Pediatric brainstem gangliogliomas show overexpression of neuropeptide prepronociceptin (PNOC) by microarray and immunohistochemistry

BACKGROUND

Gangliogliomas (GGs) primary to brainstem are rare, with the overwhelming majority of GGs occurring in supratentorial, especially temporal lobe, locations. A less favorable prognosis exists for brainstem GGs, despite their usually identical WHO grade I status. Few large clinical series, and limited biological information, exists on these tumors, especially gene expression.

PROCEDURE

Seven pediatric brainstem GGs, all with classic histological features, seen at our institution since 2000 were identified. Frozen section material was available for gene expression microarray profiling from five of seven brainstem GGs and compared with that from three non-brainstem pediatric GGs.

RESULTS

Significant upregulation of a number of genes was identified, most of which were involved in pathways of neural signaling, embryonic development, and pattern specification in pediatric brainstem GGs compared to non-brainstem. The single largest upregulated gene was a 256-fold increase in the expression of the neuropeptide prepronociceptin (PNOC); the protein product of this gene has been implicated in neuronal growth. Overexpression was validated by Western blot and by immunohistochemistry (IHC). Strong IHC expression of PNOC was seen in neoplastic neurons of 7/7 brainstem GGs, but was significantly weaker in non-brainstem GGs, and completely negative in normal pediatric autopsy brainstem controls.

CONCLUSIONS

PNOC IHC was often superior to IHC for NeuN, synaptophysin, or neurofilament for highlighting neoplastic neurons.

Clinical implications of growth hormone-secreting tumor subtypes

Growth hormone (GH) pituitary tumors are almost always benign adenomas, yet are associated with significant morbidity and mortality. Surgical and medical responses of GH tumors are often incomplete, and therefore predictors of residual or recurrent disease are needed. Clinical features, including patient gender, age or size of adenoma, have proven to be unreliable predictors of recurrence. Differing clinical behavior between the two GH tumor subtypes, sparsely granulated (SG) versus densely granulated (DG), has been reported, but has not been used routinely in clinical management. SG tumors are more common in younger patients (<50 years), and are usually larger tumors. SG tumors have been reported to be less responsive to somatostatin analogs (SSA) than DG tumors. The mechanisms underlying these potential differences in tumor behavior, however, are poorly defined. Subsets (up to 50 %) of DG adenomas harbor a gsp mutation that can activate cAMP that provides a theoretical intracellular target for somatostatin therapy. In contrast, some SG tumors have reduced somatostatin receptor expression and mutations in the extracellular domain of the GH receptor that may contribute to SSA resistance. While DG versus SG growth hormone adenomas are readily distinguished by immunohistochemistry, other less common GH adenoma variants still require electron microscopy (EM) for confident subclassification. Whether these less common variants possess unique clinical features is unknown. Research is needed to identify clinically relevant biomarkers of GH pituitary tumors that predict risk of recurrence and response to medical therapy.

Identification of growth arrest and DNA-damage-inducible gene beta (GADD45beta) as a novel tumor suppressor in pituitary gonadotrope tumors

Gonadotrope and null cell pituitary tumors cause significant morbidity, often presenting with signs of hypogonadism together with visual disturbances due to mass effects. Surgery and radiation are the only therapeutic options to date. To identify dysregulated genes and pathways that may play a role in tumorigenesis and/or progression, molecular profiling was performed on 14 gonadotrope tumors, with nine normal human pituitaries obtained at autopsy serving as controls. Bioinformatic analysis identified putative downstream effectors of tumor protein 53 (p53) that were consistently repressed in gonadotrope pituitary tumors, including RPRM, P21, and PMAIP1, with concomitant inhibition of the upstream p53 regulator, PLAGL1(Zac1). Further analysis of the growth arrest and DNA damage-inducible (GADD45) family revealed no change in the p53 target, GADD45α, but identified repression of GADD45β in pituitary tumors in addition to the previously reported inhibition of GADD45γ. Overexpression of GADD45β in LβT2 mouse gonadotrope cells blocked tumor cell proliferation and increased rates of apoptosis in response to growth factor withdrawal. Stable gonadotrope cell transfectants expressing increased GADD45β showed decreased colony formation in soft agar, confirming its normal role as a tumor suppressor. Unlike previous studies of GADD45γ in pituitary tumors and α and β in other tumors, bisulfite sequencing showed no evidence of hypermethylation of the GADD45β promoter in human pituitary tumor samples to explain the repression of its expression. Thus, GADD45β is a novel pituitary tumor suppressor whose reexpression blocks proliferation, survival, and tumorigenesis. Together these studies identify new targets and mechanisms to explore in pituitary tumor initiation and progression.

Neutrophil degranulation and immunosuppression in patients with GBM: restoration of cellular immune function by targeting arginase I

PURPOSE

The source of glioblastoma (GBM)-associated immunosuppression remains multifactorial. We sought to clarify and therapeutically target myeloid cell-derived peripheral immunosuppression in patients with GBM.

EXPERIMENTAL DESIGN

Direct ex vivo T-cell function, serum Arginase I (ArgI) levels, and circulating myeloid lineage populations were compared between patients with GBM and normal donors or patients with other intracranial tumors. Immunofunctional assays were conducted using bulk and sorted cell populations to explore the potential transfer of myeloid cell-mediated immunosuppression and to identify a potential mechanism for these effects. ArgI-mediated immunosuppression was therapeutically targeted in vitro through pharmacologic inhibition or arginine supplementation.

RESULTS

We identified a significantly expanded population of circulating, degranulated neutrophils associated with elevated levels of serum ArgI and decreased T-cell CD3ζ expression within peripheral blood from patients with GBM. Sorted CD11b(+) cells from patients with GBM were found to markedly suppress normal donor T-cell function in coculture, and media harvested from mitogen-stimulated GBM peripheral blood mononuclear cell (PBMC) or GBM-associated mixed lymphoid reactions showed ArgI levels that were significantly higher than controls. Critically, T-cell suppression in both settings could be completely reversed through pharmacologic ArgI inhibition or with arginine supplementation.

CONCLUSIONS

These data indicate that peripheral cellular immunosuppression in patients with GBM is associated with neutrophil degranulation and elevated levels of circulating ArgI, and that T-cell function can be restored in these individuals by targeting ArgI. These data identify a novel pathway of GBM-mediated suppression of cellular immunity and offer a potential therapeutic window for improving antitumor immunity in affected patients.

May 2001: 32 year old female with dural mass encircling cervical spinal cord

The May COM. A 32-year-old woman with a history of previous mastoid surgery presented with bilateral extremity weakness and ambulatory instability. MRI revealed a dural-based mass completely encircling the upper cervical spinal cord. Workup was significant for an abnormally elevated c-ANCA, positive at a dilution of 1:128. A portion of the lesion was removed by a posterior surgical approach to decompress the cervical cord. Histologic examination of the dura showed a dense granulomatous infiltrate with vasculitis and giant cells; coupled with the positive c-ANCA, the process was felt to be most consistent with Wegener's granulomatosis. Wegener's granulomatosis infrequently involves the dura or meninges and has not previously been reported to affect dura of the cervical cord. Symptomatic improvement followed surgical decompression and high-dose corticosteroid therapy, with resultant resolution of an elevated c-ANCA titer.

Favorable prognosis in patients with high-grade glioma with radiation necrosis: the University of Colorado reoperation series

PURPOSE

To analyze the pathology, outcomes, and prognostic factors in patients with high-grade glioma undergoing reoperation after radiotherapy (RT).

METHODS AND MATERIALS

Fifty-one patients with World Health Organization Grade 3-4 glioma underwent reoperation after prior RT. The median dose of prior RT was 60 Gy, and 84% received chemotherapy as part of their initial treatment. Estimation of the percentage of necrosis and recurrent tumor in each reoperation specimen was performed. Pathology was classified as RT necrosis if ≥80% of the specimen was necrotic and as tumor recurrence if ≥20% was tumor. Predictors of survival were analyzed using log-rank comparisons and Cox proportional hazards regression.

RESULTS

The median interval between the completion of RT and reoperation was 6.7 months (range, 1-59 months). Pathologic analysis showed RT necrosis in 27% and recurrence in 73% of cases. Thirteen patients required a reoperation for uncontrolled symptoms. Among them, 1 patient (8%) had pathology showing RT necrosis, and 12 (92%) had tumor recurrence. Median survival after reoperation was longer for patients with RT necrosis (21.8 months vs. 7.0 months, p=0.047). In 7 patients with Grade 4 tumors treated with temozolomide-based chemoradiation with RT necrosis, median survival from diagnosis and reoperation were 30.2 months and 21.8 months, respectively.

CONCLUSIONS

Patients with RT necrosis at reoperation have improved survival compared with patients with tumor recurrence. Future efforts to intensify local therapy and increase local tumor control in patients with high-grade glioma seem warranted.

Acute hemorrhagic leukoencephalitis: a critical entity for forensic pathologists to recognize

Acute hemorrhagic leukoencephalopathy (AHLE) is a rare, acute disorder characterized by perivenular demyelination and diffuse hemorrhagic necrosis of the central nervous system. AHLE is thought to represent a hyperacute form of acute disseminated encephalomyelitis. AHLE is associated with a greater morbidity and mortality and, fortunately, is much less common than acute disseminated encephalomyelitis. Since most cases of AHLE result in patient demise, forensic pathologists should be cognizant of this entity and consider it in their differential diagnosis.Here we describe an interesting case of a previously healthy 11-year-old boy who initially complained of vague gastroenteritis-like symptoms while visiting a mountain lake. The boy's symptoms evolved to include severe headache and dizziness, necessitating a visit to a rural emergency department. He presented with focal neurologic findings, and head computed tomography (CT) scan confirmed thalamic edema. Cerebrospinal fluid analysis was suggestive of infectious etiology, and multiple empiric therapies were initiated. He was transferred to our institution, and his clinical status continued to worsen. Given the poor prognosis, the family requested withdrawal of supportive care. On day 14 of symptoms the boy succumbed to his illness. An autopsy was requested to further characterize the proximate cause of death.AHLE often presents with abrupt onset of fever, neck stiffness, seizure, and/or focal neurologic signs several days following a viral illness or vaccination. Thus, AHLE can clinically mimic a direct central nervous system infection or a toxic ingestion. AHLE has a very poor prognosis, with rapid deterioration and death usually occurring within days to one week after onset of symptoms. The cause for AHLE is unclear. An autoimmune pathophysiology is likely, with immune cross-reactivity between myelin basic protein moieties and various infectious agent antigens. Treatment for AHLE is not well-established; some authors describe in recent literature that a combination of immunosuppressant medications and/or therapeutic plasma exchange may be of benefit in treating AHLE.

PARP1 expression in pediatric central nervous system tumors

BACKGROUND

Despite advances in therapy, outcome in many high-grade pediatric central nervous system (CNS) tumors remains poor. The focus of neuro-oncology research has thus turned towards identifying novel therapeutic targets. Poly(ADP-ribose) polymerase-1 (PARP1) is a DNA repair protein that has been studied in a variety of malignancies and may interfere with therapy-induced DNA damage, however expression in pediatric CNS tumors is unknown.

PROCEDURE

We evaluated PARP1 mRNA expression in 81 pediatric CNS tumors using microarray technology. Protein expression was examined by Western blot.

RESULTS

PARP1 mRNA is highly expressed in high-grade tumors (P < 0.0001). PARP1 mRNA expression was greater in high-grade glioma than pilocytic astrocytoma (P = 3.5 x 10(-5)) and in large cell medulloblastoma over classic medulloblastoma (P = 0.0053). PARP1 protein was also prominent in high-grade tumors (P = 0.022).

CONCLUSION

These findings indicate that PARP1 is expressed in high-grade pediatric CNS tumors, implicating PARP1 inhibition as a potential therapeutic target.

Osteochondroma of the convexity: pathologic-neuroimaging correlates of a lesion that mimics high-grade meningioma

Intracranial chondromas are uncommon benign lesions usually attached to dura and located over the convexity of the skull. Osteochondromas are even rarer and additionally contain a benign bony component. Both lesions are reportedly difficult to distinguish from meningiomas on pre-operative neuroimaging studies, although few detailed pathologic-neuroimaging correlation studies have appeared in the literature, particularly for intracranial osteochondromas. A 33-year-old woman with a 4-year history of headaches presented with recent onset of left-sided muscle spasms and weakness. Two days prior to admission to our hospital, neuroimaging studies had shown a large right convexity mass with unusual multifocal bright signal intensities throughout an otherwise isointense mass. The bright signals were interpreted as showing multifocal hemorrhage and the mass was felt to be a convexity meningioma. However, subsequent catheter angiography characterized the lesion as being avascular. The mass was resected en bloc. Extensive histological sectioning revealed a benign osteochondroma predominantly composed of lobules of hypocellular cartilage. Microdissection of the different components revealed that the multifocal, spicule-like bright foci interpreted as hemorrhage on neuroimaging studies were instead foci of benign bone containing metaplastic bone marrow with trilineage hematopoietic cell populations and adipose tissue. Centrally, the hilum of the lesion contained avascular loose connective tissue. No recent or remote hemorrhage was identified anywhere in the lesion. Rare convexity osteochondromas may be mistaken for high-grade meningiomas on neuroimaging studies; their avascular nature, coupled with their complex signal pattern can serve as clues to the correct pre-operative diagnosis.

Decrease in the numbers of dendritic cells and CD4+ T cells in cerebral perivascular spaces due to natalizumab

OBJECTIVE

To extend our studies on the prolonged and differential effect of natalizumab on T lymphocyte numbers in the cerebrospinal fluid, we investigated the number and phenotypes of leukocytes and the expression of major histocompatibility complex (MHC) classes I and II in cerebral perivascular spaces (CPVS). We hypothesized that natalizumab reduces the number of antigen presenting cells in CPVS.

DESIGN

A case-control study in which inflammatory cell numbers in the CPVS of cerebral tissue were assessed by immunohistochemical staining.

SUBJECTS

A patient with multiple sclerosis (MS) who developed progressive multifocal leukoencephalopathy (PML) during natalizumab therapy. Controls included location-matched cerebral autopsy material of patients without disease of the central nervous system, patients with MS not treated with natalizumab, and patients with PML not associated with natalizumab therapy.

RESULTS

The absolute number of CPVS in the patient with MS treated with natalizumab was significantly lower than in the control groups owing to extensive destruction of the tissue architecture. The expression of MHC class II molecules and the number of CD209+ dendritic cells were significantly decreased in the CPVS of the patient with MS treated with natalizumab. No CD4+ T cells were detectable.

CONCLUSIONS

Our observations may explain the differential and prolonged effects of natalizumab therapy on leukocyte numbers in the cerebrospinal fluid.

Radiation-induced meningiomas: clinical, cytogenetic, and microarray features

Limited information exists about the clinical and biological features of radiation-induced meningiomas (RIMs), particularly those that follow high-dose therapeutic radiation. We report our experience with 20 patients with RIMs (16 following high-dose radiotherapy) treated at our institution from 1993-2006. Patients (14 female, 6 male) had intervals from first radiotherapy to RIM diagnosis of 11-63 years; 12 had at least one RIM occur at an interval of 30 years or more after initial radiotherapy. Multiple RIMs were seen in six patients, with one patient developing his six RIMs sequentially over a 22-year interval. Most RIMs could be managed surgically, either with a single extensive resection or additional resection(s). Adjuvant stereotactic radiosurgery, external beam radiation, or chemotherapy were required in a minority (n = 6). Most were WHO grade I meningiomas. Complex karyotypes were found in three of four cases and abnormalities of chromosome 1p and/or LOH 1p36 were identified in five of 11 informative cases. Gene-expression microarray analysis of RIMs (n = 5) compared to non-RIMs (MEN, n = 6) and a panel of other tumors (n = 62) showed that RIM gene-expression was similar to that seen in MEN, and by clustering analysis did not separate from them. However, microarray comparative gene-expression analysis did demonstrate a few genes with significant differences in the expression level in RIM versus MEN. Of note, NF2 was under-expressed in four of five RIMs (P = 0.0065), at a similar level as measured in MEN.

Hemispherectomy in a premature neonate with linear sebaceous nevus syndrome

A male neonate with seizures, linear sebaceous nevus syndrome and hemimegalencephaly underwent hemispherectomy at 36 weeks' gestational age. He has had no clinical seizures in the 13 months since surgery but continues to have sharp wave activity over some parts of the intact hemisphere. He has moderate developmental delay and a mild hemiparesis but is making developmental progress.

Unique molecular characteristics of radiation-induced glioblastoma

Radiation-induced glioblastomas (RIGs) represent a significant proportion of glioblastomas (GBMs) seen in children and young adults and manifest poor prognosis. Little is known about their underlying biology, although limited studies have suggested no unique histologic or cytogenetic characteristics to distinguish them from de novo GBMs. In this study, we confirmed that a series of 5 RIGs showed no unique histologic or cytogenetic features compared with de novo pediatric GBMs, prompting us to further investigate RIGs using gene expression microarray profiling and Western blot analysis. Despite the inability of histologic and molecular genetic studies to identify distinguishing features between RIGs and pediatric GBMs, gene microarrays suggested significant differences between these 2 tumor types, at least those occurring in pediatric patients. Pediatric RIGs show greater homogeneity of gene expression than do de novo pediatric GBMs. Greater overlap was detected in gene expression patterns between RIGs and pilocytic astrocytomas than between RIGs and GBMs, medulloblastomas, ependymomas, atypical teratoid rhabdoid tumors, or rhabdomyosarcomas, suggesting a common precursor cell for RIG and pilocytic astrocytoma. Western blot analyses confirmed that ErbB3, Sox10, and platelet-derived growth factor receptor-alpha proteins were consistently expressed in RIGs but rarely in pediatric GBMs.

Molecular array analyses of 51 pediatric tumors shows overlap between malignant intracranial ectomesenchymoma and MPNST but not medulloblastoma or atypical teratoid rhabdoid tumor

Gene microarray has been used to identify prognostic markers and genes of interest for therapeutic targets; a less common use is to show possible histogenetic relationships between rare tumor types and more common neoplasms. Intracranial malignant ectomesenchymoma (MEM) is a pediatric tumor postulated to arise from neural crest cells that contain divergent neuroectodermal and mesenchymal tissues, principally mature ganglion cells and rhabdomyosarcoma (RMS). We investigated a case of MEM by molecular, cytogenetic, and gene array analyses and compared results with our previously unpublished series of 51 pediatric tumors including conventional RMS, Ewing sarcoma (EWS), medulloblastoma (MED), atypical teratoid rhabdoid tumor (ATRT), and malignant peripheral nerve sheath tumor (MPNST); the latter is a sarcoma also with potential for divergent differentiation. Standard cytogenetic analyses and RT-PCR testing for the classic gene rearrangements seen in RMS [t(2;13)-PAX3/FKHR] and EWS ([t(11;22) & t(21;22)-EWS/FLI-1 & EWS/ERG), were used for characterization of the MEM, with gene expression microarray analyses on all tumor types. Gene rearrangement studies were negative in MEM. Gene expression microarray analyses showed tight clustering of the MEM with the MPNST (n = 2), but divergence from other pediatric tumors. MEM and MPNST both showed complex karyotypes, but without diagnostic translocations. Despite the presence of malignant skeletal muscle differentiation in the MEM, gene array testing showed no overlap with RMS, MED, or ATRT, but rather with MPNST. This suggests a common stem cell origin or embryonic gene recapitulation for these tumors and provides novel insights into their underlying biology.

Characterization of glioblastomas in young adults

Most adult glioblastoma multiformes (GBMs) present in patients 45-70 years old; tumors occurring at the extremes of the adult age spectrum are uncommon, and seldom studied. We hypothesized that young-adult GBMs would differ from elderly-adult and from pediatric GBMs. Cases were identified from years 1997 to 2005. Demographic and histological features, MIB-1 and TP53 immunohistochemical findings and epidermal growth factor receptor (EGFR) amplification status by fluorescence in situ hybridization were compiled and correlated with survival. Twenty-eight (74%) of our 38 young-adult GBM patients had primary de novo tumors, two of which occurred in patients with cancer syndromes. Two additional GBMs were radiation-induced and eight (21%) were secondary GBMs. Seven patients were identified as long-term (>3 years) survivors. Six of 38 cases manifested unusual morphological features, including three epithelioid GBMs, one rhabdoid GBM, one gliosarcoma and one small cell GBM containing abundant, refractile, eosinophilic inclusions. MIB-1 index emerged as the most important prognosticator of survival (P < 0.005). Although there was a trend between extent of necrosis, TP53 immunohistochemical expression, and EGFR amplification status and survival, none reached statistical significance. GBMs in young adults are a more inhomogeneous tumor group than GBMs occurring in older adult patients and show features that overlap with both pediatric and adult GBMs.

An adult case of leukoencephalopathy with intracranial calcifications and cysts

We describe a 44-year-old woman with progressive headache, ataxia, and seizures in association with multifocal cerebral and cerebellar leukoencephalopathy, intracranial calcifications, and cysts. The cause of death was intracerebellar hemorrhage while taking warfarin. Pathologic features on biopsy included angiomatous-like blood vessels, intense gliosis, and Rosenthal fiber formation in the white matter. Genetic analyses did not identify any significant mutations in two candidate genes.

An algorithmic approach to the brain biopsy--part II

CONTEXT

The formulation of appropriate differential diagnoses for a slide is essential to the practice of surgical pathology but can be particularly challenging for residents and fellows. Algorithmic flow charts can help the less experienced pathologist to systematically consider all possible choices and eliminate incorrect diagnoses. They can assist pathologists-in-training in developing orderly, sequential, and logical thinking skills when confronting difficult cases.

OBJECTIVE

To present an algorithmic flow chart as an approach to formulating differential diagnoses for lesions seen in surgical neuropathology.

DESIGN

An algorithmic flow chart to be used in teaching residents.

RESULTS

Algorithms are not intended to be final diagnostic answers on any given case. Algorithms do not substitute for training received from experienced mentors nor do they substitute for comprehensive reading by trainees of reference textbooks. Algorithmic flow diagrams can, however, direct the viewer to the correct spot in reference texts for further in-depth reading once they hone down their diagnostic choices to a smaller number of entities. The best feature of algorithms is that they remind the user to consider all possibilities on each case, even if they can be quickly eliminated from further consideration.

CONCLUSIONS

In Part II, we assist the resident in arriving at the correct diagnosis for neuropathologic lesions containing granulomatous inflammation, macrophages, or abnormal blood vessels.

An algorithmic approach to the brain biopsy--part I

CONTEXT

The formulation of appropriate differential diagnoses for a slide is essential to the practice of surgical pathology but can be particularly challenging for residents and fellows. Algorithmic flow charts can help the less experienced pathologist to systematically consider all possible choices and eliminate incorrect diagnoses. They can assist pathologists-in-training in developing orderly, sequential, and logical thinking skills when confronting difficult cases.

OBJECTIVE

To present an algorithmic flow chart as an approach to formulating differential diagnoses for lesions seen in surgical neuropathology.

DESIGN

An algorithmic flow chart to be used in teaching residents.

RESULTS

Algorithms are not intended to be final diagnostic answers on any given case. Algorithms do not substitute for training received from experienced mentors nor do they substitute for comprehensive reading by trainees of reference textbooks. Algorithmic flow diagrams can, however, direct the viewer to the correct spot in reference texts for further in-depth reading once they hone down their diagnostic choices to a smaller number of entities. The best feature of algorithms is that they remind the user to consider all possibilities on each case, even if they can be quickly eliminated from further consideration.

CONCLUSIONS

In Part I, we assist the resident in learning how to handle brain biopsies in general and how to distinguish nonneoplastic lesions that mimic tumors from true neoplasms.

Overlapping features of extrapontine myelinolysis and acquired chronic (non-Wilsonian) hepatocerebral degeneration

Central pontine myelinolysis (CPM, osmotic demyelination syndrome) and acquired chronic hepatocerebral degeneration (ACHD) both occur in patients with liver failure, but are not thought to be caused by similar etiopathogenic mechanisms despite the fact that occasional patients exhibit both disorders. In our autopsy practice we have recently encountered three patients with the pontine lesions of acute or subacute osmotic demyelination syndrome, coupled with superimposed non-Wilsonian ACHD. All three patients had well-documented rapid elevations in serum sodium proximate to their demise, as well as terminal liver failure. A close intermingling and juxtaposition of lesions with severe demyelination and macrophage breakdown [thought to represent extrapontine myelinolysis (EPM)] to those with vacuolization of myelin but no cellular reaction or myelin loss (ACHD) was noted within some of the same anatomic areas. Particular overlap was seen in lesions at the cerebral cortical gray-white junction and in pencil fibers of the striatum. In these areas it was difficult to be certain whether the lesions were due to EPM or ACHD. We concluded that there was a synergism between the two disorders and raise the possibility that there may be factors common to both disorders that lead to similar anatomic sites for involvement.

TGF-beta2 inhibition augments the effect of tumor vaccine and improves the survival of animals with pre-established brain tumors

TGF-beta2 secretion by high grade gliomas has been implicated as one of the major factors contributing to tumor growth, alterations in the host immune response to tumor, and failure of gliomas to respond to current immunotherapy strategies. We hypothesized that targeted delivery and inhibition of TGF-beta2 by TGF-beta2 antisense oligonucleotides (AS-ODNs) would overcome tumor-induced immunosuppression and enhance the capacity of tumor vaccines to eradicate established brain tumors. Utilizing the mRNA sequences of TGF-beta2, specific AS-ODNs were constructed and tested for their ability to inhibit TGF-beta2 production in 9L glioma cells. The effect of combining local intracranial administration of antisense ODNs with systemic tumor vaccine was examined. Fisher 344 rats were vaccinated subcutaneously with irradiated 9L tumor cells 3 days after intracranial tumor implantation. Four days after vaccination, ODNs were administered into the tumor mass and survival was followed. ODNs delivered locally distributed widely within the brain tumor mass and inhibited TGF-beta2 expression. Survival of tumor-bearing rats treated with the combination of local antisense and systemic tumor vaccine was significantly enhanced (mean survival time (MST): 48.0 days). In contrast, MST for animals treated with nonsense plus vaccine, vaccine alone, antisense alone or PBS showed no survival advantage and no statistical differences between groups (33.5 days, 29.0 days, 37.5 days, and 31.5 days, respectively). Our data supports the hypothesis that local administration of antisense TGF-beta2 ODNs combined with systemic vaccination can increase efficacy of immunotherapy and is a novel, potentially clinically applicable, strategy for high-grade glioma treatment.