PDGFRB and neoplasm: Based on western blots from our previous study [25] we anticipated either (i) the claudin-low tumor cells would be more sensitive to PDGFR inhibition as these cells express higher levels of PDGFR and thus were more dependent on PDGFR signaling for migration and proliferation or (ii) the higher levels of PDFGR found in the claudin-low tumor cells would render these cells more resistant to PDGFR inhibition as higher concentrations of Sunitinib or Regorafenib would be required to competitively block PDGFR signaling.