Tumor suppressor activity of glucocorticoid receptor in the prostate.

Glucocorticoids are extensively used in combination chemotherapy of advanced prostate cancer (PC). Little is known, however, about the status of the glucocorticoid receptor (GR) in PC. We evaluated over 200 prostate samples and determined that GR expression was strongly decreased or absent in 70-85% of PC. Similar to PC tumors, some PC cell lines, including LNCaP, also lack GR. To understand the role of GR, we reconstituted its expression in LNCaP cells using lentiviral approach. Treatment of LNCaP-GR cells with the glucocorticoids strongly inhibited proliferation in the monolayer cultures and blocked anchorage-independent growth. This was accompanied by upregulation of p21 and p27, down-regulation of cyclin D1 expression and c-Myc phosphorylation. Importantly, the activation of GR resulted in normalized expression of PC markers hepsin, AMACR, and maspin. On the signaling level, GR decreased expression and inhibited activity of the MAP-kinases (MAPKs) including p38, JNK/SAPK, Mek1/2 and Erk1/2. We also found that activation of GR inhibited activity of numerous transcription factors (TF) including AP-1, SRF, NF-kappaB, p53, ATF-2, CEBPalpha, Ets-1, Elk-1, STAT1 and others, many of which are regulated via MAPK cascade. The structural analysis of hepsin and AMACR promoters provided the mechanistic rationale for PC marker downregulation by glucocorticoids via inhibition of specific TFs. Our data suggest that GR functions as a tumor suppressor in prostate, and inhibits multiple signaling pathways and transcriptional factors involved in proliferation and transformation.

The tumor suppressor effect of the glucocorticoid receptor in skin is mediated via its effect on follicular epithelial stem cells.

Glucocorticoids are potent inhibitors of mouse skin tumorigenesis. The glucocorticoid control of cellular functions is mediated via the glucocorticoid receptor (GR), a well-known transcription factor. Recently, we generated transgenic mice overexpressing GR under control of the keratin5 (K5) promoter, and showed that K5.GR animals are resistant to skin carcinogenesis. Follicular epithelial stem cells (SCs), located in the bulge region of the hair follicle, are believed to be one of the target cells for skin carcinogenesis. We found that the number of putative hair follicle SC detected as label-retaining cells was significantly less in the K5.GR transgenics compared to wild type (w.t.) littermates. We also showed that GR overexpression led to a reduction in the clonogenicity of the follicular epithelial SCs. We evaluated the global effect of GR on gene expression in a population of follicular SC-enriched bulge keratinocytes isolated by fluorescence activated cell sorting. We found that GR affected the expression of numerous bulge SC 'signature' genes, genes involved in the maintenance of SC and progenitor cells of non-epidermal origin and proapoptotic genes. Our findings underscore the important role of GR signaling in the homeostasis of follicular epithelial SCs, and suggest that the reduction in their number may underlie the tumor suppressor effect of GR in the skin.

[Protein engineering of uridine phosphorylase from Escherichia coli K-12. I. Cloning and expression of uridine phosphorylase genes from Klebsiella aerogenes and Salmonella typhimurium in E. coli]. / Belkovaia inzheneriia uridinofosforilazy iz Escherichia coli K-12. I. Klonirovanie i ékspressiia v E. coli genov uridinofosforilaz iz Klebsiella aerogenes i Salmonella typhimurium.

Genes of uridine phosphorylases (udp) from Klebsiella aerogenes and Salmonella typhimurium were cloned and expressed. Highly effective producer strains of the corresponding proteins were constructed. Enzymic properties of the UPases obtained were studied and compared with those from the Escherichia coli enzyme. Mutant forms of UPase from E. coli (D5E, D5N, D5A) were prepared by site-directed mutagenesis techniques. It was shown that the Asp5 residue plays an insignificant role in the formation of the active form of the protein.