Chemoprevention of prostate cancer with selenium: an update on current clinical trials and preclinical findings

Prostate cancer is the most common cancer diagnosed and the second leading cause of cancer-related deaths in men in the United States. The etiological factors that give rise to prostate cancer are not known. Therefore, it is not possible to develop primary intervention strategies to remove the causative agents from the environment. However, secondary intervention strategies with selenium (Se) compounds and other agents represent a viable option to reduce the morbidity and mortality of prostate cancer. In this review, we discuss ongoing clinical trials. In addition, we discuss preclinical mechanistic studies that provide insights into the biochemical and molecular basis for the anti-carcinogenic activity of both inorganic and organic forms of Se.     

Identification of the VirB4-VirB8-VirB5-VirB2 pilus assembly sequence of type IV secretion systems

Type IV secretion systems mediate the translocation of virulence factors (proteins and/or DNA) from Gram-negative bacteria into eukaryotic cells. A complex of 11 conserved proteins (VirB1-VirB11) spans the inner and the outer membrane and assembles extracellular T-pili in Agrobacterium tumefaciens. Here we report a sequence of protein interactions required for the formation of complexes between VirB2 and VirB5, which precedes their incorporation into pili. The NTPase Walker A active site of the inner membrane protein VirB4 is required for virulence, but an active site VirB4 variant stabilized VirB3 and VirB8 and enabled T-pilus formation. Analysis of VirB protein complexes extracted from the membranes with mild detergent revealed that VirB2-VirB5 complex formation depended on VirB4, which identified a novel T-pilus assembly step. Bicistron expression demonstrated direct interaction of VirB4 with VirB8, and analyses with purified proteins showed that VirB5 bound to VirB8 and VirB10. VirB4 therefore localizes at the basis of a trans-envelope interaction sequence, and by stabilization of VirB8 it mediates the incorporation of VirB5 and VirB2 into extracellular pili.     

Shikonin selectively induces apoptosis in human prostate cancer cells through the endoplasmic reticulum stress and mitochondrial apoptotic pathway

Background

Despite the recent progress in screening and therapy, a majority of prostate cancer cases eventually attain hormone refractory and chemo-resistant attributes. Conventional chemotherapeutic strategies are effective at very high doses for only palliative management of these prostate cancers. Therefore chemo-sensitization of prostate cancer cells could be a promising strategy for increasing efficacy of the conventional chemotherapeutic agents in prostate cancer patients. Recent studies have indicated that the chemo-preventive natural agents restore the pro-apoptotic protein expression and induce endoplasmic reticulum stress (ER stress) leading to the inhibition of cellular proliferation and activation of the mitochondrial apoptosis in prostate cancer cells. Therefore reprogramming ER stress-mitochondrial dependent apoptosis could be a potential approach for management of hormone refractory chemoresistant prostate cancers. We aimed to study the effects of the natural naphthoquinone Shikonin in human prostate cancer cells.

Results

The results indicated that Shikonin induces apoptosis in prostate cancer cells through the dual induction of the endoplasmic reticulum stress and mitochondrial dysfunction. Shikonin induced ROS generation and activated ER stress and calpain activity. Moreover, addition of antioxidants attenuated these effects. Shikonin also induced the mitochondrial apoptotic pathway mediated through the enhanced expression of the pro-apoptotic Bax and inhibition of Bcl-2, disruption of the mitochondrial membrane potential (MMP) followed by the activation of caspase-9, caspase-3, and PARP cleavage.

Conclusion

The results suggest that shikonin could be useful in the therapeutic management of hormone refractory prostate cancers due to its modulation of the pro-apoptotic ER stress and mitochondrial apoptotic pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0127-1) contains supplementary material, which is available to authorized users.     

Deformability in the cleavage site of primary microRNA is not sensed by the double‐stranded RNA binding domains in the microprocessor component DGCR8

The prevalence of double‐stranded RNA (dsRNA) in eukaryotic cells has only recently been appreciated. Of interest here, RNA silencing begins with dsRNA substrates that are bound by the dsRNA‐binding domains (dsRBDs) of their processing proteins. Specifically, processing of microRNA (miRNA) in the nucleus minimally requires the enzyme Drosha and its dsRBD‐containing cofactor protein, DGCR8. The smallest recombinant construct of DGCR8 that is sufficient for in vitro dsRNA binding, referred to as DGCR8‐Core, consists of its two dsRBDs and a C‐terminal tail. As dsRBDs rarely recognize the nucleotide sequence of dsRNA, it is reasonable to hypothesize that DGCR8 function is dependent on the recognition of specific structural features in the miRNA precursor. Previously, we demonstrated that noncanonical structural elements that promote RNA flexibility within the stem of miRNA precursors are necessary for efficient in vitro cleavage by reconstituted Microprocessor complexes. Here, we combine gel shift assays with in vitro processing assays to demonstrate that neither the N‐terminal dsRBD of DGCR8 in isolation nor the DGCR8‐Core construct is sensitive to the presence of noncanonical structural elements within the stem of miRNA precursors, or to single‐stranded segments flanking the stem. Extending DGCR8‐Core to include an N‐terminal heme‐binding region does not change our conclusions. Thus, our data suggest that although the DGCR8‐Core region is necessary for dsRNA binding and recruitment to the Microprocessor, it is not sufficient to establish the previously observed connection between RNA flexibility and processing efficiency. Proteins 2015; 83:1165–1179. © 2015 Wiley Periodicals, Inc.     

Regional Variation in Pig Farmer Awareness and Actions Regarding Japanese Encephalitis in Nepal: Implications for Public Health Education

Japanese encephalitis (JE) is a mosquito-borne zoonotic disease that has pigs as the major amplifying hosts. It is the most important cause of viral encephalitis in people in Nepal and is spreading in its geographic distribution in that country. Pig farming is increasing in Nepal due to reducing cultural biases against pigs and government programs to support pig farming for poverty alleviation. Major strategies for JE prevention and control include education, vector control, and immunization of people and pigs. This study used a survey of 400 pig farmers in 4 areas of Nepal with different JE and pig farming histories to explore regional variations in farmer awareness and actions towards JE, the association of awareness and actions with farm and farmer variables, and the implications of these associations for public health education. Exposure to JE risk factors was common across pig farms and pig farming districts but there were significant district level differences in knowledge and practices related to on-farm JE risk reduction. Social factors such as literacy, gender, and cultural practices were associated with farmer attitudes, knowledge and practices for JE control. JE vaccine uptake was almost non-existent and mosquito control steps were inconsistently applied across all 4 districts. Income was not a determining factor of the differences, but all farmers were very poor. The low uptake of vaccine and lack of infrastructure or financial capacity to house pigs indoors or away from people suggest that farmer personal protection should be a priority target for education in Nepal. This study re-enforces the need to attack root causes of people’s personal disease prevention behaviours and take into account local variation in needs and capacities when designing health or agriculture education programs.     

Virodhamine,an endocannabinoid,induces megakaryocyte differentiation by regulating MAPK activity and function of mitochondria

Endocannabinoids are well‐known regulators of neurotransmission by activating the cannabinoid (CB) receptors. Endocannabinoids are being used extensively for the treatment of various neurological disorders such as Alzheimer's and Parkinson's diseases. Although endocannabinoids are well studied in cell survival, proliferation, and differentiation in various neurological disorders and several cancers, the functional role in the regulation of blood cell development is less examined. In the present study, virodhamine, which is an agonist of CB receptor‐2, was used to examine its effect on megakaryocytic development from a megakaryoblastic cell. We observed that virodhamine increases cell adherence, cell size, and cytoplasmic protrusions. Interestingly, we have also observed large nucleus and increased expression of megakaryocytic marker (CD61), which are the typical hallmarks of megakaryocytic differentiation. Furthermore, the increased expression of CB2 receptor was noticed in virodhamine‐induced megakaryocytic cells. The effect of virodhamine on megakaryocytic differentiation could be mediated through CB2 receptor. Therefore, we have studied virodhamine induced molecular regulation of megakaryocytic differentiation; mitogen‐activated protein kinase (MAPK) activity, mitochondrial function, and reactive oxygen species (ROS) production were majorly affected. The altered mitochondrial functions and ROS production is the crucial event associated with megakaryocytic differentiation and maturation. In the present study, we report that virodhamine induces megakaryocytic differentiation by triggering MAPK signaling and ROS production either through MAPK effects on ROS‐generating enzymes or by the target vanilloid receptor 1‐mediated regulation of mitochondrial function.     

Immunomodulatory effects of cytokine-induced expansion of cytotoxic lymphocytes in a mouse model of lupus-like disease

Background aimsCertain therapies (e.g., daclizumab) that promote expansion of natural killer (NK) cells are associated with clinical amelioration of disease in the context of multiple sclerosis and associated mouse models. The clinical benefits are putatively attributable to an enhanced capacity of NK cells to kill activated pathogenic T cells. Whether a parallel approach will also be effective in systemic lupus erythematosus (lupus), a multi-organ autoimmune disease driven by aberrant responses of self-reactive T and B cells, is unclear.MethodsIn the present study, the authors assess the therapeutic impact of IL-2- and IL-15-based strategies for expanding NK cells on measures of lupus-like disease in a mouse model.ResultsUnexpectedly, cytokine-mediated expansion of cytotoxic lymphocytes aggravated immunological measures of lupus-like disease. Depletion studies revealed that the negative effects of these cytokine-based regimens can largely be attributed to expansion of CD8 T cells rather than NK cells.ConclusionsThese results provoke caution in the use of cytokine-based therapeutics to treat co-morbid cancers in patients with lupus and highlight the need for new methods to selectively expand NK cells to further assess their clinical value in autoimmune disease.     

Micropropagation of Hedychium coronarium J. Koenig through rhizome bud

An optimized protocol was developed for in vitro plant regeneration of a medicinally important herb Hedychium coronarium J. Koenig using sprouted buds of rhizomes. The rhizomes with sprouted bud were inoculated on Murashige and Skoog (Physiol Plant 15:473–497, 1962) medium (MS) supplemented with either N⁶-benzyladenine (BA) alone (1.0–4.0 mg L⁻¹) or in combination with 0.5 mg L⁻¹ naphthalene acetic acid (NAA). Of these combinations, MS supplemented with a combination of 2.0 mg L⁻¹ BA and 0.5 mg L⁻¹ NAA was most effective. In this medium, best shoots (3.6) and roots (4.0) regeneration was observed simultaneously with an average shoot and root length of 4.7 cm and 4.2 cm respectively. Regeneration of shoots and roots in the same medium at the same time (One step shoot and root regeneration) reduced the time for production of in vitro plantlets and eliminates the media cost of rooting. Cent-percent (100 %) success in plant establishment was observed in both gradual acclimatization process as well as when plants were directly transferred to outdoor in clay pots containing a mixture of garden soil and sand (2:1) without any sequential acclimatization stage.