Chen Xiu-Xu, Lai Mao-De, Zhang Yong-Liang, Huang Qiong
Department of Pathology, School of Medicine, Zhe Jiang University, Hang Zhou, 310031, Zhejiang Province, China.
World J Gastroenterol. 2002 Oct;8(5):841-6. doi: 10.3748/wjg.v8.i5.841.
Our previous studies showed increased sensitivity to 5-FU in colon cancer cell lines with microsatellite instability, and considered that mutations of TGFbeta-R II, IGF IIR, RIZ gene might enhance the potentials of cell growth and proliferation, which increased the sensitivity to 5-FU. Here we compared the distribution of cell cycle and P53 status between two human colon cancer cell lines with different sensitivity to 5-FU. Because mechanistic differences exist between 5-FU and CDDP, we also analyzed the efficacy of CDDP and combination therapy on two human colon cancer cell lines.
We compared the sensitivity to CDDP of these two cell lines by MTT assay. Distribution of cell cycle under treatment of 5-FU, CDDP alone or both was analyzed by Flow Cytometry, and expression of P53 was detected by immunocytochemical staining.
SW480 cells were more sensitive to CDDP than LoVo cells at the concentrations above 16 micromol/l (Ratio of absorption is 0.64 and 0.79 at 16 micromol/l, respectively; P<0.01). Efficacy of combination therapy was conversely lower than that of single-therapy of 5-FU (Ratio of absorption in LoVo+5-FU, SW480+5-FU, LoVo+5-FU+CDDP and SW480+5-FU+CDDP is 0.53, 0.54, 0.72, 0.78, respectively; P<0.01). LoVo cells were negative whereas SW480 cells positive in P53 expression. 5-FU induced G1-phase arrest in both cell lines, but LoVo cells peaked 24 hours earlier than SW480 cells, and 48 hours earlier for an apparent hypodiploid DNA. However, CDDP showed the contrary, inducing S-phase arrest, and SW480 cells peaking 36 hours earlier. Both cell lines showed hypodipliod nuclei 48 hours after CDDP treatment. Percentage of cells in G1-phase and S-phase dominated alternatively under combination therapy in both cell lines.
These results suggest that colon cancer cells with microsatellite instability are more sensitive to 5-FU, whereas more resistant to CDDP. Combination therapy of 5-FU and CDDP shows fewer efficacies than 5-FU single-therapy, although it can render a cell cycle arrest. P53 may be involved in the shift of G1-phase to S-phase, but inessentially.
我们之前的研究表明，微卫星不稳定的结肠癌细胞系对5-氟尿嘧啶（5-FU）的敏感性增加，并认为转化生长因子β受体II（TGFbeta-R II）、胰岛素样生长因子II受体（IGF IIR）、RIZ基因的突变可能增强细胞生长和增殖的潜能，从而增加对5-FU的敏感性。在此，我们比较了对5-FU敏感性不同的两个人结肠癌细胞系之间的细胞周期分布和P53状态。由于5-FU和顺铂（CDDP）之间存在机制差异，我们还分析了CDDP及联合治疗对两个人结肠癌细胞系的疗效。
我们通过MTT法比较这两种细胞系对CDDP的敏感性。采用流式细胞术分析单独使用5-FU、CDDP或两者联合处理后的细胞周期分布，通过免疫细胞化学染色检测P53的表达。
在浓度高于16微摩尔/升时，SW480细胞比LoVo细胞对CDDP更敏感（在16微摩尔/升时吸光度比值分别为0.64和0.79；P<0.01）。联合治疗的疗效反而低于5-FU单药治疗（LoVo + 5-FU、SW480 + 5-FU、LoVo + 5-FU + CDDP和SW480 + 5-FU + CDDP的吸光度比值分别为0.53、0.54、0.72、0.78；P<0.01）。LoVo细胞P53表达为阴性，而SW480细胞为阳性。5-FU使两种细胞系均发生G1期阻滞，但LoVo细胞比SW480细胞提前24小时达到峰值，对于明显的亚二倍体DNA则提前48小时。然而，CDDP则相反，诱导S期阻滞，且SW480细胞提前36小时达到峰值。CDDP处理48小时后，两种细胞系均出现亚二倍体细胞核。联合治疗时，两种细胞系中G1期和S期细胞百分比交替占主导。
这些结果表明，微卫星不稳定的结肠癌细胞对5-FU更敏感，而对CDDP更耐药。5-FU与CDDP联合治疗的疗效低于5-FU单药治疗，尽管它可导致细胞周期阻滞。P53可能参与了G1期向S期的转变，但并非必需。
