Mycobacterium avium induces HIV upregulation through mechanisms independent of cytokine induction.

Mycobacterium avium complex (MAC) can induce upregulation of HIV. To investigate the underlying mechanisms, the effect of MAC-induced cytokines on HIV replication was first studied. Semiquantitative RT-PCR, followed by Northern blot analysis, revealed that mRNA encoding IL-6 and TNF-alpha was induced by MAC. However, production of these cytokines was undetectable and the addition of anti-cytokine antibodies to coinfected cells could only minimally block the MAC effect on HIV. Infection of U38 cells with MAC resulted in enhancement of HIV-1 LTR-CAT transcription. In addition, transient transfection of U937 cells with full-length wild-type as well as NF-kappaB-binding site-deleted mutant HIV-1 LTR-CAT constructs revealed that MAC-induced HIV-LTR CAT is NF-kappaB dependent. These findings, together with our previous work, indicate that MAC-induced cytokine expression increases the formation of NF-kappaB, which in turn enhances HIV-1 LTR-CAT transcription. However, additional factor(s) yet to be elucidated may play a more significant role in MAC-mediated HIV-upregulation.

Parathyroid hormone-related protein expression in the human colon: immunohistochemical evaluation.

Parathyroid hormone-related protein (PTHrP) has been shown to be the primary factor responsible for humoral hypercalcemia of malignancy. In addition to its hypercalcemic action, PTHrP has been implicated as an autocrine modulator of growth and differentiation, as well as an early response gene in some tissues. Several different types of tumors have been evaluated for the presence of PTHrP immunoreactivity. In the present study, we evaluated the expression of PTHrP by immunohistochemical staining in tissue samples from normal colorectal mucosa, polyps, and colorectal carcinoma removed from the same patients (n = 10 each). We have used a commercially available monoclonal antibody directed against epitopes between amino acids [53-64] which share no homology to parathyroid hormone (PTH). In normal colon, 94.3 per cent of the tissue samples were negative for PTHrP immunoreactivity. In polyps of the colon, only 22.6 per cent of the cells showed positive immunostaining, whereas 91.5 per cent of the samples from colon cancer stained positive for PTHrP. In the case of polyps, the intensity of staining was 1-3+; however, all of the samples from adenocarcinoma stained with 4+ intensity. In the positive samples, the immunoreactivity was present throughout the cytoplasm of the glandular epithelium. Omission of primary antibody, as well as substitution of the primary antibody by a negative control monoclonal antibody or non-immune rabbit serum, resulted in a negative reaction. All analyses were performed in duplicate, and the data have been presented as mean +/- SEM. Differences in normal polyps, carcinoma of the colon, and PTHrP expression were tested for statistical significance by student's t test. Our results show the expression of PTHrP is enhanced in colon cancer tissue as compared to normal colorectal mucosa and polyps. In addition, the expression appears to be greater in polyp than in normal colon. The role of PTHrP in the pathogenesis of colon cancer deserves further study.

Androgen induces ornithine decarboxylase gene expression in colonic cell line HT-29.

UNLABELLED: Carcinoma of the colon is the second most common cancer among men and women combined in the United States. PURPOSE: Ornithine decarboxylase (ODC) is the first and key regulatory enzyme in the polyamine biosynthesis pathway and is regulated by various factors. Polyamines are believed to participate in cellular proliferation and differentiation. High levels of polyamines and ODC activity are associated with rapid cell growth, particularly in tumor tissues. Regulation of this enzyme in vivo has important clinical implications. In the present study, we used Northern analysis and mobility shift assay to investigate whether ODC gene expression is regulated by androgens in the three human colonic cell lines, SW620, HT-29, and Caco-2. METHODS: Cell lines were maintained in Dulbecco's Modified Eagle's medium/F12 supplemented with 5 percent fetal bovine serum. At 60 percent confluency, medium was replaced with steroid-depleted medium, and incubation continued for 24 hours. Following this period, medium was replaced with fresh steroid-free medium containing 1 nM dihydrotestosterone. RESULTS: Dihydrotestosterone stimulated ODC messenger ribonucleic acid expression only in HT-29 colonic cell line. Studies using electrophoretic mobility shift assays of nuclear extracts also showed a binding pattern with SP1 and NF-kappaB regulatory sequences only in testosterone-treated HT-29 cells. CONCLUSION: These results suggest that androgens may play an important role in the growth of HT-29 colonic cell lines.

Effects of sex steroids on cell growth and C-myc oncogene expression in LN-CaP and DU-145 prostatic carcinoma cell lines.

The prostate gland is dependent on androgens for the maintenance of its normal growth and functional integrity. Initially, growth of the majority of prostate tumours can be manipulated by endocrine therapy. In the present study, we evaluated the effects of sex steroids on the cell growth and expression of the C-myc oncogene in two human prostatic adenocarcinoma cell lines. We found that dihydrotestosterone increases the proliferation rate of prostatic cells, and amplification of C-myc oncogene is hormone-dependent. We also demonstrated a positive correlation between the number of cells positive for C-myc oncogene and oncoprotein in hormone-treated prostate cell lines.

Androgen regulation of gene expression in primary epithelial cells of the mouse kidney.

In proximal tubule cells of the mouse kidney, transcription of a number of genes is induced by androgens. Although a great deal of molecular and genetic information on the induction process has accumulated, the lack of an appropriate cell culture system for DNA transfection studies has hampered efforts to identify and characterize in detail the molecular factors that mediate the response. In the present paper, we have examined a primary renal epithelial cell culture system. We show that in response to androgens, these cells undergo induction of five messenger RNAs that are induced in the intact kidney; thus, the effects of androgens on renal gene expression derive from a direct action of the hormone on proximal tubule cells. The response does not occur in cells from Tfm animals, indicating that androgen receptor is required. Differences in patterns of androgen-inducible messenger RNA expression between mouse species are reflected by similar differences in the cultured cells. Interestingly, the kinetics of induction in culture seem to be distinct from those in the intact kidney, suggesting that a factor or factors differing between the whole animal and tissue culture environments influence the response. Transient transfection experiments with the primary cells showed that the 5'-flanking region of the androgen-regulated RP2 gene, which includes nucleotides -1500 to +42 and contains a glucocorticoid response element that binds the androgen receptor, does not mediate androgen-responsive transcription; thus, this region, and the glucocorticoid response element within it, are either insufficient for, or are not involved in, the gene's response to hormone.