CASP3 and neoplasm: Consistently, the level of active caspase-3 was decreased in Hepa1-6 and 4T1 cells that were cultured in serum-free CM-FL (Figure 2E and 2F), indicating that fibrotic microenvironment may promote the chemotaxis of tumor cells to the lungs and inhibit the apoptosis of tumor cells seeded in the lungs.