Expression of Apoptosis and Autophagy Genes in HeLa and HEK 293 Cells under Conditions of Nutrient Deprivation

Abstract

The goal of the study was a comparing the degree of development of autophagy in the human cervical carcinoma cells of HeLa-V and HeLa-R sublines and non-tumor human embryonic kidney cells HEK 293 under two types of starvation conditions – 24- and 48-h culture in serum-free DMEM medium and 4-h incubation in Earle’s minimal medium. The work assessed cell viability using MTT method and the expression of apoptosis (BCL2, BAX, CASP3) and autophagy (ULK1, BECN1, ATG5, ATG14, MAP1LC3B) genes using real-time PCR. Cultivation under serum starvation and Earl’s medium resulted in a significant decrease in the viability of HEK 293 cells, but had no influence on HeLa-V and HeLa-R cells. In the tumor cells of both lines, the expression of anti-apoptotic gene BCL2 increased, while in HEK 293 cells the BCL2/BAX ratio decreased and CASP3 gene was activated. In HeLa-V and HeLa-R cells, nutrient deprivation induced the stimulation of various combinations of genes ULK1, BECN1, ATG5 and ATG14 implicated in the initial stages of autophagy, but none of the treatments affected the expression of MAP1LC3B gene. In HEK 293 cells, serum starvation led to increase in expression level of BECN1, ATG5, ATG14 and MAP1LC3B genes. Thus, stimulation of autophagy in HeLa cells, especially HeLa-R, prevents the development of apoptotic processes, while in HEK 293 cells the processes of apoptosis and autophagy occur in parallel. Culture in the serum-free DMEM for 48 h appears to be most effective way to induce autophagy in tumor cell lines and, accordingly, the most suitable model for studying the role of autophagy in the development of their resistance to apoptotic pathway of death.