Targeting tumor cells with cytokine-induced killer cells and bifunctional peptides

Abstract

Antimicrobial peptides have gained much attention in clinical research due to their extensive possibilities of application beyond antimicrobial use. The modification of antimicrobial peptides enables the peptides to target particular cancer cells, improving the specificity and efficiency of the treatment. In this study, TP2-<em>D</em>-Tox, a derivate of TP-<em>D</em>-Tox, demonstrated a superior anti-tumor activity towards renal carcinoma, Caki-2 and breast carcinoma, SK-BR-3. TP-and TP2-<em>D</em>-Tox were shown to penetrate the cells via clathrin-mediated endocytosis, triggered by binding to S100A9 and the subunits of non-muscle myosin IIa, including MYL6 in Caki-2 and MYL12A, MYL12B in SK-BR-3. TP2-<em>D</em>-Tox interaction with HSPB1 was observed to protect the intracellular peptide against the immediate proteolytic inactivation. Higher affinity of TP2-<em>D</em>-Tox towards these ligand proteins might have contributed to their larger therapeutic indices compared to TP-<em>D</em>-Tox. <br/> Despite the occurrence of similar stress responses, our investigation revealed that TP- and TP2-<em>D</em>-Tox induced a distinctly regulated cell death in Caki-2 and SK-BR-3 cells in caspase-independent manner. The intracellular presence of the peptides evoked mitochondrial dysfunctions, elevation of cytosolic calcium, generation of reactive oxygen species and formation of MLKL oligomers in the plasma membrane preceding the necroptotic cell death in Caki-2 or necrotic cell death in SK-BR-3. <br/> TP2-<em>D</em>-Tox superiority in triggering cell death represented a promising approach to bypass the caspase-dependent apoptosis-resistance issue impairing therapeutic responses of many cancer treatments. Combining TP2-<em>D</em>-Tox and CIK cells as cancer therapy may bypass several cancer resistance phenotypes forfeiting the neoevolutionary advantages.<br/> The TP2-<em>D</em>-Tox-CIK cells combination cancer therapy revealed a greater efficacy in decimating Caki-2 and SK-BR-3 cells. Although the combination therapy failed to show therapeutic benefits over TP2-<em>D</em>-Tox monotreatment against Caki-2 monolayer, their antitumor activity demonstrated synergistic interactions in combating Caki-2 spheroids and SK-BR-3 in both models. The TP2-<em>D</em>-Tox-CIK cells combination therapy might have bypassed the limitation of the classical synergistic combination, which promotes the competitive advantage of cancer cells to developed single-treatment resistance annulling the overall efficacy of the combination therapy.