title: Aminolevulinic Acid-Based Tumor Detection and Therapy: Molecular Mechanisms and Strategies for Enhancement.
abstract: Aminolevulinic acid (ALA) is the first metabolite in the heme biosynthesis pathway in humans. In addition to the end product heme, this pathway also produces other porphyrin metabolites. Protoporphyrin (PpIX) is one heme precursor porphyrin with good fluorescence and photosensitizing activity. Because tumors and other proliferating cells tend to exhibit a higher level of PpIX than normal cells after ALA incubation, ALA has been used as a prodrug to enable PpIX fluorescence detection and photodynamic therapy (PDT) of lesion tissues. Extensive studies have been carried out in the past twenty years to explore why some tumors exhibit elevated ALA-mediated PpIX and how to enhance PpIX levels to achieve better tumor detection and treatment. Here we would like to summarize previous research in order to stimulate future studies on these important topics. In this review, we focus on summarizing tumor-associated alterations in heme biosynthesis enzymes, mitochondrial functions and porphyrin transporters that contribute to ALA-PpIX increase in tumors. Mechanism-based therapeutic strategies for enhancing ALA-based modalities including iron chelators, differentiation agents and PpIX transporter inhibitors are also discussed.
authors.affiliation: Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, PA 19104, USA. xyang1349@mail.usciences.edu.
authors.forename: Xue
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, PA 19104, USA. ppalasuberniam@mail.usciences.edu.
authors.forename: Pratheeba
authors.initials: P
authors.lastname: Palasuberniam
authors.affiliation: Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, PA 19104, USA. dkraus@mail.usciences.edu.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kraus
authors.affiliation: Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, PA 19104, USA. b.chen@usciences.edu.
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
mesh_terms: D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D000818:Animals; D006418:Heme / Q000378:metabolism; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011524:Protoporphyrins / Q000378:metabolism
chemical_list: D017319:Photosensitizing Agents; D011524:Protoporphyrins; D006418:Heme; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX
keywords: aminolevulinic acid (ALA); fluorescence; heme biosynthesis; photodynamic therapy (PDT); protoporphyrin IX (PpIX); tumor detection