Calmodulin protects androgen receptor from calpain-mediated breakdown in prostate cancer cells

Although inactivation of the androgen receptor (AR) by androgen-ablation or anti-androgen treatment has been frontline therapy for disseminated prostate cancer for over 60 years, it is not curative because castration-resistant prostate cancer cells retain AR activity. Therefore, curative strategy should include targeted elimination of AR protein. Since AR binds to calmodulin (CaM), and since CaM-binding proteins are targets of calpain (Cpn)-mediated proteolysis, we studied the role of CaM and Cpn in AR breakdown in prostate cancer cells. Whereas the treatment of prostate cancer cells individually with anti-CaM drug or calcimycin, which increases intracellular Ca(++) and activates Cpn, led to minimal AR breakdown, combined treatment led to a precipitous decrease in AR protein levels. This decrease in AR protein occurred without noticeable changes in AR mRNA levels, suggesting an increase in AR protein turnover rather than inhibition of AR mRNA expression. Thus, CaM inactivation seems to sensitize AR to Cpn-mediated breakdown in prostate cancer cells. Consistent with this possibility, purified recombinant human AR (rhAR) underwent proteolysis in the presence of purified Cpn, and the addition of purified CaM to the incubation blocked rhAR proteolysis. Together, these observations demonstrate that AR is a Cpn target and AR-bound CaM plays an important role in protecting AR from Cpn-mediated breakdown in prostate cancer cells. These observations raise an intriguing possibility that anti-CaM drugs in combination with Cpn-activating agents may offer a curative strategy for the treatment of prostate cancer, which relies on AR for growth and survival.     

Chromosomal Integration of Adenoviral Vector DNA In Vivo

So far there has been no report of any clinical or preclinical evidence for chromosomal vector integration following adenovirus (Ad) vector-mediated gene transfer in vivo. We used liver gene transfer with high-capacity Ad vectors in the FAH^Δexon5 mouse model to analyze homologous and heterologous recombination events between vector and chromosomal DNA. Intravenous injection of Ad vectors either expressing a fumarylacetoacetate hydrolase (FAH) cDNA or carrying part of the FAH genomic locus resulted in liver nodules of FAH-expressing hepatocytes, demonstrating chromosomal vector integration. Analysis of junctions between vector and chromosomal DNA following heterologous recombination indicated integration of the vector genome through its termini. Heterologous recombination occurred with a median frequency of 6.72 × 10⁻⁵ per transduced hepatocyte, while homologous recombination occurred more rarely with a median frequency of 3.88 × 10⁻⁷. This study has established quantitative and qualitative data on recombination of adenoviral vector DNA with genomic DNA in vivo, contributing to a risk-benefit assessment of the biosafety of Ad vector-mediated gene transfer.Recombinant adenovirus (Ad) vectors are under clinical development for different applications, including tumor therapy, vaccination, and gene therapy. Today, the largest number of clinical gene transfer trials has been based on Ad vectors (http://www.wiley.co.uk/genmed/clinical). Several Ad vectors are in phase III clinical trials, and two products have already been approved in China. The occurrence of malignancies due to retroviral integration and oncogene activation in a clinical trial for the treatment of children with SCID-X1 (10) has pointed to the need for a thorough preclinical evaluation of potential genotoxic effects due to chromosomal integration of gene transfer vectors as an important part of the overall risk-benefit analysis. Detailed information on genotoxicity following gene transfer is available for vectors derived from viruses of the Retroviridae and Parvoviridae families (2, 20, 23, 26, 46). Between 60 and 75% of integrations of retrovirus, lentivirus, or adeno-associated virus (AAV)-based vectors take place in or close to genes.Chromosomal integration of Ad vector DNA following gene transfer in cell culture has been analyzed in only a few studies, and even less is known about Ad vector integration in vivo. Since the life cycle of wild-type adenovirus is extrachromosomal, Ad vectors are perceived to be nonintegrating vectors. However, in earlier studies it was observed that injection of hamsters with wild-type adenovirus type 12 (Ad12) resulted in tumor formation due to chromosomal integration of virus DNA and expression of the E1A/E1B oncoproteins (33). Recent in vitro studies with Ad vectors with E1 deletions have demonstrated the occurrence of vector integration following transduction of transformed cell lines and primary cells, with the frequencies of homologous and heterologous recombination being between 10⁻³ and 10⁻⁶ and between 10⁻³ and 10⁻⁵ per cell, respectively, depending on the conditions used (12, 14, 28, 36, 37, 42, 43). Since clinical gene transfer trials, including prophylactic vaccination of healthy volunteers against infectious diseases, are performed with large amounts of vector (in general, between 10¹⁰ and 10¹³ particles), it is possible that substantial integration of adenoviral vector DNA might also occur in vivo even if integration rates were low. However, so far there has been no attempt to experimentally address the issue of Ad vector integration in vivo. We used the FAH^Δexon5 mouse model (8) of tyrosinemia type I (MIM 27670) to analyze potential homologous and heterologous recombination events between Ad vector DNA and chromosomal DNA in vivo. Tyrosinemia type I is caused by the lack of fumarylacetoacetate hydrolase, an enzyme that is involved in the tyrosine degradation pathway and that converts fumarylacetoacetate into fumaric acid and acetoacetic acid in hepatocytes (38). Loss of fumarylacetoacetate hydrolase (FAH) activity in hepatocytes results in the accumulation of toxic and mutagenic metabolites in a cell-autonomous fashion, leading after birth to an acute hepatopathy and later in life to a chronic hepatopathy. Liver damage can be prevented both in humans and in FAH-deficient animals by the administration of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC), which blocks the tyrosine degradation pathway by inhibiting 4-hydroxphenyl pyruvate dioxygenase, thereby preventing the accumulation of the toxic compounds. The murine FAH gene is located on chromosome 7, contains 14 exons, and spans 20.5 kb.The autosomal recessive FAH^Δexon5 mouse model, in which exon 5 is disrupted by the insertion of a NeoR gene (8), has been a useful system to analyze chromosomal integration of AAV, retrovirus, Sleeping Beauty transposon, and plasmid DNA in hepatocytes (13, 25, 27, 31). Similar to human tyrosinemia type I patients with spontaneous reversions of point mutations (18), FAH-expressing hepatocytes have a strong growth advantage over FAH^−/− hepatocytes, and the developing nodules, consisting of FAH-positive [FAH⁺] hepatocytes, can be easily distinguished in an environment of FAH^−/− hepatocytes. Following injection of an FAH-expressing Ad vector with the E1 deletion (30) into FAH^−/− mice, the development of FAH⁺ nodules in the livers of the experimental animals was observed, suggesting potential chromosomal integration of vector DNA. Since transgene expression from vectors with the E1 deletion is transient, in part due to viral toxicity and an immune response directed to viral proteins expressed from the vector, integration events and their characterization were not possible. We reasoned that the use of high-capacity Ad (HC-Ad) vectors (also called “helper-dependent” or “gutless” Ad vectors) (41) not expressing any viral proteins would allow reliable data on Ad vector integration in vivo to be obtained.     

Brugia malayi infection in Meriones unguiculatus: antibody response to recombinant BmR1

BmR1 recombinant antigen has previously been shown to demonstrate high sensitivity and specificity in the serological diagnosis of brugian filariasis in humans. In this study, the pattern of recognition of antibody to BmR1 during Brugia malayi infection was investigated by employing Meriones unguiculatus as the experimental model. Thirty two gerbils were infected subcutaneously with 120 L(3); and two control groups each comprising 25 animals were employed. ELISA using BmR1 was used to detect filaria-specific IgG antibodies elicited by the gerbils; using sera collected from the day 1 until day 150 post-inoculation (p.i.). The results showed that BmR1 detected B. malayi infection in gerbils harboring adult worms irrespective of the presence of circulating microfilaria, and was exemplified by positive ELISA results in nine a microfilaraemic animals that harbored live adult worms. The initial time of the antibody recognition was at day 8 p.i. and the antibody titre showed some correlation with adult worm burden.     

Covalent interaction between proform of eosinophil major basic protein (proMBP) and pregnancy-associated plasma protein-A (PAPP-A) is a cell-mediated event and required for proMBP inhibition of the catalytic activity of PAPP-A

This study was undertaken to determine the mechanism by which proform of eosinophil major basic protein (proMBP) inhibits the IGFBP-4 proteolytic activity of pregnancy-associated plasma protein (PAPP)-A. Co-overexpression of PAPP-A with proMBP in 293T cells, or co-incubation of 293T cells, respectively, overexpressing proMBP and PAPP-A resulted in the formation of a covalent proMBP-PAPP-A complex and inhibition of IGFBP-4 proteolysis. Similar results were obtained when recombinant proMBP and PAPP-A were incubated in the presence of U2 osteosarcoma cells or when recombinant proMBP was added to the U2 cells overexpressing PAPP-A. In contrast, no formation of covalent proMBP-PAPP-A complex or inhibition of IGFBP-4 proteolysis was observed when recombinant proMBP and PAPP-A were incubated under cell-free conditions, although proMBP was able to interact with PAPP-A in a non-covalent manner. These new findings suggest that formation of covalent proMBP-PAPP-A complex is a cell-mediated event and is required for proMBP to inhibit the catalytic activity of PAPP-A.     

Chemotherapeutic potential of Cayratia trifolia L nhexane extract on A2780 cells

It is of interest to report the chemotherapeutic (drug target based) potential of n-hexane Cayratia trifolia L. (C.trifolia) extract on A2780 cell lines. mRNA and protein expression analysis of the human chemokine receptor (CXCR4) and human epidermal growth factor receptors-2 (HER2) were studied using RT-PCR analysis and western blot analysis. The results show significant cell growth inhibition with minimal IC50 values of 46.25 ± 0.42 micro g/mL against A2780 cell lines. mRNA and protein expression were considerably reduced in C. trifoliatreated A2780 cell lines for further consideration as a chemotherapeutic agents.     

Amyloid-like fibrils from a domain-swapping protein feature a parallel, in-register conformation without native-like interactions

The formation of amyloid-like fibrils is characteristic of various diseases, but the underlying mechanism and the factors that determine whether, when, and how proteins form amyloid, remain uncertain. Certain mechanisms have been proposed based on the three-dimensional or runaway domain swapping, inspired by the fact that some proteins show an apparent correlation between the ability to form domain-swapped dimers and a tendency to form fibrillar aggregates. Intramolecular β-sheet contacts present in the monomeric state could constitute intermolecular β-sheets in the dimeric and fibrillar states. One example is an amyloid-forming mutant of the immunoglobulin binding domain B1 of streptococcal protein G, which in its native conformation consists of a four-stranded β-sheet and one α-helix. Under native conditions this mutant adopts a domain-swapped dimer, and it also forms amyloid-like fibrils, seemingly in correlation to its domain-swapping ability. We employ magic angle spinning solid-state NMR and other methods to examine key structural features of these fibrils. Our results reveal a highly rigid fibril structure that lacks mobile domains and indicate a parallel in-register β-sheet structure and a general loss of native conformation within the mature fibrils. This observation contrasts with predictions that native structure, and in particular intermolecular β-strand interactions seen in the dimeric state, may be preserved in "domain-swapping" fibrils. We discuss these observations in light of recent work on related amyloid-forming proteins that have been argued to follow similar mechanisms and how this may have implications for the role of domain-swapping propensities for amyloid formation.     

Experimental approach for assessing the outcome accuracy of antibody microarray experiments

An experimental strategy for quality control of antibody microarray analyses is proposed. The method utilizes proteins that are prepared for regular antibody microarray experiments. There is no need to use exogenous positive or negative reference markers and no need to determine the absolute concentration of each individual protein in the sample. Validation experiments support the basic principle of the proposed approach. This method can be a useful tool for assessing the outcome accuracy of microarray experiments.