Analysis And Identification Of Obesity-related Genes In Breast Cance

Objective: Breast cancer is the leading cause of cancer death in women,and studies have shown that obesity is a very important risk factor for breast cancer.Compared with non-obese women,obese women with breast cancer have higher grade and larger tumours,more extensive lymph node involvement,more rapid tumour metastasis,and poorer overall survival and prognosis.The pathogenesis of obesity in relation to early breast cancer is not fully understood.This study analysed and identified obesity-associated genes in breast cancer to provide new ideas and potential targets for early diagnosis and treatment of obesity-associated breast cancer.Methods:(1)The breast cancer dataset GSE42568 and the normal breast tissue dataset GSE33526 from obese women were obtained from the Gene Expression Omnibus database.(2)Principal component analysis was performed on the breast cancer dataset GSE42568 using the Facto Mine R,factoextra package of the R software.Obesity-related differentially expressed genes in breast cancer were screened using the Limma package of the R software.Venn diagrams were plotted using EVenn software to show the relationship between the two datasets,and heat and volcano plots were generated using the heat map and ggplot2 tools of R software to show the expression levels of the top 40 differentially expressed genes.(3)The biological functions and pathways associated with ORDEGs were then analysed using GO and KEGG enrichment.(4)To study the protein-protein interaction of obesity-related genes in breast cancer,the STRING database was used to analyse the ORDEGs to construct a molecular interaction network,and the hub genes in the network were screened using the built-in Cyto Hubba plug-in.The co-expressed gene network was investigated using the Gene MANIA database.(5)The major pathways and functional characteristics of the hub genes were further validated using Metascape software.(6)Quantitative real-time q PCR,WB and IHC were used to identify the expression levels of the 10 hub genes in paraneoplastic,non-obese and obese breast cancer tissues,respectively.Results:(1)The results of PCA principal component analysis analysed the sample scatter of breast cancer dataset GSE42568 showed mutual aggregation,indicating that the reproducibility of breast cancer gene dataset GSE42568 was relatively good,while there was good differentiation between the two groups of obese women normal breast tissue dataset GSE33526 and breast cancer tissue dataset GSE42568.(2)The results of the Venn diagram constructed by EVenn software showed that the breast cancer dataset GSE42568 contained 3973 expressed genes and the obese female normal breast tissue dataset GSE33526 contained 744 expressed genes,with a total of 394 overlapping genes between the two datasets,including 286 up-regulated genes and 108 down-regulated genes.(3)These genes are mainly involved in the regulation of lipid metabolism,alcohol metabolism and fatty acid metabolism,and are mainly localised in cellular components such as muscle membranes,lipid droplets and collagen-containing extracellular matrix,and are associated with molecular functions such as oxidoreductase activity,amide binding and steroid dehydrogenase activity.The 108down-regulated genes were mainly enriched in biological processes such as epithelial cell morphogenesis,skin development and embryonic epithelial cell formation,mainly in cellular components such as apical region,apical plasma membrane and apical junctional complex,and were associated with molecular functions such as peptide myosin V binding,cell adhesion mediator activity and N-acetylaminogalactosyltransferase activity.(4)The results of the KEGG enrichment analysis showed that the upregulated DEGs were mainly involved in signalling pathways such as PPAR,insulin and fatty acid metabolism.The downregulated DEGs were associated with cell adhesion molecules,cancer proteoglycans and Hippo signalling pathways.(5)Analysis of the ORDEGs using the STRING database and visualisation using Cytoscape software revealed a total of 386 nodes and 827 edges in the PPI network of ORDEGs.(6)The 10 highest scoring hub genes in the PPI network of ORDEGs such as SCD,DGAT2,PPARG,LPL,GPAM,PCK1,MLXIPL,CIDEC,ACSL1 and ACACB were screened using the Cytohubba plugin.The PPI network consisting of 10 hub genes and their co-expressed genes was analysed using the Gene MANIA database,with a co-expression rate of 87.91%.(7)The results showed that they were mainly enriched in biological processes such as triglyceride metabolism,fatty acid metabolism and regulation of fatty acid metabolism,and mainly involved in signalling pathways such as lipid metabolism pathway,AMPK signalling pathway,activation of gene expression by SREBF(SREBP)and insulin resistance pathway.(8)The results of q PCR,WB and IHC showed that the expression levels of SCD,LPL,GPAM,ACACB,PCK1 and ACSL1 in the non-obese breast cancer tissues were higher than those in the normal breast tissue group,while the expression levels of SCD,LPL,GPAM,ACACB,PCK1 and ACSL1 in the obese breast cancer tissues were significantly higher than those in the non-obese and normal breast tissue groups.Conclusion: Ten hub genes associated with obesity and breast cancer were screened from the breast cancer dataset GSE42568 and normal breast tissue dataset GSE33526 of obese women by multiplex bioinformatic analysis.The expression levels of SCD,LPL,GPAM,PCK1,ACSL1 and ACACB were significantly higher in obese breast cancer tissues than in normal breast tissues and non-obese breast cancer tissues,respectively,using q PCR,WB and IHC.This provides new ideas and potential targets for early diagnosis and treatment of obesity-related breast cancer.