Leucine-zipper protein, LDOC1, inhibits NF-kappaB activation and sensitizes pancreatic cancer cells to apoptosis

A Small Family of Sushi-Class Retrotransposon-Derived Genes in Mammals and Their Relation to Genomic Imprinting

Ty3/gypsy retrotransposons are rare in mammalian genomes despite their abundance in invertebrate and other vertebrate classes. Here we identify a family of nine conserved mammalian genes with homology to Ty3/gypsy retrotransposons but which have lost their ability to autonomously retrotranspose. Of these, five map to the X chromosome while the remaining four are autosomal. Comparative phylogenetic analyses show them to have strongest homology to the sushi-ichi element from Fugu rubripes. Two of the autosomal gene members, Peg10 and Rtl1, are known to be imprinted, being expressed from the paternally inherited chromosome homologue. This suggests, consistent with the host-parasite response theory of the evolution of the imprinting mechanism, that parental-origin specific epigenetic control may be mediated by genomic "parasitic" elements such as these. Alternatively, these elements may preferentially integrate into regions that are differentially modified on the two homologous chromosomes such as imprinted domains and the X chromosome and acquire monoallelic expression. We assess the imprinting status of the remaining autosomal members of this family and show them to be biallelically expressed in embryo and placenta. Furthermore, the methylation status of Rtl1 was assayed throughout development and was found to resemble that of actively, silenced repetitive elements rather than imprinted sequences. This indicates that the ability to undergo genomic imprinting is not an inherent property of all members of this family of retroelements. Nonetheless, the conservation but functional divergence between the different members suggests that they have undergone positive selection and acquired distinct endogenous functions within their mammalian hosts.

Role of inflammation in pancreatic carcinogenesis and the implications for future therapy

BACKGROUND

The link between inflammation and pancreatic cancer has been observed for a number of gastrointestinal neoplasms. This review examines the role of inflammation in pancreatic carcinogenesis and how it can be utilised to develop new therapies against pancreatic cancer.

METHODS

A literature review of Pubmed, Medline and Web of Science databases was undertaken using the key words, pancreatic cancer, inflammation, inducible nitric oxide, interleukins, pro-inflammatory cytokines, cyclooxygenase-2, NF-kappa B, reactive oxygen species, DNA adducts, lipoxygenases, chemoprevention.

RESULTS

Epidemiological evidence and molecular studies both in vitro and in vivo all support the hypothesis that inflammation plays an important in the initiation and progression of pancreatic tumours.

CONCLUSION

Sustained damage caused by chronic inflammation may precede the onset of frank malignancy by a significant interval. As such, suppression of inflammatory changes and oxidative damage, may help delay or even prevent the inception of pancreatic neoplasia.

Differential inhibition of UVB-induced AP-1 and NF-kappaB transactivation by components of the jun bZIP domain

Potential targets for chemoprevention of nonmelanoma skin cancer include UV-induced nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1) activation in keratinocytes. Inhibition of both these ultraviolet light B (UVB)-induced transcription factors has been shown with the dominant-negative c-jun mutant, TAM67; however, its mechanism of action has not yet been determined. Here we demonstrated that transient transfection of a mouse keratinocyte cell line (308) with a dominant-negative phosphorylation mutant of c-Jun before exposure to 250 J/m(2) UVB inhibits transactivation mediated by both AP-1 and NF-kappaB transcription factors to levels below those of UVB exposed controls. Through the utilization of immunoprecipitation techniques, protein-protein interactions between NF-kappaB family members IkappaBalpha, IkappaBbeta, p50, and p65 (Rel-A) were identified with an Xpress tagged dominant-negative c-Jun (TAM67) protein. Expression of the leucine zipper domain of the TAM67 protein inhibited UVB-induced NF-kappaB transactivation but not AP-1 transactivation. Expression of the bZIP domain of the TAM67 protein was able to inhibit transactivation mediated by both transcription factors. These data demonstrate that TAM67 is able to inhibit two significant UVB-induced molecular targets AP-1 and NF-kappaB, and that the inhibition of these two transcription factor families is potentially due to protein-protein interactions between different regions of the dominant-negative c-Jun protein.

A major locus for hereditary prostate cancer in Finland: localization by linkage disequilibrium of a haplotype in the HPCX region

BACKGROUND

Prostate cancer (PRCA) is the most common cancer in males in the western world. In Finland PRCA has an age-adjusted incidence of 81.5 per 100,000. We previously reported that in Finland, the late-onset cases in families with "no-male-to-male" (NMM) transmission of PRCA accounted for most of the linkage to the HPCX region (Xq27-28). The aim of the present study was to test for linkage disequilibrium (LD) and haplotype-sharing around marker DXS1205 between cases from hereditary prostate cancer (HPC) families and population controls. The initial allelic association was performed between 108 PRCA cases and 257 population controls genotyped for 23 markers in the Xq26-28 region. This resulted in a highly significant nominal one-sided Fisher's exact P-value of 0.0003 for allele ''180'' of marker DXS1205. Subsequently, a similar level of significance was observed for the same allele for marker DXS1205 (P=0.0002) when comparing 60 NMM cases and 257 controls. These results were still significant after Bonferroni correction for multiple testing. Fine mapping efforts included the genotyping of four additional markers D3S2390, bG82i1.9, bG82i1.1, bG82i1.0 and four single nucleotide polymorphisms (SNPs) to augment the original markers around DXS1205.

RESULTS

Our major finding is that markers extending from ''D3S2390'' to ''bG82i1.0'' flank the critical locus, about 150 kb. Levin and Bertell's LD measure (delta), a guide to localization of a possible variant, was 0.42 and 0.41 for alleles of markers bG82i1.9 and DXS1205, respectively.

CONCLUSIONS

In this study, the most significant haplotype comprised the three tightly linked, contiguous markers: ''cen-bG82i1.9-SNP-Hap B-bG82i1.1-tel'' [''197-2-234''] among several possible haplotypes (nominal Fisher's one-sided P=0.003). The two transcription units mapping within this interval are the LDOC1 and SPANXC genes. Positional cloning of the HPCX gene(s) is being facilitated by this exploration of the Xq26-28 region. This study represents the first report identifying a haplotype in the Xq27-28 region for an association between HPCX and X-linked prostate cancer with no-male-to-male transmission in the Finnish population.

LDOC1, a novel MZF-1-interacting protein, induces apoptosis

LDOC1 was isolated as a gene encoding a leucine-zipper protein whose expression was decreased in pancreatic and gastric cancer cell lines in 1999. Here, we found that overexpression of LDOC1 caused externalization of the cell membrane phosphatidylserine, which was characteristic for early-phase apoptotic events, and reduced cell viability in some human cell lines. The apoptotic process was triggered by a loss of the mitochondrial membrane potential, leading to both caspase-3-dependent and -independent pathways. Furthermore, a transcription factor, MZF-1, was revealed to interact with LDOC1 and enhance the activity of LDOC1 for inducing apoptosis.

Transposable elements as a source of genetic innovation: expression and evolution of a family of retrotransposon-derived neogenes in mammals

A family of functional neogenes called Mart, related to the gag gene of Sushi-like long terminal repeat retrotransposons from fish and amphibians, is present in the genome of human (11 genes) and other primates, as well as in mouse (11 genes), rat, dog (12 genes), cat, and cow. Mart genes have lost their capacity of retrotransposition through non-functionalizing rearrangements having principally affected long terminal repeats and pol open reading frame. Most Mart genes are located on the X chromosome in different mammals. Sequence database analysis suggested that Mart genes are present in opossum (marsupial), but absent from the genome of chicken. Hence, the Mart gene family might have been formed from Sushi-like retrotransposon(s) after the split of birds and mammals (310 myr ago), but before the divergence between placental mammals and marsupials (170 myr ago). RT-PCR analysis showed that at least six Mart genes are expressed during mouse embryonic development, with in situ hybridization analysis revealing rather ubiquitous expression patterns. Mart expression was also detected in adult mice, with some genes being expressed in all tissues tested, while others showed a much more restricted expression pattern. Although additional analysis will be required to establish the function of the retrotransposon-derived Mart neogenes, these observations support the evolutionary importance of retrotransposable elements as a source of genetic novelty.

A family of neofunctionalized Ty3/gypsy retrotransposon genes in mammalian genomes

A family of at least eleven genes called Mar related to long terminal repeat retrotransposons from the Ty3/gypsy group, including two genes previously identified as such, is present in human and mouse genomes. Single orthologous copies were identified for most Mar genes in different mammals. All of them have lost essential structural features necessary for autonomous retrotransposition before divergence between mouse and human. Three Mar genes also have introns at identical positions in human and mouse. Hence, Mar genes do not correspond to functional retrotransposons. Mar genes evolved under purifying selection, strongly suggesting that they are not pseudogenic relics but rather neofunctionalized retrotransposon genes. All putative Mar proteins display sequence similarity to the capsid-like domain of the Gag protein of Tf1/Sushi retrotransposons. In addition, three Mar proteins have conserved the Gag CCHC zinc finger motif, suggesting a role in nucleic acid binding. Some Mar genes have also retained from their retrotransposon origin a -1 ribosomal frameshifting between the gag-related open reading frame and a region encoding a putative aspartyl protease domain. EST analysis revealed that the majority of Mar genes are expressed in brain as well as in other tissues and organs. Some Mar proteins might function as transcription factors or be involved in the control of cell proliferation and apoptosis. Strikingly, as many as eight Mar genes are located on the X chromosome in human, mouse and other mammals, and at least two of the autosomal genes are subject to imprinting. We suggest that retrotransposons might be a source for epigenetically regulated genes. Epigenetic regulation of these neogenes might be derived from the cellular defense mechanisms having controlled their retrotransposon ancestor.

Cell death pathways in pancreatitis and pancreatic cancer

The understanding of the regulation of apoptosis and necrosis, the two principal cell death pathways, is becoming exceedingly important in investigations of the pathogenesis and treatment of pancreatitis and pancreatic cancer. For example, in acute pancreatitis significant amounts of pancreatic necrosis are associated with increased morbidity and mortality. Thus, determining the key steps regulating necrosis should provide insights into potential therapeutic strategies for improving outcome in these patients. On the other hand, in pancreatic cancer various survival mechanisms act to prevent cell death, resulting in promotion of tumor growth and metastasis. Resistance of pancreatic cancer to apoptosis is the key factor preventing responses to therapies. Investigations of the regulation of cell death mechanisms specific to pancreatic cancer should lead to improvements in our current therapies for this disease. The present review is designed to provide information about cell death pathways in pancreatitis and pancreatic cancer with reference to areas that need further investigation, as well as to provide measurement techniques adapted to pancreatic tissue and cells.

The SPANX gene family of cancer/testis-specific antigens: rapid evolution and amplification in African great apes and hominids

Human sperm protein associated with the nucleus on the X chromosome (SPANX) genes comprise a gene family with five known members (SPANX-A1, -A2, -B, -C, and -D), encoding cancer/testis-specific antigens that are potential targets for cancer immunotherapy. These highly similar paralogous genes cluster on the X chromosome at Xq27. We isolated and sequenced primate genomic clones homologous to human SPANX. Analysis of these clones and search of the human genome sequence revealed an uncharacterized group of genes, SPANX-N, which are present in all primates as well as in mouse and rat. In humans, four SPANX-N genes comprise a series of tandem duplicates at Xq27; a fifth member of this subfamily is located at Xp11. Similarly to SPANX-A/D, human SPANX-N genes are expressed in normal testis and some melanoma cell lines; testis-specific expression of SPANX is also conserved in mouse. Analysis of the taxonomic distribution of the long and short forms of the intron indicates that SPANX-N is the ancestral form, from which the SPANX-A/D subfamily evolved in the common ancestor of the hominoid lineage. Strikingly, the coding sequences of the SPANX genes evolved much faster than the intron and the 5' untranslated region. There is a strong correlation between the rates of evolution of synonymous and nonsynonymous codon positions, both of which are accelerated 2-fold or more compared to the noncoding sequences. Thus, evolution of the SPANX family appears to have involved positive selection that affected not only the protein sequence but also the synonymous sites in the coding sequence.