Molecular and Cellular Pathobiology Genetic Ablation of Cav1 Differentially Affects Melanoma Tumor Growth and Metastasis in Mice: Role of Cav1 in Shh Heterotypic Signaling and Transendothelial Migration

Both cell-autonomous and non–cell-autonomous factors contribute to tumor growth and metastasis of melanoma. The function of caveolin-1 (Cav1), a multifunctional scaffold protein known to modulate several biologic processes in both normal tissue and cancer, has been recently investigated inmelanoma cancer cells, but its role in the melanoma microenvironment remains largely unexplored. Here, we show that orthotopic implantation of B16F10 melanoma cells in the skin of Cav1KO mice increases tumor growth, and co-injection of Cav1-deficient dermal fibroblasts with melanoma cells is sufficient to recapitulate the tumor phenotype observed in Cav1KO mice. Using indirect coculture experiments with fibroblasts and melanoma cells combined with cytokine analysis, we found that Cav1-deficient fibroblasts promoted the growth of melanoma cells via enhanced paracrine cytokine signaling. Specifically, Cav1-deficient fibroblasts displayed increased ShhN expression, which heterotypically enhanced the Shh signaling pathway in melanoma cells. In contrast to primary tumor growth, the ability of B16F10 melanoma cells to form lung metastases was significantly reduced in Cav1KOmice. This phenotype was associated mechanistically with the inability of melanoma cells to adhere to and to transmigrate through a monolayer of endothelial cells lacking Cav1. Together, our findings show that Cav1 may regulate different mechanisms during primary melanoma tumor growth and metastatic dissemination. Cancer Res; 72(9); 2262–74. 2012 AACR. Introduction Tumors are heterogeneous microenvironments that consist of both neoplastic and nonneoplastic cells (tumor–stroma). Tumor growth and the consequent metastatic dissemination of tumor cells result from continuous reciprocal interactions between cancer cells and their surrounding stroma (1, 2). Cutaneous melanoma remains the most aggressive type of skin cancer and both cell-autonomous and non–cell-autonomous mechanisms are necessary for melanoma growth and metastasis (3). Recent research, in fact, has shown that stromal cells (fibroblasts and endothelial cells) support the growth and dissemination of melanoma cells by modulating angiogenesis, secreting growth factors and cytokines, and contributing to extracellular matrix deposition and degradation (4). Thus, identifying novel mechanisms critically regulating tumor– stroma interactions may be therapeutically relevant in this type of cancer. Caveolae are specialized microdomains of the plasma membrane enriched in the scaffold protein caveolin-1 (Cav1; refs. 5, 6). Because of the multitude of interacting proteins described, Cav1 has been implicated in the modulation of many biologic processes in both normal tissues and cancer (7, 8). Although much research has primarily focused on determining the function of Cav1 in cancer cells, recent studies have started to investigate the function of Cav1 protein in the tumor microenvironment (9, 10). Indeed, Cav1 is highly expressed in endothelial cells and fibroblasts, two of the cell types that are normally involved in stromal remodeling during melanoma progression (3). In addition, the angiogenesis defects (11) and impaired skin wound healing (12) displayed by Cav1KO mice suggest that loss of Cav1 in the stromal compartment may functionally affect tumor–stroma interactions in melanomagenesis. To examine this issue, we used Cav1KO mice to determine whether stromal Cav1 may affect the growth and metastatic ability of B16F10 melanoma cells. We show that absence of Cav1 promotes the growth of intradermally implanted B16F10 melanoma cells in mice. Indirect coculture experiments and Authors' Affiliations: Departments of Cancer Biology/Stem Cell Biology & Regenerative Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania; Department of Medical Sciences, Universit a Piemonte Orientale "A. Avogadro", Novara; and Department of Biology, Roma Tre University, Rome, Italy Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Corresponding Authors: Franco Capozza, Kimmel Cancer Center, 940 BLSB, 233S 10th Street, Philadelphia, PA 19107. Phone: 215-955-5333; Fax: 215-923-1098; E-mail: [email protected]; and Michael P. Lisanti, [email protected] doi: 10.1158/0008-5472.CAN-11-2593 2012 American Association for Cancer Research. Cancer Research Cancer Res; 72(9) May 1, 2012 2262 on July 22, 2017. © 2012 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from Published OnlineFirst March 6, 2012; DOI: 10.1158/0008-5472.CAN-11-2593