Development of a novel monoclonal antibody that binds to most HLA-A allomorphs in a conformation-dependent yet peptide-promiscuous fashion.

Specificity analyses of peptide binding to human leukocyte antigen (HLA)-A molecules have been hampered due to a lack of proper monoclonal antibodies (mAbs) for certain allomorphs, such as the prevalent HLA-A1 for Caucasians and HLA-A11 for Asians. We developed a mAb that recognizes a conformational epitope common to most HLA-A allomorphs. The mAb, named A-1, does not discriminate peptides by amino acid sequences, making it suitable for measuring peptide binding. A stabilization assay using TAP-deficient cell lines and A-1 was developed to investigate the specificity of peptide binding to HLA-A molecules. Regarding the evolution of HLA-A genes, the A-1 epitope has been conserved among most HLA-A allomorphs but was lost when the HLA-A gene diversified into the HLA-A*32, HLA-A*31, and HLA-A*33 lineages together with HLA-A*29 after bifurcating from the HLA-A*25 and HLA-A*26 branchs. The establishment of A-1 is expected to help researchers investigate the peptide repertoire and develop computational tools to identify cognate peptides. Since no HLA-A locus-specific mAb has been available, A-1 will also be useful for analyzing the locus-specific regulation of the HLA gene expression.

Cells of origin of squamous epithelium, dysplasia and cancer in the head and neck region after bone marrow transplantation.

Secondary solid tumors that occur after hematopoietic stem cell transplantation (HSCT) are late complications of HSCT. Previously, secondary solid tumors were considered to be recipient-derived cells because transplanted cells do not contain epithelial cells. Recently, however, not only donor­derived epithelial cells but also donor-derived secondary solid tumors have also been reported in mice and humans. It means that circulating bone marrow-derived stem cells (BMDCs) including hematopoietic stem cells include the stem cells of many tissue types and the precancerous cells of many solid tumors. In most reports of donor-derived secondary solid tumors, however, tumors contained a low proportion of BMDC-derived epithelial cells in mixed solid tumor tissues. To our knowledge, there are only five known cases of completely donor-derived tumor tissues, i.e., four oral SCCs and a pharyngeal SCC. In this study, we analyzed five human clinical samples of solid tumors, i.e., two esophageal squamous cell carcinomas (SCCs), two oral SCCs and a tongue carcinoma. In the oral and tongue, completely donor-derived tissues were not observed, but in esophagus a completely donor-derived esophageal epidermis and SCC were observed for the first time. In addition, in another esophageal SCC patient, a completely donor-derived dysplasia region of esophageal epidermis was observed near recipient-derived SCC. This study suggests that BMDC-derived cells include the stem cells of esophageal epidermis and the precancerous cells of esophageal SCC and can differentiate into esophageal epithelium and esophageal SCC.

Reduced level of the BCL11B protein is associated with adult T-cell leukemia/lymphoma.

BACKGROUND: Adult T-cell leukemia/lymphoma (ATLL) develops in a small proportion of human T-cell leukemia virus type I (HTLV-I)-infected individuals. However, the mechanism by which HTLV-I causes ATLL has not been fully elucidated. To provide fundamental insights into the multistep process of leukemogenesis, we have mapped the chromosomal abnormalities in 50 ATLL cases to identify potential key regulators of ATLL. RESULTS: The analysis of breakpoints in one ATLL case with the translocations t(14;17)(q32;q22-23) resulted in the identification of a Kruppel zinc finger gene, BCL11B, which plays a crucial role in T-cell development. Among the 7 ATLL cases that we examined by immunofluorescence analysis, 4 displayed low and one displayed moderate BCL11B signal intensities. A dramatically reduced level of the BCL11B protein was also found in HTLV-I-positive T-cell lines. The ectopic expression of BCL11B resulted in significant growth suppression in ATLL-derived cell lines but not in Jurkat cells. CONCLUSIONS: Our genetic and functional data provide the first evidence that a reduction in the level of the BCL11B protein is a key event in the multistep progression of ATLL leukemogenesis.

HELIOS-BCL11B fusion gene involvement in a t(2;14)(q34;q32) in an adult T-cell leukemia patient.

To provide fundamental insights into the leukemogenesis of adult T-cell leukemia/lymphoma (ATLL), we performed a molecular analysis of the chromosomal abnormalities in one ATLL case with a novel reciprocal translocation: t(2;14)(q34;q32). Using fluorescence in situ hybridization with cosmid probes derived from the 14q32 region, we characterized the rearranged 14q32 allele. Molecular cloning of the breakpoint revealed that the reciprocal translocation fused the 5' proximal region of the B-cell lymphoma 11B (BCL11B) gene segment (on 14q32) to the third intron of the HELIOS gene (on 2q34). Reverse transcription-polymerase chain reaction analysis of the leukemia cells revealed that a substantial level of the HELIOS-BCL11B fusion mRNA was expressed relative to the level of wild-type (WT)-BCL11B derived from the intact allele. In contrast, an aberrant HELIOS isoform was detected at a low level of expression compared to the expression of normal HELIOS isoforms. Functional analysis of the HELIOS-BCL11B fusion protein revealed reduced transcriptional suppression activity compared to that of the WT-BCL11B due to the loss of the N-terminal friend of GATA-repression motif, which functions as a metastasis-associated protein 2 binding site. We also found abnormal subnuclear localization of the ectopically expressed fusion protein compared to the localization of WT-BCL11B to subnuclear speckles in HEK293T cells. Our results suggest that dysfunction of the BCL11B gene plays an important role in the development of ATLL.