Expression and immunotherapeutic targeting of the SSX family of cancer-testis antigens in prostate cancer

Molecular biomarkers in prostate cancer tumorigenesis and clinical relevance

Prostate cancer (PCa) is the second most frequent type of cancer in men and assessing circulating tumor cells (CTCs) by liquid biopsy is a promising tool to help in cancer early detection, staging, risk of recurrence evaluation, treatment prediction and monitoring. Blood-based liquid biopsy approaches enable the enrichment, detection and characterization of CTCs by biomarker analysis. Hence, comprehending the molecular markers, their role on each stage of cancer development and progression is essential to provide information that can help in future implementation of these biomarkers in clinical assistance. In this review, we studied the molecular markers most associated with PCa CTCs to better understand their function on tumorigenesis and metastatic cascade, the methodologies utilized to analyze these biomarkers and their clinical significance, in order to summarize the available information to guide researchers in their investigations, new hypothesis formulation and target choice for the development of new diagnostic and treatment tools.

Higher Expression Levels of SSX1 and SSX2 in Patients with Colon Cancer: Regulated In Vitro by the Inhibition of Methylation and Histone Deacetylation

Background and Objectives: Colon cancer (CC) has a high mortality rate and is often diagnosed at an advanced stage in Saudi Arabia. Thus, the identification and characterization of potential new cancer-specific biomarkers are imperative for improving the diagnosis of CC by detecting it at an early stage. Cancer-testis (CT) genes have been identified as potential biomarkers for the early diagnosis of various cancers. Among the CT genes are those belonging to the SSX family. In order to assess the usefulness of SSX family genes as cancer biomarkers for the detection of early-stage CC, the goal of this research was to validate the expressions of these genes in patients with CC and in matched patients with normal colons (NCs). Materials and Methods: RT-PCR assays were used to analyze the SSX1, SSX2, and SSX3 family gene expression levels in 30 neighboring NC and CC tissue samples from male Saudi patients. Epigenetic alterations were also tested in vitro using qRT-PCR analysis to determine whether reduced DNA methyltransferase or histone deacetylation could stimulate SSX gene expression via 5-aza-2'-deoxycytidine and trichostatin treatments, respectively. Results: The RT-PCR results showed SSX1 and SSX2 gene expression in 10% and 20% of the CC tissue specimens, respectively, but not in any of the NC tissue specimens. However, no SSX3 expression was detected in any of the examined CC or NC tissue samples. In addition, the qRT-PCR results showed significantly higher SSX1 and SSX2 expression levels in the CC tissue samples than in the NC tissue samples. The 5-aza-2'-deoxycytidine and trichostatin treatments significantly induced the mRNA expression levels of the SSX1, SSX2, and SSX3 genes in the CC cells in vitro. Conclusions: These findings suggest that SSX1 and SSX2 are potentially suitable candidate biomarkers for CC. Their expressions can be regulated via hypomethylating and histone deacetylase treatments, subsequently providing a potential therapeutic target for CC.

Cancer Resistance to Immunotherapy: Comprehensive Insights with Future Perspectives

Cancer immunotherapy is a type of treatment that harnesses the power of the immune systems of patients to target cancer cells with better precision compared to traditional chemotherapy. Several lines of treatment have been approved by the US Food and Drug Administration (FDA) and have led to remarkable success in the treatment of solid tumors, such as melanoma and small-cell lung cancer. These immunotherapies include checkpoint inhibitors, cytokines, and vaccines, while the chimeric antigen receptor (CAR) T-cell treatment has shown better responses in hematological malignancies. Despite these breakthrough achievements, the response to treatment has been variable among patients, and only a small percentage of cancer patients gained from this treatment, depending on the histological type of tumor and other host factors. Cancer cells develop mechanisms to avoid interacting with immune cells in these circumstances, which has an adverse effect on how effectively they react to therapy. These mechanisms arise either due to intrinsic factors within cancer cells or due other cells within the tumor microenvironment (TME). When this scenario is used in a therapeutic setting, the term “resistance to immunotherapy” is applied; “primary resistance” denotes a failure to respond to treatment from the start, and “secondary resistance” denotes a relapse following the initial response to immunotherapy. Here, we provide a thorough summary of the internal and external mechanisms underlying tumor resistance to immunotherapy. Furthermore, a variety of immunotherapies are briefly discussed, along with recent developments that have been employed to prevent relapses following treatment, with a focus on upcoming initiatives to improve the efficacy of immunotherapy for cancer patients.

Immune-related pan-cancer gene expression signatures of patient survival revealed by NanoString-based analyses

The immune system plays a central role in the onset and progression of cancer. A better understanding of transcriptional changes in immune cell-related genes associated with cancer progression, and their significance in disease prognosis, is therefore needed. NanoString-based targeted gene expression profiling has advantages for deployment in a clinical setting over RNA-seq technologies. We analysed NanoString PanCancer Immune Profiling panel gene expression data encompassing 770 genes, and overall survival data, from multiple previous studies covering 10 different cancer types, including solid and blood malignancies, across 515 patients. This analysis revealed an immune gene signature comprising 39 genes that were upregulated in those patients with shorter overall survival; of these 39 genes, three (MAGEC2, SSX1 and ULBP2) were common to both solid and blood malignancies. Most of the genes identified have previously been reported as relevant in one or more cancer types. Using Cibersort, we investigated immune cell levels within individual cancer types and across groups of cancers, as well as in shorter and longer overall survival groups. Patients with shorter survival had a higher proportion of M2 macrophages and γδ T cells. Patients with longer overall survival had a higher proportion of CD8+ T cells, CD4+ T memory cells, NK cells and, unexpectedly, T regulatory cells. Using a transcriptomics platform with certain advantages for deployment in a clinical setting, our multi-cancer meta-analysis of immune gene expression and overall survival data has identified a specific transcriptional profile associated with poor overall survival.

SSX addiction in melanoma propagates tumor growth and metastasis

Cancer/testis antigens are receiving attention as targets for cancer therapy due to their germ- and cancer cell-restricted expression. However, many of these antigens are inconsistently expressed among cancer types and individual tumors. Here, we show that members of the SSX cancer/testis antigen family comprise attractive targets in the majority of melanoma patients, as SSX is expressed in more than 90% of primary melanomas and metastases and plays a critical role in metastatic progression. Accordingly, SSX silencing in melanoma mouse xenograft models reduced tumor growth and completely abolished the formation of metastatic lesions in lungs and livers. Mechanistically, we demonstrate that silencing SSX in melanoma cells induces cell cycle S-phase stalling, leading to proliferative arrest and enhanced apoptosis, which elucidates the inhibitory effect of SSX loss on tumor growth and colonization capacity. Silencing SSX further compromised the capacity of melanoma cells to migrate and invade, influencing these cells’ capability to spread and colonize. Taken together, these studies highlight SSX proteins as pivotal targets in melanoma with implications for blocking metastatic progression.

Childhood Obesity-Related Mechanisms: MicroRNome and Transcriptome Changes in a Nested Case-Control Study

Childhood obesity could contribute to adulthood obesity, leading to adverse health outcomes in adults. However, the mechanisms for how obesity is developed are still unclear. To determine the epigenome-wide and genome-wide expression changes related with childhood obesity, we compared microRNome and transcriptome levels as well as leptin protein levels in whole bloods of 12 obese and 24 normal children aged 6 years. miR-328-3p, miR-1301-3p, miR-4685-3p, and miR-6803-3p were negatively associated with all obesity indicators. The four miRNAs were also associated with 3948 mRNAs, and separate 475 mRNAs (185 among 3948 mRNAs) were associated with all obesity indicators. The 2533 mRNAs (64.2%) among the 3948 mRNAs and 286 mRNAs (60.2%) among the 475 mRNAs were confirmed as targets of the four miRNAs in public databases through miRWalk 2.0. Leptin protein was associated with miR-6803-3p negatively and all obesity indicators positively. Using DAVID bioinformatics resources 6.8, top three pathways for obesity-related gene set were metabolic pathways, pathways in cancer, and PI3K-Akt signaling pathway. The top three obesity-related disease classes were metabolic, cardiovascular, and chemdependency. Our results support that childhood obesity could be developed through miRNAs-related epigenetic mechanism and, further, these obesity-related epigenetic changes could control the pathways related with the development of various diseases.

Safety and preliminary immunogenicity of JNJ-64041809, a live-attenuated, double-deleted Listeria monocytogenes-based immunotherapy, in metastatic castration-resistant prostate cancer

Background

The safety and immunogenicity of JNJ-64041809 (JNJ-809), a live-attenuated, double-deleted Listeria monocytogenes (LADD Lm)-based immunotherapy targeting 4 relevant prostate cancer antigens, was evaluated in a phase 1 study in patients with metastatic castration-resistant prostate cancer (mCRPC).

Methods

Men with progressive mCRPC who had received ≥2 prior approved therapies were enrolled. Primary study objectives were to determine the recommended phase 2 dose (RP2D) and to evaluate the safety and immunogenicity of JNJ-809.

Results

A total of 26 patients received JNJ-809 (1 × 10⁸ CFU (n = 6); 1 × 10⁹ CFU (n = 20)). No dose-limiting toxicities were reported, and 1 × 10⁹ CFU was selected as the RP2D. The most common adverse events (AEs) reported were chills (92%), pyrexia (81%), and fatigue (62%). The most frequent grade ≥3 AEs were lymphopenia (27%) and hypertension (23%). Serious AEs were reported in 27% of patients including 1 patient with grade 3 intestinal obstruction. JNJ-809 transiently induced peripheral cytokines, including interferon-γ, interleukin-10, and tumor necrosis factor-α. Of the 7 patients evaluable for T cell responses at the 1 × 10⁹ CFU dose, evidence of post-treatment antigenic responses were observed in 6 to the Listeria antigen listeriolysin O and in 5 to ≥1 of the 4 encoded tumor antigens. Best overall response was stable disease in 13/25 response-evaluable patients. The study was terminated early as data collected were considered sufficient to evaluate safety and immunogenicity.

Conclusions

JNJ-809 has manageable safety consistent with other LADD Lm-based therapies. Limited antigen-specific immune responses were observed, which did not translate into objective clinical responses.

A Novel Immune-Related Seventeen-Gene Signature for Predicting Early Stage Lung Squamous Cell Carcinoma Prognosis

With the increasingly early stage lung squamous cell carcinoma (LUSC) being discovered, there is an urgent need for a comprehensive analysis of the prognostic characteristics of early stage LUSC. Here, we developed an immune-related gene signature for outcome prediction of early stage LUSC based on three independent cohorts. Differentially expressed genes (DEGs) were identified using CIBERSORT and ESTMATE algorithm. Then, a 17-immune-related gene (RPRM, APOH, SSX1, MSGN1, HPR, ISM2, FGA, LBP, HAS1, CSF2, RETN, CCL2, CCL21, MMP19, PTGIS, F13A1, C1QTNF1) signature was identified using univariate Cox regression, LASSO regression and stepwise multivariable Cox analysis based on the verified DEGs from 401 cases in The Cancer Genome Atlas (TCGA) database. Subsequently, a cohort of GSE74777 containing 107 cases downloaded from Gene Expression Omnibus (GEO) database and an independent data set consisting of 36 frozen tissues collected from National Cancer Center were used to validate the predictive value of the signature. Seventeen immune-related genes were identified from TCGA cohort, which were further used to establish a classification system to construct cases into high- and low-risk groups in terms of overall survival. This classifier was still an independent prognostic factor in multivariate analysis. In addition, another two independent cohorts and different clinical subgroups validated the significant predictive value of the signature. Further mechanism research found early stage LUSC patients with high risk had special immune cell infiltration characteristics and gene mutation profiles. In conclusion, we characterized the tumor microenvironment and established a highly predictive model for evaluating the prognosis of early stage LUSC, which may provide a lead for effective immunotherapeutic options tailored for each subtype.

Nuclear overexpression levels of MAGE-A3 predict poor prognosis in patients with prostate cancer

Melanoma antigen gene A3 (MAGE-A3) is one of the most immunogenic cancer testis antigens and is common in various types of cancers. In this study, for the first time, we performed immunohistochemical analysis to evaluate the expression of MAGE-A3 in 153 prostate tissue samples including prostate cancer (PCa), benign prostatic hyperplasia (BPH), and high-grade prostatic intraepithelial neoplasia (HPIN). Increased both nuclear and cytoplasmic expression of MAGE-A3 was significantly found in PCa tissues compared with both HPIN and BPH tissues (nuclear expression at p = 0.011, and cytoplasmic expression at p = 0.034; for both comparisons p < 0.0001, respectively). A significant correlation was observed between higher nuclear and cytoplasmic expressions of MAGE-A3 with Gleason score (p < 0.0001 and 0.006, respectively). Increased expression of MAGE-A3 was associated with shorter biochemical recurrence-free survival (BCR-FS) and disease-free survival (DFS) of patients (p = 0.042 and = 0.0001, respectively). In multivariate analysis, nuclear expression of MAGE-A3 and Gleason score (≤7 vs >7) was independent predictors of the DFS (both; p = 0.019). Nuclear expression of MAGE-A3 was also significantly related to BCR-FS (p = 0.015). MAGE-A3 can be considered as a predictor for poor prognosis and an option for vaccine immunotherapy in patients with PCa.

T-cell-engaging Therapy for Solid Tumors

T-cell engagers (TCE) are a rapidly evolving novel group of treatments that have in common the concurrent engagement of a T-cell surface molecule and a tumoral cell antigen. Bispecific antibodies and genetically engineered adoptive cell therapies, as chimeric antigen receptors or T-cell receptors, have similarities and differences among their mechanisms of action, toxicity profiles, and resistance pathways. Nevertheless, the success observed in the hematologic field has not been obtained with solid tumors yet, as they are biologically more complex and have few truly tumor-specific cell surface antigens that can be targeted with high avidity T cells. Different strategies are under study to improve their short-term perspective, such as new generations of more active TCEs, multi-target or combination of different treatments approaches, or to improve the manufacturing processes. A comprehensive review of TCEs as a grouped treatment class, their current status, and research directions in their application to solid tumors therapeutics are discussed here.

Novel Insights Into Epigenetic Reprogramming and Destabilization of Pericentromeric Heterochromatin in Cancer

Pericentromeric heterochromatin is maintained in a condensed structure by repressive epigenetic control mechanisms and perturbation of these may cause diseases. The chromosome 1q12 region harbors the largest pericentromeric heterochromatin domain in the genome and is among the most common breakpoints in both solid and hematopoietic cancers. Furthermore, the 1q arm is frequently amplified in cancer and this may support tumorigenesis by increasing the dosage of the many oncogenes of this genomic region. Recent studies have provided insight into the mechanisms leading to loss of 1q12 stability and 1q amplification and DNA hypomethylation seems to play a prominent role. This may be the result of decreased activity of DNA methyltransferases and instrumental for 1q12 destabilization or arise secondary to perturbation of other important epigenetic mechanisms that control repression of pericentromeric heterochromatin. Polycomb proteins were recently demonstrated to epigenetically reprogram demethylated 1q12 pericentromeric heterochromatin in premalignant and malignant cells to form large subnuclear structures known as polycomb bodies. This may influence the regulation and stability of 1q12 pericentromeric heterochromatin and/or the distribution of polycomb factors to support tumorigenesis. This review will discuss recent insight into the epigenetic perturbations causing the destabilization of 1q12 pericentromeric heterochromatin and its possible implications for tumor biology.

Resistance mechanisms in melanoma to immuneoncologic therapy with checkpoint inhibitors

Checkpoint inhibitors act by blocking physiologic mechanisms coopted by tumor cells to evade immune surveillance, restoring the immune system's ability to identify and kill malignant cells. These therapies have dramatically improved outcomes in multiple tumor types with durable responses in many patients, leading to FDA approval first in advanced melanoma, then in many other malignancies. However, as experience with checkpoint inhibitors has grown, populations of patients who are primary nonresponders or develop secondary resistance have been the majority of cases, even in melanoma. Mechanisms of resistance include those inherent to the tumor microenvironment, the tumor cells themselves, and the function of the patient's native immune cells. This review will discuss resistance to checkpoint inhibitors in melanoma as well as possible methods to restore sensitivity.

Epigenetic mechanisms of tumor resistance to immunotherapy

The recent impact of cancer immunotherapies has firmly established the ability and importance of the immune system to fight malignancies. However, the intimate interaction between the highly dynamic tumor and immune cells leads to a selection process driven by genetic and epigenetic processes. As the molecular pathways of cancer resistance mechanisms to immunotherapy become increasingly known, novel therapeutic targets are being tested in combination with immune-stimulating approaches. We here review recent insights into the molecular mechanisms of tumor resistance with particular emphasis on epigenetic processes and place these in the context of previous models.

The role of Cancer/Testis Antigens in Multiple Myeloma pathogenesis and their application in disease monitoring and therapy

A unique group of genes, encoding tumour associated antigens, known as the Cancer/Testis Antigens (CTAs), have been explored as novel markers of disease progression and as targets of immunotherapy in several cancers, including the haematological malignancy Multiple Myeloma (MM). This review aims to update the knowledge of CTA involvement in MM pathogenesis and how their potential as biomarkers for disease monitoring and targets of immunotherapy has been explored in the MM disease arena. Despite the initial promise of these antigens, their use as immunotherapy targets has not been successful, yet with a greater understanding of their role in disease pathogenesis they may still have a significant role to play as biomarkers of disease and therapeutic targets.

Expression analysis of cancer-testis genes in prostate cancer reveals candidates for immunotherapy

Prostate cancer is a prevalent disorder among men with a heterogeneous etiological background. Several molecular events and signaling perturbations have been found in this disorder. Among genes whose expressions have been altered during the prostate cancer development are cancer-testis antigens (CTAs). This group of antigens has limited expression in the normal adult tissues but aberrant expression in cancers. This property provides them the possibility to be used as cancer biomarkers and immunotherapeutic targets. Several CTAs have been shown to be immunogenic in prostate cancer patients and some of the have entered clinical trials. Based on the preliminary data obtained from these trials, it is expected that CTA-based therapeutic options are beneficial for at least a subset of prostate cancer patients.

NY-ESO-1 Based Immunotherapy of Cancer: Current Perspectives

NY-ESO-1 or New York esophageal squamous cell carcinoma 1 is a well-known cancer-testis antigen (CTAs) with re-expression in numerous cancer types. Its ability to elicit spontaneous humoral and cellular immune responses, together with its restricted expression pattern, have rendered it a good candidate target for cancer immunotherapy. In this review, we provide background information on NY-ESO-1 expression and function in normal and cancerous tissues. Furthermore, NY-ESO-1-specific immune responses have been observed in various cancer types; however, their utility as biomarkers are not well determined. Finally, we describe the immune-based therapeutic options targeting NY-ESO-1 that are currently in clinical trial. We will highlight the recent advancements made in NY-ESO-1 cancer vaccines, adoptive T cell therapy, and combinatorial treatment with checkpoint inhibitors and will discuss the current trends for future NY-ESO-1 based immunotherapy. Cancer treatment has been revolutionized over the last few decades with immunotherapy emerging at the forefront. Immune-based interventions have shown promising results, providing a new treatment avenue for durable clinical responses in various cancer types. The majority of successful immunotherapy studies have been reported in liquid cancers, whereas these approaches have met many challenges in solid cancers. Effective immunotherapy in solid cancers is hampered by the complex, dynamic tumor microenvironment that modulates the extent and phenotype of the antitumor immune response. Furthermore, many solid tumor-associated antigens are not private but can be found in normal somatic tissues, resulting in minor to detrimental off-target toxicities. Therefore, there is an ongoing effort to identify tumor-specific antigens to target using various immune-based modalities. CTAs are considered good candidate targets for immunotherapy as they are characterized by a restricted expression in normal somatic tissues concomitant with a re-expression in solid epithelial cancers. Moreover, several CTAs have been found to induce a spontaneous immune response, NY-ESO-1 being the most immunogenic among the family members. Hence, this review will focus on NY-ESO-1 and discuss the past and current NY-ESO-1 targeted immunotherapeutic strategies.

Inducible expression of cancer-testis antigens in human prostate cancer

Immune tolerance to self-antigens can limit robust anti-tumor immune responses in the use of tumor vaccines. Expression of novel tumor associated antigens can improve immune recognition and lysis of tumor cells. The cancer-testis antigen (CTA) family of proteins has been hypothesized to be an ideal class of antigens due to tumor-restricted expression, a subset of which have been found to induce antibody responses in patients with prostate disease. We demonstrate that CTA expression is highly inducible in five different Prostate Cancer (PC) cell lines using a hypomethylating agent 5-Aza-2′-deoxycytidine (5AZA) and/or a histone deacetylase inhibitor LBH589. These CTAs include NY-ESO1, multiple members of the MAGE and SSX families and NY-SAR35. A subset of CTAs is synergistically induced by the combination of 5AZA and LBH589. We developed an ex vivo organ culture using human PC biopsies for ex vivo drug treatments to evaluate these agents in clinical samples. These assays found significant induction of SSX2 in 9/9 distinct patient samples and NY-SAR35 in 7/9 samples. Further, we identify expression of SSX2 in circulating tumor cells (CTC) from patients with advanced PC. These results indicate that epigenetic modifying agents can induce expression of a broad range of neoantigens in human PC and may serve as a useful adjunctive therapy with novel tumor vaccines and checkpoint inhibitors.

SSX2 regulates focal adhesion but does not drive the epithelial to mesenchymal transition in prostate cancer

Prostate cancer is the most commonly diagnosed malignancy for men in the United States. Metastatic prostate cancer, the lethal form of the disease, has a life expectancy of approximately five years. Identification of factors associated with this transition to metastatic disease is crucial for future therapies. One such factor is the SSX gene family, a family of cancer/testis antigens (CTA) transcription factors which have been shown to be aberrantly expressed in other cancers and associated with the epithelial to mesenchymal transition (EMT). We have previously shown that SSX expression in prostate cancers was restricted to metastatic tissue and not primary tumors. In this study, we have identified SSX2 as the predominant SSX family member expressed in prostate cancer, and found its expression in the peripheral blood of 19 of 54 (35%) prostate cancer patients, with expression restricted to circulating tumor cells, and in 7 of 15 (47%) metastatic cDNA samples. Further, we examined SSX2 function in prostate cancer through knockdown and overexpression in prostate cancer cell lines. While overexpression had little effect on morphology or gene transcript changes, knockdown of SSX2 resulted in an epithelial morphology, increased cell proliferation, increased expression of genes involved in focal adhesion, decreased anchorage independent growth, increased invasion, and increased tumorigenicity in vivo. We conclude from these findings that SSX2 expression in prostate cancer is not a driver of EMT, but is involved in processes associated with EMT including loss of focal adhesion that may be related to tumor cell dissemination.

Beyond the androgen receptor II: New approaches to understanding and treating metastatic prostate cancer; Report from the 2017 Coffey-Holden Prostate Cancer Academy Meeting

INTRODUCTION

The 2017 Coffey-Holden Prostate Cancer Academy (CHPCA) Meeting, "Beyond the Androgen Receptor II: New Approaches to Understanding and Treating Metastatic Prostate Cancer," was held in Carlsbad, California from June 14-17, 2017.

METHODS

The CHPCA is an annual scientific conference hosted by the Prostate Cancer Foundation (PCF) that is uniquely designed to produce extensive and constructive discussions on the most urgent and impactful topics concerning research into the biology and treatment of metastatic prostate cancer. The 2017 CHPCA Meeting was the 5th meeting in this annual series and was attended by 71 investigators focused on prostate cancer and a variety of other fields including breast and ovarian cancer.

RESULTS

The discussions at the meeting were concentrated on topics areas including: mechanisms and therapeutic approaches for molecular subclasses of castrate resistant prostate cancer (CRPC), the epigenetic landscape of prostate cancer, the role of DNA repair gene mutations, advancing the use of germline genetics in clinical practice, radionuclides for imaging and therapy, advances in molecular imaging, and therapeutic strategies for successful use of immunotherapy in advanced prostate cancer.

DISCUSSION

This article reviews the presentations and discussions from the 2017 CHPCA Meeting in order to disseminate this knowledge and accelerate new biological understandings and advances in the treatment of patients with metastatic prostate cancer.

Prostate Cancer Cells Express More Androgen Receptor (AR) Following Androgen Deprivation, Improving Recognition by AR-Specific T Cells

Androgen deprivation is the primary therapy for recurrent prostate cancer, and agents targeting the androgen receptor (AR) pathway continue to be developed. Because androgen-deprivation therapy (ADT) has immmunostimulatory effects as well as direct antitumor effects, AR-targeted therapies have been combined with other anticancer therapies, including immunotherapies. Here, we sought to study whether an antigen-specific mechanism of resistance to ADT (overexpression of the AR) may result in enhanced AR-specific T-cell immune recognition, and whether this might be strategically combined with an antitumor vaccine targeting the AR. Androgen deprivation increased AR expression in human and murine prostate tumor cells in vitro and in vivo The increased expression persisted over time. Increased AR expression was associated with recognition and cytolytic activity by AR-specific T cells. Furthermore, ADT combined with vaccination, specifically a DNA vaccine encoding the ligand-binding domain of the AR, led to improved antitumor responses as measured by tumor volumes and delays in the emergence of castrate-resistant prostate tumors in two murine prostate cancer models (Myc-CaP and prostate-specific PTEN-deficient mice). Together, these data suggest that ADT combined with AR-directed immunotherapy targets a major mechanism of resistance, overexpression of the AR. This combination may be more effective than ADT combined with other immunotherapeutic approaches. Cancer Immunol Res; 5(12); 1074-85. ©2017 AACR.

Generation of human MHC (HLA-A11/DR1) transgenic mice for vaccine evaluation

The rapid occurrence of emerging infectious diseases demonstrates an urgent need for a new preclinical experimental model that reliably replicates human immune responses. Here, a new homozygous humanized human leukocyte antigen (HLA)-A11/DR1 transgenic mouse (HLA-A11(+/+)/DR01(+/+)/H-2-β2m(-/-)/IAβ(-/-)) was generated by crossing HLA-A11 transgenic (Tg) mice with HLA-A2(+/+)/DR01(+/+)/H-2-β2m(-/-)/IAβ(-/-) mice. The HLA-A11-restricted immune response of this mouse model was then examined. HLA-A11 Tg mice expressing a chimeric major histocompatibility complex (MHC) molecule comprising the α1, α2, and β2m domains of human HLA-A11 and the α3 transmembrane and cytoplasmic domains of murine H-2D(b) were generated. The correct integration of HLA-A11 and HLA-DR1 into the genome of the HLA-A11/DR1 Tg mice (which lacked the expression of endogenous H-2-I/II molecules) was then confirmed. Immunizing mice with a recombinant HBV vaccine or a recombinant HIV-1 protein resulted in the generation of IFN-γ-producing cytotoxic T lymphocyte (CTL) and antigen-specific antibodies. The HLA-A11-restricted CTL response was directed at HLA immunodominant epitopes. These mice represent a versatile animal model for studying the immunogenicity of HLA CTL epitopes in the absence of a murine MHC response. The established animal model will also be useful for evaluating and optimizing T cell-based vaccines and for studying differences in antigen processing between mice and humans.

Vaccination with High-Affinity Epitopes Impairs Antitumor Efficacy by Increasing PD-1 Expression on CD8+ T Cells

Antitumor vaccines encoding self-antigens generally have low immunogenicity in clinical trials. Several approaches are aimed at improving vaccine immunogenicity, including efforts to alter encoded epitopes. Immunization with epitopes altered for increased affinity for the major histocompatibility complex (MHC) or T-cell receptor (TCR) elicits greater numbers of CD8 T cells but inferior antitumor responses. Our previous results suggested that programmed death 1 (PD-1) and its ligand (PD-L1) increased on antigen-specific CD8 T cells and tumor cells, respectively, after high-affinity vaccination. In this report, we use two murine models to investigate whether the dose, MHC affinity, or TCR affinity of an epitope affected the antitumor response via the PD-1/PD-L1 axis. T cells activated with high-affinity epitopes resulted in prolonged APC:T-cell contact time that led to elevated, persistent PD-1 expression, and expression of other checkpoint molecules, in vitro and in vivo Immunization with high-affinity epitopes also decreased antitumor efficacy in the absence of PD-1 blockade. Thus, APC:T-cell contact time can be altered by epitope affinity and lead to therapeutically relevant changes in vaccine efficacy mediated by changes in PD-1 expression. These findings have implications for the use of agents targeting PD-1 expression or function whenever high-affinity CD8 T cells are elicited or supplied by means of vaccination or adoptive transfer. Cancer Immunol Res; 5(8); 630-41. ©2017 AACR.

Mini-intronic plasmid vaccination elicits tolerant LAG3+ CD8+ T cells and inferior antitumor responses

Increasing transgene expression has been a major focus of attempts to improve DNA vaccine-induced immunity in both preclinical studies and clinical trials. Novel mini-intronic plasmids (MIPs) have been shown to cause elevated and sustained transgene expression in vivo. We sought to test the antitumor activity of a MIP, compared to standard DNA plasmid immunization, using the tumor-specific antigen SSX2 in an HLA-A2-restricted tumor model. We found that MIP vaccination elicited a greater frequency of antigen-specific CD8⁺ T cells when compared to conventional plasmid, and protected animals from subsequent tumor challenge. However, therapeutic vaccination with the MIP resulted in an inferior antitumor effect, and CD8⁺ tumor-infiltrating lymphocytes from these mice expressed higher levels of surface LAG3. Antitumor efficacy of MIP vaccination could be recovered upon antibody blockade of LAG3. In non-tumor bearing mice, MIP immunization led to a loss of epitope dominance, attenuated CD8⁺ cytokine responses to the dominant p103 epitope, and increased LAG3 expression on p103-specific CD8⁺ T cells. Further, LAG3 expression on CD8⁺ T cells was associated with antigen dose and persistence in spite of DNA-induced innate immunity. These data suggest that for antitumor immunization, approaches leading to increased antigen expression following vaccination might optimally be combined with LAG3 inhibition in human trials. On the other hand, mini-intronic vector approaches may be a superior means to elicit LAG3-dependent tolerance in the treatment of autoimmune diseases.

Novel cancer antigens for personalized immunotherapies: latest evidence and clinical potential

The clinical success of monoclonal antibody immune checkpoint modulators such as ipilimumab, which targets cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and the recently approved agents nivolumab and pembrolizumab, which target programmed cell death receptor 1 (PD-1), has stimulated renewed enthusiasm for anticancer immunotherapy, which was heralded by Science as 'Breakthrough of the Year' in 2013. As the potential of cancer immunotherapy has been recognized since the 1890s when William Coley showed that bacterial products could be beneficial in cancer patients, leveraging the immune system in the treatment of cancer is certainly not a new concept; however, earlier attempts to develop effective therapeutic vaccines and antibodies against solid tumors, for example, melanoma, frequently met with failure due in part to self-tolerance and the development of an immunosuppressive tumor microenvironment. Increased knowledge of the mechanisms through which cancer evades the immune system and the identification of tumor-associated antigens (TAAs) and negative immune checkpoint regulators have led to the development of vaccines and monoclonal antibodies targeting specific tumor antigens and immune checkpoints such as CTLA-4 and PD-1. This review first discusses the established targets of currently approved cancer immunotherapies and then focuses on investigational cancer antigens and their clinical potential. Because of the highly heterogeneous nature of tumors, effective anticancer immunotherapy-based treatment regimens will likely require a personalized combination of therapeutic vaccines, antibodies and chemotherapy that fit the specific biology of a patient's disease.

An Optimization-Driven Analysis Pipeline to Uncover Biomarkers and Signaling Paths: Cervix Cancer

Establishing how a series of potentially important genes might relate to each other is relevant to understand the origin and evolution of illnesses, such as cancer. High-throughput biological experiments have played a critical role in providing information in this regard. A special challenge, however, is that of trying to conciliate information from separate microarray experiments to build a potential genetic signaling path. This work proposes a two-step analysis pipeline, based on optimization, to approach meta-analysis aiming to build a proxy for a genetic signaling path.

Nicotinic acetylcholine receptors induce c-Kit ligand/Stem Cell Factor and promote stemness in an ARRB1/ β-arrestin-1 dependent manner in NSCLC

Lung cancer remains the leading cause of cancer-related deaths worldwide. β-arrestin-1 (ARRB1), a scaffolding protein involved in the desensitization of signals arising from activated G-protein-coupled receptors (GPCRs), has been shown to play a role in invasion and proliferation of cancer cells, including nicotine-induced proliferation of human non–small cell lung cancers (NSCLCs). In this study, we identified genes that are differentially regulated by nicotine in an ARRB1/β-arrestin-1 dependent manner in NSCLC cells by microarray analysis. Among the identified genes, SCF (Stem cell factor) strongly differentiated smokers from non-smokers in the Director's Challenge Set expression data and its high expression correlated with poor prognosis. SCF, a major cytokine is the ligand for the c-Kit proto-oncogene and was found to be over expressed in human lung adenocarcinomas, but not squamous cell carcinomas. Data presented here show that transcription factor E2F1 can induce SCF expression at the transcriptional level and depletion of E2F1 or ARRB1/β-arrestin-1 could not promote self-renewal of SP cells. These studies suggest that nicotine might be promoting NSCLC growth and metastasis by inducing the secretion of SCF, and raise the possibility that targeting signalling cascades that activate E2F1 might be an effective way to combat NSCLC.

Augmenting antitumor immune responses with epigenetic modifying agents

Epigenetic silencing of immune-related genes is a striking feature of the cancer genome that occurs in the process of tumorigenesis. This phenomena impacts antigen processing and antigen presentation by tumor cells and facilitates evasion of immunosurveillance. Further modulation of the tumor microenvironment by altered expression of immunosuppressive cytokines impairs antigen-presenting cells and cytolytic T-cell function. The potential reversal of immunosuppression by epigenetic modulation is therefore a promising and versatile therapeutic approach to reinstate endogenous immune recognition and tumor lysis. Pre-clinical studies have identified multiple elements of the immune system that can be modulated by epigenetic mechanisms and result in improved antigen presentation, effector T-cell function, and breakdown of suppressor mechanisms. Recent clinical studies are utilizing epigenetic therapies prior to, or in combination with, immune therapies to improve clinical outcomes.

Ectopic expression of cancer/testis antigen SSX2 induces DNA damage and promotes genomic instability

SSX cancer/testis antigens are frequently expressed in melanoma tumors and represent attractive targets for immunotherapy, but their role in melanoma tumorigenesis has remained elusive. Here, we investigated the cellular effects of SSX2 expression. In A375 melanoma cells, SSX2 expression resulted in an increased DNA content and enlargement of cell nuclei, suggestive of replication aberrations. The cells further displayed signs of DNA damage and genomic instability, associated with p53-mediated G1 cell cycle arrest and a late apoptotic response. These results suggest a model wherein SSX2-mediated replication stress translates into mitotic defects and genomic instability. Arrest of cell growth and induction of DNA double-strand breaks was also observed in MCF7 breast cancer cells in response to SSX2 expression. Additionally, MCF7 cells with ectopic SSX2 expression demonstrated typical signs of senescence (i.e. an irregular and enlarged cell shape, enhanced β-galactosidase activity and DNA double-strand breaks). Since replication defects, DNA damage and senescence are interconnected and well-documented effects of oncogene expression, we tested the oncogenic potential of SSX2. Importantly, knockdown of SSX2 expression in melanoma cell lines demonstrated that SSX2 supports the growth of melanoma cells. Our results reveal two important phenotypes of ectopic SSX2 expression that may drive/support tumorigenesis: First, immediate induction of genomic instability, and second, long-term support of tumor cell growth.

Synaptonemal complex protein 3 is a prognostic marker in cervical cancer

Synaptonemal complex protein 3 (SCP3), a member of Cor1 family, is up-regulated in various cancer cells; however, its oncogenic potential and clinical significance has not yet been characterized. In the present study, we investigated the oncogenic role of SCP3 and its relationship with phosphorylated AKT (pAKT) in cervical neoplasias. The functional role of SCP3 expression was investigated by overexpression or knockdown of SCP3 in murine cell line NIH3T3 and human cervical cancer cell lines CUMC6, SiHa, CaSki, and HeLa both in vitro and in vivo. Furthermore, we examined SCP3 expression in tumor specimens from 181 cervical cancer and 400 cervical intraepithelial neoplasia (CIN) patients by immunohistochemistry and analyzed the correlation between SCP3 expression and clinicopathologic factors or survival. Overexpression of SCP3 promoted AKT-mediated tumorigenesis both in vitro and in vivo. Functional studies using NIH3T3 cells demonstrated that the C-terminal region of human SCP3 is important for AKT activation and its oncogenic potential. High expression of SCP3 was significantly associated with tumor stage (P = 0.002) and tumor grade (P<0.001), while SCP3 expression was positively associated with pAKT protein level in cervical neoplasias. Survival times for patients with cervical cancer overexpressing both SCP3 and pAKT (median, 134.0 months, n = 68) were significantly shorter than for patients with low expression of either SCP3 or pAKT (161.5 months, n = 108) as determined by multivariate analysis (P = 0.020). Our findings suggest that SCP3 plays an important role in the progression of cervical cancer through the AKT signaling pathway, supporting the possibility that SCP3 may be a promising novel cancer target for cervical cancer therapy.

Oncogenic functions of the cancer-testis antigen SSX on the proliferation, survival, and signaling pathways of cancer cells

SSX is a transcription factor with elusive oncogenic functions expressed in a variety of human tumors of epithelial and mesenchymal origin. It has raised substantial interest as a target for cancer therapy since it elicits humoral responses and displays restricted expression to cancer, spermatogonia and mesenchymal stem cells. Here, we investigated the oncogenic properties of SSX by employing a RNA interference to knock-down the endogenous expression of SSX in melanoma and osteosarcoma cell lines. Depletion of SSX expression resulted in reduced proliferation with cells accumulating in the G1 phase of the cell cycle. We found that the growth promoting and survival properties of SSX are mediated in part though modulation of MAPK/Erk and Wnt signaling pathways, since SSX silencing inhibited Erk-mediated signaling and transcription of cMYC and Akt-1. We also found that SSX forms a transient complex with β-catenin at the G1-S phase boundary resulting in the altered expression of β-catenin target genes such as E-cadherin, snail-2 and vimentin, involved in epithelial-mesenchymal transitions. Importantly the silencing of SSX expression in in vivo significantly impaired the growth of melanoma tumor xenografts. Tumor biopsies from SSX silenced tumors displayed reduced cyclin A staining, indicative of low proliferation and predominantly cycloplasmic β-catenin compared to SSX expressing tumors. The present study demonstrates a previously unknown function of SSX, that as an oncogene and as a tumor target for the development of novel anti-cancer drugs.

Development of a T cell receptor targeting an HLA-A*0201 restricted epitope from the cancer-testis antigen SSX2 for adoptive immunotherapy of cancer

The clinical success of adoptive immunotherapy of cancer relies on the selection of target antigens that are highly expressed in tumor cells but absent in essential normal tissues. A group of genes that encode the cancer/testis or cancer germline antigens have been proposed as ideal targets for immunotherapy due to their high expression in multiple cancer types and their restricted expression in immunoprivileged normal tissues. In the present work we report the isolation and characterization of human T cell receptors (TCRs) with specificity for synovial sarcoma X breakpoint 2 (SSX2), a cancer/testis antigen expressed in melanoma, prostate cancer, lymphoma, multiple myeloma and pancreatic cancer, among other tumors. We isolated seven HLA-A2 restricted T cell receptors from natural T cell clones derived from tumor-infiltrated lymph nodes of two SSX2-seropositive melanoma patients, and selected four TCRs for cloning into retroviral vectors. Peripheral blood lymphocytes (PBL) transduced with three of four SSX2 TCRs showed SSX2_41-49 (KASEKIFYV) peptide specific reactivity, tumor cell recognition and tetramer binding. One of these, TCR-5, exhibited tetramer binding in both CD4 and CD8 cells and was selected for further studies. Antigen-specific and HLA-A*0201-restricted interferon-γ release, cell lysis and lymphocyte proliferation was observed following culture of TCR engineered human PBL with relevant tumor cell lines. Codon optimization was found to increase TCR-5 expression in transduced T cells, and this construct has been selected for development of clinical grade viral vector producing cells. The tumor-specific pattern of expression of SSX2, along with the potent and selective activity of TCR-5, makes this TCR an attractive candidate for potential TCR gene therapy to treat multiple cancer histologies.

SSX2-4 expression in early-stage non-small cell lung cancer

The expression of cancer/testis antigens SSX2, SSX3, and SSX4 in non-small cell lung cancers (NSCLC) was examined, since they are considered promising targets for cancer immunotherapy due to their immunogenicity and testis-restricted normal tissue expression. We characterized three SSX antibodies and performed immunohistochemical staining of 25 different normal tissues and 143 NSCLCs. The antibodies differed in binding to two distinctive splice variants of SSX2 that exhibited different subcellular staining patterns, suggesting that the two splice variants display different functions. SSX2-4 expression was only detected in 5 of 143 early-stage NSCLCs, which is rare compared to other cancer/testis antigens (e.g. MAGE-A and GAGE). However, further studies are needed to determine whether SSX can be used as a prognostic or predictive biomarker in NSCLC.

Senescent remodeling of the innate and adaptive immune system in the elderly men with prostate cancer

Despite years of intensive investigation that has been made in understanding prostate cancer, it remains a major cause of death in men worldwide. Prostate cancer emerges from multiple alterations that induce changes in expression patterns of genes and proteins that function in networks controlling critical cellular events. Based on the exponential aging of the population and the increasing life expectancy in industrialized Western countries, prostate cancer in the elderly men is becoming a disease of increasing significance. Aging is a progressive degenerative process strictly integrated with inflammation. Several theories have been proposed that attempt to define the role of chronic inflammation in aging including redox stress, mitochondrial damage, immunosenescence, and epigenetic modifications. Here, we review the innate and adaptive immune systems and their senescent remodeling in elderly men with prostate cancer.

Tumour antigens recognized by T lymphocytes: at the core of cancer immunotherapy

In this Timeline, we describe the characteristics of tumour antigens that are recognized by spontaneous T cell responses in cancer patients and the paths that led to their identification. We explain on what genetic basis most, but not all, of these antigens are tumour specific: that is, present on tumour cells but not on normal cells. We also discuss how strategies that target these tumour-specific antigens can lead either to tumour-specific or to crossreactive T cell responses, which is an issue that has important safety implications in immunotherapy. These safety issues are even more of a concern for strategies targeting antigens that are not known to induce spontaneous T cell responses in patients.

DNA vaccines encoding altered peptide ligands for SSX2 enhance epitope-specific CD8+ T-cell immune responses

Plasmid DNA serves as a simple and easily modifiable form of antigen delivery for vaccines. The USDA approval of DNA vaccines for several non-human diseases underscores the potential of this type of antigen delivery method as a cost-effective approach for the treatment or prevention of human diseases, including cancer. However, while DNA vaccines have demonstrated safety and immunological effect in early phase clinical trials, they have not consistently elicited robust anti-tumor responses. Hence many recent efforts have sought to increase the immunological efficacy of DNA vaccines, and we have specifically evaluated several target antigens encoded by DNA vaccine as treatments for human prostate cancer. In particular, we have focused on SSX2 as one potential target antigen, given its frequent expression in metastatic prostate cancer. We have previously identified two peptides, p41-49 and p103-111, as HLA-A2-restricted SSX2-specific epitopes. In the present study we sought to determine whether the efficacy of a DNA vaccine could be enhanced by an altered peptide ligand (APL) strategy wherein modifications were made to anchor residues of these epitopes to enhance or ablate their binding to HLA-A2. A DNA vaccine encoding APL modified to increase epitope binding elicited robust peptide-specific CD8+ T cells producing Th1 cytokines specific for each epitope. Ablation of one epitope in a DNA vaccine did not enhance immune responses to the other epitope. These results demonstrate that APL encoded by a DNA vaccine can be used to elicit increased numbers of antigen-specific T cells specific for multiple epitopes simultaneously, and suggest this could be a general approach to improve the immunogenicity of DNA vaccines encoding tumor antigens.

Expression screening of cancer/testis genes in prostate cancer identifies NR6A1 as a novel marker of disease progression and aggressiveness

BACKGROUND

Cancer/Testis (CT) genes are expressed in male gonads, repressed in most healthy somatic tissues and de-repressed in various somatic malignancies including prostate cancers (PCa). Because of their specific expression signature and their associations with tumor aggressiveness and poor outcomes, CT genes are considered to be useful biomarkers and they are also targets for the development of new anti-cancer immunotherapies. The aim of this study was to identify novel CT genes associated with hormone-sensitive prostate cancer (HSPC), and castration-resistant prostate cancer (CRPC).

METHODS

To identify novel CT genes we screened genes for which transcripts were detected by RNA profiling specifically in normal testis and in either HSPC or CRPC as compared to normal prostate and 44 other healthy tissues using GeneChips. The expression and clinicopathological significance of a promising candidate--NR6A1--was examined in HSPC, CRPC, and metastatic site samples using tissue microarrays.

RESULTS

We report the identification of 98 genes detected in CRPC, HSPC and testicular samples but not in the normal controls. Among them, cellular levels of NR6A1 were found to be higher in HSPC compared to normal prostate and further increased in metastatic lesions and CRPC. Furthermore, increased NR6A1 immunoreactivity was significantly associated with a high Gleason score, advanced pT stage and cancer cell proliferation.

CONCLUSIONS

Our results show that cellular levels of NR6A1 are correlated with disease progression in PCa. We suggest that this essential orphan nuclear receptor is a potential therapeutic target as well as a biomarker of PCa aggressiveness.

Vaccination using peptides spanning the SYT-SSX tumor-specific translocation

Evaluation of: Kawaguchi S, Tsukahara T, Ida K et al. SYT-SSX breakpoint peptide vaccines in patients with synovial sarcoma: a study from the Japanese Musculoskeletal Oncology Group. Cancer Sci. 103(9), 1625-1630 (2012). The identification of genetic translocations as key tumor-initiating events has led to the development of novel antigen-specific vaccines targeting these tumor-specific breakpoint regions. Previous studies have evaluated vaccines targeting the breakpoints in the BCR-ABL translocation in patients with chronic myelogenous leukemia and EWS-FLI1 in patients with Ewing sarcoma. In the article under evaluation, the authors evaluated a peptide vaccine targeting the breakpoint in the SYT-SSX translocation, the genetic translocation essentially pathognomonic for synovial sarcoma. This is the second small clinical trial reported by this group using HLA-A24-binding peptides as vaccine antigens. In this four-arm trial, using a native or HLA-A24-optimized SYT-SSX peptide with or without adjuvant plus IFN-α, they immunized patients with metastatic synovial sarcoma. Immune responses were evaluated by delayed-type hypersensitivity testing and tetramer analysis. No robust evidence of immune response to the target epitope was detected. Some patients treated with peptide in adjuvant plus IFN-α had stable disease. These results suggest that future similar studies might best evaluate patients with a lower burden of disease, consider alternative immunization approaches to the SYT-SSX target antigen and consider the efficacy of IFN-α alone for the treatment of synovial sarcoma.

Identification of potential biomarkers from microarray experiments using multiple criteria optimization

Microarray experiments are capable of determining the relative expression of tens of thousands of genes simultaneously, thus resulting in very large databases. The analysis of these databases and the extraction of biologically relevant knowledge from them are challenging tasks. The identification of potential cancer biomarker genes is one of the most important aims for microarray analysis and, as such, has been widely targeted in the literature. However, identifying a set of these genes consistently across different experiments, researches, microarray platforms, or cancer types is still an elusive endeavor. Besides the inherent difficulty of the large and nonconstant variability in these experiments and the incommensurability between different microarray technologies, there is the issue of the users having to adjust a series of parameters that significantly affect the outcome of the analyses and that do not have a biological or medical meaning. In this study, the identification of potential cancer biomarkers from microarray data is casted as a multiple criteria optimization (MCO) problem. The efficient solutions to this problem, found here through data envelopment analysis (DEA), are associated to genes that are proposed as potential cancer biomarkers. The method does not require any parameter adjustment by the user, and thus fosters repeatability. The approach also allows the analysis of different microarray experiments, microarray platforms, and cancer types simultaneously. The results include the analysis of three publicly available microarray databases related to cervix cancer. This study points to the feasibility of modeling the selection of potential cancer biomarkers from microarray data as an MCO problem and solve it using DEA. Using MCO entails a new optic to the identification of potential cancer biomarkers as it does not require the definition of a threshold value to establish significance for a particular gene and the selection of a normalization procedure to compare different experiments is no longer necessary.

Presence of antigen-specific somatic allelic mutations and splice variants do not predict for immunological response to genetic vaccination

Background

Antigen-specific anti-tumor vaccines have demonstrated clinical efficacy, but immunological and clinical responses appear to be patient-dependent. We hypothesized that naturally-occurring differences in amino acid sequence of a host’s target antigen might predict for immunological outcome from genetic vaccination by presentation of epitopes different from the vaccine.

Methods

Using peripheral blood cells from 33 patients who had been treated with a DNA vaccine encoding prostatic acid phosphatase (PAP), we sequenced the exons encoding PAP and PSA genes from somatic DNA to identify single nucleotide polymorphisms. In addition, mRNA was collected to detect alternative splice variants of PAP.

Results

We detected four synonymous coding mutations of PAP among 33 patients; non-synonymous coding mutations were not identified. Alternative splice variants of PAP were detected in 22/27 patients tested. The presence of detectable splice variants was not predictive of immunological outcome from vaccination. Immune responses to peptides encoded by these splice variants were common (16/27) prior to immunization, but not associated with immune responses elicited with vaccination.

Conclusions

These results suggest that antigen-specific immune responses detectable after treatment with this genetic vaccine are specific for the host-encoded antigen and not due to epitope differences between the vaccine and a particular individual’s somatic coding sequence.

Cancer/testis antigens and urological malignancies

Cancer/testis antigens (CTAs) are a group of tumour-associated antigens (TAAs) that display normal expression in the adult testis--an immune-privileged organ--but aberrant expression in several types of cancers, particularly in advanced cancers with stem cell-like characteristics. There has been an explosion in CTA-based research since CTAs were first identified in 1991 and MAGE-1 was shown to elicit an autologous cytotoxic T-lymphocyte (CTL) response in a patient with melanoma. The resulting data have not only highlighted a role for CTAs in tumorigenesis, but have also underscored the translational potential of these antigens for detecting and treating many types of cancers. Studies that have investigated the use of CTAs for the clinical management of urological malignancies indicate that these TAAs have potential roles as novel biomarkers, with increased specificity and sensitivity compared to those currently used in the clinic, and therapeutic targets for cancer immunotherapy. Increasing evidence supports the utilization of these promising tools for urological indications.

Tumor-associated antigens for specific immunotherapy of prostate cancer

Prostate cancer (PCa) is the most common noncutaneous cancer diagnosis and the second leading cause of cancer-related deaths among men in the United States. Effective treatment modalities for advanced metastatic PCa are limited. Immunotherapeutic strategies based on T cells and antibodies represent interesting approaches to prevent progression from localized to advanced PCa and to improve survival outcomes for patients with advanced disease. CD8⁺ cytotoxic T lymphocytes (CTLs) efficiently recognize and destroy tumor cells. CD4⁺ T cells augment the antigen-presenting capacity of dendritic cells and promote the expansion of tumor-reactive CTLs. Antibodies mediate their antitumor effects via antibody-dependent cellular cytotoxicity, activation of the complement system, improving the uptake of coated tumor cells by phagocytes, and the functional interference of biological pathways essential for tumor growth. Consequently, several tumor-associated antigens (TAAs) have been identified that represent promising targets for T cell- or antibody-based immunotherapy. These TAAs comprise proteins preferentially expressed in normal and malignant prostate tissues and molecules which are not predominantly restricted to the prostate, but are overexpressed in various tumor entities including PCa. Clinical trials provide evidence that specific immunotherapeutic strategies using such TAAs represent safe and feasible concepts for the induction of immunological and clinical responses in PCa patients. However, further improvement of the current approaches is required which may be achieved by combining T cell- and/or antibody-based strategies with radio-, hormone-, chemo- or antiangiogenic therapy.

Cancer/testis antigens: novel tools for discerning aggressive and non-aggressive prostate cancer

The introduction of serum prostate-specific antigen (PSA) in the 1980s has dramatically altered and benefited the initial diagnosis of prostate cancer. However, the widespread use of PSA testing has resulted in overdetection and overtreatment of potentially indolent disease. Thus, a clinical dilemma today in the management of prostate cancer is to discern men with aggressive disease who need definitive treatment from men whose disease are not lethal. Although several serum and tissue biomarkers have been evaluated during the past decade, improved markers are still needed to enhance the accuracy, with which patients at risk can be discerned and treated more aggressively. The cancer/testis antigens (CTAs) are a group of proteins that are restricted to the testis in the normal adult, but are aberrantly expressed in several types of cancers. Because of their restricted expression pattern, the CTAs represent attractive biomarker candidates for cancer diagnosis/prognosis. Furthermore, several studies to date have reported the differential expression of CTAs in prostate cancer. Here, we review recent developments that demonstrate the potential of the CTAs as biomarkers to discern the aggressive phenotype of prostate cancer.