A further similarity with HPRT deficiency was the observed guanine nucleotide depletion induced by an inhibition of IMPDH with low levels of mycophenolic acid in human neuroblastoma DA line LAN5, which developed less extensive neurite outgrowth and branching, similar to that observed in cultured HPRT-deficient DA neurons [71]. Here, HPRT1 is linked to neuroblastoma.