RXRA and colonic neoplasm: In addition, the repression of PI3K/AKT1 activity by treatment with the AKT1 inhibitor MK2206 or the PI3K inhibitor BYL719 completely blocked the effect of TTC7B on RXRA expression in colon cancer cells, whereas the repression of MEK/ERK activity by treatment with the MEK1/2 inhibitor U0126 or selumetinib did not (Figure 7C).