Research/Clinical Interest Description: Dr. Bjornsti’s research focuses on the mechanism of action of the anticancer agent camptothecin, which disrupts the function of the enzyme DNA topoisomerase 1 (Top1). The enzyme allows a tumor cell to unwind its DNA so it can be replicated or transcribed. Dr. Bjornsti investigates how the camptothecin class of anticancer drugs interferes with Top1 activity to selectively kill dividing tumor cells. A second focus of her research is the antitumor activity of rapamycin, an antibiotic that selectively inhibits signaling by the target of rapamycin (TOR) kinase. Dr. Bjornsti has shown that TOR signaling protects cells from DNA damage when the DNA is being replicated. These findings provide the rationale for combining camptothecin and rapamycin analogs in cancer treatment.