HPV16 genetic variation and the development of cervical cancer worldwide.

BACKGROUND: Factors that favour a small proportion of HPV16 infections to progress to cancer are still poorly understood, but several studies have implicated a role of HPV16 genetic variation. METHODS: To evaluate the association between HPV16 genetic variants and cervical cancer risk, we designed a multicentre case-control study based on HPV16-positive cervical samples (1121 cervical cancer cases and 400 controls) from the International Agency for Research on Cancer biobank. By sequencing the E6 gene, HPV16 isolates were classified into variant lineages and the European (EUR)-lineage isolates were subclassified by the common polymorphism T350G. RESULTS: Incidence of variant lineages differed between cases and controls in Europe/Central Asia (P=0.006, driven by an underrepresentation of African lineages in cases), and South/Central America (P=0.056, driven by an overrepresentation of Asian American/North American lineages in cases). EUR-350G isolates were significantly underrepresented in cervical cancer in East Asia (odds ratio (OR)=0.02 vs EUR-350T; 95% confidence interval (CI)=0.00-0.37) and Europe/Central Asia (OR=0.42; 95% CI=0.27-0.64), whereas the opposite was true in South/Central America (OR=4.69; 95% CI=2.07-10.66). CONCLUSION: We observed that the distribution of HPV16 variants worldwide, and their relative risks for cervical cancer appear to be population-dependent.

HPV infection in women with and without cervical cancer in Conakry, Guinea.

BACKGROUND: Cervical cancer incidence in western Africa is among the highest in the world. METHODS: To investigate human papillomavirus (HPV) infection in Guinea, we obtained cervical specimens from 831 women aged 18-64 years from the general population of the capital Conakry and from 77 locally diagnosed invasive cervical cancers (ICC). Human papillomavirus was detected using a GP5+/6+ PCR-based assay. RESULTS: Among the general population, the prevalence of cervical abnormalities was 2.6% by visual inspection and 9.5% by liquid-based cytology. Fourteen of 15 high-grade squamous intraepithelial lesions were visual inspection-negative. Human papillomavirus prevalence was 50.8% (32.1% for high-risk types) and relatively constant across all age groups. Being single or reporting > or =3 sexual partners was significantly associated with HPV positivity. HPV16 was the most common type, both among the general population (7.3%) and, notably in ICC (48.6%). HPV45 (18.6%) and HPV18 (14.3%), the next most common types in ICC, were also more common in ICC than in HPV-positive women with normal cytology from the general population. CONCLUSION: The heavy burden of HPV infection and severe cervical lesions in Guinean women calls for new effective interventions. Sixty-three per cent of cervical cancers are theoretically preventable by HPV16/18 vaccines in Guinea; perhaps more if some cross-protection exists with HPV45.

Loss of p53 or p73 in human papillomavirus type 38 E6 and E7 transgenic mice partially restores the UV-activated cell cycle checkpoints.

We have previously shown that human keratinocytes expressing E6 and E7 from the cutaneous human papillomavirus (HPV) type 38 have high levels of a specific form of p53, which in turn activate the transcription of DeltaNp73 gene. Expression of HPV38 E6 and E7 in mouse skin also promotes p53 and DeltaNp73 accumulation. Interestingly, keratinocytes of these mice do not undergo cell cycle arrest after skin ultraviolet (UV) irradiation. Here, we provide several lines of evidence that DeltaNp73 expression and lack of the UV response are directly linked. Loss of p53 gene in HPV38 E6/E7 transgenic mice abolished DeltaNp73 expression and partially restored the UV-activated cell cycle checkpoints. Similarly, loss of p73, and consequently DeltaNp73, led to restoration of the p53 pathways. In fact, keratinocytes of p73-/- HPV38 E6/E7 transgenic mice upon UV irradiation express high levels of p21(WAF1) and are cell cycle arrested. Thus, HPV38 E6 and E7, via DeltaNp73 accumulation, are able to alter the regulation of cell cycle checkpoints activated by UV radiation. These data suggest that UV and HPV may cooperate in skin carcinogenesis.

The X-linked lymphoproliferative syndrome gene product SH2D1A associates with p62dok (Dok1) and activates NF-kappa B.

The X-linked lymphoproliferative syndrome (XLP) is a genetic disorder in which affected males have a morbid or fatal response to Epstein-Barr virus infection. The XLP deficiency has been mapped to a gene encoding a 128-residue protein, SH2D1A, which is comprised principally of a Src homology 2 (SH2) domain. We now report that SH2D1A associates with Dok1, a protein that interacts with Ras-GAP, Csk, and Nck. An SH2D1A SH2 domain mutant that has been identified in XLP does not associate with Dok1, in accord with the hypothesis that this interaction is linked to XLP. The association of SH2D1A with Dok1 also depends on phosphorylation of Dok1 Y(449) in the sequence ALYSQVQK. Further, overexpression of SH2D1A is found to activate NF-kappaB in 293T cells. NF-kappaB activation by SH2D1A does not depend on the wild-type SH2 domain and is inhibited by a dominant-negative IkappaB kinase beta. Thus, SH2D1A can affect multiple intracellular signaling pathways that are potentially important in the normal effective host response to Epstein-Barr virus infection.

SH2D1A mutation analysis for diagnosis of XLP in typical and atypical patients.

X-linked lymphoproliferative disease (XLP) is a rare inherited immunodeficiency to Epstein-Barr virus (EBV). The gene responsible for XLP has recently been identified as the four-exon SH2D1A gene encoding a 128-amino-acid protein that contains an SH2-domain. Functional studies indicate the SH2D1A protein acts as a regulator of at least two signal transduction pathways initiated by the cell surface molecules SLAM and 2B4, respectively, and possibly related to the host immune response to EBV infection. We have carried out a systematic mutation study of the SH2D1A gene in our series of 19 typical and 8 atypical XLP patients by polymerase chain reaction (PCR), reverse transcription/PCR, and sequencing, and have reconstructed the haplotypes of the patients. Four out of the 13 mutations detected are previously unreported. The identification of SH2D1A mutations in carriers from all three XLP families screened and the detection of mutations in two out of eight atypical patients indicates the usefulness of a DNA-based diagnosis for XLP disease.

De novo retrotransposition of unbiased sequences in a human breast cancer cell clone.

It has been demonstrated recently that certain repetitive sequences and even expressed single-copy genes are capable of retrotransposition, but little is known about the endogenous or exogenous modifiers of this process in human cells. Retrotransposition may contribute to gene inactivation and genetic instability in cancer development. We have used the human cell line MCF-7 to generate a method for investigating de novo retrotransposition in breast cancer cells. The strategy employs a reporter construct transfected into MCF-7 cells that encodes neomycin phosphotransferase gene (neoR) sequences interrupted by an intron derived from the gamma-globin gene and sandwiched between two promoters in opposite orientation; the phosphotransferase is not produced in transfected cells expressing the plasmid until transposition via a spliced antisense neoR RNA intermediate has occurred, conferring a functional gene product and thereby resistance to G418. A stable transfectant line that showed presence of reporter plasmid DNA and expression of reporter antisense neoR was obtained and used to demonstrate spontaneous retrotransposition of neoR sequences: tester cells were subjected to selection in G418 medium, and neomycin-resistant clones were isolated at a frequency of 10(-7). A simple PCR-based prescreening of colonies fixed and stained in Petri dishes can be used to verify intronless neoR DNA. Expanded populations of G418-resistant colonies were determined to be derived from reporter sequences that had transposed via an RNA intermediate by Southern blot genotyping. This experimental assay may be used for exploring endogenous and environmental factors that influence host cell-mediated retrotransposition of unbiased cellular sequences in breast tumor cells. Genes Chromosomes Cancer 26:84-91, 1999.

A new candidate region for the positional cloning of the XLP gene.

X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterised by selective susceptibility to Epstein-Barr virus and frequent association with malignant lymphomas chiefly located in the ileocecal region, liver, kidney and CNS. Taking advantage of a large bacterial clone contig, we obtained a genomic sequence of 197620 bp encompassing a deletion (XLP-D) of 116 kb in an XLP family, whose breakpoints were identified. The study of potential exons from this region in 40 unrelated XLP patients did not reveal any mutation. To define the critical region for XLP and investigate the role of the XLP-D deletion, detailed haplotypes in a region of approximately 20 cM were reconstructed in a total of 87 individuals from 7 families with recurrence of XLP. Two recombination events in a North American family and a new microdeletion (XLP-G) in an Italian family indicate that the XLP gene maps in the interval between DXS1001 and DXS8057, approximately 800 kb centromeric to the previously reported familial microdeletion XLP-D.

High-resolution mapping of the X-linked lymphoproliferative syndrome region by FISH on combed DNA.

X-linked lymphoproliferative syndrome is an inherited immunodeficiency for which the responsible gene is currently unknown. Several megabase-sized deleted regions mapping to Xq25 have been identified in XLP patients, and more recently a 130-kb deletion has been reported (Lamartine et al., 1996; Lanyi et al., 1996). To establish a physical map of this deleted region and to identify the XLP gene, two cosmid contigs were established (Lamartine et al., 1996). However, the physical map of this region is still uncompleted and controversial and three points remain unsolved: (1) the centromeric-telomeric orientation of the whole region, (2) the relative orientation of the two contigs, and (3) the size of the gap between the two contigs. To provide a definitive answer to these questions, high-resolution mapping by fluorescence in situ hybridization on combed DNA and molecular approaches were combined to establish the physical map of the XLP region over 600 kb. Our results identified a gap of 150 kb between the two contigs, established the relative orientation of one contig to the other, and determine the centromeric-telomeric orientation of the whole region. Our results show that the order of the marker over this region is: cen.1D10T7-DF83-DXS982.tel.

Epstein-Barr virus-transforming protein latent infection membrane protein 1 activates transcription factor NF-kappaB through a pathway that includes the NF-kappaB-inducing kinase and the IkappaB kinases IKKalpha and IKKbeta.

The Epstein-Barr virus oncoprotein latent infection membrane protein 1 (LMP1) is a constitutively aggregated pseudo-tumor necrosis factor receptor (TNFR) that activates transcription factor NF-kappaB through two sites in its C-terminal cytoplasmic domain. One site is similar to activated TNFRII in associating with TNFR-associated factors TRAF1 and TRAF2, and the second site is similar to TNFRI in associating with the TNFRI death domain interacting protein TRADD. TNFRI has been recently shown to activate NF-kappaB through association with TRADD, RIP, and TRAF2; activation of the NF-kappaB-inducing kinase (NIK); activation of the IkappaB alpha kinases (IKKalpha and IKKbeta); and phosphorylation of IkappaB alpha. IkappaB alpha phosphorylation on Ser-32 and Ser-36 is followed by its degradation and NF-kappaB activation. In this report, we show that NF-kappaB activation by LMP1 or by each of its effector sites is mediated by a pathway that includes NIK, IKKalpha, and IKKbeta. Dominant negative mutants of NIK, IKKalpha, or IKKbeta substantially inhibited NF-kappaB activation by LMP1 or by each of its effector sites.

Epstein-Barr virus-infected B cells of males with the X-linked lymphoproliferative syndrome stimulate and are susceptible to T-cell-mediated lysis.

Primary infection with the Epstein-Barr virus (EBV) results in fatal infectious mononucleosis in up to 70% of males affected by the X-linked lymphoproliferative syndrome (XLP). This rare disease is often associated with diverse natural killer (NK)-, B- and T-cell deficiencies. We describe experiments testing whether the B lymphocytes of affected males play a role in the pathogenesis of XLP due to a low susceptibility to T-cell-mediated immunity. Using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry we detected in these B cells the expression of viral proteins EBNA-1, EBNA-2, EBNA-3A, EBNA-3C, LMP-1 and LMP-2A, which provide targets for cytotoxic T cells. Major histocompatibility complex (MHC) class I, MHC class II and the B7 costimulatory molecule were present on the cell surface. Accordingly, the EBV-infected B cells were lysed in 51Cr-release assays by T lymphocytes sharing MHC determinants with the targets. This MHC-restricted and specific lysis was confirmed in competition experiments using MHC-specific monoclonal antibodies (MAbs) and synthetic peptides. XLP-derived LCLs could also induce MHC class I-restricted memory and cytotoxic T lymphocytes. Thus, these XLP-derived B cells resembled normal LCIs in vitro with respect to induction of EBV-specific cytotoxic T cells (CTL), the ability to present EB viral antigens and the susceptibility to EBV-specific and MHC-restricted CTL-mediated killing. The failure of the immune system to eliminate these virus-infected B cells in XLP is clearly not caused by a B-cell-specific defect.

Cancer incidence in Conakry, Guinea: first results from the Cancer Registry 1992-1995.

We have registered 2,064 cases of cancer among the inhabitants of Conakry, Guinea, during 1992-1994, corresponding to age-standardized incidence rates (ASRs) of 83.3 per 100,000 in men and 110.5 per 100,000 in women. As elsewhere in West Africa, the principal cancer of men was liver cancer (ASR 32.6), with modest rates of stomach (ASR 6.2) and prostate (ASR 8.1) cancers. In women, cervix cancer was the dominant malignancy (ASR 46.0), followed by liver cancer (ASR 12.5) and breast cancer (ASR 10.9). In contrast to contemporary East and Central Africa, Kaposi's sarcoma remained rare (only 4 cases). In the childhood age group, relatively high incidence rates were found for Hodgkin's disease, Burkitt's lymphoma and, especially, retinoblastoma.

Molecular cloning and mapping of a human cDNA (PA2G4) that encodes a protein highly homologous to the mouse cell cycle protein p38-2G4.

We have identified a novel human gene with strong homology to the mouse Pa2g4 cell cycle gene. This novel gene (called PA2G4) belongs to a gene family with members in several chromosome regions: 3q24-q25, 6q22, 9q21, 12q13, 18q12, 20p12 and Xq25. A composite cDNA of 1697 nucleotides was isolated. The sequence of this cDNA predicts a protein of 394 amino acids. The deduced amino acid sequence of this human protein shows very strong homology to the mouse protein p38-2G4. The cDNA analyzed probably corresponds to a functional copy found at 12q13.

Localization of the human phosphotyrosine phosphatase-related genes (h-PRL-1) to chromosome bands 1p35-p34, 17q12-q21, 11q24-q25 and 12q24.

The h-PRL-1 gene codes for a new phosphotyrosine phosphatase that may play an important role in the control of basic cellular processes such as cell growth and proliferation. Using the cDNA of the h-PRL-1 gene as a probe, we examined a somatic mouse and hamster x human hybrid panel and found that chromosomes 1, 17 and 11 harbor sequences homologous to h-PRL-1. By in situ hybridization of metaphase spreads, subchromosomal localizations were determined at bands 1p35-p34, 17q12-q21 and 11q24-q25; in addition, a faint signal was detected at 12q24. The chromosomal assignment of the genes homologous to h-PRL-1 will help the investigation of its possible involvement in human diseases involving genetic alteration at these chromosomal regions.

Low frequency of p16/CDKN2 gene mutations in esophageal carcinomas.

Mutational analysis of the p16/CDKN2 gene was conducted by direct sequencing of the whole coding sequence (exons 1-3 and flanking splicing sites) in 21 esophageal squamous-cell carcinomas and 3 adenocarcinomas from a high-incidence area of Italy. Two inactivating mutations were found in exon 1 of the gene (both in squamous-cell carcinoma), whereas no mutations were detected in exon 2, where most of the sequence changes reported so far have been located, or in exon 3. Southern blot analysis of exon 2 in this set of samples and in a complementary set of 12 tumor samples from France did not show homozygous deletions or detectable gene rearrangements. Thus, p16/CDKN2 gene alterations do not appear to play a major role in the group of patients examined.

Physical map and cosmid contig encompassing a new interstitial deletion of the X-linked lymphoproliferative syndrome region.

The X-linked lymphoproliferative syndrome (XLP) is an inherited immuno-deficiency to Epstein-Barr virus infection that has been mapped to chromosome Xq25. Molecular analysis of XLP patients from ten different families identified a small interstitial constitutional deletion in 1 patient (XLP-D). This deletion, initially defined by a single marker, DF83, known to map to interval Xq24-q26.1, is nested within a previously reported and much larger deletion in another XLP patient (XLP-739). A cosmid minilibrary was constructed from a single mega-YAC and used to establish a contig encompassing the whole XLP-D deletion and a portion of the XLP-739 deletion. Based on this contig, the size of the XLP-D deletion can be estimated at 130 kb. The identification of this minimal deletion, within which at least a portion of the XLP gene is likely to reside, should greatly facilitate efforts in isolating the gene.

A 100-kb physical and transcriptional map around the EDH17B2 gene: identification of three novel genes and a pseudogene of a human homologue of the rat PRL-1 tyrosine phosphatase.

In this paper, we describe the physical map and transcriptional organisation of a 100-kb region with the BRCA1 locus at 17q12-21. Using the cDNA of the EDH17B2 gene as a probe, we screened a human genomic cosmid library. Positive cosmid clones were aligned and a contig around the EDH17B2 gene was established, expanding the previously reported map. In order to identify genes located in this region, we used the cosmid inserts to select cDNAs from a human ovarian cDNA library. Among the clones identified, cDNA OV-1 corresponds to a human homologue of a rat PRL-1 tyrosine phosphatase gene that shows enhanced expression during hepatic regeneration and in some tumour cell lines. Neither the OV-1 nor the PRL-1 protein shares strong homology with any previously characterised phosphotyrosine phosphatase, suggesting that they probably belong to a new phosphatase family. In an attempt to characterise the OV-1 gene, we found that the genomic sequence present on chromosome 17 probably corresponds to a nonfunctional copy of the gene, as it contains several sequence changes that disrupt the potential coding information of the gene. Three other cDNAs, corresponding to unrelated genes, were also identified and characterised. They did not reveal striking homologies in database sequence comparison and therefore represent new genes localised on chromosome 17q, in a region that frequently shows loss of heterozigosity in sporadic breast and ovarian cancers.

Prevalence of exposure to aflatoxin and hepatitis B and C viruses in Guinea, West Africa.

The prevalence of exposure to aflatoxin, hepatitis B virus (HBV), and hepatitis C virus (HCV), three important risk factors for hepatocellular carcinoma, was examined in Guinea, West Africa. A total of 75 sera were collected from men living in the Kindia region of lower Guinea. The sera were analysed by immunoassay for aflatoxin covalently bound to serum albumin as a marker of aflatoxin exposure. Over 90% of the sera contained detectable adduct levels, the highest level being 385 pg aflatoxin B1-lysine equivalent per mg albumin. Eleven subjects (14.7%) were positive for hepatitis B surface antigen in the serum and these subjects had a tendency to have higher aflatoxin-albumin adduct levels than the other subjects (mean level 70.4 pg/mg compared to 44.1 pg/mg), but the difference was not statistically significant (P = 0.23). Eight subjects were positive for antibodies to HCV antigens and, interestingly, seven of these were from one ethnic group, Mandinka (25% prevalence). These data demonstrate that all three exposures are prevalent in Guinea and that the prevalence of these risk factors is comparable to that observed in other countries in West Africa. It is now important to assess the public health impact of these exposures in this country.

Physical mapping of Xq24-25 around loci closely linked to the X-linked lymphoproliferative syndrome locus: an overlapping YAC map and linkage between DXS12, DXS42, and DXS37.

We have localized several markers in the Xq24-25 region containing DXS12, DXS42 and DXS37 which are closely linked to the X-linked lymphoproliferative syndrome (XLP) locus. A 850-kb restriction map has been established by mapping overlapping YACs and showed that DXS12 and DXS42 are physically linked within about 50 kb. DXS37 is separated from these two loci at a maximum distance of 3,700 kb. Several new probes have been generated which will contribute to further physical mapping of this region.

Assignment of the gene for neuroendocrine protein 7B2 (SGNE1 locus) to mouse chromosome region 2[E3-F3] and to human chromosome region 15q11-q15.

The gene for 7B2, a protein found in the secretory granules of neural and endocrine cells (gene symbol SGNE1) was localized to the E3-F3 region of mouse chromosome 2 and to the q11-q15 region of human chromosome 15. This was determined by in situ hybridization, using a mouse 7B2 cDNA and an intronic fragment of the corresponding human gene as probes. The respective locations of SGNE1 in the two species correlate with the conservation of loci between these subregions of mouse chromosome 2 and human chromosome 15. Clinically, the human SGNE1 DNA fragment may serve as a molecular probe of this locus in both the Prader-Willi and the Angelman syndromes, which are often accompanied by submicroscopic chromosomal deletions in the 15q11-15q13 region.

Multipoint linkage mapping of the Xq25-q26 region in a family affected by the X-linked lymphoproliferative syndrome.

We have performed, in a large Swiss family, a study of linkage between various DNA markers in the Xq24-27 region and the locus for the X-linked lymphoproliferative syndrome (XLP). Our results indicated that the marker DXS37 in Xq25-q26 is genetically linked to the XLP syndrome. The multipoint linkage analysis showed that the disease locus is distal to DXS11, but proximal to the hypoxanthine phosphoribosyl-transferase gene (HPRT).