Processable rubber compositions contain a vulcanized fluorocarbon elastomer and functional filler dispersed in a matrix of a thermoplastic polymeric material. Further provided are methods for screening to identify agonists and antagonists of cancer antigens associated with gp 100 related cancers and malignancies. By selection of suitable amounts of these filler components, a polymer compound with a predetermined nonlinear current-voltage characteristic deviating from these two characteristics can be formed in this way. In some embodiments, the polymer foams can be formed within a body cavity.