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目的：探讨依托泊苷、顺铂和紫外线照射对结肠癌细胞分化抑制因子1（ ID1）表达的影响及其机制。方法采用依托泊苷、顺铂和紫外线照射处理HCT116细胞，采用Western blot和实时荧光定量PCR方法检测ID1蛋白和mRNA的表达。建立稳定过表达ID1蛋白的HCT116细胞系，检测外源过表达ID1对化疗药物及紫外线照射诱导细胞凋亡的影响。结果紫外线照射组HCT116细胞的凋亡率为（58．70±1．55）％，与对照组[（1．10±0．07）％]比较，差异有统计学意义（P＜0．05）；顺铂组HCT116细胞的凋亡率为（35．80±0．92）％，与对照组[（1．20±0．13）％]比较，差异有统计学意义（P＜0．05）；依托泊苷组HCT116细胞的凋亡率为（21．00±0．72）％，与对照组[（3．50±0．23）％]比较，差异有统计学意义（P＜0．05）。依托泊苷与细胞中ID1蛋白的稳定性无关（P＞0．05），但降低ID1 mRNA的稳定性（ P＜0．05）。经紫外线、顺铂和依托泊苷作用后，稳定过表达ID1的细胞HCT116ID1的凋亡率分别为（23．80±0．82）％、（17．80±1．34）％和（13．40±0．53）％，低于空载细胞HCT116control的凋亡率[分别为（41．10±1．61）％、（30．40±2．67）％和（22．50±3．47）％]，差异均有统计学意义（均P＜0．05）。结论依托泊苷通过加速ID1 mRNA的降解速率实现对ID1的表达下调。 ID1抑制药物诱导的结肠癌细胞的凋亡。降低ID1的生物活性可能成为肿瘤治疗的新策略。

Objective To investigate the changes of ID1 expression in tumor cells treated with etoposide, cisplatin and ultraviolet ( UV) irradiation, and explore the effect of ID1 on chemotherapeutic drug-and UV-induced apoptosis.Methods In the present study, upon onset of apoptosis induced by various kinds of inducers such as etoposide, cisplatin and UV irradiation, the expression level of ID1 was detected by Western blot and real-time PCR.We also analyzed the half-life of ID1 protein and stability of ID1 mRNA respectively by cycloheximide inhibition test and RT-PCR.Annexin-V assay was carried out to evaluate the contribution of ID1 protein to chemotherapeutic drug-and UV-induced apoptosis.Results ID1 expression presented a profound down-regulation in the HCT116 cells treated with etoposide, cisplatin and UV irradiation( P<0.05 for all) .The apoptosis in the UV irradiation group, cisplatin group, etoposide group was (58.70±1.55)%, (35.80±0.92)%and (21.00±0.72)%, respectively, significantly higher than that of the control group(1.10±0.07)%, (1.20±0.13)%and (3.50±0.23)%(P<0.05 for all).Upon etoposide treatment, ID1 expression level was decreased via induction of mRNA instability, but not the protein degradation changes.Additionally, ectopic expression of ID1 in the HCT116 cells alleviated etoposide-, cisplatin-and UV-induced apoptosis.The results of flow eytometry revealed that the percentage of apoptotic cells in the ID1 group under the treatment of etoposide, cisplatin and UV irradiation was (23.80±0.82)%, (17.80±1.34)%and (13 .40±0.53)%,respectively , significantly lower than that in the empty vector group (41.10±1.61)%, (30.40±2.67)%and (22.50±34.7 )% (P<0.05 for all).Conclusoi ns These observations indicate that the treatment with etoposide reduces the amount of ID1 by induction of mRNA instability, and exogenously introduced ID1 protects cells against etoposide-, cisplatin-and UV irradiation-induced apoptosis.Inhibition of the ID1 bioactivity may become a new strategy in cancer treatment.