Letters to the Editor 251 BTG1 deletions do not predict outcome in Down syndrome acute lymphoblastic leukemia

Leukemia (2013) 27, 251–252; doi:10.1038/leu.2012.199 incidence of relapse (CIR) was constructed by the method of Kalbfleisch and Prentice and compared by the Gray test. All 116 DS ALL patients were classified as B-cell precursor ALL Children with Down syndrome (DS) have an increased risk of and treated with curative intent. The median age was 5.1 years developing acute myeloid and B-cell precursor acute lympho- (range 1.3–23.2), the median WBC was 14 Â 109/l (range 1.2–400) blastic leukemia (BCP-ALL).1 The prognosis of DS ALL is at best and 65% of the patients were male. The median follow up time for similar and often inferior to that of sporadic ALL (non-DS) survivors was 4.6 years (range 1.3 months—15.3 years). patients.2,3 DS ALL is characterized by unique biological features In total, we found 8/116 (6.9%) deletions of BTG1, a frequency when compared with non-DS ALL. For instance, DS ALL has lower than described by Lundin et al.14 in DS ALL and similar to a lower frequency of the favorable genetic abnormalities other non-DS B-cell precursor ALL series.7,9 Remarkably, all eight t(12;21)(p13;q22) (ETV6–RUNX1) and the unfavorable t(9;22)(q34;q11) patients showed a nearly identical deletion pattern in which the (BCR-ABL1),3,4 butahigherfrequencyofJAK2 mutations and CRLF2 BTG1 area 1, area 2 and exon 2 probes were deleted, whereas exon rearrangements.5,6 Using genome-wide screening techniques, several 1 was retained (6 Â monoallelic, 2 Â biallelic). Due to statistical (novel) genomic aberrations involved in the pathogenesis of power, we excluded one patient from the analysis who had a (non-) DS ALL were identified.7,8 The potential prognostic impact monoallelic amplification of the BTG1 area 2 probe. This patient of most of these novel aberrations and whether these patients also had a CRLF2 aberration, but the karyotype of this patient may benefit from specific therapies targeted to these unique showed no other aberration than the constitutional trisomy 21. genetic features needs to be investigated further. She remains in CR for 410 years. The median age of DS ALL The B-cell translocation gene 1 (BTG1) was recently described patients with a deletion of BTG1 was 5.4 years (range 2.7–23.2), the as a recurrent lesion in pediatric BCP-ALL.7,9,10 It was originally median WBC was 59 Â 109/l (range 11.3–390) and 62% of the identified as a translocation partner of c-MYC in B-cell chronic patients were male. This is different from the cohort of Lundin lymphocytic leukemia.11,12 BTG1 is a highly conserved gene and et al.,14 who reported a high median age of 12 years in patients belongs to the family of BTG/TOB genes.11,13 It has a role in several with a BTG1 deletion and a WBC of 25 Â 109/l. Interestingly they crucial cellular processes, such as proliferation, and apoptosis. reported that BTG1 deletions occurred in predominantly male Recently, Lundin et al.14 reported on a high frequency of BTG1 patients (80%), which is different from our cohort (62% male). deletions (B29%) in DS ALL. However, the study included a BTG1 deletions were not mutually exclusive of other genomic limited number of DS ALL patients (n ¼ 17) and hence may not be aberrations (for example, IKZF1 in four patients, CRLF2 in four an accurate estimate of the frequency of BTG1 deletions in DS ALL. patients). As previously described,7,9,10 BTG1 deletions were mainly Therefore, we investigated the frequency of BTG1 deletions in a found in patients with ETV6–RUNX1-positive ALL (38% vs 12% in large series of DS ALL patients and in addition analyzed the the BTG1 wild-type group; P ¼ 0.02). prognostic significance of BTG1 abnormalities. Interestingly, BTG1 regulates the glucocorticoid receptor-dependent We screened a population-based cohort of 116 DS ALL patients response in leukemic cells,15 and it is therefore implicated that enrolled in consecutive DCOG and UK treatment protocols (DCOG loss of this gene perhaps contributes to a poor outcome.14,15 ALL 8, 9 and 10 and UK ALL ALL97, ALL97/99 and ALL2003).8 Unfortunately, data were available on clinical response to 1 week Clinical and cell-biological data, including cytogenetics, were of prednisone for only two patients with a BTG1 deletion; both available for all cases. DCOG and UK centrally reviewed diagnosis, were good responders. No significant differences in long-term classification and clinical follow-up of the patients. The Institutional clinical outcome between wild type and BTG1 deleted cases Review Board approved the investigations, and informed consent were detected: 5-year EFS 67±5% vs 60±18% (P ¼ 0.4), OS 72±5% was obtained according to local law and regulations. vs 60±18% (P ¼ 0.3), CIR 17±4% vs 15±15% (P(Gray) ¼ 0.9). To identify BTG1 deletions, we performed multiplex ligation- A stepwise multivariate Cox regression model was performed, dependent probe amplification (MLPA) analysis using the SALSA which included WBC X50 Â 109, age X10 years and mutational MLPA kit P335-A3 ALL-IKZF1 (MRC Holland, Amsterdam, the status of BTG1, IKZF1 and ETV6–RUNX1 (Table 1). Deletions of BTG1 Netherlands), which contains probes for selected B-cell development did not predict for prognosis with a hazard ratio (HR) for EFS of and differentiation genes.8 The BTG1 gene is covered by four probes, 1.97 (95% CI 0.6–6.8); P ¼ 0.29 and OS HR 2.24 (95% CI 0.6–7.9; probes to exon 1, exon 2 and two additional probes localized to the P ¼ 0.2). Instead, IKZF1 appeared to be the strongest independent highly conserved promoter region of the gene (area 1 and 2). The full risk factor for EFS, with a HR EFS 2.45 (95% CI 1.2–5.1; P ¼ 0.02), 8 list and location of the MLPA probes can be downloaded from the as previously described by us. MRC Holland website (http://www.mrc-holland.com). Peak heights In conclusion, we could not confirm the high frequency of BTG1 o0.7 (0.75 for MRC UKALL samples) and 41.3 times the control deletions as previously described in a small series of DS ALL, but peak height were considered abnormal, with those o0.7 (0.75) found a prevalence similar to non-DS ALL patients. Moreover, representing deletions, and those 41.3 representing duplications. BTG1 deletions did not predict for dismal outcome in DS ALL The Kaplan–Meier method was used to estimate the 5-year probability patients in contrast to IKZF1 aberrations. Further research is of overall survival (OS), and event-free survival (EFS); survival estimates needed to identify other potential players and cooperating events were compared using the log-rank test. OS was measured from in the leukemogenesis in DS children. the date of diagnosis to the date of last follow-up or date of death from any cause. EFS was calculated from the date of diagnosis to the date of last follow-up or to the first event, including relapse, failure CONFLICT OF INTEREST to achieve complete remission (CR) and death in CR. Cumulative The authors declare no conflict of interest.

Accepted article preview online 17 July 2012; advance online publication, 7 August 2012

& 2013 Macmillan Publishers Limited Leukemia (2013) 233 – 258 Letters to the Editor 252 Table 1. Results of multivariate analysis for event-free survival, overall REFERENCES survival and relapse-free survival 1 Hasle H, Clemmensen IH, Mikkelsen M. Risks of leukaemia and solid tumours in individuals with Down’s syndrome. Lancet 2000; 355: 165–169. Outcome Variable HR 95% CI P-value 2 Whitlock JA, Sather HN, Gaynon P, Robison LL, Wells RJ, Trigg M et al. Clinical characteristics and outcome of children with Down syndrome and acute lympho- EFS BTG1 1.97 0.57–6.84 0.29 blastic leukemia: a Children’s Cancer Group study. Blood 2005; 106: 4043–4049. IKZF1 2.45 1.18–5.07 0.02 3 Buitenkamp T, Forestier E, Heerema NA, van den Heuvel MM, Pieters R, de Haas V ETV6–RUNX1 0.22 0.03–1.74 0.15 et al. Acute Lymphoblastic Leukemia in children with Down Syndrome: a report from WBC X50 Â 109 2.55 0.88–7.39 0.08 the Ponti di Legno Study group. ASH: San Diego, 2011. 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Phase 1b study of lenalidomide in combination with rituximab-CHOP (R2-CHOP) in patients with B-cell lymphoma

Leukemia (2013) 27, 252–255; doi:10.1038/leu.2012.172 association with standard 21-day R-CHOP (R2-CHOP). Dose of lenalidomide was assessed during the first two cycles. Secondary objectives were to assess the safety and efficacy of R2-CHOP for a We were very interested by the article by Nowakowski et al.1 maximum of six cycles. describing the combination of lenalidomide and R-CHOP Patients from 18 to 70 years of age had documented B-cell in patients with aggressive lymphoma. Our group conducted CD20-positive lymphoma: mantle cell lymphoma, marginal zone a similar phase 1b study of this combination in a lymphoma, lymphocytic lymphoma, follicular lymphoma, diffuse patient population with predominantly indolent B-cell large B-cell lymphoma or histological transformation from low lymphoma. grade to high grade lymphoma. Lenalidomide (5, 10, 15, 20 or The primary objective of the study was to determine the 25 mg once daily) was escalated in serial patient cohorts using a recommended dose of lenalinomide administered for 14 days in standard 3 þ 3 design. Each cycle of R2-CHOP comprised the

Accepted article preview online 26 June 2012; advance online publication, 13 July 2012

Leukemia (2013) 233 – 258 & 2013 Macmillan Publishers Limited