A missense mutation in KIT kinase domain 1 correlates with imatinib resistance in gastrointestinal stromal tumors.

KIT gain of function mutations play an important role in the pathogenesis of gastrointestinal stromal tumors (GISTs). Imatinib is a selective tyrosine kinase inhibitor of ABL, platelet-derived growth factor receptor (PDGFR), and KIT and represents a new paradigm of targeted therapy against GISTs. Here we report for the first time that, after imatinib treatment, an additional specific and novel KIT mutation occurs in GISTs as they develop resistance to the drug. We studied 12 GIST patients with initial near-complete response to imatinib. Seven harbored mutations in KIT exon 11, and 5 harbored mutations in exon 9. Within 31 months, six imatinib-resistant rapidly progressive peritoneal implants (metastatic foci) developed in five patients. Quiescent residual GISTs persisted in seven patients. All six rapidly progressive imatinib-resistant implants from five patients show an identical novel KIT missense mutation, 1982T-->C, that resulted in Val654Ala in KIT tyrosine kinase domain 1. This novel mutation has never been reported before, is not present in pre-imatinib or post-imatinib residual quiescent GISTs, and is strongly correlated with imatinib resistance. Allelic-specific sequencing data show that this new mutation occurs in the allele that harbors original activation mutation of KIT.

The value of fluorescence in situ hybridization in the diagnosis and prognosis of chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia. Prognosis is related to clinical staging and cytogenetic findings. Conventional cytogenetic analysis of CLL reveals abnormalities in approximately one third of patients. Fluorescence in situ hybridization (FISH) is analytically more sensitive than conventional cytogenetics for specific chromosomal abnormalities. To evaluate the usefulness of FISH in CLL, a study of 100 CLL patients comparing conventional cytogenetics and a commercially available multiprobe FISH kit was undertaken. One hundred consecutive CLL patients (67 males, 33 females) were studied. The male-female patient ratio was approximately 2.0 to 1. Twenty-eight percent (28/98) of patients had abnormal karyotypes by conventional cytogenetics (one patient had no specimen for conventional cytogenetics and one had an unanalyzable karyotype), and of those 19/100 (19%) had more than one chromosomal abnormality. Sixty-four percent (64/100) of the patients were positive for at least one abnormality by the FISH probes used. The following abnormalities were noted with FISH: 11q22 ATM, 23/100 (23%); trisomy 12, 11/100 (11%); 13q14.3, 40/100 (40%); 13q34.3, 4/100 (4%); 17p13.1, 12/100 (12%). Conventional karyotypes revealed 2 patients with abnormalities of chromosome 6 (which FISH did not address); 11 with abnormalities of 11 or 11q; 6 with trisomy 12; and 4 with abnormalities of 17. Aberrations of 11q and 17p are reported to have a poor prognosis in CLL. FISH can identify abnormalities missed with conventional cytogenetics and is helpful in diagnosis, prognosis, and evaluation of therapy for CLL. Additional chromosomal changes are identified with conventional cytogenetics that are not addressed by the multiprobe FISH kit.

Independent prognostic significance of day 21 cytogenetic findings in newly-diagnosed acute myeloid leukemia or refractory anemia with excess blasts.

BACKGROUND AND OBJECTIVES: We investigated whether cytogenetic findings (CG) on day 21 (D21) of the first course of chemotherapy predicted subsequent outcome in patients who presented with CG abnormalities. DESIGN AND METHODS: D21 CG analysis was performed in 197 patients. RESULTS: Nineteen percent of the patients had exclusively abnormal metaphases (AA), 31% had only normal metaphases (NN), 39% had normal and abnormal metaphases (AN), and 11% had insufficient metaphases (0/0) on D21. A complete response was achieved in 79% of patients with NN, 60% with AN, 27% of those with AA, and 32% of those with 0/0. INTERPRETATIONS AND CONCLUSIONS: Disease-free survival in CR was longest in patients who had > or =1 normal metaphase on D21, with this finding being independent of D21 marrow and initial CG results. D21 CG can be used in therapeutic decision-making.

Establishment and characterization of a new mantle cell lymphoma cell line M-1.

A new mantle cell lymphoma cell line, M-1, was established from peripheral blood mononuclear cells of a patient with a diagnosis of blastoid variant of mantle cell lymphoma in leukemic phase. This cell line showed cell surface antigens identical to the original tumor and demonstrated the profile of a mature B-cell phenotype typical of mantle cell lymphoma: positive for CD5, CD19, CD20, sIgM and FMC7, and negative for CD3, CD10 and CD23. Cytogenetically, the M-1 cell line showed chromosomal alterations similar to the initial clinical specimen, among which a translocation t(11;14) (q13;q32) resulting in the overexpression of cyclin D1 as well as additional abnormalities involving chromosomes 3, 9 and 10. This cell line was used as a model to investigate the activity of the three drugs doxorubicin, cyclophosphamide and vincristine, commonly used in the treatment of mantle cell lymphoma patients. The effect of the drugs was evaluated by a 24 h cytotoxicity test and a 7-days anti-proliferation test using a microculture tetrazolium-based assay (MTT). Both assays indicated a higher sensitivity of the cell line to vincristine when compared to doxorubicin and cyclophosphamide. The characterization of a new mantle cell lymphoma cell line is a unique tool for studying the biology of this subtype of lymphoma for which only a few cell lines have been established.

Translocation (11;16)(q23;p13) acute myelogenous leukemia and myelodysplastic syndrome.

The purpose of this study is to examine the relationship of t(11;16)(q23;p13) to the type of myeloproliferative disorder noted by hematopathology. Previously, t(11;16) has been reported in fewer than 20 patients, all with the diagnosis of therapy-related (secondary) acute myelogenous leukemia (sAML) or myelodysplastic syndrome (MDS). Putative involved genes are the MLL on 11q23 and CBP at 16p13. Data from The University of Texas M. D. Anderson Cancer Center (UTMDACC) Cytogenetics Laboratory revealed 3 patients with t(11;16) observed during the past 5 years. Two of the patients had a prior diagnosis of non-Hodgkin lymphoma (NHL) and had been treated with chemotherapy, which included cyclophosphamide. The other patient presented with de novo AML and no history of cancer or chemotherapy. Two of the 3 patients had t(11;16) as the sole cytogenetic abnormality. One patient had a t(11;16) clone that included t(9;21) and t(10;21) as additional changes. Translocation (11;16) has previously been reported only as being therapy-related. In this study, the t(11;16) was seen in 2 patients with previous lymphomas treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP). A single patient with apparently de novo AML constitutes the first reported instance of non-treatment associated t(11;16) AML.