PTBP1 and osteosarcoma: The results of qRT‐PCR analysis showed that the expression of SLC31A1 mRNA was down‐regulated in osteosarcoma tissues, especially lower in chemotherapy‐insensitive osteosarcoma tissues, and there was a negative correlation between the expression of SLC31A1 and PTBP1 in osteosarcoma tissue (Figure 4A,B).