Effects of combination therapy of docetaxel with selenium on the human breast cancer cell lines MDA-MB-231 and MCF-7

Seleno-Warfare against Cancer: Decoding Antitumor Activity of Novel Acylselenoureas and Se-Acylisoselenoureas

Currently, cancer remains a global health problem. Despite the existence of several treatments, including chemotherapy, immunotherapy, and radiation therapy, the survival rate for most cancer patients, particularly those with metastasis, remains unsatisfactory. Thus, there is a continuous need to develop novel, effective therapies. In this work, 22 novel molecules containing selenium are reported, including seven Se-acylisoselenoureas synthesized from aliphatic carbodiimides as well as acylselenoureas with the same carbo- and heterocycles and aliphatic amines. After an initial screening at two doses (50 and 10 µM) in MDA-MB-231 (breast), HTB-54 (lung), DU-145 (prostate), and HCT-116 (colon) tumor cell lines, the ten most active compounds were identified. Additionally, these ten hits were also submitted to the DTP program of the NCI to study their cytotoxicity in a panel of 60 cancer cell lines. Compound 4 was identified as the most potent antiproliferative compound. The results obtained showed that compound 4 presented IC50 values lower than 10 µM in the cancer cell lines, although it was not the most selective one. Furthermore, compound 4 was found to inhibit cell growth and cause cell death by inducing apoptosis partially via ROS production. Overall, our results suggest that compound 4 could be a potential chemotherapeutic drug for different types of cancer.

Antiproliferative Effect of Inorganic and Organic Selenium Compounds in Breast Cell Lines

Triple-negative breast cancer (TNBC) is an aggressive, fast-growing tumor that is more likely to spread to distant organs. Among women diagnosed with breast cancer, the prevalence of TNBC is 20%, and treatment is currently limited to chemotherapy. Selenium (Se), an essential micronutrient, has been explored as an antiproliferative agent. Therefore, this study aimed to evaluate the effects of exposure to organic (selenomethionine, ebselen, and diphenyl diselenide) and inorganic (sodium selenate and sodium selenite) Se molecules in different breast cell lines. The compounds were tested at 1, 10, 50, and 100 μM for 48 h in the non-tumor breast cell line (MCF-10A) and TNBC derivatives cell lines (BT-549 and MDA-MB-231). The effects of Se on cell viability, apoptotic and necrotic processes, colony formation, and cell migration were analyzed. Exposure to selenomethionine and selenate did not alter the evaluated parameters. However, selenomethionine had the highest selectivity index (SI). The exposure to the highest doses of selenite, ebselen, and diphenyl diselenide resulted in antiproliferative and antimetastatic effects. Selenite had a high SI to the BT cell line; however, the SI of ebselen and diphenyl diselenide was low in both tumoral cell lines. In conclusion, the Se compounds had different effects on the breast cell lines, and additional tests are needed to reveal the antiproliferative effects of Se compounds.

Metabolism and Anticancer Mechanisms of Selocompounds: Comprehensive Review

Selenium (Se) is an essential micronutrient with several functions in cellular and molecular anticancer processes. There is evidence that Se depending on its chemical form and the dosage use could act as a modulator in some anticancer mechanisms. However, the metabolism of organic and inorganic forms of dietary selenium converges on the main pathways. Different selenocompounds have been reported to have crucial roles as chemopreventive agents, such as antioxidant activity, activation of apoptotic pathways, selective cytotoxicity, antiangiogenic effect, and cell cycle modulation. Nowadays, great interest has arisen to find therapies that could enhance the antitumor effects of different Se sources. Herein, different studies are reported related to the effects of combinatorial therapies, where Se is used in combination with proteins, polysaccharides, chemotherapeutic agents or as nanoparticles. Another important factor is the presence of single nucleotide polymorphisms in genes related to Se metabolism or selenoprotein synthesis which could prevent cancer. These studies and mechanisms show promising results in cancer therapies. This review aims to compile studies that have demonstrated the anticancer effects of Se at molecular levels and its potential to be used as chemopreventive and in cancer treatment.

Overcoming the blood–brain barrier for the therapy of malignant brain tumor: current status and prospects of drug delivery approaches

Besides the broad development of nanotechnological approaches for cancer diagnosis and therapy, currently, there is no significant progress in the treatment of different types of brain tumors. Therapeutic molecules crossing the blood–brain barrier (BBB) and reaching an appropriate targeting ability remain the key challenges. Many invasive and non-invasive methods, and various types of nanocarriers and their hybrids have been widely explored for brain tumor treatment. However, unfortunately, no crucial clinical translations were observed to date. In particular, chemotherapy and surgery remain the main methods for the therapy of brain tumors. Exploring the mechanisms of the BBB penetration in detail and investigating advanced drug delivery platforms are the key factors that could bring us closer to understanding the development of effective therapy against brain tumors. In this review, we discuss the most relevant aspects of the BBB penetration mechanisms, observing both invasive and non-invasive methods of drug delivery. We also review the recent progress in the development of functional drug delivery platforms, from viruses to cell-based vehicles, for brain tumor therapy. The destructive potential of chemotherapeutic drugs delivered to the brain tumor is also considered. This review then summarizes the existing challenges and future prospects in the use of drug delivery platforms for the treatment of brain tumors.

Role of TRPM2 in brain tumours and potential as a drug target

Ion channels are ubiquitously expressed in almost all living cells, and are the third-largest category of drug targets, following enzymes and receptors. The transient receptor potential melastatin (TRPM) subfamily of ion channels are important to cell function and survival. Studies have shown upregulation of the TRPM family of ion channels in various brain tumours. Gliomas are the most prevalent form of primary malignant brain tumours with no effective treatment; thus, drug development is eagerly needed. TRPM2 is an essential ion channel for cell function and has important roles in oxidative stress and inflammation. In response to oxidative stress, ADP-ribose (ADPR) is produced, and in turn activates TRPM2 by binding to the NUDT9-H domain on the C-terminal. TRPM2 has been implicated in various cancers and is significantly upregulated in brain tumours. This article reviews the current understanding of TRPM2 in the context of brain tumours and overviews the effects of potential drug therapies targeting TRPM2 including hydrogen peroxide (H₂O₂), curcumin, docetaxel and selenium, paclitaxel and resveratrol, and botulinum toxin. It is long withstanding knowledge that gliomas are difficult to treat effectively, therefore investigating TRPM2 as a potential therapeutic target for brain tumours may be of considerable interest in the fields of ion channels and pharmacology.

Relationship Between Selenium in Human Tissues and Breast Cancer: a Meta-analysis Based on Case-Control Studies

Breast cancer is a common malignant tumor in women, and the anti-cancer effect of selenium (Se) is recognized. This meta-analysis was designed to determine the relationship between selenium levels in human tissue and breast cancer risk. Literatures published before August 2020 were systematically screened through PubMed, Web of Science, Scopus, and Elsevier. The related publication quality was evaluated by the Newcastle-Ottawa scale. We used random effect models for calculation and conducted sensitivity analysis and evaluation of publication bias. We identified 18 case-control studies, including 3374 women diagnosed with breast cancer and 3582 healthy controls. The results showed that the difference between the case group and the control group was - 0.53 μg/l [95%CI - 0.72 to - 0.34] (P < 0.001). Subgroup analysis showed a serum difference of - 1.14 μg/l [95%CI - 1.70 to - 0.58] (P < 0.001). The value of plasma was - 0.21 μg/l [95% CI - 0.37 to - 0.04] (P = 0.014). The value of toenail was - 0.21 μg/l [95% CI - 0.38 to - 0.03] (P = 0.021). In contrast, selenium levels in hair were not significantly associated with breast cancer risk. In the case-control studies, it was observed that selenium level in human tissues was negatively correlated with the risk of breast cancer, which may improve the understanding of the effects of selenium on human health.

Selenium inhibits growth of trastuzumab-resistant human breast cancer cells via downregulation of Akt and beclin-1

The response rate to treatment with trastuzumab (Tz), a recombinant humanized anti-HER2 monoclonal antibody, is only 12–34% despite demonstrated effectiveness on improving the survival of patients with HER2-positive breast cancers. Selenium has an antitumor effect against cancer cells and can play a cytoprotective role on normal cells. This study investigated the effect of selenium on HER2-positive breast cancer cells and the mechanism in relation to the response of the cells to Tz. HER2-positive breast cancer cell lines, SK-BR-3 as trastuzumab-sensitive cells, and JIMT-1 as Tz-resistant cells were treated with Tz and sodium selenite (selenite). Cell survival rates and expression of Her2, Akt, and autophagy-related proteins, including LC3B and beclin 1, in both cell lines 72 h after treatment were evaluated. Significant cell death was induced at different concentrations of selenite in both cell lines. A combined effect of selenite and Tz at 72 h was similar to or significantly greater than each drug alone. The expression of phosphorylated Akt (p-Akt) was decreased in JIMT-1 after combination treatment compared to that after only Tz treatment, while p-Akt expression was increased in SK-BR-3. The expression of beclin1 increased particularly in JIMT-1 after only Tz treatment and was downregulated by combination treatment. These results showed that combination of Tz and selenite had an antitumor effect in Tz-resistant breast cancer cells through downregulation of phosphorylated Akt and beclin1-related autophagy. Selenite might be a potent drug to treat Tz-resistant breast cancer by several mechanisms.

Selenium attenuates docetaxel-induced apoptosis and mitochondrial oxidative stress in kidney cells

Docetaxel (DTX) is a chemotherapeutic agent, and it is used for the treatment of several cancers including prostate and glioblastoma, but it results in many adverse effects in normal tissues, including kidney. The cytoprotective properties of selenium (Se) against adverse effects of DTX were reported in several normal cells, except kidney cell lines. The purpose of this study was to investigate the effects of Se on DTX-induced nephrotoxicity in normal kidney cell lines. The human embryonic kidney 293 (HEK293) cells were divided into four groups as control, Se (200 nmol/l for 10 h), DTX (10 nmol/l for 48 h), and DTX+Se. Laser confocal microscope fluorescence intensity of apoptosis (annexin V and propidium iodide), mitochondrial membrane depolarization, reactive oxygen species production, and lipid peroxidation levels were increased in the cells by the DTX treatments, although cell number, cell viability, reduced glutathione and glutathione peroxidase values were decreased by the treatments. The fluorescence intensities and values were recovered in the DTX+Se group of the cells by Se treatment. In conclusion, DTX-induced adverse effects were recovered through inhibition of apoptosis and mitochondrial oxidative stress through upregulation of reduced glutathione and glutathione peroxidase in the normal kidney (HEK293) cells. Combination therapy of DTX and Se could be used as an effective strategy for protection of kidney cells against adverse effects of DTX.

Use of Anticancer Platinum Compounds in Combination Therapies and Challenges in Drug Delivery

As one of the leading and most important metal-based drugs, platinum-based pharmaceuticals are widely used in the treatment of solid malignancies. Despite significant side effects and acquired drug resistance have limited their clinical applications, platinum has shown strong inhibitory effects for a wide assortment of tumors. Drug delivery systems using emerging technologies such as liposomes, dendrimers, polymers, nanotubes and other nanocompositions, all show promise for the safe delivery of platinum-based compounds. Due to the specificity of nano-formulations; unwanted side-effects and drug resistance can be largely averted. In addition, combinational therapy has been shown to be an effective way to improve the efficacy of platinum based anti-tumor drugs. This review first introduces drug delivery systems used for platinum and combinational therapeutic delivery. Then we highlight some of the recent advances in the field of drug delivery for combinational therapy; specifically progress in leveraging the cytotoxic nature of platinum-based drugs, the combinational effect of other drugs with platinum, while evaluating the drug targeting, side effect reducing and sitespecific nature of nanotechnology-based delivery platforms.

Selenium Enhances the Apoptotic Efficacy of Docetaxel Through Activation of TRPM2 Channel in DBTRG Glioblastoma Cells

The rate of mitosis of cancer cells is significantly higher than normal primary cells with increased metabolic needs, which in turn enhances the generation of reactive oxygen species (ROS) production. Higher ROS production is known to increase cancer cell dependence on ROS scavenging systems to counteract the increased ROS. Therapeutic options which selectively modulate the levels of intracellular ROS in cancers are likely candidates for drug discovery. Docetaxel (DTX) has demonstrated antitumor activity in preclinical and clinical studies. It is thought that DTX induces cell death through excessive ROS production and increased Ca²⁺ entry. The Ca²⁺ permeable TRPM2 channel is activated by ROS. Selenium (Se) has been previously used to stimulate apoptosis for the treatment of glioblastoma cells resistant to DTX. However, the potential mechanism(s) of the additive effect of DTX on TRPM2 channels in cancer cells remains unclear. The aim of this study was to evaluate the effect of combination therapy of DTX and Se on activation of TRPM2 in DBTRG glioblastoma cells. DBTRG cells were divided into four treatment groups: control, DTX (10 nM for 10 h), Se (1 μM for 10 h), and DTX+Se. Our study showed that apoptosis (Annexin V and propidium iodide), mitochondrial membrane depolarization (JC1), and ROS production levels were increased in DBTRG cells following treatment with Se and DTX respectively. Cell number and viability, and the levels of apoptosis, JC1, ROS, and [Ca²⁺]_i, induced by DTX, were further increased following addition of Se. We also observed an additive increase in the activation of the NAD-dependent DNA repair enzyme poly (ADP-ribose) polymerase-1 (PARP-1) activity, which was accompanied by a decline in its essential substrate NAD⁺. As well, the Se- and DTX-induced increases in intracellular Ca²⁺ florescence intensity were decreased following treatment with the TRPM2 antagonist N-(p-amylcinnamoyl) anthranilic acid (ACA). Therefore, combination therapy with Se and DTX may represent an effective strategy for the treatment of glioblastoma cells and may be associated with TRPM2-mediated increases in oxidative stress and [Ca²⁺]_i.

Organoselenium Compounds as Novel Adjuvants of Chemotherapy Drugs-A Promising Approach to Fight Cancer Drug Resistance

Malignant diseases present a serious public health burden and their treatment with traditional chemotherapy cannot be considered an all-round solution, due to toxic side effects. Selenium compounds (Se-compounds) have received substantial attention in medicinal chemistry, especially in experimental chemotherapy, both as cytotoxic agents and adjuvants in chemotherapy. A checkerboard microplate method was applied to study the drug interactions of Se-compounds and clinically relevant chemotherapeutic drugs against the multidrug-resistant (MDR) subtype of mouse t-lymphoma cells overexpressing the ABCB1 transporter. Se-compounds showed synergistic interactions with chemotherapeutic agents targeting the topoisomerase enzymes or the microtubule apparatus. The ketone-containing selenoesters showed synergism at lower concentrations (1.25 µM). Most of the tested compounds interacted antagonistically with alkylating agents and verapamil. A thiophene-containing Se-compound showed synergism with all tested drugs, except cisplatin. While the exact mechanism of drug interactions is yet unknown, the potency of the selenocompounds as efflux pump inhibitors or the potentiation of their efficacy as reactive oxygen species modulators may play a role in their complementary activity against the tested MDR lymphoma cell line.

Selenium uptake through cystine transporter mediated by glutathione conjugation

Selenium (Se) is an essential trace element and is regarded as a protective agent against cancer. In particular, antioxidant effects of selenoenzymes contribute to cancer prevention. Se can also produce reactive oxygen species and, thereby, exert cancer-selective cytotoxicity. Selenodiglutathione (SDG) is a primary Se metabolite conjugated to two glutathione (GSH) moieties. SDG increases intracellular Se accumulation and is more toxic than selenous acid (H₂SeO₃), but the mechanisms for importing Se compounds into cells are not fully understood. Here, we propose a novel mechanism for importing Se, in the form of SDG. Cellular intake of Se compounds was assessed based on Se accumulation, as detected by ICP-MS. SDG incorporation was decreased in the presence of thiols (GSH, cysteine or their oxidized forms, GSSG and cystine), whereas H₂SeO₃ uptake was increased by addition of GSH or cysteine. Cellular SDG uptake was decreased by pretreatment with specific inhibitors against gamma-glutamyl transpeptidase (GGT) or the cystine/glutamate antiporter (system x_c^-). Furthermore, siRNA against xCT, which is the light chain component of system x_c^-, significantly decreased SDG incorporation. These data suggest an involvement of SDG in Se incorporation, with SDG processed at the cell surface by GGT, leading to formation of selenodicysteine which, in turn, is likely to be imported via xCT. Because GGT and xCT are highly expressed in cancer cells, these mechanisms mediated by the cystine transporter might underlie the cancer-selective toxicity of Se. In addition, the system described in our study appears to represent a physiological transport mechanism for the essential element Se.

Selenium and Breast Cancer Risk: Focus on Cellular and Molecular Mechanisms

Selenium (Se) is a micronutrient with promising breast cancer prevention and treatment potential. There is extensive preclinical evidence of Se mammary carcinogenesis inhibition. Evidence from epidemiological studies is, however, unclear and intervention studies are rare. Here, we examine Se chemoprotection, chemoprevention, and chemotherapy effects in breast cancer, focusing on associated cellular and molecular mechanisms. Se exerts its protective actions through multiple mechanisms that involve antioxidant activities, induction of apoptosis, and inhibition of DNA damage, cell proliferation, angiogenesis, and invasion. New aspects of Se actions in breast cancer have emerged such as the impact of genetic polymorphisms on Se metabolism and response, new functions of selenoproteins, epigenetic modulation of gene expression, and long-term influence of early-life exposure on disease risk. Opportunity exists to design interventional studies with Se for breast cancer prevention and treatment taking into consideration these key aspects.

Oral bioavailability and evaluation of docetaxel–nicotinamide complex loaded chitosan nanoparticles

DTX–NA/NPs, synergism of DTX–NA complex and positively charged chitosan nanoparticles, can considerably enhance oral bioavailability.

Enantioselective and Synergetic Toxicity of Axial Chiral Herbicide Propisochlor to SP2/0 Myeloma Cells

The axial chiral herbicide propisochlor is used to control weeds. Different enantiomers of a compound usually have different biological activities. It is unclear how the toxicities of the propisochlor enantiomers differ. Propisochlor enantiomers, separated by high-performance liquid chromatography, were tested on SP2/0 myeloma cells. Cytotoxicity and apoptosis were measured, and interactions between the enantiomers were evaluated. The rac-propisochlor, pure R-(+) isomer, and pure S-(-) isomer inhibited cell proliferation and induced apoptosis. The rac-propisochlor, R-(+) isomer, and S-(-) isomer half maximal effective concentration values after 24 h of incubation were 111 ± 0.15, 68 ± 0.09, and 99 ± 0.21 μM, respectively. R-(+) isomer induced the most apoptosis. R-(+) isomer was ∼1.63 times more cytotoxic than rac-propisochlor and ∼1.46 times more cytotoxic than S-(-) isomer. Antagonistic cytotoxic interactions were found between R-(+) and S-(-) isomers. This is the first time the toxicities of these enantiomers and antagonism between the enantiomers have been reported. The antagonism indicates that the ecotoxicological effects of the enantiomers should be investigated.

Pathological response rate in hormone-positive breast cancer patients treated with neoadjuvant FEC and triweekly docetaxel: a case series

We recently reported that neoadjuvant 5-FU, epirubicin, and cyclophosphamide (FEC) followed by weekly paclitaxel and/or trastuzumab induced a high pathological complete response (pCR) rate in hormone-negative patients. The present study examined the therapeutic efficacy of neoadjuvant FEC followed by triweekly docetaxel and/or trastuzumab in the treatment of hormone-positive patients. Between February 2012 and December 2013, 16 hormone-positive patients with local breast cancer (luminal A type: six patients; luminal B type: two patients; luminal HER2 type: eight patients) were included in the study. The histological type of the primary cancer was invasive ductal carcinoma in all patients. The cancer stages in the 16 women who received this regimen were stage I in five (31.3%), IIA in four (25.0%), IIB in five (31.3%), IIIB in one (6.3%), and IIIC in one (6.3%). Regarding clinical TNM classification, five patients were T1N0M0, one was T1N1M0, three were T2N0M0, five were T2N1M0, one was T3N2M0, and one was T4N0M0. The pCR was evaluated using resected tissue after neoadjuvant chemotherapy according to the evaluation criteria of the Japanese Breast Cancer Society. Patients were classified into pathologic responders (grade 2: 50.0% of all patients: 2/6 of luminal A type; 6/8 of Luminal HER2 type) and nonresponders (grades 0 and 1: 50.0% of all patients: 4/6 of luminal A type; 2/2 of luminal B type; 2/8 of luminal HER2 type) according to the grade of the tumor. The pCR rate was 0%. Hematologic and nonhematologic toxicity was reversible and manageable. This study demonstrated that neoadjuvant FEC followed by triweekly docetaxel and/or trastuzumab did induce a high pathologic response in luminal HER2 type, but not in luminal A and B types, and did not induce a high pCR rate in the hormone-positive patients.

Selenate specifically sensitizes drug-resistant cancer cells by increasing apoptosis via G2 phase cell cycle arrest without P-GP inhibition

The purpose of this study was to identify conditions that will increase the sensitivity of drug-resistant cancer cells. Selenium derivatives have been shown to present anti-cancer properties in the clinic. Currently, selenate, selenite, selenomethionine (SeMet), methyl-selenocysteine (MSC), and methaneselenic acid (MSA) are the most common selenium derivatives used as drugs in humans. Herein, we tested whether these selenium derivatives can sensitize KBV20C cancer cells, which are highly resistant to anti-cancer drugs such as vincristine. All five drugs could sensitize KBV20C cells to the same extent as they sensitized the sensitive parent KB cells, suggesting that selenium-derived drugs can be used for drug-resistant cancer cells. We also observed that these drugs did not inhibit the P-glycoprotein (P-gp) pumping-out ability, suggesting that the sensitization by selenium-derived drugs does not depend on P-gp activity in resistant KBV20C cells. Interestingly, using a cell viability assay, microscopic observation, and Hoechst staining, we found that selenate highly sensitized drug-resistant KBV20C cells by activating the apoptotic pathway, when compared to sensitive KB cells. Furthermore, we investigated why selenate sensitizes resistant KBV20C cells. Selenate-induced toxicity was associated with an increase in G2-phase cell cycle arrest in KBV20C cells, suggesting that the selenate-induced increase in apoptosis resulted from cell cycle arrest in resistant KBV20C cells. Our findings may contribute to the development of selenate-based therapies for patients resistant to cancer drugs.