Abstract 5238: Clinical significance of GET4 expression in colorectal cancer
Authors: Koike Kensuke , Masuda Takaaki , Sato Kuniaki , Motomura Yuushi , Takahashi Jyunnichi , Shimizu Dai , Kuramitsu Shotaro , Fujii Atsushi , Kitagawa Akihiro , Noda Miwa , tsuruda Yusuke , Ootu Hajime , Kuroda Yousuke , Eguchi Hidetoshi , Nakagawa Takashi , Mimori Koushi 
Published: August 2019

Background: Colorectal cancer (CRC) is one of the most common cancers worldwide and the second leading cause of cancer-related deaths in developed countries, with the majority of deaths being attributed to distant metastasis. Therefore, it is necessary to identify a novel biomarker for cancer progression and metastasis, one that could also be a useful therapeutic target in CRC. Amplification of chromosome 7p is frequent in CRC, and it has been considered to harbor driver genes that promote tumorigenesis or tumor progression by the gain of function. We aimed to identify novel candidate driver genes on chromosome 7p and to clarify the clinical significance of their expression in CRC.

Material and Methods: 1. We selected the candidate genes that satisfied the following criteria using CRC data from The Cancer Genome Atlas (TCGA). 1) The DNA copy number and mRNA expression are positively correlated with each other, 2) overexpressed in the tumor tissues compared to the normal tissues. 2. The mRNA expression of the candidate genes was measured in 147 surgically-resected CRC tissues and the paired normal tissues in our hospital by quantitative RT-PCR. The differences of mRNA expression between CRC tissues and normal tissues were analyzed by Mann Whitney U-test. 3. Survival analysis between high and low expression group of the candidate genes was performed by the Kaplan-Meier method. Correlation between the mRNA expression of the candidate genes and the clinicopathological factors were analyzed by Fisher’s exact test. 4. Gene Set Enrichment Analysis (GSEA) was performed in CRC data from TCGA to clarify the correlation between the candidate genes and gene sets that are associated with tumorigenesis or tumor progression.

Results: The Golgi to ER traffic protein 4 (GET4) was identified as a candidate driver gene. GET4 is known to be one factor of the BCL2-associated athanogene 6 (BAG6) chaperone complex and function as a regulator for the nucleo-cytoplasmic transport of BAG6. The BAG6 complex is implicated in diverse cellular processes including apoptosis, co-chaperone, and DNA damage response. The expression of GET4 was significantly higher in CRC tissues than in normal colon tissues (p=0.03), and it correlated with depth invasion (p=0.02), and lymphatic invasion (p=0.01). The high GET4 expression group had a significantly poorer prognosis than the low expression group (p=0.02). On multivariate analysis, distant metastasis was an independent prognostic factor affecting OS (p&lt;0.05) with hazard ratios (95% CI) of 66.6 (5.46-1649.3) among clinicopathological factors. GSEA showed that GET4 expression was negatively correlated with the pathway associated with the Rb-related protein p130, which belongs to the RB gene family proved to be a tumor suppressor.

Conclusions: GET4 could be a promising driver gene of CRC on chromosome 7p possibly through regulating the location of BAG6. GET4 may be a therapeutic target as well as a poor prognostic biomarker in CRC.

Note: This abstract was not presented at the meeting.

Citation Format: Kensuke Koike, Takaaki Masuda, Kuniaki Sato, Yuushi Motomura, Jyunnichi Takahashi, Dai Shimizu, Shotaro Kuramitsu, Atsushi Fujii, Akihiro Kitagawa, Miwa Noda, Yusuke tsuruda, Hajime Ootu, Yousuke Kuroda, Hidetoshi Eguchi, Takashi Nakagawa, Koushi Mimori. Clinical significance of GET4 expression in colorectal 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 5238.