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TAL1 expression does not occur in the majority of T‐ALL blasts
Author(s) -
Delabesse Eric,
Bernard Muriel,
Meyer ValÉrie,
Smit Linda,
Pulford Karen,
Cayuela JeanMichel,
Ritz Jermoe,
Bourquelot Priscille,
Strominger Jack L.,
Valensi FranÇoise,
Macintyre Elizabeth A.
Publication year - 1998
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.1998.00807.x
Subject(s) - expression (computer science) , medicine , computer science , programming language
The TAL1 gene is disrupted by translocation or deletion ( tal d ) in up to 30% of T‐cell acute lymphoblastic leukaemia (T‐ALL), leading to aberrant transcriptional activation, as a SIL‐TAL1 fused transcript in tal d . It has been suggested that TAL1 transcription occurs in approximately 50% of a T‐ALLs without apparent rearrangement. SIL‐TAL1 was positive in 15/60 (25%) of T‐ALL, whereas wild‐type TAL1 transcripts were detected in all 13 SIL‐TAL1 and in 19/43 (44%) T‐ALL without SIL‐TAL1 . To investigate the cellular origin of TAL1 we exploited the fact that GATA1 and TAL1 are co‐ordinately expressed in non‐lymphoid haemopoietic cells, whereas only the latter is found in T‐ALL. GATA1 was detected in 10/23 (43%) TAL1 ‐negative T‐ALLs but in 17/19 (89%) ‘unexplained’ TAL1 ‐positive cases, suggesting a common non‐lymphoid cellular origin. Immunocytochemical analysis with a TAL1‐specific monoclonal antibody showed nuclear expression in the blasts of 10/34 (29%) cases, including 8/10 SIL‐TAL1 + and two RT‐PCR TAL1 + , SIL‐TAL1 − cases. In the remaining cases TAL1 expression was restricted to a minor population (< 5%) of larger, strongly TAL1‐positive cells which comprised erythroid cells, CD34 + CD3 − precursors and an unidentified TAL1 + CD45 − population which morphologically resembled monocytes/macrophages. We therefore suggest that appropriate diagnostic evaluation of T‐ALL should include molecular detection of SIL‐TAL1 transcripts and in situ immunocytochemical detection of TAL1 protein expression by leukaemic blasts. This approach will enable accurate analysis of the prognostic significance of TAL1 deregulation in T‐ALL.