Triptolide exerts significant effects on the cell cycle across various cancer types, predominantly inducing G0/G1 phase arrest by enhancing the expression of cell cycle inhibitors in multiple myeloma (RPMI 8266) cells and suppressing proliferating cell nuclear antigen and Cyclin D1 in airway smooth muscle (ASMCs) cells in response to PDGF stimulation, thereby decreasing cell proliferation [1001, 1002]. The gene discussed is PCNA; the disease is cancer.