Histopathological investigation of glioblastomas resected under bevacizumab treatment

Hypoxia-inducible factor 1alpha and vascular endothelial growth factor in Glioblastoma Multiforme: a systematic review going beyond pathologic implications

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor characterized by extensive heterogeneity and vascular proliferation. Hypoxic conditions in the tissue microenvironment are considered a pivotal player leading tumor progression. Specifically, hypoxia is known to activate inducible factors, such as hypoxia-inducible factor 1alpha (HIF-1α), which in turn can stimulate tumor neo-angiogenesis through activation of various downward mediators, such as the vascular endothelial growth factor (VEGF). Here, we aimed to explore the role of HIF-1α/VEGF immunophenotypes alone and in combination with other prognostic markers or clinical and image analysis data, as potential biomarkers of GBM prognosis and treatment efficacy. We performed a systematic review (Medline/Embase, and Pubmed database search was completed by 16th of April 2024 by two independent teams; PRISMA 2020). We evaluated methods of immunoassays, cell viability, or animal or patient survival methods of the retrieved studies to assess unbiased data. We used inclusion criteria, such as the evaluation of GBM prognosis based on HIF-1α/VEGF expression, other biomarkers or clinical and imaging manifestations in GBM related to HIF-1α/VEGF expression, application of immunoassays for protein expression, and evaluation of the effectiveness of GBM therapeutic strategies based on HIF-1α/VEGF expression. We used exclusion criteria, such as data not reporting both HIF-1α and VEGF or prognosis. We included 50 studies investigating in total 1319 GBM human specimens, 18 different cell lines or GBM-derived stem cells, and 6 different animal models, to identify the association of HIF-1α/VEGF immunophenotypes, and with other prognostic factors, clinical and macroscopic data in GBM prognosis and therapeutic approaches. We found that increased HIF-1α/VEGF expression in GBM correlates with oncogenic factors, such as miR-210-3p, Oct4, AKT, COX-2, PDGF-C, PLDO3, M2 polarization, or ALK, leading to unfavorable survival. Reduced HIF-1α/VEGF expression correlates with FIH-1, ADNP, or STAT1 upregulation, as well as with clinical manifestations, like epileptogenicity, and a favorable prognosis of GBM. Based on our data, HIF-1α or VEGF immunophenotypes may be a useful tool to clarify MRI-PET imaging data distinguishing between GBM tumor progression and pseudoprogression. Finally, HIF-1α/VEGF immunophenotypes can reflect GBM treatment efficacy, including combined first-line treatment with histone deacetylase inhibitors, thimerosal, or an active metabolite of irinotecan, as well as STAT3 inhibitors alone, and resulting in a favorable tumor prognosis and patient survival. These data were supported by a combination of variable methods used to evaluate HIF-1α/VEGF immunophenotypes. Data limitations may include the use of less sensitive detection methods in some cases. Overall, our data support HIF-1α/VEGF's role as biomarkers of GBM prognosis and treatment efficacy.

Status of alternative angiogenic pathways in glioblastoma resected under and after bevacizumab treatment

Glioblastoma multiforme (GBM) acquires resistance to bevacizumab (Bev) treatment. Bev affects angiogenic factors other than vascular endothelial growth factor (VEGF), which are poorly understood. We investigated changes in angiogenic factors under and after Bev therapy, including angiopoietin-1 (ANGPT1), angiopoietin-2 (ANGPT2), placental growth factor (PLGF), fibroblast growth factor 2, and ephrin A2 (EphA2). Fifty-four GBM tissues, including 28 specimens from 14 cases as paired specimens from the same patient obtained in three settings: initial tumor resection (naïve Bev), tumors resected following Bev therapy (effective Bev), and recurrent tumors after Bev therapy (refractory Bev). Immunohistochemistry assessed their expressions in tumor vessels and its correlation with recurrent MRI patterns. PLGF expression was higher in the effective Bev group than in the naïve Bev group (p = 0.024) and remained high in the refractory Bev group. ANGPT2 and EphA2 expressions were higher in the refractory Bev group than in the naïve Bev group (p = 0.047 and 0.028, respectively). PLGF expression was higher in the refractory Bev group compared with the naïve Bev group for paired specimens (p = 0.036). PLGF was more abundant in T2 diffuse/circumscribe patterns (p = 0.046). This is the first study to evaluate angiogenic factors other than VEGF during effective and refractory Bev therapy in patient-derived specimens.

An exploratory prospective phase II study of preoperative neoadjuvant bevacizumab and temozolomide for newly diagnosed glioblastoma

PURPOSE

This multi-institutional phase I/II study was conducted to confirm the safety and explore the clinical utility of preoperative Bevacizumab (Bev) for newly diagnosed glioblastoma (GB).

METHODS

Patients were enrolled based on magnetic resonance imaging (MRI) findings typically suggestive of GB. Preoperative Bev and temozolomide (TMZ) were administered at doses of 10 mg/kg on day 0 and 150 mg/m2 on days 1-5, respectively. Surgical resection was performed between days 21 and 30, inclusive. The safety and efficacy were evaluated in a total of 15 cases by progression-free survival (PFS), changes in tumor volume, Karnofsky Performance Scale (KPS) and Mini-Mental State Examination (MMSE) scores after preoperative therapy.

RESULTS

Tumor resection was performed on a mean of day 23.7. Pathological diagnosis was GB, isocitrate dehydrogenase (IDH)-wildtype in 14 cases and GB, IDH-mutant in 1 case. Severe adverse events possibly related to preoperative Bev and TMZ were observed in 2 of the 15 patients, as wound infection and postoperative hematoma and thrombocytopenia. KPS and MMSE scores were significantly improved with preoperative therapy. Tumor volume was decreased in all but one case on T1-weighted imaging with contrast-enhancement (T1CE) and in all cases on fluid-attenuated inversion recovery, with mean volume decrease rates of 36.2% and 54.0%, respectively. Median PFS and overall survival were 9.5 months and 16.5 months, respectively.

CONCLUSION

Preoperative Bev and TMZ is safe as long as the instructions are followed. The strategy might be useful for GB in some patients, not only reducing tumor burden, but also improving patient KPS preoperatively.

TRIAL REGISTRATION NUMBER

UMIN000025579, jRCT1031180233 https://jrct.niph.go.jp/latest-detail/jRCT1031180233 . Registration Date: Jan. 16, 2017.

From signalling pathways to targeted therapies: unravelling glioblastoma's secrets and harnessing two decades of progress

Glioblastoma, a rare, and highly lethal form of brain cancer, poses significant challenges in terms of therapeutic resistance, and poor survival rates for both adult and paediatric patients alike. Despite advancements in brain cancer research driven by a technological revolution, translating our understanding of glioblastoma pathogenesis into improved clinical outcomes remains a critical unmet need. This review emphasises the intricate role of receptor tyrosine kinase signalling pathways, epigenetic mechanisms, and metabolic functions in glioblastoma tumourigenesis and therapeutic resistance. We also discuss the extensive efforts over the past two decades that have explored targeted therapies against these pathways. Emerging therapeutic approaches, such as antibody-toxin conjugates or CAR T cell therapies, offer potential by specifically targeting proteins on the glioblastoma cell surface. Combination strategies incorporating protein-targeted therapy and immune-based therapies demonstrate great promise for future clinical research. Moreover, gaining insights into the role of cell-of-origin in glioblastoma treatment response holds the potential to advance precision medicine approaches. Addressing these challenges is crucial to improving outcomes for glioblastoma patients and moving towards more effective precision therapies.

18F-Fluoromisonidazole-Positron Emission Tomography and Immunohistochemistry Verified Tumor Oxygenation, Stemness, and Immunosupportive Microenvironment After Preoperative Neoadjuvant Bevacizumab for Newly Diagnosed Glioblastoma

BACKGROUND

Cancer stemness and immunosuppressive tumor microenvironment (TME) in accordance with tumor oxygenation are variable during bevacizumab (Bev) therapy for glioblastoma (GBM). Positron emission tomography (PET) using 18F-fluoromisonidazole (FMISO) reflects hypoxic TME. The aim of this study was to compare FMISO-PET and immunohistochemical findings of tumor oxygenation in the TME of GBM during Bev treatment.

METHODS

Seven patients with newly diagnosed IDH-wildtype GBM underwent FMISO-PET during follow-up. Three patients received preoperative neoadjuvant Bev (neo-Bev) and subsequently underwent surgical resection. Reoperation was performed at the recurrence. FMISO-PET was performed before and after neo-Bev. Four patients who underwent tumor resection without neo-Bev were included as the control group. Expressions of hypoxic markers (carbonic anhydrase; CA9), stem cell markers (nestin, FOXM1), and immunoregulatory molecules (CD163, FOXP3, PD-L1) in tumor tissues were analyzed by immunohistochemistry (IHC).

RESULTS

All 3 patients treated with neo-Bev showed decrease in FMISO accumulation in accordance with expressions of CA9 and FOXM1 compared with the control group. Two of these 3 patients at the recurrence showed increase in FMISO accumulation. IHC showed increased CA9-and FOXM1-positive cells in recurrent tumors. Expression of PD-L1 tended to be lower after neo-Bev compared with the control group.

CONCLUSIONS

FMISO-PET effectively visualized TME oxygenation after neo-Bev. Increased FMISO accumulation at the time of recurrence, even under Bev treatment, suggests that FMISO-PET might be useful for monitoring the duration of Bev efficacy by reflecting tumor oxygenation.

The strange Microenvironment of Glioblastoma

Glioblastoma (GB) is the most common and aggressive primary brain tumor, with poor patient survival and lack of effective therapies. Late advances trying to decipher the composition of the GB tumor microenvironment (TME) emphasized its role in tumor progression and potentialized it as a therapeutic target. Many components participate critically to tumor development and expansion such as blood vessels, immune cells or components of the nervous system. Dysmorphic tumor vasculature brings challenges to optimal delivery of cytotoxic agents currently used in clinics. Also, massive infiltration of immunosuppressive myeloid cells and limited recruitment of T cells limits the success of conventional immunotherapies. Neuronal input seems also be required for tumor expansion. In this review, we provide a comprehensive report of vascular and immune component of the GB TME and their cross talk during GB progression.

Clinical, histopathological and molecular risk factors for recurrence of pilocytic astrocytomas: brainstem/spinal location, nestin expression and gain of 7q and 19 are associated with early tumor recurrence

Pilocytic astrocytomas (PAs) are benign tumors. However, clinically aggressive PAs despite benign histology have been reported, and histological and molecular risk factors for prognosis have not been elucidated. 38 PAs were studied for clinical, histological, and molecular factors, including tumor location, extent of resection, post-operative treatment, glioma-associated molecules (IDH1/2, ATRX, BRAF, FGFR1, PIK3CA, H3F3A, p53, VEGF, Nestin, PD-1/PD-L1), CDKN2A/B deletion, and chromosomal number aberrations, to see if there is any correlation with patient's progression-free survival (PFS). Brainstem/spinal location, extent of resection and post-operative treatment, and VEGF-A, Nestin and PD-L1 expression, copy number gain of chromosome 7q or 19, TP53 mutation were significantly associated with shorter PFS. None of the histological parameters was associated with PFS. Multivariate analyses demonstrated that high Nestin expression, gain of 7q or 19, and extent of removal were independently predictive for early tumor recurrence. The brainstem/spinal PAs appeared distinct from those in the other sites in terms of molecular characteristics. Clinically aggressive PAs despite benign histology exhibited high Nestin expression. Brainstem/spinal location, extent of resection and some molecular factors including Nestin expression and gains of 7q and 19, rather than histological parameters, may be associated with early tumor recurrence in PAs.

Impact of Neoadjuvant Bevacizumab on Neuroradiographic Response and Histological Findings Related to Tumor Stemness and the Hypoxic Tumor Microenvironment in Glioblastoma: Paired Comparison Between Newly Diagnosed and Recurrent Glioblastomas

Background

Previously, we reported that bevacizumab (Bev) produces histological and neuroradiographic alterations including changes in tumor oxygenation, induction of an immunosupportive tumor microenvironment, and inhibition of stemness. To confirm how those effects vary during Bev therapy, paired samples from the same patients with newly diagnosed glioblastoma (GBM) who received preoperative neoadjuvant Bev (neoBev) were investigated with immunohistochemistry before and after recurrence.

Methods

Eighteen samples from nine patients with newly diagnosed GBM who received preoperative neoBev followed by surgery and chemoradiotherapy and then autopsy or salvage surgery after recurrence were investigated. The expression of carbonic anhydrase 9 (CA9), hypoxia-inducible factor-1 alpha (HIF-1α), nestin, and Forkhead box M1 (FOXM1) was evaluated with immunohistochemistry.

For comparison between neoBev and recurrent tumors, we divided the present cohort into two groups based on neuroradiographic response: good and poor responders (GR and PR, respectively) to Bev were defined by the tumor regression rate on T1-weighted images with gadolinium enhancement (T1Gd) and fluid-attenuated inversion recovery images. Patterns of recurrence after Bev therapy were classified as cT1 flare-up and T2-diffuse/T2-circumscribed. Furthermore, we explored the possibility of utilizing FOXM1 as a biomarker of survival in this cohort.

Results

A characteristic “pseudo-papillary”-like structure containing round-shaped tumor cells clustered adjacent to blood vessels surrounded by spindle-shaped tumor cells was seen only in recurrent tumors. Tumor cells at the outer part of the “pseudo-papillary” structure were CA9-positive (CA9+)/HIF-1α+, whereas cells at the inner part of this structure were CA9−/HIF-1α+ and nestin+/FOXM1+. CA9 and HIF-1α expression was lower in T1Gd-GR and decreased in the “T2-circumscribed/T2-diffuse” pattern compared with the “T1 flare-up” pattern, suggesting that tumor oxygenation was frequently observed in T1Gd-GR in initial tumors and in the “T2-circumscribed/T2-diffuse” pattern in recurrent tumors. FOXM1 low-expression tumors tended to have a better prognosis than that of FOXM1 high-expression tumors.

Conclusion

A “pseudo-papillary” structure was seen in recurrent GBM after anti-vascular endothelial growth factor therapy. Bev may contribute to tumor oxygenation, leading to inhibition of stemness and correlation with a neuroimaging response during Bev therapy. FOXM1 may play a role as a biomarker of survival during Bev therapy.

Wnt and PI3K/Akt/mTOR Survival Pathways as Therapeutic Targets in Glioblastoma

Glioblastoma (GBM) is a devastating type of brain tumor, and current therapeutic treatments, including surgery, chemotherapy, and radiation, are palliative at best. The design of effective and targeted chemotherapeutic strategies for the treatment of GBM require a thorough analysis of specific signaling pathways to identify those serving as drivers of GBM progression and invasion. The Wnt/β-catenin and PI3K/Akt/mTOR (PAM) signaling pathways are key regulators of important biological functions that include cell proliferation, epithelial–mesenchymal transition (EMT), metabolism, and angiogenesis. Targeting specific regulatory components of the Wnt/β-catenin and PAM pathways has the potential to disrupt critical brain tumor cell functions to achieve critical advancements in alternative GBM treatment strategies to enhance the survival rate of GBM patients. In this review, we emphasize the importance of the Wnt/β-catenin and PAM pathways for GBM invasion into brain tissue and explore their potential as therapeutic targets.

Histopathological investigation of the 1p/19q-codeleted gliomas resected following alkylating agent chemotherapy

PURPOSE

Lower grade gliomas with 1p/19q codeletion are often responsive to chemotherapy, and several of these have been treated using upfront chemotherapy and subsequent resection following tumor volume decrease. This study aimed to elucidate the histological changes and the mechanism of recurrence after alkylating agent chemotherapy in 1p/19-codeleted gliomas.

METHODS

Fourteen 1p/19q-codeleted gliomas resected following tumor volume decrease after alkylating agent chemotherapy were included and compared with their pre-chemotherapy specimens. Histological changes were investigated using hematoxylin-eosin staining, and changes in proliferative activity, status of glioma stem cells (GSCs), and tumor-infiltrating macrophages were assessed using immunohistochemistry for Ki-67/MIB-1, CD68 as a pan-macrophage/monocyte marker, CD163 as a presumed marker of M2 polarity, and nestin and CD133 as markers of GSCs.

RESULTS

The most frequent histological findings following chemotherapy included a sparse glial background and abundant foamy cell infiltration. The Ki-67/MIB-1 index decreased and the number of CD68 + cells increased after chemotherapy. The increasing rate of CD68 + cells in the post-/pre-chemotherapy specimens was inversely correlated with patient prognosis but not tumor response. The number of CD163 + cells, M2/M1 + M2 ratio, and the ratio of GSCs to total tumor cells increased after chemotherapy, and those in the post-chemotherapy specimens were negatively correlated with patient prognosis. There was a correlation between the M2/M1 + M2 ratio and the ratio of GSCs in both pre- and post-chemotherapy specimens.

CONCLUSION

GSCs in conjunction with M2 macrophages constitute the mechanism of resistance to and recurrence after alkylating agent chemotherapy in 1p/19q-codeleted gliomas.

Anti-angiogenic therapies in the management of glioblastoma

Angiogenesis is a central feature of glioblastoma (GBM), with contribution from several mechanisms and signaling pathways to produce an irregular, poorly constructed, and poorly connected tumor vasculature. Targeting angiogenesis has been efficacious for disease control in other cancers, and given the (I) highly vascularized environment in GBM and (II) correlation between glioma grade and prognosis, angiogenesis became a prime target of therapy in GBM as well. Here, we discuss the therapies developed to target these pathways including vascular endothelial growth factor (VEGF) signaling, mechanisms of tumor resistance to these drugs in the context of disease progression, and the evolving role of anti-angiogenic therapy in GBM.

The role of c-Met and VEGFR2 in glioblastoma resistance to bevacizumab

Dismal prognosis of glioblastoma (GBM) prompts for the identification of response predictors and therapeutic resistance mechanisms of current therapies. The authors investigated the impact of c-Met, HGF, VEGFR2 expression and microvessel density (MVD) in GBM patients submitted to second-line chemotherapy with bevacizumab. Immunohistochemical expression of c-Met, HGF, VEGFR2, and MVD was assessed in tumor specimens of GBM patients treated with bevacizumab, after progression under temozolomide. Survival analysis was evaluated according to the expression of the aforementioned biomarkers. c-Met overexpression was associated with a time-to-progression (TTP) after bevacizumab of 3 months (95% CI, 1.5-4.5) compared with a TTP of 7 months (95% CI, 4.6-9.4) in patients with low or no expression of c-Met (p = 0.05). VEGFR2 expression was associated with a TTP after bevacizumab of 3 months (95% CI, 1.8-4.2) compared with a TTP of 7 months (95% CI, 5.7-8.3) in patients with no tumoral expression of VEGFR2 (p = 0.009). Concomitant c-Met/VEGFR2 overexpression was associated with worse overall survival (13 months) compared with concomitant c-Met/VEGFR2 negative expression (19 months; p = 0.025). Our data support the hypothesis that c-Met and VEGFR2 overexpression have a role in the development of glioblastoma early resistance and might predict poorer responses to anti-angiogenic therapies.

Update on Chemotherapeutic Approaches and Management of Bevacizumab Usage for Glioblastoma

Glioblastoma, the most common primary brain tumor in adults, has one of the most dismal prognoses in cancer. In 2009, bevacizumab was approved for recurrent glioblastoma in the USA. To evaluate the clinical impact of bevacizumab as a first-line drug for glioblastoma, two randomized clinical trials, AVAglio and RTOG 0825, were performed. Bevacizumab was found to improve progression-free survival (PFS) and was reported to be beneficial for maintaining patient performance status as an initial treatment. These outcomes led to bevacizumab approval in Japan in 2013 as an insurance-covered first-line drug for glioblastoma concurrently with its second-line application. However, prolongation of overall survival was not evinced in these clinical trials; hence, the clinical benefit of bevacizumab for newly diagnosed glioblastomas remains controversial. A recent meta-analysis of randomized controlled trials of bevacizumab combined with temozolomide in recurrent glioblastoma also showed an effect only on PFS, and the benefit of bevacizumab even for recurrent glioblastoma is controversial. Here, we discuss the clinical impact of bevacizumab for glioblastoma treatment by reviewing previous clinical trials and real-world evidence by focusing on Japanese experiences. Moreover, the efficacy and safety of bevacizumab are summarized, and we provide suggestions for updating the approaches and management of bevacizumab.

Emerging Pharmacological Treatments for Cerebral Edema: Evidence from Clinical Studies

Cerebral edema, a common and often fatal companion to most forms of acute central nervous system disease, has been recognized since the time of ancient Egypt. Unfortunately, our therapeutic armamentarium remains limited, in part due to historic limitations in our understanding of cerebral edema pathophysiology. Recent advancements have led to a number of clinical trials for novel therapeutics that could fundamentally alter the treatment of cerebral edema. In this review, we discuss these agents, their targets, and the data supporting their use, with a focus on agents that have progressed to clinical trials.

Leptomeningeal Spread in Glioblastoma: Diagnostic and Therapeutic Challenges

BACKGROUND

Glioblastoma (GBM) is the most common and aggressive primary malignant brain tumor. Leptomeningeal spread (LMS) is a severe complication of GBM, raising diagnostic and therapeutic challenges in clinical routine.

METHODS

We performed a review of the literature focused on LMS in GBM. MEDLINE and EMBASE databases were queried from 1989 to 2019 for articles describing diagnosis and therapeutic options in GBM LMS, as well as risk factors and pathogenic mechanisms.

RESULTS

We retrieved 155 articles, including retrospective series, case reports, and early phase clinical trials, as well as preclinical studies. These articles confirmed that LMS in GBM remains (a) a diagnostic challenge with cytological proof of LMS obtained in only 35% of cases and (b) a therapeutic challenge with a median overall survival below 2 months with best supportive care alone. For patients faced with suggestive clinical symptoms, whole neuroaxis magnetic resonance imaging and cerebrospinal fluid analysis are both recommended. Liquid biopsies are under investigation and may help prompt a reliable diagnosis. Based on the literature, a multimodal and personalized therapeutic approach of LMS, including surgery, radiotherapy, systemic cytotoxic chemotherapy, and intrathecal chemotherapies, may provide benefits to selected patients. Interestingly, molecular targeted therapies appear promising in case of actionable molecular target and should be considered.

CONCLUSION

As the prognosis of glioblastoma is improving over time, LMS becomes a more common complication. Our review highlights the need for translational studies and clinical trials dedicated to this challenging condition in order to improve diagnostic and therapeutic strategies.

IMPLICATIONS FOR PRACTICE

This review summarizes the diagnostic tools and applied treatments for leptomeningeal spread, a complication of glioblastoma, as well as their outcomes. The importance of exhaustive molecular testing for molecular targeted therapies is discussed. New diagnostic and therapeutic strategies are outlined, and the need for translational studies and clinical trials dedicated to this challenging condition is highlighted.

Resolution of Spatial and Temporal Heterogeneity in Bevacizumab-Treated Breast Tumors by Eigenspectra Multispectral Optoacoustic Tomography

Understanding temporal and spatial hemodynamic heterogeneity as a function of tumor growth or therapy affects the development of novel therapeutic strategies. In this study, we employed eigenspectra multispectral optoacoustic tomography (eMSOT) as a next-generation optoacoustic method to impart high accuracy in resolving tumor hemodynamics during bevacizumab therapy in two types of breast cancer xenografts (KPL-4 and MDA-MB-468). Patterns of tumor total hemoglobin concentration (THb) and oxygen saturation (sO₂) were imaged in control and bevacizumab-treated tumors over the course of 58 days (KPL-4) and 16 days (MDA-MB-468), and the evolution of functional vasculature "normalization" was resolved macroscopically. An initial sharp drop in tumor sO₂ and THb content shortly after the initiation of bevacizumab treatment was followed by a recovery in oxygenation levels. Rim-core subregion analysis revealed steep spatial oxygenation gradients in growing tumors that were reduced after bevacizumab treatment. Critically, eMSOT imaging findings were validated directly by histopathologic assessment of hypoxia (pimonidazole) and vascularity (CD31). These data demonstrate how eMSOT brings new abilities for accurate observation of entire tumor responses to challenges at spatial and temporal dimensions not available by other techniques today. SIGNIFICANCE: Accurate assessment of hypoxia and vascularization over space and time is critical for understanding tumor development and the role of spatial heterogeneity in tumor aggressiveness, metastasis, and response to treatment.

Dynamic contrast-enhanced magnetic resonance imaging for monitoring the anti-angiogenesis efficacy in a C6 glioma rat model

BACKGROUND

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is useful in predicting responses to angiogenic therapy of malignant tumors.

PURPOSE

To observe the dynamics of DCE-MRI parameters in evaluating early effects of antiangiogenic therapy in a C6 glioma rat model.

MATERIAL AND METHODS

The Bevacizumab or vehicle treatment was started from the 14th day after glioma model was established. The treated and control groups (n = 13 per group) underwent DCE-MRI scans on days 0, 1, 3, 5, and 7 after treatment. Tumor volume was calculated according to T2-weighted images. Hematoxylin and eosin, microvessel density (MVD), and proliferating cell nuclear antigen (PCNA) examination were performed on day 7. The MRI parameters between the two groups were compared and correlations with immunohistochemical scores were analyzed.

RESULTS

The average tumor volume of treated group was significantly lower than that of control group on day 7 (81.764 ± 1.043 vs. 103.634 ± 3.868 mm³, P = 0.002). K^trans and K_ep decreased in the treated group while they increased in the control group. The differences were observed on day 5 (K^trans: 0.045 ± 0.018 vs. 0.093 ± 0.014 min^-1, P < 0.001; K_ep: 0.062 ± 0.018 vs. 0.134 ± 0.047 min^-1, P = 0.005) and day 7 (K^trans: 0.032 ± 0.010 vs. 0.115 ± 0.025 min^-1, P < 0.001; K_ep: 0.045 ± 0.016 vs. 0.144 ± 0.042 min^-1, P < 0.001). The difference of V_e was observed on day 5 (0.847 ± 0.248 vs. 0.397 ± 0.151, P = 0.009) and 7 (0.920 ± 0.154 vs. 0.364 ± 0.105, P = 0.006). K^trans and K_ep showed positive correlations with MVD and V_e showed negative correlation with PCNA.

CONCLUSION

DCE-MRI can assess the changes of early effects of anti-angiogenic therapy in preclinical practice.

Clinical and histopathological analyses of VEGF receptors peptide vaccine in patients with primary glioblastoma - a case series

BACKGROUND

The expression of vascular endothelial growth factor (VEGF)-A/ VAGF receptors (VEGFRs) signaling plays a pivotal role in the tumor angiogenesis and the development of the immunosuppressive tumor microenvironment in glioblastomas. We have previously conducted exploratory clinical studies investigating VEGFRs peptide vaccination with and without multiple glioma oncoantigens in patients with recurrent high-grade gliomas. Recently, an exploratory clinical investigation of VEGFRs peptide vaccination was conducted in patients with progressive neurofibromatosis type 2. Those studies suggested that cytotoxic T lymphocytes (CTLs) induced by the vaccination can directly kill a wide variety of cells associated with tumor growth, including tumor vessels, tumor cells, and immunosuppressive cells expressing VEGFR1 and/or 2. In the present study, synergistic activity of the combination of VEGFRs peptide vaccination with chemotherapy was evaluated.

METHODS

We performed the first clinical trial to assess VEGFR1 and 2 vaccination along with temozolomide (TMZ) -based chemoradiotherapy for the patients with primary glioblastomas. Furthermore, histopathological changes after the vaccination were evaluated using paired pre- and post- vaccination specimens.

RESULTS

The disappearance of radiographically enhanced lesion was observed in 2 patients after the vaccination, including one in which the methylation of the O6-methylguanine-DNA methyltransferase (MGMT) promoter was not observed. The histopathological findings of pre- and post-vaccination specimens demonstrated that tumor vessels showed negative or slight VEGFRs expressions after the vaccination and most endothelial cells were covered with PDGFR-β-positive pericytes. Notably, CTLs induced by VEGFRs peptide vaccination attacked not only tumor vessels but also tumor cells and regulatory T cells expressing VEGFRs even in recurrent tumors.

CONCLUSIONS

VEGFR1 and 2 vaccination may have a preliminary synergistic effect when administered with TMZ. The limitation of the present study was the paucity of the number of the samples. Further studies involving more patients are warranted to confirm the findings of this study.

TRIAL REGISTRATION

This study was registered as UMIN000013381 (University Hospital Medical Information Network-Clinical Trial Registry: UMIN-CTR) on 5 March, 2014 and with the Japan Registry of Clinical Trials (jRCT) as jRCTs031180170 on 1 March, 2019.

Alterations of the tumor microenvironment in glioblastoma following radiation and temozolomide with or without bevacizumab

Background

The immunosuppressive tumor microenvironment (TME) contributes to the tumor progression and treatment failure. Our previous study demonstrated alterations in the TME during bevacizumab (Bev) therapy in human glioblastoma (GB) specimens obtained from patients who underwent surgical resection. Continuous Bev administration downregulates the expression of programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1), suppresses the infiltration of tumor associated macrophages (TAMs) and regulatory T cells (Tregs), and increases cytotoxic T lymphocytes (CTLs) infiltration. However, one may argue that these immunosupportive effects might also be induced by radiation therapy (RT) or temozolomide (TMZ), and they cannot necessarily be attributed to Bev alone.

Methods

In the present study, changes in the molecules relevant to the TME were analyzed by immunohistochemistry using paired pre- and post-treatment samples of malignant glioma specimens from 15 patients who received RT and TMZ therapy without Bev.

Results

The expression levels of CD34, vascular endothelial growth factor (VEGF)-A, VEGF receptor 2 (VEGFR2), HIF-1α, CA9, nestin, CD4, CD8, CD163, PD-1, and PD-L1 were not significantly changed after the treatment with RT and TMZ. However, VEGFR1 expression and the number of Foxp3-positive cells tended to be upregulated and increased after the treatment (P=0.058, P=0.082, respectively).

Conclusions

This was the first study to show the alterations of TME following RT and TMZ therapy using paired pre- and post-treatment malignant glioma samples. Long-term treatment of RT and TMZ might worsen immunosuppressive TME in malignant gliomas.

Difference in the hypoxic immunosuppressive microenvironment of patients with neurofibromatosis type 2 schwannomas and sporadic schwannomas

BACKGROUND

Neurofibromatosis type 2 (NF2) patients uniformly develop multiple schwannomas. The tumor-microenvironment (TME) is associated with hypoxia and consists of immunosuppressive cells, including regulatory T cells (Tregs) and tumor-associated macrophages (TAMs). The hypoxic TME of NF2 schwannomas remains unclear. In addition, no comparative study has investigated immunosuppressive cells in NF2 and sporadic schwannomas.

METHODS

In 22 NF2 and 21 sporadic schwannomas, we analyzed the immunohistochemistry for Ki-67, hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor receptor 1 (VEGFR1) and VEGFR2, platelet derived growth factor receptor-beta (PDGFR-β), programmed cell death-1 (PD-1)/ programmed cell death ligand-1 (PD-L1), Foxp3, CD163, CD3, and CD8 to assess the immunosuppressive TME.

RESULTS

Most vessels in sporadic schwannomas exhibited slight or negative VEGFR1 and 2 expressions with pericytes coverage. In contrast, large vessels in NF2 schwannomas exhibited strong VEGFR1 and 2 expressions without pericytes. The number of CD3⁺, CD8⁺, and CD163⁺ cells was significantly higher in NF2 schwannomas than in sporadic ones. The expression of PD-L1 and nestin positive cell ratio was higher in NF2 schwannomas than that in sporadic ones. The number of CD163⁺ cells, nestin positive cell ratio, and HIF-1α expression were significantly associated with shorter progression-free survival in NF2 schwannomas.

CONCLUSIONS

This study presents the clinicopathological features of the differences in immunosuppressive cells and the expression of immune checkpoint molecules between NF2 and sporadic schwannomas. Hypoxic TME was first detected in NF2-schwannomas, which was associated with the tumor progression.

The role of vascular endothelial growth factor in the hypoxic and immunosuppressive tumor microenvironment: perspectives for therapeutic implications

The microvasculature and immune cells are major components of the tumor microenvironment (TME). Hypoxia plays a pivotal role in the TME through hypoxia-inducible factor 1-alpha (HIF-1α) which upregulates vascular endothelial growth factor (VEGF). VEGF, an angiogenesis stimulator, suppresses tumor immunity by inhibiting the maturation of dendritic cells, and induces immunosuppressive cells such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells. HIF-1α directly induces immune checkpoint molecules. VEGF/VEGF receptor (VEGFR)-targeted therapy as a cancer treatment has not only anti-angiogenic effects, but also immune-supportive effects. Anti-angiogenic therapy has the potential to change the immunological "cold tumors" into the "hot tumors". Glioblastoma (GB) is a hypervascular tumor with high VEGF expression which leads to development of an immuno suppressive TME. Therefore, in the last decade, several combination immunotherapies with anti-angiogenic agents have been developed for numerous tumors including GBs. In particular, combination therapy with an immune checkpoint inhibitor and VEGF/VEGFR-targeted therapy has been suggested as a synergic treatment strategy that may show favorable changes in the TME. In this article, we discuss the cross talk among immunosuppressive cells exposed to VEGF in the hypoxic TME of GBs. Current efficient combination strategies using VEGF/VEGFR-targeted therapy are reviewed and proposed as novel cancer treatments.

Impacts on Histological Features and 11C-Methyl-L-methionine Uptake After "One-Shot" Administration with Bevacizumab Before Surgery in Newly Diagnosed Glioblastoma

BACKGROUND: Bevacizumab (BEV), an antiangiogenic agent, induces dramatic normalization of the tumor vasculature in glioblastoma. This study aimed to clarify how one-time administration of BEV changes histological features in glioblastoma and how histological changes affect the uptake of ¹¹C-methyl-L-methionine (¹¹C-met) as an amino-acid tracer. MATERIALS AND METHODS: Subjects were 18 patients with newly diagnosed glioblastoma who were assigned to two groups: BEV group, single intravenous administration of BEV before surgical tumor removal; and control group, surgical tumor removal alone. After surgery, we compared the densities of tumor cells and microvessels, and microvascular structures including vascular pericytes and L-type amino acid transporter-1 (LAT1) between the BEV and control groups. Correlations between ¹¹C-met uptake on positron emission tomography before surgery, microvascular density, and LAT1 expression were assessed in each group. RESULTS: BEV induced significant reductions in microvascular density, while tumor cell density and proliferation were retained in the BEV group. Percentages of vessels with pericytes and vascular endothelium with LAT1 expression were lower in the BEV group than in controls. Uptake of ¹¹C-met correlated significantly with microvascular density in the BEV group but not with LAT1expression. CONCLUSIONS: The present study showed that even one course of BEV administration induced reductions in microvessels, vascular pericytes, and LAT1 expression in glioblastomas. One course of BEV therapy also reduced ¹¹C-met uptake, which might have been largely attributed to reductions in microvessels rather than reductions in LAT1 expression.

Prognostic significance of VEGF receptors expression on the tumor cells in skull base chordoma

BACKGROUND

Chordoma is a rare refractory neoplasm that arises from the embryological remnants of the notochord, which is incurable using any multimodality therapy. Vascular endothelial growth factor (VEGF) is a potent activator of angiogenesis that is strongly associated with the tumor-immune microenvironment. These factors have not been elucidated for chordomas.

METHODS

To evaluate the characteristics of vascular and tumor cells in chordoma, we first analyzed the expression of VEGF receptor (VEGFR) 1, VEGFR2, CD34, and Brachyury in a cell line and 54 tumor tissues. Patients with primary skull base chordomas were divided into the following two groups as per the tumor growth rate: patients with slow progression (SP: < 3 mm/year) and those with rapid progression (RP: ≥ 3 mm/year). Thus, the expressions of VEGF-A, VEGFR 1, and VEGFR2 on tumor cells; tumor infiltrative immune cells, including regulatory T cells (Tregs) and tumor-associated macrophages (TAMs); and immune-checkpoint molecules (PD-1/PD-L1) were analyzed with the clinical courses, especially in a comparison between the two groups.

RESULTS

In chordomas, both VEGFR1 and VEGFR2 were strongly expressed not only on vascular endothelial cells, but also on tumor cells. The recurrent cases showed significantly higher VEGFR1 expressions on tumor cells than the primary cases. The expression of VEGF-A was significantly higher in RP than that in SP group. The numbers of CD163+ TAMs and Foxp3+ Tregs were higher in RP than that in SP group.

CONCLUSIONS

Expression of VEGFR1 and VEGFR2 on tumor cells and immunosuppressive tumor-microenvironment were related to tumor growth in patients with chordomas.

Immunological and vascular characteristics in cavernous sinus meningioma

OBJECTIVES

It is difficult to treat cavernous sinus (CS) meningiomas because of their complex vascular and neurological structures. Recently, immunotherapy has become an attractive therapeutic modality, but the role of tumor immune microenvironment is yet to be investigated for CS meningiomas. In the current study, these molecular and histopathological characteristics were examined in CS meningiomas.

METHODS

The present study used twenty-eight meningioma tissues arising in two different locations (8 CS and 20 convexity meningiomas). Immunohistochemical analyses were performed with CD3, CD4, CD8, Foxp3, CD163, PDGFR-β, VEGF receptors 1 & 2 (VEGFR-1, VEGFR-2), VEGF-A and HIF-1α. Quantitative polymerase chain reaction (qPCR) was performed to assess the expression of Foxp3, VEGF-A, CD163, VEGFRs-1 & 2 and HIF-1α.

RESULTS

The numbers of different tumor-infiltrating immune cells, such as immunosuppressive cells, were significantly lower in CS meningiomas compared with convexity meningiomas. Analysis of the vascular characteristics showed the vessels in the CS meningiomas were covered with PDGFR-β-positive pericytes and were negative or had only very low amounts of VEGFR-1 and VEGFR-2. However, most vessels in convexity meningiomas showed high VEGFRs expression and were not covered with pericytes. Immunohistochemical and qPCR analyses revealed that the expression of HIF-1α, VEGF-A and VEGFRs-1 & 2 was lower in CS meningiomas.

CONCLUSION

Fewer immunocompetent cells were observed in CS meningiomas compared with convexity meningiomas. Lower expression of VEGF-A, VEGFRs-1 and 2, and the vascular structure may contribute to this specific immune microenvironment.

Analysis of Tumor Angiogenesis and Immune Microenvironment in Non-Functional Pituitary Endocrine Tumors

Cavernous sinus (CS) invasion is an aggressive behavior exhibited by pituitary neuroendocrine tumors (PitNETs). The cause of CS invasion in PitNETs has not been fully elucidated. The tumor immune microenvironment, known to promote aggressive behavior in various types of tumors, has not been examined for PitNETs. Vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) signaling is strongly associated with the tumor immune microenvironment. In the present study, these molecular and histopathological characteristics were examined in invasive non-functional PitNETs (NF-PitNETs). Twenty-seven patients with newly diagnosed NF-PitNETs (with CS invasion: 17, without CS invasion: 10) were analyzed by immunohistochemistry for VEGF-A/VEGFR1 and 2, hypoxia-inducible Factor (HIF), tumor-infiltrating lymphocytes, immunosuppressive cells including regulatory T cells (Tregs) and tumor-associated macrophages (TAMs), and immune checkpoint molecules. Previously validated tumor proliferation markers including mitotic count, Ki-67 index, and p53 were also analyzed for their expressions in NF-PitNETs. VEGF-A and VEGFR1 were expressed on not only vascular endothelial cells, but also on tumor cells. The expressions of VEGF-A and VEGFR1 were significantly higher in NF-PitNETs with CS invasion. The number of TAMs and the expression of PD-L1 were also significantly higher in NF-PitNETs with CS invasion than in NF-PitNETs without CS invasion. The high expression of VEGF-A and VEGFR1 and associated immunosuppressive microenvironment were observed in NF-PitNETs with CS invasion, suggesting that a novel targeted therapy can be applied.

Imaging necrosis during treatment is associated with worse survival in EORTC 26101 study

OBJECTIVE

Imaging necrosis on MRI scans was assessed and compared to outcome measures of the European Organisation for Research and Treatment of Cancer 26101 phase III trial that compared single-agent lomustine with lomustine plus bevacizumab in patients with progressive glioblastoma.

METHODS

MRI in this post hoc analysis was available for 359 patients (lomustine = 127, lomustine + bevacizumab = 232). First, imaging necrosis at baseline being formally measurable (>10 × 10 mm, given 2 slices) was assessed. At weeks 6 and 12 of treatment, it was analyzed whether this necrosis remained stable or increased >25% calculated by 2 perpendicular diameters or whether necrosis developed de novo. Univariate and multivariate associations of baseline necrosis with overall survival (OS) and progression-free survival (PFS) were tested by log-rank test. Hazard ratios (HR) with 95% confidence interval were calculated by Cox model.

RESULTS

Imaging necrosis at baseline was detected in 191 patients (53.2%) and was associated with worse OS and PFS in univariate, but not in multivariate analysis. Baseline necrosis was predictive for OS in the lomustine-only group (HR 1.46, p = 0.018). At weeks 6 and 12 of treatment, increase of baseline necrosis and de novo necrosis were strongly associated with worse OS and PFS in univariate and multivariate analysis (PFS both p < 0.001, OS univariate p < 0.001, multivariate p = 0.0046).

CONCLUSION

Increase of and new development of imaging necrosis during treatment is a negative prognostic factor for patients with progressive glioblastoma. These data call for consideration of integrating the assessment of imaging necrosis as a separate item into the MRI response assessment criteria.

Correlation of radiological and immunochemical parameters with clinical outcome in patients with recurrent glioblastoma treated with Bevacizumab

BACKGROUND

Some phase 2 trials had reported encouraging progression-free survival with Bevacizumab in monotherapy or combined with chemotherapy in glioblastoma. However, phase 3 trials showed a significant improvement in progression free survival without a benefit in overall survival. To date, there are no predictive biomarker of response for Bevacizumab in glioblastoma.

METHODS

We used Immunochemical analysis on tumor samples and pretreatment and post-treatment perfusion-MRI to try to identify possible predictive angiogenesis-related biomarkers of response and survival in patients with glioblastoma treated with bevacizumab in the first recurrence. We analyzed histological parameters: vascular proliferation, mitotic number and Ki-67 index; molecular factors: MGMT promoter methylation, EGFR amplification and EGFR variant III; immunohistochemical: MET, Midkine, HIF1, VEGFA, VEGF-R2, CD44, Olig2, microvascular area and microvascular density; and radiological: rCBV.

RESULTS

In the statistical analysis, no significant correlation of any histological, molecular, microvascular or radiological parameters could be demonstrated with the response rate, PFS or OS with bevacizumab treatment.

CONCLUSION

Unfortunately, in this histopathological, molecular, immunohistochemical and neuroradiological study we did not find any predictive biomarker of response or survival benefit for Bevacizumab in glioblastoma.

Persistent restoration to the immunosupportive tumor microenvironment in glioblastoma by bevacizumab

Although vascular endothelial growth factor (VEGF) promotes the immunosuppressive microenvironment, the efficacy of bevacizumab (Bev) on tumor immunity has not been fully investigated. The present study used 47 glioblastoma tissues obtained at 3 different settings: tumors of initial resection (naïve Bev group), tumors resected following Bev therapy (effective Bev group), and recurrent tumors after Bev therapy (refractory Bev group). The paired samples of the initial and post-Bev recurrent tumors from 9 patients were included. The expression of programmed cell death-1 (PD-1)/PD ligand-1 (PD-L1), CD3, CD8, Foxp3, and CD163 was analyzed by immunohistochemistry. The PD-L1+ tumor cells significantly decreased in the effective or refractory Bev group compared with the naïve Bev group (P < .01 for each). The PD-1+ cells significantly decreased in the effective or refractory Bev group compared with the naïve Bev group (P < .01 for each). The amount of CD3+ and CD8+ T cell infiltration increased in the refractory Bev group compared with the naïve Bev group (CD3, P < .01; CD8, P = .06). Both Foxp3+ regulatory T cells and CD163+ tumor-associated macrophages significantly decreased in the effective or refractory Bev group compared with the naïve Bev group (Foxp3, P < .01 for each; CD163, P < .01 for each). These findings were largely confirmed by comparing paired initial and post-Bev recurrent tumors. Bevacizumab restores the immunosupportive tumor microenvironment in glioblastomas, and this effect persists during long-term Bev therapy.

Difference in Immunosuppressive Cells Between Peritumoral Area and Tumor Core in Glioblastoma

BACKGROUND

Vascular endothelial growth factor (VEGF)-A and VEGF receptor expression in the peritumoral brain zone (PBZ) differs from that in the tumor core (TC) of glioblastoma. To date, no comparative study has investigated the expression of immunosuppressive cells in the PBZ and TC of glioblastoma.

METHODS

In 10 patients with newly diagnosed glioblastoma, we used immunohistochemistry to analyze the expression of VEGF-A, hypoxia-inducible factor-1α, programmed cell death-1 (PD-1), Foxp3, CD163, CD4, and CD8 to assess the immunosuppressive microenvironment.

RESULTS

The number of Foxp3⁺ and CD163⁺ cells was significantly greater in the TC than in the PBZ and correlated with greater expression of hypoxia-inducible factor-1α and VEGF-A in the TC than in the PBZ. The number of CD8⁺ T cells was lower in the TC than in the PBZ, and the TC had more PD-1⁺CD8⁺ T cells compared with the PBZ. These results suggest that the hypoxic condition could be associated with PD-1 expression on lymphocytes, the distribution of Foxp3⁺ regulatory T cells and CD163⁺ tumor-associated macrophages.

CONCLUSIONS

The present study reports the first clinicopathologic features of the differences in immunosuppressive cells and the expression of immune checkpoint molecules between the TC and PBZ of glioblastoma.

Histopathological vascular investigation of the peritumoral brain zone of glioblastomas

To date, no histopathological vascular investigation focusing on peritumoral brain zone (PBZ) has been reported for glioblastoma. We analyzed 10 newly diagnosed cases of glioblastomas. For these PBZs, histopathological investigation was performed by hematoxylin-eosin (H&E) staining and immunohistochemistry was analyzed for CD31, CD34, Factor VIII, VEGF, VEGFR-1/2, Ki67, p53 and nestin. Although it was difficult to identify PBZ by H&E, Ki67 and p53 staining, there were apparent differences in nestin staining among PBZ, tumor core (TC), and normal zone (NZ). Therefore, in this study, we divided PBZ from TC and NZ by nestin staining. Differences in histological features, microvessel density, expression of VEGF and its receptors were assessed for PBZ, TC and NZ. The microvessel density, as determined by counting CD31, CD34 and VEGF receptors, and VEGF-A expression were lower in PBZ than TC. The expression patterns for CD31, CD34 and VEGF receptors in vessels show dissociation in PBZ. In addition, the vascular characteristics of the PBZ may correlate with findings of radiographic imaging. We provide the first clinicopathological evidence that PBZ exhibits unique angiogenic characteristics. These in situ observations will help to elucidate the mechanisms of tumor recurrence.

"Paradoxical" findings of tumor vascularity and oxygenation in recurrent glioblastomas refractory to bevacizumab

Anti-angiogenic therapy induces the apparent normalization of vascular structure, decreases microvessel density (MVD), and improves tumor oxygenation in glioblastomas (GBMs). Six initial and recurrent tumor pairs after bevacizumab (Bev) treatment were compared with GBMs from nine patients resected under neoadjuvant Bev treatment with regard to histological characteristics; MVD; MIB-1 index; and expression of vascular endothelial growth factor (VEGF) and its receptors, hypoxia markers (hypoxia-inducible factor 1 alpha, carbonic anhydrase 9), and nestin as a marker of glioma stem-like cells. In recurrent tumors post-Bev treatment, while the MVD remained low compared with the paired initial tumors (pre-Bev tumors), the expression of hypoxic markers were increased and were even higher in expression compared with the paired pre-Bev tumors in three of the six cases. MIB-1 indices were similar among the initial GBMs, neoadjuvant group, and recurrent tumors post-Bev treatment. The nestin-positive cell ratio of the post-Bev recurrent tumors was as high as that of the pre-Bev tumors. The expression of VEGF and VEGFR1 was increased in the post-Bev recurrent tumors in three and four cases, respectively, compared with the paired pre-Bev tumors. In the majority of Bev-refractory GBMs, tumor hypoxia was present with a paradoxical decrease in MVD. These findings suggest that re-activation of tumor angiogenesis is not initially involved in the acquisition of resistance to Bev.

A case of glioblastoma resected immediately after administering bevacizumab: consideration on histopathological findings and safety of surgery

Surgery after administering bevacizumab should be carefully considered particularly because of wound healing concerns. A 27-year-old man presented with multiple tumor recurrences after gross total removal of a left temporal oligodendroglioma (1p/19q-noncodeleted). Whole brain radiotherapy with concomitant temozolomide and bevacizumab was immediately prescribed; however, the patient's condition deteriorated because of brain herniation. Three days after administering bevacizumab, an emergency tumor removal with external decompression and a ventriculo-peritoneal shunt was performed. The surgery and postoperative clinical course were uneventful. On histopathological examination, the tumor showed findings such as tumor vessel thrombosis, numerous interstitial red blood cells, and cells with degraded, fragmented nuclei possibly suggesting apoptosis, which could be attributable to bevacizumab. Performing craniotomy shortly after administering bevacizumab is not recommended; however, it can still be safely performed as long as surgery and wound management is carefully performed. Vessel thrombosis might be among the mechanisms of action of bevacizumab.

Bevacizumab for malignant gliomas: current indications, mechanisms of action and resistance, and markers of response

Vascular endothelial growth factor (VEGF) is an attractive target of antiangiogenic therapy in glioblastomas. Bevacizumab (Bev), a humanized anti-VEGF antibody, is associated with the improvement of progression-free survival and performance status in patients with glioblastoma. However, randomized trials uniformly suggest that these favorable clinical effects of Bev do not translate into an overall survival benefit. The mechanisms of action of Bev appear to include the inhibition of tumor angiogenesis, as well as indirect effects such as the depletion of niches for glioma stem cells and stimulation of antitumor immunity. Although several molecules/pathways have been reported to mediate adaptation and resistance to Bev, including the activation of alternative pro-angiogenic pathways, the resistance mechanisms have not been fully elucidated; for example, the mechanism that reinduces tumor hypoxia remains unclarified. The identification of imaging characteristics or biomarkers predicting the response to Bev, as well as the better understanding of the mechanisms of action and resistance, is crucial to improve the overall clinical outcome and optimize individual therapy. In this article, the authors review the results of important clinical trials/studies, the current understanding of the mechanisms of action and resistance, and the knowledge of imaging characteristics and biomarkers predicting the response to Bev.

The brain-penetrating CXCR4 antagonist, PRX177561, increases the antitumor effects of bevacizumab and sunitinib in preclinical models of human glioblastoma

Background

Glioblastoma recurrence after treatment with the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab is characterized by a highly infiltrative and malignant behavior that renders surgical excision and chemotherapy ineffective. It has been demonstrated that anti-VEGF/VEGFR therapies control the invasive phenotype and that relapse occurs through the increased activity of CXCR4. We therefore hypothesized that combining bevacizumab or sunitinib with the novel CXCR4 antagonist, PRX177561, would have superior antitumor activity.

Methods

The effects of bevacizumab, sunitinib, and PRX177561 were tested alone or in combination in subcutaneous xenografts of U87MG, U251, and T98G cells as well as on intracranial xenografts of luciferase tagged U87MG cells injected in CD1-nu/nu mice. Animals were randomized to receive vehicle, bevacizumab (4 mg/kg iv every 4 days), sunitinib (40 mg/kg po qd), or PRX177561 (50 mg/kg po qd).

Results

The in vivo experiments demonstrated that bevacizumab and sunitinib increase the in vivo expression of CXCR4, SDF-1α, and TGFβ1. In addition, we demonstrate that the co-administration of the novel brain-penetrating CXCR4 antagonist, PRX177561, with bevacizumab or sunitinib inhibited tumor growth and reduced the inflammation. The combination of PRX177561 with bevacizumab resulted in a synergistic reduction of tumor growth with an increase of disease-free survival (DSF) and overall survival (OS), whereas the combination of PRX177561 with sunitinib showed a mild additive effect.

Conclusions

The CXC4 antagonist PRX177561 may be a valid therapeutic complement to anti-angiogenic therapy, particularly when used in combination with VEGF/VEGFR inhibitors. Therefore, this compound deserves to be considered for future clinical evaluation.

Glioma FMISO PET/MR Imaging Concurrent with Antiangiogenic Therapy: Molecular Imaging as a Clinical Tool in the Burgeoning Era of Personalized Medicine

The purpose of this article is to provide a focused overview of the current use of positron emission tomography (PET) molecular imaging in the burgeoning era of personalized medicine in the treatment of patients with glioma. Specifically, we demonstrate the utility of PET imaging as a tool for personalized diagnosis and therapy by highlighting a case series of four patients with recurrent high grade glioma who underwent 18F-fluoromisonidazole (FMISO) PET/MR (magnetic resonance) imaging through the course of antiangiogenic therapy. Three distinct features were observed from this small cohort of patients. First, the presence of pseudoprogression was retrospectively associated with the absence of hypoxia. Second, a subgroup of patients with recurrent high grade glioma undergoing bevacizumab therapy demonstrated disease progression characterized by an enlarging nonenhancing mass with newly developed reduced diffusion, lack of hypoxia, and preserved cerebral blood volume. Finally, a reduction in hypoxic volume was observed concurrent with therapy in all patients with recurrent tumor, and markedly so in two patients that developed a nonenhancing reduced diffusion mass. This case series demonstrates how medical imaging has the potential to influence personalized medicine in several key aspects, especially involving molecular PET imaging for personalized diagnosis, patient specific disease prognosis, and therapeutic monitoring.