In serum proteomics, the proliferative signalling by Erb-B2 receptor tyrosine kinase 2 (ERBB2) in cancer molecular pathway, characterised by elevated serum SHC adaptor protein 1 (SHC1), Erb-B4 receptor tyrosine kinase 4 (ERBB4), epidermal growth factor receptor (EGFR) and ERBB2, was upregulated in RAC2 (p<0.03 versus RAC1; p<0.05 versus RAC3) (table 4, supplementary table S16 and supplementary figure S5e). Here, RAC2 is linked to cancer.