Cytotoxic and Anti-Proliferative Effects of Miliusol and Its Derivative against TNBC

Background: Triple-negative breast cancer (TNBC), subtype of breast cancer, is characterized by molecular heterogeneity due to the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Absence of these receptors make it unresponsive to conventional hormone therapies suggesting an urgent necessity to develop innovative and effective treatment options for TNBC. This study aims to evaluate the cytotoxic and antiproliferative effects of miliusol, a prototype natural antitumor molecule identified from Miliusa plants1, along with its two derivatives (K1Seb2 and K1SS2), on TNBC cell lines.

Methodology: TNBC cell lines, MDA-MB-231 & MDA-MB-468, were treated with varying concentrations of miliusane compounds. The SRB assay was used to evaluate the cytotoxicity, where cell viability was determined by measuring the absorbance at 510 nm. Cells were seeded at low density (500 cell/well) for the colony-forming assay and let to proliferate for 10 days post-treatment (0.5 & 1.0 µM), followed by cell fixation, staining and count on cell proliferation.

Results: With dose-dependent decrease in cell viability, the IC50 values of miliusol and K1Seb2 were found to be 1.16 and 2.35 µM for MDA-MB-231 and 0.97 & 1.69 µM for MDA-MB-468, respectively. While IC50 of K1SS2 was reported 2.1 µM against MDA-MB-231. Additionally, the colony-forming assay demonstrated a significant reduction in colony formation at concentrations of 1 µM of miliusol and K1Seb2, indicating higher potency of the miliusanes.

Conclusion: The results demonstrate that all miliusane compounds have significant cytotoxic and antiproliferative effects on TNBC cell lines. These results imply that miliusol and its derivatives have potential as targeted treatments for TNBC, necessitates future research through mechanistic studies including wound healing tests, western blotting, and apoptotic assays. Subsequent studies must assess the compounds’ efficacy and safety in vivo, facilitating possible preclinical studies. This project was supported by Hong Kong Baptist University, Research Committee, Initiation Grant- Faculty Niche Research Areas (IG-FNRA) 2021/22, Hong Kong (RC-IG-FNRA/21- 22/SCM/01).