Combined genomic and phenotype screening reveals secretory factor SPINK1 as an invasion and survival factor associated with patient prognosis in breast cancer

Abstract

Secretory factors that drive cancer progression are attractive immunotherapeutic targets. We used a whole-genome data-mining approach on multiple cohorts of breast tumours annotated for clinical outcomes to discover such factors. We identified Serine protease inhibitor Kazal-type 1 (SPINK1) to be associated with poor survival in estrogen receptor-positive (ER+) cases. Immunohistochemistry showed that SPINK1 was absent in normal breast, present in early and advanced tumours, and its expression correlated with poor survival in ER+ tumours. In ER− cases, the prognostic effect did not reach statistical significance. Forced expression and/or exposure to recombinant SPINK1 induced invasiveness without affecting cell proliferation. However, down-regulation of SPINK1 resulted in cell death. Further, SPINK1 overexpressing cells were resistant to drug-induced apoptosis due to reduced caspase-3 levels and high expression of Bcl2 and phospho-Bcl2 proteins. Intriguingly, these anti-apoptotic effects of SPINK1 were abrogated by mutations of its protease inhibition domain. Thus, SPINK1 affects multiple aggressive properties in breast cancer: survival, invasiveness and chemoresistance. Because SPINK1 effects are abrogated by neutralizing antibodies, we suggest that SPINK1 is a viable potential therapeutic target in breast cancer.

Emerging Roles of SPINK1 in Cancer

“…Forced expression of SPINK1 induced in vitro migration and invasion but not proliferation (50,51 ). Furthermore, in an in vivo experiment, SPINK1 was shown to induce metastasis in the mouse tail-vein model (50 ). These results support recent clinical findings that show increased serum concentrations of SPINK1 in metastatic breast cancer patients (49 ) and thus indicate a role for SPINK1 in metastatic dissemination in breast cancer.…”

“…With the use of genome-wide profiling, SPINK1 was found to be a driver of aggressiveness and associated with poor survival outcome in estrogen receptor-positive breast cancer. This was also shown at the protein level in a panel of clinically annotated breast tumors (50 ).…”

“…Interestingly, this mechanism required protease inhibitor activity of SPINK1 (50 ). Forced expression of SPINK1 induced in vitro migration and invasion but not proliferation (50,51 ). Furthermore, in an in vivo experiment, SPINK1 was shown to induce metastasis in the mouse tail-vein model (50 ).…”

“…Interestingly, this mechanism required protease inhibitor activity of SPINK1 (50 ). Forced expression of SPINK1 induced in vitro migration and invasion but not proliferation (50,51 ).…”

“…Both SPINK1 antibody and the EGFR antibody cetuximab attenuated tumor growth, and the combined effect of these was stronger than that of either one alone (31 ). Monoclonal antibodies to SPINK1 have also been used in xenograft models of colon and breast cancer to attenuate tumor growth (50,51 ).…”