In the xenotransplantation model of nude mice, metformin can promote the expression of miR-26a, miR-192 and Let-7c in a dose-dependent manner, and upregulated miR-26a can inhibit the expression of HMGA1 and tumour growth, which also suggests why part of the biological effects of metformin play a role through HMGA1 112. The gene discussed is HMGA1; the disease is neoplasm.