[Proc Amer Assoc Cancer Res, Volume 47, 2006]
Tumor Biology 10: Angiogenesis Inhibitors 3
Biologic markers of angiogenesis: circulating endothelial cells in patients with advanced malignancies treated on Phase I protocol with metronomic chemotherapy and celecoxib
Przemyslaw W. Twardowski,
Paul Frankel and
Timothy W. Synold
City of Hope Cancer Center, Duarte, CA
Background: Preclinical studies demonstrate anti-angiogenic activity of low doses of chemotherapy; selective cox-2 inhibitors are also inhibitors of angiogenesis. Animal data indicates the presence of circulating endothelial cells (CEC), tumor-derived activated endothelial cells (AEC) and endothelial cell precursors (CEP). Bone marrow-derived CEPs have been shown to be incorporated into tumor vasculature.We conducted two combination Phase I studies of celecoxib (cc) with either cyclophosphamide (ctx) or etoposide (ep). Exploratory correlative studies were performed to evaluate the detectability of CECs, AECs and CEPs in patients treated with these anti-angiogenic combinations. Methods: Patients were treated with oral ctx at 50 mg daily or ep at 50 mg daily. Cc was given at 400 mg twice daily. Blood samples were collected on days 0, 7, 28 and monthly until disease progression. Blood from healthy volunteers was collected on days 0 and 28. Peripheral mononuclear cells (PMNCs) were isolated in CPT tubes, mixed with 10% DMSO / 90% bovine serum, frozen through controlled freezing and stored at -70°. Samples were stained with fluorescent antibodies and analyzed utilizing 5 color flow cytometry (Mo Flo MLS, Dako Cytomation, Ft Collins, CO). Data analysis was performed using Flowjo software (Tree Star Inc, Ashland, Ore).Cells of interest were defined as CD 45- and have following patterns of surface antigen expression : CECs - CD 34+ or CD 146+, CD 133- and CD 105-; CEPs - CD 34+, CD 133+ and CD 105-; AECs - CD 34+, CD 105+ and CD 133-. Clinical Results: Forty four heavily pretreated patients (20 F; 24 M) with various solid tumors were enrolled . Median age was 65 (23-72). Therapy was well tolerated. No responses were seen. Six patients had stable disease for at least 16 weeks. The longest duration on therapy is 420 days in a patient with metastatic thymoma who continues on therapy with ep and cc. Laboratory results: Controlled freezing of PMNCs did not affect the expression of surface antigens. Median number of CECs and CEPs detected in patients at baseline were 3.33 cells/microliter (0.11-32.96) and 0.29 cells/microliter (0-7.78), respectively. No AECs were detected. Significantly fewer CECs (p<0.001) and CEPs (p< 0.03) were detected in healthy volunteers vs. cancer patients at baseline. No consistent changes in CECs and CEPs were seen during therapy. Conclusions: The combinations of oral ctx or ep at 50 mg daily with cc at 400 mg twice daily are well tolerated with occasional prolonged disease stabilizations observed. CECs and CEPs are detectable in frozen PMNCs of cancer patients at higher levels than in normal controls, but the levels did not change significantly during therapy with our regimen. Further evaluation of CECs and CEPs in patients treated with clinically more active anti-angiogenic therapies would be of interest.
Copyright © 2006 by the American Association for Cancer Research.