RhoA/ROCK/PTEN signaling is involved in AT-101-mediated apoptosis in human leukemia cells in vitro and in vivo

Abstract

R-(−)-gossypol acetic acid (AT-101) is a natural cottonseed product that exhibits anticancer activity. However, the molecular mechanism behind the antileukemic activity of AT-101 has not been well characterized. In this study, we investigated how AT-101 induces apoptosis in human leukemia cells. Exposure to AT-101 significantly increased apoptosis in both human leukemia cell lines and primary human leukemia cells. This increase was accompanied by the activation of caspases, cytochrome c release, Bcl2-associated X protein (Bax) translocation, myeloid cell leukemia-1 (Mcl-1) downregulation, Bcl-2-associated death promoter (Bad) dephosphorylation, Akt inactivation, and RhoA/Rho-associated coiled-coil containing protein kinase 1/phosphatase and tensin homolog (RhoA/ROCK1/PTEN) activation. RhoA, rather than caspase-3 cleavage, mediated the cleavage/activation of ROCK1 that AT-101 induced. Inhibiting RhoA and ROCK1 activation by C3 exoenzyme (C3) and Y27632, respectively, attenuated the ROCK1 cleavage/activation, PTEN activity, Akt inactivation, Mcl-1 downregulation, Bad dephosphorylation, and apoptosis mediated by AT-101. Knocking down ROCK1 expression using a ROCK1-specific siRNA also significantly abrogated AT-101-mediated apoptosis. Constitutively active Akt prevented the AT-101-induced Mcl-1 downregulation, Bad dephosphorylation, and apoptosis. Conversely, AT-101 lethality was potentiated by the phosphatidylinositol 3-kinase inhibitor LY294002. In vivo, the tumor growth inhibition caused by AT-101 was also associated with RhoA/ROCK1/PTEN activation and Akt inactivation in a mouse leukemia xenograft model. Collectively, these findings suggest that AT-101 may preferentially induce apoptosis in leukemia cells by interrupting the RhoA/ROCK1/PTEN pathway, leading to Akt inactivation, Mcl-1 downregulation, Bad dephosphorylation, and Bax translocation, which culminate in mitochondrial injury and apoptosis.

Anti-cancer effect of ursolic acid activates apoptosis through ROCK/PTEN mediated mitochondrial translocation of cofilin-1 in prostate cancer

“…Therefore it has been speculated that the formation of prostate carcinoma may be associated with overexpression of RhoA (30,31). The present study observed that prostate cells expressed ROCK/PTEN protein, and the expression of ROCK/PTEN protein in prostate carcinoma is also higher than that in BPH.…”

“…The present study observed that prostate cells expressed ROCK/PTEN protein, and the expression of ROCK/PTEN protein in prostate carcinoma is also higher than that in BPH. Furthermore, the expression level of RhoA and ROCK/PTEN protein demonstrates significant positive correlation (30,31). These findings indicated that the ROCK/PTEN signal transduction pathway may participate in the occurrence of prostate carcinoma, and the expression level of ROCK/PTEN protein may be regulated and controlled by RhoA (32).…”

Rho/Rho-associated protein kinase signaling pathway‑mediated downregulation of runt-related transcription factor 2 expression promotes the differentiation of dental pulp stem cells into odontoblasts

“…These studies demonstrate that the RhoA/ROCK signaling pathway may have regulatory roles on Runx2 expression in osteoblasts and suggests that the pathway may also have a role in regulating Runx2 expression in odontoblast differentiation. In the present study, the RhoA/ROCK signaling pathway inhibitor, C3 exoenzyme (37), was used to analyze the impact of the signaling pathway in hDPSCs. Results demonstrated that C3 exoenzyme treatment significantly downregulated the protein expression levels of RhoA, ROCK and Runx2 in hDPSCs.…”

Carnosic Acid‐combined Arsenic Trioxide Antileukaemia Cells in the Establishment of NB4/SCID Mouse Model

“…TNF‐a and IL‐1b induced Gluc secretion of 3T3‐L1‐NF‐kB‐RE‐GLuc adipocytes. Carnosic acid strongly suppressed GLuc secretion induced by macrophages and on the contrary up‐regulated adiponectin secretion on 3T3‐L1‐NF‐kB‐RE‐GLuc adipocytes . CA reduced expression of IL‐1b, and TNF‐a selectively inhibited COX‐2 of inflammation‐associated genes and significantly inhibited the overproduction of nitric oxide (NO) in a dose‐dependent manner in a macrophage cell line .…”