DLC-1 suppresses non-small cell lung cancer growth and invasion by RhoGAP-dependent and independent mechanisms.

Abstract

Expression of the tumor suppressor deleted in liver cancer-1 (DLC-1) is lost in non-small cell lung (NSCLC) and other human carcinomas, and ectopic DLC-1 expression dramatically reduces proliferation and tumorigenicity. DLC-1 is a multi-domain protein that includes a Rho GTPase activating protein (RhoGAP) domain which has been hypothesized to be the basis of its tumor suppressive actions. To address the importance of the RhoGAP function of DLC-1 in tumor suppression, we performed biochemical and biological studies evaluating DLC-1 in NSCLC. Full-length DLC-1 exhibited strong GAP activity for RhoA as well as RhoB and RhoC, but only very limited activity for Cdc42 in vitro. In contrast, the isolated RhoGAP domain showed 5- to 20-fold enhanced activity for RhoA, RhoB, RhoC, and Cdc42. DLC-1 protein expression was absent in six of nine NSCLC cell lines. Restoration of DLC-1 expression in DLC-1-deficient NSCLC cell lines reduced RhoA activity, and experiments with a RhoA biosensor demonstrated that DLC-1 dramatically reduces RhoA activity at the leading edge of cellular protrusions. Furthermore, DLC-1 expression in NSCLC cell lines impaired both anchorage-dependent and -independent growth, as well as invasion in vitro. Surprisingly, we found that the anti-tumor activity of DLC-1 was due to both RhoGAP-dependent and -independent activities. Unlike the rat homologue p122RhoGAP, DLC-1 was not capable of activating the phospholipid hydrolysis activity of phospholipase C-delta1. Combined, these studies provide information on the mechanism of DLC-1 function and regulation, and further support the role of DLC-1 tumor suppression in NSCLC.

• Authors: Kevin D Healy, Louis Hodgson, Tai-Young Kim, Adam Shutes, Savitri Maddileti, Rudolph L Juliano, Klaus M Hahn, T Kendall Harden, Yung-Jue Bang, Channing J Der
• Journal: Molecular carcinogenesis (Mol Carcinog) Vol. 47 Issue 5 Pg. 326-37 (May 2008) ISSN: 1098-2744 [Electronic] United States
• PMID: 17932950 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: (c) 2007 Wiley-Liss, Inc.

Chemical References

• DLC1 protein, human
• DNA Primers
• Drug Combinations
• GTPase-Activating Proteins
• Laminin
• Proteoglycans
• Tumor Suppressor Proteins
• matrigel
• Guanosine Triphosphate
• Collagen
• PLCD1 protein, human
• Phospholipase C delta
• RHOC protein, human
• rho GTP-Binding Proteins
• rhoA GTP-Binding Protein
• rhoB GTP-Binding Protein
• rhoC GTP-Binding Protein

Topics

• Carcinoma, Non-Small-Cell Lung (metabolism, pathology, prevention & control)
• Cell Movement
• Collagen (metabolism)
• DNA Primers
• Drug Combinations
• GTPase-Activating Proteins
• Gene Expression Regulation, Neoplastic
• Genes, Tumor Suppressor (physiology)
• Guanosine Triphosphate (metabolism)
• Humans
• Hydrolysis
• Laminin (metabolism)
• Lung Neoplasms (metabolism, pathology, prevention & control)
• Neoplasm Invasiveness
• Phospholipase C delta (metabolism)
• Polymerase Chain Reaction
• Proteoglycans (metabolism)
• Tumor Cells, Cultured
• Tumor Stem Cell Assay
• Tumor Suppressor Proteins (physiology)
• rho GTP-Binding Proteins (genetics, metabolism)
• rhoA GTP-Binding Protein (genetics, metabolism)
• rhoB GTP-Binding Protein (genetics, metabolism)
• rhoC GTP-Binding Protein