RSPO3 and squamous cell lung carcinoma: RSPO3 (R-spondin-3), an activator of the canonical Wnt signaling pathway and PI3K/AKT pathway as a key regulator of angiogenesis and epithelial-mesenchymal transition, has shown low expression in colorectal cancer, squamous cell carcinoma of the lung and prostate cancer, but upregulated expression in bladder cancer, ovarian cancer and lung adenocarcinoma [47–50].