Ludmila Šebejová

Missense Mutations Located in Structural p53 DNA-Binding Motifs Are Associated With Extremely Poor Survival in Chronic Lymphocytic Leukemia

PURPOSE There is a distinct connection between TP53 defects and poor prognosis in chronic lymphocytic leukemia (CLL). It remains unclear whether patients harboring TP53 mutations represent a homogenous prognostic group. PATIENTS AND METHODS We evaluated the survival of patients with CLL and p53 defects identified at our institution by p53 yeast functional assay and complementary interphase fluorescence in situ hybridization analysis detecting del(17p) from 2003 to 2010. RESULTS A defect of the TP53 gene was identified in 100 of 550 patients. p53 mutations were strongly associated with the deletion of 17p and the unmutated IgVH locus (both P < .001). Survival assessed from the time of abnormality detection was significantly reduced in patients with both missense (P < .001) and nonmissense p53 mutations (P = .004). In addition, patients harboring missense mutation located in p53 DNA-binding motifs (DBMs), structurally well-defined parts of the DNA-binding domain, manifested a clearly shorter median survival (12 months) compared with patients having missense mutations outside DBMs (41 months; P = .002) or nonmissense alterations (36 months; P = .005). The difference in survival was similar in the analysis limited to patients harboring mutation accompanied by del(17p) and was also confirmed in a subgroup harboring TP53 defect at diagnosis. The patients with p53 DBMs mutation (at diagnosis) also manifested a short median time to first therapy (TTFT; 1 month). CONCLUSION The substantially worse survival and the short TTFT suggest a strong mutated p53 gain-of-function phenotype in patients with CLL with DBMs mutations. The impact of p53 DBMs mutations on prognosis and response to therapy should be analyzed in investigative clinical trials.

ATM mutations uniformly lead to ATM dysfunction in chronic lymphocytic leukemia: application of functional test using doxorubicin

ATM abnormalities are frequent in chronic lymphocytic leukemia and represent an important prognostic factor. Sole 11q deletion does not result in ATM inactivation by contrast to biallelic defects involving mutations. Therefore, the analysis of ATM mutations and their functional impact is crucial. In this study, we analyzed ATM mutations in predominantly high-risk patients using: i) resequencing microarray and direct sequencing; ii) Western blot for total ATM level; iii) functional test based on p21 gene induction after parallel treatment of leukemic cells with fludarabine and doxorubicin. ATM dysfunction leads to impaired p21 induction after doxorubicin exposure. We detected ATM mutation in 16% (22 of 140) of patients, and all mutated samples manifested demonstrable ATM defect (impaired p21 upregulation after doxorubicin and/or null protein level). Loss of ATM function in mutated samples was also evidenced through defective p53 pathway activation after ionizing radiation exposure. ATM mutation frequency was 34% in patients with 11q deletion, 4% in the TP53-defected group, and 8% in wild-type patients. Our functional test, convenient for routine use, showed high sensitivity (80%) and specificity (97%) for ATM mutations prediction. Only cells with ATM mutation, but not those with sole 11q deletion, were resistant to doxorubicin. As far as fludarabine is concerned, this difference was not observed. Interestingly, patients from both these groups experienced nearly identical time to first treatment. In conclusion, ATM mutations either alone or in combination with 11q deletion uniformly led to demonstrable ATM dysfunction in patients with chronic lymphocytic leukemia and mutation presence can be predicted by the functional test using doxorubicin.

Ofatumumab added to dexamethasone in patients with relapsed or refractory chronic lymphocytic leukemia: Results from a phase II study

The treatment of relapsed/refractory chronic lymphocytic leukemia (CLL) remains a challenging clinical issue. An important treatment option is the use of high‐dose corticosteroids. The purpose of this clinical trial was to determine the efficacy and toxicity of an ofatumumab–dexamethasone (O‐Dex) combination in relapsed or refractory CLL. The trial was an open‐label, multicenter, nonrandomized, Phase II study. The O‐Dex regimen consisted of intravenous ofatumumab (Cycle 1: 300 mg on day 1, 2,000 mg on days 8, 15, and 22; Cycles 2–6: 1,000 mg on days 1, 8, 15, and 22) and oral dexamethasone (40 mg on days 1–4 and 15–18; Cycles 1–6). The O‐Dex regimen was given until best response, or a maximum of six cycles. Thirty‐three patients (pts) were recruited. Twenty‐four (73%) pts completed at least three cycles of therapy. The remaining nine pts were prematurely discontinued owing to Grade 3/4 infections (seven pts), disease progression (one pt), or uncontrollable diabetes mellitus (one pt). Overall response rates/complete remissions (ORR/CR) were achieved in 22/5 pts (67/15%). The median progression‐free survival (PFS) was 10 months. In pts with p53 defects (n = 8), ORR/CR were achieved in 5/2 pts (63/25%) with a median PFS of 10.5 months. The median overall survival (OS) was 34 months. The Grades 3–5 infectious toxicity in 33% of pts represented the most frequent side effect during the treatment period. In conclusion, the O‐Dex regimen shows a relatively high ORR and CR with promising findings for PFS and OS. The study was registered at www.clinicaltrials.gov (NCT01310101). Am. J. Hematol. 90:417–421, 2015.

Specific p53 mutations do not impact results of alemtuzumab therapy among patients with chronic lymphocytic leukemia

A poor prognosis in chronic lymphocytic leukemia (CLL) is associated particularly with the presence of del(17p) aff ecting tumor suppressor gene TP53 . Th is deletion is in almost all cases of progressive leukemia accompanied by a mutation in the other TP53 allele, and in a smaller proportion of patients the TP53 mutation occurs also independently of del(17p) [1]. Recently, we demonstrated that patients with CLL harboring a missense mutation located in the p53 DNA-binding motifs (DBMs) (structurally well-defi ned parts of the DNA-binding domain) manifested a clearly shorter median survival in comparison with those having a missense mutation outside DBMs or a non-missense alteration [2]. However, a limitation of this study resulted from the unpredictable survival impact of diverse therapy given to patients with p53 mutations. Th e therapeutic approach currently taken for patients with CLL with loss and/or mutation of TP53 relies mostly on the use of agents which do not act through DNA damage followed by apoptosis induction. Th e success of this approach has been documented for the monoclonal antibody alemtuzumab. Monotherapy with alemtuzumab is now being recommended as fi rst-line therapy for patients with CLL with del(17p) [3]; however, many unresolved questions need to be addressed. For example, it is unclear whether the type of p53 mutation infl uences the outcome of alemtuzumab therapy. In an eff ort to evaluate the effi cacy of alemtuzumab therapy in relation to specifi c p53 mutations in patients with CLL, we performed a retrospective analysis. Th e patients examined ( n 111) were treated by alemtuzumab between 2003 and 2010. Th e majority of cases concerned pretreated patients ( n 108; see Table I). Our present analysis was performed in the patient cohort which was largely included in the previous survival analysis related to p53 mutation types; this study also involved patients treated with other drugs in addition to alemtuzumab [2] (overlap 88% in group 1; 82% in group 2; 0% in group 3; the groups are defi ned further below). Defects in p53 were assessed by the yeast functional assay coupled to sequencing of DNA templates from mutated yeast colonies. Th e remaining TP53 allele was analyzed using

The BCR–ABL1 T315I mutation and additional genomic aberrations are dominant genetic lesions associated with disease progression in patients with chronic myelogenous leukemia resistant to tyrosine kinase inhibitor therapy

The BCR-ABL1 T315I mutation and additional genomic aberrations are dominant genetic lesions associated with disease progression in patients with chronic myelogenous leukemia resistant to tyrosine kinase inhibitor therapy. The BCR-ABL1 T315I mutation and additional genomic aberrations are dominant genetic lesions associated with disease progression in patients with chronic myelogenous leukemia resistant to tyrosine kinase inhibitor therapy. The BCR-ABL1 T315I mutation and additional genomic aberrations are dominant genetic lesions associated with disease progression in patients with chronic myelogenous leukemia resistant to tyrosine kinase inhibitor therapy.

The p53 pathway induction is not primarily dependent on Ataxia Telangiectasia Mutated (ATM) gene activity after fludarabine treatment in chronic lymphocytic leukemia cells

Abstract The prognostic role of ATM defects is well documented in chronic lymphocytic leukemia. However, the predictive value of ATM inactivation is much less understood, even in response to common drugs like fludarabine. It has been demonstrated that CLL cells having inactive ATM exhibit defective phosphorylation of its downstream targets after fludarabine treatment. We performed alternative analysis focusing on fludarabine-induced p53 accumulation and induction of p53-downstream genes after artificial ATM inhibition and, in parallel, using cells with endogenous ATM inactivation. We show that after 24h fludarabine exposure: (i) 5 out of 8 ATM-deficient samples (63%) normally accumulated p53 protein, and (ii) all analyzed ATM-deficient samples (n = 7) manifested clear induction of p21, PUMA, BAX, and GADD45 genes. In all experiments, doxorubicin was used as a confined ATM inductor and confirmed effective ATM inactivation. In conclusion, CLL cells lacking functional ATM appear to have normal response to fludarabine regarding the p53 pathway activation.