Tumour released IL-1 cross-talks to TAMs and induces M2 polarization to an immunosuppressive phenotype via IL-1 receptor (IL-1R) and myeloid differentiation primary response gene 88 (MyD88), which requires I-kappaB kinase beta (IKKβ)-mediated nuclear factor kappa B (NF-κB) [
31,
32]. Interleukin-1 beta (IL-1β) is a critical mediator of chronic inflammation and is implicated in OSCC during early and late stages of carcinogenesis. Pro-IL-1β is upregulated in tobacco and betel quid related oral cancer, and is secreted in an inflammasome-dependent manner [
33], although it is absent in homeostatic conditions. In the presence of IL-1β TAMs suffer an upregulation of C-X-C motif chemokine receptors (CXCR), especially CXCR4, induced by the activation of extracellular signal regulated MAP kinase (ERK). Macrophages then become attracted by CXCR4 ligands, like stromal cell derived factor-1 alpha (SDF-1α) [
34]. SDF-1α is highly inducible in hypoxic and proangiogenic niches, where it reinforces the autocrine/paracrine loop that contributes to an M2 phenotype [
35]. Nevertheless, OSCC cells and TAMs together through IL-1β/IL-1R and CXCR4/ SDF-1α and via activation of the ERK signalling pathway produce tumour cell migration and invasion by inducing expression of matrix metalloproteinase (MMP) enzymes MMP-9 and MMP-13 [
36]. These important angiogenic modulating enzymes promote the acquisition of vasculature for oxygenation, nutrition, and waste disposal, which are of fundamental importance for tumour growth [
2]. Contrarily, the blockade of CXCR4 by the antagonist 1,1′-[1,4-phenylenebis(methylene)]bis-1,4,8,11-tetraazacyclotetradecane octahydrochloride (AMD3100) inhibited SDF-1 mediated lymph node metastasis [
37]. Furthermore, a rich IL-1β microenvironment promotes CXCL1 production, and through CXCR2 this induces tyrosine phosphorylation of the endothelial growth factor receptor (EGFR) [
33]. As a result, EGFR activates pathways leading to cell growth, DNA synthesis, and the expression of oncogenes like
fos and
jun [
38]. IL-1α is found in tumour cell membranes and in intracellular locations, and is produced in larger amounts than IL-1β in highly metastatic tumours. Despite the lack of evidence that demonstrates its direct participation in OSCC progression through macrophage activation, IL-1α interacts with fibroblasts in the stroma. Therefore, IL-1α acts promoting cell proliferation and upregulating the secretion of IL-8, CXCL-1, and chemokine C-C motif ligand (CCL)-7 [
39]. Coincidently, these cytokines are also commonly produced by TAMs, rising the hypothesis of a plausible interaction between OSCC and M2 cells by means of IL-1α.