BACKGROUND Prostate cancer is a heterogeneous disease, but current treatments are not based on molecular stratification. We hypothesized that metastatic, castration-resistant prostate cancers with DNA-repair defects would respond to poly(adenosine diphosphate [ADP]–ribose) polymerase (PARP) inhibition with olaparib. METHODS We conducted a phase 2 trial in which patients with metastatic, castration-resistant prostate cancer were treated with olaparib tablets at a dose of 400 mg twice a day. The primary end point was the response rate, defined either as an objective response according to Response Evaluation Criteria in Solid Tumors, version 1.1, or as a reduction of at least 50% in the prostate-specific antigen level or a confirmed reduction in the circulating tumor-cell count from 5 or more cells per 7.5 ml of blood to less than 5 cells per 7.5 ml. Targeted next-generation sequencing, exome and transcriptome analysis, and digital polymerase-chain-reaction testing were performed on samples from mandated tumor biopsies. RESULTS Overall, 50 patients were enrolled; all had received prior treatment with docetaxel, 49 (98%) had received abiraterone or enzalutamide, and 29 (58%) had received cabazitaxel. Sixteen of 49 patients who could be evaluated had a response (33%; 95% confidence interval, 20 to 48), with 12 patients receiving the study treatment for more than 6 months. Next-generation sequencing identified homozygous deletions, deleterious mutations, or both in DNA-repair genes — including BRCA1/2, ATM, Fanconi’s anemia genes, and CHEK2 — in 16 of 49 patients who could be evaluated (33%). Of these 16 patients, 14 (88%) had a response to olaparib, including all 7 patients with BRCA2 loss (4 with biallelic somatic loss, and 3 with germline mutations) and 4 of 5 with ATM aberrations. The specificity of the biomarker suite was 94%. Anemia (in 10 of the 50 patients [20%]) and fatigue (in 6 [12%]) were the most common grade 3 or 4 adverse events, findings that are consistent with previous studies of olaparib. CONCLUSIONS Treatment with the PARP inhibitor olaparib in patients whose prostate cancers were no longer responding to standard treatments and who had defects in DNA-repair genes led to a high response rate.

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Breast cancer is a heterogeneous disease, exhibiting a wide range of molecular aberrations and clinical outcomes. Here we employed paired-end transcriptome sequencing to explore the landscape of gene fusions in a panel of breast cancer cell lines and tissues. We observed that individual breast cancers harbor an array of expressed gene fusions. We identified two classes of recurrent gene rearrangements involving microtubule associated serine-threonine kinase (MAST) and Notch family genes. Both MAST and Notch family gene fusions exerted significant phenotypic effects in breast epithelial cells. Breast cancer lines harboring Notch gene rearrangements are uniquely sensitive to inhibition of Notch signaling, and over-expression of MAST1 or MAST2 gene fusions had a proliferative effect both in vitro and in vivo. These findings illustrate that recurrent gene rearrangements play significant roles in subsets of carcinomas and suggest that transcriptome sequencing may serve to identify patients with rare, actionable gene fusions.

Summary Forkhead box A1 (FOXA1) is a pioneer transcription factor that is essential for the normal development of several endoderm-derived organs, including the prostate gland1,2. FOXA1 is frequently mutated in the hormone-receptor driven prostate, breast, bladder, and salivary gland tumors3–8. However, how FOXA1 alterations affect cancer development is unclear, with FOXA1 previously ascribed both tumor suppressive9–11 and oncogenic12–14 roles. Here we assemble an aggregate cohort of 1546 prostate cancers (PCa) and show that FOXA1 alterations fall into three distinct structural classes that diverge in clinical incidence and genetic co-alteration profiles, with a collective prevalence of 35%. Class1 activating mutations originate in early PCa without ETS/SPOP alterations, selectively recur within the Wing2-region of the DNA-binding Forkhead domain (FKHD), enable enhanced chromatin mobility and binding frequency, and strongly transactivate a luminal androgen receptor (AR) program of prostate oncogenesis. By contrast, class2 activating mutations are acquired in metastatic PCa, truncate the C-terminal domain of FOXA1, enable dominant chromatin binding by increasing DNA affinity, and through TLE3 inactivation promote WNT-pathway driven metastasis. Finally, class3 genomic rearrangements are enriched in metastatic PCa, comprise of duplications and translocations within the FOXA1 locus, and structurally reposition a conserved regulatory element, herein denoted FOXA1 Mastermind (FOXMIND), to drive overexpression of FOXA1 or other oncogenes. Our study reaffirms the central role of FOXA1 in mediating AR-driven oncogenesis, and provides mechanistic insights into how different classes of FOXA1 alterations uniquely promote PCa initiation and/or metastatic progression. Furthermore, these results have direct implications in understanding the pathobiology of other hormone-receptor driven cancers and rationalize therapeutic co-targeting of FOXA1 activity.

Resistance to androgen deprivation therapies and increased androgen receptor (AR) activity are major drivers of castration resistant prostate cancer (CRPC). Although prior work focused on targeting AR directly, co-activators of AR signaling—which may represent new therapeutic targets—are relatively underexplored. Here we demonstrate that the mixed-lineage leukemia (MLL) complex, a well-known driver of MLL-fusion-positive leukemia, acts as a co-activator of AR signaling. AR directly interacts with the MLL complex via the menin MLL subunit. Menin expression is higher in castration resistant prostate cancer compared to hormone naïve prostate cancer and benign prostate and high menin expression correlates with poor overall survival. Treatment with a small molecule inhibitor of the menin-MLL interaction blocks AR signaling and inhibits the growth of castration resistant tumors in vivo in mice. Taken together, this work identifies the MLL complex as a critical co-activator of AR and a potential therapeutic target in advanced prostate cancer.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for COVID-19, employs two key host proteins to gain entry and replicate within cells, angiotensin-converting enzyme 2 (ACE2) and the cell surface transmembrane protease serine 2 (TMPRSS2). TMPRSS2 was first characterized as an androgen-regulated gene in the prostate. Supporting a role for sex hormones, males relative to females are disproportionately affected by COVID-19 in terms of mortality and morbidity. Several studies, including one employing a large epidemiological cohort, suggested that blocking androgen signaling is protective against COVID-19. Here, we demonstrate that androgens regulate the expression of ACE2, TMPRSS2, and androgen receptor (AR) in subsets of lung epithelial cells. AR levels are markedly elevated in males relative to females greater than 70 y of age. In males greater than 70 y old, smoking was associated with elevated levels of AR and ACE2 in lung epithelial cells. Transcriptional repression of the AR enhanceosome with AR or bromodomain and extraterminal domain (BET) antagonists inhibited SARS-CoV-2 infection in vitro. Taken together, these studies support further investigation of transcriptional inhibition of critical host factors in the treatment or prevention of COVID-19.