Ovarian cancer is one of the most common cancers in women and even with the currently available treatment options, including surgery, radiation, and chemotherapy, it caused 13,940 deaths in US alone in 2020. Thus, there is a continuous need for developing novel approaches for the treatment of ovarian cancer, particularly drug resistant ovarian cancer, as ovarian cancer most adversely affects the lives patients. Here in, we have designed seleno-biotin derivatives as potential therapeutics for ovarian cancer. The rational for designing these hybrid small molecules is two fold: (i) The biotin receptors are up-regulated in various carcinomas including ovarian cancer cells while being expressed at low levels in normal cells. Due to the high affinity of biotin towards BR, biotin has been used as a conjugate for several targeted imaging, sensing, and delivery in vitro and in vivo. (ii) Organoselenium compounds with appropriate selenium moieties have shown therapeutic efficacy in several pre-clinical cancer models. Therefore, we designed several analogs of biotin by conjugating selenium moieties connected through ester, selenoester, or amide functionalities and their cytotoxicities were assessed using four different ovarian cancer cell lines. Ester-linked biotin-selenocyanate compound 2, out of the other analogs, in direct comparison to biotin alone, more effectively reduced the cell viability (IC50 9.8-18.5 µM against all the tested cell lines) and induced apoptosis in ovarian cancer cells in dose dependent manner as demonstrated by the cell viability assay. It showed three times more potency (IC50 14.08 µM) than standard drugs 5-FU (IC50 48.4 µM) and cisplatin (IC50 41.0 µM) against drug-resistant Hey A8 cancer cells and three times more activity with an IC50 value of 9.8 µM as compared to 5-FU (IC50 25.92 µM) against ES-2 cells. The above findings were supported by trypan blue dye exclusion assay, Annexin V/7-AAD, Caspase 3/7 apoptosis assays and Western blotting of apoptotic proteins. Compound 2 effectively caused cell cycle arrest of the treated OVCAR-3 cells in S-phase of the cell cycle, thus causing regulatory changes in the cell cycle proteins, as evident by Western blotting. In addition, compound 2 redox cycles was demonstrated by DCFDA based reactive oxygen species estimation. These experiments demonstrate that selenium modified biotin which contains a covalently attached redox cycling selenide group has the potential for human therapeutic applications against ovarian and other cancers over-expressing biotin receptors. Citation Format: Asif Raza, Amandeep Singh, Amin Shantu, L. Mallory Boylan, Julian E. Spallholz, Arun Sharma. Novel seleno-biotin compound inhibits viability of and induces reactive oxygen species (ROS)-mediated apoptosis in ovarian cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5449.

A series of seleno-biotin analogs were synthesized and their anticancer activity and mode of action were assessed using ovarian cancer cells. Compound 2, out of the other analogs, in direct comparison to biotin alone, more effectively reduced the cell viability and induced apoptosis in ovarian cancer cell lines in a dose dependent manner as demonstrated by the cell viability assay, trypan blue dye exclusion assay, Annexin V/7-AAD, and Caspase 3/7 apoptosis assays. Furthermore, compound 2 showed efficacy better than 5-fluorouracil (5-FU) and similar to cisplatin, in vitro; notably it was more cytotoxic to drug-resistant Hey A8 cells than cisplatin. The cytotoxicity of compound 2 was primarily mediated by reactive oxygen species (ROS) as demonstrated by DCFDA based ROS estimation. Biotin receptors (BR) saturation and the use of a BR negative cell line showed a significant decline in the cytotoxic ativity of the compound 2, confirming that its activity is BR-mediated. These experiments demonstrated that selenium modified biotin which contains an ester linked redox cycling selenocyanate group has the potential for human therapeutic applications against ovarian and other cancers over-expressing BR.

Cancer is one of the main causes of human mortality worldwide and novel chemotherapeutics are required due to the limitations of conventional cancer therapies. For example, using redox selenium compounds as novel chemotherapeutics seem to be very promising. The objective of this study was to explore if folate could be used as a carrier to deliver a newly synthesised selenium derivative selenofolate into cancer cells. Particularly, the cytotoxic effects of this selenofolate compound were investigated in a variety of cancer cell types including lung, liver, and cervical cancers and specifically IGROV1 cells. Our results showed that selenofolate inhibits the growth of cancer cells in-vitro. However, despite the expectations, folate receptor alpha (FRα) was not involved in the transportation of selenofolate compound into the cells i.e. growth inhibition was independent of FRα, suggesting that multiple transporters (e.g. reduced folate carrier-1) are possibly involved in the delivery and internalisation of folate in IGROV1 cells. Additionally, selenofolate did not exert cell death through apoptosis. Instead, anti-proliferative activity showed to be the main cause of growth inhibition of selenolofate in the IGROV1 cell line. In conclusion, selenofolate inhibits the growth of cancer cells and thus, may be explored further as a potential chemotherapeutic agent.

Her/2+ breast cancer accounts for ~25% mortality in women and overexpression of Her/2 leads to cell growth and tumor progression. Trastuzumab (Tz) with Taxane is the preferred treatment for Her/2+ patients. However, Tz responsive patients often develop resistance to Tz treatment. Herein, redox selenides (RSe-) were covalently linked to Tz using a selenium (Se)-modified Bolton–Hunter Reagent forming Seleno-Trastuzumab (Se-Tz; ~25 µgSe/mg). Se-Tz was compared to Tz and sodium selenite to assess the viability of JIMT-1 and BT-474 cells. Comparative cell viability was examined by microscopy and assessed by fluorometric/enzymatic assays. Se-Tz and selenite redox cycle producing superoxide (O2•−) are more cytotoxic to Tz resistant JIMT-1 and Tz sensitive BT-474 cells than Tz. The results of conjugating redox selenides to Tz suggest a wider application of this technology to other antibodies and targeting molecules.

Previous studies have demonstrated that redox selenium compounds arrest cancer cell viability in vitro through their pro-oxidative activity by generating superoxide (O2•−). Currently, there are no efficacious treatment options for women with Triple Negative Breast Cancer (TNBC). However, the association between the over-expression of the Folate Receptor Alpha (FRA) in TNBC and other cancer cells, has led to the possibility that TNBCs might be treated by targeting the FRA with redox selenium covalent Folic Acid conjugates. The present study reports the synthesis of the redox active vitamer, Selenofolate, generating superoxide. Superoxide (O2•−) catalytic generation by Selenofolate was assessed by an in vitro chemiluminescence (CL) assay and by a Dihydroethidium (DHE) in vivo assay. Cytotoxicity of Selenofolate was assessed against the TNBC cell line MDA-MB-468 and an immortalized, mammary epithelial cell line, HME50-5E. Cytotoxicity of Selenofolate was compared to Folic Acid and sodium selenite, in a time and dose dependent manner. Selenofolate and selenite treatments resulted in greater inhibition of MDA-MB-468 cell proliferation than HME50-5E as evaluated by Trypan Blue exclusion, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) metabolic assay and Annexin V apoptosis assays. Folate receptor alpha (FRA) protein expression was assessed by Western blotting, with the experimental results showing that redox active Selenofolate and selenite, but not Folic Acid, was cytotoxic to MDA-MB-468 cells in vitro, suggesting a possible clinical option for treating TNBC and other cancers over-expressing FRA.

Objective: Group VIA elements, oxygen, sulfur and selenium can be toxic and many of their compounds are toxic to cells owing to the catalytic generation of superoxide and oxidative stress from thiol oxidations. Sulfides, (RS-) and selenides, (RSe-) of organic molecules and enzymes are often redox catalysts. In the current study, alcohols (ROH) were investigated to ascertain if oxides (RO-) of some alcohols might also ionize and redox cycle generating superoxide. Methods: The Lucigenin chemiluminescence assay was used for the detection of superoxide generation by the aliphatic alcohols and Benzyl Alcohol at 25°C and 37°C in the presence or absence of reduced glutathione (GSH). Similar Benzyl compounds of sulfur, selenium and oxygen were also tested for direct comparison of their catalytic activity. Results: Many of the alcohols tested, generated superoxide in the presence of GSH at both 25°C and 37°C, but not in the absence of GSH. Overall catalytic activity was greater at 37°C than at 25°C. Comparing the catalytic activity of equal concentrations of the S, Se and O moiety of the Benzyl compounds showed that although the catalytic alcohols did generate superoxide in the presence of GSH, but the sulfur and selenium compounds showed greater catalytic activity. Conclusion: As hypothesized, some aliphatic alcohols tested did generate superoxide similar to many sulfur and selenium analog compounds in the presence of GSH. From the results we can deduce that some alcohols may be following a redox mechanism that is similar to the S and Se compounds that redox cycle in presence of GSH generating superoxide.

Colloidal selenium, was first used to treat cancer as early as 1911 in both humans and mice. Selenium was identified as the toxic component in forage plants of sheep, cattle, and horses in the 1930s. The animal toxicity of selenium compounds was determined to be from the metabolism by animals of the elevated concentrations of Se-methylselenocysteine and selenomethionine in plants. The metabolism of both Se-methylselenocysteine and selenomethionine by animals gives rise to the metabolite, methylselenide (CH3Se-), which if in sufficient concentration oxidizes thiols and generates superoxide and other reactive oxygen species. Cancer cells that may overly express methionine gamma-lyase, or beta-lyase (methioninase), by induced viral genomic expression, are susceptible to free radical-induced apoptosis from selenomethionine or Se-methylselenocysteine supplementation.

In vitro Cytotoxic Effects of Control and Selenium Conjugated Transferrins against LeHuman leukemia is a malignancy of hematopoietic stem cells with impaired differentiation and uncontrolled proliferation. Many leukemia cell lines over-express the trans-membrane transferrin receptor (TfR) which endocytoses iron (Fe) bound Holo-transferrin (Holo-Tf). Over-expression of the TfR has permitted transferrin-mediated drug delivery targeting leukemia cells. Selenides (RSe-), can generate free radicals, i.e.; superoxide (O2.-) and other Reactive Oxygen Species (ROS) by redox cycling; oxidizing thiols (RSH) within cells following endocytosis. Superoxide generation by selenium (Se) is reported to cause cell apoptosis/necrosis due to increased endogenous oxidative stress. In the present study, Se as ROCH2CH2SeCN was covalently attached to Lysine residues of Apo-, Holo-Tf, and Human Serum Albumin (HuSA) using a Se-modified Bolton-Hunter reagent. The Se conjugated proteins were used to target the TfR and experimentally treat K562 and THP-1 leukemia cell lines. Cells were also treated with sodium selenite (10 μgSe/well) as a positive control known to cause cell death.ukemia Cell Lines K562 and THP-1.

Since 1938 several investigators have confirmed antagonistic interaction whereby the administration of selenite mitigates arsenite toxicity in mammals More recently a number of animal model and human studies have revealed that the bimolecular basis of this antagonism involves the glutathione mediated formation of major metabolite seleno-bis(S-glutathionyl)arsinium [(GS)2AsSe]- ion which is rapidly excreted through bile. To investigate whether the oral supplementation of sodium selenite will enhance the fecal excretion of arsenites in human, a limited pharmacodynamics study was carried out involving ten arsenicosis patients. However, data from five patients are reported here. Patients were screened for pre-existing hepatic diseases and they were excluded from the study. Subjects were selected based on the arsenic level in their household drinking water, hair, nail samples and diffuse melanosis symptoms. Patients received Se-77-labeled sodium selenite as oral supplement, which they ingested together with their arsenic-containing drinking water. Total selenium levels increased in both urine and feces following the co-administration of sodium selenite (800 mu g). The patients receiving a placebo showed no change in their selenium excretion. The increase in selenium levels in feces and arsenic to some extent after dosing agrees with our hypothesis that selenium supplementation promotes co-excretion of arsenic and selenium through formation of [(GS)2AsSe]- in the bile.

Within the subtypes of breast cancer, those identified as triple negative for expression of estrogen receptor α (ESR1), progesterone receptor (PR) and human epidermal growth factor 2 (HER2), account for 10–20% of breast cancers, yet result in 30% of global breast cancer-associated deaths. Thus, it is critical to develop more targeted and efficacious therapies that also demonstrate less side effects. Selenium, an essential dietary supplement, is incorporated as selenocysteine (Sec) in vivo into human selenoproteins, some of which exist as anti-oxidant enzymes and are of importance to human health. Studies have also shown that selenium compounds hinder cancer cell growth and induce apoptosis in cancer cell culture models. The focus of this study was to investigate whether selenium-antibody conjugates could be effective against triple negative breast cancer cell lines using clinically relevant, antibody therapies targeted for high expressing breast cancers and whether selenium cytotoxicity was attenuated in normal breast epithelial cells. To that end, the humanized monoclonal IgG1 antibodies, Bevacizumab and Trastuzumab were conjugated with redox selenium to form Selenobevacizumab and Selenotrastuzumab and tested against the triple negative breast cancer (TNBC) cell lines MDA-MB-468 and MDA-MB-231 as well as a normal, immortalized, human mammary epithelial cell line, HME50-5E. VEGF and HER2 protein expression were assessed by Western. Although expression levels of HER2 were low or absent in all test cells, our results showed that Selenobevacizumab and Selenotrastuzumab produced superoxide (O2•−) anions in the presence of glutathione (GSH) and this was confirmed by a dihydroethidium (DHE) assay. Interestingly, superoxide was not elevated within HME50-5E cells assessed by DHE. The cytotoxicity of selenite and the selenium immunoconjugates towards triple negative cells compared to HME-50E cells was performed in a time and dose-dependent manner as measured by Trypan Blue exclusion, MTT assay and Annexin V assays. Selenobevacizumab and Selenotrastuzumab were shown to arrest the cancer cell growth but not the HME50-5E cells. These results suggest that selenium-induced toxicity may be effective in treating TNBC cells by exploiting different immunotherapeutic approaches potentially reducing the debilitating side effects associated with current TNBC anticancer drugs. Thus, clinically relevant, targeting antibody therapies may be repurposed for TNBC treatment by attachment of redox selenium.