Spinal Dissemination of Pineal Parenchymal Tumors of Intermediate Differentiation Over 10 Years After Initial Treatment: A Case Report

Pineal parenchymal tumors (PPTs) are rare, accounting for less than 0.3% of all primary central nervous system (CNS) tumors. Pineal parenchymal tumors of intermediate differentiation (PPTID) (WHO grade 2 or 3) show an intermediate prognosis between pineocytoma and pineoblastoma. The clinical course is unknown, and the optimal treatment for PPTID, especially for recurrence, has not been determined. We report a case of PPTID with spinal dissemination over 10 years after treatment and survival for four years. A 56-year-old woman presented with headaches and diplopia. Computerized tomography (CT) and magnetic resonance imaging (MRI) revealed a pineal mass, but leptomeningeal dissemination was not identified on whole-spine MRI. Microsurgical gross total tumor resection (GTR) was performed, and the pathological diagnosis was PPTID (grade 3). In addition, a later study found it to harbor a KBTBD4 mutation. She underwent whole-brain radiation therapy with a focal boost. The patient was unable to continue chemotherapy for severe myelosuppression after the first course of treatment. Eleven years after the surgery, she was unable to walk, and a whole-spine MRI revealed multiple masses at C3-4, T4, and cauda equina. Fluorodeoxyglucose-positron emission tomography (FDG-PET) revealed accumulations of the same lesions. No recurrence was observed in the brain. A biopsy of the caudal portion was performed, and the histopathological findings were the same as those of the initial surgery. Spinal dissemination was refractory to chemotherapy but responded to whole spine radiotherapy with focal boost, and she remained tumor-free for four years. We considered good local control with a combination of GTR and subsequent radiation therapy to contribute to long-term survival. The timing of spinal radiation administration is controversial because of the tendency for late cerebrospinal dissemination. The importance of long-term follow-up of the spine and head is emphasized. In PPTID cases with good local control, withholding spinal radiation until spinal dissemination occurs may become a long-term treatment plan.

Postoperative disappearance of leptomeningeal enhancement around the brainstem in glioblastoma

PURPOSE

Leptomeningeal enhancement (LME) suggests leptomeningeal dissemination (LMD) of tumor cells, which is a complication of end-stage glioblastoma, and is associated with a poor prognosis. However, magnetic resonance imaging (MRI) occasionally indicates the disappearance of peri-brainstem LME after surgical resection of glioblastoma. Since preoperative LMD may affect treatment indications, we aimed to analyze the clinical significance of preoperative LME of the brainstem in glioblastoma.

METHODS

We retrospectively collected clinical and radiological data from consecutive patients with glioblastoma and preoperative LME of the brainstem, who were treated at our hospital between 2017 and 2020.

RESULTS

Among 112 patients with glioblastoma, nine (8%) showed preoperative LME of the brainstem. In comparison with tumors without LME, tumor size was significantly associated with the preoperative LME of the brainstem (p = 0.016). In addition, there was a trend toward significance for a relationship between deep tumor location and preoperative LME of the brainstem (p = 0.058). Notably, among six patients who underwent surgical resection for glioblastoma with LME of the brainstem, four showed significant radiological disappearance of the LME on postoperative MRI. This suggests that the LME did not result from LMD in these cases. Moreover, these four patients lived longer than would be expected from the presence of LMD. However, this LME disappearance was not observed after biopsy or chemoradiotherapy.

CONCLUSIONS

These findings suggest that preoperative LME does not necessarily indicate the presence of untreatable LMD; moreover, LME may disappear after surgical tumor resection. Thus, transient preoperative LME could be attributed to other mechanisms, including impaired venous flow due to intratumoral arteriovenous shunts, which can be resolved by reducing the tumor burden.

Long-term outcomes of multidisciplinary treatment combining surgery and stereotactic radiotherapy with Novalis for craniopharyngioma

Craniopharyngiomas are difficult to resect completely, recurrence is frequent, and hypothalamic/pituitary function may be affected after surgery. Therefore, the ideal treatment for craniopharyngiomas is local control with preservation of hypothalamic and pituitary functions. The purpose of this study is to retrospectively evaluate the long-term efficacy and adverse events of stereotactic radiotherapy (SRT) with Novalis for craniopharyngioma. This study included 23 patients with craniopharyngiomas who underwent surgery between 2006 and 2021 and underwent SRT as their first irradiation after surgery. The median post-irradiation observation period was 88 months, with the overall survival rates of 100 % at 10 years and 85.7 % at 20 years. One patient died of adrenal insufficiency 12 years after irradiation. The local control rate of the cystic component was 91.3 % at 5 years, 83.0 % at 15 years, with no increase in the solid component. No delayed impairment of visual or pituitary function due to irradiation was observed. No new hypothalamic dysfunction was observed after radiation therapy. No delayed adverse events such as brain necrosis, cerebral artery stenosis, cerebral infarction, or secondary brain tumors were also observed. SRT was safe and effective over the long term in patients irradiated in childhood as well as adults, with no local recurrence or adverse events. We believe that surgical planning for craniopharyngioma with stereotactic radiotherapy in mind is effective in maintaining a good prognosis and quality of life.

Three-year follow-up analysis of phase 1/2 study on tirabrutinib in patients with relapsed or refractory primary central nervous system lymphoma

Background

The ONO-4059-02 phase 1/2 study showed favorable efficacy and acceptable safety profile of tirabrutinib, a second-generation Bruton's tyrosine kinase inhibitor, for relapsed/refractory primary central nervous system lymphoma (PCNSL). Here, we report the long-term efficacy and safety after a 3-year follow-up.

Methods

Eligible patients were aged ≥ 20 years with histologically diagnosed PCNSL and KPS of ≥ 70. Patients received oral tirabrutinib once daily at 320 or 480 mg, or 480 mg under fasted conditions.

Results

Between October 19, 2017, and June 13, 2019, 44 patients were enrolled: 33 and 9 had relapsed and refractory, respectively. The 320, 480, and 480 mg fasted groups included 20, 7, and 17 patients, respectively. The median follow-up was 37.1 months. The overall response rate was 63.6% (95% CI: 47.8-77.6) with complete response (CR), unconfirmed CR, and partial response in 9, 7, and 12 patients, respectively. The median duration of response (DOR) was 9.2 months, with a DOR rate of 19.8%; the median progression-free survival (PFS) and median overall survival (OS) were 2.9 months and not reached, respectively, with PFS and OS rates of 13.9% and 56.7%, respectively. Adverse events occurred in 38 patients (86.4%): grade ≥ 3 in 23 (52.3%) including 1 patient with grade 5 events. KPS and quality of life (QoL) scores were well maintained among patients receiving long-term treatment.

Conclusions

The results demonstrated the long-term clinical benefit of tirabrutinib, with deep and durable response in a subset of patients and acceptable safety profile, while KPS and QoL scores were maintained.

A Rare Case of Adult Poorly Differentiated Chordoma of the Skull Base With Rapid Progression and Systemic Metastasis: A Review of the Literature

Chordoma is a rare tumor that arises from chordal tissue during fetal life. Recently, the concept of poorly differentiated chordoma, a subtype of chordoma characterized by loss of SMARCB1/INI1 with a poorer prognosis than conventional chordomas, was established. It predominantly occurs in children and is rare in adults. Here, we report a rare adult case of poorly differentiated chordoma of the skull base with a unique course that rapidly systemically metastasized and had the shortest survival time of any adult chordoma reported to date. The patient was a 32-year-old male with a chief complaint of diplopia. MRI showed a widespread neoplastic lesion with the clivus as the main locus. Endoscopic extended transsphenoidal tumor resection was performed. Pathological findings showed that the tumor was malignant, and immunohistochemistry revealed a Ki-67 labeling index of 80%, diffusely positive brachyury, and loss of INI1 expression. The final diagnosis was poorly differentiated chordoma. Postoperatively, the residual tumor in the right cavernous sinus showed rapid growth. The patient was promptly treated with gamma knife three fractions. The residual tumor regressed, but the tumor developed systemic metastasis in a short period, and the patient died seven months after diagnosis. This report of a rapidly progressing and fatal adult poorly differentiated chordoma shows the highest Ki-67 labeling index reported to date. Prompt multidisciplinary treatment should be considered when the Ki-67 labeling index is high.

Accelerating TOF-MRA: The impact of the combined use of compressed sensitivity encoding and spiral imaging

PURPOSE

To evaluate the image quality of the combined technique of compressed sensitivity encoding (CS) and spiral imaging in time-of-flight magnetic resonance angiography (TOF-MRA), which is approximately 2.5 times faster than conventional methods.

METHODS

Twenty volunteers underwent four TOF-MRA sequences: sensitivity encoding (SENSE) with acceleration factor of 4 (acquisition time: 4:55 min), CS with acceleration factor of 10.9, and spiral and CS-spiral (both 1:55 min). A quantitative image analysis (signal-to-noise ratio [SNR], contrast, and full width at half maximum [FWHM] edge criterion measurements) was performed on four TOF sequences. For qualitative image analysis, two board-certified radiologists evaluated the overall depiction of the proximal, intermediate, and distal branches in CS, spiral, and CS-spiral images using SENSE as a reference.

RESULTS

The SNR of BA in spiral and CS-spiral imaging was significantly lower than that in SENSE (p = 0.009). The contrasts of ACA and BA in CS-spiral were significantly higher and those in spiral were significantly lower than those in SENSE (p < 0.001). The FWHM in the CS image was significantly higher than that of SENSE; however, no significant differences were observed between the spiral or CS-spiral and SENSE. In qualitative analysis, the depiction of proximal vascular branches was significantly impaired in spiral than in others and that of distal vascular branches was significantly impaired in CS than in others (p < 0.001).

CONCLUSIONS

In TOF-MRA, which is approximately 2.5 times faster than conventional methods, the combined use of CS and spiral imaging demonstrated an improvement in image quality compared to either CS or spiral imaging alone.

SUMMARY STATEMENT

The image quality of Compressed SENSE and spiral imaging is particularly poor in the proximal and distal vascular branches, respectively at an extremely high acceleration factor; however, CS-spiral provided stable image quality in all regions as compared with the SENSE technique.

Lynch syndrome-associated chordoma with high tumor mutational burden and significant response to immune checkpoint inhibitors

Chordoma is a rare malignant bone tumor arising from notochordal tissue. Conventional treatments, such as radical resection and high-dose irradiation, frequently fail to control the tumor, resulting in recurrence and re-growth. In this study, genetic analysis of the tumor in a 72-year-old male patient with refractory conventional chordoma of the skull base revealed a high tumor mutational burden (TMB) and mutations in the MSH6 and MLH1 genes, which are found in Lynch syndrome. The patient and his family had a dense cancer history, and subsequent germline genetic testing revealed Lynch syndrome. This is the first report of a chordoma that has been genetically proven to be Lynch syndrome. Chordomas usually have low TMB; however, this is an unusual case, because the TMB was high, and immune checkpoint inhibitors effectively controlled the tumor. This case provides a basis for determining the indications for immunotherapy of chordoma based on the genetic analysis. Therefore, further extensive genetic analysis in the future will help to stratify the treatment of chordoma.

Two children with lymphocytic hypophysitis presenting with positive anti-rabphilin-3A antibody

Lymphocytic hypophysitis (LYH) is a rare chronic inflammatory disease characterized by lymphocytic infiltration of the anterior or posterior pituitary gland and hypothalamus. LYH is subdivided into lymphocytic adenohypophysitis (LAH), lymphocytic infundibulo-neurohypophysitis (LINH), and lymphocytic panhypophysitis (LPH) depending on the primary site. Most cases occur in adults, with few cases reported in children, and it is especially important to distinguish LYH from suprasellar malignancies, such as germ cell tumors and other neoplastic diseases. Although a biopsy is necessary for definitive diagnosis, it is desirable to be able to diagnose the disease without biopsy if possible, especially in children, because of the surgical invasiveness of the procedure. Recently, serum anti-rabphilin-3A antibodies have attracted attention as diagnostic markers for LYH, especially in LINH, but there are only a few reports on pediatric patients. In the present study, we experienced two children with LPH and LAH, respectively, who tested positive for anti-rabphilin-3A antibodies. This is the first report of children with LYH other than LINH positive for anti-rabphilin-3A antibodies, and anti-rabphilin-3A antibodies may be a useful non-invasive diagnostic marker not only for LINH but also for LYH in general. We also discuss the sensitivity and specificity of anti-rabphilin-3A antibody testing in cases where histological diagnosis has been made.

Clinicopathologic analysis of pineal parenchymal tumors of intermediate differentiation: a multi-institutional cohort study by the Kyushu Neuro-Oncology Study Group

PURPOSE

Pineal parenchymal tumors of intermediate differentiation (PPTIDs), which were recognized in the 2007 World Health Organization (WHO) classification, are rare, accounting for less than 1% of all central nervous system tumors. This rarity and novelty complicate the diagnosis and treatments of PPTID. We therefore aimed to evaluate the clinicopathological significance of this tumor.

METHODS

At 11 institutions participating in the Kyushu Neuro-Oncology Study Group, data for patients diagnosed with PPTID were collected. Central pathology review and KBTBD4 mutation analysis were applied to attain the diagnostically accurate cohort.

RESULTS

PPTID was officially diagnosed in 28 patients: 11 (39%) with WHO grade 2 and 17 (61%) with WHO grade 3 tumors. Median age was 49 years, and the male:female ratio was 1:2.1. Surgery was attempted in all 28 patients, and gross total resection (GTR) was achieved in 46% (13/28). Adjuvant radiotherapy and chemotherapy were administered to, respectively, 82% (23/28) and 46% (13/28). The 5-year progression-free survival (PFS) and overall survival rates were 64.9% and 70.4% respectively. Female sex (p = 0.018) and GTR (p < 0.01) were found to be independent prognostic factors for PFS and female sex (p = 0.019) was that for OS. Initial and second recurrences were most often leptomeningeal (67% and 100% respectively). 80% (20/25) of patients harbored a KBTBD4 mutation.

CONCLUSIONS

Female sex and GTR were independent prognostic factors in our patients with PPTID. Leptomeningeal recurrence was observed to be particularly characteristic of this tumor. The rate of KBTBD4 mutation observed in our cohort was acceptable and this could prove the accuracy of our PPTID cohort.

Macrophage colony-stimulating factor potentially induces recruitment and maturation of macrophages in recurrent pituitary neuroendocrine tumors

Although pituitary neuroendocrine tumors (PitNETs) are usually benign, some are highly invasive and recurrent. Recurrent PitNETs are often treatment-resistant and there is currently no effective evidence-based treatment. Tumor-associated macrophages (TAMs) promote tumor growth in many cancers, but the effect of TAMs on PitNETs remains unclear. This study investigated the role of TAMs in the incidence of recurrent PitNETs. Immunohistochemical analysis revealed that the densities of CD163- and CD204-positive TAMs tended to increase in recurrent PitNETs. Compared with TAMs in primary lesions, those in recurrent lesions were enlarged. To clarify the cell-cell interactions between TAMs and PitNETs, in vitro experiments were performed using a mouse PitNET cell line AtT20 and the mouse macrophage cell line J774. Several cytokines related to macrophage chemotaxis and differentiation, such as M-CSF, were elevated significantly by stimulation with macrophage conditioned medium. When M-CSF immunohistochemistry analysis was performed using human PitNET samples, M-CSF expression increased significantly in recurrent lesions compared with primary lesions. Although no M-CSF receptor (M-CSFR) expression was observed in tumor cells of primary and recurrent PitNETs, flow cytometric analysis revealed that the mouse PitNET cell line expressed M-CSFR. Cellular proliferation in mouse PitNETs was inhibited by high concentrations of M-CSFR inhibitors, suggesting that cell-to-cell communication between PitNETs and macrophages induces M-CSF expression, which in turn enhances TAM chemotaxis and maturation in the tumor microenvironment. Blocking the M-CSFR signaling pathway might be a novel therapeutic adjuvant in treating recurrent PitNETs.

Karnofsky Performance Status and quality of life in patients with relapsed or refractory primary CNS lymphoma from a phase I/II study of tirabrutinib

Background

Tirabrutinib, a second-generation inhibitor of Bruton's tyrosine kinase, was approved in March 2020 for the treatment of relapsed or refractory primary central nervous system lymphoma (r/r PCNSL) based on phase I/II studies in Japan. We previously reported the overall response rate and safety profile. We describe Karnofsky Performance Status (KPS) and the quality of life (QoL) in patients with r/r PCNSL receiving tirabrutinib based on more than 1-year follow-up data.

Methods

Patients with r/r PCNSL, age ≥20 years, and KPS ≥70 were treated with tirabrutinib once daily at a dose of 320, 480, or 480 mg under fasted conditions. QoL was assessed using questionnaires issued by the European Organization for Research and Treatment of Cancer (EORTC), namely EORTC QLQ-C30, EORTC QLQ-BN20, and EuroQol 5 dimensions 3-level (EQ-5D-3L) along with KPS.

Results

Forty-four patients (mean age, 60 years [range 29-86]) were enrolled. The median follow-up period was 14.9 months (range, 1.4-27.7). The median KPS of the patients at baseline was 80.0 (range, 70-100), and this remained constant during the treatment. The global health status/QoL in the QLQ-C30 showed significant improvements from baseline through cycles 3-17 and remained relatively constant thereafter until cycle 23. Improvements were also seen in emotional functioning and constipation in the QLQ-C30 segments. Other items of QLQ-C30 and QLQ-BN20, EQ-5D visual analog scales, and EQ-5D index were maintained during the treatment.

Conclusions

Tirabrutinib generally maintains KPS and QoL scores with some improvements in specific QoL items in patients with r/r PCNSL.

BT-5 LONG-TERM OUTCOME OF CLIVAL CHORDOMAS AT A SINGLE INSTITUTION

Purpose

Chordoma is a rare malignant tumor, about 30% of which occurs in the clivus. The purpose of this study is to investigate the outcome after treatment of clival chordoma in our institute.

Methods

Nineteen patients {M/F=11/8, mean age: 50.4 (15-72) years} who were treated between 1987 and 2021 and followed for at least 6 months were retrospectively evaluated for survival and local control rate.

Results

The cumulative survival rate was 89.2% at 5 years, 82.3% at 10 years, and 54.9% at 25 years, and the median OS was 107 (6-359) months. 4 deaths: 2 tumor deaths (1 from poorly differentiated chordoma), 2 non-tumor deaths (1 from IC rupture after heavy ion radiotherapy). The cumulative local control rate was 47.3% at 5 years and 35.5% at 10 years, with a median progression-free survival (PFS) of 41 (0-278) months. There was no difference in OS (p=0.85) or PFS (p=0.90) between the two groups, with 6 cases of gross total resection, GTR (all transsphenoidal) and 13 cases of non-GTR (9 transsphenoidal, 4 transcranial) at first surgery. In the 4 patients without irradiation (1 GTR, 3 non-GTR), no disease progression (PD) was observed, and the mean OS was 170 (69-278) months. Of the 15 patients irradiated, 6 were irradiated before PD and 9 were irradiated after PD, and there was no difference in OS or PFS between the two groups, i.e., the timing of irradiation. One patient with refractory chordoma was found to have elevated TMB levels by cancer genome testing and is currently receiving pembrolizumab, which has resulted in significant tumor shrinkage.

Conclusion

The patients with clival chordoma have a varied course, which may be due to differences in molecular biology. Cancer genome testing may provide new treatment options, such as molecularly targeted drugs and immune checkpoint inhibitors, for refractory cases.

PEDT-10 PHASE II TRIAL OF PATHOLOGY-BASED THREE-GROUP TREATMENT STRATIFICATION FOR PATIENTS WITH CNS GERM CELL TUMORS: A LONG-TERM FOLLOW-UP STUDY

Background

Phase II clinical trial funded by Ministry of Health, Labour and Welfare from 1995 to 2003 evaluated efficacy of pathology-based three-group treatment stratification for CNS germ cell tumors (GCTs). We here present long-term follow-up results.

Methods

Total 228 cases were registered. Germinoma was treated with carboplatin+etoposide (CARE) and extended-local irradiation, local irradiation was added for intermediate-prognosis-group, and poor-prognosis-group was treated with ifosfamide+cisplatin+etoposide (ICE) and whole-brain or craniospinal irradiation.

Results

Mean/median ages at diagnosis were 16.8/16 years and female-to-male ratio was 40-188. Registry included 123 germinomas, 76 intermediate-prognosis-group cases (including 38 germinoma with STGC), 28 poor-prognosis-group cases and 1 mature teratoma. Median 222-months follow-up was conducted, and 56 recurrences and 39 deaths were recorded. 10 and 20-year recurrence-free survival (RFS) for germinoma, intermediate and poor-prognosis-groups were 84/79%, 83/76% and 59/59%, respectively, and overall survival (OS) for each were 97/91%, 92/85% and 57/53%, respectively. Prognosis for germinoma with or without STGC was the same. Basal ganglia germinoma showed significantly shorter RFS but OS was not different from other locations. Median age at death was 24 years, and ages were significantly different depending on causes, such as disease-related (14 years on average) and complications (29 years). OS after recurrence at 5/10/20 years were 64/62/48%.Hormonal supplementation was seen in 82% for neurohypophyseal cases and antidiuretic hormone supplementation was most frequent (82%). Among available cases, 20-out-of-155 cases showed neoplastic/vascular complications, among which cavernous malformation was the most (n=9). Median period until complication presentation was 235 months, and the rate at 20 years was 11%.

Conclusions

Germinoma and intermediate-prognosis-group cases showed long-term survival for approximately 90%, while more intensive treatment would be necessitated for poor-prognosis-group. Long-term survivors often required hormonal supplementation, and increasing frequency of treatment-related complications was observed. There is no end of outpatient follow-up for CNS GCT patients.

Randomized phase III study of high-dose methotrexate and whole-brain radiotherapy with/without temozolomide for newly diagnosed primary CNS lymphoma: JCOG1114C

BACKGROUND

The goal was to determine whether the addition of temozolomide (TMZ) to the standard treatment of high-dose methotrexate (HD-MTX) and whole-brain radiotherapy (WBRT) for primary central nervous system lymphoma (PCNSL) improves survival.

METHODS

An open-label, randomized, phase III trial was conducted in Japan, enrolling immunocompetent patients aged 20-70 years with histologically confirmed, newly diagnosed PCNSL. After administration of HD-MTX, patients were randomly assigned to receive WBRT (30 Gy) ± 10 Gy boost (arm A) or WBRT ± boost with concomitant and maintenance TMZ for two years (arm B). The primary endpoint was overall survival (OS).

RESULTS

Between September 29, 2014 and October 15, 2018, 134 patients were enrolled, of whom 122 were randomly assigned and analyzed. At the planned interim analysis, two-year OS was 86.8% (95% confidence interval [CI]: 72.5-94.0%) in arm A and 71.4% (56.0-82.2%) in arm B. The hazard ratio was 2.18 (95% CI: 0.95 to 4.98), with the predicted probability of showing the superiority of arm B at the final analysis estimated to be 1.3%. The study was terminated early due to futility. O 6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status was measured in 115 tumors, and it was neither prognostic nor predictive of TMZ response.

CONCLUSIONS

This study failed to demonstrate the benefit of concomitant and maintenance TMZ in newly diagnosed PCNSL.

The first-in-human phase I study of a brain-penetrant mutant IDH1 inhibitor DS-1001 in patients with recurrent or progressive IDH1-mutant gliomas

BACKGROUND

Approximately 70% of lower-grade gliomas harbor isocitrate dehydrogenase 1 (IDH1) mutations, resulting in the accumulation of oncometabolite D-2-hydroxyglutarate (D-2-HG); this leads to epigenetic dysregulation, oncogenesis, and subsequent clonal expansion. DS-1001 is an oral brain-penetrant mutant IDH1 selective inhibitor. This first-in-human study investigated the safety, pharmacokinetics, pharmacodynamics, and efficacy of DS-1001.

METHODS

This was a multicenter, open-label, dose-escalation, phase I study of DS-1001 for recurrent/progressive IDH1-mutant (R132) glioma (N = 47) (NCT03030066). DS-1001 was administered orally at 125-1400 mg twice daily. Dose-escalation used a modified continual reassessment method.

RESULTS

The maximum tolerated dose was not reached. Eight patients were continuing treatment at the data cutoff. Most adverse events (AEs) were grade 1-2. Twenty patients (42.6%) experienced at least 1 grade 3 AE. No grade 4 or 5 AEs or serious drug-related AEs were reported. Common AEs (>20%) were skin hyperpigmentation, diarrhea, pruritus, alopecia, arthralgia, nausea, headache, rash, and dry skin. The objective response rates were 17.1% for enhancing tumors and 33.3% for non-enhancing tumors. Median progression-free survival was 10.4 months (95% confidence interval [CI], 6.1 to 17.7 months) and not reached (95% CI, 24.1 to not reached) for the enhancing and non-enhancing glioma cohorts, respectively. Seven on-treatment brain tumor samples showed a significantly lower amount of D-2-HG compared with pre-study archived samples.

CONCLUSIONS

DS-1001 was well tolerated with a favorable brain distribution. Recurrent/progressive IDH1-mutant glioma patients responded to treatment. A study of DS-1001 in patients with chemotherapy- and radiotherapy-naïve IDH1-mutated WHO grade 2 glioma is ongoing (NCT04458272).

Ribosomal proteins induce stem cell-like characteristics in glioma cells as an "extra-ribosomal function"

The characteristic features of plasticity and heterogeneity in glioblastoma (GB) cells cause therapeutic difficulties. GB cells are exposed to various stimuli from the tumor microenvironment and acquire the potential to resist chemoradiotherapy. To investigate how GB cells acquire stem cell-like phenotypes, we focused on ribosomal proteins, because ribosome incorporation has been reported to induce stem cell-like phenotypes in somatic cells. Furthermore, dysregulation of ribosome biogenesis has been reported in several types of cancer. We focused on ribosomal protein S6, which promotes sphere-forming ability and stem cell marker expression in GB cells. We expect that investigation of dysregulation of ribosome biogenesis and extra-ribosomal function in GB will provide new insights about the plasticity, heterogeneity, and therapeutic resistance of GB cells, which can potentially lead to revolutionary therapeutic strategies.

Hybrid deep-learning-based denoising method for compressed sensing in pituitary MRI: comparison with the conventional wavelet-based denoising method

OBJECTIVES

This study aimed to evaluate the efficacy of a combined wavelet and deep-learning reconstruction (DLR) method for under-sampled pituitary MRI.

METHODS

This retrospective study included 28 consecutive patients who underwent under-sampled pituitary T2-weighted images (T2WI). Images were reconstructed using either the conventional wavelet denoising method (wavelet method) or the wavelet and DLR methods combined (hybrid DLR method) at five denoising levels. The signal-to-noise ratio (SNR) of the CSF, hypothalamic, and pituitary images and the contrast between structures were compared between the two image types. Noise quality, contrast, sharpness, artifacts, and overall image quality were evaluated by two board-certified radiologists. The quantitative and the qualitative analyses were performed with robust two-way repeated analyses of variance.

RESULTS

Using the hybrid DLR method, the SNR of the CSF progressively increased as denoising levels increased. By contrast, with the wavelet method, the SNR of the CSF, hypothalamus, and pituitary did not increase at higher denoising levels. There was a significant main effect of denoising methods (p < 0.001) and denoising levels (p < 0.001), and an interaction between denoising methods and denoising levels (p < 0.001). For all five qualitative scores, there was a significant main effect of denoising methods (p < 0.001) and an interaction between denoising methods and denoising levels (p < 0.001).

CONCLUSIONS

The hybrid DLR method can provide higher image quality for T2WI of the pituitary with compressed sensing (CS) than the wavelet method alone, especially at higher denoising levels.

KEY POINTS

• The signal-to-noise ratios of cerebrospinal fluid progressively increased with the hybrid DLR method, with an increase in the denoising level for cerebrospinal fluid in pituitary T2WI with CS. • The signal-to-noise ratios of cerebrospinal fluid using the conventional wavelet method did not increase at higher denoising levels. • All qualitative scores of hybrid deep-learning reconstructions at all denoising levels were higher than those for the wavelet denoising method.

Atypical pituitary abscess lacking rim enhancement and diffusion restriction with an unusual organism, Moraxella catarrhalis: A case report and review of the literature

Background:

Pituitary abscess (PA) can be fatal if diagnosed late. Rim enhancement is a typical radiological finding of PA on postgadolinium T1-weighted magnetic resonance imaging (MRI). Diffusion-weighted imaging is helpful in distinguishing PA from other sellar cystic lesions. Herein, we report the first atypical case of PA showing neither rim enhancement nor diffusion restriction with an unusual organism, Moraxella catarrhalis.

Case Description:

A 77-year-old woman presented with headache, polyuria, polydipsia, and fatigue for a month before presenting to a local hospital. MRI showed pituitary enlargement with contrast enhancement. She had neither fever nor visual deficits and was followed up with hormonal replacement. Six months later, she complained of visual impairment, and MRI showed further pituitary enlargement with a thickened stalk compressing the optic chiasma. Neither rim enhancement nor diffusion restriction was observed. Endoscopic endonasal transsphenoidal surgery was performed based on the radiological diagnosis of lymphocytic hypophysitis or pituitary tumors. A thick, creamy yellow pus was drained from the sellar lesion. Intraoperative rapid histopathological findings revealed polymorphonuclear leukocytes infiltrating the pituitary gland. PA was diagnosed, and irrigation and open drainage of the abscess was performed. Bacterial culture of the pus detected M. catarrhalis by mass spectrometer, confirming the diagnosis. She underwent appropriate antibiotic administration, and her visual deficits improved.

Conclusion:

We report the first atypical case of PA showing neither rim enhancement nor diffusion restriction with M. catarrhalis. Even if preoperative findings are not suggestive of PA, it should be considered as a differential diagnosis. Intraoperative rapid histopathological findings are useful for accurately diagnosing PA and initiating appropriate surgical treatment.

CS-6 A case of poorly differentiated chordoma with systemic metastasis

A case report: The patient was a 32-year-old man with diplopia. He was diagnosed as sphenoid sinusitis on MRI by a local doctor and visited an otolaryngologist. MRI showed extensive extension of neoplastic lesions from the clivus to the sphenoid sinus to the anterior ethmoid sinuses, bilateral cavernous sinuses, and the right medial and lateral pterygoid muscles. The right Lebiere’s lymph node was enlarged and thought to be a metastatic site. Based on the rapid growth and extension of the tumor, the patient was referred to the Department of Otolaryngology at our hospital on suspicion of sinonasal carcinoma. The possibility of chordoma could not be denied, so the patient was referred to our department. The patient underwent a joint endoscopic extended transsphenoidal tumor resection. The pathological diagnosis showed mitotic and necrotic features, and the majority of the cells showed highly atypical components without mucous substrate. However, brachyury, a marker for chordoma, was diffusely positive, and there was loss of INI1 (SMARCB1) expression. The final diagnosis was poorly differentiated chordoma. Postoperatively, the tumor in the right cavernous sinus grew rapidly, and the right eye became blind due to obstruction of the superior ophthalmic vein. The patient was treated with Gamma Knife as soon as possible in the hope of local control by high-dose irradiation, and after a total of three irradiations, the residual tumor shrank markedly and symptoms improved, but systemic metastasis occurred in a short period of time and the patient died. The number of cases of poorly differentiated chordoma has been reported rarely (more than 50), and it is more common in children and even rarer in adults. We report this case with a review of the literature.

MPC-7 Clinical features of Diffuse hemispheric glioma, H3 G34-mutant in children and young adults

INTRODUCTION: H3F3A G34R/V mutated gliomas are seen predominantly in children and young adults, and have been proposed as “Diffuse hemispheric glioma, H3 G34-mutant” in cIMPACT-NOW Update 6. However, the clinical features of the tumor have not been fully elucidated.

METHODS: We retrospectively reviewed 4 cases with H3G34R mutation among 40 cases diagnosed as glioblastoma under 30 years old or primitive neuroectodermal tumor (PNET) in our hospital.

RESULTS: There were one male and three female patients with a median age of 21.5 years (range: 17–27 years). All lesions were localized in the cerebral hemispheres, and the initial symptoms were headache in two cases and seizures in two cases. On imaging, there was one case with poor contrast, and unlike the infiltrative growth pattern of the other three contrasted cases, it showed a well-defined mass lesion. DWI showed high signal in all four cases, reflecting the high cell density in histopathology. All cases were IDH-wildtype.

CONCLUSION: Although the patient background and genetic characteristics of the glioma with H3 G34R/V mutation at our institution were generally consistent with previous reports, there were some cases with atypical imaging findings. Further investigation is required for a deeper understanding of the clinical features of this tumor.

ML-17 Clinical usefulness of Tirabrutinib in recurrent PCNSL: single institute experience

Background: Primary central nervous system lymphoma (PCNSL) is a lymphoma whose primary lesion is localized in the brain and spinal cord. Treatment is a combination of high-dose methotrexate-based chemotherapy and whole-brain irradiation, often leading to recurrence. Pathologically, non-GCB type diffuse large B-cell lymphoma (DLBCL) predominates. In DLBCL, constitutive activation of B cell receptor signal (BCR) is the tumor mechanism of tumor development and growth. Tirabrutinib is an inhibitor of Bruton’s tyrosine kinase (BTK) located downstream of BCR. In a phase I / II study, an overall response rate was 64%. Currently, Tirabrutinib is used to treat relapsed or refractory PCNSL. Purpose: Tirabrutinib is a drug that has just been approved, and there are few reports of its use in clinical practice. We report on our experience with Tirabrutinib with a review of the literature. Methods: We retrospectively examined the clinical course of 11 recurrent PCNSL patients treated with Tirabrutinib at our institution. Results: The average age of the subjects was 68.7 years, and 7 cases were male. Tirabrutinib 480 mg was administered in all cases. The response rate was 60% (6/10 cases). The median progression-free survival was 4.3 months. The adverse events were Grade 3 neutropenia in 1 patient and Grade 2 skin disorder in 4 patients. Treatment was discontinued in 5 of the 11 patients due to the progression of the disease. Due to the eruption, Tirabrutinib was reduced to 320 mg in 1 patient and discontinued in 1 patient. Treatment was discontinued at the request of the patient in 1 case, and four patients are still on medication. Summary: According to the results we obtained, the response rate was the same as that in the phase I / II study, and the progression-free survival was slightly longer.

COT-18 Trends in Primary Brain Tumors in Kumamoto Prefecture with Declining Birthrate and Aging Population - Kumamoto Prefecture Brain Tumor Epidemiological Survey

Backgrounds: The demographic characteristics of Kumamoto Prefecture are that there is little population movement and the total population remains constant at about 1.8 million, but in recent years the birthrate is declining and the population is aging. We have been conducting the Kumamoto Prefecture Brain Tumor Epidemiological Survey since 1989 in cooperation with neurosurgical institutions in the prefecture. In this study, we examined whether recent demographic changes have affected the incidence of primary brain tumors (BT). Methods: Patients with primary BT were collected annually from 44 institutions in Kumamoto Prefecture (as of 2020), and the number of incidences per 100,000 population was calculated for each BT for each year, excluding patients living outside the prefecture and duplicate cases. Results: The total number of primary BT was 11441 (top 3: meningioma 40%, pituitary adenoma 17%, glioma 17%). Of 4261 men with primary BT, the top 3 were meningioma (27%), glioma (23.7%), and pituitary adenoma (18.4%)), and 7180 women (top 3: meningioma (47.7%), pituitary adenoma (16.2%), and glioma (12.9%)). The number of primary BT increased every year, and the incidence increased significantly when comparing 1989–2004 and 2005–2020 (13.6 vs. 25.0/100,000, p<0.000001). Typical brain tumors (meningioma, pituitary adenoma, glioma, schwannoma, malignant lymphoma) also increased year by year, especially asymptomatic meningioma. The median age of asymptomatic meningiomas was significantly higher than that of symptomatic meningiomas (69 vs. 65 years, p<0.0001). Gliomas increased significantly in the later stages compared with the early stages in children (0–14 years) and the elderly (65 years and older). Conclusion: Our results suggest that an increase in the number of BT such as glioblastoma, which are more common in the elderly, as well as an increase in the number of opportunities for intracranial examinations in the aging of the population may be responsible for the increased incidence of primary BT.

PEDT-5 Problem for the guideline of CNS germ cell tumors

Primary CNS germ cell tumors (GCTs) are rare neoplasms, therefore, a clinical guideline has not been established so far. While better management has been achieved over recent decades by modifying radiation coverage and selecting appropriate chemotherapy, standardization of treatment remains challenging, partly due to the low volume of cases encountered in each institution. As the incidence is higher in East Asia, including Japan, the Japan Society for Neuro-Oncology established a multidisciplinary task force to create an evidence-based guideline for CNS GCTs. The Medical Information Network Distribution Service (Minds) guideline was referred to and utilized in the course of creating this guideline. We chose 6 topics and 10 clinical questions. This guideline provides recommendations for multiple dimensions of clinical management for CNS GCTs, with particular focus on diagnostic measures including serum markers, treatment algorithms including surgery, radiotherapy and chemotherapy, and under-investigated but important areas such as treatment for recurrent cases, long-term follow-up protocols and long-term sequelae. International collaborations to set standards of clinical management for this rare tumor have proven fruitful, concurrently, many fields continue to show variance in clinical practice, partly due to the rarity of clinical encounters and the absence of documented standards. There still seem to be differences in the treatment concept between Japan and North America or Europe countries. This guideline serves the purpose of helping healthcare professionals keep up to date with current knowledge and standards of management for patients with this rare disease in daily clinical practice, as well as driving future translational and clinical research by recognizing unmet needs concerning this tumor. We discuss about the issues both already clarified and should be cleared in the future.

IM-8 Significance of IL-1 pathways in Glioblastoma

Purpose: Previous studies have revealed that macrophages affect the prognosis of glioblastoma. However, there are still many unknown parts about the mechanism. In this study, we conducted an experiment with the aim of elucidating the mechanism by which tumor associated macrophages (TAM) work on tumors in the tumor microenvironment (TME).

Method: Experiments were carried out using two glioblastoma cell strains, T98G, and U251. For clinical data, we analyzed it based on databases such as Protein Atlas, Ivy Glioblastoma Atlas, brain TIME database.

Results: In 3D culture, we confirmed that IL-1β stimulation promoted glioblastoma cell proliferation and sphere formation. The addition of IL-1β increased mRNA expression of various cytokines such as IL-6 and CXCL8, and increased phosphorylation of STAT3 in arrays. When we administered IL-6 and CXCL8, the growth was significantly increased in cells administered with IL-6 and CXCL8. As a result, we speculated that STAT3 pathway and NFκB pathway via IL-6 and CXCL8 are involved in cell proliferation by IL-1β. In order to confirm these things, western blot was performed, and it was confirmed that phosphorylation of STAT3 and NFκB were increased. In addition, STAT3 inhibitors and NFκB inhibitors suppressed tumor growth. Clinically analysis was carried out based on the database, and it was found that IL-1β and macrophages were related. Furthermore, IL-1β was found in many cases around tumor necrosis.

Discussion: This study clarifies some of the effects of IL-1β on glioblastoma. However, there are still many unknown points, and it is necessary to continue to consider them in the future.

The Japan Society for Neuro-Oncology Guideline on the Diagnosis and Treatment of Central Nervous System Germ Cell Tumors

Primary CNS germ cell tumors (GCTs) are rare neoplasms predominantly observed in the pediatric and young adult populations. In line with the hypothesis that the primordial germ cell is the cell-of-origin, histopathological examinations for this pathology involve a diverse range of components mirroring the embryogenic developmental dimensions. Chemotherapy and radiotherapy are the mainstays of treatment, with surgery having a limited role for diagnosis and debulking of residual tissue after treatment. While better management has been achieved over recent decades by modifying radiation coverage and selecting appropriate chemotherapy, standardization of treatment remains challenging, partly due to the low volume of cases encountered in each institution. As the incidence is higher in East Asia, including Japan, the Japan Society for Neuro-Oncology established a multidisciplinary task force to create an evidence-based guideline for CNS GCTs. This guideline provides recommendations for multiple dimensions of clinical management for CNS GCTs, with particular focus on diagnostic measures including serum markers, treatment algorithms including surgery, radiotherapy and chemotherapy, and under-investigated but important areas such as treatment for recurrent cases, long-term follow-up protocols and long-term sequelae. This guideline serves the purpose of helping healthcare professionals keep up to date with current knowledge and standards of management for patients with this rare disease in daily clinical practice, as well as driving future translational and clinical research by recognizing unmet needs concerning this tumor.

Macrophage/microglia-derived IL-1β induces glioblastoma growth via the STAT3/NF-κB pathway

Glioblastoma is a glioma characterized by highly malignant features. Numerous studies conducted on the relationship between glioblastoma and the microenvironment have indicated the significance of tumor-associated macrophages/microglia (TAMs) in glioblastoma progression. Since interleukin (IL)-1β secreted by TAMs has been suggested to promote glioblastoma growth, we attempted to elucidate the detailed mechanisms of IL-1β in glioblastoma growth in this study. A phospho-receptor tyrosine kinase array and RNA-sequencing studies indicated that IL-1β induced the activation of signal transducer and activator of transcription-3 and nuclear factor-kappa B signaling. Glioblastoma cells stimulated by IL-1β induced the production of IL-6 and CXCL8, which synergistically promoted glioblastoma growth via signal transducer and activator of transcription-3 and nuclear factor-kappa B signaling. By immunohistochemistry, IL-1β expression was seen on TAMs, especially in perinecrotic areas. These results suggest that IL-1β might be a useful target molecule for anti-glioblastoma therapy.

Necessity for craniospinal irradiation of germinoma with positive cytology without spinal lesion on MR imaging-A controversy

Background

Cerebrospinal fluid (CSF) cytology and spinal MR imaging are routinely performed for staging before treatment of intracranial germinoma. However, the interpretation of the results of CSF cytology poses 2 unresolved clinical questions: (1) Does positive CSF cytology correlate with the presence of spinal lesion before treatment? and (2) Is craniospinal irradiation (CSI) necessary for patients with positive CSF cytology in the absence of spinal lesion?

Methods

Multicenter retrospective analyses were performed based on a questionnaire on clinical features, spinal MR imaging finding, results of CSF cytology, treatments, and outcomes which was sent to 86 neurosurgical and 35 pediatrics departments in Japan. Pretreatment frequencies of spinal lesion on MR imaging were compared between the patients with positive and negative cytology. Progression-free survival (PFS) rates were compared between patients with positive CSF cytology without spinal lesion on MR imaging treated with CSI and with whole brain or whole ventricular irradiation (non-CSI).

Results

A total of 92 germinoma patients from 45 institutes were evaluated by both CSF cytology and spinal MR images, but 26 patients were excluded because of tumor markers, the timing of CSF sampling or incomplete estimation of spinal lesion. Of the remaining 66 germinoma patients, spinal lesions were equally identified in patients with negative CSF cytology and positive cytology (4.9% and 8.0%, respectively). Eleven patients treated with non-CSI had excellent PFS comparable to 11 patients treated with CSI.

Conclusion

CSI is unnecessary for germinoma patients with positive CSF cytology without spinal lesions on MR imaging.

[Epidemiology for Glioma]

Recently, Japan's population has been aging with a declining birth rate at an unprecedented rate compared to that worldwide, and Kumamoto Prefecture is no exception. In this chapter, we examine whether the recent changes in vital statistics have affected the incidence of glioma based on data from the latest Kumamoto Prefecture Brain Tumor Data Bank. We compare the age-adjusted incidence of glioma extracted from the Brain Tumor Registry of Japan and Central Brain Tumor Registry of the United States(CBTRUS)for the period from 1990 to 2017 when data on the annual transition of the population composition in Kumamoto Prefecture were obtained. This chapter also outlines whether there are differences in survival rates between Japan and the United States. We hope that this chapter will help you determine the future direction of glioma treatment in Japan.

Phase I/II study of tirabrutinib, a second-generation Bruton's tyrosine kinase inhibitor, in relapsed/refractory primary central nervous system lymphoma

Background

The safety, tolerability, efficacy, and pharmacokinetics of tirabrutinib, a second-generation, highly selective oral Bruton’s tyrosine kinase inhibitor, were evaluated for relapsed/refractory primary central nervous system lymphoma (PCNSL).

Methods

Patients with relapsed/refractory PCNSL, Karnofsky performance status ≥70, and normal end-organ function received tirabrutinib 320 and 480 mg once daily (q.d.) in phase I to evaluate dose-limiting toxicity (DLT) within 28 days using a 3 + 3 dose escalation design and with 480 mg q.d. under fasted conditions in phase II.

Results

Forty-four patients were enrolled; 20, 7, and 17 received tirabrutinib at 320, 480, and 480 mg under fasted conditions, respectively. No DLTs were observed, and the maximum tolerated dose was not reached at 480 mg. Common grade ≥3 adverse events (AEs) were neutropenia (9.1%), lymphopenia, leukopenia, and erythema multiforme (6.8% each). One patient with 480 mg q.d. had grade 5 AEs (pneumocystis jirovecii pneumonia and interstitial lung disease). Independent review committee assessed overall response rate (ORR) at 64%: 60% with 5 complete responses (CR)/unconfirmed complete responses (CRu) at 320 mg, 100% with 4 CR/CRu at 480 mg, and 53% with 6 CR/CRu at 480 mg under fasted conditions. Median progression-free survival was 2.9 months: 2.1, 11.1, and 5.8 months at 320, 480, and 480 mg under fasted conditions, respectively. Median overall survival was not reached. ORR was similar among patients harboring CARD11, MYD88, and CD79B mutations, and corresponding wild types.

Conclusion

These data indicate favorable efficacy of tirabrutinib in patients with relapsed/refractory PCNSL.

Trial registration

JapicCTI-173646.

So-called bifocal tumors with diabetes insipidus and negative tumor markers: are they all germinoma?

BACKGROUND

The Delphi consensus statements on the management of germ cell tumors (GCTs) failed to reach agreements on the statement that the cases with (i) pineal and neurohypophyseal bifocal lesion, (ii) with diabetes insipidus, and (iii) with negative tumor markers can be diagnosed as germinoma without histological verification. To answer this, multicenter retrospective analysis was performed.

METHODS

A questionnaire on clinical findings, histological diagnosis, and details of surgical procedures was sent to 86 neurosurgical and 35 pediatrics departments in Japan.

RESULTS

Fifty-one institutes reported 132 cases that fulfilled the 3 criteria. Tissue sampling was performed in 91 cases from pineal (n = 44), neurohypophyseal (n = 32), both (n = 6), and distant (n = 9) lesions. Histological diagnosis was established in 89 cases: pure germinoma or germinoma with syncytiotrophoblastic giant cells in 82 (92.1%) cases, germinoma and mature teratoma in 2 cases, and granulomatous inflammation in 2 cases. Histological diagnosis was not established in 2 cases. Although no tumors other than GCTs were identified, 3 (3.4%) patients had non-germinomatous GCTs (NGGCTs). None of the patients developed permanent complications after endoscopic or stereotactic biopsy. Thirty-nine patients underwent simultaneous procedure for acute hydrocephalus without permanent complications, and hydrocephalus was controlled in 94.9% of them.

CONCLUSION

All patients who fulfilled the 3 criteria had GCTs or granulomatous inflammation, but not other types of tumors. However, no fewer than 3.4% of the patients had NGGCTs. Considering the safety and the effects of simultaneous procedures for acute hydrocephalus, biopsy was recommended in such patients.

EPEN-02. EVALUATION OF TREATMENT OUTCOMES AND EXPRESSION OF EMT-RELATED TRANSCRIPTION FACTORS AS NOVEL THERAPEUTIC TARGETS IN PEDIATRIC EPENDYMOMA

OBJECTIVE

Intracranial ependymomas are common brain tumors in children. However, prognosis, especially in young children, remains poor because of the chemo- and radioresistant properties of intracranial ependymomas. Furthermore, effective treatments for intracranial ependymomas remain a challenge. The epithelial-to-mesenchymal transition (EMT) is important for invasion and metastasis in many cancers. This study aimed to evaluate and compare treatment outcomes with the expression of EMT-related transcription factors in pediatric ependymomas.

MATERIAL AND METHODS

Medical and radio-imaging data of 22 (11 boys, 11 girls) patients aged <15 years with intracranial ependymomas were reviewed from January 1983 to December 2018. Six cases were subdivided into clinicopathological-molecular subgroups and immunohistochemically analyzed for Slug and ZEB.

RESULTS

The median age at the start of treatment was 5 years (range 8 months–15 years) (9 cases were aged <3 years). The median progression-free survival (PFS) was 25.6 (range, 0.8–383.5) months; the median overall survival (OS) was 81.9 (range, 2.9–383.5) months. Extent of resection and malignant histology were significant prognostic factors for OS and PFS in multivariate analysis. There were 6 cases (2 cases of PFA, 2 of PFB, 1 of ST and 1 case of ST-RELA). Nuclear expression of ZEB1 was found in all tumors; however, that of Slug increased only in PFA and PFB tumors, which were associated with a poor prognosis.

CONCLUSION

Expression of EMT-related transcription factors was increased in pediatric ependymomas. These data suggest that EMT is a novel therapeutic target for treating pediatric intracranial ependymomas.

GCT-36. TREATMENT RESULTS AND RADIATION-INDUCED TUMORS IN CASES OF CENTRAL NERVOUS SYSTEM GERM CELL TUMOR: A LONG-TERM FOLLOW-UP STUDY IN KUMAMOTO PREFECTURE

INTRODUCTION

Central nervous system germ cell tumor (GCT) is one of the pediatric brain tumors. Although there have been epidemiological studies in the past, long-term prognosis and the late effects remained unclear. In this study, we examined GCT over the past 41 years in Kumamoto prefecture.

METHODS

Epidemiological features and complications with radiation-induced tumors were searched in patients diagnosed with GCT in the 41-year period from 1977 to 2018.

RESULTS

There were 93 patients diagnosed with GCT. These cases were divided into 14-year periods before and after incorporation of chemotherapy into the treatment, and the results for germinomas were compared. An improvement in the 10-year survival rate from 12 of 23 cases (52.2%) between 1977 and 1991 to 19 of 28 cases (67.9%) between 1992 and 2006 was observed. The 10-year survival rate for germinoma cases that received medical treatment during a more recent 5-year period between 2004 and 2009 increased to over 90%. However, 10.3% of all long-term survivors of GCT developed radiation-induced glioblastoma. The examination results showed that regardless of the tumor type, patients who received a high dose of radiation during their initial treatment developed the complication of radiation-induced glioblastoma within 10 to 25 years after their initial treatment.

CONCLUSION

This study suggests that the long-term survival rates for GCT are improving but the rate of radiation-induced glioblastoma in these cases are too high to be ignored. Long-term follow-up of at least 10 years is essential to effectively evaluate the details of treatment for pediatric brain tumors.

EPID-01. TRENDS OF INCIDENCE IN PEDIATRIC BRAIN TUMORS IN KUMAMOTO PREFECTURE, JAPAN

BACKGROUND/PURPOSE

One of the most problematic issues Japan has is a declining birthrate resulting in an aging society. There are some reports on the trends of incidence in brain tumors in the elderly, whereas few reports on those in the children. The aim of this study is to investigate the trends of incidence in childhood primary brain tumors.

METHODS

The population of children aged &lt;15 years was available from Kumamoto Prefecture’s annual census between 1990 and 2017. During the period 301 childhood primary brain tumors (124 gliomas, including astrocytic tumors and ependymomas, 35 embryonal tumors, 34 germ cell tumors, 22 craniopharyngioma, and 86 others) were registered with the Kumamoto Brain Tumor Data Bank, and investigated.

RESULTS

The average of the annual incidence rate per 100,000 child populations was 3.90 for total brain tumors, 1.63 for gliomas, 0.44 for embryonal tumors, 0.42 for germ cell tumors, 0.26 for craniopharyngioma, and 1.15 for others. Divided into the first half from 1990 to 2003 and the second half from 2004 to 2017, there was no significant difference in the incidence of brain tumors aged &lt;15 years between the two periods. However, the average of the annual incidence rate/100,000 child populations was 3.02 in the first half, while significantly increased in the second half of 4.78 (p=0.00075, t-test). DISCUSSION &

CONCLUSIONS

The average number of children aged &lt;15 years in Kumamoto Prefecture was 31,2737.9 from 1990 to 2003, while decreased remarkably to 251460.2 from 2004 to 2017. A decrease in the number of children may affect increasing the incidence rate of pediatric brain tumors.

ML-20 Outcome of high-dose methotrexate-based chemotherapy with or without Rituximab for primary central nervous system lymphoma

High-dose methotrexate based chemotherapy(HD-MTX) improved outcome of primary central nervous system lymphoma(PCNSL), but the prognosis is still poor. Recent studies showing that Rituximab is very effective for systemic lymphoma, the role of Rituximab for PCNSL is unclear. 34 patients diagnosed PCNSL received HD-MTX chemotherapy adding rituximab. Response rates were 74%(20/27) for newly diagnosed PCNSL patients, 85.7%(6/7) for recurrent PCNSL patients. Major side effects were infusion reaction and respiratory infections disease. We have to compare the outcome of HD-MTX chemotherapy retrospectively.

ML-15 The future direction of treatment development for primary central nervous system lymphoma (PCNSL)

Purpose: We found that the combination of high-dose Methotrexate (HD-MTX)-based therapy and histone deacetylase inhibitor (HDACI) had a therapeutic effect on PCNSL. In addition, this year, tirabrutinib, a Bruton’s tyrosine kinase inhibitor, was approved for marketing as a single agent for relapsed/refractory PCNSL, and new therapeutic development is expected. We will examine the treatment results of PCNSL in our department retrospectively and discuss the future direction of treatment development. METHODS: From 2001 to 2014, 82 newly diagnosed PCNSL patients treated with HD-MTX/Procarbazine (MP) as initial remission induction chemotherapy were retrospectively analyzed. RESULTS: Complete response (CR) was obtained in 38 patients (46.3%) after initial chemotherapy, and the median overall survival (OS) in the CR and non-CR groups was 2636 days and 728 days, respectively, and significantly shorter in the non-CR group (p&lt;0.01). In the CR group, 27 cases (71.1%) recurred and 12 cases received HD-MTX re-challenge (M-re), 14 cases received treatment other than M-re (1 case did not receive treatment), the median OS after relapse was 590 days. The median post-relapse progression-free survival (PFS) of the 10 patients undergoing M-re at the first relapse was 116 days, the median OS after relapse was 590 days. The median post-relapse PFS of 16 patients receiving other treatments was 428 days, the median OS after relapse was 532 days. There was no difference in PFS and OS after recurrence in treatment at the first recurrence (p=0.15, p=0.55). Conclusion: The OS of non-CR patients in the initial chemotherapy and the OS after recurrence after CR were short. The possible directions of PCNSL treatment development include 1) increasing the CR rate with initial chemotherapy and maintaining CR for a long time for newly diagnosed PCNSL, and 2) finding an effective treatment for recurrence. New drugs such as tirabrutinib and HDACIs may be breakthroughs.

ML-05 One-year follow-up data of phase I/II study of tirabrutinib in patients with relapsed or refractory primary central nervous system lymphoma

In March 2020, Tirabrutinib (TIR), a second-generation oral Bruton’s tyrosine kinase inhibitor, was approved for the indication of relapsed or refractory PCNSL (r/rPCNSL) based on the results of a phase I/II study in Japan. In this study, 44 Japanese patients with r/rPCNSL were treated with TIR QD at 320 mg, 480 mg, or 480 mg in the fasted condition (480 mg fasted QD). The primary endpoint was overall response rate (ORR) assessed by an independent review committee according to International PCNSL Collaborative Group criteria. We previously reported the results of this study with data cutoff in June 2019 (Narita et al. Neuro Oncol. 2020). In the report, 17 of 44 patients were treated with TIR at 480 mg fasted QD which is an approved dose, and had ORR of 52.9%, median progression-free survival of 5.8 months, and median overall survival of not reached (median follow-up: 3.8 months). In 44 patients, ORR was similar among patients harboring either of the oncogenic mutants CARD11, MYD88, CD79B, or wild type. Throughout the whole patients, most common adverse events (AEs) at any grade were rash (31.8%), neutropenia (22.7%), leukopenia (18.2%), and lymphopenia (15.9%), and grade ≥3 AEs were neutropenia (9.1%), lymphopenia, leukopenia, and erythema multiforme (6.8% each). One patient with 480 mg QD had grade 5 AEs (pneumocystis jirovecii pneumonia and interstitial lung disease). We will present one-year follow-up data of this study at the meeting. As of data cutoff (February 2020), 11 of 44 patients continued to receive TIR, including 6 patients with 480 mg fasted QD. Updated data for overall survival, duration of response, and time to onset of AEs will also be presented. TIR is a promising new treatment for r/rPCNSL.

CBMS-09 Intercellular communication at glioblastoma stem cell niches

Glioblastoma multiforme (GBM) contains heterogenous population of cells including a small population of GBM stem cells (GSCs), which potentially cause therapeutic resistance and tumor recurrence. GSCs harbored in special microenvironments, such as perinecrotic niche, perivascular niche, border niche. However, the mechanisms underlying the pathogenesis and maintenance of GSCs remain largely unknown. Stemness and chemo-radioresistance was promoted by not only additional mutation, but also microenvironment of GBM cells. Previously, we had reported that growth factors and cytokines secreted by oligodendrocyte lineage cells and macrophages/microglia induce stemness and chemo-radioresistance into GBM cells. Recently, Ito et al. reported that incorporation of ribosomes and ribosomal proteins into somatic cells promoted lineage trans-differentiation toward multipotency. Ribosomal proteins exist intra- and extracellularly. There is a possibility that ribosomal proteins promote stemness into cancer cells, we focused on 40S ribosomal protein S6 (RPS6), which is related to cell proliferation in lung and pancreatic cancer, but not reported in GBM. RPS6 was significantly upregulated in high-grade glioma. SiRNA-mediated RPS6 knock-down significantly suppressed the characteristics of GSCs, including their tumorsphere potential and stemness marker expression, such as Nestin and Sox2. RPS6 overexpression enhanced the tumorsphere potential of GSCs. Moreover, RPS6 expression was significantly correlated with SOX2 expression in different glioma grades. Immunohistochemistry data indicated that RPS6 was predominant detected at GSC niches, concurrently with the data from IVY GAP databases. Furthermore, RPS6 and other ribosomal proteins were upregulated in GSC-predominant areas in this database. The present results indicate that, in GSC niches, ribosomal proteins play crucial roles in the development and maintenance of GSCs and are clinically associated with chemo-radioresistance and GBM recurrence. These results suggested that intercellular communications through growth factors, cytokines, and ribosomes are regarded as new treatment targets of GBM.

NIMG-29. DEVELOPING AUTOMATIC SEGMENTATION METHOD FOR BRAIN TUMOR MR IMAGES THAT CAN BE USED AT MULTIPLE FACILITIES

BACKGROUND

Manual segmentation of brain tumor images from a large volume of MR images generated in clinical routines is difficult and time-consuming. Hence, it is imperative to develop a machine learning model for automated segmentation of brain tumor images.

PURPOSE

Machine learning models for automated MR image segmentation of gliomas may be useful. However, the image differences among facilities cause performance degradation and impede successful automatic segmentation. In this study, we proposed a method to solve this issue.

METHODS

We used the data from the Multimodal Brain Tumor Image Segmentation Benchmark (BraTS) and the Japanese cohort (JC) datasets collected from 10 facilities. Three models for tumor segmentation were developed. The BraTS model was trained on the BraTS dataset, and the JC model was trained on the JC dataset; whereas, the Fine-tuning model was a fine-tuned BraTS model using the JC dataset.

RESULTS

MR images of 544 patients were obtained for the JC dataset. Half of the JC dataset was used for independent testing. The Dice coefficient score of the JC model for the JC dataset was 0.779± 0.137, whereas that of the BraTS model was remarkably lower (0.717 ± 0.207). The mean of the Fine-tuning models for the JC dataset was 0.769 ± 0.138. There was a significant difference between the BraTS and JC models (P &lt; 0.0001) and the BraTS and Fine-tuning models (P = 0.002); however, no significant difference was observed between the JC and Fine-tuning models (P = 0.673).

CONCLUSIONS

Application of the BraTS model to heterogeneous datasets can significantly reduce its performance; however, fine-tuning can solve this issue. Since our fine-tuning method only requires less than 20 cases, this methodology is particularly useful for a facility where there are a few glioma cases.

A case of suprasellar Erdheim-Chester disease and characterization of macrophage phenotype

Erdheim-Chester disease (ECD) is a non-Langerhans form of histiocytosis that occurs in systemic organs, such as bone, the central nervous system, cardiovascular system, lungs, and kidneys. We report the case of a 68-year-old woman with a cranial pharyngeal tumor and a bone lesion in the tibia. The case was diagnosed as ECD. Pathological analysis showed the typical feature of foamy macrophage accumulation. The macrophages were positive for CD68, and negative for CD1a and S100. The BRAF V600E mutation was identified. In addition, immunohistochemistry was performed for the detailed characterization of the macrophages. The macrophages had low proliferative activity and an M2-like phenotype, and they expressed colony-stimulating factor-1 receptor (CSF1R) on the cell surface.

Histone deacetylase inhibition enhances the therapeutic effects of methotrexate on primary central nervous system lymphoma

Background

Polyglutamylation is a reversible protein modification that commonly occurs in tumor cells. Methotrexate (MTX) in tumor cells is polyglutamylated and strongly binds to dihydrofolate reductase (DHFR) without competitive inhibition by leucovorin. Therefore, tumor cells with high polyglutamylation levels are supposed to be selectively killed, whereas normal cells with lower polyglutamylation are rescued by leucovorin. This study investigated the combined effects of MTX plus histone deacetylase inhibitors (HDACIs), which upregulate MTX polyglutamylation, in primary central nervous system lymphoma (PCNSL).

Methods

We evaluated cell viability after MTX treatment and leucovorin rescue and compared the expression of folylpolyglutamate synthetase (FPGS), γ-glutamyl hydrolase (GGH), and DHFR in 2 human PCNSL-derived cell lines (HKBML and TK) and a human Burkitt lymphoma cell line (TL-1). Combination treatments were created using 4 HDACIs: panobinostat, vorinostat, sodium butyrate, and valproic acid. The expression of DHFR was examined as well as ratios of FPGS/GGH expression. The combined effects of MTX plus HDACIs were evaluated using a cell viability assay, mass spectroscopy imaging, and subcutaneous and intracranial xenograft models.

Results

HDACIs upregulated the ratio of FPGS/GGH expression resulting in increased polyglutamylation of MTX, but also downregulated expression of the target molecule of MTX: DHFR. The combination of MTX and vorinostat decreased cell viability in vitro (P < .05) and tumor volumes in a subcutaneous model (P < .0001), and prolonged survival in an intracranial model (P < .01), relative to controls.

Conclusion

HDACIs enhanced the therapeutic effect of MTX through increased polyglutamylation of MTX and concomitant downregulation of DHFR expression.

Ribosomal protein S6 promotes stem-like characters in glioma cells

Glioblastoma multiforme (GBM), a lethal brain tumor developing in the white matter of the adult brain, contains a small population of GBM stem cells (GSCs), which potentially cause chemotherapeutic resistance and tumor recurrence. However, the mechanisms underlying the pathogenesis and maintenance of GSCs remain largely unknown. A recent study reported that incorporation of ribosomes and ribosomal proteins into somatic cells promoted lineage trans-differentiation toward multipotency. This study aimed to investigate the mechanism underlying stemness acquisition in GBM cells by focusing on 40S ribosomal protein S6 (RPS6). RPS6 was significantly upregulated in high-grade glioma and localized at perivascular, perinecrotic, and border niches in GBM tissues. siRNA-mediated RPS6 knock-down significantly suppressed the characteristics of GSCs, including their tumorsphere potential and GSC marker expression; STAT3 was downregulated in GBM cells. RPS6 overexpression enhanced the tumorsphere potential of GSCs and these effects were attenuated by STAT3 inhibitor (AG490). Moreover, RPS6 expression was significantly correlated with SOX2 expression in different glioma grades. Immunohistochemistry data herein indicated that RPS6 was predominant in GSC niches, concurrent with the data from IVY GAP databases. Furthermore, RPS6 and other ribosomal proteins were upregulated in GSC-predominant areas in this database. The present results indicate that, in GSC niches, ribosomal proteins play crucial roles in the development and maintenance of GSCs and are clinically associated with chemoradioresistance and GBM recurrence.

Randomized phase III study of high-dose methotrexate and whole brain radiotherapy with or without concomitant and adjuvant temozolomide in patients with newly diagnosed primary central nervous system lymphoma: JCOG1114C

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Background: Temozolomide (TMZ) is an oral alkylating agent that penetrates the blood-brain barrier with moderate toxicity, and has shown anti-tumor activity in primary central nervous system lymphoma (PCNSL) in single arm studies. Our goal was to determine whether the addition of concomitant and adjuvant TMZ chemotherapy to standard treatment of high-dose methotrexate (HD-MTX) and whole brain radiotherapy (WBRT) for PCNSL improves survival in a randomized controlled trial. Methods: We did an open-label, randomized phase III trial at 30 hospitals in Japan enrolling immunocompetent patients (pts) aged 20-70 years with histologically confirmed newly diagnosed PCNSL. Pts enrolled at step 1 registration received HD-MTX (MTX; 3.5 g/m2 at day 1, 15, 29). Pts who received at least 1 cycle of HD-MTX were randomly assigned (1:1) at step 2 registration to receive WBRT (30 Gy) ± 10 Gy boost (control arm: A) or WBRT ± boost with concomitant TMZ (75 mg/m2 daily) and adjuvant TMZ (150-200 mg/m2 daily for 5 days every 28 days) for two years after initiation of HD-MTX or until tumor progression (experimental arm: B). Randomization was adjusted by institution, PS (0-1 / 2-3), age (≤60/≥61 years), presence or absence of intraparenchymal tumor after HD-MTX. The primary endpoint was overall survival (OS). The planned sample size was 130 pts in total, to provide an 80% power to detect a 0.52 hazard ratio (65% vs 80% in 2y-OS) for arm B to A and a one-sided alpha of 5%. Results: Between September 29, 2014 and October 15, 2018, 134 pts were enrolled, of whom 122 were randomly assigned and analyzed; 62 to arm A and 60 to arm B. At the planned interim analysis, the 2-y OS was 86.8% (95% CI: 72.5-94.0) in arm A and 71.4% (56.0-82.2) in arm B. The hazard ratio was 2.18 (95% CI: 0.95 to 4.98) with predictive probability for showing the superiority of arm B at the final analysis was calculated to be 1.3%. The study was terminated due to futility. The 2-y progression-free survival was 60.6% (43.6-73.8) in arm A and 49.9% (34.4-63.5) in arm B with a hazard ratio of 1.54 (0.88 to 2.70). The most common grade 3 and 4 toxicities were lymphopenia, observed in 7 (11.5%) pts during WBRT in arm A, 18 (30%) pts during WBRT + concomitant TMZ and 18 (37.5%) pts during adjuvant TMZ in arm B. Conclusions: This study failed to demonstrate the benefit of the addition of TMZ to WBRT and adjuvant TMZ in newly diagnosed PCNSL. Possible biomarkers including methylation status of the MGMT promoter in the tumors will be analyzed. Clinical trial information: jRCTs031180207 .

ACT-14 A FIRST-IN-HUMAN STUDY OF MUTANT IDH1 INHIBITOR DS-1001B IN PATIENTS WITH RECURRENT GLIOMAS

BACKGROUND

WHO grade II/III gliomas frequently harbor isocitrate dehydrogenase 1 (IDH1) mutations, resulting in intratumoral accumulation of oncometabolite D-2-hydroxyglutarate (D-2-HG) and subsequent clonal expansion. DS-1001b is an oral selective inhibitor of mutant IDH1 R132X that was designed to penetrate the blood-brain barrier.

METHODS

In this first-in-human, multicenter, phase I study (NCT03030066), eligible patients (pts) with recurrent/progressive IDH1 mutant glioma received DS-1001b twice daily (bid), continuous. A modified continual reassessment method was used for dose escalation. RANO and RANO-LGG criteria were used to assess tumor response. Pts who planned to undergo salvage surgery after developing progressive disease (PD) and who provided informed consent received DS-1001b treatment until surgery. Tumor samples were also obtained from those pts to measure the free form of DS-1001b and D-2-HG levels.

RESULTS

Between Jan 2017 and May 2019, DS-1001b (125–1400 mg bid) had administered for 47 pts, and 15 pts were continuing treatment. Maximum tolerated dose (MTD) was not reached. Most AEs were Gr 1–2. Gr 3 AEs were observed in 40% of pts. No Gr 4 or 5 AEs or serious drug-related AEs were reported. One dose limiting toxicity was Gr 3 white blood cell count decreased (1000 mg bid). Of 35 evaluable pts with contrast enhancing gliomas, one, five and 11 achieved complete response, partial response and stable disease (SD), respectively. Of evaluable 12 pts with contrast non-enhancing gliomas, four achieved minor response and eight achieved SD. Peak plasma concentration (Cmax) and area under the curve (AUC) increased dose-dependently.

CONCLUSIONS

DS-1001b was well tolerated up to 1400 mg bid with favorable brain distribution, and MTD was not reached. Recurrent/progressive IDH1 mutant glioma pts responded to treatment. Investigation is ongoing to determine the recommended Phase II dose. The latest data will be updated. Funding source: This study was funded by Daiichi Sankyo Co., Ltd.

MPC-16 RAPID PROGRESSIVE SPINAL DIFFUSE MIDLINE GLIOMA, A CASE REPORT

A 17-year-old boy presented with a 2-week history of lower back pain, progressive gait difficulty and sensory deficit of bilateral lower limbs. Magnetic resonance imaging of neuroaxis showed intramedullary tumor with spinal cord expansion from Th12 to L2 and irregular areas of enhancement. Emergent laminoplasty and biopsy was performed. Histopathological examination showed small atypical cells, but most cells had too much degeneration and necrosis to confirm the diagnosis definitively. Leptomeningeal dissemination caused conscious disturbance, nuchal rigidity and epilepsy. 2 weeks after decompression, we performed cordotomy again for advanced diagnosis, to be found diffuse midline glioma, H3K27M mutant by immunohistopathological examination and DAN sequence. He was treated with combination of whole brain and spine radiation therapy and chemotherapy with temozolomide and bevacizumab. He is still alive over 6 months. The clinical significance of H3K27M mutant in spinal gliomas is unclear. Further examinations are needed.

BOT-02 2-METHYLTHIO MODIFICATION OF N6-ISOPENTENYLADENOSINE IN MITOCHONDRIAL TRNAS BY CDK5RAP1 PROMOTES THE MAINTENANCE OF GLIOMA-INITIATING CELLS

2-Methylthio-N⁶-isopentenyl modification of adenosine (ms²i⁶A) is an evolutionally conserved modification that is found in mitochondrial (mt)-tRNAs. Cdk5 regulatory subunit-associated protein 1 (CDK5RAP1) specifically converts N6-isopentenyladenosine (i⁶A) to ms²i⁶A at position A37 of four mt-DNA-encoded tRNAs, and the modification regulates efficient mitochondrial translation and energy metabolism in mammals. Here, we report that the ms² conversion mediated by CDK5RAP1 in mt-tRNAs is required to sustain glioma-initiating cell (GIC)-related traits. CDK5RAP1 maintained the self-renewal capacity, undifferentiated state, and tumorigenic potential of GICs. This regulation was not related to the translational control of mt-proteins. CDK5RAP1 abrogated the antitumor effect of i⁶A by converting i⁶A to ms²i⁶A and protected GICs from excessive autophagy triggered by i⁶A. The elevated activity of CDK5RAP1 contributed to the amelioration of the cytotoxic effect of i⁶A and promoted GIC maintenance. The hypoxic microenvironment in the tumor core activated CDK5RAP1, whose activity was inversely correlated with the oxygen concentration because of two [4Fe-4S] clusters in the enzyme. This work demonstrates that CDK5RAP1 is crucial for the detoxification of endogenous i⁶A and that GICs readily utilize this mechanism for survival.

ML-03 RECONSIDERATION OF TREATMENT FOR ELDERLY PATIENTS WITH PRIMARY CENTRAL NERVE SYSTEM LYMPHOMAS

BACKGROUND

The therapeutic response to high-dose methotrexate therapy (HD-MTX) for primary central nervous system lymphoma (PCNSL) varies. Polyglutamylation (PG) is a reversible protein modification, tumor cells show frequent occurrence of PG. Intracellularly polyglutamylated MTX is not subject to competitive inhibition by leucovorin (LV). Tumor cells with high PG levels are selectively killed, whereas normal cells with lower PG are rescued by LV. We previously reported that PG is a predictor of therapeutic response to HD-MTX in PCNSL. However, PG did not affect overall survival (OS) in the elderly unlike the young patients, suggesting that there are other significant predictors in the elderly. The aim of this study is to identify the prognostic factors in aged PCNSL.

METHODS

The prognostic factors were investigated in 48 patients (M/F=23/25) aged 65 and older undergoing HD-MTX in our institute with data of area under the concentration-time curve of MTX, AUC_MTX (μmol/L/h).

RESULTS

The median OS of elderly PCNSL was 937days. In the AUC_MTX high group (median 1706.3 or more, n=24) and the low group (median below, n=24), OS was significantly shortened in the high group compared with the low group (median 728 vs 1290days, p=0.032). Even in multivariate analysis, AUC was the only independent poor prognostic factor of OS (p=0.031). On the other hand, AUC was not a prognostic factor for OS in PCNSL younger than 65 years. AUC_MTX of aged PCNSL was significantly higher compared with younger patients (p<0.01). These results suggested that PG may be a good prognostic factor of OS when AUC_MTX is low.

CONCLUSION

In the aged PCNSL, OS was shortened when AUC_MTX was high. With the results of the previous research, it is suggested that if PG levels is high in elderly PCNSL, the OS prolongation can be expected if the MTX dose is reduced.

CBMT-09. THERAPEUTIC EFFECT OF INDUCTION OF POLYGLUTAMYLATION IN HIGH-DOSE METHOTREXATE THERAPY TO PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA

BACKGROUND

Polyglutamylation is a reversible protein modification with a high occurrence rate in tumor cells. Methotrexate (MTX) incorporated into cells is polyglutamylated and strongly binds to dihydrofolate reductase without competitive inhibition by leucovorin (LV). Tumor cells with high polyglutamylation levels are selectively killed, whereas normal cells with lower polyglutamylation are rescued by LV. In this study, we investigated the therapeutic response of PCNSL to HD-MTX therapy with LV rescue based on polyglutamylation status and evaluated the combined effect of MTX and the drugs which upregulated polyglutamylation of MTX.

METHODS

Among 113 consecutive PCNSL patients who underwent HD-MTX therapy in our department between 2001 and 2014, polyglutamylation was evaluated by immunostaining in 82 cases, with relationships between polyglutamylation and therapeutic response retrospectively examined. Human malignant lymphoma cell lines were used for in vitro and in vivo experiments. The association of polyglutamylation and the response to MTX with LV rescue was assessed in these cell lines. Histone-deacetylase inhibitor (HDACI) has been reported to induce polyglutamylation by elevating folpolyglutamate synthetase (FPGS) expression, so the effects of HDACIs on polyglutamylation were evaluated. Combined effects of MTX and HDACI were evaluated by cell viability assay and xenograft mouse models.

RESULTS

The complete response rate was significantly higher in the group with polyglutamylation than in the non-polyglutamylation group [58.1% (25/43) and 33.3% (13/39), respectively] (p < 0.05), and progression-free survival was also significantly increased in the group with polyglutamylation (p < 0.01). The combined effect of MTX and HDACI was significantly enhanced in cell viability assay in vitro (p< 0.05), in subcutaneous (p< 0.001) and intracranial tumor xenografts (p< 0.001).

CONCLUSION

These findings suggested that polyglutamylation could be a predictor of therapeutic response to HD-MTX therapy with LV rescue in PCNSL. Combined therapy with HD-MTX and HDACIs might represent a promising treatment for HD-MTX resistant intractable PCNSL.

2-Methylthio Conversion of N6-Isopentenyladenosine in Mitochondrial tRNAs by CDK5RAP1 Promotes the Maintenance of Glioma-Initiating Cells

2-Methylthio-N⁶-isopentenyl modification of adenosine (ms²i⁶A) is an evolutionally conserved modification found in mitochondrial (mt)-tRNAs. Cdk5 regulatory subunit-associated protein 1 (CDK5RAP1) specifically converts N6-isopentenyladenosine (i⁶A) to ms²i⁶A at position A37 of four mt-DNA-encoded tRNAs, and the modification regulates efficient mitochondrial translation and energy metabolism in mammals. Here, we report that the ms² conversion mediated by CDK5RAP1 in mt-tRNAs is required to sustain glioma-initiating cell (GIC)-related traits. CDK5RAP1 maintained the self-renewal capacity, undifferentiated state, and tumorigenic potential of GICs. This regulation was not related to the translational control of mt-proteins. CDK5RAP1 abrogated the antitumor effect of i⁶A by converting i⁶A to ms²i⁶A and protected GICs from excessive autophagy triggered by i⁶A. The elevated activity of CDK5RAP1 contributed to the amelioration of the tumor-suppressive effect of i⁶A and promoted GIC maintenance. This work demonstrates that CDK5RAP1 is crucial for the detoxification of endogenous i⁶A and that GICs readily utilize this mechanism for survival.

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CDK5RAP1 is required to sustain the growth of GICs through ms² modification of i⁶A

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Deficit of CDK5RAP1 inhibits the growth of GIC through i⁶A accumulation

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CDK5RAP1 detoxifies i⁶A by conversion into ms²i⁶A in the mitochondria of GICs

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Mitochondria serve as antidotal machinery against i⁶A in GICs

Regulation of growth hormone biosynthesis by Cdk5 regulatory subunit associated protein 1-like 1 (CDKAL1) in pituitary adenomas

CDK5 regulatory subunit associated protein 1-like 1 (CDKAL1) is a tRNA-modifying enzyme that catalyzes 2-methylthiolation (ms²) and has been implicated in the development of type 2 diabetes (T2D). CDKAL1-mediated ms² is important for efficient protein translation and regulates insulin biosynthesis in pancreatic cells. Interestingly, an association between T2D and release of growth hormone (GH) has been reported in humans. However, it is unknown whether CDKAL1 is important for hormone production in the pituitary gland. The present study investigated the role of CDKAL1 in GH-producing pituitary adenomas (GHPAs). CDKAL1 activity was suppressed in GHPAs, as evidenced by a decrease in ms², compared with non-functioning pituitary adenomas (NFPAs), which do not produce specific hormones. Downregulation of Cdkal1 using small interfering and short hairpin RNAs increased the biosynthesis and secretion of GH in rat GH3 cells. Depletion of Cdkal1 increased the cytosolic calcium level via downregulation of DnaJ heat shock protein family (Hsp40) member C10 (Dnajc10), which is an endoplasmic reticulum protein related to calcium homeostasis. This stimulated transcription of GH via upregulation of Pit-1. Moreover, CDKAL1 activity was highly sensitive to proteostatic stress and was upregulated by suppression of this stress. Taken together, these results suggest that dysregulation of CDKAL1 is involved in the pathogenesis of GHPAs, and that modulation of the proteostatic stress response might control CDKAL1 activity and facilitate treatment of GHPAs.