h-89 and Lung-Neoplasms

The signal transduction mechanisms of pituitary adenylate cyclase activating polypeptide (PACAP) were investigated in lung cancer cells. Previously, PACAP-27 addition to NCI-H838 cells increased phosphatidylinositol turnover and intracellular cAMP leading to proliferation of lung cancer cells. Also, PACAP receptors (PAC1) regulated the tyrosine phosphorylation of ERK, focal adhesion kinase, and paxillin. In this communication, the effects of PACAP on cytosolic Ca(2+) and PYK-2 tyrosine phosphorylation were investigated. PACAP-27 increased cytosolic Ca(2+) within seconds after addition to FURA-2 AM loaded NCI-H838 cells. The increase in cytosolic Ca(2+) caused by PACAP was inhibited by PACAP(6-38) (PAC1 antagonist), U73122 (phospholipase C inhibitor), or BAPTA (calcium chelator), but not H89 (PKA inhibitor). PACAP-38, but not vasoactive intestinal peptide (VIP), addition to NCI-H838 or H1299 cells significantly increased the tyrosine phosphorylation of PYK-2 after 2 min. The increase in PYK-2 tyrosine phosphorylation caused by PACAP was inhibited by PACAP(6-38), U73122, or BAPTA, but not H89. The results suggest that PAC1 regulates PYK-2 tyrosine phosphorylation in a calcium-dependent manner.

Topics: Calcium Signaling; Cell Line, Tumor; Chelating Agents; Cytosol; Egtazic Acid; Estrenes; Focal Adhesion Kinase 2; Humans; Isoquinolines; Lung Neoplasms; Neoplasm Proteins; Peptide Fragments; Phosphodiesterase Inhibitors; Phosphorylation; Phosphotyrosine; Pituitary Adenylate Cyclase-Activating Polypeptide; Protein Kinase Inhibitors; Protein Processing, Post-Translational; Pyrrolidinones; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; Sulfonamides

Lung cancer is the leading cause of cancer-related death worldwide. Hypoxia is known to increase cancer cell migration and invasion. We have previously reported that hypoxia induces epithelial-mesenchymal transition (EMT) in lung cancer cells. However, it is unknown whether hypoxia promotes lung cancer cell migration and invasion via EMT and whether cyclic AMP (cAMP) dependent protein kinase (PKA) plays a role in this process. We found that hypoxia increased PKA activity and induced mRNA and protein expression of PKA catalytic subunit α (PKACA), and regulatory subunits R1A and R1B. Knockdown of HIF-1/2α prevented hypoxia-mediated induction of PKACA mRNA expression and PKA activity. Inhibition of PKA activity with chemical inhibitors prevented EMT induced by hypoxia and tumor growth factor β1. However, activation of PKA by forskolin and 8-Br-cAMP did not induce EMT. Furthermore, treatment with H89 and knockdown of PKACA prevented hypoxia-mediated, EMT, cell migration, and invasion, whereas overexpression of mouse PKACA rescued hypoxia-mediated migration and invasion in PKACA deficient cancer cells. Our results suggest that hypoxia enhances PKA activity by upregulating PKA gene expression in a HIF dependent mechanism and that PKA plays a key role in hypoxia-mediated EMT, migration, and invasion in lung cancer cells.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Hypoxia; Cell Line, Tumor; Cell Movement; Colforsin; Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; Cyclic AMP-Dependent Protein Kinases; Epithelial-Mesenchymal Transition; Hypoxia-Inducible Factor 1, alpha Subunit; Isoquinolines; Lung Neoplasms; Mice; RNA Interference; RNA, Small Interfering; Sulfonamides; Transforming Growth Factor beta1; Up-Regulation

Parathyroid hormone-related protein (PTHrP)-(1-34) and PTHrP-(140-173) protect lung cancer cells from apoptosis after ultraviolet (UV) irradiation. This study evaluated upstream signaling in PTHrP-mediated alteration of lung cancer cell sensitivity to apoptosis. The two peptides increased cAMP levels in BEN lung cancer cells by 15-35% in a dose-dependent fashion, suggesting signaling through protein kinase A (PKA). In line with this view, the PKA inhibitor H89 abrogated the protective effects of PTHrP-(1-34) and PTHrP-(140-173) against caspase activation and DNA loss. PKA activation by forskolin, 3-isobutyl-1-methylxanthine (IBMX), or 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate attenuated and H89 augmented apoptosis after UV exposure as indicated by caspase-3 activation, cell DNA loss, and morphological criteria. Studies with IBMX and varying doses of forskolin indicated that small increases in cAMP, on the order of those generated by IBMX alone and the PTHrP peptides, were sufficient to protect lung cancer cells from apoptosis. In summary, PTHrP-(1-34) and PTHrP-(140-173) stimulate PKA in lung carcinoma cells and protect cells against UV-induced caspase-3 activation and DNA fragmentation. PKA activation by other means also induces resistance to apoptosis, and the protective effect of the PTHrP peptide is blocked by PKA inhibition. Thus PKA appears to have a role in the regulatory effects of PTHrP on lung cancer cell survival.

Topics: Caspases; Cell Line, Tumor; Cyclic AMP-Dependent Protein Kinases; DNA Fragmentation; Humans; Isoquinolines; Lung Neoplasms; Neoplasms, Squamous Cell; Parathyroid Hormone-Related Protein; Peptide Fragments; Protein Kinase C; Protein Kinase Inhibitors; Second Messenger Systems; Sulfonamides; Ultraviolet Rays