Fig. 5

Combination of Metformin and SAHA inhibited the growth of subcutaneous tumors in mice. A, B Tumor images (A) and tumor growth curve (B) from each treatment group of the MDA-MB-231 xenograft model (n = 8). Mice were orally treated with SAHA (100 mg/kg) and metformin (200 mg/kg) alone or in combination daily for up to 4 weeks. Tumors were collected and measured 8 h after the last dosing (A) and the tumor growth curve was plotted by measuring the relative tumor volume twice per week (B). Scale bar, 1 cm. Error bars represented means ± SD from triplicates. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. C Molecular alterations in the MDA-MB-231 subcutaneous xenograft model. Tumor samples, as described in (A), were collected 8 h after the last dosing, and intratumoral molecular changes were detected using immunohistochemistry analysis. Scale bar, 20 mm. D Proposed working model. We investigated the synergistic effects of the HDAC inhibitor SAHA and metformin in TNBC using multiple computational methods (CMap, DTsyn, and DrugComb) and bioinformatics predictions (CRISPR/Cas9 screening). The results were further validated through in vitro and in vivo experiments, elucidating the underlying mechanisms. Metformin inhibits the upregulation of histone acetylation on FGFR4, thereby suppressing the feedback activation induced by SAHA. This, in turn, affects its downstream pathways (FGFR4-JAK1-STAT3, FGFR4-AKT, and FGFR4-ERK), leading to the suppression of cancer cell proliferation and anti-apoptotic responses. Additionally, metformin influences glycolysis and metabolic genes (e.g., SLC2A, LDHA, PFKL), participating in metabolic reprogramming, which enhances the efficacy of SAHA in TNBC