[Expression and significance of p53 and proliferating cell nuclear antigen in malignant tumor of maxillary sinus]

BACKGROUND & OBJECTIVE

p53 and proliferating cell nuclear antigen (PCNA) play an important role in the development of malignant tumor. This study was designed to evaluate the role of p53 and PCNA in the development of malignant tumor of maxillary sinus by detecting their expression in malignant, benign, and inflammatory lesions of maxillary sinus.

METHODS

The expressions of p53 and PCNA were detected by immunohistochemistry in 108 malignant, 19 benign, and 8 inflammatory tissues of maxillary sinus. Rank sum test was used and the levels of positive degree of p53 and PCNA were represented by mean rank.

RESULTS

The mean ranks of p53 and PCNA were 42.8 and 47.9 in inflammatory group and 50.3 and 46.8 in benign group, but 73.0 and 73.2 in malignant group, respectively. In malignant group, mean rank of p53 in squamous cell carcinoma (SCC) was 60.7, which was higher than that in adenocarcinoma (43.9). The differences were significant (P < 0.05). While from stage I to stage IV, the mean ranks of p53 were 46.6, 50.1, 56.1, and 55.0 and the mean ranks of PCNA were 60.5, 48.8, 56.1, and.

Cutaneous lipomatous neurofibroma

We report a cutaneous lipomatous neurofibroma on the skin of the left-side parietal area of approximately 9 months' duration in a 67-year-old woman. The regular distribution of adipose tissue throughout the lesion suggested that fat was an integral part of the tumor, not a metaplastic or degenerative process. To our knowledge, this type of lesion has not been documented. The main differential diagnosis embraces neurocristic cutaneous hamartoma, lipoma and its variants, cutaneous meningioma, and neural nevus with fat replacement. We propose that lipomatous neurofibroma of the skin is caused by aberrant development of adipose tissue in a neurofibroma. The lesion originated as pluripotential neural crest cells after migration. This acquired lesion could arise from local stem cells. The old suggestion that neuroectoderm is capable of mesenchymal differentiation may be relevant to the histogenesis of this neoplasm.

Solitary neurofibroma of the nasal cavity: resection with endoscopic surgery

We present a case of neurofibroma of the nasal cavity treated by endoscopic surgery. A 71-year-old female had complained of left-sided nasal obstruction for the past four years. Anterior rhinoscopy, computed tomography (CT) and magnetic resonance imaging (MRI) revealed a tumour involving the left nasal cavity. Histological and immunohistochemical examination showed the tumour to be a neurofibroma. The tumour was resected with endoscopic surgery. Neurofibroma arising in the area of the nose and paranasal sinuses is rare. We discuss the clinical and pathological characters of neurofibroma arising in the nasal cavity.

Defining the peptide nucleic acids (PNA) length requirement for PNA binding-induced transcription and gene expression

Induction of gene expression has great potential in the treatment of many human diseases. Peptide nucleic acid (PNA) as a novel DNA-binding reagent provides an ideal system to induce gene-specific expression. In our recent studies, we have demonstrated that PNA bound to double-stranded DNA targets and, therefore, generated single-stranded D-loops and induced transcription of target genes both in vitro and in vivo. Most importantly, we have demonstrated that treatment of cultured human cells with PNAs led to expression of an endogenous target gene. Therefore, the study of the molecular mechanism of PNA binding-induced gene expression will have great implications for the gene therapy of many human diseases. In the current study, we have investigated the PNA length requirement for PNA binding-induced transcription initiation. Using a series of PNAs with different lengths, we have determined that PNAs with lengths of 16 approximately 18 nt induce very high levels of transcription in a HeLa nuclear extract in vitro transcription system. Transfection of the PNA-bound GFP reporter gene plasmid into human normal fibroblast (NF) cells led to a similar result. Gel-mobility shift assays revealed very strong binding affinities of these PNAs. DNA footprinting analysis further demonstrated the specificity of PNAs binding to the targets. These results lead to important understanding of the molecular mechanism of transcription initiation and highly valuable information in PNA design, especially for PNA binding-induced, gene-specific expression.

Tumorigenic properties of neurofibromin-deficient neurofibroma Schwann cells

Dermal and plexiform neurofibromas are peripheral nerve sheath tumors that arise frequently in neurofibromatosis type 1. The goal of the present study was to examine the tumorigenic properties of neurofibromin-deficient human Schwann cells (SCs) that were found to represent a subset of SCs present in approximately half of the total neurofibromas examined. Highly enriched SC cultures were established from 10 dermal and eight plexiform neurofibromas by selective subculture using glial growth factor-2 and laminin. These cultures had low tumorigenic potential in classical in vitro assays yet several unique preneoplastic properties were frequently observed, including delayed senescence, a lack of density-limited growth, and a strong propensity to spontaneously form proliferative cell aggregates rich in extracellular matrix. Western blot analysis failed to detect full-length neurofibromin in any of the neurofibroma SC cultures, indicating that neurofibromin-deficient SCs had a substantial growth advantage. Immunohistochemical staining of the originating tumors showed the majority were comprised principally of neurofibromin-negative SCs, whereas the remainder contained both neurofibromin-negative and neurofibromin-positive SCs. Lastly, engraftment of neurofibromin-deficient SC cultures into the peripheral nerves of scid mice consistently produced persistent neurofibroma-like tumors with diffuse and often extensive intraneural growth. These findings indicate that neurofibromin-deficient SCs are involved in neurofibroma formation and, by selective subculture, provide a resource for the development of an in vivo model to further examine the role of these mutant SCs in neurofibroma histogenesis.

The angiogenic factor midkine is aberrantly expressed in NF1-deficient Schwann cells and is a mitogen for neurofibroma-derived cells

Loss of the tumor suppressor gene NF1 in neurofibromatosis type 1 (NF1) contributes to the development of a variety of tumors, including malignant peripheral nerve sheath tumors (MPNST) and benign neurofibromas. Of the different cell types found in neurofibromas, Schwann cells usually provide between 40 and 80%, and are thought to be critical for tumor growth. Here we describe the identification of growth factors that are upregulated in NF1-/- mouse Schwann cells and are potential regulators of angiogenesis and cell growth. Basic fibroblast growth factor (FGF-2), platelet-derived growth factor (PDGF) and midkine (MK) were found to be induced by loss of neurofibromin and MK was further characterized. MK was induced in human neurofibromas, schwannomas, and various nervous system tumors associated with NF1 or NF2; midkine showed an expression pattern overlapping but distinct from its homolog pleiotrophin (PTN). Immunohistochemistry revealed expression of MK in S-100 positive Schwann cells of dermal and plexiform neurofibromas, and in endothelial cells of tumor blood vessels, but not in normal blood vessels. Furthermore, MK demonstrated potent mitogenic activity for human systemic and brain endothelial cells in vitro and stimulated proliferation and soft agar colony formation of human MPNST derived S100 positive cells and fibroblastoid cells derived from an NF1 neurofibroma. The data support a possible central role for MK as a mediator of angiogenesis and neurofibroma growth in NF1. Oncogene (2001) 20, 97 - 105.

Long-term culture and characterization of human neurofibroma-derived Schwann cells

Neurofibromas are benign tumors arising from the peripheral nerve sheath and are a typical finding in neurofibromatosis type 1 (NF1). Schwann cells are the predominant cell type in neurofibromas and thus are supposed to play a major role in the pathogenesis of these tumors. It is not known, however, if NF1 mutations in Schwann cells result in an altered phenotype that subsequently leads to tumor formation. To characterize the biological properties of neurofibroma-derived Schwann cells we developed cell culture techniques that enabled us to isolate Schwann cells from neurofibromas and grow them in vitro for several weeks without significant fibroblast contamination. Neurofibroma-derived Schwann cells were characterized by altered morphology, heterogeneous growth behavior, and increased expression of the P0 antigen while several other features of normal human Schwann cells were retained. We conclude that neurofibroma-derived Schwann cells exhibit a distinct phenotype in vitro but that the observed abnormalities by themselves are insufficient to explain neurofibroma formation. Application of our improved culture conditions makes neurofibroma-derived Schwann cells readily available for further studies to define their role in tumorigenesis in neurofibromatosis type 1.

Malignant transformation of neurofibromas in neurofibromatosis 1 is associated with CDKN2A/p16 inactivation

Patients with neurofibromatosis 1 (NF1) are predisposed to develop multiple neurofibromas (NFs) and are at risk for transformation of NFs to malignant peripheral nerve sheath tumors (MPNSTs). Little is known, however, about the biological events involved in the malignant transformation of NFs. We examined the CDKN2A/p16 gene and p16 protein in NFs and MPNSTs from patients with NF1. On immunohistochemical analysis, all NFs expressed p16 protein. The MPNSTs, however, were essentially immunonegative for p16, with striking transitions in cases that contained both benign and malignant elements. None of the benign tumors had CDKN2A/p16 deletions, whereas three of six MPNSTs appeared to have homozygous CDKN2A/p16 deletions. Methylation analysis and mutation analysis of CDKN2A/p16 in MPNSTs did not reveal any abnormalities. These results show that malignant transformation of NF is associated with loss of p16 expression, which is often secondary to homozygous deletion of the CDKN2A/p16 gene. The findings suggest that CDKN2A/p16 inactivation occurs during the malignant transformation of NFs in NF1 patients and raises the possibility that p16 immunohistochemistry may provide ancillary information in the distinction of NF from MPNST.

Expression of p27(kip) and other cell cycle regulators in malignant peripheral nerve sheath tumors and neurofibromas: the emerging role of p27(kip) in malignant transformation of neurofibromas

There is little information regarding the status of cell cycle regulators in malignant peripheral nerve sheath tumors (MPNSTs) and neurofibromas (NFs). In this study, we investigated patterns of expression of p53 and pRB, cyclin-dependent kinase inhibitors (CKIs) p21 and p27, as well as cyclins D1 and E, in a cohort of 35 well-characterized MPNSTs and 16 NFs. These phenotypes were correlated with proliferative index, as assessed by Ki-67, as well as clinicopathological parameters of poor outcome. p53 nuclear overexpression was found in 10 of 35 (29%) MPNSTs, and it was lacking in NFs (P = 0.02). There were no differences in the patterns of expression of pRB, cyclin D1, and p21 between MPNSTs and NFs. However, p27 nuclear expression was present in most NFs, but it was absent in the majority of MPNSTs, which displayed cytoplasmic staining (P < 0.001). Nuclear cyclin E expression was more pronounced in MPNSTs than in NFs. We observed inverse patterns of expression for nuclear p27 and nuclear cyclin E expression. The staining profiles of cytoplasmic p27 and nuclear cyclin E expression were found to be statistically associated (P = 0.01). High Ki-67 expression was found in 20 of 34 (59%) MPNSTs but was absent in NFs (P < 0.001). Furthermore, detection of cytoplasmic p27 expression was found to be a prognostic factor for poor survival in MPNSTs (P = 0.03, relative risk = 2.4).

p53 and Ki-67 proliferating cell nuclear antigen in benign and malignant peripheral nerve sheath tumors in children

Malignant peripheral nerve sheath tumors (MPNSTs) are uncommon soft tissue tumors. In children with neurofibromatosis 1 (NF1), a MPNST often arises in a pre-existing neurofibroma, or may represent an initial manifestation without other obvious stigmata of the disease. The development of MPNSTs may be associated with instability of the p53 tumor suppressor gene since it is the most frequent genetic abnormality in soft tissue sarcomas. To assess the presence of p53 accumulation in MPNSTs and its correlation with clinical and pathologic features, we studied 12 neurofibromas (NFs), including 4 tumors with cellular features (one congenital) and 10 MPNSTs. Six MPNSTs were associated with NF1, all of which developed within a plexiform neurofibroma. Cell proliferation evaluated with an antibody to Ki-67 and nuclear p53 staining were both detected by immunohistochemistry. We found p53 positivity in 60% of MPNSTs. All NFs except the congenital tumor were p53 immunonegative (P < 0.01). Rare p53-positive nuclei were detected in the transitional zone in two of six MPNSTs arising in plexiform NFs. Ki-67 distinguished the NFs from MPNSTs (P < 0.005). Half of the NF1 patients with p53-positive MPNSTs developed recurrence or metastases or developed a second malignancy within 2 years of diagnosis, whereas patients with p53-positive sporadic MPNSTs were free of disease 1 to 7 years later. We found p53 accumulation more frequently in NF1-associated MPNSTs. p53 mutations may be an additional biologic factor to account for the poor prognosis in these tumors.

Mediastinal tumors of peripheral nervous system origin

A wide spectrum of benign and malignant tumors of peripheral nervous system origin can arise in the mediastinum. These neoplasms are more frequent in the posterior mediastinum and can develop from peripheral nerves, sympathetic and parasympathetic ganglia, and neural tube embryonic remnants. The clinicopathologic features of mediastinal schwannomas, melanotic schwannomas, neurofibromas, ganglioneuromas, granular cell tumors, malignant tumors of peripheral nerve sheath origin, malignant melanocytic tumors of peripheral nerve sheath origin, neuroblastomas, ganglioneuroblastomas, and pigmented neuroectodermal tumors of infancy are reviewed.

Perineurioma (storiform perineurial fibroma) of the kidney in a child

Perineurioma is an extremely rare benign tumor of the peripheral nervous system composed exclusively of perineurial cells. Imaging findings of this tumor are non-specific and the diagnosis is based on histologic studies. We report a case of perineurioma of the kidney in a 7-year-old girl discovered incidentally during the evaluation of a urinary tract infection. This is the first case of renal perineurioma reported in a child. We present the ultrasound and computed tomography findings of this histologically confirmed neoplasm.

[Effect of acute moderate isovolumic hemodilution on the pharmacokinetics of vecuronium]

OBJECTIVE

To determine the effect of acute moderate isovolemic hemodilution on pharmacokinetics of vecuronium.

METHODS

Twenty-six adult patients, ASA grade I, undergoing elective plastic surgery, were randomly divided equally into the control and hemodilution group. The blood samples were taken for 5 hours following intravenous bolus of 100 micrograms/kg of vecuronium in two groups. The plasma concentrations of vecuronium were determined with an improved fluorometry and the pharmacokinetic parameters were obtained by fitting the data with a 3P87 program.

RESULTS

The disposition of vecuronium can be best described by a three compartment open model. As comparison with the control group, the values of Vc and Vdss in hemodilution group were greater than that in the control, while T1/2 beta was markedly prolonged in this group. There were no significant differences in T1/2 phi, T1/2 alpha, K12, K21, K13, K31, K10, MRT, AUC, and Cl between the two groups.

CONCLUSION

Acute moderate isovolemic hemodilution could change the pharmacokinetics of vecurinium, particularly in distribution and elimination phases.

CD44 expression is aberrant in benign Schwann cell tumors possessing mutations in the neurofibromatosis type 2, but not type 1, gene

Atypical expression of CD44 splice variants has been implicated in the progression of numerous tumors. This abnormal CD44 expression is presumed to result from gene alterations that cause tumorigenic transformation. Two tumor types that have been linked to specific gene alterations are schwannomas, which have mutations in the neurofibromatosis (NF) type 2 (NF2) gene, and neurofibromas, which characteristically possess NF type 1 (NF1) gene mutations. We examined CD44 expression in normal sciatic nerves, in schwannomas with confirmed NF2 mutations, and in neurofibromas and malignant peripheral nerve sheath tumor tissue and cell lines from NF1 patients. Compared to normal nerves, schwannomas express higher total levels of CD44 and additional splice variants, whereas CD44 expression in neurofibromas is unaltered. Malignant peripheral nerve sheath tumor tissue and cell lines express the CD44v6 epitope, which is not expressed by normal Schwann cells or by other Schwann cell tumors. These data indicate that altered CD44 expression correlates strictly with mutations in the NF2 but not NF1 gene and suggest that CD44v6 might be a marker for the malignant transformation of Schwann cells.

Lipid composition and phospholipid asymmetry of membranes from a Schwann cell line

We report the total lipid composition and phospholipid asymmetry of a plasma membrane preparation isolated from a Schwann cell line (NF1T) derived from a human neurofibroma. The specific activities of three plasma membrane markers (5'-nucleotidase, Na-K-ATPase, and CNPase) were 8-fold, 12-fold, and 16-fold higher, respectively, in the plasma membrane fraction compared to the specific activities found in the total homogenate. The specific activities of the marker enzymes of intracellular membranes in the isolated plasma membrane fraction indicated little contamination with intracellular organelles. The enrichment of cholesterol (3-fold), sphingomyelin (3-fold), and glycolipids (cerebrosides 8-fold, sulfatides 5-fold) also indicated a high degree of purity of the plasma membrane fraction. The high content of phosphatidylinositol and phosphatidylcholine (10% and 44% of total phospholipid) and the low phosphatidylserine and phosphatidylethanolamine content (3% and 14% of the total phospholipid) were also characteristic of the plasma membrane fraction derived from this cell line. The transbilayer phospholipid distribution of the plasma membrane in intact cells and in the isolated plasma membrane fraction was investigated by using phospholipase A2 (bee venom) and sphingomyelinase (S. aureus). The phospholipid asymmetry of NF1T plasma membrane followed the general features of phospholipid asymmetry in eukaryotic cells: sphingomyelin and phosphatidylcholine were preferentially located in the outer leaflet (90% and 89%, respectively) while the aminophospholipids phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol were in the inner half of the membrane (85%, 96%, and 69%, respectively). A high percentage of the total plasma membrane phosphatidylinositol (31%) was found in the outer side of the membrane indicating a decreased asymmetric distribution for this negatively charged phospholipid. The phospholipid asymmetry found in the plasma membrane vesicle fraction corroborated the phospholipid asymmetry of the intact cells, thus confirming that the plasma membrane vesicles maintained the original orientation and lipid asymmetry after homogenization and/or sonication.

Proliferative activity, angiogenesis, and necrosis in peripheral nerve sheath tumors: a quantitative evaluation for prognosis

Malignant peripheral nerve sheath tumors (MPNSTs) are distinguished from a control group of typical benign schwannomas and neurofibromas on the basis of a set of quantitatively evaluated parameters, i.e., the cell density; the number of mitoses and apoptotic bodies; the nuclear area and shape; the number and absolute and relative areas of silver-staining nucleolar organizer regions; necrosis; and angiogenesis. Only the extent of tumor necrosis, the mitotic rate, and the parameters related to silver-staining nucleolar organizer regions discriminate between less aggressive MPNSTs (disease-free patients after 4 years of follow-up) and more aggressive MPNSTs (with recurrences or metastases during the first 4 years of follow-up).

Ras-GTP levels are elevated in human NF1 peripheral nerve tumors

Neurofibromin, the gene product of NF1, is a Ras GTPase Activating Protein. The absence of neurofibromin leads to increased levels of Ras-GTP, which contributes to the proliferation of NF1 neurogenic sarcoma cell lines. Whether this pathogenic mechanism is applicable to benign and malignant peripheral nerve tumours from NF1 and non NF1 patients is not known, due to lack of a tissue based assay. We have adapted a colorimetric enzymatic assay for determining levels of Ras bound guanine nucleotides in tissues. Ras-GTP levels were increased in NF1 neurogenic sarcomas (15 times) and benign NF1 neurofibromas (four times), compared to non NF1 schwannomas. Neurofibromin was not expressed in NF1 sarcomas, in support of its important negative Ras regulatory role in the pathogenesis of NF1 peripheral nerve tumors.

Functional nerve growth factor receptor in von Recklinghausen neurofibromatosis: an immunocytochemical and short-term culture study

Immunocytochemistry reveals 75 kDa low affinity type nerve growth factor receptor (NGFR) on the cell membrane of human neurofibroma cells of von Recklinghausen disease in vivo and in vitro. NGF-immunoreactivity is detected in the primary and cultured tumor cells. Growth augmentation of cultured neurofibroma cells by exogenous NGF is also confirmed. Phosphotyrosine-immunoreactivity is demonstrated by immunocytochemistry in the in vivo and in vitro neurofibroma cells suggesting possible phosphorylation of tyrosine residue in the NGFR or a cellular protein downstream of signal transduction through the ligand receptor system. These results indicate human neurofibroma cells possess functional NGFR and the growth is potentiated through the NGF-NGFR system in the paracrine and/or autocrine fashion.

Immunohistochemical and molecular analysis of p53, MDM2, proliferating cell nuclear antigen and Ki67 in benign and malignant peripheral nerve sheath tumours

A series of 26 malignant peripheral nerve sheath tumours (MPNST) and 24 benign peripheral nerve sheath tumours (BPNST) were analysed immunocytochemically for p53 expression and the cell proliferation markers proliferating cell nuclear antigen (PCNA) and Ki67 (with MIB1). In 23/26 MPNST, 5%-65% of the tumour cell nuclei were immunoreactive for Ki67 with MIB1 while none of the 24 BPNST had nuclear staining exceeding 5%. Greater than 50% nuclear PCNA staining was detected in 25/26 MPNST compared with 8/24 BPNST; 17/26 MPNST showed 5-100% nuclear staining for p53 (13/26 > 20%), whereas none of the BPNST had nuclear staining exceeding 1%. The Ki67, PCNA and p53 immunostaining results correlated significantly with benign versus malignant (P < 0.001, P < 0.001 and P < 0.005, respectively) as well as mitotic rate (P < 0.001, P < 0.05 and P < 0.05). Ki67 immunostaining results correlated significantly with PCNA and p53, as did p53 and Ki67 and PCNA (P < 0.001 in both). Stepwise (logistic regression forward) multivariate analysis of the variable, benign versus malignant, revealed the strongest correlations with PCNA (P = 0.007) and Ki67 (P = 0.021). Direct confirmation of the presence of p53 protein was obtained by western blot analysis of 3 MPNST and 5 BPNST. Two MPNST, showing 90% and 30% immunoreactivity, were positive for p53, while one MPNST with 5% immunoreactivity and all 5 BPNST were negative. Southern blot analysis performed on the two MPNST with high p53 protein levels revealed no amplification of the MDM2 gene, suggesting that high p53 levels in MPNST are likely to be due to mutation. The results also indicate that PCNA and Ki67 are potentially useful in distinguishing BPNST from MPNST, particularly in problematic cases of cellular schwannoma versus MPNST. The detection of p53 in a large percentage of cells of a plexiform neurofibroma giving rise to MPNST and Ki67 in 5% and 25% of cells of two similar cases suggests that malignant transformation may be detected in some cases by p53 and proliferation markers prior to overt histological evidence of malignancy.

Plexiform and other unusual variants of palisaded encapsulated neuroma

Palisaded, encapsulated neuroma (PEN) has been described as a predominantly solitary, nodular tumor; plexiform or multinodular growth patterns have not been reported in detail. We reviewed 55 PEN in order to evaluate: 1) the predominant growth patterns; 2) features that may indicate previous trauma; and 3) association with acne-like changes. Sixteen cases (29%) had growth patterns other than the solitary, nodular type. These patterns were: a) plexiform (7/16), b) multinodular (5/16), and c) fungating (4/16). Other unusual features included evidence of trauma, i.e., fibrosis, myxoid change, chronic inflammation (5/16), partially incomplete capsule (6/16), and association with acne-like features (13/16). These results suggest that: 1) plexiform or multinodular growth patterns occur relatively often in PEN; 2) some changes indicate a possible histogenetic relation to traumatic neuroma, probably via secondary traumatization; 3) a high frequency of association with acne-like changes which could imply, but does not prove, an acne-induced histogenesis; and 4) the differential diagnosis of cutaneous plexiform lesions should include PEN.

A novel glial growth inhibitory factor, gliostatin, derived from neurofibroma

Neurofibroma tissue was investigated for the presence of glial growth modulators that would suppress the proliferation of glial cells. A novel endogenous polypeptide inhibitor of proliferation and DNA synthesis in glial cells, gliostatin, was purified from the extracts of neurofibroma by a procedure comprising dye and anion-exchange column chromatography, and HPLC. A monoclonal antibody raised against partially purified gliostatin showed no cross-reactivity with known cytokines, but adsorbed the growth inhibitory activity of gliostatin and immunochemically visualized the putative gliostatin bands on western blot analyses. Although the product showed an apparent M(r) of 100,000 accompanied by an inhibitory activity on gel filtration column chromatography, it migrated at a lower apparent M(r) of 50,000 under the reducing conditions on western blotting, indicating that a homodimeric structure of native gliostatin consisted of 50-kDa subcomponents. Gliostatin was a potent growth inhibitor acting at nanomolar concentrations against all glial tumor cells and glia maturation factor-stimulated astroblasts, but not neuronal cells.