Expression of HER-2 in MCF-7 breast cancer cells modulates anti-apoptotic proteins Survivin and Bcl-2 via the extracellular signal-related kinase (ERK) and phosphoinositide-3 kinase (PI3K) signalling pathways

Aisha Siddiqa¹ , Linda M Long¹ , Liuxia Li¹ , Robert A Marciniak¹^,2^,3 and Irene Kazhdan¹

¹Department of Medicine, University of Texas Health Science Center, San Antonio, TX 78229, USA

²Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, TX 78229, USA

³South Texas Veterans Healthcare Administration, San Antonio, TX 78229, USA

author email corresponding author email

BMC Cancer 2008, 8:129doi:10.1186/1471-2407-8-129


Published:	2 May 2008

Abstract

Background

The oncoprotein HER-2 is over-expressed and/or has undergone gene amplification in between 20 to 30% of breast and ovarian cancers. HER-2 amplified breast cancer is associated with a poor prognosis and increased resistance to chemo- and hormonal therapy. Data supporting the transforming potential of HER-2 are irrefutable but the mechanism by which HER-2 contributes to this process is complex and a unified model of HER2-induced increased cell proliferation and survival has not emerged.

To understand the initial event(s) that take place by HER-2 over expression, we studied the effect of short term induction of HER-2 expression in the MCF7 breast cancer cell line.

Methods

We examined the modulation of apoptotic pathways by tetracycline-regulated HER-2 expression for 48 hrs in the MCF7 breast cancer cell line. Specific inhibitors were used to determine signalling pathways that are required for HER-2 induced up-regulation of survivin.

Results

Tetracycline regulated short term over expression of HER-2 in the MCF7 cell line increased the antiapoptotic proteins Bcl-2 and survivin levels. Significant increase of extracellular signal-related kinase (ERK) activation but not AKT1, AKT2 and STAT3 was observed in HER-2 over-expressing MCF7 cells. Specific inhibitors of ERK, and phosphoinositide-3 kinase (PI3K), inhibited the HER-2 induced up-regulation of survivin. We did not observe a change in survivin and NF-κB promoter activity in HER-2 expressing MCF7 cells.

Conclusion

Our results indicate that short term over expression of HER-2 up regulates antiapoptotic proteins Bcl-2 and survivin in MCF7 cells. We determined that survivin is up-regulated via ERK activation and PI3K signalling. Additionally we show that survivin up-regulation is not at transcriptional level. These data provide insight into the mechanism(s) by which induction of HER-2 over expression up-regulates survivin and Bcl-2 and identifies new targets for therapy of breast cancer.