Cytotoxicity of metformin against HT29 colon cancer cells contributes to mitochondrial Sirt3 upregulation

Abstract

Cancer and diabetes, the two mitochondria‐related diseases, have recently been linked to silent mating‐type information regulation 2 homolog 3 (SIRT3) activity irregularities. In this study, the effect of metformin, an antidiabetic with anticancer properties, has been evaluated on mitochondrial functionality markers, cell death pathways, and SIRT3 enzyme activity in the colon cancer cell line, HT‐29, and human embryonic kidney cells (HEK 293). HT‐29 cells were treated with metformin (5, 10, 20, 40, and 80 µM) for 24, 48, and 72 h for measuring the IC50 concentration. Reactive oxygen species (ROS) production, apoptosis, mitochondrial membrane potential, SIRT3 activity, and expression were evaluated against the colon cancer cell line, HT‐29. Results indicated a higher ROS production at 6 than 12 h with metformin treatment. Metformin modified the mitochondrial membrane potential, resulting in cell death induction. Results from SIRT3 activity and expression showed that metformin increased its activity and expression in cancer cells. In conclusion, metformin in HT‐29 cells disturbed the mitochondrial activity via increased ROS levels and SIRT3 activity, and these rapid modifications may play a key role in its cytotoxic property.

Metformin and Calcitriol Enhance 5-Fluorouracil Tumoricidal Effects in Colon Cancer By Modulating The PI3K/Akt/PTEN/mTOR Network

“…This study revealed cell cycle arrest with increased p21 and p27 alongside decreased CCND1 and CCND3 genes and proteins following in vivo and in vitro treatment with VD 3 and metformin monotherapies, con rming many reports that proclaimed suppression of cell cycle by both agents [20,21,[24][25][26][27][28]. However, in vivo, and in vitro metformin single treatment also showed higher cell death, increased gene, and protein expression of apoptosis markers and PTEN, and downregulations of the PI3K/Akt/mTOR molecules, whereas the VD 3 monotherapy effects were weaker.…”

“…A plausible explication for the disagreement between the present and the earlier in vivo and in vitro studies on the VD 3 anti-cancer e cacy could be related to the relatively shorter treatment durations ( 4weeks & 12h, respectively) in our study compared with longer timepoints (≥ 8 weeks & ≥ 24h, respectively) in the prior reports [21,32,53,54]. We also hypothesise that the superiority of metformin proapoptotic effects over VD 3 , with and without 5-FU, could involve better attenuations of the PI3K/Akt/mTOR oncogenic molecules by inducing the expression of the tumour suppressor protein, PTEN, thus promoting oxidative metabolism and subsequently mitochondrial-induced apoptosis in neoplastic cells [24][25][26][27][28]. Moreover, the triple therapy in the present study showed the best tumoricidal actions against CRC and could represent the best strategy for treating early and late stages of colon neoplasia.…”

“…In this context, the overall and cancer-speci c survival rates were signi cantly higher in diabetic CRC patients and who were using metformin relative to nonusers [51,52]. Other in vitro studies have likewise reported persuasive anti-tumorigenic effects for metformin single therapy that were depicted by marked suppression of cell cycle progression, induction of apoptosis, and inhibition of the PI3K/Akt/mTOR molecules [24][25][26][27][28]. Similarly, several epidemiological studies disclosed inverse links between serum VD levels with the prevalence of CRC [18,19].…”

“…Moreover, active vitamin D 3 (VD 3 ) attenuated the expression of the PI3K/Akt/mTOR pathway, inhibited cell proliferation and promoted apoptosis in colon cancer cell lines [20][21][22][23]. Other studies have also reported potent anti-tumorigenic effects for metformin against CRC that were portrayed by cell cycle arrest, increased apoptosis, and downregulations in the PI3K/Akt/mTOR network [24][25][26][27][28]. Additionally, others have shown enhanced tumoricidal actions against CRC by combining VD 3 or metformin with 5-FU [21,[29][30][31], as well as by adding both agents together [32,33].…”

SIRT3 and Metabolic Reprogramming Mediate the Antiproliferative Effects of Whey in Human Colon Cancer Cells

“…The majority of cancer diseases, including CRC, are characterized by mitochondrial dysfunction and increased oxidative stress with mitochondrial dysfunction affecting a wide range of metabolic pathways [11][12][13]. Mitochondrial function and integrity are controlled by the mitochondria guardian SIRT3 which acts on numerous substrates to activate fat oxidation, amino acid metabolism and electron transport [14][15][16]. In SW620 CRC cells, SIRT3 silencing led to a decreased mitochondrial biogenesis, which in turn affected cell viability [17].…”