PARENT SESSION
1:30 PM to 3:30 PM
Tuesday, April 23, 2002
Poster Session 25 Tumor Physiology and Microenvironments
Room: Nevada Exhibition Center

(P30-299) Differences in the life-time of hypoxic cells in human xenograft tumor lines.

Bussink, Johan^*,1, Ljungkvist, Anna¹, Rijken, Paulus¹, Peters, Johannes¹, Raleigh, James², van der Kogel, Albert¹, ¹ University Medical Center Nijmegen, Nijmegen, The Netherlands² University of North Carolina School of Medicine, Chapel Hill, North Carolina

ABSTRACT-
Introduction: With the use of bio-reductive hypoxic cell markers, hypoxia was found in almost all solid tumors. Recently, a double hypoxic cell marker method was developed which allowed studying treatment-induced changes in tumor cell hypoxia. After sequentially injecting the two markers a significant reduction in the hypoxic fraction was observed during carbogen breathing and a significant increase was found after hydralazine injection.Aim of the present study was to use the double hypoxic-cell marker method to analyze the life-time of hypoxic tumor cells and the migration of these cells through tumor tissue towards terminal differentiation and necrosis. Methods and results: The tumor lines that were studied originated from head and neck patients. Two bio-reductive hypoxic cell markers were used, pimonidazole and CCI-103F. The markers were sequentially injected, CCI-103F was always injected 2.5 h before the animals were killed. Pimonidazole was injected 2.5 h to 7 days before the animals were killed. The hypoxic cell markers were visualized with immunohistochemical techniques on frozen sections. Whole tissue sections and selected regions of these tissue sections were analyzed with an image analysis system. The hypoxic markers showed an excellent match in the control tumors. There was a clear difference in the life-time of hypoxic cells between the tumor lines. In tumor line SCCNij82, within 24 h only a minimal amount of tumor cell hypoxia remained and after 48 h all initially present hypoxic cells had moved towards the necrotic tumor compartment. For SCCNij3 it took 7 days before all hypoxic cells had moved towards the necrotic tumor compartment. The life-time of hypoxic cells was independent of the tumor volume doubling times. In on-going experiments tumor cell proliferation rate will be studied in relation to hypoxic cell life-time. Discussion and conclusion: By using the newly developed double hypoxic cell marker protocol, differences in the life-time of hypoxic cells were found, this may have consequences for the optimal timing of combined modality anti-cancer therapy.

KEYWORDS: pimonidazole, double hypoxic markers, hypoxia, life-time