Abstract:
Medicinal plants are part of the healthcare systems worldwide, especially in low- and middle-income countries.
African lettuce (Launaea taraxacifolia) is cultivated extensively in Africa, from Senegal in the west to Ethiopia
and Tanzania in the east, and in Southern Africa. Potential anticancer effects of L. taraxacifolia have been
suggested, but little is known about putative molecular mechanisms or potential for herb–drug interactions
through inhibition or induction of drug-metabolizing enzymes. We investigated the effects of crude aqueous
extracts of L. taraxacifolia on growth kinetics and cell cycle progression of the WHC01 esophageal cancer
cells. Antiproliferative and apoptotic effects were evaluated using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide] assay and flow cytometry, while examining, in parallel, the genes regulating
apoptosis and cell cycle in this cell culture model. In addition, we tested the inhibitory and enzyme kinetic
effects of the aqueous L. taraxacifolia using recombinant human CYP450 isozyme model systems (CYP1A2,
CYP2C9, and CYP2C19). L. taraxacifolia exhibited a significant growth inhibitory effect on the WHC01 cancer
cells. Most cell cycle genes were downregulated. Cell cycle analysis showed a G0-G1 cell cycle arrest in
WHC01 cells in the presence of L. taraxacifolia extract, accompanied by morphological changes. L. tarax-
acifolia extract treatment resulted in downregulation of expression levels of CYP1A2 ( p < 0.0005) and
CYP2C19 ( p < 0.003) by 50–70%. L. taraxacifolia extract caused reversible and time-dependent inhibition of
the recombinant CYP1A2, CYP2C9, and CYP2C19. This study provides new insights on possible anticancer
effects of L. taraxacifolia, a widely used medicinal plant in parts of Africa and across the world especially by
patients with cancer. Further mechanistic studies expanding on these observations would be timely and con-
tribute to the field of global precision medicine that requires solid understanding of drug and herb molecular
mechanisms of action and drug–herb interaction potentials, given the worldwide use of medicinal plants.
