Combined effects of Cantide and chemotherapeutic drugs on inhibition of tumor cells' growth in vitro and in vivo

Abstract

Aim: To investigate the combination effect of hTERT antisense oligonucleotide "Cantide" and three chemotherapeutic drugs (cisplatin, 5-fluorouracil (5-FU) and adriamycin (ADM)) on inhibiting the proliferation of HepG2, BGC and A549 cell lines in vitro, and to investigate the efficacy of Cantide used in combination with cisplatin (DDP) in vivo.

Methods: Cantide was transfected into these tumor cells by Lipofectin, and cell growth activity was calculated by microcytotoxicity assay. In vivo study, cells of HepG2 were implanted in Balb/c nude mice for 4 d. Then Cantide, DDP and Cantide+DDP were given intraperitoneally for 24 d respectively. The body weights of the tumor-bearing animals and their tumor mass were measured later to assess the effect of combination therapy in the nude mice. To evaluate the interaction of Cantide and these chemotherapeutic drugs, SAS software and Jin Zhengjun method were used.

Results: Combination treatments with 0.1 micromol/L Cantide reduced the IC50 of DDP, 5-FU and ADM from 1.07, 4.15 and 0.29 microg/mL to 0.25, 1.52 and 0.12 microg/mL respectively. The inhibition ability of DDP, 5-FU and ADM respectively in combination with Cantide in these tumor cells was higher than that of these drugs alone (P<0.0001). And synergism (Q > or = 1.15) was observed at the lower concentration of DDP (< or = 1 microg/mL), 5-FU (< or = 10 microg/mL) and ADM (< or = 0.1 microg/mL) with combination of Cantide. In vivo, combination treatment with Cantide and DDP produced the greater growth inhibition of human liver carcinoma cells HepG2 in nude mice (0.65+/-0.19 g tumor) compared with that when only one of these drugs was used (Cantide group: 1.05+/-0.16 g tumor, P = 0.0009<0.001; DDP group: 1.13+/-0.09 g tumor, P = 0.0001<0.001).

Conclusion: These findings indicate that Cantide may enhance therapeutic effectiveness of chemotherapeutic drugs over a wide range of tumor cells in vitro, and the combination use of Cantide and DDP can produce much higher inhibition rates, as compared with when either of these drugs was used only in vivo.

Figure 1

HepG2 cells’ growth inhibited by Cantide, DDP(A), 5-FU(B) and ADM(C) only and at the indicated combinations on HepG2 cells. The dots represent the concentrations of chemotherapeutic drugs as 0 on the dose-response curves which means treatments with Cantide only. The cells were treated with Cantide complexed to Lipofectin for 6 h at 37 °C. The medium was then replaced with media containing various concentrations of DDP, 5-FU and ADM. After 72 h of incubation, MTT assay was performed. Absorbance at 490 nm was normalized to the control, untreated cells to determine cell viability. Each value represents the mean±SD from triplicate determination.

Figure 2

Q values for the combination treatments of Cantide with DDP (A), 5-FU (B) and ADM (C) tested on HepG2 cells. Q values were calculated from the dose-response curves shown in Figure 1 and analyzed with Zheng-Jun Jin method.

Figure 3

Tumor growth curves for Balb/c nude mice after treatment with DDP, Cantide or DDP+Cantide. Points for these groups represent the average values for 7-8 mice.