Tumor-Infiltrating Cell Profiling

We also built gene expression reference profiles from tumor-infiltrating cells. These are based on the single-cell RNA-Seq data from Tirosh and colleagues (Tirosh et al., 2016 (link)) described above. We only used the non-lymphoid tissue samples to build these tumor-infiltrating cell’s profiles, avoiding in this way potential ‘normal immune cells’ present in the lymph nodes and spleen. These reference profiles (Supplementary file 2) were built in the same way as described above for the reference profiles of circulating immune cells, but based on the mean and standard deviation instead of median and interquartile range respectively, due to the nature of single-cell RNA-Seq data and gene dropout present with such technique.
When testing EPIC with these profiles for the single-cell RNA-Seq datasets, for the samples of primary tumor and other non-lymph node metastases, a leave-one-out procedure was applied: for each donor we built reference cell profiles based only on the data coming from the other donors.