Novel SOX10 indel mutations drive schwannomas through impaired transactivation of myelination gene programs

BACKGROUND

Schwannomas are common peripheral nerve sheath tumors that can cause severe morbidity given their stereotypic intracranial and paraspinal locations. Similar to many solid tumors, schwannomas and other nerve sheath tumors are primarily thought to arise due to aberrant hyperactivation of the RAS growth factor signaling pathway. Here, we sought to further define the molecular pathogenesis of schwannomas.

METHODS

We performed comprehensive genomic profiling on a cohort of 96 human schwannomas, as well as DNA methylation profiling on a subset. Functional studies including RNA sequencing, chromatin immunoprecipitation-DNA sequencing, electrophoretic mobility shift assay, and luciferase reporter assays were performed in a fetal glial cell model following transduction with wildtype and tumor-derived mutant isoforms of SOX10.

RESULTS

We identified that nearly one-third of sporadic schwannomas lack alterations in known nerve sheath tumor genes and instead harbor novel recurrent in-frame insertion/deletion mutations in SOX10, which encodes a transcription factor responsible for controlling Schwann cell differentiation and myelination. SOX10 indel mutations were highly enriched in schwannomas arising from nonvestibular cranial nerves (eg facial, trigeminal, vagus) and were absent from vestibular nerve schwannomas driven by NF2 mutation. Functional studies revealed these SOX10 indel mutations have retained DNA binding capacity but impaired transactivation of glial differentiation and myelination gene programs.

CONCLUSIONS

We thus speculate that SOX10 indel mutations drive a unique subtype of schwannomas by impeding proper differentiation of immature Schwann cells.

Spongiform leukoencephalopathy: A unique case of biopsy confirmed leukoencephalopathy secondary to toxic, non-inflammatory exposure

Toxin-induced leukoencephalopathy is a rare neurological condition that has been previously associated with intracranial radiation, chemotherapy, drugs of abuse, and environmental exposures. Herein, we present a patient with brain-biopsy proven toxin-induced leukoencephalopathy, likely secondary to multiple environmental offenders including insecticides and non-Food and Drug Administration approved anabolic steroids, opioids, and benzodiazepines. A 60-year-old man presented to our service as a direct transfer from an outside facility for evaluation of a rapidly progressive neuropsychiatric decline. Extensive workup with blood work, cerebrospinal fluid analysis, paraneoplastic panel, serial magnetic resonance imaging brain with and without contrast, and electroencephalograms were unrevealing. Magnetic resonance imaging brain showed diffuse confluent white matter disease, which was non-specific. The patient was treated with high-dose methylprednisolone and trials of intravenous immunoglobulin without any significant improvement. Finally, a brain biopsy was performed, and pathology confirmed a spongiform leukoencephalopathy, favoring a toxin-related etiology. The diagnosis of toxin-induced leukoencephalopathy should be considered in patients with steep neuropsychiatric decline and associated diffuse white matter disease. Diagnosis relies heavily on history of exposure, clinical presentation, imaging findings, and ultimately, histopathology from brain biopsy. The recognition of the clinical presentation is important to pursue the appropriate diagnostic workup and treatment.

Abstract 4644: A cell-line based TP53 expression pattern control panel with interobserver variability and next-generation sequencing analysis

Introduction: TP53 gene mutation status is known to be manifested through distinct p53 immunohistochemical staining patterns; diffuse, wild-type and null. This stratified staining pattern is routinely utilized in subtyping ovarian and endometrial cancer subtypes and distinguishing low- and high-grade serous carcinoma.

Experimental Procedure: Three ovarian cancer cell lines were used in the construction of an immunohistochemical control panel slide that highlights each respective TP53 expression pattern. Cell lines were expanded, harvested and resuspended in agarose gel and subsequently sectioned onto a microscope slide. Procured tissue specimens were submitted along with either standard control tissue or the TP53 cell line control panel to pathologists of varying experience. Next-generation sequencing analysis was performed on cases in which there was discordance in expression pattern interpretation.

Results: Interobserver variability was assessed on 44 samples between five raters of varying experience. The results were similar with the use of the TP53 expression panel (Fleiss kappa= 0.6 vs 0.53). Next-generation sequencing analysis demonstrated low-frequency variant mutations in cases in which there was reviewer discordance.

Conclusion: This study suggests the addition of a TP53 cell line expression pattern control panel could potentially increase diagnostic accuracy for ovarian and endometrial cancer subtypes and distinguishing ovarian low-grade and high-grade serous carcinoma. The cell line control has refined quality assurance potential for antibody optimization.This cell line control panel has the potential to be utilized in routine immunohistochemical staining with difficult to interpret p53 expression patterns directed to submission for next-generation sequencing.

Citation Format: Yaling Zhou, Sorana Raiciulescu, Viqar Syed, Patrick Malafronte, Justin Wells, Mica Grantham, Michael Allgaeuer, Heping Gong, Joel Moncur, Deyin Xing, John D. Andersen. A cell-line based TP53 expression pattern control panel with interobserver variability and next-generation sequencing analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4644. doi:10.1158/1538-7445.AM2017-4644

Abstract DPOC-002: A NOVEL CELL LINE BASED IMMUNOHISTOCHEMICAL TP53 EXPRESSION PATTERN CONTROL PANEL

BACKGROUND: TP53 gene mutation status is known to be manifested through distinct p53 immunohistochemical staining patterns; diffuse, “wild-type” and null. This stratified staining pattern is commonly utilized in subtyping ovarian and endometrial cancer subtypes as well as distinguishing between ovarian low- and high-grade serous carcinoma.

EXPERIMENTAL PROCEDURES: Three ovarian cancer cell lines consistently demonstrating either diffuse, wild-type or null p53 staining were utilized in the construction of an immunohistochemical control panel slide that highlights each TP53 expression pattern. Cell lines were expanded, harvested and resuspended in agarose gel and subsequently sectioned onto a microscope slide (Figure 1A). Procured tissue specimens were submitted along with either standard control tissue or the TP53 cell line control panel to three pathologists of varying experience.

RESULTS: Interobserver variability was demonstrated to be similar with the use of the TP53 expression panel (Fleiss kappa= 0.79 vs 0.76) and there was a net decrease in categorization errors. The TP53 cell line expression pattern control panel sections demonstrated consistent clean and easily interpretable diffuse, wild-type and null p53 staining (Figure 1B).

CONCLUSIONS: We developed a novel cell line-based TP53 expression pattern control panel with refined quality assurance potential that would act, as a minimum, a model for antibody optimization. This study suggests the addition of a cell line TP53 control panel could potentially increase the accuracy of identification for ovarian and endometrial cancer subtypes as well as ovarian low grade versus high-grade serous carcinoma distinction. This control panel has the potential to be utilized in other disease states where TP53 expression pattern assists in diagnosis.

Citation Format: Viqar Syed PhD, Imran Hussain, BSc, Jeptha Johnson MD, Patrick Malafronte MD, Justin Wells MD, Yaling Zhou PhD, Deyin Xing MD PhD, John D. Andersen DO. A NOVEL CELL LINE BASED IMMUNOHISTOCHEMICAL TP53 EXPRESSION PATTERN CONTROL PANEL [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr DPOC-002.

Brown-Vialetto-Van Laere syndrome: clinical and neuropathologic findings with immunohistochemistry for C20orf54 in three affected patients

Brown-Vialetto-Van Laere syndrome (BVVLS) is a rare degenerative neurological disorder characterized by pontobulbar palsy and sensorineural deafness. Since its initial description in 1894, fewer than 100 cases have been reported, and published neuropathological analyses of these cases are extremely rare. Recently, individuals with BVVLS have been found to carry mutations in the C20orf54 gene, which encodes the human homolog for a rat riboflavin transporter. We present the case of a male who presented at the age of 5 years with sensorineural deafness, as well as those of 2 infant sisters who presented at 11 and 13 months of age with weakness and ataxia, respectively. All cases were genetically confirmed. We include the 1st immunohistochemical characterization of C20orf54 expression in BVVLS and controls. Results showed punctate axonal staining in the control cases that was dramatically reduced in the 3 BVVLS cases compared to the 5 controls. This decreased staining was seen even in the neocortex, which was unaffected in the BVVLS cases by routine histology. While the implications of these results are far from definitive, and although the evaluation of more cases is needed, immunohistochemistry for the C20orf54 protein may eventually be useful, in the right clinical scenario, as a screening test when selecting cases for sequencing of the C20orf54 gene to diagnose BVVLS at autopsy.

Blind and confused

A 62-year-old man developed confusion and was diagnosed as having encephalitis. The etiology was not identified. He continued to have cognitive impairment but remained clinically stable. Five months later, he woke with bilateral vision loss. On neurological examination, he had no light perception bilaterally. The remainder of the neurological examination results were normal. Magnetic resonance imaging of the brain revealed multiple brain lesions. He was treated with steroids and plasmapheresis, with mild improvement in vision. He was then transferred to a long-term care facility, where he developed increasing confusion and ultimately died. An autopsy was performed; the differential diagnosis, neuropathology, and final diagnosis are discussed here.

Lymph node melanosis in a patient with metastatic melanoma of unknown primary

Tumoral or nodular melanosis in the skin is considered a variation of completely regressed melanoma, presenting clinically as a suspicious pigmented papule or nodule. Microscopically, the lesion consists of a nodular accumulation of heavily pigmented melanophages in the dermis, staining positive for immunohistochemical markers of histiocytic lineage (CD68) and negative for those of melanocytic lineage (S100, HMB-45, Melan-A). This process is rarely described in lymph nodes. We present a report of a patient with melanosis involving multiple lymph nodes of an axillary dissection, done for metastatic melanoma with an unknown primary, and discuss possible prognostic and treatment factors.

Cryoglobulinemia in Kidney Transplant Recipients

The aim of this study was to assess the presence of cryoglobulins, the constitution of the cryoprecipitate, as well as the possible etiology and clinical features in kidney transplant recipients. We excluded patients with clinical or laboratory evidence of autoimmune, liver or neoplasm disease, infections, blood transfusions or immunizations in the previous 3 months. Detection of cryoglobulins was obtained from the peripheral venous blood. In cases of cryoprecipitate formation it was analyzed using anti-IgG, anti-IgM, anti-IgA, anti-C3, and anti-C4 antibodies. The hepatitis C virus (HCV) was detected by the polymerase chain reaction. Thirty-nine patients were selected, of whom 23 were men and the overall mean age was 40.6 +/- 12.7 years. Cryoprecipitate was detected in 74.4% (29/39) patients. Among patients with or without cryoprecipitate formation, the serum creatinine values, the percentage of patients with proteinuria, and the posttransplantation times were similar. In patients with cryoglobulins, 37.9% (11/29) were HCV positive. The etiology was not determined for the other patients. The IgG, IgM, and IgA immunoglobulins and the complement fractions C3 and C4 were found in the cryoprecipitate. Their compositions were similar among patients with or without HCV. Few clinical features were associated with the presence of cryoglobulins, including deep venous thrombosis, cutaneous purpura and peripheral neuropathy. In conclusion, cryoglobulinemia was prevalent in kidney transplant recipients, but appeared to not affect graft function. HCV infection was the most frequently associated etiology and clinical features were infrequent.

Posttransplant diabetes mellitus in renal transplant patients with hepatitis C virus

The aim of this study was to assess the possible association between posttransplant diabetes mellitus (DM) and hepatitis C virus (HCV) infection in renal transplant recipients. This study included 124 patients who underwent renal transplantation between 1997 and 2002. Inclusion criteria were patients who were not diabetic prior to transplantation and posttransplant follow-up longer than 6 months. DM was defined as fasting blood glucose levels higher than 126 mg/dL on at least two occasions. HCV infection was detected using second- or third-generation ELISA methods and/or polymerase chain reactions for HCV-RNA. Twenty-five HCV positive (HCV+) patients were compared with 25 consecutive HCV negative (HCV-) transplant patients. Demographic and clinical data of the groups were compared. Posttransplantation DM was observed in 24% of the HCV+ patients. There were no statistical differences in age, gender, race, family history of DM, follow-up, or body mass index between the two groups. There was a higher prevalence of posttransplantation DM in HCV+ patients, but the difference did not reach statistical significance (24% vs 12%, P = NS). Alternatively, comparing patients of the two groups (n = 50) who did versus not develop DM, the incidence of posttransplantation DM was higher among HCV+ patients, but the difference did not reach statistical significance (66.6% vs 46.3%, P = NS). In conclusion, there was no association between HCV infection and the development of posttransplantation DM in this cohort of renal transplant recipients. However, there was a trend that suggested an association.