KIT and gastrointestinal stromal tumor: MiR-125a-5p. In a study on FFPE GIST samples from patients resistant to imatinib in a neoadjuvant setting, it was found that miR-125a-5p can modulate imatinib response in KIT-mutated GIST cells by regulating the expression of Protein Tyrosine Phosphatase Non-Receptor Type 18 (PTPN18).