Adenovirus 5 early region 1A does not induce expression of the Ewing sarcoma fusion product EWS-FLI1 in breast and ovarian cancer cell lines

The adenovirus 5 early region 1A (E1A) can function as a tumor suppressor g ene and is being used in clinical trials as a therapeutic agent for advance d breast, ovarian, and head and neck cancer. Recently, there has been a dis pute regarding whether transfection with the E1A gene can induce expression of the Ewing sarcoma oncogenic fusion transcript EWS-FLI1 (Sanchez-Prieto et al., Nat. Med., 5: 1076-1079, 1999; Melot and Delattre, Nat. Med., 5: 13 31, 1999; Kovar et at, Cancer Res., 60: 1557-1560, 2000). In an effort to s ettle the controversy, we tested several stable E1A transfectants of cell l ines R4DA-MB-231, MCF-7, MDA-MB-435 (breast cancer), SKOV3-ip1 (ovarian can cer), and PC-3 (prostate cancer), as well as parental and vector-transfecte d controls, HEK 293 cells, and RD-ES (Ewing sarcoma) cells, for the EWS-FLI 1 fusion product. The EWS-FLI1 transcript could not be identified with reve rse transcription-PCR in any of the 13 E1A-transfected cell lines analyzed. Furthermore, the EWS-FLI1 fusion protein could not be detected by Western blot analysis in E1A-transfected cell lines. These results suggest that E1A transfection does not necessarily lead to expression of the oncogenic EWS- FLI1 fusion transcript. Thus, the potential induction of this gene rearrang ement by E1A gene therapy is unlikely to be clinically significant in the t reatment of advanced malignant disease.