Oxidative Stress and Cellular Response to Doxorubicin: A Common Factor in the Complex Milieu of Anthracycline Cardiotoxicity

The production of reactive species is a core of the redox cycling profile of anthracyclines. However, these molecular characteristics can be viewed as a double-edged sword acting not only on neoplastic cells but also on multiple cellular targets throughout the body. This phenomenon translates into anthracycline cardiotoxicity that is a serious problem in the growing population of paediatric and adult cancer survivors. Therefore, better understanding of cellular processes that operate within but also go beyond cardiomyocytes is a necessary step to develop more effective tools for the prevention and treatment of progressive and often severe cardiomyopathy experienced by otherwise successfully treated oncologic patients. In this review, we focus on oxidative stress-triggered cellular events such as DNA damage, senescence, and cell death implicated in anthracycline cardiovascular toxicity. The involvement of progenitor cells of cardiac and extracardiac origin as well as different cardiac cell types is discussed, pointing to molecular signals that impact on cell longevity and functional competence.

Epithelial memory of inflammation limits tissue damage while promoting pancreatic tumorigenesis

Inflammation is a major risk factor for pancreatic ductal adenocarcinoma (PDAC). When occurring in the context of pancreatitis, KRAS mutations accelerate tumor development in mouse models. We report that long after its complete resolution, a transient inflammatory event primes pancreatic epithelial cells to subsequent transformation by oncogenic KRAS. Upon recovery from acute inflammation, pancreatic epithelial cells display an enduring adaptive response associated with sustained transcriptional and epigenetic reprogramming. Such adaptation enables the reactivation of acinar-to-ductal metaplasia (ADM) upon subsequent inflammatory events, thereby limiting tissue damage through a rapid decrease of zymogen production. We propose that because activating mutations of KRAS maintain an irreversible ADM, they may be beneficial and under strong positive selection in the context of recurrent pancreatitis.

The Natural cAMP Elevating Compound Forskolin in Cancer Therapy: Is It Time?

Cancer is a major public health problem and the second leading cause of mortality around the world. Although continuous advances in the science of oncology and cancer research are now leading to improved outcomes for many cancer patients, novel cancer treatment options are strongly demanded. Naturally occurring compounds from a variety of vegetables, fruits, and medicinal plants have been shown to exhibit various anticancer properties in a number of in vitro and in vivo studies and represent an attractive research area for the development of new therapeutic strategies to fight cancer. Forskolin is a diterpene produced by the roots of the Indian plant Coleus forskohlii. The natural compound forskolin has been used for centuries in traditional medicine and its safety has also been documented in conventional modern medicine. Forskolin directly activates the adenylate cyclase enzyme, that generates cAMP from ATP, thus, raising intracellular cAMP levels. Notably, cAMP signaling, through the PKA-dependent and/or -independent pathways, is very relevant to cancer and its targeting has shown a number of antitumor effects, including the induction of mesenchymal-to-epithelial transition, inhibition of cell growth and migration and enhancement of sensitivity to conventional antitumor drugs in cancer cells. Here, we describe some features of cAMP signaling that are relevant to cancer biology and address the state of the art concerning the natural cAMP elevating compound forskolin and its perspectives as an effective anticancer agent. J. Cell. Physiol. 232: 922-927, 2017. © 2016 Wiley Periodicals, Inc.

Lactic dehydrogenase and cancer: an overview

Despite the intense scientific efforts made, there are still many tumors that are difficult to treat and the percentage of patient survival in the long-term is still too low. Thus, new approaches to the treatment of cancer are needed. Cancer is a highly heterogeneous and complex disease, whose development requires a reorganization of cell metabolism. Most tumor cells downregulate mitochondrial oxidative phosphorylation and increase the rate of glucose consumption and lactate release, independently of oxygen availability (Warburg effect). This metabolic rewiring is largely believed to favour tumor growth and survival, although the underlying molecular mechanisms are not completely understood. Importantly, the correlation between the aerobic glycolysis and cancer is widely regarded as a useful biochemical basis for the development of novel anticancer strategies. Among the enzymes involved in glycolysis, lactate dehydrogenase (LDH) is emerging as a very attractive target for possible pharmacological approaches in cancer therapy. This review addresses the state of the art and the perspectives concerning LDH both as a useful diagnostic marker and a relevant molecular target in cancer therapy and management.

p53 Is a Master Regulator of Proteostasis in SMARCB1-Deficient Malignant Rhabdoid Tumors

Alterations in chromatin remodeling genes have been increasingly implicated in human oncogenesis. Specifically, the biallelic inactivation of the SWI/SNF subunit SMARCB1 results in the emergence of extremely aggressive pediatric malignancies. Here, we developed embryonic mosaic mouse models of malignant rhabdoid tumors (MRTs) that faithfully recapitulate the clinical-pathological features of the human disease. We demonstrated that SMARCB1-deficient malignancies exhibit dramatic activation of the unfolded protein response (UPR) and ER stress response via a genetically intact MYC-p19^ARF-p53 axis. As a consequence, these tumors display an exquisite sensitivity to agents inducing proteotoxic stress and inhibition of the autophagic machinery. In conclusion, our findings provide a rationale for drug repositioning trials investigating combinations of agents targeting the UPR and autophagy in SMARCB1-deficient MRTs.

Targeting CREB in Cancer Therapy: A Key Candidate or One of Many? An Update

Simple Summary

Only 5% of all drug-related targets currently move from preclinical to clinical in cancer, and just some of them achieve patient’s bedside. Among others, intratumor heterogeneity and preclinical cancer model limitations actually represent the main reasons for this failure. Cyclic-AMP response element-binding protein (CREB) has been defined as a proto-oncogene in different tumor types, being involved in maintenance and progression. Due to its relevance in tumor pathophysiology, many CREB inhibitor compounds have been developed and tested over the years. Herein, we examine the current state-of-the-art of both CREB and CREB inhibitors in cancer, retracing some of the most significant findings of the last years. While the scientific statement confers on CREB a proactive role in cancer, its therapeutic potential is still stuck at laboratory bench. Therefore, pursuing every concrete result to achieve CREB inhibition in clinical might give chance and future to cancer patients worldwide.

Abstract

Intratumor heterogeneity (ITH) is considered the major disorienting factor in cancer treatment. As a result of stochastic genetic and epigenetic alterations, the appearance of a branched evolutionary shape confers tumor plasticity, causing relapse and unfavorable clinical prognosis. The growing evidence in cancer discovery presents to us “the great paradox” consisting of countless potential targets constantly discovered and a small number of candidates being effective in human patients. Among these, cyclic-AMP response element-binding protein (CREB) has been proposed as proto-oncogene supporting tumor initiation, progression and metastasis. Overexpression and hyperactivation of CREB are frequently observed in cancer, whereas genetic and pharmacological CREB downregulation affects proliferation and apoptosis. Notably, the present review is designed to investigate the feasibility of targeting CREB in cancer therapy. In particular, starting with the latest CREB evidence in cancer pathophysiology, we evaluate the advancement state of CREB inhibitor design, including the histone lysine demethylases JMJD3/UTX inhibitor GSKJ4 that we newly identified as a promising CREB modulator in leukemia cells. Moreover, an accurate analysis of strengths and weaknesses is also conducted to figure out whether CREB can actually represent a therapeutic candidate or just one of the innumerable preclinical cancer targets.

S-Adenosylmethionine Affects ERK1/2 and Stat3 Pathways and Induces Apotosis in Osteosarcoma Cells

Osteosarcoma is a very aggressive bone tumor. Its clinical outcome remains discouraging despite intensive surgery, radiotherapy, and chemotherapy. Thus, novel therapeutic approaches are demanded. S-Adenosylmethionine (AdoMet) is a naturally occurring molecule that is synthesized in our body by methionine adenosyltransferase isoenzymes and is also available as a nutritional supplement. AdoMet is the principal methyl donor in numerous methylation reactions and is involved in many biological functions. Interestingly, AdoMet has been shown to exert antiproliferative action in various cancer cells. However, the underlying molecular mechanisms are just starting to be studied. Here, we investigated the effects of AdoMet on the proliferation of osteosarcoma U2OS cells and the underlying mechanisms. We carried out direct cell number counting, MTT and flow cytometry-based assays, and immunoblotting experiments in response to AdoMet treatment. We found that AdoMet strongly inhibits proliferation of U2OS cells by slowing-down cell cycle progression and by inducing apoptosis. We also report that AdoMet consistently causes an increase of p53 and p21 cell-cycle inhibitor, a decrease of cyclin A and cyclin E protein levels, and a marked increase of pro-apoptotic Bax/Bcl-2 ratio, with caspase-3 activation and PARP cleavage. Moreover, the AdoMet-induced antiproliferative effects were dynamically accompanied by profound changes in ERK1/2 and STAT3 protein and phosphorylation levels. Altogether, our data enforce the evidence of AdoMet acting as a biomolecule with antiproliferative action in osteosarcoma cells, capable of down-regulating ERK1/2 and STAT3 pathways leading to cell cycle inhibition and apoptosis, and provide a rationale for the possible use of AdoMet in osteosarcoma therapy.

cAMP Elevation Down-Regulates β3 Integrin and Focal Adhesion Kinase and Inhibits Leptin-Induced Migration of MDA-MB-231 Breast Cancer Cells

Breast cancer is one of the most common malignancies and a major cause of cancer death among women worldwide. The high mortality rate associated with breast cancer is mainly due to a propensity of the tumor to metastasize, even if small or undetectable. Given the relevant role of leptin in breast cancer growth and metastasis, novel strategies to counteract biological effects of this obesity-linked cytokine are warranted. Recently, we demonstrated that in MDA-MB-231 breast cancer cells, intracellular cAMP elevation completely abrogates both ERK1/2 and STAT3 phosphorylation in response to leptin. Very surprisingly, this provided evidence that when cAMP levels are increased, leptin drives cells towards apoptosis associated with a marked decrease of Bcl2 protein levels and accompanied by down-regulation of protein kinase A (PKA). The aim of the current study was to investigate the role of cAMP in leptin-associated motility of breast cancer cells. Here we show that cAMP elevation completely prevents leptin-induced migration of MDA-MB-231 breast cancer cells. Interestingly, the inhibition by cAMP-elevating agents of leptin-mediated cell migration is accompanied by a strong decrease of β3 integrin subunit and focal adhesion kinase (FAK) protein levels. Analysis of the underlying cAMP-dependent molecular mechanisms revealed that PKA blockers partly counteract the inhibition of leptin-induced migration and completely prevent the antiproliferative action by cAMP elevation. Moreover, a cAMP analogue that specifically activates Epac and not PKA has an inhibitory effect on leptin-induced cell migration as well. The present study confirms initial evidence for the efficacy of cAMP elevation against oncogenic effects of leptin, identifies β3 integrin subunit and FAK as proteins strongly down-regulated by cAMP elevation, and suggests that both cAMP/PKA- and cAMP/Epac-dependent pathways are involved in inhibition of leptin-induced migration of MDA-MB-231 breast cancer cells. The potential clinical significance and therapeutic applications of our data are discussed.

Forskolin improves sensitivity to doxorubicin of triple negative breast cancer cells via Protein Kinase A-mediated ERK1/2 inhibition

Triple negative breast cancer (TNBC) is an invasive, metastatic, highly aggressive tumor. Cytotoxic chemotherapy represents the current treatment for TNBC. However, relapse and chemo-resistance are very frequent. Therefore, new therapeutic approaches that are able to increase the sensitivity to cytotoxic drugs are needed. Forskolin, a natural cAMP elevating agent, has been used for several centuries in medicine and its safeness has also been demonstrated in modern studies. Recently, forskolin is emerging as a possible novel molecule for cancer therapy. Here, we investigate the effects of forskolin on the sensitivity of MDA-MB-231 and MDA-MB-468 TNBC cells to doxorubicin through MTT assay, flow cytometry-based assays (cell-cycle progression and cell death), cell number counting and immunoblotting experiments. We demonstrate that forskolin strongly enhances doxorubicin-induced antiproliferative effects by cell death induction. Similar effects are observed with IBMX and isoproterenol cAMP elevating agents and 8-Br-cAMP analog, but not by using 8-pCPT-2'-O-Me-cAMP Epac activator. It is important to note that the forskolin-induced potentiation of sensitivity to doxorubicin is accompanied by a strong inhibition of ERK1/2 phosphorylation, is mimicked by ERK inhibitor PD98059 and is prevented by pre-treatment with Protein Kinase A (PKA) and adenylate cyclase inhibitors. Altogether, our data indicate that forskolin sensitizes TNBC cells to doxorubicin via a mechanism depending on the cAMP/PKA-mediated ERK inhibition. Our findings sustain the evidence of anticancer activity mediated by forskolin and encourage the design of future in-vivo/clinical studies in order to explore forskolin as a doxorubicin sensitizer for possible use in TNBC patients.

Adiponectin down-regulates CREB and inhibits proliferation of A549 lung cancer cells

INTRODUCTION

Adipokines are known to play a relevant role in a number of cancer related molecular pathways. Adiponectin is a major adipokine with anti-inflammatory and beneficial metabolic actions. Furthermore, it has been shown to exert anti-carcinogenic effects in various tumor models and some clinical studies suggested an inverse relationship between circulating levels of adiponectin and an increased risk for development of malignancies. On the other hand, the cyclic AMP response element binding (CREB) transcription factor has been clearly linked to lung cancer.

METHODS

we analyzed cell proliferation, cell cycle of A549 cells treated with adiponectin as well as CREB activation status in human lung adenocarcinoma A549 cells and in non-small cell lung cancer (NSCLC) samples.

RESULTS

adiponectin treatment, at concentrations ranging between 5 and 50 μg/ml mimicking human serum levels, has a significant effect on reducing tumor cell proliferation of A549 cells, mainly by altering cell cycle progression. Importantly, we provide evidence that adiponectin clearly inhibits in a dose- and time-dependent manner CREB phosphorylation (activation) and, at least in part, also the level of CREB protein itself, preceding and accompanying the anti-proliferative effects in response to adiponectin. Moreover, in agreement with previous studies demonstrating that CREB over-expression occurs in many tumors, we also show by western-blotting from lung specimen that CREB is significantly up-regulated in NSCLC samples compared to adjacent normal tissues from six patients.

CONCLUSIONS

Overall, our results represent the first evidence of CREB inhibition by adiponectin and may provide new insight into therapeutic strategies for lung cancer.

Vanillin Prevents Doxorubicin-Induced Apoptosis and Oxidative Stress in Rat H9c2 Cardiomyocytes

Doxorubicin (doxo) is an effective anticancer compound in several tumor types. However, as a consequence of oxidative stress induction and ROS overproduction, its high cardiotoxicity demands urgent attention. Vanillin possesses antioxidant, antiproliferative, antidepressant and anti-glycating properties. Therefore, we investigated the potential vanillin protective effects against doxo-induced cardiotoxicity in H9c2 cells. Using multiparametric approach, we demonstrated that vanillin restored both cell viability and damage in response to doxo exposure. Contextually, vanillin decreased sub-G1 appearance and caspase-3 and PARP1 activation, reducing the doxo-related apoptosis induction. From a mechanistic point of view, vanillin hindered doxo-induced ROS accumulation and impaired the ERK phosphorylation. Notably, besides the cardioprotective effects, vanillin did not counteract the doxo effectiveness in osteosarcoma cells. Taken together, our results suggest that vanillin ameliorates doxo-induced toxicity in H9c2 cells, opening new avenues for developing alternative therapeutic approaches to prevent the anthracycline-related cardiotoxicity and to improve the long-term outcome of antineoplastic treatment.

Inorganic Phosphate Prevents Erk1/2 and Stat3 Activation and Improves Sensitivity to Doxorubicin of MDA-MB-231 Breast Cancer Cells

Due to its expression profile, triple-negative breast cancer (TNBC) is refractory to the most effective targeted therapies available for breast cancer treatment. Thus, cytotoxic chemotherapy represents the mainstay of treatment for early and metastatic TNBC. Therefore, it would be greatly beneficial to develop therapeutic approaches that cause TNBC cells to increase their sensitivity to cytotoxic drugs. Inorganic phosphate (Pi) is emerging as an important signaling molecule in many cell types. Interestingly, it has been shown that Pi greatly enhances the sensitivity of human osteosarcoma cell line (U2OS) to doxorubicin. We investigated the effects of Pi on the sensitivity of TNBC cells to doxorubicin and the underlying molecular mechanisms, carrying out flow cytometry-based assays of cell-cycle progression and cell death, MTT assays, direct cell number counting and immunoblotting experiments. We report that Pi inhibits the proliferation of triple-negative MDA-MB-231 breast cancer cells mainly by slowing down cell cycle progression. Interestingly, we found that Pi strongly increases doxorubicin-induced cytotoxicity in MDA-MB-231 cells by apoptosis induction, as revealed by a marked increase of sub-G1 population, Bcl-2 downregulation, caspase-3 activation and PARP cleavage. Remarkably, Pi/doxorubicin combination-induced cytotoxicity was dynamically accompanied by profound changes in Erk1/2 and Stat3 protein and phosphorylation levels. Altogether, our data enforce the evidence of Pi acting as a signaling molecule in MDA-MB-231 cells, capable of inhibiting Erk and Stat3 pathways and inducing sensitization to doxorubicin of TNBC cells, and suggest that targeting Pi levels at local sites might represent the rationale for developing effective and inexpensive strategies for improving triple-negative breast cancer therapy.

Chlorogenic acid activates ERK1/2 and inhibits proliferation of osteosarcoma cells

Osteosarcoma (OS) is a very aggressive metastatic pediatric and adolescent tumor. Due to its recurrent development of chemotherapy resistance, clinical outcome for OS patients remains poor. Therefore, discovering more effective anticancer agents is needed. Chlorogenic acid (CGA) is a phenolic compound contained in plant-related products that modulates many cellular functions and inhibits cell proliferation in several cancer types. However, few evidence is available in OS. Here, we investigate the effects of CGA in U2OS, Saos-2, and MG-63 OS cells. By multiple approaches, we demonstrate that CGA acts as anticancer molecule affecting the cell cycle and provoking cell growth inhibition mainly by apoptosis induction. We also provide evidence that CGA strongly activates extracellular-signal-regulated kinase1/2 (ERK1/2). Strikingly, ERK1/2 inhibitor PD98059 sensitizes the cells to CGA. Altogether, our data enforce the evidence of the anticancer activity mediated by CGA and provide the rationale for the development of innovative therapeutic strategies in OS cure.

Chlorogenic Acid Enhances Doxorubicin-Mediated Cytotoxic Effect in Osteosarcoma Cells

Despite the recurring outbreak of resistance mechanisms and adverse reactions, doxorubicin (Doxo) still remains the standard-of-care for several cancers, including osteosarcoma (OS). As an appealing source of phytochemical compounds, naturally occurring molecules have extensively been reported to overcome Doxo limitations in preclinical models. Unlike other dietary polyphenols, only few studies recognize chlorogenic acid (CGA) as a potential partner in combination therapy, while, conversely, its anticancer evidence is steadily growing, ultimately in OS. On this basis, herein we examine the cooperating effects between CGA and Doxo in U2OS and MG-63 human OS cells. With respect to Doxo alone, the concomitant administration of CGA further decreased cell viability and growth, promoting cell death potentially via apoptosis induction. Furthermore, a longer-lasting reduction in clonogenic potential deeply supported the CGA ability to improve Doxo efficacy in those cells. Remarkably, CGA treatment ameliorated Doxo-induced cytotoxicity in H9c2 rat cardiomyocyte cells instead. Although inactivation of p44/42 MAPK was detected in response to CGA plus Doxo, PD98059-mediated p44/42 MAPK impairment enhanced the combination outcome in OS cells. These findings firstly propose CGA as a promising chemosensitizer and cardioprotective agent in OS therapy, suggesting the p44/42 MAPK pathway as relevantly involved in CGA-mediated Doxo susceptibility.

Inorganic Phosphate as a Novel Signaling Molecule with Antiproliferative Action in MDA-MB-231 Breast Cancer Cells

Inorganic phosphate (P_i) is an essential nutrient for living organisms. It plays a key role in diverse physiological functions, including osteoblast differentiation and skeletal mineralization. Relevantly, P_i is emerging as an important signaling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression, and protein abundance in many cell types. To our knowledge, the consequences of elevated P_i on behavior of breast cancer cells have been poorly addressed. In this study we investigate the effects of P_i on proliferation of MDA-MB-231 breast cancer cells. We report that P_i inhibits proliferation of MDA-MB-231 cells by slowing cell cycle progression, without apoptosis occurrence. We found that P_i causes cells to accumulate in G1 phase in a time-dependent manner. Accordingly, G1 accumulation was associated with a decrease of cyclin A and cyclin E and an increase of cell cycle inhibitors p21 and p27 protein levels, respectively. Moreover, the P_i-induced antiproliferative effect was dynamically accompanied by profound changes in ERK1/2 and STAT3 protein and phosphorylation levels in response to P_i. Altogether, our data represent the first evidence of P_i acting as a novel signaling molecule in MDA-MB-231 breast cancer cells, capable of eliciting a strong antiproliferative action and suggest that targeting P_i levels at local sites might represent the rationale for developing novel strategies for therapeutic intervention in triple-negative breast cancer.

Inorganic phosphate in the development and treatment of cancer: A Janus Bifrons?

Inorganic phosphate (Pi) is an essential nutrient to living organisms. It is required as a component of the energy metabolism, kinase/phosphatase signaling and in the formation and function of lipids, carbohydrates and nucleic acids and, at systemic level, it plays a key role for normal skeletal and dentin mineralization. Pi represents an abundant dietary element and its intestinal absorption is efficient, minimally regulated and typically extends to approximately 70%. Maintenance of proper Pi homeostasis is a critical event and serum Pi level is maintained within a narrow range through an elaborate network of humoral interactions and feedback loops involving intestine, kidney, parathyroid gland and bone, and depends on the activity of a number of hormones, including parathyroid hormone, 1,25-dihydroxy vitamin D, and fibroblast growth factor 23 as major regulators of Pi homeostasis. Notably, Pi intake seemingly continues to increase as a consequence of chronic high-phosphorus (P) diets deriving from the growing consumption of highly processed foods, especially restaurant meals, fast foods, and convenience foods. Several recent reports have generated significant associations between high-P intake or high-serum Pi concentration and morbidity and mortality. Many chronic diseases, including cardiovascular diseases, obesity and even cancer have been proposed to be associated with high-P intakes and high-serum Pi concentrations. On the other hand, there is also evidence that Pi can have antiproliferative effects on some cancer cell types, depending on cell status and genetic background and achieve additive cytotoxic effects when combined with doxorubicin, illustrating its potential for clinical applications and suggesting that up-regulating Pi levels at local sites for brief times, might contribute to the development of novel and cheap modalities for therapeutic intervention in some tumours. Overall, the influence of Pi on cell function and the possible relationship to cancer have to be fully understood and investigated further.

Silica/Polyethylene Glycol Hybrid Materials Prepared by a Sol-Gel Method and Containing Chlorogenic Acid

Chlorogenic acid (CGA) is a very common dietary polyphenolic compound. CGA is becoming very attractive due to its potential use as preventive and therapeutic agent in many diseases, including cancer. Inorganic/organic hybrid materials are gaining considerable attention in the biomedical field. The sol-gel process provides a useful way to obtain functional organic/inorganic hybrids. The aim of this study was to synthesize silica/polyethylene glycol (PEG) hybrids with different percentages of CGA by sol-gel technique and to investigate their impact on the cancer cell proliferation. Synthesized materials have been chemically characterized through the FTIR spectroscopy and their bioactivity evaluated looking by SEM at their ability to produce a hydroxyapatite layer on their surface upon incubation with simulated body fluid (SBF). Finally, their effects on cell proliferation were studied in cell lines by direct cell number counting, MTT, flow cytometry-based cell-cycle and cell death assays, and immunoblotting experiments. Notably, we found that SiO₂/PEG/CGA hybrids exhibit clear antiproliferative effects in different tumor, including breast cancer and osteosarcoma, cell lines in a CGA dependent manner, but not in normal cells. Overall, our results increase the evidence of CGA as a possible anticancer agent and illustrate the potential for clinical applications of sol-gel synthesized SiO₂/PEG/CGA materials.

AdipoRon Affects Cell Cycle Progression and Inhibits Proliferation in Human Osteosarcoma Cells

AdipoRon (AdipoR) is the first synthetic molecule acting as a selective and potent adiponectin receptor agonist. Recently, the possible pharmacological use of AdipoR in different pathological conditions has been addressed. Interestingly, initial evidence suggests that AdipoR may have anticancer properties in different preclinical models, such as pancreatic and ovarian cancer. To our knowledge, so far no research has been directed at determining the impact of AdipoR on osteosarcoma, the most aggressive and metastatic bone malignancy occurring in childhood and adolescence age. Here, we investigate the possible antitumor effects of AdipoR in osteosarcoma cell lines. MTT and cell growth curve assays clearly indicate that AdipoR inhibits, at different extents, proliferation in both U2OS and Saos-2 osteosarcoma cell lines, the latter being more sensitive. Moreover, flow cytometry-based assays point out a significant G0/G1 phase accumulation and a contemporary S phase decrease in response to AdipoR. Consistent with the different sensitivity, a strong subG1 appearance in Saos-2 after 48 and 72 hours of treatment is also observed. The investigation of the molecular mechanisms highlights a common and initial ERK1/2 activation in response to AdipoR in both Saos-2 and U2OS cells. Interestingly, a simultaneous and dramatic downregulation of p70S6K phosphorylation, one of the main targets of mTORC1 pathway, has also been observed in AdipoR-treated Saos-2, but not in U2OS cells. Importantly, a strengthening of AdipoR-induced effects was reported upon everolimus-mediated mTORC1 perturbation in U2OS cells. In conclusion, our findings provide initial evidence of AdipoR as an anticancer molecule differently affecting various signaling pathways involved in cell cycle and cell death in osteosarcoma cells and encourage the design of future studies to further understand its pattern of activities.

Dipeptidyl Peptidase 4 Inhibition Ameliorates Chronic Kidney Disease in a Model of Salt-Dependent Hypertension

Cardiovascular diseases frequently coexist with chronic kidney disease that constitutes a major determinant of outcome in patients with heart failure. Dysfunction of both organs is related to chronic inflammation, endothelial dysfunction, oxidative stress, and fibrosis. Widespread expression of serine protease DPP4 that degrades varieties of substrates suggests its involvement in numerous physiological processes. In this study, we tested the effects of selective DPP4 inhibition on the progression of renal disease in a nondiabetic model of hypertensive heart disease using Dahl salt-sensitive rats. Chronic DPP4 inhibition positively affected renal function with a significant reduction in albuminuria and serum creatinine. DPP4 inhibition attenuated the inflammatory component by reducing the expression of NF-κB, TNFα, IL-1β, IL-6, and MCP-1. Kidney macrophages expressed GLP-1R, and DPP4 inhibition promoted macrophage polarization toward the anti-inflammatory M2 phenotype. Finally, high degrees of NADPH oxidase 4 expression and oxidation of nucleic acids, lipids, and proteins were reduced upon DPP4 inhibition. Our study provides evidence of renoprotection by DPP4 inhibition in a nondiabetic hypertension-induced model of chronic cardiorenal syndrome, indicating that DPP4 pathway remains a valid object to study in the context of chronic multiorgan diseases.

AdipoRon and Other Adiponectin Receptor Agonists as Potential Candidates in Cancer Treatments

The high mortality rate together with an ever-growing number of annual cases have defined neoplastic disorders as “the real 21st-century disease”. Its dubious distinction also results from conventional therapy failure, which has made cancer an orphan disease. Therefore, innovative and alternative therapeutic strategies are mandatory. The ability to leverage human naturally occurring anti-tumor defenses has always represented a fascinating perspective, and the immuno blockage approval in cancer treatment represents in timeline the latest success. As a multifunctional organ, adipose tissue releases a large amount of adipokines having both carcinogenic and antitumor properties. The negative correlation between serum levels and risk for developing malignancies, as well as the huge number of existing preclinical studies, have identified adiponectin as a potential anticancer adipokine. Nevertheless, its usage in clinical has constantly clashed with the inability to reproduce a mimic synthetic compound. Between 2011 and 2013, two distinct adiponectin receptor agonists were recognized, opening new scenarios even in cancer. Here, we review the first orally active adiponectin receptor agonists AdipoRon, from the discovery to the anticancer evidence. Including our latest findings in osteosarcoma models, we summarize AdipoRon and other existing agonists state-of-art, questioning about the feasibility assessment of this strategy in cancer treatment.

Forskolin Sensitizes Human Acute Myeloid Leukemia Cells to H3K27me2/3 Demethylases GSKJ4 Inhibitor via Protein Kinase A

Acute myeloid leukemia (AML) is an aggressive hematological malignancy occurring very often in older adults, with poor prognosis depending on both rapid disease progression and drug resistance occurrence. Therefore, new therapeutic approaches are demanded. Epigenetic marks play a relevant role in AML. GSKJ4 is a novel inhibitor of the histone demethylases JMJD3 and UTX. To note GSKJ4 has been recently shown to act as a potent small molecule inhibitor of the proliferation in many cancer cell types. On the other hand, forskolin, a natural cAMP raising compound, used for a long time in traditional medicine and considered safe also in recent studies, is emerging as a very interesting molecule for possible use in cancer therapy. Here, we investigate the effects of forskolin on the sensitivity of human leukemia U937 cells to GSKJ4 through flow cytometry-based assays (cell-cycle progression and cell death), cell number counting, and immunoblotting experiments. We provide evidence that forskolin markedly potentiates GSKJ4-induced antiproliferative effects by apoptotic cell death induction, accompanied by a dramatic BCL2 protein down-regulation as well as caspase 3 activation and PARP protein cleavage. Comparable effects are observed with the phosphodiesterase inhibitor IBMX and 8-Br-cAMP analogous, but not by using 8-pCPT-2'-O-Me-cAMP Epac activator. Moreover, the forskolin-induced enhancement of sensitivity to GSKJ4 is counteracted by pre-treatment with Protein Kinase A (PKA) inhibitors. Altogether, our data strongly suggest that forskolin sensitizes U937 cells to GSKJ4 inhibitor via a cAMP/PKA-mediated mechanism. Our findings provide initial evidence of anticancer activity induced by forskolin/GSKJ4 combination in leukemia cells and underline the potential for use of forskolin and GSKJ4 in the development of innovative and effective therapeutic approaches for AML treatment.

Inorganic phosphate as a signaling molecule: a potential strategy in osteosarcoma treatment

Inorganic phosphate (Pi) is an essential nutrient to living organisms. It plays a key role in diverse biological processes, including osteoblast differentiation and skeletal mineralization. Maintenance of proper Pi homeostasis is a critical event, as any deviation from that state can lead to several acute and chronic disease states and influence the ageing process and lifespan. Serum Pi level is maintained within a narrow range through a complex interplay between intestinal absorption, exchange with intracellular and bone storage pools, renal tubular reabsorption and depends mainly on the activity of Na/Pi cotransporters. Pi is abundant in the diet and intestinal absorption of Pi is efficient and minimally regulated. The kidney is a major regulator of Pi homeostasis and can increase or decrease its Pi reabsorptive capacity to accommodate Pi need. Relevantly, Pi is emerging as an important signalling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression and protein abundance in many cell types. However, little is known about the initial events involving the detection of changes in serum or local Pi concentrations and the subsequent downstream regulation cascade. Previously, we provided evidence that Pi inhibits proliferation and aggressiveness of human osteosarcoma U2OS cells identifying adenylate cyclase, beta3 integrin, Rap1, ERK1/2 as proteins whose expression and function are relevantly affected in response to Pi. More recently, we demonstrated that Pi is capable also of inducing sensitization of osteosarcoma cells to doxorubicin in a p53-dependent manner and through a mechanism involving ERK1/2 down-regulation. This review summarizes the current knowledge regarding inorganic phosphate as a novel specific signaling molecule in bone and other cell types in mammals and discuss how targeting Pi levels at local sites might represent a potential strategy for improving osteosarcoma therapy.

Synergistic cytotoxic effects of inorganic phosphate and chemotherapeutic drugs on human osteosarcoma cells

Novel therapeutic approaches are required for the treatment of osteosarcoma. Combination chemotherapy is receiving increased attention in order to identify compounds that may increase the therapeutic index of clinical anticancer drugs. In this regard, naturally occurring molecules with antitumor activity and with limited toxicity to normal tissues have been suggested as possible candidates for investigation of their synergistic efficacy in combination with antineoplastic drugs. Inorganic phosphate (Pi) is an essential nutrient for living organisms. Relevantly, Pi has emerged as an important signaling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression and protein abundance in many cell types. Previously, we showed that Pi inhibits proliferation and aggressiveness of U2OS human osteosarcoma cells and that Pi is capable of inducing sensitization of osteosarcoma cells to doxorubicin in a p53-dependent manner. In this study, we extended the role of Pi in the chemosensitivity of osteosarcoma cells to other anticancer drugs. Specifically, we report and compare the antiproliferative effects of a combination between Pi and doxorubicin, Taxol^® and 5-fluorouracil (5-FU) treatments. We found that Pi increases the antiproliferative response to both Taxol and doxorubicin to a similar extent. On the other hand, Pi did not potentiate the anticancer effects induced by 5-FU. These effects were paralleled by apoptosis induction and were cell cycle-dependent. The clinical significance of our data and their potential therapeutic applications for improving osteosarcoma treatment are discussed.