Antitumor Activity of Fascaplysin Derivatives on Glioblastoma Model In Vitro

Stupp R., Taillibert S., Kanner A.A., Kesari S., Steinberg D.M., Toms S.A., Taylor L.P., Lieberman F., Silvani A., Fink K.L., Barnett G.H., Zhu J., Henson J.W., Engelhard H.H., Chen T.C., et. al.

IMPORTANCE Glioblastoma is the most devastating primary malignancy of the central nervous system in adults. Most patients die within 1 to 2 years of diagnosis. Tumor-treating fields (TTFields) are a locoregionally delivered antimitotic treatment that interferes with cell division and organelle assembly. OBJECTIVE To evaluate the efficacy and safety of TTFields used in combination with temozolomide maintenance treatment after chemoradiation therapy for patients with glioblastoma. DESIGN, SETTING, AND PARTICIPANTS After completion of chemoradiotherapy, patients with glioblastoma were randomized (2:1) to receive maintenance treatment with either TTFields plus temozolomide (n = 466) or temozolomide alone (n = 229) (median time from diagnosis to randomization, 3.8 months in both groups). The study enrolled 695 of the planned 700 patients between July 2009 and November 2014 at 83 centers in the United States, Canada, Europe, Israel, and South Korea. The trial was terminated based on the results of this planned interim analysis. INTERVENTIONS Treatment with TTFields was delivered continuously (>18 hours/day) via 4 transducer arrays placed on the shaved scalp and connected to a portable medical device. Temozolomide (150-200 mg/m2/d) was given for 5 days of each 28-day cycle. MAIN OUTCOMES AND MEASURES The primary end point was progression-free survival in the intent-to-treat population (significance threshold of .01) with overall survival in the per-protocol population (n = 280) as a powered secondary end point (significance threshold of .006). This prespecified interim analysis was to be conducted on the first 315 patients after at least 18 months of follow-up. RESULTS The interim analysis included 210 patients randomized to TTFields plus temozolomide and 105 randomized to temozolomide alone, and was conducted at a median follow-up of 38 months (range, 18-60 months). Median progression-free survival in the intent-to-treat population was 7.1 months (95% CI, 5.9-8.2 months) in the TTFields plus temozolomide group and 4.0 months (95% CI, 3.3-5.2 months) in the temozolomide alone group (hazard ratio [HR], 0.62 [98.7% CI, 0.43-0.89]; P = .001). Median overall survival in the per-protocol population was 20.5 months (95% CI, 16.7-25.0 months) in the TTFields plus temozolomide group (n = 196) and 15.6 months (95% CI, 13.3-19.1 months) in the temozolomide alone group (n = 84) (HR, 0.64 [99.4% CI, 0.42-0.98]; P = .004). CONCLUSIONS AND RELEVANCE In this interim analysis of 315 patients with glioblastoma who had completed standard chemoradiation therapy, adding TTFields to maintenance temozolomide chemotherapy significantly prolonged progression-free and overall survival. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00916409.

Kumar S., Guru S.K., Pathania A.S., Manda S., Kumar A., Bharate S.B., Vishwakarma R.A., Malik F., Bhushan S.

In this study, we for the first time explored the cellular and molecular mechanism of anticancer properties of fascaplysin, a marine sponge‐derived alkaloid. Our study demonstrated that fascaplysin induced a cooperative interaction between apoptotic and autophagic pathways to induce cytotoxicity in HL‐60 cells. Fascaplysin treatment not only activated pro‐apoptotic events like PARP‐1 cleavage and caspase activation but also triggered autophagy signaling as shown by the increased expression of LC3‐II, ATG7and beclin. Interestingly, it was found that use of pan‐caspase inhibitor completely reversed the fascaplysin mediated cell death as analyzed by MTT and cell cycle assays. It was observed that cell death as well as the expression of pro‐death proteins was partially reversed, when key autophagy mediators ATG7 was silenced by siRNA in fascaplysin treated cells. Cooperative involvement of autophagy and apoptotic signaling in cytotoxicity was confirmed when combined silencing of pro‐apototic (PARP‐1) and autophagic (ATG‐7) signaling by respective siRNA's lead to substantial rescue of cell death induced by fascaplysin. Although, apoptosis and autophagy are two independent cell death pathways, our findings provide detailed insight by which both the pathways acted cooperatively to elicit fascaplysin induced cell death in HL‐60 cells. Our findings provide molecular insight into the anti‐cancer potential of fascaplysin by showing that both autophagic and apoptotic signaling can work together in the induction of cell death. J. Cell. Biochem. 116: 985–997, 2015. © 2015 Wiley Periodicals, Inc.

Omuro A.

IMPORTANCE Glioblastomas and malignant gliomas are the most common primary malignant brain tumors, with an annual incidence of 5.26 per 100,000 population or 17,000 new diagnoses per year. These tumors are typically associated with a dismal prognosis and poor quality of life. OBJECTIVE To review the clinical management of malignant gliomas, including genetic and environmental risk factors such as cell phones, diagnostic pitfalls, symptom management, specific antitumor therapy, and common complications. EVIDENCE REVIEW Search of PubMed references from January 2000 to May 2013 using the terms glioblastoma, glioma, malignant glioma, anaplastic astrocytoma, anaplastic oligodendroglioma, anaplastic oligoastrocytoma, and brain neoplasm. Articles were also identified through searches of the authors' own files. Evidence was graded using the American Heart Association classification system. FINDINGS Only radiation exposure and certain genetic syndromes are well-defined risk factors for malignant glioma. The treatment of newly diagnosed glioblastoma is based on radiotherapy combined with temozolomide. This approach doubles the 2-year survival rate to 27%, but overall prognosis remains poor. Bevacizumab is an emerging treatment alternative that deserves further study. Grade III tumors have been less well studied, and clinical trials to establish standards of care are ongoing. Patients with malignant gliomas experience frequent clinical complications, including thromboembolic events, seizures, fluctuations in neurologic symptoms, and adverse effects from corticosteroids and chemotherapies that require proper management and prophylaxis. CONCLUSIONS AND RELEVANCE Glioblastoma remains a difficult cancer to treat, although therapeutic options have been improving. Optimal management requires a multidisciplinary approach and knowledge of potential complications from both the disease and its treatment.

B. Bharate S., Manda S., Mupparapu N., Battini N., A. Vishwakarma R.

Marine natural products offer an abundant source of pharmacologically active agents with great diversity and complexity, and the potential to produce valuable therapeutic entities. Indole alkaloids is one of the important class of marine-derived secondary metabolites, with wide occurrence amongst variety of marine sources such as sponges, tunicates, algae, worms and microorganisms and have been extensively studied for their biological activities. Among this chemical family, a sponge-derived bis-indole alkaloid fascaplysin (1) exhibited broad range of bioactivities including antibacterial, antifungal, antiviral, anti-HIV-1-RTase, p56 tyrosine kinase inhibition, antimalarial, anti-angiogenic, antiproliferative activity against numerous cancer cell lines, specific inhibition of cyclin-dependent kinase-4 (IC(50) 350 nM) and action as a DNA intercalator. In the present review, the chemical diversity of natural as well as synthetic analogues of fascaplysin has been reviewed with a detailed account on synthetic reports and pharmacological studies. Our analysis of the structure-activity relationships of this family of compounds highlights the existence of various potential leads for the development of novel anticancer agents.

Zheng Y.L., Lu X.L., Lin J., Chen H.M., Yan X.J., Wang F., Xu W.F.

Novel anti-angiogenesis activity of fascaplysin via VEGF blockage was recently revealed by our previous study in addition to the reported cyclin-dependent kinase 4 (CDK4) selective inhibition. To uncover more details of this pharmacologically prospective property, this study further investigated whether fascaplysin had direct anti-proliferation effects on human umbilical vein endothelial cells (HUVEC), which might be contributing to anti-angiogenesis. The results showed that G1 cell cycle arrest was induced by 2.6 μM fascaplysin in a time-dependent manner, and exhibited more sensitive than hepatocarcinoma cells BeL-7402 and Hela cells. Approximately 56.09 ± 2.63% of the cells were arrested at the G1 phase after 24h, and 64.94 ± 2.07% after 36 h, comparing to the 22.82 ± 1.2% in methanol treated cells. Apoptosis of HUVEC cells was induced by 1.3 μM fascaplysin and indicated by the sub-G1, Hoechst staining, terminal deoxynucleotidyl transferase dUTP-mediated nicked end labeling (TUNEL) assay, and annexin-V and propidium (PI) label. This apoptosis response was further confirmed by the detection of active caspase-3 and by western blotting using antibodies against Bax, Bcl-2, procaspase-8, and Bid, indicating that apoptosis in HUVEC cells may involve a mitochondria pathway, by the demonstration of an increase in the Bax/Bcl-2 ratio. Together, our results suggest that the anti-angiogenesis activity of fascaplysin is through the direct effects of cell cycle arrest and apoptosis on HUVEC.

Kuzmich A.S., Fedorov S.N., Shastina V.V., Shubina L.K., Radchenko O.S., Balaneva N.N., Zhidkov M.E., Park J., Kwak J.Y., Stonik V.A.

3- and 10-Bromofascaplysins was previously found to possess cytotoxic activity. In this study, we investigated their cancer preventive and proapoptotic properties. These effects were tested on mouse skin epidermal JB6 P(+) Cl41 cell line, its stable transfectants, and human tumor HL-60, THP-1, SNU-C4, SK-MEL-28, DLD-1, MDA-MB-231, and HeLa cells using a variety of assessments, including a cell viability (MTS) assay, flow cytometry, anchorage-independent soft agar assay, luciferase assay, mitochondrial permeability assay, and Western blotting. 3- and 10-Bromofascaplysins were effective at submicromolar concentrations as the anticancer agents, which exerted their action, at least in part, through the induction of caspase-8, -9, -3-dependent apoptosis.

Zhidkov M.E., Baranova O.V., Balaneva N.N., Fedorov S.N., Radchenko O.S., Dubovitskii S.V.

A simple and practical approach for the synthesis of the marine sponge pigment fascaplysin was used for the total syntheses of its natural derivatives, the marine alkaloids 3-bromofascaplysin, 10-bromofascaplysin, and 3,10-dibromofascaplysin. The conditions of each step were revised, and as a result these compounds were produced by identical procedures with total yields of 40–43%.

Segraves N.L., Robinson S.J., Garcia D., Said S.A., Fu X., Schmitz F.J., Pietraszkiewicz H., Valeriote F.A., Crews P.

The fascaplysin class of compounds have been further investigated from six organisms consisting of four sponge collections (Fascaplysinopsis reticulata) and two tunicate collections (Didemnum sp.). This work is an extension of an earlier communication and reports the isolation of 12 new fascaplysin derivatives:  10-bromofascaplysin (7), 3,10-dibromofascaplysin (8), homofascaplysate A (9), homofascaplysin B-1 (11), 3-bromohomofascaplysins B (12), B-1 (13), and C (15), 7,14-dibromoreticulatine (17), reticulatol (20), 14-bromoreticulatol (21), and 3-bromosecofascaplysins A (22) and B (23), along with known compounds:  fascaplysin (1), reticulatine (4), 3-bromofascaplysin (6), and homofascaplysin C (14). Selected compounds were screened in a cell-based cytotoxicity assay with compounds 1, 6, and fascaplysin A (24) also screened in the NCI 60 cell line panel. A biogenetic pathway for the brominated fascaplysins and brominated related alkaloids is proposed and discussed.

Hörmann A., Chaudhuri B., Fretz H.

Association of fascaplysin with double-stranded calf thymus DNA was investigated by means of isothermal titration calorimetry, absorption spectroscopy, and circular dichroism. The UV spectroscopic data could be well interpreted in terms of a two-site model for the binding of fascaplysin to DNA revealing affinity constants of K1 = 2.5 x 10(6) M(-1) and K2 = 7.5 x 10(4) M(-1) (base pairs of DNA). Based on the typical change observed in the absorption and circular dichroism spectra, intercalation of fascaplysin is regarded as the major binding mode. The calorimetric titration curves showed an exothermic reaction which was exhausted at a 2:1 base pair/drug; ratio. This finding is in agreement with an intercalation model comprising nearest neighbor exclusion. In addition, significantly weaker non-intercalative DNA interactions can be observed at high drug concentration. By comparison of all these data with the binding behavior of known intercalating agents, it is concluded that fascaplysin intercalates into DNA.

Soni R., Muller L., Furet P., Schoepfer J., Stephan C., Zumstein-Mecker S., Fretz H., Chaudhuri B.

Small chemical molecules that interfere with biological proteins could be useful for gaining insight into the complex biochemical processes in mammalian cells. Cdk4 is a key protein whose activity is required not only for emergence of cells from quiescence but also at the G1/S transition in the cell cycle and which is misregulated in 60-70% of human cancers. We set out to identify chemical inhibitors of Cdk4 and discovered that, in vitro, fascaplysin specifically inhibited Cdk4. Molecular modelling based on the crystal structure of Cdk2 suggests that fascaplysin inhibits Cdk4 by binding to the ATP pocket of the kinase. Treatment of tumour (p16(-), pRb(+)) and normal (p16(+), pRb(+)) cell lines with fascaplysin caused G1 arrest and prevented pRb phosphorylation at sites implicated as being specific for Cdk4 kinase. Fascaplysin will therefore prove to be a useful tool in studying the consequence of Cdk4 inhibition, especially in cells containing inactivated p16.

Ichikawa K., Johnson H.M., Curtis M.A., Biswas N., Singh S., Khachatryan H.N., Gater A.E., Lin S.X., Sperry J.

Zhidkov M.E., Smirnova P.A., Grammatikova N.E., Isakova E.B., Shchekotikhin A.E., Styshova O.N., Klimovich A.A., Popov A.M.

Fascaplysins form a group of marine natural products with unique cationic five-ring coplanar backbone. Native fascaplysin exhibits a broad spectrum of bioactivities, among which the cytotoxic activity has been the most investigated. Several fascaplysin derivatives have more selective biological effects and are promising as lead compounds. Thus, the introduction of a substituent at C-9 of fascaplysin leads to a strong increase in its antimicrobial properties. Here, a comparative assessment of the antimicrobial activity of synthetic analogs of the marine alkaloids 3-bromofascaplysin, 10-bromofascaplysin, and 3,10-dibromofascaplysin, along with some of their isomers and analogs, was carried out against a panel of Gram-positive bacteria in vitro. For the first time, a significant increase in the antimicrobial activity of fascaplysin was observed when a substituent was introduced at C-3. The introduction of two bromine atoms at C-2 and C-9 enhances the antimicrobial properties by 4 to 16 times, depending on the tested strain. Evaluation of the antimicrobial potential in vivo showed that fascaplysin and 3,10-dibromofascaplysin had comparable efficacy in the mouse staphylococcal sepsis model. Additionally, 3,10-dibromofascaplysin demonstrated a strong and reliable antitumor effect in vivo on the Ehrlich carcinoma inoculated subcutaneously, with a value of tumor growth inhibition by 49.2% 20 days after treatment. However, further studies on alternative chemical modifications of fascaplysin are needed to improve its chemotherapeutic properties.

Xu M., Bai Z., Xie B., Peng R., Du Z., Liu Y., Zhang G., Yan S., Xiao X., Qin S.

Marine-derived bisindoles exhibit structural diversity and exert anti-cancer influence through multiple mechanisms. Comprehensive research has shown that the development success rate of drugs derived from marine natural products is four times higher than that of other natural derivatives. Currently, there are 20 marine-derived drugs used in clinical practice, with 11 of them demonstrating anti-tumor effects. This article provides a thorough review of recent advancements in anti-tumor exploration involving 167 natural marine bisindole products and their derivatives. Not only has enzastaurin entered clinical practice, but there is also a successfully marketed marine-derived bisindole compound called midostaurin that is used for the treatment of acute myeloid leukemia. In summary, investigations into the biological activity and clinical progress of marine-derived bisindoles have revealed their remarkable selectivity, minimal toxicity, and efficacy against various cancer cells. Consequently, they exhibit immense potential in the field of anti-tumor drug development, especially in the field of anti-tumor drug resistance. In the future, these compounds may serve as promising leads in the discovery and development of novel cancer therapeutics.

Tryapkin O.A., Kantemirov A.V., Dyshlovoy S.A., Prassolov V.S., Spirin P.V., von Amsberg G., Sidorova M.A., Zhidkov M.E.

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.

Wang C., Wang S., Li H., Hou Y., Cao H., Hua H., Li D.

Fascaplysin is a planar structure pentacyclic alkaloid isolated from sponges, which can effectively induce the apoptosis of cancer cells. In addition, fascaplysin has diverse biological activities, such as antibacterial, anti-tumor, anti-plasmodium, etc. Unfortunately, the planar structure of fascaplysin can be inserted into DNA and such interaction also limits the further application of fascaplysin, necessitating its structural modification. In this review, the biological activity, total synthesis and structural modification of fascaplysin will be summarized, which will provide useful information for pharmaceutical researchers interested in the exploration of marine alkaloids and for the betterment of fascaplysin in particular.

Jiang Y., Qiu H., Liang W., Lin J., Lin J., Liu W., Wang X., Cui W., Chen X., Wang H., Zhao L., Liang H.

Zhidkov M.E., Kaune M., Kantemirov A.V., Smirnova P.A., Spirin P.V., Sidorova M.A., Stadnik S.A., Shyrokova E.Y., Kaluzhny D.N., Tryapkin O.A., Busenbender T., Hauschild J., Rohlfing T., Prassolov V.S., Bokemeyer C., et. al.

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.

Khotimchenko R., Bryukhovetskiy I., Khotimchenko M., Khotimchenko Y.

The search for new chemical compounds with antitumor pharmacological activity is a necessary process for creating more effective drugs for each specific malignancy type. This review presents the outcomes of screening studies of natural compounds with high anti-glioma activity. Despite significant advances in cancer therapy, there are still some tumors currently considered completely incurable including brain gliomas. This review covers the main problems of the glioma chemotherapy including drug resistance, side effects of common anti-glioma drugs, and genetic diversity of brain tumors. The main emphasis is made on the characterization of natural compounds isolated from marine organisms because taxonomic diversity of organisms in seawaters significantly exceeds that of terrestrial species. Thus, we should expect greater chemical diversity of marine compounds and greater likelihood of finding effective molecules with antiglioma activity. The review covers at least 15 classes of organic compounds with their chemical formulas provided as well as semi-inhibitory concentrations, mechanisms of action, and pharmacokinetic profiles. In conclusion, the analysis of the taxonomic diversity of marine species containing bioactives with antiglioma activity is performed noting cytotoxicity indicators and to the tumor cells in comparison with similar indicators of antitumor agents approved for clinical use as antiglioblastoma chemotherapeutics.

Muthuraman A., Shaikh S.A., Ramesh M., Sikarwar M.S.

Neuroinflammation is one of the key events in the progression of multiple neurological disorders. The blood–brain barrier and blood–nerve barrier are responsible for the development of neuroinflammation via metabolic alteration, free radical generation, and lipid peroxidation. Furthermore, overexpression of biological proteins such as proinflammatory and proapoptotic mediators, activation of glial, astrocyte, oligodendrocyte, and Schwann cells also plays a key role in the development of neuroinflammation. Moreover, in some cases, alteration of cellular enzymes, ion channels, and prion proteins are also used to enhance neuroinflammation. The natural source of medicines such as plant, animal, marine, and mineral drugs plays a critical role in ameliorating the free radical, lipid peroxidation, and inflammatory cytokine-associated neuroinflammation. Some conventional medicines are involved in the regulation of neurotransmitters and ion channel function in the nervous system. However, the clinical use of conventional medicines is still questionable due to its low safety, efficacy, and higher intolerable adverse effects. The recent drug discovery process has paid greater attention toward natural medicines especially marine drugs for neuroinflammatory disorders. Some of the marine drugs have a promising role in the management of neurovascular disorders via potential antiinflammatory actions. However, the relationship between chemical structure and their biological activity remains to be explored. It is an essential part of bringing potential medicines from nature to health management. Hence, this book chapter is based on exploring the structure–activity relationship of marine drugs for neuroinflammatory disorders.

Munekata P.E., Pateiro M., Conte-Junior C.A., Domínguez R., Nawaz A., Walayat N., Movilla Fierro E., Lorenzo J.M.

Marine alkaloids comprise a class of compounds with several nitrogenated structures that can be explored as potential natural bioactive compounds. The scientific interest in these compounds has been increasing in the last decades, and many studies have been published elucidating their chemical structure and biological effects in vitro. Following this trend, the number of in vivo studies reporting the health-related properties of marine alkaloids has been increasing and providing more information about the effects in complex organisms. Experiments with animals, especially mice and zebrafish, are revealing the potential health benefits against cancer development, cardiovascular diseases, seizures, Alzheimer’s disease, mental health disorders, inflammatory diseases, osteoporosis, cystic fibrosis, oxidative stress, human parasites, and microbial infections in vivo. Although major efforts are still necessary to increase the knowledge, especially about the translation value of the information obtained from in vivo experiments to clinical trials, marine alkaloids are promising candidates for further experiments in drug development.

Dyshlovoy S.A., Kaune M., Hauschild J., Kriegs M., Hoffer K., Busenbender T., Smirnova P.A., Zhidkov M.E., Poverennaya E.V., Oh-Hohenhorst S.J., Spirin P.V., Prassolov V.S., Tilki D., Bokemeyer C., Graefen M., et. al.

Efficacy and mechanism of action of marine alkaloid 3,10-dibromofascaplysin (DBF) were investigated in human prostate cancer (PCa) cells harboring different levels of drug resistance. Anticancer activity was observed across all cell lines examined without signs of cross-resistance to androgen receptor targeting agents (ARTA) or taxane based chemotherapy. Kinome analysis followed by functional investigation identified JNK1/2 to be one of the molecular targets of DBF in 22Rv1 cells. In contrast, no activation of p38 and ERK1/2 MAPKs was observed. Inhibition of the drug-induced JNK1/2 activation or of the basal p38 activity resulted in increased cytotoxicity of DBF, whereas an active ERK1/2 was identified to be important for anticancer activity of the alkaloid. Synergistic effects of DBF were observed in combination with PARP-inhibitor olaparib most likely due to the induction of ROS production by the marine alkaloid. In addition, DBF intensified effects of platinum-based drugs cisplatin and carboplatin, and taxane derivatives docetaxel and cabazitaxel. Finally, DBF inhibited AR-signaling and resensitized AR-V7-positive 22Rv1 prostate cancer cells to enzalutamide, presumably due to AR-V7 down-regulation. These findings propose DBF to be a promising novel drug candidate for the treatment of human PCa regardless of resistance to standard therapy.

Lyakhova I., Piatkova M., Gulaia V., Romanishin A., Shmelev M., Bryukhovetskiy A., Sharma A., Sharma H.S., Khotimchenko R., Bryukhovetskiy I.

Glioblastoma is one of the most aggressive human brain tumors. Even following all the modern protocols of complex treatment, the median patient survival typically does not exceed 15 months. This review analyzes the main reasons for glioblastoma resistance to therapy, as well as attempts at categorizing the main approaches to increasing chemotherapy efficiency. Special emphasis is placed on the specific group of compounds, known as marine alkaloids and their synthetic derivatives exerting a general antitumor effect on glioblastoma cells. The unique mechanisms of marine alkaloid influence on the tumor cells prompt considering them as a promising basis for creating new chemotherapeutic agents for glioblastoma treatment.

Lyakhova I., Piatkova M., Khotimchenko Y., Zhidkov M., Kantemirov A., Khotimchenko R., Bryukhovetskiy A., Sharma A., Sharma H.S., Bryukhovetskiy I.

Glioblastoma (GB) is one of the most aggressive human brain tumors. The prognosis is unfavorable, its treatment is relatively ineffective, and the median survival is about 15 months. Medication development with new chemical compounds is one of the ways to solve the problem of current treatment inefficiency. This study is focused on the group of chemical substances, based on pentacyclic system of 12H-pyrido[1,2-a:3,4-b]diindole, and the most well-known part of this group is fascaplysin, first extracted from the sponge Fascaplysinopsis spp. We have synthesized a series of the following fascaplysin derivatives: 7-phenylfascaplysin, 3-chlorofascaplysin, 3-bromofascaplysin, 9-bromofascaplysin. The paper is aimed at analyzing the cytotoxic effect of these compounds on GB cells. Materials and methods. The study used rat glioma C6 cell line (ATCC®; cat no CCL-107), U-87MG cell line (ATCC; cat no. HTB-14™) and human glioblastoma T98-G cells (ATCC® CRL-1690™). Cell culture method, experimental pharmacological trials and γ-radiation in vitro, as well as flow cytofluorometry were used in the study. Results: Cytotoxic effect of the tested compounds is stronger than the effect of unsubstituted fascaplysin, and appears to be dose-dependent and time-dependent. 3-bromofascaplysin is more efficient for cancer cells elimination, and by the end of the experiment the amount of living cancer cells in G0 phase remained at its lowest. Cytotoxic effect of 3-bromofascaplysin on glioblastoma T98-G cells is inferior to that of TMZ, and in case of preliminary radiation treatment of cancer cells with 48 Gy the effect of the compound matches the TMZ treatment results. Conclusion: 3-Bromofascaplysin is a prospective chemical compound for development of new anti-cancer chemotherapeutic agents.

Zhidkov, Smirnova, Tryapkin, Kantemirov, Khudyakova, Malyarenko, Ermakova, Grigorchuk, Kaune, Amsberg, Dyshlovoy

A simple approach toward the synthesis of the marine sponge derived pigment fascaplysin was used to obtain the marine alkaloids 3-bromofascaplysin and 3,10-dibromofascaplysin. These compounds were used for first syntheses of the alkaloids 14-bromoreticulatate and 14-bromoreticulatine. Preliminary bioassays showed that 14-bromoreticulatine has a selective antibiotic (to Pseudomonas aeruginosa) activity and reveals cytotoxicity toward human melanoma, colon, and prostate cancer cells. 3,10-Dibromofascaplysin was able to target metabolic activity of the prostate cancer cells, without disrupting cell membrane’s integrity and had a wide therapeutic window amongst the fascaplysin alkaloids.

Meng N., Mu X., Lv X., Wang L., Li N., Gong Y.

Fascaplysin is a natural product isolated from marine sponges that exhibits broad anticancer activity. Previous studies revealed that fascaplysin-induced apoptosis and angiogenesis inhibition in vascular endothelial cells contributed to its anticancer activity. Accumulating evidence indicates that autophagy plays a significant role in mediating the function of vascular endothelial cells (VECs) and the response to cancer therapy. However, the effect of fascaplysin on VEC autophagy and the role of autophagy in fascaplysin-induced vascular endothelial cell apoptosis and angiogenesis inhibition are not clear. The present study found that fascaplysin induced autophagy in vascular endothelial cells. Suppression of autophagy using a pharmacological inhibitor (3-methyladenine) or RNA interference of an essential autophagy gene (ATG5) enhanced the cell death and anti-angiogenesis activity of fascaplysin. We further found that fascaplysin significantly increased p8 protein and reactive oxygen species (ROS) levels and decreased mitochondrial membrane potential but had no effect on the mTOR pathway in VECs. Notably, the ROS scavenger N-acetylcysteine inhibited fascaplysin-induced autophagy and increased p8 protein level. Knockdown of p8 by using RNA interference inhibited the autophagy but increased the level of ROS in VECs. Taken together, these data indicated that fascaplysin activated autophagy as a cytoprotective response via ROS and p8 in VECs. Our findings provided important insight into the response of VECs to fascaplysin and may be useful for improving the anticancer efficacy of fascaplysin.