To understand the mechanism underlying G1-phase arrest in pristimerin-treated pancreatic cancer cells, we next investigated the effect of pristimerin on the levels of proteins that regulate the progression of cells in the G1 phase, including WAF1/p21, KIP1/p27, cyclin D1, cyclin E, cdk2, cdk4, and cdk6. This evidence concerns the gene CIB1 and familial pancreatic carcinoma.