Small Cell Bladder Cancer: Treatment Patterns for Local Disease and Associated Outcomes. A Retrospective Cohort Study.

BACKGROUND: Small cell bladder cancer (SCBC) is a rare histologic subtype with relative paucity of data regarding treatment response and outcomes. We reviewed 2 databases to compare outcomes in patients with localized SCBC treated with cystectomy versus concurrent chemoradiotherapy (CCRT). We hypothesized that survival would be similar with these therapy approaches. METHODS: We retrospectively reviewed our institutional and SEER-Medicare databases to identify patients with SCBC. Overall survival (OS) was determined from the date of diagnosis to last follow-up/death. For those with nonmetastatic disease, a multivariate Cox analysis was used to compare locoregional therapy with neoadjuvant chemotherapy (NAC) + cystectomy versus CCRT. RESULTS: We identified 53 patients in our institutional database and 1166 patients in SEER-Medicare with localized SCBC. Median OS (mOS) with NAC + cystectomy was 46 months (95% CI, 21-72) and 45 months (95% CI, 0-104) in the institutional and SEER-Medicare databases, respectively, whereas mOS with CCRT was 26 months (95% CI, 5-47) and 23 months (95% CI, 18-28) in the 2 series, respectively. In multivariate analysis, NAC followed by cystectomy was associated with an approximately 30% reduction in mortality compared to CCRT in both institutional and national databases but did not reach statistical significance (Institution HR 0.71, 95% CI, 0.22-2.4, P = .58; SEER HR 0.73, 95% CI, 0.49-1.08; P = .11). CONCLUSIONS: SCBC is very aggressive with limited survival observed in our institutional and SEER-Medicare datasets regardless of locoregional therapy used. There is an unmet need to define the optimal locoregional therapy for nonmetastatic stage and identify novel therapeutic targets.

Adjuvant Chemotherapy and Survival After Radical Cystectomy in Histologic Subtype Bladder Cancer.

OBJECTIVES: Patients with histologic subtype bladder cancer (HSBC) suffer worse outcomes than those with conventional urothelial carcinoma (UC). We sought to characterize the use of adjuvant chemotherapy (AC) in HSBC after radical cystectomy (RC) using the National Cancer Database (NCDB). MATERIALS AND METHODS: We retrospectively queried the NCDB (2006-2019) for patients with non-metastatic bladder cancer (BC) who underwent RC (N = 45,797). Patients were stratified by histologic subtype and receipt of AC. Multivariable logistic regression determined associations of demographic and clinicopathologic features with receipt of AC. Multivariable Cox regression evaluated associations between receipt of any AC and overall survival (OS). RESULTS: We identified 4,469 patients with HSBC classified as squamous, adenocarcinoma, small cell, sarcomatoid, micropapillary, or plasmacytoid. Squamous comprised 31% of the HSBC cohort, followed by small cells and micropapillary. Black patients were presented with a higher prevalence of adenocarcinoma (119/322, 37.0%). Use of AC was highest in plasmacytoid and small cell (30% each) and lowest in squamous (11%). Neuroendocrine histology was independently associated with greater odds of receiving AC (HR 1.6, 95% CI 1.37-1.87), while squamous cell histology was associated with lower odds (HR 0.61, 95% CI 0.53-0.71). On multivariable Cox regression analysis, treatment with AC was associated with significantly longer OS (HR 0.69, 95% CI 0.59-0.81) and for squamous, sarcomatoid, and micropapillary cohorts after stratified by subtype. CONCLUSIONS: AC was variably used among patients with HSBC and was associated with OS benefit in such patients.

Patterns of chemotherapy use with primary radiotherapy for localized bladder cancer in patients 65 or older.

Introduction: Bladder preservation with concurrent chemoradiotherapy after maximum transurethral resection of bladder tumor is an alternative to radical cystectomy in select patients with muscle invasive bladder cancer (MIBC). Concurrent administration of radio-sensitizing chemotherapy and radiation therapy (RT) has been shown to have superior disease control compared with RT alone and can often be administered with modest added toxicity. We sought to describe national patterns of chemotherapy use. Methods: The linked surveillance, epidemiology, and end results (SEER)-Medicare database was used to identify patients with cT2-4, N0/X, M0/X BC who received radiation between 2004 and 2018. Data on demographics, clinicopathologic factors, therapy and outcomes were extracted. Concurrent utilization of chemotherapy with RT was also identified (CRT). Multivariate logistic regression (MVA) models were used to explore factors associated with receipt of chemotherapy and overall survival (OS). Results: 2190 patients met inclusion criteria. Of these, 850 (38.8%) received no chemotherapy. Among those receiving chemotherapy, the most frequent regimens were single agent carboplatin, cisplatin, or gemcitabine. Factors that were independently associated with decreased likelihood of chemotherapy use were increasing age (OR 0.93, CI 0.92 - 0.95), Hispanic race (compared with White, OR 0.62, CI 0.39 - 0.99), cT3 or T4 (compared with cT2, OR 0.70, CI 0.55 - 0.90), and lower National Cancer Institute comorbidity index (OR 0.60, CI 0.51 - 0.70) (p < 0.05). Variables independently associated with increased likelihood of receipt of chemotherapy were married status (OR 1.28, CI 1.06 - 1.54), higher socioeconomic status (OR 1.31, CI 1.06 - 1.64), and later year of diagnosis (OR 1.09, CI 1.06 - 1.12). Receipt of concurrent chemotherapy with RT was associated with superior OS compared with RT alone. Conclusion: Over a third of patients >/65 years old receiving curative-intent RT for MIBC do not receive concurrent chemotherapy. Considering the improvement in oncologic outcomes with CRT over RT alone and more options, such as low dose gemcitabine which can be administered with modest toxicity, efforts are needed to identify barriers to utilization and increase the use of radio-sensitizing chemotherapy.

A combinatorial genetic strategy for exploring complex genotype-phenotype associations in cancer.

Available genetically defined cancer models are limited in genotypic and phenotypic complexity and underrepresent the heterogeneity of human cancer. Here, we describe a combinatorial genetic strategy applied to an organoid transformation assay to rapidly generate diverse, clinically relevant bladder and prostate cancer models. Importantly, the clonal architecture of the resultant tumors can be resolved using single-cell or spatially resolved next-generation sequencing to uncover polygenic drivers of cancer phenotypes.

Citron Kinase Is a Druggable Target in Treatment-Resistant Prostate Cancer.

Prolonged treatment with androgen deprivation therapy (ADT) inevitably leads to castration-resistant prostate cancer (CRPC). Development of novel androgen-targeting agents and chemo/radiotherapies has resulted in improved survival. However, metastatic CRPC remains incurable. New therapeutics are greatly needed, and exploration of novel pathways such as the mechanisms underlying prostate cancer cell proliferation could potentially augment the natural course of CRPC. In the latest issue of Cancer Research, Rawat and colleagues delved deeply into the mechanistic role of citron kinase (CIT) in orchestrating prostate cancer proliferation and revealed its catalytic activity as a druggable target for treatment-resistant prostate cancer. The researchers utilized in vitro and in vivo methodologies to elucidate the function of CIT in mediating uncontrolled interphase progression and prostate cancer growth. Furthermore, the authors employed both androgen receptor-dependent and independent models to validate the significance of CIT kinase activity as a crucial factor in driving treatment-resistant prostate cancer growth. At a mechanistic level they determined that the E2F2-Skp2-p27 axis regulates CIT expression. Finally, they defined the landscape of CIT substrates in prostate cancer that encompasses a spectrum of cellular functions that spans key proliferation regulators to alternative splicing events. This comprehensive work provides insights into CIT as a potential biomarker for prostate cancer treatment resistance and disease progression and establishes the CIT kinase domain as a druggable target in CRPC. See related article by Rawat et al., p. 4142.

The transcription factor DUX4 orchestrates translational reprogramming by broadly suppressing translation efficiency and promoting expression of DUX4-induced mRNAs.

Translational control is critical for cell fate transitions during development, lineage specification, and tumorigenesis. Here, we show that the transcription factor double homeobox protein 4 (DUX4), and its previously characterized transcriptional program, broadly regulates translation to change the cellular proteome. DUX4 is a key regulator of zygotic genome activation in human embryos, whereas misexpression of DUX4 causes facioscapulohumeral muscular dystrophy (FSHD) and is associated with MHC-I suppression and immune evasion in cancer. We report that translation initiation and elongation factors are disrupted downstream of DUX4 expression in human myoblasts. Genome-wide translation profiling identified mRNAs susceptible to DUX4-induced translation inhibition, including those encoding antigen presentation factors and muscle lineage proteins, while DUX4-induced mRNAs were robustly translated. Endogenous expression of DUX4 in human FSHD myotubes and cancer cell lines also correlated with reduced protein synthesis and MHC-I presentation. Our findings reveal that DUX4 orchestrates cell state conversion by suppressing the cellular proteome while maintaining translation of DUX4-induced mRNAs to promote an early developmental program.

Combinatorial genetic strategy accelerates the discovery of cancer genotype-phenotype associations.

Available genetically-defined cancer models are limited in genotypic and phenotypic complexity and underrepresent the heterogeneity of human cancer. Herein, we describe a combinatorial genetic strategy applied to an organoid transformation assay to rapidly generate diverse, clinically relevant bladder and prostate cancer models. Importantly, the clonal architecture of the resultant tumors can be resolved using single-cell or spatially resolved next-generation sequencing to uncover polygenic drivers of cancer phenotypes.

Multi-level functional genomics reveals molecular and cellular oncogenicity of patient-based 3' untranslated region mutations.

3' untranslated region (3' UTR) somatic mutations represent a largely unexplored avenue of alternative oncogenic gene dysregulation. To determine the significance of 3' UTR mutations in disease, we identify 3' UTR somatic variants across 185 advanced prostate tumors, discovering 14,497 single-nucleotide mutations enriched in oncogenic pathways and 3' UTR regulatory elements. By developing two complementary massively parallel reporter assays, we measure how thousands of patient-based mutations affect mRNA translation and stability and identify hundreds of functional variants that allow us to define determinants of mutation significance. We demonstrate the clinical relevance of these mutations, observing that CRISPR-Cas9 endogenous editing of distinct variants increases cellular stress resistance and that patients harboring oncogenic 3' UTR mutations have a particularly poor prognosis. This work represents an expansive view of the extent to which disease-relevant 3' UTR mutations affect mRNA stability, translation, and cancer progression, uncovering principles of regulatory functionality and potential therapeutic targets in previously unexplored regulatory regions.

ELAC2 is a functional prostate cancer risk allele.

Stentenbach and colleagues have unveiled a functional role of a human germline mutation found in the ribonuclease (RNase) Z enzyme, ELAC2, in prostate cancer. Here, we discuss the importance of these findings in enhancing our understanding of how risk variants enable prostate cancer progression and the post-transcriptional mechanisms underlying oncogenesis.

Metastatic Bladder Cancer Expression and Subcellular Localization of Nectin-4 and Trop-2 in Variant Histology: A Rapid Autopsy Study.

BACKGROUND: Nectin-4 and Trop-2 are transmembrane targets of FDA-approved antibody-drug conjugates (ADC) Enfortumab-vedotin (EV) and Sacituzumab govitecan (SG), respectively, for the treatment of metastatic urothelial carcinoma (mUC). The expression and role of Nectin-4 and Trop-2 in mUC variant histology is poorly described. MATERIALS AND METHODS: We evaluate membranous and cytoplasmic protein expression, and mRNA levels of Nectin-4 and Trop-2 within matched primary and metastatic mUC samples to determine heterogeneity of ADC targets in mUC variants. RESULTS: Patients with mUC were consented for rapid autopsy immediately after death. Tissues from matched primary and metastatic lesions were collected. A total of 67 specimens from 20 patients were analyzed: 27 were UC, 17 plasmacytoid (PUC), 18 UC with squamous differentiation (UCSD), and 5 neuroendocrine (NE); 10 from primary and 57 from metastatic sites. All histology except NE expressed moderate-high levels of Nectin-4 and Trop-2 by both immunohistochemistry and RNAseq. Nectin-4 demonstrated prominent cytoplasmic staining in metastatic PUC and UCSD. Trop-2 demonstrated strong cytoplasmic and membrane staining in primary and metastatic tumors. Interestingly, Nectin-4 and Trop-2 expression are positively correlated at both mRNA and protein levels. CONCLUSION: UC and non-NE variants express notable level of Nectin-4 and Trop-2 in both primary and metastatic lesions. Membrane staining of Nectin-4 and Trop-2 is present but cytoplasmic staining is a more common event in both mUC and mUC variant histology. These findings support evaluation of EV and SG in heavily treated variant histology BC and urge attention on the clinical relevance of cytoplasmic localization of ADC targets.

Sirtuin 6 is required for the integrated stress response and resistance to inhibition of transcriptional cyclin-dependent kinases.

Pancreatic ductal adenocarcinoma (PDAC) is classified into two key subtypes, classical and basal, with basal PDAC predicting worse survival. Using in vitro drug assays, genetic manipulation experiments, and in vivo drug studies in human patient-derived xenografts (PDXs) of PDAC, we found that basal PDACs were uniquely sensitive to transcriptional inhibition by targeting cyclin-dependent kinase 7 (CDK7) and CDK9, and this sensitivity was recapitulated in the basal subtype of breast cancer. We showed in cell lines, PDXs, and publicly available patient datasets that basal PDAC was characterized by inactivation of the integrated stress response (ISR), which leads to a higher rate of global mRNA translation. Moreover, we identified the histone deacetylase sirtuin 6 (SIRT6) as a critical regulator of a constitutively active ISR. Using expression analysis, polysome sequencing, immunofluorescence, and cycloheximide chase experiments, we found that SIRT6 regulated protein stability by binding activating transcription factor 4 (ATF4) in nuclear speckles and protecting it from proteasomal degradation. In human PDAC cell lines and organoids as well as in murine PDAC genetically engineered mouse models where SIRT6 was deleted or down-regulated, we demonstrated that SIRT6 loss both defined the basal PDAC subtype and led to reduced ATF4 protein stability and a nonfunctional ISR, causing a marked vulnerability to CDK7 and CDK9 inhibitors. Thus, we have uncovered an important mechanism regulating a stress-induced transcriptional program that may be exploited with targeted therapies in particularly aggressive PDAC.

Sarcomatoid Urothelial Carcinoma Is Associated With Limited Response to Neoadjuvant Chemotherapy and Poor Oncologic Outcomes After Radical Cystectomy.

INTRODUCTION: To examine oncologic outcomes and response to neoadjuvant chemotherapy (NAC) in patients with sarcomatoid urothelial carcinoma (SUC) treated with radical cystectomy (RC). MATERIALS AND METHODS: We retrospectively queried our institutional database (2003-18) and Surveillance, Epidemiology, and End Results (SEER)-Medicare (2004-2015) for patients with cT2-4, N0-2, M0 SUC and conventional UC (CUC) treated with RC. Clinicopathologic characteristics were described using descriptive statistics (t test, χ2-test and log-rank-test for group comparison). Overall (OS) and recurrence-free-survival (RFS) after RC were estimated with the Kaplan Meier method and associations with OS were evaluated with Cox proportional hazards models. RESULTS: We identified 38 patients with SUC and 287 patients with CUC in our database, and 190 patients with SUC in SEER-Medicare. In the institutional cohort, patients with SUC versus CUC had higher rates of pT3/4 stage (66% vs. 35%, P < 0.001), lower rates of ypT0N0 (6% vs. 35%, P = .02), and worse median OS (17.5 vs. 120 months, P < .001). Further, patients with SUC in the institutional versus SEER-Medicare cohort had similar median OS (17.5 vs. 21 months). In both cohorts, OS was comparable between patients with SUC undergoing NAC+RC vs. RC alone (17.5 vs. 18.4 months, P = .98, institutional cohort; 24 vs. 20 months, P = .56, SEER cohort). In Cox proportional hazards models for the institutional RC cohort, SUC was independently associated with worse OS (HR 2.3, CI 1.4-3.8, P = .001). CONCLUSION: SUC demonstrates poor pathologic response to NAC and worse OS compared with CUC, with no OS benefit associated with NAC. A unique pattern of rapid abdominopelvic cystic recurrence was identified.

Transcriptional-translational conflict is a barrier to cellular transformation and cancer progression.

We uncover a tumor-suppressive process in urothelium called transcriptional-translational conflict caused by deregulation of the central chromatin remodeling component ARID1A. Loss of Arid1a triggers an increase in a nexus of pro-proliferation transcripts, but a simultaneous inhibition of the eukaryotic elongation factor 2 (eEF2), which results in tumor suppression. Resolution of this conflict through enhancing translation elongation speed enables the efficient and precise synthesis of a network of poised mRNAs resulting in uncontrolled proliferation, clonogenic growth, and bladder cancer progression. We observe a similar phenomenon in patients with ARID1A-low tumors, which also exhibit increased translation elongation activity through eEF2. These findings have important clinical implications because ARID1A-deficient, but not ARID1A-proficient, tumors are sensitive to pharmacologic inhibition of protein synthesis. These discoveries reveal an oncogenic stress created by transcriptional-translational conflict and provide a unified gene expression model that unveils the importance of the crosstalk between transcription and translation in promoting cancer.

Defining cellular population dynamics at single-cell resolution during prostate cancer progression.

Advanced prostate malignancies are a leading cause of cancer-related deaths in men, in large part due to our incomplete understanding of cellular drivers of disease progression. We investigate prostate cancer cell dynamics at single-cell resolution from disease onset to the development of androgen independence in an in vivo murine model. We observe an expansion of a castration-resistant intermediate luminal cell type that correlates with treatment resistance and poor prognosis in human patients. Moreover, transformed epithelial cells and associated fibroblasts create a microenvironment conducive to pro-tumorigenic immune infiltration, which is partially androgen responsive. Androgen-independent prostate cancer leads to significant diversification of intermediate luminal cell populations characterized by a range of androgen signaling activity, which is inversely correlated with proliferation and mRNA translation. Accordingly, distinct epithelial populations are exquisitely sensitive to translation inhibition, which leads to epithelial cell death, loss of pro-tumorigenic signaling, and decreased tumor heterogeneity. Our findings reveal a complex tumor environment largely dominated by castration-resistant luminal cells and immunosuppressive infiltrates.

Bladder Cancer Patient-derived Organoids and Avatars for Personalized Cancer Discovery.

Prediction of treatment response has attracted growing attention in cancer research to improve clinical outcomes via individualized treatment regimens. Patient-derived organoids and xenografts are novel preclinical model systems that recapitulate the genetic and phenotypic features of parental tumors for this purpose. Organoid culture has been successfully established in multiple cancers and used for assessment of drug and immunotherapy responses. Patient-derived xenograft (PDX) models provide insights into in vivo tumor growth and metastatic potential. Continued improvements in these model systems to better maintain tumor architecture and microenvironment will advance patient-specific targeted therapies. PATIENT SUMMARY: This mini review describes up-to-date organoid and xenograft models of bladder cancer created using patient-derived tissue. These models are important for research and may provide information on mutations and expression patterns for cancer-related genes that are unique to each patient, and could facilitate personalized therapy for individual patients.

Opposing transcriptional programs of KLF5 and AR emerge during therapy for advanced prostate cancer.

Endocrine therapies for prostate cancer inhibit the androgen receptor (AR) transcription factor. In most cases, AR activity resumes during therapy and drives progression to castration-resistant prostate cancer (CRPC). However, therapy can also promote lineage plasticity and select for AR-independent phenotypes that are uniformly lethal. Here, we demonstrate the stem cell transcription factor Krüppel-like factor 5 (KLF5) is low or absent in prostate cancers prior to endocrine therapy, but induced in a subset of CRPC, including CRPC displaying lineage plasticity. KLF5 and AR physically interact on chromatin and drive opposing transcriptional programs, with KLF5 promoting cellular migration, anchorage-independent growth, and basal epithelial cell phenotypes. We identify ERBB2 as a point of transcriptional convergence displaying activation by KLF5 and repression by AR. ERBB2 inhibitors preferentially block KLF5-driven oncogenic phenotypes. These findings implicate KLF5 as an oncogene that can be upregulated in CRPC to oppose AR activities and promote lineage plasticity.

Adaptive translational pausing is a hallmark of the cellular response to severe environmental stress.

To survive, mammalian cells must adapt to environmental challenges. While the cellular response to mild stress has been widely studied, how cells respond to severe stress remains unclear. We show here that under severe hyperosmotic stress, cells enter a transient hibernation-like state in anticipation of recovery. We demonstrate this adaptive pausing response (APR) is a coordinated cellular response that limits ATP supply and consumption through mitochondrial fragmentation and widespread pausing of mRNA translation. This pausing is accomplished by ribosome stalling at translation initiation codons, which keeps mRNAs poised to resume translation upon recovery. We further show that recovery from severe stress involves ISR (integrated stress response) signaling that permits cell cycle progression, resumption of growth, and reversal of mitochondria fragmentation. Our findings indicate that cells can respond to severe stress via a hibernation-like mechanism that preserves vital elements of cellular function under harsh environmental conditions.

Defining the therapeutic selective dependencies for distinct subtypes of PI3K pathway-altered prostate cancers.

Previous studies have suggested that PTEN loss is associated with p110ß signaling dependency, leading to the clinical development of p110ß-selective inhibitors. Here we use a panel pre-clinical models to reveal that PI3K isoform dependency is not governed by loss of PTEN and is impacted by feedback inhibition and concurrent PIK3CA/PIK3CB alterations. Furthermore, while pan-PI3K inhibition in PTEN-deficient tumors is efficacious, upregulation of Insulin Like Growth Factor 1 Receptor (IGF1R) promotes resistance. Importantly, we show that this resistance can be overcome through targeting AKT and we find that AKT inhibitors are superior to pan-PI3K inhibition in the context of PTEN loss. However, in the presence of wild-type PTEN and PIK3CA-activating mutations, p110α-dependent signaling is dominant and selectively inhibiting p110α is therapeutically superior to AKT inhibition. These discoveries reveal a more nuanced understanding of PI3K isoform dependency and unveil novel strategies to selectively target PI3K signaling nodes in a context-specific manner.

Multiplexed functional genomic analysis of 5' untranslated region mutations across the spectrum of prostate cancer.

The functional consequences of genetic variants within 5' untranslated regions (UTRs) on a genome-wide scale are poorly understood in disease. Here we develop a high-throughput multi-layer functional genomics method called PLUMAGE (Pooled full-length UTR Multiplex Assay on Gene Expression) to quantify the molecular consequences of somatic 5' UTR mutations in human prostate cancer. We show that 5' UTR mutations can control transcript levels and mRNA translation rates through the creation of DNA binding elements or RNA-based cis-regulatory motifs. We discover that point mutations can simultaneously impact transcript and translation levels of the same gene. We provide evidence that functional 5' UTR mutations in the MAP kinase signaling pathway can upregulate pathway-specific gene expression and are associated with clinical outcomes. Our study reveals the diverse mechanisms by which the mutational landscape of 5' UTRs can co-opt gene expression and demonstrates that single nucleotide alterations within 5' UTRs are functional in cancer.

mRNA translation is a therapeutic vulnerability necessary for bladder epithelial transformation.

Using genetically engineered mouse models, this work demonstrates that protein synthesis is essential for efficient urothelial cancer formation and growth but dispensable for bladder homeostasis. Through a candidate gene analysis for translation regulators implicated in this dependency, we discovered that phosphorylation of the translation initiation factor eIF4E at serine 209 is increased in both murine and human bladder cancer, and this phosphorylation corresponds with an increase in de novo protein synthesis. Employing an eIF4E serine 209 to alanine knock-in mutant mouse model, we show that this single posttranslational modification is critical for bladder cancer initiation and progression, despite having no impact on normal bladder tissue maintenance. Using murine and human models of advanced bladder cancer, we demonstrate that only tumors with high levels of eIF4E phosphorylation are therapeutically vulnerable to eFT508, the first clinical-grade inhibitor of MNK1 and MNK2, the upstream kinases of eIF4E. Our results show that phospho-eIF4E plays an important role in bladder cancer pathogenesis, and targeting its upstream kinases could be an effective therapeutic option for bladder cancer patients with high levels of eIF4E phosphorylation.