Abstract:

Objective To explore the expression of 7-dehydrocholesterol reductase （DHCR7） in gastric cancer using bioinformatics methods and its relationship with clinical pathological characteristics and prognosis of gastric cancer patients. Methods DHCR7 expression in gastric cancer was analyzed using the UALCAN database； DHCR7 mRNA expression and its relationship with the prognosis of gastric cancer patients were analyzed using the Kaplan-Meier plotter database； The expression of DHCR7 and its correlation with tumor immune infiltration level were analyzed using Sangerbox 3.0 and TIMER database； Real-time fluorescence quantitative PCR was used to detect the expression of DHCR7 mRNA in gastric cancer tissues and adjacent tissues； immunohistochemical staining was conducted to detect the DHCR7 expression in gastric cancer tissues and adjacent tissues and its correlation with clinical pathological parameters； Receiver operator characteristic （ROC） curve was used to evaluate the efficacy of DHCR7 expression in the diagnosis of gastric cancer. Results The analysis results of the UALCAN database showed that there were statistically significant differences in DHCR7 mRNA expression among gastric cancer patients of different genders （χ²=18.15， P<0.001）， grades （χ²=16.32， P<0.001）， and TP53 mutation status （χ²=20.12， P<0.001）. Survival analysis showed that the 10-year overall survival （OS） rate （HR=1.55， 95%CI： 1.31-1.84， P<0.001）， 10-year progression free survival （PFS） rate （HR=1.67， 95%CI： 1.36-2.05， P<0.001）， and 10-year post progression survival （PPS） rate （HR=1.81， 95%CI： 1.43-2.28， P<0.001） of gastric cancer patients with high DHCR7 expression were significantly lower than those with low DHCR7 expression. Immune infiltration analysis showed the expression of DHCR7 was negatively correlated with the comprehensive score （r=-0.51， P<0.001）， stromal cell score （r=-0.48， P<0.001）， immune cell score （r=-0.45， P<0.001）， CD4⁺ T cells （r=-3.01， P<0.001）， macrophages （r=-0.40， P<0.001）， neutrophils （r=-0.32， P<0.001）， and dendritic cells （r=-0.37， P<0.001） infiltration levels in gastric cancer， and positively correlated with the purity of gastric cancer cells （r=0.15， P<0.001）. The qRT-PCR results showed that compared with adjacent tissues （1.86±0.51）， the expression of DHCR7 in gastric cancer tissues （3.43±0.13） was significantly upregulated， with a statistically significant difference （t=42.89， P<0.001）. The relative expression level of DHCR7 in normal gastric mucosal cells GES-1 was 1.06±0.19， and the relative expression levels in four types of gastric cancer cells （HGC-27， AGS， SNU-1， and SGC-7901） were 2.40±0.26， 1.88±0.11， 1.51±0.04， and 2.63±0.20， respectively，there were statistically significant differences in the expression of DHCR7 among the five types of cells （F=38.34， P<0.001）， and the relative expression level of DHCR7 in normal gastric mucosal cells was statistically significant different compared to the four types of gastric cancer cells mentioned above （P=0.002； P=0.003； P=0.017； P<0.001）；The immunohistochemical results showed that the high expression rate of DHCR7 in gastric cancer tissues was 80.0% （96/120）， which was significantly higher than that in adjacent tissues （68.3%） （82/120） （χ²=56.84， P<0.001）. There were statistically significant differences in tumor maximum diameter （χ²=40.17， P<0.001）， histological grade （χ²=16.20， P<0.001） and pTNM stage （χ²=16.99， P<0.001） between patients with high and low DHCR7 expression. The ROC curve results showed that the area under the curve （AUC） of DHCR7 expression level for diagnosing gastric cancer were 0.76 （based on TCGA database， 95%CI： 0.68-0.83， P<0.001） and 0.97 （120 clinical samples of gastric cancer， 95%CI： 0.95-0.99， P<0.001）， respectively. Conclusions DHCR7 is highly expressed in gastric cancer and closely associated with poor prognosis in patients， which may be a novel biomarker for the diagnosis and prognosis of gastric cancer.

Key words: Stomach neoplasms, DHCR7, Computational informatics, Prognosis, Diagnosis