Metastasis Of Human Cancer Xenografts Research Articles

Klotho Inhibits Transforming Growth Factor-β1 (TGF-β1) Signaling and Suppresses Renal Fibrosis and Cancer Metastasis in Mice

Fibrosis is a pathological process characterized by infiltration and proliferation of mesenchymal cells in interstitial space. A substantial portion of these cells is derived from residing non-epithelial and/or epithelial cells that have acquired the ability to migrate and proliferate. The mesenchymal transition is also observed in cancer cells to confer the ability to metastasize. Here, we show that renal fibrosis induced by unilateral ureteral obstruction and metastasis of human cancer xenografts are suppressed by administration of secreted Klotho protein to mice. Klotho is a single-pass transmembrane protein expressed in renal tubular epithelial cells. The extracellular domain of Klotho is secreted by ectodomain shedding. Secreted Klotho protein directly binds to the type-II TGF-β receptor and inhibits TGF-β1 binding to cell surface receptors, thereby inhibiting TGF-β1 signaling. Klotho suppresses TGF-β1-induced epithelial-to-mesenchymal transition (EMT) responses in cultured cells, including decreased epithelial marker expression, increased mesenchymal marker expression, and/or increased cell migration. In addition to TGF-β1 signaling, secreted Klotho has been shown to inhibit Wnt and IGF-1 signaling that can promote EMT. These results have raised the possibility that secreted Klotho may function as an endogenous anti-EMT factor by inhibiting multiple growth factor signaling pathways simultaneously.

Anti–αv Integrin Monoclonal Antibody Intetumumab Enhances the Efficacy of Radiation Therapy and Reduces Metastasis of Human Cancer Xenografts in Nude Rats

We previously reported that intetumumab (CNTO 95), a fully human anti-αv integrin monoclonal antibody, is a radiosensitizer in mice with xenograft tumors. Because intetumumab does not cross-react with mouse integrins, but has cross-reactivity with rat integrins, we next studied the potential combined use of radiation therapy and intetumumab in human cancer xenograft models in nude rats to assess effects on both tumor cells and the tumor microenvironment. Nude rats bearing human head and neck cancer and non-small cell lung cancer (NSCLC) xenografts were treated with intetumumab and fractionated local tumor radiotherapy. Effects on tumor growth and metastasis, blood perfusion, oxygenation, and gastrointestinal toxicity were studied. Intetumumab alone had a moderate effect on tumor growth. When combined with fractionated radiation therapy, intetumumab significantly inhibited tumor growth and produced a tumor response rate that was significantly better than with radiation therapy alone. Treatment with intetumumab also significantly reduced lung metastasis in the A549 NSCLC xenograft model. The oxygenation and blood perfusion in xenograft tumors measured by microbubble-enhanced ultrasound imaging were substantially increased after treatment with intetumumab. The combined use of intetumumab and radiation therapy reduced the microvessel density and increased apoptosis in tumor cells and the tumor microenvironment. Toxicity studies showed that treatment with intetumumab did not cause the histopathologic changes in the lungs and did not sensitize the sensitive gastrointestinal epithelium to the effect of radiation therapy. Intetumumab can potentiate the efficacy of fractionated radiation therapy in human cancer xenograft tumors in nude rats without increased toxicity.

Abstract C138: Anti-αv integrin monoclonal antibody intetumumab (CNTO 95) enhances the therapeutic efficacy of radiation therapy and reduces metastasis of human cancer xenografts in nude rats

Abstract Radiation therapy is used to treat cancer in over 50% of all cancer patients. Interaction of tumor cells with the extracellular matrix via adhesion molecules is important for survival of cancer stem cells, and may play a role in resistance to radiation therapy. Preclinical and clinical studies from our lab and others have demonstrated that a fully human anti- v integrin monoclonal antibody intetumumab (CNTO 95) may enhance the therapeutic index of radiotherapy by selective targeting of upregulated integrins on tumor cells and vascular endothelial cells of tumors. We previously reported that intetumumab is a radiosensitizer in mice with xenograft tumors. However, since intetumumab does not cross-react with mouse integrins, but has limited cross-reactivity with rat integrins, we next studied the potential of combined use of fractionated local tumor radiation therapy and intetumumab in human cancer xenograft models in nude rats in order to assess effects on both tumor cells and vasculatures. We found that intetumumab alone had a moderate effect on tumor growth in human head and neck cancer and non-small cell lung cancer xenograft models. When combined with fractionated radiation therapy, intetumumab significantly inhibited tumor growth and produced a tumor response rate that was significantly better than with radiation therapy alone (P < 0.01). The total tumor response rate (complete response and partial response) was 67% in A549 NSCLC model for intetumumab plus radiotherapy compared with 17% for radiotherapy alone. Treatment with intetumumab reduces the lung metastasis by inhibiting the homing of A549 NSCLC cells, as well as spontaneous metastasis to lung from subcutaneous tumors in A549 NSCLC xenograft model. The blood perfusion and blood volume in xenograft tumors measured by micro-bubble enhanced ultrasound image was substantially improved by treatment of intetumumab. Immunohistochemistry staining of xenograft tumor sections demonstrated that the combined use of intetumumab and radiation therapy significantly reduced the microvessel density and increased apoptosis in tumor cells and the tumor microenvironment. The oxygenation and hypoxic status of tumors treated with intetumumab with or without radiotherapy is under investigation and will be presented. Furthermore, intetumumab alone and in combination with radiation was well-tolerated and did not produce any obvious signs of systemic toxicity. An in vivo toxicity study of crypt stem cell survival in the gastrointestinal tract demonstrated that treatment with intetumumab did not alter the number of surviving crypt stem cells of duodenum, jejunum, or ileum following irradiation, suggesting that intetumumab did not sensitize the sensitive GI epithelium to the effect of radiation therapy. These results demonstrate that intetumumab can potentiate the efficacy of fractionated radiation therapy in human cancer xenograft tumors in nude rats. These findings are promising and may have high translational relevance for the treatment of patients with solid tumors. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C138.

The role of interleukin 1 in growth and metastasis of human cancer xenografts.

Interleukin 1 (IL-1) is a pluripotent cytokine that promotes angiogenesis, tumor growth, and metastasis in experimental models; its presence in some human cancers is associated with aggressive tumor biology. The purpose of these studies was to characterize the role of IL-1 in human cancers and determine if inhibition of IL-1 via its receptor antagonist, IL-1Ra, alters tumor growth and metastatic potential. IL-1 mRNA or protein levels were determined in clinical tumor samples, cancer cell lines, and xenografts using quantitative reverse transcription-PCR or ELISA. Biological activity of tumor-derived IL-1 protein was shown via induction of permeability across endothelial cell monolayers. The effects of recombinant IL-1Ra on tumor lines in culture (cell proliferation and IL-8 secretion) and in xenograft models (tumor growth, metastatic potential, and intratumoral levels of IL-8 and VEGF) were characterized. The effects of IL-1Ra-mediated regression of xenograft growth on angiogenic proteins (IL-8 and VEGF) were evaluated in an IL-1-producing melanoma (SMEL) xenograft model. IL-1 mRNA was highly expressed in more than half of all tested metastatic human tumor specimens including non-small-cell lung carcinoma, colorectal adenocarcinoma, and melanoma tumor samples. Constitutive IL-1 mRNA expression was identified in several cancer cell lines; tumor supernatant from these cell lines produced a significant increase in endothelial cell monolayer permeability, a hallmark event in early angiogenesis, in an IL-1-dependent manner. Moreover, systemic recombinant IL-1Ra resulted in significant inhibition of xenograft growth and neovessel density of IL-1-producing, but not non-IL-1-producing, tumor cell lines. Subsequent analysis of SMEL, a melanoma cell line with constitutive IL-1 production, showed that neither exogenous IL-1 nor IL-1Ra altered tumor cell proliferation rates in vitro. Gene expression analyses of IL-1Ra-treated SMEL xenografts showed a >3-fold down-regulation of 100 genes compared with control including a marked down-regulation of IL-8 and VEGF. These data show that the IL-1 gene is frequently expressed in metastases from patients with several types of human cancers. IL-1Ra inhibits xenograft growth in IL-1-producing tumors but has no direct antiproliferative effects in vitro; decreased tumor levels of IL-8 and VEGF may be an early surrogate of IL-1Ra-mediated antitumor activity. IL-1Ra may have a role alone or with other agents in the treatment of human cancers.