Cedrus atlantica extract exerts antiproliferative effect on colorectal cancer through the induction of cell cycle arrest and apoptosis

Cedrus atlantica is a tree species found in Morocco with many clinical benefits in genitourinary, musculoskeletal, and skin systems. Previous studies have reported that extracts of Cedrus atlantica have antioxidant, antimicrobial, and anticancer properties. However, its role in colorectal cancer (CRC) remains unclear. The present study investigated the effects and underlying mechanisms of Cedrus atlantica extract (CAt) using HT-29 (human colorectal adenocarcinoma) and CT-26 CRC cell lines. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to measure cell viability. Flow cytometry analysis and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay were used to study the cell cycle and cell apoptosis, respectively. The expression of cell cycle and apoptosis-associated proteins was detected by western blotting or immunohistochemical (IHC) staining. CAt showed significant inhibitory effects on the proliferation of HT-29 and CT-26 cells, and combined with the clinical drug, 5-fluorouracil (5-FU), exhibited synergistic effects. CAt induced cell cycle arrest at the G0/G1 phase through the upregulation of p53/p21 and the downregulation of cyclin-dependent kinases (CDKs)/cyclins. In addition, CAt-treated cells exhibited chromatin condensation, DNA fragmentation, and apoptotic bodies, which are typical characteristics of apoptosis activated via both the extrinsic (Fas ligand (FasL)/Fas/caspase-8) and intrinsic (Bax/caspase-9) pathways. Importantly, CAt suppressed tumor progression and prolonged the life span of mice within a well-tolerated dose. Therefore, our findings provide novel insights into the use of CAt for the treatment of CRC.