Metformin-Derived Growth Inhibition in Renal Cell Carcinoma Depends on miR-21-Mediated <b><i>PTEN</i></b> Expression

Abstract

Purpose: 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.

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“…MiR-21 is highly expressed in multiple cancers, such as epithelial cell cancer, connective tissue cancer, hematopoietic cell cancer, reproductive cell cancer and nerve cell cancer [9]. Previous studies have demonstrated that the target genes of miR-21 including phosphatase and tensin homolog detected on chromosome 10 (PTEN), Bcl-2 , TPM1 and PDCD4 which are cancer suppressed genes [10–13]. Previous studies have shown that miR-21 regulates PTEN by interacting with its target gene 3′-UTR and participates in the process of cancer occurrence and development [14–15].…”

TGF-β1 Induces Epithelial-Mesenchymal Transition of Chronic Sinusitis with Nasal Polyps through MicroRNA-21

“…PTEN and Akt pathways were associated with miR-21-induced EMT, and past research confirmed that PTEN is an miR-21-directed target gene [64-68]. Meng et al showed that if miR-21 was inhibited, expression of its target gene PTEN would upregulate [69].…”

Molecular Mechanisms of Metformin for Diabetes and Cancer Treatment

“…In addition to AMPK and mTOR, metformin has been shown to affect other oncogenic signaling pathways. Li and colleagues reported that metformin suppresses the proliferation and growth of osteosarcoma and renal cell carcinoma cells by suppressing Akt phosphorylation, which was associated with increased phosphatase and tensin (PTEN) expression ( Kalogirou et al, 2016 ; Li et al, 2018 ). Besides, metformin could activate the MEK/ERK signaling pathway to promote leukemia cell differentiation and apoptosis ( Huai et al, 2012 ).…”