Mangostin enhances efficacy of aminolevulinic acid-photodynamic therapy against cancer through inhibition of ABCG2 activity.

BACKGROUND: Aminolevulinic acid-photodynamic therapy (ALA-PDT) is gaining attention as a potential method for treating select cancers due to its high specificity and low side effect feature. ALA enters cancer cells and accumulate as protoporphyrin IX (PpIX), which will then trigger phototoxicity following light irradiation. However, it is reported that some cancer cells have reduced efficacy of ALA-PDT due to high expression of ABCG2, a transporter involved in the PpIX efflux. In this study, we evaluated the effect of mangostin, a natural compound containing anti-tumor property, on the efficacy of ALA-PDT against cancer and the mechanism involved. METHODS: We utilized TMK1 gastric cancer cell line, which has high ABCG2 expression, to evaluate the PpIX accumulation and phototoxicity exerted by ALA and mangostin co-addition. RESULTS: We found that co-addition of ALA and mangostin significantly increase the phototoxicity and PpIX accumulation in TMK1 cells. We also investigated the effect of mangostin on porphyrin-heme pathway enzymes and ABCG2 and found that the addition of mangostin reduce the activity of ABCG2, reducing PpIX efflux. CONCLUSION: These findings suggest that mangostin enhances the efficacy of ALA-PDT in cancer through inhibition of ABCG2 activity.

Cell senescence-associated porphyrin metabolism affects the efficacy of aminolevulinic acid-photodynamic diagnosis in bladder cancer.

Aminolevulinic acid-photodynamic diagnosis (ALA-PDD) is a promising alternative method to detect cancer cells because of its high specificity and low rate of side effects. Exogenous ALA is administered and accumulates as protoporphyrin IX (PpIX) in cancer cells, which then emit red fluorescence following light irradiation to enable surgeons to accurately identify and remove cancerous tissue. Recent reports suggested that PpIX failed to accumulate in some patients who underwent ALA-PDD. We hypothesized that cell senescence, which is a relatively inactive state, affects porphyrin accumulation in bladder cancer cells. In this study, we evaluated the relationship between cell senescence and porphyrin accumulation in affecting the efficacy of ALA-PDD. First, we utilized three bladder cancer cell lines to evaluate senescence-related indicators and establish a cell senescence model. Then, we identified the differences in porphyrin production and the proteins involved in porphyrin accumulation between old and young cells. We found that compared with young cells, old cells possessed higher concentration of PpIX and had lower ABCG2 expression. The increase in PpIX levels following ABCG2 inhibition is three times higher in old cells than in young cells, suggesting that cell senescence was closely related with porphyrin accumulation in cancer. In conclusion, we found that the efficacy of ALA-PDD and porphyrin accumulation was relatively high in senescent cancer cells and that inhibition of ABCG2 could improve the efficacy of ALA-PDD in young bladder cancer cells.

Metabolic shift towards oxidative phosphorylation reduces cell-density-induced cancer-stem-cell-like characteristics in prostate cancer in vitro.

Numerous cancer patients undergoing conventional cancer therapies such as radiotherapy, chemotherapy and surgical tumour removal face relapses several years or even decades later. This may be due to the presence of cancer stem cells (CSCs) that survived said therapies. In this study, we aimed to uncover the relationship between cell density and CSCs, and the role of the Warburg effect in regulating CSC-like characteristics. A prostate cancer cell line, PC3, was used in this study. To investigate the Warburg effect effect and CSC-like characteristics in prostate cancer, we measured the expression levels of glycolysis and OXPHOS-related genes, and performed spheroid forming, cell viability and various glycolysis and OXPHOS-assays. We observed that increased cell density caused a metabolic shift from glycolysis to OXPHOS and higher CSC-like characteristics. However, the use of dichloroacetate (DCA), an inhibitor of the Warburg effect, significantly inhibited the cell-density-induced metabolic shift and CSC-like characteristics. Changes in cell density strongly influenced the preferred metabolic pathway of prostate cancer cells, regulating their CSC-like characteristics. It is possible that DCA, an inhibitor of the Warburg effect, could be a novel drug used to treat CSCs by distinguishing Warburg effect, preventing future cancer relapses.

Suppression of angiotensin converting enzyme 2, a host receptor for SARS-CoV-2 infection, using 5-aminolevulinic acid in vitro.

Angiotensin converting enzyme 2 (ACE2), an entry receptor found on the surface of host cells, is believed to be detrimental to the infectious capability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Scientists have been working on finding a cure since its outbreak with limited success. In this study, we evaluated the potential of 5-aminolevulinic acid hydrochloride (ALA) in suppressing ACE2 expression of host cells. ACE2 expression and the production of intracellular porphyrins following ALA administration were carried out. We observed the reduction of ACE2 expression and intracellular porphyrins following ALA administration. ALA suppressed the ACE2 expression in host cells which might prevent binding of SARS-CoV-2 to host cells. Co-administration of ALA and sodium ferrous citrate (SFC) resulted in a further decrease in ACE2 expression and increase in intracellular heme level. This suggests that the suppression of ACE2 expression by ALA might occur through heme production. We found that the inhibition of heme oxygenase-1 (HO-1), which is involved in heme degradation, also resulted in decrease in ACE2 expression, suggesting a potential role of HO-1 in suppressing ACE2 as well. In conclusion, we speculate that ALA, together with SFC administration, might serve as a potential therapeutic approach in reducing SARS-CoV-2 infectivity through suppression of ACE2 expression.

Real-world experience with 5-aminolevulinic acid for photodynamic diagnosis of bladder cancer (2nd report): Reduced bladder recurrence after PDD-TURBT.

BACKGROUND: Photodynamic diagnosis (PDD) with administration of oral aminolevulinic acid (ALA) prior to transurethral resection of bladder tumor (TURBT) can now be used for non-muscle invasive bladder cancer (NMIBC) in clinical settings in Japan. Since ALA was first marketed, a limited number of reports have described PDD-TURBT outcomes, and the effects of resecting false-positive tissue on outcomes have not been clarified. METHODS: This study compared tumor recurrence among NMIBC patients who underwent TURBT under either white light cystoscopy (WL) or PDD. In addition, the frequency of recurrence was compared between patients with or without false-positive lesions at the time of PDD-TURBT. RESULTS: The frequency of recurrence in NMIBC patients (cumulative number of recurrences/cumulative number of follow-up days, number of recurrences/10,000 days), including progression to muscle-invasive bladder cancer (MIBC), was 12.80 in the WL-TURBT group and 5.82 in the PDD-TURBT group (p < 0.05). Tumor recurrence after TURBT was seen in 29 of 88 patients (33.0%) in the WL-TURBT group and 21 of 105 patients (20.0%) in the PDD-TURBT group (p < 0.05). Mean (± standard deviation) time to first recurrence was 249 ± 140 days in the WL-TURBT group and 419 ± 219 days in the PDD-TURBT group (p < 0.05). The frequency of recurrence in PDD-TURBT-group NMIBC patients was significantly lower in patients with resection of false-positive tissue (4.19/10,000 days) than in those without (9.00/10,000 days, p < 0.05). CONCLUSION: The frequency of recurrence was lower and the time to recurrence was longer in the PDD-TURBT group than in the WL-TURBT group. The frequency of recurrence decreased with resection of false-positive resection.

Current status of photodynamic technology for urothelial cancer.

5-Aminolevulinic acid is a new-generation photosensitizer with high tumor specificity. It has been used successfully in the diagnosis, treatment, and screening of urological cancers including bladder cancer; specifically, it has been used in photodynamic diagnosis to detect tumors by illuminating the lesion with a specific wavelength of light to produce fluorescence in the lesion after administration of 5-aminolevulinic acid, in photodynamic therapy, which induces tumor cell death via production of cytotoxic reactive oxygen species, and in photodynamic screening, in which porphyrin excretion in the blood and urine is used as a tumor biomarker after administration of 5-aminolevulinic acid. In addition to these applications in urological cancers, 5-aminolevulinic acid-based photodynamic technology is expected to be used as a novel strategy for a large number of cancer types because it is based on a property of cancer cells known as the Warburg effect, which is a basic biological property that is common across all cancers.

Efficiency of aminolevulinic acid (ALA)-photodynamic therapy based on ALA uptake transporters in a cell density-dependent malignancy model.

The effectiveness of the conventional chemotherapy for cancer are compromised as the cancer cells advances in their malignancy level as they acquired drug resistance. In this study, we aimed to evaluate the efficiency of aminolevulinic acid-photodynamic therapy (ALA-PDT) against cancer of various malignancy levels, indicated by the expression level of receptor associated nuclear factor-κB ligand (RANKL), through the expression levels of ALA uptake transporters. We established a malignancy model by gradually increasing the cell density of cancer cells. Western blotting was used to study the expression levels of RANKL, ALA uptake transporters and the cell density-dependent Yes-associated protein (YAP) under different cell densities. The amount of protoporphyrin (PpIX) produced and cell viability were then studied using high performance liquid chromatography (HPLC) and ALA-PDT assay. Our study showed that the amount of PpIX production doubled in high cell density/cancer malignancy cultures and the effectiveness of ALA-PDT when subjected to light irradiation at 635 nm are significantly at higher cancer malignancy. We observed that the expression levels of ALA uptake transporters and YAP correlated with higher cell density/cancer malignancy, suggesting a possible relationship among these three factors. These findings suggest that ALA-PDT is more effective in cancer cells of higher malignancy due to the upregulation of transporters involved in ALA uptake.

Key transporters leading to specific protoporphyrin IX accumulation in cancer cell following administration of aminolevulinic acid in photodynamic therapy/diagnosis.

The administration of aminolevulinic acid allow the formation and accumulation of protoporphyrin IX specifically in cancer cells, which then lead to photocytotoxicity following light irradiation. This compound, when accumulated at high levels, could also be used in cancer diagnosis as it would emit red fluorescence when being light irradiated. The concentration of protoporphyrin IX is pivotal in ensuring the effectiveness of the therapy. Studies have been carried out and showed the importance of various transporters in regulating the amount of these substrates by controlling the transport of various related metabolites in and out of the cell. There are many transporters involved and their expression levels are dependent on various factors, such as oxygen availability and iron ions. It is also important to note that these transporters may also have different expression levels depending on their organ. Understanding the mechanisms and the roles of these transporters are essential to ensure maximum accumulation of protoporphyrin IX, leading to higher efficiency in photodynamic therapy/diagnosis. In this review, we would like to discuss the roles of various transporters in protoporphyrin IX accumulation and how their involvement directly affect cancerous microenvironment.

Novel strategy to increase specificity of ALA-Induced PpIX accumulation through inhibition of transporters involved in ALA uptake.

BACKGROUND: Aminolevulinic acid-based photodynamic therapy (ALA-PDT) has emerged as a cancer treatment due to its high specificity and low side effects. In this study, we aimed to identify possible new drugs targeting transporters highly expressed in normal cells but not in cancer cells, to increase the specificity of ALA-PDT. METHOD: We used a total of seven cell lines, consisting of two gastric, three prostate, and two lung cell lines, for this purpose. siRNAs and inhibitors of these transporters were added, and PpIX production was evaluated using HPLC to examine the roles of transporters in ALA uptake. RESULTS: No correlation in the expression of transporters was observed among cell lines of the same origin. Two major findings were obtained: PEPT1 and PAT1 were expressed only in normal lung and prostate cells, respectively, but not in their cancerous counterparts. The inhibition of these transporters saw a significant decrease in PpIX production only in normal cells, but not in cancer cells. CONCLUSION: These findings show that the usage of drugs targeted specifically to highly expressed transporters in normal cells is essential for reducing PpIX accumulation in normal cells in order to increase the specificity of ALA-PDT in cancer.