Epigenetic control of MAGE gene expression by the KIT tyrosine kinase

The potential value of cancer-testis antigens in ovarian cancer: Prognostic markers and targets for immunotherapy

BACKGROUND

Tumor immunotherapy has become an important adjuvant therapy after surgery, radiotherapy, and chemotherapy. In recent years, the role of tumor-associated antigen (TAA) in tumor immunotherapy has become increasingly prominent. Cancer-testis antigen (CTA) is a kind of TAA that is highly restricted in a variety of tumors and can induce an immune response.

AIMS

This review article aimed to evaluate the role of CTA on the progression of ovarian cancer, its diagnostic efficacy, and the potential for immunotherapy.

METHODS

We analyzed publications and outlined a comprehensive of overview the regulatory mechanism, immunogenicity, clinical expression significance, tumorigenesis, and application prospects of CTA in ovarian cancer, with a particular focus on recent progress in CTA-based immunotherapy.

RESULTS

The expression of CTA affects the occurrence, development, and prognosis of ovarian cancer and is closely related to tumor immunity.

CONCLUSION

CTA can be used as a biomarker for the diagnosis and prognosis evaluation of ovarian cancer and is an ideal target for antitumor immunotherapy. These findings provide novel insights on CTA in the improvement of diagnosis and treatment for ovarian cancer. The successes, current challenges and future prospects were also discussed to portray its significant potential.

MAGE-I proteins and cancer-pathways: A bidirectional relationship

Data emerged from the last 20 years of basic research on tumor antigens positioned the type I MAGE (Melanoma Antigen GEnes - I or MAGE-I) family as cancer driver factors. MAGE-I gene expression is mainly restricted to normal reproductive tissues. However, abnormal re-expression in cancer unbalances the cell status towards enhanced oncogenic activity or reduced tumor suppression. Anomalous MAGE-I gene re-expression in cancer is attributed to altered epigenetic-mediated chromatin silencing. Still, emerging data indicate that MAGE-I can be regulated at protein level. Results from different laboratories suggest that after its anomalous re-expression, specific MAGE-I proteins can be regulated by well-known signaling pathways or key cellular processes that finally potentiate the cancer cell phenotype. Thus, MAGE-I proteins both regulate and are regulated by cancer-related pathways. Here, we present an updated review highlighting the recent findings on the regulation of MAGE-I by oncogenic pathways and the potential consequences in the tumor cell behavior.

Kita-Kyushu Lung Cancer Antigen-1 (KK-LC-1): A Promising Cancer Testis Antigen

Cancer has always been a huge problem in the field of human health, and its early diagnosis and treatment are the key to solving this problem. Cancer testis antigens (CTAs) are a family of multifunctional proteins that are specifically expressed in male spermatozoa and tumor cells but not in healthy somatic cells. Studies have found that CTAs are involved in the occurrence and development of tumors, and some CTAs trigger immunogenicity, which suggests a possibility of tumor immunotherapy. The differential expression and function of CTAs in normal tissues and tumor cells can promote the screening of tumor markers and the development of new immunotherapies. This article introduces the expression of Kita-Kyushu lung cancer antigen-1 (KK-LC-1), a new member of the CTA family, in different types of tumors and its role in immunotherapy.

Pathogenicity of the MAGE family

The melanoma antigen gene (MAGE) protein family is a group of highly conserved proteins that share a common homology domain. Under normal circumstances, numerous MAGE proteins are only expressed in reproduction-related tissues; however, abnormal expression levels are observed in a variety of tumor tissues. The MAGE family consists of type I and II proteins, several of which are cancer-testis antigens that are highly expressed in cancer and serve a critical role in tumorigenesis. Therefore, this review will use the relationship between MAGEs and tumors as a starting point, focusing on the latest developments regarding the function of MAGEs as oncogenes, and preliminarily reveal their possible mechanisms.

Extracellular vesicles in urological malignancies

Extracellular vesicles (EVs) are small lipid bound structures released from cells containing bioactive cargoes. Both the type of cargo and amount loaded varies compared to that of the parent cell. The characterisation of EVs in cancers of the male urogenital tract has identified several cargoes with promising diagnostic and disease monitoring potential. EVs released by cancers of the male urogenital tract promote cell-to-cell communication, migration, cancer progression and manipulate the immune system promoting metastasis by evading the immune response. Their use as diagnostic biomarkers represents a new area of screening and disease detection, potentially reducing the need for invasive biopsies. Many validated EV cargoes have been found to have superior sensitivity and specificity than current diagnostic tools currently in use. The use of EVs to improve disease monitoring and develop novel therapeutics will enable clinicians to individualise patient management in the exciting era of personalised medicine.

Oncogenic activity and cellular functionality of melanoma associated antigen A3

Cancer testis antigen Melanoma associated antigen A3 (MAGE-A3) has been subject of research for many years. Being expressed in various tumor types and influencing proliferation, metastasis, and tumor pathogenicity, MAGE-A3 is an attractive target for cancer therapy, particularly because in healthy tissues, MAGE-A3 is only expressed in testes and placenta. MAGE-A3 acts as a cellular master regulator by stimulating E3 ubiquitin ligase tripartite motif-containing protein 28 (TRIM28), resulting in regulation of various cellular targets. These include tumor suppressor protein p53 and cellular energy sensor AMP-activated protein kinase (AMPK). The restricted expression of MAGE-A3 in tumor cells makes MAGE-A3 an attractive target for vaccine-based immune therapy. However, although phase I and phase II clinical trials involving MAGE-A3-specific immunotherapeutic interventions were promising, large phase III studies failed. This article gives an overview about the role of MAGE-A3 as a cellular master switch and discusses approaches to improve MAGE-A3-based immunotherapies.

MageC2 protein is upregulated by oncogenic activation of MAPK pathway and causes impairment of the p53 transactivation function

Normal-to-tumor cell transition is accompanied by changes in gene expression and signal transduction that turns the balance toward cancer-cell phenotype, eluding by different mechanisms, the response of tumor-suppressor genes. Here, we observed that MageC2, a MAGE-I protein able to regulate the p53 tumor-suppressor, is accumulated upon MEK/ERK MAPK activation. Overexpression of H-RasV12 oncogene causes an increase in MageC2 protein that is prevented by pharmacologic inhibition of MEK. Similarly, decrease in MageC2 protein levels is shown in A375 melanoma cells (which harbor B-RafV600E oncogenic mutation) treated with MEK inhibitors. MageC2 protein levels decrease when p14ARF is expressed, causing an Mdm2-independent upregulation of p53 transactivation. However, MageC2 is refractory to p14ARF-driven downregulation when H-RasV12 is co-expressed. Using MageC2 knockout A375 cells generated by CRISPR/CAS9 technology, we demonstrated the relevance of MageC2 protein in reducing p53 transcriptional activity in cells containing hyperactive MEK/ERK signaling. Furthermore, gene expression analysis performed in cancer-genomic databases, supports the correlation of reduced p53 transcriptional activity and high MageC2 expression, in melanoma cells containing Ras or B-Raf driver mutations. Data presented here suggest that MageC2 can be a functional target of the oncogenic MEK/ERK pathway to regulate p53.

Emerging roles of the MAGE protein family in stress response pathways

The melanoma antigen (MAGE) proteins all contain a MAGE homology domain. MAGE genes are conserved in all eukaryotes and have expanded from a single gene in lower eukaryotes to ∼40 genes in humans and mice. Whereas some MAGEs are ubiquitously expressed in tissues, others are expressed in only germ cells with aberrant reactivation in multiple cancers. Much of the initial research on MAGEs focused on exploiting their antigenicity and restricted expression pattern to target them with cancer immunotherapy. Beyond their potential clinical application and role in tumorigenesis, recent studies have shown that MAGE proteins regulate diverse cellular and developmental pathways, implicating them in many diseases besides cancer, including lung, renal, and neurodevelopmental disorders. At the molecular level, many MAGEs bind to E3 RING ubiquitin ligases and, thus, regulate their substrate specificity, ligase activity, and subcellular localization. On a broader scale, the MAGE genes likely expanded in eutherian mammals to protect the germline from environmental stress and aid in stress adaptation, and this stress tolerance may explain why many cancers aberrantly express MAGEs Here, we present an updated, comprehensive review on the MAGE family that highlights general characteristics, emphasizes recent comparative studies in mice, and describes the diverse functions exerted by individual MAGEs.

Urine exosome gene expression of cancer-testis antigens for prediction of bladder carcinoma

Background

Exosomes have been regarded as emerging tools for cancer diagnosis. Tumor-derived exosomes contain molecules that enhance cancer progression and affect immune responses.

Material and methods

In the present study, we evaluated expression of seven cancer-testis antigens (CTAs) that are regarded as putative biomarkers and immunotherapeutic targets along with NMP22 in urinary exosomes of bladder cancer patients, healthy subjects and patients affected with nonmalignant urinary disorders.

Results

Exosomal expression of MAGE-B4 was significantly higher in bladder cancer patients compared with normal samples (expression ratio=2.68, P=0.01). However, its expression was lower in bladder cancer patients compared with benign prostate hyperplasia (BPH) patients (expression ratio=0.17, P=0.01). Exosomal expression of NMP22 was significantly higher in bladder cancer patients compared with BPH patients (expression ratio=9.22, P=0.02). Expressions of other genes were not significantly different between bladder cancer patients and normal/nonmalignant samples. We found significant correlation between MAGE-A3 and MAGE-B4 expressions in exosomes obtained from controls. In addition, TSGA10 expression was correlated with expression of NMP22 in both cancer patients and controls.

Conclusion

The present study provides evidences for differential expression of CTAs in urinary exosomes of bladder cancer patients and urogenital disorders and warrants further studies for assessment of their significance in cancer diagnosis and immunotherapeutic approaches.

Establishment of cancer/testis antigen profiling based on clinicopathological characteristics in resected pathological stage III non-small cell lung cancer

Background

Cancer/testis antigen (CTA) expression was found to be highly heterogeneous in previous studies. We aimed to establish a precision CTA profiling in resected stage III non-small cell lung cancer (NSCLC) and demonstrate the best CTA combination covering the widest range of NSCLC cases.

Materials and methods

The expression of 10 CTAs was evaluated in 200 resected stage III NSCLC tissue specimens at protein level. Hierarchical clustering and python programming language analyses was used to demonstrate CTA expression and coverage.

Results

The most commonly expressed CTAs for total cases were MAGEA1 (60.0%), MAGEA10 (50.0%), and KK-LC-1 (47.5%). CTA expression was histology dependent, and concurrent expression was common. The best 2, 3, and 4 CTA combination covered 72.0%, 76.5%, and 79.5% of total cases, respectively. Stratified analysis based on variable clinicopathological characteristics achieved the maximum coverage of 92.3% with only 2 CTA combination in patients with features of male sex, positive smoking history, and adenocarcinoma, compared with a 85.0% coverage when 10 CTAs were assessed. Selected CTA expression was correlated with prognosis based on subgroup analysis. No significant difference was found between CTA expression and epidermal growth factor receptor mutant status.

Conclusion

We established an individualized CTA profiling in resected stage III NSCLC based on 10 CTA expression. With the help of computer programming language, the goal of the maximum CTA expression coverage was reached by using the least CTA combination based on sex, smoking history, and histology. These results were significant for the further study of CTA-specific T-cell immunotherapy.

High expression of MAGE-A9 contributes to stemness and malignancy of human hepatocellular carcinoma

MAGE-A9, a well-characterized cancer testis antigen (CTA), belongs to a member of melanoma antigen gene (MAGE) family. In human malignancies, aberrant expression of MAGE genes correlated with poor clinical prognosis, increased tumor growth, metastases, and enrichment in stem cell populations of certain cancers. Cancer stem cells (CSCs) have been proposed to contribute to the major malignant phenotypes of liver cancer, including recurrence, metastasis and chemoresistance. However, expression and potential role of MAGE-A9 in liver cancer stem cells (LCSCs) still remain unclear. In the present study, we first analyzed the expression profiling of MAGE family genes in EpCAM+ and EpCAM- human hepatocellular carcinoma (HCC), based on public Gene Expression Omnibus (GEO) database. Among these examined MAGE members, MAGE-A9 is the only one with significantly higher expression in EpCAM+ HCC specimens as compared with EpCAM- HCC. Quantitative PCR analysis further confirmed that MAGE-A9 expression significantly elevated in a subtype of HCC patients that had features of hepatic stem/progenitor cells with high-level expression of EpCAM and α-fetoprotein (AFP). Moreover, MAGE-A9 displayed remarkably enriched expression in EpCAM+ HCC cells that were sorted by fluorescence-activated cell sorting and cultured HCC cell spheroids with characteristics of stem/progenitor cells. Functional experiments further revealed that MAGE-A9 overexpression promoted cell proliferation, colony formation, migration, chemoresistance, and tumorigenicity in the context of EpCAM+ HCC cells, whereas MAGE-A9 knockdown significantly inhibited anchorage-dependent and spheroid colony formation and in vivo tumorigenicity. Collectively, these data demonstrate that MAGE-A9 functions as an important regulator of LCSCs, and MAGE-A9 may serve as a potential therapeutic target against HCC stem/progenitor cells.

Genetic Mutations and Epigenetic Modifications: Driving Cancer and Informing Precision Medicine

Cancer treatment is undergoing a significant revolution from "one-size-fits-all" cytotoxic therapies to tailored approaches that precisely target molecular alterations. Precision strategies for drug development and patient stratification, based on the molecular features of tumors, are the next logical step in a long history of approaches to cancer therapy. In this review, we discuss the history of cancer treatment from generic natural extracts and radical surgical procedures to site-specific and combinatorial treatment regimens, which have incrementally improved patient outcomes. We discuss the related contributions of genetics and epigenetics to cancer progression and the response to targeted therapies and identify challenges and opportunities for the success of precision medicine. The identification of patients who will benefit from targeted therapies is more complex than simply identifying patients whose tumors harbour the targeted aberration, and intratumoral heterogeneity makes it difficult to determine if a precision therapy is successful during treatment. This heterogeneity enables tumors to develop resistance to targeted approaches; therefore, the rational combination of therapeutic agents will limit the threat of acquired resistance to therapeutic success. By incorporating the view of malignant transformation modulated by networks of genetic and epigenetic interactions, molecular strategies will enable precision medicine for effective treatment across cancer subtypes.

A Comprehensive Guide to the MAGE Family of Ubiquitin Ligases

Melanoma antigen (MAGE) genes are conserved in all eukaryotes and encode for proteins sharing a common MAGE homology domain. Although only a single MAGE gene exists in lower eukaryotes, the MAGE family rapidly expanded in eutherians and consists of more than 50 highly conserved genes in humans. A subset of MAGEs initially garnered interest as cancer biomarkers and immunotherapeutic targets due to their antigenic properties and unique expression pattern that is primary restricted to germ cells and aberrantly reactivated in various cancers. However, further investigation revealed that MAGEs not only drive tumorigenesis but also regulate pathways essential for diverse cellular and developmental processes. Therefore, MAGEs are implicated in a broad range of diseases including neurodevelopmental, renal, and lung disorders, and cancer. Recent biochemical and biophysical studies indicate that MAGEs assemble with E3 RING ubiquitin ligases to form MAGE-RING ligases (MRLs) and act as regulators of ubiquitination by modulating ligase activity, substrate specification, and subcellular localization. Here, we present a comprehensive guide to MAGEs highlighting the molecular mechanisms of MRLs and their physiological roles in germ cell and neural development, oncogenic functions in cancer, and potential as therapeutic targets in disease.

The MAGE protein family and cancer

The Melanoma Antigen Gene (MAGE) protein family is a large, highly conserved group of proteins that share a common MAGE homology domain. Intriguingly, many MAGE proteins are restricted in expression to reproductive tissues, but are aberrantly expressed in a wide variety of cancer types. Originally discovered as antigens on tumor cells and developed as cancer immunotherapy targets, recent literature suggests a more prominent role for MAGEs in driving tumorigenesis. This review will highlight recent developments into the function of MAGEs as oncogenes, their mechanisms of action in regulation of ubiquitin ligases, and outstanding questions in the field.

Intratumoral Heterogeneity of MAGE-C1/CT7 and MAGE-C2/CT10 Expression in Mucosal Melanoma

Mucosal melanoma is a rare disease, which differs from its cutaneous counterpart genetically and for its clinical behaviour. Moreover this is a heterogeneous disease based on the tissue of origin. As CT7 and CT10 are highly expressed in cutaneous melanoma and are immunogenic in this disease, we analysed their expression throughout the different subtypes of mucosal melanoma and tumor development. We detected a frequent expression of CT7 in primaries and corresponding metastases (55%) as well as for CT10 (30%). This expression resulted to be heterogeneous in the same tumor specimen and moreover influenced by the tissue of origin. Our results support the role of these antigens in immunotherapy for mucosal melanoma.

A Comprehensive Expression Analysis of Cancer Testis Antigens in Head and Neck Squamous Cell Carcinoma Revels MAGEA3/6 as a Marker for Recurrence

Despite significant advances in the treatment of head and neck squamous cell carcinoma (HNSCC), the survival rate has not changed in the last decades. Therefore, the development of novel therapeutic strategies is pursued. Cancer-testis antigens (CTA) are strong immunogenic proteins with a tumor-restricted expression pattern, and are considered ideal targets for tumor-specific immunotherapeutic approaches. In this study, using an in silico approach, we selected, among 139 previously described CTA, candidates to be evaluated in 89 HNSCC and 20 normal mucosa samples. SPANX-CD (71.9%), MAGEB2 (44.9%), MAGEA1 (44.9%), MAGEB6 (32.6%), and CXORF48 (27.0%) were found frequently expressed in HNSCC, and over 85% of the tumors expressed at least one of these five CTAs. The mRNA positivity of CXORF48, MAGEB6, and CRISP2 presented significant associations with recognized clinical features for poor outcome. Furthermore, MAGEA3/6 positivity was associated with significantly better disease-free survival (DFS, P = 0.014), and the expression of this antigen was shown to be an independent prognostic factor for tumor recurrence. In conclusion, one of five selected CTAs is expressed in at least 85% of the HNSCCs, suggesting a possible usage as target for immunotherapeutic approaches, and the mRNA-positivity for MAGEA3/6 is shown to be an independent marker for DFS.

CD8+ TIL recruitment may revert the association of MAGE A3 with aggressive features in thyroid tumors

Background. We aimed to investigate a possible role of MAGE A3 and its associations with infiltrated immune cells in thyroid malignancy, analyzing their utility as a diagnostic and prognostic marker. Materials and Methods. We studied 195 malignant tissues: 154 PTCs and 41 FTCs; 102 benign tissues: 51 follicular adenomas and 51 goiter and 17 normal thyroid tissues. MAGE A3 and immune cell markers (CD4 and CD8) were evaluated using immunohistochemistry and compared with clinical pathological features. Results. The semiquantitative analysis and ACIS III analysis showed similar results. MAGE A3 was expressed in more malignant than in benign lesions (P < 0.0001), also helping to discriminate follicular-patterned lesions. It was also higher in tumors in which there was extrathyroidal invasion (P = 0.0206) and in patients with stage II disease (P = 0.0107). MAGE A3+ tumors were more likely to present CD8+ TIL (P = 0.0346), and these tumors were associated with less aggressive features, that is, extrathyroidal invasion and small size. There was a trend of MAGE A3+ CD8+ tumors to evolve free of disease. Conclusion. We demonstrated that MAGE A3 and CD8+ TIL infiltration may play an important role in malignant thyroid nodules, presenting an interesting perspective for new researches on DTC immunotherapy.

Diagnostic and prognostic utility of a DNA hypermethylated gene signature in prostate cancer

We aimed to identify a prostate cancer DNA hypermethylation microarray signature (denoted as PHYMA) that differentiates prostate cancer from benign prostate hyperplasia (BPH), high from low-grade and lethal from non-lethal cancers. This is a non-randomized retrospective study in 111 local Asian men (87 prostate cancers and 24 BPH) treated from 1995 to 2009 in our institution. Archival prostate epithelia were laser-capture microdissected and genomic DNA extracted and bisulfite-converted. Samples were profiled using Illumina GoldenGate Methylation microarray, with raw data processed by GenomeStudio. A classification model was generated using support vector machine, consisting of a 55-probe DNA methylation signature of 46 genes. The model was independently validated on an internal testing dataset which yielded cancer detection sensitivity and specificity of 95.3% and 100% respectively, with overall accuracy of 96.4%. Second validation on another independent western cohort yielded 89.8% sensitivity and 66.7% specificity, with overall accuracy of 88.7%. A PHYMA score was developed for each sample based on the state of methylation in the PHYMA signature. Increasing PHYMA score was significantly associated with higher Gleason score and Gleason primary grade. Men with higher PHYMA scores have poorer survival on univariate (p = 0.0038, HR = 3.89) and multivariate analyses when controlled for (i) clinical stage (p = 0.055, HR = 2.57), and (ii) clinical stage and Gleason score (p = 0.043, HR = 2.61). We further performed bisulfite genomic sequencing on 2 relatively unknown genes to demonstrate robustness of the assay results. PHYMA is thus a signature with high sensitivity and specificity for discriminating tumors from BPH, and has a potential role in early detection and in predicting survival.

Melanoma antigen gene family A as a molecular marker of gastric and colorectal cancers

The present study aimed to evaluate the role of melanoma antigen family A (MAGEA) in gastric and colorectal cancer cell lines and clinical tissue samples. we used 10 gastric and 9 colorectal cancer cell lines, 20 early-stage and 21 advanced-stage gastric cancer tissues, 20 colon adenomas and 19 colorectal cancer tissues. Real-time RT-PCR assay was used for the determination of MAGEA mRNA levels. Western blot analysis and immunohistochemistry were used for the determination of MAGEA protein levels in cell lines and tissues, respectively. Gastric and colorectal cancer cell lines showed variable mRNA expression levels of MAGEA. The MAGEA protein was detected in 30% of gastric cancer cell lines and in 22.2% of colorectal cancer cell lines. There was a high correlation between mRNA and protein expression. Regarding the clinical samples, MAGEA expression was noted in 25, 28.6 and 31.6%, respectively in early-stage, advanced-stage gastric cancer tissues and colon adenocarcinoma, but was negative in the adjacent normal tissues of the stomach and colon as well as colon adenoma. These results indicate that MAGEA is involved in the carcinogenesis of gastric and colorectal cancer and, therefore, can be used as a diagnostic marker to predict these cancers.

Epigenetic regulation of CXCR4 expression by the ocular microenvironment

PURPOSE

Expression of the chemokine receptor CXCR4 by tumors is associated with metastatic migration and invasion of tumor cells. The importance of CXCR4 expression by uveal melanomas in metastasis to the liver was recently demonstrated when injection of CXCR4-negative uveal melanoma cells into mice resulted in reduced liver metastasis compared with CXCR4-positive uveal melanoma cells. Factors in the eye can induce downregulation of genes by epigenetic mechanisms. This study examined whether epigenetic regulation by the ocular environment induced downregulation of CXCR4 expression.

METHODS

LS174T colon cancer cells were injected in the anterior chamber (AC), subcutaneously (SC), or in the spleen capsule to induce liver metastasis in immune-deficient mice. CXCR4 gene transcription was analyzed by RT-PCR, and protein expression was determined by flow cytometry. Methyltransferase and histone deacetylase activities were determined by ELISA. Treatment with either 5-Aza-2-deoxycytidine (5-Aza) or trichostatin A (TSA) was used to induce demethylation or inhibit histone deacetylases, respectively.

RESULTS

AC-derived LS174T cells showed lower CXCR4 gene expression compared with SC-, liver-derived, or wild-type tumor cells. AC-derived LS174T tumor cells expressed methyltransferase activity compared with SC-, liver-derived, and wild-type tumor cells. Deacetylase activity was elevated in AC-derived LS174T tumor cells compared with SC-derived, liver-derived, and wild-type tumor cells. Treatment of AC-derived LS174T tumor cells with 5-Aza upregulated CXCR4 expression. TSA treatment did not restore CXCR4 expression.

CONCLUSIONS

These studies demonstrate that ocular microenvironment factors induce methylation and downregulation of tumor CXCR4 expression.

DNA hypomethylation and activation of germline-specific genes in cancer

DNA methylation, occurring at cytosines in CpG dinucleotides, is a potent mechanism of transcriptional repression. Proper genomic methylation -patterns become profoundly altered in cancer cells: both gains (hypermethylation) and losses (hypomethylation) of methylated sites are observed. Although DNA hypomethylation is detected in a vast majority of human tumors and affects many genomic regions, its role in tumor biology remains elusive. Surprisingly, DNA hypomethylation in cancer was found to cause the aberrant activation of only a limited group of genes. Most of these are normally expressed exclusively in germline cells and were grouped under the term "cancer-germline" (CG) genes. CG genes represent unique examples of genes that rely primarily on DNA methylation for their tissue-specific expression. They are also being exploited to uncover the mechanisms that lead to DNA hypomethylation in tumors. Moreover, as CG genes encode tumor-specific antigens, their activation in cancer highlights a direct link between epigenetic alterations and tumor immunity. As a result, clinical trials combining epigenetic drugs with anti-CG antigen vaccines are being considered.

Germ cell proteins in melanoma: prognosis, diagnosis, treatment, and theories on expression

Germ cell protein expression in melanoma has been shown to correlate with malignancy, severity of disease and to serve as an immunologic target for therapy. However, very little is known about the role that germ cell proteins play in cancer development. Unique germ cell pathways include those involved in immortalization, genetic evolution, and energy metabolism. There is an ever increasing recognition that within tumors there is a subpopulation of cells with stem-cell-like characteristics that play a role in driving tumorgenesis. Stem cell and germ cell biology is intertwined. Given the enormous potential and known expression of germ cell proteins in melanoma, it is possible that they represent a largely untapped resource that may play a fundamental role in tumor development and progression. The purpose of this paper is to provide an update on the current value of germ cell protein expression in melanoma diagnosis, prognosis, and therapy, as well as to review critical germ cell pathways and discuss the potential roles these pathways may play in malignant transformation.

New hypotheses for large-scale epigenome alterations in somatic cancer cells: a role for male germ-cell-specific regulators

Oncogenic cell transformation is consistently associated with alterations of the cell epigenome leading to aberrant gene repression and activation. Some of these events, such as the DNA-methylation-based silencing of tumor suppressor genes, are considered to be oncogenic themselves. A much less-studied consequence of these epigenetic misregulations is the abnormal activation of tissue-specific genes in precancerous and transformed cells. Here, we explore the idea that the aberrant expression of germ-cell-specific genes in somatic cancer cells could contribute to malignant cell transformation and cancer progression. Indeed, a significant number of papers have reported the abnormal activation of germ cell-specific genes in various somatic cancers (known as cancer testis [C/T] antigens or factors). Although in most cases the physiological function of these genes remains unknown, functional investigations suggest that they can act as potent genome, epigenome and cellular reorganizers. Hence, in view of the existing literature, we discuss the hypothesis that C/T activation in somatic cells is not only a consequence of global epigenetic deregulation, but also a cause of further large-scale alterations of the epigenome, which themselves have direct oncogenic consequences for the affected cells. Finally, we highlight the fact that C/T factors have the potential to serve as valuable markers for cancer detection, as well as provide promising targets for developing new therapeutical strategies.

Functional aspects of cytidine-guanosine dinucleotides and their locations in genes

Originally, the finding of a particular distribution of cytidine-guanosine dinucleotides (CpGs) in genomic DNA was considered to be an interesting structural feature of eukaryotic genome organization. Despite a global depletion of CpGs, genes are frequently associated with CpG clusters called CpG islands (CGIs). CGIs are prevalently unmethylated but often found methylated in pathologic situations. On the other hand, CpGs outside of CGIs are generally methylated and are found mainly in the heterochromatic fraction of the genome. Hypomethylation of those CpGs is associated with genomic instability in malignancy. Additionally, CpG-rich and CpG-poor regions, as well as CpG-shores, are defined. Usually, the methylation status inversely correlates with gene expression. Methylation of CpGs, as well as demethylation and generation of hydroxmethyl-cytosines, is strictly regulated during development and differentiation. This review deals with the relevance of the organizational features of CpGs and their relation to each other.

MAGE-C2/CT10 protein expression is an independent predictor of recurrence in prostate cancer

The cancer-testis (CT) family of antigens is expressed in a variety of malignant neoplasms. In most cases, no CT antigen is found in normal tissues, except in testis, making them ideal targets for cancer immunotherapy. A comprehensive analysis of CT antigen expression has not yet been reported in prostate cancer. MAGE-C2/CT-10 is a novel CT antigen. The objective of this study was to analyze extent and prognostic significance of MAGE-C2/CT10 protein expression in prostate cancer. 348 prostate carcinomas from consecutive radical prostatectomies, 29 castration-refractory prostate cancer, 46 metastases, and 45 benign hyperplasias were immunohistochemically analyzed for MAGE-C2/CT10 expression using tissue microarrays. Nuclear MAGE-C2/CT10 expression was identified in only 3.3% primary prostate carcinomas. MAGE-C2/CT10 protein expression was significantly more frequent in metastatic (16.3% positivity) and castration-resistant prostate cancer (17% positivity; p<0.001). Nuclear MAGE-C2/CT10 expression was identified as predictor of biochemical recurrence after radical prostatectomy (p = 0.015), which was independent of preoperative PSA, Gleason score, tumor stage, and surgical margin status in multivariate analysis (p<0.05). MAGE-C2/CT10 expression in prostate cancer correlates with the degree of malignancy and indicates a higher risk for biochemical recurrence after radical prostatectomy. Further, the results suggest MAGE-C2/CT10 as a potential target for adjuvant and palliative immunotherapy in patients with prostate cancer.

Regulation of cancer germline antigen gene expression: implications for cancer immunotherapy

Cancer germline (CG; also known as cancer-testis) antigen genes are normally expressed in germ cells and trophoblast tissues and are aberrantly expressed in a variety of human malignancies. CG antigen genes have high clinical relevance as they encode a class of immunogenic and highly selective tumor antigens. CG antigen-directed immunotherapy is undergoing clinical evaluation for the treatment of a number of solid tumor malignancies and has been demonstrated to be safe, provoke immune responses and be of therapeutic benefit. Achieving an improved understanding of the mechanisms of CG antigen gene regulation will facilitate the continued development of targeted therapeutic approaches against tumors expressing these antigens. Substantial evidence suggests epigenetic mechanisms, particularly DNA methylation, as a primary regulator of CG antigen gene expression in normal and cancer cells as well as in stem cells. The roles of sequence-specific transcription factors and signal transduction pathways in controlling CG antigen gene expression are less clear but are emerging. A combinatorial therapeutic approach involving epigenetic modulatory drugs and CG antigen immunotherapy is suggested based on these data and is being actively pursued. In this article, we review the mechanisms of CG antigen gene regulation and discuss the implications of these mechanisms for the development of cancer immunotherapy approaches targeting CG antigens.