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 patient's 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.