Abstract: OBJECTIVE To investigate the effects of active monomer PP-22 purified from Paridis Rhizoma on proliferation and apoptosis of human colorectal cancer SW620 cells, and explore the antitumous effect of PP-22 combined with 5-fluorouracil(5-FU) or lobaplatin. METHODS MTT assay and cell colone formation inhibitory assay were used to determine the inhibitory effect of PP-22 on human colorectal cancer SW620 cells. The inhibitory effect of PP-22 combined with 5-FU or lobaplatin were observed, respectively. The percentage of apoptotic cells and cell cycle distribution were determined by propidium iodide(PI) single staining flow cytometry. Western blot was used to determine the effect of PP-22 on the expression of apoptosis related proteins. RESULTS MTT assay showed that PP-22 inhibited colorectal cancer SW620 cells proliferation in dose-dependent manner. Cell colony formation inhibitory assay demonstrated that cell clones decreased with the increase of drug concentrations. Compared with PP-22 group, the chemosensitivity of PP-22 combined with 5-FU or lobaplatin was increased significantly. PI staining analysis showed that cell cycle was arrested at S phase. Western blot detecting showed that Caspase-3 and Caspase-9 were activated and degraded. The expression of Bcl-2 and Bcl-xL were downregulated and pro-apoptotic protein Bax was upregulated. CONCLUSION PP-22 inhibits the proliferation and induces apoptosis of SW620 cells. PP-22 also improves the sensitivity of SW620 cells on 5-FU and lobaplatin.