The invention provides a method for inhibiting proliferation of neural cells. The neural cells can be tumor cells, glial cells, neuronal cells, and cells of the central or peripheral nervous systems. The method comprises contacting a neural cell with a molecule that disrupts the biological activity of a granulin molecule. In one embodiment, the molecule is an antibody directed against a granulin peptide. In other embodiments, the molecule is an antisense nucleotide directed against a granulin nucleic acid molecule, or a vaccine comprising a granulin peptide or a polynucleotide encoding a granulin peptide. The invention additionally provides methods for detecting and treating cancer in a neural tissue using granulin-related molecules. Also provided is a method for indenting differentially expressed gene products that are translated from mRNA species, using antibody-based screening of a cDNA expression library. This method, termed differential immuno-absorption (DIA), can be coupled to cDNA microarray hybridization and used in the identification of genes that play a role in the malignant progression of cancer.