The Myb-p300-CREB axis modulates intestine homeostasis, radiosensitivity and tumorigenesis.

The gastrointestinal (GI) epithelium is constantly renewing, depending upon the intestinal stem cells (ISC) regulated by a spectrum of transcription factors (TFs), including Myb. We noted previously in mice with a p300 mutation (plt6) within the Myb-interaction-domain phenocopied Myb hypomorphic mutant mice with regard to thrombopoiesis, and here, changes in GI homeostasis. p300 is a transcriptional coactivator for many TFs, most prominently cyclic-AMP response element-binding protein (CREB), and also Myb. Studies have highlighted the importance of CREB in proliferation and radiosensitivity, but not in the GI. This prompted us to directly investigate the p300-Myb-CREB axis in the GI. Here, the role of CREB has been defined by generating GI-specific inducible creb knockout (KO) mice. KO mice show efficient and specific deletion of CREB, with no evident compensation by CREM and ATF1. Despite complete KO, only modest effects on proliferation, radiosensitivity and differentiation in the GI under homeostatic or stress conditions were evident, even though CREB target gene pcna (proliferating cell nuclear antigen) was downregulated. creb and p300 mutant lines show increased goblet cells, whereas a reduction in enteroendocrine cells was apparent only in the p300 line, further resembling the Myb hypomorphs. When propagated in vitro, crebKO ISC were defective in organoid formation, suggesting that the GI stroma compensates for CREB loss in vivo, unlike in MybKO studies. Thus, it appears that p300 regulates GI differentiation primarily through Myb, rather than CREB. Finally, active pCREB is elevated in colorectal cancer (CRC) cells and adenomas, and is required for the expression of drug transporter, MRP2, associated with resistance to Oxaliplatin as well as several chromatin cohesion protein that are relevant to CRC therapy. These data raise the prospect that CREB may have a role in GI malignancy as it does in other cancer types, but unlike Myb, is not critical for GI homeostasis.

Osteogenic differentiation as a result of BMP-2 plasmid DNA based gene therapy in vitro and in vivo.

Bone regeneration is one of the major focus points in the field of regenerative medicine. A well-known stimulus of bone formation is bone morphogenetic protein-2 (BMP-2), which has already been extensively used in clinical applications. We investigated the possibility of achieving osteogenic differentiation both in vitro and in vivo as a result of prolonged presence of BMP-2 using plasmid DNA-based gene therapy. By delivering BMP-2 cDNA in an alginate hydrogel, a versatile formulation is developed. High transfection efficiencies of up to 95% were obtained in both human multipotent stromal cells (MSCs) and MG-63 cells using naked DNA in vitro. Over a period of 5 weeks, an increasing amount of biologically active BMP-2 was released from the cells and remained present in the gel. In vivo, transfected cells were found after both two and six weeks implantation in naked mice, even in groups without seeded cells, thus indicating in vivo transfection of endogenous cells. The protein levels were effective in inducing osteogenic differentiation in vitro, as seen by elevated alkaline phosphatase (ALP) production and in vivo, as demonstrated by the production of collagen I and osteocalcin in a mineralised alginate matrix. We conclude that BMP-2 cDNA incorporated in alginate hydrogel appears to be a promising new strategy for minimal-invasive delivery of growth factors in bone regeneration.

Diagnostic and prognostic tissuemarkers in clear cell and papillary renal cell carcinoma.

PURPOSE: Approximately one-third of all Renal Cell Carcinoma (RCC) patients undergoing a nephrectomy face metastatic disease. The availability of novel therapeutics for metastatic patients underscores the importance of identifying patients at risk of recurrence or patients responding well to specific therapies. Unlike clear cell RCC (ccRCC), information on biomarkers for the papillary subtype (pRCC) remains limited. In this review, we identified tissue markers that are differentially expressed between subtypes and may be of diagnostic use. In addition, markers with promising prognostic power for ccRCC and/or pRCC are described and their clinical value is discussed. MATERIALS AND METHODS: To identify diagnostic markers that differentiate between pRCC and ccRCC a Pubmed search was performed, limited to original articles published in the English language between 1990 and 2009, using the terms pRCC/papillary RCC/papillary renal cell carcinoma/papillary kidney cancer, biomarker/biomarkers, protein expression, mass spectrometry and immunohistochemistry. Prognostic markers for ccRCC and pRCC were identified using the search terms kidney cancer, renal cell carcinoma, prognostic marker, biomarker and prognosis. Only markers with independent prognostic value in multivariable analysis were included. RESULTS: 25 proteins are differentially expressed between ccRCC and pRCC, reflecting the molecularly distinct nature of these subtypes. 5 of these proteins were externally validated, which shows their diagnostic potential. Whereas 48 biomarkers with independent prognostic power have been identified for ccRCC patients, only CD44, CA9, p53, Ki67 and PCNA have shown prognostic value in multiple studies. Expression of IMP-3 and VEGF-R2 are independent predictors of survival of pRCC patients, although this is shown in single studies. CONCLUSIONS: So far 5 validated diagnostic markers are able to differentiate between ccRCC and pRCC. Few independent prognostic markers have been identified for pRCC in single studies, compared to numerous biomarkers identified for the more common ccRCC. Despite the abundance of promising markers for ccRCC, their exact role in clinical decision making still needs to be established through validation studies.