P2X receptors: New players in cancer pain

Abstract

Pain is unfortunately a quite common symptom for cancer patients. Normally pain starts as an episodic experience at early cancer phases to become chronic in later stages. In order to improve the quality of life of oncological patients, anti-cancer treatments are often accompanied by analgesic therapies. The P2X receptor are adenosine triphosphate (ATP) gated ion channels expressed by several cells including neurons, cancer and immune cells. Purinergic signaling through P2X receptors recently emerged as possible common pathway for cancer onset/growth and pain sensitivity. Indeed, tumor microenvironment is rich in extracellular ATP, which has a role in both tumor development and pain sensation. The study of the different mechanisms by which P2X receptors favor cancer progression and relative pain, represents an interesting challenge to design integrated therapeutic strategies for oncological patients. This review summarizes recent findings linking P2X receptors and ATP to cancer growth, progression and related pain. Special attention has been paid to the role of P2X2, P2X3, P2X4 and P2X7 in the genesis of cancer pain and to the function of P2X7 in tumor growth and metastasis. Therapeutic implications of the administration of different P2X receptor blockers to alleviate cancer-associated pain sensations contemporarily reducing tumor progression are also discussed.

Keywords: Cancer; Pain; Adenosine triphosphate; P2X2; P2X3; P2X2/3; P2X4; P2X7

Core tip: Cancer pain is an increasing emergency as the number of oncological patients and survivors tends to growth. Oncological patients will greatly benefit of new therapies combining anti-tumor effects with a reduction of pain perception. This review gives an overview of latest literature on P2X receptors role in tumor progression and different types of cancer pain. The potential of P2X receptors as therapeutic targets in tumor is also discussed.