Integrin β5 in plasma-derived exosomal protein predicting liver-specific metastasis in advanced gastric cancer patients.

Abstract

e14521 Background: Gastric cancer (GC) is the second leading cause of cancer death in China. Liver metastasis (LM) is a highly frequent event of the advanced GC, and the patients with LM always present dismal prognosis. A predicted factor of LM is urgently established to screen out the population in high risk of LM. Tumor-derived exosomes play critical roles in cancer metastasis process. Exosomes integrin (ITG) αvβ5 is uptake by liver resident cells and linked to LM in cell lines. This study is designed to evaluate the association between exosomes ITG αvβ5 and liver metastasis, especially in HER2 positive gastric cancer. Methods: 74 untreated advanced GC patients with matched blood and tumor tissue samples and clinical features were collected in the study. Exosomal HER2, ITG αv and β5 expression were measured by enzyme-linked immunosorbent assay (ELISA) after the exosomes isolated from plasma. HER2 status of tumor tissue was determined by IHC and/or FISH. Results: Based on HER2 status of tumor tissue, we initially proved the feasibility of detecting HER2 expression from exosome. ROC curves showed the optimum exosomal HER2 expression diagnostic cutoff for HER2 positive patients was 266.38 pg/ml (sensitivity 71.4% and specificity 72.6%). In total, 27 patients were LM and the rest (n = 47) was non-LM. The median expression value of ITG αv and β5 were 57.55 pg/ml and 836.00 pg/ml, respectively. And these two median value were identified as the cutoff value for subsequent analysis, respectively. HER2 expression was merely linked to ITG β5 expression (P = 0.019), not ITG αv (P > 0.050). There was no relationship between ITG αv and LM (P = 0.629), however, ITG β5 expression presented significant association with LM (P = 0.016). We further probed the relationship between ITG and other metastasis. Results showed no correlation between any ITG and other non-liver organic metastases, like lung, bone, ovarian, lymph, and peritoneal metastasis. Besides, ITG β5 expression was also associated with LM in the HER2-positive GC patients. Conclusions: Exosomes might serve as a potential non-invasive diagnostic and screening tool. In clinical samples, ITG β5, not αv, was linked to LM, and might be a valuable biomarker in the use of predicting LM of GC, even in the HER2-positive patients.