Long-term outcome after allo-SCT: close follow-up on a large cohort treated with myeloablative regimens

We analyzed the late outcomes of 429 long-term survivors post allogeneic hematopoietic SCT (allo-HSCT) who received transplant in our center between 1981 and 2002, and were free of their primary disease for > or =2 years after allo-HSCT. Late recurrent primary malignancy was found in 58 (13.5%) patients and was the primary cause of late death. A total of 37 (8.6%) patients died of non-relapse causes at a median of 5.5 years (range, 2-15.6 years) post allo-HSCT. The major non-relapse causes of death were chronic GVHD (cGVHD), secondary malignancy and infection. The probabilities of OS and EFS were 85% (95% cumulative incidence (CI) (81-89%)) and 79% (95% CI (74-83%)) at 10 years, respectively. Long-term allo-HSCT survivors were evaluated for late complications (median follow-up, 8.6 years (range, 2.3-22.8 years)). cGVHD was diagnosed in 196 (53.1%) survivors. The endocrine and metabolic complications were hypogonadism in 134 (36.3%) patients, osteopenia/osteoporosis in 90 (24.4%), dyslipidemia in 33 (8.9%), hypothyroidism in 28 (7.6%) and diabetes in 28 (7.6%). Hypertension was diagnosed in 79 (21.4%), renal impairment in 70 (19.0%), depression in 40 (10.8%) and sexual dysfunction in 33 (8.9%) survivors. We conclude that in patients who receive allo-HSCT as treatment for hematological malignancy and who are free of their original disease 2 years post transplant, mortality is low and the probability of durable remission is high. Lifelong surveillance is recommended.

Leukocyte count as a predictor of death during remission induction in acute myeloid leukemia

Acute myeloid leukemia (AML) presenting with a high leukocyte count has been associated with an increase in induction mortality and poor results in a number of other survival measures. However, the level at which an elevated leukocyte count has prognostic significance in AML remains unclear. In this report on a series of 375 adult (non-M3) AML patients undergoing induction chemotherapy at a single institution, leukocyte count analyzed as a continuous variable is shown to be a better predictor of induction death (ID) and overall survival (OS) than a leukocyte count of > or = 100 x 10(9)/L, a value characteristically associated with "hyperleukocytosis" (HL). In this patient cohort, a presenting leukocyte count of > or = 30 x 10(9)/L had high sensitivity and specificity for predicting ID, and both performance status (PS) and leukocyte count more accurately predicted for ID than age. Considering these parameters in newly-diagnosed AML patients may facilitate the development of strategies for reducing induction mortality.

Positive impact of selective outpatient management of high-risk acute myelogenous leukemia on the incidence of septicemia

BACKGROUND

Curative intent chemotherapy for acute myelogenous leukemia (AML) leads to prolonged severe neutropenia, during which patients are highly susceptible to infection. Traditionally these high-risk patients were treated as inpatients. Our center recently implemented a selective ambulatory management policy for AML patients undergoing chemotherapy.

MATERIALS AND METHODS

A retrospective analysis was conducted to assess the occurrence of septicemia in AML patients treated over a 5 years period with curative intent chemotherapy. This review encompasses a change in policy from primarily inpatient care to selective outpatient management coupled with prophylactic antibiotic therapy.

RESULTS

A total of 294 patients, receiving 623 cycles of chemotherapy were identified. A significant decrease in septicemia was observed from the inpatient to outpatient cohort (22% to 13% P < 0.05), which correlated with the shift towards outpatient treatment of consolidation cycles. A shift from Gram-negative to Gram-positive organisms as the cause of septicemia was also detected in the outpatient cohort, likely due to the introduction of ciprofloxacin prophylaxis. No significant emerging resistance and no septicemia-related mortality were noted in the outpatient cohort.

CONCLUSION

The observed decrease in the incidence of septicemia in the ambulatory cohort adds supportive evidence to the feasibility of selective outpatient management of AML patients with respect to infectious complications.

Induction of remission in patients with acute myeloid leukemia without prolonged myelosuppression using diphtheria toxin-interleukin 3 fusion protein

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The recombinant diphtheria toxin fusion protein, DT388IL3, composed of the catalytic and translocation domains of diphtheria toxin (DT388) fused to human interleukin-3 (IL3) showed selective cytotoxicity to acute myeloid leukemia (AML) stem cells both in vitro and in vivo and was prepared for a phase I clinical study (Urieto, Protein Exp Purif 33, 123, 2004). FDA approval (BB IND#11314) and IRB approvals were obtained. Seventy-five AML patients were screened and thirty-one patients treated. The median age of treated patients was 62 years (range, 25- 81 years). There were sixteen males and fifteen females. Disease was de novo in three, first relapse in ten, second relapse in eight, and refractory in ten patients. Four patients had a history of MDS, and one had a history of secondary AML. One patient each had previously received an autologous or allogeneic stem cell transplant. Cytogenetics were unfavorable in ten, intermediate in nineteen, and not done in two. Seven patients were treated with 4 μg/kg, eight patients were treated with 5.3 μg/kg, thirteen patients treated with 7.1 μg/kg, and three patients treated with 9.4 μg/kg DT388IL3. Drug-related toxicities were mild to moderate and transient including fever, chills, hypotension, hypoxemia, and hypoalbuminemia. Consistent with an absence of toxicity to normal hematopoietic progenitors, responses occurred in the absence of prolonged myelosuppression. Among thirty evaluable patients, we have observed one CR of 8 months duration, two partial remissions (PRs) lasting one and three months and three minimal responses with clearance of peripheral blasts and marrow blast cytoreductions of 89%, 90% and 93% lasting one to two months. Dose escalation is proceeding.

No significant financial relationships to disclose.

Primary therapy for adults with T-cell lymphoblastic lymphoma with hematopoietic stem-cell transplantation results in favorable outcomes

BACKGROUND

Controversy exists regarding the role of high-dose therapy followed by stem-cell transplant (SCT) in the treatment of T-cell lymphoblastic lymphoma (T-LBL). We conducted an intention-to-treat analysis of the strategy of SCT as definitive treatment of T-LBL.

PATIENTS AND METHODS

From July 1987 to March 2005, 34 adults with T-LBL were diagnosed and treated in British Columbia. Treatment, before planned SCT, consisted of a non-Hodgkin's lymphoma (NHL)/acute lymphoblastic leukemia hybrid chemotherapy protocol (28 patients) or a standard NHL chemotherapy regimen (six patients).

RESULTS

Median follow-up of the 23 surviving patients is 51 months (range 13-142 months). Twenty-nine proceeded to SCT (four allogeneic, 25 autologous). For all 34 patients, 4-year overall survival (OS) and event-free survival (EFS) are 72% and 68%, respectively. For patients proceeding to SCT, the 4-year OS and EFS are 79% and 73%, respectively. All patients who received allografts are alive without disease at 38-141 months since diagnosis. For patients who received autografts, the 4-year EFS is 69%. Bone marrow involvement was a significant prognostic factor predicting for a worse survival (P = 0.02).

CONCLUSION

A treatment strategy for adults with chemosensitive T-LBL that includes planned consolidation with SCT in first response produces favorable long-term outcome.

Diptheria toxin-interleukin 3 fusion protein therapy of patients with elderly or relapsed/refractory acute myeloid leukemia (AML)

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Background: To target myleoid leukemic stem cells in relapsed/refractory patients, we produced a recombinant protein composed of the catalytic and translocation domains of diphtheria toxin (DT388) fused to human interleukin 3 (IL3). DT388IL3 binds to IL3 receptors on leukemic progenitors; the toxin is internalized and enzymatically inactivates protein synthesis leading to programmed cell death. We prepared a clinical batch of DT388IL3 and obtained FDA approval for a phase I study. Patients and Methods: Relapsed/refractory or elderly (≥70 years) AML patients with normal organ function and low anti-DT antibody titers were consented and given 15 minute infusions of DT388IL3 on a M-W-F for two weeks schedule. Premedication was hydrocortisone, acetaminophen, and diphenhydramine. Inter-patient dose escalation was done. Five patients at 4 ug/kg, 6 patients at 5.32 ug/kg, and 2 patients at 7.07 ug/kg received all 6 planned doses. Results: Eighteen patients have been treated as of 1/06. Median age was 58 years (25–81). There were 9 males and 9 females. One patient had de novo AML; 7 patients were in second relapse; 6 patients were in third relapse and 4 patients had refractory AML. One patient each received an autologous stem cell transplant (SCT), and an allogeneic SCT. Cytogenetics were unfavorable in 3, intermediate in 10 and not done in 5 patients. One patient each had MDS-related AML and treatment-related AML. Drug-related side effects were mild and transient including grade 3 fever, grade 2 hypotension, chills and hypoalbuminemia. Responses seen to date have been transient including a reduction in bone marrow blast index (% cellularity × fraction blasts) of pretreatment 40%, 70%, 36% and 40% converting to 8%, 4%, 4% and 4% on day 15. Conclusions: The preliminary data suggests mild toxicity with biological activity. Dose escalation is planned as per protocol.

No significant financial relationships to disclose.

Shifting to outpatient management of acute myeloid leukemia: a prospective experience

BACKGROUND

We assessed the feasibility of outpatient chemotherapy and supportive care in patients with acute myeloid leukemia (AML).

PATIENTS AND METHODS

All patients receiving curative intent chemotherapy between 09/01 and 10/02 and meeting our criteria received supportive care post induction chemotherapy as well as their entire consolidation chemotherapy cycles as outpatients. Patients received antimicrobial prophylaxis; those developing episodes of fever and not meeting the criteria for admission were treated with outpatient intravenous antibiotics.

RESULTS

Seventy-one cycles of induction chemotherapy were administered for newly diagnosed or relapsed AML. In 25 cycles the patient was discharged post chemotherapy prior to count recovery. Of these, 14 patients developed one or more febrile episodes as an outpatient and nine (36%) required readmission to hospital. Sixty-seven consolidation cycles were given on an outpatient basis. In 39 cycles there was one or more febrile episodes and in 14 (21%) admission was required. Infections were documented in four cases during induction and in 27 during consolidation. There were no treatment-related deaths.

CONCLUSIONS

Outpatient management of AML is safe and feasible using the strategies outlined in this report.

Myeloablative allografting for chronic lymphocytic leukemia: evidence for a potent graft-versus-leukemia effect associated with graft-versus-host disease

In all, 30 patients with CLL proceeded to myeloablative allogeneic BMT using related (n=20, 67%) or unrelated (n=10) donors, at the Princess Margaret Hospital (Toronto) (n=20) or the Leukemia/BMT Program of BC (Vancouver) (n=10), from 1989 to 2001. Median (range) interval from diagnosis to BMT was 4.8 (0.3-13) years, median number of prior therapies was three and median age 48 years. The preparative regimen included total body irradiation in 15 (50%). In all, 14 of 30 patients (47%) are alive, with median (range) follow up of 4.3 (2.4-10.5) years. All are in complete remission, two following therapy for post-BMT progression. Actuarial overall (OS) and event-free survival (EFS) at 5 years is 39% (OS 48% for related donor and 20% for unrelated donor BMT); cumulative incidence of nonrelapse mortality (NRM) and relapse is 47 and 19%, respectively. Both acute (RR=0.008, P=0.01) and chronic (RR=0.006, P=0.02) Graft-versus-host disease (GVHD) were associated with markedly decreased risk of relapse. Patients receiving grafts from unrelated donors had increased NRM (RR=3.6, P=0.02) and decreased OS (RR of death=3.4, P=0.002). Allogeneic BMT has resulted in long-term EFS in approximately 40% of patients with CLL. There is evidence for a strong graft-versus-leukemia effect associated with acute and chronic GVHD, resulting in near complete protection from relapse.

Characteristics and outcome of patients developing endocarditis following hematopoietic stem cell transplantation

Endocarditis is an uncommon complication of hematopoietic stem cell transplantation (HSCT). A retrospective review of 1547 patients who underwent HSCT in Vancouver between January 1986 and December 2001 was performed. In all, 20 cases of endocarditis were identified (1.3% of all patients) with nine patients having received cryopreserved autologous stem cells, six stem cells from a histocompatible sibling and five patients stem cells from an unrelated donor. Five patients had endocarditis diagnosed while alive, a median of 6 months post-HSCT, by transthoracic (four patients) or transesophageal (one patient) echocardiography. The remaining 15 cases of endocarditis were only identified post mortem. The mitral valve was the most frequently involved (10 patients) followed by the aortic valve (six patients); multivalvular disease was noted in five patients. Of the 11 affected allogeneic HSCT patients, 10 had previously developed acute graft-versus-host disease (GVHD). Causative organisms were identified in 11 patients, while nine additional cases were felt to be thrombotic in origin. Of the 20 patients, 19 died with the sole survivor alive 10 years following an aortic valve replacement. Endocarditis is an uncommon complication of HSCT usually involving the cardiac valves on the left side of the heart and is associated with a high mortality rate.

Second malignancy following high-dose therapy and autologous stem cell transplantation: incidence and risk factor analysis

To establish incidence and risk factors for development of second malignant neoplasms after high-dose chemo/radiotherapy (HDT) and autologous hematopoietic stem cell transplantation (AHSCT), the case files of 800 consecutive patients who underwent AHSCT at our institution between June 1982 and December 2000 were reviewed. In all, 26 patients developed 29 second malignancies (nine myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML), 16 solid tumors and four lymphoproliferative disorders (LPDs)) for a 15-year cumulative incidence of 11% (95% confidence interval (CI), 5-18%). These second tumors occurred at a median of 68 (range 1.5-177) months following AHSCT. The relative risk (RR) compared to the general population of developing a second malignancy following AHSCT was 3.3 (CI 2.2-4.7) P<0.001. The RR of developing MDS/AML, LPD and a solid tumor was 47.2 (CI 21.5-89.5) P<0.001, 8.1 (2.2-20.7) P=0.002 and 1.98 (1.1-3.2) P=0.009, respectively. In multivariate analysis, age >or=35 years at the time of AHSCT (P=0.001) and an interval from diagnosis to AHSCT >or=36 months (P=0.03) were associated with a greater risk of developing a second malignancy. Patients who have undergone HDT and AHSCT are at significant risk for developing a second malignancy and should receive indefinite follow-up.

NOD/SCID mice engineered to express human IL-3, GM-CSF and Steel factor constitutively mobilize engrafted human progenitors and compromise human stem cell regeneration

Transplantation of immunodeficient mice with human hematopoietic cells has greatly facilitated studies of the earliest stages of human hematopoiesis. These include demonstration of the ability of injected 'human-specific' hematopoietic growth factors to enhance the production of human cells at multiple levels of differentiation. In contrast, the effects of continuous exposure to such molecules have not been well investigated. Here, we show that nonobese diabetic severe combined immunodeficiency mice genetically engineered to produce ng/ml serum levels of human interleukin-3 (IL-3), granulocyte/macrophage-stimulating factor (GM-CSF) and Steel factor (SF) display a complex phenotype when transplanted with primitive human bone marrow (BM) or fetal liver cells. This phenotype is characterized by an enhancement of terminal human myelopoiesis and a matched suppression of terminal human erythropoiesis, with a slight reduction in human B-lymphopoiesis in the BM of the engrafted mice. Human clonogenic progenitors are more prevalent in the blood of the transplanted growth factor-producing mice and this is accompanied by a very marked reduction of more primitive human cells in the BM. Our findings suggest that long-term exposure of primitive human hematopoietic cells to elevated levels of human IL-3, GM-CSF and SF in vivo may deleteriously affect the stem cell compartment, while expanding terminal myelopoiesis.

Improved engraftment of human acute myeloid leukemia progenitor cells in beta 2-microglobulin-deficient NOD/SCID mice and in NOD/SCID mice transgenic for human growth factors

Primitive malignant progenitors defined as nonobese diabetic/severe combined immunodeficient (NOD/SCID) leukemia-initiating cells or NOD/SL-IC from patients with acute myeloid leukemia (AML) can be detected and quantitated in sublethally irradiated NOD/SCID mice. However, there is variability in the levels of bone marrow (BM) engraftment obtained after intravenous injection of cells from different AML samples. In the current study, AML cell engraftment in standard NOD/SCID mice was compared to that obtained with NOD/SCID mice transgenic for the human growth factor genes Steel factor (SF), interleukin-3 (IL-3) and granulocyte macrophage-colony-stimulating factor (GM-CSF) (N/S-S/GM/3) as well as beta 2 microglobulin-null NOD/SCID (N/S-beta 2m(-/-)) mice. Three of the eight AML samples that failed to engraft in standard NOD/SCID animals showed easily detectable and up to 70-fold increased in the number of leukemic cells in BM 8-12 weeks post-transplantation in each of the N/S-beta 2m(-/-) and N/S-S/GM/3 mouse strains. In two of the four AML samples studied at limiting dilution, the frequency of NOD/SL-IC detected was increased six- and seven-fold. Thus, in these novel mouse strains a broader spectrum of AML patient samples can be evaluated for their progenitor content and potentially studied for their response to innovative therapeutics in vivo.

Diphtheria toxin-interleukin-3 fusion protein (DT(388)IL3) prolongs disease-free survival of leukemic immunocompromised mice

The novel fusion protein DT(388)IL3, composed of the catalytic and translocation domains of diphtheria toxin (DT(388)) fused with a Met-His linker to human interleukin 3 (IL-3), was tested for anti-leukemia efficacy in an in vivo model of differentiated human acute myeloid leukemia (AML). Six-week-old female SCID mice were irradiated with 350 cGy, inoculated 24 h later with 20 million (i.v., i.p., or s.c.) TF1 cells transfected with the v-SRC oncogene, and treated i.p., starting 24 h later, with up to five daily injections of saline, DT(388)IL3 (2 microg), DT(388)GMCSF (2 microg), DAB(389)IL2 (2 microg), or cytarabine (80 microg) or two weekly injections of anti-CD33-calicheamicin conjugate (5 microg). Animals were monitored twice daily, and moribund animals killed and necropsied. Control animals had a median disease-free survival (DFS) of 37 days (i.v., n = 45), 35 days (i.p., n = 20), and 21 days (s.c., n = 20), respectively. Only 5/49 (10%) of the DT(388)IL3 treated i.v. inoculated animals died with leukemia. Median DFS with i.v., i.p. and s.c. tumor inoculated animals was prolonged by fusion protein treatment to >120 days, 66 days and 31 days (P < 0.001, = 0.0003, and = 0.0006), respectively. Median DFS with s.c. tumor inoculated animals was also prolonged by other active anti-leukemia agents (DT(388)GMCSF, cytarabine and anti-CD33-calicheamicin) relative to controls by 67%, 172% and 47% (P < 0.0001, <0.0001, and =0.0004), respectively. In contrast, median DFS with s.c. tumor inoculated animals treated with DAB(389)IL2 non-significantly reduced by 13% relative to controls (P = 0.21). Thus, DT(388)IL3 fusion protein demonstrates in vivo anti-leukemia efficacy and warrants further preclinical development for treatment of chemo-resistant, IL-3 receptor positive AML patients.

Fulminant tumour lysis syndrome in acute myelogenous leukaemia with inv(16)(p13;q22)

Tumour lysis syndrome (TLS) is caused by rapid breakdown of malignant cells resulting in electrolyte disturbances and acute renal failure. TLS has rarely been described in patients with acute myelogenous leukaemia (AML). Between November 1997 and July 2001, 114 consecutive adult AML patients aged <60 yr received induction chemotherapy consisting of cytosine arabinoside 1.5 g m(-2) q 12 h x 12 doses and daunorubicin 45 mg m(-2) d(-1) x 3 doses. During induction chemotherapy (CT), seven patients (6.1%, 95% CI 2.5-12.2) developed fulminant TLS, resulting in acute renal failure; five of these seven patients had inversion of chromosome 16 [inv(16)(p13;q22)], and one patient had a biological equivalent [t(16,16)(p13;q22)]. Four of the TLS patients underwent leukapheresis for a presenting white blood cell (WBC) count > 100 x 10(9) L(-1) prior to commencing chemotherapy, and six patients subsequently required haemodialysis for a median of 2 (range 1-8) wk. One TLS patient died of intracerebral hemorrhage on day 10 and another patient of multiorgan failure on day 17. Of the other five patients, all entered a complete remission (CR) and recovered normal renal function. Four patients remain in continuous CR [median follow-up 20 (range 12-25) months]. One patient relapsed at 12 months and again developed TLS on re-induction. In univariate analysis, TLS patients were more likely to have an elevated presentation and pre-chemotherapy WBC counts, elevated serum creatinine, and uric acid levels at presentation, as well as an inv(16). In multivariate analysis, only serum creatinine and inv(16) remained statistically significant (P < 0.001 for each). Patients with an inv(16) are a unique AML subgroup at high risk for fulminant TLS.

Immunotherapy of acute myeloid leukemia

Most patients with acute myeloid leukemia (AML) respond initially to combination chemotherapy but later relapse. These patients often die from progressive disease or toxicities of further chemotherapy. At relapse, the patients' blasts are usually resistant to the drugs to which the patient has been exposed and frequently to other cytotoxic agents as well. Nevertheless, a number of these patients may be salvaged and achieve remissions with allogeneic stem cell transplants. In such cases, the pre-transplant conditioning regimens do not appear to account for the entire anti-leukemic efficacy. Immunological mechanisms for blast killing appear critical. There is tissue culture, animal and clinical evidence that stimulated donor T cells can recognize and kill leukemic blasts through recognition of alloantigens, differentiation antigens or leukemia-specific antigens as targets. We will review the molecular mechanisms for the generation of anti-leukemic T cells and discuss methods to improve the specificity and intensity of anti-leukemic T cell responses in the setting of allogeneic stem cell transplants, donor lymphocyte infusions, autologous anti-leukemic T cell infusions, and vaccine use in AML patients.

Hoechst 33342 efflux identifies a subpopulation of cytogenetically normal CD34(+)CD38(-) progenitor cells from patients with acute myeloid leukemia

Efflux of Hoechst 33342 from normal hematopoietic cells identifies a "side population" (SP(+)) of negatively staining cells that, in the mouse, are largely CD34(-) and are enriched for primitive progenitors. To further characterize human SP(+) cells, blood or bone marrow from 16 patients with acute myeloid leukemia (AML) was analyzed for their presence, immunophenotype, and cytogenetic and functional properties, and for the relation between SP phenotype and multidrug resistance-1 (MDR-1) expression. The mean percentages of SP(+) and MDR(+) cells was 8.1% (range, 0.5%-29.9%) and 12.8% (range, 0%-54.8%), respectively, with no correlation between the 2 values. The percentages of SP(+) cells that were CD34(+)CD38(-), CD34(+)CD38(+), or CD34(-) were 12% (range, 0.4%-50%), 25% (range, 0.5%-96%), and 63% (range, 4%-99%). Cytogenetically abnormal cells were always detected in the SP(-)CD34(+)CD38(-) and SP(+)CD34(-) fractions, and abnormal colonies (CFC), long-term culture-initiating cells (LTC-IC), and nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mouse leukemia-IC were detected in the former fraction. No progenitors were detected among SP(+)CD34(-) cells in any of these assays from 9 of 10 samples. In contrast, exclusively normal cells were detected in the SP(+)CD34(+)CD38(-) fraction from 9 of 15 samples, and CFC, LTC-IC, and multilineage engraftment in NOD/SCID mice from this subpopulation were also cytogenetically normal in 6 of 8, 6 of 7, and 2 of 2 cases studied, respectively. In contrast to murine studies, primitive progenitors are enriched among SP(+)CD34(+)CD38(-) cells from patients with AML. The molecular basis for Hoechst dye efflux is uncertain because it does not appear to be related to MDR-1 expression. (Blood. 2001;97:3882-3889)

Overexpression of HOXA10 perturbs human lymphomyelopoiesis in vitro and in vivo

Several studies point to multiple members of the Hox transcription factor family as playing key roles in normal hematopoietic development, and they link the imbalanced expression of these transcription factors, in particular of the Abd-like A cluster HOX genes HOXA9 and HOXA10, to leukemogenesis. To test directly the hypothesis that HOXA10 is involved in human hematopoietic development, the gene was retrovirally overexpressed in human highly purified CD34(+)/GFP(+) hematopoietic progenitor cells derived from cord blood or fetal liver sources, and the impact of aberrant gene expression was analyzed on differentiation and proliferation in vitro and in vivo. HOXA10 misexpression profoundly impaired myeloid differentiation with a higher yield of blast cells in liquid culture and a greater than 100-fold increased generation of blast colonies after in vitro expansion or after replating of primary colonies first plated in methylcellulose directly after transduction (P < .01). Furthermore, aberrant HOXA10 expression almost completely blocked erythroid differentiation in methylcellulose (P < .02). HOXA10 deregulation also severely perturbed the differentiation of human progenitors in vivo, reducing B-cell development by 70% in repopulated NOD/SCID mice and enhancing myelopoiesis in the transduced compartment. The data provide evidence that the balanced expression of HOXA10 is pivotal for normal human hematopoietic development and that aberrant expression of the gene contributes to impaired differentiation and increased proliferation of human hematopoietic progenitor cells. These results also provide a framework to initiate more detailed analyses of HOX regulatory domains and HOX cofactors in the human system in vitro and in vivo.

Proliferative status of primitive hematopoietic progenitors from patients with acute myelogenous leukemia (AML)

One possible explanation for the competitive advantage that malignant cells in patients with acute myelogenous leukemia (AML) appear to have over normal hematopoietic elements is that leukemic progenitors proliferate more rapidly than their normal progenitor cell counterparts. To test this hypothesis, an overnight 3H-thymidine (3H-Tdr) suicide assay was used to analyze the proliferative status of malignant progenitors detected in both colony-forming cell (CFC) and long-term culture initiating cell (LTC-IC) assays from the peripheral blood of nine patients with newly diagnosed AML. Culture of AML cells in serum-free medium with 100 ng/ml Steel factor (SF), 20 ng/ml interleukin 3 (IL-3) and 20 ng/ml granulocyte colony-stimulating factor (G-CSF) for 16-24 h maintained the number of AML-CFC and LTC-IC at near input values (mean % input +/- s.d. for CFC and LTC-IC were 78 +/- 33 and 126 +/- 53, respectively). The addition of 20 muCi/ml high specific activity 3H-Tdr to these cultures reduced the numbers of both progenitor cell types from most of the patient samples substantially: mean % kill +/- s.d. for AML-CFC and LTC-IC were 64 +/- 27 and 82 +/- 16, respectively, indicating that a large proportion of both progenitor populations were actively cycling. FISH analysis of colonies from CFC and LTC-IC assays confirmed that most cytogenetically abnormal CFC and LTC-IC were actively cycling (mean % kill +/- s.d.: 68 +/- 26 and 85 +/- 13, respectively). Interestingly, in six patient samples where a significant number of cytogenetically normal LTC-ICs were detected, the % kill of these cells (74 +/- 20) was similar to that of the abnormal progenitors. These data contrast with the predominantly quiescent cell cycle status of CFC and LTC-IC previously observed in steady-state peripheral blood from normal individuals but also provide evidence that a significant proportion of primitive malignant progenitors from AML patients are quiescent and therefore may be resistant to standard chemotherapeutic regimens.

Development of a biologically distinct EBV-related lymphoproliferative disorder following autologous bone marrow transplantation for an EBV-negative post-renal allograft Burkitt's lymphoma

Post-transplant lymphoproliferative disorder (PTLD) is a known complication of both solid organ transplantation and allogeneic bone marrow transplantation (BMT) but is rarely seen following autologous BMT. We report the case of a 45 year-old female who developed Burkitt's lymphoma eight years after a renal allograft. This PTLD was found to have lambda light chain restriction, contained del(8)(q24) and add(14)(q32), and was negative for EBV on immunohistochemical and DNA-based PCR analyses. Immunoglobulin heavy chain (IgH) PCR studies revealed a prominent clonal rearrangement. She responded to intravenous cyclophosphamide and proceeded to high-dose chemoradiotherapy and mafosfamide-purged autologous BMT. Thirty-nine days post-BMT she presented with cough and fever and developed hepatic dysfunction; abnormal lymphoplasmacytoid cells were noted in the peripheral blood. Investigations revealed kappa light chain restriction, an oligoclonal IgH rearrangement, a normal karyotype and PCR studies for EBV were positive, consistent with a clinically and biologically distinct PTLD. She initially improved following discontinuation of immunosuppression, but then deteriorated abruptly and died 58 days post-BMT. It is likely that the two separate episodes of PTLD in this patient, one of which was atypical, arose as a result of both the chronic use of cyclosporine and the impairment of cell-mediated immunity associated with autologous BMT. The sequence of events in this patient should contribute to a better understanding of late-onset, EBV-negative PTLD.

Treatment of steroid-resistant acute graft-versus-host disease with rabbit antithymocyte globulin

Acute graft-versus-host disease (A-GVHD) is a life-threatening complication of allogeneic stem cell transplantation (SCT), and primary therapy consists of high-dose corticosteroids. Patients who fail to respond adequately to corticosteroids require salvage treatment, with anti-T cell antibodies being the most commonly utilized group of agents. We report our institution's experience treating steroid-resistant GVHD in 36 adult patients (median age 39 years, range 24-55) with a rabbit antithymocyte globulin product (thymoglobulin). Eleven patients had undergone sibling SCT (10 histocompatible, 1 one-antigen mismatched) and 25 patients had received unrelated donor bone marrow (17 matched, 8 one-antigen mismatched); 32 patients (89%) had grade III or IV A-GVHD. Thymoglobulin was administered in two different regimens; group 1 patients (n = 13) received 2.5 mg/kg/day x 4-6 consecutive days with maintenance of all other immunosuppressives. Group 2 patients (n = 21) were given the same dose of thymoglobulin on days 1, 3, 5, and 7 with discontinuation of cyclosporine for 14 days, during which the corticosteroid dose was held at 2-3 mg/kg/day. Two patients had severe adverse reactions to thymoglobulin (hypoxemia and hypotension) and could not complete treatment, however, in the other patients, aside from transient leukopenia (25%) and and hepatic dysfunction (25%), the antibody preparation was well tolerated. Of the 34 evaluable patients, 13 patients had a complete response (38%) and 7 patients (21%) had a partial response, for an overall response rate of 59%. Response rate was higher in group 1 patients (77%) compared to group 2 patients (48%), (p = 0.15); skin GVHD was more responsive (96% of patients) than gut GVHD (46% of patients) or hepatic GHVD (36% of patients). Opportunistic infections were a significant complication, with 11 patients developing systemic fungal infections and 9 patients serious viral infections; there were seven episodes of bacteremia following thymoglobulin treatment and one fatal protozoal infection. There were 9 patients (25%) who developed post-SCT lymphoproliferative disorder (PTLD) and 4 patients who had a relapse of underlying primary malignancy; none of these patients survived. Of the 36 patients entered on the study, only 2 patients (6%) survive, at 15+ and 34+ months post-unrelated donor SCT. Although thymoglobulin is associated with an impressive response rate when administered for advanced steroid-resistant GVHD, long-term survival is uncommon, even in responders, primarily due to the high risk of developing either an opportunistic infection or a PTLD.

Diphtheria toxin fused to human interleukin-3 is toxic to blasts from patients with myeloid leukemias

Leukemic blasts from patients with acute phase chronic myeloid leukemic and refractory acute myeloid leukemia are highly resistant to a number of cytotoxic drugs. To overcome multi-drug resistance, we engineered a diphtheria fusion protein by fusing human interleukin-3 (IL3) to a truncated form of diphtheria toxin (DT) with a (G4S)2 linker (L), expressed and purified the recombinant protein, and tested the cytotoxicity of the DTLIL3 molecule on human leukemias and normal progenitors. The DTLIL3 construct was more cytotoxic to interleukin-3 receptor (IL3R) bearing human myeloid leukemia cell lines than receptor-negative cell lines based on assays of cytotoxicity using thymidine incorporation, growth in semi-solid medium and induction of apoptosis. Exposure of mononuclear cells to 680 pM DTLIL3 for 48 h in culture reduced the number of cells capable of forming colonies in semi-solid medium (colony-forming units leukemia) > or =10-fold in 4/11 (36%) patients with myeloid acute phase chronic myeloid leukemia (CML) and 3/9 (33%) patients with acute myeloid leukemia (AML). Normal myeloid progenitors (colony-forming unit granulocyte-macrophage) from five different donors treated and assayed under identical conditions showed intermediate sensitivity with three- to five-fold reductions in colonies. The sensitivity to DTLIL3 of leukemic progenitors from a number of acute phase CML patients suggests that this agent could have therapeutic potential for some patients with this disease.

Allografting for indolent lymphoid neoplasms

BACKGROUND

Allogeneic bone marrow transplantation (BMT) has been used in patients with low-grade lymphoma (LGL) and chronic lymphocytic leukemia (CLL) with the goal of achieving long-term disease-free survival.

PATIENTS AND METHODS

Twenty-nine patients with these diagnoses (LGL = 19, CLL = 10) received allogeneic BMT between September 1995 and January 1999. Median age was 42 (range 20-52) years. Twenty-three of twenty-nine patients (79%) were Ann Arbor or Rai stage IV at the time of transplant; twenty-four (83%) had never achieved complete remission (CR). Donor source was HLA-matched sibling (20), unrelated (8) and syngeneic (1).

RESULTS

Seventeen patients are currently alive, a median of 29 months (range 1-85) post-BMT with a median KPS of 90%. Twenty-three of twenty-seven evaluable patients (85%) achieved CR post-BMT. Six patients had refractory/recurrent disease. Death occurred related to transplant complications in eight patients and underlying disease in four. Overall and event-free survival for the whole group is 51% and 44%, respectively.

CONCLUSIONS

Allogeneic BMT for young patients with advanced stage LGL or CLL is a feasible strategy that can result in achievement of long-term disease-free survival.

Quantitation of primitive and lineage-committed progenitors in mobilized peripheral blood for prediction of platelet recovery post autologous transplant

Leukapheresis collections obtained following one of four mobilization regimens from 90 cancer patients were analyzed for their content of various progenitor cell types including erythroid and granulopoietic colony-forming cells in methylcellulose (total CFC), CFC-megakaryocyte (CFC-Mk), CFC detected after 10, 35 and 56 days in long-term culture (LTC), and total CD34+ cells. The number of each of these progenitor cell types collected from individual patients varied over 1000-fold. Nevertheless, within an individual leukapheresis, there was a significant correlation between the number of CD34+ cells and each progenitor type (except day 56 LTC CFC) suggesting that all of them are mobilized by a common mechanism. Patients who had previously received extensive chemotherapy and/or radiotherapy mobilized fewer of all these cell types than those who had not. For the 65 patients who proceeded to autologous transplantation, the median times to an absolute neutrophil count (ANC) of > or =0.5 x 109/l and the last platelet transfusion post transplant were 13 and 11 days, respectively, with 14 (22%) of patients having platelet recovery delayed beyond day 21. There was no significant difference between patients who had or had not received extensive chemo/radiotherapy or among the different mobilization regimens for time to neutrophil or platelet recovery or the number of platelet or red blood cell transfusions received post transplant. Threshold doses of the different cell types transplanted (per kg of patient weight) which predicted rapid platelet recovery were 2 x 106 CD34+ cells, 5 x 105 total CFC and 2.5 x 104CFC-Mk. Corresponding thresholds for progenitor activity measured in LTC could not be established. These results further support the view that standard mobilization regimens yield progenitor numbers that are, in most cases, nonlimiting for generating neutrophil and platelet recoveries within 2 to 3 weeks after myeloablative therapy. Assessment of the CD34+ cell and/or CFC content of leukapheresis collections may identify patients in whom platelet recovery is likely to be significantly delayed although CFC-Mk enumeration does not appear to offer any unique predictive advantage.

Allogeneic bone marrow transplantation for low-grade lymphoma and chronic lymphocytic leukemia

Twenty-six patients with low-grade lymphoma (LGL) (n = 18) or chronic lymphocytic leukemia (CLL) (n = 8) received allogeneic BMTs between 1985 and 1998. Median age was 42 years, median interval from diagnosis to transplant 22 months and median number of prior treatments three. Twenty (77%) had stage IV disease; 22 (85%) had never achieved CR. Donor source was HLA matched sibling (n = 19, 73%), matched unrelated (n = 6, 23%) or syngeneic (n = 1). Conditioning therapy included total body irradiation in 23 patients and busulphan in three. Twenty-five received GVHD prophylaxis with cyclosporine A; + methotrexate (n = 19), + methylprednisolone (n = 2) or + T cell depletion of allograft +/- methotrexate (n = 4). Sixteen patients are alive, a median of 2.4 years post BMT. Death occurred due to transplant complications (n = 7) or underlying disease (n = 3). Eighteen (12 LGL, six CLL) of 22 evaluable patients (82%) achieved CR post BMT. Cumulative incidence of refractory/recurrent disease was 18% (95% confidence interval (CI) 7-42%). Overall and event-free survivals were 58% (95% CI 35-75%) and 54% (95% CI 32-72%), respectively. Allogeneic BMT for young patients with advanced LGL or CLL is feasible and can result in long-term disease-free survival.

Retroviral marking of acute myelogenous leukemia progenitors that initiate long-term culture and growth in immunodeficient mice

Rare primitive progenitors among the malignant cells from most patients with AML include AML long-term culture-initiating cells (AML LTC-IC) and NOD/SCID mouse leukemia-initiating cells (NOD/SL-IC). To evaluate the feasibility of genetic modification of these progenitors for gene marking and/ or gene therapy strategies, cells from patients with newly-diagnosed AML were cocultured with retroviral producer cells and then placed in colony (AML-CFC) assays, LTC, and injected intravenously into NOD/SCID mice. Southern blotting demonstrated transfer of the neo(r) gene to 30% to 80% of leukemic blasts when cells were cultured for 48 hours in the presence of IL-3 and steel factor (SF) prior to 48-hour coculture with viral producers. Three of six retrovirally-infected AML samples showed both engraftment in NOD/SCID mice and the presence of the neo(r) transgene in mouse tissues 8-15 weeks after injection of transduced cells. Thirteen weeks after injection of one of these samples, >80% of cells from mouse bone marrow were the progeny of two retrovirally-transduced AML progenitors. Four of the remaining five samples showed markedly reduced ability to engraft in mice after retroviral infection. Subsequent experiments demonstrated that the loss of engraftment potential took place within 24 hours of culture initiation in the absence of retroviral producers and regardless of the cytokines present. Interestingly, the majority of AML-CFC or AML LTC-IC survived the 24-hour culture period. A retroviral vector containing the murine cell surface marker heat stable antigen (HSA), which allows purification of transduced cells on immunomagnetic columns, was used to obtain an enriched population of gene-modified AML cells following an infection protocol that eliminated the 48 hours of prestimulation in IL-3 and SF and reduced coculture with viral producers to 10-36 hours. These modifications failed to improve engraftment of the infected cells. In addition, in these experiments more than 10 hours of cocultivation with viral producer cells was necessary to achieve gene transfer and expression in AML LTC-IC. These data demonstrate that although retroviral-mediated gene transfer can be achieved to AML progenitors, including NOD/SL-IC, improved culture conditions will be required before substantial numbers of such transduced primitive progenitors can be obtained. In addition, the difference in the ability of AML LTC-IC and NOD/SL-IC to survive ex vivo suggests that these assays may detect different populations of cells or that changes are induced in vitro in primitive cells which can only be detected in the mouse assay.

Growth characteristics of acute myelogenous leukemia progenitors that initiate malignant hematopoiesis in nonobese diabetic/severe combined immunodeficient mice

The use of immunodeficient mice, particularly of the nonobese diabetic/severe combined immunodeficient (NOD/SCID) strain, has allowed detection of very primitive malignant progenitors from patients with acute myelogenous leukemia (AML). To define the sensitivity and reproducibility with which the engraftment of different AML cells can be detected, 61 different samples from patients with newly diagnosed AML representing a variety of cytogenetic and French-American-British (FAB) subtypes were injected into NOD/SCID mice. Eight weeks after intravenous injection of 10(7) AML cells, the average percent of human cells in mouse bone marrow was 13.3%, with 70% of samples showing easily detectable engraftment of CD45(+) cells. AML samples with cytogenetic changes associated with a poor clinical prognosis tended to engraft to higher levels than those with changes associated with a good prognosis. Cells with FAB subtypes M3 and, to a lesser extent, M2, engrafted more poorly (P =.002 and.06, respectively) than those from other subtypes. Intraperitoneal injection of human interleukin-3 and Steel factor thrice weekly for 4 weeks did not enhance the levels of AML cell engraftment. However, AML samples that showed cytokine-independent colony growth in methylcellulose assay or expressed growth-factor mRNA in malignant blasts achieved significantly higher levels of engraftment than those which were cytokine dependent in culture or failed to express cytokine message (P <.03 and P <.02, respectively). In 6 patient samples, the frequency of NOD/SCID leukemia-initiating cells (NOD/SL-IC) varied from 0.7 to 45 per 10(7) cells, which was 200- to 800-fold lower than the frequency of AML long-term culture-initiating cells (AML LTC-IC) in the same samples. Each NOD/SL-IC will produce more than 10(6) leukemic blasts as well as many AML-CFC and AML LTC-IC as detected 8 weeks postinjection into mice. Serial transplant experiments showed the ability of NOD/SL-IC to maintain their own numbers over at least 3 to 4 weeks in vivo. The ability of these progenitors to self-renew combined with their potential to differentiate to produce large numbers of more mature progenitors and leukemic blasts suggests that the NOD/SL-IC assay identifies leukemic 'stem cells' that may maintain the malignant clone in human patients. The further use of this assay should facilitate studies of AML stem cell biology and the evolution of novel therapeutic strategies.

Expression of HOX genes, HOX cofactors, and MLL in phenotypically and functionally defined subpopulations of leukemic and normal human hematopoietic cells

To explore the possibility that deregulated HOX gene expression might commonly occur during leukemic hematopoiesis, we compared the relative levels of expression of these and related genes in phenotypically and functionally defined subpopulations of AML blasts and normal hematopoietic cells. Initially, a semi-quantitative RT-PCR technique was used to amplify total cDNA from total leukemic blast cell populations from 20 AML patients and light density cells from four normal bone marrows. Expression of HOX genes (A9, A10, B3 and B4), MEIS1 and MLL was easily detected in the majority of AML samples with the exception of two samples from patients with AML subtype M3 (which expressed only MLL). Low levels of HOXA9 and A10 but not B3 or B4 were seen in normal marrow while MLL was easily detected. PBX1a was difficult to detect in any AML sample but was seen in three of four normal marrows. Cells from nine AML patients and five normal bone marrows were FACS-sorted into CD34+CD38-, CD34+CD38+ and CD34-subpopulations, analyzed for their functional properties in long-term culture (LTC) and colony assays, and for gene expression using RT-PCR. 93 +/- 14% of AML LTC-initiating cells, 92 +/- 14% AML colony-forming cells, and >99% of normal LTC-IC and CFC were CD34+. The relative level of expression of the four HOX genes in amplified cDNA from CD34- as compared to CD34+CD38- normal cells was reduced >10-fold. However, in AML samples this down-regulation in HOX expression in CD34- as compared to CD34+CD38- cells was not seen (P < 0.05 for comparison between AML and normal). A similar difference between normal and AML subpopulations was seen when the relative levels of expression of MEIS1, and to a lesser extent MLL, were compared in CD34+ and CD34- cells (P < 0.05). In contrast, while some evidence of down-regulation of PBX1a was found in comparing CD34- to CD34+ normal cells it was difficult to detect expression of this gene in any subpopulation from most AML samples. Thus, the down-regulation of HOX, MEIS1 and to some extent MLL which occurs with normal hematopoietic differentiation is not seen in AML cells with similar functional and phenotypic properties.

Most acute myeloid leukemia progenitor cells with long-term proliferative ability in vitro and in vivo have the phenotype CD34(+)/CD71(-)/HLA-DR-

Acute myeloid leukemia (AML) occurs as the result of malignant transformation in a hematopoietic progenitor cell, which proliferates to form an accumulation of AML blasts. Only a minority of these AML cells are capable of proliferation in vitro, suggesting that AML cells may be organized in a hierarchy, with only the most primitive of these cells capable of maintaining the leukemic clone. To further investigate this hypothesis, we have evaluated a strategy for purifying these primitive cells based on surface antigen expression. As an in vitro endpoint, we have determined the phenotype of AML progenitor cells which are capable of producing AML colony-forming cells (CFU) for up to 8 weeks in suspension culture (SC) and compared the phenotype with that of cells which reproduce AML in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. AML cells were fluorescence-activated cell sorted (FACS) for coexpression of CD34 and CD71, CD38, and/or HLA-DR and the subfractions were assayed in vitro and in vivo at various cell doses to estimate purification. While the majority of primary AML CFU lacked expression of CD34, most cells capable of producing CFU after 2 to 8 weeks in SC were CD34(+)/CD71(-). HLA-DR expression was heterogeneous on cells producing CFU after 2 to 4 weeks. However, after 6 to 8 weeks in SC, the majority of CFU were derived from CD34(+)/HLA-DR- cells. Similarly, the majority of cells capable of long-term CFU production from SC were CD34(+)/CD38(-). Most cells that were capable of engrafting NOD/SCID mice were also CD34(+)/CD71(-) and CD34(+)/HLA-DR-. Engraftment was not achieved with CD34(+)/CD71(+) or HLA-DR+ subfractions, however, in two patients, both the CD34(+) and CD34(-) subfractions were capable of engrafting the NOD/SCID mice. A three-color sorting strategy combining these antigens allowed approximately a 2-log purification of these NOD/SCID leukemia initiating cells, with engraftment achieved using as few as 400 cells in one experiment. Phenotyping studies suggest even higher purification could be achieved by combining lack of CD38 expression with the CD34(+)/CD71(-) or CD34(+)/HLA DR- phenotype. These results suggest that most AML cells capable of long-term proliferation in vitro and in vivo share the CD34(+)/CD71(-)/HLA-DR- phenotype with normal stem cells. Our data suggests that in this group of patients the leukemic transformation has occurred in a primitive progenitor, as defined by phenotype, with some degree of subsequent differentiation as defined by functional assays.

Bone marrow transplantation for adults with acute leukaemia and 11q23 chromosomal abnormalities

Adults with acute leukaemia and abnormalities of chromosome 11q23 have a poor prognosis when treated with conventional chemotherapy. To determine whether more intensive therapy can improve outcome for patients with this karyotypic finding, a retrospective analysis of all patients with acute leukaemia and 11q23 abnormalities treated at our centre was performed. 12 patients were treated with conventional chemotherapy alone (CC); 20 patients received high-dose chemo/radiotherapy (HDCT) with autologous (seven patients) or allogeneic (13 patients) bone marrow transplantation (BMT). The treatment-related mortality was 25% [95% Confidence Interval (CI) 7-69%] for the CC group and 46% (CI 25-73%) for the BMT group (P = 0.69). Cumulative risk of leukaemia progression was 89% (CI 61-100%) in the CC patients and 38% (CI 12-69%) in the BMT patients (P = 0.001). The 2-year event-free survival for patients treated with CC was 8% (CI 0-31%) and for patients receiving HDCT and BMT was 34% (CI 14-54%) (P = 0.03). These results confirm that conventional chemotherapy is rarely curative for adults with acute leukaemia and 11q23 abnormalities but that HDCT with BMT can result in long-term survival in a significant proportion of patients.

Lymphoproliferative disorders following allogeneic bone marrow transplantation: the Vancouver experience

Between June 1988 and May 1996, 428 patients underwent allogeneic BMT (288 related donor (RD) and 140 unrelated donor (UD)) at the Vancouver General Hospital. Eight patients (UD six and RD two) developed a post-transplant lymphoproliferative disorder (PTLD). Median age at BMT was 38 years (range 22-51). Five of the six UD allografts were T cell depleted. Cyclosporine+/-methotrexate was used for GVHD prophylaxis. All eight patients developed GVHD; in six this was refractory to treatment with corticosteroids. Rabbit antithymocyte globulin (ATG) or an anti-CD5-ricin A chain immunotoxin (Xomazyme) was used as second-line therapy for GVHD. Presentation with PTLD occurred at median day 90.5 (range 34-282) post BMT. Five of the eight patients had a rapidly progressive course characterized by fever, lymphadenopathy, lung and liver involvement and died within 3-8 days. PTLD was an incidental finding at post mortem examination in two patients. The remaining patient had localized disease and recovered. Pathological analysis revealed two morphological patterns; diffuse large B cell lymphoma (DLBC lymphoma, five patients) and polymorphous B cell hyperplasia (PBCH, three patients). EBV expression was positive in all eight cases and monoclonality was demonstrated in seven cases. In multivariate analysis, T cell depletion of the allograft (P=0.0001, relative risk (RR)=30.5), anti-T cell therapy for GVHD (P=0.006, RR=12.7) and acute GVHD grades 3-4 (P=0.04, RR=7.7) were the significant factors for development of PTLD. In conclusion, we have identified two forms of PTLD after BMT: one is characterized by disseminated disease with a rapidly progressive and often fulminant course and the other by localized, relatively indolent disease. Morphology, EBV positivity and clonality do not appear to correlate with the clinical course. The major risk factors for development of PTLD after BMT are ex vivo T cell depletion of the allograft and in vivo anti-T cell therapy for GVHD.

Cytogenetic abnormalities in primary myelodysplastic syndrome are highly predictive of outcome after allogeneic bone marrow transplantation

Allogeneic bone marrow transplantation (BMT) is the only curative therapy available for patients with myelodysplastic syndrome (MDS). In an attempt to identify prognostic factors influencing outcome, we collected data retrospectively on 60 consecutive adult patients who had undergone BMT at our center for primary MDS or acute myelogenous leukemia evolving from preexisting primary MDS (sAML). Patients were divided into subgroups according to cytogenetic abnormalities based on a recently described International MDS Workshop categorization system. The 7-year actuarial event-free survival (EFS), relapse rate, and nonrelapse mortality (NRM) for all patients were 29% (95% confidence interval [CI], 16% to 43%), 42% (CI, 24% to 67%), and 50% (CI, 37% to 64%), respectively. The EFS for the good-, intermediate-, and poor-risk cytogenetic subgroups were 51% (CI, 30% to 69%), 40% (CI, 16% to 63%), and 6% (CI, 0% to 24%), respectively (P = .003). The corresponding actuarial relapse rates were 19% (CI, 6% to 49%), 12% (CI, 2% to 61%), and 82% (CI, 48% to 99%), respectively (P = . 002) with no difference in NRM between the subgroups. Univariate analysis showed cytogenetic category, French-American-British (FAB) subtype, and graft-versus-host disease (GVHD) prophylaxis used to be predictive of relapse and EFS. In multivariate analysis, only the cytogenetic category was predictive of EFS, with the relative risk of treatment failure for the good-, intermediate-, and poor-risk cytogenetic subgroups being 1.0, 1.5, and 3.5, respectively (P = . 004). For adults with primary MDS and sAML, even after BMT, poor-risk cytogenetics are predictive of an unfavorable outcome; novel treatment strategies will be required to improve results with allogeneic BMT in this patient population.

High incidence of extramedullary relapse of AML after busulfan/cyclophosphamide conditioning and allogeneic stem cell transplantation

While allogeneic stem cell transplantation (SCT) is curative for a significant number of patients with AML, relapse of disease within the bone marrow and/or extramedullary (EM) sites following high-dose therapy continues to limit the success of this treatment. Between October 1985 and December 1996, 81 adults underwent allogeneic SCT for de novo AML at our centre. Forty-two patients remain alive and free of leukaemia with a median follow-up of 50 months. The 5-year actuarial event-free survivals (EFS) for all patients and for those undergoing SCT in CR1 or with advanced disease were 46% (95% confidence interval (CI) 34-58%), 63% (CI 46-76%), and 19% (CI 7-36%), respectively. Twenty-two patients relapsed at a median of 8 (range 1.6-54.5) months with the actuarial risk of relapse for all, CR1 and advanced disease patients being 38%, (CI 27-52%), 23% (CI 13-40%) and 68% (CI 46-88%), respectively. Ten patients relapsed at EM sites; six of these (27% of relapses) had an isolated EM relapse at a median of 31 (range 8.5-54) months. Three of the patients with isolated EM relapse survived > or =24 months following relapse and two patients remain disease-free at 29+ and 33+ months. BuCy conditioning followed by allogeneic SCT in AML results in satisfactory EFS although there is a significant risk of late isolated EM relapse.

Malignant progenitors from patients with acute myelogenous leukemia are sensitive to a diphtheria toxin-granulocyte-macrophage colony-stimulating factor fusion protein

We have previously demonstrated that human granulocyte-macrophage colony-stimulating factor (GM-CSF) fused to a truncated diphtheria toxin (DT388-GMCSF) kills acute myelogenous leukemia (AML) cell lines bearing the GM-CSF receptor. We now report that exposure of malignant cells from 50 different patients with AML for 48 hours in culture to DT388-GMCSF reduces by a median of 1.6 logs (range, 0 to 3.7 logs) the number of leukemic cells capable of forming colonies in semisolid media (leukemic colony-forming cells [CFU-L]) with a median IC50 of 3 x 10(-12) mol/L (range, 5 to >4,000 x 10(-12) mol/L). Furthermore, the cell kill is dependent on the presence of high-affinity GM-CSF receptors on leukemic blasts, because CFU-L from 27 of 28 AML samples expressing > or = 35 GM-CSF receptors per cell were inhibited by the toxin, whereas the colony growth from all 4 leukemic samples (2 AML, 1 acute lymphoblastic leukemia [ALL], and 1 prolymphocytic leukemia [PLL]) that had less than 35 receptors per cell was unaffected by the drug. Sensitivity of CFU-L to DT388-GMCSF was seen regardless of the clinical responsiveness of the patient's leukemia to standard chemotherapy agents. In contrast, clonogenic cells from normal bone marrow formed colonies at near control numbers after exposure to much higher toxin concentrations (4 x 10(-9) mol/L) than those required to kill CFU-L from most patients. Thus, leukemic progenitors isolated directly from the peripheral blood of most AML patients show the same sensitivity to DT388-GMCSF as previously demonstrated for AML cell lines. Under the same conditions of exposure, normal hematopoietic progenitors are relatively unaffected by DT388-GMCSF, suggesting its potential as a therapeutic agent in AML.

Cytokine responsiveness of primitive progenitors in acute myelogenous leukemia

Long-term cultures (LTC) and immunodeficient (NOD/SCID) mice have been used to quantitate and characterize primitive malignant progenitors from patients with acute myelogenous leukemia (AML). In 5-week-old LTC of cells from newly diagnosed patients with AML cytogenetically abnormal as well as normal progenitors could be easily detected and their numbers increased by cytokine supplements to the cultures. Sixty percent of AML samples will engraft in NOD/SCID mouse marrow. The frequency and level of engraftment of human cells detected appears to vary among the different subtypes of AML but is not generally affected by treatment of the mice with human cytokines. Both the LTC and NOD/SCID mouse assay show promise as tools to allow characterization of differences between leukemic stem cells which maintain malignant hematopoiesis in individual patients and, more importantly, between these cells and their normal stem cell counterparts.

Detection and characterization of primitive malignant and normal progenitors in patients with acute myelogenous leukemia using long-term coculture with supportive feeder layers and cytokines

Analysis of the mitogenic activity of interleukin-3 (IL-3), Steel factor (SF), and flt-3 ligand (FL) on acute myelogenous leukemia (AML) blasts using the short-term endpoints of proliferation in 3H-thymidine (3H-Tdr) incorporation assays or methylcellulose cultures (colony assays) showed that greater than 90% of samples contained cells that were responsive to one or more of these cytokines. With this information, culture conditions that were known to support normal long-term culture-initiating cells (LTC-IC) were tested, with or without supplements of one or more of these three growth factors, for their ability to support primitive progenitors from 10 cell samples from patients with AML. In all cases cytogenetically abnormal colony forming cells (CFC) were detected after 5 weeks when AML peripheral blood or marrow cells were cocultured on preestablished, normal human marrow feeders (HMF) and/or SI/SI mouse fibroblast feeders and the number of CFC detected in these 5-week-old LTC maintained a linear relationship to the number of input AML cells. Limiting dilution analysis, performed on 6 of the 10 samples, showed the frequency of AML cells initiating LTC (AML LTC-IC) to be 5- to 300-fold lower than the frequency of AML-CFC in the same cell sample, whereas the average number of CFC produced per LTC-IC varied from 1 to 13. Surprisingly, in each case the concentration of cytogenetically normal LTC-IC detected in AML patient blood was at least 10-fold higher than that previously observed in the blood of normal individuals. "Mixed" mouse fibroblast feeders engineered to produce human G-CSF, IL-3, and SF did not enhance detection of AML LTC-IC but did increase the output of cytogenetically normal CFC from LTC of 3 of 4 patient samples. Supplementation of AML LTC with IL-3 and exogenously provided SF and/or FL increased the output of AML-CFC from 5-week-old LTC by greater than or equal to twofold with 5 of 9 patient samples, whereas in one case exogenous addition of FL reduced the output of malignant CFC from LTC. These studies show that conditions that support normal LTC-IC also allow a functionally analogous but rare AML progenitor cell type to be detected. In addition, differences in the responses of normal and leukemic cells to various cytokines active on normal LTC-IC were revealed. Further analysis of these differences may enhance our understanding of leukemogenesis and lead to observations that could be exploited therapeutically.

Sustained proliferation, multi-lineage differentiation and maintenance of primitive human haemopoietic cells in NOD/SCID mice transplanted with human cord blood

Time course studies of sublethally irradiated non-obese mice with severe combined immunodeficiency (NOD/ SCID mice) transplanted intravenously with 10(7) human cord blood cells showed a rapid and parallel regeneration of human erythroid, granulopoietic, megakaryopoietic and B-lymphoid progenitors, as well as more primitive subpopulations of CD34+ cells (defined by their multi-lineage in vitro colony-forming ability, coexpression of Thy-1, or functional activity in long-term culture-initiating cell [LTC-IC] assays), in the marrow, spleen and blood. Maximum numbers of human cells were reached within 6 weeks and were then sustained for another 18-20 weeks. 3H-thymidine suicide studies showed all types of in vitro clonogenic human progenitors tested and the human LTC-IC to be proliferating in vitro throughout this period. A 2-week course of injections of human Steel factor, interleukin-3, granulocyte-macrophage colony-stimulating factor and erythropoietin given just prior to assessment of the mice had no effect on any of these human engraftment parameters. 4-6 weeks post-transplant, the marrow of primary NOD/SCID recipients contained human cells that were able to regenerate lymphopoiesis and/or myelopoiesis in secondary irradiated NOD/SCID mice. These findings establish a baseline for the kinetics of engraftment, multi-lineage differentiation and self-renewal of human cord blood stem cells in this xenogeneic transplant model and thus set the stage for future studies of their regulation in vivo.

Lack of expression of Thy-1 (CD90) on acute myeloid leukemia cells with long-term proliferative ability in vitro and in vivo

Acute myeloid leukaemia (AML) is thought to be maintained by a small population of leukemic progenitor cells. To define the phenotype of such cells with long-term proliferative capacity in vitro and in vivo, we have used the production of leukemic clonogenic cells (CFU) after 2 to 8 weeks in suspension culture as a measure of these cells in vitro and compared their phenotype with that of cells capable of engrafting nonobese diabetic severe combined immune deficient (NOD/SCID) mice. Leukemic blast peripheral blood cells were evaluated for expression of CD34 and Thy-1 (CD90) antigens. The majority of AML blast cells at diagnosis lacked expression of Thy-1. Most primary CFU-blast and the CFU detected at up to 8 weeks from suspension cultures were CD34+/Thy-1-. AML cells that were capable of engrafting NOD/SCID mice were also found to have the CD34+/Thy-1- phenotype. However, significant engraftment was achieved using both CD34+/Thy-1- and CD34- subfractions from one AML M5 patient. These results suggest that while heterogeneity exists between individual patients, the leukemic progenitor cells that are capable of maintaining the disease in vitro and in vivo differ from normal hematopoietic progenitor cells in their lack of expression of Thy-1.

Enhanced detection, maintenance, and differentiation of primitive human hematopoietic cells in cultures containing murine fibroblasts engineered to produce human steel factor, interleukin-3, and granulocyte colony-stimulating factor

To determine whether the sensitivity of the human long-term culture-initiating cell (LTC-IC) assay could be increased, we have evaluated a spectrum of different fibroblast cell lines for their abilities to influence the number of cells detectable as LTC-IC, to influence LTC-IC maintenance, and/or to influence LTC-IC differentiation into colony-forming cells (CFC) in cocultures containing various sources of LTC-IC. In a series of initial experiments with highly purified subpopulations of CD34+ cells from normal human marrow, no significant difference could be found between any of 3 different murine stromal fibroblast cells in terms of their support of either LTC-IC detection (CFC production) or maintenance (over a 6-week period), and all were equivalent to primary human marrow feeders (HMF). On the other hand, murine M2-10B4 fibroblasts engineered to produce high levels of both human granulocyte colony-stimulating factor (G-CSF) and interleukin-3 (IL-3; 190 and 4 ng/mL, respectively), either alone or mixed 1:1 with SI/SI fibroblasts engineered to produce high levels of soluble Steel factor (SF), with or without production of the transmembrane form of SF (60 and 4 ng/ mL, respectively), stimulated the production of up to 20-fold more CFC in LTC of cells from normal human marrow, G-CSF-mobilized blood or cord blood when compared with parallel cocultures containing HMF. Limiting dilution analysis of the CFC output from all three sources of LTC-IC showed that most of this increase was due to an ability of the engineered feeders to increase the plating efficiency of the LTC-IC assay (approximately 14-fold for marrow LTC-IC and approximately 4-fold for cord blood or mobilized blood LTC-IC). Analysis of the phenotype of these additionally recruited LTC-IC from marrow showed they had the same primitive CD34+CD45RA-CD71- phenotype as conventionally defined LTC-IC. The limiting dilution studies also showed that the average number of CFC produced per LTC-IC was additionally and independently increased to yield values of 18 CFC per LTC-IC in marrow, 28 for LTC-IC in cord blood, and 25 for LTC-IC in G-CSF-mobilized blood. Replating of cells from primary LTC with different feeders into secondary LTC-IC assays containing the best combination of engineered feeders showed that LTC-IC maintenance could be significantly enhanced (up to 7-fold as compared with primary cocultures containing HMF). However, this enhancement was still not sufficient to amplify the number of LTC-IC present after 6 weeks above the input value. Thus, engineering murine fibroblasts to produce sufficient SF, G-CSF, and IL-3 can markedly enhance the detection as well as the maintenance in vitro of a very primitive population of human progenitor cells present in normal adult marrow, mobilized blood, and cord blood by providing the most sensitive assay conditions thus far described. The present findings also provide new evidence of biologic heterogeneity between different cell populations that can be operationally identified as LTC-IC, thus re-emphasizing the importance of limiting dilution analyses to distinguish between quantitative and qualitative effects on these cells.

Self-renewal of primitive human hematopoietic cells (long-term-culture-initiating cells) in vitro and their expansion in defined medium

A major goal of experimental and clinical hematology is the identification of mechanisms and conditions that support the expansion of transplantable hematopoietic stem cells. In normal marrow, such cells appear to be identical to (or represent a subset of) a population referred to as long-term-culture-initiating cells (LTC-ICs) so-named because of their ability to produce colony-forming cell (CFC) progeny for > or = 5 weeks when cocultured with stromal fibroblasts. Some expansion of LTC-ICs in vitro has recently been described, but identification of the factors required and whether LTC-IC self-renewal divisions are involved have remained unresolved issues. To address these issues, we examined the maintenance and/or generation of LTC-ICs from single CD34+ CD38- cells cultured for variable periods under different culture conditions. Analysis of the progeny obtained from cultures containing a feeder layer of murine fibroblasts engineered to produce steel factor, interleukin (IL)-3, and granulocyte colony-stimulating factor showed that approximately 20% of the input LTC-ICs (representing approximately 2% of the original CD34+ CD38- cells) executed self-renewal divisions within a 6-week period. Incubation of the same CD34+ CD38- starting populations as single cells in a defined (serum free) liquid medium supplemented with Flt-3 ligand, steel factor, IL-3, IL-6, granulocyte colony-stimulating factor, and nerve growth factor resulted in the proliferation of initial cells to produce clones of from 4 to 1000 cells within 10 days, approximately 40% of which included > or = 1 LTC-IC. In contrast, in similar cultures containing methylcellulose, input LTC-ICs appeared to persist but not divide. Overall the LTC-IC expansion in the liquid cultures was 30-fold in the first 10 days and 50-fold by the end of another 1-3 weeks. Documentation of human LTC-IC self-renewal in vitro and identification of defined conditions that permit their extensive and rapid amplification should facilitate analysis of the molecular mechanisms underlying these processes and their exploitation for a variety of therapeutic applications.

Platelet refractoriness and alloimmunization in pediatric oncology and bone marrow transplant patients

BACKGROUND

The purposes of this study were to determine the overall incidence of platelet refractoriness and alloimmunization among multiply transfused children on a medical oncology and bone marrow transplant service and to evaluate the effect of routine white cell reduction in blood components on that incidence.

STUDY DESIGN AND METHODS

The platelet transfusion records of 128 consecutive children admitted to the hospital and requiring blood component support for the treatment of disease were evaluated retrospectively. Mean corrected count increments (CCIs) for each patient were calculated for all random-donor platelet transfusions given within 7 days of the routine weekly testings of the patient's serum for lymphocytotoxic antibodies (LCTAbs). Mean CCIs for HLA-matched platelet transfusions were calculated separately for the patients receiving them.

RESULTS

Thirty-one patients (24%) had or developed persistently positive LCTAbs (patient's serum reacted with > or = 3/10 panel lymphocytes); 22 (71%) of these patients had a mean CCI < 7.5 to random-donor platelet transfusions. In contrast, of the 97 patients with negative or transiently positive LCTAbs, only 25 (26%) had a mean CCI < 7.5. The overall incidence of platelet refractoriness (CCI < 7.5) was 37 percent. Patients with acute myelogenous leukemia had a significantly (p < 0.01) reduced incidence (17%) of low CCIs, with or without positive LCTAbs, as compared to patients with other malignant or nonmalignant disorders (41%). No difference in the incidence of LCTAbs or low CCIs was seen in patients undergoing allogeneic or autologous bone marrow transplant or receiving drug therapy only. Among the 24 patients who received HLA-matched platelets, only those with positive LCTAbs showed a significant improvement in CCIs over that achieved with random-donor platelet transfusions. Routine white cell reduction in red cell and platelet components with third-generation white cell filters was performed prior to transfusion in 73 of the patients. There was no significant difference between the incidence of LCTAbs and/or low CCIs in this group and that in the 55 children receiving unfiltered transfusions.

CONCLUSION

Alloimmunization and platelet refractoriness occur in pediatric oncology and bone marrow transplant patients, but the incidence--particularly in children with acute myelogenous leukemia--appears to be low. The detection of LCTAbs predicts a poor response to random-donor platelet transfusion, but most such patients show improved CCIs with HLA-matched platelets. Routine use of white cell-reduction filters has thus far failed to eliminate alloimmunization in children requiring prolonged blood component support.

High-dose cyclophosphamide, carmustine (BCNU), and etoposide (VP16-213) with or without cisplatin (CBV +/- P) and autologous transplantation for patients with Hodgkin's disease who fail to enter a complete remission after combination chemotherapy

Patients with Hodgkin's disease (HD) who fail to enter a complete remission after an initial course of combination chemotherapy are usually considered to have an induction failure (IF); this subset of patients has an extremely poor outcome with further conventional therapy. Since 1985, we have entered 30 IF patients into protocols using conditioning with high-dose cyclophosphamide, carmustine (BCNU), and etoposide (VP16-213) with or without cisplatin (CBV +/- P) followed by autologous stem cell transplantation (ASCT) with bone marrow (19 patients), peripheral blood stem cells (PBSCs; 8 patients), or both (3 patients). All except 2 patients had previously received chemotherapy regimens for HD that contained at least 7 drugs, and 9 had received prior radiotherapy (RT). After documentation of IF, the majority of patients received some cytoreductive therapy as specified by protocol (local RT in 9, two cycles of conventional chemotherapy in 2, both modalities in 2, or high-dose cyclophosphamide to enhance PBSC collection in 11) before CBV +/- P. Five treatment-related deaths occurred, all before day 150 posttransplant. Eleven patients have had progressive HD at a median of 6 months (range, 0.1 to 45 months) after ASCT. The actuarial progression-free survival (PFS) at a median follow-up of 3.6 years (range, 0.2 to 8.2 years) is 42% (95% confidence intervals, 21% to 61%). The statistical analysis identified only prior clinical bleomycin lung toxicity as an adverse risk factor for PFS, mainly because of the increased nonrelapse mortality seen in these patients. CBV +/- P and ASCT can produce durable remission in a substantial proportion of IF HD patients who otherwise have a poor survival, and we believed ASCT approaches represent the best therapy currently available for these patients. Additional measures are needed to reduce the primary problem of disease progression despite high-dose chemotherapy and stem cell transplantation.

Quantitation, mobilization, and clinical use of long-term culture-initiating cells in blood cell autografts

Mobilized peripheral blood is increasingly used as a source of cells to provide hematopoietic reconstitution in marrow ablated patients. There is controversy as to how the engraftment potential of these preparations should be evaluated. The long-term culture-initiating cell is a very primitive hematopoietic with unique phenotypic feature. The potential role and significance of these cells in peripheral blood cell autografts is discussed.

Differential expression of homeobox genes in functionally distinct CD34+ subpopulations of human bone marrow cells

Class I homeobox (Hox) genes encode a major group of transcription factors controlling embryonic development and have been implicated in the continuing process of hematopoietic cell differentiation. They are clustered on four chromosomes and, in early development, exhibit spatially restricted expression with respect to their 3'-->5' chromosomal position. By using an improved PCR-based method for amplifying total cDNA derived from limited cell numbers, we now describe the expression of class I Hox genes in highly purified CD34+ cell subpopulations isolated from normal human bone marrow that represent functionally distinct stem and progenitor cell compartments. Our data indicate that at least 16 different Hox genes, mainly from the A and the B clusters, are expressed in one or more of these subpopulations of human hematopoietic cells. Moreover, markedly elevated expression of some of the Hox genes found at the 3' end of the A and B clusters (e.g., HoxB3) was a unique feature of the subpopulations that contained the most primitive functionally defined cells, whereas genes located in the 5' region of each cluster (e.g., HoxA10) were found to be expressed at nearly equal levels in the CD34+ subpopulations analyzed. In contrast to the findings for CD34+ cells, expression of two selected Hox genes, HoxB3 and HoxA10, was virtually extinguished in the CD34- fraction of bone marrow cells. These results demonstrate the expression of a broad range of Hox genes in primitive hematopoietic cells and point to the existence of a regulated program of Hox gene expression during their normal development.

Transplantation of patients with high risk acute myeloid leukemia in first remission with autologous marrow cultured in interleukin-2 followed by interleukin-2 administration

Relapse rates in patients after autologous bone marrow transplantation (BMT) for acute myeloid leukemia (AML) continue to be high despite the use of aggressive conditioning regimens. Based on studies in the murine system a clinical protocol was developed that utilizes immunotherapy to obtain a graft-versus-leukemia (GVL) effect both pre-BMT (to purge leukemic cells from the autograft) and post-BMT (to eradicate residual leukemia in the patient). As part of a phase I study, 10 consecutive patients (median age 41 years, range 15-60 years) with 'high risk' AML (i.e. any of the following: FAB M5, WBC of > or = 50 x 10(9)/l at diagnosis or 'unfavorable' cytogenetic abnormalities) were transplanted at a median of 32 days (range 13-128 days) after achieving first remission. Marrow cells to be autografted were first cultured for 8 days at 37 degrees C in standard long-term culture medium (containing 12.5% horse serum, 12.5% fetal calf serum and 10(-6) M hydrocortisone) to which 1000 U/ml of interleukin-2 (IL-2) was also added. During this time patients received busulfan 4 mg/kg for 4 days and cyclophosphamide 60 mg/kg for 2 days). On the day of transplantation (day 0), the cultured marrow cells were collected from the flasks and infused over 1 h. Between days 0 and 7 patients were given escalating doses of subcutaneous IL-2 (2, 4 and 6 x 10(5) U/m2/day, 3-4 patients/dose level). Side-effects attributable to IL-2 were generally mild, dose-dependent and consisted of fever and malaise.(ABSTRACT TRUNCATED AT 250 WORDS)

Autografting with cultured marrow in chronic myeloid leukemia: results of a pilot study

Incubation of chronic myeloid leukemia (CML) marrow for 10 days in vitro causes a marked and selective loss of very primitive Philadelphia chromosome (Ph)+ as compared with Ph- progenitors. We have autografted 22 patients with CML (16 in first chronic phase [group 1] and 6 with more advanced disease [group 2]) with marrow treated in this way to facilitate restoration of Ph- hematopoiesis after intensive therapy. Hematologic recovery to greater than 0.5 x 10(9)/L neutrophils occurred in 16 patients, and to greater than 20 x 10(9)/L platelets in 15 of 21 evaluable patients at a median of 29 and 48 days postautograft, respectively. Regenerating marrow cells were 100% Ph- in 13 patients and 75% to 94% Ph- in 3. Between 4 and 36 months (median 12) postautograft, Ph+ cells became detectable in all but 1 (who died in remission) of the 13 patients who achieved complete cytogenetic remission. Four of 7 evaluable patients treated with low-dose interferon alpha were returned to complete cytogenetic remission. Thirteen group 1 patients (81%) are alive 1.0 to 5.7 years (median 2.6) after autografting: 4 in complete cytogenetic remission, 2 in hematologic remission, 6 in chronic phase, and 1 in myeloid blast phase. Three group 2 patients (50%) are alive at 2.6, 3.8, and 4.3 years after autografting: 1 in partial cytogenetic remission, 1 in chronic phase, and 1 in accelerated phase. Thus, autografts of cultured marrow can result in prolonged restoration of Ph- hematopoiesis for some patients with CML.

Kinetics of committed and primitive blood progenitor mobilization after chemotherapy and growth factor treatment and their use in autotransplants

Peripheral blood cells (PBCs) collected by leukapheresis after progenitor mobilization with chemotherapy and growth factors have been used successfully to replace marrow autografts in protocols requiring stem-cell support. Moreover, such transplants are often associated with more rapid recovery of blood cell counts than is routinely achieved with bone marrow. While conditions that mobilize colony-forming cells (CFCs) into the circulation are becoming increasingly well characterized, little information is available as to how these or other mobilizing treatments may influence the release of more primitive cells into the peripheral blood. To quantitate the peripheral blood content of such cells, we used the long-term culture-initiating cell (LTC-IC) assay, which detects a cell type that is able to produce progeny CFCs after a minimum of 5 weeks in cultures containing marrow fibroblasts. In this report, we present the findings on 21 patients who were transplanted over a 7-year period at our institution with PBCs alone. PBCs were collected in steady-state (n = 6) or during the recovery phase after high-dose cyclophosphamide (Cy; n = 15, nine with and six without additional growth factor administration). PBCs collected from another 11 patients given granulocyte colony-stimulating factor (G-CSF) were transplanted together with autologous marrow. Time-course studies of nine patients after Cy +/- granulocyte-macrophage CSF (GM-CSF) showed that CD34+ cells, CFCs, and LTC-ICs fell from normal to undetectable levels after Cy, and increased at the time of white blood cell (WBC) recovery: LTC-ICs to a mean of sixfold and CFCs to a mean of 26-fold higher than normal. The mean number of CD34+ cells, CFCs, and LTC-ICs present in the PBC harvest was twofold to 10-fold higher after mobilization than in steady-state collections; however, more than 2-log interpatient variability was observed. After PBC transplantation, the median time to a WBC count more than 10(9)/L was 12 days; polymorphonuclear leukocyte (PMN) count more than 0.5 x 10(9)/L, 15 days; and platelet count more than 20 x 10(9)/L, 17 days, although patients who received fewer than 1.5 x 10(5) CFCs/kg had a more than 50% chance of delayed count recovery (> 28 days). Patients who received Cy + GM-CSF-stimulated PBCs had more rapid and consistent platelet recoveries as compared with other groups receiving Cy mobilized or steady-state PBCs alone, and a rapid WBC recovery after Cy predicted a rapid WBC recovery after transplantation.(ABSTRACT TRUNCATED AT 400 WORDS)