Identification of Somatic Structural Variants in Solid Tumors By Optical Genome Mapping

Abstract

Genomic structural variants comprise a significant fraction of somatic mutations driving cancer onset and progression. However, such variants are not readily revealed by standard next generation sequencing. Optical genome mapping (OGM) surpasses short read sequencing in detecting large (>500bp) and complex structural variants (SVs) but requires isolation of ultra-high molecular weight DNA from the tissue of interest. We have successfully applied a protocol involving a paramagnetic nanobind disc to a wide range of solid tumors. Using as little as 6.5mg of input tumor tissue, we show successful extraction of high molecular weight genomic DNA that provides a high genomic map rate and effective coverage by optical mapping. We demonstrate the systems utility at identifying somatic SVs affecting functional and cancer-related genes for each sample. Duplicate/triplicate analysis of select samples shows intra-sample reliability but also intra-sample heterogeneity. We also demonstrate that simply filtering SVs based on a GRCh38 human control database provides high positive and negative predictive values for true somatic variants. Our results indicate that the solid tissue DNA extraction protocol, OGM and SV analysis can be applied to a wide variety of solid tumors to capture SVs across the entire genome with functional importance in cancer prognosis and treatment.