Psammaplysin F increases the efficacy of bortezomib and sorafenib through regulation of stress granule formation

Stress Granule Core Protein-Derived Peptides Inhibit Assembly of Stress Granules and Improve Sorafenib Sensitivity in Cancer Cells

Upon a variety of environmental stresses, eukaryotic cells usually recruit translational stalled mRNAs and RNA-binding proteins to form cytoplasmic condensates known as stress granules (SGs), which minimize stress-induced damage and promote stress adaptation and cell survival. SGs are hijacked by cancer cells to promote cell survival and are consequently involved in the development of anticancer drug resistance. However, the design and application of chemical compounds targeting SGs to improve anticancer drug efficacy have rarely been studied. Here, we developed two types of SG inhibitory peptides (SIPs) derived from SG core proteins Caprin1 and USP10 and fused with cell-penetrating peptides to generate TAT-SIP-C1/2 and SIP-U1-Antp, respectively. We obtained 11 SG-inducing anticancer compounds from cell-based screens and explored the potential application of SIPs in overcoming resistance to the SG-inducing anticancer drug sorafenib. We found that SIPs increased the sensitivity of HeLa cells to sorafenib via the disruption of SGs. Therefore, anticancer drugs which are competent to induce SGs could be combined with SIPs to sensitize cancer cells, which might provide a novel therapeutic strategy to alleviate anticancer drug resistance.

Role of stress granules in tumorigenesis and cancer therapy

Stress granules (SGs) are membrane-less organelles that cell forms via liquid-liquid phase separation (LLPS) under stress conditions such as oxidative stress, ER stress, heat shock and hypoxia. SG assembly is a stress-responsive mechanism by regulating gene expression and cellular signaling pathways. Cancer cells face various stress conditions in tumor microenvironment during tumorigenesis, while SGs contribute to hallmarks of cancer including proliferation, invasion, migration, avoiding apoptosis, metabolism reprogramming and immune evasion. Here, we review the connection between SGs and cancer development, the limitation of SGs on current cancer therapy and promising cancer therapeutic strategies targeting SGs in the future.

Stress granules: functions and mechanisms in cancer

Stress granules (SGs) are non-enveloped structures formed primarily via protein and RNA aggregation under various stress conditions, including hypoxia and viral infection, as well as oxidative, osmotic, and heat-shock stress. SGs assembly is a highly conserved cellular strategy to reduce stress-related damage and promote cell survival. At present, the composition and dynamics of SGs are well understood; however, data on the functions and related mechanisms of SGs are limited. In recent years, SGs have continued to attract attention as emerging players in cancer research. Intriguingly, SGs regulate the biological behavior of tumors by participating in various tumor-associated signaling pathways, including cell proliferation, apoptosis, invasion and metastasis, chemotherapy resistance, radiotherapy resistance, and immune escape. This review discusses the roles and mechanisms of SGs in tumors and suggests novel directions for cancer treatment.

Psammaplysins: Insights from Natural Sources, Structural Variations, and Pharmacological Properties

Marine natural products (MNPs) continue to be in the spotlight in the global drug discovery endeavor. Currently, more than 32,000 structurally diverse secondary metabolites from marine sources have been isolated, making MNPs a vital source for researchers to look for novel drug candidates. The marine-derived psammaplysins possess the rare and unique 1,6-dioxa-2-azaspiro [4.6] undecane backbone and are represented by 44 compounds in the literature, mostly from sponges of the order Verongiida. Compounds with 1,6-dioxa-2-azaspiro [4.6] undecane moiety exist in the literature under five names, including psammaplysins, ceratinamides, frondoplysins, ceratinadins, and psammaceratins. These compounds displayed significant biological properties including growth inhibitory, antimalarial, antifouling, protein tyrosine phosphatase inhibition, antiviral, immunosuppressive, and antioxidant effects. In this review, a comprehensive literature survey covering natural occurrence of the psammaplysins and related compounds, methods of isolation, structural differences, the biogenesis, and biological/pharmacological properties, will be presented.

Stress Granules in the Anti-Cancer Medications Mechanism of Action: A Systematic Scoping Review

Stress granule (SG) formation is a well-known cellular mechanism for minimizing stress-related damage and increasing cell survival. In addition to playing a critical role in the stress response, SGs have emerged as critical mediators in human health. It seems logical that SGs play a key role in cancer cell formation, development, and metastasis. Recent studies have shown that many SG components contribute to the anti-cancer medications' responses through tumor-associated signaling pathways and other mechanisms. SG proteins are known for their involvement in the translation process, control of mRNA stability, and capacity to function in both the cytoplasm and nucleus. The current systematic review aimed to include all research on the impact of SGs on the mechanism of action of anti-cancer medications and was conducted using a six-stage methodological framework and the PRISMA guideline. Prior to October 2021, a systematic search of seven databases for eligible articles was performed. Following the review of the publications, the collected data were subjected to quantitative and qualitative analysis. Notably, Bortezomib, Sorafenib, Oxaliplatin, 5-fluorouracil, Cisplatin, and Doxorubicin accounted for the majority of the medications examined in the studies. Overall, this systematic scoping review attempts to demonstrate and give a complete overview of the function of SGs in the mechanism of action of anti-cancer medications by evaluating all research.

Hiding in Plain Sight: Formation and Function of Stress Granules During Microbial Infection of Mammalian Cells

Stress granule (SG) formation is a host cell response to stress-induced translational repression. SGs assemble with RNA-binding proteins and translationally silent mRNA. SGs have been demonstrated to be both inhibitory to viruses, as well as being subverted for viral roles. In contrast, the function of SGs during non-viral microbial infections remains largely unexplored. A handful of microbial infections have been shown to result in host SG assembly. Nevertheless, a large body of evidence suggests SG formation in hosts is a widespread response to microbial infection. Diverse stresses caused by microbes and their products can activate the integrated stress response in order to inhibit translation initiation through phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α). This translational response in other contexts results in SG assembly, suggesting that SG assembly can be a general phenomenon during microbial infection. This review explores evidence for host SG formation in response to bacterial, fungal, and protozoan infection and potential functions of SGs in the host and for adaptations of the pathogen.

Targeting stress granules: A novel therapeutic strategy for human diseases

Stress granules (SGs) are assemblies of mRNA and proteins that form from mRNAs stalled in translation initiation in response to stress. Chronic stress might even induce formation of cytotoxic pathological SGs. SGs participate in various biological functions including response to apoptosis, inflammation, immune modulation, and signalling pathways; moreover, SGs are involved in pathogenesis of neurodegenerative diseases, viral infection, aging, cancers and many other diseases. Emerging evidence has shown that small molecules can affect SG dynamics, including assembly, disassembly, maintenance and clearance. Thus, targeting SGs is a potential therapeutic strategy for the treatment of human diseases and the promotion of health. The established methods for detecting SGs provided ready tools for large-scale screening of agents that alter the dynamics of SGs. Here, we describe the effects of small molecules on SG assembly, disassembly, and their roles in the disease. Moreover, we provide perspective for the possible application of small molecules targeting SGs in the treatment of human diseases.

Role of Chikungunya nsP3 in Regulating G3BP1 Activity, Stress Granule Formation and Drug Efficacy

BACKGROUND

Ras-GTPase activating protein SH3-domain-binding proteins (G3BP) are a small family of RNA-binding proteins implicated in regulating gene expression. Changes in expression of G3BPs are correlated to several cancers including thyroid, colon, pancreatic and breast cancer. G3BPs are important regulators of stress granule (SG) formation and function. SG are ribonucleoprotein (RNP) particles that respond to cellular stresses to triage mRNA resulting in transcripts being selectively degraded, stored or translated resulting in a change of gene expression which confers a survival response to the cell. These changes in gene expression contribute to the development of drug resistance. Many RNA viruses, including Chikungunya (and potentially Coronavirus), dismantle SG so that the cell cannot respond to the viral infection. Non-structural protein 3 (nsP3), from the Chikungunya virus, has been shown to translocate G3BP away from SG. Interestingly in cancer cells, the formation of SG is correlated to drug-resistance and blocking SG formation has been shown to reestablish the efficacy of the anticancer drug bortezomib.

METHODS

Chikungunya nsP3 was transfected into breast cancer cell lines T47D and MCF7 to disrupt SG formation. Changes in the cytotoxicity of bortezomib were measured.

RESULTS

Bortezomib cytotoxicity in breast cancer cell lines changed with a 22 fold decrease in its IC₅₀ for T47D and a 7 fold decrease for MCF7 cells.

CONCLUSIONS

Chikungunya nsP3 disrupts SG formation. As a result, it increases the cytotoxicity of the FDA approved drug, bortezomib. In addition, the increased cytotoxicity appears to correlate to improved bortezomib selectivity when compared to control cell lines.

Mechanisms of tRNA-derived fragments and tRNA halves in cancer treatment resistance

The tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs) are newly discovered noncoding RNAs in recent years. They are derived from specific cleavage of mature and pre-tRNAs and expressed in various cancers. They enhance cell proliferation and metastasis or inhibit cancer progression. Many studies have investigated their roles in the diagnosis, progression, metastasis, and prognosis of various cancers, but the mechanisms through which they are involved in resistance to cancer treatment are unclear. This review outlines the classification of tRFs and tiRNAs and their mechanisms in cancer drug resistance, thus providing new ideas for cancer treatment.

Synthesis of a Unique Psammaplysin F Library and Functional Evaluation in Prostate Cancer Cells by Multiparametric Quantitative Single Cell Imaging

The spirooxepinisoxazoline alkaloid psammaplysin F (1) was selected as a scaffold for the generation of a unique screening library for both drug discovery and chemical biology research. Large-scale extraction and isolation chemistry was performed on a marine sponge (Hyattella sp.) collected from the Great Barrier Reef in order to acquire >200 mg of the desired bromotyrosine-derived alkaloidal scaffold. Parallel solution-phase semisynthesis was employed to generate a series of psammaplysin-based urea (2-9) and amide analogues (10-11) in low to moderate yields. The chemical structures of all analogues were characterized using NMR and MS data. The absolute configuration of psammaplysin F and all semisynthetic analogues was determined as 6R, 7R by comparison of ECD data with literature values. All compounds (1-11) were evaluated for their effect on cell cycle distribution and changes to cancer metabolism in LNCaP prostate cancer cells using a multiparametric quantitative single-cell imaging approach. These investigations identified that in LNCaP cells psammaplysin F and some urea analogues caused loss of mitochondrial membrane potential, fragmentation of the mitochondrial tubular network, chromosome misalignment, and cell cycle arrest in mitosis.

Cytotoxic Psammaplysin Analogues from the Verongid Red Sea Sponge Aplysinella Species

As part of our ongoing interest to identify bioactive chemical entities from marine invertebrates, the Red Sea specimen of the Verongid sponge Aplysinella species was studied. Repeated chromatographic fractionation of the methanolic extract of the sponge and HPLC purification of the cytotoxic fractions led to the isolation and the identification of two new compounds, psammaplysin Z and 19-hydroxypsammaplysin Z (1 and 2), together with the previously reported psammaplysins A (3) and E (4). The structural determination of 1-4 was supported by interpretation of their NMR and high-resolution mass spectra. Psammaplysins A and E displayed cytotoxic activity against MBA-MB-231 and HeLa cell lines with IC50 values down to 0.29 µM. On the other hand, psammaplysin Z and 19-hydroxypsammaplysin Z were moderately cytotoxic, indicating the importance of the terminal amine and 2-(methylene)cyclopent-4-ene-1,3-dione moieties in 3 and 4 for potent cytotoxic activity.