Furthermore, a recent study proposes a far-reaching model (using serial single-cell RNA sequencing) of paracrine signaling mediated by the activity of cyclooxygenase (COX-2) enzyme activity and production of the proinflammatory mediator, prostaglandin E2 (PGE2), by prolactin receptor (PLR+)-expressing tumor cells (Zheng et al., 2019). Here, PRLR is linked to neoplasm.