Eri Matsuki

Identification of Loss of p16 Expression and Upregulation of MDR-1 as Genetic Events Resulting from Two Novel Chromosomal Translocations Found in a Plasmablastic Lymphoma of the Uterus

Purpose: To establish cell lines from the patient with plasmablastic lymphoma, who was immunologically competent including negative human immunodeficiency virus (HIV) serology, and analyze the unique chromosomal translocations seen in the cell lines in order to unveil the pathogenesis of this tumor, which had no evidence of Epstein-Barr virus involvement. Experimental Design: Establishment of the cell lines was attempted by inoculating the patients lymph node biopsy specimen subcutaneously to immunodeficient mice. Comparative genomic hybridization (CGH) array and FISH analysis were performed to identify breakpoints of the two chromosomal translocations. Of the 4 candidate genes identified by FISH analysis to be involved in the translocations, reverse transcription-PCR, Western blot, flow cytometry, and proliferation assay were performed to identify the exact genes involved. Results: Analysis of the cell lines identified loss of p16 at the protein level by chromosomal translocation of t(9;13) and upregulation of MDR-1 by t(4;7). The cell lines expressing MDR-1 acquired resistance to chemotherapeutic agents such as cisplatin and doxorubicin, but not bortezomib. Expression of B lymphoid lineage marker genes of these cell lines was negative for paired box 5 (Pax5) or PR domain containing 1, with ZNF domain (PRDM1), but was positive for X-box binding protein 1 (Xbp1). Conclusions: We established three novel cell lines of plasmablastic lymphoma. Characterization of the unique chromosomal translocation identified loss of p16 and upregulation of MDR-1 at protein level. Expression of Xbp1(s), which is involved in the maturation of plasma cells, corresponded to the plasmablastic appearance of the tumor. These cell lines may be a useful tool to understand the pathophysiology of the disease and to develop novel treatment strategies. Clin Cancer Res; 17(8); 2101–9. ©2011 AACR.

A novel factor XII mutation, FXII R84P, causing factor XII deficiency in a patient with hereditary spastic paraplegia.

Hereditary factor XII (FXII) deficiency is a clinically asymptomatic, autosomal recessive disorder. We have experienced a rare case of FXII deficiency in a patient previously diagnosed with hereditary spastic paraplegia (HSP). The patient had no major bleeding episodes and presented with a prolonged activated partial thromboplastin time (APTT) at hospital administration. Sequencing of the FXII gene revealed a novel missense mutation at exon 4 that substitutes arginine 84 to proline (R84P). To elucidate the molecular mechanism of FXII deficiency, wild-type and R84P mutant FXII cDNA were transiently expressed in CHO cells. We found that secretion but not synthesis of R84P mutant protein was markedly reduced compared to wild type. These results indicated that R84P mutation might impair the intracellular transport or secretion of FXII protein of the cells and could be a useful tool for the analysis of structure-function relationship and intracellular protein transport of FXII protein in the future.

CXorf48 is a potential therapeutic target for achieving treatment-free remission in CML patients

Although the introduction of tyrosine kinase inhibitors (TKIs) has improved overall survival of patients with chronic myeloid leukemia (CML), about half of the patients eventually relapse after cessation of TKIs. In contrast, the remainder of the patients maintain molecular remission without TKIs, indicating that the patients’ immune system could control proliferation of TKI-resistant leukemic stem cells (LSCs). However, the precise mechanism of immunity against CML-LSCs is not fully understood. We have identified a novel immune target, CXorf48, expressed in LSCs of CML patients. Cytotoxic T cells (CTLs) induced by the epitope peptide derived from CXorf48 recognized CD34+CD38− cells obtained from the bone marrow of CML patients. We detected CXorf48-specific CTLs in the peripheral blood mononuclear cells from CML patients who have discontinued imatinib after maintaining complete molecular remission for more than 2 years. Significantly, the relapse rate of CXorf48-specific CTL-negative patients was 63.6%, compared to 0% in CXorf48-specific CTL-positive patients. These results indicate that CXorf48 could be a promising therapeutic target of LSCs for immunotherapy to obtain durable treatment-free remission in CML patients.

Monitoring of immunity against leukemia stem cell in CML patients after cessation of TKI

Meeting abstracts Tyrosine kinase inhibitors (TKIs) have improved overall survival of patients with chronic myeloid leukemia (CML). Moreover, it has been reported that some of the patients achieve treatment-free remission (TFR) after cessation of TKIs, even though leukemic stem cells (LSC) of CML