Purpose: The biguanides Metformin (MET) and to a lesser extent Buformin (BUF) have recently been shown to exert anticancer effects. In particular MET targets cancer stem cells (CSCs) in a variety of cancer types. These compounds have not been extensively tested for combination therapy.
Objectives: In this study we investigated in vitro the anticancer activity of MET and BUF alone or in combination with 2-deoxy-D-glucose (2-DG), or WZB-117 (WZB), which are a glycolysis and a GLUT-1 inhibitor, respectively, in H460 human lung cancer cells growing under three different culture conditions with varying degrees of stemness: 1) Routine Culture Conditions (RCCs), 2) Floating Lung Tumorspheres (LTSs) that are enriched for stem-like cancer cells and 3) Adherent cells under prolonged periods (8-12 days) of serum starvation (PPSS): These cells are highly resistant to conventional anticancer drugs such as Paclitaxel, Hydroxyurea and Colchicine and display increased level of stemnes markers.
Experimental setup: For cells growing under RCCs and under PPSS, cell viability was measured by the MTT assay. Viability of LTS was evaluated by the CCK assay. Clonogenicity was evaluated by the colony formation assays.
Results: As single agents MET, BUF, 2-DG and WZB-117 potently inhibited the viability of cells growing under RCCs. These results were confirmed by the colony forming assay. Both MET and BUF showed a strong synergistic effect when used in combination with 2-DG. A weak potentiation was observed when used with WZB-117. Under RCCs H460 cells were more sensitive to MET and BUF and WZB-117 compared to non-tumorigenic Beas-2B cells. While LTSs were less sensitive to each single drug, both MET or BUF in combination with 2-DG showed a strong synergistic effect and reduced cell viability to similar levels compared to the parental H460 cells. Adherent cells growing under PPSS were also less sensitive to each single drug and MET and BUF showed a strong synergistic effect on cell viability in combination with 2-DG.
We are currently evaluating the generation of reactive oxygen species (ROS) and the signaling pathways involved in the antiproliferative effects of these agents as single drugs as well as in combination.
Conclusions: Overall our data demonstrates that combination of BGs with either 2-DG or WZB-117 have a “Broad - spectrum” anticancer activities targeting cells growing under a variety of cell culture conditions with varying degrees of stemness. These properties may be useful to overcome the chemoresistance due to intratumoral heterogeneity found in lung cancer.
Citation Format: Juan Sebastian Yakisich, Neelam Azad, Anand V. Iyer. Broad-spectrum anticancer activities of the biguanides metformin and buformin in combination with 2-deoxy-glucose or WZB-117 in human lung cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 277.