COL1A1 and cancer: However, while treatment of luminal cancer cell lines with recombinant TGFβ (rTGFβ) increased FN1 and COL1A1 expression, the magnitude of the effect was smaller, and a longer treatment was needed in cells with high endogenous ThPOK levels (T47D), compared to cells with lower levels (MCF7) (Figs. 5d and S9b).