Hyperproliferation, induction of c-Myc and 14-3-3sigma, but no cell fragility in keratin-10-null mice.
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In the past, keratins have been established as structural proteins. Indeed, mutations in keratin 10 (K10) and other epidermal keratins lead to severe skin fragility syndromes. Here, we present adult K10-/- mice, which reveal a novel connection between the regulation of cell proliferation and K10. Unlike most keratin mutant mice, the epidermis of adult K10-/- mice showed no cytolysis but displayed hyperproliferation of basal keratinocytes and an increased cell size. BrdU labelling revealed a shortened transition time for keratinocytes migrating outwards and DAPI staining of epidermal sheets uncovered an impaired organization of epidermal proliferation units. These remarkable changes were accompanied by the induction of c-Myc, cyclin D1, 14-3-3sigma and of wound healing keratins K6 and K16. The phosphorylation of Rb remained unaltered. In line with the downregulation of K10 in squamous cell carcinomas and its absence in proliferating cells in vivo, our data suggest that the tissue-restricted expression of some members of the keratin gene family not only serves structural functions. Our results imply that the altered composition of the suprabasal cytoskeleton is able to alter the proliferation state of basal cells through the induction of c-Myc. A previous model based on transfection of K10 in immortalized human keratinocytes suggested a direct involvement of K10 in cell cycle control. While those experiments were performed in human cultured keratinocytes, our data establish, that in vivo, K10 acts by an indirect control mechanism in trans. (+info)
Mechanisms of SEPA 0009-induced tumorigenesis in v-rasHa transgenic Tg.AC mice.
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Genetically engineered mouse models with altered oncogene or tumor suppressor gene activity have been utilized recently for carcinogen identification. The v-rasHa transgenic Tg.AC mouse, with its enhanced susceptibility to skin tumorigenesis, is thought to be well suited for examining the carcinogenicity of topically applied agents. Tg.AC mice were used to examine the carcinogenicity of SEPA 0009, a rationally designed organic molecule designed to enhance drug penetration through the skin. Fifty mg SEPA 0009/kg body weight, 1500 mg SEPA 0009/kg body weight, or the vehicle alone was applied daily to the skin of Tg.AC mice. Nontransgenic FVB/N mice were also treated with the vehicle alone or 1500 mg SEPA 0009. Daily application of a high-dose of SEPA 0009 caused severe and chronic irritation by 1 week that was maintained throughout the experiment. The irritation was accompanied by increased proliferation, increased apoptosis, and expression of the wound-associated keratin 6. High-dose SEPA 0009 induced squamous papillomas in Tg.AC, but not in nontransgenic mice, by 6 weeks. In mice treated with the high dose SEPA 0009, transgene expression was detected in papillomas at week 9, well after the onset of skin irritation and hyperplasia. In contrast, low-dose SEPA 0009 was not irritating to the skin and did not induce papillomas. Thus, SEPA 0009-induced tumorigenesis was associated with chronic and severe irritation. We propose that SEPA 0009-induced tumorigenesis in Tg.AC mice proceeds through an indirect mechanism that is secondary to cutaneous irritation. (+info)
MDM2 protein expression is a negative prognostic marker in breast carcinoma.
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The protein encoded by the MDM2 oncogene inhibits the function of p53, leading to increased cell growth, avoidance of apoptosis, tolerance of genetic instability, and resistance to chemotherapy. The present study was performed to evaluate the relationship between MDM2 protein expression and survival in breast carcinoma. Two series of cases were used in this study: the first to identify the cutoff to be used in the interpretation of MDM2 immunostaining and perform preliminary survival analysis, and a second, independent series, to validate the findings from the first series and to perform multivariate analysis. For both series, archival sections of tissue microarrays were stained with anti-MDM2 antibody (NeoMarkers, Fremont, CA, USA) and MDM2 staining intensity was scored semiquantitatively. In the first series, 49 of 362 (14%) interpretable cases were positive for MDM2 expression, with 35 (10%) showing weak positivity and 14 (4%) strong positivity. Patients with MDM2-positive tumours had a significantly worse disease-specific survival than patients with MDM2-negative tumours (P=0.0022, 10-year DSS 61% (95% CI: 45-73) vs 73% (95% CI: 67-77)). No significant difference in survival was observed between patients with strongly and weakly MDM2-positive tumours (P=0.3). Accordingly, in the independent validation series weak and strong MDM2 positivity were combined and considered to be MDM2 positive. MDM2 expression was seen in 230/1747 (13%) interpretable cases in this series, with a significant difference (P<0.0001) in DSS between MDM2-negative and MDM2-positive cases (10 year DSS 58% (95% CI: 51-64) vs 73% (95% CI: 70-75)). MDM2 was an independent prognostic marker (HR=1.35, P=0.02) in a Cox regression model including MDM2 expression, tumour grade, nodal status, ER status and tumour size. Immunohistochemical studies of MDM2 in more than 2000 breast carcinomas show that MDM2 is an independent negative prognostic marker. (+info)
Phenotypic evaluation of the basal-like subtype of invasive breast carcinoma.
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Microarray profiling of invasive breast carcinomas has identified five distinct subtypes of tumors (luminal A, luminal B, normal breast-like, HER2 overexpressing, and basal-like) that are associated with different clinical outcomes. The basal-like subtype is associated with poor clinical outcomes and is the subtype observed in BRCA1-related breast cancers. The aim of this study was to characterize the histologic and immunophenotypic properties of breast basal-like carcinomas that were first positively identified using DNA microarray analysis. Detailed histologic review was performed on 56 tumors with known microarray profiles (23 basal-like, 23 luminal, and 12 HER2+). Immunohistochemistry for estrogen receptor (ER), HER2, EGFR, smooth muscle actin (SMA), p63, CD10, cytokeratin 5/6, cytokeratin 8/18, and vimentin was performed on 18 basal-like, 16 luminal, and 12 HER2+ tumors. The basal-like tumors were grade 3 ductal/NOS (21/23) or metaplastic (2/23) carcinomas that frequently showed geographic necrosis (17/23), a pushing border of invasion (14/23), and a stromal lymphocytic response (13/23). Most basal-like tumors showed immunoreactivity for vimentin (17/18), luminal cytokeratin 8/18 (15/18), EGFR (13/18), and cytokeratin 5/6 (11/18), while positivity for the myoepithelial markers SMA (4/18), p63 (4/18) and CD10 (2/18) was infrequent. All basal-like tumors tested were ER- and HER2-. Morphologic features significantly associated with the basal-like subtype included markedly elevated mitotic count (P<0.0001), geographic tumor necrosis (P=0.0003), pushing margin of invasion (P=0.0001), and stromal lymphocytic response (P=0.01). The most consistent immunophenotype seen in the basal-like tumors was negativity for ER and HER2, and positivity for vimentin, EGFR, cytokeratin 8/18, and cytokeratin 5/6. The infrequent expression of myoepithelial markers in basal-like carcinomas does not support a direct myoepithelial cell derivation of these tumors. These findings should further assist in the identification of basal-like carcinomas in clinical specimens, facilitating treatment and epidemiologic studies of this tumor subtype. (+info)
The diagnostic utility of immunohistochemistry in distinguishing between epithelioid mesotheliomas and squamous carcinomas of the lung: a comparative study.
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As both mesotheliomas and squamous carcinomas can present a wide variety of morphological patterns, they can on occasion be confused. Recently, some groups of investigators have called attention to the difficulties that sometimes exist in distinguishing between these malignancies and the need to define a panel of markers that can assist in reaching the correct diagnosis. The aim of the present study is to compare the value of the various immunohistochemical markers currently available for the diagnosis of mesothelioma and squamous carcinoma of the lung. A total of 30 epithelioid pleural mesotheliomas exhibiting a solid or predominantly solid pattern, and 30 nonkeratinizing squamous carcinomas of the lung were investigated for the expression of the following markers: podoplanin, calretinin, mesothelin, WT1, keratin 5/6, keratin 7, p63, carcinoembryonic antigen (CEA), MOC-31, Ber-EP4, B72.3, BG-8 (Lewis(y)), leu-M1 (CD15), and thyroid transcription factor-1 (TTF-1). All 30 (100%) of the mesotheliomas reacted for calretinin, mesothelin and keratin 7, 93% each for podoplanin, WT1 and keratin 5/6, 13% for Ber-EP4, 7% each for p63, MOC-31 and BG-8, and 0% for B72.3, CEA, leu-M1 and TTF-1. All 30 (100%) of the squamous carcinomas were positive for p63 and keratin 5/6, 97% for MOC-31, 87% for Ber-EP4, 80% for BG-8, 77% for CEA, 57% for keratin 7, 40% for calretinin and B72.3, 30% for leu-M1, 27% for mesothelin, 15% for podoplanin, and 0% for WT 1 and TTF-1. After analyzing the results, it is concluded that from a practical point-of-view, a combination of two positive mesothelioma markers (WT1 and calretinin or mesothelin) with two negative mesothelioma markers (p63 and MOC-31) would allow the differential diagnosis to be established between epithelioid mesotheliomas and squamous carcinomas of the lung in nearly all instances. (+info)
Distribution and significance of nerve growth factor receptor (NGFR/p75NTR) in normal, benign and malignant breast tissue.
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Nerve growth factor receptor (NGFR) is a transmembrane glycoprotein without intrinsic tyrosine kinase activity, whose expression is not restricted to neural cells. NGFR is reported to act as a tumour suppressor, negatively regulating cell growth and proliferation. NGFR expression was immunohistochemically analysed in normal breast tissue and in 140 benign, biphasic and preinvasive breast lesions, in 22 tumours with myoepithelial differentiation and in two cohorts of breast cancer patients: a series of 245 invasive breast carcinomas studied with tissue microarrays and 37 high-grade invasive ductal carcinomas with basal-like immunophenotype. NGFR consistently displayed membrane reactivity in myoepithelial cells arranged as a continuous layer around normal ducts and lobular units, intralobular fibroblasts, vascular adventitia and nerve bundles. Myoepithelial cells of benign proliferations and pre-invasive lesions were consistently positive for NGFR. Scattered NGFR-positive cells were observed in solid areas of six out of nine cases of hyperplasia of usual type, whereas in flat atypia, lobular carcinoma in situ and virtually all cases of ductal carcinoma in situ (97.5%), NGFR was restricted to the myoepithelial layer. Positivity for NGFR was observed in 11 out of 245 (4.5%) breast carcinomas, nine out of 20 (45%) metaplastic breast carcinomas and 14 out of 37 (38%) basal-like breast carcinomas. NGFR expression in invasive tumours significantly correlated with that of cytokeratins 5/6 (P<0.05), 14 (P<0.0001) and 17 (P<0.0005) and EGFR (P<0.0001) and displayed an inverse correlation with oestrogen and progesterone receptors (both, P<0.0001). NGFR showed a statistically significant association with longer disease-free (P<0.05) and overall survival (P<0.01) in the cohort of patients with basal-like carcinomas. This study demonstrates the usefulness of NGFR as a new adjunct marker to identify myoepithelial cells in preinvasive lesions and myoepithelial differentiation in breast carcinomas. Furthermore, provisional data in a small number of basal-like breast carcinomas suggest that NGFR may identify a subgroup of basal-like breast carcinomas with good prognosis. (+info)
Prognostic significance of basal-like phenotype and fascin expression in node-negative invasive breast carcinomas.
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PURPOSE: Basal-like phenotype tumors are frequently found among BRCA1 germ-line mutated breast carcinomas. They are biologically aggressive and have a tendency towards visceral metastasis when untreated. Nevertheless, it has been suggested that they respond to chemotherapy better than other types of tumors. Fascin expression has been associated with lung metastasis in breast cancer. The aim of this study was to determine whether basal-like phenotype and fascin were related in both sporadic and familial tumors and with prognosis in node-negative sporadic breast cancers. EXPERIMENTAL DESIGN: 230 nonfamilial and 28 hereditary node-negative invasive breast carcinomas were immunohistochemically analyzed using tissue microarrays. Tumors that were estrogen receptor/HER2 negative and cytokeratin 5/6 and/or epidermal growth factor receptor positive were considered to have a basal-like phenotype. RESULTS: A basal-like phenotype was found in 11.9% of sporadic cancers. Among patients not receiving adjuvant chemotherapy, a basal-like phenotype was associated with poor prognosis (P = 0.001, log-rank test) whereas no such association was found in patients receiving it. Tumors with a basal-like phenotype showed local recurrence (17.4%) or visceral metastasis (13%) but not bone metastasis (P = 0.001). Fascin expression was observed in 25.1% of sporadic invasive breast carcinomas and was associated with the basal-like phenotype, but not with prognosis or recurrence pattern. Fascin was expressed in 83.3% and 16.7% BRCA1- and BRCA2-associated carcinomas, respectively (P = 0.048). CONCLUSIONS: Basal-like tumors had a tendency towards visceral metastasis and their prognosis was dependent on the use of postoperative chemotherapy. Although fascin expression was associated with the basal-like phenotype, it was not associated with their metastatic behavior. Fascin expression is frequent in BRCA1-associated tumors. (+info)
Keratin 6 is not essential for mammary gland development.
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INTRODUCTION: Keratin 6 (K6) has previously been identified as a marker of early mammary gland development and has also been proposed to be a marker of mammary gland progenitor cells. However, the function of K6 in the mammary gland was not known, so we examined the expression pattern of the protein during both embryonic and postnatal mammary development, as well as the mammary gland phenotype of mice that were null for both K6a and K6b isoforms. METHOD: Immunostaining was performed to determine the expression pattern of K6a throughout mammary gland development, from the embryonic mammary bud to lactation. Double immunofluorescence was used to co-localize K6 with known markers of mammary gland development. Wild-type and K6ab-null mammary tissues were transplanted into the cleared fat pads of nude mice and the outgrowths were analyzed for morphology by whole-mount staining and for markers of mammary epithelium by immunostaining. Finally, progesterone receptor (PR) and bromodeoxyuridine co-localization was quantified by double immunofluorescence in wild-type and K6ab-null mammary outgrowths. RESULTS: Here we report that K6 is expressed earlier than described previously, by embryonic day 16.5. K6a is the predominant isoform expressed in the mammary gland, localized in the body cells and luminal epithelial cells but not in the cap cells or myoepithelial cells. Co-localization studies showed that most K6a-positive cells express steroid receptors but do not proliferate. When both the K6a and K6b genes are deleted, mammary gland development appears normal, with similar expression of most molecular markers examined in both the pubertal gland and the mature gland. Loss of K6a and K6b, however, leads to an increase in the number of steroid-receptor-positive cells, and increased co-localization of steroid receptor expression and proliferation was observed. CONCLUSION: Although K6a was not essential for mammary gland development, loss of both K6a and K6b resulted in an increase in PR-positive mammary epithelial cells and decreased proliferation after exposure to steroid hormones. There was also increased co-localization of PR and bromodeoxyuridine, suggesting alterations in patterning events important for normal lobuloalveolar development. (+info)