PBGD has been suggested to play an important role in elevated ALA-PpIX production in tumor cells based on the findings that increased PBGD expression or activity is associated with cell transformation [19,20], and the upregulation of PBGD enzymatic activity has been found in some cancer cells [21,22,23] and after ALA stimulation [24,25]. The gene discussed is HMBS; the disease is neoplasm.