However, in another study, it was shown that PXR was downregulated in colon tumors and the ectopic upregulation of PXR inhibited cell proliferation and elevated G0/G1 cell cycle arrest by upregulating p21(WAF1/CIP1) and reducing E2F1 expression in HT-29 cells. The gene discussed is CDKN1A; the disease is colonic neoplasm.