Abstract
Globally, lung cancer has remained the leading cause of morbidity and mortality in men
and women. To enhance photodynamic therapeutic effects in vitro, the present study was designed
to reduce dose-dependence in photodynamic therapy (PDT) and evaluate the anticancer effects of
Dicoma anomala (D. anomala) root extracts (i.e., chloroform (Chl), ethyl acetate (EtOAc), and methanol
(MeOH)) on A549 lung cancer cells. The most active extract of D. anomala (D.A) was used to
establish the 50% inhibitory concentration (IC50), which was further used to evaluate the anticancer
efficacy of D.A in combination with ZnPcS4-mediated PDT IC50. The study further evaluated cell
death mechanisms by cell viability/ cytotoxicity (LIVE/DEADTM assay), flow cytometry (Annexin Vfluorescein
isothiocyanate (FITC)-propidium iodide (PI) staining), immunofluorescence (p38, p53, Bax,
and caspase 3 expressions), and fluorometric multiplex assay (caspase 8 and 9) 24 h post-treatment
with IC50 concentrations of ZnPcS4-mediated PDT and D.A MeOH root extract. Morphological
changes were accompanied by a dose-dependent increase in cytotoxicity, decrease in viability, and
proliferation in all experimental models. Apoptosis is the highly favored cell death mechanism
observed in combination therapy groups. Apoptotic activities were supported by an increase in the
number of dead cells in the LIVE/DEADTM assay, and the upregulation of p38, p53, Bax, caspase 3, 8,
and 9 apoptotic proteins. In vitro experiments confirmed the cytotoxic and antiproliferative effects of
D.A root extracts in monotherapy and in combination with ZnPcS4-mediated PDT. Taken together,
our findings demonstrated that D.A could be a promising therapeutic candidate worth exploring in
different types of cancer.