Frequent genomic imbalances in chromosomes 17, 19, and 22q in peripheral nerve sheath tumours detected by comparative genomic hybridization analysis

Neurofibromin Deficiency Causes Epidermal Growth Factor Receptor Upregulation through the Activation of Ras/ERK/SP1 Signaling Pathway in Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheet Tumor

Neurofibromatosis type 1 (NF1) is an autosomal dominant human genetic disorder. The progression of benign plexiform neurofibromas to malignant peripheral nerve sheet tumors (MPNSTs) is a major cause of mortality in patients with NF1. Although elevated epidermal growth factor receptor (EGFR) expression plays a crucial role in the pathogenesis of MPNST, the cause of EGFR overexpression remains unclear. Here, we assessed EGFR expression levels in MPNST tissues of NF1 patients and NF1 patient-derived MPNST cells. We found that the expression of EGFR was upregulated in MPNST tissues and MPNST cells, while the expression of neurofibromin was significantly decreased. Manipulation of NF1 expression by NF1 siRNA treatment or NF1-GAP-related domain overexpression demonstrated that EGFR expression levels were closely and inversely correlated with neurofibromin levels. Notably, knockdown of the NF1 gene by siRNA treatment augmented the nuclear localization of phosphorylated SP1 (pSP1) and enhanced pSP1 binding to the EGFR gene promoter region. Our results suggest that neurofibromin deficiency in NF1-associated MPNSTs enhances the Ras/ERK/SP1 signaling pathway, which in turn may lead to the upregulation of EGFR expression. This study provides insight into the progression of benign tumors and novel therapeutic approaches for treatment of NF1-associated MPNSTs.

Brachial plexus tumors extending into the cervicothoracic spine: a review with operative nuances and outcomes

BACKGROUND

The rarity and anatomical complexity of brachial plexus tumors (BPTs) impose many challenges onto surgeons performing surgical resections, especially when these tumors invade the cervicothoracic spine. Treatment choices and surgery outcomes heavily depend on anatomical location and tumor type.

METHODS

The authors performed an extensive review of the published literature (PubMed) focusing on "brachial plexus tumors" that identified invasion of the cervicothoracic spine.

RESULTS

The search yielded 2774 articles pertaining to "brachial plexus tumors". Articles not in the English language or involving cervicothoracic spinal invasion were excluded.

CONCLUSIONS

Recent research has shown that the most common method used to resect tumors of the proximal roots is the dorsal subscapular approach. Despite its association with high morbidity rate, this technique offers excellent exposure to the spinal roots and intraforaminal portion of the spinal nerve. The dorsal approach is used to resect recurrent lower trunk tumors and dumbbell-shaped neurofibromas, yet it is also the least common overall approach used in brachial plexus tumor resections. The ventral or anterior technique is commonly used to resect tumors at the cord to division level, and root to trunk level. Motor complications, transient nerve palsy, and bleeding are among the most common complications of the anterior supraclavicular approach. Further controlled studies are needed to fully determine the optimal surgical approach used to obtain the best outcomes and least complications for each type of brachial plexus tumor.

Analysis of copy number variants in 11 pairs of monozygotic twins with neurofibromatosis type 1

Phenotypic variability among individuals with neurofibromatosis type 1 (NF1) has long been a challenge for clinicians and an enigma for researchers. Members of the same family and even identical twins with NF1 often demonstrate variable disease expression. Many mechanisms for this variability have been proposed. We have performed an exploratory study of copy number variants (CNVs) as a possible source of phenotypic variability in NF1. We enrolled 11 pairs of monozygotic (MZ) twins with NF1 and their parents, catalogued their clinical characteristics, and utilized a single nucleotide polymorphism (SNP) microarray to identify CNVs in blood and saliva. The 11 twin pairs showed high concordance for presence and number of café-au-lait spots, cutaneous neurofibromas, IQ, and ADHD. They were more likely to be discordant for optic pathway glioma, plexiform neurofibromas, skeletal manifestations, and malignancy. Microarray analysis identified a total of 81 CNVs meeting our conservative criteria, 37 of which overlap known genes. Of interest, three CNVs were previously unreported. Microarray analysis failed to ascertain any CNV differences within twin pairs, between twins and parents, or between tissues in any one individual. Results of this small pilot study did not demonstrate any de novo CNV events in our MZ twin pairs, nor were de novo CNVs overrepresented in these individuals with NF1. A much larger sample size would be needed to form any conclusions about the role of CNVs in NF1 variable expressivity. Alternative explanations for discordant phenotypes include epigenetic changes, smaller genetic alterations, or environmental factors. © 2016 Wiley Periodicals, Inc.

Protein expression of BIRC5, TK1, and TOP2A in malignant peripheral nerve sheath tumours--A prognostic test after surgical resection

No consensus treatment regime exists beyond surgery for malignant peripheral nerve sheath tumours (MPNST), and the purpose of the present study was to find new approaches to stratify patients with good and poor prognosis and to better guide therapeutic intervention for this aggressive soft tissue cancer.

From a total of 67 MPNSTs from Scandinavian patients with and without neurofibromatosis type 1, 30 MPNSTs were investigated by genome‐wide RNA expression profiling and 63 MPNSTs by immunohistochemical (IHC) analysis, and selected genes were submitted to analyses of disease‐specific survival.

The potential drug target genes survivin (BIRC5), thymidine kinase 1 (TK1), and topoisomerase 2‐alpha (TOP2A), all encoded on chromosome arm 17q, were up‐regulated in MPNST as compared to benign neurofibromas. Each of them was found to be independent prognostic markers on the gene expression level, as well as on the protein level. A prognostic profile was identified by combining the nuclear expression scores of the three proteins. For patients with completely resected tumours only 15% in the high risk group were alive after two years, as compared to 78% in the low risk group.

In conclusion, we found a novel protein expression profile which identifies MPNST patients with inferior prognosis even after assumed curative surgery. The tested proteins are drug targets; therefore the expression profile may provide predictive information guiding the design of future clinical trials. Importantly, as the effect is seen on the protein level using IHC, the biomarker panel can be readily implemented in routine clinical testing.

Genomic and molecular aberrations in malignant peripheral nerve sheath tumor and their roles in personalized target therapy

Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors with a high rate of local recurrence and a significant tendency to metastasize. Its dismal outcome points to the urgent need to establish better therapeutic strategies for patients harboring MPNSTs. The investigations of genomic and molecular aberrations in MPNSTs which detect many chromosomal aberrations, pathway abnormalities, and specific molecular aberrant events would supply multiple potential therapy targets and contribute to achievement of personalized medicine. The involved genes in the significant gains aberrations include BIRC5, CCNE2, DAB2, DDX15, EGFR, DAB2, MSH2, CDK6, HGF, ITGB4, KCNK12, LAMA3, LOXL2, MET, and PDGFRA. The involved genes in the significant deletion aberrations include CDH1, GLTSCR2, EGR1, CTSB, GATA3, SULT2A1, GLTSCR2, HMMR/RHAMM, LICAM2, MMP13, p16/INK4a, RASSF2, NM-23H1, and TP53. These genetic aberrations involve in several important signaling pathways such as TFF, EGFR, ARF, IGF1R signaling pathways. The genomic and molecular aberrations of EGFR, IGF1R, SOX9, EYA4, TOP2A, ETV4, and BIRC5 exhibit great promise as personalized therapeutic targets for MPNST patients.

Transgenic mice overexpressing neuregulin-1 model neurofibroma-malignant peripheral nerve sheath tumor progression and implicate specific chromosomal copy number variations in tumorigenesis

Patients with neurofibromatosis type 1 (NF1) develop benign plexiform neurofibromas that frequently progress to become malignant peripheral nerve sheath tumors (MPNSTs). A genetically engineered mouse model that accurately models plexiform neurofibroma-MPNST progression in humans would facilitate identification of somatic mutations driving this process. We previously reported that transgenic mice overexpressing the growth factor neuregulin-1 in Schwann cells (P(0)-GGFβ3 mice) develop MPNSTs. To determine whether P(0)-GGFβ3 mice accurately model human neurofibroma-MPNST progression, cohorts of these animals were monitored through death and were necropsied; 94% developed multiple neurofibromas, with 70% carrying smaller numbers of MPNSTs. Nascent MPNSTs were identified within neurofibromas, suggesting that these sarcomas arise from neurofibromas. Although neurofibromin expression was maintained, P(0)-GGFβ3 MPNSTs exhibited Ras hyperactivation, as in human NF1-associated MPNSTs. P(0)-GGFβ3 MPNSTs also exhibited abnormalities in the p16(INK4A)-cyclin D/CDK4-Rb and p19(ARF)-Mdm-p53 pathways, analogous to their human counterparts. Array comparative genomic hybridization (CGH) demonstrated reproducible chromosomal alterations in P(0)-GGFβ3 MPNST cells (including universal chromosome 11 gains) and focal gains and losses affecting 39 neoplasia-associated genes (including Pten, Tpd52, Myc, Gli1, Xiap, and Bbc3/PUMA). Array comparative genomic hybridization also identified recurrent focal copy number variations affecting genes not previously linked to neurofibroma or MPNST pathogenesis. We conclude that P(0)-GGFβ3 mice represent a robust model of neurofibroma-MPNST progression useful for identifying novel genes driving neurofibroma and MPNST pathogenesis.

Survival meta-analyses for >1800 malignant peripheral nerve sheath tumor patients with and without neurofibromatosis type 1

There are conflicting reports as to whether malignant peripheral nerve sheath tumor (MPNST) patients with neurofibromatosis type 1 (NF1) have worse prognosis than non-NF1 MPNST patients. Large clinical studies to address this problem are lacking due to the rareness of MPNST. We have performed meta-analyses testing the effect of NF1 status on MPNST survival based on publications from the last 50 years, including only nonoverlapping patients reported from each institution. In addition, we analyzed survival characteristics for 179 MPNST patients from 3 European sarcoma centers. The meta-analyses including data from a total of 48 studies and >1800 patients revealed a significantly higher odds ratio for overall survival (OR(OS)) and disease-specific survival (OR(DSS)) in the non-NF1 group (OR(OS) = 1.75, 95% confidence interval [CI] = 1.28-2.39, and OR(DSS) = 1.68, 95% CI = 1.18-2.40). However, in studies published in the last decade, survival in the 2 patient groups has been converging, as especially the NF1 group has shown improved prognosis. For our own MPNST patients, NF1 status had no effect on overall or disease-specific survival. The compiled literature from 1963 to the present indicates a significantly worse outcome of MPNST in patients with NF1 syndrome compared with non-NF1 patients. However, survival for the NF1 patients has improved in the last decade, and the survival difference is diminishing. These observations support the hypothesis that MPNSTs arising in NF1 and non-NF1 patients are not different per se. Consequently, we suggest that the choice of treatment for MPNST should be independent of NF1 status.

The 4q12 amplicon in malignant peripheral nerve sheath tumors: consequences on gene expression and implications for sunitinib treatment

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNST) are highly aggressive tumors which originate from Schwann cells and develop in about 10% of neurofibromatosis type 1 (NF1) patients. The five year survival rate is poor and more effective therapies are needed. Sunitinib is a drug targeting receptor tyrosine kinases (RTK) like PDGFRalpha, c-Kit and VEGFR-2. These genes are structurally related and cluster on chromosomal segment 4q12.

METHODOLOGY/PRINCIPAL FINDINGS

Here we characterize this region by multiplex ligation-dependent probe amplification (MLPA) in MPNST. Our probe set encompasses the 3 adjacent RTK genes (PDGFRA, KIT, KDR) and 6 flanking genes. We found amplification of several genes within this region in a subset of MPNST and MPNST cell lines. Transcript and protein expression of PDGFRA matched well with its increased copy number suggesting a central role of PDGFRA within the amplicon. Studying the effect of sunitinib on 5 MPNST cell lines revealed that cell line S462 harboring the 4q12 amplicon was extremely sensitive to the drug with an IC50 below 1.0 microM. Moreover, sunitinib induced apoptosis and prevented PDGF-AA induced signaling via PDGFRalpha as determined by western blotting. Co-expression of VEGF and its receptor VEGFR-2 (KDR) was present in MPNST cell lines suggesting an autocrine loop. We show that VEGF triggered signal transduction via the MAPK pathway, which could be blocked by sunitinib.

CONCLUSIONS/SIGNIFICANCE

Since multiple receptors targeted by sunitinib are expressed or over-expressed by MPNST cells sunitinib appears as an attractive drug for treatment of MPNST patients. Presence of the 4q12 amplicon and subsequent over-expression of PDGFRA might serve as predictive markers for efficacy of sunitinib.

Loss of Y chromosome in the malignant peripheral nerve sheet tumor of a patient with Neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is one of the most commonly inherited autosomal dominant disorders. In order to determine whether genomic alterations and/or chromosomal aberrations involved in the malignant progression of NF1 were present in a Korean patient with NF1, molecular and cytogenetic analyses were performed on the pathologically normal, benign, and malignant tissues and primary cells cultured from those tissues of the patient. The comparative genomic hybridization (CGH) array revealed a Y chromosome loss in the malignant peripheral nerve sheet tumor (MPNST) tissue. G-banding analysis of 50 metaphase cells showed normal chromosomal patterns in the histopathologically normal and benign cultured cells, but a mosaic Y chromosome loss in the malignant cells. The final karyotype for the malignant cells from MPNST tissue was 45,X,-Y[28]/46,XY[22]. The data suggest that the somatic Y chromosome loss may be involved in the transformation of benign tumors to MPNSTs.

Genomic changes in chromosomes 10, 16, and X in malignant peripheral nerve sheath tumors identify a high-risk patient group

PURPOSE

The purpose of this study was to identify genetic aberrations contributing to clinical aggressiveness of malignant peripheral nerve sheath tumors (MPNSTs).

PATIENTS AND METHODS

Samples from 48 MPNSTs and 10 neurofibromas were collected from 51 patients with (n = 31) or without (n = 20) neurofibromatosis type 1 (NF1). Genome-wide DNA copy number changes were assessed by chromosomal and array-based comparative genomic hybridization (CGH) and examined for prognostic significance. For a subset of 20 samples, RNA microarray data were integrated with the genome data to identify potential target genes.

RESULTS

Forty-four (92%) MPNSTs displayed DNA copy number changes (median, 18 changes per tumor; range, 2 to 35 changes). Known frequent chromosomal gains at chromosome arms 8q (69%), 17q (67%), and 7p (52%) and losses from 9p (50%), 11q (48%), and 17p (44%) were confirmed. Additionally, gains at 16p or losses from 10q or Xq identified a high-risk group with only 11% 10-year disease-specific survival (P = .00005). Multivariate analyses including NF1 status, tumor location, size, grade, sex, complete remission, and initial metastatic status showed that the genomic high-risk group was the most significant predictor of poor survival. Several genes whose expression was affected by the DNA copy number aberrations were identified.

CONCLUSION

The presence of specific genetic aberrations was strongly associated with poor survival independent of known clinical risk factors. Conversely, within the total patient cohort with 34% 10-year disease-specific survival, a low-risk group was identified: without changes at chromosomes 10q, 16p, or Xq in their MPNSTs, the patients had 74% 10-year survival.

Malignant peripheral nerve sheath tumor associated with neurofibromatosis type 1, with metastasis to the heart: a case report

A rare case is presented of a 61-year-old man with a malignant peripheral nerve sheath tumor associated with neurofibromatosis type 1, with metastasis to the heart. The primary tumor originated in the right thigh in 1982. Since then, the patient has had repeated local recurrences in spite of repeated surgical treatment and adjuvant chemotherapy. He has developed previous metastases of the lung and heart. The patient died of cardiac involvement.

PDGFRA, PDGFRB, EGFR, and downstream signaling activation in malignant peripheral nerve sheath tumor

We investigated the activation of platelet-derived growth factor (PDGF) receptor A (PDGFRA), PDGF receptor B (PDGFRB), epidermal growth factor receptor (EGFR), and their downstream pathways in malignant peripheral nerve sheath tumors (MPNSTs). PDGFRA, PDGFRB, and EGFR were immunohistochemically, biochemically, cytogenetically, and mutationally analyzed along with the detection of their cognate ligands in 16 neurofibromatosis type 1 (NF1)-related and 11 sporadic MPNSTs. The activation of the downstream receptor pathways was also studied by means of v-akt murine thymoma viral oncogene homolog (AKT), extracellular signal-regulated kinase (ERK), and mammalian target of rapamycin (mTOR) Western blotting experiments, as well as rat sarcoma viral oncogene homolog (RAS), v-raf murine sarcoma viral oncogene homolog B1 (BRAF), phosphoinositide-3-kinase, catalytic, alpha polypeptide (PI3KCA), and phosphatase and tensin homolog deleted on chromosome ten (PTEN) mutational analysis and fluorescence in situ hybridization. PDGFRA, PDGFRB, and EGFR were expressed/activated, with higher levels of EGFR expression/phosphorylation paralleling increasing EGFR gene copy numbers in the NF1-related cases (71%). Autocrine loop activation of these receptors along with their coactivation were suggested by the expression of the cognate ligands in the absence of mutations and the presence of receptor tyrosine kinase (RTK) heterodimers, respectively. Both MPNST groups showed AKT, ERK, and mTOR expression/phosphorylation. No BRAF, PI3KCA, or PTEN mutations were found in either group of MPNSTs, but 18% of the sporadic MPNSTs showed RAS mutations. PTEN monosomy segregated with the NF1-related cases (50%, p = 0.018), but PTEN protein was expressed in all but two cases. In conclusion, PDGFRA, PDGFRB, and EGFR seem to be promising molecular targets for tailored treatments in MPNST. In particular, the ligand- and heterodimerization-dependent RTK activation/expression coupled with a downstream signaling phosphorylation, mediated by the upstream receptors or RAS activation, may provide a rationale to apply combined RTK and mTOR inhibitor treatments both to sporadic and NF1-related cases.

Identification of p53 as a strong predictor of survival for patients with malignant peripheral nerve sheath tumors

The purpose of this study was to identify new prognostic biomarkers with clinical impact in malignant peripheral nerve sheath tumor (MPNST), a highly aggressive malignancy for which no consensus therapy exists besides surgery. We have used tissue microarrays (TMAs) to assess in situ expression of 14 cell-cycle-regulating proteins in 64 well-characterized MPNST patients: 36 sporadic and 28 with neurofibromatosis type 1 (NF1). We developed a new software application for evaluation and logistics of the TMA images and performed a literature survey of cell cycle proteins in MPNST. For NF1-associated patients, there was a clear association between nuclear expression of p53 and poor survival (p = 0.004). Among the other proteins analyzed, we also found significant associations between survival and clinical variables, but none were as strong as that for p53. For the total series of MPNSTs, p53 was shown to be an independent predictor of survival, and patients without remission, with tumor size larger than 8 cm, and with positive p53 expression had a 60 times greater risk of dying within the first 5 years compared with the remaining patients (p = 0.000002). This is the most comprehensive study of in situ protein expression in MPNST so far, and expressed p53 was found to be a strong surrogate marker for outcome. Patients in complete remission with a primary p53-positive MPNST diagnosis may be considered in a high-risk subgroup and candidates for adjuvant treatment.

DNA copy number changes in high-grade malignant peripheral nerve sheath tumors by array CGH

Background

Malignant peripheral nerve sheath tumors (MPNSTs) are rare and highly aggressive soft tissue tumors showing complex chromosomal aberrations. In order to identify recurrent chromosomal regions of gain and loss, and thereby novel gene targets of potential importance for MPNST development and/or progression, we have analyzed DNA copy number changes in seven high-grade MPNSTs using microarray-based comparative genomic hybridization (array CGH).

Results

Considerable more gains than losses were observed, and the most frequent minimal recurrent regions of gain included 1q24.1-q24.2, 1q24.3-q25.1, 8p23.1-p12, 9q34.11-q34.13 and 17q23.2-q25.3, all gained in five of seven samples. The 17q23.2-q25.3 region was gained in all five patients with poor outcome and not in the two patients with disease-free survival. cDNA microarray analysis and quantitative real-time reverse transcription PCR were used to investigate expression of genes located within these regions. The gene lysyl oxidase-like 2 (LOXL2) was identified as a candidate target for the 8p23.1-p12 gain. Within 17q, the genes topoisomerase II-α (TOP2A), ets variant gene 4 (E1A enhancer binding protein, E1AF) (ETV4) and baculoviral IAP repeat-containing 5 (survivin) (BIRC5) showed increased expression in all samples compared to two benign tumors. Increased expression of these genes has previously been associated with poor survival in other malignancies, and for TOP2A, in MPNSTs as well. In addition, we have analyzed the expression of five micro RNAs located within the 17q23.2-q25.3 region, but none of them showed high expression levels compared to the benign tumors.

Conclusion

Our study shows the potential of using DNA copy number changes obtained by array CGH to predict the prognosis of MPNST patients. Although no clear correlations between the expression level and patient outcome were observed, the genes TOP2A, ETV4 and BIRC5 are interesting candidate targets for the 17q gain associated with poor survival.

Germline and somatic NF1 gene mutation spectrum in NF1-associated malignant peripheral nerve sheath tumors (MPNSTs)

About 10% of neurofibromatosis type 1 (NF1) patients develop malignant peripheral nerve sheath tumors (MPNSTs) and represent considerable patient morbidity and mortality. Elucidation of the genetic mechanisms by which inherited and acquired NF1 disease gene variants lead to MPNST development is important. A study was undertaken to identify the constitutional and somatic NF1 mutations in 34 MPNSTs from 27 NF1 patients. The NF1 germline mutations identified in 22 lymphocytes DNA from these patients included seven novel mutations and a large 1.4-Mb deletion. The NF1 germline mutation spectrum was similar to that previously identified in adult NF1 patients without MPNST. Somatic NF1 mutations were identified in tumor DNA from 31 out of 34 MPNSTs, of which 28 were large genomic deletions. The high prevalence (>90%) of such deletions in MPNST contrast with the =or<20% found in benign neurofibromas and is indicative of the involvement of different mutational mechanisms in these tumors. Coinactivation of the TP53 gene by deletion, or by point mutation along with NF1 gene inactivation, is known to exacerbate disease symptoms in NF1, therefore TP53 gene inactivation was screened. DNA from 20 tumors showed evidence for loss of heterozygosity (LOH) across the TP53 region in 11 samples, with novel TP53 point mutations in four tumors.

Sarcomas in children with neurofibromatosis type 1-poor prognosis despite aggressive combined therapy in four patients treated in a single oncological institution

OBJECTS

Patients with neurofibromatosis type 1 (NF1) are predisposed to developing soft tissue sarcomas (STS).

MATERIALS AND METHODS

We report on four cases of STS diagnosed in locally advanced, unresectable stages in children with NF1 (three girls, one boy; age = 8 months-14 years). All patients received protocols for STS: Cooperative Weichteilsarkomstudie 91, 96 and 2002. One patient with limb rhabdomyosarcoma entered complete remission but developed late metastatic relapse and died of progression despite complete excision and autologous bone marrow transplantation. The other patient with bladder rhabdomyosarcoma died of neutropenia-related sepsis without remission. Patients with malignant peripheral nerve sheet tumour and malignant triton tumour located in the pelvis did not respond to therapy. One of them died of disease progression, while the other is disease-free 6 years post-therapy after mutilating tumour resection.

CONCLUSION

STS in NF1 seem to display poor prognosis in spite of combined therapy; thus, children with NF1 should remain under detailed control of the oncologist.

Tumors of the brachial plexus

✓Tumors of the brachial plexus are relatively rare and present a clinical challenge for the neurosurgeon. The management of these tumors therefore requires not only an understanding of the complex anatomy of the brachial plexus but also an appreciation of the appropriate surgical approach to the various tumors that may be encountered. Over a 30-year period (1969–1999), 226 patients with brachial plexus tumors were evaluated and surgically treated by the senior authors (R.L.T., D.G.K.). In the present paper they review the most common benign and malignant brachial plexus tumors and discuss management and surgical principles established through their experience at the Louisiana State University Health Sciences Center.

Identification of a novel amplicon at distal 17q containing theBIRC5/SURVIVINgene in malignant peripheral nerve sheath tumours

Previous studies have suggested that amplification of genes, notably the TOP2A gene, on chromosome arm 17q may be important for the development of malignant peripheral nerve sheath tumour (MPNST). In order to study the frequency, distribution, and chromosomal organization of rearrangements at 17q, interphase and metaphase fluorescence in situ hybridization (FISH) were used to evaluate copy number changes at 17q in 28 MPNSTs. Increased copy numbers were seen for the ERBB2 and TOP2A genes in eight and nine cases, respectively, supporting a potential role for these two genes in MPNST tumourigenesis. Net gain of distal 17q material was observed in 16 of the 28 MPNSTs, with high-level gain in three cases, and was associated with poor outcome. Among the 26 patients for whom follow-up data were available, gain of distal 17q was present in 11 of 12 tumours that had metastasized, compared with 4 of 14 of those that had not metastasized. Detailed FISH mapping analysis of metaphase spreads identified a 2 Mb commonly gained/amplified region at 17q25. Among the genes mapping to this region, BIRC5, which encodes the baculoviral IAP repeat-containing protein 5/survivin protein, is a strong candidate target gene for amplification, as it has been previously shown to be overexpressed in neurofibromatosis type 1-associated MPNST. Three other genes that co-amplified with BIRC5 represent other potential candidate genes: PTDSR involved in apoptosis; SEPT9 overexpressed in human malignant brain tumours; and SOCS3 involved in cell survival and differentiation of neurons.

COL1A1-PDGFB fusion in a pediatric Bednar tumor with 2 copies of a der(22)t(17;22)

We present a 10-year-old girl with a pure Bednar tumor (pigmented dermatofibrosarcoma protuberans) of the right shoulder. Cytogenetic analysis demonstrated 47 chromosomes with 2 copies of a derivative chromosome 22, der(22)t(17;22)(q22;q13). Fluorescence in situ hybridization (FISH) analysis demonstrated the COL1A1-PDGFB fusion on both der(22) chromosomes. By RT-PCR and sequencing, we observed a fusion of the COL1A1 exon 41 with PDGFB exon 2. This pure pediatric Bednar tumor in a child, like childhood dermatofibrosarcoma protuberans, had a linear structural abnormality rather than a ring chromosome that is more commonly encountered in adult Bednar and dermatofibrosarcoma protuberans tumors. The underlying molecular abnormality in this pediatric Bednar tumor is the same as in dermatofibrosarcoma protuberans.

Comparative genomic hybridization study of perivascular epithelioid cell tumor: molecular genetic evidence of perivascular epithelioid cell tumor as a distinctive neoplasm

Perivascular epithelioid cell tumor (PEComa) is a neoplasm composed chiefly of HMB-45-positive epithelioid cells with clear to granular cytoplasm and a perivascular distribution. Such tumors have been reported in different organs under a variety of designations. The cytogenetic features of these neoplasms have not been well studied. We collected 9 tumors (5 of kidney, 1 of prostate, 1 of urinary bladder, 1 of the pelvic cavity soft tissue, and 1 of uterus) from 8 patients, including one patient with tuberous sclerosis complex. The paraffin blocks of tumor tissue were submitted for comparative genomic hybridization analyses. Gross chromosomal aberrances were observed in all cases. The frequent imbalances were losses on chromosome 19 (8 cases), 16p (6 cases), 17p (6 cases), 1p (5 cases), and 18p (4 cases) and gains on chromosome X (6 cases), 12q (6 cases), 3q (5 cases), 5 (4 cases), and 2q (4 cases). The frequent deletion of 16p in which TSC2 gene is located indicates the oncogenetic relationship of PEComas with angiomyolipoma as a TSC2-linked neoplasm. From a molecular genetic perspective, the recurrent chromosomal alterations in both renal and extrarenal tumors further support the concept of PEComa as a distinctive tumor entity regardless of anatomic location.

Chromosomal aberrations and microsatellite instability of malignant peripheral nerve sheath tumors: a study of 10 tumors from nine patients

Malignant peripheral nerve sheath tumor (MPNST) is an uncommon soft tissue neoplasm with a poor prognosis, occurring sporadically or associated with neurofibromatosis type 1 (NF1); however, the histogenesis of MPNST remains unclear, especially in sporadic tumors. There are two major forms of genomic instability in human cancer: chromosomal instability (CIN) and microsatellite instability (MSI). An inverse relationship has recently been demonstrated between CIN and MSI in colorectal cancers. CIN and MSI are suggested to be individual pathways, which are involved in the pathogenesis and which may lead to specific clinical and pathological characteristics. To elucidate the chromosomal aberration as a consequence of CIN and MSI status of MPNST, we karyotyped 10 MPNSTs from nine patients, and examined the MSI of seven microsatellite markers using high-resolution fluorescence microsatellite analysis; 2 out of 10 cases (20%) had normal karyotypes, and 8 out of 10 cases (80%) revealed structural and numerical chromosomal aberrations. Three of the 10 cases (30%) showed near triploidy. The most frequent aberration was -22 (40%), followed by +2, +14, -13, -17, and -18 (30% each). An MSI-low status was observed in 30% of cases; the remaining cases showed microsatellite stability. These findings suggest that chromosomal aberration as a consequence of CIN has a greater role in the pathogenesis of MPNST than does that due to MSI.

Molecular cytogenetic analysis in the study of brain tumors: findings and applications

Classic cytogenetics has evolved from black and white to technicolor images of chromosomes as a result of advances in fluorescence in situ hybridization (FISH) techniques, and is now called molecular cytogenetics. Improvements in the quality and diversity of probes suitable for FISH, coupled with advances in computerized image analysis, now permit the genome or tissue of interest to be analyzed in detail on a glass slide. It is evident that the growing list of options for cytogenetic analysis has improved the understanding of chromosomal changes in disease initiation, progression, and response to treatment. The contributions of classic and molecular cytogenetics to the study of brain tumors have provided scientists and clinicians alike with new avenues for investigation. In this review the authors summarize the contributions of molecular cytogenetics to the study of brain tumors, encompassing the findings of classic cytogenetics, interphase- and metaphase-based FISH studies, spectral karyotyping, and metaphase- and array-based comparative genomic hybridization. In addition, this review also details the role of molecular cytogenetic techniques in other aspects of understanding the pathogenesis of brain tumors, including xenograft, cancer stem cell, and telomere length studies.

Chromosomal imbalances in some benign orbital tumours

PURPOSE

To examine benign orbital tumours for chromosomal imbalances.

METHODS

Specimens obtained from orbital tumours were screened for chromosomal imbalances using high resolution comparative genomic hybridization (CGH). The imbalances detected by CGH were confirmed by using fluorescence in situ hybridization (FISH) and loss of heterozygosity (LOH) analysis.

RESULTS

Chromosomal gains or losses were seen in 4/6 pleomorphic adenomas (gains at 8q; losses at 4p, 5p, 8p, 11p and 14q), 2/4 schwannomas (losses at 16p and 22q), and 1/9 cavernous haemangiomas (losses at 13q). Compared to previous studies of pleomorphic adenomas using G-band analysis, chromosomal imbalances were more frequently detected by using CGH. Gains of 8q11-q22 and losses of 4p15-pter, 11p12-p15, and 14q12-q23 in pleomorphic adenomas, losses of 16p12-p13 in schwannomas, and losses of 13q32-qter in cavernous haemangiomas have not been reported previously.

CONCLUSIONS

A range of chromosomal imbalances was detected even within tumours of the same histological subtype. We did not observe common chromosomal gains or losses that were characteristic for orbital presentation of the tumours. The clinical relevance of the abnormalities is uncertain, but they may indicate the position of genes that could play a role in tumour development.

Benign Epithelioid Peripheral Nerve Sheath Tumors of the Soft Tissues

Benign epithelioid peripheral nerve sheath tumors (BEPNSTs) have not been fully characterized, and their relationship to conventional schwannoma and neurofibroma has not been satisfactorily established. Herein, we detail the clinicopathologic features of 33 examples of BEPNST. The study included 22 females and 11 males ranging in age from 2 to 68 years (median, 31.5 years). Only one patient probably has neurofibromatosis type 1. The tumors were predominantly dermal/subcutaneous in location (85%) and involved the lower limb (n=15), upper limb (n=11), trunk (n=4), and head/neck (n=3). The lesions ranged in size from 0.3 to 6.8 cm (median, 1.1 cm). Microscopically, the tumors were generally well-circumscribed, uninodular, or multinodular masses. Twenty-six lesions were encapsulated. Tumors consisted of trabeculae, loosely arranged nodules, and cohesive nests of epithelioid tumor cells immersed in collagenous, myxohyaline, or chiefly myxoid stroma. A bland spindled cell component comprising 5% to 40% of the tumor was noted in 15 cases. Mitotic activity ranged from 0 to 6 mitoses/50 high power fields (mean, 1.5 mitoses/50 high power fields) with no abnormal division figures identified. Five lesions were considered atypical based on presence of focal nuclear/nucleolar enlargement and hyperchromasia. Immunohistochemical reactivity for Schwann cell-related markers in tumor cells included S-100 protein (20 of 20 cases), collagen type IV (10 of 10), laminin (8 of 8), nerve growth factor receptor, p75(7 of 8), CD57 (6 of 9), and glial fibrillary acidic protein (8 of 15). CD34-positive fibroblast-like cells were identified in all 12 neoplasms tested. Anti-epithelial membrane antigen highlighted perineurial cells in 9 of the 11 encapsulated tumors. Anti-neurofilament protein did not identify intralesional neuraxons in the 10 tumors evaluated. Eighteen tumors were subtyped as epithelioid neurofibromas. The remaining 15 cases showed some histologic features suggestive of schwannoma, but their uniform cellularity, absence of nuclear palisading, and presence of a significant CD34-positive spindled cell population in 5 cases led to their classification as "BEPNST of indeterminate histogenesis." Evaluation for loss of heterozygosity in 2 cases demonstrated deletion of genetic material on chromosome 22q and 17q involving NF2 and NF1 loci. However, sequencing of NF2 coding sequences revealed no mutations. Follow-up for 18 patients (median interval, 13.5 years), including 4 patients with tumors exhibiting cytologic atypia, revealed a nondestructive recurrence or persistent disease in 3 patients whose tumors lacked atypia, but no evidence of metastatic spread or tumor-related death. BEPNSTs are usually small neoplasms located in superficial soft tissue and have an excellent prognosis after complete local excision. Accurate subclassification of some of these lesions is difficult based on currently available techniques.

Molecular profiling of malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1, based on large-scale real-time RT-PCR

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a complex range of clinical symptoms. The hallmark of NF1 is the onset of heterogeneous (dermal or plexiform) benign neurofibromas. Plexiform neurofibromas can give rise to malignant peripheral nerve sheath tumors (MPNSTs), and the underlying molecular mechanisms are largely unknown.

Results

To obtain further insight into the molecular pathogenesis of MPNSTs, we used real-time quantitative RT-PCR to quantify the mRNA expression of 489 selected genes in MPNSTs, in comparison with plexiform neurofibromas.

The expression of 28 (5.7%) of the 489 genes was significantly different between MPNSTs and plexiform neurofibromas; 16 genes were upregulated and 12 were downregulated in MPNSTs.

The altered genes were mainly involved in cell proliferation (MKI67, TOP2A, CCNE2), senescence (TERT, TERC), apoptosis (BIRC5/Survivin, TP73) and extracellular matrix remodeling (MMP13, MMP9, TIMP4, ITGB4). More interestingly, other genes were involved in the Ras signaling pathway (RASSF2, HMMR/RHAMM) and the Hedgehog-Gli signaling pathway (DHH, PTCH2). Several of the down-regulated genes were Schwann cell-specific (L1CAM, MPZ, S100B, SOX10, ERBB3) or mast cell-specific (CMA1, TPSB), pointing to a depletion and/or dedifferentiation of Schwann cells and mast cells during malignant transformation of plexiform neurofibromas.

Conclusion

These data suggest that a limited number of signaling pathways, and particularly the Hedgehog-Gli signaling pathway, may be involved in malignant transformation of plexiform neurofibromas. Some of the relevant genes or their products warrant further investigation as potential therapeutic targets in NF1.

Comparative Genomic Hybridization in Central and Peripheral Nervous System Tumors of Childhood and Adolescence

Brain tumors amount to less than 2% of all malignant neoplasms. However, they account for approximately 20% of all childhood cancers and are the leading cause of cancer mortality among children. Recently, enormous progress has been achieved in the field of pediatric neuro-oncology regarding the classification of children's brain tumors, as well as the understanding of the genetic events involved in their pathogenesis; thus leading to an emerging role of molecular diagnostic approaches using novel tools. Comparative genomic hybridization (CGH) is a technique that has revolutionized cytogenetic knowledge in the past decade. It permits the detection of chromosomal copy number changes without the need for cell culturing and gives a global overview of chromosomal gains and losses throughout the whole genome of a tumor. A survey of CGH-related publications on central and peripheral nervous system tumors in the pediatric and adolescent population revealed 884 cases. The CNS tumor groups most frequently examined by CGH were embryonal tumors (268 cases/30.3%) and ependymomas (241/27.2%), followed by astrocytic (163/18.4%), peripheral nerve (73/8.2%), choroid plexus tumors (56/6.3%), and craniopharyngiomas (38/4.3%). The most common CNS tumor entities were medulloblastomas (238/26.9%), classic ependymomas (160/18.1%), anaplastic ependymomas (70/7.9%), pleomorphic xanthoastrocytomas (53/6.0%), and pilocytic astrocytomas (50/5.6%). This article provides a short review of the CGH technique and its pitfalls, summarizes the current CGH-related data on pediatric brain tumors and muses on the future of CGH.

Fluorescence in situ hybridization analysis of allelic losses involving the long arm of chromosome 17 in NF1-associated neurofibromas

Neurofibromatosis type 1 (NF1) is a common autosomal dominant condition associated with germline mutations of the NF1 gene located at chromosome band 17q11.2. Molecular analysis of a number of NF1-specific tumors has shown the inactivation of both NF1 alleles during tumorigenesis, supporting the tumor suppressor hypothesis for the NF1 gene. Using interphase dual-color fluorescence in situ hybridization (FISH) technique on paraffin-embedded tissues, we studied 11 plexiform, 4 cutaneous, and 6 subcutaneous neurofibromas. Cytogenetic analysis was conducted using two probes, one specific for the NF1 region (RP11-229K15) and one for the centromeric region of chromosome 17 as control. No large somatic deletions were found. Only in one of the plexiform neurofibromas loss of a whole chromosome 17 was observed. If we assume that dual-color FISH analysis is sensitive enough to detect the majority of large somatic deletions present, then other mutational mechanisms affecting the NF1 gene are probably involved in neurofibroma formation, and other tumor suppressor genes may play an important role in NF1 tumorigenesis.

Microsatellite instability and expression of hMLH1 and hMSH2 proteins in ovarian endometrioid cancer

Microsatellite instability and loss of heterozygosity has been implicated in ovarian carcinogenesis. The reported frequency of microsatellite instability in human ovarian cancer varies significantly owing to the use of heterogeneous tumor histotypes and various microsatellite markers in different laboratories. In this study, we determined the frequency of microsatellite instability in 74 ovarian endometrioid carcinomas using four microsatellite markers (BAT25, BAT26, D5S346, D17S250), and examined hMLH1 and hMSH2 protein expression. In all, 20% of the tumors were microsatellite instability high (two or more markers showing instability) and 12% were microsatellite instability low (one marker showed instability). Loss of hMLH1 and/or hMSH2 expression was found in nine of 15 microsatellite instability-high tumors. The microsatellite instability-high phenotype tended to occur more frequently in low-grade tumors (P=0.053), but did not correlate with clinical stage. Totally, 38% of cases also displayed loss of heterozygosity at D17S250; this loss of heterozygosity was associated with high clinical stage (P=0.097). Our results indicate that both microsatellite and loss of heterozygosity at D17S250 are involved in the development of ovarian endometrioid carcinoma.

Evaluation of NF2 and NF1 tumor suppressor genes in distinctive gastrointestinal nerve sheath tumors traditionally diagnosed as benign schwannomas: s study of 20 cases

A significant percentage of conventional schwannomas, whether sporadic or associated with neurofibromatosis 2 (NF2), show loss of heterozygosity (LOH) at NF2 and/or NF2 inactivating mutations. Similarly, a significant percentage of neurofibromas show LOH at NF1 and/or NF1 inactivating mutations. There are no molecular genetic data on gastrointestinal (GI) nerve sheath tumors traditionally diagnosed as benign schwannomas, rare neoplasms possibly derived from the schwannian elements dispersed between the smooth muscle fibers. In this study, we analyzed 1 esophageal, 16 gastric, 1 small intestinal, and 2 colonic tumors of such type. Histologically, all were spindle cell neoplasms positive for S-100 protein, vimentin, and glial fibrillary acidic protein, and negative for smooth muscle markers, KIT, CD34, neurofilament proteins, and HMB45. Focal or extensive lymphoid cuffs, often containing germinal centers, were present in most cases. None of the patients had NF2 or NF1. Chromosomes 22 and 17, particularly NF2 and NF1 loci, were analyzed for LOH in all GI tumors and for comparative purposes in 10 conventional schwannomas. LOH on 22q was seen in 40% of conventional schwannomas but in only 5% (1 of 20) of GI schwannomas. PCR amplification followed by direct sequencing of PCR products failed to identify mutations in NF2 coding sequences (exons 1-15) in 13 cases, including a case with LOH on 22q. Losses on 17q involving NF1 were seen in both GI and conventional schwannomas in 50% and 33% of analyzed tumors, respectively. LOH at NF1 might be one of the genetic features seen in peripheral nerve sheath tumors from different locations and should be interpreted with caution. However, lack of NF2 alterations strongly supports the hypothesis that GI schwannomas represent a morphologically and genetically distinct group of peripheral nerve sheath tumors that are different from conventional schwannomas.

Bednár tumor associated with dermal melanocytosis: melanocytic colonization or neuroectodermal multidirectional differentiation?

BACKGROUND

Neuroectodermal differentiation or melanocytic colonization are the opposing theories of histogenesis for the Bednár tumor or pigmented dermatofibrosarcoma protuberans (DFSP).

OBSERVATION

A 31-year-old African-American woman presented with a 2-cm blue-black shoulder nodule of 1-year duration. Punch biopsy revealed a CD34+, Factor XIIIa-DFSP, harboring numerous, pigmented spindle S100+, Mart-1+ and HMB-45+ cells. Subsequent wide excision demonstrated pigmented dendritic and spindled cells widely scattered throughout the dermis of the 3-cm excisional margins and punch biopsy specimens of normal skin from both shoulders. This latter process was interpreted as dermal melanocytosis (nevus of Ito). The dermal pigmented spindle cells were Mart-1+ and CD34-, and were associated with non-pigmented CD34+, cytologically banal spindle cells, which were more numerous in the excisional margins than the contralateral shoulder.

CONCLUSION

Reported herein is a singular case of Bednár tumor associated with dermal melanocytosis. Although the coexistence of these processes implicates colonization of the DFSP by constituent dermal melanocytes, the mixed immunophenotype (CD34+ or Mart-1+ cells) of dispersed dermal spindle cells hints at the possibility of a common cell of origin: the putative neuromesenchymal cell. In effect, the Bednár tumor could represent one part of a spectrum of neural crest-derived dermal tumors that includes dermal melanocytosis, cellular blue nevus and conventional DFSP.