Among malignancies, lung cancer is the major cause of cancer death. Despite the advance in lung cancer therapy, the five-year survival rate is extremely restricted due to therapeutic failure and disease relapse. Targeted therapies selectively inhibiting certain molecules in cancer cells have been accepted as promising ways to control cancer. In lung cancer, evidence has suggested that the myeloid cell leukemia 1 (Mcl-1) protein, an anti-apoptotic member of the Bcl-2 family, is a target for drug action. Herein, we report the Mcl-1 targeting activity of renieramycin T (RT), a marine-derived tetrahydroisoquinoline alkaloid that was isolated from the Thai blue sponge Xestospongia sp. RT was shown to be dominantly toxic to lung cancer cells compared to the normal cells in the lung. The cytotoxicity of this compound toward lung cancer cells was mainly exerted through apoptosis induction. For the mechanism of action, we found that RT mediated activation of p53 protein and caspase-9 and -3 activations. While others Bcl-2 family proteins (Bcl-2, Bak, and Bax) were minimally changed in response to RT, Mcl-1 protein was dramatically diminished. We further performed the cycloheximide experiment and found that the half-life of Mcl-1 was significantly shortened by RT treatment. When MG132, a potent selective proteasome inhibitor, was utilized, it could restore the Mcl-1 level. Furthermore, immunoprecipitation analysis revealed that RT significantly increased the formation of Mcl-1-ubiquitin complex compared to the non-treated control. In conclusion, we report the potential apoptosis induction of RT with a mechanism of action involving the targeting of Mcl-1 for ubiquitin-proteasomal degradation. As Mcl-1 is critical for cancer cell survival and chemotherapeutic failure, this novel information regarding the Mcl-1-targeted compound would be beneficial for the development of efficient anti-cancer strategies or targeted therapies.

Myeloid cell leukemia 1 (Mcl-1) and B-cell lymphoma 2 (Bcl-2) proteins are promising targets for cancer therapy. Here, we investigated the structure–activity relationships (SARs) and performed molecular docking analysis of renieramycin T (RT) and its analogues and identified the critical functional groups of Mcl-1 targeting. RT have a potent anti-cancer activity against several lung cancer cells and drug-resistant primary cancer cells. RT mediated apoptosis through Mcl-1 suppression and it also reduced the level of Bcl-2 in primary cells. For SAR study, five analogues of RT were synthesized and tested for their anti-cancer and Mcl-1- and Bcl-2-targeting effects. Only two of them (TM-(–)-18 and TM-(–)-4a) exerted anti-cancer activities with the loss of Mcl-1 and partly reduced Bcl-2, while the other analogues had no such effects. Specific cyanide and benzene ring parts of RT’s structure were identified to be critical for its Mcl-1-targeting activity. Computational molecular docking indicated that RT, TM-(–)-18, and TM-(–)-4a bound to Mcl-1 with high affinity, whereas TM-(–)-45, a compound with a benzene ring but no cyanide for comparison, showed the lowest binding affinity. As Mcl-1 helps cancer cells evading apoptosis, these data encourage further development of RT compounds as well as the design of novel drugs for treating Mcl-1-driven cancers.

Aberrant cellular Myc (c-Myc) is a common feature in the majority of human cancers and has been linked to oncogenic malignancies. Here, we developed a novel c-Myc-targeting compound, N, N-bis (5-ethyl-2-hydroxybenzyl) methylamine (EMD), and present evidence demonstrating its effectiveness in targeting c-Myc for degradation in human lung carcinoma. EMD exhibited strong cytotoxicity toward various human lung cancer cell lines, as well as chemotherapeutic-resistant patient-derived lung cancer cells, through apoptosis induction in comparison with chemotherapeutic drugs. The IC 50 of EMD against lung cancer cells was approximately 60 mM. Mechanistically, EMD eliminated c-Myc in the cells and initiated caspase-dependent apoptosis cascade. Cycloheximide chase assay revealed that EMD tended to shorten the half-life of c-Myc by approximately half. The cotreatment of EMD with the proteasome inhibitor MG132 reversed its c-Myc-targeting effect, suggesting the involvement of ubiquitinmediated proteasomal degradation in the process. We further verified that EMD strongly induced the ubiquitination of c-Myc and promoted protein degradation. c-Myc inhibition and apoptosis induction were additionally shown in hematologic malignant K562 cells, indicating the generality of the observed EMD effects. Altogether, we identified EMD as a novel potent compound targeting oncogenic c-Myc that may offer new opportunities for lung cancer treatment. SIGNIFICANCE STATEMENTThe deregulation of c-Myc is frequently associated with cancer progression. This study examined the effect of a new compound, N, N-bis (5-ethyl-2-hydroxybenzyl) methylamine (EMD), in targeting c-Myc in several lung cancer cell lines and drug-resistant primary lung cancer cells. EMD induced dramatic c-Myc degradation through a ubiquitin-proteasomal mechanism. The promising anticancer and c-Myc-targeted activities of EMD support its use in potential new approaches to treat c-Myc-driven cancer.

Background/Aim: Epithelial to mesenchymal transition (EMT) is a cellular process that facilitates cancer metastasis. Therefore, therapeutic approaches that target EMT have garnered increasing attention. The present study aimed to examine the in vitro effects of ephemeranthol A on cell death, migration, and EMT of lung cancer cells. Materials and Methods: Ephemeranthol A was isolated from Dendrobium infundibulum. Non-small cell lung cancer cells H460 were treated with ephemeranthol A and apoptosis was evaluated by Hoechst 33342 staining. Anoikis resistance was determined by soft agar assay. Wound healing assay was performed to test the migration. The regulatory proteins of apoptosis and cell motility were determined by western blot. Results: Treatment with ephemeranthol A resulted in a concentration-dependent cell apoptosis. At non-toxic concentrations, the compound could inhibit anchorage-independent growth of the cancer cells, as indicated by the decreased colony size and number. Ephemeranthol A also exhibited an inhibitory effect on migration. We further found that ephemeranthol A exerts its antimetastatic effects via inhibition of EMT, as indicated by the markedly decrease of N-cadherin, vimentin, and Slug. Furthermore, the compound suppressed the activation of focal adhesion kinase (FAK) and protein kinase B (Akt) proteins,

The Akt-mTOR signal is important for the survival and proliferation of cancer cells and has become an interesting drug target. In this study, five resveratrol derivatives were evaluated for anticancer activity and Akt/mTOR targeting activity in non-small lung cancer cell lines. The effects of resveratrol derivatives on cell proliferation were assessed by 2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, nucleus staining, and colony formation assay. Furthermore, the effect of resveratrol derivatives on proliferation-related protein expression was analyzed by immunofluorescence and Western blotting. For the structure–activity relationship (SAR), results reveal that two derivatives of resveratrol which are 4,4′-(ethane-1,2-diyl) bis(2-methoxyphenol) (RD2) and the 4-(3-hydroxy-4-methoxyphenethyl)-2-methoxyphenol (RD3) had very similar structures but exerted different cytotoxicity. The IC50 of RD2 and RD3 were 108.6 ± 10.82 and more than 200 µM in the A549 cell line and 103.5 ± 6.08 and more than 200 µM in H23 cells, respectively. RD2 inhibited cell proliferation and induced apoptosis when compared with the control, while RD3 caused minimal effects. Cells treated with RD2 exhibited apoptotic nuclei in a concomitant with the reduction of cellular p-Akt and p-mTOR. RD3 had minimal effects on such proteins. According to these results, molecular docking analysis revealed a high-affinity interaction between RD2 and an Akt molecule at the ATP-binding and the allosteric sites, indicating this RD2 as a potential Akt inhibitor. This study provides useful information of resveratrol derivatives RD2 for treating lung cancer via Akt/mTOR inhibition.