Interactions between RhoA-GTPase and cGMP/cAMP ignalling influence both the vascular disrupting and anti-angiogenic activities of combretastatin A-4-Phosphate


Year:

Session type:

Chryso Kanthou, Gillian Tozer

University of Sheffield, UK

Abstract

Combretastatin A-4-Phosphate (CA-4-P) is the lead compound of a growing group of tubulin-binding tumour Vascular Disrupting Agents (VDA). RhoA-GTPase ignalling is activated by CA-4-P in endothelial cells and is hypothesised to be central to tumour vascular disruption [1,2]. Our previous studies demonstrated a protective effect by nitric oxide (NO) against the damaging vascular effects of CA-4-P via unknown mechanisms [3]. cGMP, downstream of NO, and cAMP, inhibit RhoA by PKG and PKA-mediated phosphorylation respectively, and are therefore possible modulators of CA-4-P activity.

Cultured endothelial cells were treated with cAMP/cGMP analogues, RhoA inhibitor C3 exoenzyme, or Rho kinase inhibitor Y27632 prior to CA-4-P. Similar to Rho inhibitors [1], cAMP/cGMP analogues prevented CA-4-P-mediated actin remodelling, disruption of VE-cadherin junctions, rise in permeability and phosphorylation of the Rho kinase target, myosin light chain kinase. Low doses of CA-4-P (1-10 nM) inhibited migration after monolayer wounding and abolished lamellipodia at the leading edge of migrating cells. cAMP/cGMP analogues and Rho inhibitors re-established cell movement in the presence of CA-4-P.

Our data demonstrate important interactions between cGMP/cAMP and RhoA signalling, which influence both vascular disrupting and anti-angiogenic CA-4-P activities. Furthermore, our data suggest a link between NO and Rho signalling, thus providing a potential explanation of the protective effects of NO in vivo. These data point to cAMP/cGMP as targets for improving the efficacy of tubulin-binding VDAs.

References

[1] Kanthou & Tozer, 2002; Blood 99:2060.

[2] Tozer et al, 2005; Nat Rev Cancer 5:423.

[3] Tozer et al, 1999; Cancer Res 59: 1626.

Acknowledgements

This research was supported by Cancer Research UK.

Combretastatin A-4-Phosphate (CA-4-P) is the lead compound of a growing group of tubulin-binding tumour Vascular Disrupting Agents (VDA). RhoA-GTPase ignalling is activated by CA-4-P in endothelial cells and is hypothesised to be central to tumour vascular disruption [1,2]. Our previous studies demonstrated a protective effect by nitric oxide (NO) against the damaging vascular effects of CA-4-P via unknown mechanisms [3]. cGMP, downstream of NO, and cAMP, inhibit RhoA by PKG and PKA-mediated phosphorylation respectively, and are therefore possible modulators of CA-4-P activity.

Cultured endothelial cells were treated with cAMP/cGMP analogues, RhoA inhibitor C3 exoenzyme, or Rho kinase inhibitor Y27632 prior to CA-4-P. Similar to Rho inhibitors [1], cAMP/cGMP analogues prevented CA-4-P-mediated actin remodelling, disruption of VE-cadherin junctions, rise in permeability and phosphorylation of the Rho kinase target, myosin light chain kinase. Low doses of CA-4-P (1-10 nM) inhibited migration after monolayer wounding and abolished lamellipodia at the leading edge of migrating cells. cAMP/cGMP analogues and Rho inhibitors re-established cell movement in the presence of CA-4-P.

Our data demonstrate important interactions between cGMP/cAMP and RhoA signalling, which influence both vascular disrupting and anti-angiogenic CA-4-P activities. Furthermore, our data suggest a link between NO and Rho signalling, thus providing a potential explanation of the protective effects of NO in vivo. These data point to cAMP/cGMP as targets for improving the efficacy of tubulin-binding VDAs.

References

[1] Kanthou & Tozer, 2002; Blood 99:2060.

[2] Tozer et al, 2005; Nat Rev Cancer 5:423.

[3] Tozer et al, 1999; Cancer Res 59: 1626.

Acknowledgements

This research was supported by Cancer Research UK.

Share this abstractTweet about this on TwitterPrint this pageShare on FacebookEmail this to someoneShare on LinkedIn