Effect of circular RNA hsa_circ_0000231 interacting with HnRNPK on proliferation, migration, and apoptosis in breast cancer

To explore the effects of the interaction between circular RNA hsa_circ_0000231 and HnRNPK on the proliferation, migration and apoptosis in breast cancer.

Microarray analysis was used to investigate the expression profile of circRNAs in 4 pairs of breast cancer tissues and corresponding adjacent normal tissues. A total of 35 breast cancer tissue specimens were collected from the patients admitted in the First Affiliated Hospital of Chongqing Medical University from September 2019 to January 2021. qRT-PCR was carried out to detect the relative expression of hsa_circ_0000231, and fluorescence in situ hybridization (FISH) assay was performed to observe its location and expression in the cells. Breast cancer MCF-7 and SK-BR-3 cells were transfected with the interference vector of hsa_circ_0000231 respectively. Then cell wound healing assay, CCK-8 assay, EdU cell proliferation assay, clone formation experiment, hoechst33342 staining, TUNEL, flow cytometry and Transwell assay were adopted to determine cell migration, invasion, proliferation and apoptosis, and Western blotting was employed to measure the expression of CCND2, CCND1 and CDK4 after the knockdown. The effect of hsa_circ_0000231 on the growth of transplanted tumors was observed in nude mice. RNA pulldown assay was performed to identify hsa_circ_0000231-associated proteins, and FISH-immunofluorescence (IF) assay were employed to clarify the subcellular localization of hsa_circ_0000231 and HnRNPK. qRT-PCR and Western blotting were conducted to detect the expression of c-Myc.

Circular RNA hsa_circ_0000231 was highly expressed in breast cancer tissues (P<0.001) and breast cancer cells (P<0.01). Down-regulation of hsa_circ_0000231 inhibited the proliferation, migration and invasion of breast cancer cells, induced cell apoptosis, led to cell cycle arrest in G₁ phase, and obviously decreased the expression of CCND2, CCND1 and CDK4. The results of in vivo experiments showed that knockdown of hsa_circ_0000231 inhibited the growth of tumor xenograft. HnRNPK was co-localized in the nucleus with hsa_circ_0000231, and interacted with hsa_circ_0000231 to promote c-Myc expression.

Knockdown of hsa_circ_0000231 could suppress the proliferation, migration and invasion of breast cancer cells, induce cell apoptosis and cell cycle arrest, and inhibit tumor growth in vivo. The interaction of hsa_circ_0000231 with HnRNPK enhances the expression of c-Myc, and thus promotes the occurrence and development of breast cancer.