Ryota Tamura

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.

Histopathological investigation of glioblastomas resected under bevacizumab treatment

To date, no clinical observations have been reported for histopathological changes in human gliomas under antiangiogenic treatment. We collected six glioblastomas resected under bevacizumab treatment. Histopathological investigation was performed by hematoxilyn-eosin staining and immunohistochemistry for CD34, VEGF, VEGFR1/2, HIF-1α, CA9, and nestin as compared to eleven control glioblastomas to assess the differences in histological features, microvessel density, expression of VEGF and its receptors, tumor oxygenation, and status of glioma stem-like cells. In the six tumors resected under bevacizumab, microvascular proliferation was absent, and microvessel density had significantly decreased compared with that of the controls. The expressions of VEGF and its receptors were downregulated in two cases of partial response. HIF-1α or CA9 expression was decreased in five of the six tumors, whereas the decreased expression of these markers was noted in only one of the 11 control glioblastomas. The expression of nestin significantly decreased in the six tumors compared with that of the controls, with the remaining nestin-positive cells being relatively concentrated around vessels. We provide the first clinicopathological evidence that antiangiogenic therapy induces the apparent normalization of vascular structure, decrease of microvessel density, and improvement of tumor oxygenation in glioblastomas. These in situ observations will help to optimize therapy.

GH-Producing Pituitary Adenoma and Concomitant Rathke’s Cleft Cyst: A Case Report and Short Review

Concomitant pituitary adenoma (PA) and Rathkes cleft cyst (RCC) are rare. In some cases, such PA is known to produce pituitary hormones. A 53-year-old man was admitted to our hospital with a diagnosis of lacunar infarction in the left basal ganglia. Magnetic resonance imaging (MRI) incidentally showed a suprasellar mass with radiographic features of RCC. When he consulted with a neurosurgical outpatient clinic, acromegaly was suspected based on his appearance. A diagnosis of growth hormone- (GH-) producing PA was confirmed from hormonal examinations and additional MRI. Retrospectively, initial MR images also showed intrasellar mass that is compatible with the diagnosis of PA other than suprasellar RCC. The patient underwent endonasal-endoscopic removal of the PA. Since we judged that the RCC of the patient was asymptomatic, only the PA was completely removed. The postoperative course of the patient was uneventful and GH levels gradually normalized. Only 40 cases of PA with concomitant RCC have been reported to date, including 13 cases of GH-producing PA. In those 13 cases, RCC tended to be located in the sella turcica, and suprasellar RCC like this case appears rare. In a few cases, concomitant RCCs were fenestrated, but GH levels normalized postoperatively as in the cases without RCC fenestration. If radiographic imaging shows typical RCC, and PA is not obvious at first glance, the possibility of concomitant PA still needs to be considered. In terms of treatment, removal of the RCC is not needed to achieve hormone normalization.

The importance of amyloid β protein in cerebrospinal fluid when you recognize convexal subarachnoid hemorrhage.

Background: Convexal subarachnoid hemorrhage (cSAH) is sometimes experienced in cerebral amyloid angiopathy (CAA), but ones that are repeated within a brief time period are not common. Also, it is often difficult to diagnose CAA when you experience a case of cSAH. Methods: We examined the clinical course of 2 cases that showed cSAH repeatedly. We examined cerebrospinal fluid (CSF) concentrations of amyloid β protein (Aβ) 40 and 42 and tau protein as additional evidence for a diagnosis of CAA. Results: Case 1 presented with transient motor paresis of the left hand and case 2 with transient sensory disturbance of the left hand. CT scans showed cSAH on the right central sulcus in both patients. Case 1 showed development of intracerebral hemorrhage on the frontal lobe near the right central sulcus. Case 2 showed relapse of cSAH with recurrence of the same symptoms. These cases could not be diagnosed by image analysis, but were considered CAA by Aβ40, Aβ42 and tau protein in CSF. Conclusion: Aβ in CSF can be presented here as support for the diagnosis of CAA that is difficult to diagnose by Boston criteria.

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.

Unusual Magnetic Resonance Imaging Findings of a Glioblastoma Arising During Treatment with Lenvatinib for Thyroid Cancer

BACKGROUND Glioblastoma (GBM) is a lesion radiologically characterized by magnetic resonance imaging findings, such as ring enhancement with extensive perifocal edema and a butterfly appearance extending into the bilateral lobes. However, these characteristic findings could be changed by antiangiogenic therapy, with decreased contrast enhancement and improved perifocal edema. Herein, we report a case of GBM that arose during treatment with a tyrosine kinase inhibitor for another cancer. CASE DESCRIPTION A 57-year-old man presented with seizures. Until the seizure onset, he had been treated with the multireceptor tyrosine kinase inhibitor lenvatinib for 4 years for thyroid cancer and its metastasis to the thoracic vertebral body. Magnetic resonance imaging revealed a slightly high intensity lesion in the left frontal base area on T2-weighted or fluid-attenuated inversion recovery images, and the lesion showed only faint enhancement on T1-weighted images after gadolinium administration. Total resection was performed and the histopathologic diagnosis was GBM. However, grade IV histology was observed in only a limited area, and most of the specimen showed lower grade histology with moderate vascularization that lacked microvascular proliferation. CONCLUSIONS Lenvatinib, which is antiangiogenic, might have affected the radiologic characteristics, as well as the pathology of the tumor. Brain tumors arising during treatment with receptor tyrosine kinases for other cancers could show atypical imaging findings.

Giant Cell Tumor of the Skull: Review of the Literature.

BACKGROUND Giant cell tumors (GCTs) are rare in the skull. The present report describes a case with a primary GCT located in the temporal bone and reviews the relevant literature. We also propose a treatment strategy for GCT of the skull. CLINICAL PRESENTATION A 41-year-old man presented with headache and auditory disturbance. Radiologic images showed a lytic expansive extradural lesion originating primarily from the right temporal bone and expanding into the middle cranial fossa and the infratemporal fossa. A biopsy specimen of the lesion was obtained from the external auditory meatus. Total removal was performed with temporal craniectomy, mandibular condylar process removal, tympanoplasty, and mastoidectomy. DISCUSSION The rate of recurrence of GCTs is related to complete resection and location of the GCT rather than to the degree of invasiveness. Some of the mononuclear cells and stromal cells in GCT express receptor activator of nuclear factor κ-β ligand (RANKL). Because inhibition of RANKL and bisphosphonate therapy might eliminate giant cells, this approach might be useful for recurrent or unresectable GCTs of the skull. CONCLUSIONS Preoperative diagnosis by biopsy is important in determining the therapeutic strategy of GCTs. Complete resection is important to reduce the recurrence rate of GCTs in the skull.

Primary Neuroendocrine Tumor in Brain

The incidence of brain metastases for neuroendocrine tumor (NET) is reportedly 1.5~5%, and the origin is usually pulmonary. A 77-year-old man presented to our hospital with headache and disturbance of specific skilled motor activities. Computed tomography (CT) showed a massive neoplastic lesion originating in the left temporal and parietal lobes that caused a mass edematous effect. Grossly, total resection of the tumor was achieved. Histological examination revealed much nuclear atypia and mitotic figures. Staining for CD56, chromogranin A, and synaptophysin was positive, indicating NET. The MIB-1 index was 37%. Histopathologically, the tumor was diagnosed as NET. After surgery, gastroscopy and colonoscopy were performed, but the origin was not seen. After discharge, CT and FDG-PET (fluoro-2-deoxy-d-glucose positron emission tomography) were performed every 3 months. Two years later we have not determined the origin of the tumor. It is possible that the brain is the primary site of this NET. To our knowledge, this is the first reported case of this phenomenon.

Dual role of macrophage in tumor immunity

Macrophages are significant in immune responses, assuming a defensive role. In contrast, macrophages often cause undesirable changes. These reactions are processes by which macrophages express different functional programs in response to microenvironmental signals, defined as M1/M2 polarization. Tumor immunity has been acknowledged for contributing to the elucidation of the mechanism and clinical application in cancer therapy. One of the mechanisms for the refractoriness to cancer immunotherapy is the production of inhibitory cytokines by tumor cells or macrophages. Therefore, therapeutic strategy targeting macrophage or macrophage-derived cytokines may be effective and attractive. This review aims to investigate macrophage-associated pathophysiology and biological behavior in cancers, especially related to microenvironment, such as hypoxia, and current topics regarding some therapies involving macrophages.

“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.