Timp2 loss-of-function mutation and rTIMP2 treatment in murine lung cancer models: alteration of myeloid response and suppression of tumorigenesis
TIMP2 inhibits metalloproteinase activity and possesses metalloproteinase-independent functions that regulate cell growth, invasion, and gene expression. Although mounting evidence suggests TIMP2 can reduce tumor burden and metastasis the demonstration of these effects using in vivo tumor models are lacking. In this study, we examine the effects of functional mutation of Timp2 and administration of recombinant TIMP2 in models of both orthotopic and heterotopic murine lung cancer using the syngeneic Lewis Lung carcinoma cells (LL/2-luc2). Mice harboring a functional mutation of TIMP2 (mT2) display a marked increase in tumor growth and mortality, enhanced tumor micro-vasculature, and greater infiltration of myeloid-derived cells compared to wt mice, suggesting that reduced TIMP2 function results in enhanced presence of pro-tumorigenic, immunosuppressive myeloid cells. Treatment with recombinant TIMP2 reduced primary tumor growth in both genotypes. Transcriptional profiling of lung tissues from non-tumor-bearing mice reveals minimal changes in mice. However, orthotopic, lung tumor-bearing mice demonstrate significant changes in gene expression that are genotype-dependent. In tumor-bearing wt mice TIMP2-treatment reduced the expression of upstream oncogenic mediators. In comparison, treatment of mT2 mice resulted in an immunomodulatory phenotype, as suggested by enhanced activity of Il4, Il2, and Ifng. A heterotopic model of LL/2 generating metastatic pulmonary tumors demonstrated that daily administration of recombinant TIMP2, while also reducing primary tumor growth, significantly altered transcriptional profiles in the lungs of wt mice, suggesting modification of the metastatic niche. These changes result in the downregulation of cell-stress responses, as evidenced by reduced expression of heat shock proteins. In summary, we describe how TIMP2 exerts novel, anti-tumor effects in a murine model of lung cancer and that rTIMP2 treatment supports a normalizing effect on the tumor microenvironment. These findings support the concept that TIMP2 displays homeostatic functions to reverse cell stress signaling in addition to inhibition of metalloproteinases. Overall design: To assess the effects of Timp2 mutation on pulmonary tumor progression, and determine the therapeutic success of daily recombinant TIMP2 treatment in pulmonary tumor bearing mice.