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Expression of granule protein mRNAs in acute promyelocytic leukemia
R K Hirata1, S T Chen, S C Weil
1Department of Pathology and Cell Biology, Cardeza Foundation, Thomas Jefferson University Medical College, Philadelphia, Pennsylvania 19107.
Abstract:
The granule proteins are among the most abundant and characteristic proteins of myeloid cells. They are essential for the antimicrobial activity of these cells and they provide important markers for the differentiation stage of the myeloid series and for the diagnosis of myeloid leukemias. In acute promyelocytic leukemia (APL) there is high production of myeloperoxidase, and its cytochemical detection as well as the t(15;17) chromosomal translocation are important markers in the diagnosis of this acute myelogenous disease. The expression of other granule protein genes in APL has not been systematically determined. We have used the reverse transcriptase-polymerase chain reaction (RT-PCR) method to determine the pattern of expression of granule protein genes at the mRNA level in APL cells. We have examined the expression of the primary granule proteins defensin, myeloperoxidase, elastase, and cathepsin G; the secondary granule proteins lactoferrin, collagenase, and transcobalamin; as well as lysozyme, a protein reportedly found in both primary and secondary granules. mRNAs for all of these granule proteins were present in normal bone marrow mononuclear cells. We found that APL cells from three patients contain, in addition to myeloperoxidase mRNA, mRNAs for elastase, cathepsin G, and lysozyme. One patient had faint but detectable lactoferrin mRNA signal, but collagenase and transcobalamin mRNAs were not detectable in this patient. Defensin mRNA was found in one of the three APL patients, and all the primary granule protein mRNAs measured were found to be expressed in the APL cell line NB4. None of the secondary granule protein mRNAs measured were detectable in NB4 cells. After treatment with retinoic acid (RA), which induces neutrophil maturation of these cells, weak induction of lactoferrin and collagenase but not transcobalamin was observed. However, in view of the weak transcobalamin signal observed in normal bone marrow, the absence of transcobalamin in RA-induced NB4 cells must be interpreted with caution. Interestingly, elastase and cathepsin G mRNA disappeared after RA induction, whereas defensin and myeloperoxidase mRNAs remained present. These findings indicate that granule protein mRNAs are regulated separately and differently, and that only minimal expression of secondary granule protein genes can occur in APL cells.
Insights
This study investigated granule protein gene expression in acute promyelocytic leukemia (APL) cells using RT-PCR. Findings reveal distinct regulation of these essential myeloid cell proteins in APL and during neutrophil maturation.
Area of Science:
- Hematology
- Molecular Biology
- Oncology
Background:
- Granule proteins are crucial for myeloid cell function and serve as diagnostic markers for myeloid leukemias.
- Acute promyelocytic leukemia (APL) is characterized by high myeloperoxidase production, but the expression of other granule protein genes remains largely uncharacterized.
- Understanding granule protein gene expression in APL is vital for refining diagnostic strategies and exploring therapeutic targets.
Purpose of the Study:
- To systematically determine the mRNA expression patterns of various granule proteins in acute promyelocytic leukemia (APL) cells.
- To investigate the differential regulation of granule protein genes in APL cells and their response to retinoic acid (RA) treatment.
Main Methods:
- Utilized reverse transcriptase-polymerase chain reaction (RT-PCR) to analyze mRNA levels of primary (defensin, myeloperoxidase, elastase, cathepsin G) and secondary (lactoferrin, collagenase, transcobalamin) granule proteins, plus lysozyme.
- Examined granule protein mRNA expression in primary APL patient cells and the APL cell line NB4.
- Assessed changes in mRNA expression following retinoic acid (RA) induced neutrophil maturation of NB4 cells.
Main Results:
- APL cells expressed myeloperoxidase, elastase, cathepsin G, and lysozyme mRNAs; lactoferrin and defensin mRNAs were detected in some patients.
- Collagenase and transcobalamin mRNAs were generally undetectable in APL cells, while NB4 cells showed no secondary granule protein mRNA expression.
- RA treatment induced lactoferrin and collagenase mRNA in NB4 cells, but elastase and cathepsin G mRNAs decreased, indicating differential gene regulation.
Conclusions:
- Granule protein mRNAs are differentially regulated in APL cells, with limited expression of secondary granule protein genes.
- Retinoic acid treatment induces specific granule protein gene expression changes, highlighting distinct regulatory pathways during myeloid differentiation.
- These findings contribute to a deeper understanding of myeloid cell biology and APL pathogenesis.