Young M R, Young M E, Lozano Y, Coogan M, Bagash J M
Department of Research Services, Hines V.A. Hospital, Hines, IL 60141.
Int J Cancer. 1991 Aug 19;49(1):150-5. doi: 10.1002/ijc.2910490127.
Lewis lung carcinoma (LLC) clones were used in in vitro models for dissemination to identify mechanisms regulating the stimulation of metastatic LLC-LN7 migration by prostaglandin E2 (PGE2) or forskolin plus 3-isobutyl-I-methylxanthine (IBMX), and the lack of responsiveness to generated cAMP in non-metastatic LLC-C8 cells. The regulatory subunits of protein kinase A (PKA) from LLC-LN7 cells bound more 8-N3-32P-cAMP, even though production of regulatory subunits was equal to that in LLC-C8 cells. Protein kinase C (PKC) differentially regulated PKA activation in the LLC variants. PKC activation inhibited PGE2-stimulated migration by LLC-LN7 cells. Inhibition of PKC with staurosporine stimulated LLC-LN7 cell migration to a level comparable with that induced by PGE2. However, PGE2 did not further stimulate the migration of staurosporine-treated cells. The PGE2 or staurosporine stimulation of LLC-LN7 cell migration was dependent on PKA activation. The effects that modulation of PKA and PKC had on LLC-LN7 cell migration paralleled the effects on endogenous protein phosphorylation. LLC-LN7 cell autophosphorylation was stimulated to a similar degree by PGE2, forskolin plus IMBX, staurosporine, or the combination of staurosporine and forskolin plus IBMX. In contrast, neither migration nor autophosphorylation was stimulated in non-metastatic LLC-C8 cells by cAMP elevation or by PKC inhibition. Autophosphorylation, although not migration, of LLC-C8 cells was stimulated by forskolin plus IBMX when PKC activity was inhibited. These results suggest that the increased PKA response of metastatic LLC-LN7 cells is contributed by an increased binding of cAMP by the PKA regulatory subunits and a reduced level of regulation by PKC.
刘易斯肺癌（LLC）克隆用于体外转移模型，以确定调节前列腺素E2（PGE2）或福斯可林加3 - 异丁基 - 1 - 甲基黄嘌呤（IBMX）刺激转移性LLC - LN7细胞迁移的机制，以及非转移性LLC - C8细胞对生成的环磷酸腺苷（cAMP）缺乏反应的机制。尽管LLC - LN7细胞中蛋白激酶A（PKA）调节亚基的产生量与LLC - C8细胞中的相等，但LLC - LN7细胞的PKA调节亚基结合更多的8 - N3 - 32P - cAMP。蛋白激酶C（PKC）对LLC变异体中的PKA激活有不同的调节作用。PKC激活抑制LLC - LN7细胞受PGE2刺激的迁移。用星形孢菌素抑制PKC可刺激LLC - LN7细胞迁移至与PGE2诱导的水平相当。然而，PGE2并未进一步刺激经星形孢菌素处理的细胞的迁移。PGE2或星形孢菌素对LLC - LN7细胞迁移的刺激依赖于PKA激活。PKA和PKC调节对LLC - LN7细胞迁移的影响与对内源性蛋白磷酸化的影响相似。PGE2、福斯可林加IMBX、星形孢菌素或星形孢菌素与福斯可林加IBMX的组合对LLC - LN7细胞自磷酸化的刺激程度相似。相比之下，cAMP升高或PKC抑制均未刺激非转移性LLC - C8细胞的迁移或自磷酸化。当PKC活性被抑制时，福斯可林加IBMX可刺激LLC - C8细胞的自磷酸化，但不刺激其迁移。这些结果表明，转移性LLC - LN7细胞中PKA反应的增加是由于PKA调节亚基对cAMP的结合增加以及PKC调节水平降低所致。
