Cdk4-Cyclin D1 and Cdk2-Cyclin E/A Phosphorylate Different Sites in the RB Protein

Abstract p27 cyclin-dependent kinase inhibitor downregulation is essential for transition to the S phase of the cell cycle. Thus, proliferating cells in reactive lymphoid tissue show no detectable p27 expression. Nevertheless, anomalous high p27 expression has been shown to be present in a group of aggressive B-cell lymphomas with high proliferation index and adverse clinical outcome. This suggests that abnormally accumulated p27 protein has been rendered functionally inactive. We analyzed the causes of this anomalous presence of p27 in a group of aggressive B-cell lymphomas, including 54 cases of diffuse large B-cell lymphomas and 20 Burkitt’s lymphomas. We simultaneously studied them for p27, cyclin D3, cyclin D2, cyclin D1, and cyclin E expression, because it has been stated that high levels of expression of cyclin D1 or E lead to increased p27 levels in some cell types. A statistically significant association between p27 and cyclin D3 expression was found for the group as a whole. Additionally, when dividing the cases according to the level of expression of cyclin D3 by reactive germinal centers, it was observed that cases with stronger cyclin D3 expression also show higher p27 expression. The relationship between both proteins was also shown at a subcellular level by laser confocal studies, showing that in cases with high expression of both proteins there was a marked colocalization. Additional evidence in favor of p27 sequestration by cyclin D3 was provided by coimmunoprecipitation studies in a Burkitt’s cell line (Raji) showing the existence of cyclin D3/p27 complexes and the absence of CDK2/p27 complexes. These results could support the hypothesis that there are cyclin D3/p27 complexes in a subset of aggressive B-cell lymphomas in which p27 lacks the inhibitory activity found when it is bound to cyclin E/CDK2 complexes. This interaction between both proteins could lead to an abnormal nuclear accumulation, detectable by immunohistochemical techniques.

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C-myc expression in adrenocortical tumours

Journal of Clinical Pathology ◽

10.1136/jclinpath-2017-204503 ◽

2017 ◽

Vol 71 (2) ◽

pp. 129-134 ◽

Cited By ~ 1

Author(s):

Mirkka Pennanen ◽

Jaana Hagström ◽

Ilkka Heiskanen ◽

Timo Sane ◽

Harri Mustonen ◽

...

Keyword(s):

Cyclin D1 ◽

Imaging Techniques ◽

Cyclin E ◽

Histopathological Diagnosis ◽

Beta Catenin ◽

The Novel ◽

Clinical Issue ◽

Adrenocortical Tumours ◽

Resolution Imaging ◽

Related Proteins

AimsWidespread use of high-resolution imaging techniques and thus increased prevalence of adrenal lesions has made diagnostics of adrenocortical tumours an increasingly important clinical issue. In non-metastatic tumours, diagnosis is based on histology. New or enhanced information for clinicopathological diagnosis, revealing the malignant potential of the tumour, could emerge by means of biomarkers. The connection of proto-oncogene c-myc to adrenocortical neoplasias is poorly known, although the Wnt/beta-catenin pathway, one of the signalling pathways leading to induction of c-myc expression, has been connected to development of adrenocortical neoplasias. We studied c-myc expression in adrenocortical tumours and investigated molecules associated with the signalling pathway of c-myc, including cell cycle-related proteins p27, cyclin E and cyclin D1.MethodsWe studied 195 consecutive adult patients with 197 primary adrenocortical tumours. Histopathological diagnosis was determined by Weiss score and the novel Helsinki score. C-myc, cyclin D1, cyclin E and p27 expressions were determined by immunohistochemistry.ResultsBenign adenomas showed prominent nuclear c-myc expression comparable to that of normal adrenocortical cells, whereas carcinomas showed increased cytoplasmic expression. Strong cytoplasmic and weak nuclear c-myc expressions associated with malignancy and adverse outcome. C-myc staining did not correlate with cyclin E. Cyclin D1 correlated with cytoplasmic c-myc expression and to a lesser extent with nuclear c-myc. P27 correlated with cytoplasmic c-myc, but not with nuclear c-myc. P27 correlated with cyclin E.ConclusionsStrong cytoplasmic c-myc expression and weak nuclear expression in adrenocortical tumours associated with malignancy and shorter survival.

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Anomalous High p27/KIP1 Expression in a Subset of Aggressive B-Cell Lymphomas Is Associated With Cyclin D3 Overexpression. p27/KIP1—Cyclin D3 Colocalization in Tumor Cells

Blood ◽

10.1182/blood.v94.2.765.414a29_765_772 ◽

1999 ◽

Vol 94 (2) ◽

pp. 765-772 ◽

Cited By ~ 2

Author(s):

Margarita Sánchez-Beato ◽

Francisca I. Camacho ◽

Juan C. Martı́nez-Montero ◽

Ana I. Sáez ◽

Raquel Villuendas ◽

...

Keyword(s):

B Cell ◽

Cyclin D1 ◽

Kinase Inhibitor ◽

Cyclin E ◽

Cyclin D3 ◽

Nuclear Accumulation ◽

Proliferation Index ◽

B Cell Lymphomas ◽

Proliferating Cells ◽

P27 Kip1

p27 cyclin-dependent kinase inhibitor downregulation is essential for transition to the S phase of the cell cycle. Thus, proliferating cells in reactive lymphoid tissue show no detectable p27 expression. Nevertheless, anomalous high p27 expression has been shown to be present in a group of aggressive B-cell lymphomas with high proliferation index and adverse clinical outcome. This suggests that abnormally accumulated p27 protein has been rendered functionally inactive. We analyzed the causes of this anomalous presence of p27 in a group of aggressive B-cell lymphomas, including 54 cases of diffuse large B-cell lymphomas and 20 Burkitt’s lymphomas. We simultaneously studied them for p27, cyclin D3, cyclin D2, cyclin D1, and cyclin E expression, because it has been stated that high levels of expression of cyclin D1 or E lead to increased p27 levels in some cell types. A statistically significant association between p27 and cyclin D3 expression was found for the group as a whole. Additionally, when dividing the cases according to the level of expression of cyclin D3 by reactive germinal centers, it was observed that cases with stronger cyclin D3 expression also show higher p27 expression. The relationship between both proteins was also shown at a subcellular level by laser confocal studies, showing that in cases with high expression of both proteins there was a marked colocalization. Additional evidence in favor of p27 sequestration by cyclin D3 was provided by coimmunoprecipitation studies in a Burkitt’s cell line (Raji) showing the existence of cyclin D3/p27 complexes and the absence of CDK2/p27 complexes. These results could support the hypothesis that there are cyclin D3/p27 complexes in a subset of aggressive B-cell lymphomas in which p27 lacks the inhibitory activity found when it is bound to cyclin E/CDK2 complexes. This interaction between both proteins could lead to an abnormal nuclear accumulation, detectable by immunohistochemical techniques.

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