We compared the transcriptomes of marrow-derived mesenchymal stem cells (MSCs) with differentiated adipocytes, osteocytes, and chondrocytes derived from these MSCs. Using global gene-expression profiling arrays to detect RNA transcripts, we have identified markers that are specific for MSCs and their differentiated progeny. Further, we have also identified pathways that MSCs use to differentiate into adipogenic, chondrogenic, and osteogenic lineages. We identified activin-mediated transforming growth factor (TGF)-␤ signaling, platelet-derived growth factor (PDGF) signaling and fibroblast growth factor (FGF) signaling as the key pathways involved in MSC differentiation. The differentiation of MSCs into these lineages is affected when these pathways are perturbed by inhibitors of cell surface receptor function. Since growth and differentiation are tightly linked processes, we also examined the importance of these 3 pathways in MSC growth. These 3 pathways were necessary and sufficient for MSC growth. Inhibiting any of these pathways slowed MSC growth, whereas a combination of TGF-␤, PDGF, and ␤-FGF was sufficient to grow MSCs in a serum-free medium up to 5 passages. Thus, this study illustrates it is possible to predict signaling pathways active in cellular differentiation and growth using microarray data and experimentally verify these predictions. (Blood. 2008;112:295-307)

The stress hormone epinephrine is known to elicit multiple systemic effects that include changes in cardiovascular parameters and immune responses. However, information about its direct action on cancer cells is limited. Here we provide evidence that epinephrine reduces sensitivity of cancer cells to apoptosis through interaction with ␤ 2 -adrenergic receptors. The antiapoptotic mechanism of epinephrine primarily involves phosphorylation and inactivation of the proapoptotic protein BAD by cAMP-dependent protein kinase. Moreover, BAD phosphorylation was observed at epinephrine concentrations found after acute and chronic psychosocial stress. Antiapoptotic signaling by epinephrine could be one of the mechanisms by which stress promotes tumorigenesis and decreases the efficacy of anti-cancer therapies.Epinephrine levels are sharply increased in response to acute stress and can be continuously elevated during persistent stress and depression (1, 2). Sustained increases of epinephrine were implicated in pathogenesis of stress-related immunosuppression proposed as the primary mechanism by which stress and depression may increase tumor incidence and promote metastatic growth (2, 3). However, several reports have questioned whether immunosuppression alone is sufficient to explain stress-induced tumor growth, and some studies have found no correlation between stress and cancer (2, 4). Thus, more information about the mechanisms by which stress hormones affect tumors is necessary to resolve the controversy over the connection between stress and cancer. One potential mechanism may involve direct effects of epinephrine on cancer cells.Cancer cell lines of various origins, including prostate tumors, express ␤ 2 -adrenergic receptors (␤ 2 -ARs) 4 that bind epinephrine and norepinephrine (5-7). ␤ 2 -ARs belong to superfamily A of seven-transmembrane G protein-coupled receptors (GPCRs) (8). Epinephrine binding leads to activation of GTPase and dissociation of ␣ and ␤␥ subunits of heterotrimeric G proteins. Depending on the cell context, this may trigger multiple signaling pathways, including the Ras/extracellular signal-regulated kinase, NFB, and cAMP-dependent protein kinase (PKA) pathways, which regulate diverse cellular responses, such as proliferation, differentiation, secretion, or apoptosis (9).Since resistance to apoptosis has been implicated in cancer pathogenesis (10), we decided to analyze the effects of the ␤ 2 -AR agonist epinephrine on apoptosis in prostate cancer cells. In this paper, we demonstrate that epinephrine reduces sensitivity of prostate cancer cells to apoptosis via ␤ 2 -AR/PKA signaling that triggers BAD phosphorylation at S112. This antiapoptotic mechanism operates in the prostate cancer cell lines LNCaP and C4-2 and in the breast cancer cell line MDA-MB231. Our findings suggest that stress may contribute to cancer etiology and therapeutic resistance by decreasing sensitivity of cancer cells to apoptosis. EXPERIMENTAL PROCEDURESCell Lines and Transfection-LNCaP and C4-2 cells were a gift from Leland C...

The classical function of Vitamin D, which involves mineral balance and skeletal maintenance, has been known for many years. With the discovery of vitamin D receptors in various tissues, several other biological functions of vitamin D are increasingly recognized and its role in many human diseases like cancer, diabetes, hypertension, cardiovascular, and autoimmune and dermatological diseases is being extensively explored. The non-classical function of vitamin D involves regulation of cellular proliferation, differentiation, apoptosis, and innate and adaptive immunity. In this review, we discuss and summarize the latest findings on the non-classical functions of vitamin D at the cellular/molecular level and its role in complex human diseases.

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Background: Vitamin D is a secosteroid, which was initially known for its skeletal role; however, in recent years, its functions in different organs have been increasingly recognized. In this review, we will provide an overview of vitamin D functions in the skin physiology with specific focus on its role in certain inflammatory skin conditions such as psoriasis and atopic dermatitis. Methods: A comprehensive literature search was carried out in PubMed and Google Scholar databases using keywords like “vitamin D,” “skin,” “atopic dermatitis,” and “psoriasis.” Only articles published in English and related to the study topic were included in this review. Results: Vitamin D is integrally connected to the skin for its synthesis, metabolism, and activity. It regulates many physiological processes in the skin ranging from cellular proliferation, differentiation, and apoptosis to barrier maintenance and immune functions. Vitamin D deficiency is associated with the risk of psoriasis and atopic dermatitis, and several clinical/observational studies have suggested the beneficial effect of vitamin D in the therapy of these 2 inflammatory skin disorders. Conclusions: Vitamin D exerts a pleiotropic effect in the skin and could be an important therapeutic option for psoriasis and atopic dermatitis.

Repertoire composition, quantity, and qualitative functional ability are the parameters that define virusspecific T-cell responses and are linked with their potential to control infection. We took advantage of the segregation of different hepatitis B virus (HBV) genotypes in geographically and genetically distinct host populations to directly analyze the impact that host and virus variables exert on these virus-specific T-cell parameters. T-cell responses against the entire HBV proteome were analyzed in a total of 109 HBV-infected subjects of distinct ethnicities (47 of Chinese origin and 62 of Caucasian origin). We demonstrate that HBV-specific T-cell quantity is determined by the virological and clinical profiles of the patients, which outweigh any influence of race or viral diversity. In contrast, HBV-specific T-cell repertoires are divergent in the two ethnic groups, with T-cell epitopes frequently found in Caucasian patients seldom detected in Chinese patients. In conclusion, we provide a direct biological evaluation of the impact that host and virus variables exert on virus-specific T-cell responses. The discordance between HBV-specific CD8 T-cell repertoires present in Caucasian and Chinese subjects shows the ability of HLA micropolymorphisms to diversify T-cell responses and has implications for the rational development of therapeutic and prophylactic vaccines for worldwide use.

The radiotoxicity of 125I in Chinese hamster V79 lung fibroblasts has been studied following extracellular (Na125I), cytoplasmic [125I]iododihydrorhodamine (125I-DR), and nuclear (125IUdR) localization of the radionuclide. Exposure of the cells for 18 h to Na125I (less than or equal to 7.4 MBq/ml) had no effect on survival. A similar exposure to 125I-DR produced a survival curve with a distinct shoulder and with a mean lethal dose (D37) of 4.62 Gy to the nucleus. While this value compares well with the 5.80 Gy X-ray D37 dose, it is in contrast to the survival curve obtained with DNA-bound 125IUdR which is of the high LET type and has a D37 of 0.80 Gy to the nucleus. Furthermore, when the uptake of 125I into DNA is reduced by the addition of nonradioactive IUdR or TdR to the medium and the survival fraction is determined as a function of 125I contained in the DNA, a corresponding increase in survival is observed. This work demonstrates the relative inefficiency of the Auger electron emitter 125I when located in the cytoplasm or outside the cell. It indicates that a high dose deposited within the cytoplasm contributes minimally to radiation-induced cell death and that radiotoxicity depends not upon the specific activity of IUdR but upon the absolute amount of 125I that is associated with nuclear DNA.

It has been demonstrated that vasoactive intestinal polypeptide, epidermal growth factor, and chronic activation of phosphatidylinositol 3-kinase can protect prostate cancer cells from apoptosis; however, the signaling pathways that they use and molecules that they target are unknown. We report that vasoactive intestinal polypeptide, epidermal growth factor, and phosphatidylinositol 3-kinase activate independent signaling pathways that phosphorylate the proapoptotic protein BAD. Vasoactive intestinal polypeptide operated via protein kinase A, epidermal growth factor required Ras activity, and effects of phosphatidylinositol 3-kinase were predominantly mediated by Akt. BAD phosphorylation was critical for the antiapoptotic effects of each signaling pathway. None of these survival signals was able to rescue cells that express BAD with mutations in phosphorylation sites, whereas knockdown of BAD expression with small hairpin RNA rendered cells insensitive to apoptosis. Taken together, these results identify BAD as a convergence point of several antiapoptotic signaling pathways in prostate cells.