Capacitative calcium entry and transient receptor potential canonical 6 expression control human hepatoma cell proliferation.
Store-operated calcium entry (SOCE) is the main Ca(2+) influx pathway involved in controlling proliferation of the human hepatoma cell lines Huh-7 and HepG2. However, the molecular nature of the calcium channels involved in this process remains unknown. Huh-7 and HepG2 cells express transient receptor potential canonical 1 (TRPC1) and TRPC6, as well as STIM1 and Orai1, and these 4 channels are the most likely candidates to account for the SOCE in these cells. We generated stable TRPC6-overexpressing or TRPC6-knockdown Huh-7 clones, in which we investigated correlations between the presence of the protein, the rate of cell proliferation, and SOCE amplitude. TRPC6-overexpressing Huh-7 cells proliferated 80% faster than did untransfected cells and their SOCE amplitude was 160% higher. By contrast, proliferation rate was 50% lower and SOCE amplitude 85% lower in TRPC6-knockdown clones than in untransfected cells. OAG (olyl acetyl glycerol)-induced calcium entry was similar in all cells, and small interfering RNA (siRNA) against TRPC1 had no effect on SOCE amplitude, highlighting the relationship among SOCE, TRPC6 and cell proliferation in Huh-7 cells. SOCE amplitude was reduced by STIM1 and Orai1 knockdowns, suggesting possible cooperation between these proteins and TRPC6 in these cells. Endothelial growth factor and hepatocyte growth factor increased TRPC6 expression and SOCE amplitude in Huh-7 cells, and cyclin D1 expression was decreased by STIM1, Orai1, and TRPC6 knockdowns.


CONCLUSIONS
TRPC6 was very weakly expressed in isolated hepatocytes from healthy patients and expressed more strongly in tumoral samples from the liver of a cancer patient, strongly supporting a role for these calcium channels in liver oncogenesis.
Institut National de Santé et recherche Médicale (INSERM), U800, IFR143, Université Sciences et Technologies Lille 1, F-59655, Villeneuve d'Ascq, France.
Charbel
C
El Boustany
Gabriel
G
Bidaux
Antoine
A
Enfissi
Philippe
P
Delcourt
Natalia
N
Prevarskaya
Thierry
T
Capiod
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000209:etiology / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D016213:Cyclins / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000209:etiology / Q000378:metabolism* / Q000473:pathology*; D008565:Membrane Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D000071740:ORAI1 Protein; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D000074287:TRPC6 Cation Channel
D015220:Calcium Channels; D016213:Cyclins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D012333:RNA, Messenger; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C096351:transient receptor potential cation channel, subfamily C, member 1; D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D002118:Calcium