Study Of The Expression Of P2Y₂ Receptor In Salivary Adenoid Cystic Carcinoma And The Effect Of Its Agonist

Background and Objective: Human salivary adenoid cystic carcinoma (SACC) is one of the most common salivary malignant tumors and the most unique tumor in the oral and maxillofacial regions with strong infiltrative growth and distant metastasis potency. Local recurrence and distant metastasis could often be detected after operation. The mechanisms of recurrence and metastasis is not very clear now. Adenosine Triphosphate (ATP), as the extracellular signaling molecule, is one of the transmitters, and stimulates two receptors on the cell surfaces to regulate many physiological reactions by the second messenger system. P2Y receptors(G-protein coupled type)exist in various kinds of tissues extensively and the functions are different. Different subsets of P2Y receptors execute special physiological function through different intra-cellular signal transduction pathway activated by G-protein. Rapaport reported that purine nucleotide had anticancer activity at first.ATP could inhibit the growth of many human tumors cells, such as prostatic carcinoma,breast cancer,colon carcinoma,liver cancer,ovarian cancer,carcinoma of stomach and so on according to the recent study and research,and ATP could also relieve the repellency of nonmalignant tissues to chemotherapy and radiotherapy. In western countries, ATP applied in treating terminal cancer have been used in smallscale clinical test. Other anticancer mechanisms of ATP have not been reported yet,except that ATP activated cell surface receptors and the second messenger system regulation effect. ATP could inhibit the proliferation of some cancer cells in vitro through activating P2Y purinoceptor on the cancer cell surface according to the report. However,there is not any report about the relation of SACC andP2Y2 purinoceptor yet.In this study, we confirmed that the existence of P2Y2 receptor on the cell surface by applying immunocytochemistry method. We also studied the inhibiting effects on the cells SACC-83 and SACC-LM through the effect of ATP,which would provide the scientific theory evidence of further study the mechanism of infiltrative growth and distant metastasis of SACC.Methods: In this study, Human salivary adenoid cystic carcinoma cells SACC-83 and SACC-LM were cultured in vitro, we measured the expression of P2Y2 receptor on the cells by immunocytochemical method; We observed the variation of cell morphology and number through inverted microscope; we measured the inhibition of the two cells at different concentration of ATP and different time by MTT method.Results:The results of immunocytochemistry showed that P2Y2 purinoceptor was positive in SACC-83 and SACC-LM cells, which were stained deep brown(positive)on the cell membranes, and stained light brown(weakly positive) in the kytoplasm, but there was not positive in the negative control. The result of observation by inverted microscope demonstrated that the cell population decreased progressively with the increasing of ATP concentration. The results of the cell proliferation inhibition measured by MTT method showed that ATP had obvious inhibiting effect on SACC-83 and SACC-LM cells(P<0.05),the inhibiting effect on SACC-LM cells was stronger than on SACC-83 cells, and there was a positive correlation between the inhibiting effect and ATP concentration or action time. Namely, the inhibition ratio increased with the increasing of ATP concentration and the extension of action time.Conclusions:(1) P2Y2 purinoceptor exists both in SACC-83 and SACC-LM cells, but there is not obvious difference in both cells.(2)There is inhibition effect of ATP on cell proliferation in both SACC-83 and SACC-LM cells, and the inhibition ratio has positive correlation with dose or time. The inhibiting effect on SACC-LM cells was stronger than on SACC-83 cells, but the mechanism of action need further study.(3)ATP has a good prospect as a effective anticancer drug.