PIK3IP1 and urinary bladder cancer: To determine if PIK3IP1 upregulation is necessary and sufficient for GSK-126 sensitivity in ARID1A-deficient bladder cancer cells, we generated an array of dual ARID1A/PIK3IP1 stable knockdown cells and ARID1Akd/PIK3IP1 stable overexpression cells (Figure 5, A and C).