Varied Photon Radiation Sources Produce Differences in Cellular Response.

In vitro studies allow evaluation of normal or cancer cell responses to radiation, either alone or in combination with agents used to modify these biological responses. Ionizing radiation can be produced by a variety of particles and sources, with varying energy spectra, interaction probabilities, linear energy transfer, dose uniformity, dose rates, and delivery methods. Multiple radiation sources have been used to irradiate cells in the published literature. However, the equivalence of response in cell culture models across radiation sources has not been rigorously established. Moreover, current reporting of radiation source parameters lacks consistency and rigor which may impact the reproducibility of pre-clinical data between laboratories. Relevant choices of radiation source are also of high importance due to growing interest in comparing photon versus particle radiation effect on biological responses. Therefore, this study robustly evaluates the cellular response (cell survival, apoptosis, and DNA damage) of three distinct cell lines using four unique photon generating radiation sources. We hypothesize there may be subtle differences across the radiation sources, without an appreciable difference in cellular response. The four photon irradiation energies investigated, 662 keV, 100 kVp, 220 kVp, 6 MV, did produce subtle differences in DNA damage and cell survival when treating three distinct tumor cell lines. These variations in cellular response emphasize the need to carefully consider irradiation source, energy, and dose rate depending on study goal and endpoint.

A review of Plks: Thinking outside the (polo) box.

The polo-like kinase (Plk) family is comprised of five different members (Plk1-5), each with their own distinct functions. Plk family members participate in pivotal cell division processes as well as in non-mitotic roles. Importantly, Plk expression has been correlated with various disease states, including cancer. Multiples therapies, which primarily target Plk1, are currently being investigated alone or in combination with other agents for clinical use in different cancers. As the role of Plks in disease progression becomes more prominent, it is important to outline their functions as cell cycle regulators and more. This review summarizes the structure and both mitotic and non-mitotic functions of each of the five Plk family members, sequentially. Additionally, the proposed mechanisms for how Plks contribute to tumorigenesis and the therapeutics currently under investigation are outlined.