Current uses and resistance mechanisms of enzalutamide in prostate cancer treatment.

INTRODUCTION: Prostate cancer continues to be a major cause of morbidity and mortality for men worldwide. Enzalutamide, a second-generation non-steroidal antiandrogen that blocks androgen receptor (AR) transcriptional activity, is a treatment for biochemically-recurrent, metastatic, castration sensitive, and castration resistant tumors. Unfortunately, most patients ultimately develop resistance to enzalutamide, making long-term treatment with this agent challenging. AREAS COVERED: We performed a literature search of PubMed without date restrictions to investigate the literature surrounding enzalutamide and discuss the current uses of enzalutamide, proposed mechanisms driving resistance, and summarize current efforts to mitigate this resistance. EXPERT OPINION: Enzalutamide is an effective prostate cancer therapy that is currently used in biochemically-recurrent and metastatic disease, and for both castration sensitive and castration resistant tumors. Unfortunately, resistance to enzalutamide occurs in each of these scenarios. In the clinical setting, enzalutamide-resistant tumors are either AR-driven or AR-indifferent. AR-dependent resistance mechanisms include genomic or epigenomic events that result in enhanced AR signaling. Tumors that do not require AR signaling instead may depend on alternative oncogenic pathways. There are numerous strategies to mitigate enzalutamide resistance, including concurrent use of PARP inhibitors or immune therapies. Additional work is required to uncover novel approaches to treat patients in the enzalutamide-resistant setting.

Androgen production, uptake, and conversion (APUC) genes define prostate cancer patients with distinct clinical outcomes.

BACKGROUND: Prostate cancer (PC) is driven by aberrant signaling of the androgen receptor (AR) or its ligands, and androgen deprivation therapies (ADT) are a cornerstone of treatment. ADT responsiveness may be associated with germline alterations in genes that regulate androgen production, uptake, and conversion (APUC). METHODS: We analyzed whole-exome sequencing (WES) and whole transcriptome sequencing (WTS) data from prostate tissues (SU2C/PCF, TCGA, GETx). We also interrogated the Caris POA DNA (592-gene/whole exome) and RNA (whole transcriptome) NGS databases. Algorithm for Linking Activity Networks (ALAN) was used to quantify all pairwise gene-to-gene associations. Real-world overall survival (OS) was determined from insurance claims data using Kaplan-Meier estimates. RESULTS: Six APUC genes (HSD3B1, HSD3B2, CYP3A43, CYP11A1, CYP11B1, CYP17A1) exhibited coalescent gene behavior in a cohort of metastatic tumors (n = 208). In the Caris POA dataset, the 6 APUC genes (APUC-6) exhibited robust clustering in primary prostate (n = 4,490) and metastatic (n = 2,593) biopsies. Surprisingly, tumors with elevated APUC-6 expression had statically lower expression of AR, AR-V7, and AR signaling scores suggesting ligand-driven disease biology. APUC-6 genes instead associated with the expression of alternative steroid hormone receptors, ESR1/2 and PGR. We used RNA expression of AR or APUC-6 genes to define two subgroups of tumors with differential association with hallmark pathways and cell surface targets. CONCLUSIONS: The APUC-6 high/AR-low tumors represented a subgroup of patients with good clinical outcomes in contrast to the AR-high or neuroendocrine prostate cancers. Altogether, measuring the aggregate expression of APUC-6 genes in current genomic tests identifies PCs that are ligand- (rather than AR-) driven and require distinct therapeutic strategies. FUNDING: NCI/NIH 1R37CA288972-01, NCI Cancer Center Support P30 CA077598, DOD W81XWH-22-2-0025, R01 CA249279.

A Case of Fibroblast Growth Factor Receptor Fusion-Positive Intrahepatic Cholangiocarcinoma With Humoral Hypercalcemia of Malignancy.

Humoral hypercalcemia of malignancy (HHM) comprises the majority of cases with malignancy-related hypercalcemia and is mediated by elevated parathyroid hormone-related peptide (PTHrP). HHM is rare in cholangiocarcinoma and has been reported only in a few case reports and series. We report a case of a 63-year-old male with a history of locally advanced fibroblast growth factor receptor (FGFR) fusion-positive intrahepatic cholangiocarcinoma who presented with recurrent HHM. The first episode of his hypercalcemia occurred 15 months after the initial diagnosis of cholangiocarcinoma and coincided with disease progression. The hypercalcemia was treated with zoledronic acid, and an FGFR inhibitor was started for the treatment of his malignancy. The second hypercalcemia episode occurred nine months later, with evidence of further disease progression. HHM is associated with poor clinical outcomes; a high index of suspicion should be present to identify and treat this complication in cases of cholangiocarcinoma promptly. With an increased understanding of the molecular alterations underlying cholangiocarcinoma, it will also be necessary to further evaluate its co-occurrence with HHM as the specific molecular alterations in this setting could lay the groundwork for targeted therapies and improve risk stratification for these patients.

Mutational signature-based identification of DNA repair deficient gastroesophageal adenocarcinomas for therapeutic targeting.

Homologous recombination (HR) and nucleotide excision repair (NER) are the two most frequently disabled DNA repair pathways in cancer. HR-deficient breast, ovarian, pancreatic and prostate cancers respond well to platinum chemotherapy and PARP inhibitors. However, the frequency of HR deficiency in gastric and esophageal adenocarcinoma (GEA) still lacks diagnostic and functional validation. Using whole exome and genome sequencing data, we found that a significant subset of GEA, but very few colorectal adenocarcinomas, show evidence of HR deficiency by mutational signature analysis (HRD score). High HRD gastric cancer cell lines demonstrated functional HR deficiency by RAD51 foci assay and increased sensitivity to platinum chemotherapy and PARP inhibitors. Of clinical relevance, analysis of three different GEA patient cohorts demonstrated that platinum treated HR deficient cancers had better outcomes. A gastric cancer cell line with strong sensitivity to cisplatin showed HR proficiency but exhibited NER deficiency by two photoproduct repair assays. Single-cell RNA-sequencing revealed that, in addition to inducing apoptosis, cisplatin treatment triggered ferroptosis in a NER-deficient gastric cancer, validated by intracellular GSH assay. Overall, our study provides preclinical evidence that a subset of GEAs harbor genomic features of HR and NER deficiency and may therefore benefit from platinum chemotherapy and PARP inhibitors.

Identifying regulators of aberrant stem cell and differentiation activity in colorectal cancer using a dual endogenous reporter system.

Aberrant stem cell-like activity and impaired differentiation are central to the development of colorectal cancer (CRC). To identify functional mediators of these key cellular programs, we engineer a dual endogenous reporter system by genome-editing the SOX9 and KRT20 loci of human CRC cell lines to express fluorescent reporters, broadcasting aberrant stem cell-like and differentiation activity, respectively. By applying a CRISPR screen targeting 78 epigenetic regulators with 542 sgRNAs to this platform, we identify factors that contribute to stem cell-like activity and differentiation in CRC. Perturbation single cell RNA sequencing (Perturb-seq) of validated hits nominate SMARCB1 of the BAF complex (also known as SWI/SNF) as a negative regulator of differentiation across an array of neoplastic colon models. SMARCB1 is a dependency and required for in vivo growth of human CRC models. These studies highlight the utility of biologically designed endogenous reporter platforms to uncover regulators with therapeutic potential.

Utilizing a dual endogenous reporter system to identify functional regulators of aberrant stem cell and differentiation activity in colorectal cancer.

Aberrant stem cell-like activity and impaired differentiation are central to the development of colorectal cancer (CRC). To identify functional mediators that regulate these key cellular programs in CRC, we developed an endogenous reporter system by genome-editing human CRC cell lines with knock-in fluorescent reporters at the SOX9 and KRT20 locus to report aberrant stem cell-like activity and differentiation, respectively, and then performed pooled genetic perturbation screens. Constructing a dual reporter system that simultaneously monitored aberrant stem cell-like and differentiation activity in the same CRC cell line improved our signal to noise discrimination. Using a focused-library CRISPR screen targeting 78 epigenetic regulators with 542 sgRNAs, we identified factors that contribute to stem cell-like activity and differentiation in CRC. Perturbation single cell RNA sequencing (Perturb-seq) of validated hits nominated SMARCB1 of the BAF complex (also known as SWI/SNF) as a negative regulator of differentiation across an array of neoplastic colon models. SMARCB1 is a dependency in CRC and required for in vivo growth of human CRC models. These studies highlight the utility of a biologically designed endogenous reporter system to uncover novel therapeutic targets for drug development.

Cyclin D1 depletion interferes with oxidative balance and promotes cancer cell senescence.

Expression of cyclin D1 (CCND1) is required for cancer cell survival and proliferation. This is presumably due to the role of cyclin D1 in inactivation of the RB tumor suppressor. Here, we investigated the pro-survival function of cyclin D1 in a number of cancer cell lines. We found that cyclin D1 depletion facilitated cellular senescence in several cancer cell lines. Senescence triggered by cyclin D1 depletion was more extensive than that caused by the prolonged CDK4 inhibition. Intriguingly, the senescence caused by cyclin D1 depletion was independent of RB status of the cancer cell. We identified a build-up of intracellular reactive oxygen species in the cancer cells that underwent senescence upon depletion of cyclin D1 but not in those cells where CDK4 was inhibited. The higher ROS levels were responsible for the cell senescence, which was instigated by the p38-JNK-FOXO3a-p27 pathway. Therefore, expression of cyclin D1 prevents cancer cells from undergoing senescence, at least partially, by keeping the level of intracellular oxidative stress at a tolerable sub-lethal level. Depletion of cyclin D1 promotes the RB-independent pro-senescence pathway and the cancer cells then succumb to the endogenous oxidative stress levels.This article has an associated First Person interview with the first author of the paper.