Frequency of MED12 mutations in phyllodes tumors: Inverse correlation with histologic grade

Phyllodes tumor (PT) is a rare breast biphasic tumor with a potential risk of recurrence and metastasis. In this study, the frequency of MED12 mutations in 176 PTs (49 benign, 49 borderline, and 78 malignant) was determined and the prognostic effect of these mutations in malignant type PT was evaluated. Analysis of MED12 mutations was performed by Sanger sequencing targeting the hotspot mutation region (exon 2) of MED12. Immunohistochemistry was also applied for evaluation of MED12 protein expression on tissue microarray blocks for 133 PTs including 50 benign, 50 borderline, and 33 malignant cases. A notable difference in the frequency of MED12 mutations was found according to histologic grade (71.4% of benign PTs, 51% of borderline PTs, 26.9% of malignant PTs; P < 0.001). MED12 protein expression was not correlated with MED12 mutation status. Patients with malignant PTs that harbored MED12 mutations demonstrated improved disease‐free survival (DFS) compared with those without MED12 mutation (P = 0.07). MED12 mutation was a common molecular alteration in PT and the frequency of MED12 mutation decreased with increasing histologic grade. In malignant PT, MED12 exon 2 mutations showed improved DFS but without significance. © 2016 Wiley Periodicals, Inc.     

MED12 exon 2 mutations in histopathological uterine leiomyoma variants

Uterine leiomyomas, or fibroids, are the most common human tumors. Based on histopathology, they can be divided into common leiomyomas and various relatively rare subtypes that mimic malignancy in one or more aspects. Recently, we showed that exon 2 of mediator complex subunit 12 (MED12) is mutated in up to 70% of common fibroids. To investigate the frequency of MED12 exon 2 mutations in histopathological uterine leiomyoma variants, we screened altogether 206 lesions, including 69 histopathologically common leiomyomas, 59 cellular (23 cellular and 36 highly cellular), 18 atypical and 26 mitotically active leiomyomas, as well as 34 uterine fibroid samples from 14 hereditary leiomyomatosis and renal cell cancer patients with a heterozygous germ line mutation in fumarate hydratase (FH). The uterine leiomyoma variants harbored MED12 exon 2 mutations significantly less frequently than common leiomyomas (P=2.93 × 10⁻⁸). In all, 6 mutations were detected among cellular fibroids (6/67; 8.96%), 3 among atypical fibroids (3/18; 16.67%) and 10 among mitotically active fibroids (10/26; 38.46%). Only mitotically active fibroids displayed a mutation frequency that was not statistically different from common leiomyomas (P=0.11). Three MED12 exon 2 mutations were detected among 34 tumors with a heterozygous germ line FH mutation (P=5.28 × 10⁻⁷). None of these tumors displayed biallelic inactivation of FH. Our results suggest that MED12 mutation positivity is a key characteristic of common leiomyomas. Cellular and atypical fibroids, in particular, may arise through different molecular mechanisms. The results also propose that MED12 and biallelic FH mutations may be mutually exclusive.     

Caveolin expression is common among benign and malignant smooth muscle and adipocyte neoplasms.

The caveolins belong to a newly described group of membrane-scaffolding proteins. Their presence in benign endothelial cells has been used to discriminate benign from malignant vascular neoplasms. The extent of caveolin expression in cutaneous mesenchymal neoplasms has not yet been evaluated, and thus the diagnostic utility of these antibodies is not yet known. In our study, we immunohistochemically examined a spectrum of tumors derived from smooth muscle and adipocytes for caveolin expression. We found that both benign and malignant smooth muscle tumors and tumors comprised of adipocytes expressed caveolins. The presence of this protein in a range of mesenchymal neoplasms is important to know about as this decreases the reported specificity of a positive finding. It is doubtful that caveolin down-regulation contributes to the pathogenesis of liposarcomas and leiomyosarcomas. This finding also may suggest a common origin between endothelial cells and other mesenchymal cells.     

Androgen metabolism in malignant and benign bone tumors

The comparison of activities of the key enzymes of androgen metabolism in morphological variants of bone sarcomas and benign tumors suggests that malignant tumors of different histogenesis not only metabolize the main androgen testosterone, but also inactivate 5α-dihydrotestosterone, the main regulatory androgen in bones. It is possible that androgen metabolism in bone tumors is aimed at the formation of other androgens, in particular, 3α-and 5β-diols, which can be involved in regulatory processes in bone tissue. Further studies will disclose clinical significance of androgen metabolism and individual androgens in human bone tumors. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 1, pp. 90–92, January, 2000     

CEA and NCA in benign and malignant breast tumors

The involvement of Nonspecific Crossreacting Antigen (NCA) in the immunohistological demonstration of Carcino Embryonic Antigen (CEA) in 56 benign and 92 malignant lesions of the breast was analyzed. For this purpose, the authors utilized both polyclonal antisera and monoclonal antibodies. Polyclonal anti-CEA sera were used after absorption with normal tissue antigens, in order to remove crossreactivity, and without such an absorption. Ninety-three percent of breast carcinomas, 85% of mastopathic lesions not associated with a carcinoma, and 66% of fibroadenomas showed positive reactions with commercial unabsorbed polyclonal anti-CEA serum, which contained antibodies to NCA, whereas incubation with monospecific anti-CEA antiserum resulted in 42% positivity in carcinomas and negativity in mastopathic lesions and fibroadenomas. Forty-eight percent of breast cancer, 84% of mastopathic lesions, and 50% of the fibroadenomas contained NCA in different quantities. The staining pattern of carcinomas and fibroadenomas obtained with unabsorbed anti-CEA antibody and anti-NCA did not run parallel in all cases. Monoclonal antibodies against CEA and NCA confirmed the results obtained with polyclonal antiserum. This study suggests a cancer specificity of CEA in breast lesions.     

Distribution of MED12 mutations in fibroadenomas and phyllodes tumors of the breast—implications for tumor biology and pathological diagnosis

Somatic mutations in exon 2 of MED12 have been described in benign and malignant smooth muscle cell tumors suggesting a functional role in these neoplasms. Recently fibroadenomas of the breast were also reported to harbor MED12 mutations. Hence, we explored MED12 mutations in fibroepithelial tumors of the breast, histological subtypes of fibroadenomas and phyllodes tumors, to validate and extend previous efforts. Using conventional Sanger sequencing, we profiled 39 cases of fibroepithelial breast tumors comprising classic histological subtypes of fibroadenomas as well as benign and malignant phyllodes tumors for mutations in exon 2 of MED12. MED12 mutations were detected in 60% of all tumor samples with the majority being missense mutations affecting codon 44. Additionally, we report novel in‐frame deletions that have not been described previously. Sixty‐two percent of the fibroadenomas harbored mutated MED12 with intracanalicular fibroadenomas being the most frequently mutated histological subtype (82%). Of note, 8/11 of benign phyllodes tumors had MED12 mutations while only 1/5 of malignant phyllodes tumors showed mutations in exon 2 of MED12. In conclusion, we confirm the frequent occurrence of MED12 mutations in fibroadenomas, provide evidence that most intracanalicular fibroadenomas closely resembling benign phyllodes as well as benign phyllodes tumors harbor MED12 mutations, and conclude that MED12 mutations in malignant phyllodes tumors appear to be relatively rare. © 2015 Wiley Periodicals, Inc.     

Mediator MED23 plays opposing roles in directing smooth muscle cell and adipocyte differentiation

The Mediator complex functions as a control center, orchestrating diverse signaling, gene activities, and biological processes. However, how Mediator subunits determine distinct cell fates remains to be fully elucidated. Here, we show that Mediator MED23 controls the cell fate preference that directs differentiation into smooth muscle cells (SMCs) or adipocytes. Med23 deficiency facilitates SMC differentiation but represses adipocyte differentiation from the multipotent mesenchymal stem cells. Gene profiling revealed that the presence or absence of Med23 oppositely regulates two sets of genes: the RhoA/MAL targeted cytoskeleton/SMC genes and the Ras/ELK1 targeted growth/adipogenic genes. Mechanistically, MED23 favors ELK1–SRF binding to SMC gene promoters for repression, whereas the lack of MED23 favors MAL–SRF binding to SMC gene promoters for activation. Remarkably, the effect of MED23 on SMC differentiation can be recapitulated in zebrafish embryogenesis. Collectively, our data demonstrate the dual, opposing roles for MED23 in regulating the cytoskeleton/SMC and growth/adipogenic gene programs, suggesting its “Ying-Yang” function in directing adipogenesis versus SMC differentiation.     

Ultrastructural observations on smooth muscle tumors

The ultrastructure of a series of primary and metastatic smooth muscle tumors is reviewed. Myofilaments and other smooth muscle features were present in all primary leiomyosarcomas of the soft tissues and uterus. They were also present but were less plentiful in most of the metastatic leiomyosarcomas. Electron microscopy is therefore a useful method to establish the diagnosis of a suspected leiomyosarcoma. Stromal tumors of the gastro-intestinal tract may require correlated immunocytochemical and ultrastructural studies for their identification: 9 of the 50 cases examined were positive with immunostaining for S-100 protein, and 16 tumors with epithelioid transformation did not show evidence of smooth muscle differentiation by electron microscopy.     

Blood group isoantigens in human benign and malignant vascular tumors

Summary Paraffin material of 31 benign and malignant vascular tumors was investigated with respect to their blood group isoantigen (BG) content by the mixed cell agglutination reaction (MCAR). In capillary hemangioma, BG was found in endothelial cells as well as in solid buds. Benign hemangioendothelioma found in children differed from that found in adults in that in juvenile cases only endothelial cells expressed BG whereas in adult cases BG isoantigenity was present in endothelial cells as well as in intercapillary cellular elements. In pericytomas only endothelial cells were BG positive, whereas the tumor cells lacked BG. Similar results were obtained with glomus tumors. All but one hemangiosarcoma were BG negative. In one case, however, which probably resembled a true malignant hemangioendothelioma (Stout and Lattes, 1967) the tumor cells contained BG in conspicuous amounts.     

The DNA methylome of benign and malignant parathyroid tumors

The role of DNA methylation of CpG islands in parathyroid tumorigenesis has not been analyzed in an unbiased, systematic fashion. DNA was isolated from normal and pathologic parathyroid tissues, bisulphite modified and analyzed using the Infinium HumanMethylation27 BeadChip. Distinct hierarchical clustering of genes with altered DNA methylation profiles in normal and pathologic parathyroid tissue was evident. Comparing normal parathyroid tissue with parathyroid adenomas, 367 genes were significantly altered, while 175 genes significantly differed when comparing parathyroid carcinomas and normal parathyroid tissues. A comparison between parathyroid adenomas and parathyroid carcinomas identified 263 genes with significantly distinct methylation levels. Results were confirmed for certain genes in a validation cohort of 40 parathyroid adenomas by methylation-specific PCR. Genes of known or putative importance in the development of parathyroid tumors showed significant and frequent hypermethylation. DNA hypermethylation of CDKN2B, CDKN2A, WT1, SFRP1, SFRP2, and SFRP4 was associated with reduced gene expression in both benign and malignant parathyroid tumors. Treatment with 5-aza-2'-deoxycytidine of primary cell cultures restores expression of hypermethylated genes in benign and malignant parathyroid tumors. In conclusion, the unbiased, genome-wide study of the parathyroid tumor DNA methylome identified a number of genes with altered DNA methylation patterns of putative importance to benign and malignant parathyroid tumorigenesis.     

Cell cultures in uterine leiomyomas: Rapid disappearance of cells carrying MED12 mutations

Uterine leiomyomas (UL) are the most frequent symptomatic human tumors. Nevertheless, their molecular pathogenesis is not yet fully understood. To learn more about the biology of these common neoplasms and their response to treatment, cell cultures derived from UL are a frequently used model system, but until recently appropriate genetic markers confirming their origin from the tumor cell population were lacking for most UL, i.e., those not displaying karyotypic abnormalities. The identification of MED12 mutations in the majority of UL makes it possible to trace the tumor cell population during in vitro passaging in the absence of cytogenetic abnormalities. The present study is addressing the in vitro survival of cells carrying MED12 mutations and its association with karyotypic alterations. The results challenge numerous in vitro studies into the biology and behavior of leiomyomas. Cells of one genetic subtype of UL, i.e., those with rearrangements of the high mobility AT‐hook 2 protein gene (HMGA2), seem to be able to proliferate in vitro for many passages whereas tumor cells from the much more frequent MED12‐mutated lesions barely survive even the first passages. Apparently, for the most frequent type of human UL no good in vitro model seems to exist because cells do not survive culturing. On the other hand, this inability may point to an Achilles' heel of this type of UL. © 2014 Wiley Periodicals, Inc.     

Epidermal growth factor receptors in malignant and benign tumors in children

The radioligand technique was used to study the amount of epidermal growth factor receptors (EGFR) in malignant and benign tumors in 32 children aged 8 months to 17 years. The membranous fraction of 11 of the 32 tumors studied showed EGFR equal to 10.1 to 1327 fmol/mg (163.0 +/- 117.5 fmol/mg, median 38.0 fmol/mg). The greatest amount of EGFR was found in breast fibroadenomas. There was no clear relationship of the frequency and level of EGFR expression to a nosological tumor entity in children. A possible role of the EGFR system in tumors in children is discussed.     

h-Caldesmon as a specific marker for smooth muscle tumors. Comparison with other smooth muscle markers in bone tumors

Caldesmon is a protein widely distributed in smooth and non-smooth muscle cells and is thought to regulate cellular contraction. Its isoform, high-molecular-weight caldesmon (h-CD), was demonstrated to be specific for smooth muscle cells and smooth muscle tumors of the soft tissue and to never be expressed in myofibroblasts. We performed an immunohistochemical study to examine h-CD expression in the following bone tumors: conventional and non-conventional osteosarcoma, 13; malignant fibrous histiocytoma of bone, 5; giant cell tumors of bone, 5; chondroblastoma, 3; metastatic leiomyosarcoma, 2; and rhabdomyosarcoma, 1. Frequent immunoreactivity for muscle actin (alpha-smooth muscle actin or muscle-specific actin) was seen in 11 of 13 osteosarcomas and all other tumors, whereas h-CD was expressed intensely only in 2 leiomyosarcomas. h-CD is considered a specific and useful marker to distinguish smooth muscle tumor from bone tumors with myoid differentiation.