Preclinical evaluation of transcriptional targeting strategies for carcinoma of the breast in a tissue slice model system

INTRODUCTION: In view of the limited success of available treatment modalities for metastatic breast cancer, alternative and complementary strategies need to be developed. Adenoviral vector mediated strategies for breast cancer gene therapy and virotherapy are a promising novel therapeutic platform for the treatment of breast cancer. However, the promiscuous tropism of adenoviruses (Ads) is a major concern. Employing tissue specific promoters (TSPs) to restrict transgene expression or viral replication is an effective way to increase specificity towards tumor tissues and to reduce adverse effects in non-target tissues such as the liver. In this regard, candidate breast cancer TSPs include promoters of the genes for the epithelial glycoprotein 2 (EGP-2), cyclooxygenase-2 (Cox-2), α-chemokine SDF-1 receptor (stromal-cell-derived factor, CXCR4), secretory leukoprotease inhibitor (SLPI) and survivin. METHODS: We employed E1-deleted Ads that express the reporter gene luciferase under the control of the promoters of interest. We evaluated this class of vectors in various established breast cancer cell lines, primary breast cancer cells and finally in the most stringent preclinical available substrate system, constituted by precision cut tissue slices of human breast cancer and liver. RESULTS: Overall, the CXCR4 promoter exhibited the highest luciferase activity in breast cancer cell lines, primary breast cancer cells and breast cancer tissue slices. Importantly, the CXCR4 promoter displayed a very low activity in human primary fibroblasts and human liver tissue slices. Interestingly, gene expression profiles correlated with the promoter activities both in breast cancer cell lines and primary breast cancer cells. CONCLUSION: These data suggest that the CXCR4 promoter has an ideal 'breast cancer-on/liver-off' profile, and could, therefore, be a powerful tool in Ad vector based gene therapy or virotherapy of the carcinoma of the breast

Isolation and expansion of functional differentiating mesenchymal stem cells with a serum deprived medium.

The infusion of mesenchymal stem cells (MSC) is an increasingly utilized therapeutic approach for congenital and acquired diseases in regenerative medicine. Recently, MSC have been used for the treatment of graft-versus-host disease after allogeneic stem cell transplantation[1]. These strategies require ex vivo MSC expansion with media containing fetal bovine serum (FBS). Since the use of FBS may be associated with immunological responses against the cultured MSC[2] and may unknowingly transmit prions[4], the development of a serum free medium (SFM) for MSC isolation and expansion is essential for the widely applicable MSC therapy. We evaluated a novel serum deprived medium (Quantum 333R) for the isolation and expansion of MSC as compared to the standard medium (SM), DMEM + 10% FBS. Fibroblastoid colony forming unit (CFU-F), as MSC progenitors, and MSC expansion potential were considered as measurable parameters. The number of CFU-F found at 14 days of culture in the SFM (average: 1 CFU-F/ 1.78 x 105 bone marrow mononuclear cells, BMMNC) and the SM (1 CFU-F/ 2.3 x 105 BMMNC) were similar (p=0.18 t-test), but the trend suggested that the SFM may be superior. Passage 5 MSC in both culture conditions showed similar percentages of proliferating, i. e. BrdU+ cells: 7,5% (+/– 1,3%) and 10% (+/– 2,1%) in MSF and in SM, respectively. Flow cytometric analysis of MSC for side and forward scatter properties showed that MSCSFM were smaller in the side scatter than MSC SM. Further immunophenotypical characterization showed, in the MSCSFM, the absence of CD45, CD34, CD31 and the presence of CD90, CD105, CD73 confirming the phenotype of the "classical" MSCSM. CD73 and CD105 were upregulated in MSCSFM in comparison to MSCSM. Still, MSCSFM retained the capacity to inhibit the cytokine-induced proliferation of PBMC as reported for MSCSM. In addition, to test the differentiation potential of MSCSFM, the cells were successfully driven into osteogenic, adipogenic, myogenic and chondrogenic phenotypes. Our data support that Quantum 333R is able to isolate and expand MSC clonogenic precursors without affecting their proliferation, immunophenotype, differentiation and immunomodulatory potentials, thus suggesting a superior technique to isolate clinical grade cell population for safer clinical applications

Isolation and expansion of functional differentiating mesenchymal stem cells with a serum deprived medium.

The infusion of mesenchymal stem cells (MSC) is an increasingly utilized therapeutic approach for congenital and acquired diseases in regenerative medicine. Recently, MSC have been used for the treatment of graft-versus-host disease after allogeneic stem cell transplantation[1]. These strategies require ex vivo MSC expansion with media containing fetal bovine serum (FBS). Since the use of FBS may be associated with immunological responses against the cultured MSC[2] and may unknowingly transmit prions[4], the development of a serum free medium (SFM) for MSC isolation and expansion is essential for the widely applicable MSC therapy. We evaluated a novel serum deprived medium (Quantum 333R) for the isolation and expansion of MSC as compared to the standard medium (SM), DMEM + 10% FBS. Fibroblastoid colony forming unit (CFU-F), as MSC progenitors, and MSC expansion potential were considered as measurable parameters. The number of CFU-F found at 14 days of culture in the SFM (average: 1 CFU-F/ 1.78 x 105 bone marrow mononuclear cells, BMMNC) and the SM (1 CFU-F/ 2.3 x 105 BMMNC) were similar (p=0.18 t-test), but the trend suggested that the SFM may be superior. Passage 5 MSC in both culture conditions showed similar percentages of proliferating, i. e. BrdU+ cells: 7,5% (+/\u2013 1,3%) and 10% (+/\u2013 2,1%) in MSF and in SM, respectively. Flow cytometric analysis of MSC for side and forward scatter properties showed that MSCSFM were smaller in the side scatter than MSC SM. Further immunophenotypical characterization showed, in the MSCSFM, the absence of CD45, CD34, CD31 and the presence of CD90, CD105, CD73 confirming the phenotype of the "classical" MSCSM. CD73 and CD105 were upregulated in MSCSFM in comparison to MSCSM. Still, MSCSFM retained the capacity to inhibit the cytokine-induced proliferation of PBMC as reported for MSCSM. In addition, to test the differentiation potential of MSCSFM, the cells were successfully driven into osteogenic, adipogenic, myogenic and chondrogenic phenotypes. Our data support that Quantum 333R is able to isolate and expand MSC clonogenic precursors without affecting their proliferation, immunophenotype, differentiation and immunomodulatory potentials, thus suggesting a superior technique to isolate clinical grade cell population for safer clinical applications