STAT3 and neoplasm: Similarly, the membrane-associated Hsp72 on tumor-derived exosomes was reported to mediate STAT3-dependent immunosuppressive function of MDSCs by triggering STAT3 activation in a Toll-like receptor- (TLR-) 2/MyD88-dependent manner [62], although the role of TLR2 in this process remains controversial [63, 64].