Across TCGA pan-cancer cohorts, SI mass-spec protein differs between tumor and matched normal tissue in 1 of 18 cancer types tested, making tumor–normal expression one of SI’s most consistent transcriptional readouts.
The strongest signal is observed in colon adenocarcinoma (COAD), where SI mass-spec protein is repressed in tumor relative to normal tissue. In most cancer types SI is over-expressed in tumor, although a few such as COAD show the opposite, repressed pattern.
COAD are the cancer types where SI tumor–normal differential expression is most reproducible.