Transcriptomic data from normal tissues and cancer samples were obtained with the Affymetrix technology “Affymetrix.GeneChip. HG-U133_Plus_2.” We used data available either on the GEO Web site (http://www.ncbi.nlm.nih.gov/geo/) or from our own lung tumor series (GSE30219). The data were analyzed as described in the Supplementary Materials and Methods.
Thresholds of expression for germline- and placenta-restricted genes were established as described in the Supplementary Materials and Methods.