Gene expression profiles of variants of B16OVA melanoma cells established from different host immunological conditions

To establish cancer cells escaping from host immunity, we used murine B16 melanoma cell line expressing ovalbumin (B16OVA) and inoculated into mice immunized with OVA. Using this model, we established cell lines after the in vivo passage through distinct immunological condition. B16OVA tumor exposed to OVA-specific CD8+ T cell immunity in OVA-immunized B6 mice were isolated and established five variants (IMM1, 2, 8). For comparison, B16OVA tumors from non-immunized naïve B6 mice or OVA-immunized IFN-gamma-deficient mice were also isolated and established four variants, namely NIMM (1, 3, 4) cell lines or GKO-IMM (1, 2, 3) cell lines, respectively. Regarding the immunogenicity of different variants of B16OVA cells (NIMM, IMM. GKO-IMM) to tumor antigen-specific immunity, IMM, NIMM or GKO-IMM cell lines were re-challenged to OVA-immunized B6 mice. Contrary to NIMM and GKO-IMM cell lines, IMM cell lines showed progressive growth in OVA-immunized mice upon re-challenge. These results suggest IMM cell lines acquire the ability to escape from OVA-specific anti-tumor immune response. In order to understand the molecular mechanism behind in IMM cell lines to acquire the resistance to host immunity, we analyzed comprehensive gene expression of those cell lines using DNA microarray.