LEP and obesity due to melanocortin 4 receptor deficiency: Despite evidence from in vitro studies supporting a mitogenic role for leptin in PDAC cells (Mendonsa et al, 2015; Harbuzariu et al, 2017), our data showed that obesity can accelerate pancreatic tumorigenesis in vivo in the absence of leptin (Lepob/ob) or its receptor (Leprdb/db) (Chung et al, 2020), arguing against leptin itself being an essential driver of obesity-associated PDAC development.