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

Label-Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications

Autofluorophores are endogenous fluorescent compounds that naturally occur in the intra and extracellular spaces of all tissues and organs. Most have vital biological functions - like the metabolic cofactors NAD(P)H and FAD+, as well as the structural protein collagen. Others are considered to be waste products - like lipofuscin and advanced glycation end products - which accumulate with age and are associated with cellular dysfunction. Due to their natural fluorescence, these materials have great utility for enabling non-invasive, label-free assays with direct ties to biological function. Numerous technologies, with different advantages and drawbacks, are applied to their assessment, including fluorescence lifetime imaging microscopy, hyperspectral microscopy, and flow cytometry. Here, the applications of label-free autofluorophore assessment are reviewed for clinical and health-research applications, with specific attention to biomaterials, disease detection, surgical guidance, treatment monitoring, and tissue assessment - fields that greatly benefit from non-invasive methodologies capable of continuous, in vivo characterization.

In vitro evaluation of the efficacy of photodynamic therapy using 5-ALA on homologous feline mammary tumors in 2D and 3D culture conditions and a mouse subcutaneous model with 3D cultured cells

BACKGROUND

Numerous studies have shown that photodynamic therapy (PDT) has a therapeutic effect on mammary tumor cells, with 5-aminolevulinic acid (5-ALA-HCL) being a commonly used photosensitizer for PDT. Feline mammary tumors (FMTs) are relatively common. However, the cytotoxic and antitumor effects of 5-ALA-PDT on FMTs have not been clarified. To this end, we evaluated the therapeutic effect of 5-ALA-PDT on FMTs through in vitro experiments using an FMT FKR cell line established for this study.

METHODS

We performed 5-ALA-PDT in 2D-cultured FKR-A (adherent cells) and 3D-cultured FKR-S (spheroid cells) cells and performed a series of studies to evaluate the cell viability and determine the protoporphyrin IX (PpIX) content in the cells as well as the expression levels of mRNAs associated with PpIX production and release. An in vivo study was performed to assess the effectiveness of 5-ALA-PDT.

RESULTS

There was a significant difference in the concentration of PpIX in FMT cells under different incubation culture modes (2D versus 3D culture). The concentration of PpIX in FMT cells was correlated with the differences in cell culture (2D and 3D) as well as the expression levels of genes such as PEPT1, PEPT2, FECH, and HO-1.

CONCLUSIONS

In the in vitro study, 5-ALA-PDT had a stronger inhibitory effect on 3D-cultured FKR-S cells, which resemble the internal environment of organisms more closely. We also observed a significant inhibitory effect of 5-ALA-PDT on FMT cells in vivo. To our knowledge, this is the first study on 5-ALA-PDT for FMTs under both 2D and 3D conditions.

C5α secreted by tumor mesenchymal stem-like cells mediates resistance to 5-aminolevulinic acid-based photodynamic therapy against glioblastoma tumorspheres

PURPOSE

Advancements in photodynamic diagnosis (PDD) and photodynamic therapy (PDT) as a standard care in cancer therapy have been limited. This study is aimed to investigate the clinical availability of 5-aminolevulinic acid (5-ALA)-based PDD and PDT in glioblastoma (GBM) patient-derived tumorspheres (TSs) and mouse orthotopic xenograft model.

METHODS

PDT was performed using a 635 nm light-emitting diode (LED). Transcriptome profiles were obtained from microarray data. For knockdown of C5α, siRNA was transfected into tumor mesenchymal stem-like cells (tMSLCs). The invasiveness of TSs was quantified using collagen-based 3D invasion assays.

RESULTS

Treatment with 1 mM 5 ALA induced distinct protoporphyrin IX (PpIX) fluorescence in GBM TSs, but not in non-tumor cells or tissues, including tMSLCs. These observations were negatively correlated with the expression levels of FECH, which catalyzes the conversion of accumulated PpIX to heme. Furthermore, the 5-ALA-treated GBM TSs were sensitive to PDT, thereby significantly decreasing cell viability and invasiveness. Notably, the effects of PDT were abolished by culturing TSs with tMSLC-conditioned media. Transcriptome analysis revealed diverse tMSLC-secreted chemokines, including C5α, and their correlations with the expression of stemness- or mesenchymal transition-associated genes. By adding or inhibiting C5α, we confirmed that acquired resistance to PDT was induced via tMSLC-secreted C5α.

CONCLUSIONS

Our results show substantial therapeutic effects of 5-ALA-based PDT on GBM TSs, suggesting C5α as a key molecule responsible for PDT resistance. These findings could trigger PDT as a standard clinical modality for the treatment of GBM.

A PPIX-binding probe facilitates discovery of PPIX-induced cell death modulation by peroxiredoxin

While heme synthesis requires the formation of a potentially lethal intermediate, protoporphyrin IX (PPIX), surprisingly little is known about the mechanism of its toxicity, aside from its phototoxicity. The cellular protein interactions of PPIX might provide insight into modulators of PPIX-induced cell death. Here we report the development of PPB, a biotin-conjugated, PPIX-probe that captures proteins capable of interacting with PPIX. Quantitative proteomics in a diverse panel of mammalian cell lines reveal a high degree of concordance for PPB-interacting proteins identified for each cell line. Most differences are quantitative, despite marked differences in PPIX formation and sensitivity. Pathway and quantitative difference analysis indicate that iron and heme metabolism proteins are prominent among PPB-bound proteins in fibroblasts, which undergo PPIX-mediated death determined to occur through ferroptosis. PPB proteomic data (available at PRIDE ProteomeXchange # PXD042631) reveal that redox proteins from PRDX family of glutathione peroxidases interact with PPIX. Targeted gene knockdown of the mitochondrial PRDX3, but not PRDX1 or 2, enhance PPIX-induced death in fibroblasts, an effect blocked by the radical-trapping antioxidant, ferrostatin-1. Increased PPIX formation and death was also observed in a T-lymphoblastoid ferrochelatase-deficient leukemia cell line, suggesting that PPIX elevation might serve as a potential strategy for killing certain leukemias.

5-Aminolevulinic Acid as a Theranostic Agent for Tumor Fluorescence Imaging and Photodynamic Therapy

5-Aminolevulinic acid (ALA) is a naturally occurring amino acid synthesized in all nucleated mammalian cells. As a porphyrin precursor, ALA is metabolized in the heme biosynthetic pathway to produce protoporphyrin IX (PpIX), a fluorophore and photosensitizing agent. ALA administered exogenously bypasses the rate-limit step in the pathway, resulting in PpIX accumulation in tumor tissues. Such tumor-selective PpIX disposition following ALA administration has been exploited for tumor fluorescence diagnosis and photodynamic therapy (PDT) with much success. Five ALA-based drugs have now received worldwide approval and are being used for managing very common human (pre)cancerous diseases such as actinic keratosis and basal cell carcinoma or guiding the surgery of bladder cancer and high-grade gliomas, making it the most successful drug discovery and development endeavor in PDT and photodiagnosis. The potential of ALA-induced PpIX as a fluorescent theranostic agent is, however, yet to be fully fulfilled. In this review, we would like to describe the heme biosynthesis pathway in which PpIX is produced from ALA and its derivatives, summarize current clinical applications of ALA-based drugs, and discuss strategies for enhancing ALA-induced PpIX fluorescence and PDT response. Our goal is two-fold: to highlight the successes of ALA-based drugs in clinical practice, and to stimulate the multidisciplinary collaboration that has brought the current success and will continue to usher in more landmark advances.

Targeted implementation strategies of precise photodynamic therapy based on clinical and technical demands

With the development of materials science, photodynamic-based treatments have gradually entered clinics. Photodynamic therapy is ideal for cancer treatment due to its non-invasive and spatiotemporal properties and is the first to be widely promoted in clinical practice. However, the shortcomings resulting from the gap between technical and clinical demands, such as phototoxicity, low tissue permeability, and tissue hypoxia, limit its wide applications. This article reviews the available data regarding the pharmacological and clinical factors affecting the efficacy of photodynamic therapy, such as photosensitizers and oxygen supply, disease diagnosis, and other aspects of photodynamic therapy. In addition, the synergistic treatment of photodynamic therapy with surgery and nanotechnology is also discussed, which is expected to provide inspiration for the design of photodynamic therapy strategies.

Active site architecture of coproporphyrin ferrochelatase with its physiological substrate coproporphyrin III: Propionate interactions and porphyrin core deformation

Coproporphyrin ferrochelatases (CpfCs) are enzymes catalyzing the penultimate step in the coproporphyrin-dependent (CPD) heme biosynthesis pathway, which is mainly utilized by monoderm bacteria. Ferrochelatases insert ferrous iron into a porphyrin macrocycle and have been studied for many decades, nevertheless many mechanistic questions remain unanswered to date. Especially CpfCs, which are found in the CPD pathway, are currently in the spotlight of research. This pathway was identified in 2015 and revealed that the correct substrate for these ferrochelatases is coproporphyrin III (cpIII) instead of protoporphyrin IX, as believed prior the discovery of the CPD pathway. The chemistry of cpIII, which has four propionates, differs significantly from protoporphyrin IX, which features two propionate and two vinyl groups. These findings let us to thoroughly describe the physiological cpIII-ferrochelatase complex in solution and in the crystal phase. Here, we present the first crystallographic structure of the CpfC from the representative monoderm pathogen Listeria monocytogenes bound to its physiological substrate, cpIII, together with the in-solution data obtained by resonance Raman and UV-vis spectroscopy, for wild-type ferrochelatase and variants, analyzing propionate interactions. The results allow us to evaluate the porphyrin distortion and provide an in-depth characterization of the catalytically-relevant binding mode of cpIII prior to iron insertion. Our findings are discussed in the light of the observed structural restraints and necessities for this porphyrin-enzyme complex to catalyze the iron insertion process. Knowledge about this initial situation is essential for understanding the preconditions for iron insertion in CpfCs and builds the basis for future studies.

FECH Expression Correlates with the Prognosis and Tumor Immune Microenvironment in Clear Cell Renal Cell Carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is, by far, the most prevalent and fatal kind of kidney cancer. Ferrochelatase (FECH) is an enzyme that performs a significant function in the onset and progression of many distinct kinds of malignant tumors. Nevertheless, its predictive usefulness in renal clear cell carcinoma (RCC) has not yet been fully investigated.

Methods

FECH expression in ccRCC and healthy adjoining tissues was primarily screened utilizing data sourced from The Cancer Genome Atlas (TCGA) and subsequently validated using data from an independent cohort derived from the Gene Expression Omnibus (GEO) and the Human Protein Atlas HPA databases. The relationship among FECH expression, clinicopathological parameters, and overall survival (OS) was assessed utilizing multivariate analysis and Kaplan–Meier survival curves. Additionally, the protein networks with FECH interaction were constructed with the aid of the online Search Tool for the Retrieval of Interacting Genes/Proteins (STRING). Gene ontology (GO) analysis, and gene set enrichment analysis (GSEA) were conducted based on TCGA data, and a single-sample GSEA was utilized to explore the link between FECH expression and the infiltration status of immune cells in the tumor. The Gene Expression Profiling Interactive Analysis (GEPIA) and TIMER databases were utilized to investigate the relationships of FECH expression with the infiltrating immune cells and the matching gene marker sets.

Results

FECH expression was shown to be substantially lowered in ccRCC tumors as opposed to that observed in normal tissues (p < 0.05). Lower levels of FECH expression were shown to have a strong association with higher grades of cancer and more advanced TNM stages. The findings of multivariate and univariate analyses illustrated that the OS in patients with ccRCC with low FECH expression is shorter in contrast with that in the high FECH expression group (p < 0.05). It was discovered that CPOX and frataxin are key proteins that interact with FECH. ccRCC with FECH deficiency was linked to the lack of infiltrating immune cells and their respective marker sets, which included CD4+ T cells.

Conclusion

In ccRCC, decreased FECH expression was linked to disease progression, unfavorable prognosis, and impaired immune cell infiltration.

Evolutionary Trend Analysis of Research on 5-ALA Delivery and Theranostic Applications Based on a Scientometrics Study

5-aminolevulinic acid (5-ALA) has been extensively studied for its sustainability and broad-spectrum applications in medical research and theranostics, as well as other areas. It’s a precursor of protoporphyrin IX (PpIX), a sustainable endogenous and naturally-existing photosensitizer. However, to the best of our knowledge, a scientometrics study based on the scientific knowledge assay of the overall situation on 5-ALA research has not been reported so far, which would be of major importance to the relevant researchers. In this study, we collected all the research articles published in the last two decades from the Web of Science Core Collection database and employed bibliometric methods to comprehensively analyze the dataset from different perspectives using CiteSpace. A total of 1595 articles were identified. The analysis results showed that China published the largest number of articles, and SBI Pharmaceuticals Co., Ltd. was the most productive institution that sponsored several of the most productive authors. The cluster analysis and burst detections indicated that the improvement of photodynamic efficacy theranostics is the up-to-date key direction in 5-ALA research. Furthermore, we emphatically studied nanotechnology involvement in 5-ALA delivery and theranostics research. We envision that our results will be beneficial for researchers to have a panorama of and deep insights into this area, thus inspiring further exploitations, especially of the nanomaterial-based systems for 5-ALA delivery and theranostic applications.

Small-molecule inhibitors of ferrochelatase are antiangiogenic agents

Activity of the heme synthesis enzyme ferrochelatase (FECH) is implicated in multiple diseases. In particular, it is a mediator of neovascularization in the eye and thus an appealing therapeutic target for preventing blindness. However, no drug-like direct FECH inhibitors are known. Here, we set out to identify small-molecule inhibitors of FECH as potential therapeutic leads using a high-throughput screening approach to identify potent inhibitors of FECH activity. A structure-activity relationship study of a class of triazolopyrimidinone hits yielded drug-like FECH inhibitors. These compounds inhibit FECH in cells, bind the active site in cocrystal structures, and are antiangiogenic in multiple in vitro assays. One of these promising compounds was antiangiogenic in vivo in a mouse model of choroidal neovascularization. This foundational work may be the basis for new therapeutic agents to combat not only ocular neovascularization but also other diseases characterized by FECH activity.

Analysis of Factors Affecting 5-ALA Fluorescence Intensity in Visualizing Glial Tumor Cells-Literature Review

Glial tumors are one of the most common lesions of the central nervous system. Despite the implementation of appropriate treatment, the prognosis is not successful. As shown in the literature, maximal tumor resection is a key element in improving therapeutic outcome. One of the methods to achieve it is the use of fluorescent intraoperative navigation with 5-aminolevulinic acid. Unfortunately, often the level of fluorescence emitted is not satisfactory, resulting in difficulties in the course of surgery. This article summarizes currently available knowledge regarding differences in the level of emitted fluorescence. It may depend on both the histological type and the genetic profile of the tumor, which is reflected in the activity and expression of enzymes involved in the intracellular metabolism of fluorescent dyes, such as PBGD, FECH, UROS, and ALAS. The transport of 5-aminolevulinic acid and its metabolites across the blood–brain barrier and cell membranes mediated by transporters, such as ABCB6 and ABCG2, is also important. Accompanying therapies, such as antiepileptic drugs or steroids, also have an impact on light emission by tumor cells. Accurate determination of the factors influencing the fluorescence of 5-aminolevulinic acid-treated cells may contribute to the improvement of fluorescence navigation in patients with highly malignant gliomas.

Targeting glioblastoma stem cells: The first step of photodynamic therapy

Glioblastoma is one of the most malignant types of brain cancer. Evidence suggests that within gliomas there is a small subpopulation of cells with the capacity for self-renewal, called glioma stem cells. These cells could be responsible for tumorigenesis, chemo and radioresistance, and finally for the recurrence of the tumor. Fluorescence-guided resection have improved the results of treatment against this disease, prolonging the survival of patients by a few months. Also, clinical trials have reported potential improvements in the therapeutic response after photodynamic therapy. Thus far, there are few published works that show the response of glioblastoma stem-like cells to photodynamic therapy. Here, we present a brief review exclusively commenting on the therapeutic approaches to eliminate glioblastoma stem cells and on the research publications about this topic of glioblastoma stem cells in relation to photodynamic therapy. It is our hope that this review will be useful to provide an overview about what is known to date on the topic and to promote the generation of new ideas for the eradication of glioblastoma stem cells by photodynamic treatment.

Down-regulation of IGHG1 enhances Protoporphyrin IX accumulation and inhibits hemin biosynthesis in colorectal cancer by suppressing the MEK-FECH axis

Immunoglobulin γ-1 heavy chain constant region (IGHG1) is a functional isoform of immunoglobulins and plays an important role in the cytolytic activity of immune effector cells. Dysregulated IGHG1 was implicated in the occurrence and development of various tumors. Protoporphyrin IX (PpIX) is an endogenous fluorophore and is used in photodynamic therapy, which induces the generation of reactive oxygen species to initiate the death of tumor cells. However, the roles of IGHG1 in the colorectal cancer cell proliferation and PpIX accumulation have not been reported yet. Data from qRT-PCR and western blot analysis showed that IGHG1 was up-regulated in the colorectal cancer cells. Colorectal cancer cells were then transfected with shRNA targeting IGHG1 to down-regulate IGHG1 and conducted with Cell Counting Kit 8 (CCK8) and colony formation assays. Results demonstrated that shRNA-mediated down-regulation of IGHG1 decreased cell viability of colorectal cancer and suppressed cell proliferation. Moreover, PpIX accumulation was promoted and the hemin content was decreased by the silence of IGHG1. Interference of IGHG1 reduced the phosphorylated extracellular signal-regulated kinase (ERK) and ferrochelatase (FECH) expression, resulting in retarded cell proliferation in an MEK-FECH axis-dependent pathway.

Small molecule kinase inhibitors enhance aminolevulinic acid-mediated protoporphyrin IX fluorescence and PDT response in triple negative breast cancer cell lines

SIGNIFICANCE

We demonstrate that clinically used kinase inhibitors such as lapatinib can be used for enhancing aminolevulinic acid (ALA) for tumor fluorescence imaging and photodynamic therapy (PDT).

AIM

ALA is used as a prodrug for protoporphyrin IX (PpIX) fluorescence-guided tumor resection and PDT. Our previous studies indicate that tumors with high ABCG2 activity exhibit low PpIX fluorescence, which hampers the application of ALA. We aim to determine whether clinically used ABCG2-interacting kinase inhibitors increase ALA-PpIX fluorescence and PDT.

APPROACH

PpIX fluorescence was determined by spectrofluorometry, flow cytometry, and confocal microscopy after ALA alone or in combination with kinase inhibitors in triple negative breast cancer (TNBC) cell lines. Cytotoxicity was examined after ALA-PDT alone or in combination with kinase inhibitors. Effect of single and combination treatments on apoptosis was assessed by Western blot.

RESULTS

Four kinase inhibitors (lapatinib, PD169316, sunitinib, gefitinib) significantly increased ALA-PpIX fluorescence and PDT response in TNBC cells with ABCG2 activity, but not in MCF10A nontumor breast epithelial cell line without ABCG2 activity. Confocal microscopic imaging showed that PpIX fluorescence was weak and diffuse after ALA alone, which was greatly enhanced by kinase inhibitors, particularly in the mitochondria. Lapatinib was the only inhibitor that significantly reduced PpIX efflux in cell culture medium and showed stronger enhancement of PDT response than other kinase inhibitors. Lapatinib, in combination with ALA, induced tumor cells to undergo apoptosis, whereas no apoptosis was detected after each individual treatment.

CONCLUSIONS

Although all four kinase inhibitors were able to enhance ALA-PpIX fluorescence and PDT, lapatinib exhibited the strongest enhancement effect. As an FDA-approved kinase inhibitor for breast cancer treatment, lapatinib is ready to be used in combination with ALA for therapeutic enhancement in tumors with elevated ABCG2 activity. This rational combination approach warrants further investigation in tumor models.

Alectinib treatment improves photodynamic therapy in cancer cell lines of different origin

Background

Photodynamic therapy with a photosensitizer such as protoporphyrin-IX, a light sensitive metabolite of heme synthesis, is a highly selective treatment for various carcinomas. In previous studies, we found a significant down regulation of the relevant enzyme ferrochelatase in gastrointestinal carcinomas leading to an accumulation of protoporphyrin-IX within the tumor cells. Recent studies showed that a novel anti-cancer drug, Alectinib, an orally available, highly selective, potent second-generation inhibitor of anaplastic lymphoma tyrosinkinase binds to ferrochelatase. Therefore, we were interested to see whether Alectinib treatment might lead to an accumulation of protoporphyrin IX.

Methods

Tumor cells of different origin were cultured, treated with LED-light and Alectinib. Results were gained by flow cytometry, immunohistochemistry and western blotting. Apoptosis was determined by flow cytometric analysis of Annexin V-FITC stained cells. In addition, cells were counterstained with propidium iodide to distinguish early apoptotic cells and late apoptotic/necrotic cells.

Results

Here, we report that photodynamic treatment of tumor cell lines of different origin in combination with Alectinib increased protoporphyrin-IX specific fluorescence and concomitantly cell death.

Conclusions

The usage of Alectinib could be another step for enhancing the effectiveness of photodynamic therapy. Further experiments will show whether photodynamic therapy in combination with Alectinib could be a new strategy for the treatment of e.g. peritoneal disseminated carcinomas.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08667-x.

Sublingual administration of 5-aminolevulinic acid for laser-induced photodiagnostics and photodynamic therapy of oral cavity and larynx cancers

BACKGROUND

The study aimed to develop a method for sublingual administration of 5-aminolevulinic acid to patients and evaluate its effectiveness in fluorescence diagnostics and photodynamic therapy of neoplasms of the oral cavity and larynx.

METHODS

The boundaries of the neoplasms were established by the video-fluorescence diagnostics and clarified using spectral-fluorescent diagnosis before and after photodynamic therapy.

RESULTS

The fluorescence diagnostics demonstrated a high accumulation of protoporphyrin IX, induced by sublingual administration of 5-aminolevulinic acid to patients before the photodynamic therapy and photobleaching of protoporphyrin IX in pathologically altered tissues after the photodynamic therapy. Glucose contained in the sublingual dose supports active transport of 5-ALA into the cells. It increases the PpIX accumulation in the cells, therefore improving the PD and PDT efficacy.

CONCLUSION

The study and the initially obtained results demonstrated the possibility and effectiveness of laser-induced photodiagnostics and photodynamic therapy with sublingual administration of 5-ALA to patients with premalignant lesions of the oral cavity and larynx. It can eliminate the threat of the transformation of these diseases into malignant tumors and prevent the need for surgical treatment.

Nanomedicines for Endometriosis: Lessons Learned from Cancer Research

Endometriosis is an incurable gynecological disease characterized by the abnormal growth of endometrium-like tissue, characteristic of the uterine lining, outside of the uterine cavity. Millions of people with endometriosis suffer from pelvic pain and infertility. This review aims to discuss whether nanomedicines that are promising therapeutic approaches for various diseases have the potential to create a paradigm shift in endometriosis management. For the first time, the available reports and achievements in the field of endometriosis nanomedicine are critically evaluated, and a summary of how nanoparticle-based systems can improve endometriosis treatment and diagnosis is provided. Parallels between cancer and endometriosis are also drawn to understand whether some fundamental principles of the well-established cancer nanomedicine field can be adopted for the development of novel nanoparticle-based strategies for endometriosis. This review provides the state of the art of endometriosis nanomedicine and perspective for researchers aiming to realize and exploit the full potential of nanoparticles for treatment and imaging of the disorder.

MEK reduces cancer-specific PpIX accumulation through the RSK-ABCB1 and HIF-1α-FECH axes

The efficacy of aminolevulinic acid (5-ALA)-based photodynamic diagnosis (5-ALA-PDD) and photodynamic therapy (5-ALA-PDT) is dependent on 5-ALA-induced cancer-specific accumulation of protoporphyrin IX (PpIX). We previously reported that inhibition of oncogenic Ras/MEK increases PpIX accumulation in cancer cells by reducing PpIX efflux through ATP-binding cassette sub-family B member 1 (ABCB1) and ferrochelatase (FECH)-catalysed PpIX conversion to haem. Here, we sought to identify the downstream pathways of Ras/MEK involved in the regulation of PpIX accumulation via ABCB1 and FECH. First, we demonstrated that Ras/MEK activation reduced PpIX accumulation in RasV12-transformed NIH3T3 cells and HRAS transgenic mice. Knockdown of p90 ribosomal S6 kinases (RSK) 2, 3, or 4 increased PpIX accumulation in RasV12-transformed NIH3T3 cells. Further, treatment with an RSK inhibitor reduced ABCB1 expression and increased PpIX accumulation. Moreover, HIF-1α expression was reduced when RasV12-transformed NIH3T3 cells were treated with a MEK inhibitor, demonstrating that HIF-1α is a downstream element of MEK. HIF-1α inhibition decreased FECH activity and increased PpIX accumulation. Finally, we demonstrated the involvement of RSKs and HIF-1α in the regulation of PpIX accumulation in human cancer cell lines. These results demonstrate that the RSK-ABCB1 and HIF-1α-FECH axes are the downstream pathways of Ras/MEK involved in the regulation of PpIX accumulation.

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

Aminolevulinic acid (ALA) has been approved as an intraoperative molecular imaging probe for protoporphyrin IX (PpIX) fluorescence-guided resection of glioma. Here we explored its potential application for renal cell carcinoma (RCC) that is showing increased incidence in recent years. ALA-mediated PpIX in cell lysates (intracellular) and culture medium was measured in five human RCC cell lines (786-O, 769-P, A-704, Caki-1, Caki-2) and a non-tumor human kidney epithelial cell line HK-2 by spectrofluorometry and flow cytometry. The activity of PpIX bioconversion enzyme ferrochelatase (FECH) and PpIX efflux transporter ABCG2 was determined to correlate with the PpIX level. We found that ALA-PpIX fluorescence was highly variable among RCC cell lines and A-704 was the only RCC cell line exhibiting significantly higher intracellular PpIX than HK-2 cells. Neither the intracellular PpIX level nor the total amount of PpIX (including PpIX in cell lysates and the medium) had significant correlation with the activity of FECH or ABCG2. To enhance the intracellular PpIX, cells were treated with Ko143, a pharmacological inhibitor of ABCG2. Ko143 significantly increased the intracellular PpIX in cell lines with ABCG2 activity, but not in cell lines with little ABCG2 activity. In fact, there was a positive correlation between the ABCG2 activity and Ko143-induced PpIX enhancement across kidney cell lines. To identify clinically relevant ABCG2 inhibitors, small molecule inhibitors targeting various cell signaling pathways, some of which are known to inhibit ABCG2, were evaluated for the enhancement of ALA-PpIX in Caki-2 cells that had the highest ABCG2 activity in the RCC cell panel. Our screening led to the identification of several clinically available inhibitors that significantly increased the intracellular PpIX. Particularly, kinase inhibitor lapatinib exhibited the strongest enhancement effect. These clinical inhibitors can be used for the enhancement of ALA-PpIX fluorescence in tumors with elevated ABCG2 activity.

Near-infrared imaging and optical coherence tomography for intraoperative visualization of tumors

Surgical excision is the foundation of treatment for early-stage solid tumors in man and companion animals. Complete excision with appropriate margins of surrounding tumor-free tissue is crucial to survival. Intraoperative imaging allows real-time visualization of tumors, assessment of surgical margins, and, potentially, lymph nodes and satellite metastatic lesions, allowing surgeons to perform complete tumor resections while sparing surrounding vital anatomic structures. This Review will focus on the use of near-infrared imaging and optical coherence tomography for intraoperative tumor visualization.

Fluorescence Imaging of Breast Tumors and Gastrointestinal Cancer

Optical imaging offers a high potential for noninvasive detection and therapy of cancer in humans. Recent advances in instrumentation for diffuse optical imaging have led to new capabilities for the detection of cancer in highly scattering tissue such as the female breast. In particular, fluorescence imaging was made applicable as a sensitive technique to image molecular probes in vivo. We review recent developments in the detection of breast cancer and fluorescence-guided surgery of the breast by contrast agents available for application on humans. Detection of cancer has been investigated with the unspecific contrast agents "indocyanine green" and "omocianine" so far. Hereby, indocyanine green was found to offer high potential for the differentiation of malignant and benign lesions by exploiting vessel permeability for macromolecules as a cancer-specific feature. Tumor-specific molecular targeting and activatable probes have been investigated in clinical trials for fluorescence-guided tumor margin detection. In this application, high spatial resolution can be achieved, since tumor regions are visualized mainly at the tissue surface. As another example of superficial tumor tissue, imaging of lesions in the gastrointestinal tract is discussed. Promising results have been obtained on high-risk patients with Barrett´s esophagus and with ulcerative colitis by administering 5-aminolevulinic acid which induces accumulation of protoporphyrin IX serving as a tumor-specific fluorescent marker. Time-gated fluorescence imaging and spectroscopy are effective ways to suppress underlying background from tissue autofluorescence. Furthermore, recently developed tumor-specific molecular probes have been demonstrated to be superior to white-light endoscopy offering new ways for early detection of malignancies in the gastrointestinal tract.

Loss of ferrochelatase is protective against colon cancer cells: ferrochelatase a possible regulator of the long noncoding RNA H19

Background

Ferrochelatase (FECH) is the last enzyme of the heme biosynthesis pathway. Deficiency in FECH was associated with many diseases, including protoporphyria. Correlation studies showed that variations of FECH expression was detected in human carcinomas and more specifically in colon cancer. Nevertheless, the potential role of FECH in colon cancer carcinogenesis in vitro was not depicted yet.

Methods

A small interfering RNA (siRNA) was used to knockdown FECH in human Caco-2 colon cancer cells. The effect of FECH down-regulation on the cellular proliferation, the migration and the expression of target genes was assessed in cancer cells and compared to human normal fibroblasts.

Results

Following FECH down-regulation, our results demonstrated that the proliferation of Caco-2 cells was not affected. Furthermore, the migration of cancer and normal cells was affected, only when an additional stress factor (H₂O₂) was applied to the medium. The expression of twist, snail, hypoxia induced factor (HIF-1α) and vascular endothelial growth factor (VEGF) was reduced in Caco-2 cells. Conversely, VEGF and HIF-1α expression were upregulated by up to 2 folds in control fibroblasts. Interestingly, the pro-carcinogenic long noncoding RNA (LncRNA) H19 was 70% down-regulated in Caco-2 cells upon FECH down regulation whereas no effect was observed in normal fibroblasts.

Conclusions

In conclusion, we showed that loss of FECH is protective against colon cancer tumorigenesis in vitro and this effect could possibly be mediated through inhibition of H19.

Impact of thiosemicarbazones on the accumulation of PpIX and the expression of the associated genes

Thiosemicarbazone derivatives are known for their broad biological activity including their antitumor potency. The aim of the current study was to examine the effect of a novel series of non-toxic iron chelators on the accumulation of protoporphyrin IX after external 5-aminolevulonic acid administration. From this series we selected one the most promising derivative which causes a pronounced increase in the concentration of protoporphyrin IX. The increase of the photosensitizer concentration is necessary for the trigger the efficient therapeutic effect of the photodynamic reaction. For selected compound 2 we performed an examination of a panel of the genes that are involved in the heme biosynthesis and degradation. Results indicated the crucial roles of ferrochelatase and heme oxygenase in the described processes. Surprisingly, there was a strict dependence on the type of the tested cell line. A decrease in the expression of the two aforementioned enzymes after incubation with compound 2 and 5-aminolevulonic acid is a commonly known fact and we detected this trend for the MCF-7 and HCT 116 cell lines. However, we noticed the upregulation of the tested targets for the Hs683 cells. These unconventional results prompted us to do a more in-depth analysis of the described processes. In conclusion, we found that compound 2 is a novel, highly effective booster of photodynamic therapy that has prospective applications.

In order for the light to shine so brightly, the darkness must be present-why do cancers fluoresce with 5-aminolaevulinic acid?

Photodynamic diagnosis and therapy have emerged as a promising tool in oncology. Using the visible fluorescence from photosensitisers excited by light, clinicians can both identify and treat tumour cells in situ. Protoporphyrin IX, produced in the penultimate step of the haem synthesis pathway, is a naturally occurring photosensitiser that visibly fluoresces when exposed to light. This fluorescence is enhanced considerably by the exogenous administration of the substrate 5-aminolaevulinic acid (5-ALA). Significantly, 5-ALA-induced protoporphyrin IX accumulates preferentially in cancer cells, and this enhanced fluorescence has been harnessed for the detection and photodynamic treatment of brain, skin and bladder tumours. However, surprisingly little is known about the mechanistic basis for this phenomenon. This review focuses on alterations in the haem pathway in cancer and considers the unique features of the cancer environment, such as altered glucose metabolism, oncogenic mutations and hypoxia, and their potential effects on the protoporphyrin IX phenomenon. A better understanding of why cancer cells fluoresce with 5-ALA would improve its use in cancer diagnostics and therapies.

Linking Cancer Metabolic Dysfunction and Genetic Instability through the Lens of Iron Metabolism

Iron (Fe) is an essential element that plays a fundamental role in a wide range of cellular functions, including cellular proliferation, DNA synthesis, as well as DNA damage and repair. Because of these connections, iron has been strongly implicated in cancer development. Cancer cells frequently have changes in the expression of iron regulatory proteins. For example, cancer cells frequently upregulate transferrin (increasing uptake of iron) and down regulate ferroportin (decreasing efflux of intracellular iron). These changes increase the steady-state level of intracellular redox active iron, known as the labile iron pool (LIP). The LIP typically contains approximately 2% intracellular iron, which primarily exists as ferrous iron (Fe²⁺). The LIP can readily contribute to oxidative distress within the cell through Fe²⁺-dioxygen and Fenton chemistries, generating the highly reactive hydroxyl radical (HO^•). Due to the reactive nature of the LIP, it can contribute to increased DNA damage. Mitochondrial dysfunction in cancer cells results in increased steady-state levels of hydrogen peroxide and superoxide along with other downstream reactive oxygen species. The increased presence of H₂O₂ and O₂^•- can increase the LIP, contributing to increased mitochondrial uptake of iron as well as genetic instability. Thus, iron metabolism and labile iron pools may play a central role connecting the genetic mutational theories of cancer to the metabolic theories of cancer.

Ferrochelatase Deficiency Abrogated the Enhancement of Aminolevulinic Acid-mediated Protoporphyrin IX by Iron Chelator Deferoxamine

Aminolevulinic acid (ALA) is a prodrug that is metabolized in the heme biosynthesis pathway to produce protoporphyrin IX (PpIX) for tumor fluorescence detection and photodynamic therapy (PDT). The iron chelator deferoxamine (DFO) has been widely used to enhance PpIX accumulation by inhibiting the iron-dependent bioconversion of PpIX to heme, a reaction catalyzed by ferrochelatase (FECH). Tumor response to DFO treatment is known to be highly variable, and some tumors even show no response. Given the fact that tumors often exhibit reduced FECH expression/enzymatic activity, we examined how reducing FECH level affected the DFO enhancement effect. Our results showed that reducing FECH level by silencing FECH in SkBr3 breast cancer cells completely abrogated the enhancement effect of DFO. Although DFO enhanced ALA-PpIX fluorescence and PDT response in SkBr3 vector control cells, it caused a similar increase in MCF10A breast epithelial cells, resulting in no net gain in the selectivity toward tumor cells. We also found that DFO treatment induced less increase in ALA-PpIX fluorescence in tumor cells with lower FECH activity (MDA-MB-231, Hs 578T) than in tumor cells with higher FECH activity (MDA-MB-453). Our study demonstrates that FECH activity is an important determinant of tumor response to DFO treatment.

Augmentation of 5-Aminolevulinic Acid Treatment of Glioblastoma by Adding Ciprofloxacin, Deferiprone, 5-Fluorouracil and Febuxostat: The CAALA Regimen

The CAALA (Complex Augmentation of ALA) regimen was developed with the goal of redressing some of the weaknesses of 5-aminolevulinic acid (5-ALA) use in glioblastoma treatment as it now stands. 5-ALA is approved for use prior to glioblastoma surgery to better demarcate tumor from brain tissue. 5-ALA is also used in intraoperative photodynamic treatment of glioblastoma by virtue of uptake of 5-ALA and its preferential conversion to protoporphyrin IX in glioblastoma cells. Protoporphyrin IX becomes cytotoxic after exposure to 410 nm or 635 nm light. CAALA uses four currently-marketed drugs—the antibiotic ciprofloxacin, the iron chelator deferiprone, the antimetabolite 5-FU, and the xanthine oxidase inhibitor febuxostat—that all have evidence of ability to both increase 5-ALA mediated intraoperative glioblastoma demarcation and photodynamic cytotoxicity of in situ glioblastoma cells. Data from testing the full CAALA on living minipigs xenotransplanted with human glioblastoma cells will determine safety and potential for benefit in advancing CAALA to a clinical trial.

Accumulation of protoporphyrin IX in medulloblastoma cell lines and sensitivity to subsequent photodynamic treatment

BACKGROUND

Medulloblastoma (MB) is the most common malignant primary brain tumor of childhood. High risk patients still have a poor outcome, and especially young patients suffer from standard therapy induced sequelae. Therefore, other therapeutic options need to be explored. In glioblastoma (GBM), application of 5-aminolaevulinic acid (5-ALA) results in selective accumulation of protoporphyrin IX (PPIX) in the tumor cells, which can be exploited during fluorescence-guided surgery to increase the extent of resection or for photodynamic therapy (PDT) induced phototoxicity. It is not entirely clear, whether MB cells accumulate PPIX and are sensitive to PDT.

METHODS

Human MYC-amplified (Med8A and D283) and non-amplified (UW228-2 and ONS76) MB cell lines were incubated for 2, 4 or 6 h with increasing doses (0-100 μg/ml) of 5-ALA, and PPIX accumulation was determined by flow cytometry. To assess sensitivity to 5-ALA/PDT, cells were incubated with 5-ALA and subsequently exposed to laser light of 635 nm wavelength (18.75 J/cm²). After an additional 24 h culture period, viability of cells was quantified using the WST-1 assay. Expression of ferrochelatase was detected by reverse transcription and quantitative polymerase chain reaction. Ferrochelatase activity was quantified by measuring the enzymatic conversion of PPIX to zinc-protoporphyrin. Expression of the ABCG2 transporter protein CD338 was detected by flow cytometry.

RESULTS

All MB cell lines showed a time- and dose-dependent accumulation of PPIX after exposure to exogenous 5-ALA and became sensitive to 5-ALA/PDT-induced phototoxicity. PPIX accumulation was reduced compared to U373 GBM cells at shorter incubation periods and limiting 5-ALA doses. Moreover, not all MB cells became PPIX positive and overall phototoxicity was lower in the MB cell lines. Notably, the MYC-amplified MB cells demonstrated a more pronounced photosensitivity compared to their non-amplified counterparts. There was no difference in expression of ferrochelatase, but enzymatic activity appeared to be reduced in the MB cells compared to U373 GBM cells, whereas CD338 was expressed on the MB cells only.

CONCLUSION

Medulloblastoma cell lines accumulate PPIX after application of 5-ALA and become sensitive to PDT, associated with low ferrochelatase expression and activity. Photosensitivity is more pronounced in MYC-amplified cell lines. In contrast to GBM cells, however, PPIX accumulation appears to be reduced, restricted to a subset of cells and associated with lower photosensitivity of the MB cell lines, possibly due to expression of the ABCG2 transporter protein CD338 on MB cells.

Early detection of colorectal adenocarcinoma: a clinical decision support tool based on plasma porphyrin accumulation and risk factors

BACKGROUND

An increase in naturally-occurring porphyrins has been described in the blood of subjects bearing different kinds of tumors, including colorectal, and this is probably related to a systemic alteration of heme metabolism induced by tumor cells. The aim of our study was to develop an artificial neural network (ANN) classifier for early detection of colorectal adenocarcinoma based on plasma porphyrin accumulation and risk factors.

METHODS

We measured the endogenous fluorescence of blood plasma in 100 colorectal adenocarcinoma patients and 112 controls using a conventional spectrofluorometer. Height, weight, personal and family medical history, use of alcohol, red meat, vegetables and tobacco were all recorded. An ANN model was built up from demographic data and from the integral of the fluorescence emission peak in the range 610-650 nm. We used the Receiver Operating Characteristic (ROC) curve to assess performance in distinguishing colorectal adenocarcinoma patients and controls. A liquid chromatography-high resolution mass spectrometry (LC-HRMS) analytical method was employed to identify the agents responsible for native fluorescence.

RESULTS

The fluorescence analysis indicated that the integral of the fluorescence emission peak in the range 610-650 nm was significantly higher in colorectal adenocarcinoma patients than controls (p < 0.0001) and was weakly correlated with the TNM staging (Spearman's rho = 0.224, p = 0.011). LC-HRMS measurements showed that the agents responsible for the fluorescence emission were mainly protoporphyrin-IX (PpIX) and coproporphyrin-I (CpI). The overall accuracy of our ANN model was 88% (87% sensitivity and 90% specificity) with an area under the ROC curve of 0.83.

CONCLUSIONS

These results confirm that tumor cells accumulate a diagnostic level of endogenous porphyrin compounds and suggest that plasma porphyrin concentrations, indirectly measured through fluorescence analysis, may be useful, together with risk factors, as a clinical decision support tool for the early detection of colorectal adenocarcinoma. Our future efforts will be aimed at examining how plasma porphyrin accumulation correlates with survival and response to therapy.

Fluorescent contrast agents for tumor surgery

Cancer is a leading cause of cases of mortality worldwide. The most effective method to cure solid tumors is surgery. Every year, >50% of cancer patients receive surgery to remove solid tumors. Surgery may increase the cure rate of most solid tumors by 4–11 fold. Surgery has many challenges, including identifying small lesions, locating metastases and confirming complete tumor removal. Fluorescence guidance describes a new approach to improve surgical accuracy. Near-infrared fluorescence imaging allows for real-time early diagnosis and intraoperative imaging of lesion tissue. The results of previous preclinical studies in the field of near-infrared fluorescence imaging are promising. This review provides examples introducing the three kinds of fluorescent dyes: The passive fluorescent dye indocyanine green, which has been approved by the Food and Drug Administration for clinical use in the USA, the fluorescent prodrug 5-aminolevulinic acid, a porphyrin precursor in the heme synthesis, and biomarker-targeted fluorescent dyes, which allow conjugation to different target sites.

Enhancement of Cancer-Specific Protoporphyrin IX Fluorescence by Targeting Oncogenic Ras/MEK Pathway

Protoporphyrin IX (PpIX) is an endogenous fluorescent molecule that selectively accumulates in cancer cells treated with the heme precursor 5-aminolevulinic acid (5-ALA). This cancer-specific accumulation of PpIX is used to distinguish tumor from normal tissues in fluorescence-guided surgery (FGS) and to destroy cancer cells by photodynamic therapy (PDT). In this study, we demonstrate that oncogenic Ras/mitogen-activated protein kinase kinase (MEK) pathway can modulate PpIX accumulation in cancer cells.

Methods: To identify Ras downstream elements involved in PpIX accumulation, chemical inhibitors were used. To demonstrate the increase of PpIX accumulation by MEK inhibition, different human normal and cancer cell lines, BALB/c mice bearing mammary 4T1 tumors and athymic nude mice bearing human tumors were used. To identify the mechanisms of PpIX regulation by MEK, biochemical and molecular biological experiments were conducted.

Results: Inhibition of one of the Ras downstream elements, MEK, promoted PpIX accumulation in cancer cells treated with 5-ALA, while inhibitors against other Ras downstream elements did not. Increased PpIX accumulation with MEK inhibition was observed in different types of human cancer cell lines, but not in normal cell lines. We identified two independent cellular mechanisms that underlie this effect in cancer cells. MEK inhibition reduced PpIX efflux from cancer cells by decreasing the expression level of ATP binding cassette subfamily B member 1 (ABCB1) transporter. In addition, the activity of ferrochelatase (FECH), the enzyme responsible for converting PpIX to heme, was reduced by MEK inhibition. Finally, we found that in vivo treatment with MEK inhibitors increased PpIX accumulation (2.2- to 2.4-fold) within mammary 4T1 tumors in BALB/c mice injected with 5-ALA without any change in normal organs. Similar results were also observed in a human tumor xenograft model.

Conclusion: Our study demonstrates that inhibition of oncogenic Ras/MEK significantly enhances PpIX accumulation in vitro and in vivo in a cancer-specific manner. Thus, suppressing the Ras/MEK pathway may be a viable strategy to selectively intensify PpIX fluorescence in cancer cells and improve its clinical applications in FGS.

5-ALA fluorescence of cerebral metastases and its impact for the local-in-brain progression

Aim of the present study was to analyze the oncological impact of 5-ALA fluorescence of cerebral metastases. A retrospective analysis was performed for 84 patients who underwent 5-ALA fluorescence-guided surgery of a cerebral metastasis. Dichotomized fluorescence behavior was correlated to the histopathological subtype and primary site of the metastases, the degree of surgical resection on an early postoperative MRI within 72 hours after surgery, the local in-brain-progression rate and the overall survival. 34/84 metastases (40.5%) showed either strong or faint and 50 metastases (59.5%) no 5-ALA derived fluorescence. Neither the primary site of the cerebral metastases nor their subtype correlated with fluorescence behavior. The dichotomized 5-ALA fluorescence (yes vs. no) had no statistical influence on the degree of surgical resection. Local in-brain progression within or at the border of the resection cavity was observed in 26 patients (30.9%). A significant correlation between 5-ALA fluorescence and local in-brain-progression rate was observed and patients with 5-ALA-negative metastases had a significant higher risk of local recurrence compared to patients with 5-ALA positive metastases. After exclusion of the 20 patients without any form of adjuvant radiation therapy, there was a trend towards a relation of the 5-ALA behavior on the local recurrence rate and the time to local recurrence, although results did not reach significance anymore. Absence of 5-ALA-induced fluorescence may be a risk factor for local in-brain-progression but did not influence the mean overall survival. Therefore, the dichotomized 5-ALA fluorescence pattern might be an indicator for a more aggressive tumor.

Protoporphyrinogen oxidase is involved in the fluorescence intensity of 5-aminolevulinic acid-mediated laser-based photodynamic endoscopic diagnosis for early gastric cancer

BACKGROUND/AIM

Laser-based photodynamic endoscopic diagnosis (LPDED) is a type of endoscopic diagnosis that uses the fluorescence caused by the photochemical reaction that occurs when a fluorescent substance is irradiated by a light of a specific wavelength. Although 5-aminolevulinic acid (5-ALA) can detect early gastric cancer (EGC) during LPDED, there is an unresolved issue of the differences in fluorescence intensity among histopathological types of gastric cancer. Thus, the aim of the present study was to assess whether protoporphyrinogen oxidase (PPOX), involved in the activation of protoporphyrin IX, can affect the fluorescence intensity in EGC.

METHODS

Thirty-three gastric tumor lesions in 30 patients were assessed by LPDED using a prototype endoscope equipped with a blue laser ray to cause excitation following oral 5-ALA administration. The tumors were then resected by endoscopic submucosal dissection or laparoscopic surgery. PPOX expression was examined immunohistochemically in the excised specimens. To explore the mechanisms of histopathological diversity in PPOX and coproporphyrinogen oxidase (CPOX) expression of EGC, immunohistochemical analysis was performed using 75 surgically resected specimens of diverse EGCs.

RESULTS

Among the 33 lesions, 26 tumors were detectable by LPDED, whereas seven were undetectable. Between the LPDED-positive and negative groups, there was a significant difference in histopathology. The expression of PPOX was higher in tubular adenocarcinoma (tub) than in signet-ring cell carcinoma (sig). There were significant differences in PPOX and CPOX expression scores of the surgically resected specimens among tub, poorly differentiated adenocarcinoma (por), and sig.

CONCLUSION

PPOX protein expression could be involved in the fluorescence intensity of LPDED in EGC, possibly reflecting histopathological features.

Involvement of protoporphyrin IX accumulation in the pathogenesis of isoniazid/rifampicin-induced liver injury: the prevention of curcumin

Combination of isoniazid (INH) and rifampicin (RFP) causes liver injury frequently among tuberculosis patients. However, mechanisms of the hepatotoxicity are not entirely understood. Protoporphyrin IX (PPIX) accumulation, as an endogenous hepatotoxin, resulting from isoniazid and rifampicin co-therapy (INH/RFP) has been reported in PXR-humanized mice. Aminolevulinic acid synthase1 (ALAS1), ferrochelatase (FECH) and breast cancer resistance protein (BCRP) play crucial roles in PPIX synthesis, metabolism and transport, respectively. Herein, this study focused on the role of INH/RFP in these processes. We observed PPIX accumulation in human hepatocytes (L-02) and mouse livers. FECH expression was initially found downregulated both in L-02 cells and mouse livers and expression levels of ALAS1 and BCRP were elevated in L-02 cells after INH/RFP treatment, indicating FECH inhibition and ALAS1 induction might confer a synergistic effect on PPIX accumulation. Additionally, our results revealed that curcumin alleviated INH/RFP-induced liver injury, declined PPIX levels and induced FECH expression in both L-02 cells and mice. In conclusion, our data provide a novel insight in the mechanism of INH/RFP-induced PPIX accumulation and evidence for understanding pathogenesis of INH/RFP-induced liver injury, and suggest that amelioration of PPIX accumulation might be involved in the protective effect of curcumin on INH/RFP-induced liver injury.

Assessing the efficacy of coherent anti-Stokes Raman scattering microscopy for the detection of infiltrating glioblastoma in fresh brain samples

Coherent anti-Stokes Raman scattering (CARS) microscopy is an emerging technique for identification of brain tumors. However, tumor identification by CARS microscopy on bulk samples and in vivo has been so far verified retrospectively on histological sections, which only provide a gross reference for the interpretation of CARS images without matching at cellular level. Therefore, fluorescent labels were exploited for direct assessment of the interpretation of CARS images of solid and infiltrative tumors. Glioblastoma cells expressing green fluorescent protein (GFP) were used for induction of tumors in mice (n = 7). The neoplastic nature of cells imaged by CARS microscopy was unequivocally verified by addressing two-photon fluorescence of GFP on fresh brain slices and in vivo. In fresh unfixed biopsies of human glioblastoma (n = 10), the fluorescence of 5-aminolevulinic acid-induced protoporphyrin IX was used for identification of tumorous tissue. Distinctive morphological features of glioblastoma cells, i.e. larger nuclei, evident nuclear membrane and nucleolus, were identified in the CARS images of both mouse and human brain tumors. This approach demonstrates that the chemical contrast provided by CARS allows the localization of infiltrating tumor cells in fresh tissue and that the cell morphology in CARS images is useful for tumor recognition. Experimental glioblastoma expressing green fluorescent protein.

A comparative evaluation of diffuse reflectance and Raman spectroscopy in the detection of cervical cancer

Optical spectroscopic techniques show improved diagnostic accuracy for non-invasive detection of cervical cancers. In this study, sensitivity and specificity of two in vivo modalities, i.e diffuse reflectance spectroscopy (DRS) and Raman spectroscopy (RS), were compared by utilizing spectra recorded from the same sites (67 tumor (T), 22 normal cervix (C), and 57 normal vagina (V)). Data was analysed using principal component - linear discriminant analysis (PC-LDA), and validated using leave-one-out-cross-validation (LOOCV). Sensitivity, specificity, positive predictive value and negative predictive value for classification between normal (N) and tumor (T) sites were 91%, 96%, 95% and 93%, respectively for RS and 85%, 95%, 93% and 88%, respectively for DRS. Even though DRS revealed slightly lower diagnostic accuracies, owing to its lower cost and portability, it was found to be more suited for cervical cancer screening in low resource settings. On the other hand, RS based devices could be ideal for screening patients with centralised facilities in developing countries.

Her2 oncogene transformation enhances 5-aminolevulinic acid-mediated protoporphyrin IX production and photodynamic therapy response

Enhanced protoporphyrin IX (PpIX) production in tumors derived from the administration of 5-aminolevulinic acid (ALA) enables the use of ALA as a prodrug for photodynamic therapy (PDT) and fluorescence-guided tumor resection. Although ALA has been successfully used in the clinic, the mechanism underlying enhanced ALA-induced PpIX production in tumors is not well understood. Human epidermal growth receptor 2 (Her2, Neu, ErbB2) is a driver oncogene in human cancers, particularly breast cancers. Here we showed that, in addition to activating Her2/Neu cell signaling, inducing epithelial-mesenchymal transition and upregulating glycolytic enzymes, transfection of NeuT (a mutated Her2/Neu) oncogene in MCF10A human breast epithelial cells significantly enhanced ALA-induced PpIX fluorescence by elevating some enzymes involved in PpIX biosynthesis. Furthermore, NeuT-transformed and vector control cells exhibited drastic differences in the intracellular localization of PpIX, either produced endogenously from ALA or applied exogenously. In vector control cells, PpIX displayed a cell contact-dependent membrane localization at high cell densities and increased mitochondrial localization at low cell densities. In contrast, no predominant membrane localization of PpIX was observed in NeuT cells and ALA-induced PpIX showed a consistent mitochondrial localization regardless of cell density. PDT with ALA caused significantly more decrease in cell viability in NeuT cells than in vector cells. Our data demonstrate that NeuT oncogene transformation enhanced ALA-induced PpIX production and altered PpIX intracellular localization, rendering NeuT-transformed cells increased response to ALA-mediated PDT. These results support the use of ALA for imaging and photodynamic targeting Her2/Neu-positive tumors.

Chronic Treatment with Isoniazid Causes Protoporphyrin IX Accumulation in Mouse Liver

Isoniazid (INH) can cause hepatotoxicity. In addition, INH is contraindicated in patients suffering from porphyrias. Our metabolomic analysis revealed that chronic treatment with INH in mice causes a hepatic accumulation of protoporphyrin IX (PPIX). PPIX is an intermediate in the heme biosynthesis pathway, and it is also known as a hepatotoxin. We further found that INH induces delta-aminolevulinate synthase 1 (ALAS1), the rate-limiting enzyme in heme biosynthesis. We also found that INH downregulates ferrochelatase (FECH), the enzyme that converts PPIX to heme. In summary, this study illustrated that chronic treatment with INH causes PPIX accumulation in mouse liver in part through ALAS1 induction and FECH downregulation. This study also highlights that drugs can disrupt the metabolic pathways of endobiotics and increase the risk of liver damage.

In situ production of ROS in the skin by photodynamic therapy as a powerful tool in clinical dermatology

Photodynamic therapy (PDT) is a clinical modality of photochemotherapy based on the accumulation of a photosensitizer in target cells and subsequent irradiation of the tissue with light of adequate wavelength promoting reactive oxygen species (ROS) formation and cell death. PDT is used in several medical specialties as an organ-specific therapy for different entities. In this review we focus on the current dermatological procedure of PDT. In the most widely used PDT protocol in dermatology, ROS production occurs by accumulation of the endogenous photosensitizer protoporphyrin IX after treatment with the metabolic precursors 5-methylaminolevulinic acid (MAL) or 5-aminolevulinic acid (ALA). To date, current approved dermatological indications of PDT include actinic keratoses (AK), basal cell carcinoma (BCC) and in situ squamous cell carcinoma (SCC) also known as Bowen disease (BD). With regards to AKs, PDT can also treat the cancerization field carrying an oncogenic risk. In addition, an increasing number of pathologies, such as other skin cancers, infectious, inflammatory or pilosebaceous diseases are being considered as potentially treatable entities with PDT. Besides the known therapeutic properties of PDT, there is a modality used for skin rejuvenation and aesthetic purposes defined as photodynamic photorejuvenation. This technique enables the remodelling of collagen, which in turn prevents and treats photoaging stygmata. Finally we explore a new potential treatment field for PDT determined by the activation of follicular bulge stem cells caused by in situ ROS formation.

Detection of cervical lesions by multivariate analysis of diffuse reflectance spectra: a clinical study

Diffuse reflectance (DR) spectroscopy is a non-invasive, real-time, and cost-effective tool for early detection of malignant changes in squamous epithelial tissues. The present study aims to evaluate the diagnostic power of diffuse reflectance spectroscopy for non-invasive discrimination of cervical lesions in vivo. A clinical trial was carried out on 48 sites in 34 patients by recording DR spectra using a point-monitoring device with white light illumination. The acquired data were analyzed and classified using multivariate statistical analysis based on principal component analysis (PCA) and linear discriminant analysis (LDA). Diagnostic accuracies were validated using random number generators. The receiver operating characteristic (ROC) curves were plotted for evaluating the discriminating power of the proposed statistical technique. An algorithm was developed and used to classify non-diseased (normal) from diseased sites (abnormal) with a sensitivity of 72 % and specificity of 87 %. While low-grade squamous intraepithelial lesion (LSIL) could be discriminated from normal with a sensitivity of 56 % and specificity of 80 %, and high-grade squamous intraepithelial lesion (HSIL) from normal with a sensitivity of 89 % and specificity of 97 %, LSIL could be discriminated from HSIL with 100 % sensitivity and specificity. The areas under the ROC curves were 0.993 (95 % confidence interval (CI) 0.0 to 1) and 1 (95 % CI 1) for the discrimination of HSIL from normal and HSIL from LSIL, respectively. The results of the study show that DR spectroscopy could be used along with multivariate analytical techniques as a non-invasive technique to monitor cervical disease status in real time.

Aminolevulinic Acid-Based Tumor Detection and Therapy: Molecular Mechanisms and Strategies for Enhancement

Aminolevulinic acid (ALA) is the first metabolite in the heme biosynthesis pathway in humans. In addition to the end product heme, this pathway also produces other porphyrin metabolites. Protoporphyrin (PpIX) is one heme precursor porphyrin with good fluorescence and photosensitizing activity. Because tumors and other proliferating cells tend to exhibit a higher level of PpIX than normal cells after ALA incubation, ALA has been used as a prodrug to enable PpIX fluorescence detection and photodynamic therapy (PDT) of lesion tissues. Extensive studies have been carried out in the past twenty years to explore why some tumors exhibit elevated ALA-mediated PpIX and how to enhance PpIX levels to achieve better tumor detection and treatment. Here we would like to summarize previous research in order to stimulate future studies on these important topics. In this review, we focus on summarizing tumor-associated alterations in heme biosynthesis enzymes, mitochondrial functions and porphyrin transporters that contribute to ALA-PpIX increase in tumors. Mechanism-based therapeutic strategies for enhancing ALA-based modalities including iron chelators, differentiation agents and PpIX transporter inhibitors are also discussed.

ABCG2 transporter inhibitor restores the sensitivity of triple negative breast cancer cells to aminolevulinic acid-mediated photodynamic therapy

Photosensitizer protoporphyrin IX (PpIX) fluorescence, intracellular localization and cell response to photodynamic therapy (PDT) were analyzed in MCF10A normal breast epithelial cells and a panel of human breast cancer cells including estrogen receptor (ER) positive, human epidermal growth factor receptor 2 (HER2) positive and triple negative breast cancer (TNBC) cells after treatment with PpIX precursor aminolevulinic acid (ALA). Although PpIX fluorescence was heterogeneous in different cells, TNBC cells showed significantly lower PpIX level than MCF10A and ER- or HER2-positive cells. PpIX fluorescence in TNBC cells also had much less mitochondrial localization than other cells. There was an inverse correlation between PpIX fluorescence and cell viability after PDT. Breast cancer cells with the highest PpIX fluorescence were the most sensitive to ALA-PDT and TNBC cells with the lowest PpIX level were resistant to PDT. Treatment of TNBC cells with ABCG2 transporter inhibitor Ko143 significantly increased ALA-PpIX fluorescence, enhanced PpIX mitochondrial accumulation and sensitized cancer cells to ALA-PDT. Ko143 treatment had little effect on PpIX production and ALA-PDT in normal and ER- or HER2-positive cells. These results demonstrate that enhanced ABCG2 activity renders TNBC cell resistance to ALA-PDT and inhibiting ABCG2 transporter is a promising approach for targeting TNBC with ALA-based modality.

Expression of Genes Involved in Porphyrin Biosynthesis Pathway in the Human Renal Cell Carcinoma

Renal cell carcinoma (RCC) remains one of the greatest challenges of urological oncology and is the third leading cause of death in genitourinary cancers. Surgery may be curative when patients present with localized disease. Our previous results demonstrated the autofluorescence of blood PpIX in primary RCC mouse model and an increase in fluorescence intensity as a function of growth of the subcutaneous tumor mass. In another work, a nice correlation between the growth of the tumor mass and tissue fluorescence intensity was found. The aim of this study was to evaluate the expression profile of porphyrin biosynthesis pathway-related genes of human kidney cells. We used two kidney cell lines, one normal (HK2) and another malignant (Caki-1). Endogenous and 5-aminolevolinic acid (ALA) induced protoporphyrin IX (PpIX) HK2 and Caki-1 cells were analyzed by fluorescence spectroscopy. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to measure mRNA of those genes. Emission spectra were obtained by exciting the samples at 405 nm. For ALA untreated cells the maximum fluorescence intensity was detected at 635 nm. The mean peak area of emission spectra in both cells types increased linearly in function of cell number. Besides, basal levels of PpIX autofluorescence of each cell concentration of HK2 samples were significantly lower than those of Caki-1 samples. For ALA-treated cells the mean PpIX spectra shows PpIX emission peak at 635 nm with a shoulder at 700 nm. Analysis of PpIX fluorescence intensity ratio between tumor cells and HK2 cells showed that fluorescence intensity was, on average, 26 times greater in tumor cells than in healthy cells. qRT-PCR revealed that in Caki-1 ALA-treated cells, PEPT gene was significantly up-regulated and FECH and HO-1 genes were significantly down regulated in comparison with HK2 ALA-treated cells. In conclusion, our results demonstrate the preferential accumulation of ALA-induced PpIX in human RCC and also indicate that PEPT1, FECH and HO-1 genes are major contributors to this accumulation.