| Summary: | 博士 === 國立陽明大學 === 臨床醫學研究所 === 102 === Dysregulation of multiple signaling cascades, which could be regulated by protein phosphorylation and protein-protein interactions (PPIs), is often detected in cancers. Deciphering the signaling pathway networks via PPIs at the cellular level is a promising approach for targeting cancers but remains incomplete. The final goal of this study is to establish the PPI-pathway network in cancers for elucidating new therapeutic candidates. Here, we used an in situ proximity ligation assay (in situ PLA) to systematically identify the EGFR phosphorylation change and 624 endogenous PPIs in cancer cells. Fourteen EGFR phosphorylation sites were characterized with distinct EGF dependency upon EGFR genotypes in lung cancer cell. We demonstrated a novel interaction, EGFR-AURKA, which might mediate AURKA-elicited phosphorylation at EGFR-Thr654 and -Ser1046 in EGFR mutant lung cancer cells. Moreover, we detected 67 endogenous PPIs among 21 interlinked pathways in hepatocellular carcinoma (HCC) cells. The expression of novel interaction, CRKL-FLT1 is strongly correlated with the migratory ability of HCC. CRKL and the CRKL-FLT1 were identified as novel prognosis markers by immunohistochemical analysis of 192 HCC patients. We also uncovered the HCC patients with lower expression of FLT1 was associated with hypertension. In addition to HCC, 557 endogenous PPIs in HeLa cells were validated for pathway network. Based on Reactome annotations, 90 PPIs of them were cross-talk PPIs linking 17 signaling pathways. The top 2 connected cross-talk PPIs are MAPK3-DAPK1 and FAS-PRKCA interactions, which link 9 and 8 pathways, respectively. In summary, this study not only prove the concept that functional exploration of a disease network with PPI-pathway network can be used to discover novel biomarkers, but also establish the systematic profile of PPIs for comprehensive analysis of the human interactome.
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