In this study, Immunocaspase-3 gene was transfected into Jurkat T lymphocytes and the targeted proapoptotic protein Immunocaspase-3 was stably secreted.Its entry to ErbB2 positive SKBr3 breast carcinoma cell line was observed by indirect immunofluorescence staining.Growth of SKBr3 cells was significantly inhibited when they were cultured with medium containing Immunocaspase-3.Next, Immunocaspase-3 gene was cloned into retrovirus vector pLNCX, which was then transfected into PA317 cells to package. Packaged cells producing high titer pseudoviruses were acquired and the pseudoviruses were harvested to infect PBMCs, which had been stimulated to division. The latter were selected and administered to nude mice bearing SKBr3 tumors through tail vein. The results showed that the treatment contributed to an inhibition of tumor growth and prolonged the lifetime of nude mice bearing SKBr3 tumor.The efficiency of inhibition of tumor reached 73.25%, and the average lifetime of treated nude mice was 80.95% longer than that of control group. Immunohistochemical examination revealed the exclusive distribution of Immunocaspase-3proteins only in the tumor tissue samples; and TUNEL assay confirmed the occurrence of apoptosis in tumor cells. The present study suggests that Immunocaspase-3 secreted by T lymphocytes can selectively bind and enter into ErbB2 positive breast cancer cells, where it exhibits a proapoptotic activity and causes tumor suppression in an in vivo tumor model.