Reactivation of apolipoprotein II gene transcription by cycloheximide reveals two steps in the deactivation of estrogen receptor-mediated transcription.

In this report, we describe apolipoprotein II (apoII) gene expression in cell lines derived by stable expression of the chicken estrogen receptor in LMH chicken hepatoma cells. In cell lines expressing high levels of receptor (LMH/2A), apoII gene expression is increased by estrogen 300-fold compared with levels in the receptor-deficient parent LMH line. LMH/2A cells show apoII mRNA induction and turnover kinetics similar to those in chicken liver. Inhibition of protein synthesis with cycloheximide (CHX) or puromycin following estrogen withdrawal superinduces apoII mRNA without affecting apoII mRNA stability. Superinduction is due to an estrogen-independent reactivation of apoII gene transcription. The apoII gene can be reactivated by CHX for up to 24 h following hormone withdrawal, suggesting that the gene is in a repressed yet transcriptionally competent state. These results reveal two distinct events necessary for termination of estrogen receptor-mediated transcription. The first event, removal of hormone, is sufficient to stop transcription when translation is ongoing. The second event is revealed by the CHX-induced superinduction of apoII mRNA following hormone withdrawal. This superinduction suggests that deactivation of estrogen receptor-mediated transcription requires a labile protein. Furthermore, reactivation of apoII gene expression by CHX and estrogen is additive, suggesting that estrogen is unable to overcome repression completely. Thus, a labile protein may act to repress estrogen receptor-mediated transcription of the apoII gene.

Isolation and characterization of clones for the rat hepatic lipase gene upstream regulatory region.

Genomic clones for 2287 nucleotides of the 5' flanking region, 135 nucleotides of the first exon, and 283 nucleotides of the first intron of the hepatic lipase gene were characterized. The predominant start site for transcription was identified by primer extension and S1 nuclease analyses to be 50 bases upstream of the ATG initiation codon. Based on the location of the major transcription start site, the functional TATA box is located 29 nucleotides upstream. Putative response elements for AP-2, cAMP, OCT-1, C/EBP, estrogen, glucocorticoids, sterols and thyroid hormone were located in this gene. Also a putative liver-specific element for apolipoproteins, C3P, was identified.

Response of children with high-risk acute lymphoblastic leukemia treated with and without cranial irradiation: a report from the Children's Cancer Group.

PURPOSE: Intensified intrathecal (i.t.) chemotherapy without cranial radiation therapy (CRT) prevents CNS relapse in children with low-risk and intermediate-risk acute lymphoblastic leukemia (ALL). In the current study, high-risk ALL patients who achieved a rapid early response (RER) to induction chemotherapy were randomized to receive intensive systemic chemotherapy and presymptomatic CNS therapy that consisted of either i.t. methotrexate (MTX) and CRT or intensified i.t. MTX alone. PATIENTS AND METHODS: Children (n = 636) with high-risk ALL (aged 1 to 9 years and WBC count > or = 50,000/microL or age > or = 10 years, excluding those with lymphomatous features) who achieved an RER (< or = 25% marrow blasts on day 7) to induction therapy and lacked CNS disease at diagnosis were randomized to receive systemic therapy with either i.t. MTX and CRT (regimen A, n = 317) or intensified i.t. MTX alone (regimen B, n = 319). RESULTS: Interim analysis in July 1993 revealed 3-year event-free survival (EFS) estimates of 82.1% +/- 4.0% (SD)and 70.4% +/- 4.2% for patients treated on regimens A and B, respectively (P = .004). As of January 1996, outcome had changed: 5-year EFS estimates were 69.1% +/- 3.4% and 75.0% +/- 2.7% for regimens A and B, respectively (P = 0.50). Marrow relapses comprised 57 events on regimen A and 43 events on regimen B. Fewer late events occurred on regimen B. CONCLUSION: For high-risk pediatric ALL patients who show an RER to induction therapy and are treated with systemic Children's Cancer Group (CCG)-modified Berlin-Frankfurt-Munster (BFM) chemotherapy, presymptomatic CNS therapy that consists of either i.t. MTX plus CRT or intensified i.t. MTX alone results in a similar 5-year EFS outcome. Furthermore, intensified i.t. MTX may protect against late bone marrow relapse.

Prognostic impact of trisomies of chromosomes 10, 17, and 5 among children with acute lymphoblastic leukemia and high hyperdiploidy (> 50 chromosomes).

PURPOSE: Children with acute lymphoblastic leukemia (ALL) and high hyperdiploidy (> 50 chromosomes) have improved outcome compared with other ALL patients. We sought to identify cytogenetic features that would predict differences in outcome within this low-risk subset of ALL patients. MATERIALS AND METHODS: High-hyperdiploid ALL patients (N = 480) were enrolled between 1988 and 1995 on Children's Cancer Group (CCG) trials. Karyotypes were determined by conventional banding. Treatment outcome was analyzed by life-table methods. RESULTS: Patients with 54 to 58 chromosomes had better outcome than patients with 51 to 53 or 59 to 68 chromosomes (P = .0002). Patients with a trisomy of chromosome 10 (P<.0001), chromosome 17 (P = .0002), or chromosome 18 (P = .004) had significantly improved outcome compared with their counterparts who lacked the given trisomy. Patients with a trisomy of chromosome 5 had worse outcome than patients lacking this trisomy (P = .02). Patients with trisomies of both chromosomes 10 and 17 had better outcome than those with a trisomy of chromosome 10 (P = .09), a trisomy of chromosome 17 (P =.01), or neither trisomy (P<.0001). Multivariate analysis indicated that trisomy of chromosome 10 (P = .001) was the most significant prognostic factor for high-hyperdiploid patients, yet trisomy of chromosome 17 (P =.02) or chromosome 5 (P = .01) and modal chromosome number (P = .02) also had significant multivariate effects. CONCLUSION: Trisomy of chromosomes 10 and 17 as well as modal chromosome number 54 to 58 identify subgroups of patients with high-hyperdiploid ALL who have a better outcome than high-hyperdiploid patients who lack these cytogenetic features. Trisomy of chromosome 5 confers poorer outcome among high-hyperdiploid patients.

Randomized comparison of cisplatin/vincristine/fluorouracil and cisplatin/continuous infusion doxorubicin for treatment of pediatric hepatoblastoma: A report from the Children's Cancer Group and the Pediatric Oncology Group.

PURPOSE: Previous studies demonstrated that chemotherapy with either cisplatin, vincristine, and fluorouracil (regimen A) or cisplatin and continuous infusion doxorubicin (regimen B) improved survival in children with hepatoblastoma. The current trial is a randomized comparison of these two regimens. PATIENTS AND METHODS: Patients (N = 182) were enrolled onto study between August 1989 and December 1992. After initial surgery, patients with stage I-unfavorable histology (UH; n = 43), stage II (n = 7), stage III (n = 83), and stage IV (n = 40) hepatoblastoma were randomized to receive regimen A (n = 92) or regimen B (n = 81). Patients with stage I-favorable histology (FH; n = 9) were treated with four cycles of doxorubicin alone. RESULTS: There were no events among patients with stage I-FH disease. Five-year event-free survival (EFS) estimates were 57% (SD = 5%) and 69% (SD = 5%) for patients on regimens A and B, respectively (P =.09) with a relative risk of 1.54 (95% confidence interval, 0.93 to 2.5) for regimen A versus B. Toxicities were more frequent on regimen B. Patients with stage I-UH, stage II, stage III, or stage IV disease had 5-year EFS estimates of 91% (SD = 4%), 100%, 64% (SD = 5%), and 25% (SD = 7%), respectively. Outcome was similar for either regimen within disease stages. At postinduction surgery I, patients with stage III or IV disease who were found to be tumor-free had no events; those who had complete resections achieved a 5-year EFS of 83% (SD = 6%); other patients with stage III or IV disease had worse outcome. CONCLUSION: Treatment outcome was not significantly different between regimen A and regimen B. Excellent outcome was achieved for patients with stage I-UH and stage II hepatoblastoma and for subsets of patients with stage III disease. New treatment strategies are needed for the majority of patients with advanced-stage hepatoblastoma.

Clinical features and treatment outcome of childhood T-lineage acute lymphoblastic leukemia according to the apparent maturational stage of T-lineage leukemic blasts: a Children's Cancer Group study.

PURPOSE: Leukemic cells from T-lineage acute lymphoblastic leukemia (ALL) patients are thought to originate from T-lymphocyte precursors corresponding to discrete stages of T-cell ontogeny. Here we sought to determine the influence of leukemic cell apparent maturational stage on treatment outcomes in pediatric T-lineage ALL. PATIENTS AND METHODS: From 1983 through 1993, 407 pediatric T-lineage ALL patients were enrolled onto two sequential series of risk-adjusted treatment protocols of the Children's Cancer Group. In the current analysis, T-lineage ALL patients were immunophenotypically classified as follows: CD7+ CD2- CD5- pro-thymocyte leukemia (pro-TL), CD7+ (CD2 or CD5)+ CD3- immature TL, and CD7+ CD2+ CD5+ CD3+ mature TL. RESULTS: Similar induction outcomes of 91.4%, 97.1%, and 98.3% were obtained by the pro-, immature, and mature TL groups, respectively. Four-year event-free survival (EFS) was lower for pro-TL patients (57.1%; SD = 8.4%,) compared with immature and mature TL patients (68.5%; SD = 3.5%; and 77.1%; SD = 4.0%, respectively) with an overall significance of .05 (log-rank test) or .04 (log-rank trend test). Relative hazards rates (RHR) were 2.11 and 1.22 for pro-TL and immature TL versus mature TL, respectively. Highly significant differences were found for overall survival (P = .005, log-rank test; P = .009, log-rank trend test). Multivariate analysis confirmed that the prognostic influence of ontogeny grouping was independent of that of other prognostic factors. CONCLUSION: Leukemic cells of the pro-TL maturation stage identify a small subgroup of T-lineage ALL patients who have a significantly worse EFS outcome than patients whose cells are of a more mature stage of development.

Clinical significance of translocation t(1;19) in childhood acute lymphoblastic leukemia in the context of contemporary therapies: a report from the Children's Cancer Group.

PURPOSE: The nonrandom translocation t(1;19) has been associated with poor outcome in pediatric B-lineage acute lymphoblastic leukemia (ALL). Because most patients treated by contemporary therapies now achieve improved outcomes, we have reassessed the prognostic significance of t(1;19). PATIENTS AND METHODS: Cytogenetic data were accepted for 1,322 children (<21 years old) with newly diagnosed ALL enrolled between 1988 and 1994 on risk-adjusted studies of the Children's Cancer Group (CCG). Forty-seven patients (3.6%) were t(1;19) positive (+); 1,275 (96.4%) were t(1;19) negative (-). Clinical characteristics and treatment outcome were compared using standard methods. RESULTS: Translocation (1;19)+ patients were more likely than t(1;19)- patients to be 10 years of age or greater (P < .001) or CD10+ CD19+ CD34- (P < .0001), or nonwhite (P = .02). Patients with a balanced t(1;19) were less likely to be hyperdiploid than patients with an unbalanced der(19)t(1;19). Event-free survival (EFS) was similar for the overall group of t(1;19)+ and t(1;19)- patients, with 4-year estimates of 69.5% (SD, 6.8%) and 74.8% (SD, 1.3%; P = .48), respectively. However, patients with unbalanced der(19)t(1;19) had significantly better outcomes than patients with balanced t(1;19): 4-year EFS were 80.6% (SD, 7.1%) and 41.7% (SD, 13.5%), respectively (P = .003). These differences were maintained within the individual studies analyses and after exclusion of t(1;19)+ patients whose cells were hyperdiploid with more than 50 chromosomes. CONCLUSION: The overall group of t(1;19)+ patients, as well as the subgroup with an unbalanced der(19)+ (1;19) had outcomes similar to that of t(1;19)- patients, whereas patients with balanced t(1;19) had poorer outcomes. Thus, although the overall prognostic significance of t(1;19) has been obviated by contemporary risk-adjusted protocols, the balanced t(1;19) translocation remains an adverse prognostic factor.

Duration of hospitalization as a measure of cost on Children's Cancer Group acute lymphoblastic leukemia studies.

PURPOSE: We used duration of hospitalization as a surrogate for cost and event-free survival as a measure of effectiveness to estimate the cost-effectiveness ratios of various treatment regimens on Children's Cancer Group trials for acute lymphoblastic leukemia. PATIENTS AND METHODS: The analyses included 4,986 children (2 to 21 years of age) with newly diagnosed acute lymphoblastic leukemia enrolled onto risk-adjusted protocols between 1988 and 1995. Analyses were based on a model of 100 patients. The marginal cost-effectiveness ratio (hospital days per additional patient surviving event-free) was the difference in total duration of hospitalization divided by the difference in number of event-free survivors at 5 years for two regimens. Relapse-adjusted marginal cost of frontline therapy was the difference in total duration of hospitalization for frontline therapy plus relapse therapy divided by the difference in number of event-free survivors at 5 years on the frontline therapy for two regimens. RESULTS: One or two delayed intensification (DI) phases, augmented therapy, and dexamethasone all improved outcome. Marginal cost-effectiveness of these regimens compared with the control regimens was 133 days per patient for DI, 117 days per patient for double DI, and 41 days per patient for augmented therapy. Dexamethasone resulted in 17 fewer days per patient. Relapse-adjusted marginal costs were 68 days per patient for DI and 52 days for double DI. Augmented therapy and dexamethasone-based therapy resulted in 16 and 82 fewer hospital days, respectively. The estimated cost-effectiveness for treating any first relapse was 250 days per patient. CONCLUSION: DI, double DI, augmented therapy, and dexamethasone-based therapy are cost-effective strategies compared with current treatment of first relapse.

Frequency and clinical significance of cytogenetic abnormalities in pediatric T-lineage acute lymphoblastic leukemia: a report from the Children's Cancer Group.

PURPOSE: Nonrandom chromosomal translocations are frequently observed in pediatric patients with acute lymphoblastic leukemia (ALL). Specific translocations, such as t(4;11) and t(9;22), identify subgroups of B-lineage ALL patients who have an increased risk of treatment failure. The current study was conducted to determine the prognostic significance of chromosomal translocations in T-lineage ALL patients. MATERIALS AND METHODS: The study included 169 children with newly diagnosed T-lineage ALL enrolled between 1988 and 1995 on risk-adjusted protocols of the Children's Cancer Group (CCG) who had centrally reviewed cytogenetics data. Outcome analyses used standard life-table methods. RESULTS: Presenting features for the current cohort were similar to those of concurrently enrolled patients for whom cytogenetic data were not accepted on central review. The majority of patients (80.5%) were assigned to CCG protocols for high-risk ALL and 86.4% had pseudodiploid (n = 80) or normal diploid (n = 66) karyotypes; modal chromosome number was not a significant prognostic factor. Overall, 103 of 169 (61%) patients had an abnormal karyotype, including 31 with del(6q), 29 with 14q11 breakpoints, 15 with del(9p), 11 with trisomy 8, nine with 11q23 breakpoints, nine with 14q32 translocations, and eight with 7q32-q36 breakpoints. Thirteen patients had the specific 14q11 translocation t(11;14)(p13;q11) and all were classified as poor risk. Patients with any of these translocations had outcomes similar to those with normal diploid karyotypes. CONCLUSION: Chromosomal abnormalities, including specific nonrandom translocations, were frequently observed in a large group of children with T-lineage ALL, but were not significant prognostic factors for this cohort. Thus, contemporary intensive treatment programs result in favorable outcomes for the majority of T-lineage ALL patients, regardless of karyotypic abnormalities, and such features do not identify patients at higher risk for relapse.

Abnormalities of chromosome bands 13q12 to 13q14 in childhood acute lymphoblastic leukemia.

PURPOSE: Little is known about nonrandom deletions of chromosome bands 13q12 to 13q14 (13q12-14) in acute lymphoblastic leukemia (ALL). We determined the prognostic significance of cytogenetically identified breakpoints in 13q12-14 in children with newly diagnosed ALL treated on Children's Cancer Group protocols from 1988 to 1995. PATIENTS AND METHODS: Breakpoints in 13q12-14 were identified in 36 (2%) of the 1,946 cases with accepted cytogenetic data. Outcome analysis used standard life-table methods. RESULTS: Seventeen patients (47%) with an abnormal 13q12-14 were classified, according to the National Cancer Institute (NCI), as poor risk, and 15 patients (42%) were standard risk; four (11%) were infants less than 12 months of age. Eight cases had balanced rearrangements of 13q12-14, 27 patients had a partial loss of 13q, and one had both a partial gain and a partial loss. The most frequent additional abnormalities among these patients were an abnormal 12p, a del(6q), a del(9p), a 14q11 breakpoint, and an 11q23 breakpoint. Nineteen patients were pseudodiploid, 10 were hyperdiploid, and seven were hypodiploid. Patients with an abnormal 13q12-14 had significantly worse event-free survival than patients lacking such an abnormality, with estimates at 6 years of 61% (SD = 14%) and 74% (SD = 1%), respectively (P =.04; relative risk = 1.74). Overall survival, however, was similar for the two groups (P =.25). The prognostic effect of an abnormal 13q was attenuated in a multivariate analysis adjusted for NCI risk status and ploidy (P =.72). CONCLUSION: Aberrations of 13q12-14 may contribute to leukemogenesis of childhood ALL and confer increased risk of treatment failure but are associated with other poor-risk features.

Treatment outcome and prognostic factors for infants with acute lymphoblastic leukemia treated on two consecutive trials of the Children's Cancer Group.

PURPOSE: Infants represent a very poor risk group for acute lymphoblastic leukemia (ALL). We report treatment outcome for such patients treated with intensive therapy on consecutive Children's Cancer Group (CCG) protocols. PATIENTS AND METHODS: Between 1984 and 1993, infants with newly diagnosed ALL were enrolled onto CCG-107 (n = 99) and CCG-1883 (n = 135) protocols. Postconsolidation therapy was more intensive on CCG-1883. On both studies, prophylactic treatment of the CNS included both high-dose systemic chemotherapy and intrathecal therapy, in contrast to whole-brain radiotherapy, which was used in earlier studies. RESULTS: Most patients (>95%) achieved remission with induction therapy. The most frequent event was a marrow relapse (46 patients on CCG-107 and 66 patients on CCG- 1883). Four-year event-free survival was 33% (SE = 4.7%) on CCG-107 and 39% (SE = 4.2%) on CCG- 1883. Both studies represent an improvement compared with a 22% (SE = 5.1%) event-free survival for historical controls. Four-year cumulative probabilities of any marrow relapse or an isolated CNS relapse were, respectively, 49% (SE = 5%) and 9% (SE = 3%) on CCG-107 and 50% (SE = 5%) and 3% (SE = 2%) on CCG-1883, compared with 63% (SE = 6%) and 5% (SE = 3%) for the historical controls. Independent adverse prognostic factors were age less than 3 months, WBC count of more than 50,000/microL, CD10 negativity, slow response to induction therapy, and presence of the translocation t(4;11). CONCLUSION: Outcome for infants on CCG-107 and CCG- 1883 improved, compared with historical controls. Marrow relapse remains the primary mode of failure. Isolated CNS relapse rates are low, indicating that intrathecal chemotherapy combined with very-high-dose systemic therapy provides adequate protection of the CNS. The overall unsatisfactory outcome observed for the infant ALL population warrants the future use of novel alternative therapies.

Children's Cancer Group trials in childhood acute lymphoblastic leukemia: 1983-1995.

Since 1968, the Children's Cancer Group (CCG) has treated more than 16,000 children with acute lymphoblastic leukemia (ALL). Herein, we report improvements obtained in CCG trials during two successive series of studies (1983-1988 and 1989-1995). Overall, 10-year EFS was 62% +/- 10% for the 1983-1988 series and 72% +/- 1% for the 1988-1995 series (P< 0.0001). Five-year cumulative rates of isolated CNS relapses were 5.9% and 4.4%. Therapy based on the Berlin-Frankfurt-Münster 76/79 study improved outcomes for intermediate and higher risk patients in the first series. For intermediate risk patients, delayed intensification (DI) was most crucial for improved outcome and cranial irradiation was safely replaced with maintenance intrathecal methotrexate, providing patients received intensified systemic therapy. In the second series, randomized trials showed better outcome with one vs no DI phase for lower risk patients, with two vs one DI phase for intermediate risk patients, and with the CCG 'augmented regimen' for higher risk patients with a slow day 7 marrow response. Cranial irradiation was safely replaced with additional intrathecal methotrexate for higher risk patients with a rapid day 7 marrow response. In a subsequent study, substitution of dexamethasone in place of prednisone in induction and maintenance improved outcome for standard risk patients. All patients received dexamethasone in DI. These successful treatment strategies form the basis for our current ALL trials.

Paucity of leukemic progenitor cells in the bone marrow of pediatric B-lineage acute lymphoblastic leukemia patients with an isolated extramedullary first relapse.

Isolated extramedullary relapse in childhood acute lymphoblastic leukemia (ALL) may be accompanied by occult bone marrow disease. We used a highly sensitive assay to quantify leukemic progenitor cells (LPCs) in the bone marrow of such patients. Multiparameter flow cytometry and blast colony assays were used to detect LPCs in the bone marrow of 31 pediatric B-lineage ALL patients with an isolated extramedullary first relapse. Sites of relapse were central nervous system (22 patients), testes (7 patients), and eye (2 patients). Bone marrow (BM) LPC counts ranged from 0/10(6) mononuclear cells (MNCs) to 356/10(6) MNCs (mean +/- SE, 27.8+/-13.1/10(6) MNCs). LPCs were undetectable in 19 patients (61%). The BM LPC burden at the time of extramedullary relapse was similar, regardless of site (Wilcoxon P = 0.77) or time of relapse (Wilcoxon P = 0.80). Compared with higher risk, standard risk at initial diagnosis showed a trend for increased BM LPC burden (mean +/- SE, 44.6+/-17.1 versus 7.5+/-3.3; Wilcoxon P = 0.22). After successful postrelapse induction chemotherapy, LPC counts in 21 evaluated patients ranged from 0/10(6) to 175/10(6) MNCs (mean +/- SE, 15.9+/-9.6/10(6) MNCs). By comparison, LPC burden was higher after successful induction chemotherapy among children with an early BM relapse (range, 0 to 3262/ 106 MNC; mean +/- SE, 166+/-107; Wilcoxon P = 0.11). Thus, not all patients with an extramedullary relapse have occult systemic failure with substantial involvement of the bone marrow, and after reinduction therapy, LPC counts were lower in these patients than in patients treated for an overt BM first relapse.

Amino acid differences in the N-terminus of C(H)2 influence the relative abilities of IgG2 and IgG3 to activate complement.

The four human IgG isotypes are highly conserved in amino acid sequence, but show differential ability to activate complement (C'): IgG3 and IgG1 are very active, IgG2 is active under certain conditions, and IgG4 is inactive. Although the second constant domain [C(H)2] is critical for C' activation, the individual amino acids that confer isotype-specific activity have not been identified. We have generated a series of mutants between IgG2 and IgG3, resulting in the exchange of the four N-terminal and six C-terminal polymorphic residues within C(H)2. Mutants containing the N-terminus of the C(H)2 of IgG3 were as effective as wildtype IgG3 in C1q binding, C1 activation and terminal complex (MAC) formation, but had reduced ability to effect C'-mediated lysis. IgG2 and mutants containing the N-terminal portion of the C(H)2 of IgG2 were reduced compared to IgG3 in activating C1, binding C1q and inducing assembly of the MAC, and were inactive in mediating lysis of target cells. Thus, the amino acid sequence differences in the N-terminus of C(H)2 play a critical role in determining the relative abilities of IgG2 and IgG3 to bind C1q and activate the C' cascade although additional residues of C(H)2 must be involved in mediating optimal target cells lysis. The sequence of the N-terminus of C(H)2 was less critical in determining C4 and C3 binding. Characterization of domain exchange mutants suggests that intermediate steps may be partly dependent on domains other than C(H)2. IgGs that do not direct target cell lysis nevertheless activate intermediate steps in the pathway, which may contribute to immune complex-associated disorders.

Bone marrow leukemic progenitor cell content in pediatric T-lineage acute lymphoblastic leukemia patients with an isolated extramedullary first relapse.

Isolated extramedullary relapse in childhood acute lymphoblastic leukemia (ALL) is associated frequently with the T-lineage immunophenotype and may be accompanied by occult bone marrow disease. We employed highly sensitive multiparameter flow cytometry and blast colony assays to quantify the leukemic progenitor cell (LPC) burden in the pretreatment bone marrows of 15 pediatric T-lineage ALL patients with an isolated extramedullary first relapse. Sites of extramedullary relapse were CNS (11 patients), testes (3 patients), and both CNS and testes (1 patient). Bone marrow LPC were detectable in 8 patients (53%) and undetectable in 7 patients (47%) at day 0 of post-relapse induction therapy, with LPC counts ranging from 0/10(6) mononuclear cells (MNC) to 518/10(6) MNC (mean +/- SEM, 50+/-34/10(6) MNC). Five of 9 patients with an early relapse (< 18 months after achieving a first complete remission [CR1]) and 3 of 6 patients with a late relapse (> or = 18 months from CR1) had detectable bone marrow LPC at day 0. Five of 8 patients with NCI-defined poor risk ALL and 3 of 7 patients with NCI-defined standard risk ALL had detectable LPC at day 0. Following post-relapse induction chemotherapy. LPC counts were detectable in bone marrows of 4 of 6 evaluated patients. Thus, approximately half of the extramedullary relapse T-lineage ALL patients studied had substantial occult involvement of the bone marrow. These findings may partly explain the previously observed poor prognosis of T-lineage patients following a CNS relapse.

Primary blasts from infants with acute lymphoblastic leukemia cause overt leukemia in SCID mice.

The establishment of an in vivo animal model system for infant acute lymphoblastic leukemia (ALL) would allow the testing of new agents against primary leukemic cells from infant ALL patients. We have demonstrated previously that growth of B-lineage leukemic cells in mice with severe combined immunodeficiency (SCID) was a significant prognostic factor for children with high risk ALL. We now have examined the significance of this prognostic variable for 13 infants with newly diagnosed ALL treated at participating institutions of the Children's Cancer Group (CCG). Chromosomal translocations were detected in 10/12 evaluated cases, including five with t(4;11), one each with t(7;9) and t(7;11), t(1;19), and t(9;22), and two with t(11;19). Twelve of the thirteen infants with ALL achieved remissions following induction chemotherapy. Primary leukemic cells from 8 of the 13 infants caused overt leukemia in SCID mice. Among these 8 SCID+ infants, 7 were CD10- and seven had cytogenetic or molecular evidence of an 11q23 rearrangement. Six of the 8 SCID+ infants have relapsed; only 2 remain in remission following chemotherapy or bone marrow transplant. However, among the 5 SCID- infants there were also two relapses. These data are suggestive of a poorer outcome for SCID+ infants, but larger numbers of patients must be analyzed to assess their statistical significance. In summary, we have established a SCID mouse model for human infant ALL that will be useful for 1) predicting short-term and long-term outcome of patients, 2) testing pharmacokinetics, efficacy, and toxicity of new agents, and 3) elucidating the in vivo mechanisms of chemotherapeutic drug resistance in infant ALL.

Distinct in vivo engraftment and growth patterns of t(1;19)+/E2A-PBX1+ and t(9;22)+/BCR-ABL+ human leukemia cells in SCID mice.

The SCID mouse represents a valuable tool for assessing growth characteristics and drug sensitivity of human leukemic cells. We have examined differences in the engraftment patterns in SCID mice of primary human leukemic cells isolated from children (< 21 years old) with either t(1;19)+/E2A-PBX1+ or t(9;22)+/BCR-ABL+ acute lymphoblastic leukemia. Leukemic cells from 13/24 t(1;19)+/E2A-PBX1+ patients caused overt leukemia in SCID mice. Macroscopic lesions were evident in 6/13 cases, with multiple sites involved in some mice: hepatomegaly,(3) splenomegaly(4), thymic enlargement; liver tumors(1), kidney tumors(1), abdominal tumors(1). Microscopic lesions in SCID mouse organs were present in all 13 cases and involved the bone marrow, brain, heart, gut, liver, kidney, lung, ovary, pancreas, skeletal muscle, spleen, and thymus. Leukemic cells from 5/20 t(9;22)+/BCR-ABL+ patients caused overt leukemia in SCID mice. Notably, macroscopic lesions (splenomegaly; leukemic bones; hepatic tumors) were observed in only 1 case. In all 5 cases, microscopic lesions were found in the mouse bone marrow. Additional microscopic lesions were restricted to skeletal muscle, spleen, and mesentery (1 case) or thymus (1 case). These findings differ markedly from those of t(1;19)+/E2A-PBX1+ leukemic cells due to the lack of involvement of major organs such as liver, pancreas, kidney, skin, or brain. These data illustrate the biological heterogeneity of childhood ALL and suggest that the differential risks associated with t(1;19)+/E2A-PBX1+ and t(9;22)+/BCR-ABL ALL might arise from unique engraftment and proliferation capabilities of the respective leukemic cell populations.

Clinical significance of deletions of chromosome arm 6q in childhood acute lymphoblastic leukemia: a report from the Children's Cancer Group.

We have compared outcome for 167 (9.0%) children with a del(6q) and 1713 (91%) children without a del(6q) treated on Children's Cancer Group (CCG) risk-adjusted treatment protocols for acute lymphoblastic leukemia (ALL). Thirty-three patients had a del(6q) as the sole aberration; 22 patients had a del(6q) only as a secondary abnormality. Thirty-six cases had a del(6q) and high hyperdiploidy (>50 chromosomes). Six patients with a del(6q) also had +16 and 8 patients had loss of a sex chromosome. Frequent recurring breakpoints were q13, q15, q21, q23, and q25. Patients with a del(6q) were more likely to have T-lineage ALL (p < 0.001), a mediastinal mass (p = 0.01), and higher WBC counts (p = 0.04), although only half of these patients were classified as poor risk. Event-free survival at 6 years was similar for patients with or without a del(6q), with estimates of 77% (SD = 5%) and 74% (SD = 2%), respectively (p = 0.44). This finding was also observed within NCI poor and standard risk groups. Thus, cytogenetically detectable del(6q) is not associated with adverse risk in pediatric ALL.

Prognostic significance of B-lineage leukemic cell growth in SCID mice: a Children's Cancer Group Study.

Primary leukemic cells isolated from children (N = 681 ) with newly diagnosed B-lineage ALL enrolled on risk-adjusted treatment protocols of the Children's Cancer Group (CCG) were injected via the tail vein into 7-10 week old SCID mice. Leukemic cells from 104 of 681 patients (15.3%) were able to engraft and proliferate in one or more SCID mouse organs. These SCID+ patients were somewhat more likely than SCID patients to be older than 10 years of age (p = 0.03) and have WBC counts >20,000/microL (p = 0.04), but the groups were similar with respect to all other presenting features. Event-free survival (EFS) outcome at 3 years of follow-up was similar for SCID+ patients compared with SCID- patients (79.2%, SD = 5. 1% vs. 84.8%, SD = 2.8%; p = 0.20). Overall survival also was similar between the two groups (p = 0.93). This result was maintained within the subgroups of lower risk (N = 448) and higher risk (N = 233) patients. However, there were trends for poorer outcome among patients whose cells caused overt leukemia in SCID mice and infiltrated either 6 or more organs (p = 0.03), skeletal muscle (p = 0.0003), kidney (p = 0.05), or spleen (p = 0.06). Thus, engraftment of primary leukemic cells in SCID mice was not a significant predictor of outcome for the aggregate population of B-lineage ALL patients, the majority of whom were low risk, treated according to contemporary intensive chemotherapy programs of the CCG. However, development of disseminated overt leukemia and infiltration of SCID mouse skeletal muscle by primary leukemic cells from adjacent bone marrow may reflect a biologically more aggressive disease and identify patients at higher risk for treatment failure.

Poor treatment outcome of Philadelphia chromosome-positive pediatric acute lymphoblastic leukemia despite intensive chemotherapy.

Children with Philadelphia (Ph) chromosome positive (+) acute lymphoblastic leukemia (ALL) represent a subgroup at very high risk for treatment failure. This study included 1322 children enrolled between 1988 and 1994 on CCG risk-adjusted studies for ALL who had centrally reviewed cytogenetic data. Thirty patients had a t(9;22) and are referred to as Ph+; 1292 were Ph-. 23 of these 30 patients were treated on the CCG-1882 high risk ALL protocol. The event-free survival (EFS) outcome in CCG-1882 was significantly worse for Ph+ compared with Ph- patients, with 4-year estimates of 11.3% (SD = 9.8%) and 73.4% (SD = 2.3%), respectively (p < 0.0001).