Abstract 1766: High expression of ARHGEF2 is associated with poor prognosis via c-Myc signaling in patients with pancreatic cancer
Authors: Nakao Yosuke , Nakagawa Shigeki , Yamashita Yo-ichi , Itoyama Rumi , Yusa Toshihiko , Umezaki Naoki , Yamao Takanobu , Miyata Tatsunori , Okabe Hirohisa , Imai Katsunori , Hayashi Hiromitsu , Chikamoto Akira , Baba Hideo 
Published: August 2019

Abstract
Background: Pancreatic cancer remains a lethal malignancy with a dismal five year survival rate of less than ten percent. ARHGEF2 is one of the Rho guanine exchange factor (RhoGEF). RhoGEF is a microtubule-associated guanine nucleotide exchange factor for the Rho family of small GTPases. We aimed to reveal the association between ARHGEF2 expression and patients’ prognosis, or the downstream pathways of ARHGEF in pancreatic cancer.
Methods: For the gene selection, we used the cohort of 102 patients who underwent curative resection for pancreatic cancer from GSE21501 in which the DNA microarray were performed to assess the association with molecular pathways and the prognosis of patients. Pathway analysis was performed by GSEA (gene set enrichment analysis) using HALLMARK geneset.
As a validation cohort, 200 patients underwent curative resection for pancreatic cancer at Kumamoto University from April 2004 to March 2018 were enrolled. The immunohistochemical (IHC) staining was performed to evaluate the expression of ARHGEF2 and c-Myc. IHC was evaluated with the intensity and area of immunoreactivity of ARHGEF2 and c-Myc and scored each factors from 0 to 2. The staining index (ranging from 0 to 4) was calculated by multiplying intensity and area. Low expression was defined from 0 to 1, and high expression was from 2 to 4.
Result: In GSE21501 (n=102), the patients were separated into high- (upper 50%, n = 51) and low- (lower 50%, n = 51) ARHGEF2 groups. High-ARHGEF2 group had significantly poor overall survival than low-ARHGEF group (p = 0.01). Moreover, high ARHGEF2 group was associated with high lymph node metastasis (p=0.03). The GSEA
analysis revealed that the high ARHGEF expression was significantly associated with “HALLMARK-MYC-TARGET-V2” geneset (p=0.04). Also high ARHGEF expression was significantly associated with CDC25A (p=0.006) which is the downstream gene of c-MYC pathway and regulates cell cycle, suggesting that ARHGEF promote cell cycle via MYC signaling.
In immunohistochemistry, the high ARHGEF2 group (n = 122) had shorter recurrence free survival (RFS) (p = 0.0014) and poor overall survival (OS) (p = 0.0036). In addition, in the comparisons of clinicopathological factors between the high ARHGEF2 and the low ARHGEF2 groups, there were significantly larger tumor size and higher lymph node positive rate in the high ARHGEF2 group. In the multivariate analysis for RFS, high CA19-9 value, R1 resection and high ARHGEF2 expression were independent poor prognostic factors. In the multivariate analysis for OS, high CA19-9 value, tumor size (&gt; 40 mm), lymph node metastasis and high ARHGEF2 expression were independently associated with poor prognosis. According to immunohistochemistry, ARHGEF2 and c-Myc have a significant positive correlation.
Conclusion: High expression of ARHGEF2 is associated with poor prognosis via c-Myc signaling in patients with pancreatic cancer.
Citation Format: Yosuke Nakao, Shigeki Nakagawa, Yo-ichi Yamashita, Rumi Itoyama, Toshihiko Yusa, Naoki Umezaki, Takanobu Yamao, Tatsunori Miyata, Hirohisa Okabe, Katsunori Imai, Hiromitsu Hayashi, Akira Chikamoto, Hideo Baba. High expression of ARHGEF2 is associated with poor prognosis via c-Myc signaling in patients with pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1766.