Viruses in human cancers

Strategic use of nanomaterials as double-edged therapeutics to control carcinogenesis via regulation of dysbiosis and bacterial infection: current status and future prospects

The human microbiome plays a crucial role in modulating health and disease susceptibility through a complex network of interactions with the host. When the delicate balance of this microbial ecosystem is disrupted, it often correlates with the onset of systemic diseases. An over-abundance of pathogenic microorganisms within the microbiome has been implicated as a driving factor in the development of disease conditions such as diabetes, obesity, and chronic infections. It has been observed that microbiome dysbiosis perturbs metabolic, inflammatory, and immunological pathways, potentially facilitating carcinogenesis. Furthermore, the metabolites associated with microbial dysbiosis exert multifaceted effects, including metabolic interference, host DNA damage, and tumor promotion, further underscoring the microbiome's significance in several of the cancers. This new exploration of microbiome involvement in carcinogenesis needs additional patient sample analysis, which could provide new insights into cancer diagnosis and treatment. However, treating these diseases using drugs, traditional methods, etc. has resulted in multi-drug resistance, and this has eventually made the situation worrisome. This review highlights the importance of nanotechnology, which may tackle these pathogenic conditions simultaneously by targeting common receptors present in bacteria and cancer. Herein, we have explained how nanotechnology may come to the forefront for these treatments. It explores the potential of non-antibiotic disinfectants, i.e., nanoparticles (NPs) with dual targeting capabilities against microbes and cancer cells, using mechanisms such as ROS generation and DNA damage while minimizing the chances of drug resistance.

Are There More Human Cancer Viruses Left to Be Found?

Of the thousands of viruses infecting humans, only seven cause cancer in the general population. Tumor sequencing is now a common cancer medicine procedure, and so it seems likely that more human cancer viruses already would have been found if they exist. Here, we review cancer characteristics that can inform a dedicated search for new cancer viruses, focusing on Kaposi sarcoma herpesvirus and Merkel cell polyomavirus as the most recent examples of successful genomic and transcriptomic searches. We emphasize the importance of epidemiology in determining which cancers to examine and describe approaches to virus discovery. Barriers to virus discovery, such as novel genomes and viral suppression of messenger RNA expression, may exist that prevent virus discovery using existing approaches. Optimally virus hunting should be performed in such a way that if no virus is found, the tumor can be reasonably excluded from having an infectious etiology and new information about the biology of the tumor can be found.

Strategies for Human Tumor Virus Discoveries: From Microscopic Observation to Digital Transcriptome Subtraction

Over 20% of human cancers worldwide are associated with infectious agents, including viruses, bacteria, and parasites. Various methods have been used to identify human tumor viruses, including electron microscopic observations of viral particles, immunologic screening, cDNA library screening, nucleic acid hybridization, consensus PCR, viral DNA array chip, and representational difference analysis. With the Human Genome Project, a large amount of genetic information from humans and other organisms has accumulated over the last decade. Utilizing the available genetic databases, Feng et al. (2007) developed digital transcriptome subtraction (DTS), an in silico method to sequentially subtract human sequences from tissue or cellular transcriptome, and discovered Merkel cell polyomavirus (MCV) from Merkel cell carcinoma. Here, we review the background and methods underlying the human tumor virus discoveries and explain how DTS was developed and used for the discovery of MCV.

Viruses and oral cancer. Is there a link?

Oral squamous cell carcinoma (OSCC) is the most common malignant tumour of the oral cavity. The aetiology of epithelial cancer of the head and neck is considered to be a multifactorial, sequential process. DNA viruses are found in many different cancers and are also capable of transforming cells to a malignant phenotype. Human Papilloma Virus (HPV) has been proposed as risk factors in OSCC development and HPV type 16 is the most important subtype. Other oncogenic virus species i.e., Epstein-Barr Virus and Herpes Simplex Virus Type 1 have been proposed to be involved in oral carcinogenesis. However, no convincing evidence exist that they are an established risk factor in OSCC. Therefore more studies are needed in order to clarify the different aspects of virus involvement. Here, we review the existing literature on viral involvement in oral cancer.

Human keratinocyte cultures in the investigation of early steps of human papillomavirus infection

Human papillomaviruses (HPVs) are non-enveloped DNA viruses that are highly tropic for mucosal and cutaneous epithelia. The HPV life cycle is tightly linked to epithelial cell differentiation, where HPVs only infect the basal proliferating keratinocytes, and progeny virus assembly and release only occurs in differentiated upper-layer keratinocytes. Therefore, human keratinocyte monolayer cultures provide a useful model to study the early stages of HPV infection. However, previous reports have shown some conflicting results of virus-host interactions during HPV entry, which may be partly attributable to the different cell culture models used to examine these steps of HPV infection. Thus, there is a need to have a standardized in vitro model system to study virus-host interactions during HPV entry. Here, we describe the three most widely accepted keratinocyte models for studying HPV infection: primary human foreskin keratinocytes, normal immortalized keratinocytes, and transformed HaCaT keratinocytes. We also describe methods to genetically manipulate these cells, enabling the study of candidate host genes that may be important during HPV infection. Lastly, we outline simple and robust methods to assay HPV infectivity, which can be used to determine whether knockdown or overexpression of a particular gene affects HPV entry.

[Can we prevent or cure infection-related cancers?]

Infections are an important cause of cancer in the world, representing approximately 16% of the neoplasia. Ten infectious agents have been classified as carcinogens of group I. Four of these pathogens (Helicobacter pylori, hepatitis B and C viruses, and some human papillomavirus) are responsible for 95% of cases of infection-related cancers. The carcinogenesis mechanisms are multiple, either direct via certain proteins from these microorganisms, or more often indirect through chronic inflammation. This allowed to consider prevention of certain cancers, for example with a prophylactic vaccine strategy. Advances were also made in the curative field. However, efforts remain to be done to discover new infectious causes of cancer and refine the understanding of the mechanisms of carcinogenesis, for a better targeting of anticancer therapeutics.

Multiple infections and cancer: implications in epidemiology

Approximately 18% of the global cancer burden has been attributed to infectious agents, with estimates ranging from 7% in developed countries to about 22% in developing countries. Chronic infections caused by the hepatitis B and C viruses, human papilloma viruses (HPV), and Helicobacter pylori (H. pylori) are reported to be responsible for approximately 15% of all human cancers. Interestingly, although many of the infectious agents that have been associated with cancer--such as HPV, Epstein-Barr virus (EBV), and H. pylori--are highly prevalent in the world, most infected individuals do not develop cancer but remain lifelong carriers. Malignancies associated with infectious agents may result from prolonged latency as a result of chronic infections. Pathogenic infections are necessary but are not sufficient for cancer initiation or progression. Cancer initiation may require additional cofactors, including secondary infections. Therefore, in patients with chronic infection with one agent, secondary co-infection with another agent may serve as an important co-factor that may cause cancer initiation and progression. Additionally, opportunistic co-infections could significantly inhibit response to cancer treatment and increase cancer mortality. Co-infections are relatively common in areas with a high prevalence of infectious agents, especially in developing countries. These co-infections can cause an imbalance in the host immune system by affecting persistence of and susceptibility to malignant infections. Several articles have been published that focus on infectious agents and cancer. In this article, we discuss the role of infectious agents in malignancies, highlight the role of multiple/co-infections in cancer etiology, and review implications for cancer epidemiology.

Human papillomavirus infection is inhibited by host autophagy in primary human keratinocytes

Human papillomavirus (HPV) infection is severely limited in its natural host, primary human keratinocytes. Our data show HPV infectivity in primary keratinocytes is over 100- and 1,000-fold lower than in established keratinocyte cell lines NIKS and HaCaT, respectively. Here, we show that the basal level of autophagy in primary human foreskin keratinocytes (HFKs) is higher than in immortalized keratinocytes, and that HPV16 virions significantly induce autophagy in HFKs. Interestingly, HPV16 infectivity is dramatically enhanced by knockdown of essential autophagy genes as well as biochemical inhibition of autophagy. The increase in HPV16 infectivity by autophagy inhibition is most significant in HFKs, showing an inverse correlation with basal HPV16 infectivity in HFK, NIKS, HaCaT, and 293FT cells. Further, inhibition of autophagy delays degradation of HPV16 capsid proteins during virus trafficking, indicating that host autophagy induced by HPV16 virions inhibits infection of primary keratinocytes through rapid degradation of viral capsid proteins.

Activation of the unfolded protein response by 2-deoxy-D-glucose inhibits Kaposi's sarcoma-associated herpesvirus replication and gene expression

Lytic replication of the Kaposi's sarcoma-associated herpesvirus (KSHV) is essential for the maintenance of both the infected state and characteristic angiogenic phenotype of Kaposi's sarcoma and thus represents a desirable therapeutic target. During the peak of herpesvirus lytic replication, viral glycoproteins are mass produced in the endoplasmic reticulum (ER). Normally, this leads to ER stress which, through an unfolded protein response (UPR), triggers phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α), resulting in inhibition of protein synthesis to maintain ER and cellular homeostasis. However, in order to replicate, herpesviruses have acquired the ability to prevent eIF2α phosphorylation. Here we show that clinically achievable nontoxic doses of the glucose analog 2-deoxy-d-glucose (2-DG) stimulate ER stress, thereby shutting down eIF2α and inhibiting KSHV and murine herpesvirus 68 replication and KSHV reactivation from latency. Viral cascade genes that are involved in reactivation, including the master transactivator (RTA) gene, glycoprotein B, K8.1, and angiogenesis-regulating genes are markedly decreased with 2-DG treatment. Overall, our data suggest that activation of UPR by 2-DG elicits an early antiviral response via eIF2α inactivation, which impairs protein synthesis required to drive viral replication and oncogenesis. Thus, induction of ER stress by 2-DG provides a new antiherpesviral strategy that may be applicable to other viruses.

Viral hit and run-oncogenesis: genetic and epigenetic scenarios

It is well documented that viral genomes either inserted into the cellular DNA or co-replicating with it in episomal form can be lost from neoplastic cells. Therefore, "hit and run"-mechanisms have been a topic of longstanding interest in tumor virology. The basic idea is that the transient acquisition of a complete or incomplete viral genome may be sufficient to induce malignant conversion of host cells in vivo, resulting in neoplastic development. After eliciting a heritable change in the gene expression pattern of the host cell (initiation), the genomes of tumor viruses may be completely lost, i.e. in a hit and run-scenario they are not necessary for the maintenance of the malignant state. The expression of viral oncoproteins and RNAs may interfere not only with regulators of cell proliferation, but also with DNA repair mechanisms. DNA recombinogenic activities induced by tumor viruses or activated by other mechanisms may contribute to the secondary loss of viral genomes from neoplastic cells. Viral oncoproteins can also cause epigenetic dysregulation, thereby reprogramming cellular gene expression in a heritable manner. Thus, we expect that epigenetic scenarios of viral hit and run-tumorigenesis may facilitate new, innovative experiments and clinical studies in spite of the fact that the regular presence of a suspected human tumor virus in an early phase of neoplastic development and its subsequent regular loss have not been demonstrated yet. We propose that virus-specific "epigenetic signatures", i.e. alterations of the host cell epigenome, especially altered DNA methylation patterns, may help to identify viral hit and run-oncogenic events, even after the complete loss of tumor viruses from neoplastic cells.

Human papillomavirus detection and typing in thin prep cervical cytologic specimens comparing the Digene Hybrid Capture II Assay, the Roche Linear Array HPV Genotyping Assay, and the Kurabo GeneSquare Microarray Assay

Three methods for the detection of HPV DNA were compared in cervical cytologic specimens: the Digene Hybrid Capture II Assay (HC), the Roche Linear Array HPV Genotyping Assay (LA) and the Kurabo GeneSquare Microarray (GS). The main goals of the study were to correlate cytology with HPV detection and to determine agreement between assay pairs for HPV detection. Thin-prep Pap smears were performed and supernates were tested by HC, LA, and GS. For specimens reacting with the HPV 52/33/35/58 probe in the LA assay, type-specific PCR was performed for HPV types 52, 33, 35, or 58. Binomial proportions and kappa coefficients were calculated for agreement between assays. Cytology results and supernatant were available for 202 subjects. HPV detection increased with worsening cytologic abnormality in all three assays. For all cytologic groups, LA and GS detected more HPV (all and oncogenic) than HC. However, for detection of oncogenic HPV types represented in all three assays, differences between assays were less pronounced. The highest agreement was between LA and GS. In four of 12 specimens reacting with the HPV 52/33/35/58 probe in the LA assay but deemed HPV 52-LA-negative using an algorithm provided by the manufacturer, the presence of HPV 52 was confirmed using type-specific HPV 52 PCR. All four of these specimens were also GS-positive for HPV 52.

Human papillomavirus infection and its association with cervical dysplasia in Ecuadorian women attending a private cancer screening clinic

Women living in Latin American countries bear a disproportionate burden of cervical cancer, a condition caused by infection with the human papillomavirus (HPV). We performed a study in Santa Elena, Guayas (currently Santa Elena Province), Ecuador, to determine how often HPV could be detected in women attending a private cancer screening clinic. Participants underwent a Pap test, and vaginal and cervical swabs were performed for HPV testing by the polymerase chain reaction (PCR). Each participant completed a verbally administered survey. The mean age of 302 participants was 37.7 years (range 18 to 78 years). The majority of cervical and vaginal specimens contained sufficient DNA to perform PCR. Overall, 24.2% of the participants had either a cervical or vaginal swab that tested positive for HPV. In general, there was a good correlation between the HPV types detected in the cervical and vaginal swabs from the participants, but vaginal swabs were more likely to contain HPV DNA than were cervical swabs. The high-risk HPV types 16, 52, 58, and 59 and the low-risk HPV types 62, 71, 72, and 83 were the most frequently detected HPV types. The number of lifetime sexual partners was positively associated with detection of any HPV type, detection of oncogenic HPV, and abnormal Pap smears. Further studies are needed to determine if these results are representative of all Ecuadorian women and to determine if cervical cancers in Ecuadorian women are caused by the same HPV types found in the swab specimens obtained in this study.

Familial risk for gastric carcinoma: an updated study from Sweden

Reliable data on familial risks are important for clinical counselling and cancer genetics. However, the estimates of familial risk of gastric cancer vary widely. We examined the risk of familial gastric cancer using the updated Swedish Family-Cancer Database with 5358 patients among offspring and 36 486 patients among parents. There were 133 families with one parent and one offspring diagnosed with gastric cancer, and 20 families with two affected offspring. Familial standardised incidence ratios (SIRs) were 1.63 and 2.93 when parents and siblings presented with gastric cancer, respectively. The high sibling risk was owing to cancer in the corpus (SIR 7.28). The SIR for cardia cancer was 1.54 when parents were diagnosed with any gastric cancer. Cardia cancer associated with oesophageal cancer, particularly with oesophageal adenocarcinoma. Among specific histologies, signet ring cancer showed an increase. A few associations were noted for discordant sites, including the urinary bladder and the endometrium. H. pylori infection, although not measured in the present study, is probably an important risk factor for the high sibling risk of corpus cancer. Familial clustering of cardia cancer is independent of H. pylori infection, and may have a genetic basis. The familial association of cardia cancer with oesophageal adenocarcinoma may provide aetiological clues.

DNA tumor viruses and human cancer

There is a strong association between viruses and the development of human malignancies. A group of oncogenic DNA viruses exists in the human population today, members of which serve as infectious agents of cancer worldwide. The group includes the Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, human papillomaviruses and human polyomaviruses. Globally, it is estimated that 20% of all cancers are linked to infectious agents. Studies of DNA viruses have contributed to our current understanding of the key molecular players in the transformation process. Research has also shed light on the molecular mechanisms of tumorigenesis that are employed by these viruses and there are indications that cofactors could be required for viral oncogenicity in some cases.

Familial risks for cervical tumors in full and half siblings: etiologic apportioning

Many studies have shown familial aggregation for cervical cancer, but they have been unable to distinguish between shared environmental and genetic effects. Full and half-siblings were identified from the nationwide Swedish Family-Cancer Database, including invasive and in situ cervical cancers in women up to age 70 years. Half-siblings were defined through a common father or mother. Standardized incidence ratios, adjusted for several variables, were calculated for proband-wise risks between full and half-siblings. The familial risk for full siblings was 1.84, compared with 1.40 for maternal and 1.27 for paternal half-siblings. These data were used to apportion familial risk for cervical tumors in full siblings into a heritable component, accounting for 64%, and an environmental component, accounting for 36% of the total risk. No evidence for gene-environment interactions was found. The intractable difficulty in separating cervical cancer causation will be an obstacle for a successful identification of susceptibility genes.

Heritable and environmental components in cervical tumors

The familial risk of 18,199 women with invasive and/or in situ cervix cancers when compared with that of 72,796 women free of cervical tumors was analyzed. The risk of cervical tumors was significantly higher for women with a mother and/or sister(s) with cervical tumors (odds ratio (OR) = 1.79, 95% CI: 1.71-1.88) than with an affected grandmother and/or aunt(s) (OR = 1.28, 1.22-1.35). This risk did not differ according to the family side of the affected relative. Taking the familial risk of 1.28 for second-degree relatives as the best estimate of a true heritable effect for 25% of gene sharing, the calculated heritable effect for full siblings, sharing 50% of their genes, would correspond to an OR of 1.56. This model suggests, as a best estimate, a heritable component of 71% and an environmental component of 29% in young familial cervical tumors. The data imply that familial risks for cervical tumors are best explained by complex multifactorial mechanisms.

Familial Lung Cancer and Aggregation of Smoking Habits: A Simulation of the Effect of Shared Environmental Factors on the Familial Risk of Cancer

BACKGROUND

Tobacco smoking is the principal cause of lung cancer. The risk of lung cancer in the offspring of lung cancer patients is about twice higher than the risk in the general population. The present study investigated the contribution of shared smoking habits to the familial clustering of lung cancer.

METHODS

We estimated the relative risk of lung cancer attributable to smoking according to the extent to which smokers transmit their smoking habits to the offspring (heritability of smoking), the prevalence of smoking in the general population, and the risk of lung cancer for smokers compared with nonsmokers.

FINDINGS

The relative risk of lung cancer for the offspring of lung cancer patients attributable to smoking was 1.19 when published data on smoking practice were modeled (i.e., assuming that the heritability of smoking was 0.5, the smoking prevalence 40%, and the odds ratio of lung cancer for smokers versus nonsmokers was 20).

INTERPRETATION

Most familial cases of lung cancer cannot be attributed to shared smoking habits. The example of smoking can be used for other familial cancers, for which no strong environmental risk factors are usually known, to infer the primary role for heritable genes.

Human papillomavirus type 16 in head and neck carcinogenesis

The aetiology of squamous cell carcinomas of the head and neck (HNSCC) is multifactorial. Oncogenic human papillomaviruses (HPVs), a causative agent in uterine cervical cancer, have also been repeatedly detected in HNSCC, especially in squamous cell carcinomas of tonsils. Approximately half the HPV DNA-positive HNSCC contain detectable E6/E7 transcripts with wild-type p53, reduced pRb and overexpressed p16 in the tumours. HPV-16 is the predominant type and exists in episomal, integrated, or mixed forms. Tonsillar carcinomas have a remarkably higher viral load than carcinomas at other sites of the head and neck region. HPV-16 DNA has also been detected in tumour-free tonsils. Infection by oncogenic HPVs is a necessary but not a sufficient cause of cancers. Studies on the molecular mechanisms underlying HPV-associated carcinogenesis are difficult, because HPV is not easy to propagate in vitro. HPV-immortalised human tonsillar epithelial cell lines may provide an in vitro model to study co-factors for the HPV-associated tonsillar cancers and to test the effects of anti-viral and anti-tumour agents.

Familial association of colorectal adenocarcinoma with cancers at other sites

Data on the familial associations of colorectal cancer (CRC) of adenocarcinoma histology are limited, but they are of interest because they may give us clues about as yet unknown family clusters. We calculated standardised incidence ratios (SIRs) for right- and left-sided colon cancer and rectal cancer in offspring using data from the Swedish Family-Cancer Database covering familial tumours from 1991 to 2000. The offspring were at an increased risk of developing colon adenocarcinoma when parents presented with CRC (SIR 1.81), endometrial (SIR 1.52) and kidney (SIR 1.42) cancers. The SIRs in siblings were increased when a co-sibling was diagnosed with CRC (SIR 3.26), myeloma (SIR 2.65) and leukaemia (SIR 2.53). Right-sided colon cancer was associated with familial pancreatic, squamous cell skin cancers, thyroid gland cancer and Hodgkin's disease. Left-sided colon cancer was associated with testicular cancers. Rectal cancer was associated with cervical and genital cancers in mothers. Most of the findings were consistent with data on known cancer syndromes. A new association was noted where rectal cancer in offspring was related to cervical and female genital cancers in mothers through an unknown mechanism. Hodgkin's disease and myeloma were also associated with right-sided colon cancer in offspring. The association with carcinoma of the testis, renal parenchyma, skin and leukaemia need to be confirmed in an independent series.

TP73 alterations in cervical carcinoma

Infection with human papillomaviruses (HPV) is essential in the carcinogenesis of the uterine cervix. However, a complex interrelation between viral and cellular genes is necessary for cell-cycle control deregulation and development and progression of cervical cancer induction. The TP73 gene is localized in 1p36.3 band, which is often deleted by loss of heterozygosity (LOH) in human cancers. We analyzed the p73 cytosine thymine polymorphism and LOH in this locus by polymerase chain reaction restriction fragment length polymorphism in 134 DNA samples from biopsies of 67 primary untreated invasive cervix tumors and the corresponding peripheral blood. Genotype frequencies of 56.7% for homozygous genotype GC/GC and 43.3% for heterozygous genotype GC/AT were found. The presence of the GC/AT genotype in tumors was associated with lower age at menarche (P=0.039) and high parity (P=0.015). In 20.0% of DNA tumor samples, the AT allele was lost compared with their DNA normal blood pairs. The AT allele was conserved in women with high parity. This was not the case in the group with low parity, with 33.3% of patients showing loss of the AT allele in tumor DNA (P=0.041). These results suggest that TP73 genetic alterations may contribute to the genesis and/or progression of cervical carcinoma in an HPV-infected transformation zone under prolonged exposure to events related to pregnancy.

Infection with human papillomavirus alters expression of the small proline rich proteins 2 and 3

Human papillomavirus (HPV) does not induce lysis of infected keratinocytes, and the exact mechanisms of viral escape are not known. As keratinocytes differentiate, the cornified cell envelope (CCE) develops, providing a protective barrier to the host. Our prior studies have identified abnormalities in CCEs isolated from genital epithelium infected with HPV 11 (a low-risk HPV type) and HPV 59 (a high-risk HPV type). These abnormalities included reduced thickness and increased fragility compared to CCEs in healthy epithelium. Transcription of loricrin is also reduced in HPV 11- and 59-infected epithelium. In this study, uninfected and HPV 11- or 59-infected human genital epithelium were examined for expression of the small proline rich proteins (SPRs), which serve as cross-linking proteins within the CCE. Limiting cycle RT-PCR was performed to detect the various SPR transcripts in HPV 11- and 59-infected, or uninfected epithelium. Immunohistochemical analysis and immunoblot assays were performed to analyze the distribution and quantity of SPR2A, SPR2B, and SPR3. SPR2B transcripts were moderately increased in the HPV 11- and 59-infected tissues and SPR3 transcripts were significantly increased in HPV 11-infected tissues and minimally increased in HPV 59-infected tissues. SPR2B protein quantities were moderately increased while SPR2A was not significantly changed. SPR3 protein, while not present in uninfected epithelium, was detected in abundance in HPV 11-infected tissue. We conclude that low-risk and high-risk HPVs share the ability to alter expression of CCE proteins, although the exact mechanisms may differ. Expression of individual SPRs differed between these types and these alterations may play a role in fragility of CCEs in HPV infection.

Human papillomavirus type 59 immortalized keratinocytes express late viral proteins and infectious virus after calcium stimulation

Human papillomavirus type 59 (HPV 59) is an oncogenic type related to HPV 18. HPV 59 was recently propagated in the athymic mouse xenograft system. A continuous keratinocyte cell line infected with HPV 59 was created from a foreskin xenograft grown in an athymic mouse. Cells were cultured beyond passage 50. The cells were highly pleomorphic, containing numerous abnormally shaped nuclei and mitotic figures. HPV 59 sequences were detected in the cells by DNA in situ hybridization in a diffuse nuclear distribution. Southern blots were consistent with an episomal state of HPV 59 DNA at approximately 50 copies per cell. Analysis of the cells using a PCR/reverse blot strip assay, which amplifies a portion of the L1 open reading frame, was strongly positive. Differentiation of cells in monolayers was induced by growth in F medium containing 2 mM calcium chloride for 10 days. Cells were harvested as a single tissue-like sheet, and histologic analysis revealed a four-to-six cell-thick layer. Transcripts encoding involucrin, a cornified envelope protein, and the E1/E4 and E1/E4/L1 viral transcripts were detected after several days of growth in F medium containing 2 mM calcium chloride. The E1/E4 and L1 proteins were detected by immunohistochemical analysis, and virus particles were seen in electron micrographs in a subset of differentiated cells. An extract of differentiated cells was prepared by vigorous sonication and was used to infect foreskin fragments. These fragments were implanted into athymic mice. HPV 59 was detected in the foreskin xenografts removed 4 months later by DNA in situ hybridization and PCR/reverse blot assay. Thus, the complete viral growth cycle, including production on infectious virus, was demonstrated in the HPV 59 immortalized cells grown in a simple culture system.

Improving cancer therapy by non-genotoxic activation of p53

Inactivation of p53 function is a common event in cancer. Approximately 50% of human tumours express mutant p53 and there is evidence that in others, including many childhood tumours, p53 function is impaired in other ways. These defects in p53 function may be due to the alteration of cellular factors that modulate p53 or to the expression of viral oncoproteins. Radiotherapy and many of the chemotherapeutic drugs currently used in cancer treatment are potent activators of p53. However, most of these therapies have a serious drawback, and that is the long-term consequences of their DNA damaging effects. Here, we review the discoveries in p53 research that are most significant to the development of new therapies based on the induction of the transcriptional activity of p53 in a non-genotoxic way and discuss the situations in which this type of approach may be most beneficial.

Infection with the oncogenic human papillomavirus type 59 alters protein components of the cornified cell envelope

Infection of the genital tract with human papillomaviruses (HPVs) leads to proliferative and dysplastic epithelial lesions. The mechanisms used by the virus to escape the infected keratinocyte are not well understood. Infection of keratinocytes with HPV does not cause lysis, the mechanism used by many viruses to release newly formed virions. For HPV 11, a type associated with a low risk of neoplastic disease, the cornified cell envelope (CCE) of infected keratinocytes is thin and fragile, and transcription of loricrin, the major CCE protein, is reduced. The effects of high-risk HPV infection on components of the CCE have not been previously reported. HPV 59, an oncogenic genital type related to HPV types 18 and 45 was identified in a condylomata acuminata lesion. An extract of this lesion was used to infect human foreskin fragments, which were grown in athymic mice as xenografts. Continued propagation using extracts of xenografts permitted growth of additional HPV 59-infected xenografts. CCEs purified from HPV 59-infected xenografts displayed subtle morphologic abnormalities compared to those derived from uninfected xenografts. HPV 59-infected xenografts revealed dysplastic-appearing cells with mitotic figures. Detection of loricrin, involucrin, and cytokeratin 10 was reduced in HPV 59-infected epithelium, while small proline-rich protein 3 (SPR3) was increased. Reduction in loricrin was most apparent in regions of epithelium containing abundant HPV 59 DNA. Compared to uninfected epithelium, loricrin transcription was decreased in HPV 59-infected epithelium. We conclude that HPV 59 shares with HPV 11 the ability to alter CCE components and to specifically reduce transcription of the loricrin gene. Because loricrin is the major CCE protein, a reduction in this component could alter the physical properties of the CCE, thus facilitating virion release.

Serological cross-reactivities between antibodies to simian virus 40, BK virus, and JC virus assessed by virus-like-particle-based enzyme immunoassays

Enzyme immunoassays (EIAs) for detection of serum antibodies to simian virus 40 (SV40), BK virus (BKV), and JC virus (JCV) were developed by using virus-like-particles (VLPs) produced in insect cells from recombinant baculoviruses expressing the VP1 protein of the respective virus. Rhesus macaque sera with neutralizing antibodies to SV40 showed a high level of reactivity in the SV40 VLP-based EIA, and these sera also showed lower levels of reactivity in the BKV and JCV VLP-based EIAs. Rhesus macaque sera negative for neutralizing antibodies to SV40 were negative in all three EIAs. Competitive binding assays showed that SV40 VLPs inhibited BKV reactivity. In rhesus macaque sera, high optical density (OD) values for antibodies to SV40 VLPs were correlated with high OD values for antibodies to BKV but not with high OD values for antibodies to JCV VLPs. Human sera with neutralizing antibodies to SV40 were more reactive to SV40 VLPs than human sera without neutralizing antibodies to SV40. The greater SV40 reactivities of human sera were correlated with greater reactivities to BKV VLPs but not JCV VLPs. These data suggest that cross-reactivity with BKV antibodies may account for part of the low-level SV40 reactivity seen in human sera. With their greater versatility and their suitability for large-scale testing, the VLP-based EIAs for SV40, BKV, and JCV are likely to contribute to a better understanding of the biology of these viruses.

Epidemiological research on cancer with a focus on Europe

Cancer has been a growing public health problem throughout the last century. Cancer mortality rates in both sexes combined in the European Union (EU) reached a peak in 1988. Thereafter, they declined by 9.4% in 1998. Likewise, lung cancer rates in the EU for both sexes combined increased by 58% between 1960 and 1988, but declined by 14% in 1998. Over a third of the decline was accounted for by lung cancer alone and approximately half by the combination of tobacco-related neoplasms. About half of the decline in total cancer mortality not attributable to tobacco derived from the steady fall in mortality from gastric cancer. The remaining half, including favourable trends in colorectal, breast, testis and lymphoid neoplasms, can be at least in part attributed to advancements in cancer diagnosis and treatment. The major causes of cancer and hence the most important priorities for research will be reviewed, with a specific focus on European priorities for research.

Glomerulonephritis and malignancy: a population-based analysis

BACKGROUND

An association between glomerulonephritis and malignant tumors has previously both been found and discarded in clinical series, but to our knowledge never has been tested in a population-based setting.

METHODS

The Danish Kidney Biopsy Registry includes all kidney biopsies performed from 1985. Using a unique personal identification number, each person in the registry to the National Population Registry and the Danish Cancer Registry were linked. Cancer occurrence after the biopsy was compared in patients with morphological, glomerular diseases with that of the general Danish population, taking into account sex, age, calendar period and time since biopsy, and the 95% confidence interval (95% CI) for the observed-to-expected rates was calculated, assuming a Poisson distribution. Cancer occurrence was stratified to <1 year, 1 to 4, and >or=5 years after a biopsy.

RESULTS

A total of 102 de novo cancers were found in 1958 patients. These cancers represent a two- to threefold excess of the expected number at <1 and 1 to 4, but not >or=5 years after a biopsy. Non-Hodgkin's lymphomas were observed six to eight times more than expected. Cancer excess was seen in glomerulonephritides with a known or suspected virus etiology.

CONCLUSIONS

The excess cancer rate could be the result of underlying undiagnosed tumors whose antigens have initiated glomerulonephritis, or the immunosuppressive therapy that initiated or energized tumor cells. Based on the findings in our study, there is some support for an association to persistent viruses causing first the glomerulonephritides and then the malignancies, perhaps through a common pathogenesis. This calls for other studies to be done that are specifically designed to investigate this issue, with more data on patient characteristics and confounders.

Cancer risks among long-standing spouses

We estimated risks for concordant and discordant cancers in spouses in order to quantify cancer risks from the shared environment. The study was restricted to spouses who had one or more children in common and who lived together for at least 15 years after the first child's birth. The nation-wide Family-Cancer Database was used as the source of family and cancer data. Standardised incidence ratios were calculated for concordant and discordant cancers in spouses after 50 years of age. Among the 18 cancer sites considered, only three sites, stomach, lung and bladder, showed concordant increases of cancer among spouses, standardised incidence ratios ranging only from 1.19 to 1.38. Additionally, gastric and pancreatic cancer were associated among spouses, as did many cancers which were related to tobacco smoking or human papilloma virus infection. By contrast, standardised incidence ratios of colon, rectal, renal and skin cancers showed no increases among spouses. Shared lifestyle among family members seems to explain only a small proportion of familial cancer susceptibility. Because lifestyles are likely to differ more between parents and offspring than between spouses, familial cancer risks between parents and offspring are even more likely to be due to heritable than environmental effects.

Second primary cancers after anogenital, skin, oral, esophageal and rectal cancers: etiological links?

The Swedish Family-Cancer Database was used to analyze second cancers after oral, esophageal, rectal, cervical, genital and skin (squamous cell carcinoma) cancers. A strong and consistent association of second cancers was observed at all these sites, in men and women. As a novel finding, an association of rectal cancer with the human papillomavirus (HVP)-related cancers was shown. New evidence on an excess of skin cancer with the HPV-related cancers was also provided. As an epidemiological study, the associations were strong and often supported by a number of comparisons. These could not be explained by bias or long-term treatment related effects. However, whether the findings on rectal and skin cancer are due to HPV or other infections, transient or inherited depressed immune function or other constitutional factors remains to be established.

A prospective seroepidemiological study of human herpesvirus-8 infection and the risk of multiple myeloma

Presence of the Human Herpesvirus 8 (HHV8) genome has been reported in the bone marrow of multiple myeloma (MM) patients. So far, serological studies of HHV8 and MM have been inconsistent but have not included prospective epidemiological studies. We evaluated whether HHV8 infection is associated with increased risk for MM in a prospective population-based study of 39 000 Finnish subjects who donated serum samples in the period 1968-72. Serum samples from 47 subjects who developed MM during a 23-year follow-up and 224 age, area of residence and sex-matched subjects who remained healthy over a similar follow-up period were evaluated for HHV8 antibodies at enrollment, as assayed both with an immunofluorescence assay (IFA) for lytic and latent HHV8 antigens and by Western blot (WB) with three recombinant HHV8 proteins (ORFs 65, 73 and K8.1A). HHV8 seropositivity for at least one HHV8 protein on WB was found in 7% of the Finnish population and was not associated with the risk of developing MM (Relative Risk (RR) = 0.89, Confidence Interval (CI): 0.25-3.25). HHV8 seropositivity for lytic and latent antigens in the IFA was found in 16% and 0.4% of the Finnish population and tended to associate with risk of MM (RR = 2.02, CI: 0.94-4.33 and RR = 10.00, CI: 0.91-110.29, respectively). In conclusion, no statistically significant evidence for an association between HHV8 infection and the risk of future MM was found.

Tonsillar and other upper aerodigestive tract cancers among cervical cancer patients and their husbands

The study aimed at probing the possible role of human papillomavirus (HPV) infection in squamous cell carcinomas of the upper aerodigestive tract, with a special reference to tonsillar cancer. We used the Swedish Family Cancer Database to analyse second cancers in the upper aerodigestive tract of women first diagnosed with in-situ or invasive cervical cancer. First cancers of their husbands were also analysed. Standardized incidence ratios (SIRs) were calculated for female and male cancers, adjusted for age at diagnosis, period, sex, socio-economic status and residential area. Among women, increases were observed at many sites, but tonsillar cancers were increased only among women aged 50 years or more at diagnosis of in-situ cervical cancer (SIR 2.58). The increases at these sites are probably ascribed to the effects HPV, smoking, alcohol or their interaction. Husbands of cervical cancer patients developed an excess (SIR over 2.00) of both tonsillar cancer (SIR 2.39 when wife with in-situ cancer and SIR 2.72 when wife with invasive cervical cancer) and cancer of the tongue. The excess of tonsillar cancer among husbands of women with HPV-associated neoplastic lesions of the cervix supports the a priori hypothesis that HPV may be involved in tonsillar carcinogenesis.

Overview of vaccinology with special reference to papillomavirus vaccines

Viruses that belong to six different families are a significant cause for neoplasia in man and animals. Among them are the Papillomaviruses that cause uterine cervical cancer in women. Efforts to develop prophylactic vaccines against viruses that cause cancer are now a major research engagement. Vaccinology, the science of vaccines, engages the sciences of immunology and of microbiology, both relying heavily on molecular biology. Successful development of vaccines relies on extensive knowledge of immunology and vaccinology. Present efforts to develop vaccines against cervical cancer caused by Papillomaviruses are focused on use of the structural antigens L1 and L2 of the virus and on the oncoproteins E6 and E7. Work on Papillomavirus vaccines has been brilliantly conceived and executed and some of vaccines are now in clinical trial. Success may follow and Papillomavirus vaccine may join with the hepatitis B virus anti-cancer vaccine in the battle against cancers of man.