O1-9-4 - KRAS mutations of colorectal cancer -clinical analysis as a prognostic factor and in vitro assay of proliferation-

Abstract

Background: Mutations of KRAS gene are recognized as a prognostic factor in colorectal cancer (CRC).Methods: We analyzed 92 patients diagnosed with metastatic or recurrent CRC between 2005 and 2014 in Shinshu University Hospital. The prognostic value of the mutations of exon 2 (codon 12 and 13) of KRAS and the clinical and pathological variables of these tumors were estimated. Additionally, we established an in vitro assay which could evaluate the proliferation ability of CRC cells with KRAS mutations. KRAS mutations (G12D, G12V and G13D) and wild-type KRAS genes were retrovirally transduced into Caco-2 cells, a human colon cancer cell line. Gene-transduced cells producing fluorescence with GFP and parent cells were mixed and cultured. On the 12th day, GFP positive ratios were determined by flow cytometry, and relative proliferation rates were calculated.Results: KRAS mutations were present in 36 (39.1%) of all patients. No significant differences were identified between overall survival (OS) rates of patients with KRAS mutations (median OS, 25.0 months) and those with wild-type KRAS genes (median OS, 43.0 months) (P = 0.170). However, patients with KRAS mutations tended to demonstrate a decreased OS rate. Univariate analysis identified that age (≥70) and tumor grade (poorly differentiated or mucinous type) acted as prognostic factors that influenced OS rate. Multivariate analysis identified that age [hazard ratio (HR), 2.12; P = 0.014] and tumor grade [hazard ratio (HR), 4.267; P = 0.000] were adverse prognostic factors for OS rates. In vitro assay, cells with each KRAS mutation showed significantly higher proliferation ability compared with those of wild-type KRAS genes (P = 0.029, 0.032 and 0.002, respectively).Conclusion: In the present study, KRAS mutations could not be a prognostic factor in metastatic or recurrent CRC patients. But the in vitro assay proved higher proliferation ability of the cells with KRAS mutations than those with wild-type KRAS genes. Background: Mutations of KRAS gene are recognized as a prognostic factor in colorectal cancer (CRC). Methods: We analyzed 92 patients diagnosed with metastatic or recurrent CRC between 2005 and 2014 in Shinshu University Hospital. The prognostic value of the mutations of exon 2 (codon 12 and 13) of KRAS and the clinical and pathological variables of these tumors were estimated. Additionally, we established an in vitro assay which could evaluate the proliferation ability of CRC cells with KRAS mutations. KRAS mutations (G12D, G12V and G13D) and wild-type KRAS genes were retrovirally transduced into Caco-2 cells, a human colon cancer cell line. Gene-transduced cells producing fluorescence with GFP and parent cells were mixed and cultured. On the 12th day, GFP positive ratios were determined by flow cytometry, and relative proliferation rates were calculated. Results: KRAS mutations were present in 36 (39.1%) of all patients. No significant differences were identified between overall survival (OS) rates of patients with KRAS mutations (median OS, 25.0 months) and those with wild-type KRAS genes (median OS, 43.0 months) (P = 0.170). However, patients with KRAS mutations tended to demonstrate a decreased OS rate. Univariate analysis identified that age (≥70) and tumor grade (poorly differentiated or mucinous type) acted as prognostic factors that influenced OS rate. Multivariate analysis identified that age [hazard ratio (HR), 2.12; P = 0.014] and tumor grade [hazard ratio (HR), 4.267; P = 0.000] were adverse prognostic factors for OS rates. In vitro assay, cells with each KRAS mutation showed significantly higher proliferation ability compared with those of wild-type KRAS genes (P = 0.029, 0.032 and 0.002, respectively). Conclusion: In the present study, KRAS mutations could not be a prognostic factor in metastatic or recurrent CRC patients. But the in vitro assay proved higher proliferation ability of the cells with KRAS mutations than those with wild-type KRAS genes.