KRAS mutation, which occurs in ∼ 95% of pancreatic ductal adenocarcinoma (PDA), has been shown to program tumor metabolism. MCT4 is highly upregulated in a subset of PDA with a glycolytic gene expression program and poor survival. Models with high levels of MCT4 preferentially employ glycolytic metabolism. Selectively in such "addicted" models, MCT4 attenuation compromised glycolytic flux with compensatory induction of oxidative phosphorylation and scavenging of metabolites by macropinocytosis and autophagy. In spite of these adaptations, MCT4 depletion induced cell death characterized by elevated reactive oxygen species and metabolic crisis. Cell death induced by MCT4-depletion was augmented by inhibition of compensatory pathways. In xenograft models, MCT4 had a significant impact on tumor metabolism and was required for rapid tumor growth. Together, these findings illustrate the metabolic diversity of PDA described by MCT4, delineate pathways through which this lactate transporter supports cancer growth, and demonstrate that PDA can be rationally targeted based on metabolic addictions.

SummaryBRD4 belongs to the bromodomain and extraterminal (BET) family of chromatin reader proteins that bind acetylated histones and regulate gene expression. Pharmacological inhibition of BRD4 by BET inhibitors (BETi) has indicated antitumor activity against multiple cancer types. We show that BRD4 is essential for the repair of DNA double-strand breaks (DSBs) and mediates the formation of oncogenic gene rearrangements by engaging the non-homologous end joining (NHEJ) pathway. Mechanistically, genome-wide DNA breaks are associated with enhanced acetylation of histone H4, leading to BRD4 recruitment, and stable establishment of the DNA repair complex. In support of this, we also show that, in clinical tumor samples, BRD4 protein levels are negatively associated with outcome after prostate cancer (PCa) radiation therapy. Thus, in addition to regulating gene expression, BRD4 is also a central player in the repair of DNA DSBs, with significant implications for cancer therapy.

Cdc48 (also called VCP and p97) is an abundant protein that plays essential regulatory functions in a broad array of cellular processes. Working with various cofactors, Cdc48 utilizes its ATPase activity to promote the assembly and disassembly of protein complexes. Here, we review key biological functions and regulation of Cdc48 in ubiquitin-related events. Given the broad employment of Cdc48 in cell biology and its intimate ties to human diseases (e.g., amyotrophic lateral sclerosis), studies of Cdc48 will bring significant insights into the mechanism and function of ubiquitin in health and diseases.

Recently, the combination of androgen deprivation therapy (ADT) and radiation therapy (RT) has been shown to block the androgen receptor (AR)-driven DNA damage response (DDR) and enhance RT-mediated cell kill of prostate cancer (PCa). Since ADT may induce expression of AR splice variants (ARVs) we hypothesized that ARVs can drive DDR and mediate resistance to combined ADT and RT. Herein, we demonstrate that ARVs can increase the clonogenic survival of PCa cells following RT in an ADT-independent manner. RT induces the interaction between ARVs and a DDR driver, the DNA-dependent protein kinase catalytic subunit (DNA-PKc). Pharmacological inhibition of DNA-PKc blocks its interaction with ARVs and results in persistence of DNA damage, increased tumor cell kill and improved PCa cell survival following RT. These results indicate that combinatorial targeting of DNA-PKc with ADT and RT may be an effective strategy for overcoming radioresistance when treating clinically localized PCa.

Oncology, Taiho, Pfizer, and Vertex Pharmaceuticals, and which has a commercial interest in abiraterone, PARP inhibition in DNA repair-defective cancers, and PI3K/ AKT pathway inhibitors (no personal income). JDB was named an inventor, with no financial interest, for US patent 8,822,438 ("Methods and compositions for treating cancer"). He has been the co-investigator or principal investigator of many industry-sponsored clinical trials.