Functional Study On The PIP5KL1 In Tumorigenesis

Phosphatidylinositol-4-phosphate 5-kinase-like 1 (PIP5KL1), the forth member of phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks) type I, acts as a scaffold for localization and activation of PIP5Ks activity , which in turn increases phosphatidylinositol-3, 4, 5-bisphosphate [PI(3, 4, 5)P] levels. It has been reported that PIP5KL1 is closely associated with cell viability by using cell-based high-throughput assay, and further study showed that PIP5KL1 can induce necrosis and apoptosis of 293 T cells. But the other physiological/pathological roles of PIP5KL1, especially in the human cancer is still lacking.First, we constructed a plasmid pET32a-PIP5KL1 to get the PIP5KL1 protein in E. coli, and purified PIP5KL1 fusion protein for future study by affinity chromatography. Then we got anti-PIP5KL1 polyclonal antibodies by using purified PIP5KL1 fusion protein as immunogen. These antibodies are suitable for detecting PIP5KL1 by ELISA, Western blotting and Immunofluorescence microscopy. Second, we successfully constructed a plasmid pcDNA3.1-PIP5KL1 and transfected it into cervical cancer cell line Hela and gastric cancer cell line BGC823. The results showed that over-expression of PIP5KL1 can inhibit cell proliferation and migration compared with control groups. Over-expression of PIP5KL1 in Hela cells can also inhibit tumor formation in nude mice. These results suggested that PIP5KL1 can inhibit the tumor cell proliferation both in vitro and in vivo.In order to study the correlation between PIP5KL1 and carcinoma, we assayed the difference expression of PIP5KL1 in human gastric cancer (81 samples) and normal tissue (32 samples) via TMAs. The data indicated that PIP5KL1 expression correlates with the development of human gastric cancer, and suggested that PIP5KL1 may suppress tumor development. It is extremely significant that our finding provided a validation for the importance of PIP5KL1 in gastric cancer. But the precise mechanism is poorly defined. Furthermore, PIP5KL1 overexpression significantly inhibited serum-induced Akt1 activation, which probably accounts for their inhibitory effect on cell proliferation and migration.Taken together, the studies presented a direct evidence that PIP5KL1 play an important role in the inhibition of tumor cell proliferation and migration. More importantly, We found that PIP5KL1 appear to be a potential tumor suppressor in gastric cancer. This is the first time providing the most updated and intriguing findings about the role of PIP5KL1 in gastric tumor development.