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Introduction
Cancer is a complex and intrinsically heterogeneous disease (1). An increased understanding of the mechanisms underlying the progression of human cancer may aid the identification of novel therapeutic targets. Next generation sequencing methods have enabled the development of a series of public databases, including The Cancer Genome Atlas (TCGA) (2) and the Gene Expression Profiling Interactive Analysis (GEPIA) (3) and Genotype-Tissue Expression databases (4), which may be used to investigate the heterogeneity and complexity of cancer. Gastric cancer (GC) is one of the most common tumors of the digestive system. The prognosis of patients with locally advanced GC is poor, and the 5-year survival rate is <50% (5). In the past decades, studies have focused on identifying novel diagnostic and prognostic biomarkers for several types of human cancer, including GC. For example, TIMP metallopeptidase inhibitor 2 (TIMP2) was identified as a prognostic marker for GC, and increased expression of TIMP2 was correlated with a shorter survival time in patients with GC (6). However, effective biomarkers to improve the survival time of patients with GC are still required.
Collagen type VIII α 1 chain (COL8A1) encodes one of the two α chains of collagen type VIII (7), which had been revealed to play a role in atherogenesis and vascular remodeling, presumably through modification of cell migration and proliferation (8,9). COL8A1 is produced in the cornea, aortic endothelial cells and intraglomerular mesangial cells (10,11). COL8A1 was found to promote the growth of smooth muscle cells, suggesting that it serves important roles in regulating cell biology (7). Moreover, previous studies have revealed that COL8A1 may be implicated in cancer progression. Di et al (12) used weighted gene co-expression network analysis to report that COL8A1 was an important stage-associated gene in bladder cancer. Shang et al (13) reported that COL8A1 was associated with the development and diagnosis of colon cancer. Furthermore, the knockdown of COL8A1 suppressed cell growth and invasion of hepatocarcinoma cells (14). However, despite the aforementioned studies, the expression pattern and molecular functions of COL8A1 in human cancer remain largely unclear.
The present study evaluated the mRNA levels of COL8A1 across different human cancer types and investigated the association between COL8A1 expression and survival time using TCGA database. Integrated analysis revealed that COL8A1 was upregulated across...