Short communication Apoptotic effect of gossypol on human lymphocytes Erkan Yurtcu 1 , Mehmet Ali Ergun 2 , Adnan Menevse 2 * 1 Hematology Laboratory, Gazi University, 06510, Besevler, Ankara, Turkey 2 Department of Medical Biology and Genetics, Gazi University, 06510, Besevler, Ankara, Turkey Received 6 January 2003; revised 8 May 2003; accepted 14 July 2003 Abstract The overall objective of this study was to determine the effect of gossypol on human lymphocytes. Blood samples were taken from healthy donors and lymphocytes were cultured with various concentrations of gossypol (25–150 μM). The percentage of apoptotic cells was determined by assessing DNA fragmentation by agarose gel electrophoresis; morphological features of apoptosis were assessed by light microscopy. The concentrations of gossypol required to induce apoptosis in human lymphocytes without causing necrosis through cytotoxic effects were between 25–50 μM.  2003 Published by Elsevier Ltd. Keywords: Gossypol; Apoptosis; Human lymphocyte 1. Introduction Chemicals with different mechanisms of action are necessary to improve the outcome and survival of children with acute myeloid leukemia (AML) and lym- phoid leukemia (ALL). During the past decade it has become apparent that many chemotherapeutic agents are effective because they induce apoptosis in leukemic cells (Fisher, 1994; Hannun, 1997; Kersey, 1997). Many of these agents, such as anthracyclins (Burden and Osheroff, 1998), spicamycin (Stine et al., 2000) and other alkylating agents (Belousova, 1977), can induce differ- entiation of leukemic cells. Their initial mode of action is to damage chromosomal DNA directly and cause it to fragment. It is presumed that the fragmented DNA then serves to activate an apoptotic response (Hannun, 1997). Apoptosis is a genetically programmed mechanism of cell death often characterized by internucleosomal DNA cleavage (Szondy, 1997). During apoptotic cell death, several distinct events take place: chromatin fragmen- tation and condensation, cell shrinkage, membrane blebbing and finally disintegration of cell into membrane-bound pyknotic apoptotic bodies that can be recognized morphologically under the light microscope (Balci et al., 1999). In the present study we used gossypol, which is a specific inhibitor of DNA synthesis in HeLa and Chinese hamster ovary cells (Wang and Rao, 1984). Gossypol, a polyphenolic compound naturally occurring in cotton- seed, was originally identified as a male antifertility agent and has been used as an effective male contracep- tive drug for many years. It has several proposed clinical applications; antitrypanosomal, antimalarial, anti- tumour and antiviral, inhibiting enveloped viruses in- cluding HIV (Dao et al., 2000; Wang et al., 2000). Clinical trials indicate that gossypol is also promising as a treatment for adrenal, prostate and mammary carcinomas, gliomas, endometriosis and uterine myoma (Han et al., 1987). Recent evidence suggests that it may affect cell cycle distribution and cell cycle regulators such as cyclin D1 and Rb in human mammary tumour cells (Ligueros et al., 1997). However, information on the mechanism of gossypol-induced antitumor activity is limited. The aim of this study was to investigate the effect of gossypol on human lymphocyte differentiation, using a DNA fragmentation assay. We found that gossypol was able to induce differentiation of lymphocytes treated with different concentrations of gossypol; there was * Corresponding author. Tel.: +90-312-214-10-00x6932; fax: +90-312-212-46-47 E-mail address: amenevse@yahoo.com (A. Menevse). Cell Biology International 27 (2003) 791–794 Cell Biology I nternational www.elsevier.com/locate/cellbi 1065-6995/03/$ - see front matter  2003 Published by Elsevier Ltd. doi:10.1016/S1065-6995(03)00168-9