LACK OF RADIATION DOSE OR QUALITY DEPENDENCE OF EPITHELIAL-TO-MESENCHYMAL TRANSITION (EMT) MEDIATED BY TRANSFORMING GROWTH FACTOR β

Purpose: Epithelial-to-mesenchymal transition (EMT) is a phenotype that alters cell morphology, disrupts morphogenesis, and increases motility. Our prior studies have shown that the progeny of human mammary epithelial cells (HMECs) irradiated with 2 Gy undergoes transforming growth factor beta (TGF-beta) mediated EMT. In this study we determined whether radiation dose or quality affected TGF-beta-mediated EMT. Methods and Materials: HMECs were cultured on tissue culture plastic or in Matrigel (HI) Biosciences, San Jose, CA) and exposed to low or high linear energy transfer (LET) and TGF-beta (400 pg/mL). Image analysis was used to measure membrane-associated E-cadherin, a marker of functional epithelia, or fibronectin, a product of mesenchymal cells, as a function of radiation dose and quality. Results: E-cadherin was reduced in TGF-beta treated cells irradiated with low-LET radiation doses between 0.03 and 2 Gy compared with untreated, unirradiated cells or TGF-beta treatment alone. The radiation quality dependence of TGF-beta-mediated EMT was determined by use of 1 GeV/amu (gigaelectron volt / atomic mass unit) Fe-56 ion particles at the National Aeronautics and Space Administration's Space Radiation Laboratory. On the basis of the relative biological effectiveness of 2 for Fe-56 ion particles' clonogenic survival, TGF-beta-treated HMECs were irradiated with equitoxic 1-Gy Fe-56 ion or 2-Gy Cs-137 radiation in monolayer. Furthermore, TGF-beta treated HMECs irradiated with either high- or low-LET radiation exhibited similar loss of E-cadherin and gain of fibronectin and resulted in similar large, poorly organized colonies when embedded in Matrigel. Moreover, the progeny of HMECs exposed to different fluences of Fe-56 ion underwent TGF-beta-mediated EMT even when only one-third of the cells were directly traversed by the particle. Conclusions: Thus TGF-beta mediated EMT, like other non-targeted radiation effects, is neither radiation dose nor quality dependent at the doses examined. (c) 2011 Elsevier Inc.