TGFB1 and cancer: Mechanical signals regulate cell death of several cancer types.21 To determine if direct application of LIV to breast cancer cells influences cell death, MDA-MB-231 human breast cancer cells were exposed to 20-min bouts of LIV (0.3 g, 90 Hz) once- or twice-daily for three days, in the presence or absence of TGF-β1.