Effect of the Anticancer Drug Temozolomide on the Stem-Like Phenotype of Glioblastoma Cells

Primary central nervous system tumors account for less than 1.5 percent of all new cancer cases diagnosed each year, most of which are anaplastic astrocytomas or malignant gliomas. The most aggressive form of glioma, glioblastoma, remains incurable to this day. Gliomas are usually treated with a combination of surgery, radiation therapy, and chemotherapy, which aim to kill cancer cells. Despite the destructive effect of this treatment on cells, there are certain types of cells in glioma tissue, characterized as glioblastoma stem cells (GSCs), which manage to avoid the destructive effects of therapy and are able to infiltrate surrounding CNS tissues and continue to multiply successfully. Currently, there is still a lack of knowledge about the molecular mechanisms that determine the resistance of GSC cells to chemotherapy; therefore it is necessary to study the properties of these cells and their response to therapeutic reagents in more detail. The aim of this study was to determine the effect of the anticancer drug temozolomide (TMZ) on the stem-like phenotype of glioblastoma cells. The glioblastoma cell line A172 was used for this purpose, which was cultured in a stemness-inducing medium in non-adherent plates. Under these conditions, the cells form spheroid structures. The expression of the stem cell phenotype was determined by SOX2 expression using the RT-PCR method. In the next stage of the experiment, the stem-like cells (spheroids) and control cells were transferred to conventional plates in a cell differentiation-promoting medium enriched with fetal calf serum and treated with TMZ. The effect of TMZ on the stemness of A172 cells was observed by measuring the expression of the stemness genes SOX2, OCT4, and MYC using the RT-PCR method. The results revealed that under stemness-promoting conditions, A172 cells showed changes in the expression of SOX2, OCT4, and MYC. These changes were suppressed when the cells were cultured under normal conditions. However, in the case of MYC, this suppression was slower when the cells were treated with TMZ, suggesting that TMZ may help maintain stem-like properties.