The association between 11C-methionine uptake, IDH gene mutation, and MGMT promoter methylation in patients with grade II and III gliomas.

AIM: To evaluate the association between 11C-methionine positron-emission tomography (11C-methionine PET) findings, isocitrate dehydrogenase (IDH) gene mutation, and O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation in patients with grade II and III gliomas. MATERIALS AND METHODS: Data were collected from 40 patients with grade II and III gliomas who underwent both magnetic resonance imaging (MRI) and 11C-methionine PET as part of their pre-surgical examination. IDH mutation was examined via DNA sequencing, and MGMT promoter methylation via quantitative methylation-specific polymerase chain reaction (PCR). RESULTS: A threshold of MGMT promoter methylation of 1% was significantly associated with tumour/normal tissue (T/N) ratio. The T/N ratio in samples with MGMT promoter methylation ≥1% was higher than that in samples with MGMT promoter methylation <1%, and the difference was statistically significant (p=0.011). Reliable prediction of MGMT promoter methylation (<1% versus ≥1%) was possible using the T/N ratio under the receiver operator characteristic (ROC) curve with a sensitivity and specificity of 75% each (cut-off value=1.6: p=0.0226, area under the ROC curve [AUC]=0.76172). Conversely, the T/N ratio had no association with IDH mutation (p=0.6). The ROC curve revealed no reliable prediction of IDH mutation using the T/N ratio (p=0.606, AUC=0.60577). CONCLUSION: 11C-methionine PET parameters can predict MGMT promoter methylation but not IDH mutation status. 11C-methionine uptake may have limited potential to reflect DNA methylation processes in grade II and III gliomas.

Tumor antigens isolated from a patient with vitiligo and T-cell-infiltrated melanoma.

Serological identification of tumor antigens by cDNA expression cloning is a technique used to isolate cDNAs encoding tumor antigens that are recognized by IgG antibodies in sera from cancer patients. It is also useful for the isolation of tumor antigens recognized by T cells. We applied this method to identify melanoma antigens recognized by the serum from a patient with a good prognosis who had T-cell-infiltrated melanoma and vitiligo. By screening a lambda phage cDNA library constructed from a highly pigmented melanoma cell line, SKmel23, with the patient's serum, 50 positive cDNA clones consisting of 26 distinct antigens were isolated. Of these, 20 encoded known proteins, and 6 encoded previously uncharacterized ones. The most frequently isolated clone, which we named KU-MEL-1, was unknown previously but was homologous to partial cDNA sequences registered in the expressed sequence tag database. Reverse transcription-PCR and Northern blot analysis demonstrated that KU-MEL-1 was strongly expressed in most melanoma cell lines, melanoma tissue samples, and cultured melanocytes and weakly expressed in cell lines derived from other types of tumors, as well as in some normal tissues, including testis. Western blot analysis with polyclonal murine antibody generated by immunization with the recombinant KU-MEL-1 protein demonstrated that the KU-MEL-1 protein was preferentially expressed in melanoma cells and melanocytes. IgG antibodies against KU-MEL-1 were detected in the sera from 9 of 26 melanoma patients and from some patients with other cancers, including brain tumor, esophageal cancer, colon cancer, and chronic myelogenous leukemia, but were not detected in sera from 30 healthy individuals. Although the IgG specific for KU-MEL-1 was not detected in sera from 12 vitiligo patients, it was detected in sera from 7 of 11 patients with Vogt-Koyanagi-Harada disease that is thought to be an autoimmune disease against melanocytes. These results suggest that KU-MEL-1 may be a useful target for the development of diagnostic and therapeutic methods for patients with various cancers, particularly with melanoma, as well as patients with autoimmune diseases against melanocytes.

Membrane-type matrix metalloproteinase-1 and -3 activity in primate smooth muscle cells.

Membrane-type matrix metalloproteinases-1 and -3 (MT1- and MT3-MMPs) are expressed by activated smooth muscle cells (SMCs) both in vitro and in vivo (19). To define their functions in SMCs, we transduced MT1- and MT3-MMP cDNAs into baboon SMCs by using adenoviral vectors. Overexpression of MT1-MMP increased the conversion of proMMP-2 to the intermediate and active forms. In contrast, in MT3-MMP-overexpressing cells, MMP-2 was activated partially. Immunoblot analyses revealed that MT1-MMP protein was present in the SMCs and accumulated in the presence of the synthetic MMP inhibitor, BB94, or tissue inhibitor of metalloproteinase-2 (TIMP-2). However, MT3-MMP protein was detectable only when BB94, but not TIMP-2, was present. Zymographic analyses showed that MT3-MMP had much stronger casein- and gelatin-degrading activities than did MT1-MMP. Furthermore, when MT3-MMP and MT1-MMP were coexpressed, MT1-MMP degradation was enhanced; this result supports the possibility that MT3-MMP can degrade MT1-MMP. SMCs overexpressing either MT1- or MT3-MMP exhibited altered morphology, without changing their proliferation. This alteration was prevented by BB94 addition. The cells, which underwent this change, showed reduced adhesion to both collagen and fibronectin and increased migration in a Boyden chamber. The present study demonstrates that MT1- and MT3-MMPs have different enzymatic activities but may nevertheless affect SMC function in the same way.

Isolation of a new melanoma antigen, MART-2, containing a mutated epitope recognized by autologous tumor-infiltrating T lymphocytes.

Using cDNA expression cloning, a cDNA encoding a novel human melanoma Ag, MART-2 (melanoma Ag recognized by T cells-2), recognized by HLA-A1-restricted CD8(+) T cells from tumor-infiltrating lymphocytes (TIL1362) was isolated from an autologous melanoma cell line, 1362 mel. Homologous sequences to the cDNA had been registered in the EST database. This gene encoded an uncharacterized protein expressed ubiquitously in most normal and cancer cells. A mutation (A to G transition) was found in the cDNA obtained from the1362 mel melanoma cell line in the sequences encoding the phosphate binding loop (P-loop) that resulted in loss of the ability to bind GTP. Transfection of NIH-3T3 with the mutated MART-2 did not result in the development of significant foci. By screening 36 various cancer cell lines using single-strand conformation polymorphism, a possible mutation in the P-loop of MART-2 was found in one squamous cell lung cancer cell line, EBC1. The T cell epitope for TIL1362, FLEGNEVGKTY, was identified to be encoded by the mutated sequence of the MART-2 Ag. The mutation substituted glycine in the normal peptide with glutamic acid at the third amino acid of the epitope, which is an important primary anchor amino acid for HLA-A1 peptide binding. The normal peptide, FLGGNEVGKTY, was not recognized by TIL1362, suggesting that this T cell response was specific for the autologous tumor. Although transforming activity was not detected in the NIH-3T3 assay, MART-2 with the mutation in the P-loop may be involved in the generation of melanoma through a loss of GTP binding activity.

Control of smooth muscle cell function by membrane-type matrix metalloproteinases.

Vascular smooth muscle cells (SMCs) express membrane-type matrix metalloproteinases-1 and -3 (MT1- and MT3-MMPs). Expression is induced by PDGF in culture or by balloon injury in rat carotid arteries. In this study, we tried to define their functions in SMCs by transducing MT1- and MT3-MMP cDNAs into baboon-cultured SMCs, using adenoviral vectors. Overexpression of MT1-MMP increased the conversion of proMMP-2 to the activated form. In contrast, in MT3-MMP overexpressing cells, MMP-2 activation was partial. However, both MT1- and MT3-MMP overexpression elicited morphological alterations (cell rounding), which was prevented by BB94 addition. The cells, which underwent this change, showed reduced adhesion to matrices and increased migration in a Boyden chamber.

T cell immune responses against melanoma and melanocytes in cancer and autoimmunity.

T cell responses specific for melanoma cells and melanocytes appear to be involved in the rejection of melanoma tumors, as well as in the development of autoimmune reactions in patients with Vogt-Koyanagi-Harada disease (VKH), sympathetic ophthalmia, or autoimmune vitiligo. Some of the target antigens for those T cells have been isolated using cDNA expression cloning with melanoma reactive T cells derived from lymphocytes tumor infiltrating (TIL) of patients with melanoma. These include melanocyte specific proteins, such as tyrosinase, TRP1, TRP2, gp100, and MART-1, cancer-testis antigens, and mutated peptides derived from genetic alterations in melanoma cells. Some of the melanoma reactive T cells appear to respond to cryptic or subdominant self epitopes in melanosomal proteins. Modification of those epitopes to increase their immunogenicity by replacement of amino acids at primary anchor residues for peptide/MHC binding, allowed an improvement in immunotherapy for patients with melanoma. Targets for autoreactive T cells against melanocytes in those autoimmune disorders remain to be identified. Isolation of novel target antigens is important for understanding these pathological T cell responses, as well as for developing new diagnostic and treatment methods for these diseases. A variety of techniques, including cDNA expression cloning with T cells, serological analysis of recombinant cDNA expression libraries (SEREX), cDNA subtraction with representational differential analysis (RDA), and serial analysis of gene expression (SAGE) are now being applied to identify novel melanoma/melanocyte antigens recognized by T cells and antibodies.

Transcription initiation mediated by initiator binding protein in Saccharomyces cerevisiae.

Many instances of the initiator element in the core promoter of protein-coding genes have been reported in mammalian cells and their viruses, but only one has been reported in the yeast Saccharomyces cerevisiae at the GAL80 gene. The initiator element of GAL80 directs transcription by itself and interacts with a nuclear protein designated yeast initiator binding factor (yIF). Here we show that yIF in a partially purified sample binds the sequence from -18 to +10 of GAL80. By employing a selected and amplified binding procedure, we have determined the preferred sequence for yIF binding to be -2 CACTN +3 (N indicates any nucleotide). Binding affinity of selected sequences to yIF correlated with their initiator-directed transcription in vivo, suggesting that the yIF-initiator interaction mediates transcription from the initiator in yeast. We also suggest that sequences flanking the preferred sequence affect both yIF binding and initiator activity.