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Updated: Aug 16, 2026

Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo
Published on: February 6, 2015
Radiation sensitizing effect of estramustine is not dependent on apoptosis
Kaarlo Ståhlberg1, Kalevi Kairemo, Krista Erkkilä
1Department of Urology, Helsinki University Central Hospital, Helsinki, Finland. kaarlo.stahlberg@hus.fi
Background:
Estramustine is an anti-mitotic cytostatic drug that also enhances the effect of radiotherapy. The mechanism of radiosensitization is not thoroughly known. Since both radiotherapy and estramustine induce apoptosis in prostate cancer cells, we conducted an experiment to show whether radiosensitization is mediated by apoptosis.
Materials And Methods:
DU-145 human prostate cancer cells were xenografted to nude mice and treated with estramustine for 2 weeks and external radiation for 3 to 6 days (18 to 36 Gy). Tumor regression was measured mechanically and the rate of apoptosis defined by the amount of low molecular weight DNA fragmentation. Follow-up time was 1 to 18 days.
Results:
The tumor size regressed in the group of mice receiving both radiotherapy and estramustine. Four weeks after the treatment, apoptosis was accentuated in the tumors treated with estramustine or radiation but not with their combination.
Conclusion:
Estramustine potentiates radiotherapy, but not by enhancing radiation-induced apoptosis.
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