Cancer Immune Therapy Edited by G. Stuhler and P. Walden ...

330 16 Immunocytokines: Versatile Molecules for Biotherapy of Malignant Disease
16.5
Melanoma
16.5.1
Treatment of Tumor Metastases with Immunocytokines
Human melanoma tumors reveal up-regulated expression of an array of gangliosides,
including disialoganglioside GD2. However, even though gangliosides can
cross species barriers, murine B16 melanoma cells failed to express ganglioside GD2
and were thus transfected with human genes encoding for two enzymes catalyzing
the last steps of GD2 biosynthesis, b-1,4-N-acetylgalactosaminyltransferase and
a-2,8-siatyltransferase. These transduced B16 melanoma cells stably expressed GD2,
bound the ch14.18±IL-2 fusion protein, and formed experimental hepatic and pulmonary
metastases in syngeneic C57BL/6 mice following intrasplenic or i.v. injection
[61].
Immunotherapy of established hepatic and pulmonary melanoma metastases in
C57BL/6J mice with ch14.18±IL-2 fusion protein 1 week after tumor cell inoculation
completely eradicated established metastases in the vast majority of mice. A typical
example depicting the eradication of established pulmonary metastases shown in
Tab. 16.3. This was also indicated by histologic examination of tissue sections. Moreover,
the treatment effect was specific since a non-specific fusion protein directed
against the human epidermal growth factor receptor, ch225±IL-2, not expressed on
B16 cells or its subline B78-pD3T-31, did not show any antitumor effect [61]. The efficacy
of fusion protein therapy in eradicating established hepatic metastases of melanoma
was further demonstrated by a 2-fold increase in lifespan of only ch14.18±
IL-2 immunocytokine-treated mice. This is illustrated in Fig. 16.4.
Immunocytokine therapy also overcame heterogeneity of the tumor docking sites as
indicated by a successful eradication of melanoma metastases achieved when a small
percentage of tumor cells expressing the GD2 docking site were admixed with GD2negative
cells and could still be successfully employed as in vivo targets [62]. This tumor
cell killing was dependent on CD8 + T cells. In fact, we demonstrated the presence
of clonotypic T cells in tumor lesions in both IL-2 immunocytokine-treated
Tab. 16.3 Effect of the tumor-specific antibody-IL-2 fusion protein on established pulmonary
metastases
Treatment No. of foci Lung weight (g)
None >500, >500, >500, >500, >500, >500, >500 0.39+0.16
rIL-2 + ch14.18 82, 151, 154, 163, >500, >500, >500, >500 0.37+0.10
ch14.18±IL-2 0,0,0,0,0,0,0,0 0.19+0.09
Experimental pulmonary metastases were induced by i. v. injection of 5610 6 B78-pD3T-31 cells. Treatment
was started 1 week thereafter and consisted of daily i. v. administration of 8 mg chimeric mAb
ch14.18 + 24 000 IU recombinant IL-2, of 8 mg of the tumor-specific fusion protein ch14.18±IL-2 for
7 consecutive days.