Journal Article

Growth arrest by the LKB1 tumor suppressor: induction of p21<sup>WAF1/CIP1</sup>

Marianne Tiainen, Kari Vaahtomeri, Antti Ylikorkala and Tomi P. Mäkelä

in Human Molecular Genetics

Volume 11, issue 13, pages 1497-1504
Published in print June 2002 | ISSN: 0964-6906
Published online June 2002 | e-ISSN: 1460-2083 | DOI:
Growth arrest by the LKB1 tumor suppressor: induction of p21WAF1/CIP1

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Germline mutations of the LKB1 tumor suppressor gene lead to Peutz–Jeghers syndrome (PJS), with a predisposition to cancer. LKB1 encodes for a nuclear and cytoplasmic serine/threonine kinase, which is inactivated by mutations observed in PJS patients. Restoring LKB1 activity into cancer cell lines defective for its expression results in a G1 cell cycle arrest. Here we have investigated molecular mechanisms leading to this arrest. Reintroduced active LKB1 was cytoplasmic and nuclear, whereas most kinase-defective PJS mutants of LKB1 localized predominantly to the nucleus. Moreover, when LKB1 was forced to remain cytoplasmic through disruption of the nuclear localization signal, it retained full growth suppression activity in a kinase-dependent manner. LKB1-mediated G1 arrest was found to be bypassed by co-expression of the G1 cyclins cyclin D1 and cyclin E. In addition, the protein levels of the CDK inhibitor p21WAF1/CIP1 and p21 promoter activity were specifically upregulated in LKB1-transfected cells. Both the growth arrest and the induction of the p21 promoter were found to be p53-dependent. These results suggest that growth suppression by LKB1 is mediated through signaling of cytoplasmic LKB1 to induce p21 through a p53-dependent mechanism.

Journal Article.  5400 words.  Illustrated.

Subjects: Genetics and Genomics

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