Synthesis and biological evaluation of santacruzamate A and analogs as potential anticancer agents

Progress in the discovery and development of anticancer agents from marine cyanobacteria

Covering 2010-April 2024There have been tremendous new discoveries and developments since 2010 in anticancer research based on marine cyanobacteria. Marine cyanobacteria are prolific sources of anticancer natural products, including the tubulin agents dolastatins 10 and 15 which were originally isolated from a mollusk that feeds on cyanobacteria. Decades of research have culminated in the approval of six antibody-drug conjugates (ADCs) and many ongoing clinical trials. Antibody conjugation has been enabling for several natural products, particularly cyanobacterial cytotoxins. Targeting tubulin dynamics has been a major strategy, leading to the discovery of the gatorbulin scaffold, acting on a new pharmacological site. Cyanobacterial compounds with different mechanisms of action (MOA), targeting novel or validated targets in a range of organelles, also show promise as anticancer agents. Important advances include the development of compounds with novel MOA, including apratoxin and coibamide A analogues, modulating cotranslational translocation at the level of Sec61 in the endoplasmic reticulum, largazole and santacruzamate A targeting class I histone deacetylases, and proteasome inhibitors based on carmaphycins, resembling the approved drug carfilzomib. The pipeline extends with SERCA inhibitors, mitochondrial cytotoxins and membrane-targeting agents, which have not yet advanced clinically since the biology is less understood and selectivity concerns remain to be addressed. In addition, efforts have also focused on the identification of chemosensitizing and antimetastatic agents. The review covers the state of current knowledge of marine cyanobacteria as anticancer agents with a focus on the mechanism, target identification and potential for drug development. We highlight the importance of solving the supply problem through chemical synthesis as well as illuminating the biological activity and in-depth mechanistic studies to increase the value of cyanobacterial natural products to catalyze their development.

Folic acid functionalization for targeting self-assembled paclitaxel-based nanoparticles

Hetero-nanoparticles self-assembled from a conjugate bearing folic acid as the targeting agent, and another bearing paclitaxel as the active agent are reported. Hetero-nanoparticles containing varying percentages of folic acid conjugates are characterised, and their biological activity is determined.

Design, Multicomponent Synthesis, and Anticancer Activity of a Focused Histone Deacetylase (HDAC) Inhibitor Library with Peptoid-Based Cap Groups

In this work, we report the multicomponent synthesis of a focused histone deacetylase (HDAC) inhibitor library with peptoid-based cap groups and different zinc-binding groups. All synthesized compounds were tested in a cellular HDAC inhibition assay and an MTT assay for cytotoxicity. On the basis of their noteworthy activity in the cellular HDAC assays, four compounds were further screened for their inhibitory activity against recombinant HDAC1-3, HDAC6, and HDAC8. All four compounds showed potent inhibition of HDAC1-3 as well as significant inhibition of HDAC6 with IC₅₀ values in the submicromolar concentration range. Compound 4j, the most potent HDAC inhibitor in the cellular HDAC assay, revealed remarkable chemosensitizing properties and enhanced the cisplatin sensitivity of the cisplatin-resistant head-neck cancer cell line Cal27CisR by almost 7-fold. Furthermore, 4j almost completely reversed the cisplatin resistance in Cal27CisR. This effect is related to a synergistic induction of apoptosis as seen in the combination of 4j with cisplatin.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Cellular analysis of the action of epigenetic drugs and probes

Small molecule drugs and probes are important tools in drug discovery, pharmacology, and cell biology. This is of course also true for epigenetic inhibitors. Important examples for the use of established epigenetic inhibitors are the study of the mechanistic role of a certain target in a cellular setting or the modulation of a certain phenotype in an approach that aims toward therapeutic application. Alternatively, cellular testing may aim at the validation of a new epigenetic inhibitor in drug discovery approaches. Cellular and eventually animal models provide powerful tools for these different approaches but certain caveats have to be recognized and taken into account. This involves both the selectivity of the pharmacological tool as well as the specificity and the robustness of the cellular system. In this article, we present an overview of different methods that are used to profile and screen for epigenetic agents and comment on their limitations. We describe not only diverse successful case studies of screening approaches using different assay formats, but also some problematic cases, critically discussing selected applications of these systems.

Synthesis and biological evaluation of santacruzamate A analogues for anti-proliferative and immunomodulatory activity

Santacruzamate A (SCA) is a natural product isolated from a Panamanian marine cyanobacterium, previously reported to have potent and selective histone deacetylase (HDAC) activity. To optimize the enzymatic and cellular activity, 40 SCA analogues were synthesized in a systematic exploration of the zinc-binding group (ZBG), cap terminus, and linker region. Two cap group analogues inhibited proliferation of MCF-7 breast cancer cells, with analogous increased degranulation of cytotoxic T cells (CTLs), while one cap group analogue reduced CTL degranulation, indicative of suppression of the immune response. Additional testing of these analogues resulted in reevaluation of the previously reported SCA mechanism of action. These analogues and the resulting structure-activity relationships will be of interest for future studies on cell proliferation and immune modulation.