Introduction: Drug resistance in different types of cancer arise serious concerns in oncology. Different genes and signaling pathways are responsible for this resistance. K-ras is one of the important signaling pathways in cancer. This pathway is activated in 50% of all types of cancer. In this study we aimed to study the effect of silencing RAS signaling pathway on the response of Hct116 as a colon cancer cell line to 5-flurouracil and oxaliplatin as the common chemotherapeutic drugs.

Materials and methods: Two oligonucleotides silencing the wild type k-ras were selected by different online programs such as Dharmcon, Invitrogen and Promega. After insertion of these oligonucleotides into psilencer neo2.1, they were transfected into HCT116 cell line. Thereafter the lethality of 5-fluouracil and oxaliplatin in these cells was assessed by XTT proliferation assay kit.

Results:

Plasmids containing oligonucleotides silencing wild type were named p565ks and p688ks according to the site of silencing within the k-ras mRNA. Quantitative PCR analysis showed that silencing k-ras was more profound in HCT565ks. After stably transfecting Hct116 cell line with these plasmids, these cells were named HCT565ks and HCT688ks. While the LC50 of 5-flurouracil for Hct116 was 13-15µM, for HCT565ks and HCT688ks, it was 37.5-40 µM and 22.5-25 µM. While the LC50 of oxaliplatin for HCT116 was 8.75 µM, in HCT565ks and HCT688ks LC50s were 0.35 µM and 0.3 µM. These data showed that silencing k-ras have made the cells more resistant to 5-flurouracil while it increased the sensitivity of cells to lethal effects of oxaliplatin.

Conclusion: In conclusion silencing k-ras had different effects on the response of cells to different chemotherapeutic drugs. This can urge us to be more cautious about prescribing RAS inhibiting drugs as it may cause the cells to become more resistant to some chemotherapeutic drugs such as 5-flurouracil while they may be killed more by other drugs such as oxaliplatin.

Citation Format: Ladan Teimoori-Toolabi, Kayhan Azadmanesh, Mohammadreza Khorramizadeh, Saba Hashemi. K-ras Silencing has diverse effect on the response of cells to chemotherapeutic drugs. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3769. doi:10.1158/1538-7445.AM2014-3769

©2014 American Association for Cancer Research.
2014