Bcl-XL expression is regulated by epidermal growth factor (EGF) in mammary epitelial cells (HC11)

ROMORINI, L.; COSO, O.A.; PECCI, A

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

SAIB

EGF activates signalling pathways associated with cell proliferation and apoptosis. The HC11 mouse mammary epithelial cell line is a useful in vitro model system for studying mammary cell proliferation and differentiation. It was previously reported that EGF reverts confluent HC11 cells apoptosis and increases Bcl-2 (anti-apoptotic protein) levels. The bcl-x gene (a member of the bcl-2 family) codifies different protein isoforms with opposite functions, i.e: Bcl-XL (anti-apoptotic) and Bcl-XC (pro-apoptotic). We have studied the regulation of Bcl-X by EGF and the signalling pathways involved. DNA ladder and violet crystal staining shown an apoptosis revertion of confluent HC11 cells with EGF (100 ng/ml) treatment. This effect was totally blocked by JNK inhibitor (SP), partially blocked by PI3K inhibitor (LY) and not affect by MEK/ERK1/2 inhibitor (PD). Western Blot analysis of Bcl-XL at confluent HC11 cells shown a 1,9 fold increase of the protein with EGF (100 ng/ml, 5 hours treatment). This activation was impared with SP and LY kinases but not with PD. bcl-XL and bcl-Xc mRNA levels were then quantified by Real Time PCR with specific primers for each isoform. The results shown that EGF increases the bcl-XL/bcl-Xc ratio (23,1 times vs control) which indicates an antiapoptotic environment. SP and LY inhibitors totally revert this increase and PD inhibitor does it only partially. Conclusion: EGF reverts confluent HC11 cells apoptosis, increases Bcl-XL protein expression and the bcl-XL/bcl-Xc mRNAs ratio, being JNK and PI3K the kinases involved.