Fluorescence-based discrimination of breast cancer cells by direct exposure to 5-aminolevulinic acid

Enhancing 5-ALA-PDT efficacy against resistant tumor cells: Strategies and advances

As a precursor of protoporphyrin IX (PpIX), an endogenous pro-apoptotic and fluorescent molecule, 5-Aminolevulinic acid (5-ALA) has gained substantial attention for its potential in fluorescence-guided surgery as well as photodynamic therapy (PDT). Moreover, 5-ALA-PDT has been suggested as a promising chemo-radio sensitization therapy for various cancers. However, insufficient 5-ALA-induced PpIX fluorescence and the induction of multiple resistance mechanisms may hinder the 5-ALA-PDT clinical outcome. Reduced efficacy and resistance to 5-ALA-PDT can result from genomic alterations, tumor heterogeneity, hypoxia, activation of pathways related to cell surveillance, production of nitric oxide, and most importantly, deregulated 5-ALA transporter proteins and heme biosynthesis enzymes. Understanding the resistance regulatory mechanisms of 5-ALA-PDT may allow the development of effective personalized cancer therapy. Here, we described the mechanisms underlying resistance to 5-ALA-PTD across various tumor types and explored potential strategies to overcome this resistance. Furthermore, we discussed future approaches that may enhance the efficacy of treatments using 5-ALA-PDT.

The therapeutic efficacy of 5-ALA based photodynamic therapy and chemotherapy combination in triple negative breast cancer cells

Triple negative breast cancer (TNBC) is one of the subtypes of breast cancer characterized by a heterogeneous and aggressive nature. Photodynamic therapy (PDT) has drawn significant attention in cancer treatment. However, solubility of photosensitizer, penetration problems into a target tissue and insufficient oxygen concentration limit the effectiveness of PDT. To overcome these limitations and to reduce the side effects of chemotherapy, combination treatment modalities play an essential role in cancer treatment. In this study, we aimed to investigate the combination efficacy of cisplatin-based chemotherapy and 5-Aminolevulinic acid (5-ALA)/PDT in TNBC cells and healthy breast cells in vitro. To determine the effect of the combination effects of cisplatin and 5-ALA/PDT on TNBC cells, two treatment protocols (simultaneous and sequential combination therapy) were evaluated compared with cisplatin and 5-ALA/PDT monotherapy and WST-1, Annexin V assay, acridine orange (AO) and mitochondrial staining were performed. Our findings showed that MDA-MB-231 TNBC cell viability was significantly decreased following simultaneous combination treatment compared to cisplatin and 5-ALA/PDT monotherapy. Additionally, simultaneous combination treatment was more effective than sequential combination treatment. The simultaneous combination treatment of 2.5 µM cisplatin and 5-ALA/PDT at 6 J/cm2 and 9 J/cm2 induced 46.78% and 53.6% total apoptotic death, respectively in TNBC cells compared with monotherapies (cisplatin (37.88%) and 5-ALA/PDT (6 J/cm2: 31.48% and 9 J/cm2: 37.78%). Additionally, cisplatin and 5-ALA/PDT combination treatment resulted in nuclear fragmentation and mitochondrial damage due to apoptosis. Our results suggest that cisplatin and 5-ALA/PDT simultaneous combination therapy could be a promising new alternative strategy for treating TNBC. However, further studies are required to assess the underlying molecular mechanisms of cisplatin and 5-ALA/PDT combination treatment at the molecular level.

An innovative approach to detect circulating tumor cells

In cancer research, circulating tumor cells (CTCs) were identified as the main drivers of metastasis. They are vital for early detection and prevention of metastasis during cancer treatment. Even though continuous progress in research offers more and more tools to combat cancer, we still lack a proper arsenal of therapeutics. Especially in tumors with close to no targeting options, like triple-negative breast cancer, early detection is often the main difference between successful and failed therapy. When such tumors are detected too late, they may have already produced plenty of CTCs, likely causing metastasis, which is the primary reason for tumor-associated deaths. Detecting those CTCs early on could substantially impact therapy outcomes and the 5-year survival rate. In our study, we developed and evaluated a reliable and affordable CTC screening method based on flow cytometry and 5-aminolevulinic acid (5-ALA) staining. We successfully established a circulation model for 5-ALA and CTCs research and demonstrated that the method can detect an average of 11 ± 3.3 CTCs out of 10,000 peripheral blood mononuclear cells, representing as low as approximately 0.1 % with a reasonable number of false positive events. Additionally, we present initial results on a theranostic approach using 5-ALA converted to protoporphyrin IX. The outcomes of this study might contribute significantly to the further development of CTC detection and the overall detection and treatment of cancer.

Deep UV-excited fluorescence microscopy installed with CycleGAN-assisted image translation enhances precise detection of lymph node metastasis towards rapid intraoperative diagnosis

Rapid and precise intraoperative diagnosing systems are required for improving surgical outcomes and patient prognosis. Because of the poor quality and time-intensive process of the prevalent frozen section procedure, various intraoperative diagnostic imaging systems have been explored. Microscopy with ultraviolet surface excitation (MUSE) is an inexpensive, maintenance-free, and rapid imaging technique that yields images like thin-sectioned samples without sectioning. However, pathologists find it nearly impossible to assign diagnostic labels to MUSE images of unfixed specimens; thus, AI for intraoperative diagnosis cannot be trained in a supervised learning manner. In this study, we propose a deep-learning pipeline model for lymph node metastasis detection, in which CycleGAN translate MUSE images of unfixed lymph nodes to formalin-fixed paraffin-embedded (FFPE) sample, and diagnostic prediction is performed using deep convolutional neural network trained on FFPE sample images. Our pipeline yielded an average accuracy of 84.6% when using each of the three deep convolutional neural networks, which is a 18.3% increase over the classification-only model without CycleGAN. The modality translation to FFPE sample images using CycleGAN can be applied to various intraoperative diagnostic imaging systems and eliminate the difficulty for pathologists in labeling new modality images in clinical sites. We anticipate our pipeline to be a starting point for accurate rapid intraoperative diagnostic systems for new imaging modalities, leading to healthcare quality improvement.

Spotlight on porphyrins: Classifications, mechanisms and medical applications

Photodynamic therapy (PDT) and sonodynamic therapy (SDT) are non-invasive treatment methods with obvious inhibitory effect on tumors and have few side effects, which have been widely concerned and explored by researchers. Sensitizer is the main factor in determining the therapeutic effect of PDT and SDT. Porphyrins, a group of organic compounds widespread in nature, can be activated by light or ultrasound and produce reactive oxygen species. Therefore, porphyrins as sensitizers in PDT have been widely explored and investigated for many years. Herein, we summarize the classical porphyrin compounds and their applications and mechanisms in PDT and SDT. The application of porphyrin in clinical diagnosis and imaging is also discussed. In conclusion, porphyrins have good application prospects in disease treatment as an important part of PDT or SDT, and in clinical diagnosis and imaging.

5-Aminolevulinic acid hydrochloride enhances bupivacaine-induced hypotension in spontaneously hypertensive rats

PURPOSE

Oral administration of 5-aminolevulinic acid hydrochloride (5-ALA-HCl) has been reported to enhance the hypotensive effects associated with anesthetics, especially in elderly hypertensive patients treated with antihypertensive agents. The present study aimed to clarify the effects of antihypertensive-agent- and anesthesia-induced hypotension by 5-ALA-HCl in spontaneously hypertensive rats (SHRs).

METHODS

We measured blood pressure (BP) of SHRs and normotensive Wistar Kyoto (WKY) rats treated with amlodipine or candesartan before and after administration of 5-ALA-HCl. We also investigated the change in BP following intravenous infusion of propofol and intrathecal injection of bupivacaine in relation to 5-ALA-HCl administration.

FINDINGS

Oral administration of 5-ALA-HCl significantly reduced BP in SHRs and WKY rats with amlodipine and candesartan. Infusion of propofol significantly reduced BP in SHRs treated with 5-ALA-HCl. Intrathecal injection of bupivacaine significantly declined SBP and DBP in both SHRs and WKY rats treated with 5-ALA-HCl. The bupivacaine-induced decline in SBP was significantly larger in SHRs compared with WKY rats.

CONCLUSION

These findings suggest that 5-ALA-HCl does not affect the antihypertensive agents-induced hypotensive effect, but enhances the bupivacaine-induced hypotensive effect, especially in SHRs, indicating that 5-ALA may contribute to anesthesia-induced hypotension via suppression of sympathetic nerve activity in patients with hypertension.

Enlarging the Scope of 5-Aminolevulinic Acid-Mediated Photodiagnosis towards Breast Cancers

Today, most research on treating cancers targets one single cancer, often because of the very specific operation principle of the therapy. For instance, immunotherapies require the expression of a particular antigen, which might not be expressed in all cancers or in all patients. What about metastases? Combination therapies are promising but require treatment personalization and are an expensive approach that many health systems are not willing to pay for. Resection of cancerous tissues may be conducted beforehand. However, the precise location and removal of tumors are in most cases, hurdles that require margins to prevent recurrence. Herein, we further demonstrate the wide application of aminolevulinate-based photodynamic diagnosis and therapy toward breast cancers. By selecting four breast cancer cell lines that represent the main breast tumor subtypes, we investigated their ability to accumulate the fluorescent protoporphyrin IX upon treatment with the marketed 5-aminolevulinic acid hexyl ester (ALA-Hex) or our new and more stable derivative PSI-ALA-Hex. We found that all cell lines were able to accumulate PpIX under a few hours independent of their hormonal status with both treatments. Additionally, this accumulation was less dose-dependent with PSI-ALA-Hex and induced similar or higher fluorescence intensity than ALA-Hex in three out of four cell lines. The toxicity of the two molecules was not different up to 0.33 mM. However, PSI-ALA-Hex was more toxic at 1 mM, even though lower concentrations of PSI-ALA-Hex led to the same PpIX accumulation level. Additional illumination with blue light to induce cell death by generating reactive oxygen species was also considered. The treatments led to a dramatic death of the BT-474 cells under all conditions. In SK-BR-3 and MCF-7, ALA-Hex was also very efficient at all concentrations. However, increasing doses of PSI-ALA-Hex (0.33 and 1 mM) surprisingly led to a higher viability rate. In contrast, the triple-negative breast cancer cells MDA-MB-231 showed a higher death induction with higher concentrations of ALA-Hex or PSI-ALA-Hex. Derivatives of ALA seem promising as fluorescence-guided resection tools and may enable subsequent completion of cancer cell destruction by blue light irradiation.

A Recap of Heme Metabolism towards Understanding Protoporphyrin IX Selectivity in Cancer Cells

Mitochondria are essential organelles of mammalian cells, often emphasized for their function in energy production, iron metabolism and apoptosis as well as heme synthesis. The heme is an iron-loaded porphyrin behaving as a prosthetic group by its interactions with a wide variety of proteins. These complexes are termed hemoproteins and are usually vital to the whole cell comportment, such as the proteins hemoglobin, myoglobin or cytochromes, but also enzymes such as catalase and peroxidases. The building block of porphyrins is the 5-aminolevulinic acid, whose exogenous administration is able to stimulate the entire heme biosynthesis route. In neoplastic cells, this methodology repeatedly demonstrated an accumulation of the ultimate heme precursor, the fluorescent protoporphyrin IX photosensitizer, rather than in healthy tissues. While manifold players have been proposed, numerous discrepancies between research studies still dispute the mechanisms underlying this selective phenomenon that yet requires intensive investigations. In particular, we wonder what are the respective involvements of enzymes and transporters in protoporphyrin IX accretion. Is this mainly due to a boost in protoporphyrin IX anabolism along with a drop of its catabolism, or are its transporters deregulated? Additionally, can we truly expect to find a universal model to explain this selectivity? In this report, we aim to provide our peers with an overview of the currently known mitochondrial heme metabolism and approaches that could explain, at least partly, the mechanism of protoporphyrin IX selectivity towards cancer cells.

Effects of Supplemental Drugs on Hexaminolevulinate (HAL)-Induced PpIX Fluorescence in Bladder Cancer Cell Suspensions

Seven different inhibitors of the heme metabolic pathway were applied in combination with HAL to study the formation of PpIX in bladder cancer HT1197 and normal fibroblast HFFF2 cells ex vivo, specifically with the aim to increase the fluorescence contrast between cancer and non-cancer cells. The mRNA expression of enzymes involved in the heme biosynthesis pathway were measured via PCR following incubation with the drugs in order to link the fluorescence levels and metabolic activity. The exogenous administration of HAL does lead to cancer-specific PpIX accumulation. However, the contrast between cancer and normal cells in suspension was not enhanced by the enzyme inhibitors and iron-chelating agents tested, nor did the mRNA expression necessarily correlate with the fluorescence intensity. The results indicate that a difference in the metabolic activity of cells in suspension may limit the applicability of exogenous enzyme inhibitor administration as a mean to improve the fluorescence-based detection of cancer cells shed in body fluids.

5-Aminolevulinic Acid-Induced Protoporphyrin IX Fluorescence Imaging for Tumor Detection: Recent Advances and Challenges

5-Aminolevulinic acid (5-ALA) is a natural amino acid and a precursor of heme and chlorophyll. Exogenously administered 5-ALA is metabolized into protoporphyrin IX (PpIX). PpIX accumulates in cancer cells because of the low activity of ferrochelatase, an enzyme that metabolizes PpIX to heme. High expression of 5-ALA influx transporters, such as peptide transporters 1/2, in cancer cells also enhances PpIX production. Because PpIX radiates red fluorescence when excited with blue/violet light, 5-ALA has been used for the visualization of various tumors. 5-ALA photodynamic diagnosis (PDD) has been shown to improve the tumor removal rate in high-grade gliomas and non-muscular invasive bladder cancers. However, 5-ALA PDD remains a challenge as a diagnostic method because tissue autofluorescence interferes with PpIX signals in cases where tumors emit only weak signals, and non-tumorous lesions, such as inflammatory sites, tend to emit PpIX fluorescence. Here, we review the current outline of 5-ALA PDD and strategies for improving its diagnostic applicability for tumor detection, focusing on optical techniques and 5-ALA metabolic pathways in both viable and necrotic tumor tissues.

Investigation of the therapeutic effect of 5-aminolevulinic acid based photodynamic therapy on hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a heterogeneous type of cancer and current treatment options limit successful therapy outcomes. Photodynamic therapy (PDT) has attracted attention as an alternative approach in the treatment of different types of cancer. However, there is no study in the literature regarding the effect of PDT on HCC, in vitro. Therefore, the aim of this study was to determine the cytotoxic and apoptotic effects of 5-aminolevulinic acid (5-ALA)/PDT on two different HCC cell lines in terms of hepatitis B virus (HBV) infection. The therapeutic effects of 5-ALA-based PDT on HCC cell lines (Huh-7 and SNU-449) were evaluated by PpIX-fluorescence accumulation, WST-1 analysis, Annexin V analysis, and acridine orange/ethidium bromide staining after irradiation with different light doses through diode laser. The results showed that 1 mM 5-ALA displayed higher PpIX fluorescence in the SNU-449 cell line than the Huh-7 cell line after 4 h of incubation. After irradiation with different light doses (3, 6, 9, and 12 J/cm²), 5-ALA significantly reduced the proliferation of HCC cells and induced apoptotic cell death (p < 0.01). Furthermore, SNU-449 cells were more responsive to 5-ALA-based PDT than Huh-7 cells due to possibly its molecular features as well as viral HBV status. Our preliminary data obtained from this study may contribute to the development of 5-ALA/PDT-based treatment strategies in the treatment of HCC. However, this study could be improved by the elucidation of the molecular mechanisms of cell death induced by 5-ALA/PDT in HCC cells, the use of different photosensitizer, light sources, and in vivo experiments.

Metabolism-based isolation of invasive glioblastoma cells with specific gene signatures and tumorigenic potential

Background

Glioblastoma (GBM) is a highly aggressive brain tumor with rapid subclonal diversification, harboring molecular abnormalities that vary temporospatially, a contributor to therapy resistance. Fluorescence-guided neurosurgical resection utilizes the administration of 5-aminolevulinic acid (5-ALA) generating individually fluorescent tumor cells within a background population of non-neoplastic cells in the invasive tumor region. The aim of the study was to specifically isolate and interrogate the invasive GBM cell population using a novel 5-ALA-based method.

Methods

We have isolated the critical invasive GBM cell population by developing 5-ALA-based metabolic fluorescence-activated cell sorting. This allows purification and study of invasive cells from GBM without an overwhelming background "normal brain" signal to confound data. The population was studied using RNAseq, real-time PCR, and immunohistochemistry, with gene targets functionally interrogated on proliferation and migration assays using siRNA knockdown and known drug inhibitors.

Results

RNAseq analysis identifies specific genes such as SERPINE1 which is highly expressed in invasive GBM cells but at low levels in the surrounding normal brain parenchyma. siRNA knockdown and pharmacological inhibition with specific inhibitors of SERPINE1 reduced the capacity of GBM cells to invade in an in vitro assay. Rodent xenografts of 5-ALA-positive cells were established and serially transplanted, confirming tumorigenicity of the fluorescent patient-derived cells but not the 5-ALA-negative cells.

Conclusions

Identification of unique molecular features in the invasive GBM population offers hope for developing more efficacious targeted therapies compared to targeting the tumor core and for isolating tumor subpopulations based upon intrinsic metabolic properties.

Fabrication of a cell-recognition/electron-transfer/cross-linker, peptide-immobilized electrode for the sensing of K562 cells

We designed an electrode that has the ability to sense a target cell. This new electrode is intended for use in cell recognition via electron-transfer and cross-linker peptide immobilization. Myelopeptide-4 (MP-4:FRPRIMTP) is a marrow-origin peptide that interacts with receptors of the human leukemia cell line (K562 cells), and allows their differentiation. The YYYYC electron-transfer peptide improves the electron-transfer accessibility from an electroactive compound to an electrode. Oligoalanine plays the role of a cross-linker that immobilizes a peptide series (Ac-FRPRIMTPYYYYCAAAAA) to collagen, which then allows it to be cast onto an electrode. Use of the electrode with a peptide increased the peak currents of [Fe(CN)₆]^4-/3- and also improved the reversibility of redox. These improvements are due to the interaction between [Fe(CN)₆]^4-/3- and the peptide. When electrochemical impedance spectroscopy (EIS) measurements were carried out using a collagen/peptide probe-immobilized electrode, the electron transfer resisitance was lower than that without the peptide. The detection of K562 cells was based on an increase in resistance, because MP-4 was bound to the receptors on the cell surface. The responses were linear and ranged in number from 27 to 2,000 cells/mLwith a detection limit of 8 cells/mL. Recoveries of 50 and 1,000 cells/mL in human serum were accomplished at rates of 98 and 101%, respectively. Consequently, the proposed procedure is a powerful new concept for cytosensing.

Fluorescence-based discrimination of breast cancer cells by direct exposure to 5-aminolevulinic acid

Protoporphyrin IX-fluorescence measurement is a powerful in situ approach for cancer detection after oral/topical administration of 5-aminolevulinic acid. However, this approach has not been clinically established for breast cancer, probably due to insufficient delivery of 5-aminolevulinic acid to the mammary glands. In the present study, we directly exposed breast cancer cells to 5-aminolevulinic acid to assess their discrimination via protoporphyrin IX-fluorescence. Fluorescence intensity (FI) was measured in the human breast cancer cell lines MCF7 and MDA-MB-231 and breast epithelial cell line MCF10A by confocal microscopy and flow cytometry. After 5-aminolevulinic acid exposure for 2 hours, protoporphyrin IX-FI in MCF7 and MDA-MB-231 cells significantly increased with marked cell-to-cell variability, whereas that in MCF10A cells increased moderately. Combined exposure of the cancer cells to 5-aminolevulinic acid and Ko143, a specific inhibitor of ATP-binding cassette transporter G2, further increased protoporphyrin IX-FI and alleviated the cell-to-cell variability in MCF7 and MDA-MB-231 cells, indicating improvement in the reproducibility and accuracy for fluorescence-based cancer detection. The increased FI by combined administration of these two drugs was also demonstrated in cells obtained via fine needle aspiration from mouse xenograft models inoculated with MDA-MB-231 cells. Furthermore, a cutoff value for increased protoporphyrin IX-FI ratio, before and after exposure to these drugs, clearly discriminated between cancer and noncancer cells. Taken together, direct exposure to 5-aminolevulinic acid and Ko143 may be a promising strategy for efficient fluorescence-based detection of breast cancer cells ex vivo using fine needle aspiration.