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Secreted protein, acidic and rich in cysteine (SPARC), is a matricellular glycoprotein with growth-inhibitory and antiangiogenic functions. Although SPARC has been implicated as a tumor suppressor in humans, its function in normal or malignant hematopoiesis has not previously been studied. We found that the leukemic cells of AML patients with MLL gene rearrangements express low to undetectable amounts of SPARC whereas normal hematopoietic progenitors and most AML patients express this gene. SPARC RNA and protein levels were also low or undetectable in AML cell lines with MLL translocations. Consistent with its tumor suppressive effects in various solid tumor models, exogenous SPARC protein selectively reduced the growth of cell lines with MLL rearrangements by inhibiting cell cycle progression from G1 to S phase. The lack of SPARC expression in MLL-rearranged cell lines was associated with dense promoter methylation. However, we found no evidence of methylation-based silencing of SPARC in primary patient samples. Our results suggest that low or absent SPARC expression is a consistent feature of AML cells with MLL rearrangements and that SPARC may function as a tumor suppressor in this subset of patients. A potential role of exogenous SPARC in the therapy of MLL-rearranged AML warrants further investigation.

Childhood acute lymphoblastic and myeloid leukemias are stratified into molecular and cytogenetic subgroups important for prognosis and therapy. Studies have shown that gene expression profiles can discriminate between leukemia subtypes. Thus, proteome analysis similarly holds the potential for characterizing different subtypes of childhood leukemia. We used surface-enhanced laser desorption/ionization time-of-flight mass spectrometry to analyze cell lysates from childhood leukemia cell lines as well as pretreatment leukemic bone marrow derived from childhood leukemia cases. Comparison of the acute myeloid leukemia (AML) cell line, Kasumi, and the biphenotypic myelomonocytic cell line, MV4;11, with the acute lymphoblastic leukemia (ALL) cell lines, 697 and REH, revealed many differentially expressed proteins. In particular, one 8.3 kDa protein has been identified as a C-terminal truncated ubiquitin. Analysis of childhood leukemia bone marrow showed differentially expressed proteins between AML and ALL, including a similar peak at 8.3 kDa, as well as several proteins that differentiate between the ALL t(12;21) and hyperdiploid subtypes. These results demonstrate the potential for proteome analysis to distinguish between various forms of childhood leukemia. Future analyses are warranted to validate these findings and to investigate the role of the C-terminal truncated ubiquitin in the etiology of ALL.

The purpose of this study was to assess the effect of the multidrug resistance modulator cyclosporine (CsA) on the pharmacokinetics of etoposide and mitoxantrone in children with de novo acute myeloid leukemia (AML). Serial blood samples for pharmacokinetic studies were obtained in 38 children over a 24-h period following cytotoxin treatment with or without CsA on days 1 and 4. Drug concentrations were quantitated using validated HPLC methods, and pharmacokinetic parameters were determined using compartmental modeling with an iterative two-stage approach, implemented on ADAPT II software. Etoposide displayed a greater degree of interindividual variability in clearance and systemic exposure than mitoxantrone. With CsA treatment, etoposide and mitoxantrone mean clearance declined by 71% and 42%, respectively. These effects on clearance, in combination with the empiric 40% dose reduction for either cytotoxin, resulted in a 47% and 12% increases in the mean AUC for etoposide and mitoxantrone, respectively. There were no differences in the rates of stomatitis or infection between the two groups. CsA treatment resulted in an increased incidence of hyperbilrubinemia, which rapidly reversed upon conclusion of drug therapy. The variability observed in clearance, combined with the empiric 40% dose reduction of the cytotoxins, resulted in statistically similar systemic exposure and similar toxicity.

Long-term follow-up observations are reported on 427 patients who received one of three different intensified therapies in total therapy study X for acute lymphoblastic leukemia (ALL). In the trial for 'standard-risk' ALL, 154 of 309 patients in complete remission were randomized to receive high-dose methotrexate (HDMTX, 1 g/m2) periodically during the first 72 of 120 weeks of standard continuation therapy with 6-mercaptopurine and oral MTX; the remaining 155 patients received 1800 cGy cranial irradiation and intrathecal MTX, followed by 6-mercaptopurine/MTX therapy interrupted from week 36-71 for substitution of two other pairs of drugs. At 9 years of follow-up, significantly higher proportions of patients in the HDMTX group have maintained complete remissions (64 +/- 7%, SE, vs. 52 +/- 6%, p = 0.03), hematologic remissions (73 +/- 6% vs. 62 +/- 6%, p = 0.03), and testicular remissions (94 +/- 5% vs. 80 +/- 8%, p = 0.03); however, the proportion continuing in central nervous system remission has been lower (84 +/- 5% vs 93 +/- 4%, p = 0.02). In the evaluation of teniposide/cytarabine and delayed cranial irradiation for 'high-risk' ALL, 36 +/- 9% of 101 patients are predicted to be event-free survivors at 9 years. Altogether, 217 (51%) of the 427 patients are event-free survivors after at least 7 years of follow-up (median, 9 years); an additional 75 patients are alive and free of leukemia for a median of 6.4 years after successful remission retrieval therapy, boosting the total number of long-term survivors to 292 (68%). These results establish the efficacy of HDMTX for patients with standard-risk ALL and indicate the potential of teniposide/cytarabine for use in multiagent regimens for patients with high-risk disease. The overall survival figure, 68%, affords a benchmark for other studies assessing long-term outcome in ALL.

Of 251 consecutive cases of childhood acute nonlymphocytic leukemia (ANLL) seen at St. Jude Children's Research Hospital over a 12-year period, 16 (6.4%) were classified as promyelocytic according to the French-American-British definition. Patients with this form of leukemia were older at diagnosis than the group representing all other ANLL subtypes (median age, 14.8 vs. 9.0 years); they had lower leukocyte counts (median, 4.5 vs. 25.9 x 10(9)/liter), and a higher percentage were girls (68% vs. 44%). They also were much more likely to have a coagulation abnormality (75% vs. 13%). Only 44% of the promyelocytic group achieved complete remission, compared with 79% of the remaining patients (p = 0.001); however, after a median follow-up of 3.5 years, all but two of the responding patients with promyelocytic leukemia remain in complete remission. The majority of induction failures in the promyelocytic group (six of nine) resulted from complications that developed during periods of marrow hypoplasia or before hypoplasia was induced; whereas in the comparison group, more than half of the patients who failed had evidence of absolute or relative drug resistance. It is concluded that acute promyelocytic leukemia in children differs sufficiently from other subtypes of childhood ANLL to justify clinical trials of selective therapy. Recommendations for the use of heparin and blood component support in these patients are given.

The clinical and cell growth characteristics of 11 children with monosomy 7 presenting as preleukemia (eight cases) or acute nonlymphoblastic leukemia (three cases) were studied. Anemia was common to all patients, with nine showing leukocytosis, seven thrombocytopenia, and one thrombocytosis. There was a striking predominance of males (M/F ratio, 10:1) and a young median age (3 years). Preleukemia evolved to acute nonlymphoblastic leukemia in five patients and to myelofibrosis in one. In vitro studies of bone marrow progenitor cells cultured in leukocyte feeder-stimulated agar revealed abnormal cell proliferative patterns, most often an increased number of small clusters, for all 11 subjects. The cells of some preleukemic patients showed increased growth even in the absence of an exogenous source of colony-stimulating factor, suggesting autonomous growth or possibly autocrine stimulation. Combination chemotherapy or bone marrow transplantation failed to induce complete remission in the seven patients who were treated. Our findings in these 11 cases confirm the poor prognosis of monosomy 7 presenting as preleukemia in children. The in vitro studies suggest an association between altered cell growth in vitro and clinical evolution to frank leukemia.