Effects of CT-Xp gene knock down in melanoma cell lines.

Cancer/testis (CT) genes are encoded by genes that are normally expressed only in the human germ line but which are activated in various malignancies. CT proteins are frequently immunogenic in cancer patients and their expression is highly restricted to tumors. They are thus important targets for anticancer immunotherapy. In several different tumor types, the expression of CT-X genes is associated with advanced disease and poor outcome, indicating that their expression might contribute to tumorigenesis. CT-X genes encoding members of the MAGE protein family on Xq28 have been shown to potentially influence the tumorigenic phenotype. We used small interfering RNA (siRNA) to investigate whether CT-X mapping to the short arm of the X-chromosome might also have tumorigenic properties and therefore be potentially targeted by functional inhibitors in a therapeutic setting. siRNAs specific to GAGE, SSX and XAGE1 were used in cell proliferation, migration and cell survival assays using cell lines derived from melanoma, a tumor type known to present high frequencies of expression of CT antigens. We found that of these, those specific to GAGE and XAGE1 most significantly impeded melanoma cell migration and invasion and those specific to SSX4 and XAGE1 decreased the clonogenic survival of melanoma cells. Our results suggest that GAGE, XAGE1 and SSX4 might each have a role in tumor progression and are possible therapeutic targets for the treatment of melanoma and other malignancies.

Immunologic correlates of the abscopal effect in a patient with melanoma.

The abscopal effect is a phenomenon in which local radiotherapy is associated with the regression of metastatic cancer at a distance from the irradiated site. The abscopal effect may be mediated by activation of the immune system. Ipilimumab is a monoclonal antibody that inhibits an immunologic checkpoint on T cells, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). We report a case of the abscopal effect in a patient with melanoma treated with ipilimumab and radiotherapy. Temporal associations were noted: tumor shrinkage with antibody responses to the cancer-testis antigen NY-ESO-1, changes in peripheral-blood immune cells, and increases in antibody responses to other antigens after radiotherapy. (Funded by the National Institutes of Health and others.).

The role of angiogenesis in the pathogenesis of psoriasis.

Psoriasis is a multifactorial skin disorder with known systemic consequences. While most recent studies point to a predominantly Th17-driven process, psoriasis also lies at the crossroads linking the pathways of angiogenesis and inflammation. Mediators such as VEGF and angiopoietin-2 play significant roles in the pathophysiology and may even account for the maintenance of the chronic inflammatory state. Targets in this shared pathway may offer alternative avenues for therapy.

Maspin expression, angiogenesis, prognostic parameters, and outcome in malignant melanoma.

BACKGROUND: Maspin is a serine protease inhibitor that is thought of as a tumor suppressor because of observations that loss of maspin expression in breast, prostate, and oral cancer is associated with poor prognosis. In addition, maspin may function as an inhibitor of angiogenesis. However, it has been correlated with malignant behavior in pancreatic and ovarian cancer. The role of maspin in malignant melanoma (MM) has not yet been systematically examined. OBJECTIVE: We aimed to examine the immunohistochemical expression of maspin and several proangiogenic factors (vascular endothelial growth factor, transforming growth factor-beta, alphaVbeta3 integrin, cyclooxygenase-2, and CD44) in MM and correlate each to angiogenesis, tumor thickness, and outcome. METHODS: In all, 77 formalin-fixed, paraffin-embedded MM samples were immunostained for maspin and other proangiogenic factors (vascular endothelial growth factor, transforming growth factor-beta, alphaVbeta3 integrin, cyclooxygenase-2, and CD44) and were correlated with angiogenesis as mean microvessel density. Three normal-appearing skin samples and 10 nevi were also immunostained for maspin. Breslow thickness, Clark level, clinical stage, and follow-up information were obtained for outcome analysis. RESULTS: Immunohistochemical analysis revealed strong nuclear melanocytic maspin expression in all 10 nevi (half of which were dysplastic) but none in melanocytes from 3 normal-appearing skin samples. Strong nuclear maspin staining was demonstrated in 78% of radial phase melanoma and 46% of vertical growth phase melanoma. In addition, there was a significant inverse relationship between maspin and microvessel density (P = .018) and tumor thickness greater than 0.76 mm (P = .007), indicating that maspin is expressed in thinner tumors with less angiogenesis. Conversely, vascular endothelial growth factor expression, Clark level, and Breslow thickness all significantly correlated with microvessel density (P = .047, P = .027, and P = .011, respectively). Cyclooxygenase-2 expression significantly correlated with thicker tumors (P = .006) but not with angiogenesis (P = .714). In addition, Clark level, Breslow thickness, and stage were all significant predictors of overall survival (P < .001, P = .005, and P < .001, respectively). LIMITATIONS: This study represents a single institution. CONCLUSION: These results demonstrate maspin expression in nevi and radial growth phase melanoma, but this expression seems to be lost in the transition from radial growth phase to vertical growth phase melanoma. In addition, maspin is correlated with decreased angiogenesis and tumor thickness less than 0.76 mm in MM. These results indicate maspin may function as a tumor suppressor in MM.

CTdatabase: a knowledge-base of high-throughput and curated data on cancer-testis antigens.

The potency of the immune response has still to be harnessed effectively to combat human cancers. However, the discovery of T-cell targets in melanomas and other tumors has raised the possibility that cancer vaccines can be used to induce a therapeutically effective immune response against cancer. The targets, cancer-testis (CT) antigens, are immunogenic proteins preferentially expressed in normal gametogenic tissues and different histological types of tumors. Therapeutic cancer vaccines directed against CT antigens are currently in late-stage clinical trials testing whether they can delay or prevent recurrence of lung cancer and melanoma following surgical removal of primary tumors. CT antigens constitute a large, but ill-defined, family of proteins that exhibit a remarkably restricted expression. Currently, there is a considerable amount of information about these proteins, but the data are scattered through the literature and in several bioinformatic databases. The database presented here, CTdatabase (http://www.cta.lncc.br), unifies this knowledge to facilitate both the mining of the existing deluge of data, and the identification of proteins alleged to be CT antigens, but that do not have their characteristic restricted expression pattern. CTdatabase is more than a repository of CT antigen data, since all the available information was carefully curated and annotated with most data being specifically processed for CT antigens and stored locally. Starting from a compilation of known CT antigens, CTdatabase provides basic information including gene names and aliases, RefSeq accession numbers, genomic location, known splicing variants, gene duplications and additional family members. Gene expression at the mRNA level in normal and tumor tissues has been collated from publicly available data obtained by several different technologies. Manually curated data related to mRNA and protein expression, and antigen-specific immune responses in cancer patients are also available, together with links to PubMed for relevant CT antigen articles.

Genome-wide analysis of cancer/testis gene expression.

Cancer/Testis (CT) genes, normally expressed in germ line cells but also activated in a wide range of cancer types, often encode antigens that are immunogenic in cancer patients, and present potential for use as biomarkers and targets for immunotherapy. Using multiple in silico gene expression analysis technologies, including twice the number of expressed sequence tags used in previous studies, we have performed a comprehensive genome-wide survey of expression for a set of 153 previously described CT genes in normal and cancer expression libraries. We find that although they are generally highly expressed in testis, these genes exhibit heterogeneous gene expression profiles, allowing their classification into testis-restricted (39), testis/brain-restricted (14), and a testis-selective (85) group of genes that show additional expression in somatic tissues. The chromosomal distribution of these genes confirmed the previously observed dominance of X chromosome location, with CT-X genes being significantly more testis-restricted than non-X CT. Applying this core classification in a genome-wide survey we identified >30 CT candidate genes; 3 of them, PEPP-2, OTOA, and AKAP4, were confirmed as testis-restricted or testis-selective using RT-PCR, with variable expression frequencies observed in a panel of cancer cell lines. Our classification provides an objective ranking for potential CT genes, which is useful in guiding further identification and characterization of these potentially important diagnostic and therapeutic targets.

ECSA/DPPA2 is an embryo-cancer antigen that is coexpressed with cancer-testis antigens in non-small cell lung cancer.

PURPOSE: Cancer cells recapitulate many behaviors of pluripotent embryonic cells such as unlimited proliferation, and the capacity to self-renew and to migrate. Embryo-cancer sequence A (ECSA), later named developmental pluripotency associated-2 (DPPA2), is an embryonic gene initially isolated from pluripotent human preimplantation embryos. We hypothesized that ECSA/DPPA2 would be quiescent in most normal tissues but expressed in cancers and may therefore be a useful target for immunotherapy. EXPERIMENTAL DESIGN: ECSA/DPPA2 expression was examined in a panel of normal and tumor tissue by reverse transcription PCR, quantitative real-time PCR, and immunohistochemistry. A panel of 110 non-small cell lung cancers (NSCLC) were further investigated for the presence of ECSA/DPPA2 transcripts and several cancer testis antigens (CTA). Sera from 104 patients were analyzed for spontaneous ECSA/DPPA2 antibody production by ELISA and Western blot. RESULTS: ECSA/DPPA2 transcripts were limited to normal testis, placenta, bone marrow, thymus, and kidney but expressed in a variety of tumors most notably in 30% of NSCLC. Enrichment for CTAs in ECSA/DPPA2-positive NSCLC was observed. Immunohistochemistry confirmed nuclear and cytoplasmic localization in subpopulations of cells with coexpression of the CTA MAGE-A3. Antibodies to recombinant ECSA/DPPA2 protein were detected in the sera of 4 of 104 patients with NSCLC but not in healthy controls. CONCLUSIONS: The restricted expression in normal tissues, expression in tumors with coexpression of CTAs, and spontaneous immunogenicity indicate that ECSA/DPPA2 is a promising target for antigen-specific immunotherapy in NSCLC.

Monoclonal antibody MX35 detects the membrane transporter NaPi2b (SLC34A2) in human carcinomas.

Mouse monoclonal antibody MX35 was developed against ovarian cancer. The antibody showed homogeneous reactivity with approximately 90% of human ovarian epithelial cancers and with a limited number of normal tissues by immunohistochemistry. Although mAb MX35 has been used in a number of clinical trials in ovarian cancer, it has been difficult to define the molecular identity of MX35. We report here that mAb MX35 recognizes the sodium-dependent phosphate transport protein 2b (NaPi2b) in human cancer cells. This conclusion is based on several lines of experimental evidence, including 1) the identification of SLC34A2, the gene coding for NaPi2b, by immunoscreening an ovarian cancer cell line cDNA expression library with mAb MX35; 2) mass spectrometry sequencing of peptides obtained by fragmentation from mAb MX35 affinity-purified antigen, which show complete sequence homology to amino acid sequences in NaPi2b; 3) selective down-regulation of SLC34A2 gene expression by RNA interference and the resulting loss of mAb MX35 binding to MX35-expressing human cancer cells; and 4) the demonstration of specific mAb MX35 reactivity with recombinant fusion proteins and with synthetic peptides of the putative largest extracellular loop of NaPi2b. We further show that NaPi2b in cancer cells is expressed on the cell surface as a heavily N-glycosylated protein, with evidence of additional post-translational modifications such as palmitoylation and the formation of disulfide bridges in the major extracellular loop. Membrane transporter molecules, such as NaPi2b, represent a new family of potential cell surface targets for the immunotherapy of cancer with monoclonal antibodies.

PLAC1, a trophoblast-specific cell surface protein, is expressed in a range of human tumors and elicits spontaneous antibody responses.

Identification of genes that are upregulated in tumors, and whose normal expression excludes adult somatic tissues but includes germline and/or embryonic tissues, has resulted in a rich variety of cancer antigens that are attractive targets for cancer vaccine and other therapeutic approaches. In the present study, we extended this approach to include genes strongly and restrictively expressed in the placenta by mining publicly available SAGE and EST databases. We identified a number of genes with high expression in placenta and different cancer types but with relatively restricted expression in normal tissues. The gene with the most distinctive expression pattern was found to be PLAC1, which encodes a putative cell surface protein that is highly expressed in placenta, testis, cancer cell lines and lung tumors. Hence we have designated it CT92. We found by ELISA that PLAC1 is immunogenic in a subset of cancer patients and healthy women. Its physical and expression characteristics render it a potential target for both active and passive cancer immunotherapeutic strategies.

Physical interaction of two cancer-testis antigens, MAGE-C1 (CT7) and NY-ESO-1 (CT6).

Cancer/testis (CT) antigens are the protein products of germ line-associated genes that are activated in a wide variety of tumors and can elicit autologous cellular and humoral immune responses. CT antigens can be divided between those that are encoded on the X chromosome (CT-X antigens) and those that are not (non-X CT antigens). Among the CT-X antigens, the melanoma antigen gene (MAGE) family, defined by a shared MAGE homology domain (MHD), is the largest. CT-X genes are frequently expressed in a coordinate manner in cancer cells, and their expression appears to be modulated by epigenetic mechanisms. The expression of CT-X genes is associated with advanced disease and poor outcome in different tumor types. We used the yeast two-hybrid system to identify putative MHD-interacting proteins. The MHD of MAGE-C1 (CT7) was used as bait to screen a human testis cDNA library. This study identified NY-ESO-1 (CT6) as a MAGE-C1 binding partner. Immunoprecipitation and immunofluorescence staining confirmed MAGE-C1 interaction with NY-ESO-1, and cytoplasmic co-localization of both proteins in melanoma cells. Co-expression of these two genes was found to occur in cancer cell lines from different origins, as well as in primary tumors (multiple myeloma and non-small cell lung cancer samples). This is the first report of direct interaction between two CT antigens and may be pertinent in the light of the frequently coordinated expression of these proteins.

Glycoprotein A34, a novel target for antibody-based cancer immunotherapy.

To identify novel, tissue-restricted cell surface proteins in cancer which can serve as targets for antibody-based diagnostics and therapeutics, a translated version of the expressed sequence tag database (tblastn) was mined for transcripts with similarity to the glycoprotein A33 (GPA33) colon cancer antigen. A novel human transcript, termed A34, was identified which encoded a putative cell surface protein, GPA34, which is approximately 30% identical to GPA33 and other members of the junctional adhesion molecule (JAM) family. Conventional end-point and quantitative real-time RT-PCR showed that A34 mRNA expression is highly tissue-restricted, as it is expressed predominantly in stomach and testis. A34 mRNA was also detected in 6/19 (31%) gastric cancers, 8/16 (50%) esophageal carcinomas, and 4/17 (23%) ovarian cancers, but not in lung, breast or colon carcinomas. A murine monoclonal antibody (mAb A34) was generated to the extracellular domain of the A34 protein and used to biochemically and immunohistochemically characterize the A34 antigenic system. The mAb A34 specifically recognized glycoproteins ranging in apparent size from 55-70 kDa, present in normal gastric mucosa and in COS-7 cells transfected with A34 cDNA. Of 31 different normal tissues examined by immunohistochemistry, GPA34 protein expression was detected primarily in normal stomach mucosa and testicular germ cells, and in the tumor cells of 5/17 (29%) gastric cancers, 7/11 (63%) esophageal cancers, and 2/21 (9%) ovarian cancers, in agreement with gene expression results. The A34 antigen and monoclonal antibody may be of considerable value for immunotherapy of different types of cancer.

Cancer-testis genes are coordinately expressed and are markers of poor outcome in non-small cell lung cancer.

PURPOSE: Cancer-testis genes mapping to the X chromosome have common expression patterns and show similar responses to modulators of epigenetic mechanisms. We asked whether cancer-testis gene expression occurred coordinately, and whether it correlated with variables of disease and clinical outcome of non-small cell lung cancer (NSCLC). EXPERIMENTAL DESIGN: Tumors from 523 NSCLC patients undergoing surgery were evaluated for the expression of nine cancer-testis genes (NY-ESO-1, LAGE-1, MAGE-A1, MAGE-A3, MAGE-A4, MAGE-A10, CT7/MAGE-C1, SSX2, and SSX4) by semiquantitative PCR. Clinical data available for 447 patients were used to correlate cancer-testis expression to variables of disease and clinical outcome. RESULTS: At least one cancer-testis gene was expressed by 90% of squamous carcinoma, 62% of bronchioloalveolar cancer, and 67% of adenocarcinoma samples. Statistically significant coexpression was observed for 34 of the 36 possible cancer-testis combinations. Cancer-testis gene expression, either cumulatively or individually, showed significant associations with male sex, smoking history, advanced tumor, nodal and pathologic stages, pleural invasion, and the absence of ground glass opacity. Cox regression analysis revealed the expression of NY-ESO-1 and MAGE-A3 as markers of poor prognosis, independent of confounding variables for adenocarcinoma of the lung. CONCLUSIONS: Cancer-testis genes are coordinately expressed in NSCLC, and their expression is associated with advanced disease and poor outcome.

Identification of cancer/testis-antigen genes by massively parallel signature sequencing.

Massively parallel signature sequencing (MPSS) generates millions of short sequence tags corresponding to transcripts from a single RNA preparation. Most MPSS tags can be unambiguously assigned to genes, thereby generating a comprehensive expression profile of the tissue of origin. From the comparison of MPSS data from 32 normal human tissues, we identified 1,056 genes that are predominantly expressed in the testis. Further evaluation by using MPSS tags from cancer cell lines and EST data from a wide variety of tumors identified 202 of these genes as candidates for encoding cancer/testis (CT) antigens. Of these genes, the expression in normal tissues was assessed by RT-PCR in a subset of 166 intron-containing genes, and those with confirmed testis-predominant expression were further evaluated for their expression in 21 cancer cell lines. Thus, 20 CT or CT-like genes were identified, with several exhibiting expression in five or more of the cancer cell lines examined. One of these genes is a member of a CT gene family that we designated as CT45. The CT45 family comprises six highly similar (>98% cDNA identity) genes that are clustered in tandem within a 125-kb region on Xq26.3. CT45 was found to be frequently expressed in both cancer cell lines and lung cancer specimens. Thus, MPSS analysis has resulted in a significant extension of our knowledge of CT antigens, leading to the discovery of a distinctive X-linked CT-antigen gene family.

Zinc release from protein kinase C as the common event during activation by lipid second messenger or reactive oxygen.

Zinc is a structural component of many regulatory molecules including transcription factors and signaling molecules. We report that two alternate signaling pathways of protein kinase C (PKC) activation involving either the lipid second messengers (diacylglycerol and its mimetics, the phorbol esters) or reactive oxygen converge at the zinc finger of the regulatory domain. They all trigger the release of zinc ions. An increase in intracellular free Zn(2+) was observed by confocal microscopy in intact cells treated with phorbol ester or by mild oxidation. The source of liberated Zn(2+) was traced to PKC and particularly the zinc finger domains. The activated form of native PKCalpha contained significantly less Zn(2+) than the resting form. Furthermore, purified recombinant PKC protein fragments shed stoichiometric amounts of Zn(2+) upon reaction with diacylglycerol, phorbol ester, or reactive oxygen in vitro. Our results offer new insight into the regulation of PKC. Far from cementing rigid structures, zinc actually is the linchpin that orchestrates dynamic changes in response to specific signals, allowing kinase activity to be turned on or off.

Activation of c-Raf kinase by ultraviolet light. Regulation by retinoids.

The present study highlights retinoids as modulators of c-Raf kinase activation by UV light. Whereas a number of retinoids, including retinol, 14-hydroxyretroretinol, anhydroretinol (AR), and retinoic acid bound the c-Raf cysteine-rich domain (CRD) with equal affinity in vitro as well as in vivo, they displayed different, even opposing, effects on UV-mediated kinase activation; retinol and 14-hydroxyretroretinol augmented responses, whereas retinoic acid and AR were inhibitory. Oxidation of thiol groups of cysteines by reactive oxygen, generated during UV irradiation, was the primary event in c-Raf activation, causing the release of zinc ions and, by inference, a change in CRD structure. Retinoids modulated these oxidation events directly: retinol enhanced, whereas AR suppressed, zinc release, precisely mirroring the retinoid effects on c-Raf kinase activation. Oxidation of c-Raf was not sufficient for kinase activation, productive interaction with Ras being mandatory. Further, canonical tyrosine phosphorylation and the action of phosphatase were essential for optimal c-Raf kinase competence. Thus, retinoids bound c-Raf with high affinity, priming the molecule for UV/reactive oxygen species-mediated changes of the CRD that set off GTP-Ras interaction and, in context with an appropriate phosphorylation pattern, lead to full phosphotransferase capacity.