Macrophage-colony stimulating factor inhibits the growth of human ovarian cancer cells in vitro Y. Kawakami a,b, *, N. Nagai a , K. Ohama a , K. Zeki b , Y. Yoshida b , E. Kuroda b , U. Yamashita b a Department of Obstetrics and Gynecology, Hiroshima University School of Medicine, Kasumi 1-2-3, Hiroshima, Minami-ku, 734-8551, Japan b Department of Immunology, University of Occupational and Environmental Health, Kitakyushu, Japan Received 21 January 2000; received in revised form 9 May 2000; accepted 11 May 2000 Abstract The eect of macrophage-colony stimulating factor (M-CSF), which regulates the growth and dierentiation of haematopoietic progenitor cells on the growth of ovarian cancer cells was investigated in three ovarian cancer cell lines in vitro. The spontaneous growth of these cells was signi®cantly inhibited by the addition of M-CSF in a concentration-dependent manner over 96 h of cul- turing. The maximum response was obtained with 10 ng/ml (3857 U/ml) of M-CSF by counting the viable cell number using the trypan blue exclusion assay. [ 3 H]-thymidine incorporation by these cells was also suppressed following a 96-h incubation with M-CSF. The inhibitory eect of M-CSF was reversed by the addition of anti-M-CSF monoclonal antibody. Flow cytometric analysis revealed that the treated ovarian cancer cells arrested at the G0/G1 phase of the cell cycle. These cells expressed M-CSF receptors on their surface as detected by Scatchard plot analysis using 125 I-labelled M-CSF. These results indicate that M-CSF has an anti- tumour activity for ovarian cancer cells and suggest that it can be applied for the treatment of this disease. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: M-CSF; Ovarian cancer; Growth inhibition; Cell cycle and M-CSF receptor 1. Introduction Ovarian cancer has the lowest overall survival rate of all the gynecological malignancies. Frequently, at the time of diagnosis most patients already have advanced disease that has spread beyond the pelvis and into the peritoneal cavity. Cytoreductive surgery and combina- tion chemotherapy are mainly performed as an annual treatment, but can not improve the prognosis. There- fore, it is necessary to understand the mechanism of growth regulation of the tumour cells and develop novel strategies for therapy. In ovarian cancer, it has been reported that a variety of cytokines and haematopoietic factors, including interleukin (IL)-1a, b, IL-6, IL-10, IL- 11, interferon (IFN)-g, tumour necrosis factor (TNF)-a and transforming growth factor (TGF)-a, are expressed and are attributed to either progression or regression of ovarian cancer cells [1±8]. Macrophage-colony stimulating factor (M-CSF) belongs to a family of glycoprotein growth factors and is mainly produced by stromal and immunocompetent cells. M-CSF induces the proliferation, dierentiation and survival of haematopoietic cells [9]. Recently, it was reported that the c-fms proto-oncogene product is rela- ted to the M-CSF receptor and overexpression of M-CSF and its receptor led to the proliferation of ovarian carci- noma cells [10,11]. Elevated serum or ascitic M-CSF levels and overexpression of M-CSF and its receptor in patients with ovarian carcinoma is associated with poor prognosis [12±15]. Moreover, M-CSF also induces the maturation of some leukaemic cells and solid tumour cells [16±19]. In gynecological malignancies, M-CSF could be used to treat or to prevent myelosuppression during chemo- therapy. However, the eect of M-CSF on the growth of gynecological malignant tumour cells has not been extensively evaluated. The purpose of this current 0959-8049/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0959-8049(00)00282-3 European Journal of Cancer 36 (2000) 1991±1997 www.ejconline.com * Corresponding author. Tel.: +81-89-932-1111; fax: +81-89-931- 2428. E-mail address: ykawaka@shikoku- cc.go.jp (Y. Kawakami).