RU486 increases radiosensitivity and restores apoptosis through modulation of HPV E6/E7 in dexamethasone-treated cervical carcinoma cells.
OBJECTIVE
Cervical carcinoma tumors containing radioresistant cells are associated with decreased local control and survival. Therefore, strategies to increase cell kill during radiotherapy have a clear rationale. It was previously determined that treatment with the corticosteroid dexamethasone increased radioresistance and decreased apoptosis in C4-1 cervical carcinoma cells. The goal of this study was to determine whether hormone antagonists, specifically Mifepristone (RU486), could reverse the effects of dexamethasone on clonogenic survival and apoptosis following gamma-irradiation.


METHODS
Cervical carcinoma cell line C4-1 cells were exposed to 1 microM dexamethasone in the presence or absence of 1 microM Mifepristone (RU486), a hormone antagonist, and irradiation. Cells were analyzed for steroid-dependent HPV E6/E7 mRNA expression (by Northern blot analysis), clonogenic survival, and apoptosis (by Annexin V staining and the DNA fragmentation assay). In addition, p53 protein levels were determined by Western blot analysis.


RESULTS
The hormone antagonist RU486 reversed dexamethasone-dependent upregulation of E6/E7 mRNA and restored radiation-induced p53 expression, apoptosis, and clonogenic survival to levels similar to those observed following irradiation alone.


CONCLUSIONS
RU486 reverses glucocorticoid-dependent upregulation of HPV E6/E7, which corresponds to restoration of p53 expression, and restores radiosensitivity and apoptosis following gamma-irradiation. Therefore, it appears that along with radiation, RU486 may be a beneficial agent in the treatment of hormone-reactive cervical tumors.
Kamradt
M C
MC
Department of Cell Biology, Neurobiology and Anatomy, Loyola University Medical Center, Maywood, Illinois 60153, USA.
Mohideen
N
N
Vaughan
A T
AT
D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival; D004273:DNA, Neoplasm / Q000032:analysis; D004268:DNA-Binding Proteins; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology*; D006801:Humans; D015735:Mifepristone / Q000494:pharmacology*; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism*; D027383:Papillomaviridae / Q000235:genetics; D030361:Papillomavirus Infections; D012333:RNA, Messenger / Q000096:biosynthesis; D011836:Radiation Tolerance / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D015854:Up-Regulation; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy* / Q000378:metabolism
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; C052633:E7 protein, Human papillomavirus type 18; D005938:Glucocorticoids; D006727:Hormone Antagonists; D009856:Oncogene Proteins, Viral; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D015735:Mifepristone; D003907:Dexamethasone