PDE5 inhibition eliminates cancer stem cells via induction of PKA signaling

Rethinking of phosphodiesterase 5 inhibition: the old, the new and the perspective in human health

The phosphodiesterases type 5 (PDE5) are catalytic enzymes converting the second messenger cyclic guanosine monophosphate (cGMP) to 5' GMP. While intracellular cGMP reduction is associated with several detrimental effects, cGMP stabilization associates with numerous benefits. The PDE5 specific inhibitors, PDE5i, found their explosive fortune as first-line treatment for erectile dysfunction (ED), due to their powerful vasoactive properties. The favorable effect for ED emerged as side-effect when PDE5i were originally proposed for coronary artery disease (CAD). From that point on, the use of PDE5i captured the attention of researchers, clinicians, and companies. Indeed, PDE5-induced intracellular cGMP stabilization offers a range of therapeutic opportunities associated not only with vasoactive effects, but also with immune regulatory/anti-inflammatory actions. Chronic inflammation is acknowledged as the common link underlying most non-communicable diseases, including metabolic and cardiac diseases, autoimmune and neurodegenerative disorders, cancer. In this scenario, the clinical exploitation of PDE5i is undeniably beyond ED, representing a potential therapeutic tool in several human diseases. This review aims to overview the biological actions exerted by PDE5i, focusing on their ability as modulators of inflammation-related human diseases, with particular attention to inflammatory-related disorders, like cardiac diseases and cancer.

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.

Piperlongumine based nanomedicine impairs glycolytic metabolism in triple negative breast cancer stem cells through modulation of GAPDH & FBP1

BACKGROUND

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and exhibits high rate of chemoresistance, metastasis, and relapse. This can be attributed to the failure of conventional therapeutics to target a sub-population of slow cycling or quiescent cells called as cancer stem cells (CSCs). Therefore, elimination of CSCs is essential for effective TNBC treatment.

PURPOSE

Research suggests that breast CSCs exhibit elevated glycolytic metabolism which directly contributes in maintenance of stemness, self-renewability and chemoresistance as well as in tumor progression. Therefore, this study aimed to target rewired metabolism which can serve as Achilles heel for CSCs population and have far reaching effect in TNBC treatment.

METHODS

We used two preclinical models, zebrafish and nude mice to evaluate the fate of nanoparticles as well as the therapeutic efficacy of both piperlongumine (PL) and its nanomedicine (PL-NPs).

RESULTS

In this context, we explored a phytochemical piperlongumine (PL) which has potent anti-cancer properties but poor pharmacokinetics impedes its clinical translation. So, we developed PLGA based nanomedicine for PL (PL-NPs), and demonstrated that it overcomes the pharmacokinetic limitations of PL, along with imparting advantages of selective tumor targeting through Enhanced Permeability and Retention (EPR) effect in zebrafish xenograft model. Further, we demonstrated that PL-NPs efficiently inhibit glycolysis in CSCs through inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by modulating glutathione S-transferase pi 1 (GSTP1) and upregulation of fructose-1,6-bisphosphatase 1 (FBP1), a rate-limiting enzyme in gluconeogenesis. We also illustrated that inhibition of glycolysis results in overall tumor regression in two preclinical models.

CONCLUSION

This study discusses novel mechanism of action by which PL acts on CSCSs. Taken together our study provides insight into development of PL based nanomedicine which could be exploited in clinics to achieve complete eradication of TNBC by targeting CSCs.

Drug repurposing and structure-based discovery of new PDE4 and PDE5 inhibitors

Phosphodiesterase-4 (PDE4) and PDE5 responsible for the hydrolysis of intracellular cAMP and cGMP, respectively, are promising targets for therapeutic intervention in a wide variety of diseases. Here, we report the discovery of novel, drug-like PDE4 inhibitors by performing a high-throughput drug repurposing screening of 2560 approved drugs and drug candidates in clinical trial studies. It allowed us to identify eight potent PDE4 inhibitors with IC50 values ranging from 0.41 to 2.46 μM. Crystal structures of PDE4 in complex with four compounds, namely ethaverine hydrochloride (EH), benzbromarone (BBR), CX-4945, and CVT-313, were further solved to elucidate molecular mechanisms of action of these new inhibitors, providing a solid foundation for optimizing the inhibitors to improve their potency as well as selectivity. Unexpectedly, selectivity profiling of other PDE subfamilies followed by crystal structure determination revealed that CVT-313 was also a potent PDE5 inhibitor with a binding mode similar to that of tadalafil, a marketed PDE5 inhibitor, but distinctively different from the binding mode of CVT-313 with PDE4. Structure-guided modification of CVT-313 led to the discovery of a new inhibitor, compound 2, with significantly improved inhibitory activity as well as selectivity towards PDE5 over PDE4. Together, these results highlight the utility of the drug repurposing in combination with structure-based drug design in identifying novel inhibitors of PDE4 and PDE5, which provides a prime example for efficient discovery of drug-like hits towards a given target protein.

Controlled delivery of sildenafil by β-Cyclodextrin-decorated sulfur-doped carbon nanodots: a synergistic activation of ROS signaling in tumors overexpressing PDE-5

Fluorescent sulfur- and nitrogen-doped carbon nanodots (CDs) are zero-dimensional nanoparticles that mediate ROS production in cancer cells, displaying inherent anticancer properties. Thus, they have been proposed as nanotheranostic tools useful in image-guided cancer therapy. Here, we try to show that cancerous cells (high PDE-5 expression) receiving sildenafil delivered by CDs-based nanostructures promote positive reinforcement of PDE-5-mediated cell death via the overexpression of genes involved in the production of ROS. We explored the regioselective Huisgen cycloaddition between azide-β-cyclodextrin and CDs-alkyne to synthetize homogeneous nanostructures, named CDs-PEG4-β-Cdx, consisting of CDs functionalized at the surface with β-cyclodextrins capable of including high amount drugs such as sildenafil (>20 % w/w), and releasing them in a controlled manner. We investigated how CDs-PEG4-β-Cdx bearing sildenafil enter cells, enhancing ROS production and cell death specifically in cancer cells overexpressing PDE-5. These nanoplatforms go beyond the bounds of EPR-based nanomedicines in which carriers are conceived as inert vehicles of toxic drugs. Our findings enable the development of clever anticancer nanoplatforms that synergistically combine nanomedicines that perturb the mitochondrial electron transport chain (ROS production) with PDE-5 inhibitors which trigger oxidative stress specifically in cancer cells regardless of their location.

Phosphodiesterase-5 Inhibitor Use in Robot Assisted Radical Prostatectomy Patients Is Associated with Reduced Risk of Death: A Propensity Score Matched Analysis of 1,058 Patients

PURPOSE

We investigated whether the use of a phosphodiesterase-5 inhibitor (PDE5i) after robot assited radical prostatectomy has a survival benefit over non-use patients because there are controversial results on the association between PDE5i use and survival outcomes for prostate cancer patients in literature.

MATERIALS AND METHODS

We designed a retrospective, matched, large-sample cohort study of 5,545 patients who underwent robot assisted radical prostatectomy (RARP) during 2013-2021 in a single institute. The exclusion criteria was patients who were aged >70 years at surgery, American Society of Anesthesiologists (ASA) physical status classification grade 4 or 5, history of other malignancies, patients who started PDE5i 6 months after survery and patients with follow up period less than 24 months after surgery. Among the 1,843 included patients, 1,298 were PDE5i users, and 545 were PDE5i non-users. We performed propensity score matching (PSM) of PDE5i users (n=529) with non-users (n=529) by adjusting for the variables of age, Gleason grade group, pathological T stage, preoperative ASA physical status grade, and International Index of Erectile Function score.

RESULTS

There were no significant difference in patient characteristics according to PSM. Kaplan-Meier curve revealed the difference of overall survival for PDE5i users and non-users (clustered log-rank test p<0.05). In a stratified Cox regression analysis, PDE5i use after RARP was associated with improved overall survival and reduced risk of death (hazard ratio 0.43; confidence interval 0.24-0.79; p=0.007). The limitation of this study was that the indication for the prescription of PDE5i was not given.

CONCLUSIONS

PDE5i administration after RARP were associated with overall survival of patients with prostate cancer. A further randomized control trial may reveal whether routine use of PDE5i after prostatectomy can improve survival of prostate cancer patient.

N6-methyladenosine (m6A) in cancer stem cell: From molecular mechanisms to therapeutic implications

The emergence of drug resistance and metastasis has long been a difficult problem for cancer treatment. Recent studies have shown that cancer stem cell populations are key factors in the regulation of cancer aggressiveness, relapse and drug resistance. Cancer stem cell (CSC) populations are highly plastic and self-renewing, giving them unique metabolic, metastatic, and chemotherapy resistance properties. N6-methyladenosine (m6A) is the most abundant internal modification of mRNA and is involved in a variety of cell growth and development processes, including RNA transcription, alternative splicing, degradation, and translation. It has also been linked to the development of various cancers. At present, the important role of m6A in tumour progression is gradually attracting attention, especially in the tumour stemness regulation process. Abnormal m6A modifications regulate tumour metastasis, recurrence and drug resistance. This paper aims to explore the regulatory mechanism of m6A in CSCs and clinical therapy, clarify its regulatory network, and provide theoretical guidance for the development of clinical targets and improvement of therapeutic effects.

KK-LC-1 as a therapeutic target to eliminate ALDH+ stem cells in triple negative breast cancer

Failure to achieve complete elimination of triple negative breast cancer (TNBC) stem cells after adjuvant therapy is associated with poor outcomes. Aldehyde dehydrogenase 1 (ALDH1) is a marker of breast cancer stem cells (BCSCs), and its enzymatic activity regulates tumor stemness. Identifying upstream targets to control ALDH⁺ cells may facilitate TNBC tumor suppression. Here, we show that KK-LC-1 determines the stemness of TNBC ALDH⁺ cells via binding with FAT1 and subsequently promoting its ubiquitination and degradation. This compromises the Hippo pathway and leads to nuclear translocation of YAP1 and ALDH1A1 transcription. These findings identify the KK-LC-1-FAT1-Hippo-ALDH1A1 pathway in TNBC ALDH⁺ cells as a therapeutic target. To reverse the malignancy due to KK-LC-1 expression, we employ a computational approach and discover Z839878730 (Z8) as an small-molecule inhibitor which may disrupt KK-LC-1 and FAT1 binding. We demonstrate that Z8 suppresses TNBC tumor growth via a mechanism that reactivates the Hippo pathway and decreases TNBC ALDH⁺ cell stemness and viability.

Functional Axis of PDE5/cGMP Mediates Timosaponin-AIII-Elicited Growth Suppression of Glioblastoma U87MG Cells

Glioblastoma (GBM) is the most aggressive brain tumor, with high mortality. Timosaponin AIII (TIA), a steroidal saponin isolated from the medicinal plant Anemarrhena asphodeloides Bge., has been shown to possess anticancer properties in various cancer types. However, the effect of TIA on GBM is unknown. In this study, we reveal that TIA not only inhibited U87MG in vitro cell growth but also in vivo tumor development. Moreover, we found that the cause of TIA-induced cell growth suppression was apoptosis. When seeking to uncover antitumor mechanisms of TIA, we found that TIA diminished the expression of cGMP-specific phosphodiesterase 5(PDE5) while elevating the levels of guanylate cyclases (sGCβ), cellular cGMP, and phosphorylation of VASP^ser239. Following the knockdown of PDE5, PDE5 inhibitor tadalafil and cGMP analog 8-Bro-cGMP both inhibited cell growth and inactivated β-catenin; we reason that TIA elicited an antitumor effect by suppressing PDE5, leading to the activation of the cGMP signaling pathway, which, in turn, impeded β-catenin expression. As β-catenin is key for cell growth and survival in GBM, this study suggests that TIA elicits its anti-tumorigenic effect by interfering with β-catenin function through the activation of a PDE5/cGMP functional axis.

Novel Non-Cyclooxygenase Inhibitory Derivative of Sulindac Inhibits Breast Cancer Cell Growth In Vitro and Reduces Mammary Tumorigenesis in Rats

The nonsteroidal anti-inflammatory drug (NSAID) sulindac demonstrates attractive anticancer activity, but the toxicity resulting from cyclooxygenase (COX) inhibition and the suppression of physiologically important prostaglandins precludes its long-term, high dose use in the clinic for cancer prevention or treatment. While inflammation is a known tumorigenic driver, evidence suggests that sulindac's antineoplastic activity is partially or fully independent of its COX inhibitory activity. One COX-independent target proposed for sulindac is cyclic guanosine monophosphate phosphodiesterase (cGMP PDE) isozymes. Sulindac metabolites, i.e., sulfide and sulfone, inhibit cGMP PDE enzymatic activity at concentrations comparable with those associated with cancer cell growth inhibitory activity. Additionally, the cGMP PDE isozymes PDE5 and PDE10 are overexpressed during the early stages of carcinogenesis and appear essential for cancer cell proliferation and survival based on gene silencing experiments. Here, we describe a novel amide derivative of sulindac, sulindac sulfide amide (SSA), which was rationally designed to eliminate COX-inhibitory activity while enhancing cGMP PDE inhibitory activity. SSA was 68-fold and 10-fold less potent than sulindac sulfide (SS) in inhibiting COX-1 and COX-2, respectively, but 10-fold more potent in inhibiting growth and inducing apoptosis in breast cancer cells. The pro-apoptotic activity of SSA was associated with inhibition of cGMP PDE activity, elevation of intracellular cGMP levels, and activation of cGMP-dependent protein kinase (PKG) signaling, as well as the inhibition of β-catenin/Tcf transcriptional activity. SSA displayed promising in vivo anticancer activity, resulting in a 57% reduction in the incidence and a 62% reduction in the multiplicity of tumors in the N-methyl-N-nitrosourea (MNU)-induced model of breast carcinogenesis. These findings provide strong evidence for cGMP/PKG signaling as a target for breast cancer prevention or treatment and the COX-independent anticancer properties of sulindac. Furthermore, this study validates the approach of optimizing off-target effects by reducing the COX-inhibitory activity of sulindac for future targeted drug discovery efforts to enhance both safety and efficacy.

Development of Nucleoside Diphosphate-Bearing Fragile Histidine Triad-Imaging Fluorescence Probes with Well-Tuned Hydrophobicity for Intracellular Delivery

Fluorescence-guided cancer surgery can dramatically improve recurrence rates and postoperative quality of life of patients by accurately distinguishing the boundary between normal and cancer tissues during surgery, thereby minimizing excision of normal tissue. One promising target in early stage cancer is fragile histidine triad (FHIT), a cancer suppressor protein with dinucleoside triphosphate hydrolase activity. In this study, we have developed fluorescence probes containing a nucleoside diphosphate moiety, which dramatically improves the reactivity and specificity for FHIT, and a moderately lipophilic ester moiety to increase the membrane permeability. The ester moiety is cleaved by ubiquitous intracellular esterases, and then, FHIT in the cells specifically cleaves nucleoside monophosphate. The remaining phosphate moiety is rapidly cleaved by ubiquitous intracellular phosphatases to release the fluorescent dye. We confirmed that this probe can detect FHIT activity in living cells. A comprehensive evaluation of the effects of various ester moieties revealed that probes with CLogP = 5-7 showed good membrane permeability and were good substrates of the target enzyme; these findings may be helpful in the rational design of other multiple phosphate-containing probes targeting intracellular enzymes.

Identifying General Tumor and Specific Lung Cancer Biomarkers by Transcriptomic Analysis

The bioinformatic pipeline previously developed in our research laboratory is used to identify potential general and specific deregulated tumor genes and transcription factors related to the establishment and progression of tumoral diseases, now comparing lung cancer with other two types of cancer. Twenty microarray datasets were selected and analyzed separately to identify hub differentiated expressed genes and compared to identify all the deregulated genes and transcription factors in common between the three types of cancer and those unique to lung cancer. The winning DEGs analysis allowed to identify an important number of TFs deregulated in the majority of microarray datasets, which can become key biomarkers of general tumors and specific to lung cancer. A coexpression network was constructed for every dataset with all deregulated genes associated with lung cancer, according to DAVID’s tool enrichment analysis, and transcription factors capable of regulating them, according to oPOSSUM´s tool. Several genes and transcription factors are coexpressed in the networks, suggesting that they could be related to the establishment or progression of the tumoral pathology in any tissue and specifically in the lung. The comparison of the coexpression networks of lung cancer and other types of cancer allowed the identification of common connectivity patterns with deregulated genes and transcription factors correlated to important tumoral processes and signaling pathways that have not been studied yet to experimentally validate their role in lung cancer. The Kaplan–Meier estimator determined the association of thirteen deregulated top winning transcription factors with the survival of lung cancer patients. The coregulatory analysis identified two top winning transcription factors networks related to the regulatory control of gene expression in lung and breast cancer. Our transcriptomic analysis suggests that cancer has an important coregulatory network of transcription factors related to the acquisition of the hallmarks of cancer. Moreover, lung cancer has a group of genes and transcription factors unique to pulmonary tissue that are coexpressed during tumorigenesis and must be studied experimentally to fully understand their role in the pathogenesis within its very complex transcriptomic scenario. Therefore, the downstream bioinformatic analysis developed was able to identify a coregulatory metafirm of cancer in general and specific to lung cancer taking into account the great heterogeneity of the tumoral process at cellular and population levels.

Phosphodiesterase 5 inhibitor sildenafil potentiates the antitumor activity of cisplatin by ROS-mediated apoptosis: a role of deregulated glucose metabolism

Cyclic nucleotide phosphodiesterase 5 (PDE5) has been recently identified to play a crucial role in the progression of many cancers. PDE5 promotes tumorigenesis by dysregulating various cellular processes such as proliferation, apoptosis, angiogenesis, and invasion and migration. Interestingly, multiple studies have reported the promising chemosensitizing potential of PDE5 inhibitor sildenafil in breast, colon, prostate, glioma, and lung cancers. However, to date, the chemosensitizing action of sildenafil is not evaluated in T cell lymphoma, a rare and challenging neoplastic disorder. Hence, the present investigation was undertaken to examine the chemosensitizing potential of sildenafil against T cell lymphoma along with elucidation of possible involvement of altered apoptosis and glucose metabolism. The experimental findings of this study showed that sildenafil enhances the cytotoxic ability of cisplatin by apoptosis induction through altering the levels of apoptosis regulatory molecules: Bcl-2, Bax, cytochrome c (Cyt c), cleaved caspase-3, and poly (ADP-ribose) polymerase (PARP). These molecular alterations were possibly driven by sildenafil through reactive oxygen species (ROS). Sildenafil deregulates glucose metabolism by markedly lowering the expression of glycolysis regulatory molecules, namely glucose transporter 1 (GLUT1), lactate dehydrogenase A (LDHA), hexokinase II (HKII), pyruvate kinase M2 (PKM2), and pyruvate dehydrogenase kinase 1 (PDK1) via suppressing hypoxia-inducible factor 1-alpha (HIF-1α) expression. Hence, sildenafil potentiates the tumor cell killing ability of cisplatin by augmenting ROS production through switching the glucose metabolism from glycolysis to oxidative phosphorylation (OXPHOS). Overall, our study demonstrates that sildenafil might be a promising adjunct therapeutic candidate in designing novel combinatorial chemotherapeutic regimens against T cell lymphoma.

Piperlongumine loaded PLGA nanoparticles inhibit cancer stem-like cells through modulation of STAT3 in mammosphere model of triple negative breast cancer

TNBC exhibits higher rate of chemoresistance, metastasis, and relapse among all subtypes of breast cancer. This malignant statein TNBC is due to self-renewing sub-population of cells called cancer stem cells (CSCs). They are major caveats in TNBC treatment and need to be obliterated. In this regard, we explored piperlongumine (PL) that has remarkable anti-cancerous property but poor pharmacokinetics limits its application. So, to enhance its biological activity we developed PLGA based nanoformulation for PL (PL-NPs) and examined anti-CSCs effects of PL and PL-NPs in mammospheres. Results indicated that PL-NPs have higher cellular uptake than PL in mammospheres. Further, we demonstrated that PL-NPs remarkably inhibit various characteristics of CSCs like expression of ALDH, self-renewability, chemoresistance, and EMT in mammopsheres. We next investigated the possible mechanism underlying these multi-modal effects, and found that inhibition of STAT3 might be the driving force. In order to confirm this, we used colivelin a potent synthetic peptide activator of STAT3 in combination with treatments and found that anti-CSCs effects of PL and PL-NPs were reversed. Taken together, our data indicates that PL-NPs show enhanced inhibition of CSCs through downregulation of STAT3 and provides insight into development of PL based nanomedicine for targeting CSCs in TNBC.

Autophagy inhibits cancer stemness in triple-negative breast cancer via miR-181a-mediated regulation of ATG5 and/or ATG2B

Autophagy has a dual role in the maintenance of cancer stem cells (CSCs), but the precise relationship between autophagy and cancer stemness requires further investigation. In this study, it was found that luminal and triple‐negative breast cancers require distinct therapeutic approaches because of their different amounts of autophagy flux. We identified that autophagy flux was inhibited in triple‐negative breast cancer (TNBC) CSCs. Moreover, miRNA‐181a (miR‐181a) expression is upregulated in both TNBC CSCs and patient tissues. Autophagy‐related 5 (ATG5) and autophagy‐related 2B (ATG2B) participate in the early formation of autophagosomes and were revealed as targets of miR‐181a. Inhibition of miR‐181a expression led to attenuation of TNBC stemness and an increase in autophagy flux. Furthermore, treatment with curcumin led to attenuation of cancer stemness in TNBC CSCs; the expression of ATG5 and ATG2B was enhanced and there was an increase of autophagy flux. These results indicated that ATG5 and ATG2B are involved in the suppression of cancer stemness in TNBC. In summary, autophagy inhibits cancer stemness through the miR‐181a‐regulated mechanism in TNBC. Promoting tumor‐suppressive autophagy using curcumin may be a potential method for the treatment of TNBC.

Pros and Cons of Pharmacological Manipulation of cGMP-PDEs in the Prevention and Treatment of Breast Cancer

The cyclic nucleotides, cAMP and cGMP, are ubiquitous second messengers responsible for translating extracellular signals to intracellular biological responses in both normal and tumor cells. When these signals are aberrant or missing, cells may undergo neoplastic transformation or become resistant to chemotherapy. cGMP-hydrolyzing phosphodiesterases (PDEs) are attracting tremendous interest as drug targets for many diseases, including cancer, where they regulate cell growth, apoptosis and sensitization to radio- and chemotherapy. In breast cancer, PDE5 inhibition is associated with increased intracellular cGMP levels, which is responsible for the phosphorylation of PKG and other downstream molecules involved in cell proliferation or apoptosis. In this review, we provide an overview of the most relevant studies regarding the controversial role of PDE inhibitors as off-label adjuvants in cancer therapy.

Sildenafil Citrate Downregulates PDE5A mRNA Expression in Women with Recurrent Pregnancy Loss without Altering Angiogenic Factors-A Preliminary Study

In our previous study, we showed that sildenafil citrate (SC), a selective PDE5A blocker, modulated NK cell activity in patients with recurrent pregnancy loss, which correlated with positive pregnancy outcomes. It was found that NK cells had a pivotal role in decidualization, angiogenesis, spiral artery remodeling, and the regulation of trophoblast invasion. Thus, in the current study, we determined the effects of SC on angiogenic factor expression and production, as well as idNK cell activity in the presence of nitric synthase blocker L-NMMA. Methods: NK cells (CD56⁺) were isolated from the peripheral blood of 15 patients and 15 fertile women on MACS columns and cultured in transformation media containing IL-15, TGF-β, and AZA—a methylation agent—for 7 days in hypoxia (94% N₂, 1% O₂, 5% CO₂). Cultures were set up in four variants: (1) with SC, (2) without SC, (3) with NO, a synthase blocker, and (4) with SC and NO synthase blocker. NK cell activity was determined after 7 days of culturing as CD107a expression after an additional 4h of stimulation with K562 erythroleukemia cells. The expression of the PDE5A, VEGF-A, PIGF, IL-8, and RENBP genes was determined with quantitative real-time PCR (qRT-PCR) using TaqMan probes and ELISA was used to measure the concentrations of VEGF-A, PLGF, IL-8, Ang-I, Ang-II, IFN–γ proteins in culture supernatants after SC supplementation. Results: SC downregulated PDE5A expression and had no effect on other studied angiogenic factors. VEGF-A expression was increased in RPL patients compared with fertile women. Similarly, VEGF production was enhanced in RPL patients’ supernatants and SC increased the concentration of PIGF in culture supernatants. SC did not affect the expression or concentration of other studied factors, nor idNK cell activity, regardless of NO synthase blockade.

High-Risk HPV16 E6 Activates the cGMP/PKG Pathway Through Glycosyltransferase ST6GAL1 in Cervical Cancer Cells

Alterations in glycosylation regulate fundamental molecular and cellular processes of cancer, serving as important biomarkers and therapeutic targets. However, the potential association and regulatory mechanisms of E6 oncoprotein on glycosylation of cervical cancer cells are still unclear. Here, we evaluated the glycomic changes via using Lectin microarray and determined the corresponding enzymes associated with endogenous high-risk HPV16 E6 expression in cervical cancer cells. α-2,6 sialic acids and the corresponding glycosyltransferase ST6GAL1 were significantly increased in E6 stable-expressing HPV- cervical cancer C33A cells. Clinical validation further showed that the expression of ST6GAL1 was significantly increased in patients infected with high-risk HPV subtypes and showed a positive association with E6 in cervical scraping samples. Interfering ST6GAL1 expression markedly blocked the oncogenic effects of E6 on colony formulation, proliferation, and metastasis. Importantly, ST6GAL1 overexpression enhanced tumorigenic activities of both E6-positive and E6-negative cells. Mechanistical investigations revealed that E6 depended on activating YAP1 to stimulate ST6GAL1 expression, as verteporfin (inhibitor of YAP1) significantly suppressed the E6-induced ST6GAL1 upregulation. E6/ST6GAL1 triggered the activation of downstream cGMP/PKG signaling pathway and ODQ (inhibitor of GMP production) simultaneously suppressed the oncogenic activities of both E6 and ST6GAL1 in cervical cancer cells. Taken together, these findings indicate that ST6GAL1 is an important mediator for oncogenic E6 protein to activate the downstream cGMP/PKG signaling pathway, which represents a novel molecular mechanism and potential therapeutic targets for cervical cancer.

Integration of Transcriptomics and Metabolomics to Reveal the Molecular Mechanisms Underlying Rhodium Nanoparticles-Based Photodynamic Cancer Therapy

Rhodium nanoparticles have recently been described as promising photosensitizers due to their low toxicity in the absence of near-infrared irradiation, but their high cytotoxicity when irradiated. Irradiation is usually carried out with a laser source, which allows the treatment to be localized in a specific area, thus avoiding undesirable side effects on healthy tissues. In this study, a multi-omics approach based on the combination of microarray-based transcriptomics and mass spectrometry-based untargeted and targeted metabolomics has provided a global picture of the molecular mechanisms underlying the anti-tumoral effect of rhodium nanoparticle-based photodynamic therapy. The results have shown the ability of these nanoparticles to promote apoptosis by suppressing or promoting anti- and pro-apoptotic factors, respectively, and by affecting the energy machinery of tumor cells, mainly blocking the β-oxidation, which is reflected in the accumulation of free fatty acids and in the decrease in ATP, ADP and NAD+ levels.

Tadalafil Reverses the Effect of Three-Dimensional Cell Culture System on Stem Cell Features in A549 and SK-MES-1

Background: Non-small cell lung cancer is the most common type of lung cancer and is a frequent cause of death. In our research, A549 and SK-MES-1 were used to assess the effect of three-dimensional (3D) culture compared to that of two-dimensional (2D) monolayers in cell proliferation, migration, and invasion, response to chemotherapy, as well as the expression of epithelial to mesenchymal transition (EMT) and cancer stem cell (CSC)-related markers. As tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor with the potential to target CSC maintenance in multiple cancer cell lines, we assessed its function in 3D culture and detected the downstream pathway genes. Methods: We compared the viability and proliferation capacity of A549 and SK-MES-1 cells in 2D and 3D culture by cell counting kit (CCK)-8, foci formation, and Live/Dead double stain (Operetta CLS High content screening). Migration, invasion, and other functions were also assessed. To elucidate the underlying mechanisms, the expression of EMT and CSC markers was analyzed by quantitative real-time PCR (qPCR) and Western blot. Results: A549 and SK-MES-1 cells formed spheroids heterogeneous in shape and size. In our 3D spheroid systems, cells went through EMT, and were also capacitated with higher stemness and chemoresistance. Combination use of tadalafil and cisplatin showed higher chemotherapy efficiency in the 3D model, compared to that of the 2D cell culture. Conclusion: Our research aims at the notable differences between these two cellular systems in terms of cell functions, EMT, and stemness-associated gene expression and chemo-response. We showed that a commonly used drug, tadalafil, showed more pronounced inhibitory effects when cells were cultured in the 3D model. Since the 3D culture system could imitate the in vivo behavior of cancer cells within the tumor, we advocate that this system is superior to traditional 2D culture and should be used in the investigation of new therapeutic compounds.

Sildenafil prevents HDACi-induced Epstein-Barr virus reactivation through the PKG pathway in NK/T cell lymphoma; potential implications for HDACi-mediated fatal complications

Romidepsin, a histone deacetylase (HDAC) inhibitor, has been approved for the treatment of relapsed and refractory peripheral T-cell lymphoma. However the use of romidepsin reportedly causes potent EBV (Epstein-Barr virus) reactivation leading to severe adverse events in patients with natural killer (NK)/T-cell lymphoma (NKTL). As inhibition of EBV lytic cycle reactivation may help prevent romidepsin-induced adverse events in NKTL, we herein set out to identify a safe and effective drug for inhibiting EBV reactivation and examine its mechanism of inhibition. EBV reactivation was evaluated by qRT-PCR of BZLF1 and BRLF1 mRNA expression, qPCR of EBV DNA, and immunoblotting of viral EA-D protein. High-throughput screening of FDA-approved drugs was performed to identify safe and effective molecules and test their effect on romidepsin-induced EBV reactivation in the EBV-positive NKTL cell lines, SNK6 and NK92MI. We found that phosphodiesterase 5 (PDE5) inhibitors, including sildenafil (Viagra; Pfizer), appeared to be nontoxic and effective inhibitors of romidepsin-induced EBV reactivation. Clinical relevance was investigated by qPCR of EBV in two primary effusion samples of NKTL patients. We also investigated the molecular consequences downstream of sildenafil-induced PDE5 inhibition in NKTL cells. A negative correlation was established between the cGMP/PKG pathway and EBV reactivation in NKTL cells. On a molecular level, PDE5 inhibition downregulates BZLF1 and BRLF1 through cGMP/PKG signaling-induced ZNF overexpression. Co-treatment with romidepsin and sildenafil (inhibiting HDAC and PDE5, respectively) showed a synergistic inhibitory effect on NKTL cells, highlighting PDE5 as an attractive target for future therapy in NKTL.

Novel molecular regulators of breast cancer stem cell plasticity and heterogeneity

Tumors consist of heterogeneous cell populations, and tumor heterogeneity plays key roles in regulating tumorigenesis, metastasis, recurrence and resistance to anti-tumor therapies. More and more studies suggest that cancer stem cells (CSCs) promote tumorigenesis, metastasis, recurrence and drug resistance as well as are the major source for heterogeneity of cancer cells. CD24^-CD44⁺ and ALDH⁺ are the most common markers for breast cancer stem cells (BCSCs). Previous studies showed that different BCSC markers label different BCSC populations, indicating the heterogeneity of BCSCs. Therefore, defining the regulation mechanisms of heterogeneous BCSCs is essential for precisely targeting BCSCs and treating breast cancer. In this review, we summarized the novel regulators existed in BCSCs and their niches for BCSC heterogeneity which has been discovered in recent years, and discussed their regulation mechanisms and the latest corresponding cancer treatments, which will extend our understanding on BCSC heterogeneity and plasticity, and provide better prognosis prediction and more efficient novel therapeutic strategies for breast cancer.

New Approaches in Oncology for Repositioning Drugs: The Case of PDE5 Inhibitor Sildenafil

The use of already-approved drugs to treat new or alternative diseases has proved to be beneficial in medicine, because it reduces both drug development costs and timelines. Most drugs can be used to treat different illnesses, due their mechanisms of action are not restricted to one molecular target, organ or illness. Diverging from its original intent offers an opportunity to repurpose previously approved drugs to treat other ailments. This is the case of sildenafil (Viagra), a phosphodiesterase-5 (PDE5) inhibitor, which was originally designed to treat systemic hypertension and angina but is currently commercialized as erectile dysfunction treatment. Sildenafil, tadalafil, and vardenafil are PDE5 inhibitors and potent vasodilators, that extend the physiological effects of nitric oxide and cyclic guanosine monophosphate (cGMP) signaling. Although most of the biological implications of these signaling regulations remain unknown, they offer a large therapeutic potential for several diseases. In addition, some PDE5 inhibitors' molecular effects seem to play a key role in different illnesses such as kidney disease, diabetes mellitus, and cancer. In this review, we discuss the molecular effects of PDE5 inhibitors and their therapeutic repurposing in different types of cancer.

The novel ZEB1-upregulated protein PRTG induced by Helicobacter pylori infection promotes gastric carcinogenesis through the cGMP/PKG signaling pathway

Helicobacter pylori (H. pylori) is listed as a class I carcinogen in human gastric cancer; however, the underlying mechanisms are poorly understood. In this study, we identified Protogenin (PRTG) was upregulated in both gastric cancer tissues and H. pylori-infected tissues by analyzing dysregulated genes in TCGA and GEO databases. Importantly, upregulated PRTG predicted poor prognosis of gastric cancer patients and integrative analysis revealed that PRTG served as an oncogenic protein in gastric cancer and was required for H. pylori-mediated tumorigenic activities in in vitro cellular and in vivo tumor-bearing mouse models. Mechanistically, H. pylori infection enhanced PRTG expression by promoting transcriptional factor ZEB1 stabilization and recruitment to the PRTG promoter, and which then activated the sub-following cGMP/PKG signaling pathway in bioinformatic and cellular studies. Cellular studies further confirmed that PRTG depended on activating cGMP/PKG axis to promote proliferation, metastasis, and chemoresistance of gastric cancer cells. The PKG inhibitor KT5823 played synergistic anti-tumor effects with cisplatin and paclitaxel to gastric cancer cells in in vitro cellular and in vivo tumor-bearing mouse models. Taken together, our findings suggested that H. pylori infection depends on ZEB1 to induce PRTG upregulation, and which leading to the development and progression of gastric cancer through activating cGMP/PKG signaling pathway. Blocking PRTG/cGMP/PKG axis, therefore, presents a promising novel therapeutic strategy for gastric cancer.

Limiting Self-Renewal of the Basal Compartment by PKA Activation Induces Differentiation and Alters the Evolution of Mammary Tumors

Differentiation therapy utilizes our understanding of the hierarchy of cellular systems to pharmacologically induce a shift toward terminal commitment. While this approach has been a paradigm in treating certain hematological malignancies, efforts to translate this success to solid tumors have met with limited success. Mammary-specific activation of PKA in mouse models leads to aberrant differentiation and diminished self-renewing potential of the basal compartment, which harbors mammary repopulating cells. PKA activation results in tumors that are more benign, exhibiting reduced metastatic propensity, loss of tumor-initiating potential, and increased sensitivity to chemotherapy. Analysis of tumor histopathology revealed features of overt differentiation with papillary characteristics. Longitudinal single-cell profiling at the hyperplasia and tumor stages uncovered an altered path of tumor evolution whereby PKA curtails the emergence of aggressive subpopulations. Acting through the repression of SOX4, PKA activation promotes tumor differentiation and represents a possible adjuvant to chemotherapy for certain breast cancers.

Metabolic rewiring in the promotion of cancer metastasis: mechanisms and therapeutic implications

Tumor metastasis is the major cause of mortality from cancer. Metabolic rewiring and the metastatic cascade are highly intertwined, co-operating to promote multiple steps of cancer metastasis. Metabolites generated by cancer cells influence the metastatic cascade, encompassing epithelial-mesenchymal transition (EMT), survival of cancer cells in circulation, and metastatic colonization at distant sites. A variety of molecular mechanisms underlie the prometastatic effect of tumor-derived metabolites, such as epigenetic deregulation, induction of matrix metalloproteinases (MMPs), promotion of cancer stemness, and alleviation of oxidative stress. Conversely, metastatic signaling regulates expression and activity of rate-limiting metabolic enzymes to generate prometastatic metabolites thereby reinforcing the metastasis cascade. Understanding the complex interplay between metabolism and metastasis could unravel novel molecular targets, whose intervention could lead to improvements in the treatment of cancer. In this review, we summarized the recent discoveries involving metabolism and tumor metastasis, and emphasized the promising molecular targets, with an update on the development of small molecule or biologic inhibitors against these aberrant situations in cancer.

FTO-Dependent N 6-Methyladenosine Modifications Inhibit Ovarian Cancer Stem Cell Self-Renewal by Blocking cAMP Signaling

N 6-Methyladenosine (m6A) is the most abundant modification of mammalian mRNAs. RNA methylation fine tunes RNA stability and translation, altering cell fate. The fat mass- and obesity-associated protein (FTO) is an m6A demethylase with oncogenic properties in leukemia. Here, we show that FTO expression is suppressed in ovarian tumors and cancer stem cells (CSC). FTO inhibited the self-renewal of ovarian CSC and suppressed tumorigenesis in vivo, both of which required FTO demethylase activity. Integrative RNA sequencing and m6A mapping analysis revealed significant transcriptomic changes associated with FTO overexpression and m6A loss involving stem cell signaling, RNA transcription, and mRNA splicing pathways. By reducing m6A levels at the 3'UTR and the mRNA stability of two phosphodiesterase genes (PDE1C and PDE4B), FTO augmented second messenger 3', 5'-cyclic adenosine monophosphate (cAMP) signaling and suppressed stemness features of ovarian cancer cells. Our results reveal a previously unappreciated tumor suppressor function of FTO in ovarian CSC mediated through inhibition of cAMP signaling. SIGNIFICANCE: A new tumor suppressor function of the RNA demethylase FTO implicates m6A RNA modifications in the regulation of cyclic AMP signaling involved in stemness and tumor initiation.

Protein Kinase A Distribution in Meningioma

Deregulation of intracellular signal transduction pathways is a hallmark of cancer cells, clearly differentiating them from healthy cells. Differential intracellular distribution of the cAMP-dependent protein kinases (PKA) was previously detected in cell cultures and in vivo in glioblastoma and medulloblastoma. Our goal is to extend this observation to meningioma, to explore possible differences among tumors of different origins and prospective outcomes. The distribution of regulatory and catalytic subunits of PKA has been examined in tissue specimens obtained during surgery from meningioma patients. PKA RI subunit appeared more evenly distributed throughout the cytoplasm, but it was clearly detectable only in some tumors. RII was present in discrete spots, presumably at high local concentration; these aggregates could also be visualized under equilibrium binding conditions with fluorescent 8-substituted cAMP analogues, at variance with normal brain tissue and other brain tumors. The PKA catalytic subunit showed exactly overlapping pattern to RII and in fixed sections could be visualized by fluorescent cAMP analogues. Gene expression analysis showed that the PKA catalytic subunit revealed a significant correlation pattern with genes involved in meningioma. Hence, meningioma patients show a distinctive distribution pattern of PKA regulatory and catalytic subunits, different from glioblastoma, medulloblastoma, and healthy brain tissue. These observations raise the possibility of exploiting the PKA intracellular pathway as a diagnostic tool and possible therapeutic interventions.

Repurposing mechanistic insight of PDE-5 inhibitor in cancer chemoprevention through mitochondrial-oxidative stress intervention and blockade of DuCLOX signalling

BACKGROUND

This study evaluates the anti-cancer effects of Tadalafil (potent PDE-5 inhibitor) in female albino wistar rats against n-methyl n-nitrosourea induced mammary gland carcinogenesis.

METHODS

The animals were selected and randomly divided among four groups and each group contains six animals per group. The animal tissue and serum samples were evaluated for the presence of antioxidant parameters and the cellular morphology was studied using carminic staining, haematoxylin staining and scanning electron microscopy followed by immunoblotting analysis.

RESULTS

On the grounds of hemodynamic recordings and morphology, n-methyl n-nitrosourea treated group showed distorted changes along with distorted morphological parameters. For morphological analysis, the mammary gland tissues were evaluated using scanning electron microscopy, whole mount carmine staining, haematoxylin and eosin staining. The serum samples were evaluated for the evaluation of oxidative stress markers and inflammatory markers. The level of caspase 3 and 8 were also evaluated for the estimation of apoptosis. The fatty acid profiling of mammary gland tissue was evaluated using fatty acid methyl esters formation. The mitochondrial mediated apoptosis and inflammatory markers were evaluated using immunoblotting assay.

CONCLUSION

The results confirm that Tadalafil treatment restored all the biological markers to the normal and its involvement in mitochondrial mediated death apoptosis pathway along with inhibition of inflammatory markers.

Robustness of Nutrient Signaling Is Maintained by Interconnectivity Between Signal Transduction Pathways

Systems biology approaches provide means to study the interplay between biological processes leading to the mechanistic understanding of the properties of complex biological systems. Here, we developed a vector format rule-based Boolean logic model of the yeast S. cerevisiae cAMP-PKA, Snf1, and the Snf3-Rgt2 pathway to better understand the role of crosstalk on network robustness and function. We identified that phosphatases are the common unknown components of the network and that crosstalk from the cAMP-PKA pathway to other pathways plays a critical role in nutrient sensing events. The model was simulated with known crosstalk combinations and subsequent analysis led to the identification of characteristics and impact of pathway interconnections. Our results revealed that the interconnections between the Snf1 and Snf3-Rgt2 pathway led to increased robustness in these signaling pathways. Overall, our approach contributes to the understanding of the function and importance of crosstalk in nutrient signaling.

Breast cancer stem cells: Features, key drivers and treatment options

The current view is that breast cancer is a stem cell disease characterized by the existence of cancer cells with stem-like features and tumor-initiating potential. These cells are made responsible for tumor dissemination and metastasis. Common therapies by chemotherapeutic drugs fail to eradicate these cells and rather increase the pool of cancer stem cells in tumors, an effect that may increase the likelyhood of recurrence. Fifteen years after the first evidence for a small stem-like subpopulation playing a major role in breast cancer initiation has been published a large body of knowledge has been accumulated regarding the signaling cascades and proteins involved in maintaining stemness in breast cancer. Differences in the stem cell pool size and in mechanisms regulating stemness in the different breast cancer subtypes have emerged. Overall, this knowledge offers new approaches to intervene with breast cancer stem cell activity. New options are particularly needed for the treatment of triple-negative breast cancer subtype, which is particularly rich in cancer stem cells and is also the subtype for which specific therapies are still not available.