ABSTRACT
The activity, expression and function of phosphodiesterase 4 (PDE 4) were investigated in the HMG human gingiva-derived malignant melanoma cell line. A specific PDE4 inhibitor, rolipram, inhibited PDE activity in homogenates of HMG cells, and PDE4B and 4D mRNAs were detected by RT-PCR in RNA from HMG cells. Two specific PDE4 inhibitors, rolipram and Ro-20-1724, and an adenylate cyclase activator, forskolin, increased intracellular cAMP in HMG cells. Cell growth induced by rolipram, Ro-20-1724, and forskolin was inhibited by the H-89 protein kinase A (PKA) inhibitor. However, in contrast to effects of H-89, two other PKA inhibitors, KT5720 and PKI, did not inhibit rolipram-induced cell growth. A cAMP analogue that selectively activates Epac, 8-pCPT-2'-O-Me-cAMP, also promoted the growth of HMG cells. These findings suggested that PDE4, PDE4B and/or 4D regulate cell growth through cAMP targets in the HMG malignant melanoma cell line. There have been no previous studies of positive regulation of cell growth by PDE4 inhibition, suggesting that it may be possible to target PDE4 in therapy for human malignant melanoma.
Subject(s)
3',5'-Cyclic-AMP Phosphodiesterases/biosynthesis , Melanoma/enzymology , Melanoma/pathology , 3',5'-Cyclic-AMP Phosphodiesterases/antagonists & inhibitors , 3',5'-Cyclic-AMP Phosphodiesterases/genetics , 3',5'-Cyclic-AMP Phosphodiesterases/metabolism , Alternative Splicing , Cell Growth Processes/drug effects , Cell Growth Processes/physiology , Cell Line, Tumor , Cyclic AMP/analogs & derivatives , Cyclic AMP/metabolism , Cyclic AMP/pharmacology , Cyclic AMP-Dependent Protein Kinases/metabolism , Cyclic Nucleotide Phosphodiesterases, Type 4 , Gingiva/pathology , Humans , Melanoma/genetics , Melanoma/metabolism , Protein Kinase Inhibitors/pharmacology , RNA, Messenger/biosynthesis , RNA, Messenger/geneticsABSTRACT
Phosphodiesterase (PDE) 3 has been characterized in isolated rat submandibular acini. PDE3 activity was detected in homogenates of isolated rat submandibular acini; little or no PDE3 activity was found in ducts. About 62% of PDE3 activity in the acini was recovered in the supernatant fractions; 38% in particulate fractions. In the acini, but not ducts, PDE3A mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The PDE3-specific inhibitor, cilostamide, increased the ratio of apomucin mRNA/18s rRNA, as quantified by real-time RT-PCR. Our results indicate that PDE3A may be important in regulating cAMP pools that control acini functions.
Subject(s)
3',5'-Cyclic-AMP Phosphodiesterases/metabolism , Submandibular Gland/enzymology , 3',5'-Cyclic-AMP Phosphodiesterases/antagonists & inhibitors , 3',5'-Cyclic-AMP Phosphodiesterases/genetics , Animals , Cells, Cultured , Cyclic Nucleotide Phosphodiesterases, Type 3 , Gene Expression , Male , Phosphodiesterase Inhibitors/pharmacology , Quinolones/pharmacology , RNA, Messenger/genetics , Rats , Rats, Wistar , Reverse Transcriptase Polymerase Chain Reaction/methods , Submandibular Gland/cytologyABSTRACT
Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that HOSM-1 cells, an osteosarcoma cell line established from human mandible, expressed mRNA for osteoblastic markers, such as alkaline phosphatase, osteonectin, osteocalcin and parathyroid hormone receptor, thus exhibiting an osteoblastic phenotype. We have investigated a possible role of cyclic nucleotide phosphodiesterases (PDEs) in osteosarcoma cells. RT-PCR analysis revealed that HOSM-1 cells expressed mRNA for PDE4A, 4B and 4C. In addition, rolipram, a specific inhibitor of PDE4, inhibited HOSM-1 cell proliferation. The finding that PDE4 is involved in proliferation of osteosarcoma cells suggests the possibility that PDE4 may be a new target for antitumor therapy.