Androgen Deprivation Upregulates SPINK1 Expression and Potentiates Cellular Plasticity in Prostate Cancer
Tiwari R, Manzar N, Bhatia V, Yadav A, Carskadon S, Gupta N, Zoubeidi A, Palanisamy N, and Ateeq B. Androgen Deprivation Upregulates SPINK1 Expression and Potentiates Cellular Plasticity in Prostate Cancer. Cancer Res 2019; 79(13).
The Serine Peptidase Inhibitor, Kazal type 1 (SPINK1) overexpression represents the second-largest prostate cancer (PCa) subtype associated with increased risk of recurrence and poor prognosis. Regardless of molecular subtype, androgen-deprivation therapy (ADT) remains the mainstay treatment for locally advanced and metastatic PCa patients. However, majority of the treated individuals eventually progress to castration-resistant stage and a subset of these patients develop ADT-induced neuroendocrine prostate cancer. Despite evidences of detrimental effects of ADT on PCa, possible role of androgen signaling in SPINK1-mediated prostate oncogenesis remains unexplored. Here, we show that androgen receptor (AR) functions as a direct transcriptional repressor of SPINK1, and blocking AR signaling relieves its repression, leading to upregulation of SPINK1. In agreement, we observe an inverse association between SPINK1 levels and AR expression across multiple patient cohorts, and in neuroendocrine differentiated LNCaP cells. We show that AR and its corepressor, the RE1-silencing transcription factor (REST), occupy SPINK1 promoter and inhibits its transcription. On the other hand, in the absence of AR, lineage reprogramming factor SOX2 in turn binds to SPINK1 promoter leading to its positive transcriptional regulation in androgen-deprived conditions with concomitant increase in neuroendocrine markers. Additionally, stable knockdown of SPINK1 results in reduced epithelial-mesenchymal transition, decreased stemness and drug resistance. Collectively, our findings provide a plausible explanation to the paradoxical clinical outcomes of ADT, arising due to increase in SPINK1 levels. Finally, we emphasize the need to take a well-informed decision prior to ADT and develop alternative therapeutic strategies for castrate-resistant PCa patients.