Disclosed is a method of treating cancer, comprising administering to a mammal in need thereof a therapeutically effective amount of a compound that inhibits a plurality of mammalian DASH serine proteases. Also disclosed is a method of (a) increasing antitumor immunity, (b) stimulating or enhancing an immune response, (c) treating a condition characterized by abnormal cell proliferation, (d) increasing cytokine and/or chemokine production, or (e) stimulating or enhancing production of T-cells, in a mammal, comprising administering to a mammal in need thereof an effective amount of a compound that inhibits a plurality of mammalian DASH serine proteases. For example, the compound that inhibits a plurality of mammalian DASH serine proteases may be t-butylGly-boroPro.