Metformin-Derived Growth Inhibition in Renal Cell Carcinoma Depends on miR-21-Mediated PTEN Expression.
OBJECTIVE
Metformin (MF) acts as a tumour-suppressor in renal cell carcinoma (RCC) by inhibiting the AKT/mTOR pathway via AMPK activation. Here, we explore the influence of miR-21 and its target gene PTEN on MF effects in CAKI-1 and CAKI-2 cells.


METHODS
Proliferation assays (MTS) and qRT-PCR after transient transfection with pre- and anti-miR-21 and MF treatment were conducted. AMPK-dependency was assessed via transfection of siAMPK. The expression of PTEN, AKT and miR-21 after transient pre-miR-21 transfection and MF treatment was analysed.


RESULTS
We demonstrate that CAKI-1 cells, which were found to be less sensitive towards MF, showed a significant higher miR-21 and lower PTEN expression than CAKI-2. This was confirmed in a primary RCC collective (n = 28): miR-21 and PTEN expression correlated negatively. MF treatment lowered miR-21 AMPK-dependently and increased PTEN expression in the cell lines. Ectopic miR-21 regulation modulated MF sensitivity. Western blot analysis showed that pre-miR-21 transfection and MF treatment regulated PTEN expression with impact on pAKT levels in the cells.


CONCLUSIONS
We show that differing MF sensitivity in RCC cells is associated with and mediated through the regulation of miR-21/PTEN expression with an impact on subsequent AKT signalling. This provides imaginable clinical implications regarding MF therapy of RCC patients for the future.
Department of Urology and Paediatric Urology, Julius Maximilians University Medical Centre of Wx00FC;rzburg, Wx00FC;rzburg, Germany.
Charis
C
Kalogirou
Daniel
D
Schäfer
Markus
M
Krebs
Florian
F
Kurz
Andreas
A
Schneider
Hubertus
H
Riedmiller
Burkhard
B
Kneitz
Daniel
D
Vergho
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor / Q000187:drug effects; D049109:Cell Proliferation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007680:Kidney Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D035683:MicroRNAs / Q000378:metabolism*; D008875:Middle Aged; D009392:Nephrectomy; D009399:Nephrons / Q000601:surgery; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014162:Transfection
C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D008687:Metformin; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human