Phenylboronic acid selectively inhibits human prostate and breast cancer cell migration and decreases viability

Evaluation of Boric Acid Treatment on microRNA-127-5p and Metastasis Genes Orchestration of Breast Cancer Stem Cells

Coregulation of microRNAs (miRNAs) and cancer stem cells (CSCs) is very important in carcinogenesis. miR-127-5p is known to be downregulated in breast cancer. In this study, we aimed to investigate how boric acid (BA), known for its previously unstudied anti-cancer properties, would affect the expression of miR127-5p and genes responsible for breast cancer stem cells (BC-SCs) metastasis. BC-SCs were isolated from human breast cancer cells (MCF-7) by immunomagnetic cell separation and characterized with flow cytometry and sphere formation. The viability of BC-SCs and the determination of its IC50 value in response to boric acid (BA) were assessed via the MTT assay. Boric acid exhibited dose- and time-dependent inhibition of cell viability in cells. The IC50 doses of boric acid in MCF-7 cells and BC-SCs were 45.69 mM and 41.27 mM, respectively. The impact of BA on the expression of metastatic genes and miR127-5p was elucidated through RT-qPCR analysis. While the expression of the COL1A1 (p < 0.05) and VIM (p < 0.01) was downregulated, the expression of the miR-127-5p, ZEB1 (p < 0.01), CDH1 (p < 0.05), ITGB1 (p < 0.05), ITGA5 (p < 0.05), LAMA5 (p < 0.01), and SNAIL (p < 0.05), was up-regulated in dose-treated BC-SCs (p < 0.001) to the RT-qPCR results. Our findings suggest that boric acid could induce miR-127-5p expression. However, it cannot be said that it improves the metastasis properties of breast cancer stem cells.

Does Boric Acid Inhibit Cell Proliferation on MCF-7 and MDA-MB-231 Cells in Monolayer and Spheroid Cultures by Using Apoptosis Pathways?

Most breast cancers originate in the lobules or ducts of the breast. Breast cancer as the second main cause of death among women in the world is the most common kind of cancer in women. Studies have been conducted to find the optimal treatment for breast cancer. Moreover, the therapeutic effects of different drugs and substances on this disease have been intensively researched. Boric acid accounts for 96% of the boron content in body fluids, and its derivatives are absorbed by the human body. It is assumed to be represented as (B(OH)2). Experimental studies have shown a reduction of cell proliferation and stimulation of apoptosis in some melanoma, prostate, and colon cancer cell lines through boric acid. The aim of this study was to investigate if boric acid could be used for treating breast cancer. The impacts of boric acid on the human breast carcinoma cell lines MCF-7 and MDA-MB-231 were studied with TUNEL, BrdU, caspase-3, and endo-G immunohistochemical studies in 3D and 2D culture systems. Furthermore, we conducted a qRT-PCR study to show changes in the expression of some genes involved in apoptosis. Suppression of cell proliferation through boric acid-inducing apoptosis was observed both in 3D and 2D culture conditions. These results are compatible with the gene expression results. The ENDOG, CASP3, CASP8, and CASP9 gene expression significantly changed at all time intervals in MCF-7 and MD-MB-231 cell lines boric acid can potentially treat breast cancer as an anti-cancer agent candidate.

Investigation of cytotoxic antiproliferative and antiapoptotic effects of nanosized boron phosphate filled sodium alginate composite on glioblastoma cancer cells

BACKGROUND

The effects of nanosized boron phosphate-filled sodium alginate composite gel (SA/BP) on the biological characteristics of three types of glioblastoma multiforme (GBM) cells (C6, U87MG and T98G) were examined in this study. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay was used to determine the cytotoxicity of the composite gel on GBM, which was then compared to L929 healthy cells. Furthermore, wound healing, apoptosis, and colony formation capacities were evaluated. The investigation revealed that the SA/BP composite gel was successful in all GBM cells and could be used as a treatment agent for GBM and/or other invasive cancer types.

METHODS AND RESULTS

According to the results, the SA/BP composite gel had no effect on healthy fibroblast cells but had a lethal effect on all glioblastoma cells. Additionally, the wound healing method was used to examine the effect of the SA/BP composite gel on cell migration. It was discovered that the wound closed in 24 h in untreated control group cells, while the SA/BP composite gel closed up to 29.62%, 26.77% and 11.31% of the wound for C6, U87MG and T98G cell lines respectively. SA/BP significantly reduced cell migration in cancer cells. The effect of the generated SA/BP composite gel on cell colony development was assessed using a colony formation assay, and the cells reduced colony formation for all GBMs. It was roughly 45% for 24 h and 30% for 48 h when compared to the control group for C6 cells, 33%(24 h) and 40%(48 h) for U87MG cells, 40%(24 h) and 43%(48 h) for T98G cells. DAPI(4',6-Diamidino-2-phenylindole) and JC-1(5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine, iodide) staining to evaluate apoptosis revealed that the SA/BP composite gel dramatically enhanced the frequency of all GBMs undergoing apoptosis.

CONCLUSIONS

In line with experimental findings, it was observed that the SA/BP composite gel system did not affect healthy fibroblast cells but had a cytotoxic effect on glioblastoma cells, significantly reduced cell migration and colony-forming capacity of cells, and significantly increased apoptosis and depolarization of cell membranes. Based on all these findings, it can be said that SA/BP composite gel has cytotoxic, antiproliferative and antiapoptotic effects on different glioblastoma cells.

Homogeneous Pt nanostructures surface functionalized with phenylboronic acid phosphonic acid derivatives as potential biochemical nanosensors and drugs: SERS and TERS studies

Here, surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS) were used to characterize the selective adsorption of N-substituted 4-[(NH-R)(phosphono)-S-methyl]phenylboronic acids on the surface of platinum nanoparticles (PtNPs) from an aqueous solution and from air. The nature of the interaction of the studied compounds with the PtNPs/H₂ O and PtNPs/air interfaces was discussed and compared. For this purpose, 4-[(N-anilino)(phosphono)-S-methyl]phenylboronic acid (1-PBA-PA) and its two analogs (2-PBA-PA and bis{1-PBA-PA}) as well as the PtNPs were synthesized in surfactant/ion-free solution via a synthetic route that allows control of the size and morphology of the NPs. The positively charged PtNPs with a size of ~12 nm were characterized by ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD).

Cream production and biological in vivo/in vitro activity assessment of a novel boron-based compound derived from quercetin and phenyl boronic acid

Boronic acids constitute an important class of synthetic intermediates due to their high chemical stability, ease of use, moderate organic Lewis acid properties, reduced reactivity profiles and numerous biological activities such as antibacterial and antioxidant. The present study documents the synthesis and characterization of a novel boronic ester compound (3,5,7-trihydroxy-2- (2-phenyl benzo [d] [1,3,2] dioxaborol-5-yl) -4H-chromen-4-a) which was derived from phenyl boronic acid and quercetin. The new boron-based compound was used in the cream formulation after evaluating its antioxidant, antibacterial, anti-enzyme, anticancer activities and electrochemical oxidation behaviour. Furthermore, the cream has been dermatologically and microbiologically tested. Also, histological evaluation of the agent was estimated on multiple rat organs by hematoxylin-eosin staining method. Antioxidant potential of the new compound was tested by ABTS cation radical (IC₅₀: 0.11 ± 0.01 µg/mL), DPPH free radical scavenging (IC₅₀: 0.14 ± 0.01 µg/mL), and CUPRAC (A_0.5: 1.73 ± 0.16 µg/mL) methods, respectively. The compound determined to have a dominant antioxidant activity. In addition, the synthesized compound had no toxic effect on the healthy cell line (PDF), while having a very high (IC₅₀: 18.76 ± 0.62 µg/mL) cytotoxic effect on the cancerous cell line (MCF-7). In general, the compound showed moderate acetylcholinesterase enzyme activity (IC₅₀: 115.63 ± 1.16 µg/mL), high butyrylcholinesterase (IC₅₀: 3.12 ± 0.04 µg/mL), antiurease (IC₅₀: 1.10 ± 0.06 µg/mL), and antithyrosinase (IC₅₀: 11.52 ± 0.46 µg/mL) enzyme activities. In addition, the compound was found to be effective against Escherichia coli (ATCC 25922) bacteria studied at concentrations of 6.50 mg/mL. Moreover, the test results of the boronic ester compound used in the cream formulation demonstrated that it was microbiologically and dermatologically appropriate. Histologic analysis showed that the control group and experimental group were at similar properties without significant change. The phenyl boronic acid derivative compound synthesized from quercetin may have higher biological activity potential than quercetin. Due to the high biological activity potential of the synthesized compound, it has the potential to be used in food, feed, pharmaceutical and cosmetic industries.

Boric acid exert anti-cancer effect in poorly differentiated hepatocellular carcinoma cells via inhibition of AKT signaling pathway

BACKGROUND

The possible anti-cancer properties of boron, a trace element for humans, have been demonstrated in various experimental and epidemiological studies, although the effects of boron on liver cancer are unclear. In the present study we evaluate the effects of boric acid on the cell lines of hepatocellular carcinoma (HCC) of the liver, as the leading form of liver cancer, for which a poorly-differentiated HCC cell line (Mahlavu cell line) was used.

METHODS

The anti-cancer effect of boric acid was investigated with a cell viability assay, apoptosis analysis, cell migration analysis, cell morphology analysis, colony formation assay and 3D cell culture techniques. Also, the effect of boric acid on the AKT signaling pathway was determined through a western blot analysis.

RESULTS

Boric acid was found to reduce cell viability in a dose- and time-dependent manner, and decreased survival, colony formation ability, migration capability and HCC cell tumor spheroid growth in HCC cell lines, while also inducing apoptosis, autophagy and morphological alteration. Furthermore, boric acid inhibited AKT phosphorylation, and anticancer biological responses in HCC cells were observed only in cells in which AKT phosphorylation was suppressed by boric acid.

CONCLUSION

Our results suggest that boric acid might be a promising therapeutic candidate in hepatocellular carcinoma via the inhibition of AKT signaling pathway.

Boric acid suppresses cell proliferation by TNF signaling pathway mediated apoptosis in SW-480 human colon cancer line

BACKGROUND/AIM

Colon cancer is one of the most common cancers. Treatment success and survival rates are not high enough with current approaches. Therefore, there is a need to develop new agents and treatment methods. Boric acid is the most frequently observed form of boron. Some epidemiological data suggest that environmental exposure to boric acid reduces the incidence of prostate cancer in men, cervical and lung cancers in women. Experimental studies show, boric acid reduces cell proliferation and stimulates apoptosis in some prostate, melanoma, breast cancer cell lines. In this study, it was investigated whether boric acid could be a new candidate molecule that could be used in the treatment of colon cancer.

MATERIALS AND METHODS

The effects of boric acid on human colon adenocarcinoma cell line SW-480 were investigated with BrdU, TUNEL, Caspase-3, and AIF immunohistochemical studies in both 2D and 3D culture systems. In addition, a qRT-PCR study was carried out to determine the expression changes in key genes that take part in apoptosis.

RESULTS

We observed that boric acid suppresses cell proliferation and induces apoptosis both in 2D and 3D culture conditions. In addition, as a result of qRt-PCR studies, it was revealed that the observed apoptotic process was related to the TNF signaling pathway.

CONCLUSION

Boric acid can be considered as a potential anti-cancer agent candidate for colon cancer treatment.

DATA AVAILABILITY

All data generated or analyzed during this study are included in this published article.

Determination of the Influence of Various Factors on the Character of Surface Functionalization of Copper(I) and Copper(II) Oxide Nanosensors with Phenylboronic Acid Derivatives

In this work, we attempt to determine the influence of the oxidation state of copper [Cu(I) vs Cu(II)], the nature of the interface (solid/aqueous vs solid/air), the incubation time, and the structure of N-substituted phenylboronic acids (PBAs) functionalizing the surface of copper oxide nanostructures (NSs) on the mode of adsorption. For this purpose, 4-[(N-anilino)(phosphono)-S-methyl]phenylboronic acid (1-PBA) and its two analogues (2-PBA and bis{1-PBA}) and the copper oxide NSs were synthesized in a surfactant-/ion-free solution via a synthetic route that allows controlling the size and morphology of NSs. The NSs were characterized by scanning electron microscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, and X-ray diffraction, which confirmed the formation of spherical Cu2O nanoparticles (Cu2ONPs) with a size of 1.5 μm to 600 nm crystallized in a cubic cuprite structure and leaf-like CuO nanostructures (CuONSs) with dimensions of 80-180 nm in width and 400-700 nm in length and crystallized in a monoclinic structure. PBA analogues were deposited on the surface of the copper oxide NSs, and adsorption was investigated using surface-enhanced Raman spectroscopy (SERS). The changes in the orientation of the molecule relative to the substrate surface caused by the abovementioned factors were described, and the signal enhancement on the copper oxide NSs was determined. This is the first study using vibrational spectroscopy for these compounds.

From cow manure to bioactive carbon dots: a light-up probe for bioimaging investigations, glucose detection and potential immunotherapy agent for melanoma skin cancer

Bioactive carbon dots (C-dots) with ca. 4 nm were successfully produced with singular photophysical properties, low-toxicity and interesting immunological response. The optical properties of the C-dots were investigated and the "light-up" behaviour enabled them to be explored in glucose detection and bioimaging experiments (mitochondrial selective probe). C-dots were not selective to the tumour region and several fluorescent spots were visualized spread on animal bodies. The histology investigations showed that cancer-bearing mice treated with C-dots presented a large number of regions with necrosis and inflammatory infiltrates, which were not identified for cancer-bearing mice without the treatment. These results suggested that C-dots have the potential to be explored as an immune therapy agent for melanoma skin cancer.

Non-isotope enriched phenylboronic acid-decorated dual-functional nano-assembles for an actively targeting BNCT drug

The feasibility of boron neutron capture therapy (BNCT) greatly depends on the selective accumulation of ¹⁰B in tumors. The p-boronophenylalanine-fructose (BPA-f) complex has been established as a conventional BNCT agent due to its preferential uptake into tumors, which is driven by amino acid transporters. However, the retention of BPA-f in tumors is highly limited because of an antiport mechanism, which is regulated by a gradient of amino acid concentration across the cancer cell membrane. Thus, to preserve a high ¹⁰B concentration in tumors, patients are inevitably subjected to a constant intravenous infusion. To this end, we employed a phenylboronic acid (PBA)-decorated polymeric nanoparticle (Nano^PBA) as a sialic acid-targeting BNCT agent. In this manner, the PBA can exhibit dual functionalities, i.e., exhibiting a neutron capture capacity and hypersialyated cancer cell targeting effect. Our developed Nano^PBA possesses a supramolecular structure composed of a core and shell comprised of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) segments, respectively. The PBA moiety is installed at the PEG end, providing an unusually strong targeting effect, supposedly via multivalent binding onto the cancer cell membrane. As in BNCT, we verified the feasibility of Nano^PBA against a B16 melanoma-bearing mouse model. By virtue of efficient tumor targeting, even at a 100-fold lower dose than BPA-f, the Nano^PBA achieved a potent antitumor effect.

High Concentrations of Boric Acid Trigger Concentration-Dependent Oxidative Stress, Apoptotic Pathways and Morphological Alterations in DU-145 Human Prostate Cancer Cell Line

Boric acid is known to regulate the proliferation of cancer cells. Prostate cancer is among the types of cancer with high mortality in men. There are a few numbers of studies investigating the effects of boric acid on prostate cancer cells. The objective of the present study was to assess the effects of boric acid at concentrations higher than that can be achieved in blood by dietary intake on DU-145 human prostate cancer cells for 24 h. Firstly, we determined the cytotoxic activity of boric acid (0 to 12.5 mM) on DU-145 human prostate cancer cells by using 3-(4, 5-dimethylthiazol, 2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) and defined the IC50 concentration of boric acid. Then, by employing the doses found in MTT, the levels of antioxidant-oxidant molecules and apoptotic proteins were measured and morphological changes were evaluated. We have concluded that boric acid caused oxidative stress, inhibition of cell growth, apoptosis, and morphological alterations in a concentration-dependent manner in DU-145 cells. Furthermore, treatments with increasing boric acid concentrations decreased the antioxidant levels in cells. We actually revealed that boric acid, known as an antioxidant, may prevent cell proliferation by acting as an oxidant in certain doses. Although the high IC50 concentration of boric acid is perceived to be negative, we think it provides important background for subsequent studies.

Arylboronic acids inhibit P2X7 receptor function and the acute inflammatory response

The P2X7 receptor (P2X7R) is an ion channel which is activated by interactions with the extracellular ATP molecules. The molecular complex P2X7R/ATP induces conformational changes in the protein subunits, opening a pore in the ion channel macromolecular structure. Currently, the P2X7R has been studied as a potential therapeutic target of anti-inflammatory drugs. Based on this, a series of eight boronic acids (NO) analogs were evaluated on the biologic effect of this pharmacophoric group on the human and murine P2X7R. The boronic acids derivatives NO-01 and NO-12 inhibited in vitro human and murine P2X7R function. These analogs compounds showed effect better than compound BBG and similar to inhibitor A740003 for inhibiting dye uptake, in vitro IL-1β release and ATP-induced paw edema in vivo. In both, in vitro and in vivo assays the compound NO-01 showed to be the hit compound in the present series of the arylboronic acids analogs. The molecular docking suggests that the NO derivatives bind into the upper body domain of the P2X7 pore and that the main intermolecular interaction with the two most active NO derivatives occur with the residues Phe 95, 103 and 293 by hydrophobic interactions and with Leu97, Gln98 and Ser101 by hydrogen bonds.. These results indicate that the boronic acid derivative NO-01 shows the lead compound characteristics to be used as a scaffold structure to the development of new P2X7R inhibitors with anti-inflammatory action.

Boron's neurophysiological effects and tumoricidal activity on glioblastoma cells with implications for clinical treatment

Purpose: To define the actions of boron on normal neurophysiology and glioblastoma growth. Materials and Methods: PubMed and other relevant databases were searched. Results: Discovery of novel boron compounds in treatment of glioblastoma is being actively investigated, but the majority of such studies is focused on the synthesis of boron compounds as sensitizers to Boron Neutron Capture Therapy (BNCT). Nonetheless, the translational functionality of boron compounds is not limited to BNCT as many boron compounds possess direct tumoricidal activity and there is substantial evidence that certain boron compounds can cross the blood-brain barrier. Moreover, boron-containing compounds interfere with several tumorigenic pathways including intratumoral IGF-I levels, molybdenum Fe-S containing flavin hydroxylases, glycolysis, Transient Receptor Potential (TRP) and Store Operated Calcium Entry (SOCE) channels. Conclusions: Boron compounds deserve to be studied further in treatment of systemic cancers and glioblastoma due to their versatile antineoplastic functions.

Antifibrotic Effect of Boric Acid in Rats with Epidural Fibrosis

BACKGROUND

Epidural fibrosis is a major problem after spine surgery, with some patients having recurrent symptoms secondary to excessive formation of scar tissue resulting in neurologic compression. We used a rat laminectomy model to determine if topical application of boric acid could be helpful in the prevention of epidural fibrosis.

METHODS

Rats were randomly assigned to 2 control and 2 experimental groups (n = 8 for each group). The negative control group received no surgery, and the positive control group underwent laminectomy only. Experimental groups were classified according to the study agents applied onto the dura mater after laminectomy at the L3 level: 2.5% boric acid solution and 5% boric acid solution. The extent of epidural fibrosis was assessed 4 weeks later macroscopically and histopathologically.

RESULTS

Boric acid reduced epidural fibrosis in rats after laminectomy. The effect of 5% boric acid solution was more pronounced (P < 0.05) compared with the 2.5% solution.

CONCLUSIONS

The antifibrotic effect of boric acid solution for the prevention of epidural fibrosis suggests that boric acid should be further evaluated in future studies for the prevention of epidural fibrosis.

Synthesis and Evaluation of the Anticancer and Trypanocidal Activities of Boronic Tyrphostins

Molecules containing an (cyanovinyl)arene moiety are known as tyrphostins because of their ability to inhibit proteins from the tyrosine kinase family, an interesting target for the development of anticancer and trypanocidal drugs. In the present work, (E)-(cyanovinyl)benzeneboronic acids were synthesized by Knoevenagel condensations without the use of any catalysts in water through a simple protocol that completely avoided the use of organic solvents in the synthesis and workup process. The in vitro anticancer and trypanocidal activities of the synthesized boronic acids were also evaluated, and it was discovered that the introduction of the boronic acid functionality improved the activity of the boronic tyrphostins. In silico target fishing with the use of a chemogenomic approach suggested that tyrosine-phosphorylation-regulated kinase 1a (DYRK1A) was a potential target for some of the designed compounds.

Discovering simple phenylboronic acid and benzoxaborole derivatives for experimental oncology - phase cycle-specific inducers of apoptosis in A2780 ovarian cancer cells

Objective The aim of the study was to evaluate the antiproliferative potential of simple phenylboronic acid and benzoxaborole derivatives as well as to provide preliminary insight into their mode of action in cancer cells in vitro. Methods The antiproliferative activity was assessed in five diverse cancer cell lines via the SRB method (sulforhodamine B) or MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method after 72 h of treatment. Further studies of the mechanism of action consisted of the influence of the compounds on cell cycle progression and apoptosis induction, which was assessed by flow cytometry, caspase-3 enzymatic activity, fluorescence microscopy and western blot analysis. Results A clear structure-activity relationship was observed for both groups of compounds with several representatives evaluated as highly active antiproliferative agents with low micromolar [Formula: see text] values. 2-Fluoro-6-formylphenylboronic acid (18) and 3-morpholino-5-fluorobenzoxaborole (27) exhibited strong cell cycle arrest induction in G₂/M associated with caspase-3 activation in an A2780 ovarian cancer cell line. These events were accompanied by a mitotic catastrophe cell morphology and an increased percentage of aneuploid and tetraploid cells. Further experiments indicated that the compounds were phase cycle-specific agents since cells co-treated with hydroxyurea were less sensitive. The observed cell cycle arrest resulted from significant p21 accumulation and was associated neither with cyclin B1 nor β-tubulin degradation. Conclusion Phenylboronic acid and benzoxaborole derivatives were found to be highly promising antiproliferative and proapoptotic compounds with a cell cycle-specific mode of action. The presented data support their candidacy for further studies as a novel class of potential anticancer agents.

Injectable Coacervate Hydrogel for Delivery of Anticancer Drug-Loaded Nanoparticles in vivo

In this study, bortezomib (BTZ, a cytotoxic water-insoluble anticancer drug) was encapsulated in micellar nanoparticles having a catechol-functionalized polycarbonate core through a pH-sensitive covalent bond between phenylboronic acid (PBA) in BTZ and catechol, and these drug-loaded micelles were incorporated into hydrogels to form micelle/hydrogel composites. A series of injectable, biodegradable hydrogels with readily tunable mechanical properties were formed and optimized for sustained delivery of the BTZ-loaded micelles through ionic coacervation between PBA-functionalized polycarbonate/poly(ethylene glycol) (PEG) "ABA" triblock copolymer and a cationic one having guanidinium- or thiouronium-functionalized polycarbonate as "A" block. An in vitro release study showed the pH dependence in BTZ release. At pH 7.4, the BTZ release from the micelle/hydrogel composite remained low at 7%, whereas in an acidic environment, ∼85% of BTZ was released gradually over 9 days. In vivo studies performed in a multiple myeloma MM.1S xenograft mouse model showed that the tumor progression of mice treated with BTZ-loaded micelle solution was similar to that of the control group, whereas those treated with the BTZ-loaded micelle/hydrogel composite resulted in significant delay in the tumor progression. The results demonstrate that this hydrogel has great potential for use in subcutaneous and sustained delivery of drug-loaded micelles with superior therapeutic efficacy.

Phenylboronic Acid Templated Gold Nanoclusters for Mucin Detection Using a Smartphone-Based Device and Targeted Cancer Cell Theranostics

A phenylboronic acid templated gold nanocluster probe was developed to detect biomarker mucin by a noninvasive fluorescence-based method using a point-of-care smartphone-based fluorescence detection device. The gold nanocluster probe is able to detect mucin specifically. The same probe was applied for in vitro targeted bioimaging of HeLa and Hep G2 cancer cells, and it demonstrated specific therapeutic effects toward cancer cells as well as multicellular tumor spheroids imparting theranostic properties. The module is found to be more effective toward HeLa cells, and a pathway of cell death was established using flow-cytometry-based assays.

Some boron compounds of semicarbazones: antimicrobial activity and precursor for the sol–gel transformation to nanosized boron oxide

Biologically active boron Schiff base compounds: precursors for the low temperature synthesis of B₂O₃ and B₇O.

The importance of boron in biological systems

Boron is an essential element for plants and probably essential for human and animal health. Boron has a broad range of physiological effects on biological systems at low concentrations, whereas it is toxic to at high concentrations. Eventhough there are many studies on boron's biological effects and toxicity, more information is needed to understand the mechanisms of its action. The aim of the current work is to review boron's function, transport and toxicity in different biological systems.

In vitro and in vivo antitumour effects of phenylboronic acid against mouse mammary adenocarcinoma 4T1 and squamous carcinoma SCCVII cells

The cytotoxic activity of phenylboroxine acid was evaluated in vitro on mouse mammary adenocarcinoma 4T1, mouse squamous cell carcinoma SCCVII, hamster lung fibroblast V79 and mouse dermal fibroblasts L929 cell lines. The cytotoxic effects were dose dependent for all tested tumour and non-tumour cell lines. Under in vivo conditions, three application routes of phenylboronic acid were studied: intra-peritoneal (i.p.), intra-tumour (i.t.) and per-oral. After tumour transplantation in syngeneic mice, phenylboronic acid was shown to slow the growth of both tumour cell lines (4T1 and SCCVII) compared with the control. The inhibitory effects were pronounced during the application of phenylboronic acid. For both tested tumour cell lines, the most prominent antitumour effect was obtained by intraperitoneal administration, followed significantly by oral administration.

A Study on the Anticarcinogenic Effects of Calcium Fructoborate

Evidences about the preventive and therapeutic effects of boron compounds on cancer have been increasing in the last years. Although calcium fructoborate (CaFB) is used as a nutritional supplement, data about its preventive and therapeutic effects on neoplastic transformations are limited. In the present study, the various concentrations of CaFB were applied to the MDA-MB-231 metastatic breast cancer cell line. First, we examined the cytotoxic effect and IC₅₀ value of CaFB by MTT assay. For the evaluation of the DNA damage, apoptosis and metastatic potential, expression levels of ATM, pATM, PARP, p53, p-p53, caspase-3, caspase-9, and VEGF were investigated by using immunoblotting and immunohistochemical methods. Cell viability was significantly reduced at 50 μM CaFB treatment. pATM, p-p53, and caspase-9 levels increased significantly in all groups; furthermore, there was approximately 12.5-, 2.4-, and 10.7-fold increase, respectively, for 100 μM CaFB treatment. ATM and p53 levels did not change with CaFB treatment, but PARP levels significantly 2.5-fold decreased. While VEGF immunoreactivity decreased in all groups, significant increase in caspase-3 immunoreactivity was observed only in the group treated with 50 μM CaFB (p < 0,001). Our results imply that CaFB may have therapeutic potential as well as preventive benefits in cancer.

Activation of the EIF2α/ATF4 and ATF6 Pathways in DU-145 Cells by Boric Acid at the Concentration Reported in Men at the US Mean Boron Intake

Fruits, nuts, legumes, and vegetables are rich sources of boron (B), an essential plant nutrient with chemopreventive properties. Blood boric acid (BA) levels reflect recent B intake, and men at the US mean intake have a reported non-fasting level of 10 μM. Treatment of DU-145 prostate cancer cells with physiological concentrations of BA inhibits cell proliferation without causing apoptosis and activates eukaryotic initiation factor 2 (eIF2α). EIF2α induces cell differentiation and protects cells by redirecting gene expression to manage endoplasmic reticulum stress. Our objective was to determine the temporal expression of endoplasmic reticulum (ER) stress-activated genes in DU-145 prostate cells treated with 10 μM BA. Immunoblots showed post-treatment increases in eIF2α protein at 30 min and ATF4 and ATF6 proteins at 1 h and 30 min, respectively. The increase in ATF4 was accompanied by an increase in the expression of its downstream genes growth arrest and DNA damage-induced protein 34 (GADD34) and homocysteine-induced ER protein (Herp), but a decrease in GADD153/CCAAT/enhancer-binding protein homologous protein (CHOP), a pro-apoptotic gene. The increase in ATF6 was accompanied by an increase in expression of its downstream genes GRP78/BiP, calreticulin, Grp94, and EDEM. BA did not activate IRE1 or induce cleavage of XBP1 mRNA, a target of IRE1. Low boron status has been associated with increased cancer risk, low bone mineralization, and retinal degeneration. ATF4 and BiP/GRP78 function in osteogenesis and bone remodeling, calreticulin is required for tumor suppressor p53 function and mineralization of teeth, and BiP/GRP78 and EDEM prevent the aggregation of misfolded opsins which leads to retinal degeneration. The identification of BA-activated genes that regulate its phenotypic effects provides a molecular underpinning for boron nutrition and biology.

Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment

High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment.

Use of soluble boron compounds in prostate cancer therapy is hampered by their short half-life time and low effectiveness. Here, the authors show that boron nitride nanospheres with controlled boron release can reduce proliferation of prostate cancer cells and inhibit tumour growth in animal models.

Boric Acid Reduces the Formation of DNA Double Strand Breaks and Accelerates Wound Healing Process

Boron is absorbed by the digestive and respiratory system, and it was considered that it is converted to boric acid (BA), which was distributed to all tissues above 90 %. The biochemical essentiality of boron element is caused by boric acid because it affects the activity of several enzymes involved in the metabolism. DNA damage repair mechanisms and oxidative stress regulation is quite important in the transition stage from normal to cancerous cells; thus, this study was conducted to investigate the protective effect of boric acid on DNA damage and wound healing in human epithelial cell line. For this purpose, the amount of DNA damage occurred with irinotecan (CPT-11), etoposide (ETP), doxorubicin (Doxo), and H₂O₂ was determined by immunofluorescence through phosphorylation of H2AX^(Ser139) and pATM^(Ser1981) in the absence and presence of BA. Moreover, the effect of BA on wound healing has been investigated in epithelial cells treated with these agents. Our results demonstrated that H2AX^(Ser139) foci numbers were significantly decreased in the presence of BA while wound healing was accelerated by BA compared to that in the control and only drug-treated cells. Eventually, the results indicate that BA reduced the formation of DNA double strand breaks caused by agents as well as improving the wound healing process. Therefore, we suggest that boric acid has important therapeutical effectiveness and may be used in the treatment of inflammatory diseases where oxidative stress and wound healing process plays an important role.

Formulation of benzoxaborole drugs in PLLA: from materials preparation to in vitro release kinetics and cellular assays

A complete investigation on the incorporation of simple benzoxaboroles into PLLA-based films was carried out.

Synthesis and Characterization of 8-O-Carboxymethylpyranine (CM-Pyranine) as a Bright, Violet-Emitting, Fluid-Phase Fluorescent Marker in Cell Biology

To avoid spectral interference with common fluorophores in multicolor fluorescence microscopy, a fluid-phase tracer with excitation and emission in the violet end of the visible spectrum is desirable. CM-pyranine is easily synthesized and purified. Its excitation and emission maxima at 401.5 nm and 428.5 nm, respectively, are well suited for excitation by 405-nm diode lasers now commonly available on laser-scanning microscopes. High fluorescence quantum efficiency (Q = 0.96) and strong light absorption (ε405 > 25,000 M-1cm-1) together make CM-pyranine the brightest violet aqueous tracer. The fluorescence spectrum of CM-pyranine is invariant above pH 4, which makes it a good fluid-phase marker in all cellular compartments. CM-pyranine is very photostable, is retained for long periods by cells, does not self-quench, and has negligible excimer emission. The sum of its properties make CM-pyranine an ideal fluorescent tracer. The use of CM-pyranine as a fluid-phase marker is demonstrated by multicolor confocal microscopy of cells that are also labeled with lipid and nuclear markers that have green and red fluorescence emission, respectively.

Multilayered Thin Films from Boronic Acid-Functional Poly(amido amine)s

PURPOSE

To investigate the properties of phenylboronic acid-functional poly(amido amine) polymers (BA-PAA) in forming multilayered thin films with poly(vinyl alcohol) (PVA) and chondroitin sulfate (ChS), and to evaluate their compatibility with COS-7 cells.

METHODS

Copolymers of phenylboronic acid-functional poly(amido amine)s, differing in the content of primary amine (DAB-BA-PAA) or alcohol (ABOL-BA-PAA) side groups, were synthesized and applied in the formation of multilayers with PVA and ChS. Biocompatibility of the resulting films was evaluated through cell culture experiments with COS-7 cells grown on the films.

RESULTS

PVA-based multilayers were thin, reaching ~100 nm at 10 bilayers, whereas ChS-based multilayers were thick, reaching ~600 nm at the same number of bilayers. All of the multilayers are stable under physiological conditions in vitro and are responsive to reducing agents, owing to the presence of disulfide bonds in the polymers. PVA-based films were demonstrated to be responsive to glucose at physiological pH at the investigated glucose concentrations (10-100 mM). The multilayered films displayed biocompatibility in cell culture experiments, promoting attachment and proliferation of COS-7 cells.

CONCLUSIONS

Responsive thin films based on boronic acid functional poly(amido amine)s are promising biocompatible materials for biomedical applications, such as drug releasing surfaces on stents or implants. Graphical Abstract Layer-by-Layer Assembly.

Boric acid induces cytoplasmic stress granule formation, eIF2α phosphorylation, and ATF4 in prostate DU-145 cells

Dietary boron intake is associated with reduced prostate and lung cancer risk and increased bone mass. Boron is absorbed and circulated as boric acid (BA) and at physiological concentrations is a reversible competitive inhibitor of cyclic ADP ribose, the endogenous agonist of the ryanodine receptor calcium (Ca⁺²) channel, and lowers endoplasmic reticulum (ER) [Ca²⁺]. Low ER [Ca²⁺] has been reported to induce ER stress and activate the eIF2α/ATF4 pathway. Here we report that treatment of DU-145 prostate cells with physiological levels of BA induces ER stress with the formation of stress granules and mild activation of eIF2α, GRP78/BiP, and ATF4. Mild activation of eIF2α and its downstream transcription factor, ATF4, enables cells to reconfigure gene expression to manage stress conditions and mild activation of ATF4 is also required for the differentiation of osteoblast cells. Our results using physiological levels of boric acid identify the eIF2α/ATF pathway as a plausible mode of action that underpins the reported health effects of dietary boron.

Disodium pentaborate decahydrate (DPD) induced apoptosis by decreasing hTERT enzyme activity and disrupting F-actin organization of prostate cancer cells

Animal and cell culture studies have showed that boron and its derivatives may be promising anticancer agents in prostate cancer treatment. Thus, DU145 cells were treated with disodium pentaborate decahydrate (DPD) for 24, 48, and 72 h in order to investigate the inhibitor effect and mechanisms of DPD. Then, cell proliferation, telomerase enzyme activity, actin polymerization, and apoptosis were detected by WST-1 assay, qRT-PCR, immunofluorescence labeling, and flow cytometry, respectively. We found that DPD inhibited the growth of human prostate cancer cell line DU145 at the concentration of 3.5 mM for 24 h. Our results demonstrated that 7 mM of DPD treatment prevented the telomerase enzyme activity at the rate of 38 %. Furthermore, DPD has an apoptotic effect on DU145 cells which were examined by labeling DNA breaks. With 7 mM of DPD treatment, 8, 14, and 41 % of apoptotic cells were detected for 24, 48, and 72 h, respectively. Additionally, immunofluorescence labeling showed that the normal organization of actin filaments was disrupted in DPD-exposed cells, which is accompanied by the alteration of cell shape and by apoptosis in targeted cells. Taken together, the results indicate that DPD may exert its cytotoxicity at least partly by interfering with the dynamic properties of actin polymerization and decreasing the telomerase activity. Eventually, for the first time, the results of this study showed that DPD suppressed the activity of telomerase in DU145 cells, and therefore, we suggested that DPD could be an important agent for its therapeutic potential in the treatment of prostate cancer.

Phenylboronic acid is a more potent inhibitor than boric acid of key signaling networks involved in cancer cell migration

Previous studies from our lab have shown that both boric (BA) and phenylboronic- acid (PBA) inhibit the migration of prostate cancer cell lines, as well as non-tumorigenic prostate cells. Our results indicate that PBA is more potent than BA in targeting metastatic and proliferative properties of cancer cells. Here we focus on the impact of BA and PBA on Rho family of GTP-binding proteins and their downstream targets. Treatment with 1mM PBA and BA decreases activities of RhoA, Rac1, and Cdc42 in DU-145 metastatic prostate cancer cells, but not in normal RWPE-1 prostate cells. Furthermore, ROCKII activity and phosphorylation of myosin light chain kinase decrease as a result of either PBA or BA treatment in DU-145 cells, suggesting these compounds target actomyosin-based contractility.