Loss of MMP-8 in ductal carcinoma in situ (DCIS)-associated myoepithelial cells contributes to tumour promotion through altered adhesive and proteolytic function.

BACKGROUND: Normal myoepithelial cells (MECs) play an important tumour-suppressor role in the breast but display an altered phenotype in ductal carcinoma in situ (DCIS), gaining tumour-promoter functions. Matrix metalloproteinase-8 (MMP-8) is expressed by normal MECs but is lost in DCIS. This study investigated the function of MMP-8 in MECs and the impact of its loss in DCIS. METHODS: Primary normal and DCIS-associated MECs, and normal (N-1089) and DCIS-modified myoepithelial (ß6-1089) cell lines, were used to assess MMP-8 expression and function. ß6-1089 lacking MMP-8 were transfected with MMP-8 WT and catalytically inactive MMP-8 EA, and MMP-8 in N-1089 MEC was knocked down with siRNA. The effect on adhesion and migration to extracellular matrix (ECM), localisation of α6ß4 integrin to hemidesmosomes (HD), TGF-ß signalling and gelatinase activity was measured. The effect of altering MEC MMP-8 expression on tumour cell invasion was investigated in 2D and 3D organotypic models. RESULTS: Assessment of primary cells and MEC lines confirmed expression of MMP-8 in normal MEC and its loss in DCIS-MEC. Over-expression of MMP-8 WT but not MMP-8 EA in ß6-1089 cells increased adhesion to ECM proteins and reduced migration. Conversely, knock-down of MMP-8 in N-1089 reduced adhesion and increased migration. Expression of MMP-8 WT in ß6-1089 led to greater localisation of α6ß4 to HD and reduced retraction fibre formation, this being reversed by MMP-8 knock-down in N-1089. Over-expression of MMP-8 WT reduced TGF-ß signalling and gelatinolytic activity. MMP-8 knock-down enhanced TGF-ß signalling and gelatinolytic activity, which was reversed by blocking MMP-9 by knock-down or an inhibitor. MMP-8 WT but not MMP-8 EA over-expression in ß6-1089 reduced breast cancer cell invasion in 2D and 3D invasion assays, while MMP-8 knock-down in N-1089 enhanced cancer cell invasion. Staining of breast cancer cases for MMP-8 revealed a statistically significant loss of MMP-8 expression in DCIS with invasion versus pure DCIS (p = 0.001). CONCLUSIONS: These data indicate MMP-8 is a vital component of the myoepithelial tumour-suppressor function. It restores MEC interaction with the matrix, opposes TGF-ß signalling and MMP-9 proteolysis, which contributes to inhibition of tumour cell invasion. Assessment of MMP-8 expression may help to determine risk of DCIS progression.

Pleiotropic functions of the tumor- and metastasis-suppressing matrix metalloproteinase-8 in mammary cancer in MMTV-PyMT transgenic mice.

INTRODUCTION: Matrix metalloproteinase-8 (MMP-8; neutrophil collagenase) is an important regulator of innate immunity that has oncosuppressive actions in numerous tumor types. METHODS: We have intercrossed Mmp8-null mice with the Polyoma virus middle T oncogene-driven (MMTV-PyMT) mouse model of mammary cancer to explore the effects of loss of MMP-8 on the incidence and progression of mammary carcinomas. RESULTS: In this aggressive mouse model of breast cancer, loss of MMP-8 accelerated tumor onset even further, such that 90% of MMTV-PyMT; Mmp8-null female mice were tumor-bearing at the time of weaning. Throughout the 14 weeks of the model, tumor burden increased in homozygous Mmp8-null mice compared to Mmp8-wild-type and -heterozygote animals. Likewise, lung metastasis dramatically increased in the MMTV-PyMT; Mmp8-null mice. Immunohistochemistry revealed that tumors in wild-type, Mmp8-heterozygotes and -null animals had similar vascular density at 8 weeks, but at 10 weeks Mmp8-wild-type tumors had a lower vascularity than their heterozygote and null counterparts. No differences in macrophage infiltration were apparent throughout primary tumor development, though at 10 weeks a drop in neutrophil infiltrates was observed in Mmp8-wild-type tumors. Using quantitative real-time RT-PCR, we tracked the expression of the entire Mmp and Timp gene families, observing a significant decrease in Mmp3 expression in Mmp8-null tumors compared to wild-type and heterozygotes throughout the time course of the model, which was confirmed at the protein level. CONCLUSIONS: These findings provide novel insight into the suppressive action of MMP-8 on mammary tumorigenesis and metastasis, and indicate that the loss of MMP-8 likely has pleiotropic effects on innate immunity and angiogenesis that are reflected in changes in the protease web.

Matrix metalloproteinase 8 (collagenase 2) induces the expression of interleukins 6 and 8 in breast cancer cells.

Matrix metalloproteinase 8 (MMP-8) is a tumor-suppressive protease that cleaves numerous substrates, including matrix proteins and chemokines. In particular, MMP-8 proteolytically activates IL-8 and, thereby, regulates neutrophil chemotaxis in vivo. We explored the effects of expression of either a WT or catalytically inactive (E198A) mutant version of MMP-8 in human breast cancer cell lines. Analysis of serum-free conditioned media from three breast cancer cell lines (MCF-7, SK-BR-3, and MDA-MB-231) expressing WT MMP-8 revealed elevated levels of IL-6 and IL-8. This increase was mirrored at the mRNA level and was dependent on MMP-8 catalytic activity. However, sustained expression of WT MMP-8 by breast cancer cells was non-permissive for long-term growth, as shown by reduced colony formation compared with cells expressing either control vector or E198A mutant MMP-8. In long-term culture of transfected MDA-MB-231 cells, expression of WT but not E198A mutant MMP-8 was lost, with IL-6 and IL-8 levels returning to base line. Rare clonal isolates of MDA-MB-231 cells expressing WT MMP-8 were generated, and these showed constitutively high levels of IL-6 and IL-8, although production of the interleukins was no longer dependent upon MMP-8 activity. These studies support a causal connection between MMP-8 activity and the IL-6/IL-8 network, with an acute response to MMP-8 involving induction of the proinflammatory mediators, which may in part serve to compensate for the deleterious effects of MMP-8 on breast cancer cell growth. This axis may be relevant to the recognized ability of MMP-8 to orchestrate the innate immune system in inflammation in vivo.

Stability assessment of serum tumour markers: Calcitonin, chromogranin A, thyroglobulin and anti-thyroglobulin antibodies.

BACKGROUND: There is limited published data on the stability of calcitonin, chromogranin A, thyroglobulin and anti-thyroglobulin antibodies in serum. The aim of this study was to determine stability at three temperature conditions over 7 days, reflecting current laboratory practices. METHODS: Surplus serum was stored at room temperature, refrigerated and in the freezer; for 1, 3, 5 and 7 days. Samples were analysed in batch and analyte concentrations compared to that of a baseline sample. Measurement Uncertainty of the assay was used to determine the Maximal Permissible Difference and thus the stability of the analyte. RESULTS: Calcitonin was found to be stable for at least 7 days in the freezer but only 24 h refrigerated. Chromogranin A was stable for 3 days when refrigerated and only 24 h at room temperature. Thyroglobulin and anti-thyroglobulin antibodies were stable under all conditions for 7 days. CONCLUSION: This study has enabled the laboratory to increase the add-on time limit of Chromogranin A to 3 days, and up to 60 min for calcitonin and inform optimal storage and transportation conditions for referring specimens.

Matrix metalloproteinases: protective roles in cancer.

The original notion that matrix metalloproteinases (MMPs) act as tumour and metastasis-promoting enzymes by clearing a path for tumour cells to invade and metastasize has been challenged in the last decade. It has become clear that MMPs are involved in numerous steps of tumour progression and metastasis, and hence are now considered to be multifaceted proteases. Moreover, more recent experimental evidence indicates that some members of the MMP family behave as tumour-suppressor enzymes and should therefore be regarded as anti-targets in cancer therapy. The complexity of the pro- and anti-tumorigenic and -metastatic functions might partly explain why broad-spectrum MMP inhibitors failed in phase III clinical trials. This review will provide a focussed overview of the published data on the tumour-suppressive behaviour of MMPs.