Extracellular cGMP Levels Predict the Response of C4-1 Cervical Cancer Cells to Ionizing Radiation
Urine cyclic guanosine monophosphate (cGMP) has been proposed as a prognostic biomarker for therapy response and the risk of relapse of cervical cancer after treatment with radiotherapy (RT). In the present study, an During exponential growth, C4-1 cells were exposed to IR with doses between 2 and 12 Gy. The cells were harvested at intervals between one and six days. The effect of IR on cell growth and extracellular cGMP levels was dose- as well as time-dependent. Three and six days after IR, the cell fractions were reduced with identical sensitivity (ED50 of 1.9 and 1.8 Gy, respectively). The extracellular cGMP levels showed a fall from the first day to sixth day, both in control and after irradiation (2 and 4 Gy), but with somewhat higher levels after IR. However, the extracellular cGMP levels increased after 8 and 12 Gy exposure by 100% and 270%, respectively. When the data were presented as extracellular cGMP levels (% above control), a clear dose- and time-dependency were observed. From a translational perspective, extracellular cGMP levels may be used to monitor effects and be a potential tool for individualization of radiation therapy (RT).