Abstract: Objective To investigate the role of human membrane associated sialidase (Neu3) in multidrug resistance (MDR) of K562 cells. Method K562 cells and K562/ADM cells were treated with DNR alone or the combination with DNR and NeuAC2en.The cells survival rate was measured by MTT assay; the expression of MDR related factors and apoptosis related factors, such as MDR, MRP, MGMT, GST, Bcl-xl, Bcl-2 and Bax were determined by western blot and RT-PCR; Neu3 activity was detected by TBA reaction. Result The survival rate of K562/ADM cells was higher than that of K562 cells; NeuAC2en showed synergistic effect with DNR(P<0.01); Neu3 activity of both K562 and K562/ADM cells decreased after DNR or NeuAC2en induction and the decrease degree was the most statistically significant in the combination treatment group(P<0.01). Under the identical condition, the protein expression of P-gp and Neu3 and the mRNA expression of MDR1, Neu3, Bcl-xl and Bcl-2 increased with comparison to K562 cells. The mRNA level of Bax in K562 and K562/ADM groups was not changed significantly. MDR1, Neu3,Bcl-xl and Bcl-2 decreased after DNR induction and down-regulated most obviously in the groups treated by DNR combined with NeuAC2en. Conclusion Neu3 may be related with multidrug resistance of K562/ADM cell through regulating apoptosis and the expression of MDR1.

Key words: human membrane-associated sialidase, MDR, K562