HPV16 E7-impaired keratinocyte differentiation leads to tumorigenesis via cell cycle/pRb/involucrin/spectrin/adducin cascade

Here, we used codon usage technology to generate two codon-modified human papillomavirus (HPV)16 E7 genes and, together with wild-type E7, to construct three HPV16 E7 gene plasmids: Wt-E7, HB1-E7, and HB2-E7. The three HPV 16 E7 plasmids were used to investigate how HPV16 E7 protein was expressed in different cells and how this oncoprotein deregulated cellular and molecular events in human keratinocytes to induce carcinogenesis. We discovered that codon usage of HPV16 E7 gene played a key role in determining expression of E7 oncoprotein in all tested cells. HPV16 E7 inhibited significantly expression of pRb to impair keratinocyte differentiation and disrupted development of skin epidermis in mice. HPV16 E7 increased substantially the number of G0/G1 cells associated with upregulation of cyclin D2 and downregulation of cyclin B1 in keratinocytes. HPV16 E7 not only inhibited expression of involucrin and α-spectrin but also disrupted the organization of involucrin filaments and spectrin cytoskeleton. Furthermore, HPV16 E7 inhibited expression of β-adducin, destroyed its cytoskeletal structure and induced phosphorylation of β-adducin^(Ser662) in keratinocytes. Importantly, HPV16 E7 induced carcinogenesis in mice associated with expression of phosphorylated β-adducin^(Ser662) and its nucleus-translocation. In conclusion, we provided evidence that HPV16 E7 oncoprotein inhibited keratinocyte differentiation in vitro and in vivo leading to carcinogenesis through cell cycle arrest and disruption of pRb/involucrin/spectrin/adducin cascade.

Minimal essential region for krüppel-like factor 5 expression and the regulation by specificity protein 3-GC box binding

Krüppel-like factor 5 (KLF5) transcriptionally controls the proliferation-differentiation balance of epithelium and is overexpressed in carcinomas. Although genomic region modifying KLF5 expression is widespread in different types of cells, the region that commonly regulates basal expression of the genes across cell-types is uncertain. In this study we determined the minimal essential region for the expression and its regulatory transcription factors using oral carcinoma cells. A reporter assay defined a 186bp region downstream of the transcription start site and a cluster of six GC boxes (GC1-GC6) as the minimal essential region. Mutation in the GC1 or GC6 regions but not other GC boxes significantly decreased the reporter expression. The decrease by the GC1 mutation was reproduced in the 2kbp full-length promoter, but not by the GC6 mutation. Additionally, specificity proteins (Sp) that can be expressed in epithelial cells and bind GC box, Sp3 co-localized with KLF5 in oral epithelium and carcinomas and chromatin immunoprecipitation analyses showed Sp3 as the prime GC1-binding protein. Inhibition of Sp-GC box binding by mithramycin A and knockdown of Sp3 by the short interfering RNA decreased expression of the reporter gene and endogenous KLF5. These data demonstrate that a 186bp region is the minimal essential region and that Sp3-GC1 binding is essential to the basal expression of KLF5.

β-Adducin siRNA disruption of the spectrin-based cytoskeleton in differentiating keratinocytes prevented by calcium acting through calmodulin/epidermal growth factor receptor/cadherin pathway

Here, we report that siRNA transfection of β-adducin significantly disrupted the spectrin-based cytoskeleton and cytoskeletal arrangements of both β-adducin and PKCδ by substantially inhibiting the expression of β-adducin, spectrin and PKCδ proteins in differentiating keratinocytes. However, extracellular Ca2+ treatment blocked the inhibitory effects of the β-adducin siRNA. Ca2+ also prevented the significant down-regulation of two differentiation markers involucrin and K1/10 and the distinct up-regulation of proliferation marker K14 in β-adducin siRNA transfected keratinocytes. In addition, β-adducin knockdown resulted in a substantial reduction of epidermal growth factor receptor (EGFR), cadherin and β-catenin and enhanced phosphorylation of EGFR on tyrosine 1173 and Ca2+ prevented these changes. Furthermore, Ca2+ blocked the inhibitory effects of β-adducin siRNA on the expression of calmodulin, phosphorylated-calmodulin (P-CaM((Tyr138))) and myristoylated alanine-rich C-kinase substrate (MARCKS) in keratinocytes. Co-immunoprecipitation studies further revealed that calmodulin, not MARCKS, strongly interacted with EGFR, cadherin and β-catenin. Our data suggest that Ca2+ plays an important role in regulating the expression and function of β-adducin to sustain normal organization of the spectrin-based cytoskeleton and the differentiation properties in keratinocytes through the calmodulin/EGFR/cadherin signaling pathway.

Identification of genes and candidate agents associated with pancreatic cancer

Pancreatic cancer is a malignant neoplasm originating from transformed cells arising in tissues forming the pancreas. A major challenge in current cancer research is biological interpretation of complexity of cancer somatic mutation profiles. It has been suggested that several molecular alterations may play important roles in pancreatic carcinogenesis. In this study, by using the GSE28735 affymetrix microarray data accessible from Gene Expression Omnibus (GEO) database, we identified differentially expressed genes (DEGs) between paired pancreatic cancer tissues and adjacent nontumor tissues, followed the protein-protein interaction of the DEGs. Our study identified thousands of DEGs involved in regulation of cell cycle and apoptosis in progression of pancreatic cancer. Sp1 was predicted to be the major regulator by transcription factors analysis. From the protein-protein interaction networks, we found that Tk1 might play an important role in the progression of pancreatic cancer. Finally, we predicted candidate agents, including tomatidine and nialamide, which may be used as drugs to treat pancreatic cancer. In conclusion, our data provide a comprehensive bioinformatics analysis of genes and pathways which may be involved in the progression of pancreatic cancer.

Sequence polymorphisms at the growth hormone GH1/GH2-N and GH2-Z gene copies and their relationship with dairy traits in domestic sheep (Ovis aries)

The purpose was to analyze the growth hormone GH1/GH2-N and GH2-Z gene copies and to assess their possible association with milk traits in Sarda sheep. Two hundred multiparous lactating ewes were monitored. The two gene copies were amplified separately and each was used as template for a nested PCR, to investigate single strand conformation polymorphism (SSCP) of the 5'UTR, exon-1, exon-5 and 3'UTR DNA regions. SSCP analysis revealed marked differences in the number of polymorphic patterns between the two genes. Sequencing revealed five nucleotide changes at the GH1/GH2-N gene. Five nucleotide changes occurred at the GH2-Z gene: one was located in exon-5 (c.556G > A) and resulted in a putative amino acid substitution G186S. All the nucleotide changes were copy-specific, except c.*30delT, which was common to both GH1/GH2-N and GH2-Z. Variability in the promoter regions of each gene might have consequences on the expression level, due to the involvement in potential transcription factor binding sites. Both gene copies influenced milk yield. A correlation with milk protein and casein content was also evidenced. These results may have implications that make them useful for future breeding strategies in dairy sheep breeding.

Disruption of spectrin-like cytoskeleton in differentiating keratinocytes by PKCδ activation is associated with phosphorylated adducin

Spectrin is a central component of the cytoskeletal protein network in a variety of erythroid and non-erythroid cells. In keratinocytes, this protein has been shown to be pericytoplasmic and plasma membrane associated, but its characteristics and function have not been established in these cells. Here we demonstrate that spectrin increases dramatically in amount and is assembled into the cytoskeleton during differentiation in mouse and human keratinocytes. The spectrin-like cytoskeleton was predominantly organized in the granular and cornified layers of the epidermis and disrupted by actin filament inhibitors, but not by anti-mitotic drugs. When the cytoskeleton was disrupted PKCδ was activated by phosphorylation on Thr505. Specific inhibition of PKCδ^(Thr505) activation with rottlerin prevented disruption of the spectrin-like cytoskeleton and the associated morphological changes that accompany differentiation. Rottlerin also inhibited specific phosphorylation of the PKCδ substrate adducin, a cytoskeletal protein. Furthermore, knock-down of endogenous adducin affected not only expression of adducin, but also spectrin and PKCδ, and severely disrupted organization of the spectrin-like cytoskeleton and cytoskeletal distribution of both adducin and PKCδ. These results demonstrate that organization of a spectrin-like cytoskeleton is associated with keratinocytes differentiation, and disruption of this cytoskeleton is mediated by either PKCδ^(Thr505) phosphorylation associated with phosphorylated adducin or due to reduction of endogenous adducin, which normally connects and stabilizes the spectrin-actin complex.

Codon usage roles in human papillomavirus

Human papillomavirus (HPV) genomes, similar to other virus genomes, frequently have a G + C content significantly different from their host species. The HPV genomes show a strong codon usage bias to 18 codons, with 14 showing T at the third position amongst degenerately encoded amino acids. The codon usage pattern in HPV genome plays an important role, which regulates low or non-translational expression of the viral capsid genes and results in very weak protein expression of oncogenes in a wide range of mammalian cells. Codon modification has been proved to be a powerful technology to overcome the translational blockage and weak expression of both HPV capsid genes and oncogenes in different expression systems. Furthermore, keratinocytes are the host cells of HPV infection; the codon usage in HPV capsid genes matches available aminoacyl-tRNAs in differentiated keratinocytes to modulate their protein expression. HPV DNA vaccines with codon optimization have been shown to have higher immunogenicity and induce both strong cellular and humoral responses in animal models, which may be a promising form of therapeutic HPV vaccines.

IGF1 mRNA isoform expression in the cervix of HPV-positive women with pre-cancerous and cancer lesions

Human papillomavirus (HPV) plays a crucial role in cervical cancer etiology. However, not all HPV-infected women develop cancer, indicating that additional cellular factors facilitate carcinogenesis. The aim of this study was to analyze the expression profile of insulin-like growth factor 1 (IGF1) isoforms in the context of FOX2, SP1 and IGF1 receptor (IGF1R) expression during HPV-dependent cervical carcinogenesis. One hundred and nine epithelial tissue samples from women with pre-cancerous and cancer lesions of the cervix were analyzed. HPV DNA was identified by PCR, and real-time PCR was used to quantify the expression levels of the analyzed genes. All IGF1 mRNA splicing isoforms were up-regulated in pre-cancerous cells, and a shift in the balance towards mitogenic IGF1Eb was observed in the cancer samples. IGF1 expression was controlled mainly by the P1 promoter, and an increase in P2 usage was observed in the cancer. Correlations between IGF1 mRNA splicing isoforms and the FOX2 splicing factor, as well as P1/P2 activity and SP1 transcription factor expression levels were detected. No correlation was observed between the expression of IGF1 and its receptor IGF1R. Our results suggest that IGF1, in particular its splicing profile, may be an additional prognostic factor in cervical carcinogenesis.