Glioblastoma Metabolism: Insights and Therapeutic Strategies.

Tumor metabolism is emerging as a potential target for cancer therapies. This new approach holds particular promise for the treatment of glioblastoma, a highly lethal brain tumor that is resistant to conventional treatments, for which improving therapeutic strategies is a major challenge. The presence of glioma stem cells is a critical factor in therapy resistance, thus making it essential to eliminate these cells for the long-term survival of cancer patients. Recent advancements in our understanding of cancer metabolism have shown that glioblastoma metabolism is highly heterogeneous, and that cancer stem cells exhibit specific metabolic traits that support their unique functionality. The objective of this review is to examine the metabolic changes in glioblastoma and investigate the role of specific metabolic processes in tumorigenesis, as well as associated therapeutic approaches, with a particular focus on glioma stem cell populations.

p16 Immunohistochemical Expression as a Surrogate Assessment of CDKN2A Alteration in Gliomas Leading to Prognostic Significances.

CDKN2A is a tumor suppressor gene encoding the p16 protein, a key regulator of the cell cycle. CDKN2A homozygous deletion is a central prognostic factor for numerous tumors and can be detected by several techniques. This study aims to evaluate the extent to which immunohistochemical levels of p16 expression may provide information about CDKN2A deletion. A retrospective study was conducted in 173 gliomas of all types, using p16 IHC and CDKN2A fluorescent in situ hybridization. Survival analyses were performed to assess the prognostic impact of p16 expression and CDKN2A deletion on patient outcomes. Three patterns of p16 expression were observed: absence of expression, focal expression, and overexpression. Absence of p16 expression was correlated with worse outcomes. p16 overexpression was associated with better prognoses in MAPK-induced tumors, but with worse survival in IDH-wt glioblastomas. CDKN2A homozygous deletion predicted worse outcomes in the overall patient population, particularly in IDH-mutant 1p/19q oligodendrogliomas (grade 3). Finally, we observed a significant correlation between p16 immunohistochemical loss of expression and CDKN2A homozygosity. IHC has strong sensitivity and high negative predictive value, suggesting that p16 IHC might be a pertinent test to detect cases most likely harboring CDKN2A homozygous deletion.

Molecular Heterogeneity in BRAF-Mutant Gliomas: Diagnostic, Prognostic, and Therapeutic Implications.

Over the last few decades, deciphering the alteration of molecular pathways in brain tumors has led to impressive changes in diagnostic refinement. Among the molecular abnormalities triggering and/or driving gliomas, alterations in the MAPK pathway reign supreme in the pediatric population, as it is encountered in almost all low-grade pediatric gliomas. Activating abnormalities in the MAPK pathway are also present in both pediatric and adult high-grade gliomas. Across those alterations, BRAF p.V600E mutations seem to define homogeneous groups of tumors in terms of prognosis. The recent development of small molecules inhibiting this pathway retains the attention of neurooncologists on BRAF-altered tumors, as conventional therapies showed no significant effect, nor prolonged efficiency on the high-grade or low-grade unresectable forms. Nevertheless, tumoral heterogeneity and especially molecular alteration(s) associated with MAPK-pathway abnormalities are not fully understood with respect to how they might lead to the specific dismal prognosis of those gliomas and/or affect their response to targeted therapies. This review is an attempt to provide comprehensive information regarding molecular alterations related to the aggressiveness modulation in BRAF-mutated gliomas and the current knowledge on how to use those targeted therapies in such situations.

All pineal tumors expressing germ cell tumor markers are not necessarily germ cell tumors: histopathological and molecular study of a midline primary intracranial sarcoma DICER1-mutant.

Primary intracranial sarcoma DICER1-mutant is a rare and newly recognized tumor type introduced in the 2021 WHO Classification of Central Nervous System Tumors. It is defined as a spindle cell sarcoma dysplaying eosinophilic intracytoplasmic globules, myogenic differentiation, and DICER1 gene mutation, either somatic or germline. Most reported cases were hemispheric except one, recently described in the pineal region. Here, we report the case of a 12 year-old boy with a pineally located tumor. Despite midline location, poorly differenciated morphology and germ cell marker expression, the association of DICER1 and NF1 hotspot mutations and a specific DNA methylation signature finally lead to the diagnosis of primary intracranial sarcoma DICER1-mutant instead of germ cell tumor. Furthermore, our molecular exploratory results involved a pathway, which was not previously evidenced in those DICER1 mutated cerebral sarcoma that is the canonical Wnt signaling driving likely a part of oncogenesis in this newly described pineal entity.

Retrospective and integrative analyses of molecular characteristics and their specific imaging parameters in pediatric grade 1 gliomas.

BACKGROUND: Pediatric low-grade gliomas (PLGG) are the most common brain tumors diagnosed during childhood and represent a heterogeneous group associating variable molecular abnormalities. To go further and develop specific statistical patterns between tumor molecular background, imaging features, and patient outcome, a retrospective study was performed in a group of non-neurofibromatosis type 1 (non-NF1) grade 1 PLGGs. PATIENTS AND METHODS: Seventy-eight children, followed from 2004 to 2017, were retrospectively reported. In this population, we analyzed radiological and molecular parameters. Their therapeutic management comprised surgery or surgery plus chemotherapies. RESULTS: Considering all 78 patients, 59 had only a surgical removal and 19 patients were treated with postoperative chemotherapy. Twelve progressions were reported in the partially resected and chemotherapeutic groups, whereas four deaths occurred only in the highly treated patients. As expected, in the global cohort, PLGG with BRAF p.V600E and/or CDKN2A loss exhibited poor outcomes and we evidenced significant associations between those molecular characteristics and their imaging presentation. In the chemo-treated patients, when associating initial and 6-month magnetic resonance imaging (MRI) parameters to the molecular features, the good risk situations were significantly linked to the presence of a large tumor cyst at diagnosis and the appearance during treatment of a higher cystic proportion that we called cystic conversion. CONCLUSION: So, additionally to the presence of BRAF p.V600E or CDKN2A deletion in grade 1 PLGGs, the absence on diagnostic MRI of cystic parts and/or cystic conversion at 6-month chemotherapy were significantly linked to a worst prognosis and response to treatment. These imaging features should be considered as prognostic markers in future PLGG studies.

Direct Targeting KRAS Mutation in Non-Small Cell Lung Cancer: Focus on Resistance.

KRAS is the most frequently mutated oncogene in non-small cell lung cancers (NSCLC), with a frequency of around 30%, and encoding a GTPAse that cycles between active form (GTP-bound) to inactive form (GDP-bound). The KRAS mutations favor the active form with inhibition of GTPAse activity. KRAS mutations are often with poor response of EGFR targeted therapies. KRAS mutations are good predictive factor for immunotherapy. The lack of success with direct targeting of KRAS proteins, downstream inhibition of KRAS effector pathways, and other strategies contributed to a focus on developing mutation-specific KRAS inhibitors. KRAS p.G12C mutation is one of the most frequent KRAS mutation in NSCLC, especially in current and former smokers (over 40%), which occurs among approximately 12-14% of NSCLC tumors. The mutated cysteine resides next to a pocket (P2) of the switch II region, and P2 is present only in the inactive GDP-bound KRAS. Small molecules such as sotorasib are now the first targeted drugs for KRAS G12C mutation, preventing conversion of the mutant protein to GTP-bound active state. Little is known about primary or acquired resistance. Acquired resistance does occur and may be due to genetic alterations in the nucleotide exchange function or adaptative mechanisms in either downstream pathways or in newly expressed KRAS G12C mutation.

Temozolomide-Acquired Resistance Is Associated with Modulation of the Integrin Repertoire in Glioblastoma, Impact of α5ß1 Integrin.

Despite extensive treatment, glioblastoma inevitably recurs, leading to an overall survival of around 16 months. Understanding why and how tumours resist to radio/chemotherapies is crucial to overcome this unmet oncological challenge. Primary and acquired resistance to Temozolomide (TMZ), the standard-of-care chemotherapeutic drug, have been the subjects of several studies. This work aimed to evaluate molecular and phenotypic changes occurring during and after TMZ treatment in a glioblastoma cell model, the U87MG. These initially TMZ-sensitive cells acquire long-lasting resistance even after removal of the drug. Transcriptomic analysis revealed that profound changes occurred between parental and resistant cells, particularly at the level of the integrin repertoire. Focusing on α5ß1 integrin, which we proposed earlier as a glioblastoma therapeutic target, we demonstrated that its expression was decreased in the presence of TMZ but restored after removal of the drug. In this glioblastoma model of recurrence, α5ß1 integrin plays an important role in the proliferation and migration of tumoral cells. We also demonstrated that reactivating p53 by MDM2 inhibitors concomitantly with the inhibition of this integrin in recurrent cells may overcome the TMZ resistance. Our results may explain some integrin-based targeted therapy failure as integrin expressions are highly switchable during the time of treatment. We also propose an alternative way to alter the viability of recurrent glioblastoma cells expressing a high level of α5ß1 integrin.

Molecular Mechanism of EGFR-TKI Resistance in EGFR-Mutated Non-Small Cell Lung Cancer: Application to Biological Diagnostic and Monitoring.

Non-small cell lung cancer (NSCLC) is the most common cancer in the world. Activating epidermal growth factor receptor (EGFR) gene mutations are a positive predictive factor for EGFR tyrosine kinase inhibitors (TKIs). For common EGFR mutations (Del19, L858R), the standard first-line treatment is actually third-generation TKI, osimertinib. In the case of first-line treatment by first (erlotinib, gefitinib)- or second-generation (afatinib) TKIs, osimertinib is approved in second-line treatment for patients with T790M EGFR mutation. Despite the excellent disease control results with EGFR TKIs, acquired resistance inevitably occurs and remains a biological challenge. This leads to the discovery of novel biomarkers and possible drug targets, which vary among the generation/line of EGFR TKIs. Besides EGFR second/third mutations, alternative mechanisms could be involved, such as gene amplification or gene fusion, which could be detected by different molecular techniques on different types of biological samples. Histological transformation is another mechanism of resistance with some biological predictive factors that needs tumor biopsy. The place of liquid biopsy also depends on the generation/line of EGFR TKIs and should be a good candidate for molecular monitoring. This article is based on the literature and proposes actual and future directions in clinical and translational research.

Biological Relevance of RGD-Integrin Subtype-Specific Ligands in Cancer.

Integrins are heterodimeric transmembrane proteins able to connect cells with the micro-environment. They represent a family of receptors involved in almost all the hallmarks of cancer. Integrins recognizing the Arg-Gly-Asp (RGD) peptide in their natural extracellular matrix ligands have been particularly investigated as tumoral therapeutic targets. In the last 30 years, intense research has been dedicated to designing specific RGD-like ligands able to discriminate selectively the different RGD-recognizing integrins. Chemists' efforts have led to the proposition of modified peptide or peptidomimetic libraries to be used for tumor targeting and/or tumor imaging. Here we review, from the biological point of view, the rationale underlying the need to clearly delineate each RGD-integrin subtype by selective tools. We describe the complex roles of RGD-integrins (mainly the most studied αvß3 and α5ß1 integrins) in tumors, the steps towards selective ligands and the current usefulness of such ligands. Although the impact of integrins in cancer is well acknowledged, the biological characteristics of each integrin subtype in a specific tumor are far from being completely resolved. Selective ligands might help us to reconsider integrins as therapeutic targets in specific clinical settings.

Hypoxic Environment and Paired Hierarchical 3D and 2D Models of Pediatric H3.3-Mutated Gliomas Recreate the Patient Tumor Complexity.

BACKGROUND: Pediatric high-grade gliomas (pHGGs) are facing a very dismal prognosis and representative pre-clinical models are needed for new treatment strategies. Here, we examined the relevance of collecting functional, genomic, and metabolomics data to validate patient-derived models in a hypoxic microenvironment. METHODS: From our biobank of pediatric brain tumor-derived models, we selected 11 pHGGs driven by the histone H3.3K28M mutation. We compared the features of four patient tumors to their paired cell lines and mouse xenografts using NGS (next generation sequencing), aCGH (array comparative genomic hybridization), RNA sequencing, WES (whole exome sequencing), immunocytochemistry, and HRMAS (high resolution magic angle spinning) spectroscopy. We developed a multicellular in vitro model of cell migration to mimic the brain hypoxic microenvironment. The live cell technology Incucyte© was used to assess drug responsiveness in variable oxygen conditions. RESULTS: The concurrent 2D and 3D cultures generated from the same tumor sample exhibited divergent but complementary features, recreating the patient intra-tumor complexity. Genomic and metabolomic data described the metabolic changes during pHGG progression and supported hypoxia as an important key to preserve the tumor metabolism in vitro and cell dissemination present in patients. The neurosphere features preserved tumor development and sensitivity to treatment. CONCLUSION: We proposed a novel multistep work for the development and validation of patient-derived models, considering the immature and differentiated content and the tumor microenvironment of pHGGs.

Synergistic Anti-Tumor Effect of mTOR Inhibitors with Irinotecan on Colon Cancer Cells.

Advanced colorectal cancer has a poor prognosis because of metastasis formation and resistance to combined therapies. Downstream of PI3K/Akt and Ras/MAPK pathways, the mTOR kinase plays a decisive role in treatment failure. We previously established that irinotecan has antiangiogenic properties and it is known that new mammalian target of rapamycin (mTOR) catalytic AZD inhibitors, unlike rapamycin, target both mTORC1 and mTORC2. Thus, we hypothesized that the complete inhibition of the PI3K/AKT/mTOR/HIF-1α axis with mTOR catalytic inhibitors and low doses of irinotecan may have antitumor effects. We showed that the AZD8055 and AZD2014 inhibitors were much more potent than rapamycin to reduce cell viability of four colon cell lines. On the other hand, whereas AZD2014 alone inhibits migration by 40%, the drug combination led to 70% inhibition. Similarly, neither irinotecan nor AZD2014 significantly reduced cell invasion, whereas a combination of the two inhibits invasion by 70%. In vivo, irinotecan and AZD2014 combination drastically reduced ectopic patient-derived colon tumor growth and this combination was more potent than Folfox or Folfiri. Finally, the combination totally inhibited liver and lung metastases developed from orthotopic implantation of SW480 cells. Thus, the use of mTOR catalytic inhibitors, in association with other chemotherapeutic agents like irinotecan at low doses, is potentially a hope for colon cancer treatment.