Ian Tracy

TP53 mutation profile in Chronic Lymphocytic Leukemia: Evidence for a disease specific profile from a comprehensive analysis of 268 mutations

The TP53 mutation profile in chronic lymphocytic leukemia (CLL) and the correlation of TP53 mutations with allele status or associated molecular genetics are currently unknown. We performed a large mutation analysis of TP53 at four centers and characterized the pattern of TP53 mutations in CLL. We report on 268 mutations in 254 patients with CLL. Missense mutations appeared in 74% of cases compared with deletions and insertions (20%), nonsense (4%) and splice site (2%) mutations. The majority (243 of 268) of mutations were located in the DNA-binding domain. Transitions were found in 131 of 268 mutations, with only 41 occurring at methylated CpG sites (15%), suggesting that transitions at CpGs are uncommon. The codons most frequently mutated were at positions 175, 179, 248 and 273; in addition, we detected a common 2-nt deletion in the codon 209. Most mutations (199 of 259) were accompanied by deletion of the other allele (17p–). Interestingly, trisomy 12 (without 17p–) was only found in one of 60 cases with TP53 mutation (without 17p–) compared with 60 of 16 in the cohort without mutation (P=0.006). The mutational profile was not different in the cohorts with and without previous therapy, suggesting that the mechanism underlying the development of mutations may be similar, independent of treatment.

A subset of Binet stage A CLL patients with TP53 abnormalities and mutated IGHV genes have stable disease

TP53 abnormalities consistently emerge as the most significant adverse prognostic factor in multivariate analyses of both prospective and retrospective studies in early and advanced chronic lymphocytic leukaemia (CLL).1 In view of the higher response rates often achieved with alemtuzumab-containing regimens compared with alkylating agent and/or purine analogue therapy2 and the possibility of long-term disease-free survival following allogeneic transplantation in some patients, there is an increasing consensus for screening for TP53 abnormalities in CLL patients who fulfil the International Workshop on Chronic Lymphocytic Leukemia (IWCLL) recommendations for initiating therapy.

The frequency of TP53 gene defects differs between chronic lymphocytic leukaemia subgroups harbouring distinct antigen receptors

In chronic lymphocytic leukaemia (CLL) tumour initiation and progression are linked to the interplay between cellextrinsic and cell-intrinsic mechanisms. Cell-extrinsic mechanisms relate to the crosstalk of CLL cells with their microenvironment through various receptors, including the B-cell receptor (BcR).

A new minimal deleted region at 11q22.3 reveals the importance of interpretation of diminished FISH signals and the choice of probe for ATM deletion screening in chronic lymphocytic leukemia

Deletion of ATM detected by fluorescent in situ hybridization (FISH) in chronic lymphocytic leukemia predicts short treatment free survival and poor outcome following alkylator/purine analogue therapy. We describe five cases, with a diminished ATM FISH signal, investigated by TP53 mutation/dysfunction studies and single nucleotide polymorphism (SNP) array. The diminished signal represented loss of the ATM gene, which could have been missed were the cases not further investigated. These rare cases highlight the need for careful consideration of the choice of probe and interpretation of unusual signal patterns in FISH screening. We define a new minimal region of deletion at 11q22.3.

Type C TP53-CDKN1A pathway dysfunction occurs independently of CDKN1A gene polymorphisms in chronic lymphocytic leukaemia and is associated with TP53 abnormalities.

Deletions and/or mutations of TP53 are associated with poor prognosis in patients with chronic lymphocytic leukaemia (CLL), even when these abnormalities are not present in the predominant clonal population (Rossi et al, 2014). Dysfunction of the TP53-CDKN1A (p21) pathway correlates strongly with TP53 structural abnormalities (Carter et al, 2004; Best et al, 2008), however 9 5% of unselected CLL cases have been reported to have an impaired CDKN1A response to DNA damage despite normal TP53 upregulation, termed Type C dysfunction (Johnson et al, 2009). In the UK CLL4 trial, Type C dysfunction was documented in 13/278 (4 7%) of patients at entry and was associated with short progression-free survival (Lin et al, 2012). In half of these cases, Type C dysfunction was associated with two polymorphisms of CDKN1A (p21) in the absence of structural abnormalities of TP53; namely C/A (Ser/Arg) at CDKN1A codon 31 (CDKN1A-cod31) and C/C rather than C/T in the 30UTR (Johnson et al, 2009). We carried out CDKN1A genotyping in 208 samples from a series of 418 cases on which TP53 functional and structural data was available. TP53-CDKN1A function was assessed as previously described (Best et al, 2008) using the classifications of Carter et al (2004). Of 418 cases analysed, 290 (69 4%) showed normal function and 13 (3 1%), 76 (18 2%) and 39 (9 3%) showed Type A, B and C dysfunction respectively (Fig 1A). The relative incidence of dysfunctional cases was not significantly different between our series and that of Johnson et al (2009) (v = 3 542, 2 degrees of freedom, P =

Defining the prognosis of early stage chronic lymphocytic leukaemia patients

Approximately 70% of chronic lymphocytic leukaemia (CLL) patients present with early stage disease, therefore defining which patients will progress and require treatment is a major clinical challenge. Here, we present the largest study of prognostic markers ever carried out in Binet stage A patients (n = 1154) with a median follow‐up of 8 years. We assessed the prognostic impact of lymphocyte doubling time (LDT), immunoglobulin gene (IGHV) mutation status, CD38 expression, ZAP‐70 expression and fluorescence in situ hybridization (FISH) cytogenetics with regards to time to first treatment (TTFT) and overall survival (OS). Univariate analysis revealed LDT as the most prognostic parameter for TTFT, with IGHV mutation status most prognostic for OS. CD38 expression, ZAP‐70 expression and FISH were also prognostic variables; combinations of these markers increased prognostic power in concordant cases. Multivariate analysis revealed that only LDT, IGHV mutation status, CD38 and age at diagnosis were independent prognostic variables for TTFT and OS. Therefore, IGHV mutation status and CD38 expression have independent prognostic value in early stage CLL and should be performed as part of the routine diagnostic workup. ZAP‐70 expression and FISH were not independent prognostic markers in early stage disease and can be omitted at diagnosis but FISH analysis should be undertaken at disease progression to direct treatment strategy.

Defining the prognosis of early stage chronic lymphocytic leukaemia patients.

Approximately 70% of chronic lymphocytic leukaemia (CLL) patients present with early stage disease, therefore defining which patients will progress and require treatment is a major clinical challenge. Here, we present the largest study of prognostic markers ever carried out in Binet stage A patients (n = 1154) with a median follow‐up of 8 years. We assessed the prognostic impact of lymphocyte doubling time (LDT), immunoglobulin gene (IGHV) mutation status, CD38 expression, ZAP‐70 expression and fluorescence in situ hybridization (FISH) cytogenetics with regards to time to first treatment (TTFT) and overall survival (OS). Univariate analysis revealed LDT as the most prognostic parameter for TTFT, with IGHV mutation status most prognostic for OS. CD38 expression, ZAP‐70 expression and FISH were also prognostic variables; combinations of these markers increased prognostic power in concordant cases. Multivariate analysis revealed that only LDT, IGHV mutation status, CD38 and age at diagnosis were independent prognostic variables for TTFT and OS. Therefore, IGHV mutation status and CD38 expression have independent prognostic value in early stage CLL and should be performed as part of the routine diagnostic workup. ZAP‐70 expression and FISH were not independent prognostic markers in early stage disease and can be omitted at diagnosis but FISH analysis should be undertaken at disease progression to direct treatment strategy.