Search

Reversing abnormal gene silencing in cancer cells due to DNA hypermethylation of promoter CpG islands may offer new cancer prevention or therapeutic approaches. Moreover, such approaches may be broadly applicable to enhance the efficacy of radiotherapy, chemotherapy, or immunotherapy. Here, we demonstrate the powerful utility of a novel gene reporter system to permit studies of the dynamics, mechanisms, and translational relevance of candidate therapies of this type in human colon cancer cells. The reporter system is based on in situ modification of the endogenous locus of the tumor-suppressor gene SFRP1, a pivotal regulator of the Wnt pathway that is silenced by DNA hypermethylation in many colon cancers. The modified SFRP1-GFP reporter allele used remained basally silent, like the unaltered allele, and it was activated only by drug treatments that derepress gene silencing by reversing DNA hypermethylation. We used the established DNA methyltransferase inhibitor (DNMTi) 5-aza-deoxycitidine (DAC) to show how this system can be used to address key questions in the clinical development of epigenetic cancer therapies. First, we defined conditions for which clinically relevant dosing could induce sustained induction of RNA and protein. Second, we found that, in vivo, a more prolonged drug exposure than anticipated was essential to derepress gene silencing in significant cell numbers, and this has implications for generating effective anticancer responses in patients with hematopoietic or solid tumors. Finally, we discovered how histone deacetylase inhibitors (HDACi) alone, when administered to cells actively replicating DNA, can robustly reexpress the silenced gene with no change in promoter methylation status. Taken together, our findings offer a new tool and insights for devising optimal clinical experiments to evaluate DNMTi and HDACi, alone or in combination, and with other cancer treatments, as agents for the epigenetic management and prevention of cancer., (©2014 American Association for Cancer Research.)

Karenitecin is a highly lipophilic camptothecin analogue with a lactone ring that is relatively resistant to inactivating hydrolysis under physiologic conditions. This phase I clinical trial was conducted to determine the maximum tolerated dose (MTD) of karenitecin in adults with recurrent malignant glioma (MG), to describe the effects of enzyme-inducing antiseizure drugs (EIASDs) on its pharmacokinetics, and to obtain preliminary evidence of activity. Karenitecin was administered intravenously over 60 min daily for 5 consecutive days every 3 weeks to adults with recurrent MG who had no more than one prior chemotherapy regimen. The continual reassessment method was used to escalate doses, beginning at 1.0 mg/m(2)/day, in patients stratified by EIASD use. Treatment was continued until disease progression or treatment-related dose-limiting toxicity (DLT). Plasma pharmacokinetics was determined for the first daily dose of karenitecin. Thirty-two patients (median age, 52 years; median KPS score, 90) were accrued. Seventy-eight percent had glioblastoma, and 22% had anaplastic glioma. DLT was reversible neutropenia or thrombocytopenia. The MTD was 2.0 mg/m(2) in daggerEIASD patients and 1.5 mg/m(2) in -EIASD patients. The mean (+/-SD) total body clearance of karenitecin was 15.9 +/- 9.6 liters/h/m(2) in daggerEIASD patients and 10.2 +/- 3.5 liters/h/m(2) in -EIASD patients (p = 0.02). No objective responses were observed in 11 patients treated at or above the MTD. The total body clearance of karenitecin is significantly enhanced by the concurrent administration of EIASDs. This schedule of karenitecin, a novel lipophilic camptothecin analogue, has little activity in recurrent MG.

Purpose: A phase II trial of the novel camptothecin karenitecin (BNP1350) was conducted to determine its efficacy and tolerability in patients with metastatic melanoma. Patients were biopsied to determine topoisomerase expression at baseline and response to therapy., Patients and Methods: Eligible patients had metastatic melanoma with up to three prior chemotherapy and/or any number of immunotherapy regimens. Treatment consisted of an i.v. infusion of 1 mg/m(2) karenitecin daily for 5 days with cycles repeated every 3 weeks. Fine-needle aspiration biopsies were done before treatment and on day 3 to determine topoisomerase expression from patients' tumors., Results: Forty-three patients were evaluable for response and toxicity. Most patients (72%) had stage M1C disease and were previously exposed to chemotherapy (56%). The investigational agent was well tolerated with limited gastrointestinal side effects or fatigue. The major toxicity seen was reversible noncumulative myelosuppression. One patient had a complete response after 11 months of therapy. No partial responses were seen, but 33% of the patients had disease stabilization lasting > or =3 months. Topoisomerase I, IIalpha, and IIbeta expression and localization were determined in a subset of patients. Topoisomerase I expression was highest, followed by topoisomerase IIbeta and topoisomerase IIalpha., Conclusion: Karenitecin was a well-tolerated investigational agent in this phase II study; side effects were generally mild and mostly hematologic. Karenitecin has significant activity in metastatic melanoma. Melanoma metastases express high levels of topoisomerase I. We did not observe any compensatory increase in topoisomerase II upon treatment with karenitecin.