Aggressive phenotypic and genotypic features in pediatric and NF2-associated meningiomas: a clinicopathologic study of 53 cases.

Pediatric and NF2-associated meningiomas are uncommon and poorly characterized in comparison to sporadic adult cases. In order to elucidate their molecular features, we analyzed MIB-1, progesterone receptor (PR), NF2, merlin, DAL-1, DAL-1 protein, and chromosomal arms 1p and 14q in 53 meningiomas from 40 pediatric/NF2 patients using immunohistochemistry and dual-color fluorescence in situ hybridization (FISH). Fourteen pediatric (42%) patients, including 5 previously undiagnosed patients, had NF2. The remaining 19 (58%) did not qualify. All 7 of the adult patients had NF2. Meningioma grading revealed 21 benign (40%), 26 atypical (49%), and 6 anaplastic (11%) examples. Other aggressive findings included high mitotic index (32%), high MIB-1 LI (37%), aggressive variant histology (e.g. papillary, clear cell) (25%), brain invasion (17%), recurrence (39%), and patient death (17%). FISH analysis demonstrated deletions of NF2 in 82%, DAL-1 in 82%, 1p in 60%, and 14q in 66%. NF2-associated meningiomas did not differ from sporadic pediatric tumors except for a higher frequency of merlin loss in the former (p = 0.020) and a higher frequency of brain invasion in the latter (p = 0.007). Thus, although pediatric and NF2-associated meningiomas share the common molecular alterations of their adult, sporadic counterparts, a higher fraction are genotypically and phenotypically aggressive. Given the high frequency of undiagnosed NF2 in the pediatric cases, a careful search for other features of this disease is warranted in any child presenting with a meningioma.

Allelic loss on chromosome band 18p11.3 occurs early and reveals heterogeneity in breast cancer progression.

We examined the stage specificity and heterogeneity of 18p11 alterations in a series of tumors representing 96 microdissected samples. Significant loss of heterozygosity (LOH) (63%) was found, with 56% occurring early in ductal carcinoma in situ. Although most cases indicated LOH was clonally inherited, heterogeneity for 18p LOH occurred in 27% of tumors. When compared with other LOH data, 18p LOH was found in conjunction with allelic deletion on 3p, 9p, 17p and 17q, while 13q, 16q, and 11p were less frequently associated. These analyses suggest chromosome 18p11 alteration is a common and early event in breast disease.

Merlin, DAL-1, and progesterone receptor expression in clinicopathologic subsets of meningioma: a correlative immunohistochemical study of 175 cases.

The molecular pathogenesis of meningiomas is poorly characterized. Loss of NF2 (merlin) expression has been reported in 30%-80% of all sporadic meningiomas. Recently, we found that loss of expression for a second Protein 4.1-family tumor suppressor. DAL-1, is also common. A biologically important role for progesterone receptor (PR) has also been proposed based on its reported inverse relationship with tumor grade. In order to better define the pathogenetic roles of these proteins, we studied the merlin, DAL-1, and PR immunoprofiles in 175 fully characterized meningiomas, including nonrecurring versus recurring benign, proliferative versus brain invasive atypical and anaplastic subtypes. Loss of expression for either Protein 4.1-family tumor suppressor (merlin or DAL-1) was almost universal (92%), with combined losses being common (58%). Individually, absence of merlin or DAL-1 protein was detected in 74% and 76% respectively, with no significant differences among the 5 subsets. PR immunoreactivity was commonly associated with retained DAL-1 expression (p < 0.001) and with tumor grade, with 51% of benign, 21% of atypical, and 11% of anaplastic tumors staining positive (p < 0.001). We conclude that PR immunohistochemistry may have diagnostic utility in meningothelial neoplasms. Protein 4.1-family tumor suppressor losses are likely important early events in meningioma pathogenesis, whereas PR expression is associated with benignity.

Loss of DAL-1, a protein 4.1-related tumor suppressor, is an important early event in the pathogenesis of meningiomas.

Meningiomas are common nervous system tumors, whose molecular pathogenesis is poorly understood. To date, the most frequent genetic alteration detected in these tumors is loss of heterozygosity (LOH) on chromosome 22q. This finding led to the identification of the neurofibromatosis 2 (NF2) tumor suppressor gene on 22q12, which is inactivated in 40% of sporadic meningiomas. The NF2 gene product, merlin (or schwannomin), is a member of the protein 4.1 family of membrane-associated proteins, which also includes ezrin, radixin and moesin. Recently, we identified another protein 4.1 gene, DAL-1 (differentially expressed in adenocarcinoma of the lung) located on chromosome 18p11.3, which is lost in approximately 60% of non-small cell lung carcinomas, and exhibits growth-suppressing properties in lung cancer cell lines. Given the homology between DAL-1 and NF2 and the identification of significant LOH in the region of DAL-1 in lung, breast and brain tumors, we investigated the possibility that loss of expression of DAL-1 was important for meningioma development. In this report, we demonstrate DAL-1 loss in 60% of sporadic meningiomas using LOH, RT-PCR, western blot and immunohistochemistry analyses. Analogous to merlin, we show that DAL-1 loss is an early event in meningioma tumorigenesis, suggesting that these two protein 4.1 family members are critical growth regulators in the pathogenesis of meningiomas. Furthermore, our work supports the emerging notion that membrane-associated alterations are important in the early stages of neoplastic transformation and the study of such alterations may elucidate the mechanism of tumorigenesis shared by other tumor types.

Use of horizontal ultrathin gel electrophoresis to analyze allelic deletions in chromosome band 11p15.5 in gliomas.

The prognosis for most patients with astrocytic glioma is poor, and postoperative life expectancy has not significantly improved in the last decade despite advances in diagnosis, surgery, and adjuvant therapy. Progress has been made, however, in cataloging the genetic alterations that occur in these tumors. Studying the allelic changes using loss of heterozygosity analysis has proven to be a reliable and rapid way of identifying genetic alterations fundamental to the pathology of this disease. In this study, we used a series of fluorescent-labeled markers and a new horizontal ultrathin gel electrophoresis technology (HUGE; GeneSys Technologies, Inc.) to analyze loss of heterozygosity on 11p15 in a series of 24 matched normal/tumor glioma pairs that included both anaplastic astrocytomas and glioblastomas. These studies significantly narrowed the region harboring a putative 11p15.5 glioma-associated gene and further suggest that a second gene involved in the pathogenesis of brain tumors may exist, centromeric, in bands 11p15.5-p15.4.

A novel member of the NF2/ERM/4.1 superfamily with growth suppressing properties in lung cancer.

A novel putative tumor suppressor gene and member of the NF2/ERM/ 4.1 superfamily was isolated using Differential Display PCR (DDPCR) on primary lung tumors. When reintroduced into nonexpressing non-small cell lung carcinoma cell lines, this gene, named DAL-1 (for Differentially expressed in Adenocarcinoma of the Lung), was shown to suppress growth. In addition, significantly reduced expression (>50%) of DAL-1 was measured in 39 primary non-small cell lung carcinoma tumors as compared with patient-matched normal lung tissue. Immunocytochemical staining with a polyclonal anti-DAL-1 antibody localized the protein to the plasma membrane, particularly at cell-cell contact points, a pattern reminiscent of other members of the protein 4.1 superfamily including ezrin and NF2. The data suggest DAL-1 is a novel membrane-associated protein with potential to play an important role in the origin and progression of lung cancer.

Switch from monoallelic to biallelic human IGF2 promoter methylation during aging and carcinogenesis.

We have previously linked aging, carcinogenesis, and de novo methylation within the promoter of the estrogen receptor (ER) gene in human colon. We now examine the dynamics of this process for the imprinted gene for insulin-like growth factor II (IGF2). In young individuals, the P2-4 promoters of IGF2 are methylated exclusively on the silenced maternal allele. During aging, this promoter methylation becomes more extensive and involves the originally unmethylated allele. Most adult human tumors, including colon, breast, lung, and leukemias, exhibit increased methylation at the P2-4 IGF2 promoters, suggesting further spreading during the neoplastic process. In tumors, this methylation is associated with diminished or absent IGF2 expression from the methylated P3 promoter but maintained expression from P1, an upstream promoter that is not contained within the IGF2 CpG island. Our results demonstrate a remarkable evolution of methylation patterns in the imprinted promoter of the IGF2 gene during aging and carcinogenesis, and provide further evidence for a potential link between aberrant methylation and diseases of aging.

High-density marker analysis of 11p15.5 in non-small cell lung carcinomas reveals allelic deletion of one shared and one distinct region when compared to breast carcinomas.

The presence of a non-small cell lung carcinoma (NSCLC)-related gene or genes on chromosome band 11p15.5 is of particular interest, given the specific loss of heterozygosity (LOH) measured in this region for lung as well as many other pediatric and adult neoplasms. We have undertaken high-density polymorphic marker analysis in 30 matched normal and NSCLC tumor samples using 11 PCR-based polymorphic markers positioned approximately every 2-3 cM throughout 11p15.5. These studies have confirmed the presence of two distinct regions of LOH for NSCLC in 11p15.5. In 9 of 13 (69%) tumors with measurable LOH, allelic deletion was restricted to 11p15.5, indicating that whole chromosome 11 loss is not a common event in NSCLC. Furthermore, one-half of these tumors showed independent deletion events for each LOH region, while the remaining tumor regions of LOH extended to include all four markers in between. Only two tumors showed LOH for the more telomeric region alone. Furthermore, the location of these two potentially distinct tumor suppressor genes has been significantly refined to a 3-cM area in the telomeric region between D11S1363 and tyrosine hydroxylase (TH) and a 10-cM area in the more proximal part of 11p15.5 between D11S988 and D11S926. Interestingly, the telomeric region of LOH in NSCLC overlaps with the reported location of one of two breast carcinoma-related tumor suppressor genes, but the proximal allelic deletion area for these two tumor types are clearly distinct. Our studies suggest that chromosome band 11p15.5 harbors a minimum of three separate loci, the loss of which is implicated in these two common adult neoplasms.