Impact of HOX11L2 and TAL1/SCL Expression in T-Cell Acute Lymphoblastic Leukaemia (T-ALL): Results of the FRALLE 93 Protocol.
Authors: Ballerini Paola , Cayuela Jean-michel , Asnafi Vahid , Fasola Sylvie , Auclerc Marie-francoise , Perel Yves , Lejars5 Odile , Debre6 Marianne , Michel7 Gerard , Gandemer8 Virginie , Pautard9 Brigitte , Leblanc Thierry , Macintyre Elizabeth , Leverger Guy , Baruchel Andre , Landman-Parker Judith 
Published: October 2019

Abstract
The most frequent oncogenic activation events characterized in childhood T acute lymphoblastic leukemia (T-ALL) result in the transcriptional activation of genes coding for transcription factors. The main genes are TAL1/SCL, a member of the basic region helix-loop-helix gene family, HOX11L2 a member of the homeobox-containing protein family. Conflicting results have been reported concerning molecular epidemiology and prognostic values of these markers (Cavé Blood2003:103442–445, Ferrando Cancer Cell 2002, Dicciani Blood 2003 abs 67) we therefore analysed retrospectively 200 pts treated in the French protocol FRALLE 93 for T-ALL between 11/93 and 12/99. Pts were stratified according to prednisone response at D8 ( good or poor : GPR or PPR) and bone marrow at D21. Pts with D8 PPR or M3 received an intensified treatment with genoidentical or autologous transplant in CR1. Molecular analysis was possible for 79/200 T-ALL samples. Clinical caracteristics were not significantly different between population with or without molecular analysis male (n=121) (69% vs 70%), median age 8.4y (range1.1–19.5) vs 9.2y, median leucocytosis 140.109 (0.6–736) vs 171.915 109 (<50 n=23, 50–99 n=8, >100 n=48), mediastinal involvement 72% vs 71% ,CNS+ 4% vs 5%, CD 10 neg 54% vs 52%. Steroid response PPR n=37/73, GPR n=36/73 and D21 bone marrow status (M3 n=10, M2 n=11) were similar. CR was obtained in 72/79 pts (91%) after first induction therapy and 2 deaths occurs during induction treatment. With a median follow-up of 63 months (2–123), 5 y OS , EFS and DFS is 62 %± 9 and 54% ±10. SIL-TAL1/SCL fusion was detected in 20/79 (25%) pts; expression of HOX11L2 was observed in 14/79 (17%) pts. These activations are mutually exclusive and they allow the subclassification of 42 % of the patients. Median leucocytosis was significantly higher in SIL-TAL1/SCL pts (p=0.01) but other significant features ( ie median age, D8 response, D21 status) were not significantly different between each group. OS and EFS for TAL1/SCL , HOX11L2+ and none of these were respectively 81%±10, 43%±13, 62%± 7 and 80%±10 , 42%± 13, 55%± 7. OS and EFS D8 PPR/GPR were 47%± 9 vs 78% ±7 (p=0.009) and 41%±8 vs 71%±7 (p= 0.008); OS and EFS M2M3 vs M1 D21 bone marrow status were 45%± 15 vs 70% ±6 (p=0.05) and 36%±10 vs 66%± 6 (p= 0.018). In multivariate Cox model analysis, D8 steroid response and HOX11L2 expression were significantly associated with adverse event (failure or relapse) Risk Ratio :3 and 2.6 - p=0.008 and 0.03 and a higher risk of death Risk Ratio : 4.1 and 3.4 -p=0.061 and 0.05. Finally HOX11L2 expression and D8 PPR are independently associated with poor outcome in FRALLE 93 protocol analysis which confirms our previous report. Discrepancies among series may be explained by confounding factors such as differences in median leucocytes value(140.109 in our study) and treatment.