Abstract 3620: Enhancing clinical utility of NGS with reduced bias, low DNA input, library construction

Early detection and diagnosis of cancer substantially increases the likelihood for successful treatment. Tools that aid in detecting and diagnosing cancer early, therefore, have the potential to greatly impact the clinical outcome for cancer patients. Next Generation Sequencing (NGS) has emerged as an important tool in this area. The technology is sensitive, fast and high throughput to allow sequencing of many samples at once. Unfortunately, many clinical samples go unanalyzed because they do not yield sufficient quantities of DNA to generate NGS libraries or the libraries generated require so many rounds of PCR amplification that they display extreme sequence bias. Bias not only hampers data analysis, but also increases costs by requiring excess sequencing to obtain sufficient coverage over all relevant genomic regions. To enable the increased use of NGS in the clinic and reduce the amount of sequence bias generated during library preparation, we have developed a PCR free library construction method that uses low quantities of DNA as input. As an initial test of the method, we generated PCR free libraries from 100ng, 50ng and 25ng of human genomic DNA. The libraries where pooled and sequenced on the Illumina NextSeq 500 instrument to approximately 10X coverage. All libraries, irrespective of input amount, showed minimal AT/GC bias and excellent coverage distributions, with most bases covered within 5X of the expected coverage depth. In addition, regions identified as difficult to sequence (Aird, D., et.al., 2011 and Ross, M. G., et.al., 2013) showed coverage at near expected levels for all libraries. This method can easily be adapted for use with extremely low DNA inputs by the introduction of a minimal number of PCR cycles. In fact, we have used this method to construct high quality NGS libraries with picogram quantities of DNA input. Standard library construction methods require DNA inputs of 2ug to 500ng when PCR amplification is omitted. This new method utilizes inputs as low as 25ng to generate high-quality PCR free libraries and picogram quantities when amplification is performed. We are currently investigating the possibility of reducing input levels further and exploring the limits of the method with low quality DNA samples. Interestingly, we have observed substantial sample loss during DNA shearing and reaction cleanup. Samples that do not require fragmentation, such as DNA isolated from plasma (cfDNA) and low quality FFPE DNA, may reduce the input requirements even further. Finally, this new method utilizes low sample and reagent volumes, possibly paving the way for its use in microfluidic devices. Citation Format: Lynne Apone, Pingfang Liu, Vaish Panchapakesa, Deyra Rodriguez, Karen Duggan, Krishnan Keerthana, Nicole Nichols, Yanxia Bei, Julie Menin, Brad Langhorst, Christine Sumner, Christine Chater, Joanna Bybee, Laurie Mazzola, Danielle Rivizzigno, Fiona Stewart, Eileen Dimalanta, Theodore Davis. Enhancing clinical utility of NGS with reduced bias, low DNA input, library construction. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3620.