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Direct relationship between radiobiological hypoxia in tumors and monoclonal antibody detection of EF5 cellular adducts
Author(s) -
Lee Jungeun,
Siemann Dietmar W.,
Koch Cameron J.,
Lord Edith M.
Publication year - 1996
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19960729)67:3<372::aid-ijc11>3.0.co;2-a
Subject(s) - clonogenic assay , tumor hypoxia , monoclonal antibody , flow cytometry , hypoxia (environmental) , carbogen , chemistry , cancer research , antibody , microbiology and biotechnology , pathology , in vitro , biology , immunology , oxygenation , radiation therapy , medicine , biochemistry , oxygen , organic chemistry
While the potential importance of hypoxia in limiting the sensitivity of tumor cells to ionizing radiation has long been appreciated, methods for accurately quantifying the number of radiation‐resistant hypoxic cells within tumors have been lacking. We have used the pentafluorinated derivative [2‐(2‐nitro‐IH‐imidazol‐l‐yl)‐N‐(2,2,3,3,3‐pentafluoropropyl)‐acetamide] of etanidazole (EF5), which binds selectively to hypoxic cells. The adducts formed between EF5 and cellular proteins in the hypoxic cells were detected using the specific monoclonal antibody (MAb), ELK3‐51 conjugated to the flurochrome Cy3, and the number of hypoxic cells was quantified by flow cytometry. To verify the validity of this technique for the detection of hypoxic cells, mice bearing KHT sarcomas were treated with various agents to alter tumor oxygenation and hence vary the fraction of radiobiologically hypoxic tumor cells. The percentage of EF5 binding cells was then compared directly with the clonogenic survival of the tumor cells following radiation treatment under the various pretreatment conditions. The results showed that allowing the mice to breathe carbogen (5% CO 2 /95% O 2 ) prior to irradiation reduced clonogenic cell survival approx. 6‐fold and led to an absence of cells binding high levels of EF5. In contrast, pretreating the tumor‐bearing animals with either hydralazine, which decreased tumor blood flow, or phenylhydrazine hydrochloride, which made the mice anemic, increased tumor cell survival following irradiation 2‐ to 4‐fold, indicative of an increase in the fraction of hypoxic tumor cells. EF5 measurements made under identical conditions illustrated a shift in the cells in the tumor to high EF5 binding. Our results demonstrate that flow cytometric measurement by fluorescent MAb binding to EF5 adducts may relate directly to radiobiological hypoxia in KHT tumors measured by conventional methods. © 1996 Wiley‐Liss, Inc.