| ATP and its related compounds are widespread transmitters for extracellular communication in many cell types. By coupling to the receptors for purines and pyrimidines (P receptors) on the membrane, ATP is involved in a large variety of cellular physiological and biochemical functions. In the pathologic state of tumour, apoptosis, ischemia, inflammation, wound healing, pain, etc., the endogenic ligands of the P receptors play very important roles. P receptors are divided into two major classes termed adenosine or P1 receptors, at which adenosine is the principal natural ligand, and P2 receptors, at which ATP, ADP, UTP and UDP are the principal natural ligands. Until now, four P1 receptors subtypes (A1, A2A, A2B and A3) have been identified, and all coupled to G proteins with distinct tissue distribution and pharmacological properties. The P2 receptors are divided into two categories: the ligand-gated ion channel receptors (P2X) and the G protein-coupled receptors (P2Y). Cloning studies have revealed seven subtypes of P2X receptors, named P2X1-7 respectively, and several subtypes of P2Y receptors including P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13 and P2Y14.In recent years, Chinese and overseas researchers focus their attention on the antineoplasmic activities of ATP and its analogues. Its effects in vivo and in vitro on different types of leukaemia, neuroglioma, melanoma, malignant hepatomas, breast cancer, ovarian carcinoma, pulmonary carcinoma, prostatic carcinoma, esophageal carcinoma, gastric carcinoma were reported. Rapaport firstly reported that AMP, ADP and ATP, injected intraperitoneally into tumor-bearing mice, exhibited significant anticancer activity. The antineoplasmic activity of extracellular ATP on the mice was not induced by the improvement of host's immunity, but by the direct effects of ATP on the...
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