ALBERT

Description: The C-Myb transcription factor is essential for hematopoiesis, including in the T-cell lineage. The C-Myb locus is a common site of retroviral insertional mutagenesis, however no recurrent genomic involvement has been reported in human malignancies. Here, we identified 2 types of genomic alterations involving the C-MYB locus at 6q23 in human T-cell acute leukemia (T-ALL). First, we found a reciprocal translocation, t(6;7)(q23;q34), that juxtaposed the TCRB and C-MYB loci (n = 6 cases). Second, a genome-wide copy-number analysis by array-based comparative genomic hybridization (array-CGH) identified short somatic duplications that include C-MYB (MYBdup, n = 13 cases of 84 T-ALL, 15%). Expression analysis, including allele-specific approaches, showed stronger C-MYB expression in the MYB-rearranged cases compared with other T-ALLs, and a dramatically skewed C-MYB allele expression in the TCRB-MYB cases, which suggests that a translocation-driven deregulated expression may overcome a cellular attempt to down-regulate C-MYB. Strikingly, profiling of the T-ALLs by clinical, genomic, and large-scale gene expression analyses shows that the TCRB-MYB translocation defines a new T-ALL subtype associated with a very young age for T-cell leukemia (median, 2.2 years) and with a proliferation/mitosis expression signature. By contrast, the MYBdup alteration was associated with the previously defined T-ALL subtypes.

Description: In September 2003, the French CML study group (Fi-LMC) activated the four armed randomized SPIRIT trial comparing imatinib 400mg with imatinib 600mg, imatinib 400mg + ara-C and imatinib 400mg + pegylated interferon in newly diagnosed CML in chronic phase. The molecular monitoring was centralized and performed, according to the EAC protocol, in duplicate on the same BCR-ABL cDNA among two French laboratories (Bordeaux and Lille). Data were expressed as BCR-ABL/ABLx100 on the new internationally agreed scale (IS) using a conversion factor of 1.33 and 0.80 for Bordeaux and Lille respectively. A good correlation between the two laboratories was observed. During the first year of follow-up the quantification was performed each three months (M0 to M12). In May 2006, 297 of the 492 enrolled pts had a follow up of more than 12 months, and 263 pts were analysed at M12. Using the IS, the median values of the BCR-ABL/ABL normalized ratios were 90%, 6,4%, 0.68%, 0.32% and 0.16% at M0, M3, M6, M9, and M12 respectively. At M12, 15%, 29%, 27%, 17% and 12% of the pts presented a BCR-ABL/ABL ratio lower than 0.01%, 0.1% ,1%, 10%, and 100% respectively. Overall, 71% of the pts presented a ratio lower than 1%. Conventional cytogenetic data were available for 193 pts at M12: 156 pts (80%) were in complete cytogenetic response (CCR), 25 pts (13%) were in major cytogenetic response (MCR) and 12 pts (6.2%) were in minor or a lack of cytogenetic response. Among pts with a BCR-ABL transcript ratio lower than 1%, all except four were in CCR. The last 4 cases were in MCR associated with BCR-ABL ratios of: 0.96% for one pt, 0.08% and 0.12% for 2 pts (who further reached CCR at 6 and 18 months) and 0.128% for the last one. Percentages of Philadelphia positive metaphase (Ph+) were 4%, 6%, 5 % and 15% respectively. Among the 30 pts with a BCR-ABL ratio 〉 5%, none were in CCR and only 18 pts were in MCR. Among the 27 pts presenting a BCR-ABL ratio in the 1%–5% intervals, 20 pts were in CCR and 7 pts were in MCR (5 pts with Ph+ lower than 10% and two pts with 16% and 20% Ph+). In conclusion, our findings suggest that a ROC statistical test will be able to determine critical BCR-ABL/ABL ratios associated to CCR in our study. Nevertheless, at M12 the percentage of available data was superior using molecular than cytogenetic monitoring, suggesting that molecular monitoring expressed with the new international scale is probably sufficient fore more than 85 % of the pts treated by IM solely or in association.

Description: Cytogenetics and expression studies have pointed out an increasing number of oncogenes in T-cell acute lymphoblastic leukemias (T-ALL), demonstrating the complexity of T-ALL oncogenesis and the requirement for a network of cooperative genomic events. Here, we identified two types of genomic alterations involving the C-MYB locus at 6q23 in human T-ALL, both associated with transcriptional deregulation. First, using a TCRB-based FISH screening, we found a new reciprocal translocation, t(6;7)(q23;q34), that juxtaposed the TCRB and C-MYB loci (n=6 cases). Breakpoints were fully characterized at the molecular level in 3 cases. Second, a genome wide copy-number analysis by array-CGH (customized 4K BAC/PAC arrays) identified short cryptic duplications which always include the C-MYB gene (MYBdup, n=11 out of 80 primary pediatric and adult T-ALL, 14%). Somatic origin of the genomic gain was demonstrated using paired leukemic and remission samples. The minimal region of gain was mapped to 230 Kb using 244K oligonucleotide a-CGH, and fiber-FISH demonstrated tandem duplication. Interestingly, these genomic events are reminiscent of the frequent myb retroviral insertions in murine leukemia. Expression analysis by RQ-PCR and microarrays data showed stronger C-MYB expression in the MYB-rearranged cases compared to other T-ALLs and normal controls (thymus, BM, and PBL). Moreover, allele-specific approaches showed a dramatically skewed allele expression in the TCRB-MYB cases, suggesting that the translocation-driven deregulated expression overcomes a cellular attempt to downregulate C-MYB. Considering that the C-MYB transcription factor has been involved at several key steps throughout normal thymic differentiation, these data strongly suggest that deregulation of C-MYB due to genomic events is oncogenic in T-ALL. Integrated analysis of clinical, genomic, and large-scale gene expression data showed that the MYB translocation defines a new T-ALL subtype. Strikingly, 5 out of 6 patients with the translocation had a very young age for T-cell leukemia (1.1, 1.3, 1.8, 2.5, and 2.9 year-old; median 2.2 versus 9.4 year-old for 355 pediatric T-ALL in the FRALLE 93/2000 pediatric trials, p

Description: In September 2003, the French CML study group (Fi-LMC) activated the four armed randomized SPIRIT trial comparing imatinib 400mg with imatinib 600mg, imatinib 400mg + ara-C and imatinib 400mg + pegylated interferon in newly diagnosed CML in chronic phase. The molecular monitoring was centralized and performed, according to the EAC protocol, in duplicate on the same BCR-ABL cDNA among two French laboratories (Bordeaux and Lille). Data were expressed as BCR-ABL/ABLx100 on the new internationally agreed scale (IS) using a conversion factor of 1.33 and 0.80 for Bordeaux and Lille respectively. A good correlation between the two laboratories was observed. During the first year of follow-up the quantification was performed each three months (M0 to M12). In May 2006, 297 of the 492 enrolled pts had a follow up of more than 12 months, and 263 pts were analysed at M12. Using the IS, the median values of the BCR-ABL/ABL normalized ratios were 90%, 6,4%, 0.68%, 0.32% and 0.16% at M0, M3, M6, M9, and M12 respectively. At M12, 15%, 29%, 27%, 17% and 12% of the pts presented a BCR-ABL/ABL ratio lower than 0.01%, 0.1%, 1%, 10%, and 100% respectively. Overall, 44% of the pts reached the Major Molecular Response (MMR). Results were also expressed using individual M12/M0 ratio. At M12 13%, 29%, 28%, 17% and 13% of the pts presented a 4 log, 3 log, 2 log, 1 log and 0 log reduction respectively. Overall, 42% of the pts presented an individual 3 log reduction. Despite very similar results between the two means of expression, the pts distribution was different due to unlike individual BCR-ABL transcript level at MO. Furthermore, the analysis of 75 paired samples before (at diagnosis) and after (at inclusion) hydroxyurea treatment (5 days to 1.2 months) revealed BCR-ABL/ABL ratios of 129% and 108% respectively, confirming the 0.2 log difference previously reported by A. Hochhaus et al. In conclusion, expression of the data using the new IS or the individual M12/M0 ratio was very similar in our experience regarding the percentage of each subgroup but the pts distribution was different and a longer follow up would be useful to define the best method. However, the good correlation observed in the IRIS trial between MMR and progression, the influence of hydroxyurea treatment on BCR-ABL level, the good correlation observed among laboratories and the need of harmonisation of expressed results influenced our choice for the new IS. The application of this recommendation is in progress in the great majority of the molecular French laboratories.