Combined genomic and phenotype screening reveals secretory factor SPINK1 as an invasion and survival factor associated with patient prognosis in breast cancer.
Bottom Line: In ER- cases, the prognostic effect did not reach statistical significance.However, down-regulation of SPINK1 resulted in cell death.Intriguingly, these anti-apoptotic effects of SPINK1 were abrogated by mutations of its protease inhibition domain.
Affiliation: Cancer Biology and Pharmacology, Genome Institute of Singapore.Show MeSH
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Mentions: As part of our cellular screen for SPINK1 induced phenotypes, we had found that knockdown of SPINK1 attenuated invasion of breast cancer cell lines and that this effect could be rescued using SPINK-CM but not by Vec-CM (Figs S9 and 10A of Supporting information). We extended this analysis using recombinant SPINK1 and found that in two invasive breast cancer cell lines, MDA-MB-231 and BT549, SPINK1-CM significantly increased invasion by 2–3 fold (Fig 10B). Non-invasive MCF10A and MCF-7 cells do not invade in 24 h. After 48 h, these cells show a relative increase in invasion, however, the total number of cells was extremely low (Fig S10 of Supporting information). Importantly, we found that induction of cellular invasion in MDA MB 231 and BT-549 cells could be specifically immuno-neutralized by anti-SPINK1 antibodies (Fig 10C, Fig S11 of Supporting information). We then tested whether the invasive property of SPINK1 was due to its activity as a trypsin/serine protease inhibitor. We exposed K18YCM to MDA-MB-231 cells, and found that K18YCM retained the ability to induce cellular invasion like wild-type (WT) SPINK1-CM, suggesting that active protease inhibitor function is not necessary (Fig 10D). Similar effects were observed in BT549 cells (data not shown). Thus, the anti-apoptotic and the pro-invasive activity of SPINK1 are separable by its protease inhibitor function.
Affiliation: Cancer Biology and Pharmacology, Genome Institute of Singapore.