Background: Cinnamic Acid (CA), also known as 3-phenyl-2-propenoic acid, is a naturally occurring
aromatic fatty acid found commonly in cinnamon, grapes, tea, cocoa, spinach and celery. Various studies
have identified CA to have anti-proliferative action on glioblastoma, melanoma, prostate and lung carcinoma
Objective: Our objective was to investigate the molecular mechanism underlying the cytotoxic effect of CA in
killing MDA-MB-231 triple negative breast cancer cells.
Methods: We performed MTT assay and trypan blue assay to determine cell viability and cell death, respectively.
Comet analysis was carried out to investigate DNA damage of individual cells. Furthermore, AO/EtBr
assay and sub-G1 analysis using flow cytometry were used to study apoptosis. Protein isolation followed by
immunoblotting was used to observe protein abundance in treated and untreated cancer cells.
Results: Using MTT assay, we have determined CA to reduce cell viability in MDA-MB-231 breast cancer cells
and tumorigenic HEK 293 cells but not in normal NIH3T3 fibroblast cells. Subsequently, trypan blue assay and
comet assay showed CA to cause cell death and DNA damage, respectively, in the MDA-MB-231 cells. Using
AO/EtBr staining and sub-G1 analysis, we further established CA to increase apoptosis. Additionally, immunoblotting
showed the abundance of TNFA, TNF Receptor 1 (TNFR1) and cleaved caspase-8/-3 proapoptotic
proteins to increase with CA treatment. Subsequently, blocking of TNFA-TNFR1 signalling by small
molecule inhibitor, R-7050, reduced the expression of cleaved caspase-8 and caspase-3 at the protein level.
Conclusion: Thus, from the above observations, we can conclude that CA is an effective anticancer agent that
can induce apoptosis in breast cancer cells via TNFA-TNFR1 mediated extrinsic apoptotic pathway.