ACTA1 and cancer: When fibroblasts were co-cultured with HT-29 TS for 6 days, prominent changes were observed in cell morphology and α-SMA expression levels: upon co-culture with cancer cells, fibroblasts showed signs of activation including increased levels of α-SMA and F-actin expression and F-actin stress fiber rendering the elongated spindle shape of fibroblasts (Fig 5A).