Membrane androgen receptor activation induces apoptotic regression of human prostate cancer cells in vitro and in vivo.

Nongenomic androgen actions imply mechanisms different from the classical intracellular androgen receptor (iAR) activation. We have recently reported the identification of a membrane androgen receptor (mAR) on LNCaP human prostate cancer cells, mediating testosterone signal transduction within minutes. In the present study we provide evidence that activation of mAR by nonpermeable, BSA-coupled testosterone results in 1) inhibition of LNCaP cell growth (with a 50% inhibitory concentration of 5.08 nM, similar to the affinity of testosterone for membrane sites); 2) induction in LNCaP cells of both apoptosis and the proapoptotic Fas protein; and 3) a significant decrease in migration, adhesion, and invasion of iAR-negative DU145 human prostate cancer cells. These actions persisted in the presence of antiandrogen flutamide or after decreasing the content of iAR in LNCaP cells by iAR antisense oligonucleotides. Testosterone-BSA was also effective in inducing apoptosis of DU145 human prostate cancer cells, negative for iAR, but expressing mAR sites. In LNCaP cell-inoculated nude mice, treatment with testosterone-BSA (4.8 mg/kg body weight) for 1 month resulted in a 60% reduction of tumor size compared with that in control animals receiving only BSA, an effect that was not affected by the antiandrogen flutamide. Our findings suggest that activators of mAR may represent a new class of antitumoral agents of prostate cancer.

Membrane testosterone binding sites in prostate carcinoma as a potential new marker and therapeutic target: study in paraffin tissue sections.

BACKGROUND: Steroid action is mediated, in addition to classical intracellular receptors, by recently identified membrane sites, that generate rapid non-genomic effects. We have recently identified a membrane androgen receptor site on prostate carcinoma cells, mediating testosterone rapid effects on the cytoskeleton and secretion within minutes. METHODS: The aim of this study was to investigate whether membrane androgen receptors are differentially expressed in prostate carcinomas, and their relationship to the tumor grade. We examined the expression of membrane androgen receptors in archival material of 109 prostate carcinomas and 103 benign prostate hyperplasias, using fluorescein-labeled BSA-coupled testosterone. RESULTS: We report that membrane androgen receptors are preferentially expressed in prostate carcinomas, and they correlate to their grade using the Gleason's microscopic grading score system. CONCLUSION: We conclude that membrane androgen receptors may represent an index of tumor aggressiveness and possibly specific targets for new therapeutic regimens.

Expression of the proliferation-associated nuclear protein MIB-1 and its relationship with microvascular density in bone marrow biopsies of patients with myelodysplastic syndromes.

The myelodysplastic syndromes (MDS) are a group of disorders characterized by dysplastic hemopoiesis and an increased risk of leukemic transformation. The process of angiogenesis has been implicated in the pathogenesis and evolution of MDS. In this study the proliferative activity and extent of angiogenesis was examined in bone marrow samples from 54 patients with MDS in relation to clinicopathologic features. Cellular proliferation and microvascular density (MVD) were examined immunohistochemically, using the monoclonal antibody MIB-1 (Ki-67) and an anti-CD34 monoclonal antibody respectively. Serum concentrations of interleukin-6 (IL-6) were measured by ELISA. The results showed that the MIB-1 Labeling Index (MIB-1 LI), MVD and IL-6 increased significantly with advancing severity of disease. Among the MDS-FAB subtypes, MIB-1 LI, MVD and IL-6 were significantly higher in RAEB-t, RAEB and CMML in comparison to RA and RARS (p < 0.0001 in all cases). Similarly, MIB-1 and MVD were increased in patients with score 3 in comparison to scores 0 and 1 in the IPSS system (p < 0.05). All parameters studied were significantly higher in patients versus controls. We conclude that cellular proliferative activity and angiogenesis are associated with disease progression in MDS patients.

Membrane androgen binding sites are preferentially expressed in human prostate carcinoma cells.

BACKGROUND: Prostate cancer is one of the most frequent malignancies in males. Nevertheless, to this moment, there is no specific routine diagnostic marker to be used in clinical practice. Recently, the identification of a membrane testosterone binding site involved in the remodeling of actin cytoskeleton structures and PSA secretion, on LNCaP human prostate cancer cells has been reported. We have investigated whether this membrane testosterone binding component could be of value for the identification of prostate cancer. METHODS: Using a non-internalizable testosterone-BSA-FITC analog, proven to bind on membrane sites only in LNCaP cells, we have investigated the expression of membrane testosterone binding sites in a series of prostate carcinomas (n = 14), morphologically normal epithelia, taken from areas of the surgical specimens far from the location of the carcinomas (n = 8) and benign prostate hyperplasia epithelia (n = 10). Isolated epithelial cells were studied by flow cytometry, and touching preparations, after 10-min incubation. In addition, routine histological slides were assayed by confocal laser microscopy. RESULTS: We show that membrane testosterone binding sites are preferentially expressed in prostate carcinoma cells, while BPH and non-malignant epithelial cells show a low or absent binding. CONCLUSIONS: Our results indicate that membrane testosterone receptors might be of use for the rapid routine identification of prostate cancer, representing a new diagnostic marker of the disease.

Bone marrow microvascular density and angiogenic growth factors in multiple myeloma.

There is evidence that angiogenesis plays an important role in the progression of multiple myeloma (MM). Hepatocyte growth factor (HGF) and tumor necrosis factor-alpha (TNF-alpha) are cytokines that potently stimulate angiogenesis. We evaluated the microvascular density (MVD) of bone marrow biopsies (after immunostaining with anti-CD34 antibodies) and serum levels of HGF and TNF-alpha in 43 patients with newly diagnosed MM. Twenty-four of these patients reached a plateau phase after treatment and were reevaluated for MVD, HGF and TNF-alpha. MVD values and serum levels of HGF and TNF-alpha were elevated in newly diagnosed MM patients in comparison with healthy controls. Pre-treatment MVD, HGF and TNF-alpha increased with advancing stage of MM disease. In patients reaching the plateau phase, a significant reduction in MVD, HGF and TNF-alpha levels occurred. A positive correlation was noted between pre-treatment MVD and serum levels of TNF-alpha and lactic dehydrogenase but not with HGF. However, HGF strongly correlated with beta2-microglobulin (beta2M), TNF-alpha and lactate dehydrogenase (LDH). We conclude that angiogenesis in MM, as expressed by the bone marrow MVD and the serum levels of angiogenic molecules such as HGF and TNF-alpha, increases with advancing clinical stage and decreases after effective chemotherapy.