Thus, to better understand the attenuated phenotype of ∆F4L∆J2R VACV, we used immunoblotting to evaluate the protein levels of cellular TK1, RRM2, and p53R2 in irradiated senescence-enriched GBM cell lines and non-irradiated controls, expecting that a decrease in levels of these proteins might explain the attenuation of the virus in senescence cells. Here, TK1 is linked to glioblastoma.