TJP2 and breast cancer: In addition, they applied parallel reaction monitoring (PRM), a quantitative mass spectrometry (MS) approach, to verify four phosphoproteins: cGMP-dependent protein kinase 1 (PKG1), Ral GTPase-activating protein subunit alpha-2 (RALGAPA2), nuclear transcription factor, X-box-binding protein 1 (NFX1), and tight junction protein 2 (TJP2), which showed significant upregulation in breast cancer patients [2].