Effective treatment of spontaneous metastases derived from a poorly immunogenic murine mammary carcinoma by combined dendritic–tumor hybrid vaccination and adoptive transfer of sensitized T cells

Curative immunotherapy against spontaneous metastases of poorly immunogenic tumors has been difficult to demonstrate, but it is highly relevant to clinical disease conditions. The 4T1 mammary carcinoma shares many characteristics of human mammary cancer. Here, mice with 4T1 spontaneous metastases were treated effectively with a combination of dendritic (DC)–tumor hybrid vaccination and adoptive transfer of tumor-draining lymph node-derived immune T cells. This strategy significantly prolonged survival and cured some mice. In this model, the combined immunotherapy induced a dramatic increase of T cells in the lung where metastases were located and in the spleen where tumor was not present. The mechanism of increasing numbers of T cells is likely attributed to the ability of DC–tumor hybrids to stimulate vigorous proliferation of adoptively transferred T cells rather than to promote their infiltration into tumor-harboring and lymphoid organs. Taken together, the combined approach may be useful for clinical development of cancer immunotherapy.