S1PR1 and neoplasm: In the search for a possible regulatory mechanism for mir-92a and lipocalin-2, studies have focused on apoptotic cell-derived sphingosine-1-phosphate (S1P), which induces the production and release of lipocalin-2 by human macrophages through the S1P-S1PR1-signal transducer and activator of transcription 3 (STAT3)-lipocalin-2 axis in lymphangiogenesis and tumor metastasis [37, 38].