STAT3 and kidney cancer: It was found that Hsp70 was abundantly present in exosomes secreted by mouse kidney cancer cells (Renca cells), upregulated the expression of arginase 1 (ARG-1), iNOS, interleukin 6 (IL-6) and VEGF and induced the expression of MDSCs by phosphorylating STAT3 (p-STAT3) pathway, thus promoting tumour growth [75, 89].