Aggressive vestibular schwannomas showing postoperative rapid growth - their association with decreased p27 expression

Tumor Microenvironment in Sporadic Vestibular Schwannoma: A Systematic, Narrative Review

Although diagnosis and treatment of vestibular schwannomas (VSs) improved in recent years, no factors have yet been identified as being capable of predicting tumor growth. Molecular rearrangements occur in neoplasms before any macroscopic morphological changes become visible, and the former are the underlying cause of disease behavior. Tumor microenvironment (TME) encompasses cellular and non-cellular elements interacting together, resulting in a complex and dynamic key of tumorigenesis, drug response, and treatment outcome. The aim of this systematic, narrative review was to assess the level of knowledge on TME implicated in the biology, behavior, and prognosis of sporadic VSs. A search (updated to November 2022) was run in Scopus, PubMed, and Web of Science electronic databases according to the PRISMA guidelines, retrieving 624 titles. After full-text evaluation and application of inclusion/exclusion criteria, 37 articles were included. VS microenvironment is determined by the interplay of a dynamic ecosystem of stromal and immune cells which produce and remodel extracellular matrix, vascular networks, and promote tumor growth. However, evidence is still conflicting. Further studies will enhance our understanding of VS biology by investigating TME-related biomarkers able to predict tumor growth and recognize immunological and molecular factors that could be potential therapeutic targets for medical treatment.

Acute Vestibular Syndrome and ER Presentations of Dizziness

Acute vestibular syndrome (AVS) describes sudden onset, severe, continuous dizziness that persists for more than 24 hours. Its wide differential presents a diagnostic challenge. Vestibular neuritis is the most common cause, but stroke, trauma, medication effects, infectious, and inflammatory causes all present similarly. The TiTrATE model (Timing, Triggers, And Targeted Exam) is systematic way to evaluate these patients, and the HINTS Plus exam (Head Impulse, Nystagmus, Test of Skew, plus hearing loss) is critical in differentiating central and peripheral causes. The importance of recognizing risk factors for stroke and the role of imaging is also discussed.

Near Total Versus Gross Total Resection of Large Vestibular Schwannomas: Facial Nerve Outcome

BACKGROUND

Large vestibular schwannomas (VSs) with brainstem compression are generally reserved for surgical resection. Surgical aggressiveness must be balanced with morbidity from cranial nerve injury. The purpose of the present investigation is to evaluate the clinical presentation, management modality, and patient outcomes following near total resection (NTR) vs gross total resection (GTR) of large VSs.

OBJECTIVE

To assess facial nerve outcome differences between GTR and NTR patient cohorts.

METHODS

Between January 2010 and March 2018, a retrospective chart review was completed to capture patients continuously who had VSs with Hannover grades T4a and T4b. NTR was decided upon intraoperatively. Primary data points were collected, including preoperative symptoms, tumor size, extent of resection, and postoperative neurological outcome.

RESULTS

A total of 37 patients underwent surgery for treatment of large and giant (grade 4a and 4b) VSs. Facial nerve integrity was preserved in 36 patients (97%) at the completion of surgery. A total of 27 patients underwent complete resection, and 10 had near total (>95%) resection. Among patients with GTR, 78% (21/27) had House-Brackmann (HB) grade I-II facial nerve function at follow-up, whereas 100% (10/10) of the group with NTR had HB grade I-II facial nerve function. Risk of meningitis, cerebrospinal fluid leak, and sinus thromboses were not statistically different between the 2 groups. There was no stroke, brainstem injury, or death. The mean follow-up was 36 mo.

CONCLUSION

NTR seems to offer a benefit in terms of facial nerve functional outcome compared to GTR in surgical management of large VSs without significant risk of recurrence.

YAP-Mediated Recruitment of YY1 and EZH2 Represses Transcription of Key Cell-Cycle Regulators

The Hippo pathway regulates cell proliferation and organ size through control of the transcriptional regulators YAP (yes-associated protein) and TAZ. Upon extracellular stimuli such as cell-cell contact, the pathway negatively regulates YAP through cytoplasmic sequestration. Under conditions of low cell density, YAP is nuclear and associates with enhancer regions and gene promoters. YAP is mainly described as a transcriptional activator of genes involved in cell proliferation and survival. Using a genome-wide approach, we show here that, in addition to its known function as a transcriptional activator, YAP functions as a transcriptional repressor by interacting with the multifunctional transcription factor Yin Yang 1 (YY1) and Polycomb repressive complex member enhancer of zeste homologue 2 (EZH2). YAP colocalized with YY1 and EZH2 on the genome to transcriptionally repress a broad network of genes mediating a host of cellular functions, including repression of the cell-cycle kinase inhibitor p27, whose role is to functionally promote contact inhibition. This work unveils a broad and underappreciated aspect of YAP nuclear function as a transcriptional repressor and highlights how loss of contact inhibition in cancer is mediated in part through YAP repressive function. SIGNIFICANCE: This study provides new insights into YAP as a broad transcriptional repressor of key regulators of the cell cycle, in turn influencing contact inhibition and tumorigenesis.

Contemporary Molecular Biology of Sporadic Vestibular Schwannomas: A Systematic Review and Clinical Implications

In light of missing systematic reviews in the literature, the objective of this paper is to present the contemporary knowledge on the molecular biology of vestibular schwannomas (VS), based on a systematic literature search. In addition, current and prospected medical therapy based on molecular biology is addressed. A systematic literature search was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The systematic search was performed in the Pubmed and Embase databases. The following were the words searched: acoustic neuroma/vestibular schwannoma, molecular biology, gene, and microRNA. Specific inclusion and exclusion criteria were determined prior to search. The systematic search rendered 486 articles, ultimately yielding 69 included articles, whereas 35 were from relevant references. The occurrence of at least one mutation in the merlin gene was reported to range between 54% and 76%, whereas the loss of heterozygosity (LOH) corresponding to chromosome 22 occurs in 25% to 83% of sporadic VS. Global gene expression studies indicate that a number of genes other than merlin are at play. No high-level methylation of the merlin gene has been found. Several miRNAs are deregulated in tumor tissue, among others let-7d, miR-221, and miR-21. The acquired knowledge on molecular biology has led to several clinical implementations. Lack of the tumor suppressor merlin plays a principal role in the development of VS. Existing knowledge on the molecular biology has led to the first attempts of targeted medical treatment to prevent tumor growth. Future research is likely to introduce potential imaging markers with prognostic value and new targets for medical therapy.

Preclinical validation of anti-nuclear factor-kappa B therapy to inhibit human vestibular schwannoma growth

Vestibular schwannomas (VSs), the most common tumors of the cerebellopontine angle, arise from Schwann cells lining the vestibular nerve. Pharmacotherapies against VS are almost non-existent. Although the therapeutic inhibition of inflammatory modulators has been established for other neoplasms, it has not been explored in VS. A bioinformatic network analysis of all genes reported to be differentially expressed in human VS revealed a pro-inflammatory transcription factor nuclear factor-kappa B (NF-κB) as a central molecule in VS pathobiology. Assessed at the transcriptional and translational level, canonical NF-κB complex was aberrantly activated in human VS and derived VS cultures in comparison to control nerves and Schwann cells, respectively. Cultured primary VS cells and VS-derived human cell line HEI-193 were treated with specific NF-κB siRNAs, experimental NF-κB inhibitor BAY11-7082 (BAY11) and clinically relevant NF-κB inhibitor curcumin. Healthy human control Schwann cells from the great auricular nerve were also treated with BAY11 and curcumin to assess toxicity. All three treatments significantly reduced proliferation in primary VS cultures and HEI-193 cells, with siRNA, 5 μM BAY11 and 50 μM curcumin reducing average proliferation (±standard error of mean) to 62.33% ± 10.59%, 14.3 ± 9.7%, and 23.0 ± 20.9% of control primary VS cells, respectively. These treatments also induced substantial cell death. Curcumin, unlike BAY11, also affected primary Schwann cells. This work highlights NF-κB as a key modulator in VS cell proliferation and survival and demonstrates therapeutic efficacy of directly targeting NF-κB in VS.

Global gene expression profiling and tissue microarray reveal novel candidate genes and down-regulation of the tumor suppressor gene CAV1 in sporadic vestibular schwannomas

BACKGROUND

The vestibular nerve is the predilection site for schwannomas. Few transcriptomic studies have been performed on solely sporadic vestibular schwannomas (VSs).

OBJECTIVE

To detect genes with altered expression levels in sporadic VSs.

METHODS

We studied 25 VSs and 3 tibial nerves (controls) with the ABI 1700 microarray platform. Significance analysis of microarrays was performed to explore differential gene expression. Selected genes were validated with quantitative reverse transcriptase polymerase chain reaction. A tissue microarray was constructed for immunohistochemistry. Neurofibromatosis type II cDNA was sequenced for mutations.

RESULTS

The VSs formed 2 clusters based on the total expression of 23,055 genes. Tumor size, previous Gamma Knife surgery, neurofibromatosis type II mutations, and cystic tumors were distributed equally in both. Significance analysis of microarrays detected 1650 differentially expressed genes. On the top 500 list, several cancer-related genes with an unrecognized role in VSs were down-regulated: CAV1, TGFB3, VCAM1, GLI1, GLI2, PRKAR2B, EPHA4, and FZD1. Immunohistochemistry showed no CAV1 expression in the VSs. The ERK pathway was the central core in the network linking the differentially expressed genes. The previously reported VS candidate genes SPARC, PLAT, and FGF1 were up-regulated. Nineteen of 25 VSs had NF2 mutations.

CONCLUSION

Using microarray technology, we identified novel genes and pathways with a putative role in VSs, confirmed previous candidate genes, and found cancer-related genes with no reported role in VSs. Among these, down-regulation of CAV1 at both the mRNA and protein levels is of particular interest because this tumor suppressor normally is expressed in Schwann cells.

Robot-assisted resection of paraspinal Schwannoma

Resection of retroperitoneal tumors is usually performed using the anterior retroperitoneal approach. Our report presents an innovative method utilizing a robotic surgical system. A 50-yr-old male patient visited our hospital due to a known paravertebral mass. Magnetic resonance imaging showed a well-encapsulated mass slightly abutting the abdominal aorta and left psoas muscle at the L4-L5 level. The tumor seemed to be originated from the prevertebral sympathetic plexus or lumbosacral trunk and contained traversing vessels around the tumor capsule. A full-time robotic transperitoneal tumor resection was performed. Three trocars were used for the robotic camera and working arms. The da Vinci Surgical System® provided delicate dissection in the small space and the tumor was completely removed without damage to the surrounding organs and great vessels. This case demonstrates the feasibility of robotic resection in retroperitoneal space. Robotic surgery offered less invasiveness in contrast to conventional open surgery.

Cyclin D1 expression and facial function outcome after vestibular schwannoma surgery

HYPOTHESIS

The proto-oncogen cyclin D1 has been implicated in the development and behavior of vestibular schwannoma. This study evaluates the association between cyclin D1 expression and other known prognostic factors in facial function outcome 1 year after vestibular schwannoma surgery.

METHODS

Sixty-four patients undergoing surgery for vestibular schwannoma were studied. Immunohistochemistry analysis was performed with anticyclin D1 in all cases. Cyclin D1 expression, as well as other demographic, clinical, radiologic, and intraoperative data, was correlated with 1-year postoperative facial function.

RESULTS

Good 1-year facial function (Grades 1-2) was achieved in 73% of cases. Cyclin D1 expression was found in 67% of the tumors. Positive cyclin D1 staining was more frequent in patients with Grades 1 to 2 (75%) than in those with Grades 3 to 6 (25%). Other significant variables were tumor volume and facial nerve stimulation after tumor resection. The area under the receiver operating characteristics curve increased when adding cyclin D1 expression to the multivariate model.

CONCLUSION

Cyclin D1 expression is associated to facial outcome after vestibular schwannoma surgery. The prognostic value of cyclin D1 expression is independent of tumor size and facial nerve stimulation at the end of surgery.

Cyclin D1 expression and histopathologic features in vestibular schwannomas

OBJECTIVE

To evaluate cyclin D1 expression in vestibular schwannoma and its relationship with histologic, clinical, and radiologic features.

PATIENTS

Twenty-one patients with histologically confirmed vestibular schwannoma.

INTERVENTION

Immunohistochemistry analysis was performed with anticyclin D1. Histopathologic features studied included Antoni pattern and nuclear and stromal degenerative changes. Clinical charts, audiometric data, and magnetic resonance imaging characteristics were reviewed.

MAIN OUTCOME MEASURES

Cyclin D1 expression and its association with histologic, clinical, and radiologic findings.

RESULTS

Cyclin D1 expression was found in 52% of cases. Cyclin D1 expression was more frequent in right-sided tumors (p = 0.02) and in tumors with nuclear degenerative changes (p < 0.0001). Patients with negative cyclin D1 expression had longer duration of deafness (p = 0.02) and higher 2,000-Hz hearing thresholds (p = 0.04) than cyclin D1+ patients.

CONCLUSION

Cyclin D1 expression, present in nearly half of the cases, may play a role in the development of these tumors. Further studies are needed to fully understand the contributions of histopathologic and immunohistochemical factors to vestibular schwannoma biological activity.