SPHK1 and carcinoma of esophagus: Key points to note are the differential and increased expression of SphK and S1PRs during the mesenchymal transition and the aggressive invasive stages of oesophageal squamous cell carcinoma; increased levels of SphK1 and serum S1P all correlated with metastasis-positivity in lymph nodes in most oesophageal cancer patients [113].