Phytoestrogen Suppresses Efflux of the Diagnostic Marker Protoporphyrin IX in Lung Carcinoma

Abstract

One promising method to visualize cancer cells is based on the detection of the fluorescent photosensitizer protoporphyrin IX (PpIX) synthesized from 5-aminolevulinic acid (ALA), but this method cannot be used in cancers that exhibit poor PpIX accumulation. PpIX appears to be pumped out of cancer cells by the ABC transporter G2 (ABCG2), which is associated with multidrug resistance. Genistein is a phytoestrogen that appears to competitively inhibit ABCG2 activity. Therefore, we investigated whether genistein can promote PpIX accumulation in human lung carcinoma cells. Here we report that treatment of A549 lung carcinoma cells with genistein or a specific ABCG2 inhibitor promoted ALA-mediated accumulation of PpIX by approximately 2-fold. ABCG2 depletion and overexpression studies further revealed that genistein promoted PpIX accumulation via functional repression of ABCG2. After an extended period of genistein treatment, a significant increase in PpIX accumulation was observed in A549 cells (3.7-fold) and in other cell lines. Systemic preconditioning with genistein in a mouse xenograft model of lung carcinoma resulted in a 1.8-fold increase in accumulated PpIX. Long-term genistein treatment stimulated the expression of genes encoding enzymes involved in PpIX synthesis, such as porphobilinogen deaminase, uroporphyrinogen decarboxylase, and protoporphyrinogen oxidase. Accordingly, the rate of PpIX synthesis was also accelerated by genistein pretreatment. Thus, our results suggest that genistein treatment effectively enhances ALA-induced PpIX accumulation by preventing the ABCG2-mediated efflux of PpIX from lung cancer cells and may represent a promising strategy to improve ALA-based diagnostic approaches in a broader set of malignancies.

Evaluation of aminolevulinic acid-mediated protoporphyrin IX fluorescence and enhancement by ABCG2 inhibitors in renal cell carcinoma cells

“…Another kinase inhibitor gefitinib was found to increase intracellular PpIX and cytotoxicity induced by ALA-PDT in human glioma cell lines (26). Genistein, a kinase inhibitor and isoflavone phytoestrogen, has recently been shown to increase ALA-PpIX in a lung cancer tumor model (27) and human glioma cells (28).…”

A Novel 89Zr-labeled DDS Device Utilizing Human IgG Variant (scFv): “Lactosome” Nanoparticle-Based Theranostics for PET Imaging and Targeted Therapy

“…A separate study demonstrated the use of genistein, a phytoestrogen that appears to competitively inhibit ABCG2 for the enhancement of ALA-induced PpIX accumulation [177]. This study showed that genistein promoted the accumulation of PpIX in A549 cell lines both in vitro and in vivo by preventing ABCG2-mediated PpIX efflux and upregulating the gene expression of heme synthesis enzymes.…”

“…Estrogen-depleted rats were found to reduce ALA-induced PpIX levels in their tumors suggesting that estrogen and the phytoestrogen genistein may accelerate the accumulation of PpIX via ERβ signaling. This study reported that ALA-induced PpIX accumulation was increased by 3.7 times in vitro and 1.8 times in vivo, following pre-treatment with genistein [177]. Although PpIX was found to selectively accumulate in tumors [164], ALA-based PDD and PDT remained unsatisfactory in diagnosing some tumors that accumulate insufficient amounts of PpIX.…”

Photodynamic Therapy Using a Novel Phosphorus Tetraphenylporphyrin Induces an Anticancer Effect via Bax/Bcl-xL-related Mitochondrial Apoptosis in Biliary Cancer Cells

“…Other studies have similarly shown that the efficacy of PDT with various photosensitizers has a clear correlation with their fluorescence intensity [ 11 , 25 ]. Overexpression of adenosine triphosphate-binding cassette (ABC) efflux transporters, such as ABCB1 (multidrug resistance protein 1 (MDR1)/permeability glycoprotein (P-gp)), ABCC1 (multidrug resistance-associated protein 1 (MRP1)) and breast cancer resistance protein ABCG2 (BCRP), is a key factor in PDT resistance in colon adenocarcinoma and lung carcinoma cells [ 14 , 20 , 51 ]. P-gp and BCRP are highly expressed in HepG2 cells [ 10 , 24 ], which may be related to lower accumulation of Ptpp in these cells compared to NOZ cells.…”