Epithelioid hemangioendothelioma, an ultra-rare cancer: a consensus paper from the community of experts

Epithelioid hemangioendothelioma (EHE) is an ultra-rare, translocated, vascular sarcoma. EHE clinical behavior is variable, ranging from that of a low-grade malignancy to that of a high-grade sarcoma and it is marked by a high propensity for systemic involvement. No active systemic agents are currently approved specifically for EHE, which is typically refractory to the antitumor drugs used in sarcomas. The degree of uncertainty in selecting the most appropriate therapy for EHE patients and the lack of guidelines on the clinical management of the disease make the adoption of new treatments inconsistent across the world, resulting in suboptimal outcomes for many EHE patients. To address the shortcoming, a global consensus meeting was organized in December 2020 under the umbrella of the European Society for Medical Oncology (ESMO) involving >80 experts from several disciplines from Europe, North America and Asia, together with a patient representative from the EHE Group, a global, disease-specific patient advocacy group, and Sarcoma Patient EuroNet (SPAEN). The meeting was aimed at defining, by consensus, evidence-based best practices for the optimal approach to primary and metastatic EHE. The consensus achieved during that meeting is the subject of the present publication.

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This consensus paper provides key recommendations on the management of epithelioid hemangioendothelioma (EHE).

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Recommendations followed a consensus meeting between experts and a representative of the EHE advocacy group and SPAEN.

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Authorship includes a multidisciplinary group of experts from different institutions from Europe, North America and Asia.

Abstract PD4-13: Estrogen receptor-negative breast adenomyoepitheliomas are driven by co-occurring HRAS hotspot and PI3K pathway gene mutations: A genetic and functional analysis

Introduction:Adenomyoepithelioma (AME) of the breast is a rare biphasic tumor, characterized by epithelial and myoepithelial differentiation. Although AMEs have an indolent clinical course, a subset may progress to carcinoma and metastasize. We sought to define the mutational landscape of AMEs and investigate the functional impact of recurrent pathogenic mutations identified in these tumors.

Methods: Thirty-one AMEs were subjected to whole-exome sequencing (WES, n=8) or massively parallel sequencing targeting all coding regions of 410 key cancer genes and intronic and regulatory regions of selected genes (n=23). Somatic genetic alterations were defined using state-of-the-art bioinformatics algorithms. In an additional set of 12 AMEs, Sanger sequencing analysis of HRAS, PIK3CA and AKT1 was performed. Non-tumorigenic estrogen receptor (ER)-negative mammary epithelial cells (i.e. MCF10A, MCF10A with a PIK3CA H1047R mutation knock-in and MCF12A) were utilized for functional studies using both conventional monolayer and three-dimensional (3D) culture assays.

Results: 27 (63%) and 16 (37%) AMEs were ER-positive and ER-negative, respectively. ER-negativity was significantly associated with histologic features predictive of a more aggressive behavior, with a higher number of mutations and copy number alterations, and with a distinct mutational profile as compared to ER-positive AMEs. Of the 27 ER-positive AMEs, 12 cases (44%) harbored PIK3CA hotspot mutations, and 5 PIK3CA wild-type cases displayed E17K AKT1 hotspot mutations. By contrast, of the 16 ER-negative AMEs, 9 (56%), 9 (56%) and 3 (19%) harbored HRAS, PIK3CA (mostly E545K and H1047R hotspots) and PIK3R1 mutations, respectively. Strikingly, all HRAS mutations were restricted to ER-negative AMEs, affected the hotspot codon Q61 (Q61R/K), and all but one co-occurred with PIK3CA or PIK3R1 mutations. In addition, HRAS Q61 hotspot mutations were significantly associated with necrosis (p=0.01) and high mitotic rates (p=0.03). CDKN2A homozygous deletions were also detected only in ER-negative AMEs (19%) and found to be significantly associated with progression to carcinoma (p=0.001). Forced expression of HRAS Q61R in MCF10A and MCF12A cells resulted in i) increased proliferation and transformation, ii) an irregular growth pattern in 3D organotypic cell cultures, iii) partial loss of the epithelial phenotype, and iv) acquisition of myoepithelial differentiation, which was more overt in PIK3CA-mutant MCF10A cells. HRAS Q61Rinduced hyperactivation of the PI3K pathway, but both PI3K and MAPK pathways likely contributed to the RAS-mediated proliferation, which was completely arrested by combined AKT and MEK inhibition.

Conclusion: AMEs are phenotypically and genetically heterogeneous. Whilst pathogenic mutations in PI3K pathway-related genes occur across the spectrum of lesions, HRAS Q61 hotspot mutations are restricted to ER-negative AMEs. Our genomic and functional analyses indicate that HRAS Q61 mutations are driver events in the pathogenesis of ER-negative AMEs and, in conjunction with mutant PIK3CA, may lead to the acquisition of myoepithelial differentiation in breast epithelial cells.

Citation Format: Geyer FC, Li A, Papanastasiou AD, Smith A, Selenica P, Burke KA, Edelweiss M, Wen H-C, Piscuoglio S, Schultheis AM, Martelotto LG, Pareja F, Kumar R, Brandes A, Lozada J, Macedo GS, Muenst S, Terracciano LM, Jungbluth A, Foschini MP, Wen HY, Brogi E, Palazzo J, Rubin BP, Ng CKY, Norton L, Varga Z, Ellis IO, Rakha E, Chandarlapatty S, Weigelt B, Reis-Filho JS. Estrogen receptor-negative breast adenomyoepitheliomas are driven by co-occurring HRAS hotspot and PI3K pathway gene mutations: A genetic and functional analysis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD4-13.

Mechanism of action of a WWTR1(TAZ)-CAMTA1 fusion oncoprotein

The WWTR1 (protein is known as TAZ)-CAMTA1 (WC) fusion gene defines epithelioid hemangioendothelioma, a malignant vascular cancer. TAZ (transcriptional coactivator with PDZ binding motif) is a transcriptional coactivator and end effector of the Hippo tumor suppressor pathway. It is inhibited by phosphorylation by the Hippo kinases LATS1 and LATS2. Such phosphorylation causes cytoplasmic localization, 14-3-3 protein binding and the phorphorylation of a terminal phosphodegron promotes ubiquitin-dependent degradation (the phosphorylation of the different motifs has several effects). CAMTA1 is a putative tumor suppressive transcription factor. Here we demonstrate that TAZ-CAMTA1 (TC) fusion results in its nuclear localization and constitutive activation. Consequently, cells expressing TC display a TAZ-like transcriptional program that causes resistance to anoikis and oncogenic transformation. Our findings elucidate the mechanistic basis of TC oncogenic properties, highlight that TC is an important model to understand how the Hippo pathway can be inhibited in cancer, and provide approaches for targeting this chimeric protein.

A nonrandom association of gastrointestinal stromal tumor (GIST) and desmoid tumor (deep fibromatosis): case series of 28 patients

BACKGROUND

Gastrointestinal stromal tumors (GISTs) and desmoid tumors (DTs) are two rare mesenchymal tumor. Anecdotal reports of individuals with both diseases led us to make the hypothesis that the association is a nonrandom event as the probability would be extremely low to observe such cases if they were independent events.

PATIENTS AND METHODS

We evaluated the existence of patients with GIST and DT in a large multicenter cohort at 10 institutions in the United States, Australia and Europe. Data on gender, age at diagnosis, KIT, PDGFRA, CTNNB1 mutation status and follow-up time after diagnosis were collected.

RESULTS

We identified 28 patients diagnosed with both tumors. DT was diagnosed after GIST in 75% of patients and concomitantly in 21%. In only one case (4%), GIST was diagnosed after DT. KIT or PDGFRA mutations were detected in 12 of 14 GIST, 9 in KIT exon 11, 2 in KIT exon 9 and 1 in PDGFRA.

CONCLUSION

A statistical analysis of these 28 cases suggests a nonrandom association between GIST and DT. Further studies may be able to elucidate the underlying biology responsible for this association.

Protein kinase C iota as a therapeutic target in alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma is an aggressive pediatric cancer exhibiting skeletal muscle differentiation. New therapeutic targets are required to improve the dismal prognosis for invasive or metastatic alveolar rhabdomyosarcoma. Protein kinase C iota (PKCι) has been shown to play an important role in tumorigenesis of many cancers but little is known about its role in rhabdomyosarcoma. Our gene expression studies in human tumor samples revealed overexpression of PRKCI. We confirmed overexpression of PKCι at the mRNA and protein level using our conditional mouse model that authentically recapitulates the progression of rhabdomyosarcoma in humans. Inhibition of Prkci by RNA interference resulted in a dramatic decrease in anchorage-independent colony formation. Interestingly, treatment of primary cell cultures using aurothiomalate (ATM), which is a gold-containing classical anti-rheumatic agent and a PKCι-specific inhibitor, resulted in decreased interaction between PKCι and Par6, decreased Rac1 activity and reduced cell viability at clinically relevant concentrations. Moreover, co-treatment with ATM and vincristine, a microtubule inhibitor currently used in rhabdomyosarcoma treatment regimens, resulted in a combination index (C. I.) of 0.470–0.793 through cooperative accumulation of non-proliferative multinuclear cells in the G2/M phase, indicating that these two drugs synergize. For in vivo tumor growth inhibition studies, ATM demonstrated a trend towards enhanced vincristine sensitivity. Overall, these results suggest that PKCι is functionally important in alveolar rhabdomyosarcoma anchorage-independent growth and tumor cell proliferation and that combination therapy with ATM and microtubule inhibitors holds promise for the treatment of alveolar rhabdomyosarcoma.

Discovery of molecular subtypes in leiomyosarcoma through integrative molecular profiling

Leiomyosarcoma (LMS) is a soft tissue tumor with a significant degree of morphologic and molecular heterogeneity. We employed integrative molecular profiling to discover and characterize molecular subtypes of LMS. Gene expression profiling was performed on 51 LMS samples. Unsupervised clustering demonstrated 3 reproducible LMS clusters. Array comparative genomic hybridization (aCGH) was performed on 20 LMS samples and demonstrated that the molecular subtypes defined by gene-expression showed distinct genomic changes. Tumors from the “muscle-enriched” cluster showed significantly increased copy number changes (p=0.04). Most muscle-enriched cases showed loss at 16q24 which contains FANCA, known to play an important role in DNA repair, and loss at 1p36 which contains PRDM16, whose loss promotes muscle differentiation. Immunohistochemistry was performed on LMS tissue microarrays (n=377) for five markers with high levels of mRNA in the muscle-enriched cluster (ACTG2, CASQ2, SLMAP,CFL2, MYLK) and demonstrated significantly correlated expression of the 5 proteins (all pairwise p < 0.005). Expression of the 5 markers was associated with improved disease-specific survival (DSS) in a multivariate Cox regression analysis (p < 0.04). In this analysis that combined gene expression profiling, aCGH and immunohistochemistry, we characterized distinct molecular LMS subtypes, provided insight into their pathogenesis, and identified prognostic biomarkers.

Combined analysis of two phase II trials of imatinib in advanced dermatofibrosarcoma protuberans (DFSP)

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Background: DFSP is an infiltrative, low-grade, dermal tumor with propensity to recur locally and occasionally metastasize. Translocation between COL1A1 on chromosome 17 and PDGFB on chromosome 22, which results in transcriptional upregulation of PDGFB, is characteristic of DFSP. Autocrine/paracrine PDGFB-mediated activation of PDGFRB drives DFSP proliferation. Two distinct phase II trials of imatinib in patients (pts) with locally advanced or metastatic DFSP were conducted, 1 in North America (SWOG) with confirmed objective response rate and 1 in Europe (EORTC) with 14 week progression-free rate as primary end-points. Methods: Pts with locally advanced or metastatic DFSP were eligible. In the EORTC trial confirmation of t(17;22) by FISH was prospectively required for participation, imatinib was started at 400mg bid, surgery was undertaken after 14 weeks if feasible and response was assessed at 14 weeks. Full accrual was to be 44 pts in one step. In the SWOG trial confirmation of t(17;22) by RT-PCR was performed after enrollment, imatinib was started at 400mg daily and response was assessed every 8 weeks. Full accrual was to be 40 pts in 2 steps. Results: 16 pts were enrolled in EORTC and 8 pts enrolled in SWOG trial. The studies were closed early because of slow accrual and regulatory approval of imatinib in DFSP. Pts age ranged from 24 to 70 yrs, DFSP was located on head/neck, trunk and extremity in 7, 11 and 6 pts, respectively, ranged in size from 1.2–49 cm and was classic, pigmented and fibrosarcomatous DFSP in 13, 1 and 7 pts, respectively. One patient did not have DFSP on central review, lacked t(17;22) and thus was ineligible. Metastases were present in 7 pts involving lung in 6 pts. 11 pts (46%) had partial response, 9 pts had stable disease and 4 pts had progressive disease as best response. Median time to progression was 1.7 yrs. Response and progression-free at 1 yr rates were similar between studies. Imatinib was stopped in 11 pts for progression, 1 pt for toxicity, 2 pts resected free of gross disease and 1 pt withdrew. Conclusions: Imatinib is active in DFSP harboring t(17;22) with an objective response rate approaching 50% and is active in fibrosarcomatous DFSP. Response rates and time to progression did not appear to differ between pts taking 400 mg daily versus 400 mg bid.

[Table: see text]

PDGFR-A is a therapeutic target in alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma is an aggressive skeletal muscle cancer of childhood. Our initial studies of rhabdomyosarcoma gene expression for patients enrolled in a national clinical trial suggested that platelet-derived growth factor receptor A (PDGFR-A) may be a mediator of disease progression and metastasis. Using our conditional mouse tumor models that authentically recapitulate the primary mutations and metastatic progression of alveolar rhabdomyosarcomas in humans, we found by immunoblotting and immunokinase assays that PDGFR-A and its downstream effectors, mitogen-activated protein kinase and Akt, were highly activated in both primary and metastatic tumors. Inhibition of PDGFR-A by RNA interference, small molecule inhibitor or neutralizing antibody had a dramatic effect on tumor cell growth both in vitro and in vivo, although resistance evolved in one-third of tumors. These results establish proof-of-principal for PDGFR-A as a therapeutic target in alveolar rhabdomyosarcoma.

Insulin receptor activation in solitary fibrous tumours

Solitary fibrous tumours (SFTs) are known to overexpress insulin-like growth factor 2 (IGF-2). The down-stream oncogenic pathways of IGF-2, however, are not clear. Here we report uniform activation of the insulin receptor (IR) pathway in SFTs, which are mesenchymal tumours frequently associated with hypoglycaemia. Whereas the IR and its downstream signalling pathways were constitutively activated in SFTs, insulin-like growth factor 1 receptor (IGF-1R) was not expressed in these tumours. We also find that SFT cells secrete IGF-2 and proliferate in serum-free medium, consistent with an IGF-2/IR autocrine loop. The aetiological relevance of IGF-2 is supported by expression of IR-A, the IR isoform with high affinity for IGF-2, in all SFTs. Our studies suggest that IR activation plays an oncogenic role in SFTs.

[Human embryonic stem cell therapy, what is the attitude of the public?]

This work discusses the manner in which the public has dealt with the ethical questions about human embryonic stem cell research. It argues that the public is not a homogenous entity, but rather consists of a number of "different publics", which at different points of the debate have discussed different aspects and different questions of this therapeutic proposal. It understands the development of human stem cell therapy not as a result of the activity of an isolated science, acting independently of society. In the contrary it considers it as a co-production of science with the different social actors, which participate in the political, ethical, and legal processes. Therefore the question if ethics is ahead or lags behind the developments in medical research becomes obsolete. Ethics is on one side the result of the effort to handle the results of biomedical research in a manner which is adequate for society at large on the other side it also influences the scientific-technological development through its own assessment.

Gastrointestinal stromal tumours: an update

Recently, there has been intense interest in the study of gastrointestinal stromal tumour (GIST); one might call it a virtual GIST revolution. This is due largely to the realization that most GISTs express KIT and harbour activating c-KIT (KIT) or platelet-derived growth factor receptor-alpha (PDGFRA) receptor tyrosine kinase mutations that can be targeted by small molecule pharmacological inhibitors. Pathologists have benefited greatly from this revolution, mainly in the form of an improved ability to classify GISTs and, even more recently, in understanding the molecular underpinnings that underlie many fascinating clinical and pathological correlations. It is the purpose of this review to summarize recent developments in GIST classification and the molecular pathogenesis of GIST.

KIT activation is a ubiquitous feature of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, and they are generally resistant to chemotherapy and radiation therapy. Most GISTs express the KIT receptor tyrosine kinase protein, and a subset of GISTs contain activating mutations within the KIT juxtamembrane region. We evaluated 48 GISTs, including 10 benign, 10 borderline, and 28 malignant cases, to determine whether KIT expression and activation are general properties of these tumors. Immunohistochemical KIT expression was demonstrated in each case. Somatic KIT mutations were found in 44 tumors (92%), of which 34 (71%) had juxtamembrane region mutations. Other GISTs had KIT mutations in the extracellular region (n = 6) and in two different regions in the tyrosine kinase domain (n = 4). Contrary to previous reports, KIT mutations were not identified preferentially in higher-grade tumors: indeed, they were found in each of 10 histologically benign GISTs. Notably, mutations in all KIT domains were associated with high-level KIT activation/phosphorylation, and KIT activation was also demonstrated in the four GISTs that lacked detectable KIT genomic and cDNA mutations. These studies underscore the role of KIT activation in GIST pathogenesis, and they suggest that activated KIT might represent a universal therapeutic target in GISTs.

The genetics of lipomatous tumors

The current classification of lipomatous neoplasms has been validated by the identification of characteristic cytogenetic and molecular genetic profiles associated with various neoplasms within the family of lipomatous tumors. The review describes characteristic cytogenetic and molecular genetic profiles and discusses their significance. The clinicopathologic features of these tumors, which are described elsewhere, will not be included in this review.

Cytologic diagnosis of gastrointestinal stromal tumor with emphasis on the differential diagnosis with leiomyosarcoma

BACKGROUND

Gastrointestinal stromal tumor (GIST) has only recently been distinguished histologically and immunochemically from morphologically similar neoplasms of the abdomen.

METHODS

The authors reviewed 15 cytologic cases of GIST (14 fine-needle aspiration [FNA] specimens and 1 peritoneal fluid specimen) and compared them with 23 cases of leiomyosarcoma (LMS) arising in the abdomen or pelvis (all FNAs). Immunochemistry (IC) was performed on both the cytologic and subsequent tissue specimens if sufficient specimen was available.

RESULTS

Cytologic samples of GISTs typically showed irregularly outlined clusters of uniform spindle cells that were spread easily without crush artifact. The cells had wispy cytoplasm with long, delicate, filamentous extensions (13 cases; 87%). A prominent vascular pattern was common (9 cases; 60%); pleomorphism (1 case; 7%) was uncommon. The LMSs showed three-dimensional, tightly cohesive, sharply marginated syncytia of spindle cells, often with nuclear crush artifact. The cytoplasm/stroma had a distinct wiry, refractile appearance (21 cases; 91%); delicate filamentous cytoplasmic extensions (5 cases; 22%) and prominent vessels (3 cases; 13%) were less common. LMSs more commonly exhibited pleomorphism (14 cases; 61%). Epithelioid cytomorphology, mitoses, and necrosis occasionally were observed in both tumor types. IC for c-kit (on cytologic material) was positive in 10 of 10 cases of GIST (usually diffuse and strong) and 2 of 19 cases of LMS (focal). CD34 positivity favored GIST (4 of 9 cases) over LMS (1 of 19 cases). Smooth muscle actin was positive in 20 of 20 LMSs (strong and diffuse) and 6 of 10 GISTs (usually focal). Desmin was positive in 12 of 20 LMSs and was only focally positive in 1 of 11 GISTs. Correlation of IC results was excellent between cytologic and tissue specimens.

CONCLUSIONS

Delicate cytoplasmic processes; a prominent vascular pattern; a lack of nuclear pleomorphism; and a c-kit-positive, desmin-negative immunoprofile are characteristic features of GIST and help distinguish these tumors from LMS in cytologic specimens.

Response to chemotherapy and predictors of survival in adult rhabdomyosarcoma

OBJECTIVE

To assess outcome and identify predictors of survival of adults with rhabdomyosarcoma.

SUMMARY BACKGROUND DATA

The literature on adult rhabdomyosarcoma is limited. Few studies have identified predictors of long-term survival in this patient population.

METHODS

Thirty-nine adults with rhabdomyosarcoma were treated between 1973 and 1996 and prospectively followed. Outcomes were assessed with respect to patient and tumor characteristics, local treatment, and response to chemotherapy.

RESULTS

Twenty-six patients had localized/locoregional disease and 13 patients had metastatic disease at presentation. Twenty-one patients underwent attempted curative resection, 27 received radiotherapy, and 37 received chemotherapy. Median follow-up for surviving patients was 152 months. The overall 5- and 10-year survival rates were 31% and 27%, respectively. Five-year survival rates for patients with tumors less than 5 cm, 5 to 10 cm, and more than 10 cm were 60%, 14%, and 0%, respectively. Patients with localized/locoregional disease at presentation had a 44% 5-year survival rate; there were no 5-year survivors among patients with metastatic disease. Patients who had a complete response to chemotherapy had a 5-year survival rate of 57%, compared with a rate of only 7% for poor responders. Metastatic disease at presentation and poor response to chemotherapy were independent predictors of death on multivariate analysis.

CONCLUSIONS

Age, location, nodal status, and histologic subtype do not appear be associated with survival in adults with rhabdomyosarcoma treated with multimodal therapy. Metastatic disease at presentation and poor response to chemotherapy are strongly associated with poor prognosis. Future systemic therapies should be targeted to patients with localized/locoregional disease and partial responders to conventional chemotherapy.

Recent progress in the classification of soft tissue tumors: role of genetics and clinical implications

Soft tissue tumors comprise a vast and heterogeneous group of neoplasms. Because different tumors often have different biological behaviors and respond differently to various therapeutic modalities, precise classification is paramount. The majority of soft tissue tumors were first delineated on the basis of morphologic and clinical findings, which in many cases were adequate to accurately separate different tumors into homogeneous groups; however, it has increasingly been appreciated that many entities are actually heterogeneous groups of tumors that have similar histologic and pathologic characteristics but differ in their clinical behavior and underlying pathogenesis. Within the past several years, great strides have been made in the purification of different entities. This accomplishment has largely been because of advances in our understanding of the molecular genetics that underlie the pathogenesis of many sarcomas and the development of new and specific tumor markers. This review highlights some important recent work in two selected soft tissue tumors-gastrointestinal stromal tumor and inflammatory myofibroblastic tumor. These examples illustrate the type of progress that is being made in the classification of soft tissue tumors.

Use of cytokeratins 7 and 20 in determining the origin of metastatic carcinoma of unknown primary, with special emphasis on lung cancer

Metastatic carcinoma of unknown primary is a common problem, accounting for up to 10-15% of all solid tumours at presentation. Proper identification of the site of origin has prognostic and therapeutic significance. Prior immunohistochemical methods to identify the site of origin have been useful in a limited number of cases. Differential cytokeratin staining may be useful in this setting, particularly in identifying metastases from lung cancer. We have identified 144 cases of metastatic carcinoma of unknown primary to bone, lung or liver at Brigham and Women's Hospital between 1 January 1997 and 1 July 1998. Cytokeratin (CK) 7 and CK20 were used in 75 of these cases to narrow down the possible sites of the primary tumours. All of these cases were ambiguous as to the site of the primary tumour. Forty-five cases were CK7+/CK20-, 15 cases were CK7-/CK20-, 9 cases were CK7-/CK20+ and 6 cases were CK7+/CK20+. Three of the cases were selected for detailed presentation and discussion as well as a discussion of the pertinent literature. Overall, the CK7+/CK20- phenotype favours a lung primary, the CK7+/CK20+ phenotype strongly favours transitional cells (urothelial) carcinoma, the CK7-/CK20+ phenotype favours colorectal carcinoma, while the CK7-/CK20- profile is not helpful.

Teneurin-2 is expressed in tissues that regulate limb and somite pattern formation and is induced in vitro and in situ by FGF8

Teneurin-2 is a member of a novel family of transmembrane proteins characterized to date in fish, birds, mammals, and Drosophila (e.g., the pair-rule gene product Ten-m). We have shown that teneurin-2 is expressed by neurons in the developing avian visual system in a pattern complementary to the expression of teneurin-1 and that recombinant teneurin-2 induces morphologic changes in neuronal cells in culture (Rubin et al., 1999). Here we have used cRNA probes to two newly identified splice variants and a teneurin-2-specific antibody to determine whether teneurin-2 is also expressed outside the nervous system. Both reverse transcriptase-polymerase chain reaction and in situ hybridization indicate that the three splice variants known so far are coexpressed at sites of pattern formation during development. Teneurin-2 mRNAs and protein are found in the developing limbs, somites, and craniofacial mesenchyme. In addition to expression of teneurin-2 by the apical ectodermal ridge, teneurin-2 transcripts also appear transiently at sites of tendon development. Teneurin-2 expression patterns were strikingly similar to those of fibroblast growth factor 8 (FGF8). In agreement with the overlapping expression pattern, FGF8-coated beads implanted into chicken limb buds induced the ectopic expression of teneurin-2 and soluble FGF8 induced teneurin-2 in limb explant cultures. Thus, teneurin-2 could act downstream of FGF8 during morphogenesis.

Isochromosome 7q in adult Wilms' tumors: diagnostic and pathogenetic implications

Wilms' tumors affecting adults are rare and are thought to have a worse prognosis than similar stage tumors in the pediatric population. To understand these tumors better, the authors reviewed their multi-institutional experience in a series of nine lesions diagnosed as Wilms' tumors in adults. In addition to histologic and immunohistochemical examination, they performed cytogenetic analysis and fluorescence in situ hybridization. On review, four cases were reclassified: two "blastema only" as Ewing's sarcoma/primitive neuroectodermal tumor and the other two as clear cell sarcoma of soft parts and sarcoma not otherwise specified (NOS). Of the remaining five cases, three exhibited biphasic histology and two were triphasic. In this group, there were three women and two men, and patient age ranged from 17 to 37 years (median age, 26 years). Tumor size was large and ranged from 10 to 31 cm (median tumor size, 12.5 cm). Histologically, the tumors showed the typical features of Wilms' tumors with varying amounts of blastema (n = 5), epithelium (n = 5), and stroma (n = 2). No tumors contained anaplasia, and persistent renal blastema was not identified in the non-neoplastic kidney in any specimen. All tumors were positive for cytokeratins (CK7, n = 3; pankeratin, n = 5), and one tumor was weakly positive for CD99 (0-13). Molecular analysis including dual color fluorescence in situ hybridization (all tumors), and cytogenetic analysis (n = 2) disclosed the presence of isochromosome 7q in three of five tumors whereas all tumors were diploid with respect to chromosome 12. Follow-up data ranged from 6 to 133 months (median follow-up, 82 months) with progression in only one patient who had stage IV disease with lymph node and lung metastases at presentation. The authors conclude that adult Wilms' tumor has been overdiagnosed. Most "blastema-only" tumors in adults are not Wilms' tumors, and in an adult, biphasic morphology should be the minimum criteria for their diagnosis. Using strict diagnostic criteria, adult Wilms' tumors have a relatively favorable prognosis. The characteristic findings of isochromosome 7q, lack of trisomy or tetrasomy for chromosome 12, and absence of persistent renal blastema suggest that the pathogenesis of Wilms' tumors in adults may be different than in the pediatric population. These genetic features may be helpful in distinguishing adult Wilms' tumors from other primary renal tumors.

Myxoid leiomyosarcoma of soft tissue, an underrecognized variant

Myxoid leiomyosarcoma is an uncommon tumor which, although previously well described in the uterus, is recognized to a lesser extent at other sites. We describe 18 cases of soft tissue leiomyosarcoma in which myxoid stroma occupied >50% of the tissue examined. Patients ranged in age from 22 to 84 years old (median, 57.5 yrs) and female patients outnumbered male patients 14 to 4. Tumor locations included the limbs (6 cases), female external genitalia (4 cases), head and neck region (3 cases), chest (2 cases), nipple, paratesticular soft tissue, and perineum (one case each). The tumors had a grossly gelatinous appearance and adopted three major histologic architectures: fascicular, reticular/microcystic, and "myxofibrosarcoma-like." The tumor cells were predominantly spindled in all cases with typical features of smooth muscle differentiation; there was a mixture of spindle and epithelioid cells in one case. No cases with pure epithelioid cytology were seen. All tumors displayed immunoreactivity for smooth muscle markers (smooth muscle actin 16/17, desmin 8/18) and, in addition, four cases were positive for keratin CAM 5.2 and three for epithelial membrane antigen. The tumors had a tendency to be morphologically lower grade (9 tumors were grade I, 8 were grade II, and only 1 was grade III). Follow up was available in 13 patients with a duration of 8 months to 41 years (median, 39 mos), and revealed local recurrences (often repeated) in five cases and metastases in two cases. There were three tumor-related deaths, of which two were the result of uncontrolled local disease. The differential diagnosis of myxoid leiomyosarcoma is broad and encompasses both benign and malignant lesions. Accurate diagnosis is critical because therapies may differ widely for entities in the differential diagnosis of myxoid leiomyosarcoma.

KIT extracellular and kinase domain mutations in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms arising in the gastrointestinal tract. GISTs express the KIT receptor tyrosine kinase, and many cases have activating mutations in the KIT juxtamembrane region. We now report an analysis of KIT cDNA and genomic sequences in eight GISTs that lack juxtamembrane region mutations. Six cases contained heterozygous exon 9 mutations in which six nucleotides, encoding Ala-Tyr, were duplicated. The other two cases contained homozygous exon 13 missense mutations, resulting in substitution of Glu for Lys(642), that were associated with constitutive KIT tyrosine phosphorylation. Sequence analysis of DNAs from nonneoplastic companion tissues revealed that both the exon 9 and exon 13 mutations were somatic. These are the first descriptions, in any tumor, of mutations in KIT exons encoding the C-terminal end of the extracellular domain and the first part of the split kinase domain. These findings indicate that KIT may be activated by mutations in at least three domains-extracellular, juxtamembrane, and kinase-in GISTs.

Composite hemangioendothelioma: a complex, low-grade vascular lesion mimicking angiosarcoma

Eight cases of a previously uncharacterized vascular neoplasm, showing varying combinations of benign, low-grade malignant, and malignant vascular components are described. Seven tumors occurred in the dermis and/or subcutis and one occurred in the oral submucosa. The patients were all adults with a median age of 39.5 years (range, 21-71 years). Five patients were men. The tumors arose predominantly in the hands and feet, and the lesions were usually of several years duration. The tumors were composed of a complex admixture of histologic components that varied from tumor to tumor, such that no two tumors looked precisely the same. This was due to variation in the proportions of each component as well as the manner in which each component was distributed throughout each lesion. The predominant histologic components were epithelioid hemangioendothelioma (HE) and retiform HE, which were each present in seven of the tumors. Areas of spindle cell HE were identified in four lesions. Angiosarcoma-like elements were identified in seven tumors. One of the tumors was associated with an arteriovenous malformation and one was associated with an area of lymphangioma circumscriptum. Of six cases with follow up (median duration, 6.5 years), three have recurred locally and, to date, only one has metastasized. We think composite HE is best regarded as a low-grade malignant vascular neoplasm, and the available data suggest that it behaves more favorably than conventional angiosarcoma. The existence of these composite lesions has led to careful reexamination of the concept of HE. The term HE, in that it is currently synonymous with a low-grade malignant vascular tumor, should be reserved for lesions that have true metastatic potential, albeit with low frequency.

Teneurins: a novel family of neuronal cell surface proteins in vertebrates, homologous to the Drosophila pair-rule gene product Ten-m

We have characterized chicken teneurin-1 and teneurin-2, two homologues of the Drosophila pair-rule gene product Ten-m and Drosophila Ten-a. The high degree of conservation between the vertebrate and invertebrate proteins suggests that these belong to a novel family. We propose to name the vertebrate members of this family teneurins, because of their predominant expression in the nervous system. The expression of teneurin-1 and -2 was investigated by in situ hybridization. We show that teneurin-1 and -2 are expressed by distinct populations of neurons during the time of axonal growth. The most prominent site of expression of chicken teneurins is the developing visual system. Recombinant teneurin-2 was expressed to assay its molecular and functional properties. We show that it is a type II transmembrane protein, which can be released from the cell surface by proteolytic cleavage at a furin site. The expression of teneurin-2 in neuronal cells led to a significant increase in the number of filopodia and to the formation of enlarged growth cones. The expression pattern of teneurins in the developing nervous system and the ability of teneurin-2 to reorganize the cellular morphology indicate that these proteins may have an important function in the formation of neuronal connections.

Skeletal and extraskeletal myxoid chondrosarcoma: related or distinct tumors?

Skeletal myxoid chondrosarcoma is a histologic variant of conventional skeletal myxoid chondrosarcoma, whereas extraskeletal myxoid chondrosarcoma is a distinct entity characterized by a reciprocal t(9;22) translocation resulting in fusion of the EWS and CHN genes. Rarely, extraskeletal myxoid chondrosarcoma can occur in bone, and it is difficult to describe such tumors, unambiguously, using the present nomenclature. Designation as "chordoid sarcoma of bone" would distinguish these cases from conventional skeletal myxoid chondrosarcoma.

Teneurin-1, a vertebrate homologue of the Drosophila pair-rule gene ten-m, is a neuronal protein with a novel type of heparin-binding domain

The Drosophila gene ten-m is the first pair-rule gene not encoding a transcription factor, but an extracellular protein. We have characterized a highly conserved chicken homologue that we call teneurin-1. The C-terminal part harbors 26 repetitive sequence motifs termed YD-repeats. The YD-repeats are most similar to the core of the rhs elements of Escherichia coli. Related repeats in toxin A of Clostridium difficile are known to bind specific carbohydrates. We show that recombinantly expressed proteins containing the YD-repeats of teneurin-1 bind to heparin. Furthermore, heparin lyase treatment of extracts of cells expressing recombinant YD-repeat protein releases this protein from high molecular mass aggregates. In situ hybridization and immunostaining reveals teneurin-1 expression in neurons of the developing visual system of chicken and Drosophila. This phylogenetic conservation of neuronal expression from flies to birds implies fundamental roles for teneurin-1 in neurogenesis. This is supported by the neurite outgrowth occurring on substrates made of recombinant YD-repeat proteins, which can be inhibited by heparin. Database searches resulted in the identification of ESTs encoding at least three further members of the teneurin family of proteins. Furthermore, the human teneurin-1 gene could be identified on chromosome Xq24/25, a region implied in an X-linked mental retardation syndrome.

Extracellular matrix and development of lamination in the dorsal lateral geniculate nucleus in the tree shrew (Tupaia belangeri)

In the tree shrew (Tupaia belangeri), the cytoarchitectonic lamination of the lateral geniculate nucleus cannot be detected at birth; it only appears during the early postnatal period. However, a laminated pattern was revealed with rapid Golgi staining and retinal afferents were segregated into the appropriate laminae well before cytoarchitectonic lamination could be seen. Both observations indicate that the extracellular matrix may play a role in the separation of lateral geniculate nucleus cells into laminae. In the present study, the organization of the extracellular matrix was investigated during development using immunohistochemical and in situ hybridization techniques. For immunohistochemistry, peanut agglutinin (PNA) lectin and antibodies against tenascin (TN) were chosen, while for in situ hybridization, mTN riboprobes were used, simultaneously, with antibodies against Vimentin (Vim) and microtubule associated protein (MAP-2). The results showed that the pattern of PNA-binding glycoproteins and that of tenascin were relatively similar, although tenascin appeared later and disappeared earlier. The first interlaminar spaces to be detected were those between layers innervated by opposite eyes. The TN specific mRNA was detected in the lateral geniculate nucleus at P0, but was no longer visible at P7. By comparing TN mRNA and Vim or MAP-2 stainings a correspondence could be observed. The extracellular matrix lamination therefore seems to precede cytoarchitectonic lamination, suggesting that the extracellular matrix may play a role in the development of laminated structures. The TN-producing cells seem to be developing astrocytes and neurons.

Clear cell sarcoma of soft parts: report of a case primary in the kidney with cytogenetic confirmation

Clear cell sarcoma of soft parts (CCSSP), also known as malignant melanoma of soft parts, is an aggressive tumor that usually presents in soft tissue and very rarely in small bowel. We report a case arising in the kidney of a 20-year-old man which was difficult to distinguish from Wilms' tumor. The tumor metastasized to the liver and lungs, and the patient died of disseminated disease 5 years after his initial presentation. Both the primary and metastatic tumors were composed predominantly of spindle cells with occasional more epithelioid areas that were inconsistently arranged in nests. In both primary and metastatic sites, the tumor surrounded and entrapped normal epithelial elements, mimicking the biphasic appearance of Wilms' tumor. The tumor cells, however, were positive for S-100 protein and HMB45 and negative for keratin and CD99, and cytogenetic analysis revealed a clonal abnormality, translocation t(12;22)(q13;q12), characteristic of CCSSP. This result was verified by fluorescence in situ hybridization on paraffin-embedded tissue, which demonstrated EWS gene-region rearrangement. CCSSP joins a growing list of tumors that typically arise in soft tissue (PNET, solitary fibrous tumor, and infantile/congenital fibrosarcoma), but can also present in the kidney and may be confused with primary renal tumors. Awareness of this possibility and the use of ancillary studies. including immunohistochemistry, cytogenetic analysis, and fluorescence in situ hybridization, are important for accurate diagnosis.

Myxoid solitary fibrous tumor: a study of seven cases with emphasis on differential diagnosis

Focal myxoid change is a well-recognized feature of solitary fibrous tumor (SFT), but to date, predominantly myxoid examples of SFT have not been reported. We describe seven cases of SFT in which stromal myxoid change affected 50% or more of the tumor examined, thus obscuring typical diagnostic features. Patients ranged in age from 35 to 68 years old (median, 45 yr), with an equal sex distribution. Tumor locations included pleura, orbit, and periparotid subcutaneous tissue, as well as four cases in deep soft tissue (two in the abdominal wall and one each in the chest wall and thigh). Myxoid areas were identified grossly in four cases. Histologically, the lesions were composed of bland spindle cells disposed haphazardly or with a lacy or reticulated appearance in a myxoid, richly vascularized stroma These myxoid areas were punctuated by small cellular aggregates in four cases, and areas showing diagnostic features of SFT were present in five of seven primary excision specimens. Atypical features suggestive of malignancy were not present in any of the cases. Immunohistochemically, all of the seven cases stained positively for CD34 and CD99 (013), and all were negative for smooth muscle actin, desmin, S-100 protein, epithelial membrane antigen, and pan-keratin. There were no recurrences or metastases reported in four patients with limited follow-up (median duration, 19 mo). Recognition of this uncommon morphologic subset of SFT is important because of possible confusion, particularly in small biopsy specimens, with a variety of myxoid spindle cell neoplasms with different biologic potential. These include low-grade fibromyxoid sarcoma, myxoid synovial sarcoma, malignant peripheral nerve sheath tumor, low-grade myxofibrosarcoma, myxoid liposarcoma, myxoid spindle cell lipoma, myxoid neurofibroma, and so-called "hemangiopericytoma."

Congenital mesoblastic nephroma t(12;15) is associated with ETV6-NTRK3 gene fusion: cytogenetic and molecular relationship to congenital (infantile) fibrosarcoma

Morphological, cytogenetic, and biological evidence supports a relationship between congenital (infantile) fibrosarcoma (CFS) and congenital mesoblastic nephroma (CMN). These tumors have a very similar histological appearance, and they are both associated with polysomies for chromosomes 8, 11, 17, and 20. Recently, CFS was shown to contain a novel t(12; 15)(p13;q25) translocation resulting in ETV6-NTRK3 gene fusion. The aims of this study were to determine whether congenital mesoblastic nephroma contains the t(12;15)(p13;q25) translocation and ETV6-NTRK3 gene fusion and whether ETV6-NTRK3 fusions, in CMN and CFS, antedate acquisition of nonrandom chromosome polysomies. To address these aims, we evaluated 1) ETV6-NTRK3 fusion transcripts by reverse transcriptase polymerase chain reaction and sequence analysis, 2) genomic ETV6-region chromosomal rearrangement by fluorescence in situ hybridization, and 3) chromosomal polysomies by karyotyping and fluorescence in situ hybridization. We report ETV6-NTRK3 fusion transcripts and/or ETV6-region rearrangement in five of six CMNs and in five of five CFSs. The ETV6-NTRK3 fusion transcripts and/or ETV-region chromosome rearrangements were demonstrated in two CMNs and one CFS that lacked chromosome polysomies. These findings demonstrate that t(12;15) translocation, and the associated ETV6-NTRK3 fusion, can antedate acquisition of chromosome polysomies in CMN and CFS. CMN and CFS are pathogenetically related, and it is likely that they represent a single neoplastic entity, arising in either renal or soft tissue locations.

Spindle cell rhabdomyosarcoma (so-called) in adults: report of two cases with emphasis on differential diagnosis

Spindle cell rhabdomyosarcoma (RMS) is a recently described variant of embryonal RMS that carries a relatively favorable prognosis when compared with other forms of RMS. To date, spindle cell RMS has been described only in children. The authors have identified two unusual cases occurring in adults using the following criteria: tumors composed mainly of fascicular, relatively monomorphic spindle-shaped cells that show unequivocal immunohistochemical and ultrastructural evidence of myogenic differentiation. The tumors were identified in a 38-year-old woman and a 56-year-old man, arising in the cheek and left hemidiaphragm, respectively. Both were treated with surgical resection and chemotherapy. The first patient died of uncontrolled local recurrence of her tumor at 27 months after diagnosis, and the second died of metastatic disease at 13 months follow-up. The tumors were composed mainly of fascicles of spindle cells with palely eosinophilic cytoplasm admixed diffusely with sparse polygonal, rounded, or strap-shaped rhabdomyoblasts with brightly eosinophilic cytoplasm and with cross-striations in the first case only. Immunostaining for muscle-related antigens showed staining for smooth-muscle actin (focal), pan-actin HHF-35, desmin, fast myosin, myoglobin, and MyoD1. Both cases were negative for S-100 protein. On electron microscopy, both cases showed neoplastic rhabdomyoblasts with clear-cut sarcomeric differentiation in many of the tumor cells. Spindle cell RMS poses special problems in differential diagnosis when arising in adults and should be distinguished from leiomyosarcoma, malignant peripheral nerve sheath tumor with heterologous rhabdomyoblastic differentiation (malignant Triton tumor), and fibrosarcoma. In view of the good prognosis afforded children with spindle cell RMS and in light of the chemoresponsive behavior of RMS in general, we feel that it is important to identify tumors that meet the criteria for spindle cell RMS occurring in the adult population. However, based on these two cases, it is possible that spindle cell RMS occurring in adults may not be associated with such a favorable outcome.

VEGF mRNA induction correlates with changes in the vascular architecture upon spinal cord damage in the rat

The multiple cellular and molecular processes induced by injury to the central nervous system (CNS) are still poorly understood. In the present study, we investigated the response of the vasculature and the expression of mRNA for the angiogenic vascular endothelial growth factor (VEGF) following X-irradiation of the spinal cord in the newborn and following traumatic spinal cord injury in the adult rat. Both lesion models induced changes in the density and the distribution pattern of blood vessels: while X-irradiation led to a permanent local increase in vascular density in the fibre tracts of the exposed segments, a transient local sprouting of vessels was induced upon traumatic spinal cord injury. In situ hybridization showed that an increase of VEGF mRNA anticipated and overlapped with the vascular responses in both lesion models. In addition to the temporal correlation of VEGF expression and vascular sprouting, there was a clear correlation in the spatial distribution patterns. Following X-irradiation, the expression of VEGF mRNA was restricted to the fibre tracts, precisely the areas where the changes in the vasculature were observed later on. Upon transection in the adult animal, VEGF was mainly detectable at the border of the lesion area, where the transient increase in vascular density could be observed. Interestingly, according to the type of lesion applied, astrocytes (X-irradiation) or inflammatory cells (presumably microglial cells or macrophages; traumatic lesion) are the cellular sources of VEGF mRNA. Our results strongly indicate that VEGF is crucially involved in mediating vascular changes following different types of injury in the CNS.

Local changes in vascular architecture following partial spinal cord lesion in the rat

Lesions of the CNS induce a complex cascade of tissue reactions. The purpose of this study was to determine the response of the vasculature to partial spinal cord transection. Adult rat spinal cords were lesioned and then examined during acute, subacute, and chronic periods for the presence of endothelial cells and blood vessels at the lesion site. The association of endothelial cells and astrocytes was examined immunohistochemically (RECA-1 and glial fibrillary associated protein, respectively). During the first 48 h following an incision lesion of the dorsal spinal cord, the vasculature was significantly decreased, concurrently with the tissue loss due to primary and secondary degeneration. Subsequently, at 4 days postlesion, vasculature repair processes were evidenced by a significant increase in the number of vessels present at the lesion center. Blood vessels even formed in areas densely packed with macrophages and tissue debris. After 1 week, the number of blood vessels declined in the lesion center and at the place of the forming caverns. These results show significant initial attempts at repair of the vasculature which do not, however, lead to the restoration of a compact tissue and cannot prevent the subsequent formation of caverns.

The cytogenetics of lipomatous tumours

Precise classification of lipomatous tumours sometimes presents a challenge to even the most experienced pathologist. Because the different types of lipomatous tumour exhibit significantly different biological behaviours, it is of utmost importance that the correct diagnosis be made. In morphologically difficult cases, identification of characteristic cytogenetic aberrations that correlate with histological subtype can facilitate the correct diagnosis.

Inhibition of PC12 cell attachment and neurite outgrowth by detergent solubilized CNS myelin proteins

Adhesion and neurite outgrowth of PC12 cells, as well as the spreading of 3T3 fibroblasts, were inhibited in a dose dependent manner by detergent solubilized mouse central nervous system myelin proteins as a tissue culture substrate. These inhibitory effects could be neutralized by the monoclonal antibody IN-1 directed against the neurite growth inhibiting proteins NI-35 and NI-250. Separation of the detergent soluble proteins of bovine spinal cord by an anion exchange column showed that the peaks of inhibitory activity for the two cell lines overlapped, such that the PC12 cells were inhibited by a larger number of fractions comprising those inhibitory for 3T3 cells. Neurite outgrowth of PC12 cells was not influenced by the myelin associated glycoprotein, MAG.

Lack of evidence that myelin-associated glycoprotein is a major inhibitor of axonal regeneration in the CNS

The MAG-deficient mouse was used to test whether MAG acts as a significant inhibitor of axonal regeneration in the adult mammalian CNS, as suggested by cell culture experiments. Cell spreading, neurite elongation, or growth cone collapse of different cell types in vitro was not significantly different when myelin preparations or optic nerve cryosections from either MAG-deficient or wild-type mice were used as a substrate. More importantly, the extent of axonal regrowth in lesioned optic nerve and corticospinal tract in vivo was similarly poor in MAG-deficient and wild-type mice. However, axonal regrowth increased significantly and to a similar extent in both genotypes after application of the IN-1 antibody directed against the neurite growth inhibitors NI-35 and NI-250. These observations do not support the view that MAG is a significant inhibitor of axonal regeneration in the adult CNS.

CNS myelin and oligodendrocytes of the Xenopus spinal cord--but not optic nerve--are nonpermissive for axon growth

In vitro assays reveal that myelin and oligodendrocytes of the Xenopus spinal cord (SC) are--unlike corresponding components of the optic nerve/tectum (OT)--nonpermissive substrates for regenerating retinal axons. The number of growth cones that crossed SC oligodendrocytes is low but increases significantly (four- to fivefold) in the presence of the antibody IN-1, in which case their numbers are similar to the number of growth cones (approximately 60%) that cross OT oligodendrocytes with or without IN-1. IN-1 neutralizes neurite growth inhibitors (NI) of rat CNS myelin, indicating that mammalian-like NI are associated with Xenopus SC myelin and oligodendrocytes but not with the OT. IN-1 immunocytochemistry on sections supports this view: SC myelin was stained with IN-1, whereas OT myelin and PNS myelin were not.

Structure of REC2, a recombinational repair gene of Ustilago maydis, and its function in homologous recombination between plasmid and chromosomal sequences

Mutation in the REC2 gene of Ustilago maydis leads to defects in DNA repair, recombination, and meiosis. Analysis of the primary sequence of the Rec2 protein reveals a region with significant homology to bacterial RecA protein and to the yeast recombination proteins Dmc1, Rad51, and Rad57. This homologous region in the U. maydis Rec2 protein was found to be functionally sensitive to mutation, lending support to the hypothesis that Rec2 has a functional RecA-like domain essential for activity in recombination and repair. Homologous recombination between plasmid and chromosomal DNA sequences is reduced substantially in the rec2 mutant following transformation. The frequency can be restored to a level approaching, but not exceeding, that observed in the wild-type strain if transformation is performed with cells containing multiple copies of REC2.

A monoclonal antibody (IN-1) which neutralizes neurite growth inhibitory proteins in the rat CNS recognizes antigens localized in CNS myelin

In previous studies two neurite growth inhibiting protein fractions of 35 and 250 kDa were identified in myelin preparations of the rat CNS. These activities were not found in the myelin of PNS. A monoclonal antibody (mAb IN-1) was raised against the 250 kDa protein fraction and selected for its ability to neutralize the inhibitory effect of CNS myelin and of both isolated protein fractions. IN-1 has been shown both in vitro and in vivo to neutralize the inhibitory effect of differentiated oligodendrocytes and CNS white matter. In the present study, the antigens of IN-1 were localized by immunohistochemistry on cryostat sections of the adult rat nervous system. The staining pattern of IN-1 was compared to that of mAbs specific for proteins found in CNS and PNS myelin. These proteins include myelin basic protein, myelin oligodendrocyte glycoprotein, and myelin associated glycoprotein. IN-1 stained white matter and myelinated fibre tracts in the CNS on sections of fresh frozen tissue fixed with 95% ethanol: 5% acetic acid (Clark's solution). Sciatic nerve myelin and spinal roots remained unstained. The staining pattern of IN-1 corresponded most closely to that of a mAb against myelin oligodendrocyte glycoprotein, a protein which occurs exclusively in CNS myelin and on differentiated oligodendrocytes.

The LEU1 gene of Ustilago maydis

The nucleotide sequence of the Ustilago maydis LEU1 gene has been determined. It contains a continuous open reading frame predicted to encode a protein of 773 amino acids with a molecular mass of 83,234 Da. The protein is homologous to alpha-isopropylmalate isomerases from prokaryotes and eukaryotes, as well as to other members of a family of structurally related isomerases.

Transition from mitosis to interphase in sea urchin first division: immunofluorescence studies of tubulin distribution in methacrylate sections

Previous immunofluorescence studies of microtubule distribution in fertilized sea urchin eggs have suffered from poor resolution caused by cell thickness, unavoidable artifacts resulting from excessive flattening, or extraction by detergents of membranes and other lipid-containing structures that may be of interest in relation to the microtubules. To avoid these difficulties, we have developed a fixation and embedding protocol based on buffered paraformaldehyde fixation and butyl-methyl methacrylate embedment, which allows immunofluorescence staining of 0.5-1 micron sections. Polymerization artifacts are reduced by polymerizing the methacrylate at a relatively low temperature (40-45 degrees C) and by flat embedding for more uniform polymerization. Using this method, we have examined mitotic stages in the first cleavage cycle of the sea urchin Strongylocentrotus purpuratus. We provide evidence that the interphase microtubules that appear after first division are not derived from the mitotic asters but are new structures growing from organizing centers within the degenerating mitotic asters. During the transition from mitosis to interphase, there is a temporary overlap of old and new microtubules to form a very large composite aster at telophase before the old structure finally disappears.