The machinery that maintains cellular and tissue homeostasis in a healthy individual is recruited and hijacked by cancer cells to support tumor growth and progression. Activation of often unpredictable alternative or complementary signaling pathways allows cancer cells to bypass the intrinsic self-destructive machinery and the limited replicative potential present in every cell for correct homeostasis maintenance. Therefore, evasion/resistance to apoptosis/cell death, self-sufficiency in growth/survival signals, and limitless replicative potential remain undoubted hallmarks of cancer, contributing to drug resistance. Herein, we specifically review antitumor strategies involving agents targeting deregulated receptor tyrosine kinases, selected epigenetic modifications, the ubiquitin-proteasome system, the unfolded protein response, the apoptotic pathway, and peculiar nucleic acid structures, with the aim of highlighting the mechanisms underlying favorable drug interaction. In this context, we focus on preclinical studies that have already been translated into clinical investigation. Particular emphasis is devoted to strategies effective in solid tumors because of the peculiarity and distinctive features of solid tumors in terms of drug delivery and relative to the impact of the tumor microenvironment.