High-throughput screening of ancient forest plant extracts shows cytotoxicity towards triple-negative breast cancer

According to the World Health Organization, womeńs breast cancer is among the most common cancers with 7.8 million diagnosed cases during 2016-2020 and encompass 15 % of all female cancer-related mortalities. These mortality events from triple-negative breast cancer are a significant health issue worldwide calling for a continuous search of bioactive compounds for better cancer treatments. Historically, plants are important sources for identifying such new bioactive chemicals for therapeutic treatments. Here we use high-throughput screening and mass spectrometry analyses of extracts from 100 plant species collected in Chinese deep-forests to detect novel bioactive breast cancer phytochemicals. First, to study the effects on viability of the plant extracts, we used a MTT and CCK-8 cytotoxicity assay employing triple-negative breast cancer (TNBC) MDA-MB-231 and normal epithelial MCF-10A cells lines and cell cycle arrest to estimate apoptosis using flow cytometry. Based on these analyses, the most potent extracts were from the Amur honeysuckle (Lonicera maackii) wood/root bark and Nigaki (Picrasma quassioides) wood/root bark. Then, 5×106 MDA-MB-231 cells were injected subcutaneously into the right hind leg of four exposed groups of nude mice i.e. Amur honeysuckle wood distilled water, Amur honeysuckle root bark ethanol, Nigaki wood ethanol or Nigaki root bark distilled water/ethanol (1:1) extract; and a tumour was allowed to grow for seven days. The four exposed groups with MBD-MB-231 breast cancer cells received gavage extracts from Amur honeysuckle and Nigaki in phosphate-buffered saline (PBS), while the control groups received only PBS. The tumour weight reduced significantly by 60.5% within 2 weeks in nude mice, while on average killing 70% of the MDA-MB-231 breast cancer cells after 48 hours treatment (MTT test). In addition, screening of target genes using the Swiss Target Prediction, STITCH, STRING and NCBI-gene database showed that the four plant extracts possess desirable activity towards several known breast cancer genes. This reflect that the extracts may kill MBD-MB-231 breast cancer cells. This is the first screening of plant extracts with high efficiency in 2 decades, showing promising results for future development of novel cancer treatments for better livelihood and lower socioeconomic burdens.