Prostate cancer: status of current treatments and emerging antisense-based therapies

Prostate cancer, like most other solid tumors, represents a heterogeneous entity consisting of a mixture of androgen-dependent and androgen-independent cells. Although proliferation of prostate tumor cells is often initially androgen-dependent, the inevitable development of androgen-insensitivity in late-stage prostate cancer renders androgen-suppressing treatments ultimately ineffective. Non-hormonal chemotherapy induces apoptosis in actively proliferating cells and is typically of little value, since prostate cancer demonstrates very slow growth kinetics. Objective response rates of < 10% and no improved survival rates have been observed in several hundred clinical studies using both experimental and approved chemotherapeutic agents. An improved understanding of the molecular mechanisms responsible for the onset of the disease, as well as the factors that control the proliferation of prostate cancer cells, have identified key changes in gene expression during cancer progression, especially from androgen-dependent to androgen-independent status. Manipulation of the genes implicated in disease progression represent an important approach for therapeutic intervention. This review summarizes recent progress that has been made with the use of antisense technology with various chemistries to modify gene expression, a strategy that seems to hold great promise for prostate cancer therapy.     

Detection of novel coupled mutations in the katG gene (His276Met, Gln295His and Ser315Thr) in a multidrug-resistant Mycobacterium tuberculosis strain from Chennai, India, and insight into the molecular mechanism of isoniazid resistance using structural bioinformatics approaches

This study reports on the structural basis of drug resistance targeting the katG gene in a multidrug-resistant Mycobacterium tuberculosis (MDR-TB) strain with two novel mutations (His276Met and Gln295His) in addition to the most commonly reported mutation (Ser315Thr). A structural bioinformatics approach was used to predict the structure of the mutant KatG enzyme (MT). Subsequent molecular dynamics and docking studies were performed to explain the mechanism of isoniazid (INH) resistance. The results show significant conformational changes in the structure of MT leading to a change in INH binding residues at the active site, with a significant increase in the inhibition constant (Ki) of 5.67 μm in the mutant KatG-isoniazid complex (MT-INH) compared with the wild-type KatG-isoniazid complex (WT-INH). In the case of molecular dynamics studies, root mean square deviation (RMSD) analysis of the protein backbone in simulated biological conditions revealed an unstable trajectory with higher deviations in MT throughout the simulation process (1 ns). Moreover, root mean square fluctuation (RMSF) analysis revealed an overall increase in residual fluctuations in MT compared with the wild-type KatG enzyme (WT), whilst the INH binding residues of MT showed a decreased fluctuation that can be observed as peak deviations. Hence, the present study suggests that His276Met, Gln295His and Ser315Thr mutations targeting the katG gene result in decreased stability and flexibility of the protein at INH binding residues leading to impaired enzyme function.     

Design, synthesis and cytotoxicity of novel chalcone analogs derived from 1-cyclohexylpyrrolidin-2-one and 2,3-dihydrobenzo[f]chromen-1-one

Two divergent series of novel chalcone analogs, one derived from 1‐cyclohexylpyrrolidin‐2‐one and the other derived from 1‐benzo[f]chromanone, were designed, synthesized and evaluated for cytotoxicity against two murine cancer cell lines. Two 1‐benzo[f]chromanone analogs, 4g and 4j yielded moderate toxicity against both melanoma B16 and lymphoma L1210 cell lines with IC₅₀ values between the range of 5 and 6 µM. With an IC₅₀ value of 3.4 µM, compound 4g was also active against human MDA‐MB‐435 melanoma cells. X‐ray structures of the β‐hydroxy ketone product ( 4a ) and the α,β‐unsaturated ketone ( 4h ) were collected, and confirm the syn‐configuration between the carbonyl moiety and the β‐vinylic proton in 4h . X‐ray structures of two 1‐cyclohexylpyrrolidin‐2‐one derivatives were also obtained, and both showed an E‐configuration for the double bond.     

Polyclonal immune responses to antigens associated with cancer signaling pathways and new strategies to enhance cancer vaccines

Aberrant signaling pathways are a hallmark of cancer. A variety of strategies for inhibiting signaling pathways have been developed, but monoclonal antibodies against receptor tyrosine kinases have been among the most successful. A challenge for these therapies is therapeutic unresponsiveness and acquired resistance due to mutations in the receptors, upregulation of alternate growth and survival pathways, or inadequate function of the monoclonal antibodies. Vaccines are able to induce polyclonal responses that can have a multitude of affects against the target molecule. We began to explore therapeutic vaccine development to antigens associated with these signaling pathways. We provide an illustrative example in developing therapeutic cancer vaccines inducing polyclonal adaptive immune responses targeting the ErbB family member HER2. Further, we will discuss new strategies to augment the clinical efficacy of cancer vaccines by enhancing vaccine immunogenicity and reversing the immunosuppressive tumor microenvironment.     

Role of the PRMT–DDAH–ADMA axis in the regulation of endothelial nitric oxide production

There is abundant evidence that the endothelium plays a crucial role in the maintenance of vascular tone and structure. One of the major endothelium-derived vasoactive mediators is nitric oxide (NO), formed in healthy vascular endothelium from the amino acid precursor l-arginine. Endothelial dysfunction is increased by various cardiovascular risk factors, metabolic diseases, and systemic or local inflammation. One mechanism that has been implicated in the development of endothelial dysfunction is the presence of elevated levels of asymmetric dimethylarginine (ADMA). Free ADMA, which is formed during proteolysis, is actively degraded by the intracellular enzyme dimethylarginine dimethylaminohydrolase (DDAH) which catalyzes the conversion of ADMA to citrulline and dimethylamine. It has been estimated that more than 70% of ADMA is metabolized by DDAH (Achan et al. [1]). Decreased DDAH expression/activity is evident in disease states associated with endothelial dysfunction and is believed to be the mechanism responsible for increased methylarginines and subsequent ADMA mediated eNOS impairment. However, recent studies suggest that DDAH may regulate eNOS activity and endothelial function through both ADMA-dependent and -independent mechanisms. In this regard, elevated plasma ADMA may serve as a marker of impaired methylarginine metabolism and the pathology previously attributed to elevated ADMA may be manifested, at least in part, through altered activity of the enzymes involved in ADMA regulation, specifically DDAH and PRMT.     

Bone marrow aplasia--a rare complication of imatinib therapy in CML patients

Imatinib mesylate therapy in CML patients is a generally well tolerated without any significant hematological adverse drug effects. However, complications like anemia and cytopenias have been described in literature. A very few case reports of bone marrow aplasia following imatinib therapy have been reported so far. We here report five patients of CML who developed bone marrow aplasia following imatinib therapy.     

Effects of larval-juvenile treatment with perchlorate and co-treatment with thyroxine on zebrafish sex ratios

The objective of this study was to determine the effect of larval-juvenile exposure to perchlorate, a thyroid hormone synthesis inhibitor, on the establishment of gonadal sex ratios in zebrafish. Zebrafish were exposed to untreated water or water containing perchlorate at 100 or 250 ppm for a period of 30 days starting at 3 days postfertilization (dpf). Recovery treatments consisted of a combination of perchlorate and exogenous thyroxine (T4; 10 nM). Thyroid histology was assessed at the end of the treatment period (33 dpf), and gonadal histology and sex ratios were determined in fish that were allowed an additional 10-day period of growth in untreated water. As expected, exposure to perchlorate caused changes in thyroid histology consistent with hypothyroidism and these effects were reversed by co-treatment with exogenous T4. Perchlorate did not affect fish survival but co-treatment with T4 induced higher mortality. However, relative to the corresponding perchlorate concentration, co-treatment with T4 caused increased mortality only at a perchlorate concentration of 100 ppm. Perchlorate alone or in the presence of T4 suppressed body length at 43 dpf relative to control values. Perchlorate exposure skewed the sex ratio toward female in a concentration-dependent manner, and co-treatment with T4 not only blocked the feminizing effect of perchlorate but also overcompensated by skewing the sex ratio towards male. Moreover, co-treatment with T4 advanced the onset of spermatogenesis in males. There was no clear association between sex ratios and larval survival or growth. We conclude that endogenous thyroid hormone plays a role in the establishment of gonadal sex phenotype during early development in zebrafish.     

Can health workers diagnose dementia in the community?

OBJECTIVE: This study attempted to evaluate sensitivity, specificity and predictive values of the diagnosis of dementia made by trained community health workers. METHOD: A total of 1,000 subjects over the age of 65 years were recruited for the study. The community health workers identified nine subjects as having dementia. This was compared against an education adjusted diagnosis of dementia made in accordance with the 10/66 dementia research group protocol. RESULTS: The sensitivity and specificity of the community health worker diagnosis was 3.8% and 99.4% respectively. The false positive rate and positive predictive values were 55.6% and 44.4%, respectively. The false negative rate and negative predictive value were 10.3% and 89.7% respectively. Similar values were obtained against a DSM IV diagnosis. Subjects with dementia who were correctly diagnosed by the community health workers and those whose condition was missed did not differ significantly on socio-demographic and clinical variables. CONCLUSION: Informal screening by community health workers resulted in low sensitivity and positive predictive values. Screening strategies in situations of low prevalence are not effective.