doi:10.1016/j.ijrobp.2004.12.086 CLINICAL INVESTIGATION Cervix G 2 /M CELL CYCLE CHECKPOINT IS FUNCTIONAL IN CERVICAL CANCER PATIENTS AFTER INITIATION OF EXTERNAL BEAM RADIOTHERAPY FERDINANDO CERCIELLO, M.D.,* BARBARA HOFSTETTER, M.S., † SHERWEIF ABDEL FATAH, M.D., ‡ MOHAMED ZAGHLOUL, M.D., ‡ BERNHARD ODERMATT, M.D., § STEPHAN BODIS, M.D.,* ZSUZSANNA VARGA, M.D., § MARTIN PRUSCHY,PH.D., † AND ILJA F. CIERNIK, M.D.* † Departments of *Radiation Oncology and § Pathology and † Laboratory of Molecular Radiobiology, Zurich University Hospital, University of Zurich, Zurich, Switzerland; ‡ National Cancer Institute of Egypt, Cairo, Egypt Purpose: To investigate changes in cancer of the uterine cervix during radiotherapy (RT) with respect to G 2 /M transition in relation to tumor cell apoptosis and changes in the tumor vasculature in cervical carcinoma. Methods and Materials: A total of 40 consecutive patients with Stage IIA–IIIB cervical cancer underwent RT without any chemotherapy. Tumor biopsy was obtained before RT and after five fractions of 1.8 Gy. The tumor samples were stained for cyclin B1, cdc2, and Ki-67, the apoptotic index, using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling staining. The tumor vasculature density was assessed. In 38 cases, the tissue samples were informative. Results: Cyclin B1 was positive in all biopsies before and after initiation of RT, and staining for cdc2 was positive in 35 (92%) of 38 biopsies before and 33 (87%) of 38 after 1 week of RT. Nuclear staining for cyclin B1 was observed in 92% of patients, staining an average of 15% of cells before RT. After initiating RT, 73% of patients showed positive staining on about 5% of tumor cells (p < 0.01). Nuclear staining for cdc2 was detected in 89% of patients, staining an average of 21% of cells before RT. After initiating RT, 79% of patients showed positive staining on 9% of cells (p < 0.01). The apoptotic index of the tumor cells increased after initiating RT, and a slight decrease in the vascular density after 1 week of RT was noted (p  0.08). Changes in G 2 /M were associated with the clinical response, but changes in apoptosis or tumor vasculature were not. Conclusion: RT leads to significant changes in the cell cycle in cervical cancer indicating intact G 2 /M checkpoint function. Targeting G 2 /M with compounds interfering with G 2 /M transition may further enhance the effect of RT in cervical cancer patients. © 2005 Elsevier Inc. Cell cycle, Cyclins, Radiotherapy, Uterine cervix cancer, Ionizing radiation, Cervical carcinoma. INTRODUCTION Cervical carcinoma can be successfully treated with ioniz- ing radiation (IR) (1). However, the mechanism by which tumor control is achieved by IR remains unclear. In partic- ular, it is unknown which cellular response mechanisms to IR are required for successful tumor control, and which sequences of the changes induced by IR will lead to tumor control. Recent work in controlled model systems has sug- gested that the effect of IR on the tumor vasculature could also be a crucial element for successful RT (2). Currently, the interplay of adaptive changes, as reflected by cell cycle arrest and changes in the vasculature leading to altered perfusion, and, thus, to changes in the nutritional status or oxygen supply of the cancer cells, may result in cancer cell death. To establish novel strategies and target better cervical cancer with novel agents enhancing IR, more knowledge about the biologic effect of IR alone in patients is warranted. Most important, the mechanism and sequence of adaptive stress responses to IR, such as cell cycle arrest or changes in the tumor vasculature, should be known in clinical practice. Recently, the addition of cisplatin to radiotherapy (RT) has led to improved disease control and survival, demonstrating the importance of modulation of the cell cycle–active tumor cells with alkylating agents enhancing the biologic effect of IR. However, combined treatment with predominantly S phase–specific agents such as antimetabolite 5-fluorouracil or ribonucleotide reductase inhibitor hydroxyurea did not seem to improve further on the cure rate of cervical carci- noma (3). Depending on the primary tumor load and genetic background of the cancer, especially in advanced-stage dis- ease, a significant fraction of patients may not have disease control by RT alone, and additional strategies targeting cervical carcinoma are warranted. Reprint requests to: Ilja F. Ciernik, M.D., Department of Radi- ation Oncology, Zurich University Hospital, University of Zurich, A NUK 14, Rämistrasse 100, Zurich 8091, Switzerland. Tel: ( +41) 1-255-3463; Fax: ( +41) 1-255-4547; E-mail: ciernik@usz.ch Supported by a Grant from the Zurich Cancer League, Switzer- land. Received July 9, 2004, and in revised form Nov 29, 2004. Accepted for publication Dec 22, 2004. Int. J. Radiation Oncology Biol. Phys., Vol. 62, No. 5, pp. 1390 –1398, 2005 Copyright © 2005 Elsevier Inc. Printed in the USA. All rights reserved 0360-3016/05/$–see front matter 1390