The present invention provides a human tumor suppressor protein having the amino acid sequence of SEQ ID NO: 2; a polynucleotide encoding the tumor suppressor protein; an expression vector containing the polynucleotide; a microorganism or animal cell transformed with the expression vector; a method for suppressing proliferation of a cancer cell which comprises introducing the expression vector into a cancer cell to induce apoptosis thereof; and a pharmaceutical composition for preventing or treating cancer which comprises a therapeutically effective amount of the polynucleotide and a pharmaceutically acceptable carrier.