Congrats to Tyron and Ivan for the acceptance of the manuscript “Cross-Correlative Single-Cell Analysis Reveals Biological Mechanisms of Nanoparticle Radiosensitization” in ACS Nano. The article is online here.
Nanoparticle radiosensitization has been well demonstrated to enhance effects of radiotherapy, motivated to improve therapeutic ratios and decrease morbidity in cancer treatment. A significant challenge exists in optimizing formulations and translation due to insufficient knowledge of the associated mechanisms which have historically been limited to physical concepts. Here we investigated a concept for the role of biological mechanisms. The mere presence of gold nanoparticles lead to a down regulation of thymidylate synthase, important for DNA damage repair in the radioresistant S phase cells. By developing a cross-correlative methodology to reveal probabilistic gold nanoparticle uptake by cell sub-populations and the associated sensitization as a function of the uptake, a number of revealing observations have been achieved. Surprisingly, for low numbers of nanoparticles a desensitization action was observed. Sensitization was discovered to preferentially impact S phase cells where impairment of the DNA damage response by the homologous recombination pathway dominates. This small but radioresistant cell population correlates with much greater proliferative ability. Thus a paradigm is presented whereby enhanced DNA damage is not necessarily due to an increase in the number of DNA Double Strand Breaks (DSBs) created, but can be from a nanoparticle-induced impairment of the damage response by down regulating repair proteins such as thymidylate synthase.