This study aimed to identify microRNAs associated with histological grade using comprehensive microRNA analysis data obtained by next-generation sequencing in early-stage invasive breast cancer. RNA-seq data from normal breast and breast cancer samples were compared to identify candidate microRNAs with different expressions using bioinformatics. A total of 108 microRNAs were significantly differentially expressed between normal breast and breast cancer tissues. Using clinicopathological information and microRNA sequencing data of 430 patients with breast cancer from The Cancer Genome Atlas (TCGA), the differences in candidate microRNAs between low- and high-grade cases were compared. Comparing the expression of the 108 microRNAs between low- and high-grade cases, 25 and 18 microRNAs were significantly upregulated and downregulated, respectively, in high-grade cases. Clustering analysis of the TCGA cohort using these 43 microRNAs identified two groups strongly predictive of histological grade. miR-3677 is a microRNA upregulated in high-grade breast cancer. The outcome analysis revealed that patients with high miR-3677 expression had a significantly worse prognosis than those with low miR-3677 expression. This study showed that microRNAs were associated with histological grade in early-stage invasive breast cancer. These findings contribute to the elucidation of a new mechanism of breast cancer growth regulated by specific microRNAs.

Lipopolysaccharides are a type of polysaccharide mainly present in the bacterial outer membrane of Gram-negative bacteria. Recent studies have revealed that lipopolysaccharides contribute to the immune response of the host by functioning as a cancer antigen. We retrospectively recruited 198 patients with gastric cancer who underwent surgery. The presence of lipopolysaccharides was determined using immunohistochemical staining, with the intensity score indicating positivity. The relationship between lipopolysaccharides and CD8, PD-L1, TGFBI (a representative downstream gene of TGF-β signaling), E-cadherin, and claudin-4 (epithelial–mesenchymal transition markers) was also investigated. Thereafter, we identified 20 patients with advanced gastric cancer receiving nivolumab and investigated the relationship between lipopolysaccharides and nivolumab sensitivity. After staining for lipopolysaccharides in the nucleus of cancer cells, 150 negative (75.8%) and 48 positive cases (24.2%) were found. The lipopolysaccharide-positive group showed increased cancer stromal TGFBI expression (p < 0.0001) and PD-L1 expression in cancer cells (p = 0.0029). Lipopolysaccharide positivity was significantly correlated with decreased E-cadherin expression (p = 0.0055) and claudin-4 expression (p = 0.029); however, no significant correlation was found between lipopolysaccharide expression and overall survival rate (p = 0.71). Among cases receiving nivolumab, the lipopolysaccharide-negative and -positive groups had a disease control rate of 66.7% and 11.8%, respectively (p = 0.049). Lipopolysaccharide positivity was associated with TGF-β signaling and epithelial–mesenchymal transition and was considered to promote therapeutic resistance to nivolumab.