Rhizochalinin Exhibits Anticancer Activity and Synergizes with EGFR Inhibitors in Glioblastoma In Vitro Models.

Rhizochalinin (Rhiz) is a recently discovered cytotoxic sphingolipid synthesized from the marine natural compound rhizochalin. Previously, Rhiz demonstrated high in vitro and in vivo efficacy in various cancer models. Here, we report Rhiz to be highly active in human glioblastoma cell lines as well as in patient-derived glioma-stem like neurosphere models. Rhiz counteracted glioblastoma cell proliferation by inducing apoptosis, G2/M-phase cell cycle arrest, and inhibition of autophagy. Proteomic profiling followed by bioinformatic analysis suggested suppression of the Akt pathway as one of the major biological effects of Rhiz. Suppression of Akt as well as IGF-1R and MEK1/2 kinase was confirmed in Rhiz-treated GBM cells. In addition, Rhiz pretreatment resulted in a more pronounced inhibitory effect of γ-irradiation on the growth of patient-derived glioma-spheres, an effect to which the Akt inhibition may also contribute decisively. In contrast, EGFR upregulation, observed in all GBM neurospheres under Rhiz treatment, was postulated to be a possible sign of incipient resistance. In line with this, combinational therapy with EGFR-targeted tyrosine kinase inhibitors synergistically increased the efficacy of Rhiz resulting in dramatic inhibition of GBM cell viability as well as a significant reduction of neurosphere size in the case of combination with lapatinib. Preliminary in vitro data generated using a parallel artificial membrane permeability (PAMPA) assay suggested that Rhiz cannot cross the blood brain barrier and therefore alternative drug delivery methods should be used in the further in vivo studies. In conclusion, Rhiz is a promising new candidate for the treatment of human glioblastoma, which should be further developed in combination with EGFR inhibitors.

Marine Compounds from the Far Eastern Organisms.

The term "Far East" implies a huge geographical region that consists of Eastern and Southeastern Asia, Eastern Russia and includes the waters of two oceans-the Pacific and Indian [...].

A New Mild Method for Synthesis of Marine Alkaloid Fascaplysin and Its Therapeutically Promising Derivatives.

Fascaplysin is a marine alkaloid which is considered to be a lead drug candidate due to its diverse and potent biological activity. As an anticancer agent, fascaplysin holds a great potential due to the multiple targets affected by this alkaloid in cancer cells, including inhibition of cyclin-dependent kinase 4 (CDK4) and induction of intrinsic apoptosis. At the same time, the studies on structural optimization are hampered by its rather high toxicity, mainly caused by DNA intercalation. In addition, the number of methods for the syntheses of its derivatives is limited. In the current study, we report a new two-step method of synthesis of fascaplysin derivatives based on low temperature UV quaternization for the synthesis of thermolabile 9-benzyloxyfascaplysin and 6-tert-butylfascaplysin. 9-Benzyloxyfascaplysin was used as the starting compound to obtain 9-hydroxyfascaplysin. However, the latter was found to be chemically highly unstable. 6-tert-Butylfascaplysin revealed a significant decrease in DNA intercalation when compared to fascaplysin, while cytotoxicity was only slightly reduced. Therefore, the impact of DNA intercalation for the cytotoxic effects of fascaplysin and its derivatives needs to be questioned.

New Marine Fungal Deoxy-14,15-Dehydroisoaustamide Resensitizes Prostate Cancer Cells to Enzalutamide.

Marine fungi serve as a valuable source for new bioactive molecules bearing various biological activities. In this study, we report on the isolation of a new indole diketopiperazine alkaloid deoxy-14,15-dehydroisoaustamide (1) from the marine-derived fungus Penicillium dimorphosporum KMM 4689 associated with a soft coral. The structure of this metabolite, including its absolute configuration, was determined by HR-MS, 1D and 2D NMR as well as CD data. Compound 1 is a very first deoxyisoaustamide alkaloid possessing two double bonds in the proline ring. The isolated compound was noncytotoxic to a panel of human normal and cancer cell lines up to 100 µM. At the same time, compound 1 resensitized prostate cancer 22Rv1 cells to androgen receptor (AR) blocker enzalutamide. The mechanism of this phenomenon was identified as specific drug-induced degradation of androgen receptor transcription variant V7 (AR-V7), which also resulted in general suppression of AR signaling. Our data suggest that the isolated alkaloid is a promising candidate for combinational therapy of castration resistant prostate cancer, including drug-resistant subtypes.

Anticancer Activity of the Marine Triterpene Glycoside Cucumarioside A2-2 in Human Prostate Cancer Cells.

Despite recent advances in the treatment of metastatic castration-resistant prostate cancer (CRPC), treatment is inevitably hampered by the development of drug resistance. Thus, new drugs are urgently needed. We investigated the efficacy, toxicity, and mechanism of action of the marine triterpene glycoside cucumarioside A2-2 (CA2-2) using an in vitro CRPC model. CA2-2 induced a G2/M-phase cell cycle arrest in human prostate cancer PC-3 cells and caspase-dependent apoptosis executed via an intrinsic pathway. Additionally, the drug inhibited the formation and growth of CRPC cell colonies at low micromolar concentrations. A global proteome analysis performed using the 2D-PAGE technique, followed by MALDI-MS and bioinformatical evaluation, revealed alterations in the proteins involved in cellular processes such as metastatic potential, invasion, and apoptosis. Among others, the regulation of keratin 81, CrkII, IL-1ß, and cathepsin B could be identified by our proteomics approach. The effects were validated on the protein level by a 2D Western blotting analysis. Our results demonstrate the promising anticancer activity of CA2-2 in a prostate cancer model and provide insights on the underlying mode of action.

New Bioactive ß-Resorcylic Acid Derivatives from the Alga-Derived Fungus Penicillium antarcticum KMM 4685.

Five new ß-resorcylic acid derivatives, 14-hydroxyasperentin B (1), ß-resoantarctines A-C (3, 5, 6) and 8-dehydro-ß-resoantarctine A (4), together with known 14-hydroxyasperentin (5'-hydroxyasperentin) (2), were isolated from the ethyl acetate extract of the fungus Penicillium antarcticum KMM 4685 associated with the brown alga Sargassum miyabei. The structures of the compounds were elucidated by spectroscopic analyses and modified Mosher's method, and the biogenetic pathways for compounds 3-6 were proposed. For the very first time, the relative configuration of the C-14 center of a known compound 2 was assigned via analyses of magnitudes of the vicinal coupling constants. The new metabolites 3-6 were biogenically related to resorcylic acid lactones (RALs); however, they did not possess lactonized macrolide elements in their structures. Compounds 3, 4 and 5 exhibited moderate cytotoxic activity in LNCaP, DU145 and 22Rv1 human prostate cancer cells. Moreover, these metabolites could inhibit the activity of p-glycoprotein at their noncytotoxic concentrations and consequently synergize with docetaxel in p-glycoprotein-overexpressing drug-resistant cancer cells.

Meroantarctines A-C, Meroterpenoids with Rearranged Skeletons from the Alga-Derived Fungus Penicillium antarcticum KMM 4685 with Potent p-Glycoprotein Inhibitory Activity.

New meroterpenoids, meroantarctines A-C (1-3), with unique 6/5/6/6, 6/5/6/5/6, and 6/5/6/5 polycyclic systems were isolated from the alga-derived fungus Penicillium antarcticum KMM 4685. Their structures were elucidated by spectroscopic methods, X-ray diffraction, and quantum chemical calculations. A biogenetic pathway for 1-3 was proposed. Meroantarctines A-C (1-3) inhibited p-glycoprotein activity and could resensitize drug-resistant cancer cells to docetaxel.

Marine Compounds and Cancer: Updates 2022.

The field of marine bioactive compounds (marine drugs) has evolved significantly in recent years [...].

1-O-Alkylglycerol Ethers from the Marine Sponge Guitarra abbotti and Their Cytotoxic Activity.

The cytotoxicity-bioassay-guided fractionation of the ethanol extract from the marine sponge Guitarra abbotti, whose 1-O-alkyl-sn-glycerol ethers (AGEs) have not been investigated so far, led to the isolation of a complex lipid fraction containing, along with previously known compounds, six new lipids of the AGE type. The composition of the AGE fraction as well as the structures of 6 new and 22 previously known compounds were established using 1H and 13C NMR, GC/MS, and chemical conversion methods. The new AGEs were identified as: 1-O-(Z-docos-15-enyl)-sn-glycerol (1), 1-O-(Z-docos-17-enyl)-sn-glycerol (2), 1-O-(Z-tricos-15-enyl)-sn-glycerol (3), 1-O-(Z-tricos-16-enyl)-sn-glycerol (4), 1-O-(Z-tricos-17-enyl)-sn-glycerol (5), and 1-O-(Z-tetracos-15-enyl)-sn-glycerol (6). The isolated AGEs show weak cytotoxic activity in THP-1, HL-60, HeLa, DLD-1, SNU C4, SK-MEL-28, and MDA-MB-231 human cancer cells. A further cytotoxicity analysis in JB6 P+ Cl41 cells bearing mutated MAP kinase genes revealed that ERK2 and JNK1 play a cytoprotective role in the cellular response to the AGE-induced cytotoxic effects.

Cytotoxic N-Methylpretrichodermamide B Reveals Anticancer Activity and Inhibits P-Glycoprotein in Drug-Resistant Prostate Cancer Cells.

N-methylpretrichodermamide B (NB) is a biologically active epidithiodiketopiperazine isolated from several strains of the algae-derived fungus Penicillium sp. Recently, we reported the first data on its activity in human cancer cells lines in vitro. Here, we investigated the activity, selectivity, and mechanism of action of NB in human prostate cancer cell lines, including drug-resistant subtypes. NB did not reveal cross-resistance to docetaxel in the PC3-DR cell line model and was highly active in hormone-independent 22Rv1 cells. NB-induced cell death was stipulated by externalization of phosphatidylserine and activation of caspase-3. Moreover, inhibition of caspase activity by z-VAD(OMe)-fmk did not affect NB cytotoxicity, suggesting a caspase-independent cell death induced by NB. The compound has a moderate p-glycoprotein (p-gp) substrate-like affinity and can simultaneously inhibit p-gp at nanomolar concentrations. Therefore, NB resensitized p-gp-overexpressing PC3-DR cells to docetaxel. A kinome profiling of the NB-treated cells revealed, among other things, an induction of mitogen-activated protein kinases JNK1/2 and p38. Further functional analysis confirmed an activation of both kinases and indicated a prosurvival role of this biological event in the cellular response to the treatment. Overall, NB holds promising anticancer potential and further structure-activity relationship studies and structural optimization are needed in order to improve its biological properties.

Study of Structure-Activity Relationships of the Marine Alkaloid Fascaplysin and Its Derivatives as Potent Anticancer Agents.

Marine alkaloid fascaplysin and its derivatives are known to exhibit promising anticancer properties in vitro and in vivo. However, toxicity of these molecules to non-cancer cells was identified as a main limitation for their clinical use. Here, for the very first time, we synthesized a library of fascaplysin derivatives covering all possible substituent introduction sites, i.e., cycles A, C and E of the 12H-pyrido[1-2-a:3,4-b']diindole system. Their selectivity towards human prostate cancer versus non-cancer cells, as well as the effects on cellular metabolism, membrane integrity, cell cycle progression, apoptosis induction and their ability to intercalate into DNA were investigated. A pronounced selectivity for cancer cells was observed for the family of di- and trisubstituted halogen derivatives (modification of cycles A and E), while a modification of cycle C resulted in a stronger activity in therapy-resistant PC-3 cells. Among others, 3,10-dibromofascaplysin exhibited the highest selectivity, presumably due to the cytostatic effects executed via the targeting of cellular metabolism. Moreover, an introduction of radical substituents at C-9, C-10 or C-10 plus C-3 resulted in a notable reduction in DNA intercalating activity and improved selectivity. Taken together, our research contributes to understanding the structure-activity relationships of fascaplysin alkaloids and defines further directions of the structural optimization.

New Guanidine Alkaloids Batzelladines O and P from the Marine Sponge Monanchora pulchra Induce Apoptosis and Autophagy in Prostate Cancer Cells.

Two new guanidine alkaloids, batzelladines O (1) and P (2), were isolated from the deep-water marine sponge Monanchora pulchra. The structures of these metabolites were determined by NMR spectroscopy, mass spectrometry, and ECD. The isolated compounds exhibited cytotoxic activity in human prostate cancer cells PC3, PC3-DR, and 22Rv1 at low micromolar concentrations and inhibited colony formation and survival of the cancer cells. Batzelladines O (1) and P (2) induced apoptosis, which was detected by Western blotting as caspase-3 and PARP cleavage. Additionally, induction of pro-survival autophagy indicated as upregulation of LC3B-II and suppression of mTOR was observed in the treated cells. In line with this, the combination with autophagy inhibitor 3-methyladenine synergistically increased the cytotoxic activity of batzelladines O (1) and P (2). Both compounds were equally active in docetaxel-sensitive and docetaxel-resistant prostate cancer cells, despite exhibiting a slight p-glycoprotein substrate-like activity. In combination with docetaxel, an additive effect was observed. In conclusion, the isolated new guanidine alkaloids are promising drug candidates for the treatment of taxane-resistant prostate cancer.

Immunotherapy in Advanced Prostate Cancer-Light at the End of the Tunnel?

Immunotherapeutic treatment approaches are now an integral part of the treatment of many solid tumors. However, attempts to integrate immunotherapy into the treatment of prostate cancer have been disappointing so far. This is due to a highly immunosuppressive, "cold" tumor microenvironment, which is characterized, for example, by the absence of cytotoxic T cells, an increased number of myeloid-derived suppressor cells or regulatory T cells, a decreased number of tumor antigens, or a defect in antigen presentation. The consequence is a reduced efficacy of many established immunotherapeutic treatments such as checkpoint inhibitors. However, a growing understanding of the underlying mechanisms of tumor-immune system interactions raises hopes that immunotherapeutic strategies can be optimized in the future. The aim of this review is to provide an overview of the current status and future directions of immunotherapy development in prostate cancer. Background information on immune response and tumor microenvironment will help to better understand current therapeutic strategies under preclinical and clinical development.

Salvage Chemotherapy with Cisplatin, Ifosfamide, and Paclitaxel in Aggressive Variant of Metastatic Castration-Resistant Prostate Cancer.

Significant progress has been achieved in the treatment of metastatic castration-resistant prostate cancer (mCRPC). However, results in patients with aggressive variant prostate cancer (AVPC) have been disappointing. Here, we report retrospectively collected data from intensively pretreated AVPC patients (n = 17; 88.2% visceral metastases; 82% elevation of neuroendocrine markers) treated with salvage chemotherapy consisting of cisplatin, ifosfamide, and paclitaxel (TIP). At the interim analysis, 60% of patients showed radiographic response or stable disease (PFS = 2.5 months; OS = 6 months). In men who responded to chemotherapy, an OS > 15 months was observed. Preclinical analyses confirmed the high activity of the TIP regimen, especially in docetaxel-resistant prostate cancer cells. This effect was primarily mediated by increased cisplatin sensitivity in the emergence of taxane resistance. Proteomic and functional analyses identified a lower DNA repair capacity and cell cycle machinery deficiency to be causative. In contrast, paclitaxel showed inconsistent effects, partially antagonizing cisplatin and ifosfamide in some AVPC models. Consequently, paclitaxel has been excluded from the TIP combination for future patients. In summary, we report for the first time the promising efficacy of TIP as salvage therapy in AVPC. Our preclinical data indicate a pivotal role for cisplatin in overcoming docetaxel resistance.

OmpF porin from Yersinia ruckeri as pathogenic factor: Surface antigenic sites and biological properties.

Bacterium Yersinia ruckeri as a pathogen induces causative agent of intestinal fish disease called enteric redmouth disease (ERM) is known. In this study, outer membrane OmpF porin from the Y. ruckeri (YrOmpF) has been identified as a pathogenic factor which affects host macrophage activation and life cycle of eukaryotic cells. Using synthetic peptides corresponding to the sequences of the outer loops of YrOmpF L1 loop of the porin is most involved in the structure of B epitopes on the surface of the microbial cell it was found. T epitopes of the isolated YrOmpF trimer not only by linear, but also by discontinuous determinants, which is due to the secondary structure of the protein are represented. It was shown that YrOmpF was twice more cytotoxic to THP-1 cells (human monocytes, cancer cells) in comparison with CHH-1 cells (Oncorhynchus keta cardiac muscle cell, non-cancer cells). It was found YrOmpF induce cell cycle S-phase arrest in both normal CHH-1 and cancer THP-1 cells. In the cancer cells observed effect was most pronounce. In addition, we have observed an induction of apoptosis in THP-1 cell line treated with YrOmpF for 48 h at IC50 (48.6 µg/ml). Significant cytotoxic effect of YrOmpF on primary mouse peritoneal macrophages been detected as well. Of note, co-incubation of macrophages with anti-YrOmpF antibodies could decrease the amount of lactate dehydrogenase, while the number of living cells significantly increased. YrOmpF stimulates the activity of the phagocytic bactericidal systems especially of the oxygen-independent subsystem it was found. Antibodies against YrOmpF decreased MPO release and CP synthesis by peritoneal macrophages and increased their viability.

Recent Updates on Marine Cancer-Preventive Compounds.

The natural compounds derived from marine organisms often exhibit unique chemical structures and potent biological activities. Cancer-preventive activity is one of the rather new activities that has emerged and been extensively studied over the last decades. This review summarizes the recent updates on the marine chemopreventive compounds covering the relevant literature published in 2013-2021 and following the previous comprehensive review by Stonik and Fedorov (Marine Drugs 2014, 12, 636-671). In the current article, only the molecules having an effect on malignant transformation (or related pathway and molecules), cancer stem cells, or carcinogen-induced in vivo tumor development were considered to be "true" cancer-preventive compounds and were, therefore, reviewed. Additionally, particular attention has been given to the molecular mechanisms of chemoprevention, executed by the reported marine compounds.

Cytotoxic Marine Alkaloid 3,10-Dibromofascaplysin Induces Apoptosis and Synergizes with Cytarabine Resulting in Leukemia Cell Death.

Myeloid leukemia is a hematologic neoplasia characterized by a clonal proliferation of hematopoietic stem cell progenitors. Patient prognosis varies depending on the subtype of leukemia as well as eligibility for intensive treatment regimens and allogeneic stem cell transplantation. Although significant progress has been made in the therapy of patients including novel targeted treatment approaches, there is still an urgent need to optimize treatment outcome. The most common therapy is based on the use of chemotherapeutics cytarabine and anthrayclines. Here, we studied the effect of the recently synthesized marine alkaloid 3,10-dibromofascaplysin (DBF) in myeloid leukemia cells. Unsubstituted fascaplysin was early found to affect cell cycle via inhibiting CDK4/6, thus we compared the activity of DBF and other brominated derivatives with known CDK4/6 inhibitor palbociclib, which was earlier shown to be a promising candidate to treat leukemia. Unexpectedly, the effect DBF on cell cycle differs from palbociclib. In fact, DBF induced leukemic cells apoptosis and decreased the expression of genes responsible for cancer cell survival. Simultaneously, DBF was found to activate the E2F1 transcription factor. Using bioinformatical approaches we evaluated the possible molecular mechanisms, which may be associated with DBF-induced activation of E2F1. Finally, we found that DBF synergistically increase the cytotoxic effect of cytarabine in different myeloid leukemia cell lines. In conclusion, DBF is a promising drug candidate, which may be used in combinational therapeutics approaches to reduce leukemia cell growth.

New Deoxyisoaustamide Derivatives from the Coral-Derived Fungus Penicillium dimorphosporum KMM 4689.

Seven new deoxyisoaustamide derivatives (1-7) together with known compounds (8-10) were isolated from the coral-derived fungus Penicillium dimorphosporum KMM 4689. Their structures were established using spectroscopic methods, X-ray diffraction analysis and by comparison with related known compounds. The absolute configurations of some alkaloids were determined based on CD and NOESY data as well as biogenetic considerations. The cytotoxic and neuroprotective activities of some of the isolated compounds were examined and structure-activity relationships were pointed out. New deoxyisoaustamides 4-6 at concentration of 1 µM revealed a statistical increase of PQ(paraquat)-treated Neuro-2a cell viability by 30-39%.

Blue-Print Autophagy in 2020: A Critical Review.

Autophagy is an elegant and complex biological process that has recently attracted much attention from the scientific community. The compounds which are capable of control and modulation of this process have a promising potential as therapeutics for a number of pathological conditions, including cancer and neurodegenerative disorders. At the same time, due to the relatively young age of the field, there are still some pitfalls in the autophagy monitoring assays and interpretation of the experimental data. This critical review provides an overview of the marine natural compounds, which have been reported to affect autophagy. The time period from the beginning of 2016 to the middle of 2020 is covered. Additionally, the published data and conclusions based on the experimental results are re-analyzed with regard to the guidelines developed by Klionsky and colleagues (Autophagy. 2016; 12(1): 1-222), which are widely accepted by the autophagy research community. Remarkably and surprisingly, more than half of the compounds reported to be autophagy activators or inhibitors could not ultimately be assigned to either category. The experimental data reported for those substances could indicate both autophagy activation and inhibition, requiring further investigation. Thus, the reviewed molecules were divided into two groups: having validated and non-validated autophagy modulatory effects. This review gives an analysis of the recent updates in the field and raises an important problem of standardization in the experimental design and data interpretation.

Marine Compounds and Cancer: Updates 2020.

By the end of the year 2020, there are nine marine-derived anticancer drugs available on the market, and the field is currently growing exponentially [...].