Neuroendocrine (NE) differentiation of advanced prostate adenocarcinoma following androgen receptor (AR) axis-directed therapy is becoming increasingly recognized. Several models of this transdifferentiation provide insight into its molecular pathogenesis and have highlighted the placental gene PEG10 for further study. Using our unique model of enzalutamide resistance (ENZR) and NE differentiation, we studied PEG10/AR interplay in enzalutamide treatment-resistant cell lines 42DENZR and 42FENZR compared to LNCaP and castration-resistant 16DCRPC cells. ENZR cell lines with positive terminal NE marker status also displayed higher baseline expression of PEG10 compared to LNCaP and 16DCRPC. Antagonism of AR activity increased PEG10 expression followed by an increase in terminal NE markers. Conversely, stimulating AR activity via androgen supplementation reversed PEG10 and NE marker expression in a time and dose-dependent manner. These results were supported by human data showing that PEG10 expression is highest in NEPC and that AR-dependent gene, PSA, is negatively correlated with PEG10 in adenocarcinoma. Further, ChIP assay confirmed binding of activated AR to the PEG10 enhancer, decreasing PEG10 expression. While PEG10 did not drive NEPC, its knockdown reduced NE markers in our cell lines. Moreover, PEG10 knockdown in vitro- and in vivo-attenuated tumor growth. Overall, these observations indicate that PEG10 is an AR-repressed gene which modulates NE markers in ENZR cells and targeting PEG10 in advanced prostate cancer with NE features is a rational and viable option.
Supplementary Figure 1. Reciprocal PEG10 and PSA expression patterns in response to androgen activity.
Supplement Figure 2. AR binds to downstream enhancer region of PEG10 gene.
Supplement Figure 3. Bright field images of LNCaP cells upon PEG10 overexpression.
Supplementary Table 1. PEG10 and PSA mRNA expression pre vs post docetaxel+androgen deprivation therapy from 2 independent cohorts. PEG10 and PSA mRNA fold changes shown in log values accompanied by corresponding p values.
Supplementary Table 2. Primer sequences for selected genes used for quantitative PCR.
Supplementary Table 3. AR binding site on PEG10 enhancer used to design ChIP primers.