Resistance to imatinib in patients with chronic myelogenous leukemia and the splice variant BCR-ABL1(35INS)

PURPOSE

In patients with chronic myelogenous leukemia (CML), point mutations in the BCR-ABL1 kinase domain are the most common cause of treatment failure with a tyrosine kinase inhibitor (TKI). It is not clear whether the splice variant BCR-ABL1(35INS) is also associated with treatment failure.

PATIENTS AND METHODS

We reviewed all CML patients who had BCR-ABL1 kinase mutation analysis performed between August 1, 2007, and January 15, 2014. Patients who had BCR-ABL1(35INS) detected had their medical records reviewed to determine response to TKI therapy.

RESULTS

Two hundred and eighty four patients had kinase mutation testing performed; of these, 64 patients (23%) had BCR-ABL1(35INS) detected. Forty-five patients were in chronic phase (70%), 10 were in accelerated phase (16%), 6 were in blastic phase (9%), and 3 were in other settings (5%). Of the 34 chronic phase patients who began therapy with imatinib, 23 patients (68%) failed therapy: 8 patients (24%) had primary refractory disease, 11 patients (32%) progressed, and 4 patients (12%) had disease progression after dose interruption. In contrast to the patients with disease progression or lack of response, none of 23 patients who were responding to imatinib had BCR-ABL1(35INS) detected. DNA sequencing of commonly mutated spliceosomal genes SF3B1, U2AF1, SRSF2, ZRSR2, SFA31, PRPF408, U2A565, and SF1 did not reveal mutations in seven BCR-ABL1(35INS) -positive patients tested.

CONCLUSIONS

The splice variant BCR-ABL1(35INS) is frequently found in patients who are resistant to imatinib. Mutations in the commonly mutated spliceosomal proteins do not contribute to this association.

Stem cell transplantation in adults with acute myelogenous leukemia, normal cytogenetics, and the FLT3-ITD mutation

Following chemotherapy, patients with acute myelogenous leukemia (AML), normal cytogenetics, and the FLT3-ITD mutation have shorter survival compared to wild type (WT) patients. To determine the role of stem cell transplantation (SCT), we performed a retrospective review of adult patients with AML who underwent SCT at our center between January 1, 2007 and December 31, 2011. Of the 200 patients transplanted, 79 patients (40%) had normal cytogenetics; of these, 17 (22%) had the FLT3-ITD mutation, 35 were WT (44%), and 27 (34%) did not have FLT3 testing performed. Clinical characteristics were similar in each group. At four years, overall survival (OS) between FLT3 positive and WT groups was similar: 0.54 (95% CI 0.29-0.75) versus 0.73 (95% CI 0.53-0.99), p=0.18. Relapse rates were also similar, 0.09 (95% CI 0.02-0.21) versus 0.12 (95% CI: 0.02-0.32); p=0.67. We conclude that SCT can abrogate the poor prognosis in FLT3-ITD positive patients.

Double minute chromosomes in glioblastoma multiforme are revealed by precise reconstruction of oncogenic amplicons

DNA sequencing offers a powerful tool in oncology based on the precise definition of structural rearrangements and copy number in tumor genomes. Here, we describe the development of methods to compute copy number and detect structural variants to locally reconstruct highly rearranged regions of the tumor genome with high precision from standard, short-read, paired-end sequencing datasets. We find that circular assemblies are the most parsimonious explanation for a set of highly amplified tumor regions in a subset of glioblastoma multiforme samples sequenced by The Cancer Genome Atlas (TCGA) consortium, revealing evidence for double minute chromosomes in these tumors. Further, we find that some samples harbor multiple circular amplicons and, in some cases, further rearrangements occurred after the initial amplicon-generating event. Fluorescence in situ hybridization analysis offered an initial confirmation of the presence of double minute chromosomes. Gene content in these assemblies helps identify likely driver oncogenes for these amplicons. RNA-seq data available for one double minute chromosome offered additional support for our local tumor genome assemblies, and identified the birth of a novel exon made possible through rearranged sequences present in the double minute chromosomes. Our method was also useful for analysis of a larger set of glioblastoma multiforme tumors for which exome sequencing data are available, finding evidence for oncogenic double minute chromosomes in more than 20% of clinical specimens examined, a frequency consistent with previous estimates.

Abstract 2989: Loss of methylation in a regulatory region of BCL2 in MDS/AML

Background:

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematopoietic disorders characterized by ineffective hematopoiesis and increased risk of progression to acute myeloid leukemia (AML). A hallmark of MDS is increased apoptosis, while AML undergoes decreased apoptosis and increased proliferation. BCL2, an anti-apoptotic protein, is overexpressed in high grade MDS and AML and may confer poor prognosis and increased chemotherapy resistance. In this study we examined the DNA methylation status of BCL2 in MDS and AML.

Methods:

We conducted DNA methylation profiling on genomic DNA extracted from bone marrows of 22 refractory anemia with ringed sideroblasts (RARS), 8 refractory anemia with excess blasts (RAEB), 21 de novo AML, 21 therapy related AML, and 7 normal volunteers. We used both Illumina 27K BeadChip and 450K BeadChip methylation arrays to assess CpG methylation. Standard student T-test was used to screen differentially methylated MDS and AML CpG sites compared to normal samples. We validated the microarray data by combined bisulfite restriction analysis (COBRA) and bisulfite sequencing.

Results:

We identified a region in the BCL2 gene body that was among the most differentially methylated in MDS and AML versus normal bone marrow. Within that amplicon, BCL2 in both RARS, a low grade MDS, and RAEB, a high grade MDS, were hypermethylated compared to normal bone marrow (43% vs 18%, 48% vs 18%, respectively, p<0.05). BCL2 in de novo AML and therapy related AML were hypomethylated compared to normal bone marrow (12% vs 35%, 13% vs 35%, respectively, p<0.05). We validated these results by COBRA and bisulfite sequencing. This region coincided with H3K27ac and H3K4m1 enhancer type marks in ENCODE data in normal cells.

Conclusions:

Our study identifies a region of BCL2 that is hypermethylated in both low and high risk MDS while hypomethylated in AML compared to normal bone marrows. We hypothesize aberrant epigenetic modification of BCL2 plays a key role in apoptosis and transformation from MDS to AML, and our data support the idea of combining demethylating drugs with BCL2 antagonists. We are currently investigating whether BCL2 protein expression correlates with methylation, and plan to map the histone marks with CHIP-seq to correlate chromatin accessibility and DNA methylation in BCL2.

Citation Format: Sangmin Lee, Naomi Galili, Stephen Nimer, Mark D. Minden, Vundavalli V. Murty, Suresh Jhanwar, Azra Raza, Benjamin Tycko. Loss of methylation in a regulatory region of BCL2 in MDS/AML. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2989. doi:10.1158/1538-7445.AM2013-2989

Acute myeloid leukemia with translocation t(8;16) presents with features which mimic acute promyelocytic leukemia and is associated with poor prognosis

Previous small series have suggested that acute myeloid leukemia with t(8;16) is a distinct morphologic and clinical entity associated with poor prognosis. We describe 18 patients with t(8;16) AML, including their clinical, cytomorphologic, immunophenotypic and cytogenetic features. Half of the patients had extramedullary disease, most commonly leukemia cutis, which often preceded bone marrow involvement and six had therapy-related AML. Patients with t(8;16) AML commonly present with clinical and pathological features that mimic APL, with promyelocytes and promyeloblast-like cells and coagulopathy in most patients. Several patients also presented with marrow histiocytes with hemophagocytosis and erythrophagocytosis. Comprehensive molecular analysis for co-occurring genetic alterations revealed a somatic mutation in RUNX1 in 1 of 6 t(8;16) patients with no known AML mutation in the remaining five t(8;16) patients. This suggests that the t(8;16) translocation could be sufficient to induce hematopoietic cell transformation to AML without acquiring other genetic alteration. These data further support classifying t(8;16) AML as a clinically and molecularly defined subtype of AML marked by characteristic clinical and cytomorphologic features that mimic APL, and is associated with very poor survival.

Fluorescence In Situ Hybridization (FISH) Analysis of Melanocytic Nevi and Melanomas

A 4-color fluorescence in situ hybridization (FISH) assay, using probes to chromosomes 11q, 6p, 6q, and 6 cent, has recently been proposed as an ancillary tool for the diagnosis of melanoma. The authors report herein their experience with this assay. To determine the sensitivity and specificity of the assay for histopathologically unequivocal cases, they analyzed 50 melanocytic nevi, 50 primary melanomas, and 15 metastatic melanomas. Of 50 melanocytic nevi, 47 were FISH negative on initial readout (test sensitivity, 94%); 49 were FISH negative after correction for tetraploidy (test specificity, 98%). Of 50 primary melanomas, 41 were FISH positive (test sensitivity, 82%). Of 15 metastatic lesions, 13 were FISH positive (test sensitivity, 85%). Of the 9 FISH-negative melanomas, 6 metastasized. The tumors of the 5 patients who had survived thick primary melanoma for more than 5 years without recurrence were all FISH positive. Half of the patients whose primary melanoma was tested by FISH had undergone sentinel lymph node (SLN) biopsy. When the authors compared the FISH results of those 25 melanomas with the SLN status, no statistically significant correlation was found. These findings document limitations of the current FISH assay. A rare nevus may be FISH positive. Some primary metastasizing melanomas are FISH negative. Even metastatic melanomas can be FISH negative. Awareness of the limitations in test sensitivity and specificity of the FISH assay is important to avoid an erroneous diagnosis by overreliance on cytogenetic findings. Correlation with clinical and histopathological findings is paramount for accurate diagnosis.

Use of Fluorescence In Situ Hybridization to Distinguish Metastatic Uveal From Cutaneous Melanoma

Metastatic lesions of malignant melanoma can on occasion be difficult to classify with regard to the primary site of origin. Given the lack of specificity of light microscopic features, ancillary studies are needed. In this study, the authors explored the possibility of distinguishing metastatic tumors derived from uveal primaries from those known to have originated from a cutaneous melanoma by fluorescence in situ hybridization (FISH) using probes for chromosome 3, 8q24, and 1p36. A total of 32 metastatic tumors were analyzed by FISH. Monosomy 3 was detected in 9 out of 16 (56.3%) cases of metastatic uveal melanoma but was not found in any of the 16 metastatic cutaneous melanomas ( P < .001). With regard to 1p36, amplifications were found in 8 out of 16 (50%) cases of metastatic cutaneous melanoma but not in any case of uveal melanoma ( P < .05). 1p36 was deleted in 3 cases of uveal and 1 case of cutaneous melanoma. Amplifications of 8q were found in 15 out of 16 (94%) cases of uveal melanoma metastases and in 12 out of 16 (75%) cases of cutaneous metastases. The findings suggest that FISH for monosomy 3 is a useful adjunct tool in the differential diagnosis of metastatic uveal versus cutaneous melanoma.

Reflex UroVysion testing in suspicious urine cytology cases

BACKGROUND

UroVysion is a US Food and Drug Administration-approved fluorescence in situ hybridization (FISH) probe set for use in the detection of recurrent urothelial carcinoma and in patients with hematuria. The objective of the current study was to evaluate the usefulness of UroVysion as a reflex test in patients with a suspicious urine cytology diagnosis. The rationale was that a more aggressive workup might be indicated in patients with a suspicious cytology diagnosis and positive UroVysion test.

METHODS

The study population included 161 urine specimens diagnosed as suspicious over a period of 12 months. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (NPV) were calculated based on the histologic and cystoscopic correlation.

RESULTS

The results using the reporting criteria suggested by the manufacturer demonstrated a sensitivity of 68.3%, a specificity of 39.7%, a PPV of 56.8%, and a NPV of 51.9%. The results using the presence of any cytogenetic abnormality as a positive FISH test demonstrated a sensitivity of 82.9%, a specificity of 21.7%, a PPV of 54.8%, and an NPV of 51.7%.

CONCLUSIONS

A negative UroVysion test did not rule out the presence of low-grade or high-grade urothelial carcinoma in urine specimens diagnosed as suspicious. The use of less strict criteria dramatically increased the sensitivity of UroVysion FISH; however, there was a marked decrease in specificity noted. The results in this current study appear to indicate that a more aggressive workup of patients with a suspicious cytology, positive UroVysion result, and negative cystoscopic evaluation is not currently justified.

The NF2 tumor suppressor gene product, merlin, inhibits cell proliferation and cell cycle progression by repressing cyclin D1 expression

Inactivation of the NF2 tumor suppressor gene has been observed in certain benign and malignant tumors. Recent studies have demonstrated that merlin, the product of the NF2 gene, is regulated by Rac/PAK signaling. However, the mechanism by which merlin acts as a tumor suppressor has remained obscure. In this report, we show that adenovirus-mediated expression of merlin in NF2-deficient tumor cells inhibits cell proliferation and arrests cells at G1 phase, concomitant with decreased expression of cyclin D1, inhibition of CDK4 activity, and dephosphorylation of pRB. The effect of merlin on cell cycle progression was partially overridden by ectopic expression of cyclin D1. RNA interference experiments showed that silencing of the endogenous NF2 gene results in upregulation of cyclin D1 and S-phase entry. Furthermore, PAK1-stimulated cyclin D1 promoter activity was repressed by cotransfection of NF2, and PAK activity was inhibited by expression of merlin. Interestingly, the S518A mutant form of merlin, which is refractory to phosphorylation by PAK, was more efficient than the wild-type protein in inhibiting cell cycle progression and in repressing cyclin D1 promoter activity. Collectively, our data indicate that merlin exerts its antiproliferative effect, at least in part, via repression of PAK-induced cyclin D1 expression, suggesting a unifying mechanism by which merlin inactivation might contribute to the overgrowth seen in both noninvasive and malignant tumors.

Maintaining the self-renewal and differentiation potential of human CD34+ hematopoietic cells using a single genetic element

Hematopoiesis is a complex process involving hematopoietic stem cell (HSC) self-renewal and lineage commitment decisions that must continue throughout life. Establishing a reproducible technique that allows for the long-term ex vivo expansion of human HSCs and maintains self-renewal and multipotential differentiation will allow us to better understand these processes, and we report the ability of the leukemia-associated AML1-ETO fusion protein to establish such a system. AML1-ETO-transduced human CD34+ hematopoietic cells routinely proliferate in liquid culture for more than 7 months, remain cytokine dependent for survival and proliferation, and demonstrate self-renewal of immature cells that retain both lymphoid and myeloid potential in vitro. These cells continue to express the CD34 cell surface marker and have ongoing telomerase activity with maintenance of telomere ends, however they do not cause leukemia in nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mice. Identification of the signaling pathways that are modulated by AML1-ETO and lead to the self-renewal of immature human progenitor cells may assist in identifying compounds that can efficiently expand human stem and progenitor cells ex vivo.

Differential recruitment of caspase 8 to cFlip confers sensitivity or resistance to Fas-mediated apoptosis in a subset of familial lymphoma patients

Resistance to Fas-mediated apoptosis (FMA) has been implicated in the pathogenesis of hematologic malignancies. Recently, a collaborative study showed that germline Fas mutations represent a genetic risk factor for the development of Hodgkin's and non-Hodgkin lymphoma. Here, we report that transformed B cell lines from familial lymphoma patients show a range of sensitivity to Fas-mediated apoptosis with lymphocytes from two patients with a marked resistance to Fas-, but not p53-mediated cell death. Fas resistance in these cells was associated with reduced recruitment of the initiator caspase 8 compared to cFlip, an inhibitor of apoptosis, to the death-inducing signaling complex (DISC). A decreased ratio of caspase 8 to cFlip in total cell extracts as well as in the DISC was associated with a profound disturbance of the Fas signaling cascade. We propose here that the relative reduction in caspase 8 to cFlip in the Fas DISC confers a survival advantage to lymphocytes and predisposes to the development of malignancy in some familial lymphoma patients.

Human granulocyte colony-stimulating factor in children with high-risk acute lymphoblastic leukemia: a Children's Cancer Group Study

PURPOSE

To investigate the effect of granulocyte colony-stimulating factor (G-CSF) on hematopoietic toxicities, supportive care requirements, time to complete intensive therapy, and event-free survival (EFS) and overall survival (OS) in children with high-risk acute lymphoblastic leukemia (HR-ALL).

PATIENTS AND METHODS

A total of 287 children with HR-ALL were randomly assigned to intensive chemotherapy regimens (New York I [NY I] or NY II) as part of the Children's Cancer Group (CCG)-1901 protocol. The induction phases consisted of five drugs (vincristine, prednisone, l-asparaginase, daunorubicin, and cyclophosphamide). Initial consolidation comprised six-agent chemotherapy combined with 18 Gy of total-brain irradiation. Patients were randomly assigned to receive G-CSF (5 microg/kg/day) during either induction or initial consolidation. A crossover study analysis was done on the 259 patients who completed both phases of therapy.

RESULTS

The mean time to neutrophil recovery (>/= 0.5 x 109/L) was reduced with G-CSF (16.7 v 19.1 days, P =.0003); however, patients who received G-CSF did not have significantly reduced episodes of febrile neutropenia (149 v 164, P =.41), positive blood cultures (57 v 61, P =.66), or serious infections (75 v 79, P =.62). Hospitalization (14.0 v 13.9 days, P =.87) and induction therapy completion times (NY I, 30.3 v 31.3 days, P =.11; NY II, 33.4 v 32.3 days, P =.40) were not significantly altered. There were no differences in 6-year EFS (P =.24) or OS (P =.54) between patients receiving or not receiving G-CSF on CCG-1901, NY I and NY II.

CONCLUSION

Children with high-risk ALL do not appear to benefit from prophylactic G-CSF.

Rare variants of ATM and risk for Hodgkin's disease and radiation-associated breast cancers

PURPOSE

In this study, we first sought to evaluate whether individuals heterozygous for ATM mutations may have an increased susceptibility to radiation-induced breast cancer (BC) after treatment for Hodgkin's disease (HD). We next sought to determine the frequency of ATM variants in patients with Hodgkin's lymphoma, regardless of coexisting BC, compared with healthy volunteers.

EXPERIMENTAL DESIGN

Full sequence analysis of ATM was performed on cDNA from peripheral blood lymphocytes from 37 cases of BC after therapeutic radiation therapy for HD and 27 comparison cases with HD and no BC treated during the same time period. The frequency of ATM variants was analyzed in the total group of 64 cases of HD and compared to allele frequencies in 128 ethnically matched controls from the same geographical region.

RESULTS

No protein-truncating ATM mutations were observed in cases with HD with or without BC. Missense mutations were more frequent in the cohort with HD compared with patients with BC following HD (P = 0.02). The median time from HD to the development of BC was 18 years in patients with ATM variants compared with 16 years in those with no ATM variants (P = 0.04). Multiple ATM variants, including one homozygous mutation, were observed in 9 HD cases.

CONCLUSIONS

Heterozygous protein-truncating or missense mutations of ATM were not associated with increased radiation-associated risk of BC after HD. The observation of multiple germ-line mutations and a homozygote suggests that rare ATM variants may constitute cancer-susceptibility alleles in a subset of cases.

Differential sensitivity to imatinib of 2 patients with metastatic sarcoma arising from dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a rare superficial sarcoma usually affecting the trunk, with significant risk of local recurrence. It is characterized by the presence of ring chromosomes or chromosomal translocations fusing the promoter of the collagen gene COL1A1 to the platelet-derived growth factor beta-chain gene PDGFB, increasing the production of PDGF locally and promoting autocrine or paracrine tumor growth. Fewer than 5% of patients with DFSP develop metastatic sarcoma, with a poor subsequent prognosis. Imatinib (STI-571) was developed as an inhibitor of the PDGF receptor tyrosine kinase and has proven clinical activity against chronic myelogenous leukemia (expressing bcr-abl) and gastrointestinal stromal tumors (expressing c-kit). We describe 2 patients with metastatic and unresectable metastases from DFSP treated with imatinib. After confirmation of negative CD117 status of 2 sarcomas arising from DFSP, patients were given imatinib 400 mg po qd and assessed at regular intervals for their tolerance and response to therapy. One patient had a transient response, then progressed rapidly and died of disease. Another patient showed a partial response to therapy after 2 months, with resolution of superior vena cava syndrome and shrinking of metastatic lung lesions. His response is ongoing after 6 months of therapy. These clinical data confirm findings from models of DFSP and support the use of imatinib in the rare setting of metastatic DFSP. Imatinib may be useful for patients with locally advanced DFSP, when other options for local therapy are limited.

Cytogenetic and morphological abnormalities in paroxysmal nocturnal haemoglobinuria

Paroxysmal nocturnal haemoglobinuria (PNH) is characterized by the expansion of a haematopoietic stem cell clone with a PIG-A mutation (the PNH clone) in an environment in which normal stem cells are lost or failing: it has been hypothesized that this abnormal marrow environment provides a relative advantage to the PNH clone. In patients with PNH, generally, the karyotype of bone marrow cells has been reported to be normal, unlike in myelodysplastic syndrome (MDS), another clonal condition in which cytogenetic abnormalities are regarded as diagnostic. In a retrospective review of 46 patients with a PNH clone, we found a karyotypic abnormality in 11 (24%). Upon follow-up, the proportion of cells with abnormal karyotype decreased significantly in seven of these 11 patients. Abnormal morphological bone marrow features reminiscent of MDS were common in PNH, regardless of the karyotype. However, none of our patients developed excess blasts or leukaemia. We conclude that in patients with PNH cytogenetically abnormal clones are not necessarily malignant and may not be predictive of evolution to leukaemia.

Sensitivity of soft tissue sarcoma cell lines to chemotherapeutic agents: identification of ecteinascidin-743 as a potent cytotoxic agent

The cytotoxic effects of ecteinascidin-743(ET-743), a novel marine natural product, were evaluated and compared with that of clinically used anticancer agents methotrexate, doxorubicin, etoposide, and paclitaxel in eight human soft tissue sarcoma (STS) cell lines. HT-1080, a fibrosarcoma cell line, and HS-42, a malignant mesodermal cell line, were the most sensitive of the cell lines to methotrexate, doxorubicin, etoposide, and paclitaxel. Other cell lines (IC50s) varied considerably and were more resistant to these agents. ET-743 was more potent than any of these agents, with IC50s in the pM range in all of the cell lines. Cytotoxicity of ET-743 was dose- and time-related (4-72 h exposure). Cytotoxic concentrations of ET-743 produced a S/G2 block in all of the cell lines tested. Three colon adenocarcinoma cell lines, HCT-8, HT-29, and HCT-116, and one breast cancer cell line, MCF-7, were 1-2 logs less sensitive to ET-743 than the STS cell lines. Cell lines were also characterized as to expression of oncogenes and tumor suppressor genes to attempt to correlate sensitivity of these cell lines to ET-743 and other chemotherapeutic agents. All of the cell lines except M8805, a malignant fibrous histiocytoma cell line, had mutations in p53 and/or overexpressed the MDM2 protein. Only HS-18, a liposarcoma cell line, lacked expression of the retinoblastoma protein. None of the cell lines had detectable expression of P-glycoprotein as measured by immunohistochemistry. ET-743 is an extremely potent cytotoxic agent against human STS cell lines and is being evaluated as an antitumor agent in this disease.

Hormonal regulation of tumor suppressor proteins in breast cancer cells

This laboratory is studying hormonal regulation of tumor suppressor proteins, p53 and retinoblastoma (pRB). Estrogen receptor and progesterone receptor positive human breast cancer cell lines, T47D and MCF-7, were utilized for determining influence of hormonal and antihormonal agents on the level of expression of p53, state of phosphorylation of pRB, and rate of cell proliferation. The expression of p53 in T47D cells grown for 4-5 days in culture medium containing charcoal-treated (stripped) fetal bovine serum declined gradually to 10% of the level seen in control (whole serum, non charcoal-treated) groups. Supplementation of culture medium containing stripped serum with 0.1-1 nM estradiol (E(2)) restored p53 to its level seen in the control within 6-24 h. Under above conditions, treatment of cells with R5020 or RU486 reduced (15-30%) the level of p53. Incubation of cells in E(2)-containing growth medium caused cell proliferation and hyperphosphorylation of pRB; the latter effect was seen maximally between 24-72 h. The E(2)-induced hyperphosphorylation of pRB and increase in the level of p53 were sensitive to the presence of ICI and 4-hydroxy tamoxifen (OHT). T47D and MCF-7 cells were also transiently transfected with a P1CAT reporter plasmid containing c-Myc responsive element and the levels of chloramphenicol acetyltransferase (CAT) activity were observed in response to various treatments. E(2) and OHT caused P1CAT induction as seen by increased CAT activity: E(2) caused an endogenous increase in the expression of an ICI-sensitive c-Myc form. These data suggest that estrogen upregulates p53 expression while progesterone downregulates this process. Further, E(2) regulates p53 level and pRB activity in a coordinated manner.

Levels of E2F-1 expression are higher in lung metastasis of colon cancer as compared with hepatic metastasis and correlate with levels of thymidylate synthase

We recently reported that forced overexpression of the transcription factor E2F-1 in human HT-1080 fibrosarcoma cells resulted in corresponding high levels of thymidylate synthase (TS) and resistance to 5-fluoropyrimidines (D. Banerjee et al., Cancer Res., 58: 4292-4296, 1998). Because colorectal metastasis to the lung has higher TS levels than liver metastasis and is less responsive to treatment with 5-fluorouracil (R. Gorlick et al., J. Clin. Oncol., 16: 1465-1469, 1998), it was, therefore, of interest to measure E2F-1 expression in these tumors. In contrast to marginally increased levels of dihydrofolate reductase and topoisomerase I in lung metastasis as compared with liver metastasis, lung tumors had a 5-fold increase in E2F-1 expression as compared with liver tumors, corresponding to the relative levels of TS in these metastases. These data indicate that there exists a close correlation between E2F-1 and TS levels and provide a rationale for targeting this transcription factor, ie., E2F-1, for the treatment of certain cancers.

Characterization of two novel sublines established from a human megakaryoblastic leukemia cell line transfected with p210(BCR-ABL)

Disease progression in chronic myelogenous leukemia (CML) is usually accompanied by chromosomal abnormalities such as an additional Ph chromosome, trisomies of chromosome 8 or 19, or i(17) in addition to the standard translocation t(9;22) (q34;q11). However, detailed studies of the various steps involved during this evolution are difficult to perform, thereby making the study of cell lines that contain the transposed genes BCR-ABL, especially those of human origin, an important focus. In this analysis we investigated the human megakaryoblastic cell line MO7e and its subline transfected with BCR-ABL, MO7e/p210. Initial studies demonstrated that the phenotype of the MO7e line was consistent with a megakaryocytic lineage as originally described and was growth factor dependent in liquid culture. The MO7e/p210 subline, however, was growth factor independent and could be further separated into two distinct sublines based on expression of glycophorin A using the monoclonal antibody R10. The subline R10 negative (R10-) was similar to the parent line MO7e but R10 positive (R10+) cells had a distinct erythroid phenotype. In addition, the R10- and R10+ sublines demonstrated strikingly different colony morphology when cultured in semisolid medium. Furthermore, R10+ cells had additional chromosomal abnormalities not detected in the R10- population. These results demonstrate that the insertion of the BCR-ABL in this human leukemia cell line resulted in two distinct subpopulations of cells, each now growth factor independent, but one with a phenotype and karyotype identical to the parent cell line and the other with a different phenotype and additional chromosomal abnormalities. These two subpopulations derived from the MO7e/p210 transfected cell line may prove useful in further understanding the multistep events that occur in the progression of this disease.

TbetaR-I(6A) is a candidate tumor susceptibility allele

We have previously described a type I transforming growth factor (TGF)-beta receptor (TbetaR-I) polymorphic allele, TbetaR-I(6A), that has a deletion of three alanines from a nine-alanine stretch. We observed a higher than expected number of TbetaR-I(6A) homozygotes among tumor and nontumor DNA from patients with a diagnosis of cancer. To test the hypothesis that TbetaR-I(6A) homozygosity is associated with cancer, we performed a case-control study in patients with a diagnosis of cancer and matched healthy individuals with no history of cancer and who were identical in their gender and their geographical and ethnic background to determine the relative germ-line frequencies of this allele. We found nine TbetaR-I(6A) homozygotes among 851 patients with cancer. In comparison, there were no TbetaR-I(6A) homozygotes among 735 healthy volunteers (P < 0.01). We also observed an excess of TbetaR-I(6A) heterozygotes in cancer cases compared to controls (14.6% versus 10.6%; P = 0.02, Fisher's exact test). A subset analysis revealed that 4 of 112 patients with colorectal cancer were TbetaR-I(6A) homozygotes (P < 0.01). Using mink lung epithelial cell lines devoid of TbetaR-I, we established stably transfected TbetaR-I and TbetaR-I(6A) cell lines. We found that, compared to TbetaR-I, TbetaR-I(6A) was impaired as a mediator of TGF-beta antiproliferative signals. We conclude that TbetaR-I(6A) acts as a tumor susceptibility allele that may contribute to the development of cancer, especially colon cancer, by means of reduced TGF-beta-mediated growth inhibition.

Complete remission after treatment of acute promyelocytic leukemia with arsenic trioxide

BACKGROUND

Two reports from China have suggested that arsenic trioxide can induce complete remissions in patients with acute promyelocytic leukemia (APL). We evaluated this drug in patients with APL in an attempt to elucidate its mechanism of action.

METHODS

Twelve patients with APL who had relapsed after extensive prior therapy were treated with arsenic trioxide at doses ranging from 0.06 to 0.2 mg per kilogram of body weight per day until visible leukemic cells were eliminated from the bone marrow. Bone marrow mononuclear cells were serially monitored by flow cytometry for immunophenotype, fluorescence in situ hybridization, reverse-transcription-polymerase-chain-reaction (RT-PCR) assay for PML-RAR-alpha fusion transcripts, and Western blot analysis for expression of the apoptosis-associated proteins caspases 1, 2, and 3.

RESULTS

Of the 12 patients studied, 11 achieved complete remission after treatment that lasted from 12 to 39 days (range of cumulative doses, 160 to 495 mg). Adverse effects were relatively mild and included rash, lightheadedness, fatigue, and musculoskeletal pain. Cells that expressed both CD11b and CD33 (antigens characteristic of mature and immature cells, respectively), and which were found by fluorescence in situ hybridization to carry the t(15;17) translocation, increased progressively in number during treatment and persisted in the early phase of complete remission. Eight of 11 patients who initially tested positive for the PML-RAR-alpha fusion transcript by the RT-PCR assay later tested negative; 3 other patients, who persistently tested positive, relapsed early. Arsenic trioxide induced the expression of the proenzymes of caspase 2 and caspase 3 and activation of both caspase 1 and caspase 3.

CONCLUSIONS

Low doses of arsenic trioxide can induce complete remissions in patients with APL who have relapsed. The clinical response is associated with incomplete cytodifferentiation and the induction of apoptosis with caspase activation in leukemic cells.

The spectrum of somatic mutations in the PIG-A gene in paroxysmal nocturnal hemoglobinuria includes large deletions and small duplications

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal blood disorder characterized by chronic hemolysis with hemoglobinuria and venous thrombosis. PNH clones arise through somatic mutations in the X-linked PIG-A gene that occur in early hematopoietic stem cells. Here we report 28 previously undescribed mutations; we confirm that somatic mutations are spread throughout the entire coding region of the PIG-A gene and that the majority are frameshift mutations producing a non-functional PIG-A protein (PIG-A(o)). In addition, we found 1 total deletion of the PIG-A gene, and 2 short nucleotide duplications. Although mutations are spread throughout the entire coding region, we observe more missense mutations in exon 2 than in the other exons. The increasing number of identified missense PIG-A mutations should help elucidate structure-function relationships in the PIG-A protein.

Higher levels of thymidylate synthase gene expression are observed in pulmonary as compared with hepatic metastases of colorectal adenocarcinoma

PURPOSE

It has been observed previously that the pulmonary metastases of colorectal adenocarcinoma are less responsive to therapy with fluorouracil (FUra) as compared with other sites of metastasis (liver, local). To investigate the basis of this chemoresistance, the levels of thymidylate synthase (TS) mRNA and protein were measured, as TS expression has been shown to be predictive of response to therapy in colorectal cancer.

MATERIALS AND METHODS

Tumors were obtained from 19 patients with metastatic colorectal cancer (12 hepatic and seven pulmonary). TS expression was measured by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and TS protein levels were measured by Western blotting. The presence of TS amplification was assessed by Southern blotting. Levels of p53 protein were determined using immunohistochemistry.

RESULTS

TS mRNA expression was shown to be significantly higher in the pulmonary metastases (mean TS/beta-actin ratio, 19.7; n = 7) as compared with the hepatic metastases (mean TS/beta-actin ratio, 4.7; n = 11) of colorectal cancer. Lower TS expression was observed in patients with hepatic metastases who had received prior FUra versus patients who had not been treated. High levels of TS expression in some samples was associated with low-level (two to three gene copies) increases in TS gene copy numbers and this was observed more frequently in the pulmonary metastatic samples. The increased gene copy numbers occurred both in samples with wild-type p53 and those with mutant p53 tumor-suppressor gene as determined by immunohistochemistry.

CONCLUSION

High levels of TS enzyme may be the basis of the lack of response of pulmonary metastases to FUra treatment.

Familial colorectal cancer in Ashkenazim due to a hypermutable tract in APC

Approximately 130,000 cases of colorectal cancer (CRC) are diagnosed in the United States each year, and about 15% of these have a hereditary component. Two well-defined syndromes, familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC), account for up to 5% of the total new cases of CRC. Truncating APC mutations are responsible for FAP, and defective mismatch repair genes cause HNPCC. However, the genes responsible for most of the familial cases are unknown. Here we report a mutation (T to A at APC nucleotide 3920) found in 6% of Ashkenazi Jews and about 28% of Ashkenazim with a family history of CRC. Rather than altering the function of the encoded protein, this mutation creates a small hypermutable region of the gene, indirectly causing cancer predisposition.

A Ph-negative chronic myeloid leukemia patient with a non-classical BCR-ABL rearrangement characterized by fluorescence in situ hybridization

A patient with chronic myeloid leukemia (CML), a normal karyotype and a BCR-ABL rearrangement is presented. Southern blot analysis detected the rearrangement, whereas RT-PCR with b2a2 and b3a2 primers did not. Fluorescence in situ hybridization (FISH) with an ABL probe (9q34.2) and an Mbcr probe (22q11) showed ABL and BCR signals on chromosome 22. Subsequent FISH studies with cosmids mapping to 9q34.3 showed normal hybridization patterns to chromosome 9, suggesting an interstitial insertion of ABL containing DNA sequences into chromosome 22 in this patient. The lack of reciprocal translocation sequences was investigated with RT-PCR, primers a1b and c7. The absence of ABL-BCR gene expression in this and other patients described in the literature with this subtype of Ph-negative CML, does not seem to have an impact on the clinical course of the disease.

The carrier frequency of the BRCA2 6174delT mutation among Ashkenazi Jewish individuals is approximately 1%

Certain germline mutations in either BRCA1 or BRCA2 confer a lifetime risk of developing breast cancer that may approach 90%. The BRCA1 185delAG mutation was found in 20% and the BRCA2 6174delT mutation in 8% of Ashkenazi Jewish women with early-onset breast cancer. The 185delAG mutation was observed in 0.9% of 858 Ashkenazi Jews unselected for a personal or family history of cancer. Assuming comparable age-specific penetrances, a carrier frequency of 0.3% was estimated for the 6174delT BRCA2 mutation. To test this hypothesis, we performed a population survey of 1,255 Jewish individuals. In two independent groups, a prevalence of approximately 1% (C.I. 0.6-1.5) was observed for the 6174delT mutation. The relative risk of developing breast cancer by age 42 was estimated to be 9.3 (C.I. 2.5-22.5) for 6174delT, compared to 31 (C.I. 11-77) for 185delAG. Analysis of 107 Ashkenazi Jewish women with breast cancer and a family history of breast or ovarian cancer confirmed a four-fold greater prevalence for the BRCA1 185delAG mutation compared to the BRCA2 6174delT mutation. Our findings suggest a difference in cumulative life-time penetrance for the two mutations. Genetic counseling for the one in 50 Ashkenazi Jewish individuals harbouring specific germline mutations in BRCA1 or BRCA2 must be tailored to reflect the different risks associated with the two mutations.

Low incidence of BRCA2 mutations in breast carcinoma and other cancers

Inherited mutant alleles of familial tumour suppressor genes predispose individuals to particular types of cancer. In addition to an involvement in inherited susceptibility to cancer, these tumour suppressor genes are targets for somatic mutations in sporadic cancers of the same type found in the familial forms. An exception is BRCA1, which contributes to a significant fraction of familial breast and ovarian cancer, but undergoes mutation at very low rates in sporadic breast and ovarian cancers. This finding suggests that other genes may be the principal targets for somatic mutation in breast carcinoma. A second, recently identified familial breast cancer gene, BRCA2 (refs 5-8), accounts for a proportion of breast cancer roughly equal to BRCA1. Like BRCA1, BRCA2 behaves as a dominantly inherited tumour suppressor gene. Individuals who inherit one mutant allele are at increased risk for breast cancer, and the tumours they develop lose the wild-type allele by heterozygous deletion. The BRCA2 coding sequence is huge, composed of 26 exons that span 10,443 bp. Here we investigate the rate of BRCA2 mutation in sporadic breast cancers and in a set of cell lines that represent twelve other tumour types. Surprisingly, mutations in BRCA2 are infrequent in cancers including breast carcinoma. However, a probable germline mutation in a pancreatic tumour cell line suggests a role for BRCA2 in susceptibility to pancreatic cancer.

Recurrent BRCA2 6174delT mutations in Ashkenazi Jewish women affected by breast cancer

The lifetime risk of breast cancer may approach 80-90% in women who have germline mutations of either of two genes, BRCA1 or BRCA2. A single BRCA1 mutation, 185delAG, has been noted in approximately 20% of Ashkenazi Jewish women with early onset breast cancer and in 0.9% of the Ashkenazi population. We recently detected a 6174delT frameshift mutation in BRCA2 in an hereditary breast cancer kindred of Ashkenazi Jewish ancestry. Here, we investigated the frequency of this mutation in 200 women with early-onset breast cancer. Six of 80 Ashkenazi Jewish women (8%) diagnosed with breast cancer before the age of 42, wer heterozygous for the 6174delT mutation, compared to none of 93 non-Jewish women diagnosed with breast cancer at the same age (P = .005). These cases were ascertained without regard to family history. Two of 27 (7%) additional Jewish families in which the proband was diagnosed with breast cancer at age 42 to 50 and had a family history of breast or ovarian cancer had germline 6174delT mutations. The results of this report suggest that a recurrent mutation of BRCA1 and a recurrent mutation BRCA2 together may account for over a quarter of all early-onset breast cancer in the setting of a personal or family history of ovarian cancer in Ashkenazi Jewish women.

Familial acute myeloid leukemia and DiGuglielmo syndrome

A family is described in which two sisters developed acute myeloblastic leukemia (AML FAB M2) and erythroleukemia (FAB M6) at ages 60 and 53, 15 years apart. Their father was diagnosed as having chronic erythremic myelosis (DiGuglielmo syndrome) 24 years earlier at age 56. Cytogenetic analysis of bone marrow blasts in the patient with AML M2 revealed a complex hyperdiploid karyotype with clonal abnormalities -3, -5, del(5)(q13q23), -8, +i(8)(q10), -11, add(11) (q23), add(12)(p13), -13, +3mar. No environmental risk factors could be identified. Hematologic and cytogenetic analysis of all living first degree relatives of the affected persons revealed hematological abnormalities, but normal constitutional karyotypes of peripheral blood lymphocytes and no induction of cytogenetic abnormalities in folate deficient medium.

A phase II pilot trial of high-dose hydroxyurea in chronic myelogenous leukemia

Suppression or eradication of the Philadelphia (Ph1) chromosome has been a major goal in the therapy of chronic myelogenous leukemia (CML). Variable levels of Ph1 chromosome negativity have been achieved using interferon-alfa, busulfan, combination chemotherapy, and allogeneic bone marrow transplantation. This study evaluated the effect of achieving a predetermined level of myelosuppression using hydroxyurea on bone marrow cytogenetics in CML. Fourteen patients with chronic phase CML received 25 cycles of therapy. Fourteen of the 25 cycles were associated with cytogenetic responses consisting of 25% or more Ph1 negative metaphases (range, 25% to 100%). Nine of the responses consisted of 50% or greater Ph1 negative metaphases. Toxicity was exclusively due to consequences of myelosuppression, including febrile neutropenia and thrombocytopenia. In chronic phase CML, hydroxyurea induces cytogenetic responses with tolerable toxicity and is an attractive agent for further study as a component of treatment strategies aimed at eradicating the Ph1 + population in CML.

Duration of the preclinical phase of chronic myelogenous leukemia: a case report

The molecular events that allow for clonal expansion of the malignant population in chronic myelogenous leukemia (CML) are poorly understood. Recent experiments in transgenic mice suggest a close temporal relationship between expression of the aberrant protein and manifestation of a hematologic neoplasm that resembles CML; tracing the same phenomenon in humans has not been possible. We studied a patient who underwent autologous bone marrow harvest after completion of chemotherapy and radiation therapy for advanced stage Hodgkin's disease. At the time of harvest his peripheral blood counts and bone marrow were morphologically normal. Sixteen months later he developed the clinical manifestations of CML. Detailed molecular evaluation of the harvested marrow showed that a small number of cells contained the Philadelphia chromosome. The time interval required for expansion of the malignant clone, as suggested by this particular patient, was at least 16 months although it is recognized that this figure may be variable.

Treatment of Philadelphia Chromosome Positive (Ph +) Chronic Myelogenous Leukemia in Blast Crisis and Ph + Acute Leukemia with High Dose Cytosine Arabinoside (HDARAC)

High dose cytosine arabinoside (HDARAC) was administered to eleven patients in the blastic phase of Philadelphia (Ph) chromosome positive chronic myelogenous leukemia (CML). Four patients presented in blastic phase and in seven patients blastic transformation had evolved from a previous chronic phase. All patients had been heavily pretreated with chronic phase drugs (hydroxyurea, myleran) or a protocol designed to treat the chronic phase (L-5 protocol) and with blastic phase regimens (anthracycline/araC combination or vincristine/prednisone). One of 11 patients achieved a complete remission (365 + days) and two patients achieved a partial response. No cytogenetic remissions were observed. The other patients were considered treatment failures with 3/8 surviving less than one month after therapy. Blasts were, at least temporarily, eliminated in all patients receiving at least 7 doses of HDARAC, although repopulation was rapid. HDARAC may be satisfactory therapy for accelerated phase CML but is minimally active in blastic phase CML.

Acquired cyclic haematopoiesis associated with a radiation-induced chromosomal abnormality with clonal, morphologically normal circulating leucocytes

A 62-year-old male with a history of vesical carcinoma treated with pelvic radiotherapy and cystectomy developed intermittent fevers associated with oral ulcers and neutropenia. Serial blood counts revealed cyclic haematopoiesis, with periodic neutropenia, lymphocytopenia, monocytopenia and thrombocytopenia. Bone marrow examination revealed intermittent hypoplasia without myelodysplasia or leukaemia. Marrow karyotype revealed a clonal chromosomal abnormality which included trisomy 8 and absence of the Y chromosome. We also provide evidence of spontaneous differentiation of the clonal marrow cells to mature leucocytes.

A study of multidrug resistance and cell kinetics in a child with near-haploid acute lymphoblastic leukemia

Marked hypodiploidy is found in a small group of patients with acute lymphoblastic leukemia (ALL) and is associated with very poor prognosis. Cells from a patient with near-haploid ALL (karyotype: 27 XY, DNA index = 0.5) were investigated by multiparameter flow cytometry at relapse and at multiple time-points during reinduction chemotherapy. The cell cycle of these near-haploid leukemic blasts and their chromatin structure was studied by acridine orange (AO) DNA/RNA flow cytometric assays. Most leukemic cells were in "G0", and no recruitment of the bone marrow cells into the G1 phase of the cell cycle was found during reinduction therapy with high dose cytosine arabinoside. After two cycles of chemotherapy, the patient achieved clinical remission, but persistent haploid cells were identified by flow cytometry and he relapsed after 8 weeks and died after 16.7 weeks. The leukemic blasts expressed very high levels of a 180 kd p-glycoprotein associated with multidrug resistance and daunomycin efflux could be blocked by verapamil. Expression of gp 180 and the verapamil effect on intracellular daunomycin concentration indicate multidrug resistance. We conclude that cell kinetic quiescence and multidrug resistance may both be factors responsible for the poor prognosis of this patient with near-haploid ALL. Further studies of this patient group should determine if these mechanisms are indeed responsible for the poor prognosis associated with near-haploid leukemia.

t(3;22)(q27;q11): a novel translocation associated with diffuse non-Hodgkin's lymphoma

Of 187 specimens of non-Hodgkin's lymphoma and four hyperplastic lymphoid proliferations with clonal chromosome abnormalities ascertained serially over a 4 1/2-year period, nine cases with t(3;22)(q27;q11) were identified. Seven of the lymphomas were diffuse tumors, predominantly large cell type. The eighth tumor, a follicular small cleaved cell lymphoma, exhibited a t(3;22) and a t(14;18)(q32;q21). The ninth case was a lymph node from a human immunodeficiency virus-positive patient which showed atypical hyperplasia. Overall survival of t(3;22) diffuse lymphoma patients was not different from that of patients with abnormal karyotypes without t(3;22). The t(3;22) diffuse tumors studied showed a disproportionate frequency of lambda light chain on their cell surfaces, a finding similar to that observed in t(8;22)(q24;q11) Burkitt's lymphomas. Our results indicate that the t(3;22)(q27;q11) is the third most common recurring translocation in diffuse non-Hodgkin's lymphoma.

Primary structure of c-kit: relationship with the CSF-1/PDGF receptor kinase family--oncogenic activation of v-kit involves deletion of extracellular domain and C terminus

The protein kinase domains of v-kit, the oncogene of the acute transforming feline retrovirus HZ4-FeSV (HZ4-feline sarcoma virus), CSF-1R (macrophage colony stimulating factor receptor) and PDGFR (platelet derived growth factor receptor) display extensive homology. Because of the close structural relationship of v-kit, CSF-1R and PDGFR we predicted that c-kit would encode a protein kinase transmembrane receptor (Besmer et al., 1986a; Yarden et al., 1986). We have now determined the primary structure of murine c-kit from a DNA clone isolated from a brain cDNA library. The nucleotide sequence of the c-kit cDNA predicts a 975 amino acid protein product with a calculated mol. wt of 109.001 kd. It contains an N-terminal signal peptide, a transmembrane domain (residues 519-543) and in the C-terminal half the v-kit homologous sequences (residues 558-925). c-kit therefore contains the features which are characteristic of a transmembrane receptor kinase. Comparison of c-kit, CSF-1R and PDGFR revealed a unique structural relationship of these receptor kinases suggesting a common evolutionary origin. The outer cellular domain of c-kit was shown to be related to the immunoglobulin superfamily. The sites of expression of c-kit in normal tissue predict a function in the brain and in hematopoietic cells. N-terminal sequences which include the extracellular domain and the transmembrane domain as well as 50 amino acids from the C-terminus of c-kit are deleted in v-kit. These structural alterations are likely determinants of the oncogenic activation of v-kit.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities at chromosome region 3p12-14 characterize clear cell renal carcinoma

In an effort to determine whether or not any characteristic chromosomal abnormalities exist in renal cancer, cytogenetic findings were correlated with tumor histology in nine cases of renal adenocarcinoma. Metaphase preparations adequate for analysis were obtained from cultures harvested between day 3 and day 21. Model chromosome number was diploid in three cases, hypodiploid in three, and hyperdiploid in the remaining three. One clear cell adenocarcinoma failed to reveal any chromosomal abnormality. Two tumors, a tubular/papillary carcinoma and an acinar/papillary carcinoma, showed the clonal abnormalities del(1)(p2l),+2,+7,+8,+12,+13,+16,+17,-21 and t(2;10)(q14-21;q26),+7q,+11q,-18, respectively. Interestingly, five of six clear cell tumors studied had clonal abnormalities affecting the short arm of chromosome #3 in the 3p12-21 region, and in the remaining case, of 15 karyotyped metaphases suitable for interpretation, one showed a deletion in 3p. These data indicate that clear cell carcinoma of the kidney may be associated with a nonrandom chromosomal abnormality involving the 3p12-14 region.

Treatment of blastic transformation of chronic myelogenous leukemia with mitoxantrone

Twenty-four patients with blastic-phase chronic myelogenous leukemia (CML) were treated with mitoxantrone. The patients included 19 whose cells were Philadelphia chromosome (Ph1+) and 5 who were either Ph1- or in whom cytogenetics were not available. Six of the 19 whose cells were Ph1+ responded and one of those who were Ph1- responded. The patients were further characterized into lymphoid or nonlymphoid on the basis of terminal deoxynucleotidyl transferase or morphology. Two of the patients with lymphoid transformation and 3 of those with nonlymphoid transformation responded. In 3 patients post-treatment cytogenetic evaluation revealed the presence of Ph1- metaphases. We conclude that mitoxantrone has modest activity in blCML and that the cytogenetic responses suggest the possibility of greater efficacy in chronic-phase CML.