Scatter factor protects epithelial and carcinoma cells against apoptosis induced by DNA-damaging agents.
Scatter factor (SF) (hepatocyte growth factor) is a cytokine that may play a role in human breast cancer invasiveness and angiogenesis. We now report that SF can block the induction of apoptosis by various DNA damaging-agents, including cytotoxic agents used in breast cancer therapy. SF protected MDA-MB-453 human breast cancer cells, EMT6 mouse mammary tumor cells and MDCK renal epithelial cells against apoptosis induced by adriamycin (ADR), X-rays, ultraviolet radiation, and other agents. Protection was observed in assays of DNA fragmentation, cell viability (MTT), and clonogenic survival. Protection of MDA-MB-453 cells against ADR was dose- and time-dependent; maximal protection required pre-incubation with 75-100 ng/ml of SF for 48 h or more. Protection required functional SF receptor (c-Met), but was not dependent on p53. Western blotting analysis revealed that pre-treatment of MDA-MB-453 cells with SF inhibited the ADR-induced decreases in the levels of Bcl-XL, an anti-apoptotic protein related to Bcl-2; and the dose-response and time course characteristics for SF-mediated increases in the Bcl-XL protein levels of ADR-treated cells were consistent with the degrees of protection against apoptosis observed under the same conditions. Furthermore, Bcl-XL levels were not down-regulated by ADR in MDA-MB-231 breast cancer cells, consistent with the finding that SF failed to protect these cells against ADR, despite the fact that they contain functional c-Met receptor. In contrast to Bcl-XL, SF blocked ADR-induced increases in c-Myc and inhibited the expression of p21WAF1/CIP1 and of the BRCA1 protein in MDA-MB-453 cells. However, SF did not cause significant changes in the cell cycle distribution of ADR-treated cells. These findings suggest that SF-mediated protection of human breast cancer cells may involve inhibition of one or more pathways required for the activation of apoptosis and may particularly target the anti-apoptotic mitochondrial membrane pore-forming protein Bcl-XL as a component of the protective mechanism. By implication, the accumulation of SF within human breast cancers may contribute to the development of a radio- or chemoresistant phenotype.
Fan
S
S
Department of Radiation Oncology, Long Island Jewish Medical Center, The Long Island Campus for the Albert Einstein College of Medicine, New Hyde Park, New York 11040, USA.
Wang
J A
JA
Yuan
R Q
RQ
Rockwell
S
S
Andres
J
J
Zlatapolskiy
A
A
Goldberg
I D
ID
Rosen
E M
EM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000209:etiology; D002277:Carcinoma / Q000209:etiology*; D002453:Cell Cycle; D002478:Cells, Cultured; D004249:DNA Damage; D004285:Dogs; D004317:Doxorubicin / Q000009:adverse effects; D004847:Epithelial Cells / Q000187:drug effects*; D005260:Female; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000209:etiology; D051379:Mice; D009153:Mutagens / Q000009:adverse effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D015398:Signal Transduction; D014965:X-Rays / Q000009:adverse effects; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; C494812:Bcl2l1 protein, mouse; D009153:Mutagens; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D017228:Hepatocyte Growth Factor; D004317:Doxorubicin; D019859:Proto-Oncogene Proteins c-met