CD20-immunotargeting of malignant melanoma.

8565 Background: Melanomas, like other malignancies, contain distinct subpopulations of cells. These subpopulations provide the cellular basis for the complex biology of the disease including phenomena such as self-renewal, differentiation, and tumor initiation, maintenance and progression, and may have major translational impact. In melanoma, several subpopulations - some with stem cell-like characteristics - have been described including one expressing CD20. Methods: multispectral imaging; xenografting onto CB17 SCID and NOD/SCID/γc-/- mice; adjuvant treatment with rituximab in 9 stage IV (M1a-c) melanoma patients, of whom the majority had received multiple prior systemic therapies. Induction treatment at 375 mg/m2 qw for 4 wk followed by maintenance therapy at 375 mg/m2 every 8 wk. Treatment was stopped after 2 years or with development of progressive disease. Results: We show by multispectral imaging that CD20 can be expressed on melanoma cells in human tumor samples. Furthermore, western blot analysi...