Abstract: The present invention also provides fusion polypeptides with a carboxy-terminal or N-terminal peptide domain (e.g., Fc, CTP, or Fc-CTP), and nucleic acid molecules encoding these polypeptides. The present invention further provides for methods of using the compositions of the invention for treatment of cancer and fibrotic diseases. The present invention also provides isolated polypeptides with a carboxy-terminal peptide (CTP) domain fused to an antibody fragment, and nucleic acid molecules encoding these polypeptides. The present invention also provides isolated polypeptides with a carboxy-terminal peptide (CTP) domain fused to the ectodomain of a receptor, and nucleic acid molecules encoding these polypeptides. Also provided are isolated fusion polypeptide molecules, with an isolated polypeptide attached to a carboxy terminus of a second polypeptide, and to nucleic acid molecules encoding these isolated fusion polypeptide molecules.