B48
ADAM Processing of TMEFF1, a potential regulator of TGF- signalling in breast cancer
Gareth Edwards1, Nazim Ali2, Vera Knauper1
1Cardiff University, UK, 2University of Manchester, UK
Background
Approximately 46,000 cases of breast cancer are diagnosed in the UK each year, leading to approximately 12,000 fatalities per year (1). TMEFF1 (a transmembrane glycoprotein with an EGF-like domain and two follistatin domains) is expressed in some breast cancer cells (2), and exhibits a growth-suppressive effect when over-expressed in brain tumour cells (2).The TGF-β co-receptor Cripto is over-expressed in 80 % of breast cancers (3). Published reports document the ability of TMEFF1 to bind Cripto in Xenopus (4), which may facilitate the inhibition of Cripto function in breast cancers. ADAMs cleave growth factors from the cell surface and are over-expressed in aggressive breast cancers (5).
Method
HEK293 cells were stably transfected with AP-tagged TMEFF1. Shedding of TMEFF1 was assayed by detection of AP activity. Western blotting was employed to assess protein degradation, and proliferation was assessed with the XTT assay.
Results
Shedding of the TMEFF1 ectodomain was induced with PMA and inhibited by the ADAM inhibitor TAPI-1, but not by the γ-secretase inhibitor DAPT. RNA interference and over-expression studies demonstrated that TMEFF1 is processed by ADAM10 and ADAM17. Shedding assays and co-immunoprecipitation indicated that TMEFF1 and Cripto form a complex in co-transfected cells. When TMEFF1 was transiently transfected into MDA-MB-231 breast cancer cells over-expressing Cripto, there was a reduction in cell proliferation.
Conclusion
The potential role of TMEFF1 in regulating breast cancer cell proliferation will be discussed.
References
[1] Cancer Research UK statistics.
[2] Gery et al. (2003). Oncogene 22:2723-7.
[3] Qi et al. (1994). Br. J. Cancer 69:903-10.
[4] Harms & Chang (2003). Genes Dev. 17:2624-9. (5) Maretzky et al. (In Press). Cancer Res.
