Nitric oxide-releasing derivatives of brefeldin A as potent and highly selective anticancer agents

Combination of brefeldin A and tunicamycin induces apoptosis in HepG2 cells through the endoplasmic reticulum stress-activated PERK-eIF2α-ATF4-CHOP signaling pathway

Background and aims

Hepatocellular carcinoma (HCC) is a malignant tumor with a high mortality rate, but there are still no effective treatments. The aim of this study was to investigate the anticancer potential of the combined use of brefeldin A (BFA) and tunicamycin (TM) in HepG2 cells, as well as the underlying mechanisms.

Methods

HepG2 cells were treated with different concentrations of BFA (0.1-2.5 mg/L) and TM (1-5 mg/L) for 24 h. DMSO (0.1 %, v/v) was used as a vehicle control. Cell viability and cell migration were measured using MTT assay and scratch wound assay, respectively. Apoptosis was detected using flow cytometry and acridine orange (AO) staining. The protein and mRNA levels of various factors involved in apoptosis (poly (ADP-ribose) polymerase-1 (PARP-1), caspase-12, caspase-3, and stearoyl-CoA desaturase 1) and endoplasmic reticulum (ER) stress (binding immunoglobulin protein (BiP), protein kinase R-like endoplasmic reticulum kinase (PERK), p-PERK, phosphorylation of eukaryotic translation initiation factor 2alpha (p-eIF2α), activating transcription factor (ATF) 4, and C/EBP homologous protein (CHOP)) were measured using Western blotting and qRT-PCR, respectively.

Results

Both BFA and TM alone significantly reduced the viability of HepG2 cells in a dose-dependent way. The co-incubation with TM (1 mg/L) further significantly reduced the viability of HepG2 cells treated with BFA (0.25 mg/L) alone (P < 0.05). BFA significantly increased the protein and mRNA levels of caspase-3 and PARP-1 (P < 0.05) compared to control and DMSO-treated cells, indicating that BFA induced apoptosis in HepG2 cells by increasing the expression of caspase-3 and PARP-1. The induction of apoptosis by BFA could be further significantly enhanced by co-incubation with TM. In addition, BFA significantly increased the mRNA levels of BiP, PERK and ATF4 (P < 0.05) compared to control and DMSO-treated cells. After co-incubation of BFA and TM, the protein levels of BiP, p-PERK, p-eIF2α and CHOP were significantly increased, indicating that TM could enhance BFA-induced ER stress in HepG2 cells through the PERK-eIF2α-ATF4-CHOP pathway.

Conclusions

BFA could induce apoptosis and ER stress, and TM could enhance the ability of BFA to induce apoptosis and ER stress in HepG2 cells through the PERK-eIF2ɑ-ATF4-CHOP pathway. The findings highlight the therapeutic potential of the combined use of BFA and TM in treating HCC.

An overview of phenylsulfonylfuroxan-based nitric oxide donors for cancer treatment

Nitric oxide (NO) is a gaseous molecule integral to numerous physiological processes, including tumor modulation, cardiovascular regulation, and systemic physiological functions. Its dual role in promoting and inhibiting tumor growth makes it a focal point of contemporary oncological research. Phenylsulfonylfuroxan, a classical NO donor, has been shown to significantly elevate NO levels, thereby inducing apoptosis and inhibiting proliferation and metastasis in tumor cells. It enhances the efficacy of chemotherapy, radiotherapy, and immunotherapy, reverses multidrug resistance (MDR), and impedes tumor progression. Notably, phenylsulfonylfuroxan have the ability to trigger ferroptosis in cancer cells by binding covalently to inhibit glutathione peroxidase 4 (GPX4). Recent developments in phenylsulfonylfuroxan-based therapies have positioned them as crucial in the advancement of cancer treatment modalities. This review elucidates the mechanism by which phenylsulfonylfuroxan releases NO and summarizes the significant advancements over the past 16 years in the research and development of phenylsulfonylfuroxan conjugates with various anticancer agents for targeted cancer therapy.

Golgi apparatus targeted therapy in cancer: Are we there yet?

Membrane trafficking within the Golgi apparatus plays a pivotal role in the intracellular transportation of lipids and proteins. Dysregulation of this process can give rise to various pathological manifestations, including cancer. Exploiting Golgi defects, cancer cells capitalise on aberrant membrane trafficking to facilitate signal transduction, proliferation, invasion, immune modulation, angiogenesis, and metastasis. Despite the identification of several molecular signalling pathways associated with Golgi abnormalities, there remains a lack of approved drugs specifically targeting cancer cells through the manipulation of the Golgi apparatus. In the initial section of this comprehensive review, the focus is directed towards delineating the abnormal Golgi genes and proteins implicated in carcinogenesis. Subsequently, a thorough examination is conducted on the impact of these variations on Golgi function, encompassing aspects such as vesicular trafficking, glycosylation, autophagy, oxidative mechanisms, and pH alterations. Lastly, the review provides a current update on promising Golgi apparatus-targeted inhibitors undergoing preclinical and/or clinical trials, offering insights into their potential as therapeutic interventions. Significantly more effort is required to advance these potential inhibitors to benefit patients in clinical settings.

The study on synthesis and vitro hypolipidemic activity of novel berberine derivatives nitric oxide donors

Berberine was used as the lead compound in the present study to design and synthesize novel berberine derivatives by splicing bromine bridges of different berberine carbon chain lengths coupled nitric oxide donors, and their lipid lowering activities were assessed in a variety of ways. This experiment synthesized 17 new berberine nitric oxide donor derivatives. Compared with berberine hydrochloride, most of the compounds exhibited certain glycerate inhibitory activity, and compounds 6a, 6b, 6d, 12b and 12d showed higher inhibitory activity than berberine, with 6a, 6b and 6d having significant inhibitory activity. In addition, compound 6a linked to furazolidone nitric oxide donor showed better NO release in experiments; In further mechanistic studies, we screened and got two proteins, PCSK9 and ACLY, and docked two proteins with 17 compounds, and found that most of the compounds bound better with ATP citrate lyase (ACLY), among which there may be a strong interaction between compound 6a and ACLY, and the interaction force was better than the target drug Bempedoic Acid, which meaning that 6a may exert hypolipidemic effects by inhibiting ACLY; moreover, we also found that 6a may had the better performance in gastrointestinal absorption, blood-brain barrier permeability, Egan, Muegge class drug principle model calculation and bioavailability.

5-(4-Hydroxyphenyl)-3H-1,2-dithiole-3-thione derivatives of brefeldin A: Design, synthesis and cytotoxicity in MDA-MB-231 human breast cancer cells

27 novel 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione derivatives of brefeldin A were designed and synthesized to make them more conducive to the cancer treatment. The antiproliferative activity of all the target compounds was tested against six human cancer cell lines and one human normal cell line. Compound 10d exhibited nearly the most potent cytotoxicity with IC₅₀ values of 0.58, 0.69, 1.82, 0.85, 0.75, 0.33 and 1.75 μM against A549, DU-145, A375, HeLa, HepG2, MDA-MB-231 and L-02 cell lines. Moreover, 10d inhibited metastasis and induced apoptosis of MDA-MB-231 cells in a dose-dependent manner. The potent anticancer effects of 10d were prompted based on the aforementioned results, the therapeutic potential of 10d for breast cancer was worth further exploration.

Penipentenone A and brefeldin A derivatives potently inhibit KRAS mutant cancer cells from an endophytic fungus Penicillium brefeldianum F4a

Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation is one of the most important carcinogenic factors in many solid tumors, which leads to the poor prognosis and therapy resistance of cancer. In order to develop direct or indirect KRAS inhibitors, one unique asymmetric dicyclopentenone penipentenone A, three undescribed brefeldin A (BFA) derivatives, and five known BFA derivatives were discovered from the endophytic fungus Penicillium brefeldianum guided by LC-MS/MS and cytotoxic activities. Their structures were elucidated by optical rotation, mass spectrometry, and NMR spectroscopic data. The absolute configurations of four undescribed compounds were elucidated by comparison of the experimental and calculated ECD spectra. The antiproliferative activities of obtained compounds against three KRAS mutant tumor cell lines and two BFA derivative-sensitive cell lines were evaluated. Besides 4-epi-15-epi-brefeldin A, the other compounds showed significant inhibitory activities against those tumor cell lines with IC₅₀ values ranging from 0.82 to 18.87 μM. Intriguingly, penipentenone A selectively inhibited KRAS mutant cancer cells SW620 (KRAS^G12V) and ASPC-1 (KRAS^G12D). BFA and four derivatives showed potent cytotoxic activities against all selected tumor cell lines H358 (KRAS^G12C), SW620 (KRAS^G12V), ASPC-1 (KRAS^G12D), PC-3, and HepG-2. These findings will provide undescribed lead compounds for developing drugs that target KRAS mutations.

Chronic nitric oxide exposure induces prostate cell carcinogenesis, involving genetic instability and a pro-tumorigenic secretory phenotype

Prostate cancer is a leading cause of cancer death in men. Inflammation and overexpression of inducible nitric oxide synthase (NOS2) have been implicated in prostate carcinogenesis. We aimed to explore the hypothesis that nitric oxide NO exerts pro-tumorigenic effects on prostate cells at physiologically relevant levels contributing to carcinogenesis. We investigated the impact of acute exposure of normal immortalised prostate cells (RWPE-1) to NO on cell proliferation and activation of DNA damage repair pathways. Furthermore we investigated the long term effects of chronic NO exposure on RWPE-1 cell migration and invasion potential and hallmarks of transformation. Our results demonstrate that NO induces DNA damage as indicated by γH2AX foci and p53 activation resulting in a G1/S phase block and activation of 53BP1 DNA damage repair protein. Long term adaption to NO results in increased migration and invasion potential, acquisition of anchorage independent growth and increased resistance to chemotherapy. This was recapitulated in PC3 and DU145 prostate cancer cells which upon chronic exposure to NO displayed increased cell migration, colony formation and increased resistance to chemotherapeutics. These findings indicate that NO may play a key role in the development of prostate cancer and the acquisition of an aggressive metastatic phenotype.

New brefeldin A-cinnamic acid ester derivatives as potential antitumor agents: Design, synthesis and biological evaluation

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and ranks third in mortality rate worldwide. Brefeldin A (BFA, 1), a natural Arf1 inhibitor, qualifies extremely superior antitumor activity against HCC while its low aqueous solubility, poor bioavailability, and high toxicity have greatly hindered its translation to the clinic. Herein, a series of BFA-cinnamic acid ester derivatives was rationally designed and synthesized via introducing active cinnamic acid and its analogues into the structure of 1. Their in vitro cytotoxic activities on five cancer cell lines, including HepG2, BEL-7402, HeLa, Eca-109 and PANC-1, were evaluated using MTT assay. As expected, favorable cytotoxic activity was observed on majority of the mono-substituted derivatives. Especially, the most potent brefeldin A 4-O-(4)-dimethylaminocinnamate (CHNQD-01269, 33) with improved aqueous solubility, demonstrated the strong cytotoxic activity against HepG2 and BEL-7402 cell lines with IC₅₀ values of 0.29 and 0.84 μM, respectively. More importantly, 33 performed low toxicity on normal liver cell line L-02 with the selectivity index (SI) of 9.69, which was more than 17-fold higher than that of 1. Results from mechanistic studies represented that 33 blocked the cell cycle in the G1 phase, and induced apoptosis via elevating reactive oxygen species (ROS) production and increasing expression of apoptosis-related proteins of HepG2 cells. Docking experiment also suggested 33 a promising Arf1 inhibitor, which was confirmed by the cellular thermal shift assay that 33 displayed a significant effect on the stability of Arf1 protein. Furthermore, 33 possessed high safety profile (MTD >100 mg/kg, ip) and favorable pharmacokinetic properties. Notably, the superior antiproliferative activity was verified in HepG2 tumor-bearing xenograft model in which 33 markedly suppressed the tumor growth (TGI = 46.17%) in nude mice at a dose of 10 mg/kg once a day for 16 d. The present study provided evidence of exploiting this series of highly efficacious derivatives, especially 33, for the treatment of HCC.

Brefeldin A Induces Apoptosis, Inhibits BCR-ABL Activation, and Triggers BCR-ABL Degradation in Chronic Myeloid Leukemia K562 Cells

BACKGROUND

Chronic myeloid leukemia (CML) is a myeloproliferative disease caused by BCR-ABL oncoprotein. Tyrosine kinase inhibitors have been developed to inhibit the activity of BCR-ABL; however, drug resistance and side effect occur in clinic application. Therefore, it is urgent to find novel drugs for CML treatment. Under the guidance of cytotoxic activity, crude extracts of 55 fungal strains from the medicinal mangrove Acanthus ilicifolius were evaluated, and one potent cytotoxic natural compound, brefeldin A (BFA), was discovered from Penicillium sp. (HS-N-29).

OBJECTIVE

This study was aimed to determine the cytotoxic activity of BFA and the effect on the activation and expression of BCR-ABL in K562 cells.

METHOD

We evaluated cytotoxic activity by MTT assay and soft agar clone assay and apoptosis and cell cycle distribution by Muse cell analyzer. The protein level of BCR-ABL and signaling molecules were detected by western blotting, and the mRNA level of BCR-ABL was determined by RT-PCR.

RESULTS

BFA inhibited cell proliferation, induced G2/M cell cycle arrest, and stimulated cell apoptosis in K562 cells. Importantly, for the first time, we revealed that BFA inhibited the activation of BCR-ABL and consequently inhibited the activation of its downstream signaling molecules in K562 cells. Moreover, we found that BFA degraded BCR-ABL without affecting its transcription in K562 cells, and BFA-induced BCR-ABL degradation was related to caspase activation while not to autophagy or ubiquitinated proteasome degradation pathway.

CONCLUSION

Our present results indicate that BFA acts as a dual functional inhibitor and degrader of BCR-ABL, and BFA is a potential compound for chemotherapeutics to overcome CML.

Nitric oxide-releasing platinum(IV) prodrug efficiently inhibits proliferation and metastasis of cancer cells

A dual-functional Pt(iv) prodrug, Pt-furoxan, can release cytotoxic cisplatin and signaling molecule NO upon cellular internalization. NO modulates the cellular response towards cisplatin, leading to a synergistic anti-proliferation effect and a promising anti-metastasis effect both in vitro and in vivo.

Nitric-Oxide-Releasing Biomaterial Regulation of the Stem Cell Microenvironment in Regenerative Medicine

Stem cell therapy has proven to be an attractive solution for the treatment of degenerative diseases or injury. However, poor cell engraftment and survival within injured tissues limits the successful use of stem cell therapy within the clinical setting. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes. Emerging evidence supports NO's diverse roles in modulating stem cell behavior, including survival, migration, differentiation, and paracrine secretion of proregenerative factors. Thus, there has been a shift in research focus to concentrate efforts on the delivery of therapeutic concentration ranges of NO to the target tissue sites. Combinatory therapies utilizing biomaterials that control NO generation and support stem cell delivery can be holistic and synergistic approaches to significantly improve tissue regeneration. Here, the focus is on recent developments of various therapeutic platforms, engineered to both transport NO and to enhance stem-cell-mediated regeneration of damaged tissues. New and emerging revelations of how the stem cell microenvironment can be regulated by NO-releasing biomaterials are also highlighted.

Hydrogen sulfide donating ent-kaurane and spirolactone-type 6,7-seco-ent-kaurane derivatives: Design, synthesis and antiproliferative properties

Motivated by our interest in hydrogen sulfide bio-chemistry and ent-kaurane diterpenoid chemistry, 14 hydrogen sulfide donating derivatives (9, 11a-c, 12a-c, 13, 14, 16a-c and 17a-b) of ent-kaurane and spirolactone-type 6,7-seco-ent-kaurane were designed and synthesized. Four human cancer cell lines (K562, Bel-7402, SGC-7901 and A549) and two normal cell lines (L-02 and PBMC) were selected for antiproliferative assay. Most derivatives showed more potent activities than the lead ent-kaurane oridonin. Among them, compound 12b exhibited the most potent antiproliferative activities, with IC₅₀ values of 1.01, 0.88, 4.36 and 5.21 μM against above human cancer cell lines, respectively. Further apoptosis-related mechanism study indicated that 12b could arrest Bel-7402 cell cycle at G1 phase and induce apoptosis through mitochondria related pathway. Through Western blot assay, 12b was shown to influence the intrinsic pathway by increasing the expression of Bax, cleaved caspase-3, cytochrome c and cleaved PARP, meanwhile suppressing procaspase-3, Bcl-2, Bcl-xL and PARP.

Bioactive Natural Spirolactone-Type 6,7-seco-ent-Kaurane Diterpenoids and Synthetic Derivatives

Diterpenoids are widely distributed natural products and have caused considerable interest because of their unique skeletons and antibacterial and antitumor activities and so on. In light of recent discoveries, ent-kaurane diterpenoids, which exhibit a wide variety of biological activities, such as anticancer and anti-inflammatory activities, pose enormous potential to serve as a promising candidate for drug development. Among them, spirolactone-type 6,7-seco-ent-kaurane diterpenoids, with interesting molecular skeleton, complex oxidation patterns, and bond formation, exhibit attractive activities. Furthermore, spirolactone-type diterpenoids have many modifiable sites, which allows for linking to various substituents, suitable for further medicinal study. Hence, some structurally modified derivatives with improved cytotoxicity activities are also achieved. In this review, natural bioactive spirolactone-type diterpenoids and their synthetic derivatives were summarized.

Antiproliferative Effects of Alkaloid Evodiamine and Its Derivatives

Alkaloids, a category of natural products with ring structures and nitrogen atoms, include most U.S. Food and Drug Administration approved plant derived anti-cancer agents. Evodiamine is an alkaloid with attractive multitargeting antiproliferative activity. Its high content in the natural source ensures its adequate supply on the market and guarantees further medicinal study. To the best of our knowledge, there is no systematic review about the antiproliferative effects of evodiamine derivatives. Therefore, in this article the review of the antiproliferative activities of evodiamine will be updated. More importantly, the antiproliferative activities of structurally modified new analogues of evodiamine will be summarized for the first time.

Recent Synthesis and Discovery of Brefeldin A Analogs

The recent development of analogs of brefeldin A (BFA), a fungal metabolite, for the improvement of BFA apoptosis-inducing activity is described. BFA has been isolated from various soil or, more recently, marine fungi and has shown versatile beneficial activities. More importantly, the apoptosis-inducing activity of BFA in cancer cells highlights the possibility of further developing this natural product as an anticancer agent. Besides its biological importance, its structural features have also gathered tremendous interest from both medicinal and synthetic chemists. By a medicinal chemistry and total synthesis approach, numerous analogs from BFA have been developed to improve its inferior bioavailability and its antiproliferative ability. In this review, the recent medicinal chemistry efforts in relation to the production of BFA analogs are extensively presented.

Nitric oxide donors for prostate and bladder cancers: Current state and challenges

Nitric oxide (NO) is an endogenous molecule that plays pivotal physiological and pathophysiological roles, particularly in cancer biology. Generally, low concentrations of NO (pico- to nanomolar range) lead to tumor promotion. In contrast, high NO concentrations (micromolar range) have pro-apoptotic functions, leading to tumor suppression, and in this case, NO is involved in immune surveillance. Under oxidative stress, inducible NO synthase (iNOS) produces high NO concentrations for antineoplastic activities. Prostate and bladder cancers are the most commonly detected cancers in men, and are related to cancer death in males. This review summarizes the state of the art of NO/NO donors in combating prostate and bladder cancers, highlighting the importance of NO donors in cancer treatment, and the limitations and challenges to be overcome. In addition, the combination of NO donors with classical therapies (radio- or chemotherapy) in the treatment of prostate and bladder cancers is also presented and discussed. The combination of NO donors with conventional anticancer drugs is reported to inhibit tumor growth, since NO is able to sensitize tumor cells, enhancing the efficacy of the traditional drugs. Although important progress has been made, more studies are still necessary to definitely translate the administration of NO donors to clinical sets. The purpose of this review is to inspire new avenues in this topic.