DDR2 and cancer: The comparison of the copy number variations (CNVs) in the entire genome as well as major cancer genes, including TP53, PTEN, EGFR, KRAS, and DDR2, indicates that DNA copy number gains and losses were retained in LCOs, which often showed clearer and more distinct signals than the original lung cancers due to the enrichment of cancer cells (Fig. 2b and Supplementary Fig. 4a)15.