Ets-1 is increased in anticancer drug-containing media and hypoxic cultures, similar to TACE

TO THE EDITOR: Hepatocellular carcinoma (HCC) is a hypervascular solid cancer characterized by a high degree of drug resistance [1]. Many patients undergo interventional radiology (IVR) such as transcatheter arterial chemoembolization (TACE) and therefore a more effective IVR drug is required. Transcatheter arterial embolization (TAE) can be carried out by embolization of the hepatic artery that feeds the tumor [2]. If this condition is taken into consideration, then the ability of drugs to increase hypoxia should be investigated. The protein level of Ets-1 has been reported to increase after exposure to hypoxia [3]. The expression of Ets-1 protein in combination with hypoxic and anticancer drugs was investigated in a 96-h culture. The human HCC cell line FLC-7 was cultured under conventional conditions at 378C in a humidified atmosphere containing 50 ml/l CO2 until the cells were 70 80% confluent. The cells were then cultured under hypoxic conditions using the AnaeroPack (Mitsubishi Gas Chemical Co., Tokyo, Japan) as the cell packaging device. The cells were sealed tightly and incubated at 378C for 96 h. In addition, the cells were cultured with 0.1 mmol/l farmorubicin (EPI) containing growth medium for 96 h. The cells were harvested and analyzed by Western blotting. Thirty micrograms of protein were separated by SDS-PAGE, transferred to a nitrocellulose membrane and stained with a specific Ets-1 mouse monoclonal antibody (1:500; Abcam Japan, Tokyo, Japan) and visualized. As shown in the Figure, expression of Ets-1 protein was observed in combination with hypoxic and anticancer drugs in a 96-h culture. Western blotting of FLC-7 protein lysates shows that Ets-1 was increased in anticancer drug-containing medium and hypoxic culture. Moreover, Ets-1 was markedly increased after administration of a combination of hypoxia and anticancer drugs. The hepatic artery is targeted to treat HCC, while the non-tumorous liver is hardly affected. The goal of regional therapy is to cause tumor necrosis and tumor control, while preserving as much functional liver tissue as possible in order to prolong the patient’s life [2]. Nevertheless, TACE has been established as a general treatment for HCC, but has not been established as radical treatment. We implemented non-radical treatment because we consider that partial HCC can survive in a state of hypoxia. Moreover, a previous report has shown that the surviving cells in HCC nodules pretreated with TAE grow faster than those in neighboring nodules, thus resulting in such cells becoming resistant to subsequent TAE treatment [4]. In another report it is suggested that the hypoxic environment in a tumor is a critical event for the acceleration of tumor progression and malignancy in HCC [5]. Ets-1 has been identified as a cellular counterpart of the v-ets oncogene in avian erythroblastosis virus E26. A previous report has suggested that, unlike in other neoplasms, Ets-1 plays a crucial role in both hepatocarcinogenesis and HCC progression, especially during the early phase [6]. The current results suggest that the development of an Ets-1 inhibiting drug may prove to be an effective treatment strategy for HCC.