Human papillomavirus infection in lung and esophageal cancers: analysis of 485 Asian cases

The emerging role of human papillomavirus in lung cancer

Lung cancer stands as one of the most lethal diseases and is the foremost cause of cancer-related mortalities worldwide. The pathophysiology of lung cancer is multifaceted, and it includes multiple cell signaling pathways and other complex factors such as oxidative stress and genetics. The association of HPV with lung carcinogenesis was first proposed in 1979, and since then, scientists worldwide have been putting forward several hypotheses to establish a relationship between this virus and lung cancer. Although studies have reported the presence of HPV in lung cancer, the exact mechanism of entry and the route of transmission have not been elucidated clearly till date. Numerous studies across the globe have detected differentially expressed HPV oncoproteins in lung cancer patients and found their association with the critical cell signaling pathways that leads to the development and progression of lung cancer. Many reports have also provided evidence stating the involvement of HPV in determining the survival status of lung cancer patients. The present review recapitulates the studies evincing the association of HPV and lung cancer, its route of transmission and mechanism of action; the detection of the virus and treatment opportunities for HPV-positive lung cancer; and the severity associated with this disease. Therefore, this will provide an explicit idea and would help to develop preventive measures and specific as well as effective treatment for HPV-associated lung carcinogenesis.

Human Papillomavirus Is Rare and Does Not Correlate with p16INK4A Expression in Non-Small-Cell Lung Cancer in a Jordanian Subpopulation

Background and Objectives: Human papillomavirus (HPV) was previously investigated in lung cancer with wide inter-geographic discrepancies. p16INK4a has been used as a surrogate for detecting high-risk HPV (HR-HPV) in some cancer types. This study assessed the evidence of HPV in non-small-cell lung cancer (NSCLC) among Jordanian patients, investigated the expression of p16INK4a, and evaluated its prognostic value and association with HPV status. Materials and Methods: The archived samples of 100 patients were used. HPV DNA detection was performed by real-time polymerase chain reaction (RT-PCR). p16INK4a expression was assessed by immunohistochemistry (IHC). The Eighth American Joint Committee on Cancer protocol (AJCC) of head and neck cancer criteria were applied to evaluate p16INK4a positivity considering a moderate/strong nuclear/cytoplasmic expression intensity with a distribution in ≥75% of cells as positive. Results: HPV DNA was detected in 5% of NSCLC cases. Three positive cases showed HR-HPV subtypes (16, 18, 52), and two cases showed the probable HR-HPV 26 subtype. p16INK4a expression was positive in 20 (20%) NSCLC cases. None of the HPV-positive tumors were positive for p16INK4a expression. A statistically significant association was identified between p16INK4a expression and the pathological stage (p = 0.029) but not with other variables. No survival impact of p16INK4a expression was detected in NSCLC cases as a group; however, it showed a statistically significant association with overall survival (OS) in squamous cell carcinoma (SqCC) cases (p = 0.033). Conclusions: This is the first study to assess HPV and p16INK4a expression in a Jordanian population. HPV positivity is rare in NSCLC among a Jordanian subpopulation. P16 INK4a reliability as a surrogate marker for HPV infection in lung cancer must be revisited.

High-Risk Human Papillomavirus Infection in Lung Cancer: Mechanisms and Perspectives

Lung cancer is a very prevalent and heterogeneous group of malignancies, and most of them are etiologically associated with tobacco smoking. However, viral infections have been detected in lung carcinomas, with high-risk human papillomaviruses (HR-HPVs) being among them. The role of HR-HPVs in lung cancer has been considered to be controversial. This issue is due to the highly variable presence of this virus in lung carcinomas worldwide, and the low viral load frequently that is detected. In this review, we address the epidemiological and mechanistic findings regarding the role of HR-HPVs in lung cancer. Some mechanisms of HR-HPV-mediated lung carcinogenesis have been proposed, including (i) HPV works as an independent carcinogen in non-smoker subjects; (ii) HPV cooperates with carcinogenic compounds present in tobacco smoke; (iii) HPV promotes initial alterations being after cleared by the immune system through a "hit and run" mechanism. Additional research is warranted to clarify the role of HPV in lung cancer.

Nuclear factor erythroid 2-related factor 2 in human papillomavirus-related cancers

High-risk human papillomavirus (HR-HPV) infection is a necessary cause for the development of cervical cancer. Moreover, HR-HPV is also associated with cancers in the anus, vagina, vulva, penis and oropharynx. HR-HPVs target and modify the function of different cell biomolecules, such as glucose, amino acids, lipids and transcription factors (TF), such as p53, nuclear factor erythroid 2-related factor 2 (Nrf2), among others. The latter is a master TF that maintains redox homeostasis. Nrf2 also induces the transcription of genes associated with cell detoxification. Since both processes are critical for cell physiology, Nrf2 deregulation is associated with cancer development. Nrf2 is a crucial molecule in HPV-related cancer development but underexplored. Moreover, Nrf2 activation is also associated with resistance to chemotherapy and radiotherapy in these cancers. This review focusses on the importance of Nrf2 during HPV-related cancer development, resistance to therapy and potential therapies associated with Nrf2 as a molecular target.

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.

Relationship between cervical esophageal squamous cell carcinoma and human papilloma virus infection and gene mutations

Cervical esophageal squamous cell carcinoma (CESCC) is rare, accounting for 5% of all esophageal carcinomas. Several diagnostic and predictive markers have been studied. However, to the best of our knowledge, no biomarker is known to determine patient management except the clinical stage. The present study aimed to evaluate whether human papilloma virus (HPV) infection, epidermal growth factor receptor (EGFR) and its pathway-related gene mutations, known to be sensitive biomarkers of oropharyngeal carcinomas, could be used as biomarkers for the prediction of the prognosis of patients with CESCC. The present retrospective study included patients with CESCC who received chemoradiotherapy or surgery. HPV infection and the genomic status of EGFR, KRAS, BRAF, NRAS and PIK3CA of each tumor sample from patients with CESCC were analyzed by in situ hybridizations (ISH) and PCR methods, respectively. The present study included 33 patients with CESCC (male/female, 29/4; median age, 62 years; age range, 41-86 years; clinical stage I/II/III/IV, 2/6/10/15). The present study detected HPV in one patient (3.0%) by ISH and PCR. Concerning the investigation of EGFR and its pathway-related gene mutations, the present study detected 15.1% of EGFR, 6.0% of NRAS, 3.5% of BRAF, 3.0% of KRAS and 3.0% for PIK3CA mutations, with no significant relationship between any gene mutations and the clinical prognostic factors. The HPV-infected patient did not exhibit any gene mutations. The present study indicated that HPV infection, EGFR and its pathway-related gene mutations rarely exist in patients with CESCC. The relationship between these biomarkers and the prognosis in patients with CESCC is still unclear.

Synergistic Carcinogenesis of HPV18 and MNNG in Het-1A Cells through p62-KEAP1-NRF2 and PI3K/AKT/mTOR Pathway

N-methyl-N´-nitro-N-nitrosoguanidine is a clear carcinogen, increasing evidence that indicates an etiological role of human papillomavirus in esophageal carcinoma. Studies have reported the synergistic effect on environmental carcinogens and viruses in recent years. On the basis of establishing the malignant transformation model of Het-1A cells induced by synergistic of HPV18 and MNNG, this study was to explore the synergistic carcinogenesis of MNNG and HPV. Our research indicated that HPV&MNNG led to a significant increase in the protein-expression levels of c-Myc, cyclinD1, BCL-2, BAX, E-cadherin, N-cadherin, mTOR, LC3II, and p62, with concomitant decreases in p21 and LC3I. HPV18 and MNNG induced accumulation of p62 and its interaction with KEAP1, which promoted NRF2 nuclear translocation. p62 loss prevents growth and increases autophagy of malignant cells by activating KEAP1/NRF2-dependent antioxidative response. In addition, PI3K and p-AKT were stimulated by HPV&MNNG, and PI3K/AKT/mTOR is positively associated with cell proliferation, migration, invasion, and autophagy during malignant transformation. Taken together, MNNG&HPV regulates autophagy and further accelerates cell appreciation by activating the p62/KEAP1/NRF2 and PI3K/AKT/mTOR pathway. MNNG&HPV may improve Het-1A cell autophagy to contribute to excessive cell proliferation, reduced apoptosis, and protection from oxidative damage, thus accelerating the process of cell malignant transformation and leading to cancerous cells.

Relationships of early esophageal cancer with human papillomavirus and alcohol metabolism

BACKGROUND

It is well known that an alcohol consumption habit together with inactive heterozygous aldehyde dehydrogenase-2 (ALDH2) is an important risk factor for the development of esophageal squamous cell carcinoma (ESCC). It remains controversial whether human papillomavirus (HPV) infection contributes to the occurrence/development of ESCC. There has been no study in which the relationship between ESCC and HPV in addition to alcohol dehydrogenase-1B (ADH1B) and ALDH2 genotypes was evaluated.

AIM

To evaluate relationships between HPV infection and development of esophageal cancer, particularly early esophageal cancer, based on ADH1B/ALDH2 polymorphisms.

METHODS

We conducted an exploratory retrospective study using new specimens, and we enrolled 145 patients who underwent endoscopic resection for superficial ESCC and had been observed for more than two years by both physical examination and endoscopic examination in Hokkaido University Hospital. Saliva was collected to analyze genetic polymorphisms of ADH1B/ALDH2. We performed in situ hybridization for resected specimens to detect HPV by using an HPV type 16/18 probe.

RESULTS

HPV was detected in 15 (10.3%) of the 145 patients with ESCC. HPV-positive rates in inactive ALDH2*1/*2 and ALDH2*1/*1 + *2/*2 were 10.8% and 9.8%, respectively (P = 1.00). HPV-positive rates in slow-metabolizing ADH1B*1/*1 and ADH1B*1/*2 + *2/*2 were 12.0% and 10.0%, respectively (P = 0.72). HPV-positive rates in the heavy or moderate alcohol consumption group and the light or rare consumption group were 11.1% and 8.7%, respectively (P = 0.68). HPV-positive rates in the heavy smoking group and the light or no smoking group were 11.8% and 8.3%, respectively (P = 0.59). The 3-year incidence rates of secondary ESCC or head and neck cancer after initial treatment in the HPV-positive and HPV-negative groups were 14.4% and 21.4% (P = 0.22), respectively.

CONCLUSION

In the present situation, HPV status is considered to be less important than other risk factors, such as alcohol consumption, smoking habit, ADH1B/ALDH2 polymorphisms, and HPV status would therefore have no effect on ESCC risk management.

Expression and role of p16 and GLUT1 in malignant diseases and lung cancer: A review

Non‐small cell lung cancer (NSCLC) is the leading cause of cancer death and in most cases it is often diagnosed at an advanced stage. Many genetic and microenvironmental factors are able to modify the cell cycle inducing carcinogenesis and tumor growth. Among the metabolic and genetic factors that come into play in carcinogenesis and tumor cell differentiation and growth there are two different proteins that should be considered which are glucose transporters (GLUTs) and p16^INK4 The first are glucose transporters which are strongly involved in tumor metabolism, notably accelerating cancer cell metabolism both in aerobic and anaerobic conditions. There are different subtypes of GLUT family factors of which GLUT 1 is the most important and widely expressed. By contrast, p16 is mainly a tumor‐suppressor protein that acts on cyclin‐dependent kinase favoring cell cycle arrest in the G1 phase. Our search focused on the action of the aforementioned factors.

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.

Human papillomavirus prevalence in lung carcinomas in Bulgaria

A possible association between high-risk human papillomaviruses (HPV) and lung cancer has been investigated for decades with discrepant results. The aim of this study was to determine the prevalence of HPV16 and 18 in Bulgarian patients with lung cancer. Two hundred and nine biopsy specimens from patients with histologically proven lung cancer and without cancer were analyzed. Each sample was subjected to three parallel PCRs using broad spectrum GP5+/6+ primers and type-specific (TS) primers for HPV types 16 and 18. Of the 132 lung carcinoma samples, 33 (25%) were positive for HPV16 and/or HPV18 by TS PCR whereas only five (3.8%) samples were HPV positive by consensus PCR. All non-malignant controls were HPV negative. HPV18 was the more prevalent, being found in 11.4% of samples, followed by HPV16 in 9.1% samples; 4.5% of lesions were positive for both HPV16 and HPV18. HPV16/18 were most prevalent in small cell carcinoma (29.2%) and least prevalent in squamous cell carcinoma (23.3%). HPV was only detected in squamous cell carcinoma and adenosquamous carcinoma by consensus PCR. This study revealed a high HPV16/18 prevalence in lung carcinoma samples from Bulgarian patients when TS PCR was used to detect them. The difference between HPV positivity as detected by consensus and by TS PCR was significant, indicating the importance of methodological issues in explaining the discrepancies between previous studies. HPV18 was more common than HPV16. No association between HPV16/18 status and histopathological diagnosis was identified.

Human papillomavirus and lung cancinogenesis: an overview

Lung cancer is the most common cause of cancer deaths worldwide. Although tobacco smoking is considered to be the main risk factor and the most well-established risk factor for lung cancer, a number of patients who do not smoke have developed this disease. This number varies between 15 % to over one-half of lung cancer cases, and the deaths from lung cancer in non-smokers are increasing every year. There are many other agents that are thought to be etiological, including diesel exhaust exposure, metals, radiation, radon, hormonal factors, cooking oil, air pollution and infectious diseases, such as human papillomavirus (HPV). Studies in various parts of the world have detected HPV DNA at different rates in lung tumors. However, the role of HPV in lung cancer is still unclear. Thus, in this review, we investigated some molecular mechanisms of HPV protein activity in host cells, the entry of HPV into lung tissue and the possible route used by the virus to reach the lung cells.

Differential diagnosis between primary lung squamous cell carcinoma and pulmonary metastasis of head and neck squamous cell carcinoma

Differentiation between lung squamous cell carcinoma and pulmonary metastasis of head and neck squamous cell carcinoma is clinically important because the prognoses and therapeutic options are considerably different. However, the clinical, pathological, and immunohistochemical diagnostic methods have not yet been fully established. Although various molecular methods have been developed, they have not yet been practically applied. A combined approach involving molecular and immunohistochemical analysis, such as one that uses antibodies selected on the basis of comprehensive genetic analysis results, may be effective. We suggest a new diagnostic criteria using the clinical characteristics and the result of immunohistochemical analysis. However, there are two underlying problems in the development of new diagnostic methods: tumor heterogeneity and determination of the diagnostic accuracy.

The role of human papillomavirus in head and neck squamous cell carcinoma: A case control study on a southern Chinese population

HPV plays a role in the development of a portion of head and neck squamous cell carcinoma (HNSCC), but only limited information on its role in southern Chinese population is available. A multicenter case-control study was conducted. HPV type, viral integration, E6/7 mRNA expression status, and TP53 mutation were determined. A total of 228 HNSCC were recruited including 137 (60.1%) oral SCC, 34 (14.9%) oropharyngeal SCC, 31 (13.6%) laryngeal SCC, 21 (9.2%) hypopharyngeal SCC, and 5 (2.2%) lip and paranasal sinus SCC. High-risk HPV infection was found in 7.5% (17/228) of HNSCC, but only a small proportion of samples had evidence of viral integration (5.3%, 12/228) or E6/7 mRNA expression (4.4%, 10/228). HPV infection with oncogenic phenotype (integration and E6/7 mRNA expression) was significantly more common in oropharyngeal SCC than controls (9/34, 26.5% vs. 0/42, 0.0%, P < 0.001). Smoking showed a significant association with HNSCC, oropharyngeal SCC, and laryngeal SCC. TP53 mutation was associated with HNSCC (P < 0.001). Older age, TP53 mutation, and HPV16 infection with oncogenic phenotypes were independently associated factors for HNSCC with odds ratios of 1.03 (1.02-1.05), 3.38 (1.71-6.66), and 9.19 (1.13-74.68), respectively. High-risk HPV infection of head and neck mucosa is not uncommon in the Hong Kong population. This study found that 26-30% of oropharyngeal carcinoma was associated with HPV infection, mostly HPV16, and that smoking which predisposes to TP53 mutations was another important risk factor.

Detection of human papillomavirus in esophageal and gastroesophageal junction tumors: A retrospective study by real-time polymerase chain reaction in an instutional experience from Turkey and review of literature

Esophageal cancer is a poor-prognosis malignancy that ranks eighth among all cancer types, and its prevalence shows differences among geographical regions. Although the most important risk factors for esophageal carcinoma are alcohol and smoking, viral infections, particularly HPV infection, are also considered among etiological agents. Our study aims to detect the presence of HPV in esophageal cancers in our patient population and to investigate its correlation with clinico-pathological parameters. We investigated the presence of HPV-DNA by real-time polymerase chain reaction in a total of 52 patients with esophageal cancer. Subtype analysis was performed in positive cases and was correlated with selected clinico-pathological parameters. Five (9.6%) of 52 tumor samples, 3 squamous cell carcinomas (3/33 cases) and 2 adenocarcinomas (2/19 cases), were HPV-DNA-positive. Subtype analysis could be performed in four HPV-DNA-positive cases, of which three were HPV type-39 and 1 was type-16. The Marmara region, where the present study was carried out, is a region with low-moderate risk for esophageal cancer, and the prevalence of HPV-DNA in these tumors is similar to the prevalence of HPV-DNA reported in the literature for regions with similar risk. In conclusion, we detected HPV DNA in a subset of esophageal and gastroesophageal junction tumors. HPV infection may have a role in esophageal carcinogenesis and high-risk HPV subtypes can particularly be considered among risk factors since the prevalence of high risk HPV infection has also been found to be increased in regions with a high risk for esophageal cancer compared to low-moderate risk regions.

Heterozygote of TAP1 Codon637 decreases susceptibility to HPV infection but increases susceptibility to esophageal cancer among the Kazakh populations

Background

The role of human papillomavirus (HPV) may be involved in the development of esophageal cancer (EC) and the polymorphic immune response gene transporter associated with antigen processing (TAP) may be involved in HPV persistence and subsequent cancer carcinogenesis. The current study aims to provide association evidence for HPV with EC, to investigate TAP1 polymorphisms in EC and assess its association with HPV statuses and EC in Kazakhs.

Methods

The HPV genotypes in 361 patients with EC and 66 controls selected from Kazakh population were evaluated using PCR. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to detect two SNPs of TAP1 in 150 cases comprised of 75 HPV⁺ and 75 HPV^- patients and 283 pure ethnic population of Kazakh and evaluate their associations with susceptibility to EC. A case-to-case comparison based on the genotyping results was conducted to address the function of TAP1 variants in the involvement of HPV.

Results

The presence of four HPV genotypes in EC tissues ― including HPV 16, 18, 31, 45 ― was significantly higher at 64.6 % than those in controls at 18.2 % (P < 0.001). Such presence was strongly associated with increased risk of EC (OR 8.196; 95 % CI 4.280–15.964). The infection of HPV16, and multi-infection of 16 and 18 significantly increase the risk for developing EC (OR 4.616, 95 % CI 2.099–10.151; and OR 6.029, 95 % CI 1.395–26.057 respectively). Heterozygote of TAP1 D637G had a significantly higher risk for developing EC (OR 1.626; 95 % CI 1.080–2.449). The odds ratio for HPV infection was significantly lower among carriers of TAP1 D637G polymorphism (OR 0.281; 95 % CI 0.144–0.551).

Conclusions

HPV infection exhibits a strong positive association with the risk of EC in Kazakhs. Heterozygote of TAP1 D637G decreases susceptibility to HPV infection in patients with EC but increases susceptibility to EC among the Kazakh populations.

Association between human papillomavirus (HPV) and oesophageal squamous cell carcinoma: a meta-analysis

SUMMARY

The oncogenic potential of human papillomaviruses (HPV) is well known in the context of cervical carcinoma; however, their role in the development of oesophageal squamous cell carcinoma (OSCC) is less clear. We aimed to determine the extent of the association between HPV infection and OSCC. A comprehensive literature search found 132 studies addressing HPV and OSCC in human cases, and a meta-analysis was performed using a random-effects model. There was evidence of an increased risk of OSCC in patients with HPV infection [odds ratio (OR) 2·69, 95% confidence interval (CI) 2·05-3·54]. The prevalence of HPV in OSCC was found to be 24·8%. There was an increased risk associated with HPV-16 infection (OR 2·35, 95% CI 1·73-3·19). Subgroup analyses showed geographical variance, with Asia (OR 2·94, 95% CI 2·16-4·00), and particularly China (OR 2·85, 95% CI 2·05-3·96) being high-risk areas. Our results confirm an increase in HPV infection in OSCC cases.

Role of Human papilloma virus infection and altered methylation of specific genes in esophageal cancer

BACKGROUND

Evaluation of Human papilloma virus (HPV) and its association with promoter methylation of candidate genes, p53 and Aurora A in esophageal cancer.

MATERIALS AND METHODS

One hundred forty-one esophageal tissue samples from different pathologies were evaluated for HPV infection by PCR, while the promoter methylation status of p53 and Aurora A was assessed by methylation-specific restriction based PCR assay. Statistical analyses were performed with MedCalc and MDR software.

RESULTS

Based on endoscopy and histopathology, samples were categorized: cancers (n=56), precancers (n=7), esophagitis (n=19) and normals (n=59). HPV infection was found to be less common in cancers (19.6%), whereas its prevalence was relatively high in precancers (71.4%), esophagitis (57.8%) and normals (45.7%). p53 promoter methylation did not show any significant difference between cancer and normal tissues, whereas Aurora A promoter methylation demonstrated significant association with disease (p=0.00016, OR:5.6452, 95%CI:2.18 to 14.6) when compared to normals. Aurora A methylation and HPV infection was found in a higher percentages of precancer (66.6%), esophagitis (54.5%) and normal (45.2%) when compared to cancers (14.2%).

CONCLUSIONS

Aurora A promoter methylation is significantly associated with esophageal cancer, but the effect of HPV infection on this epigenetic alteration is not significant. However MDR analysis showed that the hypostatic effect of HPV was nullified when the cases had Aurora methylation and tobacco exposure. Further HPV sub-typing may give an insight into its reduced prevalence in esophageal cancer verses normal tissue. However, with the present data it is difficult to assign any significant role to HPV in the etiopathology of esophageal cancer.

Prevalence of human papillomavirus among oesophageal squamous cell carcinoma cases: systematic review and meta-analysis

Background:

Oncogenic human papillomavirus (HPV) has been hypothesised as a risk factor for oesophageal squamous cell carcinoma (OSCC), but aetiological research has been limited by the varying methodology used for establishing HPV prevalence. The aims of this systematic review and meta-analysis were to estimate the prevalence of HPV DNA detected in OSCC tumours and the influence of study characteristics.

Methods:

Study-level estimates of overall and type-specific HPV prevalence were meta-analysed to obtain random-effects summary estimates.

Results:

This analysis included 124 studies with a total of 13 832 OSCC cases. The average HPV prevalence (95% confidence interval) among OSCC cases was 0.277 (0.234, 0.320) by polymerase chain reaction; 0.243 (0.159, 0.326) by in situ hybridisation; 0.304 (0.185, 0.423) by immunohistochemistry; 0.322 (0.154, 0.490) by L1 serology; and 0.176 (0.061, 0.292) by Southern/slot/dot blot. The highest HPV prevalence was found in Africa and Asia, notably among Chinese studies from provinces with high OSCC incidence rates.

Conclusions:

Future research should focus on quantifying HPV in OSCC cases using strict quality control measures, as well as determining the association between HPV and OSCC incidence by conducting large, population-based case–control studies. Such studies will provide a richer understanding of the role of HPV in OSCC aetiology.

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.

Systematic review with meta-analysis: the association between human papillomavirus infection and oesophageal cancer

BACKGROUND

Human papillomavirus (HPV) infection might be one of the potential risk factors for oesophageal cancer. However, the previous epidemiological findings were heterogeneous.

AIM

To explore the association between HPV infection and oesophageal cancer risk by means of meta-analysis.

METHODS

Studies on HPV infection and oesophageal cancer were identified, the prevalence of HPV infection and its association with oesophageal cancer risk were quantitatively summarised by meta-analysis.

RESULTS

A total of 8990 oesophageal squamous cell carcinoma (SCC) patients and 174 oesophageal adenocarcinomas patients were evaluated from 76 included studies. Summarised HPV prevalence in oesophageal SCC was 22.2% [95% confidence interval (CI), 18.3-26.7%], HPV-16 was the most frequently observed subtype with a summarised prevalence of 11.4% (95% CI: 8.2-15.7%). With respect to oesophageal adenocarcinoma, HPV prevalence was 35.0% (95% CI, 13.2-65.7%) and HPV-16 prevalence was 11.4% (95% CI: 8.2-15.7%). Due to the limited number of included studies on oesophageal adenocarcinoma, association analyses were performed to oesophageal SCC only. Significant association was observed between HPV infection and oesophageal SCC with a summarised odds ratio of 3.32 (95% CI, 2.26-4.87). According to HPV-16, the strength of the association was found to be 3.52 (95% CI, 2.04-6.07).

CONCLUSIONS

Human papillomavirus infection was observed to be associated with an increased risk of oesophageal SCC in this meta-analysis. However, due to the evident heterogeneity observed between the included studies and the strength of the association not as strong as observed for cervical cancer and laryngeal cancer, further studies are needed to clarify the relation and its underlying mechanisms.

Role of human papillomaviruses in esophageal carcinoma: an updated systematic review from 1982 to 2013

ABSTRACT: 

Tobacco, alcohol and betel quid are known etiological agents of esophageal squamous cell carcinoma (ESCC). A meta-analysis in 2012 and a literature update (1982–August 2013) identified 159 studies with a total of 11,310 ESCCs tested for the presence of human papillomaviruses (HPVs). HPV DNA was present in 30.3% of fESCCs, with substantial geographic differences. A recent meta-analysis of 21 case–control studies investigating the HPV–ESCC association showed that HPVs increase the risk of ESCC at least threefold. Vaccine-preventable HPV-16 and HPV-18 are the most commonly identified HPV types in ESCC in both low- and high-incidence settings. HPVs should now be seriously considered as etiological agents for at least a subset of ESCC, and more studies are needed to provide conclusive evidence that HPVs cause ESCC.

Detection and genotype analysis of human papillomavirus in non-small cell lung cancer patients

Although the role of human papillomavirus (HPV) in the development of uterine cervical cancer is well established, the role of HPV in lung carcinogenesis remains controversial. The detection rates of HPV DNA are subject to a wide variation from 0 to 100%. This is partly influenced by the detection techniques employed. To elucidate the impact of HPV infection on lung parenchyma, we analyzed 100 non-small cell lung cancer (NSCLC) specimens (39 squamous cell carcinomas, 50 adenocarcinomas, 5 samples with characteristics of both squamous cell and adenocarcinoma, 5 undifferentiated and 1 large cell carcinoma) from the region of Crete, Greece. Sixteen non-cancerous samples served as the negative controls. DNA was extracted from 100 paraffin-embedded tissue sections obtained from NSCLC patients. The specimens were examined for the detection of HPV DNA by Real-Time PCR using GP5+/GP6+ primers. Furthermore, the HPV-positive samples were subjected to genotyping. In contrast to the absence of viral genomes in the control samples, HPV DNA was detected in 19 NSCLC specimens (19%). In particular, 4 squamous cell carcinomas, 12 adenocarcinomas, 1 sample with characteristics of both squamous cell and adenocarcinoma, and 2 undifferentiated samples were HPV-positive. The distribution of HPV genotypes was as follows: HPV 16: eight cases (42.1%); HPV 11: three cases (15.8%); HPV 6: one case (5.2%); HPV 59: one case (5.2%); HPV 33: two cases (10.5%); HPV 31: two cases (10.5%) and HPV 18: two cases (10.5%). The presence of HPV in the tumor samples provides evidence of the potential role of HPV in NSCLC and strongly argues for additional research on this issue.

Distinct genetic aberrations in oesophageal adeno and squamous carcinoma

BACKGROUND

The two main oesophageal cancer subtypes namely adenocarcinoma and squamous cell carcinoma exhibit interesting clinical, pathological and geographical variations with the former being more common in the West and the latter in Asia.

MATERIALS AND METHODS

We evaluated status of p53, EGFR, Wnt and HPV in addition to microsatellite instability and loss of heterozygosity of several chromosomal loci in the two oesophageal cancer subtypes from India. The comparative analysis was extended to two oesophageal adenosquamous mixed cancer samples.

RESULTS

Our results reveal a high frequency of EGFR overexpression in ESCC as against EAC, while Wnt activation was a significantly more common event in EAC as against ESCC. Frequencies of p53 perturbations were not significantly different in the two subtypes. Interestingly, the EGFR and Wnt status in adenocarcinoma and squamous components of the two oesophageal adenosquamous cancer samples were identical to primary tumours. In addition, no common molecular aberration (including instability and loss of heterozygosity) in several microsatellites was detected in DNA isolated from the two components in both adenosquamous cancer samples.

CONCLUSIONS

Our results reveal the presence of distinct aberrations in oesophageal adenocarcinoma and squamous cell carcinoma which are replicated in the respective components of adenosquamous cancers. The study therefore suggests perhaps an independent origin of the two components of oesophageal adenosquamous mixed cancer.

Heterozygote of PLCE1 rs2274223 increases susceptibility to human papillomavirus infection in patients with esophageal carcinoma among the Kazakh populations

The involvement of human papillomavirus (HPV) in the carcinogenesis of esophageal squamous carcinoma remains undetermined. However, three genome-wide association studies of esophageal cancer have identified a shared susceptibility locus at 10q23 (rs2274223: A5780G) in phospholipase C epsilon 1 (PLCE1). The current study aims to present a comprehensive and novel spectrum about the HPV genotype distribution of esophageal carcinoma in Kazakhs and assess its association with PLCE1 polymorphisms. The HPV genotypes in 183 patients with esophageal cancer and 89 controls selected from the Kazakh population were evaluated using the HPV gene chip. The PLCE1 rs2274223 variant was genotyped in esophageal carcinoma patients by MALDI-ToF Mass Spectrometry. The presence of seven HPV genotypes in esophageal carcinoma tissues-including HPV 16, 18, 35, 52, 6, 11, 43-was significantly higher at 31.7% than those in controls at 9.0% (P < 0.001). Such presence was strongly associated with increased risk of esophageal carcinoma (OR 4.70; 95% CI 2.13-10.36). Among all HPV genotypes detected, HPV16 was the most common genotype identified (29.0%, OR 4.13; 95% CI 1.87-9.13), which is significantly associated with well-differentiated esophageal carcinoma (P = 0.037). HPV-positive patients were generally younger than HPV-negative patients (70.1% vs. 29.3%, P = 0.013). PLCE1 rs2274223 genotypes AG and AG/GG were significantly associated with HPV-positive patients with esophageal carcinoma (OR 2.05, 95% CI 1.03-4.08 and OR 1.98, 95% CI 1.02-3.84, respectively). These findings suggest that heterozygote of PLCE1 rs2274223 increases susceptibility to HPV infection in patients with esophageal carcinoma among the Kazakh populations.

The ‘Trojan horse’ oncogenic strategy of HPVs in childhood

HPVs are considered to be the principal cause of cervical cancer worldwide. During the last decade, their possible oncogenic involvement has also been proposed in a substantial proportion of nongenital cancers, such as breast and lung cancer. The presence of high-risk HPVs in the neonatal oral mucosa supports the transmission of HPVs from the mother to her newborn. This review presents current evidence that supports the perinatal transmission of high-risk HPVs and suggests that this may be the initial step of the oncogenic strategy of high-risk HPVs in humans. The hypothesis that children are a unique reservoir of silent high-risk HPVs, analogously to the Trojan horse, should be investigated further.

Human papillomavirus types 16 and 18 in esophagus squamous cell carcinoma: a meta-analysis

PURPOSE

A possible carcinogenic role of human papillomavirus (HPV) has been investigated in esophageal squamous cell carcinoma (ESCC) for nearly 30 years with mixed results. We performed a meta-analysis to assess the prevalence of "high-risk" HPV, HPV-16/18, in this disease. We also evaluated the association between infection with HPV-16/18 and ESCC risk by meta-analysis of case-control studies.

METHODS

Eligible studies published up to September 30, 2012 were retrieved via both computer searches of MEDLINE and EMBASE and manual review of references. A random-effects model was used to calculate summary prevalence and odds ratios (ORs) and corresponding 95% confidence intervals (CIs).

RESULTS

A total of 5755 cases of ESCC from 68 studies were included in this meta-analysis. Overall, 11.67% (95% CI, 7.74%-16.21%) of ESCC cases harbored HPV-16 and 1.82% (95% CI, 0.90%-2.95%) harbored HPV-18. In addition, meta-analysis of 10 case-control studies showed a significant increase in ESCC risk with HPV-16 infection (summary ORs = 3.55; 95% CIs, 2.05%-6.14%). However, this increased risk in ESCC was not made for HPV-18 infection (summary ORs = 1.25; 95% CIs, 0.46%-3.43%).

CONCLUSIONS

This meta-analysis indicated that HPV-16 and -18 can be detected in ESCC. HPV-16, but not HPV-18, is significantly associated with the risk of ESCC. However, it is early to conclude that both types of HPV are involved in esophageal carcinogenesis.

Statistical analysis of human papillomavirus in a subset of upper aerodigestive tract tumors

Human papilloma virus (HPV) has been detected in some upper aerodigestive tract tumors, but the correlation between HPV and these tumors is not well understood. There is also some controversy regarding this correlation because a large variation in the prevalence of HPV in these tumors has been reported. To discuss the impact of HPV infection on upper aerodigestive tract tumors, this review estimated systematically the prevalence and risk of HPV in upper aerodigestive tract tumors from studies published between 1982 and 2012. In total, 418 articles were selected, which included 273 studies on the head and neck and 145 studies on esophageal squamous cell carcinoma. The overall prevalence of HPV in the 5,467 head and neck squamous cell carcinoma specimens was 36.3%. HPV was detected more frequently in the Americas (40%), than in Asia (38.6%), Europe (32%), or others regions (30.5%). The prevalence of HPV was significantly higher in oropharyngeal (48.5%) than in oral (32.5%), laryngeal (30.7%), and unselected head and neck squamous cell carcinoma (33.3%) (P < 0.001). The pooled prevalence of HPV in the 6,912 esophageal squamous cell carcinoma cases was 38.9% and it was significantly higher in China (44%) versus other regions (31.3%) (P < 0.05). Meta-analysis showed that head and neck and esophageal squamous cell carcinoma are associated with HPV infection (combined OR: 3.58, OR for head and neck and esophageal squamous cell carcinoma: 4.20). These findings suggest that HPV might be linked etiologically to the development of some upper aerodigestive tract tumors.

The evaluation of older patients with cervical cancer

Objective

The number of elderly patients being diagnosed with cervical cancer is increasing, and the outcome of cervical cancer related to age is controversial. We conducted a retrospective analysis in patients treated for advanced cervical cancer in order to investigate patient characteristics and prognosis of older patients.

Methods

Medical records were collected of 159 patients with cervical cancer who had been treated with radiotherapy or combined radiotherapy and chemotherapy from January 2007 to January 2009. The patients were divided into two age groups: (1) patients ≥65 years old, and (2) patients <65 years old. There were 52 women in group 1, 107 in group 2. Prognosis, patient characteristics, treatment, and toxicities were evaluated.

Results

With a median follow-up of 36.5 months, local control for groups 1 and 2 was 88.5% and 79.4%, respectively. Disease-free survival for the two groups was 71.2% and 67.3%; overall survival was 73.1% and 72.9%. As shown by univariate analyses, there was no statistically significant difference between the two groups (P > 0.05). Seventy-six patients had human papillomavirus (HPV) at diagnosis (twelve women ≥65 years, 64 women ≤65 years; P = 0.000). Forty-two women tested positive for HPV 16, while 32 women tested positive for HPV 18 respectively. Pelvic and/or paraaortic lymph-node metastasis was found in 25 patients (eight in group 1, 17 in group 2; P = 0.960) on computed tomography scan. Of the 159 patients analyzed, sixteen patients (16/52) in group 1 received concurrent chemotherapy, while 96 (96/107) in group 2 completed that treatment.

Conclusions

Cervical cancer has the same prognosis in old and young women. Age may not be an independent increased risk of death in women with cervical cancer, and the age-group is at lower risk for virulent HPV strands (HPV 16/18) compared to younger patients. Treatment recommendations were implemented less often for older patients. Radiotherapy remained the most common treatment chosen for elderly patients. This confirms that there is a stronger need to pay attention to the elderly patient.

Detection of Merkel cell polyomavirus with a tumour-specific signature in non-small cell lung cancer

Background:

We searched for a viral aetiology for non-small cell lung cancer (NSCLC), focusing on Merkel cell polyomavirus (MCPyV).

Methods:

We analysed 112 Japanese cases of NSCLC for the presence of the MCPyV genome and the expressions of RNA transcripts and MCPyV-encoded antigen. We also conducted the first analysis of the molecular features of MCPyV in lung cancers.

Results:

PCR revealed that 9 out of 32 squamous cell carcinomas (SCCs), 9 out of 45 adenocarcinomas (ACs), 1 out of 32 large-cell carcinomas, and 1 out of 3 pleomorphic carcinomas were positive for MCPyV DNA. Some MCPyV DNA-positive cancers expressed large T antigen (LT) RNA transcripts. Immunohistochemistry showed that MCPyV LT antigen was expressed in the tumour cells. The viral integration sites were identified in one SCC and one AC. One had both episomal and integrated/truncated forms. The other carried an integrated MCPyV genome with frameshift mutations in the LT gene.

Conclusion:

We have demonstrated the expression of a viral oncoprotein, the presence of integrated MCPyV, and a truncated LT gene with a preserved retinoblastoma tumour-suppressor protein-binding domain in NSCLCs. Although the viral prevalence was low, the tumour-specific molecular signatures support the possibility that MCPyV is partly associated with the pathogenesis of NSCLC in a subset of patients.

Why are East Asians more susceptible to several infection-associated cancers (carcinomas of the nasopharynx, stomach, liver, adenocarcinoma of the lung, nasal NK/T-cell lymphomas)?

There are at least five cancers with uniquely high incidence amongst East and Southeast Asian ethnic groups - namely nasopharyngeal carcinoma (NPC); gastric carcinoma; hepatocellular carcinoma (HCC); adeno-carcinoma of the lung in female non-smokers and nasal NK/T-cell lymphomas. They all appear to be related to an infective cause (Epstein Barr Virus, Helicobacter pylori, hepatitis B virus). We hypothesize that a genetic bottleneck 30,000years ago at the Last Glacial Maximum could have resulted in unique genetic polymorphisms in Toll-like receptor 8, making East Asians more vulnerable to these infective associated cancers. This bottleneck could have been caused by the presence of malaria in the southern Himalayan conduit between central and East Asia; and only those with an attenuated innate immune response to the malarial parasite (perhaps reflected by the TLR8 polymorphism) were spared the ravages of cerebral malaria; allowing these people to cross into east Asia, but then rendering them susceptible to later endemic infections and their associated cancers.

Role of human papillomaviruses in esophageal squamous cell carcinoma

Esophageal cancer (EC) is responsible for almost half a million deaths worldwide annually and has a multifactorial etiology, which may account for its geographical variation in incidence. In the last 30 years the potential of human papillomaviruses (HPV) as oncogenes or co-factors in the tumorigenic process of esophageal squamous cell carcinoma (ESCC) has been widely studied. While the etiology of HPV in cervical and certain other anogenital and aerodigestive cancers has been established, results regarding its role in EC have been largely inconclusive. A causal association can be evaluated only with a case-control study, where normal controls are compared to ESCC cases for the presence of HPV. We reviewed all studies investigating ESCC tissue for HPV DNA and identified 139 that met our inclusion criteria, of which only 22 were case-control studies. Our results support previous findings of higher levels of HPV detection in high-risk ESCC regions than in areas of low risk. In addition, we confirm that the role of HPV in ESCC remains unclear, despite an accumulation of studies on the subject. The variations in investigative technique, study design and sample types tested may account for the lack of consistency in results. There is a need for a meta-analysis of all case-control studies to date, and for large, well-designed case-control studies with adequate power to investigate the association. The potential benefits of prophylactic HPV vaccines could be evaluated if HPV is identified as an etiological factor in EC, highlighting the need for further research in this area.

Geographic origin is a significant determinant of human papillomavirus prevalence in oesophageal squamous cell carcinoma: systematic review and meta-analysis

BACKGROUND

Since the first reports in 1982 suggesting an aetiological role for human papillomavirus (HPV) in a subset of oesophageal squamous cell carcinomas (ESCC), the literature reporting HPV detection in ESCC has expanded rapidly. However no formal meta-analysis of this literature has been published yet. The objective of this study was to perform a systematic review and formal meta-analysis of the literature reporting HPV detection in ESCC.

METHODS

MEDLINE and Current Contents were searched through March 2012. The effect size was calculated as event rates and their 95% confidence interval (95% CI), with homogeneity testing using Cochran's Q and I² statistics. Meta-regression was used to test the impact of study-level covariates (HPV detection method, geographic origin of study) on effect size, and potential publication bias was estimated using funnel plot symmetry (Begg and Mazumdar rank correlation, Egger's regression, and Duval and Tweedie's trim and fill method).

RESULTS

Of the 1177 abstracts found, 152 studies were determined to be eligible for this meta-analysis. These 152 studies covered a total of 10,234 ESCC cases, analysed by different HPV detection methods in different geographic regions. Of these 10,234 cases, 3135 (30.6%) tested HPV-positive, translating to an effect size of 0.372 (95% CI 0.360-0.384; fixed effects model) and 0.290 (95% CI 0.251-0.31; random effects model). When stratified by HPV detection technique, there was a significant heterogeneity between the studies, but importantly, the between-strata summary comparison was not significant (random effects model; p = 0.440). In contrast, there was significant heterogeneity between the studies from the different geographic regions. In the maximum likelihood meta-regression, HPV detection method was not a significant study-level covariate, in contrast to the geographic origin of the study, which had a significant impact (p = 0.00005) on the summary effect size estimates. No evidence for significant publication bias was found in funnel plot symmetry testing. In the sensitivity analysis, all meta-analytic results appeared robust to all (n = 151) one-by-one study removals.

CONCLUSIONS

These meta-analysis results indicate that the reported wide variability in HPV detection rates in ESCC is not due to the HPV detection techniques, but is explained by the geographic origin of the study. These data substantiate the recently elaborated concept that ESCC might have a different aetiology in low-incidence and high-incidence geographic regions, HPV playing an important role only in the latter.

Functional interaction between human papillomavirus type 16 E6 and E7 oncoproteins and cigarette smoke components in lung epithelial cells

The smoking habit is the most important, but not a sufficient cause for lung cancer development. Several studies have reported the human papillomavirus type 16 (HPV16) presence and E6 and E7 transcripts expression in lung carcinoma cases from different geographical regions. The possible interaction between HPV infection and smoke carcinogens, however, remains unclear. In this study we address a potential cooperation between tobacco smoke and HPV16 E6 and E7 oncoproteins for alterations in proliferative and tumorigenic properties of lung epithelial cells. A549 (alveolar, tumoral) and BEAS-2B (bronchial, non-tumoral) cell lines were stably transfected with recombinant pLXSN vectors expressing HPV16 E6 and E7 oncoproteins and exposed to cigarette smoke condensate (CSC) at different concentrations. HPV16 E6 and E7 expression was associated with loss of p53 stability, telomerase (hTERT) and p16(INK4A) overexpression in BEAS-2B cells as demonstrated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting (WB). In A549 cells we observed downregulation of p53 but not a significant increase of hTERT transcripts. In addition, the HPV16 E6/E7 transfected cell lines showed an increased proliferation rate and anchorage-independent growth in a HPV16 E6 and E7 expression-dependent manner. Moreover, both HPV16 E6/E7 and mock transfected cells showed an increased proliferation rate and anchorage-independent growth in the presence of 0.1 and 10 µg/mL CSC. However, this increase was significantly greater in HPV16 E6/E7 transfected cells (p<0.001). Data were confirmed by FCSE proliferation assay. The results obtained in this study are suggestive of a functional interaction between tobacco smoke and HPV16 E6/E7 oncoproteins for malignant transformation and tumorigenesis of lung epithelial cells. More studies are warranted in order to dissect the molecular mechanisms involved in this cooperation.