No abstract

Drug delivery systems offer the advantage of sustained targeted release with minimal side effect. In the present study, the therapeutic efficacy of a porous silica-calcium phosphate nanocomposite (SCPC) as a new delivery system for 5-Fluorouracil (5-FU) was evaluated in vitro and in vivo. In vitro studies showed that two formulations; SCPC50/5-FU and SCPC75/5-FU hybrids were very cytotoxic for 4T1 mammary tumor cells. In contrast, control SCPCs without drug did not show any measurable toxic effect. Release kinetics studies showed that SCPC75/5-FU hybrid provided a burst release of 5-FU in the first 24 h followed by a sustained release of a therapeutic dose (30.7 microg/day) of the drug for up to 32 days. Moreover, subcutaneous implantation of SCPC75/5-FU hybrid disk in an immunocompetent murine model of breast cancer stopped 4T1 tumor growth. Blood analyses showed comparable concentrations of Ca, P and Si in animals implanted with or without SCPC75 disks. These results strongly suggest that SCPC/5-FU hybrids can provide an effective treatment for solid tumors with minimal side effects.

The breast tumor microenvironment greatly influences tumor progression and modulates the migratory abilities of both cancer cells and macrophages, especially M2 macrophages, at the tumor site. The pleiotropic inflammatory cytokine TNFα through interactions with TNFR promotes macrophage migration and tumor cell apoptosis. The shedding of TNFR increases the concentration of sTNFR within the tumor microenvironment. We determined whether sTNFR modulates the trafficking of specific macrophage subtypes in the tumor microenvironment. Concentrations of TNFα, sTNFR1 and sTNFR2 secreted by 4T1 and NMuMG mammary epithelial cells, stroma mesenchymal stem cells, and adipocyte-derived cells were measured by cytokine arrays and ELISA. The migration of murine monocytes cultured in media promoting preferential expression of M0, M1, or M2 phenotypes toward tumor or stroma cell conditioned media (CM) was determined by transwell assays. The effects of conditioned media obtained following treatment with the sheddase inhibitor TAPI-0 on cell migration were also assessed. The concentrations of sTNFR2 secreted were drastically higher in the CMs from 4T1 cells compared to NMuMG cells (p<0.05). In addition, adipocytes secreted markedly more sTNF2 compared to D1 mesenchymal stem cells (p<0.05). sTNFR2 concentrations were significantly decreased in the presence of a sheddase inhibitor (p<0.05). The transwell migration of M2 phenotype macrophages toward 4T1-CM was significantly greater than the migration of M0 or M1 phenotype macrophages (p<0.05). Furthermore, only the migration of the M2 macrophage subtype following TAPI-0 treatment toward 4T1 CM was markedly higher (p<0.05). These results strongly suggest a role for sTNFR secreted by tumor cells and adipocytes in the infiltration of M2 phenotype macrophages within the tumor microenvironment. Whether selective prevention of sTNFR shedding may have therapeutic benefit for breast cancer patients remains to be determined. This work was supported by grants from the Department of Defense Era of Hope program (BC044778) and the National Science Foundation EFRI program (CBE0736007). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 455. doi:10.1158/1538-7445.AM2011-455

Breast epithelial cells develop into polarized and highly organized acinar and ductal structures in response to stromal cues, including extracellular matrix composition and density, which can in part be reproduced in 3D culture conditions. Here we present the effects of increasing density of stroma composition on the ability of heterotypic cultures of epithelial and mesenchymal stem cells to organize into acinar and tubular structures in in vitro 3D cultures. Normal murine mammary gland (NMuMG) cells were cultured in combination (30:70) with mouse mesenchymal stem cells (D1), in 3D matrices composed of increasing concentrations (0.8 to 8 mg/ml) of collagen I and growth-factor reduced Matrigel® (1:1). The organization of the breast-like structures was assessed by immunohistochemistry. After 3-5 days in culture, the organization and the presence of acinus-like and tubule-like structures were determined. By immunohistochemical analysis, NMuMG cells co-cultured with D1 cells formed acinar and tubular structures with the NMuMG epithelial cells surrounding a lumen composed of dead cells while the D1 cells were mostly peripheral and separated by laminin-positive basement membrane. Collagen I /Matrigel® matrices with density of 1.6 and 2.4 mg/ml were associated with significantly higher concentrations of acinus-like structures compared to other densities (p<0.05). In contrast, the high concentration (8mg/ml) matrix prevented the development of acinus-like structures (p<0.05). The number of tube-like structures was drastically reduced as the density of the collagen I / Matrigel matrix increased from 0.8 to 3.2 mg/ml (p<0.05). These results indicate that the density of the matrix influences the organization and the generation of acinus-like and duct-like structures in the mammary tissues. Whether the biomechanical and density properties of the breast extracellular matrix can be harnessed to build improved tissue culture systems to benefit breast cancer patients remains to be determined. This work was supported by grants from the Department of Defense Era of Hope program (BC044778) and the National Science Foundation EFRI program (CBE0736007). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3105. doi:10.1158/1538-7445.AM2011-3105