Circulating tumor DNA in patients with colorectal adenomas: assessment of detectability and genetic heterogeneity

• Published in: Cell death & disease 2018-08, Vol.9 (9), p.894-16, Article 894
• Main Authors: Myint, Ni Ni Moe, Verma, Ajay M., Fernandez-Garcia, Daniel, Sarmah, Panchali, Tarpey, Patrick S., Al-Aqbi, Saif Sattar, Cai, Hong, Trigg, Ricky, West, Kevin, Howells, Lynne M., Thomas, Anne, Brown, Karen, Guttery, David S., Singh, Baljit, Pringle, Howard J., McDermott, Ultan, Shaw, Jacqui A., Rufini, Alessandro
• Format: Article
• Language: English
• Subjects: 38/77; 45/22; 64/110; 82/51; Adenoma - blood; Adenoma - diagnosis; Adenoma - genetics; Adenomatous polyposis coli; Adenomatous Polyposis Coli Protein - genetics; Aged; Aged, 80 and over; Animals; Antibodies; Biochemistry; Biomarkers, Tumor - blood; Biomarkers, Tumor - genetics; Biomedical and Life Sciences; Cancer; Cell Biology; Cell Culture; Circulating Tumor DNA - isolation & purification; Colonic Neoplasms - blood; Colonic Neoplasms - diagnosis; Colonic Neoplasms - genetics; Colorectal cancer; Colorectal carcinoma; Deoxyribonucleic acid; DNA; Early Detection of Cancer - methods; Female; Genetic analysis; High-Throughput Nucleotide Sequencing; Humans; Immunology; Intestine; Life Sciences; Liquid Biopsy - methods; Male; Mice; Mice, Knockout; Middle Aged; Mismatch repair; Mutation; Polymerase Chain Reaction; Proto-Oncogene Proteins B-raf - genetics; Proto-Oncogene Proteins p21(ras) - genetics; Public health; Tumors
• ISSN: 2041-4889; 2041-4889
• DOI: 10.1038/s41419-018-0934-x

Improving early detection of colorectal cancer (CRC) is a key public health priority as adenomas and stage I cancer can be treated with minimally invasive procedures. Population screening strategies based on detection of occult blood in the feces have contributed to enhance detection rates of localized disease, but new approaches based on genetic analyses able to increase specificity and sensitivity could provide additional advantages compared to current screening methodologies. Recently, circulating cell-free DNA (cfDNA) has received much attention as a cancer biomarker for its ability to monitor the progression of advanced disease, predict tumor recurrence and reflect the complex genetic heterogeneity of cancers. Here, we tested whether analysis of cfDNA is a viable tool to enhance detection of colon adenomas. To address this, we assessed a cohort of patients with adenomas and healthy controls using droplet digital PCR (ddPCR) and mutation-specific assays targeted to trunk mutations. Additionally, we performed multiregional, targeted next-generation sequencing (NGS) of adenomas and unmasked extensive heterogeneity, affecting known drivers such as AP C, KRAS and mismatch repair (MMR) genes. However, tumor-related mutations were undetectable in patients’ plasma. Finally, we employed a preclinical mouse model of Apc -driven intestinal adenomas and confirmed the inability to identify tumor-related alterations via cfDNA, despite the enhanced disease burden displayed by this experimental cancer model. Therefore, we conclude that benign colon lesions display extensive genetic heterogeneity, that they are not prone to release DNA into the circulation and are unlikely to be reliably detected with liquid biopsies, at least with the current technologies.