Abstract 883: Angiopoietin-like protein 2, a driver of cancer cell metastasis, is a novel serum biomarker for the diagnosis and prognosis in patients with gastric cancer
Authors: Toiyama Yuji , Kitajima Takahito , Shimura Tadanobu , Imaoka Hiroki , Kondo Satoru , Ide Shozo , Okigami Masato , Yasuda Hiromi , Saigusa Susumu , Ohi Masaki , Tanaka Koji , Inoue Yasuhiro , Mhori Yasuhiko , Goel Ajay , Kusunoki Masato 
Published: May 2015

Background: Gastric carcinogenesis is regarded as a multistep process with an intestinal metaplasia-dysplasia-carcinoma sequence, which is initiated by Helicobacter pylori infection that causes a chronic active inflammation in the gastric mucosa. Angiopoietin-like protein 2 (ANGPTL2) is known to act as a causative mediator of chronic inflammation and inflammatory carcinogenesis. However, the biological role and clinical significance of ANGPTL2 expression remains poorly understood in human cancer. We investigated the functional role of ANGPTL2 and evaluated the clinical significance of its expression in both primary tumor and matched serum specimens in patients with gastric cancer (GC).

Methods: The function of ANGPTL2 in GC was investigated by siRNA using GC cell lines (MKN1 and KATO III). Next, we examined ANGPTL2 expression in GC tissues (n=192) by immunohistochemistry (IHC) to evaluate associations between its expression and various clinicopathological features. Finally, we determined serum ANGPTL2 levels from 32 GC and 23 normal controls (NC), and validated its expression levels using 194 serum samples from GC and 45 from NC to evaluate its utility as a biomarker by ELISA.

Results: Knockdown of ANGPTL2 resulted in significant induction of anoikis (p&lt;0.05) and inhibition of cell proliferation (p&lt;0.05), invasion(p&lt;0.05) and migration (p&lt;0.05) in GC cells. ANGPTL2 was overexpressed in GC tissues compared to normal gastric mucosa, and high ANGPTL2 expression was significantly associated lymph node metastasis (p=0.0001), distant metastasis (p=0.01), early recurrence (p=0.003) and poor prognosis (p=0.007) in GC patients. Serum ANGPTL2 levels in GC patients were significantly higher compared to NC (p&lt;0.05), and successfully distinguished GC patients from NC with high accuracy (AUC=0.814). Finally, validation of these results in an independent patient cohort revealed that serum ANGPTL2 levels in GC patients were significantly higher compared to NC (p&lt;0.0001), demonstrated high AUC (0.831) values with 73.0% sensitivity and 82.2% specificity to distinguish GC patients from NC. In addition, serum ANGPTL2 levels also discriminated early GC patients (stage I) from NC (AUC=0.8). High ANGPTL2 in serum rather than in tissues were significantly associated with tumor progression, and consequently emerged as an independent predictor of tumor recurrence (HR=5.05, p=0.0004) and prognosis (HR=3.6, p=0.01) in patients with GC. Of interest, serum ANGPTL2 levels closely correlated with IHC scores in matched GC tissues (r= 0.16, p=0.02).

Conclusion: Our study first reports that overexpression of ANGPTL2 in GC cells results in increased malignant potential and metastasis. Serum

ANGPTL2 expression emerged as a novel, non-invasive biomarker for the earlier diagnosis, recurrence and prognosis in patients with gastric cancer.

Citation Format: Yuji Toiyama, Takahito Kitajima, Tadanobu Shimura, Hiroki Imaoka, Satoru Kondo, Shozo Ide, Masato Okigami, Hiromi Yasuda, Susumu Saigusa, Masaki Ohi, Koji Tanaka, Yasuhiro Inoue, Yasuhiko Mhori, Ajay Goel, Masato Kusunoki. Angiopoietin-like protein 2, a driver of cancer cell metastasis, is a novel serum biomarker for the diagnosis and prognosis in patients with gastric cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 883. doi:10.1158/1538-7445.AM2014-883