DNA damage and cell death in human oral squamous cell carcinoma cells: The potential biological effects of cannabidiol.

Objective: The present study examined the in vitro effects on oral squamous cell carcinoma cells (HSC-3) of cannabidiol (CBD), the main chemical component of Cannabis, proposed as a novel adjuvant therapy in the treatment of cancers.

Design: Cell viability (MTT assay), morphology (SEM), apoptosis and cell cycle (flow cytometry), and DNA damage (phospho-γ-H2AX immunofluorescence) were evaluated. Cytotoxicity was evaluated with concentrations between 100 µM and 1 µM, and two concentrations were selected for subsequent analysis: 25 µM, as toxic dose, and 6.25 µM, as non-toxic.

Results: CBD caused a dose- and time-dependent reduction in viability of 64 %, 96 %, and 99 % with 25 µM, 50 µM and 100 µM, respectively, after 72 h (p < 0.001), cell cycle arrest in G0-G1 phase with increased apoptosis in particular at 72 h for 25 µM (p < 0.001), significant morphological alterations with 25 µM, still present even at 6.25 µM, and significantly increased cell damage considering a significant increase in the percentage of highly positive cells (5 phosphorylated γH2AX foci), which is around 29 % for 25 µM and 19 % for 6.25 µM after 24 h.

Conclusions: CBD inhibits oral cancer growth causing DNA damage. In general, induced cell cytotoxicity appears to be dose- and time-related. Doses of CBD ≥25 μM showed a high reduction in viability. CBD could possibly represent a new therapeutic molecule for its cytotoxic effects against oral squamous cell carcinoma. The mechanism involved in the suppressive effect caused by CBD needs further investigation.