Heat shock protein 90 (Hsp90) is a molecular chaperone that plays a key role in protecting the proteome. In cancer cells, this Hsp90 function is hijacked to promote cancer cell proliferation. Except for the Pimitespib (TAS-116), approved for clinical use in Japan in 2022, no Hsp90 inhibitors have yet been approved by the FDA. One of the main side effects of the current Hsp90 inhibitors tested in the clinic is their induction of the heat shock response (HSR). Therefore, identifying new inhibitors that destabilize the oncoproteins clients of Hsp90 without inducing HSR is an attractive strategy to harness the clinical potential. We previously reported that the natural product Enniatin A (EnnA) is a novel Hsp90 inhibitor satisfying this criterion. Here, we report that EnnA potently induces mitophagy in breast cancer cells. The cytoplasmic form of Hsp90 has been shown to be more abundant in the mitochondria of tumor cells compared to mitochondria of normal tissues. We show that EnnA can enter multiple compartments of cancer cells, including the mitochondria, and inhibits Hsp90. Furthermore, we show that EnnA induces mitochondrial dynamics impairment as reflected by loss of mitochondrial membrane potential, reduced oxygen consumption rate, and loss of ATP production. We also show that targeting Hsp90 by EnnA reduced the level of cox4, a component of the electron transport chain, leading to parkin-mediated mitophagy. Our data indicate that EnnA represents a member of a new class of Hsp90 inhibitors that impair mitochondrial function in cancer cells and is a promising compound to treat breast cancer. Vamsi Krishna Kommalapati, Asif Elahi, Nada M. Eisa, Michael A. Serwetnyk, Abdessamad Debbab, siva panda, Daniela Marasco, Brain Blagg, Ahmed Chadli. The cyclopeptide enniatin a inhibits the chaperone hsp90 and induces mitophagy in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3060.

The Heat-shock protein 90 (Hsp90), emerged as an exciting molecular target in the late 90s after being recognized as the driving force behind the Ansamycin antibiotic geldanamycin's antitumoral activity. Since then, extensive research has been conducted to develop Hsp90 inhibitors for clinical applications in cancer therapy. Specifically in triple-negative breast cancer (TNBC), studies have shown that using Hsp90 inhibitors as single agents, or in combination with immunotherapy can offer new leads to better therapeutic efficacy. However, traditional inhibitors targeting the N-terminal domain of Hsp90 often trigger a heat shock response (HSR) or are pan-inhibitors which results in detrimental side effects in clinical trials. Considering this, this study aims to identify and characterize small molecules that can inhibit Hsp90 and degrade its oncogenic client proteins, without inducing the HSR. Using a high-throughput progesterone reconstitution screening assay, a cyclic peptide, AD05, was identified from medicinal plant extracts and their symbiotic microorganisms. This compound is intriguing because it inhibits Hsp90 in a distinct manner from the classical N-terminal Hsp90 inhibitor tested in Phase III clinical trials; 17-N-allylamino-demethoxygeldanamycin (17-AAG) and does not induce the HSR. The binding of AD05 to Hsp90 was further characterized in purified and cell-based systems using IP linked to LC-MS, molecular docking analysis, cellular thermal shift assay (CETSA), and Western blot that showed an efficient degradation of oncogenic client proteins. AD05 exhibited significant cytotoxicity against cancer cells evaluated in MTT assays compared to normal cells, immunohistochemistry (IHC), immunofluorescence, electron microscopy, and Seahorse metabolic analyses. Our findings suggest that bioactive natural products are effective and promising inhibitors against the Hsp90 machine for cancer research and therapy. Ilham Zarguan, Sumin Lu, vamsi Krishna Kommalapati, Alisha Hussain, Dhruvi Paladiya, Wayne Fang, Lamiae Belayachi, Abdelaziz Benjouad, Abdessamad Debbab, Ahmed Chadli. Developing the cyclic peptide AD05 as a novel Hsp90 inhibitor for triple-negative breast cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3055.

Low response rates and immune-related adverse events limit the impact of cancer immunotherapy. To improve clinical outcomes, preclinical studies have shown that combining immunotherapies with N-terminal Hsp90 inhibitors resulted in improved efficacy, even though induction of an extensive heat shock response (HSR) with these inhibitors limited their clinical efficacy as monotherapies. We discovered that Enniatin A (EnnA) binds to the interface between the middle domains of the Hsp90 dimer and destabilizes Hsp90 client oncoproteins without inducing an HSR. EnnA induces cancer cell immunogenic cell death in aggressive breast cancer models and exhibits superior anti-tumor activity compared to Hsp90 N-terminal inhibitors. EnnA reprograms the tumor microenvironment in syngeneic mouse models to promote CD8+ T cell-dependent anti-tumor activity mediated through a reduced level of PD-L1 and activation of CX3CR1 pathway. We propose that EnnA is a promising anti-tumor agent with a mechanism of action involving immunogenic cancer cell toxicity and mobilization of CD8+ T cells into the tumor site. Citation Format: Nada Eisa, Vincent M. Crowley, Asif Elahi, Vamsi K. Kommalapati, Hasan Korkaya, Abdessamad Debbab, Brian Blagg, Ahmed Chadli. Targeting the chaperone Hsp90 to activate the immune system and eradicate the triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2272.

Low response rates and immune-related adverse events limit the remarkable impact of cancer immunotherapy. To improve clinical outcomes, preclinical studies have shown that combining immunotherapies with N-terminal Hsp90 inhibitors resulted in improved efficacy, even though induction of an extensive heat shock response (HSR) and less than optimal dosing of these inhibitors limited their clinical efficacy as monotherapies. We discovered that the natural product Enniatin A (EnnA) targets Hsp90 and destabilizes its client oncoproteins without inducing an HSR. EnnA triggers immunogenic cell death in triple-negative breast cancer (TNBC) syngeneic mouse models and exhibits superior antitumor activity compared to Hsp90 N-terminal inhibitors. EnnA reprograms the tumor microenvironment (TME) to promote CD8+ T cell-dependent antitumor immunity by reducing PD-L1 levels and activating the chemokine receptor CX3CR1 pathway. These findings provide strong evidence for transforming the immunosuppressive TME into a more tumor-hostile milieu by engaging Hsp90 with therapeutic agents involving novel mechanisms of action.

The endophytic fungus Chaetomium sp. was separated from the medicinal plant Salvia officinalis growing in Egypt and cultivated on solid rice medium. Chemical investigation of the EtOAc extract yielded a new hydroperoxycochliodinol derivative (1) in addition to several known compounds, which included cochliodinol (2), isocochliodinol (3), chaetomin (4), and two simple indole derivatives (5, 6). The structure of the new compound was determined by comprehensive NMR studies including DEPT, COSY, HMQC, HMBC, and HR-MS. All compounds were tested for their cytotoxic activity against L5178Y cells. Compounds 1, 2, and 4 showed cytotoxic activity with EC50 values between 3.5–5.0 μg/mL, whereas compounds 3, 5, and 6 were inactive.

Structurally diverse natural products are valued for their targeted biological activity. The challenge of working with such metabolites is their low natural abundance and complex structure, often with multiple stereocenters, precludes large-scale or unsophisticated chemical synthesis. Since select plants contain the enzymatic machinery necessary to produce specialized compounds, tissue cultures can be used to achieve key transformations for large-scale chemical and/or pharmaceutical applications. In this context, plant tissue-culture bio-transformations have demonstrated great promise in the preparation of pharmaceutical products. This review describes the capacity of cultured plant cells to transform terpenoid natural products and the specific application of such transformations over the past three decades (1988-2019).

Three secondary metabolites; dihydroxanthenone AGI-B4, syndowinin B and pitholide B were isolated for the first time from the ethyl acetate extract of the solid rice cultures of Pestalotiopsis clavispora, isolated from Phoenix reclinata Jacq. Family, Arecaceae collected in Nigeria.

Further chemical investigation of the butanol fraction of Olax mannii Oliv. (Olacaceae) methanol leaf extract led to the isolation of two new kaempferol triglycosides namely: kaempferol 3-O-[α-l-rhamnopyranosyl (1→2) α-l-arabinofuranoside]-7-O-α-l-rhamnopyranoside, (1) and kaempferol 3-O-[α-l-apiofuranosyl (1→2) β-D- galactopyranoside]-7-O-α-l-rhamnopyranoside (2). The structures of the isolated compounds were determined by detailed analysis of their one- and two-dimensional NMR and high-resolution mass spectra. The compounds were screened for antimicrobial activity against strains of bacteria and fungi.

Fractionation of n-Hexane-CH2Cl2 (1:1) extract of dried leaves of Tarchonanthus camphoratus afforded seven Sesquiterpene acids derivatives (3-8, 10) and diazomethane treatment afforded four 1-2a and 9. The structures of these compounds were determined by extensive 1D and 2D NMR analyses, We report here the isolation and characterization of unreported sesquiterpene compounds isolated for the first time from T. camphoratus.

AbstractThe structure of previously reported lateritin with hitherto unknown absolute configuration is established to be identical with beauvericin (I), a trimeric lactone of lateritin.

AbstractFrom newly isolated sesquiterpenes (I), (II), and (III) only (I) shows intermediate inhibition of NO production in a mouse peritoneal macrophage system (IC50: 15.7 μM).

•Endophytic fungus, KL.1.1 was isolated from Psidium guajava leaves.•The fungal extracts showed 100% inhibition of mouse lympohma cell line (L5178Y).•Two new cytochalasins where isolated from the extracts of this endophytic fungus.•Five known cytochalasins where also isolated.•These molecules hold potential for further development into novel anticancer drugs.

New sesquiterpenes tanacetolide A–C (1–3) were isolated from aTanacetum sinaicumextract together with known compounds (4–10).

Ethnopharmacological relevance: Olax mannii Oliv. (Olacaceae) is among the many medicinal plants used in Nigeria for the ethnomedicinal management of both cancer and inflammation. Such plants represent potential sources of innovative therapeutic agents for the treatment of cancer and other malignant disorders. While the majority of medicinal plants exert their anticancer effects by direct cytotoxicity on tumor cells, it is important that other mechanisms through which these plants can exhibit anticancer effects are investigated. Preliminary studies indicated that Olax mannii leaves are rich sources of novel flavonoid glycosides. The detailed chemistry as well the mechanisms through which these flavonoid constituents may exert their cancer chemo-preventive and therapeutic effects are, however, not yet investigated.Aim of the study: The aim of this study is to carry out a detailed chemical investigation of Olax mannii leaves and the effects of the isolated constituents on the nuclear factor kappa B (NF-kappa B) pathway.Materials and methods: A methanol leaf extract was subjected to various chromatographic separations to achieve isolation of flavonoid glycosides and the structures of the isolated compounds were elucidated by a combination of 1D and 2D NMR and high resolution mass spectrometry. Biological activities were assessed by measurement of cellular viability and proliferation using quantitative IncuCyte videomicroscopy, trypan blue staining and by quantification of the number of metabolically active K562 cells based on quantitation of ATP. The effect of the compounds on the inhibition of the NF-kappa B pathway as well as toxicity towards peripheral blood mononuclear cells to evaluate differential toxicity was also assayed.Results: Chemical investigation of the methanol leaf extract of the plant material led to the isolation of three new flavonoid triglycosides, kaempferol 3-O-[alpha-D-apiofuranosyl-(1 -> 2)-alpha-L-arabinofuranoside]-7-O-alpha-L-rhamnopyranoside (1), kaempferol 3-O-[beta-D-glucopyranosyl-(1 -> 2)-alpha-L-arabinofuranosidej-7-O-alpha-L-rhamnopyranoside (2), kaempferol 3-O-[beta-D-arabinopyranosyl-(1 -> 4)-alpha-L-rhamnopyranosidej-7-O-alpha-L-rhamnopyranoside (3), in addition to fourteen known flavonoid glycosides (4-17). Of all the tested compounds, only compound 9 (kaempferol 3-O-alpha-L-rhamnopyranoside) exhibited promising and specific antiproliferative activity on human K562 chronic myelogenous leukemia cells and dose-dependently inhibited NF-kappa B transactivation.Conclusion: The presence of this flavonoid glycoside and derivatives may account for the reported efficacy of Olax mannii leaf extract in the ethnomedicinal management of cancer and inflammation. (c) 2015 Elsevier Ireland Ltd. All rights reserved.

A chemical investigation of the endophytic fungus Epicoccum nigrum isolated from leaves of Mentha suaveolens collected in Morocco resulted in the isolation of five new polyketides, epicocconigrones A and B (1 and 2), 3-methoxyepicoccone B (3), 3-methoxyepicoccone (4), and 2,3,4-trihydroxy-6-(methoxymethyl)-5-methylbenzaldehyde (5), together with five known compounds (6-10). The structures of the new compounds were unambiguously determined by extensive analysis of the 1D and 2D NMR and mass spectroscopic data. Compounds 1 and 10 showed potent inhibition of at least 15 protein kinases with IC50 values ranging from 0.07 to 9.00 μM. Moreover, compounds 1 and 10 inhibited histone deacetylase (HDAC) activities with IC50 values of 9.8 and 14.2 μM, respectively. A preliminary structure-activity relationship is discussed. Interestingly, compounds 1 and 10 exert mainly cytostatic effects in human lymphoma RAJI and U-937 cell lines.

Neosartorin (1) was isolated from the endophytic fungus Aspergillus fumigatiaffinis. The absolute configuration of 1, including both axial and central chirality elements, was established as (aR,5S,10R,5′S,6′S,10′R) for the first time on the basis of its electronic circular dichroism (ECD) spectra aided with TDDFT–ECD calculations. Neosartorin (1) exhibited substantial antibacterial activity against a broad spectrum of Gram-positive bacterial species including staphylococci, streptococci, enterococci, and Bacillus subtilis with minimal inhibitory concentrations in the range of 4–32μg/mL. When the toxicity of 1 against eukaryotic cells was measured using a panel of different cancer cell lines such as HELA and BALB/3T3, the average IC50 values exceeded 32μg/mL.

Chemical investigation of the EtOAc extract of the fungus Chaetomium aureum, an endophyte of the Moroccan medicinal plant Thymelaea lythroides, afforded one new resorcinol derivative named chaetorcinol, together with five known metabolites. The structures of the isolated compounds were determined on the basis of one- and two-dimensional NMR spectroscopy and high-resolution mass spectrometry as well as by comparison with the literature. All compounds were tested for their activity towards the Hsp90 chaperoning machine in vitro using the progesterone receptor (PR) and rabbit reticulocyte lysate (RRL). Among the isolated compounds, only sclerotiorin efficiently inhibited the Hsp90 machine chaperoning activity. However, sclerotiorin showed no cytotoxic effect on breast cancer Hs578T, MDA-MB-231 and prostate cancer LNCaP cell lines. Interestingly, deacetylation of sclerotiorin increased its cytotoxicity toward the tested cell lines over a period of 48 h.