title: CDK9/CYCLIN T1 expression during normal lymphoid differentiation and malignant transformation.
abstract: CDK9 is a member of the CDC2-like family of kinases. Its cyclin partners are members of the CYCLIN T family (T1, T2a, and T2b) and CYCLIN K. The CDK9/CYCLIN T1 complex is very important in the differentiation programme of several cell types, controlling specific differentiation pathways. Limited data are available regarding the expression of CDK9/CYCLIN T1 in haematopoietic and lymphoid tissues. The aim of this study was to analyse the expression of the CDK9/CYCLIN T1 complex in lymphoid tissue, in order to assess its role in B- and T-cell differentiation and lymphomagenesis. CDK9/CYCLIN T1 expression was found by immunohistochemistry in precursor B and T cells. In peripheral lymphoid tissues, germinal centre cells and scattered B- and T-cell blasts in interfollicular areas expressed CDK9/CYCLIN T1, while mantle cells, plasma cells, and small resting T-lymphocytes displayed no expression of either molecule. CDK9/CYCLIN T1 expression therefore appears to be related to particular stages of lymphoid differentiation/activation. CDK9 and CYCLIN T1 were highly expressed in lymphomas derived from precursor B and T cells, from germinal centre cells, such as follicular lymphomas, and from activated T cells (ie anaplastic large cell lymphomas). Hodgkin and Reed-Sternberg cells of classical Hodgkin's lymphoma also showed strong nuclear staining. Diffuse large B-cell, Burkitt's lymphomas, and peripheral T-cell lymphomas, among T-cell lymphoproliferative disorders, showed a wide range of values. No expression of CDK9 or CYCLIN T1 was detected in mantle cell and marginal zone lymphomas. However, at the mRNA level, an imbalance in the CDK9/CYCLIN T1 ratio was found in follicular lymphoma and diffuse large B-cell lymphomas with germinal centre phenotype, and in the cell lines of classical Hodgkin's lymphomas, Burkitt's lymphomas, and anaplastic large cell lymphoma, in comparison with reactive lymph nodes. These results suggest that the CDK9/CYCLIN T1 complex may affect the activation and differentiation programme of lymphoid cells. The molecular mechanism through which the CDK9/CYCLIN T1 complex is altered in malignant transformation needs to be elucidated.
authors.affiliation: Department of Human Pathology and Oncology, University of Siena, Italy.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Bellan
authors.forename: Giulia
authors.initials: G
authors.lastname: De Falco
authors.forename: Stefano
authors.initials: S
authors.lastname: Lazzi
authors.forename: Pietro
authors.initials: P
authors.lastname: Micheli
authors.forename: Sonia
authors.initials: S
authors.lastname: Vicidomini
authors.forename: Karin
authors.initials: K
authors.lastname: Schürfeld
authors.forename: Teresa
authors.initials: T
authors.lastname: Amato
authors.forename: Annalisa
authors.initials: A
authors.lastname: Palumbo
authors.forename: Luigi
authors.initials: L
authors.lastname: Bagella
authors.forename: Elena
authors.initials: E
authors.lastname: Sabattini
authors.forename: Sabrina
authors.initials: S
authors.lastname: Bartolommei
authors.forename: Michael
authors.initials: M
authors.lastname: Hummel
authors.forename: Stefano
authors.initials: S
authors.lastname: Pileri
authors.forename: Piero
authors.initials: P
authors.lastname: Tosi
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Leoncini
authors.forename: Antonio
authors.initials: A
authors.lastname: Giordano
mesh_terms: D015153:Blotting, Western; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic / Q000378:metabolism* / Q000473:pathology; D056906:Cyclin T; D042863:Cyclin-Dependent Kinase 9 / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006801:Humans; D007124:Immunoenzyme Techniques; D016393:Lymphoma, B-Cell / Q000378:metabolism* / Q000473:pathology; D016399:Lymphoma, T-Cell / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D042863:Cyclin-Dependent Kinase 9