RETN and acute promyelocytic leukemia: However, the mRNA and protein levels of resistin were enhanced, whereas the protein level of leptin was decreased in APL cells after As2O3 or ATRA treatment (Figure 6C & D), which was accompanied by elevated resistin secretion and downregulated leptin secretion (Figure 6E) in the culture supernatant of APL cells after As2O3 treatment.