MELK is a downstream target of Del-1 and promotes breast cancer progression.

Abstract

Listen

Translate article

e12578 Background: Del-1 is a promising prognostic marker for breast cancer in our previous study. However, the downstream targets and biological effectors of Del-1 remain unclear and still untargetable in breast cancer. We performed transcriptome analysis using RNA-seq and explored the mechanism of Del-1 in regulating the progression of breast cancer to find druggable target. Methods: Total RNA was isolated using RNAiso Plus (TaKaRa, Otsu, Shiga, Japan), Libraries were prepared from total RNA using the NEBNext Ultra II Directional RNA-Seq Kit. High-throughput sequencing was performed as paired-end 100 sequencing using NovaSeq 6000 (Illumina, Inc., USA). OTSSP167(OTS167) were treated for inhibition of MELK. The effects of MELK on cell proliferation, invasion were determined using MTT, Matrigel Transwell assays. The tumoral expression of Del-1 and MELK were determined based on tissue microarrays and immunohistochemistry results from 440 early breast cancer patients. Results: To investigate Del-1 downregulation effect on breast cancer, we performed RNA-seq of Del-1 knock downed MDA-MB-231 and MCF 7-Tamoxifen resistant (TamR) cell line. Compared with si-control, MELK gene were downregulated in both knock downed cell lines. While a high Del-1 and MELK mRNA expressions were found in all the breast cancer cell lines, both expressions were significantly higher in MDA MB-231. MELK inhibitor (OTS167) treatment to breast cancer cell line MDA-MB-231 and MCF 7-TamR showed similar results as Del-1 down regulation by si-RNA. Inhibition of MELK suppressed proliferation and invasion of breast cancer cell line. Tumoral MELK expression correlate with increased aggressiveness and poor clinical outcomes in 440 breast cancer patients. Conclusions: Our results indicate that Del-1 may regulate MELK expression which has a role in breast cancer progression. In conclusion, modulation of Del-1 status by targeting MELK may be a new therapeutic strategy for breast cancer patients.