5-O-(N-Boc-l-Alanine)-Renieramycin T Induces Cancer Stem Cell Apoptosis via Targeting Akt Signaling

Anticancer potential of active alkaloids and synthetic analogs derived from marine invertebrates

In recent years, the number of cancers has soared, becoming one of the leading causes of human death. At the same time, marine anticancer substances have been the focus of marine drug research. Marine alkaloids derived from marine invertebrates like sponges are an important class of secondary metabolites, which have good bioactivities of blocking the cancer cell cycle, inducing autophagy and apoptosis of cancer cells, inhibiting cancer cell invasion and proliferation. They show potential as anticancer drug candidates. Therefore, in this review, we focus on the detailed introduction of bioactive alkaloids and their synthetic analogs from marine invertebrates, such as 4-chloro fascapysin and other 41 kinds of marine alkaloids or marine alkaloid synthetic analogs. They have significant anticancer activities on breast cancer, cervical cancer, colorectal cancer, prostate cancer, lung cancer, liver cancer, and so on. It provides new candidate compounds for anticancer drug research and provides a reference basis for marine drug resources research.

Shrimp Lipids Inhibit Migration, Epithelial-Mesenchymal Transition, and Cancer Stem Cells via Akt/mTOR/c-Myc Pathway Suppression

Shrimp is a rich source of bioactive molecules that provide health benefits. However, the high cholesterol content in shrimp oil may pose a risk. We utilized the cholesterol elimination method to obtain cholesterol-free shrimp lipids (CLs) and investigated their anticancer potential, focusing on cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT). Our study focused on CSCs and EMT, as these factors are known to contribute to cancer metastasis. The results showed that treatment with CLs at doses ranging from 0 to 500 µg/mL significantly suppressed the cell migration ability of human lung cancer (H460 and H292) cells, indicating its potential to inhibit cancer metastasis. The CLs at such concentrations did not cause cytotoxicity to normal human keratinocytes. Additionally, CL treatment was found to significantly reduce the levels of Snail, Slug, and Vimentin, which are markers of EMT. Furthermore, we investigated the effect of CLs on CSC-like phenotypes and found that CLs could significantly suppress the formation of a three-dimensional (3D) tumor spheroid in lung cancer cells. Furthermore, CLs induced apoptosis in the CSC-rich population and significantly depleted the levels of CSC markers CD133, CD44, and Sox2. A mechanistic investigation demonstrated that exposing lung cancer cells to CLs downregulated the phosphorylation of Akt and mTOR, as well as c-Myc expression. Based on these findings, we believe that CLs may have beneficial effects on health as they potentially suppress EMT and CSCs, as well as the cancer-potentiating pathway of Akt/mTOR/c-Myc.

Recent advances in the synthesis and activity of analogues of bistetrahydroisoquinoline alkaloids as antitumor agents

Ecteinascidin 743 (Et-743), also known by the trade name Yondelis®, is the pioneering marine natural product to be successfully developed as an antitumor drug. Moreover, it is the first tetrahydroisoquinoline natural product used clinically for antitumor therapy since Kluepfel, a Canadian scientist, discovered the tetrahydroisoquinoline alkaloid (THIQ) naphthyridinomycin in 1974. Currently, almost a hundred natural products of bistetrahydroisoquinoline type have been reported. Majority of these bistetrahydroisoquinoline alkaloids exhibit diverse pharmacological activities, with some family members portraying potent antitumor activities such as Ecteinascidins, Renieramycins, Saframycins, Jorumycins, among others. Due to the unique chemical structure and exceptional biological activity of these natural alkaloids, coupled with their scarcity in nature, research seeking to provide material basis for further bioactivity research through total synthesis and obtaining compound leads with medicinal value through structural modification, remains a hot topic in the field of antitumor drug R&D. Despite the numerous reviews on the total synthesis of bistetrahydroisoquinoline natural products, comprehensive reviews on their structural modification are apparently scarce. Moreover, structural modification of bioactive natural products to acquire lead compounds with improved pharmaceutical characteristics, is a crucial approach for innovative drug discovery. This paper presents an up-to-date review of both structural modification and activity of bistetrahydroisoquinoline natural products. It highlights how such alkaloids can be used as antitumor lead compounds through careful chemical modifications. This review offers valuable scientific references for pharmaceutical chemists engaged in developing novel antitumor agents based on such alkaloid modifications, as well as those with such a goal in future.

Semisynthesis of 5-O-ester derivatives of renieramycin T and their cytotoxicity against non-small-cell lung cancer cell lines

The semisynthesis of 5-O-ester derivatives of renieramycin T was accomplished through the photoredox reaction of renieramycin M (1), a bistetrahydroisoquinolinequinone alkaloid isolated from the Thai blue sponge Xestospongia sp. This process led to the conversion of compound 1 to renieramycin T (2), which was subsequently subjected to Steglich esterification with appropriate acylating agents containing linear alkyl, N-tert-butoxycarbonyl-L-amino, and heterocyclic aromatic substituent. Notably, the one-pot transformation, combining the photoredox reaction and esterification led to the formation of 7-O-ester derivatives of renieramycin S due to hydrolysis. Subsequently, the in vitro cytotoxicity of the 17 semisynthesized derivatives against human non-small-cell lung cancer (NSCLC) cells in parallel with normal cell lines was evaluated. Among the tested compounds, 5-O-(3-propanoyl) ester of renieramycin T (3b) exhibited potent cytotoxic activity with half-maximal inhibitory concentration (IC50) values at 33.44 and 33.88 nM against H292 and H460 cell lines, respectively. These values were within the same range as compound 1 (IC50 = 34.43 and 35.63 nM) and displayed twofold higher cytotoxicity compared to compound 2 (IC50 = 72.85 and 83.95 nM). The steric characteristics and aromatic orientation of the 5-O-ester substituents played significant roles in their cytotoxicity. Notably, derivative 3b induced apoptosis with minimal necrosis, in contrast to the parental compound 1. Hence, the relationship between the structure and cytotoxicity of renieramycin-ecteinascidin hybrid alkaloids was investigated. This study emphasizes the potential of the series of 5-O-ester derivatives of renieramycin T as promising leads for the further development of potential anti-NSCLC agents.

Simplified Synthesis of Renieramycin T Derivatives to Target Cancer Stem Cells via β-Catenin Proteasomal Degradation in Human Lung Cancer

Cancer stem cells (CSCs) found within cancer tissue play a pivotal role in its resistance to therapy and its potential to metastasize, contributing to elevated mortality rates among patients. Significant strides in understanding the molecular foundations of CSCs have led to preclinical investigations and clinical trials focused on CSC regulator β-catenin signaling targeted interventions in malignancies. As part of the ongoing advancements in marine-organism-derived compound development, it was observed that among the six analogs of Renieramycin T (RT), a potential lead alkaloid from the blue sponge Xestospongia sp., the compound DH_32, displayed the most robust anti-cancer activity in lung cancer A549, H23, and H292 cells. In various lung cancer cell lines, DH_32 exhibited the highest efficacy, with IC50 values of 4.06 ± 0.24 μM, 2.07 ± 0.11 μM, and 1.46 ± 0.06 μM in A549, H23, and H292 cells, respectively. In contrast, parental RT compounds had IC50 values of 5.76 ± 0.23 μM, 2.93 ± 0.07 μM, and 1.52 ± 0.05 μM in the same order. Furthermore, at a dosage of 25 nM, DH_32 showed a stronger ability to inhibit colony formation compared to the lead compound, RT. DH_32 was capable of inducing apoptosis in lung cancer cells, as demonstrated by increased PARP cleavage and reduced levels of the proapoptotic protein Bcl2. Our discovery confirms that DH_32 treatment of lung cancer cells led to a reduced level of CD133, which is associated with the suppression of stem-cell-related transcription factors like OCT4. Moreover, DH_32 significantly suppressed the ability of tumor spheroids to form compared to the original RT compound. Additionally, DH_32 inhibited CSCs by promoting the degradation of β-catenin through ubiquitin-proteasomal pathways. In computational molecular docking, a high-affinity interaction was observed between DH_32 (grid score = -35.559 kcal/mol) and β-catenin, indicating a stronger binding interaction compared to the reference compound R9Q (grid score = -29.044 kcal/mol). In summary, DH_32, a newly developed derivative of the right-half analog of RT, effectively inhibited the initiation of lung cancer spheroids and the self-renewal of lung cancer cells through the upstream process of β-catenin ubiquitin-proteasomal degradation.

Light-Mediated Transformation of Renieramycins and Semisynthesis of 4'-Pyridinecarbonyl-Substituted Renieramycin-Type Derivatives as Potential Cytotoxic Agents against Non-Small-Cell Lung Cancer Cells

The semisynthesis of renieramycin-type derivatives was achieved under mild and facile conditions by attaching a 1,3-dioxole-bridged phenolic moiety onto ring A of the renieramycin structure and adding a 4'-pyridinecarbonyl ester substituent at its C-5 or C-22 position. These were accomplished through a light-induced intramolecular photoredox reaction using blue light (4 W) and Steglich esterification, respectively. Renieramycin M (4), a bis-tetrahydroisoquinolinequinone compound isolated from the Thai blue sponge (Xestospongia sp.), served as the starting material. The cytotoxicity of the 10 natural and semisynthesized renieramycins against non-small-cell lung cancer (NSCLC) cell lines was evaluated. The 5-O-(4'-pyridinecarbonyl) renieramycin T (11) compound exhibited high cytotoxicity with half-maximal inhibitory concentration (IC₅₀) values of 35.27 ± 1.09 and 34.77 ± 2.19 nM against H290 and H460 cells, respectively. Notably, the potency of compound 11 was 2-fold more than that of renieramycin T (7) and equal to those of 4 and doxorubicin. Interestingly, the renieramycin-type derivatives with a hydroxyl group at C-5 and C-22 exhibited weak cytotoxicity. In silico molecular docking and dynamics studies confirmed that the mitogen-activated proteins, kinase 1 and 3 (MAPK1 and MAPK3), are suitable targets for 11. Thus, the structure-cytotoxicity study of renieramycins was extended to facilitate the development of potential anticancer agents for NSCLC cells.

Structural modification of resveratrol analogue exhibits anticancer activity against lung cancer stem cells via suppression of Akt signaling pathway

BACKGROUND

Compound with cancer stem cell (CSC)-suppressing activity is promising for the improvement of lung cancer clinical outcomes. Toward this goal, we discovered the CSC-targeting activity of resveratrol (RES) analog moscatilin (MOS). With slight structural modification from RES, MOS shows dominant cytotoxicity and CSC-suppressive effect.

METHODS

Three human lung cancer cell lines, namely H23, H292, and A549, were used to compare the effects of RES and MOS. Cell viability and apoptosis were determined by the MTT assay and Hoechst33342/PI double staining. Anti-proliferative activity was determined by colony formation assay and cell cycle analysis. Intracellular reactive oxygen species (ROS) were measured by fluorescence microscopy using DCFH₂-DA staining. CSC-rich populations of A549 cells were generated, and CSC markers, and Akt signaling were determined by Western blot analysis and immunofluorescence. Molecular docking and molecular dynamics (MD) simulations were used to predict the possible binding of the compound to Akt protein.

RESULTS

In this study, we evaluated the effects of RES and MOS on lung cancer and its anti-CSC potential. Compared with RES, its analog MOS more effectively inhibited cell viability, colony formation, and induced apoptosis in all lung cancer cell lines (H23, H292, and A549). We further investigated the anti-CSC effects on A549 CSC-rich populations and cancer adherent cells (A549 and H23). MOS possesses the ability to suppress CSC-like phenotype of lung cancer cells more potent than RES. Both MOS and RES repressed lung CSCs by inhibiting the viability, proliferation, and lung CSC-related marker CD133. However, only MOS inhibits the CSC marker CD133 in both CSC-rich population and adherent cells. Mechanistically, MOS exerted its anti-CSC effects by inhibiting Akt and consequently restored the activation of glycogen synthase kinase 3β (GSK-3β) and decreased the pluripotent transcription factors (Sox2 and c-Myc). Thus, MOS inhibits CSC-like properties through the repression of the Akt/GSK-3β/c-Myc pathway. Moreover, the superior inhibitory effects of MOS compared to RES were associated with the improved activation of various mechanism, such as cell cycle arrest at G2/M phase, production of ROS-mediated apoptosis, and inhibition of Akt activation. Notably, the computational analysis confirmed the strong interaction between MOS and Akt protein. MD simulations revealed that the binding between MOS and Akt1 was more stable than RES, with MM/GBSA binding free energy of - 32.8245 kcal/mol at its allosteric site. In addition, MOS interacts with Trp80 and Tyr272, which was a key residue in allosteric inhibitor binding and can potentially alter Akt activity.

CONCLUSIONS

Knowledge about the effect of MOS as a CSC-targeting compound and its interaction with Akt is important for the development of drugs for the treatment of CSC-driven cancer including lung cancer.

Marine Natural Products as Anticancer Agents 2.0

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Novel Synthetic Derivative of Renieramycin T Right-Half Analog Induces Apoptosis and Inhibits Cancer Stem Cells via Targeting the Akt Signal in Lung Cancer Cells

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.

Target Identification of 22-(4-Pyridinecarbonyl) Jorunnamycin A, a Tetrahydroisoquinoline Derivative from the Sponge Xestospongia sp., in Mediating Non-Small-Cell Lung Cancer Cell Apoptosis

A dysregulation of the cell-death mechanism contributes to poor prognosis in lung cancer. New potent chemotherapeutic agents targeting apoptosis-deregulating molecules have been discovered. In this study, 22-(4-pyridinecarbonyl) jorunnamycin A (22-(4'py)-JA), a synthetic derivative of bistetrahydroisoquinolinequinone from the Thai blue sponge, was semisynthesized by the Steglich esterification method, and its pharmacological mechanism in non-small-cell lung cancer (NSCLC) was elucidated by a network pharmacology approach. All predicted targets of 22-(4'py)-JA and genes related to NSCLC were retrieved from drug-target and gene databases. A total of 78 core targets were identified, and their associations were analyzed by STRING and Cytoscape. Gene ontology and KEGG pathway enrichment analyses revealed that molecules in mitogen-activated protein kinase (MAPK) signaling were potential targets of 22-(4'py)-JA in the induction of NSCLC apoptosis. In silico molecular docking analysis displayed a possible interaction of ERK1/2 and MEK1 with 22-(4'py)-JA. In vitro anticancer activity showed that 22-(4'py)-JA has strong cytotoxic and apoptosis-inducing effects in H460, H292 and A549 NSCLC cells. Furthermore, immunoblotting confirmed that 22-(4'py)-JA induced apoptotic cell death in an ERK/MEK/Bcl-2-dependent manner. The present study demonstrated that 22-(4'py)-JA exhibited a potent anticancer effect that could be further developed for clinical application and showed that network pharmacology approaches are a powerful tool to illustrate the molecular pathways of new drugs or compounds.

Cisplatin Induces Senescent Lung Cancer Cell-Mediated Stemness Induction via GRP78/Akt-Dependent Mechanism

Cellular senescence is linked with chemotherapy resistance. Based on previous studies, GRP78 is a signal transducer in senescent cells. However, the association between GRP78 and stem cell phenotype remains unknown. Cisplatin treatment was clarified to induce cellular senescence leading to stemness induction via GRP78/Akt signal transduction. H460 cells were treated with 5 μM of cisplatin for 6 days to develop senescence. The colony formation assay and cell cycle analysis were performed. SA-β-galactosidase staining indicated senescence. Western blot analysis and RT-PCR were operated. Immunoprecipitation (IP) and immunocytochemistry assays (ICC) were also performed. Colony-forming activity was completely inhibited, and 87.07% of the cell population was arrested in the G2 phase of the cell cycle. mRNA of p21 and p53 increased approximately by 15.91- and 19.32-fold, respectively. The protein level of p21 and p53 was elevated by 9.57- and 5.9-fold, respectively. In addition, the c-Myc protein level was decreased by 0.2-fold when compared with the non-treatment control. Even though, the total of GRP78 protein was downregulated after cisplatin treatment, but the MTJ1 and downstream regulator, p-Akt/Akt ratio were upregulated by approximately 3.38 and 1.44-fold, respectively. GRP78 and MTJ1 were found at the cell surface membrane. Results showed that the GRP78/MTJ1 complex and stemness markers, including CD44, CD133, Nanog, Oct4, and Sox2, were concomitantly increased in senescent cells. MTJ1 anchored GRP78, facilitating the signal transduction of stem-like phenotypes. The strategy that could interrupt the binding between these crucial proteins or inhibit the translocation of GRP78 might beuseful for cancer therapy.

Renieramycin T Inhibits Melanoma B16F10 Cell Metastasis and Invasion via Regulating Nrf2 and STAT3 Signaling Pathways

As one of marine tetrahydroisoquinoline alkaloids, renieramycin T plays a significant role in inhibiting tumor metastasis and invasion. However, the effect of renieramycin T on inflammation-related tumor metastasis and invasion is still unknown, and its mechanisms remain unclear. Here we established an inflammation-related tumor model by using the supernatant of RAW264.7 cells to simulate B16F10 mouse melanoma cells. The results indicate that renieramycin T suppressed RAW264.7 cell supernatant-reduced B16F10 cell adhesion to a fibronectin-coated substrate, migration, and invasion through the matrigel in a concentration-dependent manner. Moreover, Western blot results reveal that renieramycin T attenuated the phosphorylation of STAT3 and down-regulated the expression of Nrf2. Together, the above findings suggest a model of renieramycin T in suppressing B16F10 cancer cell migration and invasion. It may serve as a promising drug for the treatment of cancer metastasis.