Chemotherapy-resistant Tumors Research Articles

A phase 1b, multicenter, open-label study of valemetostat in combination with DXd antibody drug conjugates (ADCs), trastuzumab deruxtecan (T-DXd) or datopotamab deruxtecan (Dato-DXd), in patients with solid tumors.

TPS4180 Background: Valemetostat tosylate (valemetostat) is a novel, potent, and selective dual inhibitor of enhancer of zeste homolog (EZH) 2 and EZH1. Valemetostat 200 mg PO QD has demonstrated clinical efficacy and favorable tolerability in multiple hematologic malignancies. EZH2 controls gene expression, including the expression of genes involved in DNA damage response, like DNA/RNA helicase Schlafen 11 ( SLFN11). In response to DNA damage, SLFN11 binds to chromatin, causing a replication block and inducing apoptosis. Expression levels of SLFN11 indicate sensitivity to DNA-damaging agents (DDAs) in various solid tumors and are downregulated in chemotherapy-resistant tumor cells due to trimethylation of H3K27 at the SLFN11 gene locus. EZH2 inhibition by valemetostat is expected to upregulate SLFN11 and sensitize tumor cells to DDAs. Topoisomerase inhibition causes DNA strand breaks, which may synergize with valemetostat. This study will combine valemetostat with topoisomerase-I inhibitor ADCs, T-DXd or Dato-DXd, for the first time in patients (pts) with HER2-positive (HER2+) gastric cancer (GC) and non-squamous non-small-cell lung cancer (NSCLC), respectively. T-DXd is globally approved for the treatment of pts with locally advanced or metastatic HER2+ GC and other cancers, having received prior anti-HER2–based treatment. In the phase 3 TROPION-Lung01 trial, Dato-DXd significantly improved progression-free survival (PFS) vs standard chemotherapy in previously treated, locally advanced or metastatic NSCLC. Methods: This global, phase 1b, multicenter, two-part, open-label study is structured as a Master Protocol with independent sub-protocols defined by disease and treatment combination, including valemetostat + T-DXd in pts with 2L+ advanced or metastatic HER2+ GC or gastro-esophageal junction adenocarcinoma, and valemetostat + Dato-DXd in pts with 2L+ locally advanced, unresectable, or metastatic non-squamous NSCLC. Target enrollment is 70 pts per sub-protocol across 35 sites in US and Japan. Part 1 will determine the valemetostat recommended dose for expansion (RDE), combining escalating doses of valemetostat 50–200 mg PO QD with T-DXd at 5.4 mg/kg or 6.4 mg/kg (dose after first escalation) IV Q3W (GC protocol), or with fixed dose Dato-DXd 6.0 mg/kg IV Q3W (NSCLC protocol). Part 2 will evaluate the efficacy of valemetostat QD + Dato-DXd or T-DXd at the RDE. The main eligibility criteria for both protocols include at least 1 measurable lesion (per RECIST v1.1), an ECOG PS score of 0–1, and adequate organ function. Primary endpoints of this study are safety and tolerability of valemetostat in Part 1 and objective response rate in Part 2. Secondary endpoints include duration of response, PFS, overall survival and pharmacokinetics. Clinical trial information: NCT06244485 .

Activity of NAD(P)H-Oxidoreductases in Ovarian Cancer.

Reactive oxygen species (ROS) play an important and controversial role in carcinogenesis. Microsomal redox chains containing NADH- and NADPH-dependent oxidoreductases are among the main sites of intracellular ROS synthesis, but their role in the oxidative balance has not been fully studied. Here, we studied the activity of cytochrome b5 reductase (CYB5R) and cytochrome P450 reductase (CYPOR) in ovarian cancer tissues and cells isolated from peritoneal fluid, along with the antioxidant capacity of peritoneal fluid. We used the developed a chemiluminescence assay based on stimulation with NADH and NADPH, which reflects the activity of CYB5R and CYPOR, respectively. The activity of CYB5R and CYPOR was significantly higher in moderately and poorly differentiated ovarian adenocarcinomas compared with well-differentiated adenocarcinomas and cystadenomas. For the chemotherapy-resistant tumors, the activity of tissue CYB5R and CYPOR was lower compared to the non-resistant tumors. In the peritoneal fluid, the antioxidant capacity significantly increased in this series, benign tumors < well-differentiated < moderately and poorly differentiated adenocarcinomas, so the antioxidant excess was observed for moderately and poorly differentiated adenocarcinomas. The antioxidant capacity of peritoneal fluid and the activity of CYB5R and CYPOR of cells isolated from peritoneal fluid were characterized by a direct moderate correlation for moderately and poorly differentiated adenocarcinomas. These results indicate the significant role of NAD(P)H oxidoreductases and the antioxidant potential of peritoneal fluid in cancer biochemistry. The parameters studied are useful for diagnostics and prognostics. The developed assay can be used to analyze CYB5R and CYPOR activity in other tissues and cells.

EMP2 Serves as a Functional Biomarker for Chemotherapy-Resistant Triple-Negative Breast Cancer.

Breast cancer (BC) remains among the most commonly diagnosed cancers in women worldwide. Triple-negative BC (TNBC) is a subset of BC characterized by aggressive behavior, a high risk of distant recurrence, and poor overall survival rates. Chemotherapy is the backbone for treatment in patients with TNBC, but outcomes remain poor compared to other BC subtypes, in part due to the lack of recognized functional targets. In this study, the expression of the tetraspan protein epithelial membrane protein 2 (EMP2) was explored as a predictor of TNBC response to standard chemotherapy. We demonstrate that EMP2 functions as a prognostic biomarker for patients treated with taxane-based chemotherapy, with high expression at both transcriptomic and protein levels following treatment correlating with poor overall survival. Moreover, we show that targeting EMP2 in combination with docetaxel reduces tumor load in syngeneic and xenograft models of TNBC. These results provide support for the prognostic and therapeutic potential of this tetraspan protein, suggesting that anti-EMP2 therapy may be beneficial for the treatment of select chemotherapy-resistant TNBC tumors.

Natural History and Genomic Landscape of Chemotherapy-Resistant Muscle-Invasive Bladder Cancer.

Patients with residual invasive bladder cancer after neoadjuvant chemotherapy (NAC) and radical cystectomy have a poor prognosis. Data on adjuvant therapy for these patients are conflicting. We sought to evaluate the natural history and genomic landscape of chemotherapy-resistant bladder cancer to inform patient management and clinical trials. Data were collected on patients with clinically localized muscle-invasive urothelial bladder cancer treated with NAC and cystectomy at our institution between May 15, 2001, and August 15, 2019, and completed four cycles of gemcitabine and cisplatin NAC, excluding those treated with adjuvant therapies. Survival was estimated using the Kaplan-Meier method, and multivariable Cox proportional hazards models were used to identify predictors of recurrence-free survival (RFS). Genomic alterations were identified in targeted exome sequencing (Memorial Sloan Kettering Integrated Mutation Profiling of Actionable Cancer Targets) data from post-NAC specimens from a subset of patients. Lymphovascular invasion (LVI) was the strongest predictor of RFS (hazard ratio, 2.15 [95% CI, 1.37 to 3.39]) on multivariable analysis. Patients with ypT2N0 disease without LVI had a significantly prolonged RFS compared with those with LVI (70% RFS at 5 years). Lymph node yield did not affect RFS. Among patients with sequencing data (n = 101), chemotherapy-resistant tumors had fewer alterations in DNA damage response genes compared with tumors from a publicly available chemotherapy-naïve cohort (15% v 29%; P = .021). Alterations in CDKN2A/B were associated with shorter RFS. PIK3CA alterations were associated with LVI. Potentially actionable alterations were identified in more than 75% of tumors. Although chemotherapy-resistant bladder cancer generally portends a poor prognosis, patients with organ-confined disease without LVI may be candidates for close observation without adjuvant therapy. The genomic landscape of chemotherapy-resistant tumors is similar to chemotherapy-naïve tumors. Therapeutic opportunities exist for targeted therapies as adjuvant treatment in chemotherapy-resistant disease.

Abstract 5090: Development of HSPG2 targeted glycoengineered antibody-drug conjugates

Abstract Ovarian cancer is associated with poor outcomes and aggressive behaviors. Although surgical removal of tumors and chemotherapy can initially eradicate cancer, many patients eventually experience relapse with chemotherapy-resistant tumors, resulting in poor long-term outcomes and chemotherapy complications. Antibody-drug conjugates (ADCs) are formed by integrating the tumor specificity provided by antibodies (Ab) and small molecule cytotoxicity drugs and can facilitate highly targeted delivery with minimal toxicity to normal tissues. Our group has identified that the overexpression of a novel target, heparan sulfate proteoglycan 2 (HSPG2), is associated with poor prognosis and survival of high grade serous ovarian cancer (HGSOC) patients. We have developed a monoclonal antibody (AM6) that effectively targets HSPG2-expressing tumors. In this study, we used a novel glycoengineering strategy to introduce artificial azide groups at the N-glycan sites of AM6 without affecting its antigen affinity and intracellular localization. The azide groups were then used for site-specific conjugation of the cleavable dibenzyl cyclooctyne - monomethyl auristatin E (DBCO-PAB-MMAE) linker (drug conjugate) to form an AM6 antibody-drug conjugate (AM6 ADCs). Hydrophobic interaction chromatography (HIC) and liquid chromatography/quadrupole time-of-flight/mass spectrometry (LC/Q-TOF/MS) confirmed the successful conjugation of the DBCO-PAB-MMAE to the AM6. In-vitro cytotoxicity studies of AM6 ADCs in OVCAR8 (high HSPG2 expression) and CAOV3 (regular HSPG2 expression) showed the cell line dependent response with lower IC50 in OVCAR8. These results suggest that the effectiveness of AM6 ADCs is proportional to the HSPG2 expression levels of the cells. Future studies will be aimed at the in-vivo evaluation of optimized antibody-drug conjugates. Citation Format: Xiaolei Li, Swayam Prabha. Development of HSPG2 targeted glycoengineered antibody-drug conjugates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5090.

Abstract 5880: Induction of the p-glycoprotein with atorvastatin using colorectal cancer cells

Abstract Chemotherapy resistance is responsible for a majority of the cancer-associated mortalities. Efflux of the P-glycoprotein (P-gp) transporter is one of the many causes for chemotherapy resistance. The increased activity of the P-gp on the surface of the tumor cells leads to the removal chemotherapy drugs and allows a cancer to survive. The purpose of this study was to evaluate how atorvastatin impacts the P-gp expression in colorectal cancer cells. The colorectal cells, CACO2 cell line, were separated into drug treatment groups. The experimental groups were treated with the statin drug, atorvastatin, at different concentrations and doxorubicin as the positive control, for 3-4 months. Atorvastatin was selected for the study since it is a P-gp substrate and a potential inducer. Exon-spanning primers for the ABCB1 gene were used to monitor changes in mRNA expression of the P-gp. Once overexpression of the ABCB1 gene was achieved, the cells were tested for protein expression through western blots and flow cytometry. The P-pg-induced cells, which consisted of the atorvastatin-treated and doxorubicin-treated cells, and the untreated cells were then tested for chemotherapy-resistance using the PrestoBlue proliferation assay. The atorvastatin treatments were repeated for reproducibility by using two other colorectal cancer cell lines. The P-pg-induced cells, which consisted of the atorvastatin-treated and doxorubicin-treated cells, and the untreated cells were also studied for stability by removing the treatments of the atorvastatin for three months and monitoring for changes in expression of the ABCB1 gene with rt-qPCR. Drug pathways of the treated cells were also studied for expression changes using RNA Sequencing (RNA-Seq). For the results, the overexpression of the ABCB1 gene occurred in the 4th month of the study of the bi-weekly atorvastatin and doxorubicin treatments using the CACO2 cells. Protein assays were able to confirm the P-gp overexpression in the atorvastatin-treated and doxorubicin-treated cells. The chemotherapy-resistant assay revealed that the atorvastatin-treated cells were just as drug resistant to the chemotherapy as the doxorubicin-treated cells. Through the reproducibility experiment, the overexpression of the ABCB1 gene was observed in two other cell lines after long-term treatment of the drug therapy. Removal of the atorvastatin for three months revealed that the P-gp overexpression was not reversible. The RNA-Seq analysis identified other possible drug resistant markers in the atorvastatin pathway. This study implicates that late-stage cancer patients, who are treated for hypercholesterolemia, may be at higher risk for developing chemotherapy-resistant tumor cells. With the identification of chemotherapy-resistant tumors in chemotherapy-naïve cancer patients, doctors will be able to provide more precise approaches to treating patients through effective drug therapies. Citation Format: Christopher L. Farrell, Amy Messersmith, Wei Lei, Brianna Dyer. Induction of the p-glycoprotein with atorvastatin using colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5880.

Abstract B086: Targeting ATR to overcome Carboplatin resistance in triple-negative breast cancer patient-derived models

Abstract Background: Triple negative breast cancer subtype is associated with poor prognosis and is mostly treated with chemotherapy, including the DNA crosslinking agent Carboplatin. Carboplatin treatment leads to DNA damage and a cell cycle inhibition allowing DNA damage repair. However, many patients are resistant or develop resistance to Carboplatin. The identification of novel treatments against chemoresistant TNBC is a major unmet clinical need. Method: TNBC patient-derived cell lines (PDCs) from patient-derived xenografts (PDXs) generated from chemotherapy resistant tumors were used for shRNA high throughput screens to identify genetic vulnerabilities that could resensitize these cells to Carboplatin. Validation of this target was performed genetically by shRNA silencing and pharmacologically with commercially available target inhibitors both in vitro and in vivo, using Alamar Blue viability assays and calculating synergy using the Chou Talalay method. DNA damage was assessed using yH2AX expression, and apoptosis using c-PARP and Annexin V, by confocal microscopy, flow cytometry and/or western blotting. Results: We identified ataxia telangiectasia and Rad3-related protein (ATR) as a target in one of the cell lines screened and validated it with an ATR shRNA. We tested the combination of the ATR inhibitor (ATRi), Elimusertib, with Carboplatin and found the combination to be synergistic (Average CI=0.30). DNA damage was markedly increased with combination treatment and a pan-nuclear yH2AX staining together with increased pHH3 expression were observed, suggestive of mitotic catastrophe. Cells treated with Carboplatin accumulated in S phase and a shift toward G2/M when Elimusertib was added. Apoptosis was significantly increased with combination treatment. PKMYT1 and WEE1 are two kinases regulating cell cycle entry by inhibiting CDK1, which controls entry into mitosis. Carboplatin treatment resulted in an increase in PKMYT1 expression. PKMYT1 inhibition with RP6306 re-sensitized the cells to Carboplatin more than WEE1 inhibition with Adavosertib, and this synergy was further increased with low doses of Elimusertib. Gene silencing of WEE1 and PKMYT1 both re-sensitized the cells to Carboplatin, but only WEE1 silencing alone significantly prevent proliferation, suggesting the requirement of PKMYT1 activity for resistance but not for cell proliferation without Carboplatin. In vivo validation using the PDXs from which the cell lines have been derived, demonstrated a significant delayed in tumor growth and prolonged survival when combining Carboplatin with ATRi compared to Carboplatin alone in two models. Conclusion: ATR inhibition resensitizes drug resistant TNBC cells to Carboplatin both in vitro and in vivo. The combination of Carboplatin with ATRi led to DNA damage and mitotic catastrophe. PKMYT1 plays a role in Carboplatin-resistant TNBC, collaborating with ATR in managing the cell cycle response to DNA damage, and PKMYT1 inhibition also re-sensitizes cells to Carboplatin, an effect increased with the triple combination of adding ATR inhibition. Citation Format: Juliet Guay, Catherine Chabot, Cédric Darini, Marguerite Buchanan, Adriana Aguilar-Mahecha, Tim Kong, Connie Yang, Mark Basik, Sidong Huang. Targeting ATR to overcome Carboplatin resistance in triple-negative breast cancer patient-derived models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B086.

Malignant gastrointestinal neuroectodermal tumor: a case report and literature review

Introduction and importance: A malignant gastrointestinal neuroectodermal tumor (GNET) is an extremely rare primary malignant mesenchymal tumor of the gastrointestinal tract characterized by EWSR1 gene rearrangement. An optimal systemic treatment strategy for advanced/recurrent GNET has not yet been identified. Case presentation: A 24-year-old male patient was hospitalized with abdominal pain and underwent two operations for a tumor in his small intestine. Immunohistochemistry (IHC) showed strong expression of S-100 protein and SOX 10. Fluorescence in situ hybridization analysis and next-generation sequencing analysis indicated that there were EWSR gene rearrangements and the presence of EWSR-ATP1 gene fusions, respectively. The diagnosis of GNET in the small intestine was confirmed by pathology. The young patient received the fifth-line of apatinib mesylate and the sixth-line of apatinib combined with temozolomide. The two apatinib-containing regimens showed stable disease and progression-free survival of 4.7 months and 3.1 months with single-agent apatinib or apatinib combined with temozolomide, respectively. Clinical discussion: To our best knowledge, this is the first report of malignant GNET treated with apatinib and temozolomide. Apatinib-containing regimens might has antineoplastic activity against GNET. The authors reviewed the relevant reports of previous GNET treatment, summarized the clinicopathological characteristics of GNET, and found that there are no reports of apatinib for backline treatment of GNET. Conclusion: Containing apatinib may provide an additional treatment option for patients with chemotherapy-resistant GNET tumors.

Clinical, Cytogenetic and Immunophenotypic Spectra of Post-Transplant Relapse Following Allogeneic Hematopoietic Stem Cell Transplantation for Myelodysplastic Syndrome

Introduction Allogeneic hematopoietic stem cell transplantation (HCT) is a curative therapy used to treat myelodysplastic syndrome (MDS). Relapse post-HCT confers poor outcomes and subsequent therapy is not standardized. Like acute myeloid leukemia (AML), several mechanisms are known to be involved in post-HCT relapse including clonal evolution in favor of chemotherapy-resistant clones and tumor immune escape. Systemic reviews are scarce in the MDS post-HCT relapse population. Accordingly, the present study aimed to investigate clinical, cytogenetic, and immunophenotypic (IP) spectra for MDS post-HCT relapse patients (pts), along with subsequent therapies, and clinical outcomes following post-HCT relapse. Patients and methods A retrospective study was conducted and found that 231 MDS pts received HCT between April 2010 and September 2022 at the Princess Margaret Cancer Centre (PMCC). The primary endpoint was overall survival (OS) following post-HCT relapse. Secondary endpoints explored time to relapse (TTR), relapse presentation (i.e., MDS or AML), clonal evolution (i.e., changes in cytogenetics or IP profiles), and therapeutic strategies delivered after relapse. Results Of the 231 MDS pts treated with HCT, 52 (23%) relapsed in a median of 4.5 months (range 0.9-59.8 months). Twenty-five (48%) pts relapsed with MDS (i.e., blast &amp;lt;20%), while 27 (52%) relapsed with AML (i.e., blast ≥20%) in the marrow. Fifteen (65%) pts showed cytogenetic changes at the time of post-HCT relapse. Eleven (48%) of which presented with more aggressive findings (i.e., additional structural abnormalities and monosomal karyotype). Ten of 17 (59%) pts presented with changes in their IP profile at post-HCT relapse, 7 (70%) of which relapsed with AML. Combined these findings give evidence of clonal evolution in favor of more aggressive malignant clones that are often responsible for post-HCT relapse. Treatment with hypomethylating agents (HMA) alone or in combination after post-HCT relapse increased OS to 5.6 months in comparison to those not receiving HMA of whom OS was 1.4 months (p=0.0003). Stratified by disease presentation cytogenetic clonal evolution was seen in 6/12 (50%) of the post-HCT MDS relapses, and 9/11 (82%) of the post-HCT AML relapses. Cytogenetic abnormalities at diagnosis and post-HCT relapse, respectively included in descending order: structural abnormalities (n=14/23, 61%; n=20/23, 87%), complex karyotype (n=12/23, 52%; 17/23, 74%), -5/del(5q) (n=11/23, 48%; n=10/23, 43%), -7/del(7q) (n=8/23, 35%; n=11/23, 48%), monosomy karyotype (n=8/23, 35%; n=11/23, 48%), -17 (n=3/23, 13%; n=5/23, 22%), der(5)/t(5;17) (n=2/23, 9%; n=5/23, 22%), -20 (n=2/23, 9%; n=3/23, 13%), and inv(3) (n=1/23, 4%, n=2/23, 9%). Seventeen pts had paired IP profiles available both prior to HCT and at post-HCT relapse, of which 10 (59%) had profile changes of at least 1 antigen. Seven of 10 (70%) pts that relapsed with AML post-HCT had IP expression changes, compared to 3/7 (42.9%) pts that relapsed with MDS post-HCT. Summarized IP findings include reduced expression of CD7 (n=2/6, 33%), altered expression of CD34 (n=3/15, 20%), altered expression of CD117 (n=3/14, 21%), and reduced expression of HLA DR (n=4/15, 27%). The presence of IP expression changes at post-HCT relapse suggests evidence of clonal evolution or immune escape as the mechanism behind the relapsed disease. Overall survival duration was 3.97 months; the 12-month OS rate was 20.0% (10.0-32.5%). Post-HCT relapse treatments included hypomethylating agents (HMA; n=13/46, 28%), HMA with donor lymphocyte infusion (DLI; n= 7/46, 15%), HMA with Venetoclax (VEN; n=7/46, 15%), chemotherapy (n=9/46, 19%), best supportive care (8/46, 17%) and second HCT (n=2/46, 4%). Patients that received HMA with or without DLI or VEN had a longer survival duration of 5.6 months (95% CI [3.4-13.2 months]) compared to those not receiving HMA 1.4 months (95% CI [0.6-0.39 months, p=0.0003]). The 12-month survival rate was also significantly in favor of pts that received HMA following post-HCT relapse (35.3% [95% CI 17.2-54.0%] vs 4.3% [95% CI 0.3-18.0%]). Conclusion Patients with MDS undergoing HCT may relapse with either MDS or AML. The relapsed disease often shows evidence of clonal evolution in its immunophenotype and/or cytogenetic profile toward a more aggressive disease. Approaches to post-HCT relapse remain heterogenous but HMA is beneficial.

Integration of multiomics data shows down regulation of mismatch repair and tubulin pathways in triple-negative chemotherapy-resistant breast tumors

BackgroundTriple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype. Patients with TNBC are primarily treated with neoadjuvant chemotherapy (NAC). The response to NAC is prognostic, with reductions in overall survival and disease-free survival rates in those patients who do not achieve a pathological complete response (pCR). Based on this premise, we hypothesized that paired analysis of primary and residual TNBC tumors following NAC could identify unique biomarkers associated with post-NAC recurrence.Methods and resultsWe investigated 24 samples from 12 non-LAR TNBC patients with paired pre- and post-NAC data, including four patients with recurrence shortly after surgery (< 24 months) and eight who remained recurrence-free (> 48 months). These tumors were collected from a prospective NAC breast cancer study (BEAUTY) conducted at the Mayo Clinic. Differential expression analysis of pre-NAC biopsies showed minimal gene expression differences between early recurrent and nonrecurrent TNBC tumors; however, post-NAC samples demonstrated significant alterations in expression patterns in response to intervention. Topological-level differences associated with early recurrence were implicated in 251 gene sets, and an independent assessment of microarray gene expression data from the 9 paired non-LAR samples available in the NAC I-SPY1 trial confirmed 56 gene sets. Within these 56 gene sets, 113 genes were observed to be differentially expressed in the I-SPY1 and BEAUTY post-NAC studies. An independent (n = 392) breast cancer dataset with relapse-free survival (RFS) data was used to refine our gene list to a 17-gene signature. A threefold cross-validation analysis of the gene signature with the combined BEAUTY and I-SPY1 data yielded an average AUC of 0.88 for six machine-learning models. Due to the limited number of studies with pre- and post-NAC TNBC tumor data, further validation of the signature is needed.ConclusionAnalysis of multiomics data from post-NAC TNBC chemoresistant tumors showed down regulation of mismatch repair and tubulin pathways. Additionally, we identified a 17-gene signature in TNBC associated with post-NAC recurrence enriched with down-regulated immune genes.

Abstract 2689: Targeting the proteasome pathway in dactinomycin resistant Wilms tumors

Abstract Nephroblastomas or Wilms tumors are the most common pediatric renal cancer. Across all cases, the 5-year overall survival is over 90%. This is largely in part due to brute-force, chemotherapy regimens such as dactinomycin (actD) that have been routinely used to treat Wilms tumors. However, those that do respond to treatment still face a 15% chance of relapse. Patients with anaplastic tumor histology require more toxic therapies, and yet they still face a worse prognosis of only 66% 4-year survival and relapse rate of 43%. Furthermore, recurrence cuts survival rate down to 50%. With the widespread use of actD in Wilms tumors and other childhood malignancies, understanding the mechanism to recalcitrance against this chemotherapy can potentially reveal important vulnerabilities that can be exploited in the clinic. While transcriptomic and genomic analyses have been done in Wilms tumors, no targetable pathways have been identified in actD chemotherapy-resistant and anaplastic tumor cases. To that end, we performed ribosome sequencing of actD-treated anaplastic Wilms tumor cell line WiT49 and uncovered that the proteasome pathway is preferentially translated. Moreover, loss of proteasome subunits in a CRISPR library dropout screen sensitized the cells to actD. Consistent with these findings we found upregulation of proteasome subunit levels and proteasome enzymatic activity in Wilms tumor lines following actD treatment. To interrogate the effect of cotreating bortezomib with dactinomycin in vivo, we subcutaneously implanted anaplastic Wilms tumor patient-derived xenograft (PDX) lines in NOD/SCID Gamma (NSG) mice. Combinatorial treatment was found to be retard tumor growth compared to vehicle and single drug conditions. With further investigation, our findings can provide a foundation for exploring proteasome inhibitors with dactinomycin in clinical trials. Our study has important implications to improving the outcomes for not just for recurrent and anaplastic Wilms tumors, but to other pediatric cancers that use actD as well. Citation Format: Patricia Denise Ballesteros Tiburcio, Kenneth S. Chen. Targeting the proteasome pathway in dactinomycin resistant Wilms tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2689.

Abstract 1744: Chemoresistant non-small cell lung cancer: A resensitizing strategy utilizing antimuscarinics

Abstract Background: Advanced non-small cell lung cancer (NSCLC) remains a leading cause of cancer-related deaths in the United States and worldwide. This is largely due to intrinsic or acquired therapy resistance. The current study investigates the potential of a repurposed antimuscarinic overactive bladder drug to resensitize chemotherapy-resistant NSCLC to chemotherapy-induced apoptosis. Methods: The chemotherapy drug, docetaxel (DTX), resistant human NSCLC cell cultures (A549R) were established to recapitulate the clinical emergence of chemoresistance. These cultures were used to harvest total RNA for RNA-seq and qPCR. DTX-induced apoptosis was measured with crystal violet survival assay, colony formation assay, and TUNEL assay. In vivo experiments were performed by injecting A549R cells into the flanks of immunocompromised mice. Mice were treated with various agents, tumor sizes were monitored, and tumor mass was measured at the end of the experiment. Results: RNA-seq data of DTX-resistant NSCLC (A549R) cells show a 13.5-fold increase in expression of the muscarinic acetylcholine receptor 3 (CHRM3) compared to chemonaive A549 cells which was supported by qPCR analysis (16-fold increase). Oncomine clinical data from TCGA and Bild Lung suggest an increased mortality risk at 3 years is associated with increased CHRM3 expression. In vitro survival experimental results show resensitization of A549R cells to DTX-induced cell death when co-treated with the CHRM3 antagonist, darifenacin. Crystal violet cell survival assays show a 70% reduction in survival when cells are treated with darifenacin + DTX compared to DTX alone. This is supported by colony formation assay results with complete absence of colony growth in the darifenacin + DTX combination therapy group. Furthermore, cells treated with darifenacin + DTX show increased apoptosis measured by TUNEL assay compared to cells treated with DTX alone (% TUNEL positive: DTX alone = 0.9%, darifenacin + DTX = 88%). In vivo tumor measurements of injected A549R cells revealed a 91% decrease in tumor growth in the darifenacin + DTX treated mice compared to the DTX alone treated mice. Conclusion: We show that chemoresistant NSCLC has increased expression of CHRM3 which is associated with poorer clinical outcomes. Furthermore, the currently available antimuscarinic, darifenacin, which is used in the clinic to treat overactive bladder, effectively resensitizes DTX-resistant cells to DTX-induced cell death both in vitro and in vivo. This novel therapy has unique advantages over alternate approaches as it aims to save chemotherapy-eligible patients at multiple levels: 1) to resensitize chemotherapy-resistant tumors, 2) to synergize with chemotherapy for improved efficacy, and 3) to reduce the effective dose of chemotherapy, thus lowering toxic side effects. Funding provided by an INBRE Pilot Grant, and the UI start-up fund (to T.B.) Citation Format: Tyler Bland, Ethan Overfelt. Chemoresistant non-small cell lung cancer: A resensitizing strategy utilizing antimuscarinics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1744.

To Correlate the Expression of KRAS and BRAF V600e with Histological Grades and Variants in Tissue Samples of Colorectal Carcinoma

OBJECTIVES This study aimed to correlate the expression of KRAS and BRAF V600E with histological grades and variants in tissue samples of colorectal carcinoma.METHODOLOGY In this cross-sectional study total of 51 cases of Colorectal cancer (CRC) were analyzed for immunohistochemical staining using KRAS and BRAF antibodies on representative tissue blocks. Clinical and pathological records were retrieved for the collection of data. The results of the immunohistochemical analysis were correlated with the recorded clinicopathological parameters.RESULTSFifty-one cases of CRC were analyzed for immunoexpression of KRAS and BRAF V600E. The age of the patients ranged from 14 to 85 years, with a mean age of 60.96 years. Among the 51 cases, 37(72.5%) cases were males and 14(27.4%) were females. 37(72.5%) were localized to left side colon and 14(27.4%) were found in the right colon. For KRAS immunostaining, 41(80.3%) out of 51 cases showed overexpression, while the remaining 10(19.6%) cases revealed negative expression. In the case of BRAF V600E, positive expression was seen in 20(39.2%) cases, whereas 31(60.7%) cases showed negative expression of BRAFV600E. A significant association was seen between KRAS overexpression and histological variants, i.e. glandular carcinomas. CONCLUSIONOver-expression of KRAS was observed in advanced tumors. The presence of BRAF V600E mutation in the present study signifies the importance of BRAF V600E inhibitors as a potential alternate therapeutic tool in EGFR inhibitors and chemotherapy-resistant tumors.

Chemotherapy induces immune checkpoint VISTA expression in tumor cells via HIF-2alpha

Tumor cells can evade the innate and adaptive immune systems, which play important roles in tumor recurrence and metastasis. Malignant tumors that recur after chemotherapy are more aggressiveciscis, suggesting an increased ability of the surviving tumor cells to evade innate and adaptive immunity. Therefore, in order to reduce patient mortality, it is important to discover the mechanisms by which tumor cells develop resistance to chemotherapeutics. In the present study we focused on the tumor cells that survived chemotherapy. We found that chemotherapy could promote the expression of VISTA in tumor cells, and that this change was mediated by HIF-2α. In addition, VISTA overexpression on melanoma cells promoted immune evasion, and the application of the VISTA-blocking antibody 13F3 enhanced the therapeutic effect of carboplatin. These results offer an insight into the immune evasion of chemotherapy-resistant tumors, and provide a theoretical basis for the combined application of chemotherapy drugs and VISTA inhibitors to treat tumors.

Quiescent ovarian cancer cells secrete follistatin to induce chemotherapy resistance in surrounding cells in response to chemotherapy.

We recently reported that the transcription factor NFATC4, in response to chemotherapy, drives cellular quiescence to increase OvCa chemoresistance. The goal of this work was to better understand the mechanisms of NFATC4 driven OvCa chemoresistance. We used RNA-seq to identify NFATC4 mediated differential gene expression. CRISPR-Cas9 and FST neutralizing antibody were used to assess impact of loss of FST function on cell proliferation and chemoresistance. ELISA was used to quantify FST induction in patient samples and in vitro in response to chemotherapy. We found that NFATC4 upregulates follistatin (FST) mRNA and protein expression predominantly in quiescent cells and FST is further upregulated following chemotherapy treatment. FST acts in at least a paracrine manner to induce a p-ATF2 dependent quiescent phenotype and chemoresistance in non-quiescent cells. Consistent with this, CRISPR KO of FST in OvCa cells or antibody mediated neutralization of FST sensitizes OvCa cells to chemotherapy treatment. Similarly, CRISPR KO of FST in tumors increased chemotherapy-mediated tumor eradication in an otherwise chemotherapy resistant tumor model. Suggesting a role for FST in chemoresistance in patients, FST protein in the abdominal fluid of OvCa patients significantly increases within 24 hours of chemotherapy exposure. FST levels decline to baseline levels in patients no longer receiving chemotherapy with no evidence of disease. Furthermore, elevated FST expression in patient tumors is correlated with poor progression free, post-progression free, and overall survival. FST is a novel therapeutic target to improve OvCa response to chemotherapy and potentially reduce recurrence rates.

Harnessing transcriptionally driven chromosomal instability adaptation to target therapy-refractory lethal prostate cancer

Metastatic prostate cancer (PCa) inevitably acquires resistance to standard therapy preceding lethality. Here, we unveil a chromosomal instability (CIN) tolerance mechanism as a therapeutic vulnerability of therapy-refractory lethal PCa. Through genomic and transcriptomic analysis of patient datasets, we find that castration and chemotherapy-resistant tumors display the highest CIN and mitotic kinase levels. Functional genomics screening coupled with quantitative phosphoproteomics identify MASTL kinase as a survival vulnerability specific of chemotherapy-resistant PCa cells. Mechanistically, MASTL upregulation is driven by transcriptional rewiring mechanisms involving the non-canonical transcription factors androgen receptor splice variant 7 and E2F7 in a circuitry that restrains deleterious CIN and prevents cell death selectively in metastatic therapy-resistant PCa cells. Notably, MASTL pharmacological inhibition re-sensitizes tumors to standard therapy and improves survival of pre-clinical models. These results uncover a targetable mechanism promoting high CIN adaptation and survival of lethal PCa.

Competition between populations: preventing domination of resistant population using optimal control

Emergence of pesticide-resistant strains of pests, antibiotic-resistant bacteria or chemotherapy-resistant tumor cells is a major obstacle standing in the way of effective external control of undesirable growth of these populations. Once the resistant subpopulation becomes dominant the means to control the population are effectively lost. Prevention of resistance may be therefore considered one of the optimal control goals to ensure long-term controllability.In this paper we formulate nonlinear optimal control problem motivated by the question of controlling the growth of two coexisting subpopulations representing two phenotypes of the same species. However, the model we consider is a standard competition model with populations following logistic growth, and therefore it is more general and can be used also when two competing populations are taken into account. We consider a situation when the control (e.g. pesticide or drug) has effect only on the specimen belonging to one (sensitive) population while having no effect on the other (resistant) population. We use a non-standard, nonlinear objective functional in which, aside from penalizing the overall size of both populations, we include an additional, nonlinear term to ensure that the control-sensitive population remains the dominant one.It is shown how the resistance penalty gives rise to locally-optimal singular controls which are key to achieving the balance between resistant and sensitive populations whenever the subpopulations are similar in terms of the model parameters. Analytic properties of the singular arcs and the structure of optimal control are investigated. Both theoretical and numerical results strongly suggest that the optimal control contains a singular interval.

Combating challenges in CAR-T cells with engineering immunology.

Chimeric antigen receptors (CAR) T cells (CAR-T) mark a significant step towards producing safe and effective personal anticancer treatments. CAR-T strategies engineers the T cells from the patients to allow specific binding to a tumour-specific antigen. CAR-Ts are a second-wave offensive strategy to clear out remaining chemotherapy-resistant tumour cells. Though showing practical antitumor abilities in multiple haematological malignancies and solid tumour cancers, the issues of antigen escape, tumour infiltration/penetration, and toxicity side effects limit the usage of prolonged CAR-T therapies. However, engineering immunology has exploited human stem cell-based CAR-T therapies and the development of CAR-M (macrophage) therapies to combat the disadvantages of conventional CAR-T therapies. In this review, we will highlight the challenges of CAR-T therapies and combat them with engineering immunology for cancer immunotherapy.

Subpathway Analysis of Transcriptome Profiles Reveals New Molecular Mechanisms of Acquired Chemotherapy Resistance in Breast Cancer.

Simple SummaryThe use of diverse omics platforms and small sample sizes in current studies of cancer chemoresistance limits consensus regarding the molecular mechanisms underlying chemoresistance and the applicability of those study findings. We built transcriptome data for chemotherapy-resistant breast cancer samples for two cohorts and conducted pathway and subpathway analyses that revealed the activation of several molecular pathways associated with chemoresistance in Cushing’s syndrome, human papillomavirus infection, proteoglycans in cancer, fluid shear stress, and focal adhesion that have not been reported in the resistance of breast cancer to chemotherapy. However, analysis of a subset of triple-negative breast cancer samples revealed activation of the identical chemoresistance pathways.Chemoresistance has been a major challenge in the treatment of patients with breast cancer. The diverse omics platforms and small sample sizes reported in the current studies of chemoresistance in breast cancer limit the consensus regarding the underlying molecular mechanisms of chemoresistance and the applicability of these study findings. Therefore, we built two transcriptome datasets for patients with chemotherapy-resistant breast cancers—one comprising paired transcriptome samples from 40 patients before and after chemotherapy and the second including unpaired samples from 690 patients before and 45 patients after chemotherapy. Subsequent conventional pathway analysis and new subpathway analysis using these cohorts uncovered 56 overlapping upregulated genes (false discovery rate [FDR], 0.018) and 36 downregulated genes (FDR, 0.016). Pathway analysis revealed the activation of several pathways in the chemotherapy-resistant tumors, including those of drug metabolism, MAPK, ErbB, calcium, cGMP-PKG, sphingolipid, and PI3K-Akt, as well as those activated by Cushing’s syndrome, human papillomavirus (HPV) infection, and proteoglycans in cancers, and subpathway analysis identified the activation of several more, including fluid shear stress, Wnt, FoxO, ECM-receptor interaction, RAS signaling, Rap1, mTOR focal adhesion, and cellular senescence (FDR < 0.20). Among these pathways, those associated with Cushing’s syndrome, HPV infection, proteoglycans in cancer, fluid shear stress, and focal adhesion have not yet been reported in breast cancer chemoresistance. Pathway and subpathway analysis of a subset of triple-negative breast cancers from the two cohorts revealed activation of the identical chemoresistance pathways.

Neoadjuvant Systemic Therapies in Bladder Cancer

Muscle-invasive bladder cancer (MIBC) is often framed as a systemic disease given the risk of occult metastases and clinical under-staging at the time of radical cystectomy. The current standard of care for non-metastatic MIBC combines a cisplatin-based neoadjuvant chemotherapy regimen followed by radical cystectomy, pelvic lymph node dissection, and urinary reconstruction. Other systemic therapies initially developed for the metastatic setting are being explored in the neoadjuvant space with favorable clinical outcomes. Immune checkpoint inhibitors targeting the programmed cell death-1/ligand-1 (PD-1/PD-L1) axis have demonstrated promising outcomes for cisplatin-ineligible patients in the neoadjuvant setting. Other novel targeted therapies under investigation in the perioperative setting include fibroblast growth factor receptor or FGFR inhibitors and antibody drug conjugates (enfortumab vedotin targeting Nectin-4 and sacituzumab govitecan targeting Trop-2). Non-chemotherapy-based treatments have the potential to expand the application of neoadjuvant therapy for many patients, particularly those who are cisplatin-ineligible due to comorbidities or who harbor chemotherapy-resistant tumors. The expansion of neoadjuvant therapy options also provides an opportunity to characterize mechanisms of tumor resistance and elucidate tumor biology with ongoing correlative studies.