex vivo cell line treated overnight with antibodies as indicated.

Gene symbols and names

The sequences of the primers used for ChIP

Supplemental Figure 4. Body Weight of Mice for in vivo treatments. (A) Plot of percent change in body weight from pre-treatment body weight in all in-vivo treatments.

Supplemental Figure 1. NVP-CGM097 and venetoclax combination cell viability assays. Cell viability assays were performed for 16h treatment of NVP-CGM097, venetoclax, or combination at indicated concentrations, with bliss synergy scores in (A) MYCN-wild-type, p53-wild-type, (B) MYCN-amplified, p53-mutant, and (C) MYCN-wild-type, p53-mutant NB cell lines. Red indicates synergy, blue indicates antagonism. (D) Plot of Bliss sum of cell lines in A-C along with cell lines in Fig. 1B, calculated by the summation of the bliss synergy scores across the doses presented.

The sequences of the primers used for qPCR

The EWSR1-FLI1 t(11;22)(q24;q12) translocation is the hallmark genomic alteration of Ewing sarcoma, a malignancy of the bone and surrounding tissue, predominantly affecting children and adolescents. Although significant progress has been made for the treatment of localized disease, patients with metastasis or who relapse after chemotherapy have less than a 30% five-year survival rate. EWS-FLI1 is currently not clinically druggable, driving the need for more effective targeted therapies. Treatment with the H3K27 demethylase inhibitor, GSK-J4, leads to an increase in H3K27me and a decrease in H3K27ac, a significant event in Ewing sarcoma because H3K27ac associates strongly with EWS-FLI1 binding at enhancers and promoters and subsequent activity of EWS-FLI1 target genes. We were able to identify targets of EWS-FLI1 tumorigenesis directly inhibited by GSK-J4. GSK-J4 disruption of EWS-FLI1-driven transcription was toxic to Ewing sarcoma cells and slowed tumor growth in patient-derived xenografts (PDX) of Ewing sarcoma. Responses were markedly exacerbated by cotreatment with a disruptor of RNA polymerase II activity, the CDK7 inhibitor THZ1. This combination together suppressed EWS-FLI1 target genes and viability of ex vivo PDX Ewing sarcoma cells in a synergistic manner. In PDX models of Ewing Sarcoma, the combination shrank tumors. We present a new therapeutic strategy to treat Ewing sarcoma by decreasing H3K27ac at EWS-FLI1–driven transcripts, exacerbated by blocking phosphorylation of the C-terminal domain of RNA polymerase II to further hinder the EWS-FLI1–driven transcriptome.

MYCN is amplified in 20% to 25% of neuroblastoma, and MYCN-amplified neuroblastoma contributes to a large percent of pediatric cancer–related deaths. Therapy improvements for this subtype of cancer are a high priority. Here we uncover a MYCN-dependent therapeutic vulnerability in neuroblastoma. Namely, amplified MYCN rewires the cell through expression of key receptors, ultimately enhancing iron influx through increased expression of the iron import transferrin receptor 1. Accumulating iron causes reactive oxygen species (ROS) production, and MYCN-amplified neuroblastomas show enhanced reliance on the system Xc- cystine/glutamate antiporter for ROS detoxification through increased transcription of this receptor. This dependence creates a marked vulnerability to targeting the system Xc-/glutathione (GSH) pathway with ferroptosis inducers. This reliance can be exploited through therapy with FDA-approved rheumatoid arthritis drugs sulfasalazine (SAS) and auranofin: in MYCN-amplified, patient-derived xenograft models, both therapies blocked growth and induced ferroptosis. SAS and auranofin activity was largely mitigated by the ferroptosis inhibitor ferrostatin-1, antioxidants like N-acetyl-L-cysteine, or by the iron scavenger deferoxamine (DFO). DFO reduced auranofin-induced ROS, further linking increased iron capture in MYCN-amplified neuroblastoma to a therapeutic vulnerability to ROS-inducing drugs. These data uncover an oncogene vulnerability to ferroptosis caused by increased iron accumulation and subsequent reliance on the system Xc-/GSH pathway.Significance:This study shows how MYCN increases intracellular iron levels and subsequent GSH pathway activity and demonstrates the antitumor activity of FDA-approved SAS and auranofin in patient-derived xenograft models of MYCN-amplified neuroblastoma.

Supplemental data

Figure S5. Amplified MYCN sensitizes neuroblastomas to auranofin. Auranofin increases iron and glutathione levels and induces ROS-dependent ferroptotic cell death in MYCN-amplified NBs.

EWS-FLI1 increases BCL-2 expression in EWFT.

Sup. Table 2. Top 3 functional pathways from ingenuity pathways analysis (IPA) in DTC.

Purpose: EGFR inhibitors (EGFRi) are effective against EGFR-mutant lung cancers. The efficacy of these drugs, however, is mitigated by the outgrowth of resistant cells, most often driven by a secondary acquired mutation in EGFR, T790M. We recently demonstrated that T790M can arise de novo during treatment; it follows that one potential therapeutic strategy to thwart resistance would be identifying and eliminating these cells [referred to as drug-tolerant cells (DTC)] prior to acquiring secondary mutations like T790M.Experimental Design: We have developed DTCs to EGFRi in EGFR-mutant lung cancer cell lines. Subsequent analyses of DTCs included RNA-seq, high-content microscopy, and protein translational assays. Based on these results, we tested the ability of MCL-1 BH3 mimetics to combine with EGFR inhibitors to eliminate DTCs and shrink EGFR-mutant lung cancer tumors in vivo.Results: We demonstrate surviving EGFR-mutant lung cancer cells upregulate the antiapoptotic protein MCL-1 in response to short-term EGFRi treatment. Mechanistically, DTCs undergo a protein biosynthesis enrichment resulting in increased mTORC1-mediated mRNA translation of MCL-1, revealing a novel mechanism in which lung cancer cells adapt to short-term pressures of apoptosis-inducing kinase inhibitors. Moreover, MCL-1 is a key molecule governing the emergence of early EGFR-mutant DTCs to EGFRi, and we demonstrate it can be effectively cotargeted with clinically emerging MCL-1 inhibitors both in vitro and in vivo.Conclusions: Altogether, these data reveal that this novel therapeutic combination may delay the acquisition of secondary mutations, therefore prolonging therapy efficacy. Clin Cancer Res; 24(22); 5658–72. ©2018 AACR.

Purpose:It was recently demonstrated that the EWSR1-FLI1 t(11;22)(q24;12) translocation contributes to the hypersensitivity of Ewing sarcoma to PARP inhibitors, prompting clinical evaluation of olaparib in a cohort of heavily pretreated Ewing sarcoma tumors. Unfortunately, olaparib activity was disappointing, suggesting an underappreciated resistance mechanism to PARP inhibition in patients with Ewing sarcoma. We sought to elucidate the resistance factors to PARP inhibitor therapy in Ewing sarcoma and identify a rational drug combination capable of rescuing PARP inhibitor activity.Experimental Design:We employed a pair of cell lines derived from the same patient with Ewing sarcoma prior to and following chemotherapy, a panel of Ewing sarcoma cell lines, and several patient-derived xenograft (PDX) and cell line xenograft models.Results:We found olaparib sensitivity was diminished following chemotherapy. The matched cell line pair revealed increased expression of the antiapoptotic protein BCL-2 in the chemotherapy-resistant cells, conferring apoptotic resistance to olaparib. Resistance to olaparib was maintained in this chemotherapy-resistant model in vivo, whereas the addition of the BCL-2/XL inhibitor navitoclax led to tumor growth inhibition. In 2 PDXs, olaparib and navitoclax were minimally effective as monotherapy, yet induced dramatic tumor growth inhibition when dosed in combination. We found that EWS-FLI1 increases BCL-2 expression; however, inhibition of BCL-2 alone by venetoclax is insufficient to sensitize Ewing sarcoma cells to olaparib, revealing a dual necessity for BCL-2 and BCL-XL in Ewing sarcoma survival.Conclusions:These data reveal BCL-2 and BCL-XL act together to drive olaparib resistance in Ewing sarcoma and reveal a novel, rational combination therapy that may be put forward for clinical trial testing.

Figure legends for Supplementary Figures S1-S8.

Figure S1. DTCs upregulate TORC1-mediated MCL-1 translation. Figure S2. High-content cell imaging assay. Figure S3. Genetic inhibition of MCL-1 is sufficient to induce apoptosis following EGFR inhibitor treatment. Figure S4. EGFR mutant tumors (PC9) respond to EGFR inhibitor/MCL-1 inhibitor (S63845) combination therapy in vivo. Figure S5. EGFR mutant tumors (HCC827) respond to EGFR inhibitor/MCL-1 inhibitor (S63845) combination therapy in vivo. Figure S6. Upregulation of MCL-1 in EGFR mutant cell lines occurs with other insults.

Supplementary figure legends

Preclinical and clinical studies have evidenced that effective targeted therapy treatment designed against receptor tyrosine kinases (RTKs) in different solid tumor paradigms is predicated on simultaneous inhibition of both the PI3K and MEK intracellular signaling pathways. Indeed, reactivation of either pathway results in resistance to these therapies. Recently, oncogenic phosphatase SHP2 inhibitors have been developed with some now reaching clinical trials. To expand on possible indications for SHP099, we screened over 800 cancer cell lines covering over 25 subsets of cancer. We found head and neck squamous cell carcinoma (HNSCC) was the most sensitive adult subtype of cancer to SHP099. We found that, in addition to the MEK pathway, SHP2 inhibition blocks the PI3K pathway in sensitive HNSCCs, resulting in downregulation of mTORC signaling and antitumor effects across several HNSCC mouse models, including an human papillomavirus (HPV+) patient-derived xenograft. Importantly, we found low levels of the RTK ligand epiregulin identified HNSCCs that were sensitive to SHP2 inhibitor, and, adding exogenous epiregulin mitigated SHP099 efficacy. Mechanistically, epiregulin maintained SHP2–GAB1 complexes in the presence of SHP2 inhibition, preventing downregulation of the MEK and PI3K pathways. In the presence of SHP2 inhibitor, HNSCCs are highly dependent on GAB1 for their survival and knockdown of GAB1 is sufficient to block the ability of epiregulin to rescue MEK and PI3K signaling. These data connect the sensitivity of HNSCC to SHP2 inhibitors and to a broad reliance on GAB1-SHP2, revealing an important and druggable signaling axis. Overall, SHP2 inhibitors are being heavily developed and may have activity in HNSCCs, and in particular those with low levels of epiregulin. Significance: This work identifies a novel role of SHP2 inhibitor by dual downregulation of PI3K and MEK pathways, through loss of GAB1 activation and disruption of GAB1 complexes in low-epiregulin HNSCC.

Triple negative breast cancer (TNBC) accounts for over 30% of all breast cancer (BC)-related deaths, despite accounting for only 10% to 15% of total BC cases. Targeted therapy development has largely stalled in TNBC, underlined by a lack of traditionally druggable addictions like receptor tyrosine kinases (RTKs). Here, through full genome CRISPR/Cas9 screening of TNBC models, we have uncovered the sensitivity of TNBCs to the depletion of the ubiquitin-like modifier activating enzyme 1 (UBA1). Targeting UBA1 with the first-in-class UBA1 inhibitor TAK-243 induced unresolvable endoplasmic reticulum (ER)-stress and activating transcription factor 4 (ATF4)-mediated upregulation of proapoptotic NOXA, leading to cell death. c-MYC expression correlates with TAK-243 sensitivity and cooperates with TAK-243 to induce a stress response and cell death. Importantly, there was an order of magnitude greater sensitivity of TNBC lines to TAK-243 compared to normal tissue-derived cells. In five patient derived xenograft models (PDXs) of TNBC, TAK-243 therapy led to tumor inhibition or frank tumor regression. Moreover, in an intracardiac metastatic model of TNBC, TAK-243 markedly reduced metastatic burden, indicating UBA1 is a potential new target in TNBC expressing high levels of c-MYC.

The EWSR1-FLI1 t(11;22)(q24;q12) translocation is the hallmark genomic alteration of Ewing sarcoma, a malignancy of the bone and surrounding tissue, predominantly affecting children and adolescents. Although significant progress has been made for the treatment of localized disease, patients with metastasis or who relapse after chemotherapy have less than a 30% five-year survival rate. EWS-FLI1 is currently not clinically druggable, driving the need for more effective targeted therapies. Treatment with the H3K27 demethylase inhibitor, GSK-J4, leads to an increase in H3K27me and a decrease in H3K27ac, a significant event in Ewing sarcoma because H3K27ac associates strongly with EWS-FLI1 binding at enhancers and promoters and subsequent activity of EWS-FLI1 target genes. We were able to identify targets of EWS-FLI1 tumorigenesis directly inhibited by GSK-J4. GSK-J4 disruption of EWS-FLI1-driven transcription was toxic to Ewing sarcoma cells and slowed tumor growth in patient-derived xenografts (PDX) of Ewing sarcoma. Responses were markedly exacerbated by cotreatment with a disruptor of RNA polymerase II activity, the CDK7 inhibitor THZ1. This combination together suppressed EWS-FLI1 target genes and viability of ex vivo PDX Ewing sarcoma cells in a synergistic manner. In PDX models of Ewing Sarcoma, the combination shrank tumors. We present a new therapeutic strategy to treat Ewing sarcoma by decreasing H3K27ac at EWS-FLI1–driven transcripts, exacerbated by blocking phosphorylation of the C-terminal domain of RNA polymerase II to further hinder the EWS-FLI1–driven transcriptome.

Venetoclax is a small molecule inhibitor of the prosurvival protein BCL-2 that has gained market approval in BCL-2–dependent hematologic cancers including chronic lymphocytic leukemia and acute myeloid leukemia. Neuroblastoma is a heterogenous pediatric cancer with a 5-year survival rate of less than 50% for high-risk patients, which includes nearly all cases with amplified MYCN. We previously demonstrated that venetoclax is active in MYCN-amplified neuroblastoma but has limited single-agent activity in most models, presumably the result of other pro-survival BCL-2 family protein expression or insufficient prodeath protein mobilization. As the relative tolerability of venetoclax makes it amenable to combining with other therapies, we evaluated the sensitivity of MYCN-amplified neuroblastoma models to rational combinations of venetoclax with agents that have both mechanistic complementarity and active clinical programs. First, the MDM2 inhibitor NVP-CGM097 increases the prodeath BH3-only protein NOXA to sensitize p53-wild-type, MYCN-amplified neuroblastomas to venetoclax. Second, the MCL-1 inhibitor S63845 sensitizes MYCN-amplified neuroblastoma through neutralization of MCL-1, inducing synergistic cell killing when combined with venetoclax. Finally, the standard-of-care drug cocktail cyclophosphamide and topotecan reduces the apoptotic threshold of neuroblastoma, thus setting the stage for robust combination efficacy with venetoclax. In all cases, these rational combinations translated to in vivo tumor regressions in MYCN-amplified patient-derived xenograft models. Venetoclax is currently being evaluated in pediatric patients in the clinic, including neuroblastoma (NCT03236857). Although establishment of safety is still ongoing, the data disclosed herein indicate rational and clinically actionable combination strategies that could potentiate the activity of venetoclax in patients with amplified MYCN with neuroblastoma.

MYCN is amplified in 20% to 25% of neuroblastoma, and MYCN-amplified neuroblastoma contributes to a large percent of pediatric cancer–related deaths. Therapy improvements for this subtype of cancer are a high priority. Here we uncover a MYCN-dependent therapeutic vulnerability in neuroblastoma. Namely, amplified MYCN rewires the cell through expression of key receptors, ultimately enhancing iron influx through increased expression of the iron import transferrin receptor 1. Accumulating iron causes reactive oxygen species (ROS) production, and MYCN-amplified neuroblastomas show enhanced reliance on the system Xc- cystine/glutamate antiporter for ROS detoxification through increased transcription of this receptor. This dependence creates a marked vulnerability to targeting the system Xc-/glutathione (GSH) pathway with ferroptosis inducers. This reliance can be exploited through therapy with FDA-approved rheumatoid arthritis drugs sulfasalazine (SAS) and auranofin: in MYCN-amplified, patient-derived xenograft models, both therapies blocked growth and induced ferroptosis. SAS and auranofin activity was largely mitigated by the ferroptosis inhibitor ferrostatin-1, antioxidants like N-acetyl-L-cysteine, or by the iron scavenger deferoxamine (DFO). DFO reduced auranofin-induced ROS, further linking increased iron capture in MYCN-amplified neuroblastoma to a therapeutic vulnerability to ROS-inducing drugs. These data uncover an oncogene vulnerability to ferroptosis caused by increased iron accumulation and subsequent reliance on the system Xc-/GSH pathway. Significance: This study shows how MYCN increases intracellular iron levels and subsequent GSH pathway activity and demonstrates the antitumor activity of FDA-approved SAS and auranofin in patient-derived xenograft models of MYCN-amplified neuroblastoma.

Triple negative breast cancer (TNBC) accounts for over 30% of all breast cancer-related deaths, despite accounting for only 10%–15% of total breast cancer cases. Targeted therapy development has largely stalled in TNBC, underlined by a lack of traditionally druggable addictions like receptor tyrosine kinases (RTKs). Here, through full genome CRISPR/Cas9 screening of TNBC models, we have uncovered the sensitivity of TNBCs to the depletion of the Ubiquitin-Like Modifier Activating Enzyme 1 (UBA1). Targeting UBA1 with the first in-class UBA1 inhibitor TAK-243 induced unresolvable ER-stress and activating transcription factor 4 (ATF4)-mediated upregulation of pro-apoptotic NOXA, leading to cell death. In five patient derived xenograft models (PDXs) of TNBC, TAK-243 therapy led to tumor inhibition or frank tumor regression. In an intracardiac metastatic model of TNBC, TAK-243 markedly reduced metastatic burden. Importantly, there was an order of magnitude greater sensitivity of TNBC lines to TAK-243 compared to normal tissue-derived cells. Lastly, c-MYC expression correlates with TAK-243 sensitivity and cooperates with TAK-243 to induce a stress response and cell death. We posit UBA1 is an important new target in TNBC expressing high levels of c-MYC.SignificanceGenomic screening of TNBC cell lines revealed broad sensitivity to depletion of the E1 ubiquitin enzyme, UBA1. Disrupting UBA1 with the first in-class inhibitor TAK-243 in TNBC models induces ER-stress through an ATF4-NOXA axis that is dependent on c-MYC, leading to apoptosis, in vitro and in vivo, primary tumor growth inhibition and metastatic inhibition.

Triple negative breast cancer (TNBC) confers the poorest prognosis of the major subtypes of breast cancers, and often inflicts young, African-American and Hispanic women. Steadily improving survival in other subsets of breast cancers are attributed to the implementation of effective targeted therapies, which are non-chemotherapy drugs that target a specific gene in a cancer. For instance, hormone positive BCs are treated effectively with anti-hormone targeted therapy, and HER2 amplified BCs are treated effectively with anti-HER2 targeted therapy. The CRISPR/CRISPR-associated protein-9 nuclease (Cas9) system, which enables specific gene editing to occur throughout the genome, allows for broad and unbiased discovery of new drug targets. We took advantage of this system to ask whether it may identify new druggable targets to treat TNBC and performed whole genome CRISPR/cas9 screening in two TNBC cell lines, BT549 and MDA-MB-468. To account for the heterogeneity found in TNBC, we further expanded the screen into seven other TNBC cell lines, by focusing on a select number of hits from the initial screen. This helped us identify a novel druggable target in TNBC, the ubiquitin activating enzyme 1 (UBA1). We took advantage of a recently reported small molecule inhibitor of UBA1, TAK-243, which is already in clinical trial evaluation in hematological cancers. Characterization of TAK-243 in cell culture models of TNBC and ex-vivo patient-derived xenografts (PDXs) demonstrated nanomolar IC50 toxicity, which was significantly lower than for tissue-derived normal cells. Mechanistically, TAK-243 therapy induced ER stress and the unfolded protein response in TNBC both in vitro and in vivo, leading to upregulation of activation transcription factor 4 (ATF4) and ATF6. Blocking ATF4 led to loss of NOXA and TAK-243 efficacy. TAK-243 induced tumor regressions in two PDX models of TNBC. Overall, these data demonstrate UBA1 is a novel drug target in TNBC. Citation Format: Sheeba Jacob, Tia H. Turner, Ann K. Yu, Colin M. Coon, Mohammad A. Alzubi, Charles T. Jakubik, Ynes Bouck, Mikhail G. Dozmorov, Sosipatros A. Boikos, Jennifer Koblinski, Joshua C. Harrell, Cyril H. Benes, Carlotta Costa, Anthony C. Faber. Genomic screening reveals UBA1 as a potent and druggable target in diverse models of triple negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-28.

Purpose: It was recently demonstrated that the EWSR1-FLI1 t(11;22)(q24;12) translocation contributes to the hypersensitivity of Ewing sarcoma to PARP inhibitors, prompting clinical evaluation of olaparib in a cohort of heavily pretreated Ewing sarcoma tumors. Unfortunately, olaparib activity was disappointing, suggesting an underappreciated resistance mechanism to PARP inhibition in patients with Ewing sarcoma. We sought to elucidate the resistance factors to PARP inhibitor therapy in Ewing sarcoma and identify a rational drug combination capable of rescuing PARP inhibitor activity. Experimental Design: We employed a pair of cell lines derived from the same patient with Ewing sarcoma prior to and following chemotherapy, a panel of Ewing sarcoma cell lines, and several patient-derived xenograft (PDX) and cell line xenograft models. Results: We found olaparib sensitivity was diminished following chemotherapy. The matched cell line pair revealed increased expression of the antiapoptotic protein BCL-2 in the chemotherapy-resistant cells, conferring apoptotic resistance to olaparib. Resistance to olaparib was maintained in this chemotherapy-resistant model in vivo, whereas the addition of the BCL-2/XL inhibitor navitoclax led to tumor growth inhibition. In 2 PDXs, olaparib and navitoclax were minimally effective as monotherapy, yet induced dramatic tumor growth inhibition when dosed in combination. We found that EWS-FLI1 increases BCL-2 expression; however, inhibition of BCL-2 alone by venetoclax is insufficient to sensitize Ewing sarcoma cells to olaparib, revealing a dual necessity for BCL-2 and BCL-XL in Ewing sarcoma survival. Conclusions: These data reveal BCL-2 and BCL-XL act together to drive olaparib resistance in Ewing sarcoma and reveal a novel, rational combination therapy that may be put forward for clinical trial testing.

Simple Summary Synovial sarcoma is a soft-tissue sarcoma that lacks effective systemic therapy and carries poor prognosis due to frequent late local recurrence and metastases. The cancer is known to be driven in part by increased expression of the pro-survival protein BCL-2. Surprisingly, synovial sarcoma proved resistant to BCL-2 inhibitors in pre-clinical trials. We identified increased activity of a second pro-survival protein, MCL-1, as responsible for this resistance. We showed that co-targeting both BCL-2 and MCL-1 proves to be an effective therapeutic approach both in cell culture and animal models of synovial sarcoma, supporting translation into clinical trials. Abstract Synovial sarcoma (SS) is frequently diagnosed in teenagers and young adults and continues to be treated with polychemotherapy with variable success. The SS18-SSX gene fusion is pathognomonic for the disease, and high expression of the anti-apoptotic BCL-2 pathologically supports the diagnosis. As the oncogenic SS18-SSX fusion gene itself is not druggable, BCL-2 inhibitor-based therapies are an appealing therapeutic opportunity. Venetoclax, an FDA-approved BCL-2 inhibitor that is revolutionizing care in some BCL-2-expressing hematological cancers, affords an intriguing therapeutic possibility to treat SS. In addition, there are now dozens of venetoclax-based combination therapies in clinical trials in hematological cancers, attributing to the limited toxicity of venetoclax. However, preclinical studies of venetoclax in SS have demonstrated an unexpected ineffectiveness. In this study, we analyzed the response of SS to venetoclax and the underlying BCL-2 family biology in an effort to understand venetoclax treatment failure and find a therapeutic strategy to sensitize SS to venetoclax. We found remarkably depressed levels of the endogenous MCL-1 inhibitor, NOXA, in SS compared to other sarcomas. Expressing NOXA led to sensitization to venetoclax, as did the addition of the MCL-1 BH3 mimetic, S63845. Importantly, the venetoclax/S63845 combination induced tumor regressions in SS patient-derived xenograft (PDX) models. As a very close analog of S63845 (S64315) is now in clinical trials with venetoclax in AML (NCT03672695), the combination of MCL-1 BH3 mimetics and venetoclax should be considered for SS patients as a new therapy.

Venetoclax is a small molecule inhibitor of the prosurvival protein BCL-2 that has gained market approval in BCL-2-dependent hematologic cancers including chronic lymphocytic leukemia and acute myeloid leukemia. Neuroblastoma is a heterogenous pediatric cancer with a 5-year survival rate of less than 50% for high-risk patients, which includes nearly all cases with amplified

Purpose: EGFR inhibitors (EGFRi) are effective against EGFR-mutant lung cancers. The efficacy of these drugs, however, is mitigated by the outgrowth of resistant cells, most often driven by a secondary acquired mutation in EGFR, T790M. We recently demonstrated that T790M can arise de novo during treatment; it follows that one potential therapeutic strategy to thwart resistance would be identifying and eliminating these cells [referred to as drug-tolerant cells (DTC)] prior to acquiring secondary mutations like T790M. Experimental Design: We have developed DTCs to EGFRi in EGFR-mutant lung cancer cell lines. Subsequent analyses of DTCs included RNA-seq, high-content microscopy, and protein translational assays. Based on these results, we tested the ability of MCL-1 BH3 mimetics to combine with EGFR inhibitors to eliminate DTCs and shrink EGFR-mutant lung cancer tumors in vivo. Results: We demonstrate surviving EGFR-mutant lung cancer cells upregulate the antiapoptotic protein MCL-1 in response to short-term EGFRi treatment. Mechanistically, DTCs undergo a protein biosynthesis enrichment resulting in increased mTORC1-mediated mRNA translation of MCL-1, revealing a novel mechanism in which lung cancer cells adapt to short-term pressures of apoptosis-inducing kinase inhibitors. Moreover, MCL-1 is a key molecule governing the emergence of early EGFR-mutant DTCs to EGFRi, and we demonstrate it can be effectively cotargeted with clinically emerging MCL-1 inhibitors both in vitro and in vivo. Conclusions: Altogether, these data reveal that this novel therapeutic combination may delay the acquisition of secondary mutations, therefore prolonging therapy efficacy. Clin Cancer Res; 24(22); 5658–72. ©2018 AACR.

Telomerase activation is one of the key mechanisms that allow cells to bypass replicative senescence. Telomerase activity is primarily regulated at the level of transcription of its catalytic unit- hTERT. Prostate cancer (PCa), akin to other cancers, is characterized by high telomerase activity. Existing data suggest that hTERT expression and telomerase activity are positively regulated by androgenic stimuli in androgen-dependent prostate cancer (ADPC) cells. A part of the present study reaffirmed this by demonstrating a decline in the hTERT expression and telomerase activity on “loss of AR” in ADPC cells. The study further addressed 2 unresolved queries, i) whether AR-mediated signaling is of any relevance to hTERT expression in castration-resistant prostate cancer (CRPC) and ii) whether this signaling involves EGR1. Our data suggest that AR-mediated signaling negatively regulates hTERT expression in CRPC cells. Incidental support for the possibility of EGR1 being a regulator of hTERT expression in PCa was provided by i) immunolocalization of hTERT and EGR1 proteins in the same cell type (secretory epithelium) of PCa and BPH tissues; ii) significantly (p< 0.001) higher levels of both these proteins in CRPC (PC3 and DU145), compared with ADPC (LNCaP) cells. A direct evidence for the role of EGR1 in hTERT expression was evident by a significant (p

e23561 Background: While Synovial Sarcoma (SS) only accounts for about 10% of soft tissue sarcomas (STS), or ~10,000 cases/year, ~4,000 of these will be fatal. Little benefit has been seen with newer combination chemotherapies and immune checkpoint inhibitors. SS is a transcription factor-driven cancer characterized by an t(X;18) chromosomal translocation resulting in the SS18-SSX fusion gene. SS is also known to overexpress the anti-apoptotic protein BCL-2, which has been used as a diagnostic marker for SS. Venetoclax, the FDA approved BH3 mimetic which specifically inhibits BCL-2, has been used to treat BCL-2-driven hematological cancers. Yet, preclinical studies of venetoclax, currently in clinical use for BCL-2 related hematologic malignancies, have failed in SS, raising the possibility of other BCL-2 family members playing a role in resistance. Methods: Publicly available gene expression databases of SS were queried for expression of BCL-2 family member expression, including the endogenous MCL-1 inhibitor, NOXA. Six SS cell lines, including ASKA, HS-SY-II, Yamato, SW982, SYO.1, and an ex vivo line from a SS patient-derived xenograft (PDX) were tested in vitro with combinations of venetoclax and the MCL-1 inhibitor S63845, using cell viability assays. In vivo testing employed both a patient-derived xenograft (PDX) model of SS and a cell line derived (SYO.1) xenograft model. Results: Queries of published gene expression data for SS demonstrated that SS expresses low levels of the endogenous MCL-1 inhibitor, NOXA, nominating a mechanism for intrinsic venetoclax resistance in these tumors, and suggesting rational combination of venetoclax and the MCL-1 inhibitor, S63845. In vitro, SS all cell lines possessing the SS18-SSX fusion gene demonstrated synergistic sensitivity to combined S63845 and venetoclax, despite generally insensitivity to either drug as monotherapy. Importantly, in an SS PDX, we demonstrated S63845 and venetoclax synergize to induce tumor regression. In the SYO.1 xenograft model, combination therapy significantly reduced tumor growth compared to no treatment or single agent groups. Conclusions: These findings provide the preclinical rationale for translation of the rational combination of BCL-2 and MCL-1 inhibitors into clinical trials for SS.

It was recently demonstrated that theWe employed a pair of cell lines derived from the same patient with Ewing sarcoma prior to and following chemotherapy, a panel of Ewing sarcoma cell lines, and several patient-derived xenograft (PDX) and cell line xenograft models.We found olaparib sensitivity was diminished following chemotherapy. The matched cell line pair revealed increased expression of the antiapoptotic protein BCL-2 in the chemotherapy-resistant cells, conferring apoptotic resistance to olaparib. Resistance to olaparib was maintained in this chemotherapy-resistant modelThese data reveal BCL-2 and BCL-X

Zinc finger E-box-binding protein 2 (ZEB2) is known to help mediate the epithelial-to-mesenchymal transition, and thereby it facilitates cancer metastasis. This study was initiated to explore whether ZEB2 expression differs in prostate cancer (PCa,n=7) and benign prostatic hyperplasia (BPH,n=7) tissues. In PCa tissues, the levels of both immunoreactive ZEB2 and androgen receptor (AR) were found to be significantly higher (PPPARandZEB2cDNA constructs prevented the decline in invasiveness and migration to a significant extent. Additionally, ZEB2 downregulation was associated with an increase in miR200a/miR200b levels in PC3-AR cells and with a decrease in miR200a/miR200b levels in AR-silenced LNCaP cells. Thus, AR acts as a positive regulator of ZEB2 expression in androgen-dependent cells and as a negative regulator in AI PCa cells.

The present investigation reports embryo-induced modifications in the epithelial cells of the endometrium in a primate species. In vivo, epithelial cell response to the embryonic signals was assessed at the embryo attachment stage in the gestational uterus of bonnet monkeys (Macaca radiata) and in vitro response was investigated by treating human endometrial epithelial cell line (Ishikawa) with human embryo conditioned media (CM). Endometrial epithelial (EE) cells at the embryo attachment stage in bonnet monkeys revealed higher proliferation accompanied by significant up regulation (p < 0.05) in the expression of estrogen receptor (ER)α and down regulation (p < 0.05) in ERβ expression. Further gestational EE cells showed higher (p < 0.001) expression of mucin-1, except in the embryo attachment site. Also, observed were significantly higher expression (p < 0.05) and altered cytoplasmic distribution of αv and β3 integrins, when compared to non-pregnant animals. In pregnant animals, the embryo attachment zone showed differential expression of immunoreactive integrins as compared to the non-attachment zone. This suggested the role of embryo secreted factors in modulation of the epithelial cell profile. In vitro studies partially supported this assumption. Significantly higher proliferation (p < 0.05), as well as increased expression of ERα, integrin β3 and mucin-1 (p < 0.05) were observed in Ishikawa cells, on stimulation with CM. Taken together, these results indicated the proliferation and modulation in the expression of estrogen receptors and cell adhesion molecules in the EE cells; at the embryo attachment stage in bonnet monkeys. Further it is likely that embryo secreted factors contribute to some of these modifications in EE cells. This report is the first account of discrete cellular events, which occur in the uterine epithelium, at the embryo attachment stage in a primate species.

The preferred delivery systems for anticancer drugs would be the one which would have selective and effective destruction of cancer cells. In the present study etoposide (ETO) loaded nanoparticles (NP) were prepared using PLGA (ETO-PLGA NP), PLGA-MPEG block copolymer (ETO-PLGA-MPEG NP) and PLGA-Pluronic copolymer (ETO-PLGA-PLU NP) and they were evaluated for cytotoxicity and cellular uptake studies using two cancer cell lines, L1210 and DU145. The IC50 values for L1210 cells were 18.0, 6.2, 4.8 and 5.4 microM and for DU145 cells the IC50 values were 98.4, 75.1, 60.1 and 71.3 microM for ETO, ETO-PLGA NP, ETO-PLGA-MPEG NP and ETO-PLGA-PLU NP respectively. The increased cytotoxicities were attributed to increased uptake of the NPs by the cells. Moreover the ETO loaded PLGA-MPEG NP and PLGA-Pluronic NP showed a sustained cytotoxic effect till 5 days on both the cell lines. Results of the long term cytotoxicity study concluded that the drug loaded PLGA nanoparticulate formulations were efficient in decreasing the viability of the L1210 cells over a period of three days, whereas the pure drug exerted its maximum efficiency on the day one itself. Z-stack confocal images of NPs showed fluorescence activity in each section of DU 145 and L1210 cells indicating that the nanoparticles were internalized by the cells. The study concluded that ETO loaded PLGA NPs had higher cytotoxicity compared with that of the free drug and ETO-PLGA-MPEG NP and ETO-PLGA-PLU NP had higher cell uptake efficiency compared with that of ETO-PLGA NP. The developed PLGA based NPs shows promise to be used for cancer therapy.

The present investigation was aimed at developing PEGylated PLGA nanoparticles of cytarabine. PLGA Nanoparticles were prepared by modified nanoprecipitation method, optimized for mean particle size (152 ± 6 nm) and entrapment efficiency (41.1 ± 0.8%) by a 32 factorial design. The PEGylated PLGA nanoparticles of cytarabine had a zeta potential of −7.5 ± 1.3 mV and sustained the release of cytarabine for 48 h by Fickian diffusion. The IC50 values for L1210 cells were 6.5, 5.3, and 2.2 µM for cytarabine, cytarabine loaded PLGA nanoparticles and cytarabine loaded PLGA-mPEG nanoparticles respectively. Confocal microscopy and flow cytometry showed that the nanoparticles were internalized by the L1210 cells and not simply bound to their surface. Biodistribution studies showed that the PEGylated nanoparticles of cytarabine were present in significantly higher concentrations in blood circulation as well as in brain and bones and avoided RES uptake as compared to the free drug.