Background and purpose: Oxaliplatin (L-OHP) is one of the most commonly used chemotherapy drugs in colorectal cancer and L-OHP-resistance is very common in colorectal cancer therapy. This research was to discuss the reversal effect in L-OHP-resistant human colon cancer cell line LoVo/L-OHP by anemoside B4 (AB4) and tetrandrine (Tet) and to clarify their molecular mechanism. Methods: LoVo/L-OHP cells were treated for 48 h by AB4 and Tet at different concentrations to get non-toxic dose. Drug sensitivity was measured by MTT. After the treatment

the cell cycle and apoptosis of the cells were detected. Expression of P-gp mRNA

zDHHC9 mRNA and SMAD4 mRNA were detected by RT-PCR. Expression of P-gp

zDHHC9 and SMAD4 protein were detected by Western blot. Results: The IC50 of LoVo/L-OHP for L-OHP was (112.5±23.6) μg/mL

and the IC50 decreased to (62.8±21.4) μg/mL (P0.05) and (58.9±26.3) μg/mL (P0.05) after the treatment with 0.71 μg/mL AB4 and 0.45 μg/mL Tet (non-toxic dose) separately. The cell cycle experiment showed that the cells in G1 stage decreased and in S stage increased but with no statistical significance (P0.05). The cell apoptosis experiment showed that the apoptotic rate increased after the treatment with AB4 and Tet with non-toxic dose but with no statistical significance (P0.05). The RT-PCR experiment showed that the expressions of P-gp mRNA and zDHHC9 mRNA were increased and SMAD4 mRNA was decreased in LoVo/L-OHP cells compared with in LoVo cells (P0.05)

while it was found that P-gp mRNA in LoVo/L-OHP cells was decreased after the treatment with AB4 at non-toxic dose (P0.05). Western blot experiment showed the protein of P-gp in LoVo/L-OHP cells was decreased after treatment with AB4 (P0.05)

which was accordant to the PCR result. The expression of zDHHC9 protein in LoVo/L-OHP cells was decreased in LoVo/L-OHP cells after treatment with Tet (P0.05). Conclusion: AB4 and Tet have some reversal effect on resistant to L-OHP in LoVo/L-OHP cells. The molecular mechanism of the resistance reverse effect was related to down-regulation of P-gp for AB4 and down-regulation of zDHHC9 for Tet.