STAT3 and neoplasm: Depending on the tumor type, the RAS/MEK/ERK pathway acts alone or cooperates with other oncogenic pathways [e.g., JNK-, PI3K/AKT-, IL-6/STAT3, and echinoderm microtubule associated protein-like 4/anaplastic lymphoma kinase (EML4/ALK)-dependent pathways] in increasing PD-1L [124,158,159,160,161,162].