compositions and methods of use thereof for treating small cell and nonsmall cell lung cancers in mammals are disclosed . the compositions comprise substances that inhibit the lung cancer cell growth and proliferation actions of the biological response modifier vasoactive intestinal polypeptide , such as specific thymosins or analogues , derivatives and fragments thereof , anti - vasoactive intestinal polypeptide receptor polyclonal or monoclonal antibodies , and antibodies directed against the vasoactive intestinal polypeptide molecule itself .