Abstract A37: Development of screening methods to identify Translesion DNA Synthesis inhibitors

Abstract Translesion DNA synthesis (TLS) is a DNA damage tolerance process that employs specialized polymerases to bypass DNA damage during replication. Recent evidence indicates that TLS is a key process that promotes the development of resistance to cancer treatments that induce DNA damage (i.e. Cisplatin). Thus, the inhibition of TLS emerges as a promising strategy for cancer therapy. However, to date, specific chemical inhibitors of TLS are not available. The main goal of our project is to identify specific inhibitors of TLS that can be used as a proof of concept in cancer therapy by developing cell-based assays that explore TLS markers. Our rational is that since TLS polymerases recruitment to sites of DNA damage is a key step for TLS success, we can indirectly monitor TLS efficiency in a given context by studying two key markers of TLS polymerases recruitment: 1) The mono-ubiquitylation of the replication auxiliary factor PCNA and 2) the accumulation of a TLS polymerase into replication foci. We thus developed two screening methods that allow us to promptly identify inhibitors of PCNA ubiquitylation and TLS polymerases recruitment into DNA damage sites. The first marker, PCNA mono-ubiquitylation, is assessed through a western-Blot-based platform where the identification of unmodified PCNA and mono-ubiquitylated PCNA are achieved by two different antibodies coupled to fluorescent infrared detection using a fluorescence scanner. For the second marker, TLS polymerase recruitment to damage sites, we developed stable cell lines expressing TLS polymerases fused to fluorescent proteins and we analyze polymerases recruitment through an imaging-based assay. In this poster we describe the results of a pilot screening using an open source library of kinase inhibitors from GlaxoSmithKline (known as PKIS2), and the early validation of the identified hits. Citation Format: Florencia Villafañez, Alejandra Iris García, María Florencia Pansa, Sofía Carbajosa, José Luis Bocco, Gastón Soria. Development of screening methods to identify Translesion DNA Synthesis inhibitors [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr A37.

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