Citations

Abstract Matrix metalloproteinases (MMPs), a family of extracellular matrix degrading proteins, have been found to be upregulated in many human cancers and have been shown to contribute to cancer progression. There have been many aborted attempts to target MMPs therapeutically using small molecule inhibitors; the limited selectivity of most MMP inhibitors may be a major factor contributing to their poor effectiveness. As an alternative to small molecule MMP inhibitors, we are developing new methodology to create selective protein inhibitors of MMPs, based on the scaffold of the natural inhibitor TIMP-1, that may be used as protein therapeutics. Because TIMP-1 has a very short plasma half-life, we have developed methods for PEGylation that extend the plasma half-life to about 24h while preserving MMP inhibitory activity, rendering it more suitable for in vivo applications. We have also generated mutations in TIMP-1 that confer selective binding toward particular MMPs. The targets thus far pursued include MMP-9, MMP-3, and MMP-10, which represent therapeutic targets of interest in breast cancer and lung cancer. In the future, the methods developed here can be used to identify TIMP-1 variants selective toward additional MMPs, which may be of utility in the research and treatment of many human cancers. Citation Format: Christine Mehner, Jyotica Batra, Jessica Robinson, Derek C. Radisky, Evette S. Radisky. Engineering TIMP-1 for selective MMP inhibition and future use as a protein therapeutic. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5069. doi:10.1158/1538-7445.AM2013-5069

Abstract Pancreatic ductal adenocarcinoma (PDA) arises at the convergence of genetic alterations in KRAS with a fostering microenvironment shaped by immune cell influx and fibrotic changes; identification of the earliest tumorigenic molecular mediators evokes the proverbial chicken and egg problem. Matrix metalloproteinases (MMP) are key drivers of tumor progression that originate primarily from stromal cells activated by the developing tumor. Here, MMP3, known to be expressed in PDA, was found to be associated with expression of Rac1b, a tumorigenic splice isoform of Rac1, in all stages of pancreatic cancer. Using a large cohort of human PDA tissue biopsies specimens, both MMP3 and Rac1b are expressed in PDA cells, that the expression levels of the two markers are highly correlated, and that the subcellular distribution of Rac1b in PDA is significantly associated with patient outcome. Using transgenic mouse models, coexpression of MMP3 with activated KRAS in pancreatic acinar cells stimulates metaplasia and immune cell infiltration, priming the stromal microenvironment for early tumor development. Finally, exposure of cultured pancreatic cancer cells to recombinant MMP3 stimulates expression of Rac1b, increases cellular invasiveness, and activation of tumorigenic transcriptional profiles. Implications: MMP3 acts as a coconspirator of oncogenic KRAS in pancreatic cancer tumorigenesis and progression, both through Rac1b-mediated phenotypic control of pancreatic cancer cells themselves, and by giving rise to the tumorigenic microenvironment; these findings also point to inhibition of this pathway as a potential therapeutic strategy for pancreatic cancer. Mol Cancer Res; 12(10); 1430–9. ©2014 AACR.

Blood-brain barrier (BBB) dysfunction in acute liver failure (ALF) results in increased BBB permeability that often precludes the patients from obtaining a life-saving liver transplantation. It remains controversial whether matrix metalloproteinase-9 (MMP-9) from the injured liver contributes to the deregulation of BBB function in ALF. We selectively upregulated a physiologic inhibitor of MMP-9 (TIMP-1) with a single intracerebroventricular injection of TIMP-1 cDNA plasmids at 48 and 72 hours, or with pegylated-TIMP-1 protein. Acute liver failure was induced with tumor necrosis factor-α and D-(+)-galactosamine in mice. Permeability of BBB was assessed with sodium fluorescein (NaF) extravasation. We found a significant increase in TIMP-1 within the central nervous system (CNS) after the administration of TIMP-1 cDNA plasmids and that increased TIMP-1 within the CNS resulted in an attenuation of BBB permeability, a reduction in activation of epidermal growth factor receptor and p38 mitogen-activated protein kinase signals, and a restoration of the tight junction protein occludin in mice with experimental ALF. Pegylated TIMP-1 provided similar protection against BBB permeability in mice with ALF. Our results provided a proof of principle that MMP-9 contributes to the BBB dysfunction in ALF and suggests a potential therapeutic role of TIMP-1 in ALF.

Abstract PRSS3/mesotrypsin is an atypical isoform of trypsin that has been associated with breast, lung, and pancreatic cancer cell malignancy. In analyses of open source transcriptional microarray data, we find that PRSS3 expression is upregulated in metastatic prostate cancer tissue, and that expression of PRSS3 in primary prostate tumors is prognostic of systemic progression following prostatectomy. Using a mouse orthotopic model with bioluminescent imaging, we show that PRSS3/mesotrypsin is critical for prostate cancer metastasis. Silencing of PRSS3 inhibits anchorage-independent growth of prostate cancer cells in soft agar assays, and suppresses invasiveness in Matrigel transwell assays and three-dimensional (3D) cell culture models. We further show that treatment with recombinant mesotrypsin directly promotes an invasive cellular phenotype in prostate cancer cells and find that these effects are specific and require the proteolytic activity of mesotrypsin, because neither cationic trypsin nor a mesotrypsin mutant lacking activity can drive the invasive phenotype. Finally, we show that a newly developed, potent inhibitor of mesotrypsin activity can suppress prostate cancer cell invasion to a similar extent as PRSS3 gene silencing. This study defines mesotrypsin as an important mediator of prostate cancer progression and metastasis, and suggests that inhibition of mesotrypsin activity may provide a novel modality for prostate cancer treatment. Mol Cancer Res; 10(12); 1555–66. ©2012 AACR.

Abstract Matrix metalloproteinase 10 (Mmp10; stromelysin 2) is a member of a large family of structurally related matrix metalloproteinases, many members of which have been implicated in tumor progression, invasion and metastasis. However, emerging evidence suggests a possible role for Mmps in tumor initiation. Here we reveal an unexpected role for Mmp10 in the maintenance and tumorigenicity of mouse lung cancer stem-like cells (CSC). Mouse lung cancer cell cultures enriched in stem-like cells grow as undifferentiated tumor “oncospheres” that express elevated levels of the cancer stem cell markers Aldh1, CD133, Nanog, Notch3, Notch 4, Hey 1 and Hey 2. These cells also express elevated levels of Mmp10 mRNA and secrete elevated levels of Mmp10 protein. Functionally, these lung CSCs exhibit self-renewal, the ability to clonally expand, enhanced transforming potential in vitro, and enhanced tumorigenic properties when injected orthotopically into the lungs of syngeneic mice. RNAi-mediated knockdown of Mmp10 in these cells leads to a loss of stem cell marker gene expression and a dramatic inhibition of oncosphere growth, clonal expansion, transformed growth in vitro, and lung tumor formation and metastasis in vivo. In contrast, oncospheres implanted into syngeneic non-transgenic or Mmp10−/− mice show no significant difference in tumor initiation, growth or metastasis, demonstrating the importance of Mmp10 produced by cancer cells rather than the tumor microenvironment in lung tumor initiation and maintenance. Analysis of gene expression data from human tumors demonstrates that Mmp10 is elevated in many human tumor types including lung, head and neck, esophageal, colon, breast, melanoma, bladder, cervical, ovarian, prostate and brain. Furthermore, gene set enhancement analysis (GSEA) demonstrates that elevated Mmp10 expression correlates with tumor metastasis and with cancer stem-like genomic signatures in human lung tumors. Thus, Mmp10 is required for maintenance of a highly tumorigenic, cancer-initiating, metastatic stem-like cell population in lung cancer. Our data demonstrate for the first time that Mmp10 is a critical lung cancer stem cell gene and novel therapeutic target for lung cancer stem cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-204. doi:1538-7445.AM2012-LB-204

Rac1b mediates the matrix metalloproteinase–induced epithelial-mesenchymal transition in lung adenocarcinoma and is a potential therapeutic target in early-stage lung cancer.

Abstract Most breast cancer deaths are the consequence of metastasis from the primary site. In order to metastasize, tumor cells must escape the physical barriers that contain the growing primary tumor, enter the vascular system, exit the vascular system at a distant point, and colonize a distant organ. An important mediator of metastasis is matrix metalloproteinase-9, a member of the MMP family that has been found to be upregulated both in breast cancer cells and in the surrounding tumor stroma. Studies using animal models have sometimes produced apparently contradictory findings, due in part to methodology in which MMP-9 expression is suppressed throughout the host organism and throughout the course of tumor initiation and progression. To define the specific role of tumor cell-produced MMP-9 in metastasis of human breast cancer, we implemented a bioluminescent imaging animal model of metastasis in which luciferase-expressing MDA-MB-231 cells, infected either with control nontarget lentivirus (MDA-MB-231-NT) or with shRNA lentivirus targeting MMP-9 (MDA-MB-231-MMP9-KD), were orthotopically implanted into the mammary fat pads of immunocompromised mice. Tumor growth and development of lung metastases were assessed over 10 weeks using an IVIS imager. At 11 weeks mice were sacrificed, and tumor progression was assessed by ex vivo lung imaging and by immunohistochemical processing of the tumors and the lungs. Imaging studies revealed that primary tumors developing from MMP-9 knockdown cells grew more slowly throughout the course of the study (ranging from 25% to 50%), and that while the majority of the control group developed lung metastases, none of the mice injected with MDA-MB-231-MMP9-KD cells showed metastatic progression. After sacrifice, the measured tumor weight showed a median of 99 mg for the MDA-MB-231-MMP9-KD and 158 mg for the MDA-MB-231-NT tumors, showing that knockdown of MMP-9 inhibited tumor growth. Ex vivo imaging of the lungs confirmed the in vivo studies: no metastases were detected from MDA-MB-231-MMP9-KD cells, while all lungs of the MDA-MB-231-NT injected mice had detectable metastases (p=0.0079). Similarly, a single level immunohistochemical correlate found no metastases in the MDA-MB-231-MMP9-KD mice, while 3 of 4 mice with the non-target control cells showed large metastases (median 7×103 μm2). Our results demonstrate that expression of MMP-9 by human breast cancer cells plays a significant role in the progression of tumor growth and metastasis and provide insight into the potential of MMP-9 as a target for therapeutic intervention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1497. doi:10.1158/1538-7445.AM2011-1497

PRSS3/mesotrypsin is an atypical isoform of trypsin, the up-regulation of which has been implicated in promoting tumour progression. Mesotrypsin inhibitors could potentially provide valuable research tools and novel therapeutics, but small-molecule trypsin inhibitors have low affinity and little selectivity, whereas protein trypsin inhibitors bind poorly and are rapidly degraded by mesotrypsin. In the present study, we use mutagenesis of a mesotrypsin substrate, APPI (amyloid precursor protein Kunitz protease inhibitor domain), and of a poor mesotrypsin inhibitor, BPTI (bovine pancreatic trypsin inhibitor), to dissect mesotrypsin specificity at the key P2′ position. We find that bulky and charged residues strongly disfavour binding, whereas acidic residues facilitate catalysis. Crystal structures of mesotrypsin complexes with BPTI variants provide structural insights into mesotrypsin specificity and inhibition. Through optimization of the P1 and P2′ residues of BPTI, we generate a stable high-affinity mesotrypsin inhibitor with an equilibrium binding constant Ki of 5.9 nM, a >2000-fold improvement in affinity over native BPTI. Using this engineered inhibitor, we demonstrate the efficacy of pharmacological inhibition of mesotrypsin in assays of breast cancer cell malignant growth and pancreatic cancer cell invasion. Although further improvements in inhibitor selectivity will be important before clinical potential can be realized, the results of the present study support the feasibility of engineering protein protease inhibitors of mesotrypsin and highlight their therapeutic potential.