An Investigation of the Early Detection of Radiation Induced Apoptosis by 99mTc-Annexin V and 201Thallium-Chloride in a Lung Cancer Cell Line

This study aims to investigate the efficacy of in vitro Thallium-201 Chloride (Tl-201) and in vitro and in vivo Tc-99m HYNIC-coupled Annexin V (TAV) in the early detection of radiation induced apoptosis, a proxy indicator of radiation therapy (RT) efficacy. In vitro Tl-201 and TAV accumulation and efflux in non-small cell lung cancer were measured post irradiation at 5 different gamma ray doses. The replication rates (RR) of the cell lines were also measured. The same non-small cell lung cancer line was inoculated into the left femur. In vivo non-invasive Tl-201 and TAV tracer biodistribution studies were performed. Cell RR decrease with increased radiation dose was observed 48 hours after irradiation. Apoptotic cell number was found to have increased in response to 9 Gy and 12 Gy radiation dose. Tl-201 accumulation in the 9 Gy and 12 Gy irradiation groups was found to be higher than the lower irradiation groups. Quick Tl-201 efflux was observed in the 9 Gy and 12 Gy irradiated cells. At 48 hours after irradiation with 9 Gy and 12 Gy, Annexin V accumulation was found to be higher than in the control and 3-6 Gy groups. In vivo mouse model confirmed the increased TAV uptake in implanted tumors for relatively high 9 Gy irradiation as compared to non-irradiated controls. TAV may prove to be an effective radiotracer for early assessment of radiation therapy efficacy, via apoptosis, in human lung cancers.