Conversely, STAT3 activation is significantly enhanced by stimulation of macrophage-derived culture supernatant (CS) in SCLC cells, and macrophage-derived factors such as CCL4 and IL-6 are involved in the activation of STAT3 in SCLC cells [37], suggesting that TAMs probably participate in SCLC progression via STAT3 activation. This evidence concerns the gene CCL4 and small cell lung carcinoma.