GAEC1 mutations and copy number aberration is associated with biological aggressiveness of colorectal cancer

Abstract

GAEC1 (gene amplified in oesophageal cancer 1) is a transforming oncogene with tumorigenic potential observed in both oesophageal squamous cell carcinoma and colorectal cancer. Nonetheless, there has been a lack of study done on this gene to understand how this gene exert its oncogenic properties in cancer. This study aims to identify novel mutation sites in GAEC1. To do so, seventy-nine matched colorectal cancers were tested for GAEC1 mutation via Sanger sequencing. The mutations noted were investigated for the correlations with the clinicopathological parameters of the patients with the cancer. Additionally, GAEC1 copy number aberration (CNA), mRNA and protein expression were determined with the use of droplet digital (dd) polymerase chain reaction (PCR), real-time PCR and Western blot (confirmed with immunofluorescence analysis). GAEC1 mutation was noted in 8.8% (n = 7/79) of the cancer tissues including one missense mutation, four loss of heterozygosity (LOH) and two substitutions. These mutations were significantly associated with cancer perforation (p = 0.021). GAEC1 mutation is frequently associated with increased GAEC1 protein expression. Nevertheless, GAEC1 mRNA and protein are only weakly associated. Taken together, GAEC1 mutation affects GAEC1 expression and is associated with poorer clinical outcomes. This further strengthens the role of GAEC1 as an oncogene.

GAEC1 drives colon cancer progression

“…Reverse transcription was then performed using the iScript cDNA Synthesis Kit (Bio‐Rad Laboratories, Hercules, CA), and the expression changes of GAEC1 in the different cell lines were examined using Quantstudio Flex 6 qPCR system (Thermo Fisher Scientific, Waltham, MA). Samples were prepared in 20 µL volume containing 10 µL of 2x SensiFAST SYBR No‐ROX mix (Bioline, London, UK), 1 µL of 10 µM primer pair, 1 µL of 60 ng template topped up with RNase‐free water, and qPCR was performed according to the protocol previously described . Amplification efficiency of GAEC1 (MG20123) was normalized against the housekeeping gene glyceraldehyde 3‐phosphate dehydrogenase ( GAPDH ; NM_002046) with primer details, as shown in Table .…”

“…Furthermore, GAEC1 was also able to discriminate between the different ethnicities of patients with colorectal cancer . This gene was even capable of discerning between the different sites of cancer within the bowel and was frequently associated with the bioaggression of cancer …”

“…Gene amplified in esophageal cancer 1 ( GAEC1 ) is located at chromosome 7q22.1, within the first intron region of SH2 B adaptor protein 2 ( SH2B2 ) gene . GAEC1 copy changes proved significant in distinguishing between patients with colorectal cancer from the healthy population .…”

“…Interestingly, the overexpression of GAEC1 was frequently associated with GAEC1 mutation. Approximately 10% of patients with colorectal cancer have mutations within the exon region of GAEC1 . Furthermore, these patients are more likely to have a cancer with perforation of the bowel wall.…”

“…3 This gene was even capable of discerning between the different sites of cancer within the bowel 4 and was frequently associated with the bioaggression of cancer. 2 GAEC1 encodes for a protein that is predominantly expressed with the cytoplasm of colon cancer. The immunohistochemical staining intensity of GAEC1 was found to increase in a stage-dependent manner in patients with colorectal cancer.…”