Fig. 1

Schematic diagram of PPCNM. In cancer, plasma cell-free DNA (cfDNA) is primarily derived from apoptotic tumor and hematopoietic cells. Exposed DNA not bound to a nucleosome is digested, whereas nucleosome-bound DNA escapes digestion and enters the circulation. cfDNA has a nucleosome footprint, which carries information about its original tissues and could reflect its gene expression status. Because axillary lymph node (ALN)-positive and ALN-negative breast cancer patients have different gene expression signatures in tumor and hematopoietic cells, their nucleosome patterns may show difference. Therefore, we assume that the promoter coverage of cfDNA detected by whole-genome sequencing could be used to develop classifiers for predicting lymph node metastasis