Rho Kinase Regulates the Survival and Transformation of Cells Bearing Oncogenic Forms of KIT, FLT3, and BCR-ABL

Abstract

Summary We show constitutive activation of Rho kinase (ROCK) in cells bearing oncogenic forms of KIT, FLT3 and BCR-ABL, which is dependent on PI3K and Rho GTPase. Genetic or pharmacologic inhibition of ROCK in oncogene bearing cells impaired their growth as well as the growth of acute myeloid leukemia patient derived blasts and prolonged the life span of mice bearing myeloproliferative disease. Downstream from ROCK, rapid dephosphorylation or loss of expression of myosin light chain resulted in enhanced apoptosis, reduced growth and loss of actin polymerization in oncogene bearing cells leading to significantly prolonged life span of leukemic mice. In summary, we describe a pathway involving PI3K/Rho/ROCK/MLC which may contribute to myeloproliferative disease and/or acute myeloid leukemia in humans.

Pak and Rac GTPases promote oncogenic KIT–induced neoplasms

“…Primary BM cells transduced at similar efficiency were sorted to homogeneity on the basis of EGFP expression and subjected to ligand-independent (in the absence of stem cell factor) growth. As expected and previously shown (27 ), KITD814V-expressing HSC/Ps showed a significant increase in ligand-independent growth compared with WT KIT-bearing cells, however, lack of Vav1 in these cells resulted in approximately 75% repression of ligand-independent growth ( Figure 1B). Loss of Vav2 or Vav3 in primary HSC/Ps did not profoundly impact the ligand-independent growth of KITD814V-bearing cells (Supplemental Figure 1; supplemental material available online with this article; doi:10.1172/JCI67509DS1).…”

“…In a series of experiments using knockout mouse models, mouse models of MPN, dominant-negative approaches, an allosteric inhibitor of Pak, and a novel small-molecule inhibitor of Rac, we provide evidence of a mechanism of KITD814V-induced transformation and potentially novel therapeutic targets for the treatment of oncogenic KIT-bearing neoplasms. (27). Transduced cells were sorted to homogeneity on the basis of EGFP expression and used in the experiments described here.…”

RNAi profiling of primary human AML cells identifies ROCK1 as a therapeutic target and nominates fasudil as an antileukemic drug

“…Even though our data in additional primary AML donors are limited in number, they are well in line with data generated by other groups in CML. 23,42 Interestingly, both our data and 1 of the earlier reports in CML suggest that normal HSPCs are less sensitive to ROCK1 inhibition than leukemic blasts. These observations and the excellent tolerability of prolonged fasudil exposure in humans 43,44 and in our mouse model argue for the feasibility of repetitive dosing to increase peak serum levels observed after a single application of this drug 25 to levels needed for efficient ROCK1 inhibition in vivo.…”

“…To further evaluate the possible therapeutic implications of our screen, we chose ROCK1 as an example because of its known involvement in cancer biology 22,23 and because several inhibitors for this enzyme are already available. 24 First, we confirmed knockdown efficacy of ROCK1-targeting shRNAs on messenger RNA and protein levels (Figure 2A-B; supplemental Figure 4).…”

Combined inhibition of rho-associated protein kinase and EGFR suppresses the invasive phenotype in EGFR-dependent lung cancer cells

“…Several preclinical studies have demonstrated that inhibition of Rho/ROCK in cells bearing oncogenic forms of KIT, FLT3 and BCR-ABL TK reduces active levels of MYPT1 and suppresses their constitutive growth [25]. A publication by Burthem and colleagues shows that ROCK inhibitors such as Y-27632 and fasudil combined with the TKI imatinib synergistically inhibits the activity of human leukemic cells [26].…”