Effect of photodynamic therapy in the stem cell phenotype of oral squamous cell carcinoma cell lines

Abstract

Among several types of cancer that affect the oral cavity, squamous cell carcinoma (OSCC) is the most prevalent malignant neoplasm. The conventional treatment is surgery and radiotherapy alone or in a combination with cisplatin. However, despite the advances in OSCC treatment, the patients frequently present metastasis at the diagnosis and recurrence, leading to a poor prognosis. An alternative treatment to OSCC is the Photodynamic Therapy (PDT), which is based on the use of photosensitizers whose toxicity is activated by light to promote the death of target cells. Although PDT has been used to some types of cancer, its effects in OSCC is poorly understood. Most recent studies have shown that malignant neoplasms may contain a small population of cells, designated as cancer stem cells (CSC), which have indefinite proliferative potential and are responsible for tumor growth resistance to therapy. Moreover, there are few studies in the literature that aimed to investigate the effects of PDT in the CSC fraction in OSCC. Thus, this study aims to evaluate, in vitro, the effects of PDT on OSCC cellular viability, maintenance of the stem cell phenotype and the fraction of the CSC subpopulations identified by the CD44high/ESAlow (migratory profile) and CD44high/ESAhigh (epithelial profile) phenotypes. Experimental procedures to investigate the cellular viability by the MTT, Neutral Red and Violet Crystal assays, the capability to form colonies and spheres as well as the percentage of CD44 and ESA expression by flow cytometry will be performed.