We present a novel methodology to visualize
tumor cells directly in a whole mouse. This technique combines immunohistochemistry with whole mouse sectioning. It
lets one see the exact distribution of
tumor cells throughout an animal and how effectively these cells are eliminated by
cancer therapeutics. We used this technique to assess the efficacy of a T cell-specific
immunotoxin in a severe combined immunodeficient mouse model of human
T-cell leukemia. Severe combined immunodeficient mice were injected with one of two human T-cell
acute lymphoblastic leukemia cell lines (Molt 3 and Molt 13) and were either left untreated or were treated with DA7, an
immunotoxin specific for the T cell-associated
antigen CD7. Mice were sacrificed after
tumor cell injection and
immunotoxin therapy, whole mouse cross-sections were prepared, and
tumor cells in the sections were visualized by immunohistochemistry. No
tumor cells were detected in DA7-treated mice injected with Molt 3, consistent with the long-term survival of this group and the sensitivity of Molt 3 to DA7 in vitro. In contrast, DA7 treatment did not visibly eliminate
tumor cells in mice challenged with Molt 13, nor did it result in their long-term survival. Furthermore,
tumor cells were detected in areas that may have otherwise been overlooked, and their distribution differed from that of mice injected with Molt 13 alone. These analyses indicate that whole mouse sectioning will be a valuable tool for assessing residual disease in the preclinical evaluation of
cancer therapeutics.