Gene expression profiles in T cell ALL identified five different signature patterns involving different oncogenes: TLX1 (HOX11), TLX3 (HOX11L2), TAL1 plus LMO1/2, LYL1 plus LMO2 and MLL-ENL.85 Only the TLX1-expressing samples were associated with a favorable outlook in children86 87 and adults88 with T cell ALL.

Cryptic t(5;14)(q35;q32) and the overexpression of the TLX3 gene

TLX3 gene expression represents one of the five onco-genes involved in T-cell ALL. This gene is located on chromosome 5q35 and was found to be transcriptionally activated as a result of a translocation between chromosomes 5 and 14, t(5;14)(q35;q32).84 A study of samples from 23 childhood T-cell ALL patients revealed that this translocation was cryptic in five of them,84 which was corroborated by larger studies.85 86 Overexpression of TLX3 was reported by one group87 to bestow poor prognosis but this has not been substantiated by other, larger studies.85,86

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