Abstract 5534: Metformin increases AMPKα activity by inhibition of AMPKα and cell cycle proliferation in Asian gastric cancer.
Authors: Jung Hae Rim , Chang Hae Ryung , Seo Hye-Hyun , Lemos Robert , Park Hee Seo , Liang Han , Powis Garth , Kim Yon Hui 
Published: August 2014

The LKB1/AMPK signaling pathway has been well elucidated and recent evidence suggests its involvement in cancer cell biology, demonstrating that the reinforcement of the tumor suppressive functions of LKB1/AMPK is a valuable therapeutic strategy for cancers. Interest in metformin as a novel anticancer agent for breast cancer and other solid tumors continue to grow, currently being investigated in several cancer types in both neoadjuvant and metastatic settings. The biological effect of metformin on cancer cells is driven by its ability to activate AMPK through upstream kinase LKB1, tumor suppressor gene in epithelial tissues. Metformin increases intracellular AMP level, which allosterically activates AMPK. We have previously identified the AMPKα as a modulator in gastric cancer (GC) and through experimental evidence. We show the impact of LKB1/AMPK modulation of HNF4α, a dramatic suppression of cancer cell growth.

GC samples were collected and sequenced on SOLiD v 3.0 for both WT-seq and small RNA-seq. Computational analysis showed that 356 out of 18,890 genes were identified as GC related differentially expressed genes in the five-group comparison (normal, tumor stage I, II, III or IV). 28 genes were identified as stage-specific differentially expressed genes, and 13 out of the 28 genes were within the network between HNF4α and HNF1α. In order to test the anti-proliferation activity of metformin in GC cell lines associated with activation of PRKAA1, PRKAA2 and LKB1, and by HNF4α suppression, 4 GC cell lines (NCI-N87, AGS, HS 746T and MKN 45) were treated with metformin. Both PRKAA1/2 showed increased gene expression level when the cells were treated with 10mM of metformin. As for STK11 (LKB1 gene) and HNF4A gene expression level, LKB1 increased and HNF4A decreased with metformin treatment on all four cell lines. Metformin treated NCI-N87 and AGS show that it is involved in cell cycle arrest. Western-blot analysis shows, decreased protein expression of Cyclin A/B and D1 on metformin treated. Lastly, NCI-N87 xenograft study show metformin treated suppression of tumor progression compared to non-treated mouse. During the 28 day treatment of metformin, PRKAA1 and PRKAA2 expression level increased compared to the untreated with. Consistent with in vitro assay, LKB1 level was elevated in the metformin treated tumor compared to the non-treated, and HNF4α level decreased over time in the metformin treated tumor.

Study shows that AMPK is a strong therapeutic tumor suppressor target and that metformin is a potential drug for Asian early gastric cancer patient. In our research in progress, we observe potential relationships between the Wnt pathway and AMPKα in light of WNT druggability with metformin. In conclusion LKB1/AMPK by HNF4α inhibition suggests metformin could be a candidate for gastric cancer treatment, probably in combination with conventional chemotherapy and/or as a maintenance therapy.

Citation Format: Hae Rim Jung, Hae Ryung Chang, Hye-Hyun Seo, Robert Lemos, Hee Seo Park, Han Liang, Garth Powis, Yon Hui Kim. Metformin increases AMPKα activity by inhibition of AMPKα and cell cycle proliferation in Asian gastric cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5534. doi:10.1158/1538-7445.AM2013-5534