The maturation of T cells requires signaling from both cytokine and T-cell receptors to gene targets in chromatin, but how chromatin architecture influences this process is largely unknown. Here we show that thymocyte maturation post-positive selection is dependent on the nucleosome remodeling factor (NURF). Depletion of Bptf (bromodomain PHD finger transcription factor), the largest NURF subunit, in conditional mouse mutants results in developmental arrest beyond the CD4 + CD8 int stage without affecting cellular proliferation, cellular apoptosis, or coreceptor gene expression. In the Bptf mutant, specific subsets of genes important for thymocyte development show aberrant expression. We also observed defects in DNase I-hypersensitive chromatin structures at Egr1, a prototypical Bptf-dependent gene that is required for efficient thymocyte development. Moreover, chromatin binding of the sequence-specific factor Srf (serum response factor) to Egr1 regulatory sites is dependent on Bptf function. Physical interactions between NURF and Srf suggest a model in which Srf recruits NURF to facilitate transcription factor binding at Bptf-dependent genes. These findings provide evidence for causal connections between NURF, transcription factor occupancy, and gene regulation during thymocyte development.

We showed previously that exogenously administered testosterone caused age- and lobe-specific overgrowth of the prostate in Brown Norway rats. A common feature observed in testosterone-treated animals was cell hypertrophy in each of the ventral, dorsal, and lateral lobes of both young (6 mo old) and old (24 mo old) rats. By contrast, hyperplasia was seen only in the dorsal and lateral lobes of old rats treated with testosterone. These observations prompted us to examine whether age- and lobe-specific overgrowth might also occur in untreated rats as a consequence of the endogenous hormonal milieu. To this end, blood and prostates were collected from a large number (25-30 rats per group) of 4- to 6-mo-old (young) and 21- to 24-mo-old (old) Brown Norway rats. Both serum testosterone (-45%) and estradiol (-22%) concentrations decreased significantly with age, but the greater magnitude of the decrement in testosterone relative to estradiol led to a reduction in the serum testosterone:estradiol ratio. Paradoxically, although the prostate is androgen dependent, the wet weight, protein, and DNA contents increased significantly with age in the dorsal and lateral lobes of old rats despite the decrease in testosterone level. Histologic examination revealed that the increased weights and DNA contents of the dorsal and lateral lobes in old rats coincided with an increased number of epithelial cells in the distal and intermediate segments of these lobes, indicative of hyperplasia but independent of change in cell size. Taken together, these results show a spontaneous age-related overgrowth of cells in the dorsal and lateral prostatic lobes of old Brown Norway rats despite diminished serum testosterone concentrations. The aging Brown Norway rat, therefore, may be a useful model for studies of some aspects of the pathogenesis underlying spontaneous age-related prostatic hyperplasia.

Androgens are essential for development and differentiated function, as well as proliferation and survival of cells within the prostate gland. Age-related changes in the hormonal milieu, marked by a decrease in the serum androgen to estrogen ratio may contribute to the evolution of pathological changes, such as benign prostatic hyperplasia and carcinoma of the prostate gland, in older men. A similar phenomenon occurs in Brown Norway rats, in which the serum testosterone to estradiol ratio declines with age, and despite the lower serum testosterone level, age-dependent prostatic hyperplasia develops in the dorsal and lateral lobes, but not in the ventral lobe. To evaluate a role for changes in androgen action in the evolution of prostatic hyperplasia, we compared the immunostaining intensity of androgen receptor in the different prostate lobes from young (4 months of age) and old (24 months of age) Brown Norway rats. Androgen receptor immunostaining was present in the nuclei of all epithelial cells and some stromal cells throughout the prostatic ducts of each lobe from both young and old rats. Whereas androgen receptor immunostaining intensity decreased in luminal epithelial cells of the ventral prostate from old rats, it increased in luminal epithelial cells of the dorsal and lateral lobes from old rats, when compared with young rats. To validate immunocytochemical studies, Western blot analyses were performed. The total tissue level of androgen receptor decreased by 30% in the ventral lobe of old rats, whereas tissue levels of androgen receptor increased 2.7-fold and 1.3-fold in the dorsal and lateral lobes, respectively, of old rats. Similarly, the percentage of epithelial cells staining positive for the proliferation marker, proliferating cell nuclear antigen, was increased approximately 2-fold in the dorsal and lateral lobes as a function of older age. The presence of higher levels of androgen receptor and increased number of proliferating cell nuclear antigen-positive cells in the dorsal and lateral lobes of old rats suggest that changes in androgen receptor levels may be related to the lobe-specific proliferation of cells that occurs with increasing age. Additional evidence for lobe-specific regulation of androgen receptor expression was obtained from Western blots and by immunocytochemistry following castration. Androgen receptor levels in the ventral and dorsal lobes, but not the lateral lobe, of young and old rats were down-regulated in the absence of testicular androgen. However, nuclear immunostaining of androgen receptor returned by 7-10 d after castration in the ventral and dorsal lobes in the continued absence of androgen. Moreover, up-regulation of the androgen receptor level occurred more rapidly in the ventral and dorsal lobes of old, compared with young, castrated rats. Taken together, these results suggest that lobe-specific and age-dependent differences in the regulation of androgen receptor expression might lead to changes in tissue androgen responsiveness and the consequent development of lo...

The role of myeloid derived suppressor cells (MDSCs) in promoting tumorigenesis is well-established, and significant effort is being made to further characterize surface markers on MDSCs both for better diagnosis and as potential targets for therapy. Here we show that the B cell receptor adaptor molecule CD79a is unexpectedly expressed on immature bone marrow myeloid cells, and is upregulated on MDSCs generated in multiple different mouse models of metastatic but not non-metastatic cancer. CD79a on MDSCs is upregulated and activated in response to soluble factors secreted by tumor cells. Activation of CD79a on mouse MDSCs, by crosslinking with a specific antibody, maintained their immature phenotype (CD11b+Gr1+), enhanced their migration, increased their suppressive effect on T cell proliferation, and increased secretion of pro-tumorigenic cytokines such as IL-6 and CCL22. Furthermore, crosslinking CD79a on myeloid cells activated signaling through Syk, BLNK, ERK and STAT3 phosphorylation. In vivo, CD79+ myeloid cells showed enhanced ability to promote primary tumor growth and metastasis. Finally we demonstrate that CD79a is upregulated on circulating myeloid cells from lung cancer patients, and that CD79a+ myeloid cells infiltrate human breast tumors. We propose that CD79a plays a functional role in the tumor promoting effects of myeloid cells, and may represent a novel target for cancer therapy.

It is well established that androgens are central to regulation of the growth of the mammalian prostate gland. Conversely, androgen deprivation by castration induces rapid cell death in the ventral prostate via an apoptotic mechanism. To date, most studies of cell death in the rodent prostate have focused on the ventral lobe, with little attention directed to the dorsal and lateral lobes. The results presented herein demonstrate that cell death in the rat prostate gland caused by castration is lobe specific. In particular, castration caused decreases in wet weights and protein contents of all three prostatic lobes, but these events were more rapid and profound in the ventral than in the dorsal and lateral lobes. Reduced epithelial cell size was apparent in the three lobes as well. However, castration resulted in loss of DNA content in the ventral lobe only. To confirm this finding, and to examine apoptosis of individual cells, we used in situ labeling of fragmented DNA, supported by biochemical analysis of DNA integrity in agarose gels. With both approaches, significant cell death in response to castration was seen in the ventral lobe but not the dorsal and lateral lobes. Taken together, these results clearly indicate that there are lobe-specific differences in the response of the rat prostate to androgen ablation by castration, with apoptotic cell death occurring in the ventral lobe of the prostate but to a far lesser extent, if at all, in the dorsal and lateral lobes. Moreover, castration caused apoptotic death of both epithelial and stromal cells of the ventral prostate, with these cells dying throughout the ductal network of the ventral prostate rather than being restricted to a particular region. We suggest that lobe-specific differences in androgen responsiveness in the rat prostate may provide an appropriate model for the study of androgen-independent prostatic cell survival during tumor progression.