The Emerging Role of Nerves and Glia in Colorectal Cancer

Simple Summary

The influence of nerves on different types of cancers, including colorectal cancer, is increasingly recognized. The intestines are highly innervated, both from outside the intestines (extrinsic innervation) and by a nervous system of their own; the enteric nervous system (intrinsic innervation). Nerves and cancer cells have been described to communicate with each other, although the exact mechanism in colorectal cancer is not yet explored. Nerves can enhance cancer progression by secreting signaling molecules, and cancer cells are capable of stimulating nerve growth. This review summarizes the innervation of the intestines and current knowledge on the role of the nervous system in colorectal cancer. Additionally, the therapeutic potential of these new insights is discussed.

Abstract

The role of the nervous system as a contributor in the tumor microenvironment has been recognized in different cancer types, including colorectal cancer (CRC). The gastrointestinal tract is a highly innervated organ system, which is not only innervated by the autonomic nervous system, but also contains an extensive nervous system of its own; the enteric nervous system (ENS). The ENS is important for gut function and homeostasis by regulating processes such as fluid absorption, blood flow, and gut motility. Dysfunction of the ENS has been linked with multiple gastrointestinal diseases, such as Hirschsprung disease and inflammatory bowel disease, and even with neurodegenerative disorders. How the extrinsic and intrinsic innervation of the gut contributes to CRC is not fully understood, although a mutual relationship between cancer cells and nerves has been described. Nerves enhance cancer progression through the secretion of neurotransmitters and neuropeptides, and cancer cells are capable of stimulating nerve growth. This review summarizes and discusses the nervous system innervation of the gastrointestinal tract and how it can influence carcinogenesis, and vice versa. Lastly, the therapeutic potential of these novel insights is discussed.

Morphology of enteric glia in colorectal carcinoma: A comparative study of tumor site and its proximal normal margin

OBJECTIVE

Colorectal carcinoma (CRC) is the third most common cancer in the world and fifth most common cancer in India. To understand the extent of perineural invasion (PNI) in CRC it is essential to study the morphology of enteric glial cells (EGCs). The aim of the study was to analyze the numerical density of EGCs and area of myenteric ganglia (MG) in the colonic tissue samples collected from CRC patients.

MATERIAL AND METHODS

Fifteen intraoperative tissue specimens were collected from the tumor site and 2cm proximal to the upper extent of tumor. The samples were divided into four groups: group 1 (n=15): proximal tumor free colonic tissue; group 2 (n=3): well-differentiated; group 3 (n=8): moderately differentiated; group 4 (n=4): poorly differentiated adenocarcinoma. After processing the tissues were subjected to hematoxylin and eosin staining. The anti-S100β and anti-GFAP antibodies were used to observe the EGCs.

RESULTS

In the H&E stained sections the number of myenteric ganglia appeared to be decreasing with increasing grade of adenocarcinoma. Immunostaining showed significant decreasing pattern in the numerical density of EGCs per myenteric ganglion and mean area of myenteric ganglia in relation to the thickness of circular muscle, corresponding to the increasing grades of adenocarcinoma. The morphology of the EGCs remained unaltered in the colonic tissue adjacent to the tumor site.

CONCLUSION

Significant loss of EGCs and neurodegeneration corresponded with the grade of tumor emphasizing on its prognostic value. The PNI was not seen in the clear margin proximal to the tumor site.