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: Since SPINK1 protected cells from drug-induced apoptosis, we studied the expression of a panel of pro- and anti-apoptotic genes including caspase-3, caspase-8, PARP, BID, Bcl2 and phospho-Bcl2 in MCF-7 cells treated with SPINK1-CM for 2 h. As shown, apoptosis-inhibitor Bcl2 levels were upregulated without changing caspase-3, BID, PARP and caspase-8 levels (Fig 8A and S8 of Supporting information). Interestingly, in different clones of MCF-7 SPINK1 OE cells, endogenous Bcl2 and phosphor-Bcl2 increased and caspase-3 levels decreased with increasing expression of SPINK1 (Fig 8B). The decrease in caspase-3 was, however, not evident in cells treated with SPINK1-CM (Fig 8A), perhaps indicating that prolonged high expression of SPINK1 may lead to higher chemoresistance. Since previous studies showed that the protease inhibitor function of SPINK1 is necessary for some oncogenic properties of SPINK1 (Lamontagne et al, 2010), we generated a SPINK1 K18Y mutant lacking this function (Gouyer et al, 2008; Fig S5D of Supporting information). As shown in Fig 9, pretreatment of cells with SPINK1-K18Y-CM (hatched bars) was unable to protect cells from 5 FU- (panel A) or SAHA- (panel B) induced apoptosis. Together, these data show that high SPINK1 induces chemoresistance and its protease inhibitor function is critical to mediate this effect.
Affiliation: Cancer Biology and Pharmacology, Genome Institute of Singapore.