SPHK1 and neoplasm: Given the considerable evidence showing increased SphK1/S1P/S1PRs is present in many types of cancer, as discussed in this review and others [98, 223, 338, 339], there is the potential for SphK isozymes, isoforms and S1P and S1PRs as potential new biomarkers for clinical diagnosis and prognosis, for early cancer detection, as an indicator of progression and tumor aggressiveness.