A new study employing a squamous cell carcinoma murine model reported that tumor-initiating cells promote the release of IL-33 to facilitate differentiation of TGF-β-producing macrophages, upregulating IL-33 expression and increasing the invasive and drug-resistant properties of tumor-initiating cells to form a regulatory feedback loop that promotes cancer progression [240]. The gene discussed is IL33; the disease is squamous cell carcinoma.