Mutations in TAP genes are common in cervical carcinomas

The antigen processing-associated transporter gene polymorphism: Role on gene and protein expression in HPV-infected pre-cancerous cervical lesion

Human papillomavirus (HPV) is the major pathogen for cervical lesions. The evasion mechanism of the immune response and persistence of HPV infection can be influenced by polymorphisms (SNPs) in genes associated with transporter associated with antigen processing (TAP), which may change the peptide binding affinity or the TAP expression impacting the efficiency of peptide transport in the secretory pathway, and the presentation of peptides to cytotoxic T lymphocytes. This study aimed to evaluate the role of the TAP1 and TAP2 polymorphisms, TAP1, and TAP2 genes expressions, and protein levels in cervical cells presenting different degrees of pre-cancerous lesions in 296 immunocompetent women infected or not by HPV. TAP SNPs were genotyped by Sanger sequencing, and gene expression by real-time PCR. Aneuploidy was determined by DNA index using flow cytometry. TAP-1 and TAP-2 tissue expressions were evaluated by immunohistochemistry. The Asp697Gly SNP of TAP1 presented a risk for cellular aneuploidy (P=0.0244). HPV+ women had higher TAP-2 mRNA (P=0.0212) and protein (P<0.0001) levels. The TAP2D and TAP2E haplotypes were associated with the risk for aneuploidy and pre-cancerous lesions. In conclusion, nucleotide variability at the peptide binding region of peptide transporter genes, particularly of the TAP2 gene, may influence the HPV-peptide transportation from the cytosol to the endoplasmic reticulum, increasing the susceptibility to the development of high-grade cervical lesions.

Spotlight on TAP and its vital role in antigen presentation and cross-presentation

In the late 1980s and early 1990s, the hunt for a transporter molecule ostensibly responsible for the translocation of peptides across the endoplasmic reticulum (ER) membrane yielded the successful discovery of transporter associated with antigen processing (TAP) protein. TAP is a heterodimer complex comprised of TAP1 and TAP2, which utilizes ATP to transport cytosolic peptides into the ER across its membrane. In the ER, together with other components it forms the peptide loading complex (PLC), which directs loading of high affinity peptides onto nascent major histocompatibility complex class I (MHC-I) molecules that are then transported to the cell surface for presentation to CD8+ T cells. TAP also plays a crucial role in transporting peptides into phagosomes and endosomes during cross-presentation in dendritic cells (DCs). Because of the critical role that TAP plays in both classical MHC-I presentation and cross-presentation, its expression and function are often compromised by numerous types of cancers and viruses to evade recognition by cytotoxic CD8 T cells. Here we review the discovery and function of TAP with a major focus on its role in cross-presentation in DCs. We discuss a recently described emergency route of noncanonical cross-presentation that is mobilized in DCs upon TAP blockade to restore CD8 T cell cross-priming. We also discuss the various strategies employed by cancer cells and viruses to target TAP expression or function to evade immunosurveillance - along with some strategies by which the repertoire of peptides presented by cells which downregulate TAP can be targeted as a therapeutic strategy to mobilize a TAP-independent CD8 T cell response. Lastly, we discuss TAP polymorphisms and the role of TAP in inherited disorders.

Somatic Host Cell Alterations in HPV Carcinogenesis

High-risk human papilloma virus (HPV) infections cause cancers in different organ sites, most commonly cervical and head and neck cancers. While carcinogenesis is initiated by two viral oncoproteins, E6 and E7, increasing evidence shows the importance of specific somatic events in host cells for malignant transformation. HPV-driven cancers share characteristic somatic changes, including apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC)-driven mutations and genomic instability leading to copy number variations and large chromosomal rearrangements. HPV-associated cancers have recurrent somatic mutations in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and phosphatase and tensin homolog (PTEN), human leukocyte antigen A and B (HLA-A and HLA-B)-A/B, and the transforming growth factor beta (TGFβ) pathway, and rarely have mutations in the tumor protein p53 (TP53) and RB transcriptional corepressor 1 (RB1) tumor suppressor genes. There are some variations by tumor site, such as NOTCH1 mutations which are primarily found in head and neck cancers. Understanding the somatic events following HPV infection and persistence can aid the development of early detection biomarkers, particularly when mutations in precancers are characterized. Somatic mutations may also influence prognosis and treatment decisions.

Immunological and clinical significance of HLA class I antigen processing machinery component defects in malignant cells

Experimental as well as clinical studies demonstrate that the immune system plays a major role in controlling generation and progression of tumors. The cancer immunoediting theory supports the notion that tumor cell immunogenicity is dynamically shaped by the immune system, as it eliminates immunogenic tumor cells in the early stage of the disease and then edits their antigenicity. The end result is the generation of a tumor cell population able to escape from immune recognition and elimination by tumor infiltrating lymphocytes. Two major mechanisms, which affect the target cells and the effector phase of the immune response, play a crucial role in the editing process. One is represented by the downregulation of tumor antigen (TA) processing and presentation because of abnormalities in the HLA class I antigen processing machinery (APM). The other one is represented by the anergy of effector immune infiltrates in the tumor microenvironment caused by aberrant inhibitory signals triggered by immune checkpoint receptor (ICR) ligands, such as programmed death ligand-1 (PD-L1). In this review, we will focus on tumor immune escape mechanisms caused by defects in HLA class I APM component expression and/or function in different types of cancer, with emphasis on head and neck cancer (HNC). We will also discuss the immunological implications and clinical relevance of these HLA class I APM abnormalities. Finally, we will describe strategies to counteract defective TA presentation with the expectation that they will enhance tumor recognition and elimination by tumor infiltrating effector T cells.

Recent progress in vaccination against human papillomavirus-mediated cervical cancer

It has been more than 7 years since the commercial introduction of highly successful vaccines protecting against high-risk human papillomavirus (HPV) subtypes and the development of cervical cancer. From an immune standpoint, the dependence of cervical cancer on viral infection has meant that HPV proteins can be targeted as strong tumour antigens leading to clearance of the infection and the subsequent protection from cancer. Commercially available vaccines consisting of the L1 capsid protein assembled as virus-like particles (VLPs) induce neutralising antibodies that deny access of the virus to cervical epithelial cells. While greater than 90% efficacy has been demonstrated at the completion of large phase III trials in young women, vaccine developers are now addressing broader issues such as efficacy in boys, longevity of the protection and inducing cross-reactive antibody for oncogenic, non-vaccine HPV strains. For women with existing HPV infection, the prophylactic vaccines provide little protection, and consequently, the need for therapeutic vaccines will continue into the future. Therapeutic vaccines targeting HPVE6 and E7 proteins are actively being pursued with new adjuvants and delivery vectors, combined with an improved knowledge of the tumour microenvironment, showing great promise. This review will focus on recent progress in prophylactic and therapeutic vaccine development and implementation since the publication of end of study data from phase III clinical trials between 2010 and 2012.

Association of TAP gene polymorphisms and risk of cervical intraepithelial neoplasia

BACKGROUND

Transporter associated with antigen processing (TAP) is responsible for peptide loading onto class I major histocompatibility complex (MHC-I) molecules. TAP seems to facilitate the detection of HPV by MHC-I molecules and contributes to successful eradication of HPV. TAP polymorphisms could have an important impact on the course of HPV infection.

OBJECTIVE

The aim of this study is to evaluate the association between five TAP gene polymorphisms and the risk of CIN. Methods. This case-control study investigated five common TAP polymorphisms in TAP1 (1341 and 2254) and TAP2 (1135, 1693, and 1993) in 616 women with CIN and 206 controls. Associations between gene polymorphisms and risk of CIN were analysed by univariate and multivariable models. The combined effect of the five TAP gene polymorphisms on the risk for CIN was investigated by haplotype analysis.

RESULTS

No significant difference in genotype distribution of the five TAP polymorphisms was observed in women with CIN and controls. Haplotype analysis revealed that women with haplotype mut-wt-wt-wt-wt (TAP polymorphisms t1135-t1341-t1693-t1993-t2254) had a significantly lower risk for CIN, compared to women with the haplotype wt-wt-wt-wt-wt (P = 0.006; OR 0.5 [0.35-0.84]).

CONCLUSION

Identification of this haplotype combination could be used to identify women, less susceptible for development of CIN following HPV infection.

MHC class I antigen processing and presenting machinery: organization, function, and defects in tumor cells

The surface presentation of peptides by major histocompatibility complex (MHC) class I molecules is critical to all CD8(+) T-cell adaptive immune responses, including those against tumors. The generation of peptides and their loading on MHC class I molecules is a multistep process involving multiple molecular species that constitute the so-called antigen processing and presenting machinery (APM). The majority of class I peptides begin as proteasome degradation products of cytosolic proteins. Once transported into the endoplasmic reticulum by TAP (transporter associated with antigen processing), peptides are not bound randomly by class I molecules but are chosen by length and sequence, with peptidases editing the raw peptide pool. Aberrations in APM genes and proteins have frequently been observed in human tumors and found to correlate with relevant clinical variables, including tumor grade, tumor stage, disease recurrence, and survival. These findings support the idea that APM defects are immune escape mechanisms that disrupt the tumor cells' ability to be recognized and killed by tumor antigen-specific cytotoxic CD8(+) T cells. Detailed knowledge of APM is crucial for the optimization of T cell-based immunotherapy protocols.

Prevention and treatment of papillomavirus-related cancers through immunization

Cervical and other anogenital cancers are initiated by infection with one of a small group of human papillomaviruses (HPV). Virus-like particle-based vaccines have recently been developed to prevent infection with two cancer-associated HPV genotypes (HPV16, HPV18) and have been ∼95% effective at preventing HPV-associated disease caused by these genotypes in virus-naive subjects. Although immunization induces virus-neutralizing antibody sufficient to prevent infection, persistence of antibody as measured by current assays does not appear necessary to maintain protection over time. Investigators have not identified a reliable surrogate immunological marker of protection against disease following immunization. The prophylactic vaccines are not therapeutic for existing infection. Trials of HPV-specific immunotherapy have shown some efficacy for existing disease, although animal modeling suggests that a combination of immunization and local enhancement of innate immunity may be necessary for optimal therapeutic outcome. HPV prophylactic vaccines are the first vaccines designed to prevent a human cancer and are the practical outcome of a global collaborative effort between basic and applied scientists, clinicians, and industry.

Genetic variants in TAP are associated with high-grade cervical neoplasia

PURPOSE

The transporter associated with antigen processing (TAP) is essential in assembling MHC-I proteins. Human papillomavirus (HPV) evades immune recognition by decreasing class I MHC cell surface expression through down-regulation of TAP1 levels. Consistent with heterogeneity in MHC expression is the individual variability in clearing detectable HPV infections. Genetic polymorphisms in TAP genes may affect protein structure, function, and the ability to clear HPV infection.

EXPERIMENTAL DESIGN

Case-control study of women with cervical intraepithelial neoplasia (CIN) II or III (n = 114) and women without high-grade CIN (n = 366). Five nonsynonymous single nucleotide polymorphisms (SNP) in TAP1 and TAP2 were genotyped using DNA collected in cervicovaginal lavage samples using microsphere array technology (Luminex xMAP). HPV typing was done using a PCR-based system with MY09/MY11 primers. TAP1 and TAP2 SNPs were validated by direct sequencing.

RESULTS

Differences in allele distribution between women with high-grade cervical neoplasia and women without was seen for TAP1 I333V (P = 0.02) and TAP1 D637G (P = 0.01). The odds ratios (OR) for CIN III were significantly lower among carriers of the TAP1 I333V polymorphism (OR, 0.28; 95% confidence interval, 0.1-0.8), and TAP1 D637G polymorphism (OR, 0.27; 95% confidence interval, 0.1-0.7). These associations remained significant even after restricting the evaluation to women who were positive for high-risk HPV types.

CONCLUSIONS

In addition to the down-regulation of MHC-1 by oncogenic HPV, HPV pathogenesis might be facilitated by polymorphisms in the TAP proteins. Identifying TAP polymorphisms may potentially be used to identify women less susceptible to progression to high-grade CIN and cervical cancer.

No association of TAP1 and TAP2 genes polymorphism with risk of cervical cancer in north Indian population

BACKGROUND

Transporter associated with antigen processing (TAP), a member of the ATP-binding cassette transporter super family, is composed of two integral membrane proteins, TAP-1 and TAP-2. The TAP gene product is involved in the processing of endogenous peptides that bind to MHC class I molecules. Mutations and/or polymorphism within these genes could alter the efficacy of the immune response which might be relevant for the development of autoimmune diseases and cancer.

METHODS

DNA was isolated from peripheral blood sample of 200 patients with cervical cancer and 200 healthy controls. TAP1 and TAP2 allele polymorphism were determined by polymerase chain reaction.

RESULT

Significant protective OR (OR = 0.22 95% CI = 0.09-0.51, P < 0.001-OR = 0.47, 95% CI = 0.24-0.92, P = 0.02) was observed for GG and combined AG+GG genotypes of TAP2 in patients with SCC respectively. Similarly, such genotypes (GG, AG+GG) appeared same OR for patient with cervical cancer in study group (OR = 0.12, 95% CI = 0.04-0.39-P < 0.001-OR = 0.5 ,95% CI = 0.25-0.95-P = 0.03). There was decrease risk of cervical cancer in user of oral contraceptive with AG and GG genotypes of TAP2 (OR = 0.55, 95% Cl = 0.41-0.73, P = 0.002, OR = 0.09, 95% CI = 0.02-0.36, P < 0.001) respectively. In case of TAP1 gene all allelic polymorphisms showed a decrease OR in patients with cervical cancer in passive smokers and user of oral contraceptives, though, no significant

CONCLUSION

Thus, TAP1 and TAP2 genes polymorphism are not linked to cervical carcinoma, since no association was found between a particular genotype and the disease.

Genetic variation of antigen processing machinery components and association with cervical carcinoma

The antigen processing machinery (APM) plays an important role in immune recognition of virally infected and transformed cells. Defective expression of several APM components is associated with progression and clinical outcome in cervical carcinoma. Genetic variation in the genes encoding APM components is known to be associated with risk of occurrence of several malignancies. However, only limited evidence exists supporting the role of single nucleotide polymorphisms (SNPs) in APM components in cervical carcinoma. We have therefore investigated the occurrence of APM component SNP genotypes and haplotypes in cervical carcinoma. Thirteen coding SNPs in the LMP2, LMP7, TAP1, TAP2, and ERAP1 genes were genotyped in 127 cervical carcinoma patients and 124 controls. Individual genotype and allele distributions were assessed by single-marker analysis. Effects of various SNP combinations were estimated by haplotype construction and subsequent haplotype interaction analysis. Significant haplotypes were modeled on disease risk. Allele distributions at the LMP7-145, TAP2-651, ERAP1-127, and ERAP1-730 loci differed significantly between cases and controls with the major allele at the LMP7 and TAP2 loci and the minor allele at both ERAP1 loci associated with increased cervical carcinoma risk. A combination of the two haplotypes spanning these loci was associated with a three-fold increased risk (OR = 3.024; P << 0.001); approximately 12% of all cervical carcinoma occurrences were attributable to this combination. Our data indicate that combined genetic variation in the TAP2, LMP7, and ERAP1 genes is associated with increased cervical carcinoma risk.

Expression and genetic analysis of transporter associated with antigen processing in cervical carcinoma

OBJECTIVE

Transporter associated with antigen processing (TAP) loss causes human leukocyte antigen (HLA) class I downregulation which is frequently found in cervical carcinomas and their precursors. HLA class I molecules activate T-cells by antigen presentation and are therefore essential for immunological surveillance. To add to the hitherto limited knowledge of molecular mechanisms underlying TAP loss, we investigated TAP expression, loss of heterozygosity (LOH) and possible TAP mutations.

METHODS

Twenty-three cervical carcinomas and adjacent precursor lesions were stained with HLA-A-, HLA-B/C-, beta2 -microglobulin-, TAP1- and TAP2- antibodies. In order to separate tumour and non-tumour cells, cervical carcinoma samples were sorted by flow-cytometry and were subsequently analysed for LOH with 3 markers in the TAP region on chromosome 6p21.3. Mutation analysis of the complete TAP1 gene was performed.

RESULTS

Aberrant TAP1 expression was detected in 10/23 cervical carcinoma lesions and in 5/10 adjacent cervical intraepithelial neoplasia (CIN) lesions. All the lesions with low TAP expression also had reduced HLA class I expression. LOH was found in 7 out of 10 lesions with TAP loss. Mutation analysis detected no aberrations, but identified a polymorphism in the 5'-untranslated region (UTR) of the TAP1 gene in two lesions.

CONCLUSIONS

This study shows that defective TAP expression in cervical carcinoma is often associated with LOH in the TAP region but not with mutations in the TAP1 gene.

Human papillomavirus therapeutic vaccines in head and neck tumors

Head and neck cancer represents one of the most challenging diseases as the mortality remains high despite advances in early diagnosis and treatment. Human papillomavirus has been implicated in a third of head and neck squamous cell carcinomas and human papillomavirus type 16 is strongly associated with carcinomas arising from the oropharynx, the tonsil being the preferred infected site. Novel therapeutic approaches including immunotherapy are currently under investigation. Immune vaccines developed against human papillomavirus in the genital area are already available and could simultaneously protect other anatomical localizations; however, prophylactic vaccines are expected to be effective in reducing the incidence of tumors after many years and, therefore, there is an urgent need to improve therapeutic interventions, such as immunotherapy. To date, human papillomavirus therapeutic vaccines are either at the preclinical level or at early phase human trials for genital pathologies. Nevertheless, accumulating evidence from animal and clinical studies suggests that the enhancement of specific and innate immune responses is effective in clearance of the human papillomavirus infection, promoting a cautious optimism regarding the achievement of an efficacious immunotherapy. This article reviews what has been achieved and what remains to be done in the field for the development of future viral vaccines in head and neck tumors.

MHC expression and chemokine production in the murine vagina following intra-vaginal administration of ligands to toll-like receptors 3, 7 and 9

The expression of MHC class I, MHC class II and the chemokines IP-10, MIP-1alpha, RANTES, fractalkine and I-TAC has been analyzed after intra-vaginal treatment with three synthetic toll-like receptors (TLR) agonists-double-stranded RNA (poly I:C), imiquimod and CpG-rich oligonucleotides (CpG-ODN). These compounds act mainly through TLR3, TLR7 and TLR9, respectively. CpG-ODN induced an accumulation of leucocytes in the vagina, and a strong up-regulation of MHC class I expression on both leucocytes and epithelial cells. Imiquimod and poly I:C induced a weak MHC class I up-regulation in the epithelium but not in the lamina propria. Neither treatment had any profound effect on expression of MHC class II on epithelial cells but poly I:C and to a lesser extent CpG-ODN, up-regulated MHC class II staining intensity which, in the case of CpG-ODN, treatment, was associated with a strong accumulation of CD11c-positive dendritic cells. All three treatments induced an early (8h) but transient IP-10 response. Imiquimod and CpG-ODN, but not poly I:C induced an early MIP-1alpha response which remained for at least 7 days in CpG-ODN-treated animals but not in imiquimod-treated mice. Poly I:C and CpG-ODN, but not imiquimod, induced significant levels of RANTES at different time-points post-treatment. None of the treatments induced any significant changes in the levels of fractalkine, I-TAC or IFN-alpha. These studies have implications for the manipulation of the genital immune response and also improving the outcome of vaginal immunotherapy.

Vaccination Against Cervical Cancer: Hopes and Realities

Globally, carcinomas of the anogenital tract, in particular cervical cancer, remain some of the most common cancers in women, cervical cancer represents the second most frequent gynecological malignancy and the third leading cause of cancer-related death in women worldwide. The causal relationship between human papilomavirus (HPV) infection and anogenital cancer has prompted substantial interest in the development of both preventive and therapeutic vaccines against high-risk HPV types. In the past decade, several groups have shown encouraging results using experimental vaccination systems in animal models and these results have led to several current prophylactic and therapeutic vaccine clinical trials in humans. Prophylactic vaccination focuses on the induction of high titer neutralizing antibodies that are potentially protective against incident and persistent HPV infection. Two major phase II clinical trials conducted by pharmaceutical companies have demonstrated that their vaccines have 100% efficacy in preventing persistent viral DNA and its associated cellular abnormalities; however, whether they induce long-lasting protective immunity is yet to be determined. At least one US FDA approved prophylactic vaccine targeting the two most common high-risk HPVs is expected to be on the market within the next 2-3 years. Nevertheless, significant reductions in the frequency and onset of cytologic screening and incidences of HPV-related lesions are not expected to become apparent for decades due to the fact that there will be women who are already infected with HPV, the long latency period between infection and development of high-grade lesions, and lesions associated with other high-risk HPV types not being included in the vaccines. Therapeutic vaccines aim to control HPV-associated malignancies by stimulating cellular immune responses that target established HPV infections via viral proteins. Progress in the field of HPV immunotherapy has remained elusive, with clinical trials being limited to small numbers of patients. Potential treatment of precancerous lesions is unique to HPV-associated infection and cancer because of cytologic monitoring and HPV typing. Unlike more common surgical treatments for cervical lesions, active immunotherapy has the potential to address HPV persistence as the cause of lesion development in addition to leaving the patient with long-term immunity that can be reactivated if and when the patient becomes reinfected.

Classical and nonclassical HLA class I antigen and NK Cell-activating ligand changes in malignant cells: current challenges and future directions

Changes in classical and nonclassical HLA class I antigen and NK cell-activating ligand expression have been identified in malignant lesions. These changes, which are described in this chapter, are believed to play a major role in the clinical course of the disease since both HLA class I antigens and NK cell-activating ligands are critical to the interaction between tumor cells and components of both innate and adaptive immune systems. Nevertheless, there is still debate in the literature about the biologic and functional significance of HLA class I antigen and NK cell-activating ligand abnormalities in malignant lesions. The reasons for this debate are reviewed. They include (i) the incomplete association between classical HLA class I antigen changes and the clinical course of the disease; (ii) the relatively limited number of malignant lesions that have been analyzed for nonclassical HLA class I antigen and NK cell-activating ligand expression; and (iii) the conflicting data regarding the role of immunoselection in the generation of malignant cells with HLA antigen and NK cell-activating ligand abnormalities. The technical limitations associated with the assessment of HLA antigen and NK cell-activating ligand expression in malignant lesions as well as the immunological and nonimmunological variables that may confound the impact of HLA antigen and NK cell-activating ligand changes on the clinical course of the disease are also discussed. Future studies aimed at overcoming these limitations and characterizing these variables are expected to provide a solution to the current debate regarding the significance of HLA class I antigen and NK cell-activating ligand abnormalities in malignant lesions.

TAP genes and immunity

The transporter associated with antigen processing (TAP) is a member of the ATP-binding cassette transporter family that specializes in delivering cytosolic peptides to class I molecules in the endoplasmic reticulum. The TAP is a major target of genetic alteration in tumours and disruption by viral inhibitors. In some species, TAP genes have co-evolved with MHC class I molecules to deliver peptides that are customised for particular alleles. In humans, MHC class I polymorphism determines the level of tapasin-mediated association with TAP and subsequent peptide optimisation within the peptide-loading complex (PLC). MHC class I molecules that still load peptides without complexing to the TAP might be more resistant to viral interference of the PLC and less sensitive to competition for TAP by other class I allotypes.