Combination therapy using oral S-1 and targeted agents against human tumor xenografts in nude mice

Abstract

In this study, combination therapies using the oral fluoropyrimidine tegafur-gimeracil-oteracil (S-1) with several targeted agents or antibodies, were evaluated. First, the effects of tyrosine kinase inhibitors (erlotinib hydrochloride, sorafenib tosilate and sunitinib malate) against human non-small cell lung cancer (NSCLC), breast cancer and colorectal cancer were evaluated in vivo. The effects of the combination of S-1 and targeted antibodies (bevacizumab and cetuximab) against human colorectal cancers was also evaluated in vivo. S-1 and the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, erlotinib, showed a significant inhibition of growth in human NSCLC (Lu-99 and PC-9 cell lines). The antitumor activity of the combination of S-1 and erlotinib against Lu-99 and PC-9 cancer cell lines was significantly superior to either monotherapy (P<0.05). Combination therapy using the multi-tyrosine kinase inhibitors, sorafenib or sunitinib, with S-1 against breast cancer (MX-1 cell line) and NSCLC (NCI-H460 cell line) was significantly superior to either monotherapy (P<0.01). The combination of the anti-vascular endothelial growth factor antibody bevacizumab or the anti-EGFR antibody, cetuximab, with S-1 against human colorectal cancer [Col-1, KM20C (bevacizumab) and DLD-1 (cetuximab) cell lines] and a 5-fluorouracil (5-FU)-resistant cell line (KM12C/5-FU) was significantly superior to either monotherapy (p<0.01). In particular, the growth of the Col-1 cells was completely inhibited by the combination of S-1 and bevacizumab. No toxic mortalities and no significant difference in the body weight changes of the animals treated with S-1 combined with the targeted agents or with the mono-therapies were observed; therefore, the treatments appeared to be well-tolerated. Our preclinical findings indicate that the combination therapies of S-1 and targeted agents are promising treatment options.

Figure 1.

Tumor volume changes in human non-small cell lung cancer, (A) Lu-99 and (B) PC-9 cell lines, in vivo. Mice were randomized according to the tumor volumes on day 0. The mice implanted with tumors from Lu-99 and PC-9 cells were treated with the vehicle or S-1 at 8.3 or 10 mg/kg administered orally once daily on days 1–14. Erlotinib at 100 or 12.5 mg/kg, was administered orally, alone or in combination with S-1 on days 1–14. The tumor volume was measured twice a week. The values indicate the means ± SD of the RTV (n=6). ^*Overall maximal P<0.05 according to a closed testing procedure using the Aspin-Welch t-test. RTV, relative tumor volume. S-1, tegafur-gimeracil-oteracil.

Figure 2.

Tumor volume changes in (A) human breast cancer MX-1 cell line and (B) NSCLC NCI-H460 cell line, in vivo. Mice were treated with the vehicle or S-1 at 8.3 mg/kg. Sorafenib at 15 mg/kg was administered orally once daily on days 1-14, alone or in combination with S-1. The values indicate the means ± SD of the RTV (n=8). ^**Overall maximal P<0.01 according to a closed testing procedure using the Aspin-Welch t-test. NSCLC, non-small cell lung cancer; RTV, relative tumor volume. S-1, tegafur-gimeracil-oteracil.

Figure 3.

Tumor volume changes in (A) human breast cancer MX-1 cell line and (B) NSCLC NCI-H460 cell line, in vivo. Mice were treated with the vehicle or S-1 at 8.3 mg/kg. Sunitinib at 20 mg/kg was administered orally once daily on days 1–14, alone or in combination with S-1. The values indicate the means ± SD of the RTV (n=8). ^**Overall maximal P<0.01 according to a closed testing procedure using the Aspin-Welch t-test. NSCLC, non-small cell lung cancer; RTV, relative tumor volume. S-1, tegafur-gimeracil-oteracil.

Figure 4.

Tumor volume changes in human colorectal cancer, (A) Col-1 and (B) KM20C cell lines, in vivo. Mice were treated with the vehicle (○) or S-1 at 6.9 mg/kg once daily on days 1–14 orally. Bevacizumab at 5 mg/kg was administered intraperitoneally on days 1, 4, 8 and 11, alone or with S-1. The tumor volume was measured twice a week. The values indicate the means ± SD of the RTV (n=7). ^**Overall maximal P<0.01 according to a closed testing procedure using the Aspin-Welch t-test. RTV, relative tumor volume. S-1, tegafur-gimeracil-oteracil.

Figure 5.

Tumor volume changes in human colorectal cancer, (A) DLD-1, and (B) KM12C/5-FU cell lines, in vivo. Mice were treated with the vehicle or S-1 at 6.9 mg/kg once daily on days 1–14 orally. Cetuximab (40 mg/kg) was intraperitoneally administered on days 1, 4, 8 and 11 alone or with S-1. The tumor volume was measured twice a week. The values indicate the means ± SD of the RTV (n=7). ^**Overall maximal P<0.01 according to a closed testing procedure using the Aspin-Welch t-test. RTV, relative tumor volume. S-1, tegafur-gimeracil-oteracil.