Kimberly Hayes

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.

A genetically defined model for human ovarian cancer.

Disruptions of the p53, retinoblastoma (Rb), and RAS signaling pathways and activation of human telomerase reverse transcriptase (hTERT) are common in human ovarian cancer; however, their precise role in ovarian cancer development is not clear. We thus introduced the catalytic subunit of hTERT, the SV40 early genomic region, and the oncogenic alleles of human HRAS or KRAS into human ovarian surface epithelial cells and examined the phenotype and gene expression profile of those cells. Disruption of p53 and Rb pathway by SV40 early genomic region and hTERT immortalized but did not transform the cells. Introduction of HRASV12 or KRASV12 into the immortalized cells, however, allowed them to form s.c. tumors after injection into immunocompromised mice. Peritoneal injection of the transformed cells produced undifferentiated carcinoma or malignant mixed Mullerian tumor and developed ascites; the tumor cells are focally positive for CA125 and mesothelin. Gene expression profile analysis of transformed cells revealed elevated expression of several cytokines, including interleukin (IL)-1β, IL-6, and IL-8, that are up-regulated by the nuclear factor-κB pathway, which is known to contribute to the tumor growth of naturally ovarian cancer cells. Incubation with antibodies to IL-1β or IL-8 led to apoptosis in the ras-transformed cells and ovarian cancer cells but not in immortalized cells that had not been transformed. Thus, the transformed human ovarian surface epithelial cells recapitulated many features of natural ovarian cancer including a subtype of ovarian cancer histology, formation of ascites, CA125 expression, and nuclear factor-κB-mediated cytokine activation. These cells provide a novel model system to study human ovarian cancer.

Imatinib Mesylate Resistance Through BCR-ABL Independence in Chronic Myelogenous Leukemia

Imatinib mesylate (IM) binds to the BCR-ABL protein, inhibiting its kinase activity and effectively controlling diseases driven by this kinase. IM resistance has been associated with kinase mutations or increased BCR-ABL expression. However, disease progression may be mediated by other mechanisms that render tumor cells independent of BCR-ABL. To demonstrate this potential, IM-resistant cells were found in chronic myelogenous leukemia patients with continuous BCR-ABL gene expression but undetectable BCR-ABL protein expression. These cells were unresponsive to IM and acquired BCR-ABL-independent signaling characteristics. IM resistance in some patients may be mediated through loss of kinase target dependence.

Prognostic value of cytogenetics in multiple myeloma

Karyotypic studies of bone marrow were conducted in 79 previously untreated patients with multiple myeloma who received a standard programme of chemotherapy. An abnormal karyotype was observed in 46% of patients, virtually all showing multiple abnormalities consistent with a long period of preclinical clonal evolution. Patients with an abnormal pattern showed various aberrations with hyperdiploidy in 64%, pseudodiploidy in 5% and hypodiploidy in 31%. The number of chromosomes affected ranged from two to 19 (median 10), with at least one trisomy in 83%, one monosomy in 75%, and one translocation in 42% of patients. Lymphoma‐like karyotypes were present in 17% of patients with an abnormality but were not associated with atypical clinical features, such as an extramedullary mass, leukaemia, or increased serum lactate dehydrogenase. Monosomy or deletion of chromosome 13 was present in 47% of patients with an abnormal pattern, who lived for a shorter duration (median 10 months) than patients with other abnormalities (median 34 months) or with diploidy (median 35 months). The cause of the short survival of patients with monosomy or deletion of chromosome 13 was not clear, but further studies on the relationship with specific oncogenes are indicated.

Chromosomal abnormalities in Philadelphia chromosome-negative metaphases appearing during imatinib mesylate therapy in patients with Philadelphia chromosome-positive chronic myelogenous leukemia in chronic phase

Anecdotal cases of chromosomal abnormalities in Philadelphia chromosome (Ph)‐negative metaphases have been reported in patients with chronic myelogenous leukemia (CML) in the chronic phase during treatment with interferon and, more recently, with imatinib. This phenomenon is different from true clonal evolution in that the additional cytogenetic abnormality occurs in Ph‐negative cells.

Cytogenetic Findings in Lymphoplasmacytic Lymphoma/Waldenström Macroglobulinemia Chromosomal Abnormalities Are Associated With the Polymorphous Subtype and an Aggressive Clinical Course

CD137 (ILA/4-1BB), a member of the tumor necrosis factor receptor family, and its ligand are expressed on activated T lymphocytes and on antigen-presenting cells, respectively. Via bidirectional signal transduction, this receptor-ligand system regulates the activation, proliferation, and survival of T and B lymphocytes and monocytes. We used immunohistochemical studies on human tissue samples to determine in vivo CD137 expression in nonimmune tissue samples. Strong CD137 expression was found in blood vessel walls, on the endothelial layer, and on the vascular smooth muscle cells. But in 32 healthy tissue samples examined, none contained CD137-positive vessels. Also, in benign tumors (2/14) and in inflammatory tissues (2/9) only a minority had CD137-expressing vessels. However, malignant tumors had a significantly enhanced frequency of CD137-expressing blood vessels (11/34).We correlated bone marrow cytogenetic findings with morphologic and immunophenotypic data in 37 patients with lymphoplasmacytic lymphoma (LPL)/Waldenström macroglobulinemia (WM). Each LPL/WM case was classified as lymphoplasmacytoid (n = 18), lymphoplasmacytic (n = 10), or polymorphous (n = 9) using the Kiel criteria. Of 12 cases with chromosomal abnormalities, a single numeric abnormality was present in 4 and a complex karyotype in 8. The most common numeric abnormalities were and -8 in 3 cases each; the most common structural abnormality was del(6q) in 6 cases. Cytogenetic abnormalities were significantly less common in the lymphoplasmacytic and lymphoplasmacytoid groups (5/28 [18%]) compared with the polymorphous group (7/9 [78%]). Clinical follow-up was available for 28 patients for a median of 36 months. Six (67%) of 9 patients with aneuploid tumors, including 4 with polymorphous subtype, subsequently had clinical progression or developed high-grade lymphoma. In contrast, 4 (21%) of 19 patients with diploid tumors, including 1 of polymorphous type, developed clinical progression or high-grade lymphoma. We conclude that abnormal cytogenetic findings in LPL/WM correlate with the polymorphous subtype and poor prognosis.

Results of imatinib mesylate therapy in chronic myelogenous leukaemia with variant Philadelphia chromosome

Five to 10 per cent of patients with Philadelphia chromosome (Ph)‐positive chronic myelogenous leukaemia (CML) have variant translocations involving chromosomes other than 9 and 22. We investigated the characteristics and outcome of patients with variant translocations treated with imatinib. Among 721 patients, 44 (6%) had variant translocations, involving one (n = 39) or two (n = 4) additional chromosomes. Nineteen patients (44%) were in chronic (12 previously untreated), 24 (55%) in accelerated and one (2%) in blastic phase. A major cytogenetic response was achieved in 14 (74%) patients treated in chronic phase and in 14 (58%) treated in accelerated phase. Six of 13 (46%) evaluable patients had deletion of derivative chromosome 9, and there was a trend for a lower response rate in these patients. We compared the 43 patients in chronic or accelerated phase to 678 patients with classic Ph treated with imatinib. The only significant difference in clinical characteristics was a higher frequency of accelerated phase among those with variant translocations (56%) compared with those with classic translocations (38%). No differences in outcome were evident. In a multivariate analysis, variant Ph translocations had no impact in response rate, overall survival or duration of response. We conclude that patients with variant Ph translocations have a similar prognosis to those with classic Ph translocations when treated with imatinib.

Mature B-Cell Leukemias With More Than 55% Prolymphocytes A Heterogeneous Group That Includes an Unusual Variant of Mantle Cell Lymphoma

We studied 20 cases of mature B-cell leukemia with more than 55% prolymphocytes in peripheral blood or bone marrow, fulfilling the French-American-British criteria for B-cell prolymphocytic leukemia (PLL). Cases segregated into 3 groups: de novo PLL, 6; PLL occurring in patients with a previous well-established diagnosis of chronic lymphocytic leukemia (PLL-HxCLL), 10; and t(11;14)(q13;q32)-positive neoplasms, 4. All cases expressed monotypic immunoglobulin light chain, and most were positive for CD5. All t(11;14)-positive neoplasms were CD23- and uniquely positive for cyclin D1. Cytogenetic abnormalities were present in 19; in all 19, the karyotype was complex, indicating clonal evolution and genomic instability. The most frequent cytogenetic abnormality in de novo PLL involved chromosome 7 in 4 cases. Trisomy 12 or add(12p) was present in 4 cases of PLL-HxCLL. We conclude that mature B-cell leukemias with more than 55% prolymphocytes are a heterogeneous group that includes t(11;14)-positive neoplasms, which we suggest are best classified as mantle cell lymphoma. We also suggest that prolymphocytic morphologic features are a common end-stage of transformation for several B-cell neoplasms.

Cytogenetic findings in blastoid mantle cell lymphoma

A subset of mantle cell lymphoma (MCL) tumors has blastoid morphology, and a number of morphologic variants of blastoid MCL have been described in the literature. In this report, we document the cytogenetic findings in 27 cases of blastoid MCL. Conventional cytogenetic analyses were performed on bone marrow aspirates involved by MCL from 27 patients. There were 14 men and 13 women with a median age of 63 years (range, 40-79 years). Diagnostic tissue biopsy and bone marrow specimens were reviewed, and cases were divided into 2 morphologic groups: classic (12 cases) and pleomorphic (15 cases), as defined in the World Health Organization classification. All tumors had an immunophenotype compatible with MCL, were positive for cyclin D1, and carried the t(11;14). Twenty-four cases had complex karyotypes with 3 or more chromosomal abnormalities in addition to the t(11;14). In classic blastoid MCL, abnormalities of chromosomes 13, 18, and 8 were most common. In pleomorphic blastoid MCL, abnormalities of chromosomes 13, 17, and 3 were most frequent. Chromosome 22 abnormalities were detected exclusively in the pleomorphic group. Tumors in which the neoplastic cells showed prominent nucleoli had a significantly higher frequency of chromosome 17 abnormalities (P = 0.03). We conclude that blastoid MCL tumors often show complex cytogenetic aberrations. Some abnormalities correlate with morphologic features, suggesting that morphologic variants of blastoid MCL may arise via different molecular pathways.

Detection of chromosome 11q13 breakpoints by interphase fluorescence in situ hybridization. A useful ancillary method for the diagnosis of mantle cell lymphoma.

We assessed cytologic specimens from 11 mantle cell lymphomas (MCLs) and 32 other B-cell non-Hodgkin lymphomas (NHLs) for 11q13 breakpoints using a 2-color fluorescence in situ hybridization (FISH) assay that uses an 11q13 probe centered on the CCND1 gene and a centromeric chromosome 11 probe (CEP11). The number of nuclei in 200 cells were counted, and results were expressed as an 11q13/CEP11 ratio. All MCLs showed a high percentage of interphase nuclei with 3 or more 11q13 signals (mean, 74.8%; range 57%-90%). In contrast, in other B-cell NHLs the mean percentage of cells with 3 or more 11q13 signals was 9.2%. All MCLs had an elevated 11q13/CEP11 ratio (mean, 1.38). The mean ratio for other B-cell NHLs was 0.99. Two non-MCL cases, 1 large B-cell and 1 B-cell unclassified NHL, had high 11q13/CEP11 ratios of 1.15 and 1.30, respectively. Conventional cytogenetic analysis performed on the former case revealed a t(5;11)(q31;q13). Interphase FISH analysis using 11q13 and CEP11 probes is a convenient ancillary method for assisting in the diagnosis of MCL. This commercially available assay is simple to use on cytology or imprint specimens, and results can be obtained within 24 hours.