Heterogeneity Of Acute Lymphoblastic Leukemia Research Articles

Pharmacotypes across the genomic landscape of pediatric acute lymphoblastic leukemia and impact on treatment response

Contemporary chemotherapy for childhood acute lymphoblastic leukemia (ALL) is risk-adapted based on clinical features, leukemia genomics and minimal residual disease (MRD); however, the pharmacological basis of these prognostic variables remains unclear. Analyzing samples from 805 children with newly diagnosed ALL from three consecutive clinical trials, we determined the ex vivo sensitivity of primary leukemia cells to 18 therapeutic agents across 23 molecular subtypes defined by leukemia genomics. There was wide variability in drug response, with favorable ALL subtypes exhibiting the greatest sensitivity to L-asparaginase and glucocorticoids. Leukemia sensitivity to these two agents was highly associated with MRD although with distinct patterns and only in B cell ALL. We identified six patient clusters based on ALL pharmacotypes, which were associated with event-free survival, even after adjusting for MRD. Pharmacotyping identified a T cell ALL subset with a poor prognosis that was sensitive to targeted agents, pointing to alternative therapeutic strategies. Our study comprehensively described the pharmacological heterogeneity of ALL, highlighting opportunities for further individualizing therapy for this most common childhood cancer.

Pharmacotypes across the Genomic Landscape of Pediatric Acute Lymphoblastic Leukemia and Impact on Treatment Response

INTRODUCTION The current paradigm of risk stratification in childhood acute lymphoblastic leukemia (ALL) utilizes a combination of clinical features, leukemia somatic genomics and early treatment response as measured by minimal residual disease (MRD). Although ALL subtypes and MRD are strongly related to treatment outcomes, the pharmacological basis of their prognostic impact remains incompletely understood. Therefore, we sought to characterize pharmacotypes (drug sensitivities) across the complete spectrum of ALL molecular subtypes and determine their association with in vivo treatment response and survival outcomes. METHODS This was a prospective study of 805 children with newly-diagnosed ALL from Total Therapy XV, XVI, and XVII trials at St Jude Children's Research Hospital. We performed ex vivo pharmacotyping of 18 drugs on primary ALL diagnostic blasts to determine drug sensitivities (LC50 - dose required to kill 50% of leukemia cells). RNA-sequencing was performed to derive molecular subtype. We then evaluated the associations of drug LC50 with clinical features, ALL subtype, MRD, and event-free survival (Figure 1). RESULTS We analyzed 5,447 drug measurements across 23 ALL subtypes. LC50s of prednisolone, asparaginase, and mercaptopurine were associated with age, and/or with leukocyte count at diagnosis. Sensitivities to 14 of 18 drugs varied across ALL molecular subtypes. For cytotoxic agents, B-ALL subtypes with favorable prognosis (ETV6-RUNX1 and hyperdiploidy) exhibited greatest sensitivity to asparaginase and glucocorticoids, whereas high-risk subtypes (KMT2A, BCR-ABL1, and BCR-ABL1-like) were resistant. Novel subtypes DUX4 and ETV6-RUNX1-like ALL showed significant resistance to cytotoxic drugs. For targeted agents, hyperdiploid ALL was most sensitive to venetoclax, whereas TCF3-PBX1, BCR-ABL1, and T-ALL were dasatinib-sensitive. The poor-prognosis ETP-ALL was resistant to most cytotoxic drugs compared to T-ALL. Although BCR-ABL1, BCR-ABL1-like, and CRLF2 are closely related transcriptionally, these three subtypes had distinctive drug sensitivity profiles. In B-ALL, sensitivities of prednisolone, asparaginase, dexamethasone, cytarabine and thiopurines were positively correlated with MRD. By contrast, these drugs were not correlated with MRD in T-ALL. Instead, sensitivities of dasatinib and nelarabine correlated positively, and venetoclax negatively, with MRD in T-ALL. Finally, we classified patients into six functional clusters based on ALL pharmacotypes, each with distinct patterns of somatic genomic aberrations and MRD response. Drug sensitivity cluster was significantly associated with event-free survival, even after adjusting for MRD. Importantly, pharmacotyping identified a T-ALL subset with poor prognosis under conventional chemotherapy but also with unique sensitivity to targeted agents, pointing to therapeutic intervention to improve survival in this group. CONCLUSIONEx vivo drug sensitivities vary widely across ALL subtypes and strongly influence in vivo MRD. Our study comprehensively described pharmacological heterogeneity of ALL and the association of drug sensitivities with survival outcomes, providing insight into the pharmacological basis of inter-patient variability in ALL treatment outcomes and highlighting opportunities for individualizing therapy for this blood cancer. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Changing Landscape in the Treatment of Adult Acute Lymphoblastic Leukemia (ALL).

Simple SummaryThe improved understanding of acute lymphoblastic leukemia has brought with it several new therapy strategies as well as novel treatment agents. The aim of our review was to create a well-arranged overview of the currently available treatment strategies for ALL.Acute lymphoblastic leukemia (ALL) is a rare hematological malignancy characterized by proliferation and accumulation of premature lymphoid blasts. Depending on risk factors, the survival of acute lymphoblastic leukemia has significantly improved over the last decades. During the last years, measurable residual disease (MRD) assessment has evolved into one of the most sensitive markers for prognosis and risk of relapse. For this reason, measurable residual disease detection and monitoring count as standard evaluation in patients with acute lymphoblastic leukemia. Allogeneic stem cell transplantation is still the recommended treatment option for patients with high and highest risk profiles as well as for relapsed or refractory settings. The increased understanding of the pathomechanism and heterogeneity of acute lymphoblastic leukemia has led to the development of several novel therapeutic opportunities such as tyrosine-kinase inhibitors, antibody-based therapies and CAR-T cells with the aim of improving clinical outcomes. Furthermore, the major advances in disease understanding of ALL have led to the identification of different subgroups and better disease stratification. Even though novel therapy targets are constantly developed, acute lymphoblastic leukemia remains a challenging and life-threatening disease. To improve the historically unsatisfying result in therapy of adult acute lymphoblastic leukemia many clinical trials have recently been initiated to determine the optimum combination regimens of novel and old agents for adult acute lymphoblastic leukemia.

Integrated Genetic/Epigenetic Analysis Revealed High Heterogeneity of Acute Lymphoblastic Leukemia in Down Syndrome

BackgroundChildren with Down syndrome (DS), which caused by an extra copy of chromosome 21, have a 20-fold increased risk for acute lymphoblastic leukemia (ALL) compared with non-DS children. Recent genome-wide studies have revealed that DS-ALL have uncommon genetic alterations such as mutations in JAK2 , NRAS , and KRAS , mutations or overexpression of CRLF2 , suggesting the unique biological features of DS-ALL distinct from non-DS ALL. However, most of previous studies regarding molecular analysis of DS-ALL have been limited to genomic and transcriptomic characterizations, and no study showed comprehensive genetic/epigenetic overview in DS-ALL.Materials and MethodsOur cohort included 179 pediatric B-cell precursor ALL samples (61 DS-ALL and 118 non-DS-ALL). Biological subtypes are detailed in Table 1. We performed targeted deep sequencing for seven ALL-related genes in 61 DS-ALL, SNP array analysis in 43 DS-ALL, and whole transcriptome sequencing (WTS) in 25 DS-ALL and 118 non-DS-ALL samples. WTS data from 153 ALL in TARGET database were also used in this study as a validation cohort. Additionally, methylation array analysis was performed in 36 DS-ALL, 17 non-DS-ALL, and 20 DS patients without ALL. To validate gene mutations detected by WTS, Sanger sequencing was also conducted. To cluster gene expression profiling, we applied the hierarchical clustering method for expression profiling and consensus clustering for methylation profiling.ResultsTargeted deep sequencing revealed frequent gene mutations of JAK2 (23%) and RAS (31%) pathway. SNP array analysis elucidated several recurrent chromosomal deletions affecting actionable gene loci; IKZF1 (33%), PAX5 (30%), EBF1 (15%), CDKN2A (34%), and RB1 (7%). Gains of whole chromosome X (18%) and 8 (10%) were also recurrently identified. Expression profiling stratified 143 samples into 6 clusters (E1-E6 clusters), which were well correlated with biological subtypes of ALL (Figure 1). Intriguingly, DS-ALL cases were clustered into four clusters, suggesting the heterogeneity of DS-ALL. Cluster E3 included one DS-ALL, which was clustered to the branch of PAX5 -rearranged cases. SNP array analysis revealed this case had focal amplification of PAX5 . All DS-ALL cases with ETV6 - RUNX1 fusion were classified into cluster E4, which also included all ETV6 - RUNX1 fusion cases of non-DS-ALL. This cluster included one DS-ALL case without ETV6 - RUNX1 fusion. This particular case had a homozygous deletion of ETV6, implicating ETV6 - RUNX1 -like signature. DS-ALL with high hyperdiploidy (HeH) were classified into cluster E5, which also included most of HeH samples of non-DS-ALL. Among other 5 DS-ALL cases in this cluster, 2 cases showed IGH - CEBPA fusion and IGH - CEBPD fusion, respectively. Cluster E6 was characterized by BCR - ABL1 fusion and Ph-like expression profiles. In our cohort, we identified 7 DS-ALL cases as Ph-like signature, which included all JAK2 mutated samples. In this cluster, PAX5 mutation and IKZF1 mutation were detected in 2 DS-ALL cases, respectively. Notably, by using 250 genes in our hierarchical clustering, TARGET database samples were divided to similar 6 clusters (Figure 2). On the other hand, Methylation array analysis revealed unique hypermethylation of promoter regions of RUNX1 in DS-ALL. Methylation of this regions were confirmed in B-cell of DS without ALL, but not in non-DS-ALL. Furthermore, methylation array analysis categorized DS-ALL into 3 clusters (Figure 3). Cluster M1 included IGH - CEBPA fusion and IGH - CEBPD fusion cases. This cluster had worse prognosis than other 2 clusters.ConclusionOur integrated analysis enlightened the genetic and epigenetic heterogeneity of DS-ALL. Importantly, DS-ALL had genetic features corresponding to each biological subtypes same as non-DS-ALL. Our analyses also elucidated that DS-ALL had unique subtypes such as IGH - CEBPA fusion, IGH - CEBPD fusion, or PAX5 alterations. It may be a reason for worse prognoses of DS-ALL. Our result indicated risk classification or therapy of DS-ALL should be tailored by each biological subtype. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Integrated genetic and epigenetic analysis revealed heterogeneity of acute lymphoblastic leukemia in Down syndrome.

Children with Down syndrome (DS) are at a 20‐fold increased risk for acute lymphoblastic leukemia (ALL). Compared to children with ALL and no DS (non‐DS‐ALL), those with DS and ALL (DS‐ALL) harbor uncommon genetic alterations, suggesting DS‐ALL could have distinct biological features. Recent studies have implicated several genes on chromosome 21 in DS‐ALL, but the precise mechanisms predisposing children with DS to ALL remain unknown. Our integrated genetic/epigenetic analysis revealed that DS‐ALL was highly heterogeneous with many subtypes. Although each subtype had genetic/epigenetic profiles similar to those found in non‐DS‐ALL, the subtype distribution differed significantly between groups. The Philadelphia chromosome‐like subtype, a high‐risk B‐cell lineage variant relatively rare among the entire pediatric ALL population, was the most common form in DS‐ALL. Hypermethylation of RUNX1 on chromosome 21 was also found in DS‐ALL, but not non‐DS‐ALL. RUNX1 is essential for differentiation of blood cells, especially B cells; thus, hypermethylation of the RUNX1 promoter in B‐cell precursors might be associated with increased incidence of B‐cell precursor ALL in DS patients.

Is There Etiologic Heterogeneity between Subtypes of Childhood Acute Lymphoblastic Leukemia? A Review of Variation in Risk by Subtype.

Although substantial advances in the identification of cytogenomic subtypes of childhood acute lymphoblastic leukemia (ALL) have been made in recent decades, epidemiologic research characterizing the etiologic heterogeneity of ALL by subtype has not kept pace. The purpose of this review is to summarize the current literature concerning subtype-specific epidemiologic risk factor associations with ALL subtype defined by immunophenotype (e.g., B-cell vs. T-cell) and cytogenomics (including gross chromosomal events characterized by recurring numerical and structural abnormalities, along with cryptic balanced rearrangements, and focal gene deletions). In case-control analyses investigating nongenetic risk factors, home paint exposure is associated with hyperdiploid, MLL-rearranged, and ETV6-RUNX1 subtypes, yet there are few differences in risk factor associations between T- and B-ALL. Although the association between maternal smoking and ALL overall has been null, maternal smoking is associated with an increasing number of gene deletions among cases. GWAS-identified variants in ARID5B have been the most extensively studied and are strongly associated with hyperdiploid B-ALL. GATA3 single nucleotide variant rs3824662 shows a strong association with Ph-like ALL (OR = 3.14). However, there have been relatively few population-based studies of adequate sample size to uncover risk factors that may define etiologic heterogeneity between and within the currently defined cytogenomic ALL subtypes.

Evolution of Tumor Clones in Adult Acute Lymphoblastic Leukemia

Clonal instability of a tumor cell population in acute lymphoblastic leukemia (ALL) may complicate the monitoring of a minimal residual disease (MRD) by means of patient-specific targets identified at the disease onset. Most of the data concerning the possible instability of rearranged clonal TCR and IG genes during disease recurrence were obtained for ALL in children. The appropriate features of adult ALL, which are known to differ from those of childhood ALL in certain biological characteristics and prognosis, remain insufficiently studied. The aim of this study was to assess the stability of IG and TCR gene rearrangements in adult ALL. Rearrangements were identified according to the BIOMED-2 protocol (PCR followed by fragment analysis). Mismatch in clonal rearrangements at onset and relapse was identified in 83% of patients, indicating clonal instability during treatment. Clonal evolution and diversity of IG and TCR gene rearrangements may be one of the tumor progression mechanisms. New rearrangements may emerge due to residual VDJ-recombinase activity in tumor cells. Also, many clonal IG and TCR gene rearrangements may be present at different levels at a diagnosis, but less abundant clones may be "invisible" due to limited detection sensitivity. Later, major clones may disappear in the course of chemotherapy, while others may proliferate. Investigation of clonal evolution and heterogeneity in ALL and their impact on the treatment efficacy will contribute to the identification of new prognostic factors and the development of therapeutic approaches.

Cytogenetic Profile of De Novo B lineage Acute Lymphoblastic Leukemia: Determination of Frequency, Distribution Pattern and Identification of Rare and Novel Chromosomal Aberrations in Indian Patients.

Chromosomal aberrations identified in acute lymphoblastic leukemia (ALL) have an important role in disease diagnosis, prognosis and management. Information on karyotype and associated clinical parameters are essential to physicians for planning cancer control interventions in different geographical regions. In this study, we present the overall frequency and distribution patterns of chromosomal aberrations in both children and adult de novo B lineage ALL Indian patients using conventional cytogenetics, interphase FISH and multiplex RT-PCR. Among the 215 subjects, cytogenetic results were achieved in 172 (80%) patients; normal karyotype represented 37.2% and abnormal 62.8% with a distribution as follows: 15.3% hypodiploidy; 10.3% hyperdiploidy; 15.8% t(9;22); 9.8% t(1;19); 3.7% t(12;21); 2.8% t(4;11); 2.8% complex karyotypes. Apart from these, we observed several novel, rare and common chromosomal rearrangements. Also, FISH studies using LSI extra-signal dual-color probes revealed additional structural or numerical changes. These results demonstrate cytogenetic heterogeneity of ALL and confirm that the incidence of chromosomal abnormalities varies considerably. To the best of our knowledge, this is one of the largest reported series of cytogenetic investigations in Indian B-lineage ALL cases. In addition, ongoing cytogenetic studies are warranted in larger groups of B-lineage ALL cases to identify newly acquired chromosomal abnormalities that may contribute to disease diagnosis and management.

Importance of FISH combined with Morphology, Immunophenotype and Cytogenetic Analysis of Childhood/ Adult Acute Lymphoblastic Leukemia in Omani Patients.

Genetic changes associated with acute lymphoblastic leukemia (ALL) provide very important diagnostic and prognostic information with a direct impact on patient management. Detection of chromosome abnormalities by conventional cytogenetics combined with fluorescence in situ hybridization (FISH) play a very significant role in assessing risk stratification. Identification of specific chromosome abnormalities has led to the recognition of genetic subgroups based on reciprocal translocations, deletions and modal number in B or T-cell ALL. In the last twelve years 102 newly diagnosed childhood/adult ALL bone marrow samples were analysed for chromosomal abnormalities with conventional G-banding, and FISH (selected cases) using specific probes in our hospital. G-banded karyotype analysis found clonal numerical and/or structural chromosomal aberrations in 74.2% of cases. Patients with pseudodiploidy represented the most frequent group (38.7%) followed by high hyperdiploidy group (12.9%), low hyperdiploidy group (9.7%), hypodiploidy (<46) group (9.7%) and high hypertriploidy group (3.2%). The highest observed numerical chromosomal alteration was high hyperdiploidy (12.9%) with abnormal karyotypes while abnormal 12p (7.5%) was the highest observed structural abnormality followed by t(12;21)(p13.3;q22) resulting in ETV6/RUNX1 fusion (5.4%) and t(9;22)(q34.1;q11.2) resulting in BCR/ABL1 fusion (4.3%). Interestingly, we identified 16 cases with rare and complex structural aberrations. Application of the FISH technique produced major improvements in the sensitivity and accuracy of cytogenetic analysis with ALL patients. In conclusion it confirmed heterogeneity of ALL by identifying various recurrent chromosomal aberrations along with non-specific rearrangements and their association with specific immunophenotypes. This study pool is representative of paediatric/adult ALL patients in Oman.

Childhood Acute Lymphoblastic Leukemia: Progress Through Collaboration.

To review the impact of collaborative studies on advances in the biology and treatment of acute lymphoblastic leukemia (ALL) in children and adolescents. A review of English literature on childhood ALL focusing on collaborative studies was performed. The resulting article was reviewed and revised by the committee chairs of the major ALL study groups. With long-term survival rates for ALL approaching 90% and the advent of high-resolution genome-wide analyses, several international study groups or consortia were established to conduct collaborative research to further improve outcome. As a result, treatment strategies have been improved for several subtypes of ALL, such as infant, MLL-rearranged, Philadelphia chromosome-positive, and Philadelphia chromosome-like ALL. Many recurrent genetic abnormalities that respond to tyrosine kinase inhibitors and multiple genetic determinants of drug resistance and toxicities have been identified to help develop targeted therapy. Several genetic polymorphisms have been recognized that show susceptibility to developing ALL and that help explain the racial/ethnic differences in the incidence of ALL. The information gained from collaborative studies has helped decipher the heterogeneity of ALL to help improve personalized treatment, which will further advance the current high cure rate and the quality of life for children and adolescents with ALL.

Multi-Agent Chemotherapy Overcomes Steroid Resistance Conferred by a BIM Deletion Polymorphism in Pediatric Acute Lymphoblastic Leukemia (ALL)

BackgroundWe have shown previously that a novel BIM intronic deletion polymorphism was significantly associated with resistance to tyrosine kinase inhibitors (TKIs) in a chronic myeloid leukemia (CML) cohort (OR=2.94, 95% CI = 1.17-7.43, p=0.02) (Ng et al. Nature Medicine, 18: 521-528, 2012). BIM is a potent pro-apoptotic protein that binds pro-survival BCL-2 family members via its BH3 domain, and is required for apoptosis induced by a number of stimuli, including TKIs. Mechanistically, the deletion favors the generation of non-apoptotic exon 3-containing BIM splice variants that lack the BH3 domain found in exon 4. Furthermore, we found that introducing the deletion into a TKI-sensitive CML cell line, K562, was sufficient to confer resistance, and that substituting BIM function with a BH3 mimetic drug could restore sensitivity.Because BIM has also been implicated in steroid-induced apoptosis, we hypothesized that the polymorphism would contribute to response heterogeneity in ALL, where response to steroid treatment is an important prognostic factor. Hence, we used ALL as a model to study the effects of the deletion on steroid resistance and treatment outcome. ResultsFirst, we employed zinc finger nucleases to recreate the 2.9kb intronic deletion in subclones of the ALL cell line CCRF-CEM. Using qPCR, we confirmed that the BIM exon 3: exon 4 ratio was increased in the heterozygous and homozygous clones in a polymorphism dose-dependent manner. When treated with dexamethasone, the deletion-containing clones expressed lower pro-apoptotic BIM isoforms, and were rendered resistant to steroid-induced apoptosis, as determined by MTT assays and PARP and caspase 3 cleavage. These data demonstrate that the polymorphism is sufficient to confer resistance to dexamethasone, and also suggest that it might predict for inferior responses in ALL patients treated with steroid-containing regimens.To test this prediction, we genotyped 411 pediatric ALL patients from the Ma-Spore ALL 2003 study for the BIM polymorphism (Yeoh et al. J Clin Oncol. 30: 2384-92, 2012), and correlated genotype with clinical outcome. These patients were uniformly treated with a modified Berlin-Frankfurt-Münster protocol, which consisted of steroids as well as multi-agent chemotherapy including L-asparaginase and vincristine. When we compared outcome between patients with (n=50) and without (n=361) the polymorphism, there was no significant difference in either event-free survival or overall survival. Further, there was no significant enrichment in the intermediate and high Day 33 minimal residual disease group for patients with the polymorphism.To account for the lack of clinical predictive value, we hypothesized that the chemotherapy agents administered in the study overcame steroid resistance conferred by the polymorphism. Indeed, we found that either L-asparaginase or vincristine resensitized the deletion-containing clones to steroid-induced apoptosis, and that this was associated with MCL-1 downregulation, but not BIM induction. Together, our data demonstrate that BIM deletion-mediated steroid resistance can be overcome by co-administration of drugs that induce cell death via a BIM-independent manner. Importantly, such drugs include standard chemotherapy agents that lower the cellular apoptotic threshold by decreasing pro-survival molecules like MCL-1. Conclusions1. The BIM deletion polymorphism confers steroid resistance to ALL cells in vitro.2. In vitro resistance can be overcome with L-asparaginase or vincristine at clinically relevant doses.3. The BIM deletion polymorphism does not predict for poorer clinical outcome in patients treated with standard protocols, and this is likely to be because co-administration of L-asparaginase or vincristine results in BIM-independent cell death.4. Our findings suggest that selected chemotherapy agents may be used to overcome BIM deletion-associated inferior responses in cancer.5. Finally, our experience highlights the difficulties of identifying associations between genetic variants and clinical outcome in cancers treated with multiple agents, since these may employ different mechanisms of killing and cause confounding. Our earlier success in identifying the polymorphism, and its role in mediating TKI resistance in CML, is likely attributable to the fact that CML is treated with TKI mono-therapy. Disclosures:No relevant conflicts of interest to declare.

Cytologic phenotypes of B-cell acute lymphoblastic leukemia-a single center study.

Acute lymphoblastic leukemia (ALL) is a malignant disorder of lymphoid precursor cells, which could be classified according to morphological and cytochemical methods as well as immunophenotyping. Twenty patients with ALL, who had been referred to the Children's Medical Center Hospital, during the year 2007, were enrolled in this study in order to evaluate the morphologic and immunophenotypic profile of these patients. Cytologic analysis of blood and bone marrow samples revealed that the frequency of ALL-L1 was 70%, followed by ALL-L2 and ALL-L3. The onset age of the patients with ALL-L1 was significantly lower than the patients with L2/L3. Severe anemia was significantly detected more in L1 group. Flow cytometic study of bone marrow showed that 10 cases had Pre-B1 ALL and 7 cases had Pre-B2 ALL, while three cases had Pro-B ALL. Comparisons of the characteristics and clinical manifestations among these groups did not show any appreciable difference. There were an increase percentage of CD20+ cells and a decrease CD10+ cells in pre-B2 group in comparison with pre-B1 group. Fifteen patients were in standard risk and five were in high risk. Although standard risk patients were more common in the group of pre-B1, this was not significant. Our results confirm the previous reports indicating heterogeneity of ALL. Immunophenotyping is not the only diagnostic test of importance, while morphological assessment still can be used in the diagnosis and classification of the disease.

Adhesion Molecule Expression, Clinical Features and Therapy Outcome in Childhood Acute Lymphoblastic Leukemia

In view of the relevance of adhesion molecule expression for the mechanisms of homing, trafficking and spreading of malignant cells, we have investigated the expression of surface adhesion molecules in lymphoblasts from 57 acute lymphoblastic leukemia (ALL) cases and tried to correlate the adhesive phenotype with immunological typing, prognostic factors at diagnosis and clinical follow-up. Blasts from all cases expressed adhesion molecules at high rates. β1 integrin chain (CD18) was consistently found on blasts from most ALL cases; among integrins of the β2 family, LFA-1 was detected in 58% of cases, in the virtual absence of other α chains. CD54 and CD58 were expressed in variable proportions by ALL blasts and CD44 was detected in the majority of the malignant cells, whereas the CD62L selectin was only present in 24% of cases. B-lineage ALL's displayed similar adhesion molecule phenotypes irrespective of maturational stages of the leukemic cells. We found a significantly reduced expression of β2 αL integrins in the hybrid ALL cases (CD13 and/or CD33 positive). However, these cases did not show differences in clinical presentation and behaviour in comparison with patients of other groups. We did not find a significant correlation between adhesion molecule expression and well established risk factors (age, white blood cell count, central nervous system involvement, chromosomal abnormalities), with the exception of splenomegaly, that was significantly associated with CD18 expression. In the follow-up, no evidence of significant correlation between adhesive phenotype and adverse events such as leukemic relapse and death was found. In conclusion, although expression of adhesion molecules on lymphoblasts confirms the phenotypic heterogeneity of ALL, it appears that this is not relevant for the clinical aspects of the disease and for prognosis.

The value of the immunological subtypes and individual markers compared to classical parameters in the prognosis of acute lymphoblastic leukemia

The value of the immunophenotypical subtypes and individual markers was compared with classical parameters in the prognosis of 150 patients with acute lymphoblastic leukemia (ALL). Regarding the immunophenotype, common-ALL had a better prognosis than T-ALL in the children's group. However, in adults the situation was different since both null and T-ALL patients had longer survival rates than the common pre-B group. Moreover, several individual markers add interesting prognostic information, either in ALL as a whole group or within the different immunophenotypes. Thus, the expression of CD10 and TdT had a significantly favourable influence in the outcome of the whole series of patients; within the T-ALL, those cases positive for CD10 also had a longer median survival (33 versus 17 months). In addition, in the common ALL patients group the expression of a relatively mature B marker--CD20--appeared to have a favourable prognosis (27 versus 13 months). Other non lineage specific markers, such as CD9 and CD38 did not seem to influence survival. Regarding the more conventional parameters, our data suggest that the classical age prognostic classification in children (less than 15 years) and adults can be improved using two cut-off points at 11 and 35 years. Moreover, the multivariate analysis showed that this variable, together with FAB morphology and WBC counts were the best combination of parameters for predicting survival. The present study shows that although the immunophenotype helps us in understanding the biological heterogeneity of ALL, having also prognostic implications, there are other clinical and hematological features that yield stronger prognostic information.