Identification of Genes Required for Enzalutamide Resistance in Castration-Resistant Prostate Cancer Cells .

Castration-resistant prostate cancer can be treated with the antiandrogen enzalutamide, but responses and duration of response are variable. To identify genes that support enzalutamide resistance, we performed a short hairpin RNA (shRNA) screen in the bone-homing, castration-resistant prostate cancer cell line, C4-2B. We identified 11 genes ( and ) whose loss resulted in decreased cell survival in response to enzalutamide. To validate our screen, we performed transient knockdowns in C4-2B and 22Rv1 cells and evaluated cell survival in response to enzalutamide. Through these studies, we validated three genes ( and ) as supporters of enzalutamide resistance Although expression is lower in metastatic castration-resistant prostate cancer samples versus primary prostate cancer samples, knockdown of was sufficient to reduce cell survival in C4-2B and 22Rv1 cells. expression increases with Gleason grade, and the highest expression is observed in metastatic castration-resistant disease. Knockdown of reduced cell survival, and pharmacologic inhibition of MAP3K11 with CEP-1347 in combination with enzalutamide resulted in a dramatic increase in cell death. This was associated with decreased phosphorylation of AR-Serine650, which is required for maximal AR activation. Finally, although expression did not change during disease progression, knockdown of resulted in decreased AR and AR splice variant expression, likely contributing to the C4-2B and 22Rv1 decrease in cell survival. Our study has therefore identified at least three new supporters of enzalutamide resistance in castration-resistant prostate cancer cells .