Clinically aggressive prostate cancer (PCa) is linked to androgen resistance, metastasis, and expression of neuroendocrine markers. To understand mechanism(s) of neuroendocrine differentiation (NED) of PCa epithelia, we compared neuronal differentiation occurring during embryogenesis, in primary cultures of neural crest (NC) cells, and NED in PCa cell lines (LNCaP and PC3). We demonstrate, hypoxia promotes neuronal and neuroendocrine differentiation of NC cells and PCa cells, respectively, by inducing the miR-106b~25 cluster. In turn, miR-106b~25 comprised of miR-106b, miR-93 and miR-25, down-regulates the transcriptional repressor REST, which represses neuron-specific protein-coding and miRNA genes. In prostate tumors of high Gleason score (≥ 8), an inverse trend was observed between REST and miR-106b~25 induction. Employing miRNA PCR arrays, we identified miRNAs up-regulated by hypoxia in LNCaP cells and REST-knockdown in NC cells. Significantly, a subset of miRNAs (miR-9, miR-25, miR-30d and miR302b) is up-regulated in high Gleason score (≥ 8) PCa, suggesting a mechanism by which NED contributes to PCa malignancy. We propose that loss of REST and induction of this set of microRNAs can serve as potential novel clinical markers of advanced PCa.

Purpose: No standard treatment exists for platinum-refractory, recurrent/metastatic nasopharyngeal cancer (NPC). This phase II study (NCT02605967) evaluated progression-free survival (PFS) of spartalizumab, an antiprogrammed cell death protein-1 (PD-1) monoclonal antibody, versus chemotherapy, in NPC. Patients and Methods: Patients with nonkeratinizing recurrent/metastatic NPC who progressed on/after platinum-based chemotherapy were enrolled. Spartalizumab was dosed 400 mg once every 4 weeks, and chemotherapy was received per investigator's choice. Results: Patients were randomized to receive either spartalizumab (82 patients) or chemotherapy (40 patients). The most common spartalizumab treatment-related adverse events were fatigue (10.3%) and pruritus (9.3%). Median PFS in the spartalizumab arm was 1.9 months versus 6.6 months in the chemotherapy arm (P = 0.915). The overall response rate in the spartalizumab arm was 17.1% versus 35.0% in the chemotherapy arm. Median duration of response was 10.2 versus 5.7 months in the spartalizumab versus chemotherapy arms, respectively. Median overall survival was 25.2 and 15.5 months in the spartalizumab and chemotherapy arms, respectively. Tumor RNA sequencing showed a correlation between response to spartalizumab and IFNγ, LAG-3, and TIM-3 gene expression. Conclusions: Spartalizumab demonstrated a safety profile consistent with other anti–PD-1 antibodies. The primary endpoint of median PFS was not met; however, median overall survival and median duration of response were longer with spartalizumab compared with chemotherapy.

Trunk neural crest (NC) cells differentiate to neurons, melanocytes, and glia. In NC cultures, cyclic AMP (cAMP) induces melanocyte differentiation while suppressing the neuronal sympathoadrenal lineage, depending on the signal intensity. Melanocyte differentiation requires activation of CREB and cAMP-dependent protein kinase A (PKA), but the role of PKA is not understood. We have demonstrated, in NC cultures, cAMP-induced transcription of the microphthalmia-associated transcription factor gene ( Mitf ) and the RE-1 silencing transcription factor gene ( REST ), both Wnt-regulated genes. In NC cultures and zebrafish, knockdown of the corepressor of Wnt-mediated transcription C-terminal binding protein 2 (CtBP2) but not CtBP1 derepressed Mitf and REST expression and enhanced melanocyte differentiation. cAMP in NC and B16 melanoma cells decreased CtBP2 protein levels, while inhibition of PKA or proteasome rescued CtBP2 degradation. Interestingly, knockdown of homeodomain-interacting protein kinase 2 (HIPK2), a CtBP stability modulator, increased CtBP2 levels, suppressed expression of Mitf, REST, and melanocyte differentiation, and increased neuronal gene expression and sympathoadrenal lineage differentiation. We conclude that cAMP/PKA via HIPK2 promotes CtBP2 degradation, leading to Mitf and REST expression. Mitf induces melanocyte specification, and REST suppresses neuron-specific gene expression and the sympathoadrenal lineage. Our studies identify a novel role for REST in NC cell differentiation and suggest cross talk between cAMP and Wnt signaling in NC lineage specification.