SPP1 and cancer: In accordance with other series suggesting that OPN may be related to the induction of β-catenin or Wnt signaling pathways for regulating tumor progression, including resistance to apoptosis, in cancer cell lines[26,29-31], we confirmed that β-catenin can be a downstream effecter of OPN in GIST and may be regulating the expression of anti-apoptotic protein Mcl-1 (Figures 1–3).