Bakkenist Lab, University of Pittsburgh
We have openings for Postdoctoral Fellows, Graduate Students, and Technicians.
Please email: bakkenistcj@upmc.edu
Our Research Interests
Radiation therapy and many chemotherapies induce DNA damage. These therapies work because cancer cells divide more rapidly than normal cells and cancer cells acquire mutations that change their DNA damage responses and DNA repair mechanisms. Nevertheless, radiation and DNA damaging chemotherapies may not generate long-term responses as the dose of DNA damage required to kill all cancer cells may kill too many normal cells – dose limiting toxicity. We study how pharmacologic DNA damage response inhibitors can be used to increase the damage induced in cancer cells and potentiate anti-tumor immune responses. Our long-term goals are to develop new therapeutic approaches to manage human cancer.
DNA Damage Response Inhibitors
We are interested in the impact of DNA damage response inhibitors in cells that have not been treated with a DNA damaging agent as well as in cells treated with radiation and DNA damaging chemotherapy. ATM and ATR are apical signaling kinases whose activities are increased at DNA double-strand breaks and damaged replication forks, respectively. ATM and ATR orchestrate DNA repair and cell survival. ATM kinase inhibitors increase DNA damage and death in cells treated with radiation and other agents that induce DNA double-strand breaks. ATR kinase inhibitors increase DNA damage and death in cells treated with agents that damage replication forks. We study the impact of ATM and ATR kinase inhibitors in cells grown in tissue culture, tumor bearing mice, and cancer patients enrolled in clinical trials. We are particularly interested in the impact of DNA damage response inhibitors in cancer cells, T regulatory cells, and CD8+ T cells.
DNA Replication
We are interested in basic mechanisms that control DNA replication. We showed that pharmacologic ATR and CHK1 kinase inhibitors induce origin firing in mammalian cells that have not been treated with a DNA damaging agent . Accordingly, ATR and CHK1 kinase activities limit origin firing in mammalian cells in undamaged cells. This unanticipated finding is highly significant because patients enrolled in clinical trials are being treated with ATR and CHK1 inhibitors prior to radiation and DNA damaging chemotherapy.
Immune Responses
We are interested in immune responses to radiation and DNA damaging agents. We showed that ATR kinase inhibitors combine with radiation to generate a CD8+ T cell-dependent response in tumors that is associated with immunologic memory. We showed that ATR kinase inhibitors block radiation-induced immune checkpoint PD-L1 expression on cancer cells and that this indirectly increases CD8+ T cell activity in irradiated tumors. We also showed that ATR kinase inhibitors reduce the proliferation of T regulatory cells and CD8+ T cells.
DNA Damage Signaling in Cancer Patients
ATM kinase activity is associated with ATM autophosphorylation on serine-1981, and antisera that recognize phosphorylated serine-1981 are the most sensitive marker of exposure to radiation and DNA damaging agents that has been identified. We developed a quantitative assay for ATM phosphorylation on serine-1981 and showed that ATM kinase-dependent DNA damage signaling is increased in the peripheral blood mononuclear cells (PBMCs) of patients treated with targeted radiation therapy. We showed that the circulation of blood through small tumors targeted with radiation for as little as 164 or 100 seconds was sufficient to induce DNA damage signaling in PBMCs throughout the patients body. We are interested in whether this is a predictive biomarker of response to radiation therapy and whether this changes the activity of immune cells in patients treated with radiation.
Remarkably, we showed that ATM kinase-dependent DNA damage signaling is higher per unit dose of ionizing radiation in women than men. We believe this finding is highly significant and has far reaching implications for the management of cancer in women and men.
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