Antigen-specific immunity in neuroblastoma patients: antibody and T-cell recognition of NY-ESO-1 tumor antigen.

Neuroblastoma cells have been shown to express molecularly defined tumor-associated antigens, which could represent potential targets of T and/or B cell-mediated immunity. However, the existence of a spontaneous immune response to such tumor antigens in neuroblastoma patients has yet to be investigated. In the present work we addressed the issue of whether NY-ESO-1, a germ cell antigen aberrantly expressed in different tumor types, is expressed by neuroblastoma cells and may represent a target for humoral and/or cellular immune responses in neuroblastoma patients. We found that a large fraction of neuroblastoma biopsies, independently from the clinical stage and degree of tumor cell differentiation, expressed significant levels of NY-ESO-1 as assessed by reverse transcription-PCR and immunohistochemistry. NY-ESO-1-specific IgG antibodies were detected in the sera of 10% of neuroblastoma patients with stage III or IV disease, but not in patients in clinical remission or with earlier stages. This suggests that antibody production occurred as a late event in the course of disease. NY-ESO-1-specific immune responses were observed for CD4(+) and CD8(+) T cells from peripheral blood lymphocytes in 4 of 8 neuroblastoma patients, as detected by IFN-gamma enzyme-linked immunospot assay after in vitro stimulation either with the NY-ESO-1 recombinant protein or with the HLA-A2-restricted peptide NY-ESO-1(157-167). NY-ESO-1-specific CD4(+) and CD8(+) T cells were also able to recognize NY-ESO-1 expressing neuroblastoma cells. The presence of T cells specific for NY-ESO-1 antigen was not associated with the stage of disease, or to the presence or absence of NY-ESO-1 specific antibodies. We conclude that NY-ESO-1 is an immunogenic antigen in neuroblastoma patients and represents a candidate target for immune-based therapy.

BRAF alterations are associated with complex mutational profiles in malignant melanoma.

To evaluate the mutational profiles associated with BRAF mutations in human melanoma, we have studied BRAF, RAS, PTEN, TP53, CDKN2A and CDK4 genes and their expression in melanoma lesions. Owing to the lack of sufficient material from fresh specimens, we employed short-term cell lines obtained from melanoma biopsies. In all, 41 melanoma obtained from eight primary lesions, 20 nodal, 11 cutaneous and two visceral metastases from patients with sporadic (n=31), familial (n=4) and multiple melanoma (n=2) were analysed. The results revealed novel missense mutations in the BRAF, PTEN, CDKN2A and CDK4 genes. Overall, activating mutations of BRAF and loss of functional p16 and ARF were detected in the majority of melanomas (29/41, 36/41 and 29/41, respectively), while PTEN alterations/loss, NRAS and TP53 mutations occurred less frequently (6/41, 6/41 and 10/41, respectively). In the resulting 12 mutational profiles, p16/ARF loss associated with mutated BRAFV599E was the most represented (n=15). In addition, TP53 and PTEN mutations were always accompanied with BRAF alterations, while PTEN loss was found in association with CDKN2A or TP53 mutations in the absence of BRAF activation. The p16/ARFDelta+BRAF/RAS profile was significantly associated with a longer survival, while complex mutational profiles were detected in highly aggressive disease and poor survival. These data support the existence of several molecularly defined melanoma groups which likely reflect different clinical/biological behaviour, thus suggesting that a more extensive molecular classification of melanoma would significantly impact its clinical management.

DHCR24 gene expression is upregulated in melanoma metastases and associated to resistance to oxidative stress-induced apoptosis.

The DHCR24 gene encoding for the 3beta-hydroxysterol delta24-reductase, an oxidoreductase involved in cholesterol biosynthesis, was isolated by subtractive hybridization as highly expressed in a short-term melanoma cell line derived from a cutaneous metastases (S/M2) compared to that obtained from the autologous primary tumor (S/P). DHCR24 (alias seladin-1, diminuto/dwarf1 homolog) has been reported to act as an antiapoptotic factor in neurons. Gene expression analysis by Northern blot confirmed that DHCR24 was 5-fold upregulated in S/M2 compared to S/P cells. High levels of DHCR24 gene expression were detected in 13/25 melanoma metastases and in 1/7 primary melanomas by real-time PCR, indicating that upregulation of this gene may occur in melanoma progression. In S/M2 cells, high DHCR24 gene expression associated with resistance to apoptosis triggered by oxidative stress induced by exposure to hydrogen peroxide. DHCR24 gene transfer was shown to protect melanoma cells from H2O2-induced cytotoxicity. Although higher cholesterol levels were shown in S/M2 cells compared to S/P cells, DHCR24 gene transfer did not increase cholesterol content. To evaluate whether DHCR24 acts as an antiapoptotic factor in melanoma metastases, the cytotoxic effect of chemotherapeutic agents was tested in DHCR24 transfectants and in the presence of a DHCR24 inhibitor, U18666A. High DHCR24 gene expression in transfectants did not result in a higher resistance to cytotoxic agents; treatment with U18666A was cytotoxic in S/P cells with a lower DHCR24 content and showed additive cytotoxic effect only when associated with H2O2 and not with cysplatin or etoposide, indicating that the DHCR24 protective effect is exerted through an oxidative stress-specific mechanism.

CTAB-urea method purifies RNA from melanin for cDNA microarray analysis.

Melanin represents a major problem for the study of melanoma by microarrays since it is retained during RNA extraction and inhibits the enzymatic reactions used for probe preparation. Here we report a new method for cleaning RNA from melanin, based on the use of the cationic detergent cetyl-trimethylammonium bromide (CTAB)-urea for RNA precipitation. This method is easy to perform and has a low cost. Purified RNA is recovered with high quality and good yield. CTAB-urea treated RNA from highly pigmented melanoma cells can be successfully reverse transcribed and labeled to obtain probes which can be subsequently used in cDNA microarray experiments, giving consistent and reproducible results.