Clonal analysis revealed that the GDF-15 promoter upstream consists of binding sites for a variety of essential transcription factors, including specificity protein-1 (Sp1), early growth response protein-1 (EGR-1), p53, and COUP transcription factor-1 (COUP-TF1).[21,24] Wild-type p53 is a crucial tumor suppressor that exerts anti-tumor functions by causing cell cycle arrest and apoptosis in the downstream signaling pathways of DNA damage or cellular stress. Here, SP1 is linked to neoplasm.