Basic Study
Copyright ©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Feb 21, 2019; 25(7): 808-823
Published online Feb 21, 2019. doi: 10.3748/wjg.v25.i7.808
Relationships among KRAS mutation status, expression of RAS pathway signaling molecules, and clinicopathological features and prognosis of patients with colorectal cancer
Xiang-Bin Wan, Ai-Qin Wang, Jian Cao, Zhi-Chuang Dong, Ning Li, Sen Yang, Miao-Miao Sun, Zhi Li, Su-Xia Luo
Xiang-Bin Wan, Jian Cao, Zhi-Chuang Dong, Zhi Li, Department of General Surgery, the Affiliated Tumor Hospital of Zhengzhou University, Zhengzhou 450008, Henan Province, China
Ai-Qin Wang, Department of Pharmacy, The Second Affiliated Hospital of Xinxiang Medical University, Xinxiang 453002, Henan Province, China
Ning Li, Su-Xia Luo, Department of Medical Oncology, the Affiliated Tumor Hospital of Zhengzhou University, Zhengzhou 450008, Henan Province, China
Sen Yang, China-US (Henan) Hormel Cancer Institute, Zhengzhou 450008, China
Miao-Miao Sun, Department of Pathology, the Affiliated Tumor Hospital of Zhengzhou University, Zhengzhou 450008, Henan Province, China
Author contributions: Wan XB, Cao J, and Dong ZC collected and analyzed the data; Wan XB drafted the manuscript; Luo SX designed and supervised the study; Wang AQ, Li N, Yang S, Sun MM, and Li Z offered technical or material support; all authors have read and approved the final version to be published.
Supported by the Henan Department of Science and Technology, China, No. 162102310317.
Institutional review board statement: The study was approved by the Medical Ethics Committee of the Affiliated Tumor Hospital of Zhengzhou University, Zhengzhou, China, and all patients provided written informed consent.
Conflict-of-interest statement: The authors have no conflicts of interest to declare.
Data sharing statement: No additional data are available.
Open-Access: This is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Su-Xia Luo, MD, Professor, Department of Medical Oncology, the Affiliated Tumor Hospital of Zhengzhou University, No. 127, Dongming Road, Jinshui District, Zhengzhou 450008, Henan Province, China. wxbzlyy@126.com
Telephone: +86-371-65961505 Fax: +86-371-65961505
Received: November 14, 2018
Peer-review started: November 14, 2018
First decision: December 5, 2018
Revised: January 17, 2019
Accepted: January 20, 2019
Article in press: January 20, 2019
Published online: February 21, 2019
Processing time: 101 Days and 4.2 Hours
Abstract
BACKGROUND

The RAS/RAF/MEK/ERK and PI3K/AKT/mTOR signaling pathways all belong to mitogen-activated protein kinase (MAPK) signaling pathways, Mutations in any one of the upstream genes (such as the RAS gene or the BRAF gene) may be transmitted to the protein through transcription or translation, resulting in abnormal activation of the signaling pathway. This study investigated the relationship between the KRAS gene mutation and the clinicopathological features and prognosis of colorectal cancer (CRC), and the effect of KRAS mutations on its associated proteins in CRC, with an aim to clarify the cause of tumor progression and drug resistance caused by mutation of the KRAS gene.

AIM

To investigate the KRAS gene and RAS pathway signaling molecules in CRC and to analyze their relationship with clinicopathological features and prognosis

METHODS

Colorectal cancer tissue specimens from 196 patients were analyzed for KRAS mutations using quantitative polymerase chain reaction and for KRAS, BRAF, MEK, and ERK protein expression levels using immunohistochemistry of tumor microarrays. To analyze differences of RAS pathway signaling molecule expression levels in different KRAS gene status, the relationships between these parameters and clinicopathological features, 4-year progression-free survival, and overall survival were analyzed by independent sample t test, Kaplan-Meier plots, and the log-rank test. Predictors of overall and disease-free survival were assessed using a Cox proportional hazards model.

RESULTS

Of the 196 patients, 62 (32%) carried mutations in codon 12 (53/62) or codon 13 (9/62) in exon 2 of the KRAS gene. KRAS, BRAF, ERK, and MEK protein expression was detected in 71.4%, 78.8%, 64.3%, and 50.8% of CRC tissues, respectively. There were no significant differences between KRAS mutation status and KRAS, BRAF, MEK, or ERK protein levels. Positive expression of KRAS and ERK was associated with poor tumor differentiation, and KRAS expression was also associated with age < 56 years. MEK expression was significantly associated with distant metastasis (P < 0.05). The 4-year progression-free survival rate, but not overall survival rate, was significantly higher in patients with KRAS-negative tumors than in those with KRAS-positive tumors (P < 0.05), whereas BRAF, MEK, and ERK expression was unrelated to survival. Multivariate analysis showed that only the expression of KRAS protein was a risk factor for tumor recurrence (P < 0.05). No other clinicopathological factors correlated with KRAS, BRAF, MEK, or ERK expression.

CONCLUSION

KRAS gene mutations do not affect downstream protein expression in CRC. KRAS protein is associated with poor tumor differentiation, older age, and a risk of tumor recurrence.

Keywords: Colorectal cancer; KRAS gene; KRAS protein; BRAF protein; MEK protein; ERK protein

Core tip: The RAS signaling pathway plays a crucial role in the invasiveness and metastasis of tumor cells. In this study, we examined the relationship between the KRAS gene mutation status and the clinicopathological features and prognosis of colorectal cancer (CRC) patients and the expression of BRAF, MEK, and ERK proteins. We found that KRAS gene mutations do not affect downstream protein expression or the clinicopathological features of CRC. KRAS protein is associated with poor tumor differentiation, older age, and a risk of tumor recurrence. The results may contribute to our understanding of drug resistance in KRAS mutant CRC.