Abstract 3865: HAS2 promotes tumor progression by stimulating interaction of cancer stem-like cells with tumor associated macrophage and stromal cells through a paracrine loop of growth factors in the bone.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC The molecular mechanism of metastatic progression, particularly the roles of microenvironment of the metastasized organs, is as yet poorly understood. In this study, we have isolated cancer stem cell-like cells (CSC) from human breast cancer cell lines, MDA-MB231, MDA231BoM and MDA231BrM. CSC were isolated from each line using surface markers (CD24-, CD44+, ESA+) and their tumor initiating abilities were tested in animal. We then performed an analysis of global expression profile for these CSCs using the Affymetrix expression array and found that among all up-regulated genes, two genes (HAS2 and MMP1) were significantly correlated with overall- and metastasis-free survival when they were cross-examined in GEO database. To further examine the role of HAS2 in tumor metastasis in vivo, we prepared CSC from MDA231BoM with or without carrying a shRNA expression vector for HAS2. The CSC were then implanted into nude mice by intra-cardiac injection followed by oral administration of 4MU, a specific inhibitor of HAS genes. We found that the injection of CSC of MDA231BoM which expresses shRNA to HAS2 significantly improved the survival rate of animals. In addition, administration of 4MU significantly suppressed tumor metastasis of CSC, suggesting that inhibition of HAS2 can indeed reduce the incidence of metastasis in vivo. We also examined the effect of tumor associated macrophage (TAM) on growth of CSC in animals by injecting CSC of MDA231-BoM with or without TAM into the tibial bone. We found that co-injection of TAM with CSC significantly augmented the growth of tumor in their legs. Moreover, the interaction between cancer cell and TAMs enhanced secretion of PDGF-BB from TAMs which then activated stromal cells and in turn enhanced self-renewal of CSCs by secretion of FGF9 and FGF7. We also found that treatment of bone marrow stem cell (BMSC) with PDGF followed by co-culture of CSC significantly promoted proliferation of CSC. Collectively, our results suggest that TAM and BMSC promote self-renewal of CSC in bone microenvironment via direct interaction between hyaluronan and CD44. Our results also provide strong rationale to target HAS2 by using 4MU in order to block the metastatic progression of CSC in breast cancer. Citation Format: Sambad Sharma, Hiroshi Okuda, Fei Xing, Aya Kobayashi, Misako Watabe, Puspa R. Pandey, Sudha K. Pai, Wen Liu, Koji Fukuda, Megumi Iiizumi, Kounosuke Watabe. HAS2 promotes tumor progression by stimulating interaction of cancer stem-like cells with tumor associated macrophage and stromal cells through a paracrine loop of growth factors in the bone. [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 3865. doi:10.1158/1538-7445.AM2013-3865