PGP and colonic neoplasm: Unlike our results, the work by Han et al. (2008) [49] using P-gp expressing cell lines (human colon cancer cells, that naturally express the MDR1 gene, and porcine kidney cells stably transfected with the human P-gp) and piperine (50 or 100 μM for 48 h), observed a small, but significant, arrest at the G0/G1 phase of the cell cycle.