Predicting Anticancer Drug Efficacy by Assessing DNA Repair Ability

Abstract

A significant challenge in cancer therapy is the development of drug resistance by tumor cells. Evidences suggest a direct connection between DNA repair ability and tumor resistance in chemotherapy. This paper describes a new single cell halo assay (HaloChip) which was developed in our lab that can be used to quantify DNA repair ability. In this method, surface micropatterns are used to capture single cells on silicon substrate via electrostatic attraction. Attached cells are embedded inside agarose gel and treated with alkaline solution. Damaged DNAs will unwind and diffuse inside the gel with diffusion coefficients inversely proportional to DNA fragment sizes. After staining DNAs with ethidium bromide (EB), cells are imaged using fluorescence microscopy, where fluorescence signals are proportional to the amount of DNA. The level of DNA damage is quantified using a relative nuclear diffusion factor (rNDF) derived from the surface area of the nucleus and halo. DNA repair ability characterized by halo shrinkage is measured in a similar way except that damaged cells are allowed to recover. This method has been used to assess DNA repair ability of several repair competent and repair deficient cells. Further, this method has also been used to evaluate DNA repair ability of drugs in the presence of DNA repair inhibitors and under hypoxia conditions. This paper highlights the importance of understanding DNA repair ability and modulating of DNA repair processes can be used in the development of novel cancer treatment. This method has remarkable potentials to greatly improve healthcare by understanding the role of DNA repair ability in chemotherapy.