Effects of Photodynamic Therapy Mediated by Liposomal Aluminumphthalocyanine Chloride on Chemically Induced Tongue Tumors

Abstract

Human oral squamous cell carcinoma is one of the ten most frequently diagnosed cancer types and several researches are thus focused on improving therapeutic protocols against this disease. Particularly, photodynamic therapy has emerged as an effective treatment for oral carcinoma. It is mediated by a photosensitizer, a molecule that, after being light-activated, promotes the chemical reactions responsible for the production of cytotoxic species involved in photodynamic therapy. Despite of clinical approvals, several classical photosensitizers present important drawbacks. However, when associated to liposomes, these drugs have been shown to present improved characteristics, such as increased tumor accessibility and high photodynamic activity in physiological media. Therefore, this work aimed to investigate the effects of photodynamic therapy mediated by a liposomal formulation of aluminum-phthalocyanine chloride, a second generation photosensitizer, on tongue tumors induced in Swiss mice through topical application of the carcinogen 4-nitroquinoline-1-oxide. The treatment of these tumors consisted in injecting the liposomal phthalocyanine in the peritumoral area followed by irradiation of the tumor, three hours later, with laser (670 nm, 100 J/cm2). Single and double applications of this protocol were tested. The photodynamic therapy based on this liposomal aluminum-phthalocyanine, both in single and double applications, produced intense necrosis on tumor tissue accompanied by infiltration of polymorphonuclear cells and thrombi formation on tumor-associated blood vessels. These findings suggest that photodynamic therapy based on liposomal aluminum-phthalocyanine chloride is effective against chemically induced oral cancer.