Phosphorylated CXCR4 expression has a positive prognostic impact in colorectal cancer.

BACKGROUND: The CXCL12-CXCR4 chemokine axis plays an important role in cell trafficking as well as in tumor progression. In colorectal cancer (CRC), the chemokine receptor CXCR4 has been shown to be an unfavorable prognostic factor in some studies, however, the role of its activated (phosphorylated) form, pCXCR4, has not yet been evaluated. Here, we aimed to investigate the prognostic value of CXCR4 and pCXCR4 in a large cohort of CRC patients. PATIENTS AND METHODS: A tissue microarray (TMA) of 684 patient specimens of primary CRCs was analyzed by immunohistochemistry (IHC) for the expression of CXCR4 and pCXCR4 by tumor cells and tumor-infiltrating immune cells (TICs). RESULTS: The combined high expression of CXCR4 and pCXCR4 showed a favorable 5-year overall survival rate (68%; 95%CI = 59-76%) compared to tumors showing a high expression of CXCR4 only (48%; 95%CI = 41-54%). High expression of pCXCR4 was significantly associated with a favorable prognosis in a test and validation group (p = 0.015 and p = 0.0001). Moreover, we found that CRCs with a high density of pCXCR4+ tumor-infiltrating immune cells (TICs) also showed a favorable prognosis in a test and validation group (p = 0.054 and p = 0.004). Univariate Cox regression analysis for TICs revealed that a high density of pCXCR4+ TICs was a favorable prognostic marker for overall survival (HR = 0.97,95%CI = 0.96-1.00; p = 0.01). In multivariate Cox regression survival analyses a high expression of pCXCR4 in tumor cells lost its association with a better overall survival (HR = 0.99; 95%CI = 0.99-1.00, p = 0.098). CONCLUSION: Our results show that high densities of CXCR4 and pCXCR4 positive TICs are favorable prognostic factors in CRC.

Cancer-testis antigen expression in triple-negative breast cancer.

BACKGROUND: cancer-testis (CT) antigens, frequently expressed in human germline cells but not in somatic tissues, may become aberrantly reexpressed in different cancer types. The aim of this study was to investigate the expression of CT antigens in breast cancer. PATIENTS AND METHODS: a total of 100 selected invasive breast cancers, including 50 estrogen receptor (ER) positive/HER2 negative and 50 triple negative (TN), were examined for NY-ESO-1 and MAGE-A expression by immunohistochemistry. RESULTS: a significantly higher expression of MAGE-A and NY-ESO-1 was detected in TN breast cancers compared with ER-positive tumors (P = 0.04). MAGE-A expression was detected in 13 (26%) TN cancers compared with 5 (10%) ER-positive tumors (P = 0.07). NY-ESO-1 expression was confirmed in nine (18%) TN tumor samples compared with two (4%) ER-positive tumors. CONCLUSIONS: MAGE-A and NY-ESO-1 CT antigens are expressed in a substantial proportion of TN breast cancers. Because of the limited therapeutic options for this group of patients, CT antigen-based vaccines might prove to be useful for patients with this phenotype of breast cancer.

Human bone marrow mesenchymal stem cells and chondrocytes promote and/or suppress the in vitro proliferation of lymphocytes stimulated by interleukins 2, 7 and 15.

OBJECTIVES: To investigate whether human bone marrow-derived mesenchymal stem cells (BM-MSCs) and articular chondrocytes (ACs) affect the in vitro proliferation of T lymphocytes and peripheral blood mononuclear cells (PBMCs) driven by the homeostatic interleukin (IL)2, IL7 and IL15 cytokines binding to the common cytokine receptor gamma-chain (gamma(c)) in the absence of T cell receptor (TCR) triggering. METHODS: PBMCs, total T cells and T cell subsets (CD4+ and CD8+) were stimulated with IL2, IL7 or IL15 and exposed to cultured BM-MSCs and ACs at varying cell:cell ratio either in contact or in transwell conditions. Lymphocyte proliferation was measured by (3)H-thymidine uptake or by flow cytometry of carboxyfluorescein succinimidyl ester (CFSE)-labelled lymphocytes. RESULTS: MSCs and ACs enhanced and inhibited lymphocyte proliferation depending on the extent of lymphocyte baseline proliferation and on the MSC/AC to lymphocyte ratio. Enhancement was significant on poorly proliferating lymphocytes and mostly at lower MSC/AC to lymphocyte ratio. Suppression occurred only on actively proliferating lymphocytes and at high MSC/AC to lymphocyte ratio. Neither enhancement nor inhibition required cell-cell contact. CONCLUSIONS: There is a dichotomous effect of MSCs/ACs on lymphocytes proliferating in response to the homeostatic IL2, IL7 and IL15 cytokines likely to be encountered in homeostatic and autoimmune inflammatory conditions. The effect is determined by baseline lymphocyte proliferation, cell:cell ratio and is dependent on soluble factor(s). This should be taken into account when planning cellular therapy for autoimmune disease (AD) using stromal-derived cells such as MSCs.

Multiple mechanisms underlie defective recognition of melanoma cells cultured in three-dimensional architectures by antigen-specific cytotoxic T lymphocytes.

Cancer cells' growth in three-dimensional (3D) architectures promotes resistance to drugs, cytokines, or irradiation. We investigated effects of 3D culture as compared to monolayers (2D) on melanoma cells' recognition by tumour-associated antigen (TAA)-specific HLA-A(*)0201-restricted cytotoxic T-lymphocytes (CTL). Culture of HBL, D10 (both HLA-A(*)0201+, TAA+) and NA8 (HLA-A(*)0201+, TAA-) melanoma cells on polyHEMA-coated plates, resulted in generation of 3D multicellular tumour spheroids (MCTS). Interferon-gamma (IFN-gamma) production by HLA-A(*)0201-restricted Melan-A/MART-1(27-35) or gp 100(280-288)-specific CTL clones served as immunorecognition marker. Co-culture with melanoma MCTS, resulted in defective TAA recognition by CTL as compared to 2D as witnessed by decreased IFN-gamma production and decreased Fas Ligand, perforin and granzyme B gene expression. A multiplicity of mechanisms were potentially involved. First, MCTS per se limit CTL capacity of recognising HLA class I restricted antigens by reducing exposed cell surfaces. Second, expression of melanoma differentiation antigens is downregulated in MCTS. Third, expression of HLA class I molecules can be downregulated in melanoma MCTS, possibly due to decreased interferon-regulating factor-1 gene expression. Fourth, lactic acid production is increased in MCTS, as compared to 2D. These data suggest that melanoma cells growing in 3D, even in the absence of immune selection, feature characteristics capable of dramatically inhibiting TAA recognition by specific CTL.

Expression of MAGE-A cancer/testis antigens in esophageal squamous cell carcinomas.

BACKGROUND: Although the diagnosis and therapy of esophageal cancer have improved over the past decade, the prognosis remains dismal. Since MAGE-A cancer/testis antigens (CTA) are potential targets for immunotherapy, this study was aimed at evaluating their expression in these patients and its prognostic value. MATERIALS AND METHODS: Using 57B monoclonal antibody, MAGE-A CTA expression was analyzed in paraffin-embedded tumor specimens of 98 patients with esophageal squamous cell carcinoma or adenocarcinomas who had undergone surgical resection. For all patients, a postoperative follow-up of at least 4 years was available. The expression was quantified using a scoring system considering intensity and homogeneity of the immunostaining. The prognostic relevance of MAGE-A expression was analyzed in univariate analyses as well as Cox proportional hazard regression analysis. RESULTS: 57B positivity could be detected in 38 tumors (38.8%). Positive staining was observed in five out of 32 adenocarcinomas (15.2%) and in 33 out of 66 (50%) squamous cell carcinomas. MAGE-A expression did not correlate with the TNM classification, grading or age of the patients. Both univariate (p=0.88) and multivariate analyses (p = 0.82) revealed that MAGE-A expression lacked prognostic significance in esophageal carcinomas. CONCLUSION: MAGE-A was expressed in half of the squamous cell carcinomas of the esophagus, but rarely in adenocarcinomas. Although its immunodetection was insufficient for prognostic evaluation, the high expression rate suggests MAGE-A as a potential target for immunotherapy in the first group with the ability for pretherapeutic testing.

Encapsulation into sterically stabilised liposomes enhances the immunogenicity of melanoma-associated Melan-A/MART-1 epitopes.

Tumour-associated antigens (TAA)-specific vaccination requires highly immunogenic reagents capable of inducing cytotoxic T cells (CTL). Soluble peptides are currently used in clinical applications despite an acknowledged poor immunogenicity. Encapsulation into liposomes has been suggested to improve the immunogenicity of discrete antigen formulations. We comparatively evaluated the capacity of HLA-A2.1 restricted Melan-A/MART-1 epitopes in soluble form (S) or following inclusion into sterically stabilised liposomes (SSL) to be recognised by specific CTL, to stimulate their proliferation and to induce them in healthy donors' peripheral blood mononuclear cells (PBMC), as well as in melanoma-derived tumour-infiltrating lymphocytes (TIL). HLA-A2.1(+), Melan-A/MART-1-NA-8 melanoma cells served as targets of specific CTL in 51Cr release assays upon pulsing by untreated or human plasma-treated soluble or SSL-encapsulated Melan-A/MART-1 27-35 (M27-35) or 26-35 (M26-35) epitopes. These reagents were also used to stimulate CTL proliferation, measured as 3H-thymidine incorporation, in the presence of immature dendritic cells (iDC), as antigen-presenting cells (APC). Induction of specific CTL upon stimulation with soluble or SSL-encapsulated peptides was attempted in healthy donors' PBMC or melanoma-derived TIL, and monitored by 51Cr release assays and tetramer staining. Na-8 cells pulsing with SSL M27-35 resulted in a five-fold more effective killing by specific CTL as compared with equal amounts of S M27-35. Encapsulation into SSL also provided a partial (50%) protection of M27-35 from plasma hydrolysis. No specific advantages regarding M26-35 were detectable in these assays. However, at low epitope concentrations (

High-level expression of cancer/testis antigen NY-ESO-1 and human granulocyte-macrophage colony-stimulating factor in dendritic cells with a bicistronic retroviral vector.

Tumor-specific genes delivered to dendritic cells (DCs) have been used for the generation of cytotoxic T cells (CTLs), but their application has been limited on the one hand by low viral titers resulting in low transduction efficiency and poor protein production, and on the other hand by immunogenicity of the selectable marker and poor viability of the DCs. We addressed these limitations by creating a multipurpose master vector (pMV) and cloning the tumor gene NY-ESO-1, which is highly expressed in more than 50% of advanced myeloma patients. pMV was constructed from a Moloney murine leukemia virus (Mo-MuLV)-based retroviral backbone with the following features: (1) an extended packaging signal to achieve high viral titers, (2) a splice acceptor region to facilitate protein production, (3) a nonimmunogenic selectable marker, dihydrofolate reductase-L22Y (DHFR(L22Y)), to exclude the generation of CTLs against the selectable marker, (4) an internal ribosomal entry site between the tumor-specific gene (NY-ESO-1) and the selectable marker DHFR(L22Y) for coexpression of two heterologous gene products from a single bicistronic mRNA, minimizing the possibility of differential expression of these two genes, and (5) human granulocyte-macrophage colony-stimulating factor (hGM-CSF) cDNA driven by the human T-lymphotropic virus promoter to enhance DC function and viability. Recombinant virus of pMV-NY-ESO-1 was generated with vesicular stomatitis virus G envelope protein (VSV-G) in the GP2-293 cell line for efficient transduction. We present evidence that the DC phenotype is unaltered after transduction and that more than 85% of DCs express NY-ESO-1, which secrete approximately 40 ng of GM-CSF per 10(6) DCs.

MAGE-A4, a germ cell specific marker, is expressed differentially in testicular tumors.

BACKGROUND: Testicular germ cell tumors are the most common malignancy in young males, and the frequency of these tumors has risen dramatically over the last century. Because it is known that the MAGE genes are expressed in a wide variety of tumors but are expressed only in the mitotic spermatogonia (germ cells) and in the primary spermatocytes in the normal testis, the authors screened the expression of MAGE-A4 in a panel of testicular germ cell tumors. METHODS: Monoclonal antibody 57B raised against MAGE-A4 was tested immunohistochemically on 12 classical seminomas, 5 anaplastic seminomas, 10 various specimens of nonseminomatous germ cell tumors (NSGCTs), 2 combined tumors containing seminoma components, 1 Sertoli cell tumor, 2 Leydig cell tumors, and 15 carcinomas in situ (CIS). In addition, monoclonal antibody 57B was tested on embryonic gonad (age 8 weeks) and fetal gonads (ages 15 weeks, 17 weeks, and 28 weeks). RESULTS: Classical seminomas uniformly and specifically expressed MAGE-A4 compared with anaplastic seminomas and NSGCTs, which were negative for this antigen. Specific expression of MAGE-A4 also was seen in subpopulations of CIS cells, providing additional evidence for heterogeneity of the phenotype of these cells, in which it is believed that differentiation and proliferation generate seminomas and NSGCTs. Finally, MAGE-A4 was expressed in the fetal precursors of the stem germ cells from 17 weeks of gestation onward, in accordance the fact that CIS can arise from prespermatogonia in the fetus. CONCLUSIONS: MAGE-A4 can be considered a potential specific marker for normal premeiotic germ cells and germ cell tumors and can be used to characterize classical seminomas.

Immunogenicity of nonreplicating recombinant vaccinia expressing HLA-A201 targeted or complete MART-1/Melan-A antigen.

The effect on immunogenicity of different tumor T cell epitope formulations was evaluated in vitro using nonreplicating recombinant vaccinia vector expressing two forms of the melanoma-associated MART-1/Melan-A antigen. The first recombinant virus expressed a minigene encoding a fusion product between an endoplasmic reticulum (ER)-targeting signal and the HLA-A201 binding 27-35 peptide. The second viral construct encoded the complete MART-1/Melan-A protein. The capacity of HLA-A201 cells infected with either viral construct to generate and to stimulate MART-1/Melan-A 27-35 specific cytotoxic T-lymphocytes (CTL), was comparatively characterized. The results obtained here with a tumor antigen confirmed the capacity of vaccinia virus-encoded ER-minigene to generate a very strong antigenic signal. In cytotoxicity assays, recognition of target cells infected with high amounts of both recombinant viruses with activated specific CTL clones, resulted in similar lytic activity. With regard to calcium mobilization, TCR down-regulation, IFN-gamma release, and T cell proliferation assays, the targeted epitope elicited 10- to 1000-fold stronger responses. Remarkably, the immunogenic difference between the two formulations, in their respective capacity to generate CTL from naive HLA-A2 peripheral blood mononuclear cells in vitro as measured by tetramer detection, was lower (2- to 3-fold). Recombinant vectors expressing complete antigens have demonstrated their capacity to generate specific responses and such vaccines might take advantage of a broader potential of presentation. However, as demonstrated here for the HLA-A201-restricted MART-1/Melan-A immunodominant epitope, nonreplicative vaccinia virus expressing ER-targeted minigenes appear to represent a significantly more immunogenic epitope vaccine formulation.

Expression of MAGE tumour-associated antigens is inversely correlated with tumour differentiation in invasive ductal breast cancers: an immunohistochemical study.

MAGE (Melanoma antigen E) family gene products encompass tumour-associated antigens (TAAs) recognised by human leukocyte antigen (HLA)-restricted specific T-cells. Agents inducing DNA demethylation, an event typically detectable in cellular de-differentiation processes, were shown to induce the expression of MAGE genes. By using a monoclonal antibody specific for MAGE family gene products, we have studied the expression of these TAAs in a group of 144 patients with invasive ductal breast cancers. Immunohistochemical data were correlated with tumour differentiation, lymphatic vessel invasion, oestrogen receptor expression, intratumoural necrosis, lymphocytic infiltration, perineural invasion, tumour microcalcifications and axillary lymph node metastases. MAGE immunoreactivity was undetectable in non-neoplastic cells. In poorly differentiated cancers positive staining was observed in 30/63 cases (47.6%) as compared with 13/51 (25.4%) and 5/30 (16.6%) in moderately and well-differentiated tumours, respectively (P<0.05). In addition, MAGE immunoreactivity was significantly correlated with lymphatic vessel invasion and intratumoural necrosis. Moreover, a significant inverse relationship with oestrogen receptor expression was also observed. However, no significant correlation could be established between MAGE immunoreactivity and defined phenotypic characteristics of tumour infiltrating lymphocytes, including expression of CD3, CD4, CD8, CD20 or granzyme B. Thus, expression of MAGE family gene products in invasive ductal breast cancers appears to be associated with poorly differentiated histological phenotypes. These data support the concept of specific immunotherapy in highly aggressive forms of breast neoplasms. Furthermore, they suggest that MAGE immunoreactivity could represent a tumour marker of potential prognostic relevance.

High density oligonucleotide array analysis of interferon- alpha2a sensitivity and transcriptional response in melanoma cells.

Interferon alpha (IFN-alpha) represents an adjuvant therapy of proven effectiveness in increasing disease-free interval and survival in subgroups of melanoma patients. Since high doses of cytokine are required, the treatment is often accompanied by toxic side effects. Furthermore, naturally occurring insensitivity to IFN-alpha may hamper its therapeutic efficacy. Clinical, molecular or immunological markers enabling the selection of potential responders have not been identified so far. To explore the molecular basis of IFN-alpha responsiveness, we analysed the expression pattern of about 7000 genes in IFN-alpha sensitive and resistant cell lines and we compared the transcription profiles of cells cultured in the presence or absence of the cytokine using high-density oligonucleotide arrays. Melanoma cell lines were screened for their sensitivity to proliferation inhibition and HLA class I induction upon IFN-alpha treatment by standard 3H-thymidine incorporation and flow-cytometry. The study of 4 sensitive and 2 resistant cell lines allowed the identification of 4 genes (RCC1, IFI16, hox2 and h19) preferentially transcribed in sensitive cells and 2 (SHB and PKC-zeta) preferentially expressed in resistant cells. IFN-alpha stimulation resulted in the expression of a panel of 19 known inducible genes in sensitive but not in resistant cells. Moreover a group of 30 novel IFN-alpha inducible genes was identified. These data may provide a useful basis to develop diagnostic tools to select potential IFN-alpha responders eligible for treatment, while avoiding unnecessary toxicity to non-responders. Furthermore, by extending the knowledge of the polymorphic effects of IFN-alpha on gene expression, they offer novel clues to the study of its pleiotropic toxicity.

A retrogen strategy for presentation of an intracellular tumor antigen as an exogenous antigen by dendritic cells induces potent antitumor T helper and CTL responses.

Induction of an effective antitumor response requires CD4+ helper T (Th) cells to recognize antigens on the same dendritic cells (DCs) that cross-present CTL antigens. Such cross-presentation is difficult to achieve by current tumor vaccine strategies. Here, we develop a novel "Retrogen" strategy for DCs to efficiently cross-present an intracellular tumor antigen, MAGE-3, to both MHC class I and MHC class II in a cognate manner. Specifically, the MAGE-3 gene was linked to a leader sequence at its NH2 terminus for secretion and to a cell-binding domain at its COOH terminus for receptor-mediated internalization. DCs transduced with the modified MAGE-3 gene produced and secreted MAGE-3 proteins, which were efficiently taken up by DCs via receptor-mediated internalization and presented as exogenous antigens to class I and class II molecules. Immunization of mice with the transduced DCs expressing the MAGE-3 fusion protein, termed "Retrogen" for its retrograde transport/internalization after secretion, efficiently induced all arms of the adaptive antitumor immune responses. Thus, this retrogen strategy of using a unifying mechanism for DCs to cross-present an intracellular tumor antigen in a cognate manner could be generally used to improve the efficacy of tumor vaccines and immunotherapies.

Modulation of dendritic cell phenotype and mobility by tumor cells in vitro.

To gain new insights into the functional interaction between DC and neoplastic cells, we have analyzed the effects of melanoma and colorectal cancer lines on the chemotaxis and the phenotype of monocyte-derived DC in vitro. Both types of tumor cells displayed effective chemoattractive capacity towards immature, but not mature DC. Furthermore, conditioned medium of discrete melanoma lines induced upregulation of CD80, CD86, MHC class I, and MHC class II molecules on immature DC. However, de novo expression of E-cadherin and strong upregulation of CD15 could also be detected in the absence of CD83 expression. Melanoma-conditioned DC exhibited an increased adhesion capacity to a melanoma cell line in vitro and did not migrate in response to SLC chemokine. Tumor-infiltrating CD15(+) cells displaying DC morphology could also be detected by immunohistochemistry in the original tumor specimens from which discrete melanoma cell lines under investigation were derived. Colorectal cancer cell lines, although able to chemoattract immature DC, were apparently unable to modulate their phenotype. Altogether our results suggest that tumor cells can attract immature DC in vitro and, eventually, modulate their phenotype. As a result, DC mobility could be severely impaired.

NY-ESO-1 tumour associated antigen is a cytoplasmic protein detectable by specific monoclonal antibodies in cell lines and clinical specimens.

NY-ESO-1 gene encodes a novel member of the cancer/testis (CT) family of human tumour-associated antigens (TAA). Specific monoclonal antibodies (mAb) have identified the corresponding gene product in lysates of tumour cell lines as a 22 kDa protein but no data are available concerning its intracellular location or distribution within neoplastic tissues. We have generated NY-ESO-1 specific mAbs recognizing the target molecule in cytospin preparations and in sections from clinical tumour specimens. These reagents identify NY-ESO-1 TAA in melanoma cell lines expressing the specific gene as a cytoplasmic protein, sharing the intracellular location of most MAGE TAA. In a series of 12 melanoma specimens, specific staining, limited to neoplastic cells, was detectable in the five cases where NY-ESO-1 gene expression was observed. In two of them over 90% of tumour cells showed evidence of positive staining. Lower percentages of positive neoplastic cells ranging between single cells and 50% were observed in the remaining tumours. These data suggest that active specific immunotherapies targeting NY-ESO-1, alone or in combination with other TAA could be of high clinical relevance in sizeable subgroups of melanoma patients.

Naturally processed and concealed HLA-A2.1-restricted epitopes from tumor-associated antigen tyrosinase-related protein-2.

In this study, a computer-assisted reverse immunology approach was utilized in order to identify potentially antigenic peptides derived from the differentiation antigen TRP-2, a melanosomal protein frequently expressed in melanoma. Among the seven peptides complying with HLA-A2.1-binding motifs, two induced specific CD8(+) cytotoxic T lymphocytes. HLA-A2.1(+) melanoma cells expressing TRP-2 were lysed by clones specific for TRP-2(360-368) (TLDSQVMSL) peptide, thus identifying it as a naturally processed epitope. Other T-cell clones directed against TRP-2(476-484) (VMGTLVALV) were unable to lyse HLA-matched TRP-2(+) cell lines. The role of intracellular proteolytic processing in the generation of this epitope was investigated by transfecting mini-genes encoding the TRP-2(476-484) peptide alone or carrying N- or C-terminal extensions. Specific T-cell clones recognized target cells expressing the cytotoxic T-lymphocyte (CTL)-defined epitope or its C-terminally extended precursor, but failed to recognize cells expressing the N-terminally extended TRP-2(476-484) peptide, suggesting the presence of a negative processing signal (NPS). Regarding C-terminus-flanking regions, mutational analysis indicates that the GLY485 residue plays a key role in the processing of the TRP-2(476-484) epitope. Interestingly, proteasome inhibitors preventing the generation of the MART-1/Melan-A(27-35) immunodominant melanoma tumor-associated antigen (TAA) promoted detectable presentation of TRP-2(476-484) epitope in HLA-A2.1(+) and TRP-2(+) tumor lines, as witnessed by cytokine release by specific T-cell clones.

Monoclonal antibody 57B stains tumor tissues that express gene MAGE-A4.

Monoclonal antibody (Mab) 57B, which was raised against a recombinant MAGE-A3 protein, was tested for its ability to stain cells expressing various members of the MAGE-A gene family. COS-7 cells transfected with cDNAs encoding MAGE-A1, A2, A3, A4, A6, or A12 were stained, whereas those transfected with MAGE-A8, A9, A10, or A11 cDNAs were not. However, in tissue sections, we observed a different pattern of staining: the antibody effectively stained the tumors that expressed MAGE-A4 and only these tumors, regardless of the expression of the other MAGE-A genes. It seems, therefore, that at the level of MAGE gene expression found in tumors, a level clearly lower than that observed in transfected COS cells, only the MAGE-A4 protein can be reliably detected. We conclude that the 57B Mab should be useful for tumor diagnosis related to therapeutic vaccination involving MAGE-A4.

Identification of genes differentially expressed in melanoma sublines derived from a single surgical specimen characterised by different sensitivity to cytotoxic T-lymphocyte activity.

In this study we used differential display technology in an attempt to obtain an insight into the mechanisms underlying escape of tumour cells to the specific cytotoxic T cell response. A primary tumour cell line and autologous tumour infiltrating lymphocytes were raised from a metastatic melanoma sample (ME15). Upon co-culture of tumour infiltrating lymphocytes with irradiated tumour cells, CTL specific for neoplastic cells were generated and cloned. Using a CTL clone, a cytotoxicity resistant tumour subline (ME15R) was immunoselected. We applied a PCR-based differential display technique to amplify DNA sequences differentially expressed in ME15 sublines sensitive (S) or resistant (R) to specific CTL killing. 10 different sequences whose expression was exclusively detectable in ME15S cells were identified. Five of them matched with known expressed sequence tags encoding products of unidentified function. 2 showed high homology with a mitochondrial mRNA and with the gene encoding the S24 ribosomal protein. Most interestingly, genes coding for glutamine synthetase, TGF-beta-3 and PAX3, a well-characterised transcription factor, were only expressed in ME15S cells. The latter gene was found to be transcribed in all healthy tissues tested, but only in a subgroup of established melanoma cell lines. Taken together, our data underline the relevant potential of differential display technology in the molecular analysis of paired tumour lines endowed with different phenotypic characteristics. Cloning of entire open reading frames and transfection studies are warranted to clarify the role of individual differentially displayed genes in the escape of tumour cells from cellular immune response.

Expression of gene MAGE-A4 in Reed-Sternberg cells.

Genes of the MAGE-A family are expressed in several types of solid tumors but are silent in normal tissues with the exception of male germline cells, which do not carry HLA molecules.Therefore, peptides encoded by MAGE-A genes are strictly tumor-specific antigens that can be recognized by CTL and constitute promising targets for immunotherapy. The expression of 6 genes of the MAGE-A family was tested with reverse transcriptase-polymerase chain reaction in lymphoma samples. Among 38 samples of non-Hodgkin lymphoma, 1 anaplastic large cell lymphoma expressed genes MAGE-A1, -A2, -A3, -A4, and -A12, and 1 lymphoepithelioid T-cell lymphoma expressed gene MAGE-A4. Five of 18 samples (28%) from patients with Hodgkin disease expressed gene MAGE-A4. In tissue sections, staining by a monoclonal antibody that recognizes the MAGE-A4 protein was observed in 11 of 53 samples (21%) from patients with Hodgkin disease. In the positive samples, the Reed-Sternberg cells were strongly stained whereas the surrounding cells were not. These results indicate that Hodgkin disease may be a target for specific immunotherapy involving MAGE-A4 antigens.