EPAS1 and posterior cortical atrophy: To further examine the influences of increased HIF2α on the BM-MSCs-increased PCa stem cell numbers and PCa cell invasion, we applied the interruption approach via knocking-down the HIF2α in PCa cells, and results revealed that knocking-down HIF2α (Figure 2a) resulted in suppression of BM-MSCs-enhanced C4-2 stem cell population (Figure 2b) and consequent C4-2 cell invasion (Figure 2c).