Silencing of human ferrochelatase causes abundant protoporphyrin-IX accumulation in colon cancer.

Abstract

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.

• Authors: Wolfgang Kemmner, Kayiu Wan, Steffen Rüttinger, Bernd Ebert, Rainer Macdonald, Ursula Klamm, K Thomas Moesta
• Journal: FASEB journal : official publication of the Federation of American Societies for Experimental Biology (FASEB J) Vol. 22 Issue 2 Pg. 500-9 (Feb 2008) ISSN: 1530-6860 [Electronic] United States
• PMID: 17875605 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Protoporphyrins
• RNA, Messenger
• RNA, Small Interfering
• Heme
• Aminolevulinic Acid
• protoporphyrin IX
• Heme Oxygenase (Decyclizing)
• Ferrochelatase

Topics

• Aminolevulinic Acid (pharmacology)
• Cell Line, Tumor
• Colonic Neoplasms (enzymology, genetics)
• Ferrochelatase (genetics, metabolism)
• Gene Expression Regulation, Enzymologic (drug effects)
• Heme (metabolism)
• Heme Oxygenase (Decyclizing) (metabolism)
• Humans
• Protoporphyrins (metabolism)
• RNA, Messenger (genetics)
• RNA, Small Interfering (genetics)
• Stomach Neoplasms (enzymology, genetics)