Blood, Vol. 95 No. 4 (February 15), 2000:
pp. 1456-1464
Aberrant expression of active leukotriene C4 synthase
in CD16+ neutrophils from patients with chronic myeloid
leukemia
Mikael Sjölinder,
Leif Stenke,
Barbro Näsman-Glaser,
Susanne Widell,
Johanne Doucet,
Per-Johan Jakobsson, and
Jan Åke Lindgren
From the Division of Physiological Chemistry II, Department of
Medical Biochemistry and Biophysics, and the Division of Hematology,
Department of Internal Medicine, Danderyd Hospital at Karolinska
Institutet, Stockholm, Sweden, and the Division of
Hematology, Department of Internal Medicine, Karolinska Hospital at
Karolinska Institutet, Stockholm, Sweden.
Elevated leukotriene (LT)C4 synthase
activity was observed in peripheral blood granulocyte suspensions from
patients with chronic myeloid leukemia (CML). Magnetic cell sorting
(MACS) with CD16 monoclonal antibodies (mAbs), which were used to
fractionate granulocytes from CML patients and healthy individuals,
yielded highly purified suspensions of CD16+ neutrophils.
The purity of these cell fractions was verified by extensive
morphologic examination. Reverse transcriptase-polymerase chain
reaction (RT-PCR) analyses, demonstrating the absence of interleukin-4
messenger RNA (IL-4 mRNA), further confirmed the negligible
contamination of eosinophils in these fractions. Notably, purified CML
CD16+ neutrophils from all tested patients transformed
exogenous LTA4 to LTC4. These cells also
produced LTC4 after activation with ionophore A23187 or
the chemotactic peptide fMet-LeuPhe
(N-formylmethionyl-leucyl-phenylalanine). Subcellular fractionation revealed that the enzyme activity was exclusively distributed to the microsomal fraction. Expression of
LTC4 synthase mRNA in CML CD16+
neutrophils was confirmed by RT-PCR. Furthermore, Western blot analyses
consistently demonstrated expression of LTC4 synthase at
the protein level in CML CD16+ neutrophils, whereas
expression of microsomal glutathione S-transferase 2 occurred occasionally. Expectedly, LTC4 synthase activity
or expression of the protein could not be demonstrated in
CD16+ neutrophil suspensions from any of the healthy
individuals. Instead, these cells, as well as CML CD16+
neutrophils, transformed LTA4 to LTB4. The
results indicate that aberrant expression of LTC4 synthase
is a regular feature of morphologically mature CML CD16+
neutrophils. This abnormality, possibly associated with malignant transformation, can lead to increased LTC4 synthesis in
vivo. Such overproduction may be of pathophysiological relevance
because LTC4 has been demonstrated to stimulate
proliferation of human bone marrow-derived myeloid progenitor cells.
