The amplification at 13q31-q32 has been reported in not only hematopoietic malignancies but also in other solid tumors. We identified previously frequent amplification of chromosomal band 13q31-q32 in 70 cases of diffuse large B-cell lymphoma patients by conventional comparative genomic hybridization analysis. In an attempt to identify a candidate gene within this region, we used array comparative genomic hybridization and fluorescent in situ hybridization to map the 13q31-q32 amplicon. We then screened the 65 expressed sequence tags and Glypican 5 (GPC5) by reverse transcription-PCR and Northern blotting. As a result, we identified a novel gene, designated Chromosome 13 open reading frame 25 (C13orf25), which was overexpressed in B-cell lymphoma cell lines and diffuse large B-cell lymphoma patients with 13q31-q32 amplifications. However, GPC5, which has been reported to be a target gene for 13q31-q32 amplification, was truncated in one cell line, Rec1, possessing the amplification, and its expression in various cell lines with amplification at 13q31-q32 was not significantly different from that in other cell lines without amplification, suggesting that GPC5 is not likely to be the candidate gene. Additional analysis identified two major transcripts in the C13orf25 gene. The two transcripts A and B predicted open reading frames of 32 and 70-amino acid polypeptides, respectively. The former has been reported as bA121J7.2, which is conserved among species. Transcript-B also contained seven mature microRNAs in its untranslated region. These results suggest that the C13orf25 gene is the most likely candidate gene for the 13q31-q32 amplicon found in hematopoietic malignancies.

Biallelic inactivation of cancer susceptibility gene BRCA1 leads to breast and ovarian carcinogenesis. Paradoxically, BRCA1 deficiency in mice results in early embryonic lethality, and similarly, lack of BRCA1 in human cells is thought to result in cellular lethality in view of BRCA1 's essential function. To survive homozygous BRCA1 inactivation during tumorigenesis, precancerous cells must accumulate additional genetic alterations, such as p53 mutations, but this requirement for an extra genetic “hit” contradicts the two-hit theory for the accelerated carcinogenesis associated with familial cancer syndromes. Here, we show that heterozygous BRCA1 inactivation results in genomic instability in nontumorigenic human breast epithelial cells in vitro and in vivo. Using somatic cell gene targeting, we demonstrated that a heterozygous BRCA1 185delAG mutation confers impaired homology-mediated DNA repair and hypersensitivity to genotoxic stress. Heterozygous mutant BRCA1 cell clones also showed a higher degree of gene copy number loss and loss of heterozygosity in SNP array analyses. In BRCA1 heterozygous clones and nontumorigenic breast epithelial tissues from BRCA mutation carriers, FISH revealed elevated genomic instability when compared with their respective controls. Thus, BRCA1 haploinsufficiency may accelerate hereditary breast carcinogenesis by facilitating additional genetic alterations.

Accumulation of amyloid beta peptide (Abeta) in brain is a hallmark of Alzheimer's disease (AD). Inhibition of beta‐site amyloid precursor protein (APP)‐cleaving enzyme‐1 (BACE1), the enzyme that initiates Abeta production, and other Abeta‐lowering strategies are commonly tested in transgenic mice overexpressing mutant APP. However, sporadic AD cases, which represent the majority of AD patients, are free from the mutation and do not necessarily have overproduction of APP. In addition, the commonly used Swedish mutant APP alters APP cleavage. Therefore, testing Abeta‐lowering strategies in transgenic mice may not be optimal. In this study, we investigated the impact of BACE1 inhibition in non‐transgenic mice with physiologically relevant APP expression. Existing Abeta ELISAs are either relatively insensitive to mouse Abeta or not specific to full‐length Abeta. A newly developed ELISA detected a significant reduction of full‐length soluble Abeta 1–40 in mice with the BACE1 homozygous gene deletion or BACE1 inhibitor treatment, while the level of x‐40 Abeta was moderately reduced due to detection of non‐full‐length Abeta and compensatory activation of alpha‐secretase. These results confirmed the feasibility of Abeta reduction through BACE1 inhibition under physiological conditions. Studies using our new ELISA in non‐transgenic mice provide more accurate evaluation of Abeta‐reducing strategies than was previously feasible.

We have developed a novel enzyme‐linked immunosorbent assay (ELISA) system for the detection of N‐ERC/mesothelin in the serum of mesothelioma patients and have begun to examine its clinical usefulness. N‐ERC/mesothelin is a 31‐kDa protein that forms the N‐terminal fragment of the full‐length 71‐kDa ERC/mesothelin protein, and is physiologically secreted into the blood of mesothelioma patients where it can be detected using our sandwich ELISA containing two antibodies (rabbit polyclonal anti‐ERC/mesothelin antibody‐282 and mouse monoclonal antibody 7E7). Our ELISA system has thus far detected much higher serum levels of N‐ERC/mesothelin in mesothelioma patients than in healthy controls or patients with other lung or pleural diseases. In conclusion, N‐ERC/mesothelin is a promising candidate tumor marker for mesothelioma. (Cancer Sci 2006; 97: 928–932)

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin’s lymphoma and exhibits aggressive and heterogeneous clinical behavior. To genetically characterize DLBCL, we established our own array-based comparative genomic hybridization and analyzed a total of 70 cases [26 CD-positive (CD5+) DLBCL and 44 CD5-negative (CD5−) DLBCL cases]. Regions of genomic aberrations observed in >20% of cases of both the CD5+ and CD5− groups were gains of 1q21-q31, 1q32, 3p25-q29, 5p13, 6p21-p25, 7p22-q31, 8q24, 11q23-q24, 12q13-q21, 16p13, 18, and X and losses of 1p36, 3p14, 6q14-q25, 6q27, 9p21, and 17p11-p13. Because CD5 expression marks a subgroup with poor prognosis, we subsequently analyzed genomic gains and losses of CD5+ DLBCL compared with those of CD5−. Although both groups showed similar genomic patterns of gains and losses, gains of 10p14-p15 and 19q13 and losses of 1q43-q44 and 8p23 were found to be characteristic of CD5+ DLBCL. By focusing on the gain of 13q21-q34 and loss of 1p34-p36, we were also able to identify prognostically distinct subgroups among CD5+ DLBCL cases. These results suggest that array-based comparative genomic hybridization analysis provides a platform of genomic aberrations of DLBCL both common and specific to clinically distinct subgroups.