BACKGROUND AND PURPOSE: Radiotherapy (RT) is an integral treatment part for patients with head and neck squamous cell carcinoma (HNSCC), but radioresistance remains a major issue. Here, we use MitoTam, a mitochondrially targeted analogue of tamoxifen, which we aim to stimulate ferroptotic cell death with, and sensitize radioresistant cells to RT. MATERIALS AND METHODS: We assessed viability, reactive oxygen species (ROS) production, disruption of mitochondrial membrane potential, and lipid peroxidation in radiosensitive (UT-SCC-40) and radioresistant (UT-SCC-5) HNSCC cells following MitoTam treatment. To assess ferroptosis specificity, we used the ferroptosis inhibitor ferrostatin-1 (fer-1). Also, total antioxidant capacity and sensitivity to tert-butyl hydroperoxide were evaluated to assess ROS-responses. 53BP1 staining was used to assess radiosensitivity after MitoTam treatment. RESULTS: Our data revealed increased ROS, cell death, disruption of mitochondrial membrane potential, and lipid peroxidation following MitoTam treatment in both cell lines. Adverse effects of MitoTam on cell death, membrane potential and lipid peroxidation were prevented by fer-1, indicating induction of ferroptosis. Radioresistant HNSCC cells were less sensitive to the effects of MitoTam due to intrinsic higher antioxidant capacity. MitoTam treatment prior to RT led to superadditive residual DNA damage expressed by 53BP1 foci compared to RT or MitoTam alone. CONCLUSION: MitoTam induced ferroptosis in HNSCC cells, which could be used to overcome the elevated antioxidant capacity of radioresistant cells and sensitize such cells to RT. Treatment with MitoTam followed by RT could therefore present a promising effective therapy of radioresistant cancers. STATEMENT OF SIGNIFICANCE: Radiotherapy is applied in the treatment of a majority of cancer patients. Radioresistance due to elevated antioxidant levels can be overcome by promoting ferroptotic cell death combining ROS-inducing drug MitoTam with radiotherapy.

• MeSH
• dlaždicobuněčné karcinomy hlavy a krku radioterapie   farmakoterapie   patologie   MeSH
• ferroptóza * účinky léků   MeSH
• lidé MeSH
• membránový potenciál mitochondrií účinky léků   MeSH
• nádorové buněčné linie MeSH
• nádory hlavy a krku * radioterapie   patologie   farmakoterapie   MeSH
• peroxidace lipidů * účinky léků   MeSH
• reaktivní formy kyslíku * metabolismus   MeSH
• spinocelulární karcinom radioterapie   patologie   farmakoterapie   MeSH
• tamoxifen farmakologie   MeSH
• tolerance záření * účinky léků   MeSH
• viabilita buněk účinky léků   účinky záření   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Activation of the phosphatidylinositol-3-kinase (PI3-K)/protein kinase B (AKT) pathway is associated with three major radioresistance mechanisms: intrinsic radioresistance; tumour-cell proliferation; and hypoxia. Monitoring and manipulation of this signal-transduction pathway can have important implications for the management of head and neck cancer, because activation of the PI3-K/AKT pathway is a frequent event in these tumours. PI3-K/AKT signalling regulates cellular processes, including proliferation, invasion, apoptosis, and the upregulation of hypoxia-related proteins. Activation of this pathway can be caused by stimulation of receptor tyrosine kinases, such as epidermal growth factor receptor (EGFR). In clinical trials, a strong and independent association has been noted between expression of activated AKT and treatment outcome. Therefore, the search for molecular predictors of sensitivity to EGFR-directed treatment should be extended to markers of PI3-K/AKT activation. Another strategy might be the direct targeting and inhibition of this pathway. Such inhibition will enhance the efficacy of radiotherapy, by antagonising radiation-induced cellular defense mechanisms, especially in tumours that have activated the PI3-K/AKT cascade. Thus, the activation status of this pathway might be a key element for the prediction of treatment response and for therapeutic targeting in head and neck cancer.

• MeSH
• aktivace enzymů účinky záření   MeSH
• fosfatidylinositol-3-kinasy metabolismus   účinky záření   MeSH
• hypoxie buňky účinky záření   MeSH
• inhibitory fosfoinositid-3-kinasy MeSH
• lidé MeSH
• nádory hlavy a krku enzymologie   radioterapie   MeSH
• prognóza MeSH
• protoonkogenní proteiny c-akt antagonisté a inhibitory   metabolismus   účinky záření   MeSH
• signální transdukce fyziologie   účinky záření   MeSH
• spinocelulární karcinom enzymologie   radioterapie   MeSH
• Check Tag
• lidé MeSH