Distances between each cancer type and the corresponding normal tissue in reduced principal component (PC) space.

The Euclidean distance was computed between the projections of each cancer type and the associated normal tissue in the space spanned by the first two PCs of the mean gene expression matrix (as shown in Figs 1 and 2). The ‘Cancer/normal relative distance’ column contains the ratio of the distance between each cancer and normal tissue pair as visualized in Fig 1 to the average distance between the cancer and all other cancers or normal tissues. The ‘Cancer/normal-specific relative distance’ column contains a similar distance ratio computed in the space spanned by the first two PCs of cancer-specific and normal tissue-specific mean expression values as visualized in Fig 2. The ‘Distance ratio’ column contains the ratio of the ‘Cancer/normal-specific relative distance’ to the ‘Cancer/normal relative distance’.