Mehboob Ali1, David S Zuzga2, Giovanni M Pitari3. 1. Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA, USA; Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, Wexner Medical College, The Ohio State University, OH, USA. Electronic address: mehboob.ali@osumc.edu. 2. Department of Biology, La Salle University, Philadelphia, PA, USA; BioDetego LLC, Philadelphia, PA, USA. 3. Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA, USA; BioDetego LLC, Philadelphia, PA, USA.
Abstract
AIMS: Vasodilator-stimulated phosphoprotein (VASP) controls actin dynamics associated with the malignant phenotype of colorectal tumors. Oncogenic VASP function, in turn, is finely regulated by cyclic nucleotide-dependent phosphorylation of serine (Ser) residues 157 and 239, whose differential expression determines cell survival behavior in colon cancer. However, the role of differential VASP Ser phosphorylation in colorectal carcinogenesis remains unclear. MAIN METHODS: Specific VASP phosphomutant constructs were employed to selectively silence Ser157 or Ser239 phosphorylation in human colon carcinoma cells. Cyclic nucleotide-dependent manipulation of VASP Ser phosphorylation was performed with 8-bromoadenosine 3',5'-cyclic adenosine monophosphate (8-Br-cAMP) or 8-chlorophenylthio 3',5'-cyclic guanosine monophosphate (8-CPT-cGMP). Tumorigenic and locomotory phenotypes were examined in vitro with clonogenic and wound healing assays, respectively. Finally, tumor formation and growth were investigated in vivo employing two distinct xenograft models of colorectal cancer. KEY FINDINGS: Disruption of VASP Ser157 phosphorylation weakened the clonogenic and migratory abilities of human colon cancer cells, effects mimicked by 8-CPT-cGMP-dependent regulation of VASP Ser239. In contrast, inhibition of VASP Ser239 phosphorylation enhanced cell clonogenicity and migration and was phenocopied by 8-Br-cAMP-dependent regulation of VASP Ser157. Importantly, cancer cells bearing the phosphomutant construct targeting VASP Ser157 decreased, while those with the phosphomutation at Ser239 improved their abilities to establish productive tumor colonies and grow in the peritoneal cavity or subcutaneous tissues of nude mice. SIGNIFICANCE: Together, present observations suggest differential VASP Ser phosphorylation is a relevant, targetable molecular event underlying tumor formation and progression in colon cancer.
AIMS: Vasodilator-stimulated phosphoprotein (VASP) controls actin dynamics associated with the malignant phenotype of colorectal tumors. Oncogenic VASP function, in turn, is finely regulated by cyclic nucleotide-dependent phosphorylation of serine (Ser) residues 157 and 239, whose differential expression determines cell survival behavior in colon cancer. However, the role of differential VASPSer phosphorylation in colorectal carcinogenesis remains unclear. MAIN METHODS: Specific VASP phosphomutant constructs were employed to selectively silence Ser157 or Ser239 phosphorylation in humancolon carcinoma cells. Cyclic nucleotide-dependent manipulation of VASPSer phosphorylation was performed with 8-bromoadenosine 3',5'-cyclic adenosine monophosphate (8-Br-cAMP) or 8-chlorophenylthio 3',5'-cyclic guanosine monophosphate (8-CPT-cGMP). Tumorigenic and locomotory phenotypes were examined in vitro with clonogenic and wound healing assays, respectively. Finally, tumor formation and growth were investigated in vivo employing two distinct xenograft models of colorectal cancer. KEY FINDINGS: Disruption of VASPSer157 phosphorylation weakened the clonogenic and migratory abilities of humancolon cancer cells, effects mimicked by 8-CPT-cGMP-dependent regulation of VASPSer239. In contrast, inhibition of VASPSer239 phosphorylation enhanced cell clonogenicity and migration and was phenocopied by 8-Br-cAMP-dependent regulation of VASPSer157. Importantly, cancer cells bearing the phosphomutant construct targeting VASPSer157 decreased, while those with the phosphomutation at Ser239 improved their abilities to establish productive tumor colonies and grow in the peritoneal cavity or subcutaneous tissues of nude mice. SIGNIFICANCE: Together, present observations suggest differential VASPSer phosphorylation is a relevant, targetable molecular event underlying tumor formation and progression in colon cancer.