TGFB1 and neoplasm: Fig 9 reveals that treatment with TGFβ significantly decreased the incidence of mito-bulbs while exposure to 10 μM SB431542 promoted formation of mito-bulbs and substantially blocked the effects of TGFβ on mitochondrial morphology. This was not due to toxicity of SB431542 as culture and passaging of A549 cells for 4 weeks with 10 μM SB431542 did not reveal any overt toxicity (not shown). Previous studies have reported that SB431542 increases mitochondrial size in isolated organelles, and that SB431542 can act as a potent anti-tumor agent only in TGFβ-sensitive cell lines [49,50].