Impact of the immune system and immunotherapy in colorectal cancer

Abstract

The development of cancer is a multi-step process involving the gradual loss of regulation over the growth and functional capabilities of normal cells. Much research has been focused on the numerous cell intrinsic factors that govern this process; however, recent attention has turned to understanding the cell extrinsic factors in the tumor microenvironment that appear equally critical to the progression and treatment of cancer. One critical component of the tumor microenvironment is the immune system and it has become increasingly evident that the immune system plays an integral role in preventing and promoting the development of cancer. Understanding the immune cell types and pathways involved in this process has enabled the development of novel biomarkers for prognosis and accelerated the development of immune-based therapeutics, both of which have the potential to forever change the treatment paradigms for colorectal cancer (CRC). In this review, we discuss the impact of the immune system on the initiation, progression and treatment of cancer, specifically focusing on CRC.

Keywords: Immune system; colorectal cancer (CRC); immunotherapy; inflammation.

Figure 1

Diagram of key immune cells found in the tumor immune microenvironment. Multiple different immune cells can be found in tumors at different times and locations depending on multiple host and tumor factors. Many immune cells have both anti- and pro-tumor functions based on the context in which they are found.

Figure 2

Overview of different immunotherapeutics. Vaccines, adoptive T cell therapy and checkpoint inhibitors have led the vanguard for a new generation of immune-based therapies. Each therapy has a unique profile of advantages (+) and disadvantages (−). While current immunotherapies have yet to show efficacy in CRC, multiple trials are currently underway to test the potential for emerging immunotherapeutics.