Lats2, also known as Kpm, is the second mammalian member of the novel Lats tumor suppressor gene family. Recent studies have demonstrated that Lats2 negatively regulates the cell cycle by controlling G1/S and/or G2/M transition. To further understand the role of Lats2 in the control of human cancer development, we have expressed the protein in human lung cancer cells by transduction of a replication-deficient adenovirus expressing human Lats2 (Ad-Lats2). Using a variety of techniques, including Annexin V uptake, cleavage of PARP, and DNA laddering, we have demonstrated that the ectopic expression of human Lats2 induced apoptosis in two lung cancer cell lines, A549 and H1299. Caspases-3, 7, 8, and 9 were processed in the Ad-Lats2-transduced cells; however, it was active caspase-9, not caspase-8, that initiated the caspase cascade. Inhibitors specific to caspase-3 and 9 delayed the onset of Lats2-mediated apoptosis. Western blot analysis revealed that anti-apoptotic proteins, BCL-2 and BCL-xL, but not the pro-apoptotic protein, BAX, were downregulated in Ad-Lats2-transduced human lung cancer cells. Overexpression of either Bcl-2 or Bcl-xL in these cells lead to the suppression of Lats2-mediated caspase cleavage and apoptosis. These results show that Lats2 induces apoptosis through downregulating anti-apoptotic proteins, BCL-2 and BCL-xL, in human lung cancer cells.
Bibliographical noteFunding Information:
We are grateful to Dr. Catherine Verfaillie for her support and helpful advice for this research. We thank Dr. Tian Xu at Yale University for the anti-LATS2 antibody, and Dr. Robert Kratzke and David Kiang for the human lung cancer cell lines, H1299 and A549. Sandy Johnson and John D. Andersen are acknowledged for editing. We also thank Gregory Veltri and Janet Peller with their assistance for FACS and data analyses. This work is supported by a Research Scholar Grant from the American Cancer Society (RSG-02-065-01-MGO) and a Career Development Award from American Lung Association (CI-003-N) to W. Tao.
- Human Lats2
- Putative tumor suppressor