Prognostic value of innate and adaptive immunity in colorectal cancer

Linking obesity to colorectal cancer: recent insights into plausible biological mechanisms

PURPOSE OF REVIEW

This review will examine the recent scientific literature on the mechanisms that are thought to link obesity to colorectal cancer (CRC) risk.

RECENT FINDINGS

Obesity has emerged as a leading environmental risk factor for the development of CRC. However, the mechanisms underlying this relationship have not yet been fully elucidated. Recent literature has focused on inflammatory processes, adipokines, and estrogen. Obesity-enhanced inflammation is largely orchestrated by increases in adipose tissue macrophages leading to the secretion of inflammatory cytokines including tumor necrosis factor-α, monocyte chemoattractant protein-1, and interleukin-6, all of which are linked to CRC. Adiponectin is decreased with obesity and has been reported to be negatively associated with CRC, whereas leptin, which is increased, is positively associated with the disease. Estrogen has been shown to influence CRC, although its role remains controversial; some studies have implicated estrogen as being protective, whereas others have suggested it to be a risk factor. We highlight the most important recent advances that have been made on the aforementioned mechanisms that are thought to link obesity to CRC.

SUMMARY

A better understanding of the mechanisms linking obesity to CRC risk is necessary for the design of effective treatment approaches in future clinical trials.

Biomarkers in precision therapy in colorectal cancer

Colorectal cancer (CRC) is the most commonly diagnosed cancer in Europe. Because CRC is also a major cause of cancer-related deaths worldwide, a lot of research has been focused on the discovery and development of biomarkers to improve the diagnostic process and to predict treatment outcomes. Up till now only a few biomarkers are recommended by expert panels. Current TNM criteria, however, cause substantial under- and overtreatment of CRC patients. Consequently, there is a growing need for new and efficient biomarkers to ensure optimal treatment allocation. An ideal biomarker should be easily translated into clinical practice, to identify patients who can be spared from treatment or benefit from therapy, ultimately resulting in precision medicine in the future. In this review we aim to provide an overview of a number of frequently studied biomarkers in CRC and, at the same time, we will emphasize the challenges and controversies that withhold the clinical introduction of these biomarkers. We will discuss both prognostic and predictive markers of chemotherapy, aspirin therapy as well as overall therapy toxicity. Currently, only mutant KRAS, mutant BRAF, MSI and the Oncotype DX® Colon Cancer Assay are used in clinical practice. Other biomarker studies showed insufficient evidence to be introduced into clinical practice. Divergent patient selection criteria, absence of validation studies and a large number of single biomarker studies are possibly responsible. We therefore recommend that future studies focus on combining key markers, rather than analysing single markers, standardizing study protocols, and validate the results in independent study cohorts, followed by prospective clinical trials.