Aim:  Radiation therapy (RT) continues to be one of the most popular treatment options for localized prostate cancer (CaP). Understanding the mechanisms and signalling pathways of radioresistance will help to overcome recurrence after RT in CaP patients. Our objectives in this study were to developradiation resistant CaP cell lines with RT treatment, investigate whether these radiation resistant cancer cell lines are related with epithelial mesenchymal transition (EMT) and find the mechanisms and signalling pathways involved in redioresistance for future CaP treatment.

Methods: Three CaP cell lines (PC-3, DU145 and LNCaP) were treated by irradiation at a 2Gy dose each day for 5 consecutive days and the morphological changes of the RT-treated cells were recorded daily with an inverted microscope. The growth of RT-treated and untreated CaP cells were compared by a proliferation assay and the expression of EMT markers including E-cadherin, Vimentin, OCT3/4, OCT4 and SOX2 was examined by immunocytochemistry and immunofluorescence, and  further confirmed by Western blotting.

Results: We have developed three radiation resistant CaP cell lines with the morphological changes including loss of glandular pattern, vacuolated cell plasma, pleomorphic nuclei and enlarged size. We found that after 2 Gy/per day for 5 days ,the proliferation rate in RT-treated CaP cells was obviously reduced compared to those without RT treatment. The expression of Vimentin was increased in RT-treated CaP cells compared to those without RT treatment while the expression of E-cadherin, OCT3/4, OCT4 and SOX2 in RT-treated CaP cells were reduced in RT-treated CaP cells compared to un-treated CaP cells. These results are consistent with previous reports for EMT characteristic in cancer treatment. 

Conclusion: With 2Gy RT, we have developed three radiation resistant CaP cell lines with EMT characteristic which can be used for future in vitro and in vivo studies for CaP diagnosis and treatment.