Epithelial-mesenchymal transition- activating transcription factors- multifunctional regulators in cancer

The process of epithelial to mesenchymal transition(EMT), first noted during embryogenesis, has also been reported in tumor formation and leads to the development of metastatic growth. It is a naturally occurring process that drives the transformation of adhesive,non-mobile epithelial like cells into mobile cells with a mesenchymal phenotype that have ability to migrate to distant anatomical sites. Activating complex network of embryonic signaling pathways, including Wnt, Notch,hedgehog and transforming growth factor-β pathways,lead to the upregulation of EMT activating transcription factors, crucial for normal tissue development and maintenance. However, deregulation of tightly regulated pathways affecting the process of EMT has been recently investigated in various human cancers. Given the critical role of EMT in metastatic tumor formation,better understanding of the mechanistic regulation provides new opportunities for the development of potential therapeutic targets of clinical importance.

MicroRNAs,stem cells and cancer stem cells

This review discusses the various regulatory charac-teristics of microRNAs that are capable of generating widespread changes in gene expression via post translational repression of many mRNA targets and control self-renewal, differentiation and division of cells. It controls the stem cell functions by controlling a wide range of pathological and physiological processes, including development, differentiation, cellular proliferation, programmed cell death, oncogenesis and metastasis. Through either mRNA cleavage or translational repression, miRNAs alter the expression of their cognate target genes; thereby modulating cellular pathways that affect the normal functions of stem cells, turning them into cancer stem cells, a likely cause of relapse in cancer patients. This present review further emphasizes the recent discoveries on the functional analysis of miRNAs in cancer metastasis and implications on miRNA based therapy using miRNA replacement or anti-miRNA technologies in specific cancer stem cells that are required to establish their efficacy in controlling tumorigenic potential and safe therapeutics.

WNT/β-catenin signaling in urothelial carcinoma of bladder

Urothelial carcinoma of bladder is the second most prevalent genitourinary disease.It is a highly heterogeneous disease as it represents a spectrum of neoplasms,including non-muscle invasive bladder cancer(NMIBC),muscle invasive bladder cancer(MIBC)and metastatic lesions.Genome-wide approaches and candidate gene analysis suggest that malignant transformation of the bladder is multifactorial and a multitude of genes are involved in the development of MIBC or NMIBC phenotypes.Wnt signaling is being examined to control and maintain balance between stemness and differentiation in adult stem cell niches.Owing to its participation in urothelial development and maintenance of adult urothelial tissue homeostasis,the components of Wnt signaling are reported as an important diagnostic and prognostic markers as well as novel therapeutic targets.Mutations/epigenetic alterations in the key molecules of Wnt/β-catenin canonical pathway have been linked with tumorigenesis,development of drug resistance and enhanced survival.Present review extends our understanding on the functions of key regulatory molecules of canonical Wnt/β-catenin pathway in urothelial tumorigenesis by inducing cancer stem cell phenotype(UCSCs).UCSCs may be responsible for tumor heterogeneity,high recurrence rates and complex biological behavior of bladder cancer.Therefore,understanding the role of UCSCs and the regulatory mechanisms that are responsible for high relapse rates and metastasis could help to develop pathway inhibitors and augment current therapies.Potential implications in the treatment of urothelial carcinoma of bladder by targeting this pathway primarily in UCSCs as well as in bulk tumor population that are responsible for high relapse rates and metastasis may facilitate potential therapeutic avenues and better prognosis.

Emerging role of microRNAs in cancer stem cells:Implications in cancer therapy

A small subset of cancer cells that act as tumor initiating cells or cancer stem cells(CSCs) maintain self-renewal and growth promoting capabilities of cancer and are responsible for drug/treatment resistance,tumor recurrence and metastasis. Due to their potential clinical importance,many researchers have put their efforts over decades to unravel the molecular mechanisms that regulate CSCs functions. Micro RNAs(mi RNAs) which are 21-23 nucleotide long,endogenous noncoding RNAs,regulate gene expression through gene silencing at post-transcriptional level by binding to the 3'-untranslated regions or the open reading frames of target genes,thereby result in target mR NA degradation or its translational repression and serve important role in several cellular,physiological and developmental processes. Aberrant mi RNAs expression and their implication in CSCs regulation by controlling asymmetric cell division,drug/treatment resistance and metastasis make mi RNAs a tool of great therapeutic potential against cancer. Recent advancements on the biological complexities of CSCs,modulation in CSCs properties by mi RNA network and development of mi RNA based treatment strategies specifically targeting the CSCs as an attractive therapeutic targets for clinical application are being critically analysed.

Epithelial plasticity and cancer stem cells:Major mechanisms of cancer pathogenesis and therapy resistance

Epithelial-mesenchymal transition(EMT) has been linked with aggressive tumor biology and therapy resistance. It plays central role not only in the generation of cancer stem cells(CSCs) but also direct them across the multiple organ systems to promote tumor recurrence and metastasis. CSCs are reported to express stem cell genes as well as specific cell surfacemarkers and allow aberrant differentiation of progenies.It facilitates cancer cells to leave primary tumor, acquire migratory characteristics, grow into new environment and develop radio-chemo-resistance. Based on the current information, present review discusses and summarizes the recent advancements on the molecular mechanisms that derive epithelial plasticity and its major role in generating a subset of tumor cells with stemness properties and pathophysiological spread of tumor. This paper further highlights the critical need to examine the regulation of EMT and CSC pathways in identifying the novel probable therapeutic targets.These improved therapeutic strategies based on the co-administration of inhibitors of EMT, CSCs as well as differentiated tumor cells may provide improved antineoplastic response with no tumor relapse.

Epithelial plasticity in urothelial carcinoma: Current advancements and future challenges

Urothelial carcinoma(UC) of the bladder is characterized by high recurrence rate where a subset of these cells undergoes transition to deadly muscle invasive disease and later metastasizes. Urothelial cancer stem cells(UroC SCs), a tumor subpopulation derived from trans-formation of urothelial stem cells, are responsible for heterogeneous tumor formation and resistance to systemic treatment in UC of the bladder. Although the precise reason for pathophysiologic spread of tumor is not clear, transcriptome analysis of microdissected cancer cells expressing multiple progenitor/stem cell markers validates the upregulation of genes that derive epithelial-to-mesenchymal transition. Experimental studies on human bladder cancer xenografts describe the mechanistic functions and regulation of epithelial plasticity for its cancer-restraining effects. It has been further examined to be associated with the recruitment of a pool of Uro CSCs into cell division in response to damages induced by adjuvant therapies. This paper also discusses the various probable therapeutic approaches to attenuate the progressive manifestation of chemoresistance by co-administration of inhibitors of epithelial plasticity and chemotherapeutic drugs by abrogating the early tumor repopulation as well as killing differentiated cancer cells.

Mutational analysis of Ras hotspots in patients with urothelial carcinoma of the bladder

BACKGROUND Mutational activation of Ras genes is established as a prognostic factor for the genesis of a constitutively active RAS-mitogen activated protein kinase pathway that leads to cancer.Heterogeneity among the distribution of the most frequent mutations in Ras isoforms is reported in different patient populations with urothelial carcinoma of the bladder(UCB).AIM To determine the presence/absence of mutations in Ras isoforms in patients with UCB in order to predict disease outcome.METHODS This study was performed to determine the mutational spectrum at the hotspot regions of H-Ras,K-Ras and N-Ras genes by polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP)and DNA sequencing followed by their clinical impact(if any)by examining the relationship of mutational spectrum with clinical histopathological variables in 87 UCB patients.RESULTS None of the 87 UCB patients showed point mutations in codon 12 of H-Ras gene;codon 61 of N-Ras gene and codons 12,13 of K-Ras gene by PCR-RFLP.Direct DNA sequencing of tumor and normal control bladder mucosal specimens followed by Blastn alignment with the reference wild-type sequences failed to identify even one nucleotide difference in the coding exons 1 and 2 of H-Ras,NRas and K-Ras genes in the tumor and control bladder mucosal specimens.CONCLUSION Our findings on the lack of mutations in H-Ras,K-Ras and N-Ras genes could be explained on the basis of different etiological mechanisms involved in tumor development/progression,inherent genetic susceptibility,tissue specificity or alternative Ras dysfunction such as gene amplification and/or overexpression in a given cohort of patients.

Clinicohistopathological implications of phosphoserine 9 glycogen synthase kinase-3β/β-catenin in urinary bladder cancer patients

BACKGROUND Aberrant activation of phosphorylated form of glycogen synthase kinase-3β[pS9 GSK-3β(Serine 9 phosphorylation)] is known to trigger Wnt/β-catenin signal cascade but its clinicohistopathological implications in bladder carcinogenesis remain unknown.AIM To investigate the diagnostic and prognostic relevance of expressions of pS9 GSK-3β, β-catenin and its target genes in the pathobiology of bladder cancer.METHODS Bladder tumor tissues from ninety patients were analyzed for quantitative expression and cellular localization of pS9 GSK-3β by immunohistochemical(IHC) staining. Real time-quantitative polymerase chain reaction and IHC were done to check the expression of β-catenin, Cyclin D1, Snail and Slug at transcriptome and protein level respectively. Clinicohistopathological variables were obtained from histology reports, follow up and OPD visits of patients.Expressions of the markers were statistically correlated with these variables to determine their significance in clinical setting. Results were analysed using SPSS20.0 software.RESULTS Aberrant(low or no membranous/high nuclear/high cytoplasmic) expression of pS9 GSK-3β was noted in 51% patients and found to be significantly associated with tumor stage and tumor grade(P = 0.01 and 0.04; Mann Whitney U test).Thirty one percent tumors exhibited aberrant co-expression of pS9 GSK-3β andβ–catenin proteins and showed strong statistical association with tumor stage,tumor type, smoking/tobacco chewing status(P = 0.01, 0.02 and 0.04, MannWhitney U test) and shorter overall survival probabilities of patients(P = 0.02;Kaplan Meier test). Nuclear immunostaining of Cyclin D1 in tumors with altered pS9 GSK-3β/β–catenin showed relevance with tumor stage, grade and type.CONCLUSIONβ–catenin and pS9 GSK-3β proteins are identified as markers of diagnostic/prognostic significance in disease pathogenesis. Observed histopathological association of Cyclin D1 identifies it as marker of potential relevance in tumors with altered pS9 GSK-3β/β-catenin.