Background Aberrant DNA hypomethylation of the long interspersed nuclear elements (LINE-1 or L1) has been recognized as an early event of colorectal transformation. Simultaneous genetic and epigenetic analysis of colorectal adenomas may be an effective and rapid strategy to identify key biological features leading to accelerated colorectal tumorigenesis. In particular, global and/or intragenic LINE-1 hypomethylation of adenomas may represent a helpful tool for improving colorectal cancer (CRC) risk stratification of patients after surgical removal of polyps. To verify this hypothesis, we analyzed a cohort of 102 adenomas derived from 40 high-risk patients (who developed CRC in a post-polypectomy of at least one year) and 43 low-risk patients (who did not develop CRC in a post-polypectomy of at least 5 years) for their main pathological features, the presence of hotspot variants in driver oncogenes (KRAS, NRAS, BRAF and PIK3CA), global (LINE-1) and intragenic (L1-MET) methylation status. Results In addition to a significantly higher adenoma size and an older patients’ age, adenomas from high-risk patients were more hypomethylated than those from low-risk patients for both global and intragenic LINE-1 assays. DNA hypomethylation, measured by pyrosequencing, was independent from other parameters, including the presence of oncogenic hotspot variants detected by mass spectrometry. Combining LINE-1 and L1-MET analyses and profiling the samples according to the presence of at least one hypomethylated assay improved the discrimination between high and low risk lesions (p = 0.005). Remarkably, adenomas with at least one hypomethylated assay identified the patients with a significantly (p < 0.001) higher risk of developing CRC. Multivariable analysis and logistic regression evaluated by the ROC curves proved that methylation status was an independent variable improving cancer risk prediction (p = 0.02). Conclusions LINE-1 and L1-MET hypomethylation in colorectal adenomas are associated with a higher risk of developing CRC. DNA global and intragenic hypomethylation are independent markers that could be used in combination to successfully improve the stratification of patients who enter a colonoscopy surveillance program. Graphic abstract

Current multiplexing strategies for massively parallel sequencing of genomic DNA mainly rely on library indexing in the final steps of library preparation. This procedure is costly and time-consuming because a single library must be produced separately for each sample. Furthermore, library preparation is challenging in the case of low-input fixed samples, such as DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues. Here, we describe CUTseq, a method that uses restriction enzymes and in vitro transcription to barcode and amplify genomic DNA prior to library construction. We thoroughly validate CUTseq and demonstrate its applicability to both genome and exome sequencing, enabling multi-region genome profiling within single stained FFPE tissue sections, to assess intratumor heterogeneity at high spatial resolution. In conclusion, CUTseq is a versatile and cost-effective method for multiplexed DNA sequencing library preparation that can find numerous applications in research and diagnostics.

Current multiplexing strategies for massively parallel sequencing of genomic DNA mainly rely on library indexing in the final steps of library preparation. This procedure is costly and time-consuming because a single library must be produced separately for each sample. Furthermore, library preparation is challenging in the case of low-input fixed samples, such as DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues. Here, we describe CUTseq, a method that uses restriction enzymes and in vitro transcription to barcode and amplify genomic DNA prior to library construction. We thoroughly validate CUTseq and demonstrate its applicability to both genome and exome sequencing, enabling multi-region genome profiling within single stained FFPE tissue sections, to assess intratumor heterogeneity at high spatial resolution. In conclusion, CUTseq is a versatile and cost-effective method for multiplexed DNA sequencing library preparation that can find numerous applications in research and diagnostics.

Background: BRAF mutant melanoma patients are commonly treated with anti-BRAF therapeutic strategies. However, many factors, including the percentage of BRAF-mutated cells, may contribute to the great variability in patient outcomes.Patients and methods: The BRAF variant allele frequency (VAF; defined as the percentage of mutated alleles) of primary and secondary melanoma lesions, obtained from 327 patients with different disease stages, was assessed by pyrosequencing. The BRAF mutation rate and VAF were then correlated with melanoma pathological features and patients' clinical characteristics. KaplaneMeier curves were used to study the correlations between BRAF VAF, overall survival (OS), and progression-free survival (PFS) in a subset of 62 patients treated by anti-BRAF/anti-MEK therapy after metastatic progression. Results: A highly heterogeneous BRAF VAF was identified (3%-90%). Besides being correlated with age, a higher BRAF VAF level was related to moderate lymphocytic infiltration (P ¼ 0.017), to melanoma thickness according to Clark levels, (level V versus III, P ¼ 0.004; level V versus IV, P ¼ 0.04), to lymph node metastases rather than cutaneous (P ¼ 0.04) or visceral (P ¼ 0.03) secondary lesions. In particular, a BRAF VAF >25% was significantly associated with a favorable outcome in patients treated with the combination of anti-BRAF/anti-MEK drug (OS P ¼ 0.04; PFS P ¼ 0.019), retaining a significant value as an independent factor for the OS and the PFS in the multivariate analysis (P ¼ 0.014 and P ¼ 0.003, respectively). Conclusion: These results definitively support the role of the BRAF VAF as a potential prognostic and predictive biomarker in melanoma patients in the context of BRAF inhibition.