A Novel Specific oncolytic adenovirus driven by human A33 promoter for colorectal cancer therapy

CAFFERATA, E.G.A; MACCIÓ, D.R; LÓPEZ, M.V; VIALE, D.L; CARBONE, C; PODHAJCER, O.L

Rosario

Congreso; SAIB; 2006

A33 antigen is a membrane-bound protein expressed only in intestinal ephitelium and over-expressed in most colorectal cancers (CRC). A33 is found in 95% of primary and metastatic colon cancer cells but is absent in most normal tissues and other tumor types. We hypothesized that A33 promoter might be useful in the design of a conditional replicative adenovirus (CRAds). For this purpose we cloned an A33 promoter fragment (A33Pr) that extends from ?105 bp to +307 bp upstream of the luciferase gene. Using luciferase activity as a gene reporter we demonstrated that A33Pr was in average 10-fold more active in colon carcinoma cells than in melanoma or breast cancer cell lines. We next constructed a CRAd where E1A was placed under the control of A33Pr (AV22EL). The adenovirus lytic capacity of AV22EL on different cell lines was examined by crystal violet staining. AV22EL induced specific oncolysis of human CRC lines that expressed A33 and have negligible lytic capacity on cells that lacked or had minimal A33 expression. AV22EL was active in CRC cells even at a MOI of 1. AV22EL efficiently reduced tumor size when injected subcutaneosly within the tumor mass. Moreover, AV22EL was also very efficient in tumor cell killing when delivered by intravenous injections in a liver metastatic tumor mouse model. These data demostrates that AV22EL is a potential oncolytic agent for the treatment of CRC.