The Roles Of TRAIL And Its Receptors In AICD Of PBL And Apoptosis Of Human HCC

TNF related apoptosis-inducing ligand (TRAIL) is a newly discovered member of TNF family. It raises great interests in immunologists and cancer researchers for its role in the immune system and its unique function in inducing the apoptosis of numerous cancer cells while sparing non-malignant cells. In the present report, we studied the roles of TRAIL and its various receptors in the process of AICD of peripheral blood lymphocytes (PBLs) as well as in the apoptosis of hepatocellular carcinoma cells, in order to explore the mechanism of AICD and to provide the theory basis for further research in the liver cancer therapy. Our work consists of two parts. In the first section, AICD models were firstly established using fresh peripheral blood lymphocytes. Then cDNA probes for TRAIL and its five receptors, i.e., R1, R2, R3, R4, and R5 were constructed and labeled with radioactive isotype. Finally, Northern-blotting technique was performed continuously to examine the expression of TRAIL and its receptors on the PBLs at different stages of AICD. The results showed that TRAIL and R2 play a role in the process evidenced by their peaking expression in the PBLs' apoptosis, while other receptors were not involved, as their expression remained undetectable during the whole process. Our work also indicated that TRAIL and its R2 cooperate with Fas-FasL system in AICD of PBLs with the latter playing a dominant role, based on the experiment of interfering and preventing PBLs' AICD with R2 and Fas blocking peptide. In the second section, the expression of TRAIL and its five receptors was examined on various hepatocellular carcinoma cells with different sensitivity to TRAIL before and after Actinomycin D treatment. Of the five receptors, only R2 was found markedly expressed on various hapatoma cell lines. Response of R2 expression to Actinomycin D varied according to different cells with some increasing, some decreasing and some remaining unchanged. Different expression style of R2 was found even in cells with the same sensitivity to TRAIL, suggesting that the sensitivity is not only related to its receptor, but also significantly influenced by other factors.Our work may provide useful information for further exploration of TRAIL in the liver cancer therapy.