Introduction

DNA repair pathways have evolved to counteract the constant threat of endogenous and exogenous DNA damaging agents and defects in DNA repair pathways are associated with cancer-prone disorders such as xeroderma pigmentosum or Fanconi anemia. Conversely, DNA repair enzymes also counteract the effect of antitumor agents. Research in our laboratories aims to develop a deep fundamental understanding of the molecular mechanisms of DNA repair pathway and leverage this knowledge to improve cancer therapy. We believe that, despite recent advances in targeted and immune cancer therapy, cytotoxic cancer chemotherapy will continue to be used to treat the majority of tumors for the foreseeable future. We reason that through a better understanding of DNA repair mechanism, ability to characterize and quantify DNA adduct levels induced by antitumor agent and the genetic make-up of tumors, cytotoxic therapy can be deployed in a targeted way, thereby improving therapeutic outcomes while reducing side effects and the occurrence of resistance.

• Chemical Approaches for Studying DNA Repair Pathways

Studies of DNA repair pathways have greatly benefited from the generation and synthesis of DNA probes, in the form of defined site-specific substrates or specific probes for biochemical and cell biological studies. Our laboratory has been developing new methodology to synthesize chemically defined DNA interstrand crosslinks (ICLs), lesion formed by antitumor agents such as cisplatin or nitrogen mustards. We and many laboratories around the world have used these ICLs to delineate the cellular pathways of ICL repair. We are continuing to develop new synthetic probes for the study of ICL repair and other human DNA repair pathways. We are using these probes extensively to investigate various aspects of DNA repair. One recent focus has been the study of how DNA polymerases interact with structurally diverse ICLs. These studies shed new light on the role of DNA polymerases in ICL repair and insights may be used to design more effective therapeutics based on how their DNA adducts interact with DNA polymerases.

• Chemical Approaches for Studying DNA Repair Pathways

Studies of DNA repair pathways have greatly benefited from the generation and synthesis of DNA probes, in the form of defined site-specific substrates or specific probes for biochemical and cell biological studies. Our laboratory has been developing new methodology to synthesize chemically defined DNA interstrand crosslinks (ICLs), lesion formed by antitumor agents such as cisplatin or nitrogen mustards. We and many laboratories around the world have used these ICLs to delineate the cellular pathways of ICL repair. We are continuing to develop new synthetic probes for the study of ICL repair and other human DNA repair pathways. We are using these probes extensively to investigate various aspects of DNA repair. One recent focus has been the study of how DNA polymerases interact with structurally diverse ICLs. These studies shed new light on the role of DNA polymerases in ICL repair and insights may be used to design more effective therapeutics based on how their DNA adducts interact with DNA polymerases.

Mechanistic Basis of Resistance and Diagnostic Tools for Platinum Anticancer Therapy

Cisplatin, carboplatin and oxaliplatin are among the most successful and widely used antitumor agents, yet it is still not known which of the different DNA adducts formed are the most clinically relevant and how various DNA repair pathways contribute to the resistance to therapy. We are developing a mass-spectrometry based approach to detect the levels of various platinum-DNA adducts. We will use this method together with cell biology and genetics to correlate adduct levels with resistance to therapy in model- and tumor cell lines. We are using this approach to understand how cisplatin, carboplatin and oxaliplatin lesions are processed in cells and will develop it into a diagnostic and predictive tool for cisplatin therapy outcomes in the clinic. We will extend this approach to lesions formed by additional clinically important DNA damaging agents.

Hijacking Transcription-Coupled Nucleotide Excision Repair for Cancer Therapy

The NER pathway has significant impact on the responsiveness of tumors to DNA damaging drugs, such as cisplatin. High levels of the NER gene ERCC1 are indeed a reliable predictor for resistance to cisplatin treatment. By contrast, precision oncology strategies to specifically target tumors based on the NER status are not available. Using the known, but relatively rarely used, drug trabectedin as a starting point, we will study compounds that can induce breaks in the DNA only in NER-proficient cells. We will explore the specific mechanistic hypothesis for how trabectedin induces double stranded breaks in an NER-dependent fashion and explore how this unique property can be applied to treat tumor cells with elevated levels of DNA repair that are resistant to treatment with drugs, such as cisplatin.