Tumors widely express hundreds of embryonic germline genes

We have recently described a class of 756 genes that are widely expressed in cancer, while normally restricted to adult germ cells, referred to as germ cell cancer genes (GC-genes). We hypothesized that carcinogenesis involves reactivation of biomolecular processes and regulatory mechanisms that, under normal circumstances, are restricted to germline development. This would imply that cancer cells share gene expression profiles with primordial germ cells (PGCs). We therefore compared the transcriptomes of human PGCs (hPGCs) and PGC-like cells (PGCLCs) with 17 382 samples from 54 healthy somatic tissues (GTEx) and 11 003 samples from 33 tumor types (TCGA), and identified 672 GC-genes, expanding the known GC-gene pool by 387 genes (51%). Because GC-genes specific to the embryonic germline are not expressed in any adult tissue, targeting these in cancer treatment may result in fewer side effects than targeting conventional cancer/testis (CT) or GC-genes and may preserve fertility. We anticipate that our extended GC-dataset enables improved understanding of tumor development and may provide multiple novel targets for cancer treatment development.