The Th2 cytokines interleukins-4 and -13 (IL4; IL13) are acknowledged regulators of lymphocyte proliferation and activation. They have also been well-studied in the regulation of various myeloid-derived populations in tumor biology. It has become clear however, that both that cytokines can have direct effects on epithelial tumor cells expressing appropriate receptors. Changes in tumor proliferation, survival and metastatic capability have all been ascribed to IL4 and/or IL13 action. Here, we evaluate the evidence to support direct tumor-promoting roles of these cytokines. We also identify the questions that should be addressed before proceeding with therapeutic approaches based on neutralization of IL4 or IL13 pathways.

Breast cancer survival rates decrease from 99% for patients with local disease to 25% for those with distant metastases. Matrix metalloproteinases (MMPs), including MMP2, are associated with metastatic progression. We found that loss of host MMP2 reduces the proliferation of experimental metastases in the lungs and identified fibroblasts in tumour-bearing lungs as the major source of MMP2. In vitro, spheroidal mammary tumour growth was increased by co-culture with control fibroblasts isolated from tumour-bearing lungs but not when fibroblasts with stable Mmp2 knockdown were used. This result prompted us to assess whether MMP2 was responsible for a tumour-proliferative, activated fibroblast phenotype. To test this, we evaluated (i) fibroblasts from wild-type tumour-bearing lungs with or without shRNA-mediated MMP2 knockdown and (ii) normal, quiescent fibroblasts isolated from either WT or Mmp2−/− mice. Quantitative PCR revealed that Mmp2 knockdown attenuated expression of two markers of activation (α-smooth muscle actin and vimentin), but there was minimal expression in quiescent WT or Mmp2−/− fibroblasts, as expected. Placing quiescent fibroblasts under activating conditions led to increases in activation-associated transcripts in WT but not Mmp2−/− fibroblasts. Additionally, Mmp2 knockdown fibroblasts showed significantly decreased expression of the matrix transcripts collagen I, collagen IV and fibronectin. Addition of active TGFβ was sufficient to rescue the MMP2-dependent collagen I and IV expression, while MMP2-induced collagen expression was blocked with addition of TGFβ-1 neutralizing antibody. Gene expression data in stromal cells of human breast cancers reveals that MMP2 expression is also positively correlated with activation and matrix transcripts. Thus, we present a model whereby MMP2 production in tumour fibroblasts is important for TGFβ-1 activity and subsequent activation of fibroblasts to a matrix-producing, proliferation-supportive phenotype. Overall, our results reveal a previously undefined role for MMP2 in metastatic outgrowth mediated by fibroblasts, and extend the mechanisms by which MMPs contribute to tumour progression.

IntroductionDespite continued improvements in diagnosis, surgical techniques, and chemotherapy, breast cancer patients are still overcome by cancer metastasis. Tumor cell proliferation, invasion and metastasis are mediated, at least in part, through degradation of basement membrane by neutral matrix metalloproteinases (MMP) produced by tumor and stromal cells. Evidence suggests that MMP-9 plays a significant role in breast tumor cell invasion and metastasis. DNAzymes or catalytic oligonucleotides are new classes of gene targeting molecules that bind and cleave a specific mRNA, resulting in decreased protein expression.MethodsThe application of anti-MMP-9 DNAzyme (AM9D) for the treatment of primary and metastatic breast cancer was evaluated in vitro and in vivo using MDA-MB-231 cells and the MMTV-PyMT transgenic breast cancer mouse model. Spontaneously developed mammary tumors in MMTV-PyMT transgenic mice were treated intratumorally with naked AM9D, once a week for 4 weeks. The stability of DNAzyme was determined in vitro and in vivo using fluorescently labeled DNAzyme.ResultsAM9D specifically inhibited expression of MMP-9 in MDA-MB-231 cells resulting in reduced invasive property of these cells by 43%. Weekly intratumoral treatment of spontaneously developed mammary tumors in MMTV-PyMT transgenic mice was sufficient to significantly reduce the rate of tumor growth and final tumor load in a dose dependent and statistically significant manner (P < 0.05). This decrease in tumor growth was correlated with decreased MMP-9 protein production within the treated tumor tissues. Tumors treated with AM9D were also less vascularized and contained more apoptotic cells compared to control and untreated tumors.ConclusionsThese results show that targeting and down regulation of MMP-9 by AM9D could prove useful as a therapy against breast carcinoma tumor growth and invasion.

Catalytic oligonucleotides, known as DNAzymes, are a new class of nucleic acid-based gene therapy that have recently been used in preclinical animal studies to treat various cancers. In this study the systemic distribution, pharmacokinetics, and safety of intravenously administered anti-MMP (matrix metalloproteinase)-9 DNAzyme (AM9D) were determined in healthy FVB and in MMTV-polyoma virus middle T (PyMT) transgenic mice bearing mammary tumors. MMP-9 is known to be involved in tumor cell development, angiogenesis, invasion, and metastasis. Sulfur-35 ( 35 S) labeled ([ 35 S]-AM9D) administered intravenously, without the use of carrier molecules, to healthy and mammary tumor bearing MMTV-PyMT transgenic mice distributed to all major organs. The order of percentages of [35 S]-AM9D accumulation in different organs of healthy and MMTV-PyMT mice were blood > liver > kidney > lung > spleen > heart and mammary tumor > blood & liver > kidney > spleen > lung > heart, respectively. The amount of AM9D accumulated in mammary tumors 2 hours post injection was 0.6% and 0.2% higher than in either blood or liver, respectively, and its rate of initial clearance from mammary tissue was at least 50% slower than the other organs. Approximately 43% of the delivered dosage of [35 S]-AM9D was cleared from the system via feces and urine over a period of 72 hours. No evidence of acute or chronic cytotoxicity, local or widespread, associated with AM9D treatment (up to 75 mg AM9D /kg of body weight) was observed in the organs examined. These data suggest that DNAzyme in general and AM9D in particular can be used systemically as a therapeutic agent to treat patients with breast cancer or other metastatic and surgically inaccessible tumors.

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