| Abstract |
Most acute leukemias can be assigned to a specific stage of either
lymphoid or hematopoietic differentiation. However. in approximately 20%
of pediatric T-ALL there is expression of one or both of tho myeloid-
associated antigens CD13 and CD33. Conversely, in approximately 20% of
pediatric ANLL there is expression of the T lymphoid associated antigen
CD7. In order to further characterize the phenotype and genotype of mixed
lineage leukemia cells, we have established a cell line, ARR, from a CD7+,
surface CD3-(sCD3-), CD33+ T-ALL. Like the original leukemia, the ARR cell
line expressed CD7 and CD33. but not sCD3. The ARR cell line contained a
rearranged TCRbeta gene. Analysis of the mRNA phenotype using reverse
transcription PCR revealed that the ARR cell line expressed GM-CSF
receptor (GM-CSFR) alpha and beta chains, IL7 receptor, and CD3delta. Phorbol
myristate acetate (PHA) treatment induced mRNA for IL6 receptor and the
myelomonocytic antigen CD13. This mRNA phenotype after PMA stimulation was
identical to the mRNA phenotype of 3 cases of myeloid antigen (CD13, CD33)
positive T-ALL and 2 cases of T lymphoid antigen (CD7) positive ANLL. The
phenotype however was different from 1 case of T-ALL not expressing
myeloid features (My- T-ALL) and a My- T-ALL cell line (CEM). The ARR cell
line is a model of a closely related group of acute leukemias which
express transcripts for both myeloid and lymphoid growth factor receptors
and the T lymphoid specific CD3delta. This subgroup differs from My- T-ALL
and may have as its origin a leukemic progenitor cell which possesses a
unique phenotype and genotype.
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