Less cytotoxicity to combination therapy of 5-fluorouracil and cisplatin than 5-fluorouracil alone in human colon cancer cell lines.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Chen
Xiu-Xu
XX
Department of Pathology, School of Medicine, Zhe Jiang University, Hang Zhou, 310031, Zhejiang Province, China.
Lai
Mao-De
MD
Zhang
Yong-Liang
YL
Huang
Qiong
Q
D000230:Adenocarcinoma; D000964:Antimetabolites, Antineoplastic / Q000633:toxicity; D000970:Antineoplastic Agents / Q000633:toxicity; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000633:toxicity*; D002945:Cisplatin / Q000633:toxicity; D003110:Colonic Neoplasms; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005472:Fluorouracil / Q000633:toxicity; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D016196:S Phase / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D016159:Tumor Suppressor Protein p53; D002945:Cisplatin; D005472:Fluorouracil