Clinical value and potential mechanisms of COL8A1 upregulation in breast cancer: a comprehensive analysis

Abstract

Background: The situation faced by breast cancer patients, especially those with triple-negative breast cancer, is still grave. More effective therapeutic targets are needed to optimize the clinical management of breast cancer. Although collagen type VIII alpha 1 chain (COL8A1) has been shown to be downregulated in BRIP1-knockdown breast cancer cells, its clinical role in breast cancer remains unknown.

Methods: Gene microarrays and mRNA sequencing data were downloaded and integrated into larger matrices based on various platforms. Therefore, this is a multi-centered study, which contains 5048 breast cancer patients and 1161 controls. COL8A1 mRNA expression in breast cancer was compared between molecular subtypes. In-house immunohistochemistry staining was used to evaluate the protein expression of COL8A1 in breast cancer. A diagnostic test was performed to assess its clinical value. Furthermore, based on differentially expressed genes (DEGs) and co-expressed genes (CEGs) positively related to COL8A1, functional enrichment analyses were performed to explore the biological function and potential molecular mechanisms of COL8A1 underlying breast cancer.

Results: COL8A1 expression was higher in breast cancer patients than in control samples (standardized mean difference = 0.79; 95% confidence interval [CI] 0.55-1.03). Elevated expression was detected in various molecular subtypes of breast cancer. An area under a summary receiver operating characteristic curve of 0.80 (95% CI 0.76-0.83) with sensitivity of 0.77 (95% CI 0.69-0.83) and specificity of 0.70 (95% CI 0.61-0.78) showed moderate capacity of COL8A1 in distinguishing breast cancer patients from control samples. Worse overall survival was found in the higher than in the lower COL8A1 expression groups. Intersected DEGs and CEGs positively related to COL8A1 were significantly clustered in the proteoglycans in cancer and ECM-receptor interaction pathways.

Conclusions: Elevated COL8A1 may promote the migration of breast cancer by mediating the ECM-receptor interaction and synergistically interplaying with DEGs and its positively related CEGs independently of molecular subtypes. Several genes clustered in the proteoglycans in cancer pathway are potential targets for developing effective agents for triple-negative breast cancer.

Keywords: Breast cancer; COL8A1; Immunohistochemistry staining; Mechanism.

Fig. 1

General expression status of COL8A1 in breast cancer (BRCA) compared to non-BRCA tissues. A standardized mean difference (SMD) value > 0 and 95%CI with no overlap of zero indicated COL8A1 was significantly upregulated in BRCA compared to non-BRCA tissues

Fig. 2

Subgroup analysis based on the subtypes of breast cancer. The result indicated that the elevated COL8A1 expression shared no significant difference among Luminal A, Luminal B, HER-2 + , and Three Negative Breast Cancer (TNBC) subgroups

Fig. 3

Diagnostic value of COL8A1 in breast cancer (BRCA). a Summary receiver operating characteristic (sROC) curve. b Forest plot of diagnostic odd ratio (DOR). An AUC value > 0.70 and a DOR > 1 signified COL8A1 possessed moderate capability in distinguishing BRCA from non-BRCA patients. AUC, area under the curve

Fig. 4

The prognostic value of COL8A1 mRNA in breast cancer tissues. a GSE25307; b GSE35629-GPL1390; c TCGA. In the GSE25307 cohort, high COL8A1 group possessed poor overall survival condition compared to low COL8A1 group in breast cancer patients

Fig. 5

Protein expression levels of COL8A1 in breast cancer (BRCA) and normal breast tissues. a-d normal breast tissues; e–h BRCA tissues (Magnification × 200). COL8A1 was negatively stained in normal breast epithelium (a) and BRCA (e). COL8A1 was weakly stained in normal breast epithelium (b) and BRCA (f). COL8A1 was moderately stained in normal breast epithelium (c) and BRCA (g). COL8A1 was strongly stained in normal breast epithelium (d) and BRCA (h). According to staining intensity and percentage of color range, 45.2% BRCA tissues exhibited low COL8A1 expression and 54.8% BRCA tissues exhibited high COL8A1 expression. While 67.7% normal breast tissues exhibited low COL8A1 expression and 32.3% normal breast tissues exhibited high COL8A1 expression

Fig. 6

Functional enrichment based on 632 overlapping genes of upregulated DEGs and COL8A1 positively related CEGs. a Kyoto Encyclopedia of Genes and Genomes; b Disease Ontology; c Reactcome. DEGs, differentially expressed genes; CEGs, co-expressed genes

Fig. 7

GO enrichment based on 632 overlapping genes of upregulated DEGs and COL8A1 positively related CEGs. a GO analysis; b Protein-to-protein internet based on KEGG pathway: proteoglycans in cancer (ID: hsa05205); c Protein-to-protein internet based on KEGG pathway: ECM-receptor interaction (ID: hsa04512). GO, Gene Ontology; DEGs, differentially expressed genes; CEGs, co-expressed genes; KEGG, Kyoto Encyclopedia of Genes and Genomes

Fig. 8

Mutation landscapes of COL8A1 and co-expressed genes clustered in two Kyoto Encyclopedia of Genes and Genomes pathways: proteoglycans in cancer and ECM-receptor interaction