A Man with Natural Killer Cell Lymphoma Showing 46,XX and Deletion 6q

Receptor-type tyrosine-protein phosphatase κ directly targets STAT3 activation for tumor suppression in nasal NK/T-cell lymphoma

Nasal-type natural killer/T-cell lymphoma (NKTCL) is an aggressive disease characterized by frequent deletions on 6q, and constitutive activation of signal transducer and activator of transcription 3 (STAT3). Phosphorylation at Tyr705 activates STAT3, inducing dimerization, nuclear translocation, and DNA binding. In this study, we investigated whether receptor-type tyrosine-protein phosphatase κ (PTPRK), the only protein tyrosine phosphatase at 6q that contains a STAT3-specifying motif, negatively regulates STAT3 activation in NKTCL. PTPRK was highly expressed in normal NK cells but was underexpressed in 4 of 5 (80%) NKTCL cell lines and 15 of 27 (55.6%) primary tumors. Significantly, PTPRK protein expression was inversely correlated with nuclear phospho-STAT3(Tyr705) expression in NKTCL cell lines (P = .025) and tumors (P = .040). PTPRK restoration decreased nuclear phospho-STAT3(Tyr705) levels, whereas knockdown of PTPRK increased such levels in NKTCL cells. Phosphatase substrate-trapping mutant assays demonstrated the binding of PTPRK to STAT3, and phosphatase assays showed that PTPRK directly dephosphorylated phospho-STAT3(Tyr705). Restoration of PTPRK inhibited tumor cell growth and reduced the migration and invasion ability of NKTCL cells. Monoallelic deletion and promoter hypermethylation caused underexpression of PTPRK messenger RNA in NKTCL, and methylation of the PTPRK promoter significantly correlated with inferior overall survival (P = .049) in NKTCL patients treated with the steroid-dexamethasone, methotrexate, ifosfamide, l-asparaginase, and etoposide regimen. Altogether, our findings show that PTPRK underexpression leads to STAT3 activation and contributes to NKTCL pathogenesis.

Natural killer cell lymphoma/leukemia with homozygous loss ofp27/kip1

We describe a case of natural killer (NK) cell lymphoma/leukemia with only an interstitial deletion in the short arm of chromosome 12 as the primary event. Fluorescence in situ hybridization revealed that the ETV6 locus (12p13) and subtelomeric sequences are not deleted in the process. The p27/kip1 locus (12p12-13), a candidate tumor suppressor gene, was deleted on the abnormal chromosome. Sequence analysis detected an adenine nucleotide deletion in the third codon of exon 1 leading to frameshift and premature termination at codon 41 of the retained copy of p27/kip1. To the best of our knowledge, this is the first report in literature on a NK cell lymphoma/leukemia with complete loss of p27/kip1.

An extranodal nasal natural killer/T-cell lymphoma with isochromosome 7q10 as the sole cytogenetic aberration was initially diagnosed via bone marrow biopsy

We report a 58-year-old man who presented with fever, pancytopenia, hepatosplenomegaly, and "sinusitis" of his right nostril. Flow cytometric analysis of his bone marrow aspirate revealed a population of cells that were CD56+ (bright), CD2+ (dim), and CD7+ (slight brightly) but negative for CD3, CD4, CD5, CD8, CD11b, CD16, CD57, and T-cell receptors, consistent with aberrant natural killer cells. Bone marrow biopsy showed an atypical lymphoid infiltrate expressing CD56 as well as Epstein-Barr virus- encoded RNA and histiocytic hyperplasia with hemophagocytosis. Subsequent biopsy of his right nasal vestibule demonstrated an atypical lymphoid infiltrate, which was cytoplasmic CD3+, CD56+, and Epstein-Barr virus-encoded RNA positive, consistent with an extranodal nasal natural killer cell lymphoma. Conventional cytogenetic studies of the bone marrow revealed isochromosome 7q10 [i(7)(q10)] as the sole chromosomal aberration. To our knowledge, this is the first report demonstrating i(7)(q10) as a primary cytogenetic abnormality in an extranodal nasal natural killer cell lymphoma.

Donor cell leukemia: a critical review

Approximately 40 cases of DCL have been reported in the literature; cases have been reported after allografts from bone marrow, peripheral blood and cord blood. The study of these cases may provide new insights into the mechanisms of leukemogenesis. Some data suggest that the prevalence of this complication has been under-estimated. Most cases of DCL have occurred following transplantation for leukemia, but there have also been cases reported after transplantation for non-malignant conditions. Various mechanisms have been proposed to explain how DCL arise and are briefly discussed. Additional studies are needed to define with more detail both the true prevalence of this complication and its precise pathogenetic mechanism.

Genomic alterations in blastic natural killer/extranodal natural killer-like T cell lymphoma with cutaneous involvement

Natural killer and natural killer-like T cell lymphomas represent a rare type of non-Hodgkin's lymphoma originally described to involve the upper aerodigestive tract. This malignancy has been increasingly observed in other extranodal sites, particularly in the skin. Patients with cutaneous natural killer cell lymphoma generally have a poor prognosis; however, the etiology and the underlying molecular pathogenesis remain unclear. This study aimed to investigate comprehensively genomic changes in blastic natural killer and extranodal natural killer-like T cell lymphoma with cutaneous involvement. Comparative genomic hybridization showed chromosome imbalances in six of eight cases studied (75%). The mean number of chromosome imbalances per sample was 2.18+/-1.63 with similar number of gains (1.18+/-1.17) and losses (1.00+/-1.34). The most frequent DNA copy number changes observed were losses of 9/9p (83%), followed by loss of 13q and gain of 7 (67%). Similar patterns of chromosome imbalances were observed in both blastic natural killer and cutaneous natural killer-like T cell lymphomas. Loss of the RB1 gene at 13q14.2 was detected in one blastic natural killer cell lymphoma with 13q loss using a gene dosage assay, and in one cutaneous natural killer-like T cell lymphoma without 13q loss using fluorescent in situ hybridization. Genomic microarray analysis identified oncogene copy number gains of PAK1 and JUNB in three of four cases studied, and gains of RAF1, CTSB, FGFR1, and BCR in two cases. Real-time polymerase chain reaction detected amplification of CTSB and RAF1 in four of five cases analyzed, JUNB and MYCN in three cases, and REL and YES1 in two cases, respectively. In conjunction with this study, an extensive literature search for the published G-banded karyotypes of four subsets of natural killer cell lymphomas was conducted, which showed a nonrandom pattern of multiple chromosome aberrations. These results reveal consistent genetic alterations in cutaneous natural killer cell lymphomas, and provide a basis for further investigation of molecular pathogenesis in this malignancy.

A 2.6 Mb interval on chromosome 6q25.2-q25.3 is commonly deleted in human nasal natural killer/T-cell lymphoma

Natural killer (NK)/T-cell lymphoma is a special subtype of rare malignant lymphoma that is more prevalent in Asia than in America and Europe. This newly characterized haemato-lymphoid malignancy is highly aggressive and frequently present in nasal and upper aerodigestive sites. Several studies have reported the commonly deleted region of chromosome 6q21-25 in this particular type of lymphoma. To refine the smallest region of overlapping (SRO) deletion for localization of potential tumour suppressor (TS) genes, we performed loss of heterozygosity (LOH) and homozygosity mapping of deletion (HOMOD) analyses on 37 nasal and nasal-type NK/T-cell lymphoma patients using a panel of 25 microsatellite markers, covering the 6q21-q25 region. In all patients studied, LOH was detected in eight (89%) paired-sample patients, while hemizygous deletion was detected in three (11%) single-sample patients. Combination of the LOH and HOMOD results defined a distinct 3 Mb SRO on chromosome 6q25. Quantitative multiplex polymerase chain reaction analysis of 10 sequence-tagged sites further refined the putative TS-gene-containing region to a 2.6 Mb interval between TIAM2 and SNX9. Eighteen known genes/Unigene clusters and 25 hypothetical genes are located within this 2.6 Mb region, but none are previously identified TS genes. These results provide a framework for future positional cloning of novel TS gene(s) at 6q25.2-q25.3.

Multicolor-FISH analysis of a natural killer cell line (NK-92)

Relatively little is known about the cytogenetics of natural killer (NK) neoplasms, and the emergence of recurrent structural alterations involving specific chromosomal breakpoints is still in its infancy. This gap has doubtless hampered identification of the oncogene alterations posited to underly NK tumors. We describe in detail the cytogenetic rearrangements present in a cytotoxic NK cell line (NK-92) established from a patient with large granular lymphocyte (LGL) lymphoma. The NK-92 cell line is one of very few cytotoxic NK cell lines described and the first to be used clinically. Cytogenetic analysis was performed independently using two multicolor-fluorescence in situ hybridization (M-FISH) systems, the first M-FISH study of a cell line derived from a NK neoplasm. Several non-random cytogenetic features previously reported in NK cells were, thus, identified, including rearrangements of chromosomes 7 and 17, along with breakpoints at 11q23, 12q12 and 8p22/23. FISH revealed that NK-92 cells carry multiple rearrangements with distinct breakpoints at 8p resembling those previously described in NK lymphoma. Our data strengthen the claim of NK-92 to model NK neoplasms and highlight this cell line as a potential resource for mining relevant oncogenic changes therein.

Aggressive NK cell lymphoma/leukemia with clonal der(3)t(1;3) (q12;p25), del(6)(q13) and del(13)(q12q14)

We describe a 54-year-old man with CD2, CD7, and CD56-positive but CD3, CD4, and CD8-negative aggressive NK cell lymphoma/leukemia. Chromosome analysis of the peripheral blood cells showed clonal aberration consisting of 46,XY,dup(3)(p21p25),der(3)t(1;3)(q12;p25),del(5)(q13q22), del(6)(q13),del(13)(q12q14). The peripheral blood lymphoma cells contained clonal EBV-DNA by Southern blot analysis. The disease was refractory to chemotherapy and the clinical course was aggressive and rapid. Deletion 6q and deletion 13q have been frequently reported in NK cell lymphoma/leukemia. Thus, some tumor suppressor genes involving NK cell malignancies may be present in these regions.