VEGF- and LPA-induced telomerase in human ovarian cancer cells is Sp1-dependent.
OBJECTIVE
Both vascular endothelial growth factor (VEGF) and lysophosphatidic acid (LPA) are secreted by ovarian cancer cells and are known to promote cancer cell growth though the exact mechanism(s) are not completely understood. Since telomerase, a ribonucleprotein expressed in 95% of ovarian cancers, plays an important role in cellular immortalization, growth, and tumor progression, we examined whether telomerase is a molecular target of LPA and VEGF in ovarian cancer.


METHODS
Telomerase-positive ovarian carcinoma cell lines PA-1, SW 626, and one telomerase-negative, non-tumorigenic SV40 large-T antigen-transfected human ovarian surface epithelial (IOSE) cell line, FHIOSE 118, derived from normal ovarian surface epithelium were cultured with and without VEGF and LPA for 4 h and 24 h, respectively. Telomerase PCR-ELISA, RT-PCR, VEGF ELISA and luciferase assays were performed to determine the effect of VEGF and LPA on telomerase activity in ovarian cancer cells. Western blot analyses were used to examine the signaling pathway involved in telomerase regulation by VEGF and LPA.


RESULTS
We report that: (1) both VEGF and LPA upregulate telomerase activity; (2) LPA induction of telomerase activity is VEGF-dependent; (3) VEGF and LPA induction of telomerase activity is ERK 1/2-dependent; and (4) Sp1 binding sites within the proximal 976- to 378-bp regions of the hTERT promoter are essential for VEGF- and LPA-induced hTERT promoter activity.


CONCLUSIONS
Consequently, these data show the novel finding that VEGF can regulate telomerase activity in non-endothelial cells and that telomerase appears to be a novel molecular target of LPA.
Bermudez
Yira
Y
Department of Pathology and Cell Biology, University of South Florida, and H. Lee Moffitt Cancer Center, Tampa, FL 33612, USA.
Yang
Hua
H
Saunders
Beatriz O
BO
Cheng
Jin Q
JQ
Nicosia
Santo V
SV
Kruk
Patricia A
PA
D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D019098:Telomerase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*
D008246:Lysophospholipids; D016329:Sp1 Transcription Factor; D042461:Vascular Endothelial Growth Factor A; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C509186:TERT protein, human; D019098:Telomerase; C032881:lysophosphatidic acid