On the other hand, some of the genes downregulated by PC-EVs were also found to support tumor development, as C-C chemokine ligand 2 (Ccl2) (Roca et al., 2009; Li et al., 2017), Atf3 (Sha et al., 2017), Hematopoietic prostaglandin D synthase (Abbas and Janeway, 2000), Krüppel-like factor 4 (Klf4) (Kapoor et al., 2015; Wang K. et al., 2017), Nuclear receptor subfamily 4 group A member 2 (Nr4a2) (Mahajan et al., 2015), and Pghs-2 (Li et al., 2015) were linked to M2 polarization of macrophages. Here, KLF4 is linked to neoplasm.