CDK-inhibitors-associated kinase activity: a possible determinant of malignant potential in smooth muscle tumors of the external soft tissue.
There has been accumulating histological observation of leiomyoma and leiomyosarcoma of the external soft tissue regarding their differential diagnosis. The definitive diagnostic tools have not been established, however, nor have the pathological mechanisms of cell proliferation in these tumors been clarified. Herein, expression of the cyclin-dependent kinase inhibitors (CKIs), p21, p27 and p57 and their associated kinase activities were examined in 61 cases of soft tissue smooth muscle tumors. Immunohistochemical staining showed that all 3 inhibitor proteins were expressed in all cases of leiomyoma and leiomyosarcoma, but that the mean values of their labeling indices (LIs) were higher in the cases of leiomyosarcoma. In addition, the LIs of p21 and p27 were inversely correlated in total cases. Immunoblotting revealed that these proteins are expressed at higher levels in tumors, in particular, in leiomyosarcoma. When CKIs were immunoprecipitated from tissue extracts, cyclin/cdk protein complexes associated with, at least, 1 CKI were detectable only in tumor tissues. Furthermore, cdk2 or cdk4 kinase activity manifested by these cyclin/cdk/CKI complexes (CKI-associated kinase activity) was detectable exclusively from leiomyosarcoma, but not from leiomyoma. Among the cases of leiomyosarcoma, cdk2 activity was generally found associated either with p21 or p27, but not both. Statistical analysis indicated that p21- and p27 LIs are predictive of positive or negative clinical outcome, respectively. In conclusion, the participation of CKIs in active cyclin/cdk complexes in a reciprocal and redundant manner and subsequent CKI- associated kinase activity are the characteristic profiles of malignant phenotype in these tumors. Moreover, immunohistochemical detection of CKIs may provide a useful tool for evaluating patients' prognosis.
Dobashi
Y
Y
Department of Pathology, Kitasato University School of Medicine, Kanagawa, Japan. ydobashi@med.kitasato-u.ac.jp
Noguchi
T
T
Nasuno
S
S
Katayama
K
K
Kameya
T
T
D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002455:Cell Division; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D050761:Cyclin-Dependent Kinase Inhibitor p57; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007889:Leiomyoma / Q000175:diagnosis* / Q000201:enzymology; D007890:Leiomyosarcoma / Q000175:diagnosis* / Q000201:enzymology; D019042:Muscle Neoplasms / Q000175:diagnosis* / Q000201:enzymology*; D009687:Nuclear Proteins / Q000096:biosynthesis; D010641:Phenotype; D011233:Precipitin Tests; D011379:Prognosis; D012306:Risk; D012983:Soft Tissue Neoplasms / Q000175:diagnosis / Q000201:enzymology; D013997:Time Factors; D016896:Treatment Outcome; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis
C493956:CDKN1A protein, human; C493964:CDKN1C protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050761:Cyclin-Dependent Kinase Inhibitor p57; D016213:Cyclins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases