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Purpose: Propolis, a product of honeybees, has anti-tumoural, cytotoxic, anti-metastatic and anti-inflammatory properties. The aim of this study was the evaluation of the radiosensitising capacity of Propolis in human head and neck squamous cell carcinoma (HNSCC) cells. Materials and methods: HNSCC cell lines (FaDu, UT-SCC15, UT-SCC45), fibroblasts (HSF2) and keratinocytes (HaCaT) were treated with Propolis (0--250 μμg/ml; 1, 4, 24 h) without and in combination with X-rays (0--6 Gy, single dose). Clonogenic survival, proliferation, apoptosis, expression and phosphorylation of different signalling proteins were determined. Liquid chromatography-mass spectrometry (LC-MS) was performed on Propolis. Results: Propolis significantly ( P < 0.01) reduced cell growth and clonogenic survival in a time- and concentration-dependent manner. Propolis-induced apoptosis and Caspase 3 cleavage, increased phosphorylation of Extracellular signal Regulated Kinase 1/2 (ERK1/2), protein kinase B/Akt1 (Akt1) and Focal adhesion kinase (FAK). While a 1-h Propolis pretreatment was ineffective, a 3-h pretreatment significantly ( P < 0.05) radiosensitised FaDu cells. LC-MS analysis identified 14 compounds of Propolis. Conclusions: Our data show that Propolis exerts cytotoxicity in a concentration- and time-dependent manner. In one out of three HNSCC cell lines, Propolis also caused an enhancement of radiosensitivity. Future studies on Propolis will shed further light on its potential as an adjuvant to radiotherapy. [ABSTRACT FROM AUTHOR]

Purpose: Radiation therapy (RT) is a commonly used modality to treat human cancer. However, dose-limiting toxicity and resistance are major problems to improving treatment efficacy. Increasing evidence has pointed to the critical role of the tumor microenvironment and cell-extracellular matrix (ECM), specifically via β1 integrins, in modifying response to therapy, including radiation. β1 integrins have been implicated in several key processes in malignant progression and metastasis, and more recently in mediating resistance to cytotoxic chemotherapy and radiation. Evidence is mounting that β1 integrins mediate essential survival signals post-IR, through both canonical and non-canonical integrin signaling pathways that make it a highly promising therapeutic target for several solid malignancies. Conclusions: In this mini-review article, we briefly summarize the most recent emerging findings concerning β1 integrin and radiation survival that indicate the promise of β1 integrin inhibitory agents as radiosensitizers. [ABSTRACT FROM AUTHOR]