title: ROCK1 and ROCK2 are required for non-small cell lung cancer anchorage-independent growth and invasion.
abstract: Evidence is emerging that the closely related ROCK1 and ROCK2 serine/threonine kinases support the invasive and metastatic growth of a spectrum of human cancer types. Therefore, inhibitors of ROCK are under preclinical development. However, a key step in their development involves the identification of genetic biomarkers that will predict ROCK inhibitor antitumor activity. One identified mechanism for ROCK activation in cancer involves the loss of function of the DLC1 tumor suppressor gene, which encodes a GTPase activating protein (RhoGAP) for the RhoA and RhoC small GTPases. DLC-1 loss may lead to hyperactivation of RhoA/C and its downstream effectors, the ROCK kinases. We therefore determined whether loss of DLC-1 protein expression identifies non-small cell lung carcinoma (NSCLC) cell lines whose growth and invasion phenotypes are sensitive to ROCK inhibition. We identified and characterized a novel small molecule pharmacologic inhibitor of ROCK and additionally applied genetic approaches to impair ROCK1 and/or ROCK2 activity, and we determined that although NSCLC anchorage-dependent growth was ROCK-independent, both anchorage-independent growth and Matrigel invasion were ROCK-dependent. However, loss of DLC-1 expression did not correlate with ROCK activation or with OXA-06 sensitivity. Unexpectedly, suppression of ROCK1 or ROCK2 expression alone was sufficient to impair anchorage-independent growth, supporting their nonoverlapping roles in oncogenesis. Mechanistically, the block in anchorage-independent growth was associated with accumulation of cells in the G(0)-G(1) phase of the cell cycle, but not increased anoikis. We conclude that ROCK may be a useful therapeutic target for NSCLC.
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA.
authors.forename: Dominico
authors.initials: D
authors.lastname: Vigil
authors.forename: Tai Young
authors.initials: TY
authors.lastname: Kim
authors.forename: Ana
authors.initials: A
authors.lastname: Plachco
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Garton
authors.forename: Linda
authors.initials: L
authors.lastname: Castaldo
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Pachter
authors.forename: Hanqing
authors.initials: H
authors.lastname: Dong
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.forename: Brianna
authors.initials: B
authors.lastname: Tokar
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Campbell
authors.forename: Channing J
authors.initials: CJ
authors.lastname: Der
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000473:pathology*; D002455:Cell Division / Q000502:physiology*; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000473:pathology*; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D054460:rho-Associated Kinases / Q000502:physiology*
chemical_list: D051339:Actin Depolymerizing Factors; C515851:ROCK1 protein, human; C515852:ROCK2 protein, human; D054460:rho-Associated Kinases