Anomalies of the TGF-beta postreceptor signaling pathway in ovarian cancer cell lines.
Transforming growth factor-beta (TGF-beta) can cause cell cycle arrest, terminal differentiation, or apoptosis in most normal epithelial cells, whereas most malignant cell lines are resistant to TGF-beta. Mechanisms of resistance to TGF-beta caused by modulation of cell cycle regulators and/or inactivation of components of the TGF-beta signaling transduction pathway such as C-myc and Smad4 have been demonstrated in human pancreatic cancer and squamous cell carcinoma cell lines. But, this has not been shown in ovarian cancer. To investigate the potential association between loss of sensitivity to TGF-beta and expression status of transforming growth factor receptor II (T beta RII), Smad4, CDC25A and C-myc in fourteen cell lines derived from ovarian cancer, the expression levels of these genes were examined by semi-quantitative RT-PCR. Normal ovarian surface tissues were used as controls. Expression of T beta RII was detectable in all of fourteen cell lines. Expression of Smad4 was decreased in ten cell lines and nine cell lines overexpressed CDC25A, compared to normal controls. CDC25A gene was overexpressed in 88% (8/9) of tumorigenic cell lines as determined by xenografts in nude mice, and only in 20% (1/5) of non-tumorigenic cell lines (P < 0.05). C-myc was not overexpressed in any of these cell lines. The loss of sensitivity to TGF-beta of cell lines derived from ovarian cancers may be related to (1) a decreased expression of Smad4, which mediates TGF-beta induced growth inhibition; and/or (2) an overexpression of CDC25A. This overexpression correlates with increased tumorigenicity of ovarian cancer cell lines. The loss of sensitivity to TGF-beta is not associated with a lack of T beta RII.
Hu
W
W
Section of Gynecologic and Medical Therapeutics, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA. weihu@notes.mdacc.tmc.edu
Wu
W
W
Nash
M A
MA
Freedman
R S
RS
Kavanagh
J J
JJ
Verschraegen
C F
CF
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D017346:Protein Serine-Threonine Kinases; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D020687:cdc25 Phosphatases / Q000235:genetics
D004268:DNA-Binding Proteins; D016271:Proto-Oncogene Proteins c-myc; D018125:Receptors, Transforming Growth Factor beta; C497796:SMAD4 protein, human; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; C517004:CDC25A protein, human; C517005:Cdc25a protein, mouse; D020687:cdc25 Phosphatases