Abnormally high levels of CK2 and PIM-1 serine/threonine kinases have been documented in many cases of cancer. The elevation of CK2 and PIM-1 in cells entails suppression of apoptosis and implies a protective role for the kinases against cell death. Downregulation of these enzymes by chemical methods promotes apoptosis in cells. The aim of the present study was to explore the anticancer activity of inhibitors of protein kinases CK2 and PIM-1 on neoplastic cell lines in vitro. We studied a series of deoxynucleosides with various tetrahalobenzimidazoles as aglycone moiety. Cytotoxicity, induction of apoptosis by the tested inhibitors, mitochondrial membrane potential, activity of caspases, changes in cell cycle progression, as well as a mechanism of action were determined by flow cytometry and other methods. The results indicate that the studied compounds, e.g., 1-(β-D-2′-deoxyribofuranosyl)-4,5,6,7-tetrabromo-1H-benzimidazole called K164 (also termed TDB), showed diverse cytotoxicity and proapoptotic efficacy in cell lines. Our results showed that the tested compounds are potential anticancer agents for targeted therapy, particularly in the treatment of myeloid leukaemia and androgen-responsive prostate cancer.