Characterization of cancer stem cell phenotype in cisplatin-resistant oral squamous cell carcinoma cell lines

Abstract

Oral Squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide, has high morbidity and mortality rates associated with late diagnosis, local recurrence and metastasis in cervical lymph nodes. Studies suggest the presence of a subpopulation of tumor cells with unlimited capacity of proliferation, capable of self-renewal and differentiation, called cancer stem cells (CSCs). Furthermore, this subpopulation is considered responsible for initiation, progression and tumor chemoresistance in different carcinomas, including oral cancer. Regarding treatment, surgical resection associated to radio and chemotherapy is the most frequently recommended approach. However, studies show that CSCs are resistant to cisplatin, the main chemotherapy agent used in the treatment of OSCC. Consequently, only differentiated tumor cells are eliminated, while CSCs remain quiescent, strongly contributing to tumor recurrence and predominance of more resistant and aggressive tumor cell subpopulations. Considering that chemoresistance is one of the main causes of treatment failure in OSCC, the objective of this work is to develop and characterize cisplatin-resistant tumor cell subpopulations in vitro. For this purpose, SCC-9 ZsGreen parental and SCC-9 ZsGreen LN-1 metastatic SCC strains will be used, and cytotoxicity assays will be conducted by MTT. After the development of cisplatin-resistant strains, assays will include immunophenotyping (CD44 and ESA) by flow cytometry, sphere formation and gene expression of markers of the stem (CD44, BMI1 and ALDH1) and EMT phenotypes (Vimentin, SNAIL, TWIST, N- and E-cadherin), as well as molecules related to drug transport (ABC), by means of qPCR. The characterization of cell strains resistant to treatment with cisplatin offers biological support to seek therapeutic techniques based on the development of more efficient target therapies and/or adjuvants that, ultimately, might result in a better prognosis for OSCC patients.