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

Porphyrin overdrive rewires cancer cell metabolism

All cancer cells reprogram metabolism to support aberrant growth. Here, we report that cancer cells employ and depend on imbalanced and dynamic heme metabolic pathways, to accumulate heme intermediates, that is, porphyrins. We coined this essential metabolic rewiring "porphyrin overdrive" and determined that it is cancer-essential and cancer-specific. Among the major drivers are genes encoding mid-step enzymes governing the production of heme intermediates. CRISPR/Cas9 editing to engineer leukemia cell lines with impaired heme biosynthetic steps confirmed our whole-genome data analyses that porphyrin overdrive is linked to oncogenic states and cellular differentiation. Although porphyrin overdrive is absent in differentiated cells or somatic stem cells, it is present in patient-derived tumor progenitor cells, demonstrated by single-cell RNAseq, and in early embryogenesis. In conclusion, we identified a dependence of cancer cells on non-homeostatic heme metabolism, and we targeted this cancer metabolic vulnerability with a novel "bait-and-kill" strategy to eradicate malignant cells.

Fluorescence-Guided Laparoscopy after Oral Hypericin Administration for Staging of Locally Advanced Gastric Cancer-A Pilot Study

(1) Background: Laparoscopic staging is essential in gastric cancer (GC) to rule out peritoneal metastasis (PM). Hypericin, a plant-derived fluorescent compound, has been suggested to improve laparoscopic visualization of PM from GC. This prospective, single-arm, open-label clinical trial aimed to assess the feasibility and safety of oral hypericin administration as well as the suitability of fluorescence-guided laparoscopy (FGL) for improving the sensitivity and specificity of staging in GC patients (EudraCT-Number: 2015-005277-21; clinicaltrials.gov identifier: NCT-02840331). (2) Methods: GC patients received Laif® 900, an approved hypericin-containing phytopharmaceutical, once orally two to four hours before white light and ultraviolet light laparoscopy. The peritoneal cancer index was evaluated, biopsies taken and hypericin concentrations in serum and peritoneal tissue were determined by mass spectrometry. (3) Results: Between 2017 and 2021, out of 63 patients screened for eligibility, 50 patients were enrolled and treated per protocol. The study intervention was shown to be feasible and safe in all patients. Standard laparoscopy revealed suspicious lesions in 27 patients (54%), among whom 16 (59%) were diagnosed with PM. FGL identified suspicious areas in 25 patients (50%), among whom PM was confirmed in 13 cases (52%). Although hypericin concentrations in serum reached up to 5.64 ng/mL, no hypericin was detectable in peritoneal tissue biopsies. (4) Conclusions: FGL in patients with GC was shown to be feasible but futile in this study. Sufficient levels of hypericin should be ensured in target tissue prior to reassessing FGL with hypericin.

Activity-Based Fluorescence Diagnostics for Cancer

Fluorescence imaging is one of the most promising approaches to achieve intraoperative assessment of the tumor/normal tissue margins during cancer surgery. This is critical to improve the patients' prognosis, and therefore various molecular fluorescence imaging probes have been developed for the identification of cancer lesions during surgery. Among them, "activatable" fluorescence probes that react with cancer-specific biomarker enzymes to generate fluorescence signals have great potential for high-contrast cancer imaging due to their low background fluorescence and high signal amplification by enzymatic turnover. Over the past two decades, activatable fluorescence probes employing various fluorescence control mechanisms have been developed worldwide for this purpose. Furthermore, new biomarker enzymatic activities for specific types of cancers have been identified, enabling visualization of various types of cancers with high sensitivity and specificity. This Review focuses on recent advances in the design, function and characteristics of activatable fluorescence probes that target cancer-specific enzymatic activities for cancer imaging and also discusses future prospects in the field of activity-based diagnostics for cancer.

Globus Lucidus: A porcine study of an intracranial implant designed to deliver closed, repetitive photodynamic and photochemical therapy in glioblastoma

OBJECTIVE

Herein we describe initial results in a porcine model of a fully implantable device designed to allow closed, repetitive photodynamic treatment of glioblastoma (GBM).

METHODS

This implant, Globus Lucidus, is a transparent quartz glass sphere with light-emitting diodes releasing wavelengths of 630 nm (19.5 mW/cm2), 405 nm (5.0 mW/cm2) or 275 nm (0.9 mW/cm2). 5-aminolevulinic acid was the photosensitizing prodrug chosen for use with Globus Lucidus, hence the implants illuminated at 630 nm or 405 nm. An additional 275 nm wavelength-emittance was included to explore the effects of photochemical therapy (PCT) by ultraviolet (UV) light. Twenty healthy domestic pigs underwent right-frontal craniotomies. The Globus Lucidus device was inserted into a surgically created right-frontal lobe cavity. After postoperative recovery, irradiation for up to 30 min daily for up to 14 d, or continuous irradiation for up to 14.6 h was conducted.

RESULTS

Surgery, implants, and repeated irradiations using the different wavelengths were generally well tolerated. Social behavior, wound healing, body weight, and temperature remained unaffected. Histopathological analyses revealed consistent leukocyte infiltration around the intracerebral implant sites with no significant differences between experimental and control groups.

CONCLUSION

This Globus Lucidus porcine study prepares the groundwork for adjuvant, long-term, repeated PDT of the GBM infiltration zone. This is the first report of a fully implantable PDT/PCT device for the potential treatment of GBM. A preclinical effectivity study of Globus Lucidus PDT/PCT is warranted and in advanced stages of planning.

Complexes of Ruthenium(II) as Promising Dual-Active Agents against Cancer and Viral Infections

Poor responses to medical care and the failure of pharmacological treatment for many high-frequency diseases, such as cancer and viral infections, have been widely documented. In this context, numerous metal-based substances, including cisplatin, auranofin, various gold metallodrugs, and ruthenium complexes, are under study as possible anticancer and antiviral agents. The two Ru(III) and Ru(II) complexes, namely, BOLD-100 and RAPTA-C, are presently being studied in a clinical trial and preclinical studies evaluation, respectively, as anticancer agents. Interestingly, BOLD-100 has also recently demonstrated antiviral activity against SARS-CoV-2, which is the virus responsible for the COVID-19 pandemic. Over the last years, much effort has been dedicated to discovering new dual anticancer-antiviral agents. Ru-based complexes could be very suitable in this respect. Thus, this review focuses on the most recent studies regarding newly synthesized Ru(II) complexes for use as anticancer and/or antiviral agents.

Enhanced Delivery of 5-Aminolevulinic Acid by Lecithin Invasomes in 3D Melanoma Cancer Model

Photodynamic therapy (PDT) is a noninvasive therapeutic approach for the treatment of skin cancer and diseases. 5-Aminolevulinic acid is a prodrug clinically approved for PDT. Once internalized by cancer cells, it is rapidly metabolized to the photosensitizer protoporphyrin IX, which under the proper light irradiation, stimulates the deleterious reactive oxygen species (ROS) production and leads to cell death. The high hydrophilicity of 5-aminolevulinic acid limits its capability to cross the epidermis. Lipophilic derivatives of 5-aminolevulinic acid only partly improved skin penetration, thus making its incorporation into nanocarriers necessary. Here we have developed and characterized 5-aminolevulinic acid loaded invasomes made of egg lecithin, either 1,2-dilauroyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphocholine, and the terpene limonene. The obtained invasomes are highly thermostable and display a spherical morphology with an average size of 150 nm and an encapsulation efficiency of 80%; moreover, the ex vivo epidermis diffusion tests established that nanovesicles containing the terpene led to a much higher skin penetration (up to 80% in 3 h) compared to those without limonene and to the free fluorescent tracer (less than 50%). Finally, in vitro studies with 2D and 3D human cell models of melanoma proved the biocompatibility of invasomes, the enhanced intracellular transport of 5-aminolevulinic acid, its ability to generate ROS upon irradiation, and consequently, its antiproliferative effect. A simplified scaffold-based 3D skin model containing melanoma spheroids was also prepared. Considering the results obtained, we conclude that the lecithin invasomes loaded with 5-aminolevulinic acid have a good therapeutic potential and may represent an efficient tool that can be considered a valid alternative in the topical treatment of melanoma and other skin diseases.

Proton-Coupled Oligopeptide Transport (Slc15) in the Brain: Past and Future Research

This mini-review describes the role of the solute carrier (SLC)15 family of proton-coupled oligopeptide transporters (POTs) and particularly Pept2 (Slc15A2) and PhT1 (Slc15A4) in the brain. That family transports endogenous di- and tripeptides and peptidomimetics but also a number of drugs. The review focuses on the pioneering work of David E. Smith in the field in identifying the impact of PepT2 at the choroid plexus (the blood-CSF barrier) as well as PepT2 and PhT1 in brain parenchymal cells. It also discusses recent findings and future directions in relation to brain POTs including cellular and subcellular localization, regulatory pathways, transporter structure, species differences and disease states.

Deep learning based depth map estimation of protoporphyrin IX in turbid media using dual wavelength excitation fluorescence

This study presents a depth map estimation of fluorescent objects in turbid media, such as biological tissue based on fluorescence observation by two-wavelength excitation and deep learning-based processing. A U-Net-based convolutional neural network is adapted for fluorophore depth maps from the ratiometric information of the two-wavelength excitation fluorescence. The proposed method offers depth map estimation from wide-field fluorescence images with rapid processing. The feasibility of the proposed method was demonstrated experimentally by estimating the depth map of protoporphyrin IX, a recognized cancer biomarker, at different depths within an optical phantom.

Biogenic Imaging Contrast Agents

Imaging contrast agents are widely investigated in preclinical and clinical studies, among which biogenic imaging contrast agents (BICAs) are developing rapidly and playing an increasingly important role in biomedical research ranging from subcellular level to individual level. The unique properties of BICAs, including expression by cells as reporters and specific genetic modification, facilitate various in vitro and in vivo studies, such as quantification of gene expression, observation of protein interactions, visualization of cellular proliferation, monitoring of metabolism, and detection of dysfunctions. Furthermore, in human body, BICAs are remarkably helpful for disease diagnosis when the dysregulation of these agents occurs and can be detected through imaging techniques. There are various BICAs matched with a set of imaging techniques, including fluorescent proteins for fluorescence imaging, gas vesicles for ultrasound imaging, and ferritin for magnetic resonance imaging. In addition, bimodal and multimodal imaging can be realized through combining the functions of different BICAs, which helps overcome the limitations of monomodal imaging. In this review, the focus is on the properties, mechanisms, applications, and future directions of BICAs.

Fluorescence imaging of lymphangioma circumscriptum of the vulva with aminolevulinic acid and target-type narrow band ultraviolet light

Lymphangioma circumscriptum of the vulva is a rare lymphatic disorder. Defining the precise location of the lesion is required to select an appropriate treatment. Herein we present photodynamic diagnosis of lymphangioma circumscriptum of the vulva with aminolevulinic acid and target-type narrow band ultraviolet light device.

Photostable Cascade-Activatable Peptide Self-Assembly on a Cancer Cell Membrane for High-Performance Identification of Human Bladder Cancer

Missed or residual tumor burden results in high risk for bladder cancer relapse. However, existing fluorescent probes cannot meet the clinical needs because of inevitable photobleaching properties. Performance can be improved by maintaining intensive and sustained fluorescence signals via resistance to intraoperative saline flushing and intrinsic fluorescent decay, providing surgeons with sufficiently clear and high-contrast surgical fields, avoiding residual tumors or missed diagnosis. This study designs and synthesizes a photostable cascade-activatable peptide, a target reaction-induced aggregation peptide (TRAP) system, which can construct polypeptide-based nanofibers in situ on the cell membrane to achieve long-term and stable imaging of bladder cancer. The probe has two parts: a target peptide (TP) targets CD44v6 to recognize bladder cancer cells, and a reaction-induced aggregation peptide (RAP) is introduced, which effectively reacts with the TP via a click reaction to enhance the hydrophobicity of the whole molecule, assembling into nanofibers and further nanonetworks. Accordingly, probe retention on the cell membrane is prolonged, and photostability is significantly improved. Finally, the TRAP system is successfully employed in the high-performance identification of human bladder cancer in ex vivo bladder tumor tissues. This cascade-activatable peptide molecular probe based on the TRAP system enables efficient and stable imaging of bladder cancer.

Photosensitizers-Loaded Nanocarriers for Enhancement of Photodynamic Therapy in Melanoma Treatment

Malignant melanoma poses a significant global health burden. It is the most aggressive and lethal form of skin cancer, attributed to various risk factors such as UV radiation exposure, genetic modifications, chemical carcinogens, immunosuppression, and fair complexion. Photodynamic therapy is a promising minimally invasive treatment that uses light to activate a photosensitizer, resulting in the formation of reactive oxygen species, which ultimately promote cell death. When selecting photosensitizers for melanoma photodynamic therapy, the presence of melanin should be considered. Melanin absorbs visible radiation similar to most photosensitizers and has antioxidant properties, which undermines the reactive species generated in photodynamic therapy processes. These characteristics have led to further research for new photosensitizing platforms to ensure better treatment results. The development of photosensitizers has advanced with the use of nanotechnology, which plays a crucial role in enhancing solubility, optical absorption, and tumour targeting. This paper reviews the current approaches (that use the synergistic effect of different photosensitizers, nanocarriers, chemotherapeutic agents) in the photodynamic therapy of melanoma.

Five-Aminolevulinic Acid (5-ALA) Induces Heme Oxygenase-1 and Ameliorates Palmitic Acid-Induced Endoplasmic Reticulum Stress in Renal Tubules

Steatosis, or ectopic lipid deposition, is the fundamental pathophysiology of non-alcoholic steatohepatitis and chronic kidney disease. Steatosis in the renal tubule causes endoplasmic reticulum (ER) stress, leading to kidney injury. Thus, ER stress could be a therapeutic target in steatonephropathy. Five-aminolevulinic acid (5-ALA) is a natural product that induces heme oxygenase (HO)-1, which acts as an antioxidant. This study aimed to investigate the therapeutic potential of 5-ALA in lipotoxicity-induced ER stress in human primary renal proximal tubule epithelial cells. Cells were stimulated with palmitic acid (PA) to induce ER stress. Cellular apoptotic signals and expression of genes involved in the ER stress cascade and heme biosynthesis pathway were analyzed. The expression of glucose-regulated protein 78 (GRP78), a master regulator of ER stress, increased significantly, followed by increased cellular apoptosis. Administration of 5-ALA induced a remarkable increase in HO-1 expression, thus ameliorating PA-induced GRP78 expression and apoptotic signals. BTB and CNC homology 1 (BACH1), a transcriptional repressor of HO-1, was significantly downregulated by 5-ALA treatment. HO-1 induction attenuates PA-induced renal tubular injury by suppressing ER stress. This study demonstrates the therapeutic potential of 5-ALA against lipotoxicity through redox pathway.

Current Strategies in Photodynamic Therapy (PDT) and Photodynamic Diagnostics (PDD) and the Future Potential of Nanotechnology in Cancer Treatment

Photodynamic diagnostics (PDD) and photodynamic therapy (PDT) are well-established medical technologies used for the diagnosis and treatment of malignant neoplasms. They rely on the use of photosensitizers, light and oxygen to visualize or eliminate cancer cells. This review demonstrates the recent advancements in these modalities with the use of nanotechnology, including quantum dots as innovative photosensitizers or energy donors, liposomes and micelles. Additionally, this literature review explores the combination of PDT with radiotherapy, chemotherapy, immunotherapy, and surgery for treating various neoplasms. The article also focuses on the latest achievements in PDD and PDT enhancements, which seem to be very promising in the field of oncology.

Near-infrared phototheranostics of tumors with protoporphyrin IX and chlorin e6 photosensitizers

BACKGROUND

The study aims to develop a method for phototheranostics of tumors in the near-infrared (NIR) range using protoporphyrin IX (PpIX) and chlorin e6 (Ce6) photosensitizers (PSs) MATERIALS AND METHODS: Phototheranostics includes spectral fluorescence diagnostics of PS distribution and photodynamic therapy (PDT) using a single laser in the red spectral range. PpIX and Ce6 fluorescence were registered in the NIR range. PpIX and Ce6 photobleaching was determined during PDT by the change in PS fluorescence. NIR phototheranostics with PpIX and Ce6 were performed on optical phantoms and tumors of patients with oral leukoplakia and basal cell carcinoma.

RESULTS

NIR spectral fluorescence diagnostics of optical phantoms with PpIX or Ce6 is possible when fluorescence is excited by 635 or 660 nm lasers. Fluorescence intensity of PpIX and Ce6 was measured in the range of 725-780 nm. The highest values of signal-to-noise in the case of phantoms with PpIX were observed at λ_exc=635 nm, and for phantoms with Ce6 at λ_exc=660 nm. NIR phototheranostics provides the detection of tumor tissues with PpIX or Ce6 accumulation. The PSs photobleaching in the tumor during PDT occurs according to a bi-exponential law.

CONCLUSION

Phototheranostics of tumors containing PpIX or Ce6 allows fluorescent monitoring of PS distribution in the NIR range and measuring PSs photobleaching during light exposure that provides personalization of the photodynamic exposure duration to deeper tumors. Using a single laser for fluorescence diagnostics and PDT reduces patient treatment time.

Study on the effect of 5-aminolevulinic acid-mediated photodynamic therapy combined with cisplatin on human ovarian cancer OVCAR-3 ​cells

PURPOSE

This article explores the effect of 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) combined with cisplatin (CDDP) on the apoptosis of human ovarian cancer cells and the mechanism of action of the combination therapy.

MATERIALS AND METHODS

Human ovarian cancer OVCAR-3 ​cells were cultured in vitro and divided into 5-ALA/PDT group, CDDP group and combined treatment group (5-ALA/PDT combined with different concentrations of CDDP). After administration of the corresponding drugs, a CCK-8 assay was used to detect the inhibition rate of cell proliferation. After Rhodamine 123 staining, mitochondrial membrane potential changes were observed under fluorescence microscopy. The apoptosis rate and reactive oxygen species (ROS) content were detected by flow cytometry. Western blotting was used to detect protein expression.

RESULTS

The CCK-8 assay showed that CDDP in combination with 5-ALA/PDT significantly enhanced cytotoxicity compared to treatment with CDDP alone and that low doses of CDDP were sufficient to induce these combination effects. The mitochondrial membrane potential in each combination treatment group gradually decreased with increasing CDDP concentration, while the apoptosis rate and reactive oxygen species (ROS) content detected by flow cytometry gradually increased. Western blotting assay showed that the expression of bax, cleaved caspase-9, cleaved caspase-3, and cleaved PARP was increased, while the expression of bcl-2, caspase-9, caspase-3, and PARP was decreased, and the differences were statistically significant (P ​< ​0.05).

CONCLUSIONS

In summary, 5-ALA/PDT combined with CDDP can effectively inhibit cell proliferation and promote apoptosis, and this combination may induce apoptosis by activating the mitochondrial pathway.

Photodynamic Therapy for Bladder Cancers, A Focused Review†

Bladder cancer is the first cancer for which PDT was clinically approved in 1993. Unfortunately, it was unsuccessful due to side effects like bladder contraction. Here, we summarized the recent progress of PDT for bladder cancers, focusing on photosensitizers and formulations. General strategies to minimize side effects are intravesical administration of photosensitizers, use of targeting strategies for photosensitizers and better control of light. Non-muscle invasive bladder cancers are more suitable for PDT than muscle invasive and metastatic bladder cancers. In 2010, the FDA approved blue light cystoscopy, using PpIX fluorescence, for photodynamic diagnosis of non-muscle invasive bladder cancer. PpIX produced from HAL was also used in PDT but was not successful due to low therapeutic efficacy. To enhance the efficacy of PpIX-PDT, we have been working on combining it with singlet oxygen-activatable prodrugs. The use of these prodrugs increases the therapeutic efficacy of the PpIX-PDT. It also improves tumor selectivity of the prodrugs due to the preferential formation of PpIX in cancer cells resulting in decreased off-target toxicity. Future challenges include improving prodrugs and light delivery across the bladder barrier to deeper tumor tissue and generating an effective therapeutic response in an In vivo setting without causing collateral damage to bladder function.

Photodynamic therapy in oral cancer: a review of clinical studies

A significant mortality rate is associated with oral cancer, particularly in cases of late-stage diagnosis. Since the last decades, oral cancer survival rates have only gradually improved despite advances in treatment. This poor success rate is mainly due to the development of secondary tumors, local recurrence, and regional failure. Invasive treatments frequently have a negative impact on the aesthetic and functional outcomes of survivors. Novel approaches are thus needed to manage this deadly disease in light of these statistics. In photodynamic therapy (PDT), a light-sensitive medication called a photosensitizer is given first, followed by exposure to light of the proper wavelength that matches the absorbance band of the photosensitizer. The tissue oxygen-induced cytotoxic free radicals kill tumor cells directly, harm the microvascular structure, and cause inflammatory reactions at the targeted sites. In the case of early lesions, PDT can be used as a stand-alone therapy, and in the case of advanced lesions, it can be used as adjuvant therapy. The current review article discussed the uses of PDT in oral cancer therapy based on recent advances in this field.

Development of novel polymeric nanoagents and their potential in cancer diagnosis and therapy runing title: Polymeric nanoagents for cancer theranostics

Cancer has been one of the leading factors of death around the world. Cancer patients usually have low 5-year survival rates and poor life quality requiring substantial improvement. In clinic, the presenting diagnostic strategies lack sensitivity with only a small proportion of patients can be accurately identified. For diagnosed patients, most of them are at the advanced stages thus being delayed to receive treatment. Therefore, it is eager to investigate and develop highly effective and accurate techniques for cancer early diagnosis and individualized therapy. Various nanoplatforms are emerging as imaging agents and drug carriers for cancer theranostics recently. Novel polymeric nanoagents, as a potent exemplar, have extraordinary merits, such as good stability, high biosafety and high drug loading efficacy, showing the great prospect for cancer early diagnosis and precise treatment. Herein, we review the recent advances in novel polymeric nanoagents and elucidate their synthesis procedures. We further introduce the applications of novel polymeric nanoagents in cancer diagnosis, treatment, and theranostics, as well as associated challenges and prospects in this field.

Adverse Effect of Blue Light on DNA Integrity Is Accelerated by 5-Aminolevulinic Acid in HaCaT Human Keratinocyte Cells and B16F1 Murine Melanoma Cells

Several studies have suggested the potential benefits of 5-aminolevulinic acid (5-ALA)-based photodynamic therapy (PDT). 5-ALA is a precursor of heme, which generates reactive oxygen species (ROS) following photoirradiation. Some reports indicate that blue light induces intracellular ROS production. In the present study, we elucidated the effects of blue light and 5-ALA on DNA integrity in B16F1 murine melanoma and human keratinocyte HaCaT cells using a variety of comet assay techniques. Co-treatment with blue light and 5-ALA significantly decreased cell viability in both cell lines. A neutral comet assay was performed to assess DNA double-strand break (DSB) formation and blue light and 5-ALA caused DSBs. We also performed an alkali comet assay to detect single-strand breaks (SSB) and alkali labile sites (ALS). The results indicated that 5-ALA accelerated blue light-induced SSB formation. In addition, modified comet assays were done using two types of enzymes to evaluate oxidative DNA damages. The results indicated that blue light and 5-ALA generated oxidized purine and pyrimidines in both cell lines. In summary, co-treatment with 5-ALA and photoirradiation may cause unexpected DNA damage in cells and tissues.

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.

The impact of heme biosynthesis regulation on glioma aggressiveness: Correlations with diagnostic molecular markers

Background

The prognosis of diffusely infiltrating glioma patients is dismal but varies greatly between individuals. While characterization of gliomas primarily relied on histopathological features, molecular markers increasingly gained importance and play a key role in the recently published 5^th edition of the World Health Organization (WHO) classification. Heme biosynthesis represents a crucial pathway due to its paramount importance in oxygen transport, energy production and drug metabolism. Recently, we described a “heme biosynthesis mRNA expression signature” that correlates with histopathological glioma grade and survival. The aim of the current study was to correlate this heme biosynthesis mRNA expression signature with diagnostic molecular markers and investigate its continued prognostic relevance.

Materials and methods

In this study, patient data were derived from the “The Cancer Genome Atlas” (TCGA) lower-grade glioma and glioblastoma cohorts. We identified diffusely infiltrating gliomas correlating molecular tumor diagnosis according to the most recent WHO classification with heme biosynthesis mRNA expression. The following molecular markers were analyzed: EGFR amplification, TERT promoter mutation, CDKN2A/B homozygous loss, chromosome 7 + /10- aneuploidy, MGMT methylation, IDH mutation, ATRX loss, p53 mutation and 1p19q codeletion. Subsequently, we calculated the heme biosynthesis mRNA expression signature for correlation with distinct molecular glioma markers/molecular subgroups and performed survival analyses.

Results

A total of 649 patients with available data on up-to-date molecular markers and heme biosynthesis mRNA expression were included. According to analysis of individual molecular markers, we found a significantly higher heme biosynthesis mRNA expression signature in gliomas with IDH wildtype (p < 0.0005), without 1p19q codeletion (p < 0.0005), with homozygous CDKN2A/B loss (p < 0.0005) and with EGFR amplification (p = 0.001). Furthermore, we observed that the heme biosynthesis mRNA expression signature increased with molecular subgroup aggressiveness (p < 0.0005), being lowest in WHO grade 2 oligodendrogliomas and highest in WHO grade 4 glioblastomas. Finally, the heme biosynthesis mRNA expression signature was a statistically significant survival predictor after multivariate correction for all molecular markers (p < 0.0005).

Conclusion

Our data demonstrate a significant correlation between heme biosynthesis regulation and diagnostic molecular markers and a prognostic relevance independent of these established markers. Consequently, heme biosynthesis expression is a promising biomarker for glioma aggressiveness and might constitute a potential target for novel therapeutic approaches.