The invention involves peptides of from about 7 to about 50 amino acid residues in length that have epitopes that bind to more than one HLA class II protein and stimulate CD4+ T cells for treatment of cancer from one of three serine proteases overexpressed in ovarian cancer and other cancers—stratum corneum chymotryptic enzyme, matriptase, and hepsin. Since the peptides bind to more than one HLA class II protein variant, they can be used to treat cancer in most patients of a population having a variety of HLA class II alleles. The peptides can be loaded onto autologous dendritic cells of a cancer patient and infused into the patient to activate a CD4+ and CD8+ T cell response that recognizes tumor cells expressing the peptide antigen.