Progestin-induced caveolin-1 expression mediates breast cancer cell proliferation.
Progestin regulation of gene expression was assessed in the progestin-dependent murine tumor line C4HD which requires MPA, a synthetic progestin, for in vivo growth and expresses high levels of progesterone receptor (PR). By using suppressive subtractive hybridization, caveolin-1 was identified as a gene whose expression was increased with in vivo MPA treatment. By Northern and Western blot analysis, we further confirmed that caveolin-1 mRNA and protein expression increased in MPA-treated tumors as compared with untreated tumors. When primary cultures of C4HD cells were treated in vitro with MPA, caveolin-1 levels also increased, effect that was abolished by pre-treatment with progestin antagonist RU486. In addition, MPA promoted strong caveolin-1 promoter transcriptional activation both in mouse and human breast cancer cells. We also showed that MPA regulation of caveolin-1 expression involved in activation of two signaling pathways: MAPK and PI-3K. Short-term MPA treatment of C4HD cells led to tyrosine phosphorylation of caveolin-1 protein, where Src was the kinase involved. Additionally, we showed that MPA-induced association of caveolin-1 and PR, which was detected by coimmunoprecipitation and by confocal microscopy. Finally, we proved that MPA-induced proliferation of C4HD cells was inhibited by suppression of caveolin-1 expression with antisense oligodeoxynucleotides to caveolin-1 mRNA. Furthermore, we observed that inhibition of caveolin-1 expression abrogated PR capacity to induced luciferase activity from a progesterone response element-driven reporter plasmid. Comprehensively, our results demonstrated for the first time that caveolin-1 expression is upregulated by progestin in breast cancer. We also demonstrated that caveolin-1 is a downstream effector of MPA that is partially responsible for the stimulation of growth of breast cancer cells.
Salatino
M
M
Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.
Beguelin
W
W
Peters
M G
MG
Carnevale
R
R
Proietti
C J
CJ
Galigniana
M D
MD
Vedoy
C G
CG
Schillaci
R
R
Charreau
E H
EH
Sogayar
M C
MC
Elizalde
P V
PV
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051242:Caveolin 1 / Q000235:genetics / Q000502:physiology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D020935:MAP Kinase Signaling System; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011980:Receptors, Progesterone / Q000187:drug effects / Q000502:physiology; D019061:src-Family Kinases / Q000502:physiology
D051242:Caveolin 1; D011980:Receptors, Progesterone; D017258:Medroxyprogesterone Acetate; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases