Phosphodiesterase-4 promotes proliferation and angiogenesis of lung cancer by crosstalk with HIF

Abstract

Lung cancer is the leading cause of cancer death worldwide. Recent data suggest that cyclic nucleotide phosphodiesterases (PDEs) are relevant in various cancer pathologies. Pathophysiological role of phosphodiesterase 4 (PDE4) with possible therapeutic prospects in lung cancer was investigated. We exposed 10 different lung cancer cell lines (adenocarcinoma, squamous and large cell carcinoma) to hypoxia and assessed expression and activity of PDE4 by real-time PCR, immunocytochemistry, western blotting and PDE activity assays. Expression and activity of distinct PDE4 isoforms (PDE4A and PDE4D) increased in response to hypoxia in eight of the studied cell lines. Furthermore, we analyzed various in silico predicted hypoxia-responsive elements (p-HREs) found in PDE4A and PDE4D genes. Performing mutation analysis of the p-HRE in luciferase reporter constructs, we identified four functional HRE sites in the PDE4A gene and two functional HRE sites in the PDE4D gene that mediated hypoxic induction of the reporter. Silencing of hypoxia-inducible factor subunits (HIF1a and HIF2a) by small interfering RNA reduced hypoxic induction of PDE4A and PDE4D. Vice versa, using a PDE4 inhibitor (PDE4i) as a cyclic adenosine monophosphate (cAMP) -elevating agent, cAMP analogs or protein kinase A (PKA)-modulating drugs and an exchange protein directly activated by cAMP (EPAC) activator, we demonstrated that PDE4-cAMP-PKA/EPAC axis enhanced HIF signaling as measured by HRE reporter gene assay, HIF and HIF target genes expression ((lactate dehydrogenase A), LDHA, (pyruvate dehydrogenase kinase 1) PDK1 and (vascular endothelial growth factor A) VEGFA). Notably, inhibition of PDE4 by PDE4i or silencing of PDE4A and PDE4D reduced human lung tumor cell proliferation and colony formation. On the other hand, overexpression of PDE4A or PDE4D increased human lung cancer proliferation. Moreover, PDE4i treatment reduced hypoxia-induced VEGF secretion in human cells. In vivo, PDE4i inhibited tumor xenograft growth in nude mice by attenuating proliferation and angiogenesis. Our findings suggest that PDE4 is expressed in lung cancer, crosstalks with HIF signaling and promotes lung cancer progression. Thus, PDE4 may represent a therapeutic target for lung cancer therapy.

The Impact of EGFR T790M Mutations and BIM mRNA Expression on Outcome in Patients with EGFR-Mutant NSCLC Treated with Erlotinib or Chemotherapy in the Randomized Phase III EURTAC Trial

“…3). The H1975 cell line, which overexpresses PDE4, was highly sensitive to the PDE4 inhibitor rolipram (21), suggesting that the use of PDE4 inhibitors in conjunction with EGFR TKIs could represent a novel synthetic lethality approach (19).…”

“…Phosphodiesterases 4 (PDE4) isoforms A and D inhibit protein kinase A (PKA), a main cAMP effector, and activate ERK (ref. 21; Fig. 3).…”

Genomic and functional characterizations of phosphodiesterase subtype 4D in human cancers

“…Interestingly, a previous study using a sleeping beauty transposon-based screen suggested that PDE4D might function as a proliferation promoting factor in prostate cancers (12). Very recently, Pullamsetti et al found that cross-talk that occurred between PDE4 and hypoxia induciblefactor signaling might promote angiogenesis in lung cancer (13). However, the tumor-specific alterations in PDE4D genome and function are not well elucidated.…”

Identification and Validation of a Blood-Based 18-Gene Expression Signature in Colorectal Cancer

“…PDE4D was reported to be overexpressed in human prostate cancers and associated with increased tumor growth and cell migration (39). PDE4D is also expressed in lung cancer, interacting with hypoxia-inducible factor (HIF) signaling and promoting lung cancer progression (40). PDZK1IP1 was shown to be overexpressed in a variety of human cancers in the kidney, colon, lung, and breast (41).…”