Avaliação do Fator Induzido Pela Hipoxia 1-Alfa no Retinoblastoma

Abstract

Background: Retinoblastoma is the most common malignant intraocular tumor in childhood. Patients with advanced tumors, in general, respond poorly to treatment. Hypoxia is a common phenomenon for advanced tumors and is associated with resistance to chemotherapy and radiation therapy. Cells and tissues tumor microenvironment adapt to hypoxia by various routes and activation molecules associated with hypoxia. Of these, the hypoxia inducible factor 1 alpha (HIF-1-α) is the most important transcription factor that regulates the cellular response to hypoxia. Objective: To evaluate the expression of HIF- 1-α in retinoblastoma and to evaluate the proliferation of retinoblastoma cells by blocking the gene HIF-1-α. Material and Methods: 21 cases of retinoblastoma were selected from the file of The Henry C. Witelson Ocular Pathology Laboratory, McGill University, Montreal, QC, Canada. Clinical data was collected. Histopathological study and immunohistochemistry with the antibody HIF-1-α were performed in all cases. The cell line of human retinoblastoma Y79 was grown. Cells were treated with Cobalt Chloride (CoCl 2) in order to stabilize the protein HIF-1-α. After this treatment, analysis of mRNA levels of HIF-1-α was performed by PCR and western blot. Small interfering RNA (siRNA) was used to block gene HIF-1-α and, after this block, proliferation assay was performed to evaluate the effect on cell proliferation of retinoblastoma. Results: 85.7% of the cases of retinoblastoma expressed HIF-1-α. A correlation between the expression of HIF-1-α with necrosis and vitreous invasion was found. Retinoblastoma cells had a significant increase of mRNA levels of FIH-1- α after treatment with CoCl2. After blocking the gene HIF-1-α with siRNA, a significant decrease in cell proliferation of retinoblastoma cells was observed. Conclusion: It was shown that most of retinoblastomas express HIF- 1-α, and retinoblastoma cells show an increase in HIF-1-α after treatment with CoCl2. Furthermore, blockade of the gene HIF-1-α resulted in a significant reduction in cellular proliferation. Thus, drugs that inhibit HIF-1-α may be useful in the treatment of retinoblastoma, particularly in advanced cases where there is much tumor hypoxia.