Safety and Pharmacodynamics of the PDE4 Inhibitor Roflumilast in Advanced B-cell Malignancies

The multifaceted role of phosphodiesterase 4 in tumor: from tumorigenesis to immunotherapy

Phosphodiesterase 4 (PDE4) is an enzyme that specifically hydrolyzes the second messenger cAMP and has a critical role in the regulation of a variety of cellular functions. In recent years, PDE4 has attracted great interest in cancer research, and its role in tumorigenesis and development has been gradually elucidated. Research indicates that abnormal expression or heightened activity of PDE4 is associated with the initiation and progression of multiple cancers, including lung, colorectal, and hematological cancers, by facilitating cell proliferation, migration, invasion, and anti-apoptosis. Moreover, PDE4 also influences the tumor immune microenvironment, significantly immune evasion by suppressing anti-tumor immune responses, reducing T-cell activation, and promoting the polarization of tumor-associated macrophages toward a pro-tumorigenic phenotype. However, the PDE4 family may have both oncogenic and tumor-suppressive effects, which could depend on the specific type and grade of the tumor. PDE4 inhibitors have garnered substantial interest as potential anti-cancer therapeutics, directly inhibiting tumor cell growth and restoring immune surveillance capabilities to enhance the clearance of tumor cells. Several PDE4 inhibitors are currently under investigation with the aim of exploring their potential in cancer therapy, particularly in combination strategies with immune checkpoint inhibitors, to improve therapeutic efficacy and mitigate the side effects of conventional chemotherapy. This review provides an overview of PDE4 in tumorigenesis, drug resistance, immunotherapy, and the anti-tumor actions of its inhibitors, intending to guide the exploration of PDE4 as a new target in tumor therapy.

Roflumilast attenuates doxorubicin and cyclophosphamide combination-induced chemobrain in rats through modulation of NLRP3/ASC/caspase-1/GSDMD axis

AIM

The aim of this study is to investigate the neuroprotective effect of roflumilast, a phosphodiesterase-4 (PDE-4) inhibitor on cognitive impairment induced by doxorubicin (DOX)/cyclophosphamide (CP) combination therapy and to elucidate its modulatory effect on the pyroptosis pathway.

MATERIALS AND METHODS

Rats were allocated into five groups: a control group, a DOX/CP-intoxicated group, two groups receiving DOX/CP plus low-dose (0.5 mg/kg/day) or high-dose (1 mg/kg/day) roflumilast, and a roflumilast-only group. Behavioral assessments and brain tissue analyses were conducted, including histopathological staining and the measurement of inflammatory and oxidative stress markers.

FINDINGS

DOX/CP treatment resulted in cognitive impairment, abnormal brain histology. It significantly elevated the levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and malondialdehyde (MDA). Concurrently, superoxide dismutase (SOD) activity was reduced. Pyroptosis-associated markers, including nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein (ASC), caspase-1, gasdermin-D (GSDMD), and interleukin-18 (IL-18) were upregulated. Apoptotic marker caspase-3 also exhibited increased expression. Conversely, administration of roflumilast (1 mg/kg/day) for four weeks ameliorated these pathological changes. Roflumilast improved cognitive function, reduced oxidative stress, and modulated inflammatory signaling. Additionally, it suppressed pyroptotic and apoptotic pathways within hippocampal tissue.

SIGNIFICANCE

These results suggest that roflumilast exerts neuroprotective effects against chemotherapy-induced cognitive dysfunction and neurodegeneration through inhibition of the NLRP3/ASC/caspase-1/GSDMD pyroptosis pathway.

First-Line Combination of R-CHOP with the PDE4 Inhibitor Roflumilast for High-Risk DLBCL

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is a common and often fatal malignancy. The standard-of-care immunochemotherapy, R-CHOP, cures only about 60% of DLBCL patients. Improving this cure rate will likely require the effective translation of basic biology knowledge into clinical activities. We previously identified the cyclic-AMP/phosphodiesterase 4 (PDE4) axis as an important modulator of lymphomagenic processes. We also showed that the FDA-approved PDE4 inhibitor roflumilast can suppress B-cell receptor (BCR) signals, phosphoinositide 3-kinase (PI3K) activity and angiogenesis. These data suggested that combining roflumilast with R-CHOP may be beneficial in DLBCL.

METHODS

We conducted a single-center, single-arm, open-label, phase 1 study of roflumilast in combination with the standard of care, R-CHOP (Ro+R-CHOP), in pathologically proven, treatment-naïve, high-risk DLBCL patients.

RESULTS

Ro+R-CHOP was safe, and at a median follow-up time of 44 months, 70% of patients were alive and disease free (median OS not reached, PFS 44% (95% CI, 21-92). In this pilot series, we found that the addition of roflumilast suppressed PI3K activity in peripheral blood mononuclear cells, and VEGF-A secretion in the urine. We also encountered preliminary evidence to suggest that the Ro+R-CHOP combination may be particularly beneficial to patients diagnosed with high-risk genetic subtypes of DLBCL, namely MCD and A53.

CONCLUSIONS

These initial findings suggest that roflumilast may be an alternative agent able to inhibit BCR/PI3K activity and angiogenesis in DLBCL, and that the testing of Ro+R-CHOP in a larger series of genetically characterized tumors is warranted. This study was registered at ClinicalTrials.gov, number NCT03458546.

FDA-approved PDE4 inhibitors alleviate the dominant toxicity of ALS-FTD-associated CHCHD10S59L by reducing the PINK1/Parkin pathway

Background

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10 (CHCHD10) have been identified as a genetic cause of amyotrophic lateral sclerosis and/or frontotemporal dementia(ALS-FTD). In our previous studies using in vivo Drosophila model expressing CHCHD10S59L, and human cell models expressing CHCHD10S59L, we have identified that the PINK1/Parkin pathway is activated and causes cellular toxicity. Furthermore, we demonstrated that pseudo-substrate inhibitors for PINK1 and mitofusin2 agonists mitigated the cellular toxicity of CHCHD10S59L. Evidences using in vitro, in vivo genetic, and chemical tools indicate that inhibiting PINK1 would be the most promising treatment for CHCHD10S59L-induced diseases.

Methods

An in vivo human cell culture and in vivo Drosophila models expressing CHCHD10S59L mutant were utilized in this study to evaluate the effect of PDE4 inhibitors in PINK-parkin mediated cytotoxicity through immunohistochemical and seahorse assays. Data were analysed using one-way ANOVA and post-hoc Dunnett's test for statistical significance.

Results

We investigated cellular pathways that can modulate the PINK1/Parkin pathway and reduce CHCHD10S59L-induced cytotoxicity. Here, we report that FDA-approved PDE4 inhibitors reduced CHCHD10S59L-induced morphological and functional mitochondrial defects in human cells and an in vivo Drosophila model expressing C2C10HS81L. Multiple PDE4 inhibitors decreased PINK1 accumulation and downstream mitophagy induced by CHCHD10S59L.

Conclusion

These findings suggest that PDE4 inhibitors currently available in the market may be repositioned to treat CHCHD10S59L-induced ALS-FTD and possibly other related diseases, and that disease treatment with PDE4 inhibitors should include careful consideration of the PINK1/Parkin pathway, as it is generally recognized as a protective pathway.

FDA-approved PDE4 inhibitors reduce the dominant toxicity of ALS-FTD-associated CHCHD10 S59L

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10( CHCHD10 ) have been identified as a genetic cause of amyotrophic lateral sclerosis and/or frontotemporal dementia(ALS-FTD). In our previous studies using in vivo Drosophila model expressing C2C10H S81L , and human cell models expressing CHCHD10 S59L , we have identified that the PINK1/Parkin pathway is activated and causes cellular toxicity. Furthermore, we demonstrated that pseudo-substrate inhibitors for PINK1 and mitofusin2 agonists mitigated the cellular toxicity of CHCHD10 S59L . Evidences using in vitro/ in vivo genetic and chemical tools indicate that inhibiting PINK1 would be the most promising treatment for CHCHD10 S59L -induced diseases. Therefore, we have investigated cellular pathways that can modulate the PINK1/Parkin pathway and reduce CHCHD10 S59L -induced cytotoxicity. Here, we report that FDA-approved PDE4 inhibitors reduced CHCHD10 S59L -induced morphological and functional mitochondrial defects in human cells and an in vivo Drosophila model expressing C2C10H S81L . Multiple PDE4 inhibitors decreased PINK1 accumulation and downstream mitophagy induced by CHCHD10 S59L . These findings suggest that PDE4 inhibitors currently available in the market may be repositioned to treat CHCHD10 S59L -induced ALS-FTD and possibly other related diseases.

Roflumilast inhibits tumor growth and migration in STK11/LKB1 deficient pancreatic cancer

Pancreatic cancer is a malignant tumor of the digestive system. It is highly aggressive, easily metastasizes, and extremely difficult to treat. This study aimed to analyze the genes that might regulate pancreatic cancer migration to provide an essential basis for the prognostic assessment of pancreatic cancer and individualized treatment. A CRISPR knockout library directed against 915 murine genes was transfected into TB 32047 cell line to screen which gene loss promoted cell migration. Next-generation sequencing and PinAPL.py- analysis was performed to identify candidate genes. We then assessed the effect of serine/threonine kinase 11 (STK11) knockout on pancreatic cancer by wound-healing assay, chick agnosia (CAM) assay, and orthotopic mouse pancreatic cancer model. We performed RNA sequence and Western blotting for mechanistic studies to identify and verify the pathways. After accelerated Transwell migration screening, STK11 was identified as one of the top candidate genes. Further experiments showed that targeted knockout of STK11 promoted the cell migration and increased liver metastasis in mice. Mechanistic analyses revealed that STK11 knockout influences blood vessel morphogenesis and is closely associated with the enhanced expression of phosphodiesterases (PDEs), especially PDE4D, PDE4B, and PDE10A. PDE4 inhibitor Roflumilast inhibited STK11-KO cell migration and tumor size, further demonstrating that PDEs are essential for STK11-deficient cell migration. Our findings support the adoption of therapeutic strategies, including Roflumilast, for patients with STK11-mutated pancreatic cancer in order to improve treatment efficacy and ultimately prolong survival.

cAMP-PKA/EPAC signaling and cancer: the interplay in tumor microenvironment

Cancer is a complex disease resulting from abnormal cell growth that is induced by a number of genetic and environmental factors. The tumor microenvironment (TME), which involves extracellular matrix, cancer-associated fibroblasts (CAF), tumor-infiltrating immune cells and angiogenesis, plays a critical role in tumor progression. Cyclic adenosine monophosphate (cAMP) is a second messenger that has pleiotropic effects on the TME. The downstream effectors of cAMP include cAMP-dependent protein kinase (PKA), exchange protein activated by cAMP (EPAC) and ion channels. While cAMP can activate PKA or EPAC and promote cancer cell growth, it can also inhibit cell proliferation and survival in context- and cancer type-dependent manner. Tumor-associated stromal cells, such as CAF and immune cells, can release cytokines and growth factors that either stimulate or inhibit cAMP production within the TME. Recent studies have shown that targeting cAMP signaling in the TME has therapeutic benefits in cancer. Small-molecule agents that inhibit adenylate cyclase and PKA have been shown to inhibit tumor growth. In addition, cAMP-elevating agents, such as forskolin, can not only induce cancer cell death, but also directly inhibit cell proliferation in some cancer types. In this review, we summarize current understanding of cAMP signaling in cancer biology and immunology and discuss the basis for its context-dependent dual role in oncogenesis. Understanding the precise mechanisms by which cAMP and the TME interact in cancer will be critical for the development of effective therapies. Future studies aimed at investigating the cAMP-cancer axis and its regulation in the TME may provide new insights into the underlying mechanisms of tumorigenesis and lead to the development of novel therapeutic strategies.

Cyclic-AMP signalling, MYC and hypoxia-inducible factor 1α intersect to regulate angiogenesis in B-cell lymphoma

Angiogenesis and MYC expression associate with poor outcome in diffuse large B-cell lymphoma (DLBCL). MYC promotes neo-vasculature development but whether its deregulation in DLBCL contributes to angiogenesis is unclear. Examination of this relationship may uncover novel pathogenic regulatory circuitry as well as anti-angiogenic strategies in DLBCL. Here, we show that MYC expression positively correlates with vascular endothelial growth factor (VEGF) expression and angiogenesis in primary DLBCL biopsies, independently of dual expressor status or cell-of-origin classification. We found that MYC promotes VEGFA expression, a correlation that was validated in large datasets of mature B-cell tumours. Using DLBCL cell lines and patient-derived xenograft models, we identified the second messenger cyclic-AMP (cAMP) as a potent suppressor of MYC expression, VEGFA secretion and angiogenesis in DLBCL in normoxia. In hypoxia, cAMP switched targets and suppressed hypoxia-inducible factor 1α, a master regulator of VEGFA/angiogenesis in low oxygen environments. Lastly, we used the phosphodiesterase 4b (Pde4b) knockout mouse to demonstrate that the cAMP/PDE4 axis exercises additional anti-angiogenesis by directly targeting the lymphoma microenvironment. In conclusion, MYC could play a direct role in DLBCL angiogenesis, and modulation of cAMP levels, which can be achieved with clinical grade PDE4 inhibitors, has cell and non-cell autonomous anti-angiogenic activity in DLBCL.

MYC, mitochondrial metabolism and O-GlcNAcylation converge to modulate the activity and subcellular localization of DNA and RNA demethylases

Mitochondria can function as signaling organelles, and part of this output leads to epigenetic remodeling. The full extent of this far-reaching interplay remains undefined. Here, we show that MYC transcriptionally activates IDH2 and increases alpha-ketoglutarate (αKG) levels. This regulatory step induces the activity of αKG-dependent DNA hydroxylases and RNA demethylases, thus reducing global DNA and RNA methylation. MYC, in a IDH2-dependent manner, also promotes the nuclear accumulation of TET1-TET2-TET3, FTO and ALKBH5. Notably, this subcellular movement correlated with the ability of MYC, in an IDH2-dependent manner, and, unexpectedly, of αKG to directly induce O-GlcNAcylation. Concordantly, modulation of the activity of OGT and OGA, enzymes that control the cycling of this non-canonical mono-glycosylation, largely recapitulated the effects of the MYC-IDH2-αKG axis on the subcellular movement of DNA and RNA demethylases. Together, we uncovered a hitherto unsuspected crosstalk between MYC, αKG and O-GlcNAcylation which could influence the epigenome and epitranscriptome homeostasis.

Role of Roflumilast Combined with ESHAP Chemotherapy in Relapsed/Refractory Patients with Diffuse Large B-Cell Lymphoma

Purpose

There are unmet needs associated with the current treatment strategies for relapsed/refractory diffuse large B-cell lymphoma (DLBCL) due to the poor treatment outcomes of these strategies. Roflumilast, a selective phosphodiesterase-4 inhibitor used for treating chronic obstructive pulmonary disease, is effective against B-cell malignancy via phosphoinositide 3-kinase (PI3K)–activity suppression. We analyzed the effects of roflumilast combined with ESHAP (etoposide, cisplatin, methylprednisolone, and cytarabine) chemotherapy in experimental and clinical settings.

Materials and Methods

An in vitro study using lymphoma cell lines and a pilot study on relapsed/refractory DLBCL patients were conducted to investigate the effects and mechanism of the combination of roflumilast and chemotherapy. The complete response (CR), overall response rate (ORR), and 1-year progression-free survival (PFS) were analyzed.

Results

We found that roflumilast is efficient when combined with other chemotherapy drugs, especially cytarabine. Synergistic effects between these two drugs influence the translation of mammalian target of rapamycin and myeloid cell leukemia 1, resulting in apoptosis and inhibition of B-cell lymphoma proliferation. In clinical setting, the roflumilast group showed better rates of CR (46.2% vs. 34.6%), ORR (76.9% vs. 53.8%), and 1-year PFS (50.0% vs. 25.9%) compared with the control group, though not statistically significant. The roflumilast group showed a higher incidence of asthenia and gastrointestinal adverse events. However, grade 3 or 4 adverse events were similar in both groups.

Conclusion

We found that roflumilast, when combined with ESHAP chemotherapy, for relapsed/refractory DLBCL was clinically active and well tolerated. This combined treatment was able to suppress PI3K activity, which is correlated with the degree of clinical response.

Current Advances of Nitric Oxide in Cancer and Anticancer Therapeutics

Nitric oxide (NO) is a short-lived, ubiquitous signaling molecule that affects numerous critical functions in the body. There are markedly conflicting findings in the literature regarding the bimodal effects of NO in carcinogenesis and tumor progression, which has important consequences for treatment. Several preclinical and clinical studies have suggested that both pro- and antitumorigenic effects of NO depend on multiple aspects, including, but not limited to, tissue of generation, the level of production, the oxidative/reductive (redox) environment in which this radical is generated, the presence or absence of NO transduction elements, and the tumor microenvironment. Generally, there are four major categories of NO-based anticancer therapies: NO donors, phosphodiesterase inhibitors (PDE-i), soluble guanylyl cyclase (sGC) activators, and immunomodulators. Of these, NO donors are well studied, well characterized, and also the most promising. In this study, we review the current knowledge in this area, with an emphasis placed on the role of NO as an anticancer therapy and dysregulated molecular interactions during the evolution of cancer, highlighting the strategies that may aid in the targeting of cancer.

Regulation of PD-L1 expression is a novel facet of cyclic-AMP-mediated immunosuppression

Cyclic-AMP (cAMP) exerts suppressive effects in the innate and adaptive immune system. The PD-1/PD-L1 immune checkpoint down-regulates T-cell activity. Here, we examined if these two immunosuppressive nodes intersect. Using normal and malignant lymphocytes from humans, and the phosphodiesterase 4b (Pde4b) knockout mouse, we found that cAMP induces PD-L1 transcription and protein expression. Mechanistically, we discovered that the cAMP effectors PKA and CREB induce the transcription/secretion of IL-10, IL-8 and IL-6, which initiate an autocrine loop that activates the JAK/STAT pathway and ultimately increase PD-L1 expression in the cell surface. This signaling axis is disarmed at two specific nodes in subsets of diffuse large B cell lymphoma, which may help explain the variable PD-L1 expression in these tumors. In vivo, we found that despite its immunosuppressive attributes, the PDE4 inhibitor roflumilast did not decrease the clinical activity of checkpoint inhibitors, an important clinical observation given the approved use of these agents in multiple diseases. In summary, we discovered that PD-L1 induction is a part of the repertoire of immunosuppressive actions mediated by cAMP, defined a cytokine-mediated autocrine loop that executes this action and, reassuringly, showed that PDE4 inhibition does not antagonize immune checkpoint blockade in an in vivo syngeneic lymphoma model.

Apremilast Regulates the Teff/Treg Balance to Ameliorate Uveitis via PI3K/AKT/FoxO1 Signaling Pathway

Autoimmune uveitis (AU), being one of the sight-threatening ocular inflammatory disorders, has been widely regarded by ophthalmologists and immunologists as a great challenge. Apremilast, a phosphodiesterase-4 inhibitor (PDE4i), which was approved by the U.S. Food and Drug Administration (FDA) for the treatment of active psoriatic arthritis in 2014, has been attracting researchers, who are exploring its efficiency and mechanism on uveitis. In this study, we used an experimental autoimmune uveitis (EAU), a representative model for human AU, to investigate the effect of apremilast on regulating anti-inflammatory mediators. Our study demonstrated that apremilast treatment resulted in a decrease in vascular leakage, macular edema, and inflammatory cell infiltration in the retina, corresponding to decreased clinical and pathological scores. Specifically, apremilast decreased the proportion and population of Th17 cells and increased the proportion and population of T regulatory (Treg) cells. Mechanistically, apremilast may regulate Th17 and Treg cells by inhibiting the phosphorylation of the phosphoinositide 3-kinase (PI3K)/protein kinase B(AKT)/Forkhead box O1 (FoxO1) signaling pathway. These findings suggested that apremilast alleviated EAU by regulating Th17 and Treg through the PI3K/AKT/FoxO1 pathway.

PDE4 subtypes in cancer

Cyclic nucleotide phosphodiesterases (PDE) break down cyclic nucleotides such as cAMP and cGMP, reducing the signaling of these important intracellular second messengers. Several unique families of phosphodiesterases exist, and certain families are clinically important modulators of vasodilation. In the current work, we have summarized the body of literature that describes an emerging role for the PDE4 subfamily of phosphodiesterases in malignancy. We have systematically investigated PDE4A, PDE4B, PDE4C, and PDE4D isoforms and found evidence associating them with several cancer types including hematologic malignancies and lung cancers, among others. In this review, we compare the evidence examining the functional role of each PDE4 subtype across malignancies, looking for common signaling themes, signaling pathways, and establishing the case for PDE4 subtypes as a potential therapeutic target for cancer treatment.

Synthesis, antitumor activity, and molecular docking study of 2-cyclopentyloxyanisole derivatives: mechanistic study of enzyme inhibition

A series of 24 compounds was synthesised based on a 2-cyclopentyloxyanisole scaffold 3–14 and their in vitro antitumor activity was evaluated. Compounds 4a, 4b, 6b, 7b, 13, and 14 had the most potent antitumor activity (IC₅₀ range: 5.13–17.95 μM), compared to those of the reference drugs celecoxib, afatinib, and doxorubicin. The most active derivatives 4a, 4b, 7b, and 13 were evaluated for their inhibitory activity against COX-2, PDE4B, and TNF-α. Compounds 4a and 13 potently inhibited TNF-α (IC₅₀ values: 2.01 and 6.72 μM, respectively) compared with celecoxib (IC₅₀=6.44 μM). Compounds 4b and 13 potently inhibited COX-2 (IC₅₀ values: 1.08 and 1.88 μM, respectively) comparable to that of celecoxib (IC₅₀=0.68 μM). Compounds 4a, 7b, and 13 inhibited PDE4B (IC₅₀ values: 5.62, 5.65, and 3.98 μM, respectively) compared with the reference drug roflumilast (IC₅₀=1.55 μM). The molecular docking of compounds 4b and 13 with the COX-2 and PDE4B binding pockets was studied.

Highlights

Antitumor activity of new synthesized cyclopentyloxyanisole scaffold was evaluated.

The powerful antitumor 4a, 4b, 6b, 7b & 13 were assessed as COX-2, PDE4B & TNF-α inhibitors.

Compounds 4a, 7b, and 13 exhibited COX-2, PDE4B, and TNF-α inhibition.

Compounds 4b and 13 showed strong interactions at the COX-2 and PDE4B binding pockets.

Disruption of the Myc-PDE4B regulatory circuitry impairs B-cell lymphoma survival

A large body of evidence suggests that B-cell lymphomas with enhanced Myc expression are associated with an aggressive phenotype and poor prognosis, which makes Myc a compelling therapeutic target. Phosphodiesterase 4B (PDE4B), a main hydrolyzer of cyclic AMP (cAMP) in B cells, was shown to be involved in cell survival and drug resistance in diffuse large B cell lymphomas (DLBCL). However, the interrelationship between Myc and PDE4B remains unclear. Here, we first demonstrate the presence of the Myc-PDE4B feed-forward loop, in which Myc and PDE4B mutually reinforce the expression of each other. Next, the combined targeting of Myc and PDE4 synergistically prevented the proliferation and survival of B lymphoma cells in vitro and in a mouse xenograft model. We finally recapitulated this combinatorial effect in Eμ-myc transgenic mice; co-inhibition of Myc and PDE4 suppressed lymphomagenesis and restored B cell development to the wild type level that was associated with marked reduction in Myc levels, unveiling the critical role of the Myc-PDE4B amplification loop in the regulation of Myc expression and the pathogenesis of B cell lymphoma. These findings suggest that the disruption of the Myc-PDE4B circuitry can be exploited in the treatment of B cell malignancies.

Inhibition of phosphodiesterase 4D decreases the malignant properties of DLD-1 colorectal cancer cells by repressing the AKT/mTOR/Myc signaling pathway

Colorectal cancer (CRC) is a complex disease involving numerous genetic abnormalities. One of the major characteristics of CRC is enhanced Wnt signaling caused by loss-of-function mutations in the adenomatous polyposis coli (APC) gene. Previously, it has been demonstrated that the majority of malignant phenotypes following APC deletion in adult murine small intestines could be rescued when Myc, a downstream target of the Wnt pathway, was deleted. This indicated that Myc is a critical regulator of CRC development following APC loss. Previous studies reported that cyclic adenosine 3',5'-monophosphate (cAMP) can influence the AKT/mammalian target of rapamycin (mTOR) survival pathway in cancer and Myc is a critical downstream molecule of AKT/mTOR signaling. Phosphodiesterase 4D (PDE4D), a member of the cAMP-specific PDE4 family, has been associated with drug resistance in CRC. However, the association between PDE4D and Myc remains unclear. To investigate the potential role of PDE4D in Myc regulation in CRC, the present study evaluated the expression levels of PDE4 subtypes in DLD-1 CRC cells. Additionally, the effects of PDE4 inhibitors on Myc expression and oncogenic properties were analyzed by western blot analysis, reverse transcription-quantitative polymerase chain reaction, colony formation and soft agar assays. It was demonstrated that cAMP/PDE4D signals serve a critical role in regulating Myc expression in DLD-1 CRC cells. Furthermore, PDE4D was identified to be a main hydrolyzer of cAMP and suppression of PDE4D using selective inhibitors of PDE4 increased intracellular cAMP levels, which resulted in a marked decrease in the oncogenic properties of DLD-1 cells, including colony formation, cell proliferation and anchorage-independent growth. Notably, the current data imply that cAMP represses Myc expression via the downregulation of AKT/mTOR signaling, which was abolished by high PDE4D activities in DLD-1 cells. Additionally, a natural polyphenol resveratrol in combination with forskolin elevated the concentration of cAMP and enhanced the expression of Myc and the malignant phenotype of DLD-1 cells, reproducing the effect of known chemical inhibitors of PDE4. In conclusion, the present study identified that cAMP/PDE4D signaling is a critical regulator of Myc expression in DLD-1 and possibly other CRC cells.

Phosphodiesterase 4B is an effective therapeutic target in colorectal cancer

Identification of new therapeutic targets may improve the survival rate of patients with colorectal cancer (CRC). Recent studies have suggested that the level of phosphodiesterase 4B (PDE4B) is elevated in fatal/refractory diffuse large B-cell lymphoma (DLBCL), and therapeutic efficacy of a PDE4 inhibitor in B-cell lymphoma has been successfully tested in clinical settings. Here, we show that PDE4B is a potential therapeutic target in CRC. Treatment with forskolin, an activator of adenylyl cyclase (AC), increased intracellular cyclic AMP (cAMP) levels in PDE4B-low, but not PDE4B-high cells, indicating that PDE4B was a major regulator of cAMP levels in CRC cells. Furthermore, cAMP modulated the activities of AKT and AMPK in a PDE4B-dependent manner, which was associated with a marked decrease in mTOR-Myc signals and oncogenic properties of CRC cells such as anchorage-independent growth and colony formation. We found that the Myc proto-oncogene was a crucial downstream target of the AKT/mTOR and AMPK/mTOR signals that mediated cAMP-induced anti-tumor effect. A natural polyphenol resveratrol that was reported to have PDE4 inhibitory effects also showed tumor suppressive effects by inhibiting the mTOR-Myc axis. Intriguingly, we identified Myc as a transcriptional activator of PDE4B in CRC cells, which maintains the intracellular cAMP levels low and promotes cell survival. These data suggest that cAMP/PDE4B signals play a significant role in regulating the malignant phenotype of CRC cells and targeting of PDE4B should be actively pursued.

Roflumilast enhances cisplatin-sensitivity and reverses cisplatin-resistance of ovarian cancer cells via cAMP/PKA/CREB-FtMt signalling axis

OBJECTIVE

We previously demonstrated the roflumilast inhibited cell proliferation and increased cell apoptosis in ovarian cancer. In this study, we aimed to investigate the roles of roflumilast in development of cisplatin (DDP)-sensitive and -resistant ovarian cancer.

METHODS

OVCAR3 and SKOV3 were selected and the corresponding DDP-resistant cells were constructed. Cell viability, proliferation, apoptosis, cycle were performed. Expression cAMP, PKA, CREB, phosphorylation of CREB and FtMt were detected. The roles of roflumilast in development of DDP-sensitive and -resistant ovarian cancer were confirmed by xenograft model.

RESULTS

Roflumilast + DDP inhibited cell proliferation, and induced cell apoptosis and G0/G1 arrest in OVCAR3 and SKOV3 cells, roflumilast induced expression of FtMt, the activity of cAMP and PKA and phosphorylation of CREB in ovarian cancer cells and the above-effect were inhibited by H89. Downregulation of CREB inhibited the roflumilast-increased DDP sensitivity of ovarian cancer cells, and the roflumilast-induced FtMt expression and phosphorylation of CREB. Also, roflumilast reversed cisplatin-resistance, and induced expression of FtMt and activation of cAMP/PKA/CREB in DDP-resistant ovarian cancer cells. Similarly, treated with H89 or downregulation of CREB inhibited the changes induced by roflumilast. In vivo, roflumilast inhibited the development of SKOV3 or SKOV3-DDP-R xenograft models.

CONCLUSIONS

Roflumilast enhanced DDP sensitivity and reversed the DDP resistance of ovarian cancer cells via activation of cAMP/PKA/CREB pathway and upregulation of the downstream FtMt expression, which has great promise in clinical treatment.

A computational study of hedgehog signalling involved in basal cell carcinoma reveals the potential and limitation of combination therapy

BACKGROUND

The smoothened (SMO) receptor is an essential component of the Sonic hedgehog (SHH) signalling, which is associated with the development of skin basal cell carcinoma (BCC). SMO inhibitors are indicated for BCC patients when surgical treatment or radiation therapy are not possible. Unfortunately, SMO inhibitors are not always well tolerated due to severe side effects, and their therapeutical success is limited by resistance mutations.

METHODS

We investigated how common are resistance-causing mutations in two genomic databases which are not linked to BCC or other cancers, namely 1000 Genomes and ExAC. To examine the potential for combination therapy or other treatments, we further performed knowledge-based simulations of SHH signalling, in the presence or absence of SMO and PI3K/Akt inhibitors.

RESULTS

The database analysis revealed that of 18 known mutations associated with Vismodegib-resistance, three were identified in the databases. Treatment of individuals carrying such mutations is thus liable to fail a priori. Analysis of the simulations suggested that a combined inhibition of SMO and the PI3K/Akt signalling pathway may provide an effective reduction in tumour proliferation. However, the inhibition dosage of SMO and PI3K/Akt depended on the activity of phosphodiesterases (PDEs). Under high PDEs activities, SMO became the most important control node of the network. By applying PDEs inhibition, the control potential of SMO decreased and PI3K appeared as a significant factor in controlling tumour proliferation.

CONCLUSIONS

Our systems biology approach employs knowledge-based computer simulations to help interpret the large amount of data available in public databases, and provides application-oriented solutions for improved cancer resistance treatments.

Design, synthesis, and molecular modeling of heterocyclic bioisostere as potent PDE4 inhibitors

A new hybrid template was designed by combining the structural features of phosphodiesterase 4 (PDE4) inhibitors with several heterocyclic moieties which present an integral part in the skeleton of many apoptotic agents. Thirteen compounds of the synthesized hybrids displayed higher inhibitory activity against PDE4B than the reference drug, roflumilast. Further investigation indicated that compounds 13b and 20 arrested the cell cycle at the G2/M phase and the pre-G1 phase, and induced cell death by apoptosis of A549 cells in a caspase-dependent manner.

Inhibitors of phosphodiesterase as cancer therapeutics

Phosphodiesterases (PDEs) are a class of enzymes that hydrolyze cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) which is involved in many physiological processes including visual transduction, cell proliferation and differentiation, cell-cycle regulation, gene expression, inflammation, apoptosis, and metabolic function. PDEs are composed of 11 different families and each family contains different subtypes. The distribution, expression, regulation mode and sensitivity to inhibitors of each subtype are different, and they are involved in cancer, inflammation, asthma, depression, erectile dysfunction and other pathological processes of development. A large number of studies have shown that PDEs play an important role in the development of tumors by affecting the intracellular level of cAMP and/or cGMP and PDEs could become diagnostic markers or therapeutic targets. This review will give a brief overview of the expression and regulation of PDE families in the process of tumorigenesis and their anti-tumor inhibitors, which may guide the design of novel therapeutic drugs targeting PDEs for anticancer agent.

Synergistic Targeting of the Regulatory and Catalytic Subunits of PI3Kδ in Mature B-cell Malignancies

Purpose: Aberrant activation of the B-cell receptor (BCR) is implicated in the pathogenesis of mature B-cell tumors, a concept validated in part by the clinical success of inhibitors of the BCR-related kinases BTK (Bruton's tyrosine kinase) and PI3Kδ. These inhibitors have limitations, including the paucity of complete responses, acquired resistance, and toxicity. Here, we examined the mechanism by which the cyclic-AMP/PDE4 signaling axis suppresses PI3K, toward identifying a novel mechanism-based combinatorial strategy to attack BCR-dependency in mature B-cell malignancies.Experimental Design: We used in vitro and in vivo diffuse large B-cell lymphoma (DLBCL) cell lines and primary chronic lymphocytic leukemia (CLL) samples to preclinically evaluate the effects of the combination of the FDA-approved phosphodiesterase 4 (PDE4) inhibitor roflumilast and idelalisib on cell survival and tumor growth. Genetic models of gain- and loss-of-function were used to map multiple signaling intermediaries downstream of the BCR.Results: Roflumilast elevates the intracellular levels of cyclic-AMP and synergizes with idelalisib in suppressing tumor growth and PI3K activity. Mechanistically, we show that roflumilast suppresses PI3K by inhibiting BCR-mediated activation of the P85 regulatory subunit, distinguishing itself from idelalisib, an ATP-competitive inhibitor of the catalytic P110 subunit. Using genetic models, we linked the PDE4-regulated modulation of P85 activation to the oncogenic kinase SYK.Conclusions: These data demonstrate that roflumilast and idelalisib suppress PI3K by distinct mechanisms, explaining the basis for their synergism, and suggest that the repurposing of PDE4 inhibitors to treat BCR-dependent malignancies is warranted. Clin Cancer Res; 24(5); 1103-13. ©2017 AACR.

Roflumilast restores cAMP/PKA/CREB signaling axis for FtMt-mediated tumor inhibition of ovarian cancer

The abrogation of cAMP generation by overexpression of PDE isoforms promotes the inflammatory pathology, and the PDE inhibitors have showed the potential anti-inflammation effects in clinical. However, the function of PDE inhibitors in cancer treatment remains unclear. We here investigated the role of PDE4 inhibitor Roflumilast in the treatment of ovarian cancer. We found that Roflumilast could effectively inhibit the proliferation, and induce apoptosis and cell cycle arrest in two ovarian cancer cell lines OVCAR3 and SKOV3. Meanwhile, the cAMP/PKA/CREB signals was activated by Roflumilast, which was accompanied by the up-regulation of mitochondrial ferritin (FtMt) level. Interestingly, forced expression of FtMt in ovarian cancer enhanced the apoptosis and inhibited tumor growth and the PKA inhibitor H89 and knockdown of CREB significantly repressed the expression of FtMt to restore the tumor proliferation and inhibit apoptosis. In addition, we found that Roflumilast-induced phosphorylated CREB directly promoted transcription of FtMt, indicating that Roflumilast up-regulated the expression of FtMt in ovarian cancer via cAMP/PKA/CREB signals. The anti-tumor role of Roflumilast in vivo was also demonstrated, the treatment of roflumilast effectively inhibited tumor proliferation and elevated the FtMt expression to restrict the tumor growth via the activation of cAMP/PKA/CREB signals in ovarian cancer.

Biology Informs Treatment Choices in Diffuse Large B Cell Lymphoma

The effective deployment of rationally developed therapies for diffuse large B cell lymphoma (DLBCL) requires rapid assimilation of new biological data. Within this framework, here we address topical issues at the intersection of DLBCL biology and the clinic. We discuss targeting of B cell receptor (BCR) signaling, with emphasis on identifying patients who may benefit from this maneuver and how to best achieve it. We address strategies to modulate the DLBCL microenvironment, including the use of immune checkpoint inhibitors in selected DLBCL subsets, and the potential activity of alternative antiangiogenic therapies. Lastly, we highlight the emerging recognition of MYC and BCL2 coexpression as the most robust predictor of DLBCL outcome, and discuss rationally conceived experimental approaches to treat these high-risk patients.

Roflumilast treatment inhibits lung carcinogenesis in benzo(a)pyrene-induced murine lung cancer model

Roflumilast, a potent and selective inhibitor of phosphodiesterase-4 (PDE4), has been used in treatment of COPD. PDE4 inhibitor is associated with inhibition of chronic airway inflammation, oxidative stress, and mesenchymal markers in B(a)P-induced lung tumors. The aim of this study was to assess whether roflumilast alone or added to inhaled budesonide might have dose-dependent inhibition on lung carcinogenesis induced by carcinogen B(a)P in mice. Female A/J mice were given a single dose of benzo(a)pyrene. Administration of roflumilast (1mg/kg or 5mg/kg) via oral gavage and aerosolized budesonide (2.25mg/ml) began 2 weeks post-carcinogen treatment and continued for 26 weeks. Tumor load was determined by averaging the total tumor volume in each group. Benzo(a)pyrene induced an average tumor size of 9.38 ± 1.75 tumors per mouse, with an average tumor load of 19.53 ± 3.81mm³. Roflumilast 5mg/kg treatment decreased (P < 0.05) tumor load per mouse compared to the B(a)P group. Roflumilast 5mg/kg treatment significantly increased the levels of cAMP in tumors with adjacent lung tissues (P < 0.05). The expression level of PDE4D gene was decreased by roflumilast 5mg/kg treatment, significantly (P < 0.05). Compared to the B(a)P exposure group, expression levels of HIF-1α and VEGFA were attenuated by roflumilast 5mg/kg treatment (P < 0.05). High-dose roflumilast can attenuate lung carcinogenesis in B(a)P-induced murine lung cancer model. The chemopreventive effect of roflumilast might be associated with inhibition of increased cAMP-mediated inflammatory process and markers of angiogenesis in tumor tissues.

Phosphodiesterase 4 inhibitors have wide-ranging activity in B-cell malignancies

Phosphodiesterase 4 (PDE4) inhibition restores the suppressive effects of 3',5'-cyclic adenosine monophosphate in lymphocytes. In this concise review, we detail how PDE4 inhibition downmodulates the B-cell receptor (BCR)-related kinases spleen tyrosine kinase and phosphatidylinositol 3-kinase and inhibits vascular endothelial growth factor A secretion by tumor cells, inducing cancer cell apoptosis and blocking angiogenesis in the microenvironment. We describe the successful clinical repurposing of PDE4 inhibitors in B-cell malignancies, and propose that given their anti-inflammatory/immunomodulatory activity, these agents will suppress BCR signals without the toxicity associated with other targeted biological doublets.