Heme Biosynthesis Factors and 5-ALA Induced Fluorescence: Analysis of mRNA and Protein Expression in Fluorescing and Non-fluorescing Gliomas

Advancements in Image-Based Models for High-Grade Gliomas Might Be Accelerated

The first half of 2022 saw the publication of several major research advances in image-based models and artificial intelligence applications to optimize treatment strategies for high-grade gliomas, the deadliest brain tumors. We review them and discuss the barriers that delay their entry into clinical practice; particularly, the small sample size and the heterogeneity of the study designs and methodologies used. We will also write about the poor and late palliation that patients suffering from high-grade glioma can count on at the end of life, as well as the current legislative instruments, with particular reference to Italy. We suggest measures to accelerate the gradual progress in image-based models and end of life care for patients with high-grade glioma.

Effectiveness of lapatinib for enhancing 5-aminolevulinic acid-mediated protoporphyrin IX fluorescence and photodynamic therapy in human cancer cell lines with varied ABCG2 activities

5-Aminolevulinic acid (ALA) is a prodrug for protoporphyrin IX (PpIX)-mediated photodynamic therapy (PDT) and fluorescence-guided tumor surgery. We previously reported that lapatinib, a repurposed ABCG2 inhibitor, enhanced ALA-induced PpIX fluorescence and PDT by blocking ABCG2-mediated PpIX efflux. In the present study, we evaluated how the variation in ABCG2 activities/protein levels affected tumor cell response to the enhancement of PpIX/PDT by lapatinib and Ko143, an ABCG2 tool inhibitor. ABCG2 activities and protein levels were determined in a panel of human cancer cell lines. Effects of lapatinib and Ko143 on enhancing ALA-PpIX fluorescence and PDT were evaluated and correlated with tumor cell ABCG2 activities. We found that both lapatinib and Ko143 enhanced ALA-PpIX fluorescence and PDT in a dose-dependent manner, although lapatinib exhibited lower efficacy and potency than Ko143 in nearly all cancer cell lines. The EC50 of ABCG2 inhibitors for enhancing ALA-PpIX and PDT had a positive correlation with tumor cell ABCG2 activities, indicating that tumor cell lines with lower ABCG2 activities were more sensitive to ABCG2 inhibitors for PpIX/PDT enhancement. Our results suggest that, for optimal therapeutic enhancement, the dose of ABCG2 inhibitors needs to be tailored based on the ABCG2 expression/activity in tumors.

Fluorescence and immune-cell infiltration of nonneoplastic, postbrachytherapy brain tissue in 5-ALA-guided resection of recurrent anaplastic meningioma: illustrative case

BACKGROUND

5-Aminolevulinic acid (5-ALA) fluorescence-guided surgery is a well-established technique for resecting high-grade gliomas. However, its application in meningiomas, especially those previously treated with radiation therapy, remains under investigation.

OBSERVATIONS

A 48-year-old female with recurrent anaplastic meningioma, World Health Organization grade 3, underwent a right-sided craniotomy using off-label 5-ALA as a surgical adjunct. The patient had previously undergone brachytherapy seed implantation (20 × cesium 131) for tumor management. During the surgery, a large fluorescent tumor mass adjacent to the brachytherapy-treated area was resected, and the prior brachytherapy seeds were removed. Interestingly, the surrounding brain tissue in the irradiated area showed robust 5-ALA fluorescence. Pathological examination confirmed that the fluorescent brain tissue was nonneoplastic and associated with lymphocyte and macrophage infiltration.

LESSONS

This case report presents unique 5-ALA fluorescence in nonneoplastic tissue following brachytherapy, which was found during the resection of recurrent anaplastic meningioma. This phenomenon may reflect an intricate interplay among radiation therapy, immune cells, the tumor microenvironment, and 5-ALA metabolism. Given that false-positive findings in fluorescence-guided surgery can lead to unnecessary tissue resection and increased surgical morbidity, further research is warranted to elucidate the mechanisms underlying this phenomenon and its implications for meningioma surgery.

TGF-β-regulated different iron metabolism processes in the development and cisplatin resistance of ovarian cancer

The impact of different iron metabolism processes (DIMP) on ovarian cancer remains unclear. In this study, we employed various gene chips and databases to investigate the role of DIMP in the initiation and development of ovarian cancer. cBioPortal was used to determine mutations in DIMP-associated genes in ovarian cancer. Kaplan-Meier plotter was used to examine the influence of DIMP on the prognosis of ovarian cancer. By analyzing 1669 serous ovarian cancer cases, we identified a range of mutations in iron metabolism genes, notably in those coding for the transferrin receptor (19%), melanotransferrin (19%), and ceruloplasmin (10%) in the iron import process, and glucose-6-phosphate isomerase (9%), hepcidin antimicrobial peptide (9%), metal regulatory transcription factor 1 (8%), and bone morphogenetic protein 6 (8%) in the iron regulation process. Compared to the unaltered group, the group with gene alterations exhibited a higher tumor mutation burden count (43 vs. 54) and more advanced histologic grade (78.19% vs. 87.90%). Compared to the normal ovarian counterparts, a reduction in expression was observed in 9 out of the 14 genes involved in iron utilization and 4 out of the 5 genes involved in iron export in ovarian cancer; in contrast, an increase in expression was observed in 2 out of the 3 genes involved in iron storage in ovarian cancer. Furthermore, in cisplatin-resistant cells compared to cisplatin-sensitive ones, the expression of all genes in iron storage and 13 out of 14 genes in iron import was decreased, while that of 8 out of the 10 genes in iron utilization was increased. In addition, survival curve analysis indicated that a higher expression in the majority of genes in the iron import process (12/21), or a reduced expression in most genes in the iron export process (4/5) correlated with poor progression-free survival. Additionally, TGF-β could regulate the expression of most iron metabolism-associated genes; particularly, expression of genes involved in the iron storage process (2/2) was inhibited after TGF-β1 or TGF-β2 treatment. In conclusion, DIMP plays multifaceted roles in the initiation, chemo-resistance, and prognosis of ovarian cancer. Therapeutically targeting DIMP may pave the way for more tailored treatment approaches for ovarian cancer.

World Health Organization (WHO) Grade 1 Astrocytoma in a Female From Rural India: A Case Report

Astrocytomas are rare in adults and less common in the parietal and temporal regions of the brain parenchyma. The current case is of a 26-year-old female patient who presented with a four-month history of headaches and a two-month history of vomiting. The patient's MRI brain showed an ill-defined, thick-walled lesion in the right parietal and temporal region with mass effect, which on histopathology confirmed to be a case of WHO Grade 1 astrocytoma. This manuscript describes the imaging and histopathological appearance of WHO Grade 1 astrocytoma in an adult female.

Mapping high-grade glioma immune infiltration to 5-ALA fluorescence levels: TCGA data computation, classical histology, and digital image analysis

PURPOSE

Resection of high-grade gliomas has been considerably improved by 5-aminolevulinic acid (5-ALA). However, not all neurobiological properties of 5-ALA are fully understood. Specifically, potential differences in immune infiltration have not been conclusively examined, despite recent reports that immune cells might play a role. Thus, we here provide a systematic mapping of immune infiltration of different 5-ALA fluorescence levels.

METHODS

Tumor-associated macrophages (CD68, CD163), cytotoxic T cells (CD8), and regulatory T cells (FoxP3) were quantified via three methods. First, data from The Cancer Genome Atlas (TCGA) of 172 patients was examined for correlations between 5-ALA fluorescence-related mRNA expression signatures and immune markers. Second, as classical histology, 508 stained slides from 39 high-grade glioma patients were analysed semi-quantitatively by two independent reviewers, generating 1016 data points. Third, digital image analysis was performed with automated scanning and algorithm-based cell quantification.

RESULTS

TCGA mRNA data from 172 patients showed a direct, significant correlation between 5-ALA signatures and immune markers (p < 0.001). However, we were not able to confirm this finding in the here studied initial set of 39 patient histologies where we found a comparable immune infiltration in different fluorescence levels. Digital image analysis correlated excellently with standard histology.

CONCLUSION

With mapping the immune infiltration pattern of different 5-ALA categories, we are adding fundamental basic insights to the field of 5-ALA and glioma biology. The observation that a significant correlation in TCGA data did not fully translate to detectable differences in immune infiltration in first histology data warrants further investigation in larger cohorts.

Combining Pr3+-Doped Nanoradiosensitizers and Endogenous Protoporphyrin IX for X-ray-Mediated Photodynamic Therapy of Glioblastoma Cells

Glioblastoma multiforme is an aggressive type of brain cancer with high recurrence rates due to the presence of radioresistant cells remaining after tumor resection. Here, we report the development of an X-ray-mediated photodynamic therapy (X-PDT) system using NaLuF₄:25% Pr³⁺ radioluminescent nanoparticles in conjunction with protoporphyrin IX (PPIX), an endogenous photosensitizer that accumulates selectively in cancer cells. Conveniently, 5-aminolevulinic acid (5-ALA), the prodrug that is administered for PDT, is the only drug approved for fluorescence-guided resection of glioblastoma, enabling dual detection and treatment of malignant cells. NaLuF₄:Pr³⁺ nanoparticles were synthesized and spectroscopically evaluated at a range of Pr³⁺ concentrations. This generated radioluminescent nanoparticles with strong emissions from the ¹S₀ excited state of Pr³⁺, which overlaps with the Soret band of PPIX to perform photodynamic therapy. The spectral overlap between the nanoparticles and PPIX improved treatment outcomes for U251 cells, which were used as a model for the thin tumor margin. In addition to sensitizing PPIX to induce X-PDT, our nanoparticles exhibit strong radiosensitizing properties through a radiation dose-enhancement effect. We evaluate the effects of the nanoparticles alone and in combination with PPIX on viability, death, stress, senescence, and proliferation. Collectively, our results demonstrate this as a strong proof of concept for nanomedicine.

Protoporphyrin IX (PpIX) Fluorescence during Meningioma Surgery: Correlations with Histological Findings and Expression of Heme Pathway Molecules

Background: The usefulness of 5-ALA-mediated fluorescence-guided resection (FGR) in meningiomas is controversial, and information on the molecular background of fluorescence is sparse. Methods: Specimens obtained during 44 FGRs of intracranial meningiomas were analyzed for the presence of tumor tissue and fluorescence. Protein/mRNA expression of key transmembrane transporters/enzymes involved in PpIX metabolism (ABCB6, ABCG2, FECH, CPOX) were investigated using immunohistochemistry/qPCR. Results: Intraoperative fluorescence was observed in 70 of 111 specimens (63%). No correlation was found between fluorescence and the WHO grade (p = 0.403). FGR enabled the identification of neoplastic tissue (sensitivity 84%, specificity 67%, positive and negative predictive value of 86% and 63%, respectively, AUC: 0.75, p < 0.001), and was improved in subgroup analyses excluding dura specimens (86%, 88%, 96%, 63% and 0.87, respectively; p < 0.001). No correlation was found between cortical fluorescence and tumor invasion (p = 0.351). Protein expression of ABCB6, ABCG2, FECH and CPOX was found in meningioma tissue and was correlated with fluorescence (p < 0.05, each), whereas this was not confirmed for mRNA expression. Aberrant expression was observed in the CNS. Conclusion: FGR enables the intraoperative identification of meningioma tissue with limitations concerning dura invasion and due to ectopic expression in the CNS. ABCB6, ABCG2, FECH and CPOX are expressed in meningioma tissue and are related to fluorescence.

Turning on the light for brain tumor surgery: A 5-aminolevulinic acid story

To aid surgeons in more complete and safe resection of brain tumors, adjuvant technologies have been developed to improve visualization of target tissue. Fluorescence-guided surgery relies on the use of fluorophores and specific light wavelengths to better delineate tumor tissue, inflammation, and areas of blood-brain barrier breakdown. 5-aminolevulinic acid (5-ALA), the first fluorophore developed specifically for brain tumors, accumulates within tumor cells, improving visualization of tumors both at the core, and infiltrative margin. Here, we describe the background of how 5-ALA integrated into the modern neurosurgery practice, clinical evidence for the current use of 5-ALA, and future directions for its role in neurosurgical oncology. Maximal safe resection remains the standard of care for most brain tumors. Gross total resection of high-grade gliomas (HGGs) is associated with greater overall survival and progression-free survival (PFS) in comparison to subtotal resection or adjuvant treatment therapies alone.1-3 A major challenge neurosurgeons encounter when resecting infiltrative gliomas is identification of the glioma tumor margin to perform a radical resection while avoiding and preserving eloquent regions of the brain. 5-aminolevulinic acid (5-ALA) remains the only optical-imaging agent approved by the FDA for use in glioma surgery and identification of tumor tissue.4 A multicenter randomized, controlled trial revealed that 5-ALA fluorescence-guided surgery (FGS) almost doubled the extent of tumor resection and also improved 6-month PFS.5 In this review, we will highlight the current evidence for use of 5-ALA FGS in brain tumor surgery, as well as discuss the future directions for its use.

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.