Tests for IgG and IgM antibodies for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became available in February 2020. On March 4, 2020, the seventh edition of the New Coronavirus Pneumonia Prevention and Control Protocol for the novel coronavirus disease 2019 (COVID-19) was released by the National Health Commission of the People’s Republic of China and added serological diagnostic criteria.¹ A previous study of 9 pregnant women and their infants found no maternal-infant transmission of SARS-CoV-2 based on reverse transcriptase–polymerase chain reaction (RT-PCR).² We applied these new criteria to 6 pregnant women with confirmed COVID-19 and their infants because serologic criteria would allow more detailed investigation of infection in newborns.

Background/Aims: As MCF-7 and MDA-MB-231 cells are the typical cell lines of two clinical breast tumour subtypes, the aim of the present study was to elucidate the transcriptome differences between MCF-7 and MDA-MB-231 breast cancer cell lines. Methods: The mRNA, miRNA (MicroRNA) and lncRNA (Long non-coding RNA) expression profiles were examined using NGS (next generation sequencing) instrument Illumina HiSeq-2500. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analyses were performed to identify the biological functions of differentially expressed coding RNAs. Subsequently, we constructed an mRNA-ncRNA (non-coding RNA) targeting regulatory network. Finally, we performed RT-qPCR (real-time quantitative PCR) to confirm the NGS results. Results: There are sharp distinctions of the coding and non-coding RNA profiles between MCF-7 and MDA-MB-231 cell lines. Among the mRNAs and ncRNAs with the most differential expression, SLPI, SOD2, miR-7, miR-143 and miR-145 were highly expressed in MCF-7 cells, while CD55, KRT17, miR-21, miR-10b, miR-9, NEAT1 and PICSAR were over-expressed in MDA-MB-231 cells. Differentially expressed mRNAs are primarily involved in biological processes of locomotion, biological adhesion, ECM-receptor interaction pathway and focal adhesion. In the targeting regulatory network of differentially expressed RNAs, mRNAs and miRNAs are primarily associated with tumour metastasis, but the functions of lncRNAs remain uncharacterized. Conclusion: These results provide a basis for future studies of breast cancer metastasis and drug resistance.

Linc‐ROR is reported to be a potential biomarker of breast cancer, but the detailed mechanism of linc‐ROR‐mediated breast cancer regulation has not been fully studied. We aimed to explore how linc‐ROR affects proliferation, metastasis, and drug sensitivity in breast cancer. Cell lines in which linc‐ROR was overexpressed or knocked down were constructed, and the cell proliferation, colony formation, cell migration, and invasion abilities of these lines were explored. A CCK‐8 assay was performed to determine the sensitivity of the breast cancer cells to rapamycin. Next‐generation sequencing was conducted to explore the detailed regulatory mechanism of linc‐ROR; differentially expressed RNAs in the linc‐ROR‐overexpressing cell line compared with the negative control were screened out, and their target genes were chosen to perform Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes analysis, protein–protein interaction network analysis, and competing endogenous RNA (ceRNA) network analysis. The ceRNA mechanism of linc‐ROR for miR‐194‐3p, which targets MECP2, was determined through dual‐luciferase reporter assay, RT–qPCR, western blot, and rescue experiments. Finally, we found that linc‐ROR was upregulated in breast tumor tissues. linc‐ROR promoted the cell proliferation, colony formation, cell migration, and invasion of breast cancer and decreased the sensitivity of breast cancer cells to rapamycin. The overexpression of linc‐ROR triggered changes in the whole transcriptome of breast cancer cells, and a total of 85 lncRNAs, 414 microRNAs, 490 mRNAs, and 92 circRNAs were differentially expressed in the linc‐ROR‐overexpressing cell line compared with the negative control. Through a series of bioinformatic analyses, the ‘linc‐ROR/miR‐194‐3p/MECP2’ ceRNA regulatory axis was confirmed to be involved in the linc‐ROR‐mediated progression and drug sensitivity of breast cancer. In conclusion, linc‐ROR serves as an onco‐lncRNA in breast cancer and promotes the survival of breast cancer cells during rapamycin treatment by functioning as a ceRNA sponge for miR‐194‐3p, which targets MECP2.

Increasing evidence has shown that the dysregulation of microRNAs (miRNAs) is associated with drug resistance. Fulvestrant and tamoxifen represent the major endocrine drugs for the treatment of breast cancer patients, and yet little is known about the biological mechanisms of acquiring resistance to fulvestrant and tamoxifen, let alone the differences between cell lines resistant to these two drugs. Exploration of the differential miRNA profiles between these two cell lines is a useful way to further clarify these resistance mechanisms. The fulvestrant-resistant cell line (MCF7-F) and the tamoxifen-resistant cell line (MCF7-T) were established from the drug-sensitive parental MCF7 cell line using a 21-day high-dose antiestrogen induction method. Differentially expressed miRNA profiles of MCF7-F and MCF7-T were detected using microarray; then, multiple bioinformatic analyses were carried out, including protein–protein interaction network, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Compared with the parental MCF7 cell line, more miRNAs were found to be participating in the process of acquiring fulvestrant resistance than tamoxifen resistance. miR-4532, miR-486-5p, miR-138, miR-1228, and miR-3178 could be new targets for combating both fulvestrant resistance and tamoxifen resistance. miR-3188, miR-21, miR-149, and others may be associated with fulvestrant resistance, whereas miR-342 and miR-1226 may be associated with tamoxifen resistance in breast cancer cells. We found differential miRNA profiles between fulvestrant-resistant and tamoxifen-resistant breast cancer cells, but the definite mechanism involved in gaining resistance still needs further study.

Background/Aims: Numerous studies have suggested that the promoter methylation status of O6-methylguanine-DNA methyltransferase (MGMT) is significantly associated with breast cancer. However, these studies have not demonstrated consistent results. Methods: To obtain more accurate results for this possible association, we performed a meta-analysis-based study using the relevant data. A total of 14 articles were included in this meta-analysis. Results: Our study showed that the frequency of MGMT promoter methylation was significantly higher in patients with breast cancer than non-breast cancer subjects with an Odds Ratio (OR) of 4.47, a 95% Confidence Interval (CI) ranging between 1.95 - 10.25 and a P value of 0.0004. Moreover, MGMT methylation was significantly associated with the negative expression of the MGMT protein (OR = 4.65, 95%CI = 2.66 - 8.12, P < 0.00001), Oestrogen Receptor (ER)-negative tumours (OR = 1.79, 95%CI = 1.09 - 2.93, P = 0.02), postmenopausal status (OR =1.84, 95%CI = 1.18 - 2.87, P = 0.007) and histological grade III tumours (OR = 2.49, 95%CI = 1.53 - 4.07, P = 0.0003) in breast cancer patients. However, breast cancer was not significantly correlated with lymph node metastasis (OR = 1.19, 95%CI = 0.83 - 1.70, P = 0.35), Progesterone Receptor (PR) status (OR = 1.08, 95%CI = 0.58 - 2.00, P = 0.81), Human epidermal growth factor receptor - 2（HER-2/neu）status (OR = 1.01, 95%CI = 0.65 - 1.57, P = 0.97), P53 mutation (OR = 1.30, 95%CI = 0.76 - 2.21, P = 0.34) and age > 50 (OR = 1.07, 95%CI = 0.46 - 2.51, P = 0.88). Conclusions: Our study suggests that MGMT promoter methylation may be an early biomarker for the diagnosis of breast cancer.