Cloning and Comparison between Human PLD1 and PLD2 promoter activities in Human Cancer cell

Abstract

Phospholipase D (PLD), which catalyzes the hydrolysis of phosphatidylcholine (PC) to phosphatidic acid (PA) and choline, is activated in response to most mitogenic signals, and also activated in response to stimulators of vesicle transport, endocytosis, exocytosis, cell migration. PLD must be a critical regulator of cell proliferation, survival signaling, cell transformation, and tumor progression. Especially, PLD1 is a downstream target of the Ras/RalA GTPase cascade implicated in mitogenic and oncogenic signaling. Stably elevated expression of PLD2 also increased Myc expression and provided a Myc-dependent survival signal of breast cancer cell in the absence of Estriol. The expression of PLD1 and PLD2 was dramatically increased in colorectal tumors when compared with adjacent normal mucosa. To investigate the transcriptional regulation of PLD in cancer cell, PLD1 promoter region between (-)1865 and (+)9 and PLD2 promoter region between (-)2092 and (+)641 was cloned from human genomic DNA and characterized. PLD1 or PLD2 reporter DNA was constructed and analyzed by Firefly luciferase assay with human cancer cell. Several factors which were confirmed to be induced in human stomach cancer tissue were cloned from human cDNA library and investigated for its transactivation of PLD1 or PLD2 promoter. Among those factors, PDEF was the one of stable transactivators of PLD1 and PLD2 promoter in KATO III cell. In conclusion, PLD has a possible implication in carcinogenesis and progression and would be a new therapeutic target and a potential tumor marker for human cancer.