Abstract 6238: Profiling of the circulating cell-free DNA methylome for detection and subtyping of small cell lung cancers

Introduction: Small-cell lung cancer (SCLC) is a high-grade neuroendocrine carcinoma characterised by high proliferation rate and early, rapid metastatic spread. Although SCLC is treated as a homogenous disease, recent studies revealed morphologic and transcriptomic heterogeneity with several molecular subtypes described based on predominant transcription factor expression (ASCL1, NEUROD1, ATOH1, POU2F3, YAP1) (Rudin et al., 2019; Simpson et al., 2020) which in preclinical studies exhibit differing vulnerabilities raising the potential of stratified therapy. DNA methylation is also thought be an important regulator of SCLC biology (Gazdar et al., 2017) and epigenetically distinct subtypes derived from SCLC primary tumour samples reported (Poirier et al., 2015). Here, we developed a robust workflow for genome-wide DNA methylation profiling to examine the potential use of cfDNA methylation profiling for detection and subtyping of SCLC.

Results: To evaluate SCLC genome-wide DNA methylation patterns we employed a bisulfite-free enrichment-based approach (T7-MBD-seq). We tested this approach on tissue samples from preclinical models and from normal lung (n=110) and on cfDNA samples from both patients with SCLC and from non-cancer controls (n=157). Methylation profiles from preclinical models (patient-derived xenografts (PDX) and CTC derived explant (CDX) models) were comparable to previously described methylation patterns from SCLC primary tumours and were recapitulated in patients’ cfDNA samples. A tumour/normal classifier, based on 4,061 genomic regions detected as being hypermethylated in SCLC preclinical models, correctly assigned 93% and 100% cfDNA samples from patients with limited and extensive stage SCLC respectively, with a statistically significant correlation of prediction scores with disease stage (P=0.0076). Finally, to determine whether cfDNA methylation profiling could subtype SCLC patients, we built a subtype classifier, based on methylation signatures derived from 59 established SCLC cell lines. We applied the classifier to cfDNA samples from 56 patients and 10/11 with known subtypes (identified from a donor matched CDX model) were correctly classified. Overall, 73% of cfDNA samples were classified as ASCL1, 13% were classified as NEUROD1 and 14% were classified as being double negative with the distribution of the subtypes correlating closely to previously published IHC data from SCLC tissue samples (Baine et al., 2020).

Conclusions: Our data reveal two potential clinical utilities of cfDNA methylation profiling; a universally applicable liquid biopsy approach for more sensitive detection and monitoring of SCLC and molecular subtyping to ease the path to future clinical trials of subtype stratified treatments for patients with SCLC.

Citation Format: Dominic G. Rothwell, Francesca Chemi, Simon Pearce, Alex Clipson, Steven Hill, Alicia Marie Conway, Sophie Richardson, Katarzyna Murat, Rebecca Caeser, Jacklynn Egger, John T. Poirier, Alastair Kerr, Fiona Blackhall, Charles M. Rudin, Caroline Dive. Profiling of the circulating cell-free DNA methylome for detection and subtyping of small cell lung cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6238.

Ewastools: Infinium Human Methylation BeadChip pipeline for population epigenetics integrated into Galaxy

BACKGROUND

Infinium Human Methylation BeadChip is an array platform for complex evaluation of DNA methylation at an individual CpG locus in the human genome based on Illumina's bead technology and is one of the most common techniques used in epigenome-wide association studies. Finding associations between epigenetic variation and phenotype is a significant challenge in biomedical research. The newest version, HumanMethylationEPIC, quantifies the DNA methylation level of 850,000 CpG sites, while the previous versions, HumanMethylation450 and HumanMethylation27, measured >450,000 and 27,000 loci, respectively. Although a number of bioinformatics tools have been developed to analyse this assay, they require some programming skills and experience in order to be usable.

RESULTS

We have developed a pipeline for the Galaxy platform for those without experience aimed at DNA methylation analysis using the Infinium Human Methylation BeadChip. Our tool is integrated into Galaxy (http://galaxyproject.org), a web-based platform. This allows users to analyse data from the Infinium Human Methylation BeadChip in the easiest possible way.

CONCLUSIONS

The pipeline provides a group of integrated analytical methods wrapped into an easy-to-use interface. Our tool is available from the Galaxy ToolShed, GitHub repository, and also as a Docker image. The aim of this project is to make Infinium Human Methylation BeadChip analysis more flexible and accessible to everyone.

Respiratory symptoms and pulmonary function of workers employed in textile dyeing factory in Turkey

Dyes are known to be a causative agent of occupational asthma exposed to them. We evaluate respiratory symptoms among textile. The study population comprised 106 exposed workers and control (unexposed) group. Data were collected by a questionnaire. Pulmonary Function Tests (PFTs) were performed. Among the exposed workers 36.8% defined phlegm. Respiratory symptoms were not significantly different between two groups. The employment duration of the exposed workers with phlegm was longer than those without phlegm (p = 0.027). The mean % predicted of forced expiratory flow (FEF) 25-75 of the exposed workers was found to be significantly lower than the control (unexposed) group (p = 0.01). Our study suggests that textile dyeing might cause respiratory symptoms at workers.

Silicon carbide fiber-mediated DNA delivery into cells of wheat (Triticum acstivum L.) mature embryos

We have demonstrated that foreign DNA can be delivered into cells of mature embryos of wheat (Triticum aestivum L.) using silicon carbide fibers (SCF). The highest transient expression of thegusA (GUS) gene was detected when dry embryos were vortexed for 10-30 min in a SCF-DNA solution containing 90-120 g/l of sucrose. Up to 100 (on average 20-40) blue expression units per embryo were observed. Scutellum side and epiblast of the intact wheat embryos are preferentially transformed. When embryos with the coleoptilar tip removed were treated and allowed to germinate, GUS staining was observed in emerging leaf tissues. The potential of this new approach for stable transformation of wheat is under investigation. It has been found that callus tissues induced from the SCF treated embryos contain GUS-expressing sectors one month after treatment.