PLPPR4 and cancer: At present, studies on PRGs family mainly focus on neuropsychiatric diseases and nerve injuries such as epilepsy 34, 38, 39, schizophrenia 40, 41, memory disorders 35, nerve trauma 42, 43, sensory discrimination deficit 44, 45, etc. Besides, PRG-1 may be involved in cancerogenesis because the target role of LPA in cancer 33, 46.