Evaluation of 64Cu-ATSM in cell culture for potential use as a radiotherapy agent

2014 Spring.Includes bibliographical references.Oxygen status of tumors is an important clinical factor when considering treatment and potential outcomes. In radiotherapy applications, hypoxic tumors display resistance to traditional low linear energy transfer (LET) external beam radiotherapy (EBRT), instigating interest in finding alternative and more effective means to treat these tumors. 64Cu-diacetyl-bis(N4-methylthiosemicarbazone) (64Cu-ATSM) has shown clinical usefulness in imaging and experimental radiotherapy of solid state tumors due to its ability to concentrate in hypoxic tissue regions and emit radiations of multiple types, energies, and LET. Intrinsic to the potential use of 64Cu-ATSM for radiotherapy purposes is the decay mechanism of 64Cu which emits high LET Auger electrons. Presently, the biological mechanism for cell killing and DNA damage due to high LET electrons released in the decay of 64Cu is unknown. To evaluate how high LET Auger electrons play a role in cell death and DNA damage, Chinese hamster ovary (CHO) cell lines proficient and deficient in DNA nonhomologous end joining (NHEJ) DNA repair (10B2 and xrs-5 cells, respectively) were treated with 64Cu-ATSM. Colony formation assay results show similar cell survival for both cell lines treated with similar activities of 64Cu-ATSM, indicating cell lethality due to high LET radiation. Survival curves were compared for radiations of known LET to generally characterize the effective LET of 64Cu-ATSM. Additionally, chromosome aberration and H2AX DNA double strand break (DSB) studies were performed to examine DNA damage from 64Cu-ATSM. 64Cu-ATSM was also administered to multiple additional cell lines under various -oxic states to evaluate how efficiently 64Cu-ATSM is incorporated. These findings indicate better 64Cu-ATSM uptake in cancerous, canine, and potentially osteosarcoma cell lines. This research offers experimental support for various characteristics of 64Cu-ATSM that may provide potential clinical advantages over traditional EBRT to more effectively treat hypoxic tumors