Robust and precise molecular prognostic predictors for luminal breast cancer are required. This study aimed to identify key methylation sites in luminal breast cancer, as well as precise molecular tools for predicting prognosis. We compared methylation levels of normal and luminal breast cancer samples from The Cancer Genome Atlas dataset. The relationships among differentially methylated sites, corresponding mRNA expression levels and prognosis were further analysed. Differentially expressed genes in normal and cancerous samples were analysed, followed by the identification of prognostic signature genes. Samples were divided into low- and high-risk groups based on the signature genes. Prognoses of low- and high-risk groups were compared. The Gene Expression Omnibus dataset were used to validate signature genes for prognosis prediction. Prognosis of low- and high-risk groups in Luminal A and Luminal B samples from the TCGA and the Metabric cohort dataset were analyzed. We also analysed the correlation between clinical features of low- and high- risk groups as well as their differences in gene expression. Fourteen methylation sites were considered to be related to luminal breast cancer prognosis because their methylation levels, mRNA expression and prognoses were closely related to each other. The methylation level of SOSTDC1 was used to divide samples into hypo- and hyper-methylation groups. We also identified an mRNA signature, comprising eight transcripts, ESCO2, PACSIN1, CDCA2, PIGR, PTN, RGMA, KLK4 and CENPA, which was used to divide samples into low- and high-risk groups. The low-risk group showed significantly better prognosis than the high-risk group. A correlation analysis revealed that the risk score was an independent prognostic factor. Low- and high- risk groups significantly correlated with the survival ratio in Luminal A samples, but not in Luminal B samples on the basis of the TCGA and the Metabric cohort dataset. Further functional annotation demonstrated that the differentially expressed genes were mainly involved in cell cycle and cancer progression. We identified several key methylation sites and an mRNA signature for predicting luminal breast cancer prognosis. The signature exhibited effective and precise prediction of prognosis and may serve as a prognostic and diagnostic marker for luminal breast cancer.

Glutamate metabotropic receptors (GRM) play a variety of roles in neuronal cells. However, their clinical significance and biological functions in breast cancer remain unknown. RNA sequencing data of breast cancer was obtained from the TCGA dataset (v2) and mined for the expression profiles of GRM family according to cancer subtypes. mRNA expression of GRM family in breast cancer tissues and para-cancerous tissue samples as well as breast cancer cell lines were measured by qPCR. The effects of over- and under-expression of GRM4 on cell capabilities to survive, migrate and invade were determined by colony formation, transwell migration and invasion assays. To explore the upstream regulation pattern of GRM4, miRNAs that target GRM4 were predicted and validated by dual luciferase reporter assay. In addition, the mRNA and protein expression of GRM4 regulated by these miRNAs were further measured by qPCR and western blot assay. GRM4 was the only GRM member that expressed in breast cancer tissues. Ectopic expression of GRM4 was correlated with better prognosis of breast cancer patients. Overexpression of GRM4 could significantly inhibit cell proliferation, migration and invasion capacity in MDA-MB-231, while knockdown of GRM4 could promote these processes. miR-328-3p and miR-370-3p were predicted to regulate the expression of GRM4 and dual luciferase reporter assay demonstrated that miR-328-3p and miR-370-3p directly bound to the 3′ UTR of GRM4 and mutations on the binding regions on GRM4 significantly decreased the luciferase activity. qPCR demonstrated that expression of miR-328-3p and miR-370-3p was significantly decreased in breast cancer tissues and cells compared with that in control samples. However, there were no correlations between the expression of miR-328-3p and GRM4, as well as the expression of miR-370-3p and GRM4. Moreover, overexpression of miR-328-3p and miR-370-3p counteracted the inhibitory effect of GRM4-induced cell proliferation, migration and invasion. Our results suggest that GRM4 might be a tumor suppressor gene in breast cancer under the direct regulation of miR-328-3p and miR-370-3p.

Graphical Schematic of Mycoplasma hominis nucleic acid detection based on the CRISPR-Cas12a system. Clinical samples from cervical or urethral swabs were collected and incubated with lysis buffer to release nucleic acid (10 min). Extracted DNA (1 μl) is subjected to the RPA reaction with specific primers at 37°C. After 20 min, RPA product was subjected to the CRISPR-Cas12a reaction for cleavage. The collateral nuclease activity of Cas12a (250 nM) proteins were activated upon specific binding to crRNA (crRNA3, 62.5 nM) and the DNA product; thus, Cas12a cut the quenched fluorescent ssDNA reporter (125 nM) (30 min). The generated fluorescence signal would be measured by a fluorescence plate reader or visualized by lateral flow strips.