Hepatoma-derived growth factor is associated with reduced sensitivity to irradiation in esophageal cancer

Radiotherapy is a useful component of treatment for esophageal cancer. Iden tification of the genes that are differentially expressed between radiosens itive and radioresistant cancer cells is important for predicting clinical effectiveness of radiotherapy. We established human esophageal cancer cell lines resistant to X-ray. Using differential display, we obtained one gene that was expressed in radiosensitive cells but was rarely expressed in radi oresistant cells, and that gene was identical with hepatoma-derived growth factor (HDGF), an acidic polypeptide with mitogenic activity for fibroblast s. The semiquantitative reverse transcription-PCR assay confirmed that HDGF mRNA expression was reduced in established radioresistant cells, and its r eduction was associated with reduced sensitivity to irradiation. Radiothera py was more effective in clinical cases with high HDGF mRNA expression comp ared with cases with low expression (P < 0.05). The findings demonstrate th at HDGF may play an important role in radiosensitivity, and it could be a n ovel marker predicting effectiveness of radiotherapy in clinical cases.