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      Cyclin-Dependent Kinase 4 (CDK4) Expression in Pancreatic Endocrine Tumors

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          Abstract

          Background/Aims: Pancreatic endocrine tumors (PETs) occur sporadically, in association with the multiple endocrine neoplasia type 1 (MEN1) and the von Hippel-Lindau syndromes. CDK4 is central to the cell cycle control in pancreatic β cells, and we have assessed whether CDK4 expression is deregulated in 18 human sporadic or familial PETs. Methods: Real-time quantitative PCR, immunohistochemistry, DNA sequencing, and Western blot analysis were used. Results: CDK4 mRNA was expressed in all PETs within the range of the arbitrary control. CDK4 protein was absent in normal pancreatic islets but distinctly expressed in all PETs as determined by immunohistochemistry. CDK4 expression was confirmed by Western blot analysis. No significant differences of CDK4 expression were observed between the groups of benign and malignant PETs or between tumors with or without MEN1 gene mutations. CDK4 expression was not due to gene amplification, and no mutations were identified in coding exons and RNA splice sites. c-Myc is known to be overexpressed in PETs and directly augments CDK4 expression in other cell types. Analysis of consecutive tissue sections for CDK4 and c-Myc showed overlapping homo- or heterogeneous immunostaining in all 18 PETs. Conclusion: We conclude that CDK4 and c-Myc is generally expressed in benign and malignant PETs, and regardless of MEN1 mutational status. Targeting of CDK4 may present an alternative to traditional chemotherapy of PETs in the future.

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          Most cited references 27

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          Loss of Cdk4 expression causes insulin-deficient diabetes and Cdk4 activation results in beta-islet cell hyperplasia.

          To ascertain the role of cyclin-dependent kinase 4 (Cdk4) in vivo, we have targeted the mouse Cdk4 locus by homologous recombination to generate two strains of mice, one that lacks Cdk4 expression and one that expresses a Cdk4 molecule with an activating mutation. Embryonic fibroblasts proliferate normally in the absence of Cdk4 but have a delayed S phase on re-entry into the cell cycle. Moreover, mice devoid of Cdk4 are viable, but small in size and infertile. These mice also develop insulin-deficient diabetes due to a reduction in beta-islet pancreatic cells. In contrast, mice expressing a mutant Cdk4 that cannot bind the cell-cycle inhibitor P16INK4a display pancreatic hyperplasia due to abnormal proliferation of beta-islet cells. These results establish Cdk4 as an essential regulator of specific cell types.
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            Positional Cloning of the Gene for Multiple Endocrine Neoplasia-Type 1

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              Endocrine tumours of the pancreas.

              Endocrine pancreatic tumours (EPTs) are uncommon tumours occurring in approximately 1 in 100,000 of the population, representing 1-2% of all pancreatic neoplasms. Some of the tumours may be part of multiple endocrine neoplasia type one (MEN-1) syndrome or von Hippel-Lindau (vHL) disease. EPTs are classified as functioning or non-functioning tumours on the basis of their clinical manifestation. The biochemical diagnosis of EPT is based on hormones and amines released. Besides specific markers such as insulin, there are also general tumour markers such as chromogranin A, which is the most valuable marker and has been reported to be increased in plasma in 50-80% of patients with EPTs and correlates with tumour burden. The location of endocrine tumours of the pancreas includes different techniques, from endoscopic investigations to scintigraphy (e.g. somatostatin receptor scintigraphy) and positron emission tomography. The medical treatment of endocrine pancreatic tumours consists of chemotherapy, somatostatin analogues and alpha-interferon. None of these can cure a patient with malignant disease. In future, therapy will be custom-made and based on current knowledge of tumour biology and molecular genetics.
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                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2007
                September 2007
                30 July 2007
                : 86
                : 2
                : 112-118
                Affiliations
                Department of Surgical Sciences, Endocrine Unit, Uppsala University Hospital, Uppsala, Sweden
                Article
                106762 Neuroendocrinology 2007;86:112–118
                10.1159/000106762
                17664862
                © 2007 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 3, Tables: 2, References: 39, Pages: 7
                Categories
                Clinical Neuroendocrinology and Neuroendocrine Tumors

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