IFN‐γ withdrawal after immunotherapy potentiates B16 melanoma invasion and metastasis by intensifying tumor integrin αvβ3 signaling

Abstract

Immunotherapy can effectively suppress tumor, yet complete tumor eradication occurs infrequently. The metastatic potential of remnant tumor cells after immunotherapy and the underlying mechanisms have not been fully elucidated. Here, we report that the termination of immunotherapy strikingly increases the metastatic potential of remnant melanoma. This is mainly due to the withdrawal of IFN-c after immunotherapy. The relief of IFN-c stress led to the increase of avb3 integrin expression in B16 cells, which increased the adhesion of B16 cells to fibrinogen, fibronectin and laminin. Through avb3 signaling, the activation of FAK, upregulation of cdc2, production of active MMP-2 and MMP-9 and actin polymerization were intensified in B16 cells stimulated with ECM molecules 24 h after the withdrawal of IFN-c. The i.v. injection of such tumor cells into mice resulted in more metastatic tumor nodes in lung and shortened the survival of mice. The pitfall of immunotherapy termination can be remedied by the administration of recombinant CBD-HepII polypeptide of fibronectin, which effectively inhibits avb3 signaling. These findings suggest that the risk of tumor metastasis can be increased after the termination of immunotherapy, due to the withdrawal of IFN-c and that targeting avb3 signaling pathway can improve the therapeutic effect of immunotherapeutic approaches by reducing such metastatic risk. ' 2008 Wiley-Liss, Inc. Key words: immunotherapy; tumor metastasis; interferon c; integrin avb3Progress in molecular and cellular immunology during the past two decades has advanced our understanding of tumor-host interactions and opened extraordinary opportunities for the development of antitumor immunotherapy. 1 So far, there are many available approaches designed to modulate the immune system for a better efficacy in tumor immunotherapy. Although the exciting efficacy has been obtained by using these approaches, the complete tumor eradication occurs infrequently. Tumor recurrence and metastasis are frequently the final and fatal step in the progression of solid malignancies in patients after immunotherapy. It has been found that a variety of molecular alterations occur in tumors so that they become more progressive and better equipped to evade or inhibit host defenses. 2-5 However, it is still unclear which factor(s) is responsible for the inhibition of tumor metastasis during immunotherapy and what happens if such factor(s) is downregulated after immunotherapy.Interferon g (IFN-g) is an important cytokine produced by the activated lymphocytes and contributes to antitumor activity via several mechanisms, including phenotypic or functional modification of neoplastic cells, rendering them more amenable to immune recognition and attack via Fas-dependent and Fas-independent pathways. 6-9 Although IFN-g has also been found to promote tumor immune evasion by downregulating cellular level of an endogenous tumor antigen 10 and induce the negative immune regulation by upregulating B7-H1 expression, 11,12 the increase of IFN-g level is...

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“…TLR4 signaling promotes avb3-mediated adhesion and invasive migration of metastatic breast cancer cells Based on the above results, we next investigated whether TLR4 signaling could promote avb3-mediated adhesion and invasive migration, since the increased avb3 signaling could increase actin polymerization and production of MMP-9 in tumor cells in response to ECM, resulting in higher metastatic potential of tumor cells [18,[21][22][23]. As shown in Fig.…”

“…Western blot assay was done as described previously [18]. Abs were purchased from Santa Cruz Biotechnology and Cell Signaling Technology.…”

“…The relative quantity of mRNA was determined by real-time RT-PCR assays as described previously [18]. The mRNA of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as the internal control.…”

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“…Western blot assay was accomplished as described previously (34). Abs were purchased from Cell Signaling Technology (Beverly, MA) and Santa Cruz Biotechnology (Santa Cruz, CA).…”

Lipopolysaccharide initiates a bypass feedback loop of epidermal growth factor receptor signaling by HPS70-induced COX-2 in H22 hepatocarcinoma cells

“…After incubation in the presence or absence of LPS after in vitro transfection, H22 cells were transfected with TLR-4 shRNAs and/or COX-2 inhibitor (NS-398) or shRNA TLR-4 combination with COX-2 inhibitor (NS-398; 10 µM) and were lysed or homogenized for Western blot analysis, as described (12). Primary antibodies and horseradish peroxidase-conjugated secondary antibodies were purchased from Santa Cruz (Santa Cruz, CA), R&D systems (Minneapolis, CA) and Cell Signaling (Beverly, MA).…”