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.

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.

The first total synthesis of (±)-renieramycin I, which was isolated from the Indian bright blue sponge Haliclona cribricutis, is described. The key step is the selenium oxide oxidation of pentacyclic bis-p-quinone derivative (3) stereo- and regioselectively. We also report a large-scale synthesis of cribrostatin 4 (renieramycin H) via the C3-C4 double bond formation in an early stage based on the Avendaño’s protocol, from readily available 1-acetyl-3-(3-methyl-2,4,5-trimethylphenyl)methyl-piperazine-2,5-dione (8) in 18 steps (8.3% overall yield). The synthesis provides unambiguous evidence supporting the original structure of renieramycin I.

A general protocol for the asymmetric synthesis of 3-N-arylmethylated right-half model compounds of renieramycins was developed, which enabled structure–activity relationship (SAR) study of several 3-N-arylmethyl derivatives. The most active compound (6a) showed significant cytotoxic activity against human prostate cancer DU145 and colorectal cancer HCT116 cell lines (IC₅₀ = 11.9, and 12.5 nM, respectively).

Akt is a key regulatory protein of cancer stem cells (CSCs) and is responsible for cancer aggressiveness and metastasis. Targeting Akt is beneficial for the development of cancer drugs. renieramycin T (RT) has been reported to have Mcl-1 targeting activity, and the study of the structure-activity relationships (SARs) demonstrated that cyanide and the benzene ring are essential for its effects. In this study, novel derivatives of the RT right-half analog with cyanide and the modified ring were synthesized to further investigate the SARs for improving the anticancer effects of RT analogs and evaluate CSC-suppressing activity through Akt inhibition. Among the five derivatives, a compound with a substituted thiazole structure (DH_25) exerts the most potent anticancer activity in lung cancer cells. It has the ability to induce apoptosis, which is accompanied by an increase in PARP cleavage, a decrease in Bcl-2, and a diminishment of Mcl-1, suggesting that residual Mcl-1 inhibitory effects exist even after modifying the benzene ring to thiazole. Furthermore, DH_25 is found to induce CSC death, as well as a decrease in CSC marker CD133, CSC transcription factor Nanog, and CSC-related oncoprotein c-Myc. Notably, an upstream member of these proteins, Akt and p-Akt, are also downregulated, indicating that Akt can be a potential target of action. Computational molecular docking showing a high-affinity interaction between DH_25 and an Akt at the allosteric binding site supports that DH_25 can bind and inhibit Akt. This study has revealed a novel SAR and CSC inhibitory effect of DH_25 via Akt inhibition, which may encourage further development of RT compounds for cancer therapy.