Selective cytotoxic effect of Plantago lanceolata L. against breast cancer cells

Background: Plantago lanceolata L. is used in Iraqi folklore medicine to treat injuries, and its extract is prescribed by some herbalists for cancer patients. This research aimed to evaluate the effect of P. lanceolata leaf extract on breast cancer cell lines in vitro and to identify its active compounds. Crystal violet viability assay was used to determine the cytotoxicity of methanolic P. lanceolata leaf extract against various breast cancer cell lines. MCF7, AMJ13, MDAMB, and CAL51 human breast cancer cells were treated with different concentrations of the extract for 72 h. The morphology of the treated cells was examined under a phase-contrast inverted microscope. The clonogenic ability was assessed through a clonogenic assay. High-performance liquid chromatography (HPLC) analysis was performed to measure the concentrations of phenols and flavonoids in the extract. Results: The methanolic P. lanceolata leaf extract significantly inhibited the proliferation of triple-negative CAL51 cells but showed minor effect on the other breast cancer cells. In addition, at high doses, it induced cytopathic morphological changes. The clonogenic assay showed low colony formation in the exposed cells, especially CAL51 cells. Furthermore, HPLC study revealed that the methanolic extract contained important flavonoid glycosides, especially rutin, myricetin quercetin, and kaempferol. Conclusions: P. lanceolata leaf extract selectively inhibited the proliferation of CAL51 triple-negative breast cancer cells and showed minor effect on the other breast cancer cells types studied. Thus, this study showed P. lanceolata as a possible natural source of selective anti-triple-negative breast cancer drugs.