Knockdown of LKB1 Sensitizes Endometrial Cancer Cells via AMPK Activation

Abstract

Metformin is an anti-diabetic drug and has anticancer effects on various cancers. Several studies have suggested that metformin reduces cell proliferation and stimulates cell-cycle arrest and apoptosis. However, the definitive molecular mechanism of metformin in the pathophysiological signaling in endometrial tumorigenesis and metastasis is not clearly understood. In this study, we examined the effects of metformin on the cell viability and apoptosis of human cervical HeLa and endometrial HEC-1-A and KLE cancer cells. Metformin suppressed cell growth in a dose-dependent manner and dramatically evoked apoptosis in HeLa cervical cancer cells, while apoptotic cell death and growth inhibition were not observed in endometrial (HEC-1-A, KLE) cell lines. Accordingly, the p27 and p21 promoter activities were enhanced while Bcl-2 and IL-6 activities were significantly reduced by metformin treatment. Metformin diminished the phosphorylation of mTOR, p70S6K and 4E-BP1 by accelerating adenosine monophosphateactivated kinase (AMPK) in HeLa cancer cells, but it did not affect other cell lines. To determine why the anti-proliferative effects are observed only in HeLa cells, we examined the expression level of liver kinase B1 (LKB1) since metformin and LKB1 share the same signalling system, and we found that the LKB1 gene is not expressed only in HeLa cancer cells. Consistently, the overexpression of LKB1 in HeLa cancer cells prevented metformin-triggered apoptosis while LKB1 knockdown significantly increased apoptosis in HEC-1-A and KLE cancer cells. Taken together, these findings indicate an underlying biological/physiological molecular function specifically for metformin-triggered apoptosis dependent on the presence of the LKB1 gene in tumorigenesis.

Snail Promotes Cancer Cell Proliferation via Its Interaction with the BIRC3

“…Cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyl- 2 H-tetrazolium bromide (MTT) assays ( Rho et al ., 2021a ). Cells were grown at a density of 4.3×10 3 per well in 96-well plates.…”

PRR16/Largen Induces Epithelial-Mesenchymal Transition through the Interaction with ABI2 Leading to the Activation of ABL1 Kinase

“…Cells were washed twice with ice-cold PBS and disrupted in RIPA buffer with Xpert Protease Inhibitor Cocktail Solution and Xpert Phosphatase Inhibitor Cocktail Solution (GenDEPOT, Inc.) on ice for 30 min ( Rho et al ., 2021a ). Cell lysates were centrifuged at 15,000 rpm for 15 min at 4°C, and the resultant supernatants were subjected to Western blotting.…”

Loss of EMP2 Inhibits Melanogenesis of MNT1 Melanoma Cells via Regulation of TRP-2

“…Western blot analysis was conducted in accordance with a previous report ( Rho et al ., 2021 ). Cells were washed twice with PBS and whole-cell lysates were prepared in RIPA buffer containing protease inhibitor cocktail and Xpert Phosphatase Inhibitor Cocktail Solution (GenDEPOT, Barker, TX, USA) on ice for 15 min.…”

“…Cells were washed twice with PBS and whole-cell lysates were prepared in RIPA buffer containing protease inhibitor cocktail and Xpert Phosphatase Inhibitor Cocktail Solution (GenDEPOT, Barker, TX, USA) on ice for 15 min. Cell lysates were centrifuged at 15,000 rpm for 15 min at 4°C, and the resultant supernatants were subjected to Western blotting ( Rho et al ., 2021 ). The total protein concentration was quantified using Coomassie brilliant blue.…”