Nevirapine restores hormone sensitivity in undifferentiated androgen-refractory prostate carcinoma cells

13149

Background: The majority of prostate carcinomas are hormone-dependent tumors and androgen deprivation is the mainstay of therapy for advanced prostate cancer. However, androgen deprivation is ineffective on intermediate androgen-independent cells that are responsible for the hormone-refractory prostate cancer progression. Furthermore, other signaling pathways - i.e. EGF - can provide additional molecular mechanisms contributing to androgen-independent tumor progression. Reverse transcriptase (RT) inhibitors represent differentiating agents able to induce a reprogramming of gene expression in several human tumor cell models. Indeed, nevirapine and efavirenz, two widely used RT inhibitors, block the activity of endogenous RT, a gene highly expressed in tumor cells. Methods: We evaluated the ability of nevirapine to antagonize tumor growth and induce hormone sensitivity in androgen-independent human prostate tumor PC-3 cells either in vitro or in vivo. Results: Nevirapine induced the expression of several molecular markers of an androgen-dependent phenotype, such androgen receptor (AR), PSA and K18 and a reduced expression of K5, a marker of the intermediate-cell phenotype. Indeed, nevirapine enhanced the ability of prostate tumor cells to up-regulate AR in response to dihidrotestosterone. Moreover, the pharmacological inhibition of RT resulted in a significant reprogramming of gene expression, characterized by down-regulation of the notch family receptors, the EGFR1, the VEGF receptor KDR, the FGF family receptors, as well as the angiogenic factors VEGF and FGF1. Interestingly, this exocrine differentiated phenotype correlated with a reversible inhibition of cell proliferation and migration in response to nevirapine. Furthermore, the treatment of mice xenografts of prostate carcinoma cells with efavirenz and nevirapine resulted in the inhibition of tumor growth and in a reduced tumorigenic potential of cells. Conclusions: These findings suggest that RT inhibition is able to convert the androgen-independent intermediate-cell phenotype into an androgen-dependent exocrine luminal phenotype and support the need for clinical trials to test the ability of RT inhibitors and LH-RH analogs in androgen-independent prostate tumors.

No significant financial relationships to disclose.

Expression of biologically active rat apolipoprotein AIV in Escherichia coli

Rat apolipoprotein AIV (apo AIV) is a 43-kDa intestinal apolipoprotein that is important in lipid metabolism and the suppression of food intake. In this study, a full-length rat apo AIV was expressed in Escherichia coli and purified in a bioactive form. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometric analysis revealed that the isolated recombinant protein has a molecular mass of approximately 43 kDa, similar to that of natural rat apo AIV. Immunoblot analysis and N-terminal amino acid sequencing confirmed the identity of the recombinant apo AIV protein as natural rat apo AIV. The recombinant protein was functional in lipoprotein binding assays. Biological activity was assessed behaviorally in that the recombinant protein suppressed food intake of fasted rats comparably to natural rat apo AIV. Neither native nor recombinant apo AIV elicited a conditioned taste aversion (CTA) at doses that suppress feeding. These results indicate that the recombinant apo AIV is structurally and functionally indistinguishable from rat natural apo AIV, making this overexpression and purification scheme a powerful tool for future structure and function studies.

Reelin gene alleles and haplotypes as a factor predisposing to autistic disorder

Autistic disorder (MIM 209850) is currently viewed as a neurodevelopmental disease. Reelin plays a pivotal role in the development of laminar structures including the cerebral cortex, hippocampus, cerebellum and of several brainstem nuclei. Neuroanatomical evidence is consistent with Reelin involvement in autistic disorder. In this study, we describe several polymorphisms identified using RNA-SSCP and DNA sequencing. Association and linkage were assessed comparing 95 Italian patients to 186 ethnically-matched controls, and using the transmission/disequilibrium test and haplotype-based haplotype relative risk in 172 complete trios from 165 families collected in Italy and in the USA. Both case-control and family-based analyses yield a significant association between autistic disorder and a polymorphic GGC repeat located immediately 5' of the reelin gene (RELN) ATG initiator codon, as well as with specific haplotypes formed by this polymorphism with two single-base substitutions located in a splice junction in exon 6 and within exon 50. Triplet repeats located in 5' untranslated regions (5'UTRs) are indicative of strong transcriptional regulation. Our findings suggest that longer triplet repeats in the 5'UTR of the RELN gene confer vulnerability to autistic disorder.

Transforming growth factor-beta1 gene polymorphism, bone turnover, and bone mass in Italian postmenopausal women

Transforming growth factor beta1 (TGF-beta1) is abundant in bone and is an important regulator of the osteoclastic-osteoblastic interaction (coupling). The sequence variation, 713-8delC in the TGF-beta1 gene has previously been found to be associated with very low bone mass in osteoporotic women and with increased bone turnover in both osteoporotic and normal women. The possible association of this polymorphism with bone mass and bone turnover has now been investigated in 256 postmenopausal Italian women. A significant association of TGF-beta1 with bone mass was detected in the populations. Subjects carrying the sequence variation 713-8delC (Tt) genotype showed a significantly lower bone mineral density (BMD) at the hip than those without sequence variation in the genotype (TT). Individuals carrying the tt genotype have a more severe osteoporosis (P=0.0001 vs. TT and Tt genotypes). The frequency of the fragility fractures was significantly lower in individuals with TT genotype than in those with the Tt and tt genotypes (X2=21.9; P=0.006). Furthermore a significant association was found between 713-8delC and bone turnover. The results suggest a strong evidence for an association among the 713-8delC allele of the TGF-beta1 gene and the femoral BMD, the prevalence of osteoporotic fractures, and finally a high bone turnover in a sample of Italian postmenopausal women.