title: The effect of 5-aminolevulinic acid and its derivatives on protoporphyrin IX accumulation and apoptotic cell death in castrate-resistant prostate cancer cells.
abstract: OBJECTIVE
  To examine whether pharmacologically relevant zinc-binding agents are capable of depleting X-linked inhibitor of apoptosis protein in tumor cells. Our prior work reveals that treatment with zinc-chelating agents induces selective downregulation of the X-linked inhibitor of apoptosis protein in cancer cells of various origins. A precursor of the heme synthetic pathway, 5-aminolevulinic acid, is metabolized to protoporphyrin IX, which is highly reactive with zinc. We assessed whether modified versions of 5-aminolevulinic acid with lipophilic side chains can enhance efficacy and selectivity with respect to protoporphyrin IX accumulation, X-linked inhibitor of apoptosis protein depletion, and tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis in human castration-resistant prostate cancer cells.
  
  
  METHODS
  Seven modified versions of 5-aminolevulinic acid (5 esters and 2 amides) were synthesized. Levels of endogenous protoporphyrin IX were examined by flow cytometry. X-linked inhibitor of apoptosis protein expression was examined by Western blotting. terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assay was used to assess cell apoptosis. Results were compared qualitatively.
  
  
  RESULTS
  Accumulation of endogenous protoporphyrin IX by castration-resistant prostate cancer cells was shown to be directly related to the carbon chain length of the esterified 5-aminolevulinic acid derivatives. In fact, treatment with 5-aminolevulinic acid-HE was superior to that achieved by 5-aminolevulinic acid with respect to X-linked inhibitor of apoptosis protein downregulation. 5-aminolevulinic acid and 5-aminolevulinic acid-HE in combination with tumor necrosis factor-related apoptosis-inducing ligand significantly enhanced apoptotic cell death in castration-resistant prostate cancer cell lines.
  
  
  CONCLUSIONS
  Esterified derivatives of 5-aminolevulinic acid alone or in combination with other agents may provide therapeutic opportunities in the treatment of castration-resistant prostate cancer by harnessing apoptotic pathways that are triggered by cellular zinc imbalance.
authors.affiliation: Fox Chase Cancer Center, Philadelphia, PA 19111, USA. ervin.teper@fccc.edu
authors.forename: Ervin
authors.initials: E
authors.lastname: Teper
authors.forename: Peter
authors.initials: P
authors.lastname: Makhov
authors.forename: Konstantin
authors.initials: K
authors.lastname: Golovine
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Canter
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Myers
authors.forename: Alexander
authors.initials: A
authors.lastname: Kutikov
authors.forename: Steven N
authors.initials: SN
authors.lastname: Sterious
authors.forename: Robert G
authors.initials: RG
authors.lastname: Uzzo
authors.forename: Vladimir M
authors.initials: VM
authors.lastname: Kolenko
mesh_terms: D000622:Aminolevulinic Acid / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D006801:Humans; D008297:Male; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011524:Protoporphyrins / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism*; D015032:Zinc
chemical_list: D002614:Chelating Agents; D005029:Ethylenediamines; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine