The biological activity of a combined treatment of U251, U373 and T98G glioma cell lines with two anti-miR PNAs, directed against miR‑221 and miR‑222 and conjugated with an ocataarginine tail (R8-PNA-a221 and R8-PNA-a222) for efficient cellular delivery, was determined. Apoptosis was analyzed, and the effect of the combined treatment of glioma cells with either or both PNAs on the reversion of drug-resistance phenotype was assessed in the temozolomide-resistant T98G glioma cell line. Selectivity of PNA/miRNA interactions was studied by surface plasmon resonance (SPR)-based Biacore analysis. Specificity of the PNA effects at the cellular level was analyzed by RT-qPCR. These experiments support the concept that the effects of R8-PNA-a221 and R8-PNA-a222 are specific. The studies on apoptosis confirmed that the R8-PNA-a221 induces apoptosis and demonstrated the pro-apoptotic effects of R8-PNA-a222. Remarkably, increased pro-apoptotic effects were obtained with the co-administration of both anti-miR‑221 and anti-miR‑222 PNAs. In addition, co-administration of R8-PNA-a221 and R8-PNA-a222 induced apoptosis of TMZ-treated T98G cells at a level higher than that obtained following singular administration of R8-PNA-a221 or R8-PNA-a222.