PTN and neoplasm: Thus, in the TME of HER2 + IBC, abnormally active HER2 signalling can promote the release of the heparin-binding growth factor PTN from tumour cells, whereas PTN can act on B cells to promote the release of TNF from B cells, which in turn promotes necrotic apoptosis of endothelial cells to cause vascular abnormalities and ultimately promotes the inflammatory response.