Investigação de marcadores de hipóxia em neoplasias benignas e malignas de glândulas salivares e o papel do HIF-1α no carcinoma de células escamosas de boca sob radiação

Abstract

Cancer is among the most common causes of morbidity and mortality in the world. Among malignant epithelial neoplasms is squamous cell carcinoma comprising more than 90% of cancers of the head and neck, being the sixth most common type of cancer in the world represented mostly by squamous cell carcinoma (HNSCC) and in part by salivary gland neoplasias (SGNs). Oral squamous cell carcinoma (OSCC) is an important public health problem, being the most common type of oral malignancy. Tumor hypoxia is associated with increased resistance to ionizing radiation and various types of chemotherapy. The main protein of the hypoxia pathway is a factor induced by hypoxia-1α (HIF-1α), which is a transcription factor that targets several genes that promote adaptations under hypoxic conditions and has been extensively studied. High levels of expression of this protein are associated with a worse prognosis in several types of tumors. Epigenetic changes have been shown to be important in the context of head and neck neoplasms. MiR-210 is a hypoxia-induced gene, regulated by HIF-1α and exerts several roles in the cell, such as inhibiting apoptosis and increasing angiogenesis. Studies have demonstrated great potential as a biomarker for the diagnosis and prognosis of various types of neoplasias. Epigenetic changes have been shown to be important in the context of head and neck neoplasms. MiR-210 is a hypoxia-induced gene, regulated by HIF-1α and exerts several roles in the cell, such as inhibiting apoptosis and increasing angiogenesis. Studies have demonstrated great potential as a biomarker in the diagnosis and prognosis of various types of neoplasms. Bioinformatics is an important tool for the evaluation of several phenomena. The present study aimed to test two hypotheses under the impact of genetic and epigenetic components in oral squamous cell carcinoma (OSCC) and SGNs: The first hypothesis was to analyze whether the levels of HIF-1α and miR-210 hypoxia markers in benign and malignant SGNs are highly expressed and whether these hypoxic markers are involved in the main processes associated with chemotherapy in SGNs through bioinformatics analysis. Evaluation of the expression of HIF-1α and miR-210 occurred through qRT-PCR in 21 samples, including 7 (33.33%) of malignant SGNs, 7 (33.33%) benign SGNs and 7 of salivary tissue not neoplastic. Bioinformatics analysis to identify the major biological processes involved with the application of chemotherapy in (SGNs) was performed. There was no difference in HIF-1 α and miR-210 expression in either benign or malignant neoplasias of salivary glands, as compared to control, nonneoplastic salivary glands. Finally, bioinformatic analyses revealed the most robust alterations in processes specifically related to DNA and cellular division in SGNs. The second hypothesis was to analyze whether the effect of radiotherapy reduces the levels of HIF-1α and miR-210 in patients with oral squamous cell carcinoma. For this purpose, blood samples from nine patients with OSCC and nine blood samples from control patients were used, which were subjected to analysis of HIF-1α and miR-210 mRNA expression. In addition, the immortalized SCC9 cell line was subjected to hypoxia and radiation treatment, followed by migration and expression analysis of HIF-1α mRNA and miR-210. Hypoxia radiation does not decrease levels of HIF-1α and miR-210, but increases the migration capacity of neoplastic cells.