{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T08:29:45Z","timestamp":1787041785667,"version":"build-2736575974"},"reference-count":28,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T00:00:00Z","timestamp":1787011200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Cancers"],"abstract":"<jats:p>Background: Small-cell lung cancer (SCLC) has a poor prognosis because of the development of drug resistance. Our previous studies showed that the plant steroid hormone, epibrassinolide (EB), interacts with human SCLC cells through inhibition of GSK3\u03b2-mediated signaling and overcomes drug resistance. However, the latter does not occur via membrane-mediated drug efflux, a commonly reported mechanism. Methods: We investigated a novel mechanism, ferroptosis, for drug resistance and the effects of EB. Pharmacological, cellular and molecular investigations were performed. We used drug-sensitive (NCI-H69) and multi-drug-resistant (VPA) SCLC cell lines. Results: 4-hydroxynonenal (HNE), a marker for lipid peroxidation and ferroptosis, was lower in drug-resistant VPA cells than drug-sensitive cells (H69) (22 vs. 60 pg\/mg protein). Incubation with EB at a dose that reverses drug resistance in VPA cells increased HNE (94 pg\/mg). Exogenously applied HNE increased intracellular HNE and reversed drug resistance (IC50 for etoposide in VPA cells at 7.5 \u00b5M (untreated) vs. 1.0 \u00b5M (treated)). Ferrostatin, which inhibits ferroptosis, reduced HNE accumulation and increased drug resistance (IC50 for etoposide at 5.5 \u00b5M (untreated) vs. 19 \u00b5M (treated)). As measured by phosphorylation, the signaling molecule Akt was more active in drug-resistant compared to drug-sensitive SCLC cells. This activation was accompanied by increased drug resistance. Both EB and a specific inhibitor of Akt phosphorylation\/activation reversed this resistance. Akt activation was reflected in increased GSK3\u03b2 activity. The latter was also inhibited by incubation in EB. The level of the GSK3\u03b2-controlled \u201cantioxidant transcription factor\u201d NRF2 was higher in drug-resistant VPA cells than drug-sensitive H69 cells. This increase was reversed in EB-treated cells. The protein level of the \u201cantioxidant enzyme\u201d, GPX4, which chemically reduces peroxidized lipids, was higher in VPA than H69 cells (21.2 vs. 10.1 pg\/mg protein). Likewise, GPX4 enzyme activity was higher in drug-resistant than drug-sensitive cells. Incubation with EB reversed these increases. Incubation of SCLC cells with RSL3, a specific inhibitor of GPX4 activity, increased intracellular HNE and reversed drug resistance in VPA cells. Conclusions: These data indicate that ferroptosis is an important mechanism for drug resistance in SCLC cells and the plant steroid, EB, reverses drug resistance by interfering with the Akt signaling pathway and GPX4 anti-oxidant activity.<\/jats:p>","DOI":"10.3390\/cancers18162659","type":"journal-article","created":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T08:08:41Z","timestamp":1787040521000},"page":"2659","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["The Plant Steroid Hormone, Epibrassinolide, Reverses Drug Resistance in Small-Cell Lung Carcinoma Cells by Modulating Ferroptosis"],"prefix":"10.3390","volume":"18","author":[{"given":"David","family":"Sadava","sequence":"first","affiliation":[{"name":"Department of Cancer Biology and Molecular Medicine, Beckman Research Institute, City of Hope, 1500 East Duarte Rd., Duarte, CA 91010, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4482-6926","authenticated-orcid":false,"given":"Shiuan","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Cancer Biology and Molecular Medicine, Beckman Research Institute, City of Hope, 1500 East Duarte Rd., Duarte, CA 91010, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,18]]},"reference":[{"key":"ref_1","first-page":"e70043","article-title":"Cancer statistics, 2026","volume":"76","author":"Siegel","year":"2026","journal-title":"CA Cancer J. Clin."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1906","DOI":"10.1001\/jama.2025.0560","article-title":"Small cell lung cancer: A review","volume":"333","author":"Kim","year":"2025","journal-title":"JAMA"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1038\/s41572-020-00235-0","article-title":"Small cell lung cancer","volume":"7","author":"Rudin","year":"2021","journal-title":"Nat. Rev. Dis. Prim."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1112","DOI":"10.1007\/s11864-024-01245-w","article-title":"Small cell lung cancer\u2014Update on chemotherapy resistance","volume":"25","author":"Ying","year":"2024","journal-title":"Curr. Treat. Opin. Oncol."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Das, S., and Samaddar, S. (2025). Recent advances in clinical translation of small-cell lung cancer therapeutics. Cancers, 17.","DOI":"10.3390\/cancers17020255"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"664","DOI":"10.1002\/cncr.29098","article-title":"Small cell lung cancer: Where do we go from here?","volume":"121","author":"Byers","year":"2015","journal-title":"Cancer"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"526","DOI":"10.1158\/1078-0432.CCR-21-1943","article-title":"Activation of PI3K\/AKT pathway is a potential mechanism of treatment resistance in small cell lung cancer","volume":"28","author":"Jin","year":"2022","journal-title":"Clin. Can. Res."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Bebber, C.M., Muller, F., Preity, C., Weber, J., and Von Karlstdet, S. (2020). Ferroptosis in cancer cell biology. Cancers, 9.","DOI":"10.3390\/cancers12010164"},{"key":"ref_9","first-page":"176","article-title":"Ferroptosis as a potential cell death mechanism against a cisplatin-resistant lung cancer cell line","volume":"13","author":"Golbashiszadeh","year":"2023","journal-title":"Adv. Pharm. Bull."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1","DOI":"10.20517\/cdr.2024.151","article-title":"Ferroptosis related signaling pathways in cancer drug resistance","volume":"8","author":"Yang","year":"2025","journal-title":"Cancer Drug Resist."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"508","DOI":"10.1007\/s12672-025-02234-7","article-title":"Unveiling the therapeutic potential of ferroptosis in lung cancer: A comprehensive analysis and future therapeutic insights","volume":"10","author":"Song","year":"2025","journal-title":"Discov. Oncol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/S0304-3835(02)00005-8","article-title":"Transferrin overcomes drug resistance to artemisinin in human small cell lung carcinoma cells","volume":"179","author":"Sadava","year":"2002","journal-title":"Cancer Lett."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"295","DOI":"10.1105\/tpc.19.00335","article-title":"Brassinosteroids: Multidimensional regulators of plant growth, development and stress responses","volume":"32","author":"Nolan","year":"2020","journal-title":"Plant Cell"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Manghwar, H., Hussain, A., Ali, Q., and Liu, F. (2022). Brassinosteroids (BR) role in plant development and coping with different stresses. Int. J. Mol. Sci., 18.","DOI":"10.3390\/ijms23031012"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"783","DOI":"10.1016\/j.bbrc.2017.08.094","article-title":"The effect of brassinolide, a plant steroid hormone, on drug resistant small cell lung carcinoma cells","volume":"493","author":"Sadava","year":"2017","journal-title":"Biochem. Biophys. Res. Commun."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Sadava, D., and Chen, S. (2024). Molecular interactions of the plant steroid hormone epibrassinolide on human drug-sensitive and drug-resistant small cell lung carcinoma cells. Cancers, 16.","DOI":"10.3390\/cancers16223812"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Su, H., Peng, C., and Liu, Y. (2024). Regulation of ferroptosis by P13K\/Akt signaling pathways: A promising therapeutic axis in cancer. Front. Cell Dev. Biol., 12.","DOI":"10.3389\/fcell.2024.1372330"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Takahara, H., Kanazawa, T., Oshita, H., and Tomita, Y. (2024). GPX4 and FSP1 expression in lung adenocarcinoma: Prognostic implications and ferroptosis- based therapeutic strategies. Cancers, 16.","DOI":"10.3390\/cancers16223888"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1007\/BF02897284","article-title":"Characterization of etoposide-resistant small cell lung carcinoma cells","volume":"26","author":"Minato","year":"1990","journal-title":"Cancer Chemother. Pharmacol."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Sadava, D., and Chen, S. (2023). Castasterone, a plant steroid hormone, affects human small cell lung cancer cells and reverses drug resistance. Pharmaceuticals, 16.","DOI":"10.3390\/ph16020170"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"440","DOI":"10.1158\/0008-5472.CAN-09-1947","article-title":"Drug combination studies and their synergy quantification using the Chou-Talay method","volume":"70","author":"Chou","year":"2010","journal-title":"Cancer Res."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Peng, C., Chen, Y., and Jians, M. (2024). Targeting ferroptosis: A promising strategy to overcome drug resistance in breast cancer. Front. Oncol., 14.","DOI":"10.3389\/fonc.2024.1499125"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"280","DOI":"10.1038\/s41571-020-00462-0","article-title":"Broadening horizons: The role of ferroptosis in cancer","volume":"18","author":"Chen","year":"2021","journal-title":"Nat. Rev. Clin. Oncol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"101328","DOI":"10.1016\/j.redox.2019.101328","article-title":"Insight into the mechanism of ferroptosis inhibition by ferrostatin-1","volume":"28","author":"Miotto","year":"2020","journal-title":"Redox Biol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"467","DOI":"10.18632\/oncotarget.293","article-title":"Phosphorylation of AKT: A mutational analysis","volume":"2","author":"Hart","year":"2011","journal-title":"Oncotarget"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Yan, R., Lin, B., Jin, W., Tang, L., Hu, S., and Cai, R. (2023). NRF2, a superstar of ferroptosis. Antioxidants, 12.","DOI":"10.20944\/preprints202308.1554.v1"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"144","DOI":"10.1016\/j.freeradbiomed.2018.09.014","article-title":"Role of GPX4 in ferroptosis and its pharmacological implication","volume":"133","author":"Seibt","year":"2019","journal-title":"Free Radic. Biol. Med."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Sui, X., Zhang, R., Liu, S., Duan, T., Zhai, L., Zhang, L., Zhang, M., Han, X., Xiang, Y., and Xie, T. (2018). RSL3 drives ferroptosis through GPX4 inactivation and ROS production in colorectal cancer. Front. Pharmacol., 9.","DOI":"10.3389\/fphar.2018.01371"}],"container-title":["Cancers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-6694\/18\/16\/2659\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T08:16:16Z","timestamp":1787040976000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-6694\/18\/16\/2659"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,18]]},"references-count":28,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2026,8]]}},"alternative-id":["cancers18162659"],"URL":"https:\/\/doi.org\/10.3390\/cancers18162659","relation":{},"ISSN":["2072-6694"],"issn-type":[{"value":"2072-6694","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,18]]}}}