Design, synthesis, and evaluation of unsymmetrical trifluoromethyl-containing bisindolylmethane derivatives inducing endoplasmic reticulum stress in human lung adenocarcinoma.

Bisindolylmethane (BIM) is an important alkaloid derived from cruciferous plants that exhibits anti-cancer biological activity. Molecules with a BIM skeleton have long been widely recognized by medicinal chemists. Unfortunately, due to limitations in synthetic methods, research on this skeleton has mainly focused on symmetrical 3,3'-bisindolylmethane derivatives (3,3'-BIMs), wherein the two indole rings possess identical structures. In contrast, research on unsymmetrical 3,3'-BIMs has progressed slowly. Meanwhile, trifluoromethyl is a widely used "star group" in drug design due to its ability to improve pharmacological and pharmaceutical properties. To discover novel BIMs with significant anti-cancer potential and to study the variety of their structures, we designed and synthesized a series of unsymmetrical trifluoromethyl-containing BIMs based on previously reported S1-type dehydrative nucleophilic substitution by our group. These novel BIMs inhibit various cancer cells, especially lung cancer cells A549. Among them, the compound 5b effectively induces endoplasmic reticulum stress (ERS) and leads to apoptosis, demonstrating outstanding anti-non-small cell lung cancer (NSCLC) effects in vitro and in vivo, and was significantly more effective than the BIM group. The IC values of BIM and 5b against A549 cells are 54.76 ± 4.7 μM and 3.88 ± 0.1 μM, respectively. Specifically, anti-tumor activity assays in vivo found the inhibitory rates of 34.80 % for BIM and 80.32 % for 5b. Hematoxylin-eosin (H&E) results showed that 5b does not cause chronic organ damage. Clearly, 5b greatly enhances anti-cancer efficacy, effectively restraining cell colonies and proliferation in the S phase. Additionally, 5b increases the content of reactive oxygen species (ROS), causing a decline in the mitochondrial membrane potential and promoting Ca release. Further studies on the mechanism revealed that 5b induces ERS by activating the PERK-elF2α-CHOP signaling pathway, which could further regulate caspase and Bcl-2 family proteins, leading to apoptosis. These results demonstrate that 5b may be potent anticancer candidates for A549 tumor.