Abstract 3601: Evaluation and quantification of biomarkers of DNA damage in human plucked hair

Abstract

Abstract The hair follicle is a well vascularised structure that contains rapidly dividing epithelial cells. As a result it is a potentially useful surrogate biomarker for less accessible but highly similar tissues, such as rapidly proliferating tumours. We have developed an ex vivo culture method to validate target expression changes following exposure to DNA damage and/or potential therapeutics. Proof of concept studies performed ex vivo can then inform the design of clinical validation studies. Earlier work evaluated the response of targets such as pERK, pAKT and pSMAD2 to various kinase inhibitors, whilst recently we have used the model to measure the DNA damage response (DDR) following exposure to UV radiation (as a model damaging agent) and more clinically relevant chemotherapeutic agents. Human plucked hair was placed in maintenance media in the presence of known chemotherapeutic agents (such as Gemcitabine, DNA topoisomerase inhibitor I, Irinotecan and Paclitaxel) or exposed to 0.2-0.5J/cm2 UVB radiation. Hairs were then fixed at a range of time points post-exposure and longitudinal sections labelled for various markers including pChk1, gamma-H2AX, p53, Ki67 and thymine dimers (TDM1). Quantitative image analysis to measure the level of labelling was performed using an Aperio® ScanScope®. Following UVB exposure thymine dimer formation occurred immediately on the hair and was stronger on the side directly facing the source of radiation. It was followed rapidly by phosphorylation of Chk1 localised in the inner root sheath at first (10min to 1h after injury), then gamma-H2AX and p53 induction in the outer root sheath. Further studies are looking at DNA damage response in an UV dose dependent manner. Chemotherapeutic agents known for their different mechanism of actions were tested at two concentrations with various responses depending on their mechanism of action. For example, Gemcitabine, which is linked to DNA polymerase inhibition, strongly induced p53 after 24h but no gamma-H2AX activity was seen above background level. We have profiled the large panel of responses for each chemotherapeutic agent, over an acute time course. The ex vivo plucked hair follicle method is a rapid and convenient way of studying the DDR induced by exposure to various DNA damage agents. This model allows for screening of novel chemotherapeutic agents to test their efficacy in preventing or treating DNA damage. Citation Format: Aude-Marine Bonavita, Liam Walker, Adam Boanas, Nicola Tonge, Gregory Tudor, Cath Booth, Ben Reed. Evaluation and quantification of biomarkers of DNA damage in human plucked hair. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3601.