SHH and breast cancer: In MDA-MB-231 breast cancer cells, metformin (1 mM, 3 mM, and 9 mM) treatment significantly decreased the mRNA expression and protein levels of SHh, Smo, Ptch, and Gli (components of the Hh signaling mechanism) and inhibited SHh-mediated Hh signaling-induced cell proliferation in a dose and time-dependent manner [251].