Increased invasiveness of MMP-9-deficient tumors in two mouse models of neuroendocrine tumorigenesis

Abstract

Despite their apparent success in pre-clinical trials, metalloproteinase (MMP) inhibitors proved to be inefficacious in clinical settings. In an effort to understand the underlying causes of this unanticipated outcome, we modeled the consequences of long-term MMP inhibition by removing one of the major players in tumorigenesis, MMP9, in two complimentary mouse models of pancreatic neuroendocrine carcinogenesis: Myc;BclXl and RIP1-Tag2. By employing gel zymography and a fluoregenic solution assay, we first established that MMP9 is expressed and activated in Myc;BclXl tumors in an interleukin-1b-dependent manner. The genetic deletion of MMP9 in Myc;BclXl mice impairs tumor angiogenesis and growth analogous to its absence in the RIP1-Tag2 model. Notably, tumors that developed in the context of MMP9-deficient backgrounds in both models were markedly more invasive than their typical wild-type counterparts, and expressed elevated levels of pro-invasive cysteine cathepsin B. The increased invasion of MMP9-deficient tumors was associated with a switch in the spectrum of inflammatory cells at the tumor margins, involving homing of previously undetected, cathepsin-B expressing CD11b;Gr1-positive cells to the invasive fronts. Thus, plasticity in the tumor inflammatory compartment is partially responsible for changes in the expression pattern of tumorassociated proteases, and may contribute to the compensatory effects observed on MMP inhibition, hence accounting for the heightened tumor progression described in late stage clinical trials.Oncogene advance online publication, 5 March 2012; doi:10.1038/onc.2012.60Keywords: tumor; metalloproteinase; invasion; cathepsin; Myc; interleukin-1b INTRODUCTIONMatrix metalloproteinases (MMPs) are a family of zinc-dependent proteinases that contribute to development and tissue homeostasis, and modulate cancer progression by digesting a variety of substrates. Owing to the role of MMP in extracellular matrix (ECM) re-arrangement (also referred to as remodeling or degradation), and in the promotion of neoangiogenesis, it was anticipated that MMP inhibition in vivo would have an anti-tumorigenic effect. However, phase III clinical trials with an MMP inhibitor (MMPI), combined with standard-of-care chemotherapy, failed to demonstrate clinical benefit for late stage cancer patients and, remarkably, was in some cases worse than the chemotherapyonly control arm. For instance, the use of Bay 12-9566 in treating patients with pancreatic cancer reduced both median progressionfree survival and quality-of-life when compared with standard care gemcitabine.1 In another case, treatment of glioblastoma patients rendered no statistically significant survival benefits.2 Additionally, the clinical trials in small-cell lung carcinomas had to be terminated prematurely.3 This failure led to the early cessation of ongoing trials, and to reconsideration of the merit of a variety of MMPIs in clinical development by a number of pharmaceutical companies. 4 --6 The molecular mechanism behind this disappointing outc...

Combined deletion of cathepsin protease family members reveals compensatory mechanisms in cancer

“…Previous reports suggest a mechanism through which resistance to MMP inhibitors involves elevated cathepsin activity, dependent on a change in the abundance of inflammatory cells supplying these proteases (Shchors et al 2013). Thus, our data share parallels with these results and show that deletion of multiple cathepsin proteases can conversely alter MMP expression, possibly via perturbation of the protease web.…”

“…2B). Interestingly, CtsZ deletion significantly decreases RT2 tumor invasion (Akkari et al 2014), while Mmp9 ablation has been reported to unexpectedly promote tumor invasion in two independent PanNET mouse models (Shchors et al 2013), including the RT2 model used in this study. Other MMPs, including Mmp3 and Mmp13, have been implicated in the regulation of tumor development and invasion (Kessenbrock et al 2015); however, there have been no correlative studies linking these two MMPs with PanNET malignancy.…”

“…As the additive, tumor-limiting phenotype we observed at the early angiogenic islet stage in CtsB −/− S −/− RT2 tumorigenesis is reversed in end-stage lesions, we hypothesized that up-regulation and functional compensation by another factor, potentially a protease, might specifically occur later in tumor progression in the absence of both CtsB and CtsS to paradoxically promote malignancy. To investigate the potential mediators of this proposed compensation, we analyzed the expression levels of a panel of proteases and protease inhibitors that have previously been shown to be critical in cancer progression (Affara et al 2009;Shchors et al 2013;Sevenich and Joyce 2014). Analyses of mRNA expression for a panel of cathepsins, cathepsin inhibitors, and several matrix metalloproteinases (MMPs) were performed in 13.5-wk end-stage wild-type, CtsB −/− S −/− and CtsB +/− S +/− tumors ( Fig tumors was also confirmed at the protein level (Fig.…”

Systemic Ablation of MMP-9 Triggers Invasive Growth and Metastasis of Pancreatic Cancer via Deregulation of IL6 Expression in the Bone Marrow

“…Genetic models that recapitulate the heterogeneity and multistage nature of tumor progression are believed to be more predictive than xenograft models (14). Interestingly, genetic mouse models of neuroendocrine pancreatic cancer recently demonstrated that the ablation of MMP-9 gave rise to more invasive tumors (15). However, neuroendocrine tumors of the pancreas are a relatively rare condition, accounting for only 1% to 5% of the diagnosed pancreatic cancers, while the large majority of tumors are PDACs, arising from the exocrine cellular compartment (1).…”

Proteases and cytokines as mediators of interactions between cancer and stromal cells in tumours

“…For example, enhanced invasion of MMP-9-deficient tumours is associated with homing of cathepsin B-expressing leukocytes to invasive tumour fronts, facilitating invasion (Shchors et al, 2013). Finally, inefficacy of protease inhibitors may be due to non-proteolytic roles of proteases such as their interaction with other proteins (Kessenbrock et al, 2015).…”