Prognostic Factors Involved in the Epithelial–Mesenchymal Transition Process in Colorectal Cancer Have a Preponderant Role in Oxidative Stress: A Systematic Review and Meta-Analysis

SIMPLE SUMMARY: Metastasis is responsible for most of the deaths related to cancer patients. One of the hypotheses that explains the initiation of metastasis is a process called epithelial-to-mesenchymal transition (EMT), in which tumor cells change shape and acquire more aggressive properties that allows them to escape from the tumor and invade other organs. This also occurs in colorectal cancer (CRC), one of the most diagnosed types of cancer worldwide. During the past years, many scientists have discovered that certain molecules or biomarkers participating in this EMT process are able to predict the severity of the cancer and this is helping clinicians to manage treatments. Nevertheless, we think that all this information needs a detailed revision because a lot of biomarkers have been described but have not been analyzed whether they interact with each other in the same mechanism or not. Herein, we performed a bibliographic revision on this topic and identified a great number of biomarkers participating in oxidative stress, a cellular phenomenon that could have a role on the patient’s prognosis because its presence or absence on the patient’s tumor or blood had an influence on survival. Our findings suggest that oxidative stress deserves further study to understand metastasis better and to predict prognosis in a more efficient way. ABSTRACT: Epithelial-to-mesenchymal transition (EMT) is one of the most accepted mechanisms leading to metastasis, which is responsible for most of the cancer-related deaths. In order to identify EMT-related biomarkers able to predict clinical outcomes in colorectal cancer (CRC), a systematic review and meta-analysis of prognostic factors associated to overall survival (OS) and progression free survival (PFS) was conducted. The systematic literature search included studies from June 2014 to June 2019 available at PubMed and Scopus databases. Meta-analysis was performed for those markers appearing in minimum three works with a total number of 8656 participants. The rest were enlisted and subjected to functional enrichment. We identified nine clinical biomarkers and 73 EMT-related molecular biomarkers associated to OS and/or PFS in CRC. The significant enrichment of biomarkers found involved in cellular oxidoreductase activity suggests that ROS generation plays an active role in the EMT process. Clinical practice needs new biomarkers with a reliable prognostic value able to predict clinical outcomes in CRC. Our integrative work supports the role of oxidative stress in tumorigenesis and EMT progress highlighting the importance of deciphering this specific mechanism to get a better understanding of metastasis.