TPM4 and breast cancer: Many of the proteins upregulated in the serum of breast cancer patients had never been previously observed in serum using LC-MS/MS, such as paired-like homeodomain transcription factor 2 isoform b (PITX2), AKT3 kinase isoform 2 (AKT3), tissue inhibitor of metalloproteinase 3 precursor (TIMP3) [25, 26], and Tropomyosin alpha-4 chain (TMP4).