Key Markers of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia

High frequency of heat shock protein 27 overexpression is a highly effective, high-coverage marker for minimal residual disease detection in children with B-cell acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. Minimal residual disease (MRD) detection is the most powerful prognostic tool for monitoring treatment efficacy and predicting clinical outcomes. We aimed to identify key leukemia-associated markers, the proportions of differential expression in patients, and the most effective marker combination for MRD detection by flow cytometry.

METHODS

Bone marrow samples were collected from 132 pediatric patients with newly diagnosed (n = 115) or relapsed (n = 17) B-cell precursor (BCP)-ALL. We used CD19, CD10, CD34, CD45 as backbone markers to identify immature B cells and analyzed the differential expression of 18 leukemia-associated markers using seven-color multiparameter flow cytometry.

RESULTS

Leukemic cells in all 132 patients expressed leukemia-associated markers. The most commonly overexpressed marker was heat shock protein 27 (Hsp27) (108 patients, 81%), followed by CD73 (102 patients, 77%) and CD123 (80 patients, 60%). CD38 was underexpressed in 64 patients (48%). Hsp27 overexpression persisted in 50 out of 57 follow-up MRD bone marrow samples (87%) and was associated with older age at diagnosis. Hsp27 overexpression was not associated with MRD levels or genetic abnormalities including hyperdiploidy, t(12;21)/ETV6-RUNX1, t(1;19)/TCF3-PBX1, t(9;22)/BCR-ABL1, or 11q23/KMT2A rearrangements. Four remaining leukemia-associated markers (Hsp27, CD73, CD58, CD24) after in silico deletion from the original panel could collectively detect leukemia-associated cell profiles in 100% of cases in this cohort and 98% of cases in a validation cohort.

CONCLUSION

Hsp27 combined with CD73, CD58, CD24, and backbone markers allows monitoring MRD in virtually all patients with BCP-ALL.

Cysteine and glycine-rich protein 2 (CSRP2) transcript levels correlate with leukemia relapse and leukemia-free survival in adults with B-cell acute lymphoblastic leukemia and normal cytogenetics

Relapse is the major cause of treatment-failure in adults with B-cell acute lymphoblastic leukemia (ALL) achieving complete remission after induction chemotherapy. Greater precision identifying persons likely to relapse is important. We did bio-informatics analyses of transcriptomic data to identify mRNA transcripts aberrantly-expressed in B-cell ALL. We selected 9 candidate genes for validation 7 of which proved significantly-associated with B-cell ALL. We next focused on function and clinical correlations of the cysteine and glycine-rich protein 2 (CSRP2). Quantitative real-time polymerase chain reaction (RT-qPCR) was used to examine gene transcript levels in bone marrow samples from 236 adults with B-cell ALL compared with samples from normals. CSRP2 was over-expressed in 228 out of 236 adults (97%) with newly-diagnosed B-cell ALL. A prognostic value was assessed in 168 subjects. In subjects with normal cytogenetics those with high CSRP2 transcript levels had a higher 5-year cumulative incidence of relapse (CIR) and worse relapse-free survival (RFS) compared with subjects with low transcript levels (56% [95% confidence interval, 53, 59%] vs. 19% [18, 20%]; P = 0.011 and 41% [17, 65%] vs. 80% [66–95%]; P = 0.007). In multivariate analyses a high CSRP2 transcript level was independently-associated with CIR (HR = 5.32 [1.64–17.28]; P = 0.005) and RFS (HR = 5.56 [1.87, 16.53]; P = 0.002). Functional analyses indicated CSRP2 promoted cell proliferation, cell-cycle progression, in vitro colony formation and cell migration ability. Abnormal CSRP2 expression was associated with resistance to chemotherapy; sensitivity was restored by down-regulating CSRP2 expression.

Detection of minimal residual disease in childhood B-acute lymphoblastic leukemia by 4-color flowcytometry

Monitoring of minimal residual disease (MRD) is currently considered the most powerful predictor of outcome in acute lymphoblastic leukemia (ALL). Achievement of a negative MRD state assessed by multicolor flowcytometry (MFC) is an important predictor of disease-free survival (DFS) and overall survival (OS) in ALL patients. We sought to determine whether panels of antibodies combination are more suitable for detection of MRD in Childhood ALL. Eighty-four (84) patients with ALL (B-lineage subtype) were enrolled in this study. Normal template for B cell precursors was established in 15 control participants using 4-four panels of monoclonal Antibodies (Mo Abs),{CD22, CD45, CD58 and CD97 in combination with CD10, CD19, CD34}. At diagnosis, CD22 exhibited the lowest incidence of expression in only 50% of all patients, while CD45, CD58, and CD97 were expressed in 80.9, 59.5 and 92.8%, respectively. Analysis of MRD was performed for each Mo Abs combination at day 0 and day 14 post-induction of chemotherapy by 4-color (FCM). The incidence of MRD was 61.9, 70.6, 60.0 and 55.1% for CD22, CD45, CD58 and CD97, respectively. In B-ALL patients, (CD10/CD19/CD34/CD45) + (CD10/CD19/CD34/CD97) represented the highest incidence of expression of leukemic cells markers with a significant correlation with blasts count, suggesting that these are more specific for MRD detection. Also FCM is relatively cost effective for detection of MRD in ALL patients and its applicability in routine leukemia lab is valuable. MRD evaluation at the end of the induction therapy (i.e. day 35 or 42 according to the different schedules) is advised. Also, Ig/T cell receptor gene rearrangements and gene fusions analyzed by polymerase chain reaction (PCR) are preferred.