The Bisphenol A analogue Bisphenol S binds to K-Ras4B--implications for 'BPA-free' plastics

Synthesis, Biological Evaluation, and Binding Mode of a New Class of Oncogenic K-Ras4b Inhibitors

Ras proteins are implicated in some of the most common life-threatening cancers. Despite intense research during the past three decades, progress towards small-molecule inhibitors of mutant Ras proteins still has been limited. Only recently has significant progress been made, in particular with ligands for binding sites located in the switch II and between the switch I and switch II region of K-Ras4B. However, the structural diversity of inhibitors identified for those sites to date is narrow. Herein, we show that hydrazones and oxime ethers of specific bis(het)aryl ketones represent structurally variable chemotypes for new GDP/GTP-exchange inhibitors with significant cellular activity.

Targeting the Small GTPase Superfamily through Their Regulatory Proteins

The Ras superfamily of small GTPases are guanine-nucleotide-dependent switches essential for numerous cellular processes. Mutations or dysregulation of these proteins are associated with many diseases, but unsuccessful attempts to target the small GTPases directly have resulted in them being classed as "undruggable". The GTP-dependent signaling of these proteins is controlled by their regulators; guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs), and in the Rho and Rab subfamilies, guanine nucleotide dissociation inhibitors (GDIs). This review covers the recent small molecule and biologics strategies to target the small GTPases through their regulators. It seeks to critically re-evaluate recent chemical biology practice, such as the presence of PAINs motifs and the cell-based readout using compounds that are weakly potent or of unknown specificity. It highlights the vast scope of potential approaches for targeting the small GTPases in the future through their regulatory proteins.

Computational and in vitro Pharmacodynamics Characterization of 1A-116 Rac1 Inhibitor: Relevance of Trp56 in Its Biological Activity

In the last years, the development of new drugs in oncology has evolved notably. In particular, drug development has shifted from empirical screening of active cytotoxic compounds to molecularly targeted drugs blocking specific biologic pathways that drive cancer progression and metastasis. Using a rational design approach, our group has developed 1A-116 as a promising Rac1 inhibitor, with antitumoral and antimetastatic effects in several types of cancer. Rac1 is over activated in a wide range of tumor types and and it is one of the most studied proteins of the Rho GTPase family. Its role in actin cytoskeleton reorganization has effects on endocytosis, vesicular trafficking, cell cycle progression and cellular migration. In this context, the regulatory activity of Rac1 affects several key processes in the course of the cancer including invasion and metastasis. The purpose of this preclinical study was to focus on the mode of action of 1A-116, conducting an interdisciplinary approach with in silico bioinformatics tools and in vitro assays. Here, we demonstrate that the tryptophan 56 residue is necessary for the inhibitory effects of 1A-116 since this compound interferes with protein-protein interactions (PPI) of Rac1GTPase involving several GEF activators. 1A-116 is also able to inhibit the oncogenic Rac1^P29S mutant protein, one of the oncogenic drivers found in sun-exposed melanoma. It also inhibits numerous Rac1-regulated cellular processes such as membrane ruffling and lamellipodia formation. These results deepen our knowledge of 1A-116 inhibition of Rac1 and its biological impact on cancer progression. They also represent a good example of how in silico analyses represent a valuable approach for drug development.

Protein Kinase D1 (PKD1) Is a New Functional Non-Genomic Target of Bisphenol A in Breast Cancer Cells

Exposure to bisphenol A (BPA), one of the most widespread endocrine disruptors present in our environment, has been associated with the recent increased prevalence and severity of several diseases such as diabetes, obesity, autism, reproductive and neurological defects, oral diseases, and cancers such as breast tumors. BPA is suspected to act through genomic and non-genomic pathways. However, its precise molecular mechanisms are still largely unknown. Our goal was to identify and characterize a new molecular target of BPA in breast cancer cells in order to better understand how this compound may affect breast tumor growth and development. By using in vitro (MCF-7, T47D, Hs578t, and MDA-MB231 cell lines) and in vivo models, we demonstrated that PKD1 is a functional non-genomic target of BPA. PKD1 specifically mediates BPA-induced cell proliferation, clonogenicity, and anchorage-independent growth of breast tumor cells. Additionally, low-doses of BPA (≤10^{- 8} M) induced the phosphorylation of PKD1, a key signature of its activation state. Moreover, PKD1 overexpression increased the growth of BPA-exposed breast tumor xenografts in vivo in athymic female Swiss nude (Foxn1^nu/nu ) mice. These findings further our understanding of the molecular mechanisms of BPA. By defining PKD1 as a functional target of BPA in breast cancer cell proliferation and tumor development, they provide new insights into the pathogenesis related to the exposure to BPA and other endocrine disruptors acting similarly.

Soil enzyme response to bisphenol F contamination in the soil bioaugmented using bacterial and mould fungal consortium

The concept of the study resulted from the lack of accurate data on the toxicity of bisphenol F (BPF) coinciding with the need for immediate changes in the global economic policy eliminating the effects of environmental contamination with bisphenol A (BPA). The aim of the experiment was to determine the scale of the previously unstudied inhibitory effect of BPF on soil biochemical activity. To this end, in a soil subjected to increasing BPF pressure at three contamination levels of 0, 5, 50 and 500 mg BPF kg^-1 DM, responses of soil enzymes, dehydrogenases, catalase, urease, acid phosphatase, alkaline phosphatase, arylsulphatase and β-glucosidase, were examined. Moreover, the study suggested a potentially effective way of biostimulating the soil by means of bioaugmentation with a consortium of four bacterial species: Pseudomonas umsongensis, Bacillus mycoides, Bacillus weihenstephanensis and Bacillus subtilis, and the following fungal species: Mucor circinelloides, Penicillium daleae, Penicillium chrysogenum and Aspergillus niger. It was found that BPF was a controversial BPA analogue due to the fact that it contributed to the inhibition of all the enzyme activities. Dehydrogenases proved to be the most sensitive to bisphenol contamination of the soil. The addition of 5 mg BPF kg^-1 DM of soil triggered an escalation of the inhibition comparable to that for the other enzymes only after exposing them to the effects of 50 and 500 mg BPF kg^-1 DM of soil. Moreover, BPF generated low activity of urease, acid phosphatase, alkaline phosphatase and β-glucosidase. Bacterial inoculum increased the activity of urease, β-glucosidase, catalase and alkaline phosphatase. Seventy-six percent of BPF underwent biodegradation during the 5 days of the study.

Bisphenol P activates hormonal genes and introduces developmental outcomes in Chironomus tentans

The endocrine disrupting properties of bisphenol A (BPA) discharged to the environment have been newly identified by the European Chemicals Agency, increasing the need to assess the environmental endocrine disrupting potentials of its alternatives with which it shares close structural features. However, few investigations of the environmental endocrine disrupting functions of BPA analogs have been conducted to date. In this study, the endocrine disrupting effects of a BPA analog of bisphenol P (BPP) were investigated in the nonbiting midge (Chironomus tentans), a model organism in ecotoxicology. An initial ex vivo test using salivary gland cells explanted from the larvae and a subsequent in vivo test using embryos and larvae revealed the upregulatory effects of BPP on ecdysone receptor genes encoding the ecdysone receptor (EcR) and the early responsive gene E74, with a similar temporal pattern of gene activation. Partial life cycle and full life cycle toxicity tests demonstrated BPP altered embryo hatching, larval emergence, and adult sex ratio at concentrations close to the effective concentrations for hormonal genetic endpoints in embryos and larvae after 48 h of exposure. Although embryos appeared to be more sensitive to BPP than the fourth instar larvae, the impact on neither life stage seemed enough to estimate the developmental impairment of the insects. These results demonstrate the ecdysone pathway is a target of BPP, and that long-term exposure could cause apical effects on the development of C. tentans. The endocrine disrupting effects towards aquatic organisms, as well as the high persistence and bioconcentration potential, indicate an urgent need to assess the environmental risks associated with BPP.

Deriving the freshwater quality criteria of BPA, BPF and BPAF for protecting aquatic life

Bisphenol A (BPA) has been recognized by the European Chemicals Agency (ECHA) as an endocrine disruptor, and its use in thermo paper has been restricted from 2020 under the Regulation concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH). However, substances with similar structures such as bisphenol F (BPF) and bisphenol AF (BPAF) are widely used as BPA substitutes and commonly detected in aquatic environments. In this study, the water quality criteria of BPA, BPAF and BPF for protecting the aquatic life were derived to provide safety thresholds for their environment risk management. To accomplish this, the species sensitivity distribution (SSD) method was applied based on ecotoxicity data available in the literature and the supplementary toxicity test results for BPF and BPAF towards Marisa cornuarietis, Chironomus tentans and Scenedesmus obliquus. When compared with BPF, BPAF was found to be more acutely and chronically toxic to Marisa cornuarietis, Chironomus tentans and Scenedesmus obliquus, among which Chironomus tentans showed the most sensitivity. The criteria maximum concentrations (CMCs) of BPA, BPF and BPAF were derived to be 520, 227, and 43.4 μg‧L^-1, while the criteria continuous concentrations (CCCs) were 7.50, 54.0 and 26.4 μg‧L^-1, respectively. These findings indicate that BPA, BPF and BPAF posed negligible risks in typical rivers and lakes with available exposure concentrations because their measured concentrations are below their CCCs.

Allosteric Activation of GDP-Bound Ras Isoforms by Bisphenol Derivative Plasticisers

The protein family of small GTPases controls cellular processes by acting as a binary switch between an active and an inactive state. The most prominent family members are H-Ras, N-Ras, and K-Ras isoforms, which are highly related and frequently mutated in cancer. Bisphenols are widespread in modern life because of their industrial application as plasticisers. Bisphenol A (BPA) is the best-known member and has gained significant scientific as well as public attention as an endocrine disrupting chemical, a fact that eventually led to its replacement. However, compounds used to replace BPA still contain the molecular scaffold of bisphenols. BPA, BPAF, BPB, BPE, BPF, and an amine-substituted BPAF-derivate all interact with all GDP-bound Ras-Isoforms through binding to a common site on these proteins. NMR-, SOS^cat-, and GDI- assay-based data revealed a new bisphenol-induced, allosterically activated GDP-bound Ras conformation that define these plasticisers as Ras allosteric agonists.

The small GTPases Ras and Rheb studied by multidimensional NMR spectroscopy: structure and function

Ras GTPases are key players in cellular signalling because they act as binary switches. These states manifest through toggling between an active (GTP-loaded) and an inactive (GDP-loaded) form. The hydrolysis and replenishing of GTP is controlled by two additional protein classes: GAP (GTPase-activating)- and GEF (Guanine nucleotide exchange factors)-proteins. The complex interplay of the proteins is known as the GTPase-cycle. Several point mutations of the Ras protein deregulate this cycle. Mutations in Ras are associated with up to one-third of human cancers. The three isoforms of Ras (H, N, K) exhibit high sequence similarity and mainly differ in a region called HVR (hypervariable region). The HVR governs the differential action and cellular distribution of the three isoforms. Rheb is a Ras-like GTPase that is conserved from yeast to mammals. Rheb is mainly involved in activation of cell growth through stimulation of mTORC1 activity. In this review, we summarise multidimensional NMR studies on Rheb and Ras carried out to characterise their structure-function relationship and explain how the activity of these small GTPases can be modulated by low molecular weight compounds. These might help to design GTPase-selective antagonists for treatment of cancer and brain disease.