Effects of methylene blue photodynamic therapy on oral carcinoma and leukoplakia cells

OBJECTIVE: Methylene blue (MB) is a readily available and affordable substrate that can be used as a photosensitizer for photodynamic therapy (PDT). The objective of this study was to determine if PDT with MB can downregulate matrix metalloproteinases (MMPs) related to oral carcinoma. METHODS: Cell cultures of oral squamous cell carcinoma (CA‐9‐22), oral leukoplakia (MSK‐Leuk1), and immortalized keratinocytes (Rhek‐1A) were photosensitized with MB and treated with PDT. MMP‐9 gene expression was interrogated via qRT‐PCR. The 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide (MTT) assay was used to confirm the efficacy of MB PDT. RESULTS: MMP‐9 gene expression was found to be significantly decreased in oral carcinoma, leukoplakia, and immortalized keratinocytes with use of MB PDT. CONCLUSION: This work demonstrates that MB‐mediated PDT can downregulate MMPs which are critical to the invasion and metastasis of oral cancer. These results suggest that MB PDT could be a clinically significant and cost‐effective treatment for oral leukoplakia and carcinoma. LEVEL OF EVIDENCE: NA