INTRACELLULAR EXPRESSION OF AN ANTIBODY FRAGMENT-NEUTRALIZING P21 RASPROMOTES TUMOR-REGRESSION

Mutated ras genes are found in a large number of human tumors and, the refore, constitute one of the primary targets for cancer treatment. Mi croinjection of the neutralizing anti-Ras monoclonal antibody Y13-259 was previously reported to induce transient phenotypic reversion of ra s-transformed rodent fibroblasts in vitro. We have prepared a single-c hain Fv fragment (scFv) derived from Y13-259, and here, we show that i ntracellular expression of the scFv led to the specific inhibition of the Ras signaling pathway in Xenopus laevis oocytes and NIH3T3 fibrobl asts. Moreover, neutralizing Ras with the scFv specifically promoted a poptosis in vitro in human cancer cells but not in untransformed cells , As a step toward cancer gene therapy, we finally demonstrated that i ntratumor transduction of HCT116 colon carcinoma cells with the anti-R as scFv using an adenoviral vector elicited sustained tumor regression in nude mice.