Infectious complications following allogeneic stem cell transplantation: reduced-intensity vs. myeloablative conditioning regimens.

BACKGROUND: In allogeneic stem cell transplantation (allo-SCT), reduced-intensity conditioning (RIC) is known for producing less regimen-related toxicity. However, whether or not RIC reduces the risk for infection and infection-related mortality (IRM) remains controversial. METHODS: We retrospectively analyzed infectious episodes and IRMs after allo-SCTs by time period and by the intensity of the conditioning regimen (RIC [n = 81] vs. myeloablative conditioning, MAC [n = 150]). RESULTS: The cumulative incidence of any kind of infection was lower in the RIC group through the entire period (72% vs. 87%; P = 0.007). The onset of infections was deferred in the RIC group as compared with the MAC group (P = 0.012). Bacteremia occurred less frequently in the RIC group through the entire period (5% vs. 14%; P = 0.044). However, the incidences of cytomegalovirus reactivation and disease, herpes zoster, virus-associated hemorrhagic cystitis, and invasive fungal infection were not different between the two groups. Furthermore, there was no difference in relapse-free survival and IRM between the two conditioning regimens. CONCLUSION: Careful monitoring and appropriate preventive/therapeutic strategies for infectious complications, comparable to those for allo-SCT recipients with MAC, should also be applied to those with RIC, especially after engraftment.

High TOP2B/TOP2A expression ratio at diagnosis correlates with favourable outcome for standard chemotherapy in acute myeloid leukaemia.

BACKGROUND: Cytosine arabinoside-based chemotherapy coupled with anthracycline is currently the first-line treatment for acute myeloid leukaemia (AML), but diverse responses to the regimen constitute obstacles to successful treatment. Therefore, outcome prediction to chemotherapy at diagnosis is believed to be a critical consideration. METHODS: The mRNA expression of 12 genes closely involved in the actions of cytosine arabinoside and anthracycline was evaluated by real-time reverse transcriptase PCR (RT-PCR), in 54 diagnostic bone marrow specimens of M2-subtype AML. RESULTS: Low expression levels of ribonucleotide reductase M2 (RRM2) and high expression levels of topoisomerase 2 beta (TOP2B) were correlated with longer survival in a univariate analysis. Another interesting finding is that high ratios of TOP2B/RRM2 and TOP2B/TOP2 alpha (TOP2A) in a combined analysis were also shown to have a prognostic impact for longer survival with improved accuracy. Among the four markers, when adjusted for the influence of other clinical factors in multivariate analysis, the TOP2B/TOP2A ratio was significantly correlated with treatment outcomes; patients with high ratios trended toward longer disease-free survival (HR, 0.24; P=0.002) and overall survival (HR, 0.29; P=0.005). CONCLUSION: Genes with distinct expression profiles such as TOP2B/TOP2A expression ratio at diagnosis can be employed for outcome prediction after the treatment with standard regimens in AML patients with M2 subtype.

Infectious complications associated with alemtuzumab use for allogeneic hematopoietic stem cell transplantation: comparison with anti-thymocyte globulin.

OBJECTIVES: To evaluate the incidence of infectious complications after receiving alemtuzumab as part of a conditioning regimen for allogeneic hematopoietic stem cell transplantation (HSCT) in Korean patients. METHODS: From November 2004 to January 2006, 12 patients who received alemtuzumab-based conditioning regimens for allogeneic HSCT were evaluated retrospectively until death or until the end of the follow-up in July 2007; they were compared with 18 patients who received rabbit anti-thymocyte globulin (ATG)-containing conditioning regimens from January 2002 to January 2006. RESULTS: Post-engraftment infections occurred more frequently in the alemtuzumab recipients than in the ATG recipients; the mean number of infections, excluding cytomegalovirus (CMV) infections, per patient during the follow-up period was 2.6+/-1.4 vs. 1.0+/-0.8 (P=0.003), respectively. Although there was no statistical difference in the cumulative incidence of CMV infection between the 2 groups (91.7% vs. 55.6%, P=0.381), the alemtuzumab recipients had a higher incidence of CMV diseases (41.6% vs. 0%, P=0.0006) and a higher recurrence rate of CMV infection (90.0% vs. 27.3%, P=0.008) than did the ATG recipients, irrespective of the dose of alemtuzumab. Hemorrhagic cystitis (HC) (66.7% vs. 16.7%, P=0.009) and BK virus-associated HC (41.7% vs. 5.6%, P=0.026) developed more frequently in the alemtuzumab recipients. The all-cause mortality rate was not significantly different between the alemtuzumab and the ATG recipients (75% vs. 55.6%, P=0.28). CONCLUSION: Alemtuzumab recipients had a high incidence of CMV disease as well as BK virus-associated HC compared with the ATG recipients. The dose of alemtuzumab should be tailored to patients' risk; in addition, the implementation of the appropriate prophylaxis for CMV and early detection strategies for BK virus are recommended.

Clinical impact of thrombotic microangiopathy on the outcome of patients with acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation.

The impact of thrombotic microangiopathy (TMA) on outcome was studied in 148 patients with acute graft-versus-host disease (GVHD) (> or =grade II). The Blood and Marrow Transplant Clinical Trials Network's definition for TMA was used to diagnose definite TMA. Probable TMA was diagnosed when none of the features of nephropathy and neurologic abnormalities associated with definite TMA were present. Overall, TMA developed in 43 (29%) patients; 16 definite and 27 probable. The occurrence of TMA, the maximum grade of acute GVHD and initial treatment failure were associated with shorter overall and GVHD-specific survival. The development of probable as well as definite TMA affected the survival of patients with acute GVHD adversely. These results show the clinical impact of TMA on patients with acute GVHD, and suggest that the proposed definitions and grading of TMA may need to be modified.

The JAK2 V617F mutation in de novo acute myelogenous leukemias.

A missense somatic mutation in JAK2 gene (JAK2 V617F) has recently been reported in chronic myeloproliferative disorders, including polycythemia vera, essential thrombocythemia and myelofibrosis with myeloid metaplasia, strongly suggesting its role in the pathogenesis of myeloid disorders. As activation of JAK2 signaling is occurred in other malignancies as well, we have analysed 558 tissues from common human cancers, including colon, breast and lung carcinomas, and 143 acute adulthood leukemias by polymerase chain reaction -- single strand conformation polymorphism analysis. We found three JAK2 mutations in the 113 acute myelogenous leukemias (AMLs) (2.7%), but none in other cancers. The mutations consisted of two V617F mutations and one K607N mutation. None of the AML patients with the JAK2 V617F mutation had a history of previous hematologic disorders. This is the first report on the JAK2 gene mutation in AML, and the data indicated that the JAK2 gene mutation may not only contribute to the development of chronic myeloid disorders, but also to some AMLs.

Distribution of the minor histocompatibility antigens in Korean population and disparities in unrelated hematopoietic SCT.

Minor histocompatibility antigens (mHags) are polymorphic peptides presented to T lymphocytes restricted by the MHC molecule. It has been reported that disparities of mHags are a potential risk factor for GVHD after hematopoietic SCT (HSCT). Here we observed allelic frequencies of HA-1, -2 and -8 in 139 Korean healthy individuals using PCR-sequence-specific primers, and analyzed the correlation between disparity of these mHags and acute GVHD (aGVHD) in 54 patients who underwent HSCT from unrelated HLA-identical donors. The allelic frequencies in Korean healthy individuals were 39.6 and 60.4% for HA-1(H) and HA-1(R), 92.4 and 7.6% for HA-2(M) and HA-2(V), 36.7 and 63.3% for HA-8(R) and HA-8(P), respectively. The frequencies of mHags incompatibility known to be associated with aGVHD were 16.7% in HA-1, 0% in HA-2 and 25.9% in HA-8. However, the statistically significant association of aGVHD with these mHags incompatibility was not found between healthy donors and leukemia patients after unrelated HSCT. This first report about mHags in Koreans may be helpful in further defining the clinical impact of mHags disparities in HSCT and in comparing with other populations.

Anti-leukaemic role of acute GvHD after unrelated haematopoietic stem cell transplantation in intermediate- to high-risk acute myelogenous leukaemia.

Little is known about the role of acute GvHD (aGvHD) based on the concept of graft-versus-leukaemia effect (GVLE) after unrelated donor haematopoietic stem cell transplantation (uHSCT). We evaluated 67 uHSCTs performed with multinational unrelated donors for patients with AML. The median follow-up duration was 18 months (range 7-61). The majority of patients had intermediate- or high-risk cytogenetic findings. The conditioning regimen for most patients consisted of cyclophosphamide plus total body irradiation (n=56) with our standard GvHD prophylaxis containing tacrolimus plus a short course of methotrexate. The incidence of aGvHD and chronic GvHD was 50 and 52%, respectively. Eight patients (12%) have relapsed to date. The estimated overall disease-free survival (DFS) rate at 5 years was 67%. Notably fewer relapses were seen when aGvHD developed (P=0.008). Specifically, high-risk AML patients had a much lower relapse rate when they developed aGvHD (P=0.01), compared with the intermediate-risk group. Therefore, the development of aGvHD after uHSCT in AML patients is closely related to a lower relapse rate, probably in association with GVLE.

Dynamic prognostic value of the revised international prognostic scoring system following pretransplant hypomethylating treatment in myelodysplastic syndrome.

This study aimed to analyze the use of the revised International Prognostic Scoring System (IPSS-R) assessed after hypomethylating treatment (HMT) for patients with myelodysplastic syndrome (MDS) undergoing an allogeneic stem cell transplantation (SCT). Among 115 patients who received pre-SCT HMT, comparison analysis of the prognostic values between the IPSS-R at the time of HMT (IPSS-R@HMT) and at the time of SCT after HMT (IPSS-R@SCT) showed a significantly higher predictive power for overall survival (OS) of the latter. Alteration in IPSS-R risk occurred in 60%, while the patients with 'down-staged' IPSS-R@SCT showed better OS compared with those with 'unchanged' or 'up-staged' risk. On multivariate analysis in all 201 patients, IPSS-R@SCT, monosomal karyotype, treatment failure to pre-SCT treatment, and high hematopoietic cell transplantation-comorbidity index were independently associated with OS. Constructed using these factors, the MDS Transplantation Prognostic Scoring System (MTPSS) identified four risk groups with 4-year OS of 76.4% in low, 61.4% in intermediate-1 and 21.9% in intermediate-2 risk groups, whereas all in the high risk group died within 2 years after SCT (P<0.001). Our study emphasizes the need for further studies aiming to evaluate a transplantation prognostic model such as the MTPSS to make appropriate decisions for transplantation in MDS.

Patterns of C-reactive protein release following allogeneic stem cell transplantation are correlated with leukemic relapse.

The C-reactive protein (CRP) is an acute-phase protein produced by hepatocytes, and is a reliable marker of systemic inflammation, which is relevant to the release of the proinflammatory cytokines. The value of monitoring the CRP levels after stem cell transplantation (SCT) can identify patients at risk of treatment-related complications and mortality. Inflammatory cytokines facilitate donor T-cell activation via antigen presenting cells immediately after SCT. This study examined the relationship between the post-SCT CRP levels and a leukemic relapse. Fifty-four consecutively transplanted patients who relapsed after the allogeneic SCT were compared with nonrelapsing patients. The serum CRP levels were measured on day 0 and every 7 days thereafter until 4 weeks after the SCT. The mean CRP levels throughout the early post-SCT episode were significantly lower in the relapsing patients than in those who did not experience relapse (mean+/-s.e.: 26.8 +/- 6.3 vs 65.3 +/- 9.4 for first week, P = 0.001; 23.9 +/- 3.8 vs 44.6 +/- 6.6 for second week, P = 0.008). Univariate analysis showed that the CRP level on the first and second week, and graft-versus-host disease were significantly associated with a relapse. Multivariate analysis showed that the CRP level on the first week was the strongest independent variable predicting the risk of a relapse after SCT (P = 0.04). These results indicate that the serum CRP levels early after allogeneic SCT might display the graft-versus-leukemia (GvL) effect. CRP is a surrogate of the proinflammatory cytokine release that was not measured in this study. The GvL effect appears to be efficiently strengthened by the high CRP levels that may be reflecting T-cell activation.

Vascular endothelial growth factor (VEGF) is associated with reduced severity of acute graft-versus-host disease and nonrelapse mortality after allogeneic stem cell transplantation.

This study investigated whether or not there is a correlation between the changes in the serum levels of vascular endothelial growth factor (VEGF) and the outcome of allogeneic stem cell transplantation (allo-SCT). Eighty-five patients undergoing allo-SCT were prospectively studied. The serum VEGF levels were measured on days 0, +7 and +14 after transplantation. The VEGF levels decreased significantly on day +7 and recovered on day +14. The highest levels from day +7 through day +14 were categorized by cluster analysis, which were then correlated with the nonrelapse mortality (NRM). There was a significant correlation between a low VEGF level and the occurrence of severe acute graft-versus-host disease (GVHD) including grade III-IV (P=0.029). The 1-year probability of NRM in patients with a low VEGF level was 22.5% compared with 3.5% for those with a high VEGF level (P=0.024). Multivariate analysis revealed clinically defined infections (P=0.011), advanced disease (P=0.014) and a low VEGF cluster (P=0.05) to be significantly associated with the occurrence of NRM in the cohort. In conclusion, low VEGF levels after allo-SCT are associated with NRM with an exacerbated severity of acute GVHD. VEGF monitoring after a transplant might identify those patients at risk of severe transplant-related mortality.

Inhibition of UL54 and UL97 genes of human cytomegalovirus by RNA interference.

Short interfering RNAs (siRNAs), namely siUL54-1 and siU54-2 targeting UL54 (DNA polymerase) gene, and siUL97-1 and siUL97-2 targeting UL97 (phosphotransferase) gene, were used to inhibit respective genes of Human cytomegalovirus (HCMV) and consequently the virus infection process in human foreskin fibroblast (HFF) cultures. The virus infection was monitored by cell morphology (CPE), levels of UL83 and IE86 mRNAs, and virus antigen. The results showed that siUL97-2 remarkably inhibited viral CPE while other siRNAs were less inhibitory. The siRNAs reduced the levels of UL83 mRNA but not that of IE86 mRNA; again, siUL97-2 was most inhibitory. Particularly, siUL97-2 reduced the UL83 mRNA level 14, 19, 203, and 37 times at 24, 48, 72, and 96 hrs post infection (p.i.), respectively. When tested for the effect on viral antigen by immunofluorescent assay (IFA), UL97-2 exerted a marked inhibition. These results demonstrate the effectiveness of siRNAs against experimental HCMV infection and indicate their therapeutic potential.

Impact of pretransplant red cell transfusion on outcome after allogeneic stem cell transplantation in adult patients with severe aplastic anemia.

The aim of this study was to evaluate the impact of pretransplant transfusion of packed red cells (PRCs) on outcome after allogeneic stem cell transplantation (SCT) in severe aplastic anemia (SAA). A total of 221 adult SAA patients receiving allogeneic SCT were analyzed. The patients were divided into two groups according to the amount of pretransplant transfusion before SCT: the low transfusion group (⩽32 PRC units, n=164) and the high transfusion group (>32 PRC units, n=57). The incidence of engraftment failure was not different between the two groups. The incidence of acute GvHD (grades II-IV) was higher in the high transfusion group than in the low transfusion group (P=0.04), and the incidences of chronic extensive GVHD were not significantly different (P=0.136). The high transfusion group had higher 5-year transplant-related mortality (TRM) (24.8% vs 6.8%, P<0.001) and lower overall survival (OS) (72.3% vs 91.9%, P<0.001) than those in the low transfusion group. Multivariate analysis revealed that the high transfusion group and unrelated donor type were independent prognostic factors affecting OS. These results indicate that a history of higher pretransplant transfusion of PRCs was associated with increased TRM and decreased OS, suggesting that iron overload had a negative impact on outcome after SCT in SAA.

Significance of KIT exon 17 mutation depends on mutant level rather than positivity in core-binding factor acute myeloid leukemia.

KIT exon 17 mutation is a poor prognostic factor in core-binding factor acute myeloid leukemia. However, the mutation detection method used for risk assessment is not assigned. It is necessary to verify the analytical and clinical performance before applying new methods. Herein, we firstly applied a highly sensitive allele-specific, real-time quantitative PCR (AS-qPCR) assay to analyze KIT mutations, which demonstrated excellent sensitivity and specificity. Much higher incidence of KIT mutations (62.2%, 69/111) and prevalence of multiple mutations (43.5%, 30/69) were observed using AS-qPCR, which meant the existence of multiple KIT mutant subclones. The relative KIT mutant level was variable (median, 0.3 per control allele 100 copies, 0.002-532.7) and was divided into two groups: high (⩾10, n=26) and low (<10) mutant level. Interestingly, rather than mutation positivity, mutant level was found to be associated with clinical outcome. High mutant level showed significantly inferior overall survival (P=0.005) and event-free survival (P=0.03), whereas low level did not influence the prognosis. The follow-up data showed that the mutant level were along with fusion transcripts in the majority (n=29), but moved separately in some cases, including the loss of mutations (n=5) and selective proliferation of minor clones (n=2) at relapse. This study highlighted that the KIT mutation should be analyzed using sensitive and quantitative techniques and set a cutoff level for identifying the risk group.

Comparable outcomes between younger (⩽40 years) and older (>40 years) adult patients with severe aplastic anemia after HLA-matched sibling stem cell transplantation using fludarabine-based conditioning.

Allogeneic stem cell transplantation from HLA-matched siblings (MSD-SCT) for elderly patients with severe aplastic anemia (SAA) is not a widely accepted first-line treatment. Recently, fludarabine, lower-dose cyclophosphamide and antithymocyte globulin conditioning (Flu/lower-dose Cy/ATG) with lower toxicities has been investigated. To determine whether this regimen can overcome the negative effects of age, we analyzed 117 adult patients with SAA who received MSD-SCT using Flu/lower-dose Cy/ATG, and compared outcomes between 63 younger age group (YAG; ⩽40 years) and 54 older age group (OAG; >40 years) patients. No primary graft failure was observed. Neutrophil engraftment was significantly faster in the YAG compared with the OAG (12 vs 13 days; P=0.04). The incidences of acute grade II-IV (9.5% vs 9.3% at day 100; P=0.42) and chronic GVHD (8.1% vs 9.5% at 5 years; P=0.80), secondary graft failure (20.8% vs 7.9% at 5 years; P=0.11) and transplant-related mortality (5.4% and 11.1% at 5 years; P=0.91) were not significantly different between the YAG and OAG. In addition, failure-free (73.7% vs 81.0% at 5 years; P=0.73) and overall survival rates (93.7% vs 88.9% at 5 years; P=0.20) were comparable. Our results suggest that MSD-SCT using Flu/lower-dose Cy/ATG may be a feasible first-line treatment even in older patients with SAA.

Haplotype mismatched transplantation using high doses of peripheral blood CD34+ cells together with stratified conditioning regimens for high-risk adult acute myeloid leukemia patients: a pilot study in a single Korean institution.

A total of 11 high-risk Korean acute myeloid leukemia (AML) patients received stem cell transplantation from human leukocyte antigen (HLA) haploidentical donors. Specifically, for eight patients with 2-3 mismatched antigens and bidirectional vectors, we used a newly designed conditioning regimen that consists of total body irradiation, busulfex, ATG, and fludarabine. The median number of CD34+ cells infused was 15.4 x 10(6)/kg (range, 8-21.2). These patients received neither graft-versus-host disease (GvHD) prophylaxis nor post transplantation G-CSF. All of the patients who were followed up for a median of 6 months (range, 17 days-28 months) showed stable primary engraftment and had no acute GvHD or transplant-related mortality for 100 days post transplant. Three patients with high-risk or refractory disease eventually died in relapse, even with GvH-directed NK alloreactivity. However, the patients in complete remission (CR), with the exception of one patient who is alive at 18 months EFS, died at 4, 6, and 8 months post transplantation due to infections that were associated with delayed immune recovery. Our findings suggest that haploidentical transplantation represents a feasible treatment for patients with high-risk AML in CR, provided that a plan for the enhancement of immune recovery is implemented.

Impact of ABO incompatibility on outcome after allogeneic peripheral blood stem cell transplantation.

Few studies have addressed the incidence of graft-versus-host disease (GVHD) or survival after ABO-incompatible allogeneic peripheral blood stem cell transplantation (PBSCT). We analyzed the clinical outcome of ABO incompatibility after allogeneic PBSCT. A total of 89 consecutive adult patients with hematological diseases including 49 ABO-identical, 20 major, 15 minor, and five bidirectional ABO-incompatible transplants were enrolled from four medical centers in Korea. No significant difference in engraftment times, graft failure, or transfusion requirements between groups was noted. A clinical diagnosis of severe immune hemolysis or pure red cell aplasia was not made for any patient after transplantation. The incidence of acute or chronic GVHD did not statistically differ between groups. With a median follow-up duration of 13 months (range, 0.5-61 months), the 3-year overall survival estimates for the ABO-identical, major/bidirectional, and minor group were 44.6.0+/-9.0, 43.1+/-11.6, and 43.8+/-13.5%, respectively (P=0.8652), while the 3-year disease-free survival estimates were 33.8+/-7.6, 39.9+/-11.4, and 45.7+/-13.1%, respectively (P=0.8546). We observed that time to neutrophil, platelet, and red blood cell engraftment, transfusion requirements, incidence of acute or chronic GVHD, relapse, and survival were not influenced by ABO incompatibility after allogeneic PBSCT from HLA-matched sibling donors.

Quantitative fragment analysis of FLT3-ITD efficiently identifying poor prognostic group with high mutant allele burden or long ITD length.

Mutation of the fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD), which is one of the most frequent genetic alterations, strongly contributes to an increased risk of treatment failure and to poor prognosis. In this study, we established quantitative fragment analysis of FLT3-ITD simultaneously measuring mutant allele burden and length, verified the analytical performance and evaluated the clinical significance in adult acute myeloid leukemia (AML) patients. FLT3-ITD was detected in 73 of 363 adult AML patients (20.1%) and high mutant allelic burden (⩾50%, n=13) and long ITD length (⩾70 base pairs, n=15) were significantly associated with inferior overall survival (OS; P=0.002 and 0.005, respectively) and event-free survival (EFS; P=0.004 and 0.007, respectively). FLT3-ITD poor prognostic group was identified as patients with high allele burden or long ITD length (n=24), which revealed significant adverse clinical outcome for both OS (P<0.001) and EFS (P<0.001). In cytogenetically normal AML, even FLT3-ITD low allele burden and short length was associated with poorer OS (P=0.037) and EFS (P=0.044) than wild type, whose influence was overcome when hematopoietic stem cell transplantation was performed. In minimal residual disease monitoring, FLT3-ITD negativity after consolidation therapy was a valuable predictor of better OS (P<0.001) and EFS (P<0.001). FLT3-ITD poor prognostic group with high mutant allele burden or long ITD length is efficiently identified by quantitative fragment analysis.

Single monosomy as a relatively better survival factor in acute myeloid leukemia patients with monosomal karyotype.

Monosomal karyotype (MK) defined by either ⩾2 autosomal monosomies or single monosomy with at least one additional structural chromosomal abnormality is associated with a dismal prognosis in patients with acute myeloid leukemia (AML). It was detected in 174 of 3041 AML patients in South Korean Registry. A total of 119 patients who had received induction therapy were finally analyzed to evaluate the predictive factors for a positive prognosis. On multivariate analysis, single monosomy, the absence of abn(17p), ⩾10% of cells with normal metaphase and the achievement of a complete remission (CR) after induction therapy were significant factors for more favorable outcomes. Especially, single monosomy remained as a significantly independent prognostic factor for superior survival in both patients who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) in CR and who did not. Allo-HSCT in CR improved overall survival significantly only in patients with a single monosomy. Our results suggest that MK-AML may be biologically different according to the karyotypic subtype and that allo-HSCT in CR should be strongly recommended to patients with a single monosomy. For other patients, more prudent treatment strategies should be examined. Furthermore, the biological mechanism by which a single monosomy influences survival should be investigated.

Impact of IKZF1 deletions on long-term outcomes of allo-SCT following imatinib-based chemotherapy in adult Philadelphia chromosome-positive ALL.

We investigated the prognostic relevance of IKZF1 deletions in 118 adult Ph-positive ALL patients who had minimal residual disease (MRD) data under a uniform treatment of allo-SCT following first-line imatinib-based chemotherapy. IKZF1 deletions were identified in 93 patients (78.8%). IKZF1-deleted patients had a lower proportion of early-stable molecular responders compared with wild-type patients (28.0 vs 56.0%, P=0.028). After a median follow-up of 72 months, IKZF1-deleted patients had a trend for higher cumulative incidence of relapse (CIR) (38.0 vs 13.3%, P=0.052), particularly in a subgroup of early-stable molecular responders (n=40; 21.4 vs 0%, P=0.088), but comparable disease-free survival to wild-type patients. Patients with biallelic-null deletions showed higher CIR (74.6 vs 13.3%, P=0.003) and lower disease-free survival (20.0 vs 67.5%, P=0.022) than wild-type patients. In multivariate analysis, MRD kinetics were closely related to outcomes, while neither IKZF1 deletions nor their functional subtypes retained an independent statistical power. Within the limitation of sample size, however, considering both the negative impact of IKZF1 deletions on MRD kinetics and a trend for relationship between IKZF1 deletions and relapse in early-stable molecular responders, IKZF1 deletions may have a potentially additive effect on unfavorable prognosis in a specific MRD-based subgroup of adult Ph-positive ALL transplants.

Thermal sensitivity and thermal tolerance of human B-lineage acute lymphoblastic leukemia (ALL) cells.

The thermal sensitivities of four B-cell precursor acute lymphoblastic (ALL) cell lines (REH and KM-3 = pre pre B-ALL; NALM-6 and HPB-NULL = pre B-ALL), and 1 B-cell ALL (NAMALWA) cell line were studied and compared to the thermal sensitivity of the T-lineage ALL cell line MOLT-3 using an in vitro clonogenic assay system by limiting dilution. B-lineage ALL cells were as sensitive to hyperthermia as were T-lineage ALL cells. D0 values at 42 degrees C ranged from 44.9 min (NALM-6) to 85.6 min (NAMALWA), D0 values at 43 degrees C ranged from 15.3 min (NALM-6) to 35.7 min (KM-3), and D0 values at 44 degrees C ranged from 11.1 min (NALM-6) to 23.8 min (HPB-NULL). By comparison, the D0 values of MOLT-3 cells were 95.1 min at 42 degrees C, 23.8 min at 43 degrees C, and 14.7 min at 44 degrees C. The maximum log kill values which were observed ranged from 0.8 log (KM-3 and HPB-NULL) to 1.3 logs (NALM-6) at 42 degrees C, from 1.4 logs (KM-3) to 4.2 logs (NALM-6) at 43 degrees C, and from 3.8 logs (HPB-NULL) to 4.8 logs (NALM-6) at 44 degrees C. A thermal tolerant plateau was observed in the hyperthermia survival curves of REH, NALM-6, and HPB-NULL cells, providing circumstantial evidence that thermal tolerance may develop in some B-cell precursor ALL cells after 90-120 min of continuous heating. In contrast, no thermal tolerant plateau was observed in the hyperthermia survival curves of pre-pre-B-ALL/KM-3 B-cell ALL/NAMALWA or T-lineage ALL/MOLT-3 cells. The kinetics of development and decay of thermotolerance was studied for NALM-6 cells. Thermotolerance after a priming heat exposure to 42 degrees C for 30 min was maximum at 8 hr with a maximum thermotolerance ratio of 2.0, and it decayed by 24 hr. These findings extend previous studies on the thermal sensitivity of human leukemia cells and provide new information on the thermal sensitivity and thermotolerance of B-lineage ALL cells.