Key Points• UDS demonstrated that BCR-ABL KD mutations detectable with conventional methods may just be the tip of the iceberg.• The information provided by conventional Sanger sequencing may not always be sufficient to predict responsiveness to a given TKI.In chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia, tyrosine kinase inhibitor (TKI) therapy may select for drug-resistant BCR-ABL mutants. We used an ultra-deep sequencing (UDS) approach to resolve qualitatively and quantitatively the complexity of mutated populations surviving TKIs and to investigate their clonal structure and evolution over time in relation to therapeutic intervention. To this purpose, we performed a longitudinal analysis of 106 samples from 33 patients who had received sequential treatment with multiple TKIs and had experienced sequential relapses accompanied by selection of 1 or more TKI-resistant mutations. We found that conventional Sanger sequencing had misclassified or underestimated BCR-ABL mutation status in 55% of the samples, where mutations with 1% to 15% abundance were detected. A complex clonal texture was uncovered by clonal analysis of samples harboring multiple mutations and up to 13 different mutated populations were identified. The landscape of these mutated populations was found to be highly dynamic. The high degree of complexity uncovered by UDS indicates that conventional Sanger sequencing might be an inadequate tool to assess BCR-ABL kinase domain mutation status, which currently represents an important component of the therapeutic decision algorithms. Further evaluation of the clinical usefulness of UDS-based approaches is warranted. (Blood. 2013;122(9):1634-1648

Purpose: This phase II prospective study aimed to evaluate the efficacy and safety of 5-days azacytidine (5d-AZA) in patients with low-risk myelodysplastic syndromes (MDS). Second, single-nucleotide polymorphism (SNP) genetic profile and phosphoinositide-phospholipase C (PI-PLC) b1 levels were studied to evaluate possible biologic markers able to predict the hematologic response.Experimental Design: The study tested a lower intensity schedule of azacytidine. The treatment plan consisted of 75 mg/sqm/d subcutaneous administered for 5 days every 28 days, for a total of 8 cycles.Results: Thirty-two patients were enrolled in the study. The overall response rate was 47% (15 of 32) on intention-to-treat and 58% (15 of 26) for patients completing the treatment program. In this latter group, 5 (19%) achieved complete remission (CR) and 10 (38%) had hematologic improvement, according to the International Working Group (IWG) criteria. Three patients have maintained their hematologic improvement after 37, 34, and 33 months without other treatments. Moreover, 21 and 2 of 26 cases completing 8 cycles were transfusion-dependent for red blood cells and platelets at baseline, respectively. Of these, 7 (33%) and 2 (100%) became transfusion-independent at the end of the treatment program, respectively. Grade 3-4 neutropenia occurred in 28% of patients and 4 patients died early due to infections or hemorrhage. SNP results were not significantly correlated to the clinical outcome, whereas PI-PLCb1 level anticipated either positive or negative clinical responses.Conclusions: 5d-AZA is safe and effective in a proportion of patients with low-risk MDS. PI-PLCb1 gene expression is a reliable and dynamic marker of response that can be useful to optimize azacytidine therapy.

Purpose: The 9p21 locus, encoding three important tumor suppressors (p16/CDKN2A, p14/ARF, and p15/CDKN2B), is a major target of inactivation in the pathogenesis of many human tumors.Patients and Methods: To explore, at high resolution, the frequency and size of alterations affecting this locus in adult BCR-ABL1-positive acute lymphoblastic leukemia (ALL) and to investigate their prognostic value, 112 patients (101 de novo and 11 relapsed cases) were analyzed by genome-wide single-nucleotide polymorphism arrays and gene candidate deep exon sequencing. Paired diagnosis-relapse samples were further available and analyzed for 19 (19%) cases.Results: CDKN2A/ARF and CDKN2B genomic alterations were identified in 29% and 25% of newly diagnosed patients, respectively. Deletions were monoallelic in 72% of cases, and in 43% of them, the minimal overlapping region of the lost area spanned only the CDKN2A/B gene locus. An analysis conducted at relapse showed an increase in the detection rate of CDKN2A/ARF loss (47%) compared with the time of diagnosis (P ¼ 0.06). Point mutations within the 9p21 locus were found at very low levels, with only a nonsynonymous substitution in the exon 2 of CDKN2A. Of note, deletions of CDKN2A/B were significantly associated with poor outcomes in terms of overall survival (P ¼ 0.0206), disease free-survival (P ¼ 0.0010), and cumulative incidence of relapse (P ¼ 0.0014).Conclusions: Inactivation of the 9p21 locus by genomic deletion is a frequent event in BCR-ABL1-positive ALL. Deletions are frequently acquired during leukemia progression and are a poor prognostic marker of long-term outcomes. Clin Cancer Res; 17(23); 7413-23. Ó2011 AACR.