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Updated: Oct 24, 2026
Single-cell Gene Expression Using Multiplex RT-qPCR to Characterize Heterogeneity of Rare Lymphoid Populations
Published on: January 19, 2017
Genetic, phenotypic and clinical features of acute lymphoblastic leukemias expressing myeloperoxidase mRNA detected
Abstract:
Myeloperoxidase (MPO) is found in the azurophilic granules of normal myelocytic cells. Cytochemical staining for MPO activity is used clinically to distinguish myeloid from acute lymphoid leukemias (ALL). However, using a highly sensitive RT-PCR technique, it is possible to detect MPO mRNA in otherwise clear ALL. The significance of this finding remains poorly understood. We have extended our observations to a series of 57 patients with the primary diagnosis of ALL (46 patients tested at diagnosis and 11 cases at relapse). We identified 25 cases (43.8%) of MPO mRNA(+)/enzyme(-) ALL (17 B cell and eight T cell lineage). Expression of myeloid antigens (CD13 or CD33) were detected in nine of them, and remarkably, 18 cases (72%) displayed CD34. Of these 25 MPO mRNA(+) leukemias, 10 (40%) are Bcr-Abl positive (with P210 fusion transcript in five patients while the five remaining cases carried P190 transcript). Moreover, 11 of 16 myeloid negative cases were also negative for any type of Bcr-Abl and MLL rearrangement, indicating that MPO mRNA positivity is not either invariably related to that chromosomal abnormality or necessarily associated with the presence of other myeloid differentiation features. Interestingly, six of these 11 cases are T-ALL, suggesting the presence of some overlapping phase for T and myeloid lineage commitment. Taken together, these findings could suggest a separate biological disease with immature origin and bipotential differentiation capability, which involves B and T-ALL subtypes and should lead to new investigations regarding their prognostic impact.
Insights
Myeloperoxidase (MPO) mRNA is detectable in some acute lymphoid leukemias (ALL), challenging traditional diagnostics. This finding suggests a distinct ALL subtype with immature origins and potential bipotential differentiation capabilities.
Area of Science:
- Hematology
- Molecular Biology
- Oncology
Background:
- Myeloperoxidase (MPO) activity is a key diagnostic marker differentiating myeloid from lymphoid leukemias.
- Traditional cytochemistry for MPO activity may not detect MPO mRNA in certain acute lymphoid leukemias (ALL).
Purpose of the Study:
- To investigate the prevalence and significance of MPO mRNA expression in patients diagnosed with ALL.
- To explore the immunophenotypic and molecular characteristics of MPO mRNA-positive ALL cases.
Main Methods:
- Analysis of 57 ALL patients (diagnosis and relapse) using sensitive RT-PCR for MPO mRNA detection.
- Immunophenotyping for myeloid antigens (CD13, CD33) and CD34 expression.
- Molecular analysis for Bcr-Abl and MLL rearrangements.
Main Results:
- 43.8% of ALL cases (25/57) were MPO mRNA-positive but enzyme-negative.
- MPO mRNA-positive ALL frequently expressed CD34 (72%) and sometimes myeloid antigens (25%).
- 40% of MPO mRNA-positive ALL cases harbored Bcr-Abl transcripts (P210 or P190).
Conclusions:
- MPO mRNA positivity in ALL indicates a distinct biological entity, potentially with immature origins and bipotential differentiation.
- These findings challenge the strict myeloid/lymphoid classification and suggest new avenues for prognostic investigation.
- The co-occurrence in T-ALL cases suggests overlapping lineage commitment between myeloid and lymphoid lineages.
