Above a threshold cell density, cancer cells secrete IL-6 and IL-8, which synergistically activate a complex paracrine signaling pathway via Janus kinase (JAK2) and signal transducer and activator of transcription 3 (STAT3) that prompts cancer cells to form Arp2/3-dependent dendritic protrusions and undergo migration. The gene discussed is JAK2; the disease is cancer.