NIE Yue-Qi, JIANG Miao, WU Hui-Yan, DING Chang-Hao, REN Wei, CHANG Jun-Yi, CHEN Ke, DU Shao-Long, ZHANG Peng, LIU Zhong-Hua
Lung cancer poses a serious threat to global public health security. Chemotherapy, as the main strategy for cancer treatment, faces challenges such as high toxicity and drug resistance. Anticancer peptides have the potential of being developed into new anticancer drugs due to their advantages of broad-spectrum anticancer activity, rapid action, and difficulty in generating drug resistance, but they also face shortcomings such as weak activity and strong toxic side effects. The weakly acidic microenvironment of tumors (pH 6.5-6.8) provides a good idea for the design of anticancer peptides of high-efficiency and low-toxicity. Previously, we designed the acid-sensitive antibacterial peptide pHly-1 using the wolf spider (Lycosa singoriensis) toxin Lycosin-I as a template. In this study, we found that pHly-1 also had acid-sensitive anticancer activity. Further alanine scanning analysis of pHly-1 was carried out, and we obtained a mutant pHTP-2 with better acid sensitivity, whose IC50 (half maximal inhibitory concentration) against A549 cells was 15.68 μmol/L at pH 6.6 and was greater than 100 μmol/L at pH 7.4. At pH 6.6, pHTP-2 could act on various lung cancer cell lines and induce the death of A549 cells by rapid lysis; at pH 7.4, 500 μmol/L pHTP-2 had weak toxicity to red blood cells (the hemolysis rate was approximately 38%) and primary myocardial cells (the inhibition rate was 49.7%, with P< 0.05). Analysis of its charge, particle size, morphology, and secondary structure showed that at pH 6.6, the histidine in the sequence of pHTP-2 was protonated, increasing the positive charge (P<0.01), decreasing the hydrated particle size (P<0.05) and forming an α-helical structure to induce membrane lysis of A549 cells. At pH 7.4, it was deprotonated, the positive charge decreases, a β-sheet structure was formed and self-aggregation occurred, limiting its effect on the A549 cell membrane and showing weak activity. In summary, pHTP-2 could respond to the weakly acidic microenvironment of tumors to exert selective cytotoxic activity, effectively overcoming the shortcomings of anticancer peptides such as low efficiency and high toxicity. Our findings suggest that it is a high-quality lead molecule for anticancer drugs.