A novel chloroquine derivative suppresses melanoma cell growth by DNA damage through increasing ROS levels

Background: High-dose chloroquine (CQ) has been tested as anti-tumor agents, however, CQ's anti-melanoma activity is very weak. As one of the most aggressive tumors, melanoma is the leading cause of death for skin malignancies. What is more, melanoma often develops resistance to chemotherapy and radiotherapy. Therefore, the discovery of new melanoma inhibitors remains an urgent task. Method: First, we detected the effects of lj-2-66 on cell proliferation through CCK8 and Colony formation assay. Next, we examined the cell cycle and apoptosis by flow cytometry and evaluated the effect of lj-2-66 in vivo by xenograft mouse model. Then, transcriptomics sequence was used to find the pathways related to the anti-tumor effects of lj-2-66, and RT-PCR was performed to verify the differential genes. Subsequently, flow cytometry was used to analyze reactive oxygen species (ROS) level. Finally, western blot and immunofluorescence were used for revealing DNA damage. Results: Our study showed that lj-2-66 significantly inhibited the proliferation of melanoma both in vivo and in vitro and induced G2/M phase arrest and apoptosis in melanoma cells. In order to explore the possible mechanism of the anti-tumor effect of lj-2-66, we performed seq-RNA in SK-Mel-28 after treating with lj-2-66. RNA-Seq revealed that the compound regulated a variety of pathways, including cell cycle and cancer related pathways. Then, we verified the differential genes after treating with lj-2-66 by RT-PCR. In addition, we confirmed that lj-2-66 induced DNA damage by raising the level of ROS in melanoma cell lines. Furthermore, we found that lj-2-66 promoted the accumulation of ROS in BRAFi-resistant melanoma cells, thus leading to DNA damage, which arrested cell cycle at G2/M phase and induced apoptosis. Conclusions: We found a compound, lj-2-66, increases the levels of ROS in melanoma cells and causes ROS-related DNA damage, thus leading to G2/M phase arrest and apoptosis. Therefore, lj-2-66 may become a promising therapeutic drug for melanoma.