Development Of Drug Resistance Research Articles

Abstract 571: CRISPR/Cas9 screening identifies the proteasome subunit PSMC6 as key for the survival of cisplatin-resistant ovarian carcinoma cells

Abstract Ovarian carcinoma is a disease with poor prognosis, due to delays in diagnosis and the development of drug resistance. Since deregulation of the ubiquitin proteasome system may contribute to the development of drug resistance, the aim of this study was to investigate the interplay between expression of proteasome subunits and cisplatin resistance by utilizing a CRISPR/Cas9 dropout screen. Paired cisplatin-sensitive and -resistant cells (IGROV-1 and IGROV-1/Pt1) were transfected with Cas9 and transduced with gRNAs against proteasome components. Cells were collected at early (day 4) and late (day 21) time exposure and sequenced to identify genes necessary for survival. Various proteasome subunits were found to be essential for the survival of cisplatin-resistant ovarian carcinoma cells, including PSMA5, PSMC6, PSMD7, PSMD12 and PSMD14. Since PSMC6 knockout produced the greatest growth inhibitory effects, it was selected for functional studies utilizing conventional RNA interference. When IGROV-1 and IGROV-1/Pt1 cells were transfected with small interfering RNAs (siRNAs) targeting PSMC6, efficient down-regulation on the mRNA and protein level was observed. Phenotypic analyses of PSMC6 knockdown cells indicated reduced clonogenicity using both 2D and soft agar assays in parental and resistant cells associated with down-regulation of the canonical MAPK pathway. A slight but not significant increase in sensitivity to cisplatin was observed upon PSMC6 silencing in resistant cells using clonogenic assays. Finally, we carried out a pilot study using ovarian carcinoma specimens (n = 134) obtained through the institutional biobank. The samples were representative of the frequency occurrence of the various histological ovarian carcinoma subtypes. We found that PSMC6 expression, evaluated by qRT-PCR, was associated with tumor stage. These findings suggest that PSMC6 is linked to ovarian carcinoma aggressiveness and that PSMC6 targeting may be an interesting therapeutic strategy. Citation Format: Matteo Costantino, Padraig D'arcy, Luca Mirra, Cristina Corno, Giovanni L. Beretta, Johannes Gubat, Pietro Pratesi, Chiara M. Ciniselli, Paolo Verderio, Stig Linder, Paola Perego. CRISPR/Cas9 screening identifies the proteasome subunit PSMC6 as key for the survival of cisplatin-resistant ovarian carcinoma 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 571.

Abstract 5651: Personalized transcriptomic profiling for advanced prostate cancer: Guiding second-generation hormonal drug selection

Abstract Introduction: Second-generation hormonal drugs have demonstrated significant efficacy in extending the survival of patients with advanced prostate cancer. These drugs operate through two distinct molecular mechanisms: inhibition of androgen biosynthesis and blockade of the androgen receptor. However, due to concerns of side effects, concurrent usage of multiple drugs is not recommended. A notable challenge is the eventual development of drug resistance, rendering all second-generation hormonal therapies ineffective. Currently, there is a lack of guidelines for helping patients choose the most suitable drug. In the context of pharmacogenomics, genetic differences can influence drug susceptibility and efficacy, with variations in genomic sequences and regulatory mechanisms impacting drug response at the transcriptional and translational levels. Considered the rapid processing capabilities of Affymetrix transcriptomic microarrays, we hypothesized that distinct gene signatures in patients who respond well or poorly to second-generation hormonal drugs could be identified and could act as a companion diagnostic tool. Methods: We enrolled 180 advanced prostate cancer patients, who fulfilled Taiwan national health insurance criteria of using second-generation hormonal drugs, from seven medical centers or regional hospitals in Taiwan at 3 time points: prior to drug administration, 3 months after treatment started and drug resistance developed. The RNA expression data and clinical parameters were analyzed, and classification models were built using IPA and R. Good or poor responders were defined by 3-month prostate-specific antigen (PSA) lowered by 90 percent. Results:: Differential expression and enrichment analyses post-treatment highlighted the activation of NF-kappa B signaling and various immune cell pathways. Notably, pathways related to primary immunodeficiency and IL-17 became prominent following the development of drug resistance. At the initial stages, distinct alterations in cell cycle pathways, particularly G1/S and G2/M, were observed between good and poor responders. This was elucidated through principal component analysis and subsequent dbscan clustering. To further distinguish between these responder groups, we utilized an integrative approach for feature selection, combining support vector machine, random forest classifier, and lasso regression. Despite the innovative approach, the model's error rate stood at approximately 15%, attributed mainly to the limited number of cases. Conclusion: Our study highlights the potential of using transcriptomic analysis to predict responses to second-generation hormonal drugs in advanced prostate cancer, paving the way for personalized treatment strategies. However, the need for larger cohort studies is evident to refine these predictive models and enhance their accuracy. Citation Format: Li-Hsin Chang, Hao-Han Chang, Xin-Yi Lin, Shu-Chi Wang, Chih-Pin Chuu, Deng-Neng Chen, Shu-Pin Huang, Chia-Yang Li. Personalized transcriptomic profiling for advanced prostate cancer: Guiding second-generation hormonal drug selection [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 5651.

Abstract 1678: Docetaxel induces Rac1 and Cdc42 Rho GTPase activation in prostate cancer cells

Abstract Prostate cancer (PCa) is a major health burden that affects the quality of life of men worldwide. In the United States, PCa is the second leading cause of mortality among cancers that affect men. Treatment of advanced PCa aims to suppress androgen signaling and proliferation in cancer cells using anti-androgens and chemotherapy. However, the development of drug resistance is a major limitation to curing advanced prostate cancer and strategies to block mechanisms of therapy resistance would enhance treatment efficacy and potentially improve patient prognosis. Cdc42 and Rac1, members of the family of Rho GTPases, have been associated with the progression of different types of hormone-associated cancer, such as breast, ovary, and prostate, among others. The current study was designed to evaluate the role of Cdc42 and Rac1 in chemoresistant prostate cancer cells, including under castration-resistant and androgen-independent conditions. We did not observe significant differences in active (Rac-GTP) or total Rac1 levels in chemoresistant compared to parental PC3 or DU145 cells; similar findings were observed for Ccd42. Treatment of drug-naïve cells with a sublethal dose of docetaxel (10uM) induced gradual increases in Rac1-GTP up to 30 minutes in 22rv1, 60 minutes in LNCaP and DU145, and 24 hours in PC3 cells. Cdc42-GTP levels also increased with subacute docetaxel treatment up to 24 hours in 22rv1 and DU145. Chemoresistant 22rv1, PC3, and DU145 exhibited similar sensitivity to Rac1 and Ccd42 inhibitors including MB1-167, MBQ-168, EHop-097, with an IC50 of about 1uM for each compound and line. Ongoing studies are evaluating the role of these Rho-GTPases in 3-dimensional growth and survival. Citation Format: Andrea Paola López González, Jessica Colón González, María C. Santa María Fuentes, Surangani Dharmawardhane, Carlos J. Diaz Osterman. Docetaxel induces Rac1 and Cdc42 Rho GTPase activation in prostate 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 1678.

Abstract 5842: An epigenetic program that links oncogenic signaling to mitochondrial biogenesis supports leukemic cell survival in chronic lymphocytic leukemia

Abstract Therapeutic inhibition of BCR signaling using Bruton tyrosine kinase inhibitors (BTKis) has remarkable efficacy in the treatment of chronic lymphocytic leukemia (CLL). However, the efficacy of BTKis is limited by the development of drug resistance, which can be mediated through mutations in genes encoding proteins of BCR signaling pathways. Approaches targeting the BCR mutant proteins have been limited by the large heterogeneity of these mutations. In addition, BCR signaling mutations are only detected in up to two-thirds of the CLL patients who progressed with BTKi treatment, suggesting mechanisms beyond genetic mutations. We previously showed that the BCR signaling pathway impacts the chromatin landscapes of CLL B cells (Wang et al., Blood Cancer J. 2022), suggesting that epigenetic mechanisms are exploited by CLL B cells to support their survival. To gain insights into the epigenetic regulation of BTKi treatment in CLL B cells, we analyzed the genome-wide chromatin accessibility (ATAC-seq) and histone modification (H3K4me1, H3K4me3, H3K27ac, H3K27me3) profiles (CUT&Tag) of leukemic cells from 4 CLL patients on BTKi ibrutinib treatment in a sequential fashion (i.e., baseline, on ibrutinib treatment, and at relapse). We also performed the same analysis in a CLL cohort at two stages of ibrutinib treatment (baseline and while on treatment, n=20). Our studies showed that suppressing BCR signaling by BTKi leads to the downregulation of genes associated with mitochondrial translation, a key process of mitochondrial biogenesis. We also found decreased chromatin accessibility and H3K27ac deposition at the promoters of these MT genes. Interestingly, in patients who experienced disease progression on ibrutinib, there was a restoration of MT gene expression, chromatin accessibility, and H3K27ac levels at the MT gene promoters similar to baseline samples, suggesting an epigenetic-regulated MT both in BTKi treatment naïve and relapsed CLL patients. Importantly, MT inhibition led to a decreased survival of primary CLL B cells. These findings point toward an epigenetic mechanism utilized by BCR signaling to promote MT and leukemic cell survival. We then observed that the transcription factor NRF1 is enriched at the MT promoter in CLL B cells. CRISPR-mediated depletion of NRF1 led to reduced mitochondrial translation and cell survival in BCR signaling active malignant B cell lines and primary CLL B cells. These results suggest that NRF1 controls an epigenetic program linking BCR signaling to control MT, which in turn supports BCR signaling-dependent CLL B cell survival. Our findings demonstrated that BCR signaling utilizes epigenetic mechanisms that regulate mitochondrial metabolism to enhance cell survival in both treatment naïve and BTKi-relapsed CLL. These findings may provide new therapeutic directions for untreated and BTKi-relapsed CLL patients. Citation Format: Olivia M. Depies, Sutapa Sinha, Sameer Parikh, Neil Kay, Zhiquan Wang. An epigenetic program that links oncogenic signaling to mitochondrial biogenesis supports leukemic cell survival in chronic lymphocytic leukemia [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 5842.

Abstract 678: Experimental therapy of triple negative breast cancer with next-generation of MDM2 inhibitors

Abstract Patients with triple-negative breast cancer (TNBC) typically experience minimal benefits from the existing hormonal or trastuzumab-based therapies, necessitating reliance on chemotherapy as the predominant treatment approach, which, unfortunately, is limited by insufficient efficacy, significant side effects, and the development of drug resistance. These issues highlight an urgent demand for the discovery and development of more effective and safer therapeutics for TNBC. Overexpression and amplification of the MDM2 oncogene frequently occur in TNBC, which is associated with invasive and high-grade/late-stage tumors, metastasis, and recurrence, and is an independent negative prognostic factor for TNBC patients. Extensive studies have indicated that MDM2 represents a novel molecular target for TNBC. Thus far, multiple strategies aiming at MDM2 inhibition have not succeeded in Phase II-III clinical trials, largely due to factors like inadequate efficacy, significant drug toxicity, and emergence of resistance. In addition, TNBC tumors commonly harbor mutant p53, and the existing MDM2 inhibitors that block p53-MDM2 binding and depend on wild-type p53 expression in the tumor to exert anticancer effects would have little or no clinical responses or even induce resistant clones by increasing MDM2 expression and its oncogenic activity. Therefore, there is a need for developing new-generation MDM2 inhibitors that are p53-independent. We recently discovered a novel class of MDM2 degraders, representing a paradigm shift in the strategy of targeting MDM2. One of these analogs, WW68, was identified as a potent and selective MDM2 inhibitor. Its in vitro and in vivo anti-breast cancer activities and underlying mechanisms of action were evaluated in breast cancer cell lines with various p53 backgrounds. Our results demonstrate that WW68 effectively induces MDM2 protein degradation. It selectively inhibits breast cancer cell growth, decreases cell proliferation, and induces G2/M phase arrest and apoptosis in breast cancer cells, regardless of p53 status. Notably, in clinically relevant TNBC PDX models, WW68 inhibited MDM2 and suppressed tumor growth without causing host toxicity. In conclusion, WW68 represents a new class of MDM2 inhibitor that exerts its anticancer activity through directly down-regulating MDM2, and may be developed as a novel anti-TNBC therapeutic agent. (Supported by NIH R01CA214019 and R01CA240447; and DoD W81XWH2010011) Citation Format: Wei Wang, Hao Chen, Yang Xie, Sayantap Datta, Wei Li, Ruiwen Zhang. Experimental therapy of triple negative breast cancer with next-generation of MDM2 inhibitors [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 678.

Abstract 1225: Novel cellular barcoding to dissect melanoma heterogeneity and drug resistance

Abstract Melanoma is the most common cause of death in skin cancer. While the development of targeted therapies (MAPK pathway inhibitors) led to a substantial improvement in overall survival of patients with melanoma harboring the BRAFV600E mutation, approximately 40% of treated patients acquire resistance and experience tumor recurrence after one year. Melanoma drug resistance is mediated by drug-tolerant persister (DTP) cell subpopulations present in tumors. DTP cells are either intrinsically rare sub-populations pre-existing prior to therapies, or adaptive sub-populations that acquire genetic and epigenetic alterations during treatments. Our lab has established six PDX models that responded to the treatment of BRAF/MEK inhibitor combination then relapsed in six to 40 weeks. We combined cell lineage barcoding and single-cell transcriptomics to trace the emergence of DTP cells in melanoma recurrence. The recent development of cellular barcoding facilitates the labelling of tens to millions of cancer clones and enables the identification of the complex mechanisms associated with clonal fate in response to therapy and in different microenvironments. We have constructed a library of approximately 15 million barcodes into a lentiviral vector. Melanoma cells were infected with the barcode library to ensure each cell carried a unique barcode. Labelled melanoma cells were injected into NSG mice, which were then treated with BRAF/MEK inhibitors, and they developed drug resistance with prolonged treatments. Treated tumors were harvested at different timepoints until relapse. The barcodes are localized close to the polyA tail of the expressed mRNA, the 3’ end sequence of which could be retrieved simultaneously through single-cell RNA sequencing (scRNAseq). Thus, we can trace the clonal information from the relapsed tumor back to earlier timepoints such as the treatment naive tumor and minimal residual disease (MRD) stage. Our data showed that the diversity of barcodes in MRD stage had no significance compared to treatment naive tumor, while the diversity of barcodes in the relapsed tumor decreased around 10-fold from the MRD stage. The most dominant sub-populations in MRD arose from minor sub-populations in the treatment naive tumor, while most of the dominant sub-populations in the relapsed tumor were daughter cells from minor sub-populations in MRD stage. The top three sub-populations dominated 25% of the relapsed tumor. The three dominant drug-resistant sub-populations shared a similar phenotype shown by scRNAseq clusters. The data indicate that the heterogeneity of melanoma is maintained in the early treatment stage but is lost in acquired resistance. And the lineages of DTP cells change continuously under prolonged BRAF/MEKi drug pressure. Citation Format: Haiyin Li, Yeqing Chen, Jessica Kaster, Nazifa Promi, Meenhard Herlyn. Novel cellular barcoding to dissect melanoma heterogeneity and drug resistance [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 1225.

Abstract 297: Role of purine metabolism in CLL cell pathobiology and CLL disease progression

Abstract The treatment of Chronic lymphocytic leukemia (CLL) has been revolutionized in recent years, however CLL is still incurable, and the leukemic cells often develop drug resistance. Previous studies show that the interaction of CLL cells with the bone marrow (BM) microenvironment promotes spontaneous and drug induced survival. But the nature of this interaction is still in need of a full understanding. To pursue this we discerned RNA profiles using RNA-seq in paired CLL cells isolated from untreated blood and BM (n=6) and in untreated patients CLL cells (n=4) cultured alone or cocultured with BM stromal cells (BMSCs). CLL cells from blood/BM and CLL cells cultured alone or with BMSCs were examined by Western blot (WB), untargeted metabolomics (LCMS+GCMS) and preclinical drug sensitivity assays. We found upregulation of 232 genes in CLL cells from BM vs the paired blood and 917 genes in cocultured CLL cells compared to CLL cells cultured alone (p&lt0.05, fold change &gt1.5). Here we detected only 13 genes that overlap between BM and cocultured CLL cells. When we analyzed the expression of these 13 genes in blood CLL cells from a cohort of 162 untreated patients by RNA-seq we found a positive relationship between 4 (PNP, C16orf54, MOB3A, CDK2AP2) with CLL patient clinical outcome including overall survival (OS), progression free survival (PFS), and time to first treatment (TTFT) [multivariable Cox proportional hazards models, p&lt0.05]. Out of the 4 genes, purine nucleoside phosphorylase (PNP), an enzyme in the purine salvage pathway, showed the most significant association for patient’s OS, PFS, and TTFT. Metabolomic profiling indicated an increased level of purine salvage pathway metabolites adenosine, inosine, and hypoxanthine in cocultured CLL cells. WB analysis using blood CLL cells from untreated patients showed a variable PNP protein expression (high, low/no PNP) and induction in PNP protein levels were found in blood CLL cells expressing low/no PNP only when in contact with BM/BMSCs. But PNP inhibitor forodesine did not show any significant killing in high vs low/no PNP group. When we treated CLL cells from untreated patients with Bcl2 inhibitors venetoclax, S55746 and LP-118 (Bcl-2/Bcl-xl inhibitor, Newave), CLL cells showed increasing sensitivity to the Bcl2 inhibitors associated with their PNP expression (high&gtlow&gtno PNP). But a covalent and non-covalent BTKi LP-168 (Newave) cultured with CLL cells showed no difference in drug sensitivity associated with CLL PNP levels. In contrast CLL cells when treated with both venetoclax and LP-168, showed more drug sensitivity in the high PNP expressing CLL cells vs low/no PNP. These results indicate that active purine metabolism in CLL cells can contribute to differential novel agent drug responses of CLL patients. Future studies to understand the exact mechanism of how PNP relates to this differential drug sensitivity should be instructive in regard to alternate maneuvers to treat CLL. Citation Format: Sutapa Sinha, Weiguo Han, Zhiquan Wang, Kari G. Rabe, Susan L. Slager, Chantal E. McCabe, Daniel R. O'Brien, Sameer A. Parikh, Esteban Braggio, Yi Chen, Fenlai Tan, Stephen P. Anthony, Yu Chen, Bing Dai, Yue Shen, Neil E. Kay. Role of purine metabolism in CLL cell pathobiology and CLL disease progression [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 297.

Abstract 4528: Improving carboplatin therapy: A novel albumin-targeted platinum(IV) prodrug with superior anticancer activity in vivo

Abstract Platinum(II)-based chemotherapeutics are among the most commonly used anticancer drugs and are part of nearly every second treatment scheme. However, they lack in tumor specificity, causing severe sides effects, dose-dependent toxicity as well as drug resistance development. Due to their higher tolerability, platinum(IV) prodrugs are currently in the focus of interest. However, comparable to their platinum(II) counterparts, they show insufficient tumor accumulation and are frequently prematurely activated. A promising strategy to improve tumor targeting of anticancer drugs is to exploit the enhanced consumption and accumulation of albumin in the malignant tissue. Thus, we developed a new albumin-targeted maleimide-containing platinum(IV) prodrug, which releases carboplatin in a highly tumor-specific manner. The maleimide moieties enable the drug to selectively bind the endogenous albumin via its free thiol of cysteine 34. The aim of this study was to in-depth characterize the pharmacological behavior and anticancer activity in vivo of the new prodrug. To this end, several xenograft and allograft experiments were performed. To investigate tissue distribution and pharmacokinetics serum, urine, tumor and organ samples of mice were collected after drug treatment and were evaluated by (size-exclusion chromatography) inductively-coupled plasma mass spectrometry and immunohistochemistry (e.g cleaved caspase-3). These experiments revealed that the new prodrug fast and selectively binds to the serum albumin after intravenous injection, leading to an enhanced plasma half-life and an increased tumor accumulation in comparison to its corresponding platinum(II) drug carboplatin. Additionally, the new complex resulted in superior anticancer activity and prolonged overall survival based on the distinctly improved pharmacokinetic profile and enhanced apoptosis induction. In conclusion, these data support that albumin binding is a potent tool to increase the tumor specificity of platinum(IV) drugs and prevent their premature activation in other body compartments. Consequently, this very promising prodrug will be further developed towards clinical phase I testing. Citation Format: Hemma Schueffl, Regina Weinmuellner, Nadine Sommerfeld, Bernhard K. Keppler, Walter Berger, Christian R. Kowol, Petra Heffeter. Improving carboplatin therapy: A novel albumin-targeted platinum(IV) prodrug with superior anticancer activity in vivo [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 4528.

Development of a field diagnostic tool for Schistosoma mansoni Praziquantel resistant markers in selected endemic communities

Schistosomiasis is a neglected tropical disease that affects more than 200 million people and 45% of infections have been shown to occur in school-aged children. A large percentage of the disease burden lies in Africa. In 2012, the WHO outlined a roadmap for the elimination of schistosomiasis by 2020; however, this was not achieved. Treatment for schistosomiasis is by the use of Praziquantel, a drug in use for over 30 years and there is a concern for emerging drug resistance. There are several species of the genus Schistosoma causing infection in humans. For this study, Schistosoma mansoni which causes intestinal schistosomiasis will be investigated. There are reports of lowering cure rates and suboptimal response to praziquantel following several cycles of mass drug administration (MDA). Praziquantel resistance has also been reported in some countries and laboratory-bred schistosome experiments. To address the concerns of resistance, this study aims to employ a two-part approach to assess the prevalence of S. mansoni. praziquantel resistance amongst school-aged children in schistosomiasis endemic communities in Ghana and develop a diagnostic tool to aid in field assessment of infections. To achieve this, the study will attempt to answer the following research questions: 1. Is there developing S. mansoni praziquantel resistance in communities that have undergone several mass drug administrations? 2. Is there an interplay between intermediate host exposure to praziquantel and the development of praziquantel drug resistance in the definitive host?

Abstract 5598: Combined loss of the chromosome 7 genes CUX1 and EZH2 promotes chemotherapy resistance

Abstract Monosomy 7 (-7) or del(7q) are recurrent in high-risk myeloid neoplasms, including up to 50% of myeloid neoplasms arising after prior exposure to chemotherapy and/or radiation. Although putative chromosome 7 tumor suppressor genes have been identified, the effects of combinatorial 7q gene loss remain unclear. A barrier to understanding the pathogenesis of -7/del(7q) is the challenge of modeling aneuploidy in animal models. To address this knowledge gap, we established an in vivo model of del(7q) clonal hematopoiesis and drug resistance using multiplex CRISPR-Cas9 to simultaneously target four 7q genes (Cux1, Ezh2, Kmt2c, and Kmt2e) in murine hematopoietic stem cells. After chemotherapy exposure, we observe significant myeloid expansion of clones edited for both Cux1 and Ezh2. Compared to the transcriptomes of control or single gene edited cells, Cux1;Ezh2-deficient cells fail to induce DNA damage response pathways after genotoxic stress. Cux1;Ezh2-deficient cells also display reduced deposition of γH2AX after DNA damage, as well as persistent, unrepaired DNA breaks, indicating perturbations to DNA damage recognition and repair. Collectively, our data support the concept of 7q as a contiguous gene syndrome region, in which combined loss of multiple genes drives drug resistance and disease development. This work reveals a genetic interaction between CUX1 and EZH2, and sheds light on how -7/del(7q) contributes to the development and inherent drug resistance characteristic of high-risk myeloid disease. Further, our CRISPR-based approach may serve as a framework for interrogating other recurrent aneuploid events in cancer. Citation Format: Matthew R. Jotte, Angela Stoddart, Tanner C. Martinez, Yuqing Xue, Molly K. Imgruet, Megan E. McNerney. Combined loss of the chromosome 7 genes CUX1 and EZH2 promotes chemotherapy resistance [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 5598.

Abstract 4554: Novel combination therapy for treating proteasome inhibitor-resistant multiple myeloma

Abstract Multiple myeloma (MM) is an incurable plasma cell malignancy characterized by osteolytic bone disease and immunosuppression. Proteasome inhibitors (PIs) have remarkably improved the survival of MM patients, but dose-limiting toxicities and the development of drug resistance limit their long-term utility. Elevated TGF-β levels in MM patient sera correlate with drug resistance, disease progression, metastasis and poor prognosis. Therefore, we evaluated the anti-MM therapeutic potential of a TGF-β type I receptor kinase inhibitor, Vactosertib. In vitro treatment of Vactosertib synergistically inhibited the growth of bortezomib (BTZ)-resistant MM cells in combination with either BTZ or ixazomib (IXZ) by suppressing TGF-β activation of Smad2/3 and expression of PSMB5, which encodes the proteasome 5 catalytic subunit targeted by PIs. Oral administration of Vactosertib as a single agent decreased MM progression and mortality of the mice bearing BTZ-resistant MM. Vactosertib alone also attenuated PSMB5 expression and proteasome activity, reduced the expansion of CD11b+Gr-1+ myeloid derived suppressor cells (MDSCs) in bone marrow (BM) tumor microenvironment (TME), and diminished the population of Foxp3+ regulatory T cells (Treg) in the spleen. Combination therapy of Vactosertib plus PI (BTZ or IXZ) exhibited a synergistic anti-myeloma effect when compared to either Vactosertib or PI alone by greatly prolonged survival and significant a reduction in both MDSCs and Tregs. Furthermore, therapy of BCMA+ CAR T cells in combination with Vactosertib exhibited a synergistic anti-tumor effect, compared to either CAR T cells or Vactosertib. Taken together, our data provide the rationale for clinical evaluation of Vactosertib in MM and demonstrate proof-of-concept that combination of Vactosertib and either PI or cell therapy may overcome drug resistance and enhance durable patient responses. Citation Format: Byung-Gyu Kim, Sung Hee Choi, Huong Nguyen, Fu-Sen Liang, Seong-Jin Kim, John Letterio, Alex Huang. Novel combination therapy for treating proteasome inhibitor-resistant multiple myeloma [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 4554.

Abstract 4382: PKC-ι/ζ signaling is crucial for apoptosis/pyroptosis inhibition and invasiveness of glioblastoma cells through upregulation of β-catenin, PDK1/Akt1 and Smad cascades via 14-3-3

Abstract Glioblastoma (GB) is an aggressive form of brain cancer derived from astrocytes. Poor predictability of patient outcomes has limited the development of current therapeutic treatments of GB mainly due to the development of drug resistance. Comparative over-expression of atypical protein kinase C-iota and zeta (aPKC-ι/ζ) in GB cells and tissue samples were previously reported. This study establishes the downstream effects of PKC-ι/ζ attenuation on key cellular signaling which governs apoptosis, pyroptosis, survival, proliferation and epithelial-mesenchymal transition (EMT). Our data suggested that aPKC knockdown of expression induces apoptosis and works as an antecedent of pyroptosis. Data also suggested that involvement of Akt1 and PDK1 in aPKC maturation process weakened due to aPKC attenuation. aPKC attenuation downregulated Ras/Erk1 and canonical β-catenin pathways which resulted in reduced transcriptional activities of Stat3, c-Myc, c-Jun and β-catenin. In addition SNAIL1, SLUG, and PRRX1 were diminished that have been known to stimulate EMT. Proteins 14-3-3 and Smad2/3 acted as molecular adaptors between these pathways. A PKC-ι specific inhibitor 5-amino-1-(2,3-dihydroxy-4-(hydroxymethyl)cyclopentyl)-1H-imidazole-4-carboxamide (ICA-1S) and a PKC-ζ specific inhibitor 8-hydroxy-1,3,6-naphthalenetrisulfonic acid (ζ-Stat) were used to conduct in-vivo experiments using mouse models. Intravenous and oral administration of ICA-1S resulted in the reduction of tumor growth by approximately 30% in athymic nude mice for U-87 xenografts. Taken together, these results suggest that not only do aPKCs play a central role in GB progression, invasiveness, and cell survival, but that effective therapeutics can be developed to specifically target oncogenic aPKCs. Citation Format: Luke Lajmi, Wishrawana S. Ratnayake, Khandker M. Khalid, Sloan Breedy, Aaron Todman, Tracess Smalley, Christopher A. Apostolatos, Robert Hill, Mildred Acevedo-Duncan. PKC-ι/ζ signaling is crucial for apoptosis/pyroptosis inhibition and invasiveness of glioblastoma cells through upregulation of β-catenin, PDK1/Akt1 and Smad cascades via 14-3-3 [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 4382.

Abstract 3167: Impact of gemcitabine modification on redox-driven responses in pancreatic cancer organoids cultured in distinct 3D microenvironments

Abstract Pancreatic ductal adenocarcinoma (PDAC) poses a formidable challenge in oncology, characterized by its high lethality and limited treatment options. The advanced stage at diagnosis, aggressive metastasis, and the constrained efficacy of conventional therapeutic drugs collectively contribute to the grim prognosis associated with PDAC. Gemcitabine, a nucleoside analog and the longstanding standard chemotherapy for pancreatic cancer, encounters a significant hurdle in its efficacy due to the development of resistance. To establish a cancer-acquired resistance model applicable to Gem-modified drugs, it is crucial to account for the dense extracellular matrix (ECM) composition characteristic of PDAC. In this investigation, we employ three-dimensional (3D) cell culture models, specifically utilizing pancreatic cancer patient-derived organoids (PDOs) within a 3D matrix with tunable density and stiffness by incorporating variations in transglutaminase crosslinking rates. PDAC cells from different patients exhibit diverse adaptations within these altered gel matrix environments, manifesting differences in morphology, doubling time, and responses to drugs. Notably, PDAC cells display pronounced stemness characteristics in the dense matrix, featuring a more rounded and compact appearance and an increase in ABC transporters.Addressing the challenge of gemcitabine resistance, modifications such as gemcitabine conjugates with stearate (Gem-S) have shown promise in preclinical studies. Exploring the effects of both Gem and Gem-S in a viscoelastic-specific ECM model derived from PDAC patient-derived organoids, distinct responses based on matrix stiffness come to light. The physical properties of the matrix exert a significant influence on cellular function, thereby impacting the effectiveness of therapeutic agents. Intriguingly, within a stiffer environment, Gem-S demonstrates higher sensitivity compared to Gem, suggesting the potential application of Gem-S in the dense pathological PDAC environment. Further investigation reveals that Gem-S treatment induces a noteworthy increase in reactive oxygen species (ROS) and HIF-1 expression compared to Gem. Surprisingly, the role of multidrug transporters in Gem-S sensitivity is limited, while the downregulation of NRF (Nrf2) after Gem-S treatment hints at distinct mechanisms underlying the development of drug resistance. This study provides valuable insights into the intricate interplay between gemcitabine resistance and the PDAC microenvironment. Understanding the matrix-specific responses opens avenues for tailored therapeutic interventions, offering the potential for improved outcomes in PDAC patients. Citation Format: Bo Han, Shuqing Zhao, Edward Agyare, Xueyou Zhu, Jose Trevino, Sherise Rogers, Enrique Velazquez, Jason Brant, Payam Eliahoo, Jonathan Barajas, Ba Xuan Hoang. Impact of gemcitabine modification on redox-driven responses in pancreatic cancer organoids cultured in distinct 3D microenvironments [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 3167.

Abstract 2989: MicroRNA profiling in human samples and cell lines uncovers eight key players in the cisplain resistance of HGSOC

Abstract Metastasis and drug resistance remain significant contributors to cancer-related mortality globally. In ovarian cancer, a substantial 70% of cases develop resistance to the front-line therapy, cisplatin. Despite numerous proposed mechanisms for cisplatin resistance, the complete molecular events leading to this phenomenon in ovarian cancer remain incompletely understood. Mounting evidence suggests that dysregulation of microRNAs (miRNAs) plays a pivotal role in carcinogenesis, including the development of drug resistance. While various miRNAs have been identified in ovarian cancer samples and cell lines, few studies have compared miRNA expression in human paraffin ovarian samples and cisplatin-resistant high-grade serous ovarian cancer (HGSOC), the most prevalent and malignant of gynecological malignancies. This study aimed to identify key miRNAs implicated in cisplatin resistance. We performed miRNA expression profiles in RNA isolated from human paraffin ovarian tumors and ovarian cancers cell lines. Eight miRNAs were commonly increased in paraffin samples and cisplatin resistant ovarian cancer cells. Targeting these miRNAs with inhibitors significantly reduced cell proliferation by more than 50% for miR-203a, miR-96-5p, miR-10a-5p, miR-141-3p, miR-200c-3p, and miR-182-5p, and to a lesser extent, miR-296-5p and miR-1206. Inhibitors demonstrated a reduction in cell migration for all targets except miR-200c-3p and miR-10a-5p. Analysis of online databases, literature reports, and molecular pathway construction revealed that these eight miRNAs regulate key molecular pathways associated with cell proliferation, primarily through PTEN regulation in cisplatin-resistant HGSOC cells. Interrogation of the KM plotter patient database revealed that high expression of miR-1206, miR-10a, miR-141, and miR-96 correlates with a poor prognosis in ovarian cancer patients. These findings position these eight miRNAs as potential therapeutic targets and markers for cisplatin response in ovarian cancer therapy. Citation Format: Mariela Rivera-Serrano, Marienid Flores, Jose Rolon, Victor Reyes, Fatma Valiyeva, Pablo E. Vivas-Mejia. MicroRNA profiling in human samples and cell lines uncovers eight key players in the cisplain resistance of HGSOC [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 2989.

Abstract 1214: Investigating therapeutic strategies to promote immune rejection of KRASG12C inhibitor-resistant subpopulations in lung cancer

Abstract Oncogenic KRAS signaling not only promotes progression and survival of cancer cells, but it can also play a major role in suppressing anti-tumor immunity through several mechanisms, including secretion of cytokines, reduction of antigen presentation and suppression of tumor-intrinsic interferon responses. Consequently, treatment with KRASG12C inhibitors alleviates oncogenic KRAS driven immune suppression, resulting in a profound remodeling of the tumor microenvironment (TME). In immunogenic mouse models, these changes can lead to the generation of some complete responses which are dependent on the engagement of the immune system. In this project we aim to investigate whether the induction of immune responses triggered by KRASG12C inhibition can effectively target inhibitor-resistant subclones. To achieve this, we mimic the development of drug resistance by combining reporter-traced isogenic KRASG12C and KRASG12D mutant lung cancer cells, where the KRASG12D mutant cells are inherently resistant to KRASG12C inhibitors. Growth of resistant cells was monitored via in vivo luciferase imaging and end point flow cytometry. KRASG12C inhibition as monotherapy, either with the active-state KRASG12C inhibitor RMC-4998 or the inactive-state inhibitor adagrasib, led to a proliferative advantage of the drug-resistant subpopulation, suggesting that any immune response to KRASG12C inhibition in the bulk tumor population was insufficient to target the resistant cell subclones. To investigate if immune mediated elimination of resistant cells could be achieved using combinations, we assessed two strategies commonly evaluated in clinical trials with KRASG12C inhibitors: anti-PD1 blockade and SHP2 inhibition. Of note, KRASG12D mutant cells do not respond to these therapies when grown subcutaneously. Treatment of RMC-4998 in combination with either anti-PD1 or the SHP2 inhibitor RMC-4550 was able to induce complete eradication of both KRASG12C and KRASG12D mutant lung cancer cells, despite the resistant cells being insensitive to these therapies when treated in the absence of sensitive cells. Furthermore, both combinations induced immune memory towards the resistant cells. These long-term effects were dependent on the immune system as they were not observed in immune deficient mice. Immune profiling of treated tumors revealed that both combinations can result in a more profound remodeling of the TME and potentiate the immune responses. Overall, our preclinical results demonstrate that the anti-tumor responses generated by the combination of KRASG12C inhibitors with SHP2 inhibition and/or immune checkpoint blockade can result in the bystander immune mediated killing of subclones of KRASG12C inhibitor resistant cells, providing a paradigm for the development of therapeutic combinations that may be more able to counter the development of inhibitor resistance. Citation Format: Mona Tomaschko, Christopher Moore, Claire E. Pillsbury, Kangbo Ng, Sophie de Carne, Sareena Rana, Andrea de Castro, Panayiotis Anastasiou, Miriam Molina-Arcas, Julian Downward. Investigating therapeutic strategies to promote immune rejection of KRASG12C inhibitor-resistant subpopulations in lung cancer [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 1214.

Abstract 3262: Elucidating the mechanism of resistance to tyrosine kinase inhibitors in ROS1-and ALK-fusion non-small cell lung cancer: The role of CD74

Abstract The therapeutic landscape in treating advanced oncogene-mutated non-small cell lung cancer (NSCLC) was revolutionized with the advent of tyrosine kinase inhibitors (TKIs). Despite the efficacious breakthrough and improved patient outcomes, disease progresses once more due to the seemingly inevitable development of drug resistance in tumor cells. This poses a considerable predicament in the clinical management of oncogene-mutated NSCLC and signifies the importance of elucidating the mechanism of resistance in tumor cells that harbor these genomic alterations which give rise to oncogenic drivers. Recent evidence suggests that drug-tolerant persister (DTP) cells, which are tolerant to initial exposure to TKIs give rise to acquired drug-resistant cells. Currently, the mechanism by which tumor cells undergo a drug-tolerant state is not well understood in NSCLCs driven by ALK or ROS1 fusion. Previously, we identified CD74 as a gene that may play a role in a drug-tolerant state in EGFR-mutated lung cancer via single-cell RNA-sequencing (scRNA-seq). Here, we sought to determine whether the CD74 signaling also leads to resistance to TKIs in NSCLCs with ALK or ROS1 fusion. We showed that CD74 expression increased at both the mRNA and protein levels after treatment with respective TKIs in ALK and ROS1 fusion cells lines. Notably, the ALK and ROS1 fusion cell lines also exhibited an increase in mRNA expression levels of upstream and downstream genes of CD74. Additionally, we generated CD74 knock-out and overexpression models in two cells lines, HCC78 (SLC34A2-ROS1 fusion) and H2228 (EML4–ALK fusion), to further examine the role of CD74 expression in DTP cells. We demonstrated that resistance to TKIs were dependent on CD74 expression. Furthermore, it was determined that anti-CD74 antibody-drug conjugates, in combination with TKIs, synergistically induced apoptosis in these cell lines. In conclusion, our data suggest that CD74 can be a therapeutic target in NSCLC with ALK or ROS1 fusion. Citation Format: Vivian Ho, Motohiro Izumi, Meghan Lee, Daisuke Shibahara, Ikei S. Kobayashi, Susumu S. Kobayashi. Elucidating the mechanism of resistance to tyrosine kinase inhibitors in ROS1-and ALK-fusion non-small cell lung cancer: The role of CD74 [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 3262.

Abstract 5838: Un-methylation of NUDT21 promotes the development of enzalutamide resistance in prostate cancer by regulation of 3’UTR usage switch

Abstract Enzalutamide, a second-generation anti-androgen drug, is a new treatment option for castration resistant prostate cancer (CRPC) patient. However, almost all CRPC patients develop drug resistance for enzalutamide after six to twelve months of treatment. According to our current findings, 3'UTR usage switches of RNA transcripts were observed in the prostate cancer specimen after acquiring enzalutamide resistance and nudix hydrolase 21 (NUDT21), an alternative polyadenylation (APA) regulator, was overexpressed in the enzalutamide resistant (EnzaR) cells, suggesting its potential role involved in regulation of 3'UTR usage switch. However, the underlying mechanism of how NUDT21 regulates 3'UTR usage switch during the development of enzalutamide resistance is still unclear. Interestingly, a potential mono-methylation (MME) is identified in NUDT21 protein by us, and it has never been examined before. Thus, we hypothesize that MME of NUDT21 may regulate the specificity of 3'UTR usage switch and involve in the development of EnzaR. To test the idea, a monoclonal antibody recognized NUDT21 MME was generated by us. Moreover, protein arginine methyltransferase 7 (PRMT7) was identified to be responsible for adding MME to NUDT21. In addition, androgen treatment increased both expression levels of NUDT21 MME and PRMT7 while decreased the expression level of NUDT21 total form in LNCaP cells via androgen receptor (AR) dependent manner. Next, co-treatment of enzalutamide and PRMT7 inhibitor leaded to increase of un-MME form of NUDT21 and it greatly enhanced the enzalutamide resistance in LNCaP cells. Importantly, binding profile of NUDT21 total form indeed had 3'UTR usage switch from distal to proximal APA site in COUP-TFII transcript after acquiring enzalutamide resistance, while its MME form attenuated this phenomenon. In addition, expression levels of NUDT21 MME and its total form were shown to conversely express in prostate cancer specimens. Finally, un-MME form of NUDT21 promoted the cancer growth in vitro and in vivo while its MME form did not. Taken together, our results suggest that down-regulation of PRMT7 by enzalutamide may lead to decrease of NUDT21 MME level and contribute to develop enzalutamide resistance by causing the 3'UTR usage switch of NUDT21 downstream transcript. Citation Format: Shin-Chih (Kenny) Lin, Shih-Chieh Lin. Un-methylation of NUDT21 promotes the development of enzalutamide resistance in prostate cancer by regulation of 3’UTR usage switch [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 5838.

Abstract 1337: Characterization of anti-AXL CAR-NK cell therapy for the treatment of melanoma

Abstract AXL is a receptor tyrosine kinase (RTK) that is commonly expressed in metastatic melanoma and several other forms of cancer. Activation of AXL signaling is linked to tumor cell growth, invasion, metastatic transformation, drug resistance, and immune response regulation. However, treatment of metastatic melanoma continues to present clinical challenges due to its capacity to rapidly develop drug resistance, which manifests under the influence of AXL signaling. As such, AXL may be a viable antigen target for immunotherapies. Despite their successes in hematological malignancies, chimeric antigen receptor (CAR)-T cell therapies remain limited by their susceptibility to causing off-target toxicity. In contrast, natural killer (NK) cells are not associated with such risks, which makes them clinically appealing as an alternative to T cells. However, studies on the application of CAR-NK cells to treat solid tumors remain acutely scarce. To explore the clinical viability of CAR-NK cells for the treatment of metastatic melanoma, AXL-specific CAR-NK cells were generated by transfecting NK cells obtained from NK cell lines. Preliminary data from a cytotoxicity assay indicated that the cytotoxicity of CAR-NK92-MI cells against AXL-positive melanoma cell lines was significantly stronger (up to a 10-fold difference) than the corresponding parental cells. Further in vitro characterization of this CAR-NK cell line and other CAR-NK cell lines, as well as in vivo evaluation of their efficacy in a mouse xenograft model of melanoma metastasis, is underway. Citation Format: Winston Hibler, Glenn Merlino, Yan Lin Yu. Characterization of anti-AXL CAR-NK cell therapy for the treatment of melanoma [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 1337.

Relationship between Patients’ Knowledge and Medication Adherence of Tuberculosis at Islamic Hospital Pondok Kopi Jakarta

Background: Tuberculosis (TB) remains a health problem in Indonesia. Currently, the number of new TB cases in Indonesia ranks second after India. Patient compliance in using antituberculosis drugs is critical in achieving successful treatment outcomes, prevent further spread of the bacteria that cause TB and the development of drug resistance. Adherence to taking medication can be influenced by various factors, one of which is the level of knowledge.Objectives: This study was aimed to determine the relationship between the level of knowledge about TB and medication adherence of TB patients at the Jakarta Islamic Hospital Pondok Kopi.Methods: This study was conducted from May to June 2022 with a cross sectional design. The inclusion criteria in this study were TB patients who were over 18 years old, willing to become respondents, and had used antituberculosis drugs for at least one month. The level of knowledge about TB was assessed using a questionnaire and medication adherence was assessed using the MARS-5 questionnaire.Results: The number of respondents in this study was 83 patients. Most patients were male (57.83%), less than 60 years old (83.13%), and had a high school education (53.01%). The results showed that most patients (73.47%) had a good level of knowledge and were compliant with taking medication (77.11%). The level of patient knowledge about TB has a significantly moderate and positive correlation with the level of adherence in taking medication (p 0.001; r 0.517).Conclusion: increasing patients’ knowledge about TB can lead to better patients’ adherence, which may lead to better treatment outcome.

Liver cancer treatment with mitochondrial homeostasis

Systemic treatment, including molecular targeted therapy, immunotherapy, and chemotherapy, is an important means of achieving long-term survival in patients with intermediate-and advanced-stage liver cancer. However, some patients are insensitive to treatment and even develop drug resistance. Mitochondria are the center of cellular energy metabolism and, at the same time, are the priority targets for systemic therapy. Mitochondrial homeostasis plays an important role in the treatment of liver cancer. The relationship between the two advances is elucidated so as to provide better ideas for the clinical treatment of liver cancer.