Tamoxifen withdrawal in women with progressive metastatic breast cancer: a case series of six patients

Hsa_circ_0097922 promotes tamoxifen resistance and cell malignant behaviour of breast cancer cells by regulating ACTN4 expression via miR-876-3p

An increasing number of findings have verified the critical roles of circular RNAs (circRNAs) in human cancers, and chemotherapy resistance is a poor prognostic factor for breast cancer (BC). This study is designed to explore the function of hsa_circ_0097922 in the tamoxifen resistance of breast cancer. Hsa_circ_0097922, microRNA-876-3p (miR-876-3p), and alpha-actinin 4 (ACTN4) level were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell survival, proliferation, apoptosis, migration and invasion were detected by Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry, wound healing and Transwell assays. Protein levels of proliferating cell nuclear antigen (PCNA), B-cell lymphoma-2 (Bcl-2), cleaved caspase 3, matrix metalloproteinase 9 (MMP9), and ACTN4 were determined using western blot assay. Using bioinformatics software, the binding between miR-876-3p and hsa_circ_0097922 or ACTN4 was predicted, followed by confirmation by RNA immunoprecipitation (RIP) and RNA pull-down assays. A xenograft tumour model in vivo analysed the biological role of hsa_circ_0097922 on BC tumour growth and drug resistance. Hsa_circ_0097922 and ACTN4 were increased, and miR-876-3p was decreased in tamoxifen resistance BC cells. Moreover, hsa_circ_0097922 knockdown can block BC cell malignant behaviour and tamoxifen resistance in vitro. Mechanically, hsa_circ_0097922 acted as a sponge of miR-876-3p to regulate ACTN4 expression. Hsa_circ_0097922 silencing increased the drug sensitivity of BC in vivo. Hsa_circ_0097922 might regulate BC cell malignant behaviour and tamoxifen resistance partly by regulating the miR-876-3p/ACTN4 axis, hinting at a promising therapeutic target for the BC treatment.

Single Cell Sequencing in Cancer Diagnostics

Personalized medicine has been driven by improvements in genomic sequencing and analysis. For several diseases, in particular cancers, it has for nearly a decade been standard clinical practice to analyze the genome and expression of the genes of patients. The results are reflected directly in the treatment plan for the patient, in targeted medical inventions. This specialized mode of diagnostics has been restricted to account for averaged trends in the tumor. The approach sharply contrasts our knowledge on heterogeneity within tumors. Several studies further describe how treatment against one tumor subclone in some cases merely serves to provide space and support for uncontrolled growth of more aggressive subclones. In this chapter, we describe current possibilities for implementation of single cell sequencing of malignomas in clinic, as well as discuss hands-on practical advice for single cell routine diagnostics that allows for full delineation of tumor clonality.