The peptide forms as well as recombinant immunoglobulin Fc chimeras (IgG-Fc) of Notch3-derived peptides were able to induce apoptosis in tumor cells, preferentially reduced Notch3 activation and the expression of Notch3-specific target Hey1. Peptide-IgGFc chimeras could also suppress tumor growth in a Notch3-driven human lung cancer xenograft model. The gene discussed is HEY1; the disease is neoplasm.