{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T14:16:36Z","timestamp":1778681796356,"version":"3.51.4"},"reference-count":35,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,16]],"date-time":"2025-10-16T00:00:00Z","timestamp":1760572800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["CIMB"],"abstract":"<jats:p>Tempol, a synthetic nitroxide, exhibits dual antioxidant and pro-oxidant activity, requiring millimolar concentrations to induce oxidative stress, which limits its therapeutic use. Glutathione Peroxidase 4 (GPX4) is a critical lipid peroxidase that prevents ferroptosis, and its inhibition has emerged as a strategy to sensitize cancer cells to oxidative stress. To enhance Tempol\u2019s efficacy, we investigated its interaction with ML210, a GPX4 inhibitor, in human colon (HT29) and gastric (CRL-1739) cancer cell lines. We quantified cell viability, oxidative stress markers (H2O2, Total Oxidant Status (TOS), and Total Antioxidant Status (TAS)) and endoplasmic reticulum (ER) stress proteins (ATF6, GRP78, and IRE1\u03b1) in in vitro assays. Synergy was assessed using Bliss independence analysis. The combination of Tempol (2 mM) and ML210 (0.05 \u03bcM) markedly reduced viability in both cell lines. Bliss analysis revealed slight\/moderate synergy for cytotoxicity (\u0394 = +0.15 in HT29; \u0394 = +0.26 in CRL-1739) and strong synergy for H2O2 accumulation (\u0394 = +1.92\u20132.23 across replicates). In contrast, TOS showed moderate-to-strong antagonism across both cell lines, and TAS demonstrated slight synergistic or antagonistic effects. ER stress markers exhibited marker and cell line specific synergy: ATF6 showed strong synergy, IRE1\u03b1 slight synergy in both lines, and GRP78 activation was highly variable, showing strong synergy in CRL-1739 cells but moderate antagonism in HT29 cells. These findings indicate that the cooperative action of Tempol and ML210 is ROS-pool\u2013specific and pathway-selective in the ER. These findings demonstrate that ML210 potentiates Tempol\u2019s pro-oxidant pressure by targeting GPX4, selectively amplifying H2O2 accumulation and ER stress engagement without collapsing global redox balance. This study provides mechanistic rationale for redox\u2013proteostasis co-targeting in gastric and colon cancers and establishes a foundation for in vivo validation.<\/jats:p>","DOI":"10.3390\/cimb47100856","type":"journal-article","created":{"date-parts":[[2025,10,17]],"date-time":"2025-10-17T11:39:34Z","timestamp":1760701174000},"page":"856","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["GPX4 Inhibition Enhances the Pro-Oxidant and ER Stress Effects of Tempol in Colon and Gastric Cancer Cell Lines"],"prefix":"10.3390","volume":"47","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2335-1538","authenticated-orcid":false,"given":"Gorkem","family":"Ozdemir","sequence":"first","affiliation":[{"name":"Department of Gastroenterological Surgery, Adana City Training and Research Hospital, 01230 Adana, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1911-7327","authenticated-orcid":false,"given":"Halil Mahir","family":"Kaplan","sequence":"additional","affiliation":[{"name":"Department of Pharmacology, Faculty of Medicine, \u00c7ukurova University, 01330 Adana, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,16]]},"reference":[{"key":"ref_1","first-page":"209","article-title":"Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries","volume":"71","author":"Sung","year":"2021","journal-title":"CA Cancer J. 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