The role of KLF5 and its mechanism for treatment resistance in preoperative chemoradiation therapy for rectal cancer

Abstract

Background : The identification of predictive molecular markers of tumor response to preoperative radiotherapy would provide an additional tool for selecting patients most likely to benefit from treatment.

The aim of this study was to determine whether Kr？ppel-like factor 5 (KLF5) expression in pre-irradiation tumor biopsies is a useful predictive marker of tumor response in patients with rectal cancer. Additionally, we verified the up- and downstream effectors of KLF5 in chemoradiation therapy resistance.

Method : Immunohistochemistry for KLF5, Ki-67, vascular endothelial growth factor (VEGF), p53, and C-ern2 was performed on 60 pre-irradiation biopsies from patients with completely responsive (ypT0) or nonresponsive tumors after preoperative radiotherapy. We multiplied intensity and percentage of KLF5 staining to produce a weighted score for each case ranging from 0 to 12. Each factor was evaluated using several scoring methods and the association between KLF5 expression and tumor response was compared.

Result : The median patient age was 59 years. The clinical cancer stage was T3 and T4 in 50 (83.3%) and 10 (16.7%) patients, respectfully. Clinically positive lymph nodes were observed 29 patients (43.8%). Complete remission was achieved by 9 patients. VEGF, p53, and KLF5 were significantly associated with complete remission (p=0.04, p=0.05, p=0.02, respectfully). Additionally, KLF5 score was significantly associated with post-chemoradiotherapy pathologic T stage (p=0.032) and the presence of KRAS mutations (p=0.028). In vitro study, we western blot of KLF5 and DNA sequencing to check KRAS, BRAF mutation in colon cell line, HCT116, SW48, CaCO2, DLD-1, HT29. KRAS mutations were detected in DLD-1, HCT 116, and SW48 colorectal adenocarcinoma cell lines, and BRAF mutations were detected in HT-29 cell line. Stress, such as chemotherapy, radiation therapy, and UV therapy, stabilized KLF5 protein levels in a time- and dose-depended manner in HCT 116 and CaCO2 cells. We made KLF5 overexpression stable cell line with HCT 116(HCT 116 KLF5 OE). HCT 116 KLF5 OE exhibited significantly better cell viability compared to control cells, suggesting that KLF5 mediates cell survival.

Conclusion : Overexpression of KLF5 might be predictive of poor tumor regression after preoperative CRT. Although KLF5 was significantly associated with the presence of KRAS mutations, its increased expression following chemo or radiation therapy in cell lines was independent of KRAS mutation status. Our study suggests KLF5 as a possible biomarker to predict chemoradiation response.