BRCA1 and RAD51C promotor methylation in human resectable pancreatic adenocarcinoma.

BACKGROUND: Homozygous Recombination Deficiency (HRD) is associated with sensitivity to PARP-inhibitors (PARPi) in different cancer types. In pancreatic adenocarcinoma (PA) the main cause of HRD is BRCA1/2 germline mutation and patients with mutations in BRCA1/2 may benefit from PARPi. Recently other mechanisms leading to HRD were described in different cancer types, including gene mutations and epigenetic changes such as promoter hypermethylation. In PA, BRCA1 promoter hypermethylation, a known mechanism of gene silencing, was recently described. However, results are discordant between North American studies (0.7% of PA) and Asian ones (up to 60% of PA) and the association with HRD is not clear. METHODS: Here, we developed 2 quantifications methods to explore BRCA1 and RAD51C promoter methylation in a series of 121 Formalin Fixed-Paraffin-Embedded (FFPE) specimens from resected PA without neoadjuvant treatment. The methylation-specific PCR was done with 2 different methods after DNA bisulfite conversion: a digital droplet PCR, and a PCR followed by capillary electrophoresis, to score the methylated / non methylated ratios in tumor samples. Methods were validated for specificity and sensibility using 100, 20, 10, 5 and 0% methylated commercial DNA for fragment analysis with a detection cutoff of 5-10%. Limit of blank was defined as 5 dropplets/20µL for RAD51C and 1 dropplet/20µL for BRCA1 for ddPCR. Samples were reviewed by a pathologist, macrodissected before DNA extraction to obtain 50-60% of tumoral cells. DNAs were treated for bisulfite conversion and analyzed using both methods in parallel to known positive and negative controls in each run. RESULTS AND CONCLUSION: No methylation at BRCA1 or RAD51C was found in this series of PA suggesting that HRD gene promoter methylation is a rare event in European patients.

Prognostic Value and Relation with Adjuvant Treatment Duration of ctDNA in Stage III Colon Cancer: a Post Hoc Analysis of the PRODIGE-GERCOR IDEA-France Trial.

PURPOSE: Circulating tumor DNA (ctDNA) has been suggested as a major prognostic factor in resected stage-III colon cancer. We analyzed ctDNA of patients randomized in the phase III IDEA-France trial. EXPERIMENTAL DESIGN: ctDNA was tested for WIF1 and NPY by droplet digital PCR with method developed and validated for colorectal cancer. Disease-free survival (DFS) and overall survival (OS) were analyzed via multivariable analysis in patients with ctDNA samples and in sub-groups according to treatment duration (3/6 months) and disease stage (high/low-risk stage III). RESULTS: Of 2,010 randomized patients, 1,345 had available ctDNA samples (1,017 collected both post-surgery and pre-chemotherapy). More Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 (78% versus 69%) and T4 and/or N2 (40% versus 36%) were observed in patients studied (n = 1017) versus not analyzed (n = 993). There were 877 ctDNA-negative (86.2%) and 140 ctDNA-positive (13.8%) patients; their baseline characteristics were similar. With a median follow-up of 6.6 years, the 3-year DFS rate was 66.39% for ctDNA-positive patients and 76.71% for ctDNA-negative patients (P = 0.015). ctDNA was confirmed as an independent prognostic marker for DFS (adjusted HR = 1.55, 95% CI 1.13-2.12, P = 0.006) and OS (HR = 1.65, 95% CI 1.12-2.43, P = 0.011). ctDNA was prognostic in patients treated for 3 months and with T4 and/or N2 tumors, but not in those treated for 6 months and with T1-3/N1 tumors. CONCLUSIONS: In this first ctDNA assessment of a large series of patients with stage III colon cancer enrolled in phase III trial, post-surgery ctDNA was found in 13.8% of them and was confirmed as an independent prognostic marker.See related commentary by Bent and Kopetz, p. 5449.

Prevalence of BTK and PLCG2 mutations in a real-life CLL cohort still on ibrutinib after 3 years: a FILO group study.

Mutational analyses performed following acquired ibrutinib resistance have suggested that chronic lymphocytic leukemia (CLL) progression on ibrutinib is linked to mutations in Bruton tyrosine kinase (BTK) and/or phospholipase Cγ2 (PLCG2) genes. Mutational information for patients still on ibrutinib is limited. We report a study aimed to provide a "snapshot" of the prevalence of mutations in a real-life CLL cohort still on ibrutinib after at least 3 years of treatment. Of 204 patients who initiated ibrutinib via an early-access program at 29 French Innovative Leukemia Organization (FILO) centers, 63 (31%) were still on ibrutinib after 3 years and 57 provided a fresh blood sample. Thirty patients had a CLL clone ≥0.5 × 109/L, enabling next-generation sequencing (NGS); BTK and PLCG2 mutations were detected in 57% and 13% of the NGS samples, respectively. After median follow-up of 8.5 months from sample collection, the presence of a BTK mutation was significantly associated with subsequent CLL progression (P = .0005 vs no BTK mutation). Our findings support that mutational analysis should be considered in patients receiving ibrutinib who have residual clonal lymphocytosis, and that clinical trials are needed to evaluate whether patients with a BTK mutation may benefit from an early switch to another treatment.

Technical Insights into Highly Sensitive Isolation and Molecular Characterization of Fixed and Live Circulating Tumor Cells for Early Detection of Tumor Invasion.

Circulating Tumor Cells (CTC) and Circulating Tumor Microemboli (CTM) are Circulating Rare Cells (CRC) which herald tumor invasion and are expected to provide an opportunity to improve the management of cancer patients. An unsolved technical issue in the CTC field is how to obtain highly sensitive and unbiased collection of these fragile and heterogeneous cells, in both live and fixed form, for their molecular study when they are extremely rare, particularly at the beginning of the invasion process. We report on a new protocol to enrich from blood live CTC using ISET® (Isolation by SizE of Tumor/Trophoblastic Cells), an open system originally developed for marker-independent isolation of fixed tumor cells. We have assessed the impact of our new enrichment method on live tumor cells antigen expression, cytoskeleton structure, cell viability and ability to expand in culture. We have also explored the ISET® in vitro performance to collect intact fixed and live cancer cells by using spiking analyses with extremely low number of fluorescent cultured cells. We describe results consistently showing the feasibility of isolating fixed and live tumor cells with a Lower Limit of Detection (LLOD) of one cancer cell per 10 mL of blood and a sensitivity at LLOD ranging from 83 to 100%. This very high sensitivity threshold can be maintained when plasma is collected before tumor cells isolation. Finally, we have performed a comparative next generation sequencing (NGS) analysis of tumor cells before and after isolation from blood and culture. We established the feasibility of NGS analysis of single live and fixed tumor cells enriched from blood by our system. This study provides new protocols for detection and characterization of CTC collected from blood at the very early steps of tumor invasion.

Longitudinal survey of Staphylococcus aureus in cystic fibrosis patients using a multiple-locus variable-number of tandem-repeats analysis method.

BACKGROUND: Staphylococcus aureus infection in patients with cystic fibrosis (CF) is frequent and may be due to colonization by a few pathogenic lineages. Systematic genotyping of all isolates, methicillin-susceptible S. aureus (MSSA) as well as methicillin-resistant S. aureus (MRSA) is necessary to identify such lineages and follow their evolution in patients. Multiple-locus variable-number tandem repeat analysis (MLVA/VNTR) was used to survey S. aureus clinical isolates in a French paediatric CF centre. RESULTS: During a 30 months period, 108 patients, aged 2 to 21 years, regularly followed up at the centre, provided sputum for culture. From 79 patients, a total of 278 isolates were genotyped by MLVA, resolving into 110 genotypes and 19 clonal complexes (CC) composed of similar or closely related isolates. 71% of the strains were distributed into four main CCs, in term of number of isolates and number of genotypes. Spa (Staphylococcus protein A) typing was performed on representative samples, showing an excellent concordance with MLVA. In 17 patients, strains from two to four different CCs were recovered over time. On six occasions, S. aureus isolates with the same genotype were shared by 2 different patients and they belonged to one of the four main clusters. Methicillin-resistance was observed in 60% of the isolates, 90% of which belonged to the main clonal complexes CC8, CC45 and CC5. In 5 patients, methicillin-resistance of S. aureus isolates was not associated with the mecA gene: for four patients, it was due to overproduction of beta-lactamase, leading to BOR-SA (borderline S. aureus) isolates, while a strain showing probably a new modified penicillin-binding capacity (MOD-SA) was observed from one patient. CONCLUSION: Systematic genotyping of S. aureus isolates recovered from sputum of CF children allows a thorough analysis of the strains responsible for sporadic as well as chronic colonization and the follow up of their evolution over time. We show here that more than 70% of these strains belong to 4 major CCs. MSSA as well as MRSA, BOR-SA and MOD-SA isolates can persist over several years, despite antibiotic treatments.

Improved multiple-locus variable-number tandem-repeat assay for Staphylococcus aureus genotyping, providing a highly informative technique together with strong phylogenetic value.

We describe an improved multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) scheme for genotyping Staphylococcus aureus. We compare its performance to those of multilocus sequence typing (MLST) and spa typing in a survey of 309 strains. This collection includes 87 epidemic methicillin-resistant S. aureus (MRSA) strains of the Harmony collection, 75 clinical strains representing the major MLST clonal complexes (CCs) (50 methicillin-sensitive S. aureus [MSSA] and 25 MRSA), 135 nasal carriage strains (133 MSSA and 2 MRSA), and 13 published S. aureus genome sequences. The results show excellent concordance between the techniques' results and demonstrate that the discriminatory power of MLVA is higher than those of both MLST and spa typing. Two hundred forty-two genotypes are discriminated with 14 VNTR loci (diversity index, 0.9965; 95% confidence interval, 0.9947 to 0.9984). Using a cutoff value of 45%, 21 clusters are observed, corresponding to the CCs previously defined by MLST. The variability of the different tandem repeats allows epidemiological studies, as well as follow-up of the evolution of CCs and the identification of potential ancestors. The 14 loci can conveniently be analyzed in two steps, based upon a first-line simplified assay comprising a subset of 10 loci (panel 1) and a second subset of 4 loci (panel 2) that provides higher resolution when needed. In conclusion, the MLVA scheme proposed here, in combination with available on-line genotyping databases (including http://mlva.u-psud.fr/), multiplexing, and automatic sizing, can provide a basis for almost-real-time large-scale population monitoring of S. aureus.

Multiple-locus variable-number tandem-repeat analysis for longitudinal survey of sources of Pseudomonas aeruginosa infection in cystic fibrosis patients.

In order to identify the source of infection by Pseudomonas aeruginosa in patients with cystic fibrosis (CF), systematic genotyping of isolates is necessary. Multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) was used to survey the sources of P. aeruginosa infections in a French (Paris, France) pediatric CF center. Between January 2004 and December 2006, 108 patients ages 2 to 21 years who were regularly monitored at the center provided sputum for culture. P. aeruginosa was detected in 46 children, 17 of whom had primary colonization. A total of 163 isolates were recovered. MLVA was improved from a previously published method by the addition of new, informative, and easily typeable markers. Upon genotyping with 15 VNTRs, a total of 39 lineages composed of indistinguishable or closely related isolates, were observed. One of them corresponds to "clone C," which is widely distributed in Europe, and another corresponds to reference strain PA14. Six patients were colonized with two different strains, and the remaining 40 patients were colonized with a single strain. Strains from seven lineages were shared by at least two and up to four patients among a total of 20 patients. The study demonstrates that MLVA is an efficient, easy, and rapid molecular method for epidemiological surveillance for P. aeruginosa infection. The resulting data and strain genetic profiles can be queried on http://bacterial-genotyping.igmors.u-psud.fr.