Regulation of proline oxidase in colon carcinoma cells upon 5-fluorouracil treatment: role of prodh in cell death and epithelial mesenchymal transition

Official URL: http://risc01.sabanciuniv.edu/record=b1662903 (Table of Contents)

Upregulated PI3K/Akt pathway has been implicated in both pathogenesis and progression of Acute Myeloid Leukemia (AML). Two key proteins control the termination of Akt signaling: PTEN, and PH domain and leucine rich repeat protein phosphatase, PHLPP. Human PHLPP contains four major functional domains; an amino-terminal PH domain, a leucine-rich repeat region (LRR), a PP2C-like catalytic core and a PDZ binding motif. Variations in coding regions and the expression of PHLPP gene functional domains together with PI3K/Akt pathway genes; Akt-1, PTEN and caspase-3 were examined. 11 exons covering the four domains of PHLPP were screened by DHPLC analysis and the results were confirmed by direct sequencing. Various sequence variations were determined. The expression studies performed in pediatric AML patients and in CD33+ healthy bone marrow cells by qRT-PCR revealed that Akt was up-regulated, whereas PTEN, PHLPP and caspase-3 expressions were decreased (3 times, 10 times and 3 times respectively). Although the expression of LRR domain was lost, PH, PP2C-like catalytic core and PDZ binding domains expressions were detected. In pediatric AML samples lacking LRR domain expression, three different transcript variants were identified. Expression studies of PHLPP domains in various tumour tissues revealed the loss of LRR domain and PP2C like catalytic core. Western blot analysis results also confirmed the loss of intact PHLPP expression in both study groups. This is the first study evaluating sequence variations together with the expression of PHLPP functional domains. Taking all together, PHLPP gene might act as a tumour suppressor in AML leukomogenesis and tumorigenesis.