RNA interference against Biot2, a novel mouse testis-specific gene, inhibits the growth of tumor cells

RNA interference of Biot2 induces G1 phase arrest and apoptosis in mouse colorectal cancer cell line

Biot2 is a tumor-associated antigen, and it is a novel gene (GenBank EF100607) that was first identified with the SEREX technique and named by our laboratory. It is highly expressed in cancer cells and testis, with low or no expression in normal tissues. In our previous study, RNA interference of human Biot2 can inhibit tumor cell growth, and it is associated with poor prognosis of patients in clinical study; however, the mechanism of Biot2 that effects tumor growth is not yet clear. Here, in this study, we explore further the mechanism of Biot2 by silencing Biot2 in CT26 cells. It provides some theoretical basis for Biot2 as a new target for gene therapy. In CT26 cells, the expression of Biot2 was downregulated by Biot2-shRNA. It also promoted G₁ phase arrest, the expression of p16 and p21, and cell apoptosis. In the mouse model, the tumor volume and the expression of PCNA of the Biot2-shRNA group significantly decreased. These results suggest that silencing Biot2 in CT26 cells by RNA interference can inhibit cell growth in vitro and in vivo. It also induces cell cycle arrest in the G₁ phase and apoptosis throughout regulation of p16 and p21. Taken together, our data demonstrate that Biot2 can be a potential target of gene therapy.

Antitumor and anti-angiogenesis immunity induced by CR-SEREX-identified Xenopus RHAMM

Immunization with xenogeneic antigens is an attractive approach to induce cross-reactive humoral and cellular immunity to inhibit tumor growth or angiogenesis. To identify novel xenogenic targets for immunotherapy, we have developed a modified serological expression cloning (SEREX) strategy, termed Cross-reactive SEREX (CR-SEREX). Among 78 positive clones identified by CR-SEREX, Xenopus receptor for hyaluronic-acid-mediated motility (xRHAMM) was most frequently identified (18 times), indicating the strongest immunogenic potential for xenogenic immunotherapy. A DNA vaccine based on xRHAMM effectively induced a protective antitumor immunity against local tumor and lung metastasis in B16 melanoma mouse models. Angiogenesis was inhibited and cell apoptosis was increased within tumors. Antitumor activity of xRHAMM worked through stimulation of an antigen-specific cellular response as well as through a specific humoral response against RHAMM, as confirmed by the depletion of immune cell subsets in vivo. Thus, a xenogenic vaccine based on xRHAMM induced an effective immunity against B16 melanoma cells and endothelial cells.