In vivo on mice xenografted RP3 cells, siRNA RET/PTC3-SQ NPs were found to: i) inhibit tumour growth, ii) reduce RET/PTC3 oncogene and oncoprotein expressions, iii) induce cell death (cleavage of both caspase-3 and PARP-1) and iv) partially restore differentiation (decrease of Ki67 marker). The gene discussed is RET; the disease is neoplasm.