Genomic Organization, Incidence, and Localization of the SPAN-X Family of Cancer-Testis Antigens in Melanoma Tumors and Cell Lines

Human endogenous retrovirus onco-exaptation counters cancer cell senescence through calbindin

Increased levels and diversity of human endogenous retrovirus (HERV) transcription characterize most cancer types and are linked with disease outcomes. However, the underlying processes are incompletely understood. Here, we show that elevated transcription of HERVH proviruses predicted survival of lung squamous cell carcinoma (LUSC) and identified an isoform of CALB1, encoding calbindin, ectopically driven by an upstream HERVH provirus under the control of KLF5, as the mediator of this effect. HERVH-CALB1 expression was initiated in preinvasive lesions and associated with their progression. Calbindin loss in LUSC cell lines impaired in vitro and in vivo growth and triggered senescence, consistent with a protumor effect. However, calbindin also directly controlled the senescence-associated secretory phenotype (SASP), marked by secretion of CXCL8 and other neutrophil chemoattractants. In established carcinomas, CALB1-negative cancer cells became the dominant source of CXCL8, correlating with neutrophil infiltration and worse prognosis. Thus, HERVH-CALB1 expression in LUSC may display antagonistic pleiotropy, whereby the benefits of escaping senescence early during cancer initiation and clonal competition were offset by the prevention of SASP and protumor inflammation at later stages.

Biology of Cancer-Testis Antigens and Their Therapeutic Implications in Cancer

Tumour-specific antigens have been an area of interest in cancer therapy since their discovery in the middle of the 20th century. In the era of immune-based cancer therapeutics, redirecting our immune cells to target these tumour-specific antigens has become even more relevant. Cancer-testis antigens (CTAs) are a class of antigens with an expression specific to the testis and cancer cells. CTAs have also been demonstrated to be expressed in a wide variety of cancers. Due to their frequency and specificity of expression in a multitude of cancers, CTAs have been particularly attractive as cancer-specific therapeutic targets. There is now a rapid expansion of CTAs being identified and many studies have been conducted to correlate CTA expression with cancer and therapy-resistant phenotypes. Furthermore, there is an increasing number of clinical trials involving using some of these CTAs as molecular targets in pharmacological and immune-targeted therapeutics for various cancers. This review will summarise the current knowledge of the biology of known CTAs in tumorigenesis and the regulation of CTA genes. CTAs as molecular targets and the therapeutic implications of these CTA-targeted anticancer strategies will also be discussed.

The Transcriptome and Proteome Networks of Malignant Tumours Reveal Atavistic Attractors of Polyploidy-Related Asexual Reproduction

The expression of gametogenesis-related (GG) genes and proteins, as well as whole genome duplications (WGD), are the hallmarks of cancer related to poor prognosis. Currently, it is not clear if these hallmarks are random processes associated only with genome instability or are programmatically linked. Our goal was to elucidate this via a thorough bioinformatics analysis of 1474 GG genes in the context of WGD. We examined their association in protein-protein interaction and coexpression networks, and their phylostratigraphic profiles from publicly available patient tumour data. The results show that GG genes are upregulated in most WGD-enriched somatic cancers at the transcriptome level and reveal robust GG gene expression at the protein level, as well as the ability to associate into correlation networks and enrich the reproductive modules. GG gene phylostratigraphy displayed in WGD+ cancers an attractor of early eukaryotic origin for DNA recombination and meiosis, and one relative to oocyte maturation and embryogenesis from early multicellular organisms. The upregulation of cancer-testis genes emerging with mammalian placentation was also associated with WGD. In general, the results suggest the role of polyploidy for soma-germ transition accessing latent cancer attractors in the human genome network, which appear as pre-formed along the whole Evolution of Life.

Screening and Identification of Novel Potential Biomarkers for Breast Cancer Brain Metastases

Brain metastases represent a major cause of mortality among patients with breast cancer, and few effective targeted treatment options are currently available. Development of new biomarkers and therapeutic targets for breast cancer brain metastases (BCBM) is therefore urgently needed. In this study, we compared the gene expression profiles of the brain metastatic cell line MDA-MB-231-BR (231-BR) and its parental MDA-MB-231, and identified a total of 84 genes in the primary screening through a series of bioinformatic analyses, including construction of protein-protein interaction (PPI) networks by STRING database, identification of hub genes by applying of MCODE and Cytohubba algorithms, identification of leading-edge subsets of Gene Set Enrichment Analysis (GSEA), and identification of most up-regulated genes. Eight genes were identified as candidate genes due to their elevated expression in brain metastatic 231-BR cells and prognostic values in patients with BCBM. Then we knocked down the eight individual candidate genes in 231-BR cells and evaluated their impact on cell migration through a wound-healing assay, and four of them (KRT19, FKBP10, GSK3B and SPANXB1) were finally identified as key genes. Furthermore, the expression of individual key genes showed a correlation with the infiltration of major immune cells in the brain tumor microenvironment (TME) as analyzed by Tumor Immune Estimation Resource (TIMER) and Gene Expression Profiling Interactive Analysis (GEPIA), suggesting possible roles of them in regulation of the tumor immune response in TME. Therefore, the present work may provide new potential biomarkers for BCBM. Additionally, using GSEA, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Enrichment Analysis, we determined the top enriched cellular functions or pathways in 231-BR cells, which may help better understand the biology governing the development and progression of BCBM.

Cancer Immunoprevention: Current Status and Future Directions

Cancer is one of the most serious diseases affecting health and the second leading cause of death worldwide. Despite the development of various therapeutic modalities to deal with cancer, limited improvement in overall survival of patients has been yielded. Since there is no certain cure for cancer, detection of premalignant lesions, and prevention of their progression are vital to the decline of high morbidity and mortality of cancer. Among approaches to cancer prevention, immunoprevention has gained further attention in recent years. Deep understanding of the tumor/immune system interplay and successful prevention of virally-induced malignancies by vaccines have paved the way toward broadening cancer immunoprevention application. The identification of tumor antigens in premalignant lesions was the turning point in cancer immunoprevention that led to designing preventive vaccines for various malignancies including multiple myeloma, colorectal, and breast cancer. In addition to vaccines, immune checkpoint inhibitors are also being tested for the prevention of oral squamous cell carcinoma (SCC), and imiquimod which is an established drug for the prevention of skin SCC, is a non-specific immunomodulator. Herein, to provide a bench-to-bedside understanding of cancer immunoprevention, we will review the role of the immune system in suppression and promotion of tumors, immunoprevention of virally-induced cancers, identification of tumor antigens in premalignant lesions, and clinical advances of cancer immunoprevention.

The multifunctional role of SPANX-A/D protein subfamily in the promotion of pro-tumoural processes in human melanoma

Human sperm protein associated with the nucleus on the X chromosome (SPANX) genes encode a protein family (SPANX-A, -B, -C and -D), whose expression is limited to the testis and spermatozoa in normal tissues and various tumour cells. SPANX-A/D proteins have been detected in metastatic melanoma cells, but their contribution to cancer development and the underlying molecular mechanisms of skin tumourigenesis remain unknown. Combining functional and proteomic approaches, the present work describes the presence of SPANX-A/D in primary and metastatic human melanoma cells and how it promotes pro-tumoural processes such as cell proliferation, motility and migration. We provide insights into the molecular features of skin tumourigenesis, describing for the first time a multifunctional role of the SPANX-A/D protein family in nuclear function, energy metabolism and cell survival, considered key hallmarks of cancer. A better comprehension of the SPANX-A/D protein subfamily and its molecular mechanisms will help to describe new aspects of tumour cell biology and develop new therapeutic targets and tumour-directed pharmacological drugs for skin tumours.

Hypomethylated SPANXA1/A2 promotes the metastasis of head and neck squamous cell carcinoma

The aberrant expression of SPANXA1/A2 (sperm protein associated with the nucleus on the X-chromosome, family members A1/A2) has been observed in multi types of cancers. However, the roles of SPANXA1/A2 in head and neck squamous cell carcinoma (HNSCC) remain largely unknown. The expression of SPANXA1/A2 was evaluated via analyzing UCSC XENA and GEO databases. To dissect the underlying cause of silencing SPANXA1/A2-mediated suppression, cell migration and invasion were detected in SPANXA1/A2 manipulated cell lines. Western blot was performed to evaluate EMT-related factors. The methylation microarray data of SPANXA1/A2 in HNSCC from the UCSC XENA database were used to identify whether aberrant overexpressed SPANXA1/A2 is induced by aberrant DNA methylation. SPANXA1/A2 was highly expressed in tumor tissues and associated with poor survival of patients with HNSCC. Knockdown of SPANXA1/A2 inhibited migration and invasion abilities in both Cal-27 and SCC-9 cells through epithelial-mesenchymal transition (EMT) suppression. The SPANXA1/A2 expression negatively related to its DNA methylation level. SPANXA1/A2 DNA hypomethylation was associated with metastatic stage and poor survival of patients with HNSCC. A dose-dependent increase of SPANXA1/A2 mRNA was observed in both cal-27 and SCC-9 cells after treatment with 5-AZA-2'-deoxycytidine (5-AZA-CdR). We demonstrated that knockdown of SPANXA1/A2 obviously inhibited tumor cell migration and invasion through EMT suppression. DNA hypomethylation might be responsible for the aberrant SPANXA1/A2 overexpressing. SPANXA1/A2 may be used as a diagnosed and independent prognosis indicator of HNSCC, and knockdown of SPANXA1/A2 may present a new gene-based therapy for HNSCC.

SPANX Control of Lamin A/C Modulates Nuclear Architecture and Promotes Melanoma Growth

Mechanisms regulating nuclear organization control fundamental cellular processes, including the cell and chromatin organization. Their disorganization, including aberrant nuclear architecture, has been often implicated in cellular transformation. Here, we identify Lamin A, among proteins essential for nuclear architecture, as SPANX (sperm protein associated with the nucleus on the X chromosome), a cancer testis antigen previously linked to invasive tumor phenotypes, interacting protein in melanoma. SPANX interaction with Lamin A was mapped to the immunoglobulin fold-like domain, a region critical for Lamin A function, which is often mutated in laminopathies. SPANX downregulation in melanoma cell lines perturbed nuclear organization, decreased cell viability, and promoted senescence-associated phenotypes. Moreover, SPANX knockdown (KD) in melanoma cells promoted proliferation arrest, a phenotype mediated in part by IRF3/IL1A signaling. SPANX KD in melanoma cells also prompted the secretion of IL1A, which attenuated the proliferation of naïve melanoma cells. Identification of SPANX as a nuclear architecture complex component provides an unexpected insight into the regulation of Lamin A and its importance in melanoma. IMPLICATIONS: SPANX, a testis protein, interacts with LMNA and controls nuclear architecture and melanoma growth.

SPANX-A/D protein subfamily plays a key role in nuclear organisation, metabolism and flagellar motility of human spermatozoa

Human sperm protein associated with the nucleus on the X chromosome (SPANX) genes encode a protein family (SPANX-A, -B, -C and -D), whose expression is limited to the testis and spermatozoa in normal tissues and to a wide variety of tumour cells. Present only in hominids, SPANX-A/D is exclusively expressed in post-meiotic spermatids and mature spermatozoa. However, the biological role of the protein family in human spermatozoa is largely unknown. Combining proteomics and molecular approaches, the present work describes the presence of all isoforms of SPANX-A/D in human spermatozoa and novel phosphorylation sites of this protein family. In addition, we identify 307 potential SPANX-A/D interactors related to nuclear envelop, chromatin organisation, metabolism and cilia movement. Specifically, SPANX-A/D interacts with fumarate hydratase and colocalises with both fumarate hydratase and Tektin 1 proteins, involved in meeting energy demands for sperm motility, and with nuclear pore complex nucleoporins. We provide insights into the molecular features of sperm physiology describing for the first time a multifunctional role of SPANX-A/D protein family in nuclear envelope, sperm movement and metabolism, considered key functions for human spermatozoa. SPANX-A/D family members, therefore, might be promising targets for sperm fertility management.

Immunoexpression of SPANX-C in metastatic uveal melanoma

Uveal melanoma is a rare disease but it is the most common primary intraocular malignant tumor in adults with poor late prognosis. About 50% of patients will develop liver metastasis far from the enucleation within 10-15 years. Our study examined SPANX-C expression levels in primary uveal melanoma both with and without metastasis to assess if they can be used to predict metastasis. This study included a total of 55 patients, 28 males and 27 females, with uveal melanoma. A significantly high expression of SPANX-C was seen in 19/23 (82.6%) patients with metastasis, and only in 11/32 (38.5%) patients without metastasis. In conclusion, we found that SPANX-C expression could play a role in tumor progression of uveal melanoma.

Comparative Proteomics Reveal the Association between SPANX Proteins and Clinical Outcomes of Artificial Insemination with Donor Sperm

Semen analysis is used for diagnosing male infertility and evaluating male fertility for more than a century. However, the semen analysis simply represents the population characteristics of sperm. It is not a comprehensive assessment of the male reproductive potential. In this study, 20 semen samples from human sperm bank with distinctive artificial insemination with donor sperm (AID) clinical outcomes were collected and analyzed using a two-dimensional differential in-gel electrophoresis (2D-DIGE); 45 differentially expressed protein spots were obtained, and 26 proteins were identified. Most differentially expressed proteins were related to sperm motility, energy consumption, and structure. These identified proteins included several sperm proteins associated with the nucleus on the X chromosome (SPANX) proteins. This prospective study aimed to investigate the association between the expression levels of SPANX proteins and the AID clinical outcomes. The proteins identified in this study provided a reference for the molecular mechanism of sperm fertility and revealed a predictive value of the SPANX proteins.

SPANXA suppresses EMT by inhibiting c-JUN/SNAI2 signaling in lung adenocarcinoma

SPANXA (Sperm Protein Associated with the Nucleus on the X-chromosome, family members A1/A2) acts as a cancer-testis antigen expressed in normal testes, but dysregulated in various tumors. We found that SPANXA is highly expressed in low-invasive CL1-0 cells compared with isogenous high-invasive CL1-5 cells. SPANXA was preferably expressed in tumor tissues and associated with the prolonged survival of lung adenocarcinomas. SPANXA suppressed the invasion and metastasis of lung cancer cells in vitro and in vivo. By the expression microarray and pathway analysis, we found that the SPANXA-altered genes were enriched in the epithelial–mesenchymal transition (EMT) pathway. SPANXA reduced SNAI2 expression resulted in up-regulating E-cadherin. c-JUN acts as the positive-regulator of EMT. Silencing SPANXA increased c-JUN mRNA expression and blockage of c-JUN led to SNAI2 down-regulation. Our results clearly characterized SPANXA as an EMT inhibitor by suppressing c-JUN-SNAI2 axis in lung adenocarcinoma.

The cancer-testis antigens SPANX-A/C/D and CTAG2 promote breast cancer invasion

Genes that are normally biased towards expression in the testis are often induced in tumor cells. These gametogenic genes, known as cancer-testis antigens (CTAs), have been extenstively investigated as targets for immunotherapy. However, despite their frequent detection, the degree to which CTAs support neoplastic invasion is poorly understood. Here, we find that the CTA genes SPANX-A/C/D and CTAG2 are coordinately induced in breast cancer cells and regulate distinct features of invasive behavior. Our functional analysis revealed that CTAG2 interacts with Pericentrin at the centrosome and is necessary for directional migration. Conversely, SPANX-A/C/D interacts with Lamin A/C at the inner nuclear membrane and is required for the formation of actin-rich cellular protrusions that reorganize the extracellular matrix. Importantly, SPANX-A/C/D was required for breast cancer cells to spontaneously metastasize to the lung, demonstrating that CTA reactivation can be critical for invasion dependent phenotypes in vivo. Moreover, elevated SPANX-A/C/D expression in breast cancer patient tumors correlated with poor outcome. Together, our results suggest that distinct CTAs promote tumor progression by regulating complementary cellular functions that are integrated together to induce invasive behavior.

Immune surveillance in melanoma: From immune attack to melanoma escape and even counterattack

Pharmacologic inhibition of the cytotoxic T lymphocyte antigen 4 (CTLA4) and the programmed death receptor-1 (PD1) has resulted in unprecedented durable responses in metastatic melanoma. However, resistance to immunotherapy remains a major challenge. Effective immune surveillance against melanoma requires 4 essential steps: activation of the T lymphocytes, homing of the activated T lymphocytes to the melanoma microenvironment, identification and episode of melanoma cells by activated T lymphocytes, and the sensitivity of melanoma cells to apoptosis. At each of these steps, there are multiple factors that may interfere with the immune surveillance machinery, thus allowing melanoma cells to escape immune attack and develop resistance to immunotherapy. We provide a comprehensive review of the complex immune surveillance mechanisms at play in melanoma, and a detailed discussion of how these mechanisms may allow for the development of intrinsic or acquired resistance to immunotherapeutic modalities, and potential avenues for overcoming this resistance.

Effects of epithelial to mesenchymal transition on T cell targeting of melanoma cells

Melanoma cells can switch phenotype in a manner similar to epithelial to mesenchymal transition (EMT). In this perspective article, we address the effects of such phenotype switching on T cell targeting of tumor cells. During the EMT-like switch in phenotype, a concomitant change in expression of multiple tumor antigens occurs. Melanoma cells undergoing EMT escape from killing by T cells specific for antigens whose expression is downregulated by this process. We discuss melanoma antigens whose expression is influenced by EMT. We assess the effect of changes in the expressed tumor antigen repertoire on T-cell mediated tumor recognition and killing. In addition to escape from T cell immunity via changes in antigen expression, mesenchymal-like melanoma cells are generally more resistant to classical chemotherapy and radiotherapy. However, we demonstrate that when targeting antigens whose expression is unaltered during EMT, the capacity of T cells to kill melanoma cell lines in vitro is not influenced by their phenotype. When considering immune therapies such as cancer vaccination, these data suggest escape from T cell killing due to phenotype switching in melanoma could potentially be avoided by careful selection of target antigen.

Development of a novel, quantitative protein microarray platform for the multiplexed serological analysis of autoantibodies to cancer-testis antigens

The cancer-testis antigens are a group of unrelated proteins aberrantly expressed in various cancers in adult somatic tissues. This aberrant expression can trigger spontaneous immune responses, a phenomenon exploited for the development of disease markers and therapeutic vaccines. However, expression levels often vary amongst patients presenting the same cancer type, and these antigens are therefore unlikely to be individually viable as diagnostic or prognostic markers. Nevertheless, patterns of antigen expression may provide correlates of specific cancer types and disease progression. Herein, we describe the development of a novel, readily customizable cancer-testis antigen microarray platform together with robust bioinformatics tools, with which to quantify anti-cancer testis antigen autoantibody profiles in patient sera. By exploiting the high affinity between autoantibodies and tumor antigens, we achieved linearity of response and an autoantibody quantitation limit in the pg/mL range-equating to a million-fold serum dilution. By using oriented attachment of folded, recombinant antigens and a polyethylene glycol microarray surface coating, we attained minimal non-specific antibody binding. Unlike other proteomics methods, which typically use lower affinity interactions between monoclonal antibodies and tumor antigens for detection, the high sensitivity and specificity realized using our autoantibody-based approach may facilitate the development of better cancer biomarkers, as well as potentially enabling pre-symptomatic diagnosis. We illustrated the usage of our platform by monitoring the response of a melanoma patient cohort to an experimental therapeutic NY-ESO-1-based cancer vaccine; inter alia, we found evidence of determinant spreading in individual patients, as well as differential CT antigen expression and epitope usage.

Cancer testis antigens: a novel target in lung cancer

Lung cancer is the main cause of cancer mortality worldwide. This is mainly due to the fact that it is diagnosed in advanced stage patients, which are no more surgically curable. Consequently, searching for novel treatments and new modalities for early diagnosis offers great promise to improve the clinical outcome. Recently, a new group of antigens, the cancer testis antigens, have been described as possible early diagnostic tools and therapeutic targets in cancer therapy.This review will report emerging evidences of cancer testis antigens deregulation in lung cancer and explore the state of the art of their currently known role and potential as markers for early diagnosis and disease progression and targets of an immunotherapeutic approach aiming to improve the cure rate of this tumor.

Cancer-testis antigen expression and immunogenicity in AL amyloidosis

Light-chain amyloidosis (AL) is a plasma cell dyscrasia closely related to multiple myeloma. In multiple myeloma, the cancer-testis antigens (CTAs) CT7 (MAGE-C1), CT10 (MAGE-C2) and MAGE-A CTAs are expressed in up to 80% of cases. In this study, we investigated the expression and immunogenicity of several CTAs in patients with AL amyloidosis in a total of 38 bone marrow specimens by employing standard immunohistochemistry techniques on paraffin-embedded archival tissues. Plasma samples from 35 patients (27 with matched bone marrow samples) were also analyzed by ELISA for sero reactivity to a group of full-length CTA proteins. CT7 was present in 25/38 (66%) while CT10 was demonstrated in 3/38 and GAGE in 1/38 AL amyloid cases. The expression pattern was mostly focal. There were no significant differences with regard to organ involvement, response to treatment, or prognosis in CTA positive compared to negative cases. None of the specimens showed spontaneous humoral immunity to CT7, but sero reactivity was observed in individual patients to other CTAs. This study identifies CT7 as the prevalent CTA in plasma cells of patients with AL amyloidosis. Further analyses determining the biology of CTAs in AL amyloidosis and their value as potential targets for immunotherapy are warranted.

Exclusion of the 750-kb genetically unstable region at Xq27 as a candidate locus for prostate malignancy in HPCX1-linked families

Several linkage studies provided evidence for the presence of the hereditary prostate cancer locus, HPCX1, at Xq27-q28. The strongest linkage peak of prostate cancer overlies a variable region of ~750 kb at Xq27 enriched by segmental duplications (SDs), suggesting that the predisposition to prostate cancer may be a genomic disorder caused by recombinational interaction between SDs. The large size of SDs and their sequence similarity make it difficult to examine this region for possible rearrangements using standard methods. To overcome this problem, direct isolation of a set of genomic segments by in vivo recombination in yeast (a TAR cloning technique) was used to perform a mutational analysis of the 750 kb region in X-linked families. We did not detect disease-specific rearrangements within this region. In addition, transcriptome and computational analyses were performed to search for nonannotated genes within the Xq27 region, which may be associated with genetic predisposition to prostate cancer. Two candidate genes were identified, one of which is a novel gene termed SPANXL that represents a highly diverged member of the SPANX gene family, and the previously described CDR1 gene that is expressed at a high level in both normal and malignant prostate cells, and mapped 210 kb of upstream the SPANX gene cluster. No disease-specific alterations were identified in these genes. Our results exclude the 750-kb genetically unstable region at Xq27 as a candidate locus for prostate malignancy. Adjacent regions appear to be the most likely candidates to identify the elusive HPCX1 locus.

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.

A majority of the cancer/testis antigens are intrinsically disordered proteins

The cancer/testis antigens (CTAs) are a group of heterogeneous proteins that are typically expressed in the testis but aberrantly expressed in several types of cancer. Although overexpression of CTAs is frequently associated with advanced disease and poorer prognosis, the significance of this correlation is unclear since the functions of the CTAs in the disease process remain poorly understood. Here, employing a bioinformatics approach, we show that a majority of CTAs are intrinsically disordered proteins (IDPs). IDPs are proteins that, under physiological conditions in vitro, lack rigid 3D structures either along their entire length or in localized regions. Despite the lack of structure, most IDPs can transition from disorder to order upon binding to biological targets and often promote highly promiscuous interactions. IDPs play important roles in transcriptional regulation and signaling via regulatory protein networks and are often associated with dosage sensitivity. Consistent with these observations, we find that several CTAs can bind DNA, and their forced expression appears to increase cell growth implying a potential dosage-sensitive function. Furthermore, the CTAs appear to occupy "hub" positions in protein regulatory networks that typically adopt a "scale-free" power law distribution. Taken together, our data provide a novel perspective on the CTAs implicating them in processing and transducing information in altered physiological states in a dosage-sensitive manner. Identifying the CTAs that occupy hub positions in protein regulatory networks would allow a better understanding of their functions as well as the development of novel therapeutics to treat cancer.

Expression of SPANX proteins in normal prostatic tissue and in prostate cancer

The sperm protein associated with the nucleus in the X chromosome (SPANX) gene family encodes for proteins that are not only expressed in germ cells, but also in a number of tumors. In addition, SPANX genes map in an interval of the X chromosome (namely, Xq27), which has been found to be associated with familial prostate cancer by linkage analysis. The aim of this study was therefore to evaluate SPANX protein expression in normal prostate tissues and in prostate carcinoma. For this purpose, formalin-fixed and paraffin-embedded sections obtained from 15 normal (at autopsy) donors and 12 men with prostate cancer were analyzed by immunohistochemistry. About 40% of both normal and tumor prostate samples resulted SPANX positive. Signals were exclusively within the nucleus in normal prostate cells, whereas both nuclear and cytoplasmic positivity was observed in tumor cells. In conclusion, these findings showed that SPANX genes are expressed in both normal and tumor prostate gland, but the latter showed a peculiar cytoplasmic staining positivity. This suggests a possible association between SPANX over expression and prostate cancer development. Additional studies are needed to corroborate this hypothesis.

SPANX gene variation in fertile and infertile males

Protein expression data suggests that the SPANX gene family is expressed throughout spermatogenesis, including post-meiotic expression, consistent with a potential role in sperm development. The genomic architecture of this region is unstable and past studies have found evidence of variation in this gene family. This study used a novel assay to evaluate copy number variation (CNV) in SPANX gene family, in fertile and infertile men. The case group was comprised of 50 oligozoospermic and 50 azoospermic men, and the control group was comprised of 67 normozoospermic men with children. The assay, real-time quantitative PCR, evaluated CNV of the entire gene cluster containing all four SPANXA-E genes and with SPANXB, found exclusively in maturing sperm. While variation was found in both groups, average CNV patterns did not differ between fertile and infertile males. As this was a targeted assay, it was limited in scope to detect further CNV at a genome-wide level which is an area of increasing interest in the field of genomics.

Sperm associated antigen 9 expression and humoral response in chronic myeloid leukemia

Early diagnosis and cure for patients with chronic myeloid leukemia (CML) exhibit significant clinical challenges because of the disease progression from chronic phase (CP) into a rapidly fatal blast crisis. Our earlier studies suggested an association of sperm associated antigen 9 (SPAG9) with various human malignancies. The present investigation revealed that SPAG9 mRNA and protein are expressed in CML patients (88%), in K562 and KCL-22 cells. Further, SPAG9 protein expression was also detected on cell surface suggesting that this molecule may be a suitable target for immunotherapy. Interestingly, 90% CML-CP patients showed humoral response against SPAG9, suggesting its important role in early diagnostic of CML-CP. Further investigation is warranted in establishing the potential of SPAG9 as a biomarker and immunotherapeutic target for early treatment of CML-CP patients.

Cancer/testis antigens and clinical risk factors for liver metastasis of colorectal cancer: a predictive panel

PURPOSE

Accumulating evidence suggests that cancer/testis antigens may serve as indicators of tumor malignant phenotype. The purpose of this study is to evaluate cancer/testis antigen genes in predicting metastasis of colorectal cancer to the liver.

METHODS

The expression levels of 25 cancer/testis antigen genes were determined by reverse-transcription polymerase chain reaction in 288 colorectal cancer tissue samples from the primary tumor or liver metastasis. Pearson chi2 and multiple logistic regression analyses were performed to assess the association between risk factors and probability of liver metastasis of colorectal cancer.

RESULTS

No significant difference was detected between the primary tumor and liver metastasis in expression pattern of cancer/testis antigen genes in colorectal cancer tissue samples. However, 3 cancer/testis antigen genes (PAGE4, SCP-1, and SPANX) and 3 clinicopathologic parameters (lymph node involvement, vessel cancer embolus, and tumor invasion depth) correlated significantly with liver metastasis of colorectal cancer (P < .05). A logistic regression model was constructed for prediction of liver metastasis based on a panel consisting of PAGE4, lymph node involvement, and presence or absence of vessel cancer embolus. The predicted risk of liver metastasis based on the panel was consistent with the actual risk observed. The probability of developing liver metastasis as estimated by the panel was 86.9% when all 3 factors were positive, representing an up to 20% improvement in the prediction level compared with the classic methods of lymph node involvement and vessel cancer embolus.

CONCLUSIONS

A new predictive panel including PAGE4 expression may help predict liver metastasis of colorectal cancer.

A high percentage of skin melanoma cells expresses SPANX proteins

The expression of SPANX (sperm protein associated with the nucleus in the X chromosome) gene family has been reported in many tumors, such as melanoma, myeloma, glioblastoma, breast carcinoma, ovarian cancer, testicular germ cell tumors, and hematological malignancies. However, no systematic approach has so far been devised to estimate the percentage of cancer cells expressing SPANX. This study was undertaken to quantify the expression of SPANX proteins in melanomas. The expression of SPANX proteins was evaluated by immunohistochemistry in normal skin (n = 12), melanomas (n = 21), and benign nevi (n = 10), using a polyclonal antibody raised in our laboratory. Seventeen of the 21 melanomas (80.9%) examined expressed SPANX proteins. A high percentage of their cells (49.0% +/- 5.5%) stained positively for SPANX proteins compared with no expression found in normal skin cells. Benign nevi had an intermediate number of cells expressing SPANX proteins (25% +/- 8.5%), which resulted significantly higher than normal skin cells and significantly lower than skin melanoma cells. In melanoma cells, the labeling was mostly nuclear, sometimes incomplete or limited to the perinuclear wall, even if cytoplasmic staining was also seen in SPANX-positive tumor cells. In contrast, the 5 of 10 SPANX-positive nevi had a clear nuclear localization of the signal. These data suggest that the SPANX protein family is expressed in the vast majority of the melanomas tested. The mechanism(s), which brings up SPANX gene expression and the role of these proteins are not known.

Sperm-derived SPANX-B is a clinically relevant tumor antigen that is expressed in human tumors and readily recognized by human CD4+ and CD8+ T cells

PURPOSE

The sperm-derived SPANX family proteins can be found expressed in human tumors. Here, we aimed to perform a comprehensive study to evaluate immunotherapeutic relevance of one of its members, SPANX-B. We wanted to test its expression pattern in human tumors and to evaluate CD4(+) and CD8(+) T-cell responses in healthy humans after in vitro immunizations.

EXPERIMENTAL DESIGN

Expression of SPANX-B in human malignancies, including a multitumor tissue array of 145 primary tumors, was assessed using reverse transcription-PCR, Western blotting, and immunohistochemical analysis. T-cell immunogenicity and immunodominant epitopes of SPANX-B were studied using in vitro immunizations of healthy human donor-derived leukocytes.

RESULTS

SPANX-B was abundantly expressed in melanoma and carcinomas of lung, ovary, colon, and breast. In melanoma, tissue array data indicated that it was expressed in advanced and metastatic disease. Unlike most tumor-associated antigens, SPANX-B was an immunogenic antigen that was recognized by circulating T-cell precursors in healthy humans. Importantly, these T cells were readily expanded to generate SPANX-B-specific helper CD4(+) and cytolytic CD8(+) T cells that recognized unique immunodominant epitopes: at least one HLA-DR-restricted Pep-9 epitope (SPANX-B(12-23)) and two HLA-A2-restricted Pep-2 and Pep-4 epitopes (SPANX-B(23-31) and SPANX-B(57-65), respectively). CD8(+) T cells were fully functional to recognize and lyse HLA-A2-expressing tumors, including primary human melanomas.

CONCLUSIONS

SPANX-B is an immunogenic sperm-derived antigen that is expressed in several human tumors. SPANX-B is also efficiently recognized by the human T-cell immune arm, indicating its significant value for the development of protective and therapeutic cancer vaccines.

SPANX-B and SPANX-C (Xq27 region) gene dosage analysis in Sicilian patients with melanoma

The incidence of melanoma has dramatically increased in many countries (it is 4.5 cases every 100 000 inhabitants in Sicily) and Xq27 region contains genes important in cancer like the SPANX (sperm protein associated with the nucleus in the X chromosome) gene family. These genes, made up of two exons separated by an intron of about 650 base pair, are expressed in sperm cells and in many tumours, including melanoma. These observations suggested that SPANX genes, or some of them, may be involved in melanoma development. The aim of this study was to investigate the genetic variability of SPANX-B and SPANX-C in a sample of Sicilian male population including patients with melanoma of the skin and controls. A total of 99 patients were enrolled in this study. They included: 17 male patients with cutaneous melanoma and 82 normal males. Semiquantitative fluorescent multiplex PCR dosage analysis was carried out to identify the variety of classes of SPANX-B and SPANX-C genes. Sixteen and 13 genetic classes were detected for SPANX-B and SPANX-C genes, respectively. A statistical significant difference for a particular class of SPANX-C gene was found comparing patients with melanoma and controls (P=0.011). Further investigations should be conducted to confirm these observations and to evaluate the possible implication of other genes of the region Xq27-28 in melanoma.

A shared promoter region suggests a common ancestor for the human VCX/Y, SPANX, and CSAG gene families and the murine CYPT family

Many testis-specific genes from the sex chromosomes are subject to rapid evolution, which can make it difficult to identify murine genes in the human genome. The murine CYPT gene family includes 15 members, but orthologs were undetectable in the human genome. However, using refined homology search, sequences corresponding to the shared promoter region of the CYPT family were identified at 39 loci. Most loci were located immediately upstream of genes belonging to the VCX/Y, SPANX, or CSAG gene families. Sequence comparison of the loci revealed a conserved CYPT promoter-like (CPL) element featuring TATA and CCAAT boxes. The expression of members of the three families harboring the CPL resembled the murine expression of the CYPT family, with weak expression in late pachytene spermatocytes and predominant expression in spermatids, but some genes were also weakly expressed in somatic cells and in other germ cell types. The genomic regions harboring the gene families were rich in direct and inverted segmental duplications (SD), which may facilitate gene conversion and rapid evolution. The conserved CPL and the common expression profiles suggest that the human VCX/Y, SPANX, and CSAG2 gene families together with the murine SPANX gene and the CYPT family may share a common ancestor. Finally, we present evidence that VCX/Y and SPANX may be paralogs with a similar protein structure consisting of C terminal acidic repeats of variable lengths.

A yeast two-hybrid system using Sp17 identified Ropporin as a novel cancer-testis antigen in hematologic malignancies

Since most intracellular proteins are expressed with their ligands, ligands of cancer-testis (CT) antigens may also be CT in their distribution. Applying Sperm protein 17 (Sp17) as the bait in a yeast 2-hybrid system of a testicular cDNA library, 17 interacting clones were isolated and all encoded Ropporin, a spermatogenic cell-specific protein that serves as an anchoring protein for the A-kinase anchoring protein, AKAP110. Ropporin showed a very restricted normal tissue gene expression, detected only in testis and fetal liver. Ropporin mRNA could also be detected in tumor cells from patients with multiple myeloma, chronic lymphocytic leukemia and acute myeloid leukemia. Interestingly, expression of Sp17 did not necessarily predict for the expression of Ropporin suggesting that their coexpression in these tumor cells was random rather than coordinated. Ropporin gene expression in tumor cells is associated with the presence of high titer IgG antibodies against Ropporin, suggesting the in vivo translation of the mRNA into protein and the immunogenicity of the protein to the autologous hosts. Using a CT antigen as the bait in a yeast 2-hybrid system may, therefore, identify novel tumor antigen. Our results also suggest that Ropporin is a novel CT antigen in hematologic malignancies.

Mutational analysis of SPANX genes in families with X-linked prostate cancer

BACKGROUND

Previous genetic linkage studies identified a locus for susceptibility to prostate cancer called HPCX at Xq27. The candidate region contains two clusters of SPANX genes. The first cluster called SPANX-A/D includes SPANX-A1, SPANX-A2, SPANX-B, SPANX-C, and SPANX-D; the second cluster called SPANX-N includes SPANX-N1, SPANX-N2, SPANX-N3, and SPANX-N4. The SPANX genes encode cancer-testis (CT) specific antigens. Previous studies identified SPANX-B and SPANX-D variants produced by gene conversion events, none of which are associated with X-linked prostate cancer.

METHODS

In this study we applied transformation-associated recombination cloning (TAR) in yeast to analyze sequence variations in SPANX-A1, SPANX-A2, and SPANX-C genes that are resided within large chromosomal duplications. A SPANX-N1/N4 cluster was analyzed by a routine PCR analysis.

RESULTS

None of the sequence variations in the coding regions of these genes is associated with susceptibility to prostate cancer.

CONCLUSIONS

Therefore, genetic variation in the SPANX genes is not the actual target variants explaining HPCX. However, it is possible that they play a modifying role in susceptibility to prostate cancer through complex recombinational interaction.

Evolutionary diversification of SPANX-N sperm protein gene structure and expression

The sperm protein associated with nucleus in the X chromosome (SPANX) genes cluster at Xq27 in two subfamilies, SPANX-A/D and SPANX-N. SPANX-A/D is specific for hominoids and is fairly well characterized. The SPANX-N gave rise to SPANX-A/D in the hominoid lineage ∼7 MYA. Given the proposed role of SPANX genes in spermatogenesis, we have extended studies to SPANX-N gene evolution, variation, regulation of expression, and intra-sperm localization. By immunofluorescence analysis, SPANX-N proteins are localized in post-meiotic spermatids exclusively, like SPANX-A/D. But in contrast to SPANX-A/D, SPANX-N are found in all ejaculated spermatozoa rather than only in a subpopulation, are localized in the acrosome rather than in the nuclear envelope, and are expressed at a low level in several nongametogenic adult tissues as well as many cancers. Presence of a binding site for CTCF and its testis-specific paralogue BORIS in the SPANX promoters suggests, by analogy to MAGE-A1 and NY-ESO-1, that their activation in spermatogenesis is mediated by the programmed replacement of CTCF by BORIS. Based on the relative density of CpG, the more extended expression of SPANX-N compared to SPANX-A/D in nongametogenic tissues is likely attributed to differences in promoter methylation. Our findings suggest that the recent duplication of SPANX genes in hominoids was accompanied by different localization of SPANX-N proteins in post-meiotic sperm and additional expression in several nongonadal tissues. This suggests a corresponding functional diversification of SPANX gene families in hominoids. SPANX proteins thus provide unique targets to investigate their roles in the function of spermatozoa, selected malignancies, and for SPANX-N, in other tissues as well.

Expression of SpanX mRNA in testicular germ cell tumors

The function of SpanX proteins is unknown, evidence is accumulating to suggest their involvement in tumorigenesis. A locus in Xq27, where the SpanX gene family is located, has been associated with testicular germ cell tumor (TGCT) onset. Therefore, we evaluated the presence of SpanX mRNA in six TGCT cases by RT-PCR. The results showed that SpanX mRNA is present in TGCT, confirming transcriptional activity of these genes in such tumors.

Cancer-testis antigens in haematological malignancies

Immunotherapy is an attractive therapeutic option for patients with haematological malignancies. Until recently, the progress in the development of tumour vaccines for haematological malignancies had been slow due to the lack of suitable targets. Cancer-testis (CT) antigens are potentially suitable molecules for tumour vaccines of haematological malignancies because of their high immunogenicity in vivo and their relatively restricted normal tissue distribution. This review evaluates the properties and potential functions of CT antigens. We discuss the expression of CT antigens in patient with haematological malignancies and provide evidence in support of their immunogenicity in vivo in these patients. We also address the role of 'epigenetic' regulation of CT antigens in haematological malignancies and how hypomethylating agents could induce the expression of some of these antigens in tumour cells to overcome the problem of heterogeneity of expression of the antigen within individual tumour specimens. Data implicating the interaction of the promoter genes of some of these CT antigens with the MeCP2 protein also suggest the potential role of the histone deacetylase inhibitors in inducing antigen expression in tumour cells. Finally, we discuss the direction of future research in advancing the development of tumour vaccines for haematological malignancies.

CABYR Is a Novel Cancer-Testis Antigen in Lung Cancer

PURPOSE

Cancer-testis (CT) antigens are often expressed in a proportion of tumors of various types. Their restricted normal tissue expression and immunogenicity make them potential targets for immunotherapy. CABYR is a calcium-binding tyrosine phosphorylation-regulated fibrous sheath protein initially reported to be testis specific and subsequently shown to be present in brain tumors. This study was to determine whether CABYR is a novel CT antigen in lung cancer.

EXPERIMENTAL DESIGN

mRNA expression of CABYR-a/b (combination of CABYR-a and CABYR-b) and CABYR-c was examined in 36 lung cancer specimens, 14 cancer cell lines, and 1 normal cell line by conventional and real-time reverse transcription-PCR. Protein expression of CABYR was analyzed in 50 lung cancer tissues by immunohistochemistry. Antibodies specific to CABYR were analyzed in sera from 174 lung cancer patients and 60 healthy donors by ELISA and Western blot.

RESULTS

mRNA expression of CABYR-a/b and CABYR-c was observed, respectively, in 13 and 15 of 36 lung cancer tissues as well as in 3 and 5 of 14 cancer cell lines, whereas neither of them was observed in adjacent noncancerous tissues or the normal cell line. Protein expression of CABYR-a/b and CABYR-c was observed, respectively, in 20 and 19 of 50 lung cancer tissues. IgG antibodies specific to CABYR-a/b and CABYR-c were detected, respectively, in 11% and 9% of sera from lung cancer patients but not from the 60 healthy donors.

CONCLUSION

CABYR is a novel CT antigen in lung cancer and may be a promising target for immunotherapy for lung cancer patients.

SPAN-XB core promoter sequence is regulated in myeloma cells by specific CpG dinucleotides associated with the MeCP2 protein

SPAN-Xb is a novel cancer-testis antigen in multiple myeloma. We recently demonstrated that SPAN-Xb expression in myeloma cells is regulated through promoter methylation and could be upregulated by IL-7 and GM-CSF. In this present study, we set out to investigate the mechanism of SPAN-XB expression and the promoter association with the methyl-CpG binding protein (MeCP2). Elucidation of these interactions is likely shed light on potential therapeutic strategies to upregulate antigen levels for SPAN-Xb-based tumor vaccines. Using a panel of truncated promoter constructs, we localize the core sequence of SPAN-XB promoter to the 73 bp at the 3' end of the promoter, a region within the full length promoter that lacks CpG dinucleotides. Reporter gene expression assays showed that the core promoter function is significantly modulated by the adjacent CpG sequences. Chromatin immunoprecipitation assays revealed a specific association of MeCP2 with the promoter, and MeCP2 binding strongly correlated with repression of SPAN-XB gene. Reactivation of the SPAN-XB gene by 5-azacytidine treatment resulted in the loss of MeCP2 from this site. We, therefore, conclude that SPAN-XB core promoter function in myeloma cells is associated with MeCP2 protein binding and regulated by specific CpG dinucleotide sequences.

TAR cloning: insights into gene function, long-range haplotypes and genome structure and evolution

The structural and functional analysis of mammalian genomes would benefit from the ability to isolate from multiple DNA samples any targeted chromosomal segment that is the size of an average human gene. A cloning technique that is based on transformation-associated recombination (TAR) in the yeast Saccharomyces cerevisiae satisfies this need. It is a unique tool to selectively recover chromosome segments that are up to 250 kb in length from complex genomes. In addition, TAR cloning can be used to characterize gene function and genome variation, including polymorphic structural rearrangements, mutations and the evolution of gene families, and for long-range haplotyping.

Hominoid-specific SPANXA/D genes demonstrate differential expression in individuals and protein localization to a distinct nuclear envelope domain during spermatid morphogenesis

Human sperm protein associated with the nucleus on the X chromosome consists of a five-member gene family (SPANXA1, SPANXA2, SPANXB, SPANXC and SPANXD) clustered at Xq27.1. Evolved from an ancestral SPANX-N gene family (at Xq27 and Xp11) present in all primates as well as in rats and mice, the SPANXA/D family is present only in humans, bonobos, chimpanzees and gorillas. Among hominoid-specific genes, the SPANXA/D gene family is considered to be undergoing rapid positive selection in its coding region. In this study, RT-PCR of human testis mRNA from individuals showed that, although all SPANXA/D genes are expressed in humans, differences are evident. In particular, SPANXC is expressed only in a subset of men. The SPANXa/d protein localized to the nuclear envelope of round, condensing and elongating spermatids, specifically to regions that do not underlie the developing acrosome. During spermiogenesis, the SPANXa/d-positive domain migrated into the base of the head as the redundant nuclear envelope that protrudes into the residual cytoplasm. Post-testicular modification of the SPANXa/d proteins was noted, as were PEST (proline, glutamic acid, serine, and threonine rich regions) domains. It is concluded that the duplication of the SPANX-N gene family that occurred 6-11 MYA resulted in a new gene family, SPANXA/D, that plays a role during spermiogenesis. The SPANXa/d gene products are among the few examples of X-linked nuclear proteins expressed following meiosis. Their localization to non-acrosomal domains of the nuclear envelope adjacent to regions of euchromatin and their redistribution to the redundant nuclear envelope during spermiogenesis provide a biomarker for the redundant nuclear envelope of spermatids and spermatozoa.

Identification and expression profiling of 10 novel spermatid expressed CYPT genes

To identify candidate genes for poor sperm morphology, we have screened for genes expressed during spermiogenesis. We identified 10 new members of the cysteine-rich perinuclear theca (CYPT) family showing that this family contains at least 15 members, which also includes the casein kinase II target genes. Based on similarity the CYPT sequences could be divided into two groups, Cypt1-10 and the novel members Cypt12-15. The 5'-end of the CYPT family is highly similar to exon1A and part of the first intron of Zfy2. Seven CYPT genes mapped to the X chromosome; six contained an intron and one was intron-less. One CYPT gene mapped to chromosome 3 and one mapped to chromosome 9 which were both intron-less. The upstream region of the CYPT family and Zfy2 genes is conserved. For some the conservation extended over a large region, however, only about 150 nucleotides is conserved among all CYPT members and Zfy2. Nevertheless, the short conserved promoter leads to essentially identical expression profiles for the CYPT family members and Zfy2, which was clearly different from the profile of Zfy1. Expression of the CYPT family and Zfy2 preceded the expression of other spermatid-specific genes such as the transition proteins and the protamines. In situ hybridization revealed a low expression in pachytene spermatocytes from stages IX-X followed by a strong upregulation in spermatids from stage VI with maximum expression in spermatids in stages VII-VIII. The CYPT family may function in the remodeling of the spermatid nucleus before condensation of the DNA.

Cancer testis antigens--their importance in immunotherapy and in the early detection of cancer

The development of successful immunotherapeutic strategies requires the identification and characterisation of immunogenic cancer antigens that will be recognised by the host immune system, leading to tumour rejection. The concept of immunotherapy is based on the assumption that antigenic structures expressed in tumours can be used for therapeutic approaches employing the autologous immune system or by the application of immunotherapeutic reagents. Based on this concept, there is a great need to gain profound knowledge of the actual protein/antigen expression and its distribution pattern within normal tissues and cancerous tissues. Cancer testis (CT) antigens represent a unique class of tumour antigens, which are expressed in a variety of cancerous tissues and are silent in normal tissues, except for the testis. Owing to their restricted gene expression in the testis and various malignancies, CT antigens represent potential defined targets for antigen-based vaccination and antigen-directed immunotherapy to control cancer growth. Moreover, the analysis of humoral and cellular immune responses to CT antigens has proved useful for identifying novel cancer serum biomarkers with potential implications in early diagnosis of cancer.

Positive selection in the evolution of cancer

We hypothesize that forms of antagonistic coevolution have forged strong links between positive selection at the molecular level and increased cancer risk. By this hypothesis, evolutionary conflict between males and females, mothers and foetuses, hosts and parasites, and other parties with divergent fitness interests has led to rapid evolution of genetic systems involved in control over fertilization and cellular resources. The genes involved in such systems promote cancer risk as a secondary effect of their roles in antagonistic coevolution, which generates evolutionary disequilibrium and maladaptation. Evidence from two sources: (1) studies on specific genes, including SPANX cancer/testis antigen genes, several Y-linked genes, the pem homebox gene, centromeric histone genes, the breast cancer gene BRCA1, the angiogenesis gene ANG, cadherin genes, cytochrome P450 genes, and viral oncogenes; and (2) large-scale database studies of selection on different functional categories of genes, supports our hypothesis. These results have important implications for understanding the evolutionary underpinnings of cancer and the dynamics of antagonistically-coevolving molecular systems.

Dynamic structure of the SPANX gene cluster mapped to the prostate cancer susceptibility locus HPCX at Xq27

Genetic linkage studies indicate that germline variations in a gene or genes on chromosome Xq27-28 are implicated in prostate carcinogenesis. The linkage peak of prostate cancer overlies a region of approximately 750 kb containing five SPANX genes (SPANX-A1, -A2, -B, -C, and -D) encoding sperm proteins associated with the nucleus; their expression was also detected in a variety of cancers. SPANX genes are >95% identical and reside within large segmental duplications (SDs) with a high level of similarity, which confounds mutational analysis of this gene family by routine PCR methods. In this work, we applied transformation-associated recombination cloning (TAR) in yeast to characterize individual SPANX genes from prostate cancer patients showing linkage to Xq27-28 and unaffected controls. Analysis of genomic TAR clones revealed a dynamic nature of the replicated region of linkage. Both frequent gene deletion/duplication and homology-based sequence transfer events were identified within the region and were presumably caused by recombinational interactions between SDs harboring the SPANX genes. These interactions contribute to diversity of the SPANX coding regions in humans. We speculate that the predisposition to prostate cancer in X-linked families is an example of a genomic disease caused by a specific architecture of the SPANX gene cluster.

Expression of SpanX proteins in normal testes and in testicular germ cell tumours

We investigated the expression of the SpanX protein family in cells of normal testes and in testicular germ cell tumours, mainly seminomas and embryonal carcinomas, using an immunohistochemical approach. Most of the normal germ cells, belonging to spermatogonial and primary spermatocytic classes, showed a strong nuclear positivity. In contrast, post-meiotic germ cells showed diffused cytoplasmic and sometimes also perinuclear localization of the signal. The vast majority of cells were also positive in eight seminomas, six embryonal cell carcinomas and one teratocarcinoma. In all seminomas, nuclei were either exclusively or preferentially labelled; whereas, the nuclear signal intensity decreased in parallel with the appearance of some cytoplasmic staining in embryonal carcinomas. In conclusion, these data suggest that the SpanX protein family is not exclusively expressed post-meiotically and that seminomas and embryonal carcinomas may originate from SpanX-positive carcinoma-in-situ cell.

SPAN-Xb expression in myeloma cells is dependent on promoter hypomethylation and can be upregulated pharmacologically

SPAN-Xb is a novel cancer-testis antigen in multiple myeloma (MM). In this study, we determined the mechanisms regulating SPAN-Xb expression in MM. SPAN-Xb promoter sequence was first cloned into the CAT-reporter vector to determine the role of promoter methylation in the regulation of gene expression. Tumor cells were treated with 5-azacytidine and a panel of cytokines were used to determine their ability to induce SPAN-Xb expression. Bisulfite conversion with sequence analysis was applied to a panel of tumor cells and normal tissues to correlate the CpG dinucleotide hypomethylation and SPAN-Xb expression. We found that SPAN-Xb promoter function could be silenced by methylation. 5-Azacytidine induced promoter hypomethylation and resulted in SPAN-Xb expression, at both the transcript and protein levels. Hypomethylation of the CpG dinucleotides at positions -310, -307, -299 and -221 within the SPAN-Xb promoter strongly predict for SPAN-Xb expression. Both IL-7 and GM-CSF were also able to upregulate the expression of SPAN-Xb in myeloma cells, but only after the promoter sequence has been hypomethylated. Our results provide the first evidence showing the role of promoter methylation in the primary regulation of SPAN-Xb and the ability of IL-7 and GM-CSF to further enhance SPAN-Xb gene and protein expression in myeloma cells.

Cancer/testis antigens and gametogenesis: a review and "brain-storming" session

Genes expressed both in normal testis and in malignancies (Cancer/ Testis associated genes - CTA) have become the most extensively studied antigen group in the field of tumour immunology. Despite this, many fundamentally important questions remain unanswered: what is the connection between germ-cell specific genes and tumours? Is the expression of these genes yet another proof for the importance of genome destabilisation in the process of tumorigenesis?, or maybe activation of these genes is not quite random but instead related to some programme giving tumours a survival advantage?This review collates most of the recent information available about CTAs expression, function, and regulation. The data suggests a programme related to ontogenesis, mostly to gametogenesis. In the "brain-storming" part, facts in conflict with the hypothesis of random CTA gene activation are discussed. We propose a programme borrowed from organisms phylogenetically much older than humans, which existed before the differentiation of sexes. It is a programme that has served as a life cycle with prominent ploidy changes, and from which, as we know, the germ-cell ploidy cycle - meiosis - has evolved. Further work may show whether this hypothesis can lead to a novel anti-tumour strategy.

The SPANX gene family of cancer/testis-specific antigens: rapid evolution and amplification in African great apes and hominids

Human sperm protein associated with the nucleus on the X chromosome (SPANX) genes comprise a gene family with five known members (SPANX-A1, -A2, -B, -C, and -D), encoding cancer/testis-specific antigens that are potential targets for cancer immunotherapy. These highly similar paralogous genes cluster on the X chromosome at Xq27. We isolated and sequenced primate genomic clones homologous to human SPANX. Analysis of these clones and search of the human genome sequence revealed an uncharacterized group of genes, SPANX-N, which are present in all primates as well as in mouse and rat. In humans, four SPANX-N genes comprise a series of tandem duplicates at Xq27; a fifth member of this subfamily is located at Xp11. Similarly to SPANX-A/D, human SPANX-N genes are expressed in normal testis and some melanoma cell lines; testis-specific expression of SPANX is also conserved in mouse. Analysis of the taxonomic distribution of the long and short forms of the intron indicates that SPANX-N is the ancestral form, from which the SPANX-A/D subfamily evolved in the common ancestor of the hominoid lineage. Strikingly, the coding sequences of the SPANX genes evolved much faster than the intron and the 5' untranslated region. There is a strong correlation between the rates of evolution of synonymous and nonsynonymous codon positions, both of which are accelerated 2-fold or more compared to the noncoding sequences. Thus, evolution of the SPANX family appears to have involved positive selection that affected not only the protein sequence but also the synonymous sites in the coding sequence.