Frequent FHIT gene loss of heterozygosity in human papillomavirus-infected non-smoking female lung cancer in Taiwan

HPV and lung cancer: A systematic review and meta-analysis

BACKGROUND

Lung cancer has emerged as a global public health problem and is the most common cause of cancer deaths by absolute cases globally. Besides tobacco, smoke infectious diseases such as human papillomavirus (HPV) might be involved in the pathogenesis of lung cancer. However, data are inconsistent due to differences in study design and HPV detection methods.

AIM

A systematic meta-analysis was performed to examine the presence of HPV-infection with lung cancer.

METHODS AND RESULTS

All studies in all languages were considered for the search concepts "lung cancer" and "HPV" if data specific to HPV prevalence in lung cancer tissue were given. This included Journal articles as well as abstracts and conference reports. As detection method, only HPV PCR results from fresh frozen and paraffin-embedded tissue were included. Five bibliographic databases and three registers of clinical trials including MEDLINE, Embase, Cochrane Library, and ClinicalTrials.gov were searched through February 2020. A total 4298 publications were identified, and 78 publications were selected, resulting in 9385 included lung cancer patients. A meta-analysis of 15 case-control studies with n = 2504 patients showed a weighted overall prevalence difference of 22% (95% CI: 12%-33%; P < .001) and a weighted overall 4.7-fold (95% CI: 2.7-8.4; P < .001) increase of HPV prevalence in lung cancer patients compared to controls. Overall, HPV prevalence amounted to 13.5% being highest in Asia (16.6%), followed by America (12.8%), and Europe (7.0%). A higher HPV prevalence was found in squamous cell carcinoma (17.9%) compared to adenocarcinoma (P < .01) with significant differences in geographic patterns. HPV genotypes 16 and 18 were the most prevalent high-risk genotypes identified.

CONCLUSION

In conclusion, our review provides convincing evidence that HPV infection increases the risk of developing lung cancer.

Possible Oncogenic Viruses Associated with Lung Cancer

Lung cancer is the most common cause of cancer death worldwide. Tobacco smoking is the most predominant etiology for lung cancer. However, only a small percentage of heavy smokers develop lung cancer, which suggests that other cofactors are required for lung carcinogenesis. Viruses have been central to modern cancer research and provide profound insights into cancer causes. Nevertheless, the role of virus in lung cancer is still unclear. In this article, we reviewed the possible oncogenic viruses associated with lung cancer.

Human papillomavirus and lung cancer: an overview and a meta-analysis

PURPOSE

This review is devoted to assessing the prevalence of human papillomavirus (HPV) in lung cancer (LC) in the world. HPV is recognized as the etiological factor of cervical cancer, however, there is widespread evidence that this virus is detected not only in gynecological carcinomas, but also in tumors of other organs, in particular the upper respiratory tract and digestive tract.

MATERIALS AND METHODS

 A search was conducted to a depth of 29 years in the PubMed, Web of Science, Scopus, databases. The review includes 95 articles.

RESULTS

Of all the analyzed studies (9195 patients), 12 works showed a complete absence of HPV in the biological material in patients with LC. The absence of a virus among lung cancer patients has been established for Canada, the Netherlands and Singapore. The highest average percent of occurrence of this virus is shown for such countries as: Brazil, Korea, Greece and Taiwan (more than 40%). But the highest percentage of HPV occurrence by region is observed in Latin America (33.5%), followed by the Asian countries (31%), in European countries the frequency is 18%. Interestingly, the highest occurrence of high oncogenic types (16 and 18) is observed in Asia (40.3%), then in Latin America (33.6%), Europe (25.6%) and North America (15.4%). Low-oncogenic types (6 and 11) are also predominantly observed in Asia (39.9%), while in Europe and North America 30% and 12.8%, respectively. A meta-analysis of the prevalence of HPV was conducted using Comprehensive Meta-Analysis 3.0. Program, which included 26 studies, the results of which revealed: the prevalence of HPV infection in tumor lung tissue was compared with normal lung tissue OR (95% CI) = 5.38 (3.21-9.00) p < 0.0001, significance was also found for Chinese studies OR = 6.3, 95% CI 3.42-11.53, p < 0.0001, I2 = 71.8% and for nine studies in Europe OR = 6.3, 95% CI 1.8-22.18, p = 0.004, I2 = 51.0%. However, given the fact that the frequency of occurrence of HPV in lung tumor tissue varies greatly, a question may arise about the real role of HPV in LC carcinogenesis, which makes further research relevant and promising.

MiR-30c-2* negative regulated MTA-1 expression involved in metastasis and drug resistance of HPV-infected non-small cell lung cancer

BACKGROUND

MiR-30c-2* is considered to be a tumor suppressor microRNA in various cancers and is associated with gemcitabine sensitivity of lung cancer cells. Downregulation of miR-30c-2* promotes tumor invasion via increased expression of metastasis-associated protein-1. We hypothesized that downregulated expression of miR-30c-2* was involved in human papillomavirus-associated lung tumorigenesis and drug resistance.

METHODS

We examined whether expression of human papillomavirus 16/18 oncoprotein and miR-30c-2*-associated genes could be linked to patient outcome by collecting 319 lung tumors from patients with non-small cell lung cancer to determine expression of human papillomavirus 16/18 E6 protein, miR-30c-2*, and miR-30c-2* downstream metastasis-associated protein-1 mRNA by immunohistochemical and real-time polymerase chain reaction analysis.

RESULTS

Our results showed that miR-30C-2* levels were increased 45-fold in the E6-knockdown TL-1 cells when compared with levels in the parental cells. More interestingly, metastasis-associated protein-1 expression correlated negatively with miR-30C-2* and positively with human papillomavirus 16 E6 protein expression in lung tumors from lung cancer patients. Metastasis-associated protein-1 expression levels in the tumor tissues correlated positively with tumor stage and nodal metastasis. Patients with high metastasis-associated protein-1 expression, and especially patients infected with human papillomavirus, experienced a poor clinical outcome, tumor recurrence, and a poor therapeutic response compared with those with low metastasis-associated protein-1 expression.

CONCLUSION

These results showed that miR-30C-2* and levels of downstream metastasis-associated protein-1 gene expression in the tumor tissues of patients could be useful in predicting clinical outcome and therapeutic response and in selecting useful therapeutic drugs for lung cancer patients, especially patients with human papillomavirus infection.

Prevalence of human papillomavirus, Epstein-Barr virus, and cytomegalovirus in fine needle aspirates from lung carcinoma: A case-control study with review of literature

BACKGROUND

Oncogenic viruses have recently been allied with lung carcinoma, however, the causal association has not been established till date. The study was conducted to determine the prevalence of high-risk Human papillomavirus (HPV; subtypes 16, 18, 31, 33 and 45), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) in lung carcinoma using polymerase chain reaction (PCR) on fine needle aspirates.

METHODS

Fine needle aspirates of patients with lung carcinoma were included as cases. The control samples included normal lung tissue, collected at the time of medico legal autopsies. DNA was extracted from samples of both cases and controls and analysed by PCR for the presence of HPV, EBV and CMV.

RESULTS

A total of 5/73 (6.8%) cases demonstrated the presence of HPV. Of these, 3 were positive for HPV-16 and one each for HPV-18 and HPV-45. A significant association of HPV with squamous cell carcinoma (SCC) (P = 0.01) was observed. Two cases were positive for EBV; however, the difference was not statistically significant for EBV (P = 0.5) as well as CMV. None of the controls were positive for HPV, EBV or CMV.

CONCLUSION

We conclude that fine needle aspirates can serve as reliable sample for PCR based detection of viruses. A significantly higher prevalence of HPV in lung cancer and a significant association with SCC was observed, thereby, indicating a positive link between HPV and etiopathogenesis of lung carcinoma. Diagn. Cytopathol. 2016;44:987-993. © 2016 Wiley Periodicals, Inc.

Environmental exposure and HPV infection may act synergistically to induce lung tumorigenesis in nonsmokers

Most studies of lung tumorigenesis have focused on smokers rather than nonsmokers. In this study, we used human papillomavirus (HPV)-positive and HPV-negative lung cancer cells to test the hypothesis that HPV infection synergistically increases DNA damage induced by exposure to the carcinogen benzo[a]pyrene (B[a]P), and contributes to lung tumorigenesis in nonsmokers. DNA adduct levels induced by B[a]P in HPV-positive cells were significantly higher than in HPV-negative cells. The DNA adduct formation was dependent on HPV E6 oncoprotein expression. Gene and protein expression of two DNA repair genes, XRCC3 and XRCC5, were lower in B[a]P-treated E6-positive cells than in E6-negative lung cancer cells. The reduced expression was also detected immunohistochemically and was caused by increased promoter hypermethylation. Moreover, mutations of p53 and epidermal growth factor receptor (EGFR) genes in lung cancer patients were associated with XRCC5 inactivation. In sum, our study indicates that HPV E6-induced promoter hypermethylation of the XRCC3 and XRCC5 DNA repair genes and the resultant decrease in their expression increases B[a]P-induced DNA adducts and contributes to lung tumorigenesis in nonsmokers.

Effect of FHIT loss and p53 mutation on HPV-infected lung carcinoma development

High-risk human papillomavirus (HPV)16/18 infection in the development of lung cancer has previously been identified, and fragile histidine triad (FHIT) loss and p53 mutation are frequently observed in the disease. However, the association between these factors has not been well studied. The present study aimed to further investigate the significance of HPV infection, FHIT loss and p53 mutations in the development of lung cancer and their possible associations. DNA was extracted from paraffin-embedded specimens from 88 cases of squamous cell carcinoma (SCC), 56 of adenocarcinoma (AC), 36 of small cell lung carcinoma (SCLC) and 110 non-cancer control cases of lung neoplasms. The prevalence of HPV infection was determined by polymerase chain reaction analysis, and FHIT loss and p53 mutations were detected by immunohistochemistry. The χ², Fisher's exact and Pearson correlation tests were applied for statistical analysis. The results of the present study demonstrated that HPVL1 (the major capsid protein of HPV), HPV16 and HPV18 infection were more prevalent in the lung cancer samples compared with the non-cancer controls (all P<0.001). FHIT loss occurred more frequently in the lung cancer samples (44.44%) compared with the non-cancer controls (7.25%) (P<0.001). FHIT loss in the HPVL1-positive group was significantly increased compared with the HPVL1-negative group in the lung cancer cases and the non-cancer controls (P<0.05). In the lung cancer cases, the p53 mutation rates in the HPVL1- and HPV16/18-positive groups were significantly increased compared with the HPVL1- and HPV16/18-negative groups (P<0.05). In the 180 lung cancer cases, the coexistence rate of FHIT loss and a history of smoking was 38.33% (69/180; Pearson contingency coefficient of r=0.318; P<0.001). FHIT loss and p53 mutation exhibited a synergistic effect on HPV-associated lung cancer (Pearson contingency coefficient r=0.357, P<0.001). The present study demonstrated that FHIT loss may be important in the occurrence of lung cancer, particularly in lung SCCs. FHIT loss may therefore be used as an early indicator for lung cancer, particularly for patients with a history of smoking. HPV infection in lung tumorigenesis may, at least in part, be mediated through FHIT loss. FHIT loss and p53 mutation may coordinate together in the development of HPV-associated lung cancer, and accelerate the occurrence and development of lung cancer.

The effect of gender on health-related quality of life and related factors in post-lobectomy lung-cancer patients

PURPOSE

While studies have documented gender differences by histologic type among lung cancer patients, the effect of these differences on the health-related quality of life (HRQoL) of post-lobectomy lungcancer patients and related factors remain uncertain. This study examines gender-specific HRQoL and related factors in post-lobectomy lung-cancer patients.

METHODS

A cross-sectional study design was applied. A convenience sample of 231 post-lobectomy lungcancer patients was recruited from the thoracic surgery outpatient departments of two teaching hospitals in Taipei, Taiwan from March to December 2012. Patients performed a spirometry test and completed instruments that included a Beck Depression Inventory-II, an Interpersonal Support Evaluation List, and the symptom and function scales of the Quality of Life Questionnaire. Data analysis used descriptive statistics, including mean and standard deviations, frequency, and percentage values. Independent-sample Student's t-tests and multivariate analyses were used for comparative purposes.

RESULTS

This study confirmed a significant gender effect on HRQoL and HRQoL-related factors such as marital status, religious affiliation, smoking status, histologic type, symptoms, pulmonary function, depression, and family support. Moreover, multivariate analysis found gender to be a significant determinant of the HRQoL aspects of physical functioning, emotional functioning, and cognitive functioning. Finally, results indicated that factors other than gender were also significant determinants of HRQoL.

CONCLUSION

Gender impacts the HRQoL and related factors of postoperative lung-cancer patients. Therefore, gender should be considered in assessing and addressing the individual care needs of these patients in order to attain optimal treatment outcomes.

FHIT loss confers cisplatin resistance in lung cancer via the AKT/NF-κB/Slug-mediated PUMA reduction

Fragile histidine triad (FHIT) loss by the two-hit mechanism of loss of heterozygosity and promoter hypermethylation commonly occurrs in non-small cell lung cancer (NSCLC) and may confer cisplatin resistance in NSCLC cells. However, the underlying mechanisms of FHIT loss in cisplatin resistance and the response to cisplatin-based chemotherapy in NSCLC patients have not yet been reported. In the present study, inhibition concentration of 50% cell viability induced by cisplatin (IC50) and soft agar growth and invasion capability were increased and decreased in FHIT-knockdown and -overexpressing cells, respectively. Mechanistically, Slug transcription is upregulated by AKT/NF-κB activation due to FHIT loss and, in turn, Slug suppresses PUMA expression; this decrease of PUMA by FHIT loss is responsible for cisplatin resistance. In addition, cisplatin resistance due to FHIT loss can be conquered by AKT inhibitor-perifosine in xenograft tumors. Among NSCLC patients, low FHIT, high p-AKT, high Slug and low PUMA were correlated with shorter overall survival, relapse-free survival and poorer response to cisplatin-based chemotherapy. Therefore, the AKT inhibitor perifosine might potentially overcome the resistance to cisplatin-based chemotherapy in NSCLC patients with low-FHIT tumors, and consequently improve the outcome.

c-Myc suppresses microRNA-29b to promote tumor aggressiveness and poor outcomes in non-small cell lung cancer by targeting FHIT

The dual role of the microRNA-29 (miR-29) family in tumor progression and metastasis in solid tumors has been reported. Evidence for the role of miR-29 in tumor malignancy and its prognostic value in overall survival (OS) and relapse-free survival (RFS) in non-small cell lung cancer (NSCLC) remains conflicting. Mechanistic studies presented herein demonstrated that c-Myc suppressed the expression of miR-29b, promoting soft agar growth and invasion capability in lung cancer cells. Interestingly, the decrease in the expression of miR-29b by c-Myc is responsible for soft agar growth and invasiveness mediated by FHIT loss due to promoter methylation. Among patients, low expression of miR-29b and FHIT was more common in tumors with high c-Myc expression than in tumors with low c-Myc expression. Kaplan-Meier and Cox regression analysis showed that tumors with high c-Myc, low miR-29b and low FHIT expression had shorter OS and RFS periods than their counterparts. In conclusion, the decrease in the expression of miR-29b by c-Myc may be responsible for FHIT loss-mediated tumor aggressiveness and for poor outcome in NSCLC. Therefore, we suggest that restoration of the miR-29b expression using the c-Myc inhibitor might be helpful in suppressing tumor aggressiveness mediated by FHIT loss and consequently improving outcomes in NSCLC patients with tumors with low expression of FHIT.

HPV-associated lung cancers: an international pooled analysis

Human papillomavirus (HPV) is the etiologic risk factor for cervical cancer. Some studies have suggested an association with a subset of lung tumors, but the etiologic link has not been firmly established. We performed an international pooled analysis of cross-sectional studies (27 datasets, n = 3249 patients) to evaluate HPV DNA prevalence in lung cancer and to investigate viral presence according to clinical and demographic characteristics. HPV16/18 were the most commonly detected, but with substantial variation in viral prevalence between geographic regions. The highest prevalence of HPV16/18 was observed in South and Central America, followed by Asia, North America and Europe (adjusted prevalence rates = 22, 5, 4 and 3%, respectively). Higher HPV16 prevalence was noted in each geographic region compared with HPV18, except in North America. HPV16/18-positive lung cancer was less likely observed among White race (adjusted odds ratio [OR] = 0.33, 95% confidence interval [CI] = 0.12-0.90), whereas no associations were observed with gender, smoking history, age, histology or stage. Comparisons between tumor and normal lung tissue show that HPV was more likely to be present in lung cancer rather than normal lung tissues (OR = 3.86, 95% CI = 2.87-5.19). Among a subset of patients with HPV16-positive tumors, integration was primarily among female patients (93%, 13/14), while the physical status in male cases (N = 14) was inconsistent. Our findings confirm that HPV DNA is present in a small fraction of lung tumors, with large geographic variations. Further comprehensive analysis is needed to assess whether this association reflects a causal relationship.

Human papillomavirus and non-small cell lung cancer

Lung cancer is the most common cause of cancer-related deaths in the world, causing more than one million deaths worldwide each year. Human papillomavirus (HPV) are small non-enveloped DNA viruses that infect squamous epithelial cells. Relevant studies have reported lung cancer-related HPV infection rates that fluctuate between 10% and 80%, depending on the various research methods and geographical factors. Various scholars gathered statistics from global research reports and found that 22.4% of the patients with lung cancer presented with an HPV infection, which suggested that HPV infection may relate to the tumorigenesis of non-small cell lung cancer. This article will review the history and discovery of HPV, the correlation between HPV and lung cancer development, and carcinogenesis caused by HPV regulatory genes, such as p53, p21, p16INK4a, and genes related to hypermethylation and genome instability in lung cancer patients with HPV infection. In addition, because studies have highlighted the difference in clinical prognosis for HPV-positive and HPV-negative patients, articles demonstrating the correlation between HPV infection and prognosis for lung cancer patients will be reviewed.

Carcinogenic viruses and solid cancers without sufficient evidence of causal association

Viral infections are important risk factors for tumor development in humans. Selected types of cancers, either lymphomas or carcinomas, for which there is sufficient evidence in humans of a causal association with specific viruses, have been identified. Experimental and clinical data on the possible association of other tumor types and carcinogenic viruses are presently controversial. In this article, we review the current evidence on the relationship between breast, colorectal and lung cancers and carcinogenic viruses. The majority of the publications reviewed do not provide definitive evidence that the viruses studied are associated with breast, colon and lung cancers. However, since this association may be clinically relevant for some tumor subtypes (i.e., lung cancer and papillomaviruses), there is an urgent need for further investigation on this topic. Using innovative laboratory techniques for viral detection on well-defined tumor types, National and International networks against cancer should encourage and organize concerted research programs on viruses and solid cancer association.

Molecular and epigenetic analysis of the fragile histidine triad tumour suppressor gene in equine sarcoids

Background

Sarcoids are peculiar equine benign tumours. Their onset is associated with Bovine Papillomavirus type -1 or -2 (BPV-1/2) infection. Little is known about the molecular interplay between viral infection and neoplastic transformation. The data regarding papillomavirus infections in human species show the inactivation of a number of tumour suppressor genes as basic mechanism of transformation. In this study the putative role of the tumour suppressor gene Fragile Histidine Triad (FHIT) in sarcoid tumour was investigated in different experimental models. The expression of the oncosuppressor protein was assessed in normal and sarcoid cells and tissue.

Results

Nine paraffin embedded sarcoids and sarcoid derived cell lines were analysed for the expression of FHIT protein by immunohistochemistry, immunofluorescence techniques and western blotting. These analyses revealed the absence of signal in seven out of nine sarcoids. The two sarcoid derived cell lines too showed a reduced signal of the protein. To investigate the causes of the altered protein expression, the samples were analysed for the DNA methylation profile of the CpG island associated with the FHIT promoter. The analysis of the 32 CpGs encompassing the region of interest showed no significative differential methylation profile between pathological tissues and cell lines and their normal counterparts.

Conclusion

This study represent a further evidence of the role of a tumour suppressor gene in equine sarcoids and approaches the epigenetic regulation in this well known equine neoplasm. The data obtained in sarcoid tissues and sarcoid derived cell lines suggest that also in horse, as in humans, there is a possible involvement of the tumour suppressor FHIT gene in BPV induced tumours. DNA methylation seems not to be involved in the gene expression alteration. Further studies are needed to understand the basic molecular mechanisms involved in reduced FHIT expression.

Lung Cancer and Human Papilloma Viruses (HPVs): Examining the Molecular Evidence

Human papilloma virus (HPV), known to be an etiological agent for genital cancers, has been suggested also to be a possible contributory agent for lung cancer. Alternatively, lung cancer, formerly considered to be solely a smoker's disease, may now be more appropriately categorised into never smoker's and smoker's lung cancer. Through this paper we attempt to bring forth the current knowledge regarding mechanisms of HPV gaining access into the lung tissue, various strategies involved in HPV-associated tumorigenesis in lung tissue.

Allelic imbalance and abnormal expression of FHIT in endemic nasopharyngeal carcinoma: association with clinicopathological features

The FHIT gene is involved in the pathogenesis of many cancers. The aim of this study was to investigate allelic imbalance (AI) pattern at FHIT locus and alteration of FHIT gene in nasopharyngeal carcinoma (NPC) and analyzed potential correlation between AI, FHIT mRNA expression and clinicopathological factors. We examined AI, including loss of heterozygosity (LOH) and microsatellite instability (MSI), at FHIT locus in 41 cases of NPC by microsatellite analysis and FHIT gene status in 30 cases of NPC by nested reverse transcriptase-polymerase chain reaction and DNA sequencing. The frequencies of LOH and MSI at FHIT locus in NPC were 70.7% (29/41) and 36.6% (15/41), respectively. Thirteen of thirty (43.3%) NPCs exhibited aberrant FHIT transcripts. LOH and abnormal FHIT expression were correlated with advanced clinical stage and higher titers of immunoglobulin (Ig) A against Epstein-Barr virus capsid antigen (EBVCA-IgA) (p < 0.05). Abnormal FHIT expression was also correlated with tumor recurrence (p < 0.05). MSI was correlated with early clinical stage and higher titers of EBVCA-IgA (p < 0.05). AI at FHIT locus is a common event and contributes to genetic imbalance in NPC. The abnormalities of FHIT, presumably associated with genetic imbalance at FHIT locus, might be involved in the development and the tumor recurrence of NPC.

Persistent infections and their relationship with selected oncologic and non-tumor pathologies

Our earlier studies of hepatitis C virus (HCV) infection rates among blood donors at the Kyiv Municipal Blood Center revealed a 3.45% HCV+ prevalence in these "healthy" hosts. In the study here, we analyzed HCV (as well as cytomegalovirus [CMV]) prevalence among Chernobyl nuclear power plant (NPP) accident sufferers--cleanup workers, local residents, NPP workers, and convalescent patients--who suffered acute radiation syndrome (ARS) as a result of the 1986 accident, and individuals who had not been exposed to ionizing radiation (IR). Serological analyses of antibodies against each pathogen (via enzyme-linked immunosorbent assay [ELISA]) revealed the highest HCV (i.e., 27.2%) and CMV (85.6%) prevalence in the convalescent hosts. Though the HCV prevalence (reflecting a current/past infection) among the cleanup workers (and other groups) was lower (i.e., 11-25%), viral presence was "associated" with a higher incidence of selected somatic diseases, for example, thyroiditis, goiter, hypertension, Type 1 diabetes, chronic hepatitis/gastritis, in the cleanup workers. A similar scenario with respect to CMV was also seen, i.e., lower prevalence rates [relative to in ARS patients] and "association" between CMV status and incidence of chronic gastritis, arthritis, and bronchitis, in the cleanup workers and IR-non-exposed controls. Further, irrespective of CMV status, there was a clear delineation between incidence rate(s) of each of the pathologies and whether or not the person was/was not exposed in 1986. We also investigated, due to a high incidence of chronic lymphocytic leukemia (CLL) among Chernobyl sufferers, if there was homology between immunoglobulins (Igs) generated by these transformed cells and known antiviral and antimicrobial Igs. Polymerase chain reaction (PCR) analyses of Ig heavy-chain variable (IgHV) genes in cells from CLL patients who were/were not exposed in 1986 revealed a significant homology of some IgHV genes with Igs directed against infectious agents. However, no differences were found between the sequences from IR-exposed and IR-non-exposed CLL patients. Based on the findings here, we conclude that a past/ongoing presence of certain viral infections (i.e., CMV and/or HCV) in a host can modify (aggravate) the clinical course of certain somatic (i.e., non-tumor) diseases and promote malignancies (i.e., CLL), and that each of these outcomes could be modulated as a result of that host's past exposure to IR.

Incidence of human papilloma virus in lung cancer

HPV has been identified not only in gynaecological carcinomas but also in tumors of other organs, especially of the oropharynx and upper aero-digestive tract. In this study we focused on the available literature on HPV in lung carcinomas. In total, 53 publications reporting on 4508 cases were reviewed and assessed for the following parameters: continent and region of the study, number of cases, detection method, material type, HPV type, histological subtype and number of the HPV-positive cases. Overall, the mean incidence of HPV in lung cancer was 24.5%. While in Europe and the America the average reported frequencies were 17% and 15%, respectively, the mean number of HPV in asian lung cancer samples was 35.7%. There was a considerable heterogeneity between certain countries and regions. Particular high frequencies of up to 80% were seen in Okinawa (Japan) and Taichung (Taiwan). However, there were also discrepant results within the same region pointing to methodological differences and the need for validation. All lung cancer subtypes were affected and especially the high risk types 16, 18, 31 and 33 as well as the low risk types 6 and 11 were found, the later mainly in association with squamous cell carcinomas. The data suggest that HPV is the second most important cause of lung cancer after cigarette smoking and strongly argues for additional research on this issue.

Human papillomavirus 16/18 E6 oncoprotein is expressed in lung cancer and related with p53 inactivation

Inactivation of p53 by human papillomavirus 16/18 E6 plays a crucial role in cervical tumorigenesis. To investigate the involvement of HPV16/18 in lung tumorigenesis, the association between HPV16 or HPV18 E6 and p53 protein expression in 122 lung tumors was evaluated by immunohistochemistry, and data showed that HPV16/18 E6 expression correlated inversely with p53 expression, which was further confirmed by tissue in situ immunostaining. Real-time reverse transcription-PCR analysis indicated that E6-positive tumors had lower p21(WAF1/CIP1) and mdm2 mRNA levels than E6-negative tumors. To elucidate the role of E6 in p53 inactivation, we successfully established lung adenocarcinoma cell lines with or without HPV16 infection from patients' pleural effusions. Western blotting showed that E6 protein was indeed expressed in HPV16-infected cells and a lower level of p53 protein was observed in E6-positive cells compared with E6-negative cells. Moreover, the levels of p21(WAF1/CIP1) and mdm2 mRNA in E6-positive cells were lower than in E6-negative cells. The interaction of E6 with p53 protein was revealed by immunoprecipitation assay showing that p53 could be inactivated by E6 protein. Conversely, p53 proteins and p21(WAF1/CIP1) and mdm2 mRNA expressions were restored in E6-knockdown cells by RNA interference compared with control cells. These results reveal that HPV16/18 E6 may be partially involved in p53 inactivation to down-regulate p21(WAF1/CIP1) and mdm2 transcription. In conclusion, HPV16/18 E6 is indeed expressed in HPV DNA-positive lung tumors and is involved in p53 inactivation to contributing to HPV-mediated lung tumorigenesis.