Inhibition of IL-8 secretion on BxPC-3 and MIA PaCa-2 cells and induction of cytotoxicity in pancreatic cancer cells with marine natural products

Structure-Activity Relationship Study of Majusculamide D: Overcoming Metabolic Instability and Severe Toxicity with a Fluoro Analogue

Majusculamide D, isolated from the marine cyanobacterium Moorea producens, is an anticancer lipopentapeptide consisting of fatty acid, tripeptide, and pyrrolyl proline moieties. In this work, by utilizing a convergent synthetic approach, late-stage modification, and bioisostere strategy, 26 majusculamide D analogues were synthesized, and two (1i and 1j) demonstrated IC50 values < 1 nM against PANC-1 cancer cells. The results summarized a preliminary structure-activity relationship mainly at the C23, C4, C34, and C10 sites. A series of in vitro assays, including wound healing, transwell, clone formation, EdU, and western blot, confirmed that majusculamide D inhibited the migration, invasion, and proliferation of pancreatic cancer cells. The optimized fluorinated analogue 1n demonstrated a notable enhancement in stability during the mouse plasma assay (>50% left after 24 h), exhibited tumor-suppressive effects (51.5% at a dosage of 5 mg/kg), and successfully mitigated the severe toxicity (no mouse dead) observed in the group treated with majusculamide D (3 mice dead) in a xenografted mouse model.

Exploring the Biosynthetic Potential of Tistrella Species for Producing Didemnin Antitumor Agents

Didemnins are a class of cyclic depsipeptides derived from sea tunicates that exhibit potent anticancer, antiviral, and immunosuppressive properties. Although certain Tistrella species can produce didemnins, their complete biosynthetic potential remains largely unexplored. In this study, we utilize feature-based molecular networking to analyze the metabolomics of Tistrella mobilis and Tistrella bauzanensis, focusing on the production of didemnin natural products. In addition to didemnin B, we identify nordidemnin B and [hysp2]didemnin B, as well as several minor didemnin analogs. Heterologous expression of the didemnin biosynthetic gene cluster in a Streptomyces host results in the production of only didemnin B and nordidemnin B in limited quantities. Isotope-labeling studies reveal that the substrate promiscuity of the adenylation domains during biosynthesis leads to the accumulation of nordidemnin B and [hysp2]didemnin B. Additionally, precursor-directed biosynthesis is applied to generate eight novel didemnin derivatives by supplementing the culture with structurally related amino acids. Furthermore, we increased the titers of nordidemnin B and [hysp2]didemnin B by supplementing the fermentation medium with l-valine and l-isoleucine, respectively. Finally, both compounds undergo side-chain oxidation to enhance their biological activity, with their anticancer properties found to be as potent as plitidepsin.

Microcolin H, a novel autophagy inducer, exerts potent antitumour activity by targeting PITPα/β

The identification of effective drug targets and the development of bioactive molecules are areas of high need in cancer therapy. The phosphatidylinositol transfer protein alpha/beta isoform (PITPα/β) has been reported to play an essential role in integrating phosphoinositide trafficking and lipid metabolism in diverse cellular processes but remains unexplored as a potential target for cancer treatment. Herein, data analysis of clinical cancer samples revealed that PITPα/β expression is closely correlated with the poor prognosis. Target identification by chemical proteomic methods revealed that microcolin H, a naturally occurring marine lipopeptide, directly binds PITPα/β and displays antiproliferative activity on different types of tumour cell lines. Furthermore, we identified that microcolin H treatment increased the conversion of LC3I to LC3II, accompanied by a reduction of the level of p62 in cancer cells, leading to autophagic cell death. Moreover, microcolin H showed preeminent antitumour efficacy in nude mouse subcutaneous tumour models with low toxicity. Our discoveries revealed that by targeting PITPα/β, microcolin H induced autophagic cell death in tumours with efficient anti-proliferating activity, which sheds light on PITPα/β as a promising therapeutic target for cancer treatment.

A Tumor Microenvironment Model of Pancreatic Cancer to Elucidate Responses toward Immunotherapy

Pancreatic cancer is a devastating malignancy with minimal treatment options. Standard-of-care therapy, including surgery and chemotherapy, is unsatisfactory, and therapies harnessing the immune system have been unsuccessful in clinical trials. Resistance to therapy and disease progression are mediated by the tumor microenvironment, which contains excessive amounts of extracellular matrix and stromal cells, acting as a barrier to drug delivery. There is a lack of preclinical pancreatic cancer models that reconstruct the extracellular, cellular, and biomechanical elements of tumor tissues to assess responses toward immunotherapy. To address this limitation and explore the effects of immunotherapy in combination with chemotherapy, a multicellular 3D cancer model using a star-shaped poly(ethylene glycol)-heparin hydrogel matrix is developed. Human pancreatic cancer cells, cancer-associated fibroblasts, and myeloid cells are grown encapsulated in hydrogels to mimic key components of tumor tissues, and cell responses toward treatment are assessed. Combining the CD11b agonist ADH-503 with anti-PD-1 immunotherapy and chemotherapy leads to a significant reduction in tumor cell viability, proliferation, metabolic activity, immunomodulation, and secretion of immunosuppressive and tumor growth-promoting cytokines.

Marine-Inspired Drugs and Biomaterials in the Perspective of Pancreatic Cancer Therapies

Despite its low prevalence, pancreatic cancer (PC) is one of the deadliest, typically characterised as silent in early stages and with a dramatically poor prognosis when in its advanced stages, commonly associated with a high degree of metastasis. Many efforts have been made in pursuing innovative therapeutical approaches, from the search for new cytotoxic drugs and other bioactive compounds, to the development of more targeted approaches, including improved drug delivery devices. Marine biotechnology has been contributing to this quest by providing new chemical leads and materials originating from different organisms. In this review, marine biodiscovery for PC is addressed, particularly regarding marine invertebrates (namely sponges, molluscs, and bryozoans), seaweeds, fungi, and bacteria. In addition, the development of biomaterials based on marine-originating compounds, particularly chitosan, fucoidan, and alginate, for the production of advanced cancer therapies, is also discussed. The key role that drug delivery can play in new cancer treatments is highlighted, as therapeutical outcomes need to be improved to give further hope to patients.

Natural products as drugs and tools for influencing core processes of eukaryotic mRNA translation

Eukaryotic protein synthesis is the highly conserved, complex mechanism of translating genetic information into proteins. Although this process is essential for cellular homoeostasis, dysregulations are associated with cellular malfunctions and diseases including cancer and diabetes. In the challenging and ongoing search for adequate treatment possibilities, natural products represent excellent research tools and drug leads for new interactions with the translational machinery and for influencing mRNA translation. In this review, bacterial-, marine- and plant-derived natural compounds that interact with different steps of mRNA translation, comprising ribosomal assembly, translation initiation and elongation, are highlighted. Thereby, the exact binding and interacting partners are unveiled in order to accurately understand the mode of action of each natural product. The pharmacological relevance of these compounds is furthermore assessed by evaluating the observed biological activities in the light of translational inhibition and by enlightening potential obstacles and undesired side-effects, e.g. in clinical trials. As many of the natural products presented here possess the potential to serve as drug leads for synthetic derivatives, structural motifs, which are indispensable for both mode of action and biological activities, are discussed. Evaluating the natural products emphasises the strong diversity of their points of attack. Especially the fact that selected binding partners can be set in direct relation to different diseases emphasises the indispensability of natural products in the field of drug development. Discovery of new, unique and unusual interacting partners again renders them promising tools for future research in the field of eukaryotic mRNA translation.

Marine Natural Products with High Anticancer Activities

This review covers recent literature from 2012-2019 concerning 170 marine natural products and their semisynthetic analogues with strong anticancer biological activities. Reports that shed light on cellular and molecular mechanisms and biological functions of these compounds, thus advancing the understanding in cancer biology are also included. Biosynthetic studies and total syntheses, which have provided access to derivatives and have contributed to the proper structure or stereochemistry elucidation or revision are mentioned. The natural compounds isolated from marine organisms are divided into nine groups, namely: alkaloids, sterols and steroids, glycosides, terpenes and terpenoids, macrolides, polypeptides, quinones, phenols and polyphenols, and miscellaneous products. An emphasis is placed on several drugs originating from marine natural products that have already been marketed or are currently in clinical trials.

Cytotoxic Microcolin Lipopeptides from the Marine Cyanobacterium Moorea producens

Nine new linear lipopeptides, microcolins E-M (1-9), together with four known related compounds, microcolins A-D (10-13), were isolated from the marine cyanobacterium Moorea producens using bioassay-guided and LC-MS/MS molecular networking approaches. Catalytic hydrogenation of microcolins A-D (10-13) yielded two known compounds, 3,4-dihydromicrocolins A and B (14, 15), and two new derivatives, 3,4-dihydromicrocolins C and D (16, 17), respectively. The structures of these new compounds were determined by a combination of spectroscopic and advanced Marfey's analysis. Structurally unusual amino acid units, 4-methyl-2-(methylamino)pent-3-enoic (Mpe) acid and 2-amino-4-methylhexanoic acid (N-Me-homoisoleucine), in compounds 1-3 and 8, respectively, are rare residues in naturally occurring peptides. These metabolites showed significant cytotoxic activity against H-460 human lung cancer cells with IC₅₀ values ranging from 6 nM to 5.0 μM. The variations in structure and attendant biological activities provided fresh insights concerning structure-activity relationships for the microcolin class of lipopeptides.

Targeting acquired oncogenic burden in resilient pancreatic cancer: a novel benefit from marine polyphenols

The upsurge of marine-derived therapeutics for cancer treatment is evident, with many drugs in clinical use and in clinical trials. Seaweeds harbor large amounts of polyphenols and their anti-cancer benefit is linear to their anti-oxidant activity. Our studies identified three superlative anti-cancer seaweed polyphenol drug candidates (SW-PD). We investigated the acquisition of oncogenic burden in radiation-resilient pancreatic cancer (PC) that could drive tumor relapse, and elucidated the efficacy of SW-PD candidates as adjuvants in genetically diverse in vitro systems and a mouse model of radiation-residual disease. QPCR profiling of 88 oncogenes in therapy-resilient PC cells identified a 'shared' activation of 40 oncogenes. SW-PD pretreatment inflicted a significant mitigation of acquired (shared) oncogenic burden, in addition to drug- and cell-line-specific repression signatures. Tissue microarray with IHC of radiation-residual tumors in mice signified acquired cellular localization of key oncoproteins and other critical architects. Conversely, SW-PD treatment inhibited the acquisition of these critical drivers of tumor genesis, dissemination, and evolution. Heightened death of resilient PC cells with SW-PD treatment validated the translation aspects. The results defined the acquisition of oncogenic burden in resilient PC and demonstrated that the marine polyphenols effectively target the acquired oncogenic burden and could serve as adjuvant(s) for PC treatment.

Targeting lipid mediators in cancer biology

Bioactive lipids are essential components of human cells and tissues. As discussed in this review, the cancer lipidome is diverse and malleable, with the ability to promote or inhibit cancer pathogenesis. Targeting lipids within the tumor and surrounding microenvironment may be a novel therapeutic approach for treating cancer patients. Additionally, the emergence of a novel super-family of lipid mediators termed specialized pro-resolving mediators (SPMs) has revealed a new role for bioactive lipid mediators in the resolution of inflammation in cancer biology. The role of SPMs in cancer holds great promise in our understanding of cancer pathogenesis and can ultimately be used in future cancer diagnostics and therapy.

The marine natural product Scalarin inhibits the receptor for advanced glycation end products (RAGE) and autophagy in the PANC-1 and MIA PaCa-2 pancreatic cancer cell lines

Pancreatic cancer, the fourth leading cause of cancer death in the United States, has a negative prognosis because metastasis occurs before symptoms manifest. Although combination therapies are showing improvements in treatment, the survival rate for pancreatic cancer five years post diagnosis is only 8%, stressing the need for new treatments. The receptor for advanced glycation end products (RAGE) has recently emerged as a chemotherapeutic target in KRAS driven pancreatic cancers both for treatment and in chemoprevention. RAGE appears to be an important regulator of inflammatory, stress and survival pathways that lead to carcinogenesis, resistance to chemotherapy, enhanced proliferation and the high metastatic potential of pancreatic cancer. RAGE expression has been demonstrated in pancreatic cancer tumors but not in adjacent epithelial tissues. Its presence is associated with increased proliferation and metastasis. In an effort to identify novel inhibitors of RAGE among our collection of marine-derived secondary metabolites, a cell-based screening assay utilizing flow cytometry was developed. This effort led to the identification of scalarin as the active compound in a marine sponge identified as Euryspongia cf. rosea. Scalarin is a sesterterpene natural product isolated previously from a different marine sponge. Scalarin reduces the levels of RAGE and inhibits autophagy in the PANC-1 and MIA PaCa-2 pancreatic cancer cell lines. Its IC₅₀ for cytotoxicity ranges between 20 and 30 μM in the AsPC-1, PANC-1, MIA PaCa-2 and BxPC-3 pancreatic cancer cell lines. Inhibition of autophagy limits tumor growth and tumorigenesis in pancreatic cancer, making scalarin an interesting compound that may merit further study.

Marine Sponge Natural Products with Anticancer Potential: An Updated Review

Despite the huge investment into research and the significant effort and advances made in the search for new anticancer drugs in recent decades, cancer cure and treatment continue to be a formidable challenge. Many sources, including plants, animals, and minerals, have been explored in the oncological field because of the possibility of identifying novel molecular therapeutics. Marine sponges are a prolific source of secondary metabolites, a number of which showed intriguing tumor chemopreventive and chemotherapeutic properties. Recently, Food and Drug Administration-approved drugs derived from marine sponges have been shown to reduce metastatic breast cancer, malignant lymphoma, and Hodgkin's disease. The chemopreventive and potential anticancer activity of marine sponge-derived compounds could be explained by multiple cellular and molecular mechanisms, including DNA protection, cell-cycle modulation, apoptosis, and anti-inflammatory activities as well as their ability to chemosensitize cancer cells to traditional antiblastic chemotherapy. The present article aims to depict the multiple mechanisms involved in the chemopreventive and therapeutic effects of marine sponges and critically explore the limitations and challenges associated with the development of marine sponge-based anticancer strategy.

Combination curcumin and (-)-epigallocatechin-3-gallate inhibits colorectal carcinoma microenvironment-induced angiogenesis by JAK/STAT3/IL-8 pathway

Tumor microenvironment has a crucial role in cancer development and progression, whereas the mechanism of how it regulates angiogenesis is unclear. In this study, we simulated the colorectal carcinoma microenvironment by conditioned medium (CM) of colorectal carcinoma cell lines (SW620, HT-29, HCT116) supernatant or colorectal carcinoma tissue homogenate supernatant to induce normal endothelial cells (NECs). We found that colorectal carcinoma CM promoted tumor angiogenesis by coercing NECs toward tumor endothelial cells (TECs) with the activation of the JAK/STAT3 signaling pathway. Antibody array analysis showed HT-29 supernatant contained numerous angiogenesis-related proteins, especially IL-8. Interestingly, the production of IL-8 in NECs induced by HT-29 CM was also increased. We also verified the crucial role of IL-8 in promoting the CM-induced angiogenesis, as IL-8 repression by neutralizing antibody abolished the transition of NECs toward TECs. Curcumin and (-)-epigallocatechin-3-gallate (EGCG) are broadly investigated in cancer chemoprevention. However, poor bioavailability hurdles their application alone, and the mechanism of their anti-angiogenesis still need to be illuminated. Here, we found that curcumin combination with EGCG attenuated the tumor CM-induced transition of NECs toward TECs by inhibiting JAK/STAT3 signaling pathway. Furthermore, the combination of curcumin and EGCG markedly reduced tumor growth and angiogenesis in the colorectal carcinoma PDX mouse model, and the combined anti-angiogenic effect was better than that of curcumin or EGCG alone. Taken together, our findings provide a new mechanism of tumor angiogenesis, and the combination of curcumin and EGCG represents a potential anti-angiogenic therapeutic method for colorectal carcinoma.