TIMP‐2 Inhibits Triple Negative Breast Cancer Growth and Metastasis through EMT Suppression and Promotion of Vascular Normalization

Abstract

Successful tumor cell invasion requires degradation of the extracellular matrix (ECM) by matrix metalloproteases (MMPs), a large family of metalloproteinases that cleave ECM proteins. MMP synthesis and activation is tightly regulated by their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). TIMP‐2 is a multifunctional protein shown to inhibit tumor growth, invasion and metastasis independent of MMP inhibitory activity via mechanisms including alteration of the epithelial to mesenchymal transition (EMT), reduced tumor angiogenesis, and inhibition of VEGF‐A induced vascular permeability. Triple‐negative breast cancers (TNBCs) are highly vascular tumors that exhibit EMT plasticity and extensive metastatic dissemination. We explored the efficacy of recombinant TIMP‐2 (rTIMP‐2) as a preclinical therapeutic using an orthotopic mouse model which phenotypically resembles human TNBC and establishes spontaneous lung metastases. Daily rTIMP‐2 treatment (100 ug/kg/day) was initiated 10 days post tumor cell implantation and continued through day 37. Biweekly tumor measurements [tumor volume) = 1/2(length × width2)] revealed reduced primary tumor growth in rTIMP‐2 treated mice 15 days post inoculation and maximum tumor growth inhibition on day 29. Immunostaining of primary tumors demonstrated increased CK‐18 expression along with decreased CK‐14 and vimentin in rTIMP‐2 treated mice, suggesting reversal of the EMT phenotype by day 32, while lung histology showed a significant reduction in metastatic foci in rTIMP‐2 treated mice at day 52. Moreover, immunofluorescence demonstrates increased pericyte coverage and reduced vascular leakage in rTIMP‐2 treated primary TNBC tumors, showing modulation of vessel morphology and promotion of events consistent with vessel normalization. These findings suggest the therapeutic potential for rTIMP‐2 in the clinical treatment of TNBC.Support or Funding InformationThis work was funded by the NCI Center for Cancer Research Intramural Research Program Project # ZIA SC009179‐25.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.