Hideyuki Ikeda

Fanconi anemia (FA) is a rare autosomal recessive cancer susceptibility disorder characterized by cellular hypersensitivity to mitomycin C (MMC). Six FA genes have been cloned, but the gene or genes corresponding to FA subtypes B and D1 remain unidentified. Here we show that cell lines derived from FA-B and FA-D1 patients have biallelic mutations in BRCA2 and express truncated BRCA2 proteins. Functional complementation of FA-D1 fibroblasts with wild-type BRCA2 complementary DNA restores MMC resistance. Our results link the six cloned FA genes with BRCA1 and BRCA2 in a common pathway. Germ-line mutation of genes in this pathway may result in cancer risks similar to those observed in families with BRCA1 or BRCA2 mutations.

Using molecular dynamics simulations with a many-body force field, we studied the deformation of single crystal Ni and NiCu random alloy nanowires subjected to uniform strain rates but kept at 300 K. For all strain rates, the Ni nanowire is elastic up to $7.5%$ strain with a yield stress of 5.5 GPa, far above that of bulk Ni. At high strain rates, we find that for both systems the crystalline phase transforms continuously to an amorphous phase, exhibiting a dramatic change in atomic short-range order and a near vanishing of the tetragonal shear elastic constant perpendicular to the tensile direction. This amorphization which occurs directly from the homogeneous, elastically deformed system with no chemical or structural inhomogeneities exhibits a new mode of amorphization.

We have studied the patterns of antigens recognized by autologous cytolytic T lymphocytes (CTL) on two melanoma cell lines derived from metastases that were removed from patient LB33 at several years distance. Cell line LB33-MEL.A was obtained after surgery in 1988. A large number of CTL clones directed against LB33-MEL.A was obtained with blood lymphocytes collected from the patient in 1990. In vitro selection of melanoma cells that were resistant to these CTL clones indicated that at least five different antigens were recognized on LB33-MEL.A by autologous CTL. Four of these antigens were found to be presented by HLA-A28, B13, B44 and Cw6, respectively. The patient remained disease-free until 1993 when a metastasis was detected and was used to obtain cell line LB33-MEL.B. This cell line proved resistant to lysis by all the CTL clones directed against the LB33-MEL.A cells and showed no expression of HLA class I molecules except for HLA-A24. Using LB33-MEL.B cells to stimulate blood lymphocytes collected from the patient in 1994 we derived CTL clones that lysed these cells. All these CTL clones recognized a new antigen presented by HLA-A24. These results suggest that in patient LB33 the melanoma cells may have lost the expression of several HLA molecules under the selective pressure of an anti-tumor CTL response.

To date an increasing number of T-cell epitopes derived from various tumor-associated antigens have been reported, and they proved to play significant roles for tumor rejection both in vivo and in vitro. Survivin was originally identified as a member of the inhibitor of apoptosis protein family. Expression of this gene is developmentally regulated. Although survivin is expressed during normal fetal development, the expression is barely detected in terminally differentiated adult tissues except for testis, thymus, and placenta. In contrast, it is abundantly expressed in a wide variety of malignant tissues. We examined the expression of survivin and the two splicing variants survivin-2B and survivin-DeltaEx3 in various cancer cells, immortalized cells, and normal adult tissues. It was demonstrated that two splicing variants were detected in various types of cancer cells as well as survivin, and their expression was more restricted to cancer cells as compared with survivin expression. To identify HLA-A24-restricted T-cell epitopes from survivin and the variant proteins, three peptides were selected from amino acid sequence of these proteins, based on the HLA-A24-binding motif. Peptide binding assay to HLA-A24 revealed that only one peptide designated as survivin-2B80-88 (AYACNTSTL) was capable of binding to HLA-A24. By stimulating peripheral blood lymphocytes with the peptide-pulsed antigen-presenting cells, CTLs were successfully induced in vitro from five of five HLA-A24-positive cancer patients. The CTLs showed significant cytotoxicity against HLA-A24-positive survivin-2B-positive cancer cells. These data suggest that survivin-2B80-88 may be a potent T-cell epitope eliciting CTL response against a splicing variant survivin-2B, which is specifically expressed in many kinds of cancer cells.