Addition of S-1 to the Epidermal Growth Factor Receptor Inhibitor Gefitinib Overcomes Gefitinib Resistance in Non–small cell Lung Cancer Cell Lines withMETAmplification

Abstract

Purpose: Most non^small cell lung cancer (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFR) are initially responsive to EGFR tyrosine kinase inhibitors (EGFR-TKI) such as gefitinib and erlotinib, but they almost invariably develop resistance to these drugs. A secondary mutation in EGFR (T790M) and amplification of the MET protooncogene have been identified as mechanisms of such acquired resistance to EGFR-TKIs. We have now investigated whether addition of the oral fluoropyrimidine derivative S-1to gefitinib might overcome gefitinib resistance in NSCLC cell lines. Experimental Design: The effects of gefitinib on EGFR signaling and on the expression both of thymidylate synthase and of the transcription factor E2F-1 in gefitinib-resistant NSCLC cells were examined by immunoblot analysis. The effects of S-1 (or 5-fluorouracil) and gefitinib on the growth of NSCLC cells were examined in vitro as well as in nude mice. Results: Gefitinib induced down-regulation of thymidylate synthase and E2F-1 in gefitinibresistant NSCLC cells with MET amplification but not in those harboring theT790M mutation of EGFR. The combination of 5-fluorouracil and gefitinib synergistically inhibited the proliferation of cells with MET amplification, but not that of those with the T790M mutation of EGFR, in vitro. Similarly, the combination of S-1and gefitinib synergistically inhibited the growth only of NSCLC xenografts with MET amplification. Conclusions: Our results suggest that the addition of S-1to EGFR-TKIs is a promising strategy to overcome EGFR-TKI resistance in NSCLC with MET amplification.

Enhanced Anticancer Effect of the Combination of BIBW2992 and Thymidylate Synthase–Targeted Agents in Non–Small Cell Lung Cancer with the T790M Mutation of Epidermal Growth Factor Receptor

“…Combination therapy with gefitinib and S-1 did not exhibit an enhanced effect on the growth of tumors formed by H1975 cells (Fig. 5A and E), consistent with our previous findings (16). Combination therapy with gefitinib and pemetrexed also did not exhibit an enhanced antitumor effect ( Fig.…”

“…The human NSCLC cell lines PC9, PC9/ZD, HCC827, and NCI-H1975 (H1975) were obtained as described previously (16)(17)(18). All cells were cultured under a humidified atmosphere of 5% CO 2 at 37°C in RPMI 1640 (Sigma) supplemented with 10% fetal bovine serum.…”

“…A new antifolate drug, pemetrexed, has also been shown to inhibit tumor growth by targeting TS and is widely used in clinical settings (13,14). We have previously shown that gefitinib-induced downregulation of TS and E2F1, a transcription factor that regulates expression of the TS gene, is responsible for the enhanced antitumor effect of combined treatment with S-1 (15,16). However, an enhanced antitumor effect of this combination therapy on the growth of NSCLC cells harboring the T790M mutation of EGFR was not apparent as a result of continuous activation of EGFR and sustained expression of TS during gefitinib exposure.…”

Combination of Vandetanib, Radiotherapy, and Irinotecan in the LoVo Human Colorectal Cancer Xenograft Model

“…Although the best schedule and sequencing for this triple modality treatment has yet to be determined, the tumor growth delay kinetics observed in this study suggest that improvement in colorectal tumor response can be obtained by concurrent and sustained postsequencing of vandetanib with cytotoxic therapy, keeping in mind that prolonged chronic administration of the receptor tyrosine kinase inhibitors may lead to the development of resistance and the requirement for additional therapeutic agents as seen with other targeted agents, such as imatinib and gefitinib. 41,42 …”

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

“…Several combination chemotherapies using S-1 and cytotoxic agents, including irinotecan (12), CDDP (13) and taxanes (14,15), have been reported to be clinically effective. In addition, when used in combination with the targeted agent gefitinib (16), the expression of the thymidylate synthase (TS) protein and mRNA was decreased in a time-dependent manner in the presence of 5 µM 5-FU in 3 human non-small cell lung cancer (NSCLC) cell lines (Ma-1, Ma-53 and NII-H460) and the antitumor activity of S-1 was potentiated by the combined therapy. Furthermore, the exposure of the human epidermal growth factor receptor 2 (HER2) amplification-positive human gastric cancer cell lines (NCI-N87 and 4-1ST) to S-1 and epidermal HER2 inhibitors (lapatinib and trastuzumab) resulted in the downregulation of TS expression in a concentration-dependent manner.…”