Metabolic Characterization of Tumor Cell-specific Protoporphyrin IX Accumulation After Exposure to 5-Aminolevulinic Acid in Human Colonic Cells¶

Abstract

5-Aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) fluorescence has been shown to have high tumor cell selectivity in various organs, including the gastrointestinal (GI) tract. To better understand and to possibly find new approaches to therapeutic application, we investigated the uptake kinetics and consequent metabolism of ALA and PPIX, respectively. Three colon carcinoma (CaCo2, HT29, SW480) and a stromal cell line (fibroblast, CCD18) were chosen to mimic important aspects of malignant mucosa of the GI tract. Because differential PPIX concentrations in these cell lines represented the in vivo observations (ratio tumor vs normal 10:1-20:1), we analyzed the ALA uptake, mitochondrial properties and key molecules of PPIX metabolism (porphobilinogen deaminase [PBGD], ferrochelatase [FC], iron content, transferrin receptor content). The tumor-preferential PPIX accumulation is strongly influenced, but not solely determined, by activity differences between the PPIX-producing PBGD and the PPIX-converting FC, when compared with fibroblasts. Tumor-specific PPIX accumulation is generated by ALA conversion rather than by initial ALA uptake because no significant overall difference in uptake (about 0.6 lg ALA/mg protein) of ALA is seen. In conclusion, further research of tumor cell selectivity of PPIX fluorescence should focus on the mechanisms responsible for an altered PPIX metabolism to find tumor-specific target molecules, thus leading to an improved clinical practicability of ALA application and consequent endoscopy.

Enhancement of methyl-aminolevulinate photodynamic therapy by iron chelation with CP94: an in vitro investigation and clinical dose-escalating safety study for the treatment of nodular basal cell carcinoma

“…Differing PpIX accumulation between normal and tumor human colonic cells has been found to be influenced by (but not solely determined by) differences in porphobilinogen deaminase (production of PpIX) and ferrochelatase (conversion of PpIX to haem) activities [34,35]. Iron metabolism has also been shown to be altered in tumor cells.…”

Epithelial Growth Factor Receptor Expression influences 5-ALA Induced Glioblastoma Fluorescence

“…Furthermore, during surgery, the magnitude of fluorescence may be influenced by factors such as logistical changes in time of resection after 5-ALA administration, its reabsorption, and variations in its passage through the blood brain barrier. While both 5-ALA passive and active uptake mechanisms, and their consequent implication in the time rate of the induced fluorescence, are still under discussion [5][6][7][8], the interobserver variability of the 5-ALA-induced fluorescence remains unaddressed in the clinical setting.…”

“…Clinically, the exogenous, oral administration of 5-ALA is usually performed 4h prior to surgery. 5-ALA is resorbed through the upper intestine into the blood, where it diffuses through the blood-brain barrier, which has been typically disrupted by infiltrative tumor cells [5][6][7][8][9]. During fluorescence assisted tumor resection a variance of the fluorescence intensity within GBM can be observed, especially at the infiltrating zone [4,8,10].…”

“…During fluorescence assisted tumor resection a variance of the fluorescence intensity within GBM can be observed, especially at the infiltrating zone [4,8,10]. 5-ALA induced fluorescence may vary upon many factors such as cell density, proliferation index, mitochondrial mass and index and furthermore exogenous factors such as application or fading during surgery [5][6][7][8]. Schwake et al have shown that in GBM cell lines continuous exposition of 5-ALA continuously increased 5-ALA induced fluorescence up to 24 h [11].…”

Deep UV sensing of the interaction of porphyrin with bovine serum albumin protein

“…In recent years there has been a growing interest in the use of porphyrins and related compounds as therapeutic drugs. They are applied in medicine on important areas as cancer detection and photosensitizers in photodynamic therapy of cancer [3][4][5][6].…”