When Just One Phosphate Is One Too Many: The Multifaceted Interplay between Myc and Kinases.

Myc transcription factors are key regulators of many cellular processes, with Myc target genes crucially implicated in the management of cell proliferation and stem pluripotency, energy metabolism, protein synthesis, angiogenesis, DNA damage response, and apoptosis. Given the wide involvement of Myc in cellular dynamics, it is not surprising that its overexpression is frequently associated with cancer. Noteworthy, in cancer cells where high Myc levels are maintained, the overexpression of Myc-associated kinases is often observed and required to foster tumour cells' proliferation. A mutual interplay exists between Myc and kinases: the latter, which are Myc transcriptional targets, phosphorylate Myc, allowing its transcriptional activity, highlighting a clear regulatory loop. At the protein level, Myc activity and turnover is also tightly regulated by kinases, with a finely tuned balance between translation and rapid protein degradation. In this perspective, we focus on the cross-regulation of Myc and its associated protein kinases underlying similar and redundant mechanisms of regulation at different levels, from transcriptional to post-translational events. Furthermore, a review of the indirect effects of known kinase inhibitors on Myc provides an opportunity to identify alternative and combined therapeutic approaches for cancer treatment.

ERp57/PDIA3: new insight.

The ERp57/PDIA3 protein is a pleiotropic member of the PDIs family and, although predominantly located in the endoplasmic reticulum (ER), has indeed been found in other cellular compartments, such as the nucleus or the cell membrane. ERp57/PDIA3 is an important research target considering it can be found in various subcellular locations. This protein is involved in many different physiological and pathological processes, and our review describes new data on its functions and summarizes some ligands identified as PDIA3-specific inhibitors.

Tomato and Olive Bioactive Compounds: A Natural Shield against the Cellular Effects Induced by ß-Hexachlorocyclohexane-Activated Signaling Pathways.

The ß-isomer of hexachlorocyclohexane (ß-HCH) is a globally widespread pollutant that embodies all the physicochemical characteristics of organochlorine pesticides, constituting an environmental risk factor for a wide range of noncommunicable diseases. Previous in vitro studies from our group disclosed the carcinogenic potential of ß-HCH, which contributes to neoplastic transformation by means of multifaceted intracellular mechanisms. Considering the positive evidence regarding the protective role of natural bioactive compounds against pollution-induced toxicity, micronutrients from olive and tomato endowed with the capability of modulating ß-HCH cellular targets were tested. For this purpose, the solution obtained from a patented food supplement (No. EP2851080A1), referred to as Tomato and Olive Bioactive Compounds (TOBC), was administered to the androgen-sensitive prostate cancer cells LNCaP and different biochemical and cellular assays were performed to evaluate its efficiency. TOBC shows a dose-dependent significant chemoprotection by contrasting ß-HCH-induced intracellular responses such as STAT3 and AhR activation, disruption of AR signaling, antiapoptotic and proliferative activity, and increase in ROS production and DNA damage. These experimental outcomes identified TOBC as a suitable functional food to be included in a diet regimen aimed at defending cells from ß-HCH negative effects, recommending the development of tailored enriched formulations for exposed individuals.

A Comparative Analysis of Punicalagin Interaction with PDIA1 and PDIA3 by Biochemical and Computational Approaches.

In a previous work, it was shown that punicalagin, an active ingredient of pomegranate, is able to bind to PDIA3 and inhibit its disulfide reductase activity. Here we provide evidence that punicalagin can also bind to PDIA1, the main expressed form of protein disulfide isomerase (PDI). In this comparative study, the affinity and the effect of punicalagin binding on each protein were evaluated, and a computational approach was used to identify putative binding sites. Punicalagin binds to either PDIA1 or PDIA3 with a similar affinity, but the inhibition efficacy on protein reductase activity is higher for PDIA3. Additionally, punicalagin differently affects the thermal denaturation profile of both proteins. Molecular docking and molecular dynamics simulations led to propose a punicalagin binding mode on PDIA1 and PDIA3, identifying the binding sites at the redox domains a' in two different pockets, suggesting different effects of punicalagin on proteins' structure. This study provides insights to develop punicalagin-based ligands, to set up a rational design for PDIA3 selective inhibitors, and to dissect the molecular determinant to modulate the protein activity.

ß-Hexachlorocyclohexane Drives Carcinogenesis in the Human Normal Bronchial Epithelium Cell Line BEAS-2B.

Organochlorine pesticides constitute the majority of the total environmental pollutants, and a wide range of compounds have been found to be carcinogenic to humans. Among all, growing interest has been focused on ß-hexachlorocyclohexane (ß-HCH), virtually the most hazardous and, at the same time, the most poorly investigated member of the hexachlorocyclohexane family. Considering the multifaceted biochemical activities of ß-HCH, already established in our previous studies, the aim of this work is to assess whether ß-HCH could also trigger cellular malignant transformation toward cancer development. For this purpose, experiments were performed on the human normal bronchial epithelium cell line BEAS-2B exposed to 10 µM ß-HCH. The obtained results strongly support the carcinogenic potential of ß-HCH, which is achieved through both non-genotoxic (activation of oncogenic signaling pathways and proliferative activity) and indirect genotoxic (ROS production and DNA damage) mechanisms that significantly affect cellular macroscopic characteristics and functions such as cell morphology, cell cycle profile, and apoptosis. Taking all these elements into account, the presented study provides important elements to further characterize ß-HCH, which appears to be a full-fledged carcinogenic agent.

ß-Hexachlorocyclohexane: A Small Molecule with a Big Impact on Human Cellular Biochemistry.

Organochlorine pesticides (OCPs) belong to a heterogeneous class of organic compounds blacklisted by the Stockholm Convention in 2009 due to their harmful impact on human health. Among OCPs, ß-hexachlorocyclohexane (ß-HCH) is one of the most widespread and, at the same time, poorly studied environmental contaminant. Due to its physicochemical properties, ß-HCH is the most hazardous of all HCH isomers; therefore, clarifying the mechanisms underlying its molecular action could provide further elements to draw the biochemical profile of this OCP. For this purpose, LNCaP and HepG2 cell lines were used as models and were subjected to immunoblot, immunofluorescence, and RT-qPCR analysis to follow the expression and mRNA levels, together with the distribution, of key biomolecules involved in the intracellular responses to ß-HCH. In parallel, variations in redox homeostasis and cellular bioenergetic profile were monitored to have a complete overview of ß-HCH effects. Obtained results strongly support the hypothesis that ß-HCH could be an endocrine disrupting chemical as well as an activator of AhR signaling, promoting the establishment of an oxidative stress condition and a cellular metabolic shift toward aerobic glycolysis. In this altered context, ß-HCH can also induce DNA damage through H2AX phosphorylation, demonstrating its multifaceted mechanisms of action.

Modulation of STAT3 Signaling, Cell Redox Defenses and Cell Cycle Checkpoints by ß-Caryophyllene in Cholangiocarcinoma Cells: Possible Mechanisms Accounting for Doxorubicin Chemosensitization and Chemoprevention.

Cholangiocarcinoma (CCA) is an aggressive group of biliary tract cancers, characterized by late diagnosis, low effective chemotherapies, multidrug resistance, and poor outcomes. In the attempt to identify new therapeutic strategies for CCA, we studied the antiproliferative activity of a combination between doxorubicin and the natural sesquiterpene ß-caryophyllene in cholangiocarcinoma Mz-ChA-1 cells and nonmalignant H69 cholangiocytes, under both long-term and metronomic schedules. The modulation of STAT3 signaling, oxidative stress, DNA damage response, cell cycle progression and apoptosis was investigated as possible mechanisms of action. ß-caryophyllene was able to synergize the cytotoxicity of low dose doxorubicin in Mz-ChA-1 cells, while producing cytoprotective effects in H69 cholangiocytes, mainly after a long-term exposure of 24 h. The mechanistic analysis highlighted that the sesquiterpene induced a cell cycle arrest in G2/M phase along with the doxorubicin-induced accumulation in S phase, reduced the γH2AX and GSH levels without affecting GSSG. ROS amount was partly lowered by the combination in Mz-ChA-1 cells, while increased in H69 cells. A lowered expression of doxorubicin-induced STAT3 activation was found in the presence of ß-caryophyllene in both cancer and normal cholangiocytes. These networking effects resulted in an increased apoptosis rate in Mz-ChA-1 cells, despite a lowering in H69 cholangiocytes. This evidence highlighted a possible role of STAT3 as a final effector of a complex network regulated by ß-caryophyllene, which leads to an enhanced doxorubicin-sensitivity of cholangiocarcinoma cells and a lowered chemotherapy toxicity in nonmalignant cholangiocytes, thus strengthening the interest for this natural sesquiterpene as a dual-acting chemosensitizing and chemopreventive agent.

Shmt2: A Stat3 Signaling New Player in Prostate Cancer Energy Metabolism.

Prostate cancer (PCa) is a multifactorial disease characterized by the aberrant activity of different regulatory pathways. STAT3 protein mediates some of these pathways and its activation is implicated in the modulation of several metabolic enzymes. A bioinformatic analysis indicated a STAT3 binding site in the upstream region of SHMT2 gene. We demonstrated that in LNCaP, PCa cells' SHMT2 expression is upregulated by the JAK2/STAT3 canonical pathway upon IL-6 stimulation. Activation of SHTM2 leads to a decrease in serine levels, pushing PKM2 towards the nuclear compartment where it can activate STAT3 in a non-canonical fashion that in turn promotes a transient shift toward anaerobic metabolism. These results were also confirmed on FFPE prostate tissue sections at different Gleason scores. STAT3/SHMT2/PKM2 loop in LNCaP cells can modulate a metabolic shift in response to inflammation at early stages of cancer progression, whereas a non-canonical STAT3 activation involving the STAT3/HIF-1α/PKM2 loop is responsible for the maintenance of Warburg effect distinctive of more aggressive PCa cells. Chronic inflammation might thus prime the transition of PCa cells towards more advanced stages, and SHMT2 could represent a missing factor to further understand the molecular mechanisms responsible for the transition of prostate cancer towards a more aggressive phenotype.

STAT3 Post-Translational Modifications Drive Cellular Signaling Pathways in Prostate Cancer Cells.

STAT3 is an oncoprotein overexpressed in different types of tumors, including prostate cancer (PCa), and its activity is modulated by a variety of post-translational modifications (PTMs). Prostate cancer represents the most common cancer diagnosed in men, and each phase of tumor progression displays specific cellular conditions: inflammation is predominant in tumor's early stage, whereas oxidative stress is typical of clinically advanced PCa. The aim of this research is to assess the correspondence between the stimulus-specificity of STAT3 PTMs and definite STAT3-mediated transcriptional programs, in order to identify new suitable pharmacological targets for PCa treatment. Experiments were performed on less-aggressive LNCaP and more aggressive DU-145 cell lines, simulating inflammatory and oxidative-stress conditions. Cellular studies confirmed pY705-STAT3 as common denominator of all STAT3-mediated signaling. In addition, acK685-STAT3 was found in response to IL-6, whereas glutC328/542-STAT3 and pS727-STAT3 occurred upon tert-butyl hydroperoxyde (tBHP) treatment. Obtained results also provided evidence of an interplay between STAT3 PTMs and specific protein interactors such as P300 and APE1/Ref-1. In accordance with these outcomes, mRNA levels of STAT3-target genes seemed to follow the differing STAT3 PTMs. These results highlighted the role of STAT3 and its PTMs as drivers in the progression of PCa.

STAT3, a Hub Protein of Cellular Signaling Pathways, Is Triggered by ß-Hexaclorocyclohexane.

BACKGROUND: Organochlorine pesticides (OCPs) are widely distributed in the environment and their toxicity is mostly associated with the molecular mechanisms of endocrine disruption. Among OCPs, particular attention was focused on the effects of ß-hexaclorocyclohexane (ß-HCH), a widely common pollutant. A detailed epidemiological study carried out on exposed population in the "Valle del Sacco" found correlations between the incidence of a wide range of diseases and the occurrence of ß-HCH contamination. Taking into account the pleiotropic role of the protein signal transducer and activator of transcription 3 (STAT3), its function as a hub protein in cellular signaling pathways triggered by ß-HCH was investigated in different cell lines corresponding to tissues that are especially vulnerable to damage by environmental pollutants. MATERIALS AND METHODS: Human prostate cancer (LNCaP), human breast cancer (MCF-7 and MDA-MB 468), and human hepatoma (HepG2) cell lines were treated with 10 µM ß-HCH in the presence or absence of specific inhibitors for different receptors. All samples were subjected to analysis by immunoblotting and RT-qPCR. RESULTS AND CONCLUSIONS: The preliminary results allow us to hypothesize the involvement of STAT3, through both its canonical and non-canonical pathways, in response to ß-HCH. Moreover, we ascertained the role of STAT3 as a master regulator of energy metabolism via the altered expression and localization of HIF-1α and PKM2, respectively, resulting in a Warburg-like effect.