title: The cross talk between protein kinase A- and RhoA-mediated signaling in cancer cells.
abstract: The cross talk between cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) and RhoA-mediated signal transductions and the effect of this cross talk on biologic features of human prostate and gastric cancer cells were investigated. In the human gastric cancer cell line, SGC-7901, lysophosphatidic acid (LPA) increased RhoA activity in a dose-dependent manner. The cellular permeable cAMP analog, 8-chlorophenylthio-cAMP (CPT-cAMP), inhibited the LPA-induced RhoA activation and caused phosphorylation of RhoA at serine(188). Immunofluorescence microscopy, Western blotting, and green fluorescent protein (GFP)-tagged RhoA location assay in live cells revealed that RhoA was distributed in both the cytoplasm and nucleus of SGC-7901 cells. Treatment with LPA and/or CPT-cAMP did not induce obvious translocation of RhoA in the cells. The LPA treatment caused formation of F-actin in SGC-7901 cells, and CPT-cAMP inhibited the formation. In a modified Boyden chamber assay, LPA stimulated the migration of SGC-7901 cells, and CPT-cAMP dose-dependently inhibited the stimulating effect of LPA. In soft agar assay, LPA stimulated early proliferation of SGC-7901 cells, and CPT-cAMP significantly inhibited the growth of LPA-stimulated cells. In the prostate cancer cell line, PC-3, LPA caused morphologic changes from polygonal to round, and transfection with plasmid DNA encoding constitutively active RhoA(63L) caused a similar change. Treatment with CPT-cAMP inhibited the changes in both cases. However, in PC-3 cells transfected with a plasmid encoding mutant RhoA188A, LPA induced rounding, but CPT-cAMP could not prevent the change. Results of this experiment indicated that cAMP/PKA inhibited RhoA activation, and serine188 phosphorylation on RhoA was necessary for PKA to exert its inhibitory effect on RhoA activation. The cross talk between cAMP/PKA and RhoA-mediated signal transductions had significant affect on biologic features of gastric and prostate cancer cells, such as morphologic and cytoskeletal change, migration, and anchorage-independent growth. The results may be helpful in implementing novel therapeutic strategies for invasive and metastatic prostate and gastric cancers.
authors.affiliation: School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, Jiangsu 212001, China. ycchen54@ujs.edu.cn
authors.forename: Yongchang
authors.initials: Y
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
authors.forename: Fengwei
authors.initials: F
authors.lastname: Wang
authors.forename: Wenrong
authors.initials: W
authors.lastname: Xu
mesh_terms: D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D019204:GTP-Binding Proteins; D005753:Gastric Mucosa / Q000166:cytology; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology; D008297:Male; D008856:Microscopy, Fluorescence; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids; C100494:RTKN protein, human; D011993:Recombinant Fusion Proteins; D013873:Thionucleotides; D049452:Green Fluorescent Proteins; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D005982:Glutathione Transferase; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; C032881:lysophosphatidic acid