Mouse Model Of Bladder Cancer Research Articles

Silencing the Mitochondrial Gatekeeper VDAC1 as a Potential Treatment for Bladder Cancer.

The strategy for treating bladder cancer (BC) depends on whether there is muscle invasion or not, with the latter mostly treated with intravesical therapy, such as with bacillus Calmette-Guérin (BCG). However, BCG treatment is unsuccessful in 70% of patients, who are then subjected to radical cystectomy. Although immune-checkpoint inhibitors have been approved as a second-line therapy for a subset of BC patients, these have failed to meet primary endpoints in clinical trials. Thus, it is crucial to find a new treatment. The mitochondrial gatekeeper protein, the voltage-dependent anion channel 1 (VDAC1), mediates metabolic crosstalk between the mitochondria and cytosol and is involved in apoptosis. It is overexpressed in many cancer types, as shown here for BC, pointing to its significance in high-energy-demanding cancer cells. The BC cell lines UM-UC3 and HTB-5 express high VDAC1 levels compared to other cancer cell lines. VDAC1 silencing in these cells using siRNA that recognizes both human and mouse VDAC1 (si-m/hVDAC1-B) reduces cell viability, mitochondria membrane potential, and cellular ATP levels. Here, we used two BC mouse models: subcutaneous UM-UC3 cells and chemically induced BC using the carcinogen N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Subcutaneous UM-UC3-derived tumors treated with si-m/hVDAC1 showed inhibited tumor growth and reprogrammed metabolism, as reflected in the reduced expression of metabolism-related proteins, including Glut1, hexokinase, citrate synthase, complex-IV, and ATP synthase, suggesting reduced metabolic activity. Furthermore, si-m/hVDAC1-B reduced the expression levels of cancer-stem-cell-related proteins (cytokeratin-14, ALDH1a), modifying the tumor microenvironment, including decreased angiogenesis, extracellular matrix, tumor-associated macrophages, and inhibited epithelial-mesenchymal transition. The BBN-induced BC mouse model showed a clear carcinoma, with damaged bladder morphology and muscle-invasive tumors. Treatment with si-m/hVDAC1-B encapsulated in PLGA-PEI nanoparticles that were administered intravesically directly to the bladder showed a decreased tumor area and less bladder morphology destruction and muscle invasion. Overall, the obtained results point to the potential of si-m/hVDAC1-B as a possible therapeutic tool for treating bladder cancer.

Anti-Proliferative Effects of Lidocaine as an Autophagy Inducer in Bladder Cancer via Intravesical Instillation: In Vitro and Xenograft Mouse Model Experiments.

Lidocaine exerts potential anti-tumor effects on various cancer cell lines, and its intravesical instillation is considered safer than intravenous administration for bladder cancer. However, the mechanisms underlying its anti-tumor effects have not been fully elucidated. Here, we aimed to elucidate the anti-tumor molecular mechanisms of lidocaine in bladder cancer cells and a xenograft model to substantiate the efficacy of its intravesical administration. We investigated the anti-proliferative and autophagyinducing activities of lidocaine in Nara Bladder Tumor No. 2 (NBT-II) rat bladder carcinoma cells using cell viability, flow cytometry, a wound healing assay, and western blotting. We also established a xenograft mouse model of bladder cancer, and cancer growth was examined using in vivo bioluminescence imaging. Lidocaine decreased cell viability, induced G0/G1 phase cell cycle arrest, and inhibited cell migration partially via glycogen synthase kinase (GSK) 3β phosphorylation. Moreover, a combination of lidocaine and SB216763 (a GSK3β inhibitor) suppressed autophagy-related protein expression. Bafilomycin-A1 with lidocaine significantly enhanced microtubule-associated protein 1A/1B-light chain (LC3B) expression; however, it decreased LC3B expression in combination with 3-methyladenine compared to lidocaine alone. In the xenograft mouse model, the bladder cancer volume was reduced by lidocaine. Overall, lidocaine exerts anti-proliferative effects on bladder cancer via an autophagy-inducing mechanism.

Abstract 1436: Cancer associated fibroblast dependency in a model of bladder cancer

Abstract Introduction: The relationship between genotype and phenotype in targeted therapy has proven to be crucial for most kinase inhibitors. In bladder cancer, the PI3K/AKT/mTOR pathway is widely activated by mutation but untargeted. Our study focuses on developing an immunocompetent, CRISPR-edited bladder cancer mouse model that mirrors common PI3K/AKT/mTOR mutations. We aim to establish genotype-effective kinase inhibitor pairings using in vitro CRISPR-edited organoids and Cancer Associated Fibroblasts (CAFs) to create a pro-tumorigenic environment in vivo. Methods and Results: Urothelial cells were isolated from the bladder of Rosa26 Lox-Stop-Lox-Cas9/GFP transgenic mice to develop organoids. These organoids were co-edited for Trp53 and Rb1 KO, and further editing of the Pten gene resulted in a nine-fold increase in sensitivity to the kinase inhibitor ipatasertib. Despite successful engraftment into mouse bladder, these edited cells regressed before tumor formation, and intradermal injection did not yield subcutaneous tumors. An alternate model featuring a 9p21 deletion with Trp53 KO also displayed similar regression post-engraftment into bladder or skin. However, co-injection with skin-cancer-derived CAFs subcutaneously yielded palpable subcutaneous tumors that grew for 12 weeks. Enhancing orthotopic model fidelity, we established a BBN bladder-tumor-derived CAF line, leading to the formation of tumors with squamous differentiation upon intramural co-injection with edited organoids. These models displayed immune-excluded architecture and a predominance of M2 over M1 macrophages. Following our accomplishments in establishing bladder tumors, we aimed to enhance our model's adaptability by introducing common PI3K/AKT/mTOR mutations, specifically TSC1/TSC2 KO and Pik3ca hotspots, into our 9p21/Trp53 KO model. While TSC1/TSC2 KO lines exhibited elevated P-S6K signaling, they displayed resistance to Torin 1, Voxtalisib, and Everolimus—kinase inhibitors targeting mTORC1/2. In parallel, we employed CRISPR-mediated HDR to successfully introduce a Pik3ca H1047R hotspot into our 9p21/Trp53 KO model, as evidenced by increased Phosphorylation of AKT compared to wild-type 9p21/Trp53 KO cell lines. Conclusions: Our research establishes the crucial role of CAFs in bladder tumor formation. Our now established customizable model of bladder cancer is suitable for direct targeting by kinase inhibitors while providing a platform for understanding the genotype-phenotype relationship in bladder cancer. Citation Format: Henkel Valentine, Uttam Satyal, Laura Bukavina, Hassan Uddin, Yousttena Beyamin, Rhea Arya, Philip Abbosh. Cancer associated fibroblast dependency in a model of bladder 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 1436.

Abstract 5272: APL-1202 enhances anti-tumor immune response through induction of cellular stress signaling and immunogenic cell death pathway in cancer cells

Abstract Introduction: Treatment approach combining cancer cell targeted therapy and immunotherapy is an effective strategy to trigger robust tumor-specific immune responses. The aim of this study is to determine the impact of APL-1202, a clinical-stage drug candidate (NCT04813107), on cellular stress-driven immunogenic outcomes in bladder cancer cells. Methods: RNA-seq analysis was performed using bladder cancer and endothelial cell lines (A56, J82, T24, HUVEC) treated with APL-1202. Key determinants of immunogenic cell death pathway were measured by cell-surface translocation of calreticulin (flow cytometry), extracellular ATP release assay (bioluminescence) and HMGB1 secretion (ELISA) in the supernatants of cancer cells after APL-1202 treatment. Effects on the innate immune effector function was measured by flow cytometry-based phagocytosis assay consisting of Far-Red dye-stained, pre-treated bladder cancer cell lines (UMUC3, T24) in coculture with THP1-derived macrophages/immature dendritic cells or human monocyte-derived dendritic cells. In vivo, tumor end-point immune cell analysis, tumor weight and mouse survival were compared in chemically induced (BBN: N-butyl-N-(4-hydroxybutyl)-nitrosamine) orthotopic bladder cancer mice treated with APL-1202 and anti-PD1 antibody. Results: Pathway analysis of RNA-seq data from APL-1202 treated cells suggested upregulation of cellular stress-related gene signatures (oxidative stress, autophagy, P53) and pro-inflammatory responses (IL-6, IL-8, HMGB1 signaling). Conversely, downregulation of cell cycle (E2F targets, G2-M checkpoint) and IL-10 signaling suggested increased genomic stress and inflammatory switching in the treated cancer cells. Acute exposure to APL-1202 increased cell-surface translocation of calreticulin as well as extracellular release of ATP and HMGB1 in the treated T24 and UMUC3 cells. Higher percentages of phagocytic activities were detected in both THP-1-derived macrophages/immature dendritic cells and human monocyte-derived dendritic cells after coculture with APL-1202 treated T24 and UMUC3 cells compared to coculture with DMSO treated control cells. Immune phenotyping in tumors derived from BBN bladder cancer mouse model revealed increased infiltration of NK cells and CD8+ T cells. Furthermore, APL-1202 enhanced the anti-tumor effects of a therapeutic anti-PD1 antibody in mice as reflected by significantly decreased tumor weights and increased survival in a combination group with APL-1202 treatment compared to the anti-PD-1 antibody alone treatment group. Conclusion: APL-1202 may improve the efficacy of immune-checkpoint blockade therapies in bladder cancer patients by enhancing cancer cell immunogenicity and subsequent anti-tumor effector immune cell processes, particularly in tumors with deficits in antigen-specific immunity. Citation Format: Rakesh BAM, Jingmin Guan, Neetha Nanoth Vellichirammal, Murli Manohar, David Mulholland, John Sfakianos, Qiaoling Sun, Zuoan Yi, Alice Chen. APL-1202 enhances anti-tumor immune response through induction of cellular stress signaling and immunogenic cell death pathway in 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 5272.

Targeted Delivery of Catalase and Photosensitizer Ce6 by a Tumor-Specific Aptamer Is Effective against Bladder Cancer In Vivo.

Photodynamic therapy (PDT) is often applied in a clinical setting to treat bladder cancer. However, current photosensitizers report drawbacks such as low efficacy, low selectivity, and numerous side effects, which have limited the clinical values of PDT for bladder cancer. Previously, we developed the first bladder cancer-specific aptamer that can selectively bind to and be internalized by bladder tumor cells versus normal uroepithelium cells. Here, we use an aptamer-based drug delivery system to deliver photosensitizer chlorine e6 (Ce6) into bladder tumor cells. In addition to Ce6, we also incorporate catalase into the drug complex to increase local oxygen levels in the tumor tissue. Compared with free Ce6, an aptamer-guided DNA nanotrain (NT) loaded with Ce6 and catalase (NT-Catalase-Ce6) can specifically recognize bladder cancer cells, produce oxygen locally, induce ROS in tumor cells, and cause mitochondrial apoptosis. In an orthotopic mouse model of bladder cancer, the intravesical instillation of NT-Catalase-Ce6 exhibits faster drug internalization and a longer drug retention time in tumor tissue compared with that in normal urothelium. Moreover, our modified PDT significantly inhibits tumor growth with fewer side effects such as cystitis than free Ce6. This aptamer-based photosensitizer delivery system can therefore improve the selectivity and efficacy and reduce the side effects of PDT treatment in mouse models of bladder cancer, bearing a great translational value for bladder cancer intravesical therapy.

Urease-powered nanobots for radionuclide bladder cancer therapy

Bladder cancer treatment via intravesical drug administration achieves reasonable survival rates but suffers from low therapeutic efficacy. To address the latter, self-propelled nanoparticles or nanobots have been proposed, taking advantage of their enhanced diffusion and mixing capabilities in urine when compared with conventional drugs or passive nanoparticles. However, the translational capabilities of nanobots in treating bladder cancer are underexplored. Here, we tested radiolabelled mesoporous silica-based urease-powered nanobots in an orthotopic mouse model of bladder cancer. In vivo and ex vivo results demonstrated enhanced nanobot accumulation at the tumour site, with an eightfold increase revealed by positron emission tomography in vivo. Label-free optical contrast based on polarization-dependent scattered light-sheet microscopy of cleared bladders confirmed tumour penetration by nanobots ex vivo. Treating tumour-bearing mice with intravesically administered radio-iodinated nanobots for radionuclide therapy resulted in a tumour size reduction of about 90%, positioning nanobots as efficient delivery nanosystems for bladder cancer therapy.

Modulation of tumor microenvironment by targeting histone acetylation in bladder cancer

Alterations in the epigenetic machinery in both tumor and immune cells contribute to bladder cancer (BC) development, constituting a promising target as an alternative therapeutic option. Here, we have explored the effects of a novel histone deacetylase (HDAC) inhibitor CM-1758, alone or in combination with immune checkpoint inhibitors (ICI) in BC. We determined the antitumor effects of CM-1758 in various BC cell lines together with the induction of broad transcriptional changes, with focus on the epigenetic regulation of PD-L1. Using an immunocompetent syngeneic mouse model of metastatic BC, we studied the effects of CM-1758 alone or in combination with anti-PD-L1 not only on tumor cells, but also in the tumor microenvironment. In vitro, we found that CM-1758 has cytotoxic and cytostatic effects either by inducing apoptosis or cell cycle arrest in BC cells at low micromolar levels. PD-L1 is epigenetically regulated by histone acetylation marks and is induced after treatment with CM-1758. We also observed that treatment with CM-1758 led to an important delay in tumor growth and a higher CD8 + T cell tumor infiltration. Moreover, anti-PD-L1 alone or in combination with CM-1758 reprogramed macrophage differentiation towards a M1-like polarization state and increased of pro-inflammatory cytokines systemically, yielding potential further antitumor effects. Our results suggest the possibility of combining HDAC inhibitors with immunotherapies for the management of advanced metastatic BC.

MicroRNA-15a-5p suppresses hypoxia-induced tumor growth and chemoresistance in bladder cancer by binding to eIF5A2.

In various malignant tumors (including bladder cancer) poor prognosis is associated with hypoxia and therapeutic resistance. Evidence indicates that in bladder cancer, microRNAs (miRNAs) have vital functions in acquired drug resistance. However, the involvement of miRNAs in hypoxia-mediated bladder cancer doxorubicin (Dox) resistance is unknown. Herein, we showed that hypoxia and Dox treatment downregulated miR-15a-5p expression. Using UM-UC-3 and J82 bladder cancer cell lines and in vivo mouse models of bladder cancer, we confirmed that miR-15a-5p arrests tumor cell growth and Dox resistance in vitro and in vivo. Furthermore, we determined the interaction between miR-15a-5p and eukaryotic translation initiation factor 5A-2 (eIF5A2) using dual luciferase reporters and quantitative real-time reverse transcription polymerase chain reaction assays. We also showed that a miR-15a-5p agomir repressed EIF5A2 expression in bladder cancer cells, thereby inhibiting the epithelial-mesenchymal transition (EMT) induced by Dox or hypoxia. Moreover, ectopic expression of miR-15a-5p abrogated eIF5A2-mediated Dox resistance in bladder cancer cells. Collectively, these data indicated that hypoxia promotes tumor growth and chemoresistance through the HIF-1α/miR-15a-5p/eIFTA2/EMT pathway. This new finding not only has implications for improving our understanding of the Dox resistance process during bladder cancer progression but also indicates that the miR-15a-5p agomir is a promising tool to prevent Dox resistance in patients with bladder cancer.

Targeting DAD1 gene with CRISPR-Cas9 system transmucosally delivered by fluorinated polylysine nanoparticles for bladder cancer intravesical gene therapy.

Background: Intravesical chemotherapy is highly recommended after transurethral resection of bladder tumor for patients with bladder cancer (BCa). However, this localized adjuvant therapy has drawbacks of causing indiscriminate damage and inability to penetrate bladder mucosal. Methods: Fluorinated polylysine micelles (PLLF) were synthesized by reacting polylysine (PLL) with heptafluorobutyrate anhydride. Anti-apoptotic gene defender against cell death 1 (DAD1) was selected by different gene expression analysis between BCa patients and healthy individuals and identified by several biological function assays. The gene transfection ability of PLLF was verified by multiple in vitro and in vivo assays. The therapeutic efficiency of PLLF nanoparticles (NPs) targeting DAD1 were confirmed by intravesical administration using an orthotopic BCa mouse model. Results: Decorated with fluorinated chains, PLL can self-assemble to form NPs and condense plasmids with excellent gene transfection efficiency in vitro. Loading with the CRISPR-Cas9 system designed to target DAD1 (Cas9-sgDAD1), PLLF/Cas9-sgDAD1 NPs strongly inhibited the expression of DAD1 in BCa cells and induced BCa cell apoptosis through the MAPK signaling pathway. Furthermore, intravesical administration of PLLF/Cas9-sgDAD1 NPs resulted in significant therapeutic outcomes without systemic toxicity in vivo. Conclusion: The synthetized PLLF can transmucosally deliver the CRISPR-Cas9 system into orthotopic BCa tissues to improve intravesical instillation therapy for BCa. This work presents a new strategy for targeting DAD1 gene in the intravesical therapy for BCa with high potential for clinical applications.

Homologous Targeting and Adhesion Abilities of Cellular Microvesicles for Enhanced Intravesical Therapy of Bladder Cancer

AbstractBladder cancer is one of the most common clinical malignant tumors with a high recurrence rate after surgery. To improve the therapeutic effect, intravesical instillation of chemotherapeutic drugs is usually applied after surgery. However, due to the unique microenvironment in the bladder, the drug concentration is usually rapidly reduced with urinary excretion, leading to low accumulation in bladder cancer and poor therapeutic effect. Cellular microvesicles (MVs) have parental cell‐specific characteristics and hold homologous targeting and adhesion abilities to their parent cells, achieving efficient cell uptake in their parent cells. In this study, pirarubicin (THP), a clinically approved intravesical chemotherapeutic drug, is encapsulated into bladder cancer cell‐derived MVs to form THPMVs, which have high targeting and adhesion abilities to bladder cancer and facilitate intravesical therapy of bladder cancer. The results show THPMVs compared with free THP exhibited higher cellular uptake in MB49 bladder cancer cells and cause more significant apoptotic cells. After intravesical instillation into a bladder cancer mouse model, THPMVs can significantly accumulate in bladder cancer tissues, and cause an obvious reduction in bladder weights and volumes, exhibiting promising therapeutic effects. Homologous targeting and adhesion abilities of THPMVs greatly contribute to the intravesical therapy of bladder cancer.

Effective Antitumor Immunity Can Be Triggered by Targeting VISTA in Combination with a TLR3-Specific Adjuvant.

Resistance to anti-PD-1/PD-L1 treatment is often associated with accumulation of intratumoral inhibitory macrophages. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is a nonredundant immune checkpoint that can induce both T-cell and myeloid-cell immunosuppression. In this study, we found that high levels of VISTA+ immune cells were associated with advanced stage bladder cancer and predicted poor survival in patients. A combination of high infiltration of VISTA+ immune cells and PD-L1+ immune cells or PD-1+ T cells predicted the worst survival. Flow cytometry and multiplex immunofluorescence analyses confirmed that VISTA expression was higher in macrophages than in T cells or neutrophils, and only VISTA+CD163+ macrophage density predicted poor prognosis in patients with bladder cancer. Toll-like receptor (TLR) agonists are known to trigger the innate immune response in macrophages. We found that the VISTA-specific mAb 13F3 augmented the ability of a TLR3-specific adjuvant to induce macrophage activation in vitro. In the MB49 syngeneic mouse model of bladder cancer, treatment with 13F3 curbed tumor growth and prolonged survival when combined with a TLR3-specific adjuvant. The combination treatment reduced the intratumoral frequency of CD206+ anti-inflammatory macrophages and levels of the immunosuppressive molecule TGFβ1, but it upregulated expression of immunostimulatory molecules (Ifna, Ifnb, and Trail) and increased the CD8+ T cell/regulatory T-cell ratio. These findings indicate that elevated VISTA expression in immune cells, particularly macrophages, is associated with an unfavorable prognosis in patients with bladder cancer and suggest that targeting VISTA in combination with a TLR3-specific adjuvant has translational potential.

Endothelial cells are a key target of IFN-g during response to combined PD-1/CTLA-4 ICB treatment in a mouse model of bladder cancer

To explore mechanisms of response to combined PD-1/CTLA-4 immune checkpoint blockade (ICB) treatment in individual cell types, we generated scRNA-seq using a mouse model of invasive urothelial carcinoma with three conditions: untreated tumor, treated tumor, and tumor treated after CD4+ Tcell depletion. After classifying tumor cells based on detection of somatic variants and assigning non-tumor cell types using SingleR, we performed differential expression analysis, overrepresentation analysis, and gene set enrichment analysis (GSEA) within each cell type. GSEA revealed that endothelial cells were enriched for upregulated IFN-g response genes when comparing treated cells to both untreated cells and cells treated after CD4+ Tcell depletion. Functional analysis showed that knocking out IFNgR1 in endothelial cells inhibited treatment response. Together, these results indicated that IFN-g signaling in endothelial cells is a key mediator of ICB induced anti-tumor activity.

Cancer-associated Fibroblast-derived Extracellular Vesicles Mediate Immune Escape of Bladder Cancer via PD-L1/PD-1 Expression.

Bladder cancer (BCa) is a malignant urological tumor with a high prevalence and poor prognosis. Extracellular vesicles (EVs) are increasingly becoming current hotspots owing to their involvement in cancer progression. This paper probed into the action of cancer-associated fibroblast-derived EVs (CAF-EVs) in the immune escape of BCa. CAFs were identified by immunofluorescence. EVs were extracted from CAFs via ultracentrifugation and later characterized. BCa cells (T24 cell line) were co-cultured with CD8+ T cells and then treated with CAF-EVs. The uptake of EVs by T24 cells was examined by confocal laser microscopy. T24 cell apoptosis and invasion were assessed using flow cytometry and invasion assay. CD8+ T cell proliferation was evaluated using CFSE staining. The levels of cytokines (IFN-γ, IL-2, and TNF-α) were measured by ELISA. PD-L1 and PD-1 levels were determined utilizing RT-qPCR and flow cytometry. BCa mouse models were established to identify the effect of CAF-EVs on BCa progression in vivo. CAF-EVs decreased apoptosis and enhanced invasion of T24 cells, reduced proliferation of CD8+ T cells, and diminished levels of IFN-γ, IL-2, and TNF-α secreted by CD8+ T cells. CAF-EVs promoted the immune escape of T24 cells by carrying PD-L1. Downregulation of PDL1 expression in T24 cells or EVs partially counteracted the promotion of CAF-EVs on immune escape by reducing the binding of PD-L1 and PD-1. Additionally, CAF-EVs raised tumor volume and weight, upregulated PD-L1 expression, and weakened CD8+ T cell infiltration in BCa mice. CAF-EVs facilitate the immune escape of BCa by upregulating PD-L1/PD-1.

Hub gene associated with prognosis in bladder cancer is a novel therapeutic target.

Bladder cancer is a clinical and social conundrum due to its high incidence and recurrence rate. It is urgent to find new targets for the diagnosis and treatment of bladder cancer and improve the prognosis and survival rate of bladder cancer patients. We sought a prognosis-related gene, built related models of evaluated bladder cancer and identified the function of the hub gene in bladder cancer. We downloaded the data of bladder cancer patients from the TCGA database, and used differentially expressed genes (DEGs), copy number variation (CNV) and survival analysis to scan the hub genes associated with prognosis in bladder cancer. Then, multi-factor cox regression was used to obtain the bladder cancer prognosis correlation model. Then, we analyzed the relationship between the expression of hub gene and immune microenvironment of bladder cancer. The relationship between the expression of hub gene and prognosis in bladder cancer patients was verified by immunohistochemistry. Cell proliferation assay and drug sensitivity test in vivo were used to verify the inhibition of bladder cancer by targeted inhibitors. In bladder cancer, we screened seven hub genes (ACLY, CNP, NKIRAS2, P3H4, PDIA6, VPS25 and XPO1) associated with survival. Moreover, the multifactor regression model constructed with hub gene can well distinguish the prognosis of bladder cancer. Hub gene is mostly associated with immune microenvironment. Immunohistochemical results basically confirmed the importance of XPO1 in bladder cancer. Selinexor (an inhibitor of XPO1) could effectively inhibit the proliferation of bladder cancer in the cell proliferation experiments by CCK-8 assays and it could suppress the growth of bladder cancer in mouse bladder cancer model. In this study, a prognostic model with seven hub genes has provided great help for the prognosis prediction of bladder cancer patients. And XPO1 is an important target affecting the prognosis of bladder cancer, and inhibition of XPO1 can effectively inhibit bladder cancer proliferation and growth.

A phase II trial with copanlisib plus avelumab as maintenance therapy for metastatic bladder cancer after platinum-based chemotherapy.

TPS4610 Background: Bladder cancer is the tenth most common malignancy and the fourteenth most common cause of cancer death worldwide. Currently, platinum-based chemotherapy followed by avelumab maintenance immunotherapy is the first-line standard of care for advanced bladder cancer (aBC). Even though maintenance avelumab therapy has improved overall survival, its efficacy is still disappointing with a response rate of less than 10% and progression-free survival benefit of 1.7 months. The phosphoinositide 3-kinase (PI3K) pathway harbors more activating alterations than any other growth signaling pathway in aBC. Furthermore, PI3K δ and γ are expressed by immune cells and regulate their function. Activation alterations along the PI3K pathway are putative molecular drivers and can possibly be targeted for the treatment of aBC. In preclinical studies, we found that a pan-PI3K class I inhibitor, copanlisib, potentiates anti-programmed cell death 1 (PD1) antibody in syngeneic bladder cancer mouse models with or without activation alterations along the PI3K pathway (Zhu S, J Immunother Cancer. 2021). We hypothesize that copanlisib potentiates avelumab as maintenance therapy for aBC. Methods: This is a multi-center, single-arm, open-label Phase II trial with a lead-in safety phase to determine the efficacy and toxicity of combination copanlisib and avelumab maintenance therapy in aBC. The major inclusion criteria are patients with aBC without disease progression after platinum-based chemotherapy and no contraindication for avelumab and copanlisib. With a type I error of 5% and power of 80% with a log-rank test, we will need 26 patients for this study. With an attrition rate of 10%, we will enroll 29 patients from four US Department of Veterans Affairs Medical Centers. Copanlisib will be administered through intravenous infusion (IV) at 60 mg on Day 1, 8 and 15, and avelumab will be administered 800 mg IV on Day 1 and 15 of each 4-week treatment cycle for up to 26 cycles. Imaging will be repeated every two cycles during first year of therapy and thereafter every 3 cycles or clinically indicated. The primary endpoint is progression-free survival (PFS). The secondary endpoints include CT or MRI determined radiographic overall response rate, toxicity, overall survival, and molecular correlative studies. Kaplan-Meier estimates will be presented together with median PFS with 2-sided 95% confidence intervals (CI). In particular, the PFS rates at 3, 6, 9, 12 and 15 months will be estimated with corresponding 2-sided 95% CIs. Adverse events will be assessed according to CTCAE v5. Tumor response is determined according to Response Evaluation Criteria in Solid Tumors version (RECIST) 1.1 criteria. This study is currently open for enrollment. Clinical trial information: NCT05687721 .

Abstract 2884: Cancer-associated fibroblasts potentiate subcutaneous tumor growth in a novel bladder cancer mouse model with a genotype dependency

Abstract Introduction Interrogation of the relationship of genotype (mutation in relevant gene) and phenotype (sensitivity to therapy) in targeted therapy would be facilitated by the use of isogenic in vitro and in vivo models. The PI3K/AKT/mTOR pathway is widely activated but heretofore untargeted in bladder cancer. We sought to develop an immunocompetent CRISPR-edited bladder cancer mouse model that recapitulates common PI3K/AKT/mTOR mutations to study a genotype-phenotype relationship. Our in vitro CRISPR-edited organoids are immunogenic in vivo, as such, we explored utilizing Cancer-Associated Fibroblasts (CAFs) to mediate immunosuppression and promote a pro-tumorigenic environment. Methods and Results We isolated bladder urothelial cells from Rosa26 LSL-Cas9/GFP transgenic mice and grew them as organoids. Trp53 and Rb1 were co-edited to establish ‘base organoids’. As proof of concept, Pten was edited in base organoids in anticipation of developing a series of organoids with different mTOR pathway genotypes. We found that Pten-KO base organoids were 9x more sensitive to ipatasertib than Pten WT organoids. The edited urothelial cells were engrafted into mouse bladder to further test kinase inhibitor susceptibility as preclinical evidence to support human clinical trials. However, the cells successfully engrafted but disappeared after 3-4 weeks before tumors formed. Subcutaneous allografts were also rejected after 3-4 weeks and showed CD45+ immune infiltration during rejection. When cells were injected subcutaneously with CAFs, tumors persisted for 12 weeks, but only in organoids with both Trp53 loss and loss of murine chromosome 4qC4 (which is homologous to 9p21 loss in humans). 9p21 contains 3 genes which are co-deleted in ~40% of bladder cancers: MTAP, CDKN2A, and CDKN2B. Histopathological analysis of these masses confirmed their malignant nature and revealed an immune-excluded architecture. IHC staining of 9p21/Trp53 KO tumors for CD206 and CD11c revealed greater recruitment of M2 macrophages than M1 macrophages. Conclusions CAFs remodel the tumor-microenvironment in bladder cancer via the recruitment of pro-tumorigenic M2 macrophages. This may occur in a genotype-specific manner and 9p21 loss may be a requirement for some genotypes to be tumorigenic. Citation Format: Henkel Lee Valentine, Uttam Satyal, Alexander Metz, Laura Bukavina, Philip H. Abbosh. Cancer-associated fibroblasts potentiate subcutaneous tumor growth in a novel bladder cancer mouse model with a genotype dependency [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 2884.

Abstract 6: Comprehensive single-cell transcriptomic analysis of a mouse model of bladder cancer identifies endothelial cells as a principal target of interferon gamma during response to combined PD-1, CTLA-4 immune checkpoint inhibitor treatment

Abstract Bladder cancer is the tenth most common cancer worldwide, accounting for over 500,000 new cancer cases and 200,000 cancer-related deaths per year. Depending on the degree of muscle invasiveness and disease spread at the time of diagnosis, 5-year survival rates can range from as high as 96% to as low as 6%. In recent years, use of checkpoint inhibitor treatments for bladder cancer has become more common. Currently, there are five PD-1/PD-L1 checkpoint inhibitors approved by the FDA for treatment of bladder cancer and these treatments have been used across the spectrum of disease, from non-muscle invasive to metastatic disease. However, many patients still do not receive benefit from checkpoint inhibitor treatments. For example, clinical trials have shown response rates of only 20-30% in advanced disease. To improve treatment responses and identify patients who will benefit most from checkpoint inhibitor treatment, a deeper understanding of mechanisms of treatment response is needed. In an effort to explore mechanisms of response to combined PD-1/CTLA-4 checkpoint inhibitor treatment, we generated single cell RNA expression sequencing from a carcinogen-induced mouse model of muscle invasive urothelial carcinoma that included three conditions: untreated tumor, tumor treated with combination treatment, and tumor treated with combination treatment after Cd4+ T-cell depletion. After classifying tumor cells based on per cell detection of somatic variants identified using exome sequencing and assigning non-tumor cell types using SingleR, we performed differential expression, overrepresentation, and gene set enrichment analysis (GSEA) within each cell type, comparing each pairwise set of conditions. This analysis revealed that MSigDB’s hallmark interferon gamma response gene set was overrepresented across multiple cell types. Furthermore, GSEA indicated that with combined checkpoint blockade treatment, endothelial cells showed significant enrichment of upregulated interferon gamma response genes. Functional analysis demonstrated that knocking out Ifngr1 in endothelial cells inhibited the treatment response seen in wild type treated mice. Together, these results indicate that interferon gamma response in endothelial cells is a key mediator of combined PD-1/CTLA-4 checkpoint inhibitor treatment response. Citation Format: Sharon L. Freshour, Bryan Fisk, Timothy Hung-Po Chen, Haolin Shen, Matthew Mosior, Catrina Fronick, Jennifer Bolzenius, Obi L. Griffith, Vivek Arora, Malachi Griffith. Comprehensive single-cell transcriptomic analysis of a mouse model of bladder cancer identifies endothelial cells as a principal target of interferon gamma during response to combined PD-1, CTLA-4 immune checkpoint inhibitor treatment [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 6.

Abstract 1068: A precision CRISPR approach to target structural variant junctions in cancer

Abstract Background: Structural variants are common in cancer that drive tumor formation and typically occur early in carcinogenesis. Despite being a common and well-known feature of cancer, this cancer hallmark has not yet been broadly explored therapeutically in the clinic. We present a novel precision-cancer approach, KLIPP, which consists of guide RNAs that target cancer-specific structural variant junctions (SVJs) to nucleate two parts of dCas9-conjugated endonuclease, Fok1, leading to its activation and induction of toxic DSBs. Furthermore, this approach reduced tumor growth in an orthotopic bladder cancer model in mice. Methods and Materials: HCT116 colon cancer cells and UMUC3 bladder cancer cells were engineered to express combinations of SVJ-targeting sgRNAs and express Fok1-dCas9 under doxycycline (dox) regulation. The HCT116 and UMUC3 cells were treated with dox for 24 hours and assessed for DSBs at SVJs by γH2AX foci assay and γH2AX ChIP-PCR. The cells were assessed for cell death using flow cytometry measuring sub-G1 DNA content, the clonogenic survival assay (12 days), and PARP1 and caspase cleavage (after 48 h) using Western blot. Tumor growth of orthotopic xenografts of UMUC3 cells expressing Fok1-dCas9 alone or with 2 pairs of SVJ-targeting sgRNAs were assessed weekly after addition of dox to the drinking water. Bioluminescence assessment of tumor growth was monitored weekly. Results: Expression of SVJ-targeting sgRNA and the induction of Fok1-dCas9 by dox for 24 h in HCT116 colon cancer and UMUC3 bladder cancer cells, resulted in one or two γH2AX foci per cell. Using ChIP-PCR, the identity of the site of the DSB was validated to occur at the targeted SVJ. Furthermore, dox treatment for 12 days caused >50% reduced clonogenic survival that was augmented by the DNA-PK inhibitor NU7441. Further, we observed >50% induction of apoptosis when assessed by subG1 DNA content cells and PARP1 cleavage. When UMUC3 cancer cells were grown orthotopically in mice, activation of Fok1-dCas9 and together with two pairs of SVJ-targeting sgRNAs led to significantly reduced tumor growth with 7/11 mice showing no signs of tumor. Conclusions: We have developed a precision CRISPR approach based on the homodimerization of Fok1 endonuclease at sites of cancer specific SVJs to specifically induce toxic DSBs in cancer cells. Here we show that this approach led to efficient targeting of cancer cells both in cell culture and in vivo. We are currently testing the efficacy of the KLIPP approach in preclinical models of bladder and ovarian cancers using lipid nanoparticle delivery techniques. On successfully implementation of this approach, it will be transformative for cancer therapy. Further, KLIPP will be generated in a personalized way for each patient in a rapid and cost-effective way. Citation Format: Radhika Suhas Hulbatte, Huibin Yang, Natalie Gratsch, Alan Kellher, Phillip L. Palmbos, Mats Ljungman. A precision CRISPR approach to target structural variant junctions in cancer [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 1068.

Abstract 1709: MAPK pathway alterations are a targetable vulnerability in bladder cancer

Abstract Bladder cancer (BC) is the fourth most common cancer in males and accounts for about 80,000 new cases in the US. Approximately 25% patients with BC will present with muscle-invasive bladder cancer (MIBC) and for the past several decades the standard-of-care for MIBC and metastatic bladder cancer has been cisplatin-based chemotherapy. More recently, multiple immunotherapeutic agents have been approved but only a subset of patients respond to these treatments and therefore novel therapeutic strategies are needed to expand treatment options and improve clinical outcomes for BC patients. Large-scale genomic studies of MIBC have identified numerous recurrent genomic alterations including mutations, copy number alterations, and chromosomal translocations. Using publicly available patient datasets, we identified ~20% of MIBC patients harboring alterations in genes involved in the mitogen-activated protein kinase (MAPK) pathway and their upstream activators. RAF1 copy number amplification was the most predominant alteration followed by activating HRAS mutations. Leveraging our institutional cohorts of bladder cancer specimens, we defined the frequency of these alterations and validated RAF1 amplification in a subset of cases using fluorescence in situ hybridization. To functionally define the role of MAPK pathway alterations in BC, we tested activity of RAF and MEK inhibitors in BC cell line models with diverse MAPK pathway alterations including RAF1 amplification and HRAS/NRAS mutations. We found that these MAPK pathway altered models displayed increased sensitivity to RAF/MEK inhibition compared to MAPK-unaltered models. We further demonstrated the feasibility of preclinically targeting these alterations in mouse models of BC using cell line and patient-derived-xenografts. Additionally, we tested the impact of MAPK pathway modulation on tumor extrinsic properties including changes in the tumor microenvironment that could potentially affect responses to immunotherapeutic agents. Taken together, we have identified MAPK pathway alterations as a novel dependency in BC that can be targeted with emerging RAF inhibitors. Citation Format: Raie Bekele, Amruta Samant, Timothy Hanlon, Kent Mouw. MAPK pathway alterations are a targetable vulnerability in bladder cancer [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 1709.

Abstract 3277: In vivo CRISPR screening identifies PTDSS1 as a potential combinatorial target to improve immune checkpoint therapy response

Abstract Immune checkpoint therapy (ICT) has recently revolutionized the treatment paradigm for various types of cancer. However, despite the unprecedented safety and efficacy profile compared to traditional treatment options, many patients do not respond to ICT, highlighting the urgent need for novel strategies to improve ICT efficacy. Here, we used a pooled in vivo CRISPR knockout screening in a mouse bladder cancer model treated with immune checkpoint inhibitor to discover targets that may improve immunotherapy response. Our data identified Ptdss1, which encodes phosphatidylserine synthase 1, as a potential regulator of anti-PD-1 response. Depletion of Ptdss1 not only increased tumor cell immunogenicity and response to interferon gamma, but also facilitated development of an anti-tumor microenvironment. Ptdss1 depletion in tumor cells increased effector CD8+ T cells cytolytic function, decreased regulatory T cells activation and inhibitory function, increased frequency of iNOS+ myeloid cells and induced macrophage M2-to-M1 polarization. Ptdss1 knockdown induced changes in the tumor microenvironment were further amplified when combined with anti-PD-1 treatment, which translates into better tumor control and prolonged animal survival in mouse bladder cancer model. Together, our results provide insights on a new therapeutic strategy for overcoming resistance to immune checkpoint therapy through combination of PTDSS1 inhibition and PD-1 blockade. Citation Format: Jielin Liu, Swetha Anandhan, Sreyashi Basu, Yulong Chen, Sangeeta Goswami, Ashwat Nagarajan, Shelley Herbrich, Liangwen Xiong, Baoxiang Guan, Padmanee Sharma. In vivo CRISPR screening identifies PTDSS1 as a potential combinatorial target to improve immune checkpoint therapy response [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 3277.