PURPOSE:Studying the multidrug resistance(MDR) phenotype occurring in retinoblastoma and its mechanism. METHODS:Using the procedure of stepwise increase in drug concentrations to obtain a retinoblastoma subline which resistant to 600ng/ml vincristine (HXO-RB/VCR). Characteristics of this drug-resistant cell line were investigated by cell counting,drugcontents determinatin,drug sensitivity evaluation and radiation sensitivity test. RESULTS:This cell line was cross-resistant to VDS,MMC VP16，ADM ,DDP,CBP,but not resistant to BCNU and 5-Fu. It was proved to be collaterally sensitive to MTX,and the response to 60Co gamma;-ray was modified slightly in HXO-RB/VCR cell line. Intracellular levels of VCR was much higher in HXO-RB44 cells than in the resistant subline. Those cross-resistances can be reversed by verapamil partly. CONCLUSIONS:MDR and radiation resistance of retinoblastoma can be induced by exposing to VCR and reversed by verapamil partly. （Chin J Ocul Fundus Dis,1997,13: 6-9）
Objective To investigate the mechanism and clinical significance of vincristine (VCR) inhibiting gastrinproliferation effects on human colon cell line SW480. Methods Effects of VCR on the viable cell count (A value), myoinositol triphosphate (IP3, CPM value), 〔Ca2+〕i and protein kinase C (PKC) activity of human colon cell line SW480 were evaluated in vitro by MTT assay,3Hmyoinositol incorporation, fluorescence measurements and γ-32P-ATP incorporation.Results A value of VCR+PG group was lower than that of PG or control group (Ｐ＜0.01 vs control, Ｐ＜0.01 vs PG). The concentration of IP3 or 〔Ca2+〕i in VCR+PG group was lower than that in PG group (Ｐ＜0.01 vs PG); and the PKC activity of membrane was lower than that in PG group (Ｐ＜0.05 vs PG, Ｐ＞0.05 vs control). Conclusion Effects of vincristine may be through the phosphoinositide signaling pathway on gastrinstimulating cell proliferation in human colon cell line SW480. It has provided an experimental evidence for antisignaling therapy for patients with colon cancer.