S6 Kinase: A Compelling Prospect for Therapeutic Interventions

S6 kinase, a member of AGC family of protein kinases and a downstream effector of mTORC1 pathway has over the years found much relevance in maintaining a normal cellular state by virtue of its established role in regulation of cell growth and proliferation. S6 kinase activity has been linked to different cellular processes like glucose homeostasis, translational and transcriptional regulation. Hence any dysregulation in S6K1 leads to the emergence of various pathological conditions like diabetes, cancer and obesity. It is as such S6 kinase has emerged as a potential target for therapeutic interventions employed in curing such diseases. The Present Chapter reviews the regulation of S6K1, its structural organization and functions, besides highlighting its potential to act as an alternative therapeutic target for various cancerous situations exhibiting deranged mTOR signaling so as to overcome the possibility of relapses observed otherwise while using conventional drug

Genetic Alterations of RET: Possible Implications and Clinical Correlations in Thyroid Carcinogenesis

Thyroid cancers are malignant tumors in the thyroid gland. DNA polymorphisms are playing a decisive role in unscrambling the genomic basis of tumor formation and development in cancer. Thyroid cancer is influenced in a polygenic and low-penetrance manner by RET gene polymorphisms and this part of the world (North India) has not recorded any study regarding RET alterations in this very cancer. We assessed RET G691S (rs1799939), L769L (rs1800861) and S904S (rs1800863) polymorphisms by restriction fragment length polymorphism (RFLP) in order to explain their potential role in the diagnosis and prognosis of Papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC). In RET G691S polymorphism, the total dissemination of variant alleles (GA + AA) was 62.9% in cases as related to 44.5% in controls (P < 0.05). RET L769L variant alleles (TG + GG) was 70% in cases versus 88% in controls (P < 0.05). In RET S904S, occurrence of variant alleles (CG + GG) was 56% in cases versus 44% in controls (P < 0.05). G691S and L769L polymorphism advocate a “Dominant mode of inheritance”. The S904S polymorphism approves an “Additive mode of inheritance”. In conclusion, there was an over-representation of RET G691S/S904S polymorphisms and under-representation of L769L polymorphism in PTC and FTC patients. Additionally, our data suggest that some haplotypes (A T G, G T G and A T C) of RET may act as low penetrance alleles for predisposition of thyroid cancer

Targeting HMGB1 in Cellular Milieu and Elucidating its Effect in Mice Model of Endotoxemia

Bacterial endotoxin stimulates macrophages / monocytes to release various cytokines early (e.g., TNF-α, IL-1β, and IFN-γ) and late (HMGB-1) which then mediate sepsis (or endotoxemia). HMGB1 recently discovered as late mediator of sepsis, is now seen as one of main mediator of sepsis lethality and prompting investigations for development of new drugs. Present study was undertaken to screen some novel target for ameliorating HMGB1 release and investigate their effect in mice model of endotoxemia. Here we demonstrate that psychosine increases the HMGB1 in primary peritoneal macrophage cells. The psychosine induced HMGB1 may have some interesting role in pathobiology of Krabbe disease. Aloe-emodin was seen to abrogate HMGB1 release dose dependently in both RAW 264.7 cells and primary peritoneal macrophage cells. The aloe-emodin was observed to attenuate the release of pro-inflammatory cytokines (TNF-α, IL1β) and LPS – induced oxidative stress markers iNOS, HO-1. The aloe-emodin showed protective effect in endotoxemia rescuing mice from endotoxemia lethality. Aloe-emodin also decreased the systemic accumulation of proinflammatory mediators (TNF-α, IL1-β) within hours in endotoxemic mice. Endotoxemia induced multi-organ dysfunction was also ameliorated by aloe-emodin treatment depicted by serum biochemistry (ALT, ALP, BUN and creatinine) and histopathology of lung, liver and kidney. The neutrophil infiltration was also reduced in lung tissues of aloe-emodin treated mice. The inhibition of HMGB1 release by aloe-emodin and rescue of endotoxemic mice makes aloe-emodin a potential candidate for sepsis therapy

Molecular Alterations and Expression Dynamics in the Etiopathogenesis of Thyroid Cancer

Thyroid carcinoma is the most prevalent endocrine malignancy and accounts for 2% of all human cancers. In the past decade, knowledge of genetic alterations of thyroid cancer (TC) has rapidly expanded, which has provided new insights into thyroid cancer etiology and has offered novel diagnostic tools and prognostic markers that enable improved and personalized management of thyroid cancer patients. Alterations in key signaling effectors seem to be the hallmark of distinct forms of thyroid neoplasia. Mutations or rearrangements in genes that encode Mitogen activated protein kinase (MAPK) pathway effectors seem to be required for transformation. Mutations in BRAF were the most recently identified MAPK effector in thyroid cancer. BRAF V600E is the most common alteration in sporadic papillary carcinoma. Three RAS proto-oncogenes (NRAS, HRAS & KRAS) are implicated in human thyroid tumorigenesis. High incidence of thyroid cancer worldwide indicates the importance of studying genetic alterations that lead to its carcinogenesis. BRAF and RAS alterations represent a novel indicator of the progression and aggressiveness of thyroid carcinogenesis. The GSα-adenylyl cyclase-cyclic AMP (cAMP) cascade is effected in thyroid cancer. Promoter hypermethylation of multiple genes especially TSHR has been identified to play a role in thyroid cancers, in particular showing a close association with BRAF mutational status. So, the main aim of the study was to elucidate the involvement of BRAF and RAS gene mutations along with BRAF expression and thyroid-stimulating hormone receptor (TSHR) hypermethylation in North Indian patients and investigate their association with clinicopathological characteristics

Rapamycin inhibition of baculovirus recombinant (BVr) ribosomal protein S6 kinase (S6K1) is mediated by an event other than phosphorylation

<p>Abstract</p> <p>Background</p> <p>Ribosomal protein S6 kinase 1(S6K1) is an evolutionary conserved kinase that is activated in response to growth factors and viral stimuli to influence cellular growth and proliferation. This downstream effector of target of rapamycin (TOR) signaling cascade is known to be directly activated by TOR- kinase mediated hydrophobic motif (HM) phosphorylation at Threonine 412 (T412). Selective loss of this phosphorylation by inactivation of TOR kinase or activation/recruitment of a phosphatase has accordingly been implicated in mediating inhibition by rapamycin.</p> <p>Findings</p> <p>We present evidence that baculovirus driven expression of S6K1 in insect cells (Sf9) fails to activate the enzyme and instead renders it modestly active representing 4-6 folds less activity than its fully active mammalian counterpart. Contrary to the contention that viral infection activates TOR signaling pathway, we report that BVr enzyme fails to exhibit putative TOR dependent phosphorylation at the HM and the resultant phosphorylation at the activation loop (AL) of the enzyme, correlating with the level of activity observed. Surprisingly, the BVr enzyme continued to exhibit sensitivity to rapamycin that remained unaffected by mutations compromised for TOR phosphorylation (T412A) or deletions compromised for TOR binding (ΔNH _2-46/ΔCT₁₀₄).</p> <p>Conclusions</p> <p>These data together with the ability of the BVr enzyme to resist inactivation by phosphatases indicate that inhibition by rapamycin is not mediated by any phosphorylation event in general and TOR dependent phosphorylation in particular.</p

P66shc and its downstream Eps8 and Rac1 proteins are upregulated in esophageal cancers

Members of Shc (src homology and collagen homology) family, p46shc, p52shc, p66shc have known to be related to cell proliferation and carcinogenesis. Whereas p46shc and p52shc drive the reaction forward, the role of p66shc in cancers remains to be understood clearly. Hence, their expression in cancers needs to be evaluated carefully so that Shc analysis may provide prognostic information in the development of carcinogenesis. In the present study, the expression of p66shc and its associate targets namely Eps8 (epidermal pathway substrate 8), Rac1 (ras-related C3 botulinum toxin substrate1) and Grb2 (growth factor receptor bound protein 2) were examined in fresh tissue specimens from patients with esophageal squamous cell carcinoma and esophageal adenocarcinoma using western blot analysis. A thorough analysis of both esophageal squamous cell carcinoma and adenocarcinoma showed p66shc expression to be significantly higher in both types of carcinomas as compared to the controls. The controls of adenocarcinoma show a higher basal expression level of p66shc as compared to the controls of squamous cell carcinoma. The expression level of downstream targets of p66shc i.e., eps8 and rac1 was also found to be consistently higher in human esophageal carcinomas, and hence correlated positively with p66shc expression. However the expression of grb2 was found to be equal in both esophageal squamous cell carcinoma and adenocarcinoma. The above results suggest that the pathway operated by p66shc in cancers does not involve the participation of Ras and Grb2 as downstream targets instead it operates the pathway involving Eps8 and Rac1 proteins. From the results it is also suggestive that p66shc may have a role in the regulation of esophageal carcinomas and represents a possible mechanism of signaling for the development of squamous cell carcinoma and adenocarcinoma of esophagus

Cold resistance in plants: A mystery unresolved

Herbaceous temperate plants are capable of developing freezing tolerance when they are exposed to low nonfreezing temperatures. Acquired freezing tolerance involves extensive reprogramming of gene expression and metabolism. Recent full-genome transcript profiling studies, in combination with mutational and transgenic plant analyses, have provided a snapshot of the complex transcriptional network that operates under cold stress. The changes in expression of hundreds of genes in response to cold temperatures are followed by increases in the levels of hundreds of metabolites, some of which are known to have protective effects against the damaging effects of cold stress. Genetic analysis has revealed important roles for cellular metabolic signals, and for RNA splicing, export and secondary structure unwinding, in regulating cold-responsive gene expression and chilling and freezing tolerance. These results along with many of the others summarized here further our understanding of the basic mechanisms that plants have evolved to survive freezing temperatures. In addition, the findings have potential practical applications, as freezing temperatures are a major factor limiting the geographical locations suitable for growing crop and horticultural plants and periodically account for significant losses in plant productivity. Although, great progress has been made in the field but lacunae still remain since it appears that the cold resistance is more complex than perceived and involves more than one pathway