B6
Scotin is required for ER-stress mediated apoptosis and is associated with good prognosis in breast cancer
Alexandra Diot1, Alice Machado-Silva1, Marie Khoury1, Susan Bray1, Phil Quinlan1, Lee Baker1, Lee Jordan1, Alastair Thompson1, David Lane1, Borek Vojtesek2, Jean-Christophe Bourdon1
1University of Dundee, UK, 2Masaryk Memorial Cancer Institute, Brno, Czech Republic
Background
Scotin was initially identified as a p53-inducible pro-apoptotic gene in response to DNA damage. It was characterised as a transmembrane protein localized to the endoplasmic reticulum (ER) and nuclear membrane.
Method
Scotin-mediated cell death in response to ER-stress inducing drugs was analysed by in vitro cytotoxic assays. Scotin expression was determined at the mRNA and protein levels in a cohort of untreated primary breast cancers (n=250) in relation to clinical markers and clinical outcome. Scotin status was evaluated by RT-PCR and sequencing while protein expression was assessed by immunostaining of Tissue Microarray blocks.
Results
As it has recently been described that ER-stress can induce apoptosis, we investigated whether Scotin, an ER-located protein, can induce cell death in response to ER-stress inducing drugs. Our data demonstrates that Scotin expression is required for ER-stress and DNA damage mediated apoptosis in normal mouse 3T3 fibroblasts and in human cancer cells. Cells that are devoid of Scotin expression are resistant to tunicamycin and thapsigargin, two potent inducers of ER-stress.
To investigate whether Scotin expression is relevant to carcinogenesis, we analysed Scotin expression at the mRNA and protein levels in a cohort of untreated primary breast cancers (n=250) in relation to clinical markers and clinical outcome. The results presented here show that high expression of Scotin is associated with good clinical outcome of breast cancer patients independently of estrogen receptor and p53 status. Moreover, Scotin gene is frequently mutated (~10%) of human breast cancer.
Conclusion
We report for the first time that Scotin is a potent inducer of cell death in response to ER-stress and that Scotin is associated with good prognosis in breast cancer, indicating that Scotin pro-apoptotic activity may play a role in preventing carcinogenesis.
