TLR4 and neoplasm: Platelets bound by tumor cells release soluble media, such as ADP, thromboxane A2 (TXA2), or high mobility group 1 (HMGB1), which are linked to Toll-like receptor 4 (TLR4) on platelets and mediate platelet-tumor cell interactions, which increase the permeability of the blood vessel wall, thereby promoting the metastasis of tumor cells (44).