Increased death rates due to lung cancer have necessitated the search for potential novel
anticancer compounds such as carbazole derivatives. Carbazoles are aromatic heterocyclic
compounds with anticancer, antibacterial and anti-inflammatory activity. The study
investigated the ability of the novel carbazole compound (Z)-4-[9-ethyl-9aH-carbazol-3-yl)
amino] pent-3-en-2-one (ECAP) to induce cytotoxicity of lung cancer cells and its mechanism
of action. ECAP was synthesized as a yellow powder with melting point of 240-247 °C.
The 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), lipid peroxidation
and comet assays were used to assess the cytotoxic effect of the compound on A549 lung
cancer cells. Protein expression was determined using western blots, apoptosis was measured
by luminometry (caspase-3/7, -8 and -9) assay and flow cytometry was used to measure
phosphatidylserine (PS) externalisation. ECAP induced a p53 mediated apoptosis of
lung cancer cells due to a significant reduction in the expression of antioxidant defence proteins
(Nrf2 and SOD), Hsp70 (p < 0.02) and Bcl-2 (p < 0.0006), thereby up-regulating reactive
oxygen species (ROS) production. This resulted in DNA damage (p < 0.0001), upregulation
of Bax expression and caspase activity and induction of apoptosis in lung cancer
cells. The results show the anticancer potential of ECAP on lung cancer.
S1 Fig. MTT assay measured in untreated (control) and 1% DMSO (vehicle control) treated
A549 cells. The data showed no significant cytotoxicity.
S2 Fig.Western blots showing the effect of ECAP on the expression of Bax, Bcl-2, p53,
Nrf2, Hsp70 and SOD. The original western blots which were used for western blot analysis