Silencing of human ferrochelatase causes abundant protoporphyrin-IX accumulation in colon cancer.
Hemes and heme proteins are vital components of essentially every cell of virtually every eukaryote organism. Previously, we demonstrated accumulation of the heme precursor protoporphyrin-IX (PpIX) in gastrointestinal tumor tissues. To elucidate the mechanisms of PpIX accumulation by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we studied expression of the relevant enzymes of the heme synthetic pathway. Here, we describe a significant down-regulation of ferrochelatase (FECH) mRNA expression in gastric, colonic, and rectal carcinomas. Accordingly, in an in vitro model of several carcinoma cell lines, ferrochelatase down-regulation and loss of enzymatic activity corresponded with an enhanced PpIX-dependent fluorescence. Direct detection of PpIX in minute amounts was achieved by a specifically developed pulsed solid-state laser dual delay fluorimetry setup. Silencing of FECH using small interfering RNA (siRNA) technology led to a maximum 50-fold increased PpIX accumulation, imageable by a specifically adapted two-photon microscopy unit. Our results show that in malignant tissue a transcriptional down-regulation of FECH occurs, which causes endogenous PpIX accumulation. Furthermore, accumulation of intracellular PpIX because of FECH siRNA silencing provides a small-molecule-based approach to molecular imaging and molecular therapy.
Kemmner
Wolfgang
W
Max Delbrueck Center for Molecular Medicine, Robert Roessle Str 10, 13125 Berlin, Germany. wkemmner@mdc-berlin.de
Wan
Kayiu
K
Rüttinger
Steffen
S
Ebert
Bernd
B
Macdonald
Rainer
R
Klamm
Ursula
U
Moesta
K Thomas
KT
D000622:Aminolevulinic Acid / Q000494:pharmacology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000235:genetics; D005294:Ferrochelatase / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006418:Heme / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D006801:Humans; D011524:Protoporphyrins / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*; D013274:Stomach Neoplasms / Q000201:enzymology / Q000235:genetics
D011524:Protoporphyrins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D006418:Heme; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; D006419:Heme Oxygenase (Decyclizing); D005294:Ferrochelatase