Joseph M. Kim

Prognosis by tumor location in adults with spinal ependymomas.

OBJECT Ependymomas are primary central nervous system tumors that occur more frequently in the spines of adults than they do there in children. Previous studies consist mainly of retrospective single-institutional experiences or case studies. In this study, a comprehensive literature review was performed on reported cases of spinal ependymoma treated with resection to determine whether tumor location along the spinal axis conveys important prognostic information. METHODS A PubMed search was performed to identify all papers that included data on patients with spinal ependymoma. Only cases involving adult patients who underwent ependymoma resection with a clearly reported tumor location were included for analysis. Tumor locations were separated into 6 groups: cervicomedullary, cervical, cervicothoracic, thoracic, thoracolumbar, and conus + cauda equina. Kaplan-Meier survival and Cox regression analyses were performed to determine the effect of tumor location on progression-free survival (PFS) and overall survival (OS). RESULTS A total of 447 patients who underwent resection of spinal ependymomas with clearly indicated location of tumor were identified. The most common locations of spinal ependymomas were the cervical (32.0%) and conus + cauda equina (26.8%) regions. The thoracolumbar and cervicomedullary regions had the fewest tumors (accounting for, respectively, 5.1% and 3.4% of the total number of cases). The conus + cauda equina and thoracolumbar regions had the highest percentage of WHO Grade I tumors, while tumors located above these regions consisted of mostly WHO Grade II tumors. Despite the tendency for benign grades in the lower spinal regions, PFS for patients with spinal ependymomas in the lower 3 regions (thoracic, thoracolumbar, conus + cauda equina) was significantly shorter (p < 0.001) than for those with tumors in the upper regions (cervicomedullary, cervical, cervicothoracic), but the difference in OS did not achieve statistical significance (p = 0.131). CONCLUSIONS Spinal ependymomas along different regions of spinal axis have different characteristics and clinical behaviors. Tumor grade, extent of resection, and PFS varied by tumor location (upper vs lower spinal regions), while OS did not. Recurrence rates were higher for the lower spinal cord tumors, despite a greater prevalence of lower WHO grade lesions, compared with upper spinal cord tumors, suggesting that tumor location along the spinal axis is an important prognostic factor.

Overexpression of CD97 Confers an Invasive Phenotype in Glioblastoma Cells and Is Associated with Decreased Survival of Glioblastoma Patients

Mechanisms of invasion in glioblastoma (GBM) relate to differential expression of proteins conferring increased motility and penetration of the extracellular matrix. CD97 is a member of the epidermal growth factor seven-span transmembrane family of adhesion G-protein coupled receptors. These proteins facilitate mobility of leukocytes into tissue. In this study we show that CD97 is expressed in glioma, has functional effects on invasion, and is associated with poor overall survival. Glioma cell lines and low passage primary cultures were analyzed. Functional significance was assessed by transient knockdown using siRNA targeting CD97 or a non-target control sequence. Invasion was assessed 48 hours after siRNA-mediated knockdown using a Matrigel-coated invasion chamber. Migration was quantified using a scratch assay over 12 hours. Proliferation was measured 24 and 48 hours after confirmed protein knockdown. GBM cell lines and primary cultures were found to express CD97. Knockdown of CD97 decreased invasion and migration in GBM cell lines, with no difference in proliferation. Gene-expression based Kaplan-Meier analysis was performed using The Cancer Genome Atlas, demonstrating an inverse relationship between CD97 expression and survival. GBMs expressing high levels of CD97 were associated with decreased survival compared to those with low CD97 (p = 0.007). CD97 promotes invasion and migration in GBM, but has no effect on tumor proliferation. This phenotype may explain the discrepancy in survival between high and low CD97-expressing tumors. This data provides impetus for further studies to determine its viability as a therapeutic target in the treatment of GBM.

Adjuvant radiotherapy delays recurrence following subtotal resection of spinal cord ependymomas

BACKGROUND Ependymoma is the most common glial tumor of the adult spinal cord. Current consensus recommends surgical resection with gross total resection (GTR) whenever possible. We performed a comprehensive review of the literature to evaluate whether adjuvant radiotherapy after subtotal resection (STR) has any benefit. METHODS A PubMed search was performed to identify adult patients with spinal cord ependymoma who underwent surgical resection. Only patients who had clearly defined extent of resection with or without adjuvant radiotherapy were included for analysis. Kaplan-Meier and multivariate Cox regression survival analyses were performed to determine the effects of adjuvant radiotherapy on progression-free survival (PFS) and overall survival (OS). RESULTS A total of 348 patients underwent surgical resection of spinal cord ependymomas, where GTR was obtained in 77.0% (268/348) of patients. Among those who received STR, 58.8% (47/80) received adjuvant radiotherapy. PFS was significantly prolonged among those who received adjuvant radiotherapy after STR (log rank; P < .001). This prolonged PFS with adjuvant radiotherapy remained significant in multivariate Cox regression analysis (STR versus STR + RT group; hazard ratio (HR) = 2.26, P = .047). By contrast, improved OS was only associated with GTR (GTR versus STR + RT group; HR = 0.07, P = .001) and benign ependymomas (HR = 0.16, P = .001). CONCLUSIONS Surgery remains the mainstay treatment for spinal cord ependymomas, where GTR provides optimal outcomes with longest PFS and OS. Adjuvant radiotherapy prolongs PFS after STR significantly, and OS is improved by GTR and benign tumor grade only.

Overexpression of Calcium-Permeable Glutamate Receptors in Glioblastoma Derived Brain Tumor Initiating Cells

Glioblastoma multiforme is the most malignant type of primary brain tumor with a poor prognosis. These tumors consist of a heterogeneous population of malignant cells, including well-differentiated tumor cells and less differentiated cells with stem cell properties. These cancer stem cells, known as brain tumor initiating cells, likely contribute to glioma recurrence, as they are highly invasive, mobile, resistant to radiation and chemotherapy, and have the capacity to self-renew. Glioblastoma tumor cells release excitotoxic levels of glutamate, which may be a key process in the death of peritumoral neurons, formation of necrosis, local inflammation, and glioma-related seizures. Moreover, elevated glutamate levels in the tumor may act in paracrine and autocrine manner to activate glutamate receptors on glioblastoma tumor cells, resulting in proliferation and invasion. Using a previously described culturing condition that selectively promotes the growth of brain tumor initiating cells, which express the stem cell markers nestin and SOX-2, we characterize the expression of α-amino-3-hydroxy-5-methyl-4-isozolepropionic acid (AMPA)-type glutamate receptor subunits in brain tumor initiating cells derived from glioblastomas. Here we show for the first time that glioblastoma brain tumor initiating cells express high concentrations of functional calcium-permeable AMPA receptors, compared to the differentiated tumor cultures consisting of non-stem cells. Up-regulated calcium-permeable AMPA receptor expression was confirmed by immunoblotting, immunocytochemistry, and intracellular calcium imaging in response to specific agonists. Our findings raise the possibility that glutamate secretion in the GBM tumor microenvironment may stimulate brain tumor derived cancer stem cells.

Prognosis by tumor location in adults with intracranial ependymomas

Intracranial ependymomas are rare tumors in adults. Thus, factors affecting prognosis are poorly understood. We performed a study to investigate whether tumor location is an important prognostic factor in adults who undergo surgery for intracranial ependymomas. PubMed was searched to identify studies that reported clinical outcomes in adult patients with intracranial ependymoma. Data were extracted for patient and tumor characteristics, extent of resection, progression-free survival (PFS), and overall survival (OS). Tumors were categorized as supratentorial or infratentorial and extraventricular or intraventricular. Presenting clinical features and tumor characteristics were tabulated. Kaplan-Meier and multivariate Cox regression survival analyses were performed to determine PFS and OS by tumor location. Extent of resection was also analyzed by tumor location. A total of 183 patients were included in the meta-analysis. Patients presented at a mean of 8.2months with a myriad of clinical features. The mean tumor size was 3.38 cm, and 19.3% of tumors were cystic. Supratentorial tumors were most commonly located in the frontal and parietal lobes, and infratentorial tumors in the fourth ventricle. Supratentorial tumors demonstrated significantly poorer PFS (p<0.001) and OS (p=0.003) than infratentorial tumors, despite a higher rate of gross total resection (GTR) for the supratentorial tumors (72.6% versus 42.1%). Extraventricular ependymomas displayed significantly poorer PFS than intraventricular ependymomas (p=0.009). In summary, supratentorial ependymomas have significantly poorer PFS and OS than their infratentorial counterparts, despite being more conducive to GTR, suggesting increased clinical aggressiveness. Extraventricular location is also associated with significantly poorer PFS than intraventricular location.

Spinal ependymomas: Benefits of extent of resection for different histological grades

Although the World Health Organization (WHO) categorizes spinal ependymomas into three histological grades, difference in surgical outcomes between WHO grades I and II tumors are unclear. For these benign tumors, prognosis may be best determined by factors other than tumor grade alone, such as extent of resection. To analyze the effects of the extent of resection on different grades of spinal ependymomas, we performed a comprehensive literature review to identify adult spinal ependymoma patients who received surgical resection with a clearly identifiable WHO grade. A total of 175 patients were identified. While grade III tumors carried the worst prognosis as expected (p<0.001), grade I and II tumors did not differ significantly in outcomes following surgery. Overall, gross total resection (GTR, 68.7%, 114/166) provided significantly improved progression-free survival (PFS, p<0.001) and overall survival (OS, p=0.022) compared to the subtotal resection group. Surprisingly, the highest GTR rate was achieved for grade II tumors (78.8%, 78/99; p<0.001) followed by grade I (58.9%, 33/56) and grade III tumors (27.3%, 3/11). Interestingly, PFS was significantly improved by GTR for grade II tumors (p<0.001), but not for grade I (p=0.705). Similar trends, although not statistically significant, were found for OS. Our results show that while GTR provides the best overall outcomes, GTR is most effective for classic grade II ependymomas, but not for grade I ependymomas. Despite having a lower WHO grade, myxopapillary ependymomas have a lower GTR rate, and benefit less from GTR.

Na+/K+-ATPase β2-subunit (AMOG) expression abrogates invasion of glioblastoma-derived brain tumor-initiating cells

BACKGROUND Mechanisms of glioma invasion remain to be fully elucidated. Glioma cells within glioblastoma multiforme (GBM) range from well-differentiated tumor cells to less-differentiated brain tumor-initiating cells (BTICs). The β2-subunit of Na(+)/K(+)-ATPase, called the adhesion molecule on glia (AMOG), is highly expressed in normal glia but is thought to be universally downregulated in GBM. To test our hypothesis that expression of AMOG is heterogeneous in GBM and confers a less invasive phenotype, we compared it between BTICs and differentiated cells from patient-matched GBM and then tested GBM invasion in vitro after AMOG overexpression. METHODS Immunohistochemistry, immunoblotting, and real-time PCR were used to characterize AMOG protein and mRNA expression in tumor samples, BTICs, and differentiated cells. Matrigel invasion assay, scratch assay, and direct cell counting were used for testing in vitro invasion, migration, and proliferation, respectively. RESULTS While AMOG expression is heterogeneous in astrocytomas of grades II-IV, it is lost in most GBM. BTICs express higher levels of AMOG mRNA and protein compared with patient-matched differentiated tumor cells. Overexpression of AMOG decreased GBM cell and BTIC invasion without affecting migration or proliferation. Knockdown of AMOG expression in normal human astrocytes increased invasion. CONCLUSIONS AMOG expression inhibits GBM invasion. Its downregulation increases invasion in glial cells and may also represent an important step in BTIC differentiation. These data provide compelling evidence implicating the role of AMOG in glioma invasion and provide impetus for further investigation.

Prognosis by tumor location for pediatric spinal cord ependymomas

OBJECT Ependymoma is a common CNS tumor in children, with spinal cord ependymomas making up 13.1% of all ependymomas in this age group. The clinical features that affect prognosis in pediatric spinal cord ependymomas are not well understood. A comprehensive literature review was performed to determine whether a tumor location along the spinal cord is prognostically significant in children undergoing surgery for spinal cord ependymomas. METHODS A PubMed search was performed to identify all papers that contained data on patients with spinal cord ependymomas. Only pediatric patients (age < 18 years) who underwent resection with a clearly reported tumor location were included in the analysis. Myxopapillary tumors were excluded from study. Tumor location was subdivided into 6 regions: cervicomedullary, cervical, cervicothoracic, thoracic, thoracolumbar, and conus medullaris. Kaplan-Meier survival and Cox regression analyses were performed to determine the effects of tumor location on progression-free survival (PFS) and overall survival (OS). RESULTS Fifty-eight patients who underwent resection of spinal cord ependymomas were identified. Ependymomas were located all along the spinal cord but occurred with the highest frequency in the cervical region (29.3%). Progression-free survival was significantly better in patients with tumors arising in the upper portion of the spinal cord (p = 0.031), which remained significant in the multivariate Cox regression analysis (p < 0.05). Moreover, OS was significantly better in patients with upper spinal cord ependymomas than in those harboring ependymomas in the lower spinal cord (p = 0.048). CONCLUSIONS Although more common in adults, spinal ependymomas can occur anywhere along the spinal cord in the pediatric population; however, tumors occurring in the lower half of the spinal cord carry a worse prognosis with shorter PFS and OS. By comparison, ependymomas in the upper spinal cord recur later and less frequently, with little or no mortality in this patient group.