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Planta Med
DOI: 10.1055/a-2805-4670
Original Papers

Phaeosphaeride A Isolated from an Endophytic Paraphoma sp. Alleviates ABCG2-mediated Resistance to Mitoxantrone in Breast Cancer Cells

Authors

  • Alireza Tavakkoli  ‡

    1   Department of Pharmacognosy, School of Pharmacy, Urmia University of Medical Sciences, Urmia, Iran

  • Hojjat Mortazavi‡

    2   Department of Clinical Pharmacy, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

  • Mehrdad Iranshahi

    3   Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran

  • Fatemeh Kalalinia

    3   Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
    4   Department of Pharmaceutical Biotechnology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

  • Khadijeh Jamialahmadi

    3   Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran

  • Jon S. Thorson

    5   Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA
    6   Center for Pharmaceutical Research and Innovation (CPRI), College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA

  • Khaled A. Shaaban 

    5   Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA
    6   Center for Pharmaceutical Research and Innovation (CPRI), College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA

  • Fatemeh Mosaffa

    3   Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
    4   Department of Pharmaceutical Biotechnology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

This work was supported by Mashhad University of Medical Sciences (grant number: 4001118), the U. S. National Institutes of Health (R37 AI052218), the Center of Biomedical Research Excellence (COBRE) in Translational Chemical Biology (CTCB, NIH P20 GM130456), the U. S. National Institute of Food and Agriculture (USDA-NIFA-CBGP, Grant No. 2023-38821-39584), the University of Kentucky College of Pharmacy, the University of Kentucky Markey Cancer Center, and the U. S. National Center for Advancing Translational Sciences (UL1TR000117 and UL1TR001998). We also thank the University of Kentucky College of Pharmacy PharmNMR Center for analytical support. NMR data were acquired on a Bruker AVANCE NEO 600 MHz high-performance digital NMR spectrometer (supported, in part, by NIH grants P20 GM130456 (J. S. T.) and S10 OD28690).
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Abstract

The efficacy of breast cancer chemotherapies is frequently limited by multidrug resistance (MDR), partly through efflux by ABC transporters, including ABCG2. This study evaluated whether phaeosphaeride A (PPA), a fungal metabolite isolated from a Paraphoma sp. endophyte of Ferula xylorhachis, can modulate ABCG2-mediated resistance to mitoxantrone (MTX). The endophyte was cultured and extracted with ethyl acetate, and the extract was purified by column chromatography and HPLC to yield PPA, whose structure was confirmed by NMR and MS analyses. Cytotoxicity of MTX, PPA, and their combination was assessed in MCF-7- and ABCG2-overexpressing MCF-7/MX cells. MTX showed marked differential cytotoxicity (IC50 = 1.6 µM, 95% CI: 1.4 – 1.9 in MCF-7 vs. > 25 µM in MCF-7/MX; p < 0.0001), whereas PPA exhibited comparable activity in both lines (23.2 µM, 95% CI: 18.0 – 30.1 vs. 36.1 µM, 95% CI: 28.7 – 46.0; p = 0.01). Co-treatment with PPA IC50 significantly reduced MTX IC50 to 0.4 µM (95% CI: 0.3 – 0.6) in MCF-7 and 1.9 µM (95% CI: 1.2 – 2.7) in MCF-7/MX, restoring MTX sensitivity in resistant cells to near MCF-7 levels. Flow cytometry showed that PPA (IC50) increased intracellular MTX accumulation with stronger effects in MCF-7/MX cells (p < 0.0001) than in MCF-7 (p < 0.05). In combination with MTX, PPA (IC50) increased Sub-G1 apoptotic populations in both lines.

These findings demonstrate that PPA is unlikely to be a substrate of ABCG2 but functionally inhibits ABCG2-mediated efflux, contributing to the restoration of MTX sensitivity, although there may be additional mechanisms involved. PPA could be a promising MDR-reversal agent in ABCG2-driven chemotherapy resistance.

Keywords

Ferula xylorhachis - Apiaceae - Paraphoma sp. - fungal secondary metabolite - drug resistance - chemotherapy

Supporting Information

    The NMR data of PPA are presented in Table 1S. Full spectral information of PPA, including 1H NMR, 13C NMR, 1H–1H COSY, HSQC, and HMBC NMR spectra, as well as ESI-MS spectra in both positive and negative ion modes, is provided in Figures 2S–7S and is available as Supporting Information. The fluorescence emission spectra of mitoxantrone, PPA, and mitoxantrone + PPA recorded under cell-free conditions are also provided in Figure 8S.

  • Supporting Information (PDF)


Publication History

Received: 08 September 2025

Accepted after revision: 03 February 2026

Accepted Manuscript online:
04 February 2026

Article published online:
25 February 2026

© 2026. Thieme. All rights reserved.

Georg Thieme Verlag KG
Oswald-Hesse-Straße 14, 70469 Stuttgart, Germany

 

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