Tumor-draining lymph nodes (TDLN) have been used as a source of antitumor effector cells for adoptive immunotherapy of cancer. The successful use of this strategy depends largely on the immunogenicity of the tumor drained by the lymph nodes as well as the protocols for the secondary in vitro T cell activation and expansion. We constructed a eukaryotic expression vector pcDNA3.1-SEA (staphylococcal enterotoxin A) and transfected it into the B16 murine melanoma tumor cells by means of liposome-mediated transfection. We then used SEA-modified B16 cells to induce the TDLN (SEA TDLN) in syngeneic hosts. These TDLN cells were activated in vitro using anti-CD3/anti-CD28/IL-2 with or without dendritic cells (DC) pulsed with B16 tumor lysates. Wild-type (Wt) TDLN induced by using non-modified B16 tumor was used as a control. In vitro analyses showed that SEA TDLN cells proliferated more vigorously than Wt TDLN in response to anti-CD3/anti-CD28/IL-2 stimulation. Tumor lysate-pulsed DC (TPDC) significantly enhanced the proliferation of both Wt TDLN and SEA TDLN cells (p<0.05). Functionally, SEA TDLN cells activated with anti-CD3/anti-CD28/IL-2 in the presence of TPDC demonstrated the highest CTL activity and secreted the highest levels of IFNγ towards tumor cells compared with any other experimental group. Using the metastatic pulmonary tumor model, we adoptively transferred (i.v.) Wt TDLN and SEA TDLN cells sensitized in vivo respectively by B16 or SEA-B16 tumor, and activated in vitro by anti-CD3/anti-CD28/IL-2 with or without TPDC. SEA TDLN cells mediated tumor regression more effectively than Wt TDLN cells activated with anti-CD3/anti-CD28/IL-2. The addition of TPDC in culture significantly augmented the therapeutic efficacy of both Wt TDLN and SEA TDLN cells (p<0.05), with SEA-TDLN cells activated with anti-CD3/anti-CD28/IL-2 plus TPDC being the most potent effector cells in mediating tumor eradication. These results thus indicate that enforced expression of superantigen SEA in a poorly immunogenic tumor, B16, can enhance the immunogenicity of the tumor in vivo. They also support the use of autologous tumor lysate-pulsed DC during the secondary in vitro activation/expansion procedure in order to generate more potent tumor specific effector cells for adoptive immunotherapy.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]