Estrogen regulation of TRPM8 expression in breast cancer cells.
BACKGROUND
The calcium-permeable cation channel TRPM8 (melastatin-related transient receptor potential member 8) is over-expressed in several cancers. The present study aimed at investigating the expression, function and potential regulation of TRPM8 channels by ER alpha (estrogen receptor alpha) in breast cancer.


METHODS
RT-PCR, Western blot, immuno-histochemical, and siRNA techniques were used to investigate TRPM8 expression, its regulation by estrogen receptors, and its expression in breast tissue. To investigate the channel activity in MCF-7 cells, we used the whole cell patch clamp and the calcium imaging techniques.


RESULTS
TRPM8 channels are expressed at both mRNA and protein levels in the breast cancer cell line MCF-7. Bath application of the potent TRPM8 agonist Icilin (20 microM) induced a strong outwardly rectifying current at depolarizing potentials, which is associated with an elevation of cytosolic calcium concentration, consistent with established TRPM8 channel properties. RT-PCR experiments revealed a decrease in TRPM8 mRNA expression following steroid deprivation for 48 and 72 hours. In steroid deprived medium, addition of 17-beta-estradiol (E2, 10 nM) increased both TRPM8 mRNA expression and the number of cells which respond to Icilin, but failed to affect the Ca2+ entry amplitude. Moreover, silencing ERalpha mRNA expression with small interfering RNA reduced the expression of TRPM8. Immuno-histochemical examination of the expression of TRPM8 channels in human breast tissues revealed an over-expression of TRPM8 in breast adenocarcinomas, which is correlated with estrogen receptor positive (ER+) status of the tumours.


CONCLUSIONS
Taken together, these results show that TRPM8 channels are expressed and functional in breast cancer and that their expression is regulated by ER alpha.
Chodon
Dechen
D
Laboratoire de Physiologie Cellulaire et Moléculaire, JE 2530: Canaux ioniques dans cancer du sein, Faculté des Sciences, Université Picardie Jules Vernes, 33 rue Saint Leu, 80000, Amiens, France.
Guilbert
Arnaud
A
Dhennin-Duthille
Isabelle
I
Gautier
Mathieu
M
Telliez
Marie-Sophie
MS
Sevestre
Henri
H
Ouadid-Ahidouch
Halima
H
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D004958:Estradiol / Q000378:metabolism*; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011744:Pyrimidinones / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050053:TRPM Cation Channels / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
D047628:Estrogen Receptor alpha; D011744:Pyrimidinones; D012333:RNA, Messenger; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D004958:Estradiol; C490483:icilin; D002118:Calcium