Objective: To study the active sites of podophyllotoxin derivatives. Methods: Some podophyllotoxin derivatives were analyzed by quantum and mechanics method. Results: Some information was given according to the calculation results about HOMO and LUMO electron density. The C-4 position is the position for effective modification. The B ring and E ring are important active centers. Conclusion: The hole of positive charge in B ring easily combines with an acceptor within the molecular. Some quinolones with similar electronic construction to podophyllotoxin may have antitumor activity.

Chuankezhi (CKZ), a new Chinese medicine, plays an important role in immunoregulation. Cytokine-induced killer (CIK) cells have been commonly used for immunotherapy in recent years. In this study, we aimed to investigate the immunoregulatory effect of CKZ on CIK cells. Peripheral blood monocytes were isolated from healthy donors, and CIK cells were generated by culturing monocytes with interferon-gamma (IFN-γ) and interleukin 2. Different concentrations of CKZ were added on day 2. After incubation for 14 days in culture, the antitumor effects of CIK cells were measured by cytotoxicity assay. Flow cytometry was used to explore the effect of CKZ on CIK cell immunophenotype, intracellular cytokine production, and apoptosis. The effect of CKZ on the antitumor activity of CIK cells in nude mice was also investigated. CKZ increased the percentage of CD3+CD56+ CIK cells but did not significantly change the percentage of CD4+, CD8+, or CD4+CD25+ CIK cells. CKZ-conditioned CIK cells showed a greater ability to kil tumor cells, as well as a higher frequency of IFN-γand TNF-α production, compared with the CIK cells in the control group. CKZ also suppressed the apoptosis of CIK cells in vitro. Furthermore, CKZ combined with CIK cells had a stronger suppressive effect on tumor growth in vivo than the CIK, CKZ, or normal saline control groups. Our results indicate that CKZ enhances the antitumor activity of CIK cells and is a potential medicine for tumor immunotherapy.