There is provided a monoclonal antibody that binds to binds to cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), programmed death-1 (PD-1), B and T lymphocyte attenuator (BTLA), IL-10, TGFβ, or CD25, and an IL-21 polypeptide or fragment of an IL-21 polypeptide as shown in SEQ ID NO:2 from amino acid residue 30 to residue 162, for use in treating cancer in a subject.