Oncolysis of human ovarian cancers by echovirus type 1

A small number of enteroviruses possess the capacity to induce rapid and marked lytic infections in cells of various human malignancies. During screening of representative human enteroviruses for their oncolytic capacity, we observed that echovirus type 1 (EV1) displayed a high level of tropism for human ovarian cancer cells. EV1 is an enterovirus which largely causes asymptomatic infections in humans and whose tissue tropism is primarily regulated via interactions with the I domain of the alpha subunit of cell surface-expressed integrin alpha2beta1. We evaluated the capacity of wild-type EV1 to act as an oncolytic agent of ovarian cancers propagated as cell monolayers, multicellular spheroids or xenografts in SCID mice. EV1 infection of in vitro propagated ovarian cell lines expressing high levels of integrin alpha2beta1 was assessed for specific viral attachment, antibody blockade, induction of cytopathic effect and production of progeny virions. EV1 lytically infected all 8 human ovarian cancer cell lines tested (2008, DOV13, JAM, OVCA-429, OVCAR-3, OVHS-1, OAW-42 and IGROV-1) but not the immortalized normal ovarian surface epithelial cell line (HOSE) or human PBMCs. EV1 challenge was equally effective in the oncolysis of human ovarian cancer cells whether in monolayer or spheroidal environments. The therapeutic efficacy of EV1 was demonstrated by rapid reduction of tumor burden by a single viral intratumoral injection in SCID mice bearing multiple preformed s.c. xenografts. Using an in vivo i.p. human ovarian cancer xenograft model, administration of EV1 was further shown to significantly inhibit the formation and burden of ascites tumors. These findings demonstrate an important proof of principle for employing wild-type EV1 as a potential oncolytic agent in the control of human ovarian cancers.