HLA antigen changes in malignant cells: epigenetic mechanisms and biologic significance

Kinase Regulation of Human MHC Class I Molecule Expression on Cancer Cells

The major histocompatibility complex I (MHC-1) presents antigenic peptides to tumor-specific CD8⁺ T cells. The regulation of MHC-I by kinases is largely unstudied, even though many patients with cancer are receiving therapeutic kinase inhibitors. Regulators of cell-surface HLA amounts were discovered using a pooled human kinome shRNA interference-based approach. Hits scoring highly were subsequently validated by additional RNAi and pharmacologic inhibitors. MAP2K1 (MEK), EGFR, and RET were validated as negative regulators of MHC-I expression and antigen presentation machinery in multiple cancer types, acting through an ERK output-dependent mechanism; the pathways responsible for increased MHC-I upon kinase inhibition were mapped. Activated MAPK signaling in mouse tumors in vivo suppressed components of MHC-I and the antigen presentation machinery. Pharmacologic inhibition of MAPK signaling also led to improved peptide/MHC target recognition and killing by T cells and TCR-mimic antibodies. Druggable kinases may thus serve as immediately applicable targets for modulating immunotherapy for many diseases. Cancer Immunol Res; 4(11); 936-47. ©2016 AACR.

Molecular mechanisms of HLA class I-mediated immune evasion of human tumors and their role in resistance to immunotherapies

Although the human immune system can recognize and eradicate tumor cells, tumors have also been shown to develop different strategies to escape immune surveillance, which has been described for the first time in different mouse models. The evasion of immune recognition was often associated with a poor prognosis and reduced survival of patients. During the last years the molecular mechanisms, which protect tumor cells from this immune attack, have been identified and appear to be more complex than initially expected. However, next to the composition of cellular, soluble and physical components of the tumor microenvironment, the tumor cells changes to limit immune responses. Of particular importance are classical and non-classical human leukocyte antigen (HLA) class I antigens, which often showed a deregulated expression in cancers of distinct origin. Furthermore, HLA class I abnormalities were linked to defects in the interferon signaling, which have both been shown to be essential for mounting immune responses and are involved in resistances to T cell-based immunotherapies. Therefore this review summarizes the expression, regulation, function and clinical relevance of HLA class I antigens in association with the interferon signal transduction pathway and its role in adaptive resistances to immunotherapies.

Opportunities and challenges for TCR mimic antibodies in cancer therapy

INTRODUCTION

Monoclonal antibodies (mAbs) are potent cancer therapeutic agents, but exclusively recognize cell-surface targets whereas most cancer-associated proteins are found intracellularly. Hence, potential cancer therapy targets such as over expressed self-proteins, activated oncogenes, mutated tumor suppressors, and translocated gene products are not accessible to traditional mAb therapy. An emerging approach to target these epitopes is the use of TCR mimic mAbs (TCRm) that recognize epitopes similar to those of T cell receptors (TCR).

AREAS COVERED

TCRm antigens are composed of a linear peptide sequence derived from degraded proteins and presented in the context of cell-surface MHC molecules. We discuss how the nature of the TCRm epitopes provides both advantages (absolute tumor specificity and access to a new universe of important targets) and disadvantages (low density, MHC restriction, MHC down-regulation, and cross-reactive linear epitopes) to conventional mAb therapy. We will also discuss potential solutions to these obstacles.

EXPERT OPINION

TCRm combine the specificity of TCR recognition with the potency, pharmacologic properties, and versatility of mAbs. The structure and presentation of a TCRm epitope has important consequences related to the choice of targets, mAb design, available peptides and MHC subtype restrictions, possible cross-reactivity, and therapeutic activity.

Immunological battlefield in gastric cancer and role of immunotherapies

Like the wars predating the First World War where human foot soldiers were deemed tools in the battlefield against an enemy, so too are the host immune cells of a patient battling a malignant gastric cancer. Indeed, the tumour microenvironment resembles a battlefield, where the patient’s immune cells are the defence against invading tumour cells. However, the relationship between different immune components of the host response to cancer is more complex than an “us against them” model. Components of the immune system inadvertently work against the interests of the host and become pro-tumourigenic while other components soldier on against the common enemy – the tumour cell.

Uveal melanoma as a target for immune-therapy

Uveal melanoma (UM) is a rare disease that can be deadly in spite of adequate local treatment. Systemic therapy with chemotherapy is usually ineffective and new-targeted therapies have not improved results considerably. The eye creates an immunosuppressive environment in order to protect eyesight. UM cells use similar processes to escape immune surveillance. Regarding innate immunity the production of macrophage inhibiting factor (MIF) and TGF-β, added to MHC class I upregulation, inhibits the action of natural killer (NK) cells. UM cells produce cytokines such as IL-6 and IL-10 that favor macrophage differentiation to the M2 subtype, which promote tumor growth instead of an effective immune response. UM cells also impair the adaptive immune response through production of indoleamine 2,3-dioxygenase (IDO), overexpression of programmed death ligand-1 (PD-L1), alteration of FasL expression, and resistance to perforin. This biological background suggests that immunotherapy could be effective in fighting UM. A Phase II clinical trial with Ipilimumab has shown promising results with mean Overall Survival rate of ten months, and close to 50% of the patients alive at one year. Clinical trials with anti-PD1 antibodies in monotherapy and in combination with anti-CTLA4 are currently recruiting patients worldwide.

Immune escape to PD-L1/PD-1 blockade: seven steps to success (or failure)

The emergence of programmed death-ligand 1 (PD-L1)/programmed death-1 (PD-1)-targeted therapy has demonstrated the importance of the PD-L1 : PD-1 interaction in inhibiting anticancer T-cell immunity in multiple human cancers, generating durable responses and extended overall survival. However, not all patients treated with PD-L1/PD-1-targeted therapy experience tumor shrinkage, durable responses, or prolonged survival. To extend such benefits to more cancer patients, it is necessary to understand why some patients experience primary or secondary immune escape, in which the immune response is incapable of eradicating all cancer cells. Understanding immune escape from PD-L1/PD-1-targeted therapy will be important to the development of rational immune-combination therapy and predictive diagnostics and to the identification of novel immune targets. Factors that likely relate to immune escape include the lack of strong cancer antigens or epitopes recognized by T cells, minimal activation of cancer-specific T cells, poor infiltration of T cells into tumors, downregulation of the major histocompatibility complex on cancer cells, and immunosuppressive factors and cells in the tumor microenvironment. Precisely identifying and understanding these mechanisms of immune escape in individual cancer patients will allow for personalized cancer immunotherapy, in which monotherapy and combination immunotherapy are chosen based on the presence of specific immune biology. This approach may enable treatment with immunotherapy without inducing immune escape, resulting in a larger proportion of patients obtaining clinical benefit.

Utilizing cell-based therapeutics to overcome immune evasion in hematologic malignancies

Hematologic malignancies provide a suitable testing environment for cell-based immunotherapies, which were pioneered by the development of allogeneic hematopoietic stem cell transplant. All types of cell-based therapies, from donor lymphocyte infusion to dendritic cell vaccines, and adoptive transfer of tumor-specific cytotoxic T cells and natural killer cells, have been clinically translated for hematologic malignancies. The recent success of chimeric antigen receptor-modified T lymphocytes in B-cell malignancies has stimulated the development of this approach toward other hematologic tumors. Similarly, the remarkable activity of checkpoint inhibitors as single agents has created enthusiasm for potential combinations with other cell-based immune therapies. However, tumor cells continuously develop various strategies to evade their immune-mediated elimination. Meanwhile, the recruitment of immunosuppressive cells and the release of inhibitory factors contribute to the development of a tumor microenvironment that hampers the initiation of effective immune responses or blocks the functions of immune effector cells. Understanding how tumor cells escape from immune attack and favor immunosuppression is essential for the improvement of immune cell-based therapies and the development of rational combination approaches.

NLRC5/MHC class I transactivator is a target for immune evasion in cancer

Cancer cells develop under immune surveillance, thus necessitating immune escape for successful growth. Loss of MHC class I expression provides a key immune evasion strategy in many cancers, although the molecular mechanisms remain elusive. MHC class I transactivator (CITA), known as "NLRC5" [NOD-like receptor (NLR) family, caspase recruitment (CARD) domain containing 5], has recently been identified as a critical transcriptional coactivator of MHC class I gene expression. Here we show that the MHC class I transactivation pathway mediated by CITA/NLRC5 constitutes a target for cancer immune evasion. In all the 21 tumor types we examined, NLRC5 expression was highly correlated with the expression of MHC class I, with cytotoxic T-cell markers, and with genes in the MHC class I antigen-presentation pathway, including LMP2/LMP7, TAP1, and β2-microglobulin. Epigenetic and genetic alterations in cancers, including promoter methylation, copy number loss, and somatic mutations, were most prevalent in NLRC5 among all MHC class I-related genes and were associated with the impaired expression of components of the MHC class I pathway. Strikingly, NLRC5 expression was significantly associated with the activation of CD8(+) cytotoxic T cells and patient survival in multiple cancer types. Thus, NLRC5 constitutes a novel prognostic biomarker and potential therapeutic target of cancers.

The possible role of the tumour necrosis factor polymorphisms and human leucocyte antigens in the development of prostate cancer

The cause of prostate cancer (PC), one of the most common cancers found among ageing men, remains unclear, but genetic predisposition is believed to play a major role in its aetiology. The aim of the study was to examine HLA genes polymorphism and TNF polymorphisms in PC development. Patients diagnosed with PC (N = 113) and 150 healthy individuals were tested for HLA-A, HLA-B and HLA-DRB1 genes and for TNFa, TNFb and TNFd microsatellites. The comparison of patients and controls revealed a positive association of HLA-DRB1*12, TNFa2 and TNFb5, and a negative association of HLA-DRB1*13 and TNFb4 with PC. A division of patients into groups according to age, pre-operative PSA level, Gleason score (GS) and involvement of prostatic capsule, seminal vesicles or bladder neck and perineural invasion of PC demonstrated the following: a positive correlation of HLA-DRB1*12 and a negative correlation of HLA-DRB1*13 with younger patients (<65 years), GS > 7 and the positive association of prostatic capsule, seminal vesicles, bladder neck and perineural invasion of PC; TNFb4 allele's negative association with older patients displaying higher PSA levels, higher GS and positive surrounding tissue involvement; positive association of TNFb5 allele for both older and younger patients. Investigation of HLA genes and TNF microsatellites demonstrated a possible role of HLA-DRB1 and TNF regions in PC aetiology.

Expression of classical HLA class I molecules: regulation and clinical impacts: Julia Bodmer Award Review 2015

Human leukocyte antigen (HLA) class I genes are ubiquitously expressed, but in a tissue specific-manner. Their expression is primarily regulated at the transcriptional level and can be modulated both positively and negatively by different stimuli. Advances in sequencing technologies led to the identification of new regulatory variants located in the untranslated regions (UTRs), which could influence the expression. After a brief description of the mechanisms underlying the transcriptional regulation of HLA class I genes expression, we will review how the expression levels of HLA class I genes could affect biological and pathological processes. Then, we will discuss on the differential expression of HLA class I genes according to the locus, allele and UTR polymorphisms and its clinical impact. This interesting field of study led to a new dimension of HLA typing, going beyond a qualitative aspect.

NLRC5 elicits antitumor immunity by enhancing processing and presentation of tumor antigens to CD8(+) T lymphocytes

Cancers can escape immunesurveillance by diminishing the expression of MHC class-I molecules (MHC-I) and components of the antigen-processing machinery (APM). Developing new approaches to reverse these defects could boost the efforts to restore antitumor immunity. Recent studies have shown that the expression of MHC-I and antigen-processing molecules is transcriptionally regulated by NOD-like receptor CARD domain containing 5 (NLRC5). To investigate whether NLRC5 could be used to improve tumor immunogenicity, we established stable lines of B16-F10 melanoma cells expressing NLRC5 (B16-5), the T cell co-stimulatory molecule CD80 (B16-CD80) or both (B16-5/80). Cells harboring NLRC5 constitutively expressed MHC-I and LMP2, LMP7 and TAP1 genes of the APM. The B16-5 cells efficiently presented the melanoma antigenic peptide gp100_25–33 to Pmel-1 TCR transgenic CD8⁺ T cells and induced their proliferation. In the presence of CD80, B16-5 cells stimulated Pmel-1 cells even without the addition of gp100 peptide, indicating that NLRC5 facilitated the processing and presentation of endogenous tumor antigen. Upon subcutaneous implantation, B16-5 cells showed markedly reduced tumor growth in C57BL/6 hosts but not in immunodeficient hosts, indicating that the NLRC5-expressing tumor cells elicited antitumor immunity. Following intravenous injection, B16-5 and B16-5/80 cells formed fewer lung tumor foci compared to control cells. In mice depleted of CD8⁺ T cells, B16-5 cells formed large subcutaneous and lung tumors. Finally, immunization with irradiated B16-5 cells conferred protection against challenge by parental B16 cells. Collectively, our findings indicate that NLRC5 could be exploited to restore tumor immunogenicity and to stimulate protective antitumor immunity.

Hypomethylating Agents for Relapse after Allogeneic Hematopoietic Cell Transplantation in Myeloid Malignancies: A Case Series and Review of the Literature

BACKGROUND/AIMS

Relapse is a leading cause of mortality after allogeneic hematopoietic cell transplantation (HCT). Hypomethylating agents (HMAs) have immunomodulatory properties, including augmenting tumor antigen presentation that may enhance the graft-versus-leukemia effect. Moreover, inhibitory effects on T-cell activation and cytokine production may lead to a lower incidence of graft-versus-host disease (GVHD). Our aim was to describe outcomes in patients treated with HMAs for relapse after HCT.

METHODS

Subjects were retrospectively identified as patients with relapse or loss of donor chimerism after HCT for myeloid malignancies treated with HMAs at the University of Pittsburgh.

RESULTS

Thirteen patients were identified, with a median age of 57 years and a median time to relapse of 98 days. Nine of 12 (75%) evaluable patients had a complete remission (CR). Grade I-IV acute GVHD involving the liver occurred in 6 patients. Cases of acute liver GVHD were diagnosed clinically based on the elevation of liver function tests. The median survival was 14.3 months from the time of relapse.

CONCLUSION

HMAs for relapse after HCT can be effective in inducing a CR. This may be due to epigenetic changes and immunomodulatory effects that enhance the graft-versus-leukemia effect. There may be a risk of GVHD, and further exploration into pathophysiology and predisposing factors are warranted.

Integrating multidimensional omics data for cancer outcome

In multidimensional cancer omics studies, one subject is profiled on multiple layers of omics activities. In this article, the goal is to integrate multiple types of omics measurements, identify markers, and build a model for cancer outcome. The proposed analysis is achieved in two steps. In the first step, we analyze the regulation among different types of omics measurements, through the construction of linear regulatory modules (LRMs). The LRMs have sound biological basis, and their construction differs from the existing analyses by modeling the regulation of sets of gene expressions (GEs) by sets of regulators. The construction is realized with the assistance of regularized singular value decomposition. In the second step, the proposed cancer outcome model includes the regulated GEs, "residuals" of GEs, and "residuals" of regulators, and we use regularized estimation to select relevant markers. Simulation shows that the proposed method outperforms the alternatives with more accurate marker identification. We analyze the The Cancer Genome Atlas data on cutaneous melanoma and lung adenocarcinoma and obtain meaningful results.

Underground Adaptation to a Hostile Environment: Acute Myeloid Leukemia vs. Natural Killer Cells

Acute myeloid leukemia (AML) is a heterogeneous group of malignancies which incidence increases with age. The disease affects the differentiation of hematopoietic stem or precursor cells in the bone marrow and can be related to abnormal cytogenetic and/or specific mutational patterns. AML blasts can be sensitive to natural killer (NK) cell antitumor response. However, NK cells are frequently defective in AML patients leading to tumor escape. NK cell defects affect not only the expression of the activating NK receptors, including the natural cytotoxicity receptors, the NK group 2, member D, and the DNAX accessory molecule-1, but also cytotoxicity and IFN-γ release. Such perturbations in NK cell physiology could be related to the adaptation of the AML to the immune pressure and more generally to patient’s clinical features. Various mechanisms are potentially involved in the inhibition of NK-cell functions in AML, including defects in the normal lymphopoiesis, reduced expression of activating receptors through cell-to-cell contacts, and production of immunosuppressive soluble agents by leukemic blasts. Therefore, the continuous cross-talk between AML and NK cells participates to the leukemia immune escape and eventually to patient’s relapse. Methods to restore or stimulate NK cells seem to be attractive strategies to treat patients once the complete remission is achieved. Moreover, our capacity in stimulating the NK cell functions could lead to the development of preemptive strategies to eliminate leukemia-initiating cells before the emergence of the disease in elderly individuals presenting preleukemic mutations in hematopoietic stem cells.

A high number of IgG4-positive cells in gastric cancer tissue is associated with tumor progression and poor prognosis

IgG4-related disease is a newly defined disease characterized by elevated serum IgG4 levels and infiltration of affected organs by IgG4-positive plasma cells. Recently, increased IgG4 levels were reported to be closely related with malignancy. To assess the relationship between IgG4 and the progression of gastric cancer, we immunohistochemically stained in this study gastric cancer tissue samples for IgG4-positive cells using an anti-IgG4 antibody. In addition, pre- and postoperative serum concentrations of IgG4 were measured, using an enzyme-linked immunosorbent assay. In gastric cancer samples, the number of CD138-positive plasma cells was significantly lower and the number of IgG4-positive cells significantly higher than in non-cancerous gastric mucosa. The number of IgG4-positive cells was significantly correlated with gross tumor appearance, tumor depth, lymph node metastasis, venous invasion, and lymphatic invasion. Prognosis was significantly poorer in patients with a high number of IgG4-positive cells than in those with a low number. Multivariate analysis indicated that both the number of IgG4-positive cells and the depth of tumor invasion were independently prognostic of survival. In conclusion, in gastric cancer, the number of IgG4-positive cells is increased and this is closely associated with gastric cancer progression.

Major histocompatibility complex class I expression impacts on patient survival and type and density of immune cells in biliary tract cancer

BACKGROUND

Biliary tract cancers (BTC) are rare malignant tumours with a poor prognosis. Previously, we have presented a detailed characterisation of the inflammatory infiltrate in BTC. Here, we analysed the impact of the expression of major histocompatibility complex class I (MHC I) on patient survival and the quantity, as well as the quality of tumour-infiltrating immune cell types in BTC.

METHODS

MHC I expression was assessed semi-quantitatively in 334 BTC, including extrahepatic (n=129) and intrahepatic cholangiocarcinomas (n=146), as well as adenocarcinomas of the gallbladder (n=59). In addition, 71 high-grade biliary intraepithelial lesions (BilIN 3) were included. Results were correlated with data on antitumour inflammation and investigated with respect to their association with clinicopathological variables and patient survival.

RESULTS

BTC showed a wide spectrum of different MHC I expression patterns ranging from complete negativity in some tumours to strong homogenous expression in others. In BilIN 3, significantly higher MHC I expression levels were seen compared to invasive tumours (P=0.004). Patients with strong tumoural MHC I expression had a significantly higher overall survival probability (median survival benefit: 8 months; P=0.006). MHC I expression strongly correlated with the number of tumour-infiltrating T-lymphocytes (CD4(+) and CD8(+)) and macrophages.

CONCLUSIONS

Differences of MHC I expression predict patient outcome and show correlations with specific components of the inflammatory infiltrate in BTC. These findings contribute to a better understanding of immune response and immune escape phenomena in cholangiocarcinogenesis.

A combined approach of human leukocyte antigen ligandomics and immunogenicity analysis to improve peptide-based cancer immunotherapy

The breakthrough development of immune checkpoint inhibitors as clinically effective novel therapies demonstrates the potential of cancer immunotherapy. The identification of suitable targets for specific immunotherapy, however, remains a challenging task. Most peptides previously used for vaccination in clinical trials were able to elicit strong immunological responses but failed with regard to clinical benefit. This might, at least partly, be caused by an inadequate peptide selection, usually derived from established tumor-associated antigens which are not necessarily presented as human leukocyte antigen (HLA) ligands. Recently, HLA ligandome analysis revealed cancer-associated peptides, which have been used in clinical trials showing encouraging impact on survival. To improve peptide-based cancer immunotherapy, our group established a combined approach of HLA ligandomics and immunogenicity analysis for the identification of vaccine peptides. This approach is based on the identification of naturally presented HLA ligands on tumor samples, the selection of tumor-associated/tumor-specific HLA ligands and their subsequent testing for immunogenicity in vitro. In this review, we want to present our pipeline for the identification of vaccine peptides, focusing on ovarian cancer, and want to discuss differences to other approaches. Furthermore, we want to give a short outlook of a potential multi-peptide vaccination trial using the novel identified peptides.

Multiple structural and epigenetic defects in the human leukocyte antigen class I antigen presentation pathway in a recurrent metastatic melanoma following immunotherapy

Scant information is available about the molecular basis of multiple HLA class I antigen-processing machinery defects in malignant cells, although this information contributes to our understanding of the molecular immunoescape mechanisms utilized by tumor cells and may suggest strategies to counteract them. In the present study we reveal a combination of IFN-γ-irreversible structural and epigenetic defects in HLA class I antigen-processing machinery in a recurrent melanoma metastasis after immunotherapy. These defects include loss of tapasin and one HLA haplotype as well as selective silencing of HLA-A3 gene responsiveness to IFN-γ. Tapasin loss is caused by a germ-line frameshift mutation in exon 3 (TAPBP(684delA)) along with a somatic loss of the other gene copy. Selective silencing of HLA-A3 gene and its IFN-γ responsiveness is associated with promoter CpG methylation nearby site-α and TATA box, reversible after DNA methyltransferase 1 depletion. This treatment combined with tapasin reconstitution and IFN-γ stimulation restored the highest level of HLA class I expression and its ability to elicit cytotoxic T cell responses. These results represent a novel tumor immune evasion mechanism through impairing multiple components at various levels in the HLA class I antigen presentation pathway. These findings may suggest a rational design of combinatorial cancer immunotherapy harnessing DNA demethylation and IFN-γ response.

PD-L1 and HLA Class I Antigen Expression and Clinical Course of the Disease in Intrahepatic Cholangiocarcinoma

PURPOSE

More effective therapy is needed for intrahepatic cholangiocarcinoma (ICC). The encouraging clinical results obtained with checkpoint molecule-specific monoclonal antibodies (mAb) have prompted us to investigate whether this type of immunotherapy may be applicable to ICC. The aims of this study were to determine whether (i) patients mount a T-cell immune response to their ICC, (ii) checkpoint molecules are expressed on both T cells and tumor cells, and (iii) tumor cells are susceptible to recognition by cognate T cells.

EXPERIMENTAL DESIGN

Twenty-seven ICC tumors were analyzed for (i) lymphocyte infiltrate, (ii) HLA class I and HLA class II expression, and (iii) PD-1 and PD-L1 expression by T cells and ICC cells, respectively. The results of this analysis were correlated with the clinicopathologic characteristics of the patients investigated.

RESULTS

Lymphocyte infiltrates were identified in all tumors. PD-L1 expression and HLA class I antigen expression by ICC cells was observed in 8 and 11, respectively, of the 27 tumors analyzed. HLA class I antigen expression correlated with CD8(+) T-cell infiltrate. Furthermore, positive HLA class I antigen expression in combination with negative/rare PD-L1 expression was associated with favorable clinical course of the disease.

CONCLUSIONS

ICC patients are likely to mount a T-cell immune response against their own tumors. Defects in HLA class I antigen expression in combination with PD-L1 expression by ICC cells provide them with an immune escape mechanism. This mechanism justifies the implementation of immunotherapy with checkpoint molecule-specific mAbs in patients bearing ICC tumors without defects in HLA class I antigen expression.

Epigenetic changes within the promoter regions of antigen processing machinery family genes in Kazakh primary esophageal squamous cell carcinoma

The esophageal squamous cell carcinoma (ESCC) is thought to develop through a multi-stage process. Epigenetic gene silencing constitutes an alternative or complementary mechanism to mutational events in tumorigenesis. Posttranscriptional regulation of human leukocyte antigen class I (HLA-I) and antigen processing machinery (APM) proteins expression may be associated with novel epigenetic modifications in cancer development. In the present study, we determined the expression levels of HLA-I antigen and APM components by immunohistochemistry. Then by a bisulfite-sequencing PCR (BSP) approach, we identified target CpG islands methylated at the gene promoter region of APM family genes in a ESCC cell line (ECa109), and further quantitative analysis of CpG site specific methylation of these genes in cases of Kazakh primary ESCCs with corresponding non-cancerous esophageal tissues using the Sequenom MassARRAY platform. Here we showed that the development of ESCCs was accompanied by partial or total loss of protein expression of HLA-B, TAP2, LMP7, tapasin and ERp57. The results demonstrated that although no statistical significance was found of global target CpG fragment methylation level sof HLA-B, TAP2, tapasin and ERp57 genes between ESCC and corresponding non-cancerous esophageal tissues, there was significant differences in the methylation level of several single sites between the two groups. Of thesse only the global methylation level of LMP7 gene target fragments was statistically higher (0.0517±0.0357) in Kazakh esophageal cancer than in neighboring normal tissues (0.0380±0.0214, p<0.05). Our results suggest that multiple CpG sites, but not methylation of every site leads to down regulation or deletion of gene expression. Only some of them result in genetic transcription, and silencing of HLA-B, ERp57, and LMP7 expression through hypermethylation of the promoters or other mechanisms may contribute to mechanisms of tumor escape from immune surveillance in Kazakh esophageal carcinogenesis.

EBP1 protein modulates the expression of human MHC class II molecules in non-hematopoietic cancer cells

Many solid tumours including melanoma, glioblastoma, and breast carcinomas express MHC class II molecules (MHC II). The surface expression of these molecules confers to non-hematopoietic tumour cells the role of non-professional antigen presenting cells and the ability to potentially stimulate tumour-specific CD4⁺ T cell response. We studied EBP1, an ErbB3 binding protein, and the effects of p48 and p42 isoforms on the MHC II expression in U87 glioblastoma, M14 melanoma and MCF7 mammary carcinoma cell lines. We found that overexpression of p48 increases MHC II transcription in U87 and M14, through upregulation of CIITA transactivator and STAT1 phosphorylation. In addition, p48 protein influences MHC II expression by increasing mRNA stability. In melanoma and glioblastoma cell lines, p48 isoform functions as oncogene promoting tumour growth, while p42 isoform, that does not affect MHC II expression, acts as a tumour suppressor by blocking cell growth and inducing apoptosis. In contrast, p48 seems to act as tumour suppressor in breast carcinoma inhibiting proliferation, favouring apoptosis, and inducing a slight increase of MHC II expression similar to p42. Our data highlight the tissue specificity function of EBP1 isoforms and demonstrate that only the oncogene p48 activates MHC II expression in human solid tumours, via STAT1 phosphorylation, in order to affect tumour progression by triggering specific immune response.

Epigenetic drugs for cancer treatment and prevention: mechanisms of action

This review provides a brief overview of the basic principles of epigenetic gene regulation and then focuses on recent development of epigenetic drugs for cancer treatment and prevention with an emphasis on the molecular mechanisms of action. The approved epigenetic drugs are either inhibitors of DNA methyltransferases or histone deacetylases (HDACs). Future epigenetic drugs could include inhibitors for histone methyltransferases and histone demethylases and other epigenetic enzymes. Epigenetic drugs often function in two separate yet interrelated ways. First, as epigenetic drugs per se, they modulate the epigenomes of premalignant and malignant cells to reverse deregulated epigenetic mechanisms, leading to an effective therapeutic strategy (epigenetic therapy). Second, HDACs and other epigenetic enzymes also target non-histone proteins that have regulatory roles in cell proliferation, migration and cell death. Through these processes, these drugs induce cancer cell growth arrest, cell differentiation, inhibition of tumor angiogenesis, or cell death via apoptosis, necrosis, autophagy or mitotic catastrophe (chemotherapy). As they modulate genes which lead to enhanced chemosensitivity, immunogenicity or dampened innate antiviral response of cancer cells, epigenetic drugs often show better efficacy when combined with chemotherapy, immunotherapy or oncolytic virotherapy. In chemoprevention, dietary phytochemicals such as epigallocatechin-3-gallate and sulforaphane act as epigenetic agents and show efficacy by targeting both cancer cells and the tumor microenvironment. Further understanding of how epigenetic mechanisms function in carcinogenesis and cancer progression as well as in normal physiology will enable us to establish a new paradigm for intelligent drug design in the treatment and prevention of cancer.

Relative expression levels of the HLA class-I proteins in normal and HIV-infected cells

The expression level of HLA class-I proteins is known to influence pathological outcomes: pathogens downregulate HLA to evade host immune responses, host inflammatory reactions upregulate HLA, and differences among people with regard to the steady-state expression levels of HLA associate with disease susceptibility. Yet precise quantification of relative expression levels of the various HLA loci is difficult because of the tremendous polymorphism of HLA. We report relative expression levels of HLA-A, HLA-B, HLA-C, and HLA-E proteins for the specific haplotype A*02:01, B*44:02, C*05:01, which were characterized using two independent methods based on flow cytometry and mass spectrometry. PBLs from normal donors showed that HLA-A and HLA-B proteins are expressed at similar levels, which are 13-18 times higher than HLA-C by flow cytometry and 4-5 times higher than HLA-C by mass spectrometry; these differences may reflect variation in the conformation or location of proteins detected. HLA-E was detected at a level 25 times lower than that of HLA-C by mass spectrometry. Primary CD4(+) T cells infected with HIV in vitro were also studied because HIV downregulates selective HLA types. HLA-A and HLA-B were reduced on HIV-infected cells by a magnitude that varied between cells in an infected culture. Averaging all infected cells from an individual showed HLA-A to be 1-3 times higher and HLA-B to be 2-5 times higher than HLA-C by flow cytometry. These results quantify substantial differences in expression levels of the proteins from different HLA loci, which are very likely physiologically significant on both uninfected and HIV-infected cells.

Reprogramming the tumor microenvironment: tumor-induced immunosuppressive factors paralyze T cells

It has become evident that tumor-induced immuno-suppressive factors in the tumor microenvironment play a major role in suppressing normal functions of effector T cells. These factors serve as hurdles that limit the therapeutic potential of cancer immunotherapies. This review focuses on illustrating the molecular mechanisms of immunosuppression in the tumor microenvironment, including evasion of T-cell recognition, interference with T-cell trafficking, metabolism, and functions, induction of resistance to T-cell killing, and apoptosis of T cells. A better understanding of these mechanisms may help in the development of strategies to enhance the effectiveness of cancer immunotherapies.

Xilonix, a novel true human antibody targeting the inflammatory cytokine interleukin-1 alpha, in non-small cell lung cancer

BACKGROUND

Advanced non-small cell lung cancer (NSCLC) patients were treated as part of a Phase I dose escalation and expansion study evaluating a true human monoclonal antibody targeting IL-1α (Xilonix), which is intended to modulate the malignant phenotype-inhibiting tumor growth, spread and offering relief of symptoms.

METHODS

Sixteen NSCLC patients were included. Patients failed a median of 4 chemotherapy regimens, including 10/16 failing anti-EGFR therapy. Disease progression was evaluated using a multi-modal approach: tumor response, patient reported outcomes (EORTC-QLQC30), and lean body mass (LBM). Patients received infusions every 2 or 3 weeks until progression, and were followed 24 months to assess survival.

RESULTS

There were no infusion reactions, dose-limiting toxicities, or deaths due to therapy. Albeit not statistically significant, there was a trend in IL-6 (-2.6 ± 18.5 (0.1 [-2.8-2.4]), platelet counts (-11 ± 54 (-4[-36.0-1.0]), CRP (-3.3 ± 30.2 (0.4 [-10.7-1.8]) and LBM (1.0 ± 2.5 (0.4 [-0.5-2.6]). Self-reported outcomes revealed reductions in pain, fatigue and improvement in appetite. Median survival was 7.6 (IQR 4.4-11.5) months, stratification based on prior anti-EGFR therapy revealed a median survival of 9.4 months (IQR 7.6-12.5) for those pretreated (N = 10) versus a survival of 4.8 months (IQR 4.3-5.7) for those without (N = 6, logrank p = 0.187).

CONCLUSION

Xilonix was well tolerated, with gains in LBM and improvement in symptoms suggesting a clinically important response. Although not statistically significant, the survival outcomes observed for patients with and without prior anti-EGFR therapy raises intriguing questions about the potential synergy of IL-1α blockade and anti-EGFR therapy. Further study for this agent in NSCLC is warranted.

Reduced Expression of the Antigen Processing Machinery Components TAP2, LMP2, and LMP7 in Tonsillar and Base of Tongue Cancer and Implications for Clinical Outcome

OBJECTIVES: Patients with human papillomavirus (HPV)–positive tonsillar squamous cell carcinoma (TSCC) and base of tongue squamous cell carcinoma (BOTSCC) have a better clinical outcome than those with corresponding HPV-negative tumors. Moreover, there is a strong positive correlation between absent/low as opposed to strong HLA class I expression and favorable clinical outcome for HPV-positive tumors, while the reverse applies to HPV-negative tumors. The expression of the antigen processing machinery (APM) components TAP1, TAP2, LMP2, and LMP7 in these tumors in relation to HPV status, HLA class I expression, each other, and clinical outcome was therefore investigated. MATERIAL AND METHODS: Formalin-fixed paraffin-embedded TSCC and BOTSCC, derived from 151 patients and previously analyzed for HPV DNA, HLA class I, and LMP10 expression were stained by immunohistochemistry for TAP1, TAP2, LMP2, and LMP7. RESULTS: Absent/low TAP2, LMP2, and LMP7 expression, similar to HLA class I and LMP10, was common in TSCC and BOTSCC, irrespective of HPV status. Expression of TAP1 and TAP2 was correlated, as was LMP2 to LMP7. LMP2 and LMP7 expression was also associated to HLA class I expression. Moreover, absence of LMP7 was linked to increased disease-free survival in both HPV-positive and HPV-negative cases. CONCLUSION: Reduced expression of TAP2, LMP2, and LMP7 was frequent in TSCC and BOTSCC and their expression as well as that of TAP1 was often interrelated. Furthermore, low LMP7 expression correlated to better clinical outcome and may, together with HPV status, potentially be used for prediction of treatment response.

Prognostic impact of programmed cell death 1 ligand 1 expression in human leukocyte antigen class I-positive hepatocellular carcinoma after curative hepatectomy

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common solid tumors worldwide. Surgery is potentially curative, but high recurrence rates worsen patient prognosis. The interaction between the proteins programmed cell death 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1) is an important immune checkpoint. The significance of PD-L1 expression and human leukocyte antigen class I (HLA class I), recognized by CD8 T cells, in the prognosis of patients with HCC remains to be determined.

METHODS

We assessed the levels of PD-L1 and HLA class I expression on HCC samples from 80 patients who had undergone hepatectomy at our institution, and evaluated the correlations between PD-L1 and HLA class I expression and patient prognosis.

RESULTS

High HLA class I expression was correlated with significantly better recurrence-free survival (RFS), but not overall survival (OS). Multivariate analysis showed that high HLA class I expression was an independent predictor of improved RFS. Low expression of PD-L1 on HCC tended to predict better OS, but the difference was not statistically significant. PD-L1 expression on HCC correlated with the number of CD163-positive macrophages and HLA class I expression with CD3-positive cell infiltration. Univariable and multivariable analyses showed that combined PD-L1 low/HLA class I high expression on HCCs was prognostic for improved OS and RFS.

CONCLUSIONS

PD-L1 status may be a good predictor of prognosis in HCC patients with high HLA class I expression. Novel therapies targeting the PD-L1/PD-1 pathway may improve the prognosis of patients with HCC.

HLA ligandome analysis identifies the underlying specificities of spontaneous antileukemia immune responses in chronic lymphocytic leukemia (CLL)

The breakthrough development of clinically effective immune checkpoint inhibitors illustrates the potential of T-cell-based immunotherapy to effectively treat malignancies. A remaining challenge is to increase and guide the specificities of anticancer immune responses, e.g., by therapeutic vaccination or by adoptive T-cell transfer. By analyzing the landscape of naturally presented HLA class I and II ligands of primary chronic lymphocytic leukemia (CLL), we delineated a novel category of tumor-associated T-cell antigens based on their exclusive and frequent representation in the HLA ligandome of leukemic cells. These antigens were validated across different stages and mutational subtypes of CLL and found to be robustly represented in HLA ligandomes of patients undergoing standard chemo-/immunotherapy. We demonstrate specific immune recognition of these antigens exclusively in CLL patients, with the frequencies of representation in CLL ligandomes correlating with the frequencies of immune recognition by patient T cells. Moreover, retrospective survival analysis revealed survival benefits for patients displaying immune responses to these antigens. These results directly imply these nonmutant self-peptides as pathophysiologically relevant tumor antigens and encourages their implementation for cancer immunotherapy.

Immune escape mechanisms as a guide for cancer immunotherapy

Immunotherapy has demonstrated impressive outcomes for some patients with cancer. However, selecting patients who are most likely to respond to immunotherapy remains a clinical challenge. Here, we discuss immune escape mechanisms exploited by cancer and present strategies for applying this knowledge to improving the efficacy of cancer immunotherapy.

Association of high CD4-positive T cell infiltration with mutations in HLA class II-regulatory genes in microsatellite-unstable colorectal cancer

Besides being expressed on professional antigen-presenting cells, HLA class II antigens are expressed on various tumors of non-lymphoid origin, including a subset of colorectal cancers (CRC). Information about the regulation of HLA class II antigen expression is important for a better understanding of their role in the interactions between tumor and immune cells. Whether lack of HLA class II antigen expression in tumors reflects the selective immune destruction of HLA class II antigen-expressing tumor cells is unknown. To address this question, we tested whether lack of HLA class II antigen expression in CRC was associated with immune cell infiltration. We selected microsatellite-unstable (MSI-H) CRC, because they show pronounced tumor antigen-specific immune responses and, in a subset of tumors, lack of HLA class II antigen expression due to mutations inactivating HLA class II-regulatory genes. We examined HLA class II antigen expression, mutations in regulatory genes, and CD4-positive T cell infiltration in 69 MSI-H CRC lesions. Mutations in RFX5, CIITA, and RFXAP were found in 13 (28.9%), 3 (6.7%), and 1 (2.2%) out of 45 HLA class II antigen-negative tumors. CD4-positive tumor-infiltrating lymphocyte counts were significantly higher in HLA class II antigen-negative tumors harboring mutations in HLA class II-regulatory genes (107.4 T cells per 0.25 mm(2)) compared to tumors without mutations (55.5 T cells per 0.25 mm(2), p = 0.008). Our results suggest that the outgrowth of tumor cells lacking HLA class II antigen expression due to mutations of regulatory genes is favored in an environment of dense CD4-positive T cell infiltration.

Classic and nonclassic HLA class I expression in penile cancer and relation to HPV status and clinical outcome

PURPOSE

Loss of expression of HLA class I is a mechanism of immune evasion in various cancers that is often associated with a worse patient outcome. We analyzed HLA expression in a large cohort with penile cancer in relation to clinical outcome.

MATERIALS AND METHODS

We used penile cancer tissue blocks from 168 patients who underwent surgical resection between 2000 and 2009 to construct tissue microarrays. Immunohistochemical staining was done with antibodies directed against classic and nonclassic HLA molecules. HLA expression was scored semiquantitatively, divided into 3 expression groups and correlated with clinicopathological variables, including HPV and survival. Survival analysis was performed using the Kaplan-Meier method and Cox proportional hazards models.

RESULTS

Complete and partial loss of total classic HLA class I was observed in 32% and 50% of cases, and up-regulation of HLA-E and G in 16% and 13%, respectively. When corrected for relevant clinical parameters, partial HLA-A loss was significantly associated with decreased survival overall (HR 2.3, 95% CI 1.1-4.6) and in HPV negative patients alone (HR 3.4, 95% CI 1.4-8.4). Abnormal HLA-B/C, E or G expression levels were not associated with survival.

CONCLUSIONS

To our knowledge this is the first study to describe a link between HLA expression and the clinical outcome of penile cancer. HLA down-regulation occurs frequently and partial loss of HLA-A is an independent predictor of poor survival in HPV negative patients. Complete understanding of the mechanisms and relevance of HLA down-regulation and immune evasion in regard to the clinical outcome will contribute to the future design of immunotherapy interventions.

Low expression of HLA-DRA, HLA-DPA1, and HLA-DPB1 is associated with poor prognosis in pediatric adrenocortical tumors (ACT)

BACKGROUND

Low expression of HLA class II antigens has been associated with more aggressive disease in several human malignancies including adult adrenocortical tumors (ACT), but their clinical relevance in pediatric ACT needs to be investigated.

PROCEDURE

This study analyzed the expression profile of three class II histocompatibility genes (HLA-DRA, HLA-DPA1, and HLA-DPB1) in 58 consecutive pediatric ACT (13 adenomas and 45 carcinomas) by quantitative real time PCR and their association with clinical and biological features. HLA-DPA1 protein level was determined by immunohistochemistry.

RESULTS

A significant association (P < 0.01) was observed between lower expression levels of the three genes analyzed and poor prognostic factors such as age ≥ 4 years, tumor size ≥ 200 cm(3), tumor weight ≥ 100 g, and metastatic disease; the presence of an unfavorable event and death. Underexpression of the HLA-DRA, HLA-DPA1, and HLA-DPB1 genes were associated with lower 5-year event-free survival (EFS) (P = 0.017, P < 0.001, and P = 0.017, respectively). Cox multivariate analysis showed that HLA-DPA1 was an independent prognostic factor (P = 0.029) when analyzed in association with stage IV, age and tumor size. Significantly lower EFS was also observed in patients with negative/weak immunostaining for HLA-DPA1 (P = 0.002). Similar results were observed when only patients classified as having carcinomas were analyzed.

CONCLUSION

Our results suggest that lower expression of HLA-DRA, HLA-DPA1, and HLA-DPB1 genes may contribute to more aggressive disease in pediatric ACT. HLA-DPA1 immunostaining may represent potential aggressiveness marker in this tumor.

Chemical metabolic inhibitors for the treatment of blood-borne cancers

Tumor cells, including leukemic cells, remodel their bioenergetic system in favor of aerobic glycolysis. This process is called "the Warburg effect" and offers an attractive pharmacological target to preferentially eliminate malignant cells. In addition, recent results show that metabolic changes can be linked to tumor immune evasion. Mouse models demonstrate the importance of this metabolic remodeling in leukemogenesis. Some leukemias, although treatable, remain incurable and resistance to chemotherapy produces an elevated percentage of relapse in most leukemia cases. Several groups have targeted the specific metabolism of leukemia cells in preclinical and clinical studies to improve the prognosis of these patients, i.e. using L-asparaginase to treat pediatric acute lymphocytic leukemia (ALL). Additional metabolic drugs that are currently being used to treat other diseases or tumors could also be exploited for leukemia, based on preclinical studies. Finally, we discuss the potential use of several metabolic drugs in combination therapies, including immunomodulatory drugs (IMiDs) or immune cell-based therapies, to increase their efficacy and reduce side effects in the treatment of hematological cancers.

Novel tumor antigen-specific monoclonal antibody-based immunotherapy to eradicate both differentiated cancer cells and cancer-initiating cells in solid tumors

A growing body of experimental and clinical evidence strongly suggests that the resistance of cancer-initiating cells (CICs) to conventional therapies represents a major obstacle to the successful treatment of a malignant disease. To overcome this limitation a novel combinatorial tumor antigen (TA)-specific monoclonal antibody (mAb) strategy has been developed. In this strategy TA-specific mAbs are combined with chemotherapeutic agents and/or small molecules that inhibit aberrantly activated signaling pathways in cancer cells and especially in CICs. The in vitro results we have obtained indicate that this strategy is very effective in eradicating both differentiated cancer cells and CICs in several types of malignant disease. If the in vitro results have in vivo relevance, the strategy we have designed may have an impact on the treatment of malignant diseases.

PD-1- and CTLA-4-based inhibitory chimeric antigen receptors (iCARs) divert off-target immunotherapy responses

T cell therapies have demonstrated long-term efficacy and curative potential for the treatment of some cancers. However, their use is limited by damage to bystander tissues, as seen in graft-versus-host disease after donor lymphocyte infusion, or "on-target, off-tumor" toxicities incurred in some engineered T cell therapies. Nonspecific immunosuppression and irreversible T cell elimination are currently the only means to control such deleterious responses, but at the cost of abrogating therapeutic benefits or causing secondary complications. On the basis of the physiological paradigm of immune inhibitory receptors, we designed antigen-specific inhibitory chimeric antigen receptors (iCARs) to preemptively constrain T cell responses. We demonstrate that CTLA-4- or PD-1-based iCARs can selectively limit cytokine secretion, cytotoxicity, and proliferation induced through the endogenous T cell receptor or an activating chimeric receptor. The initial effect of the iCAR is temporary, thus enabling T cells to function upon a subsequent encounter with the antigen recognized by their activating receptor. iCARs thus provide a dynamic, self-regulating safety switch to prevent, rather than treat, the consequences of inadequate T cell specificity.

Targeting epigenetic mechanisms for clinical translation: enhancing the efficacy of tumor immunotherapies

The ability to evade host immune surveillance is critical for the survival of tumor cells and is correlated with poor clinical outcomes. Many tumor types have been found to downregulate expression of genes involved in antigen production, processing and presentation to evade immune detection. Recent findings suggest that the mechanisms underlying these immune evasion phenomena extend beyond alterations in DNA sequence to include epigenetic modifications of DNA and associated proteins, including hypermethylation of DNA and altered histone acetylation patterns. This review will summarize alterations in antigen presentation machinery identified in malignant cells, epigenetic mechanisms that can be employed in the downregulation of genes relevant for antigen presentation and translational strategies to target these processes to enhance the efficacy of antitumor immunotherapies.

Current trends in cancer vaccines--a bioinformatics perspective

Cancer vaccine development is in the process of becoming reality in future, due to successful phase II/III clinical trials. However, there are still problems due to the specificity of tumor antigens and weakness of tumor associated antigens in eliciting an effective immune response. Computational models to assess the vaccine efficacy have helped to improve and understand what is necessary for personalized treatment. Further research is needed to elucidate the mechanisms of activation of antigen specific cytotoxic T lymphocytes, decreased TREG number functionality and antigen cascade, so that overall improvement in vaccine efficacy and disease free survival can be attained. T cell epitomic based in sillico approaches might be very effective for the design and development of novel cancer vaccines.

Rise of iPSCs as a cell source for adoptive immunotherapy

Adoptive T cell transfer is a potentially effective strategy for treating cancer and viral infections. However, previous studies of cancer immunotherapy have shown that T cells expanded in vitro fall into an exhausted state and, consequently, have limited therapeutic effect. One way to overcome this obstacle is to use induced pluripotent stem cells (iPSCs) as a cell source for making effector T cells. In recent years, there have been several reports on generating effector T cells suitable for adoptive immunotherapy. The reported findings suggest that using iPSC technology, it may be possible to stably derive large numbers of juvenile memory T cells targeted to cancers or viruses. In this review, we describe a strategy for applying iPSC technology to immunotherapy and the characteristics of T cells derived from iPSCs. We also discuss how these technologies can be applied clinically in the future.

Blocking oncogenic RAS enhances tumour cell surface MHC class I expression but does not alter susceptibility to cytotoxic lymphocytes

Mutations in the RAS family of oncogenes are highly prevalent in human cancer and, amongst its manifold effects, oncogenic RAS impairs the expression of components of the antigen presentation pathway. This allows evasion of cytotoxic T lymphocytes (CTL). CTL and natural killer (NK) cells are reciprocally regulated by MHC class I molecules and any gain in CTL recognition obtained by therapeutic inactivation of oncogenic RAS may be offset by reduced NK cell activation. We have investigated the consequences of targeted inactivation of oncogenic RAS on the recognition by both CTL and NK cells. Inactivation of oncogenic RAS, either by genetic deletion or inactivation with an inducible intracellular domain antibody (iDAb), increased MHC class I expression in human colorectal cell lines. The common RAS mutations, at codons 12, 13 and 61, all inhibited antigen presentation. Although MHC class I modulates the activity of both CTL and NK cells, the enhanced MHC class I expression resulting from inactivation of mutant KRAS did not significantly affect the in vitro recognition of these cell lines by either class of cytotoxic lymphocyte. These results show that oncogenic RAS and its downstream signalling pathways modulate the antigen presentation pathway and that this inhibition is reversible. However, the magnitude of these effects was not sufficient to alter the in vitro recognition of tumour cell lines by either CTL or NK cells.

Cytokeratin 8-MHC class I interactions: a potential novel immune escape phenotype by a lymph node metastatic carcinoma cell line

Defective human leukocyte antigen (HLA) class I expression in malignant cells facilitates their escape from destruction by CD8(+) cytotoxic T lymphocytes. In this study, a post-translational mechanism of HLA class I abnormality that does not involve defects in the HLA subunits and antigen processing machinery components was identified and characterized. The marked HLA class I downregulation phenotype of a metastatic carcinoma cell line can be readily reversed by trypsin, suggesting a masking effect by serine protease-sensitive HLA class I-interacting factors. Co-immunoprecipitation, combined with LC-tandem mass spectrometry and immunoblotting identified these factors as cytokeratin (CK) 8 and its heterodimeric partners CK18 and CK19. Ectopic CK8/18 or CK8/19 expression in HEK293 cells resulted in surface CK8 expression with an HLA class I downregulation phenotype, while redirecting CK8/18 and CK8/19 to the endoplasmic reticulum (ER) had no such effect. This observation and the failure to constrain CK8/18 and CK8/19 membrane trafficking by an ER-Golgi transport inhibitor suggested an ER-independent route for CK8 access to HLA class I molecules. Monoclonal antibody mapping revealed a potential CK8 blockade of HLA class I-CD8 and -TCR contacts. These findings, along with the emerging role of cell surface CK8 in cancer metastasis, may imply a dual strategy for tumor cell survival in the host.

The interplay between HPV and host immunity in head and neck squamous cell carcinoma

Persistent infection with human papillomavirus (HPV) type 16 is a major risk factor for the development of head and neck squamous cell carcinoma (HNSCC), in particular oropharyngeal squamous cell carcinoma (OPSCC). The oropharyngeal epithelium differs from the mucosal epithelium at other commonly HPV16-infected sites (i.e., cervix and anogenital region) in that it is juxtaposed with the underlying lymphatic tissue, serving a key immunologic function in the surveillance of inhaled and ingested pathogens. Therefore, the natural history of infection and immune response to HPV at this site may differ from that at other anatomic locations. This review summarizes the literature concerning the adaptive immune response against HPV in the context of HNSCC, with a focus on the T-cell response. Recent studies have shown that a broad repertoire of tumor-infiltrating HPV-specific T-cells are found in nearly all patients with HPV-positive tumors. A systemic response is found in only a proportion of these. Furthermore, the local response is more frequent in OPSCC patients than in cervical cancer patients and HPV-negative OPSCC patients. Despite this, tumor persistence may be facilitated by abnormalities in antigen processing, a skewed T-helper cell response, and an increased local prevalence of T-regulatory cells. Nonetheless, the immunologic profile of HPV-positive vs. HPV-negative HNSCC is associated with a significantly better outcome, and the HPV-specific immune response is suggested to play a role in the significantly better response to therapy of HPV-positive patients. Immunoprofiling may prove a valuable prognostic tool, and immunotherapy trials targeting HPV are underway, providing hope for decreasing treatment-related toxicity.

Characterization of small spheres derived from various solid tumor cell lines: are they suitable targets for T cells?

T cell based immunotherapy has been investigated in a variety of malignancies and analyses have been mostly founded on in vitro data with tumor cell monolayers. However, three-dimensional (3D) culture models might mimic more closely the 'in vivo' conditions than 2D monolayers. Therefore, we analyzed the expression of tumor-associated antigens (TAA) and of molecules involved in antigen processing and presentation (APM) in tumor spheres, which served as an in vitro model for micrometastasis which might be enriched in tumor propagating cancer stem cells. For enrichment of sphere cells 12 human solid tumor cell lines were cultured in serum-free medium. Expression of a variety of TAA and APM were analyzed by RT-PCR and/or flow cytometry and compared to expression in corresponding adherent bulk cells grown in regular growth medium. Compared to adherent cells, spheres showed equal or higher mRNA expression levels of LMP2, LMP7 and MECL-1, of TAP1 and TAP2 transporters and, surprisingly, also of TAA including differentiation antigens. However, downregulation or loss of HLA-I and HLA-II molecules in spheres was observed in 8 of 10 and 1 of 2 cell lines, respectively, and was unresponsive to stimulation with IFN-γ. Although tumor spheres express TAA and molecules of intracellular antigen processing, they are defective in antigen presentation due to downregulation of HLA surface expression which may lead to immune evasion.

Innovative therapeutic strategies in the treatment of brain metastases

Brain metastases (BM) are the most common intracranial tumors and their incidence is increasing. Untreated brain metastases are associated with a poor prognosis and a poor performance status. Metastasis development involves the migration of a cancer cell from the bulk tumor into the surrounding tissue, extravasation from the blood into tissue elsewhere in the body, and formation of a secondary tumor. In the recent past, important results have been obtained in the management of patients affected by BM, using surgery, radiation therapy, or both. Conventional chemotherapies have generally produced disappointing results, possibly due to their limited ability to penetrate the blood-brain barrier. The advent of new technologies has led to the discovery of novel molecules and pathways that have better depicted the metastatic process. Targeted therapies such as bevacizumab, erlotinib, gefitinib, sunitinib and sorafenib, are all licensed and have demonstrated improved survival in patients with metastatic disease. In this review, we will report current data on targeted therapies. A brief review about brain metastatic process will be also presented.