α-Tocopheryl succinate induces apoptosis in erbB2-expressing breast cancer cell via NF-κB pathway

Exploring the potential of tocopherols: mechanisms of action and perspectives in the prevention and treatment of breast cancer

Currently, breast cancer is the most common cause of mortality caused by neoplasia in women worldwide. The unmet challenges of conventional cancer therapy are chemoresistance and lack of selectivity, which can lead to serious side effects in patients; therefore, new treatments based on natural compounds that serve as adjuvants in breast cancer therapy are urgently needed. Tocopherols are naturally occurring antioxidant compounds that have shown antitumor activity against several types of cancer, including breast cancer. This review summarizes the antitumoral activity of tocopherols, such as the antiproliferative, apoptotic, anti-invasive, and antioxidant effects of tocopherols, through different molecular mechanisms. According to the studies described, α-T, δ-T and γ-T are the most studied in breast tumor cells; however, α-T and γ-T show a more critical antitumor activity and significant potential as a complements to chemotherapeutic drugs against breast cancer, enhancing toxicity against tumor cells and preventing cytotoxicity in nontumor cells. However, the possible relationship between tocopherol intake, related to concentration, and the promotion of cancer in particular cases should not be ruled out, so additional studies are required to determine the correct dose to obtain the desired antitumor effect. Moreover, nanomicelles of D-α-tocopherol have promising potential as pharmaceutical excipients for drug delivery to improve the cytotoxicity and selectivity of first-line chemotherapeutics against breast cancer.

Anti-Cancer Effects of Sulfasalazine and Vitamin E Succinate in MDA-MB 231 Triple-Negative Breast Cancer Cells

Aim: Sulfasalazine (SSZ) displayed anti-cancer activities. Vitamin E succinate (VES) could inhibit cell growth in various cancer cells. However, chemical therapies were often not useful for triple-negative breast cancer cells (TNBCs) treatment. Here, this study investigated the anti-cancer effects and the mechanisms on TNBCs under combination treatment with SSZ and VES. Methods: Cell viability was analyzed by using the MTT assay. The H₂O₂ levels were determined by using lucigenin-amplified chemiluminescence method. In addition, caspase and MAPs signals were studied by using western blotting. Results: Low-dose VES antagonized the SSZ-induced cytotoxicity effects while high-dose VES promoted the SSZ-induced cytotoxicity effects on TNBCs. In addition, SSZ alone treatment activated both caspase-3 and ERK signals, however, VES alone treatment only activated JNK signals. On the other hand, activation of caspase-3, JNK, and ERK were found in SSZ plus VES-treated cells. Conclusion: Combined SSZ and VES has synergistic or antagonistic cytotoxic effects depending on VES concentration. In addition, different cytotoxic signals are induced on SSZ-treated, VES-treated and SSZ plus VES-treated cells.

MiR-1268b confers chemosensitivity in breast cancer by targeting ERBB2-mediated PI3K-AKT pathway

Chemoresistance represents a major obstacle to effective therapy for breast cancer. Emerging evidences associated aberrantly expressed miRNAs with tumor development and chemoresistance. MiR-1268b has never been studied in any cancers before, and its roles in mediating tumor progression and drug resistance are still unclear. Selected from miRNA microarray and confirmed by real-time quantitative PCR (RT-qPCR), miR-1268b was found to be significantly upregulated in drug sensitive and ERBB2 negative tissues, as well as in breast cancer patients with low clinical stage. And miR-1268b had a higher expression in chemosensitive breast cancer cell lines, compared with the chemoresistant cell line. Moreover, the results revealed that miR-1268b induced breast cancer cell apoptosis and increased cell chemosensitivity. ERBB2 was demonstrated to be the target gene of miR-1268b by dual-luciferase reporter assays, western blot, and immunocytochemistry. Furthermore, PI3KCA, AKT, BCL2 in the ERBB2-PI3K-AKT signaling pathway were found to be downstream effectors of miR-1268b. In conclusion, miR-1268b increased chemosensitivity, at least in part, via modulation of PI3K-AKT pathway by targeting ERBB2. MiR-1268b may serve as a potential therapeutic target for patients with breast cancers.

α-Tocopheryl Succinate Affects Malignant Cell Viability, Proliferation, and Differentiation

The widespread occurrence of malignant tumors motivates great attention to finding and investigating effective new antitumor preparations. Such preparations include compounds of the vitamin E family. Among them, α-tocopheryl succinate (vitamin E succinate (VES)) has the most pronounced antitumor properties. In this review, various targets and mechanisms of the antitumor effect of vitamin E succinate are characterized. It has been shown that VES has multiple intracellular targets and effects, and as a result VES is able to induce apoptosis in tumor cells, inhibit their proliferation, induce differentiation, prevent metastasizing, and inhibit angiogenesis. However, VES has minimal effects on normal cells and tissues. Due to the variety of targets and selectivity of action, VES is a promising agent against malignant neoplasms. More detailed studies in this area can contribute to development of effective and safe chemotherapeutic preparations.

Targeting mitochondrial function for the treatment of breast cancer

There are many approaches used to control breast cancer, although the most efficient strategy is the reactivation of apoptosis. Since mitochondria play an important role in cellular metabolism and homeostasis, as well as in the regulation of cell death pathways, we focus here on metabolic remodeling and mitochondrial alterations present in breast tumor cells. We review strategies including classes of compounds and delivery systems that target metabolic and specific mitochondrial alterations to kill tumor cells without affecting their normal counterparts. We present here the arguments for the improvement of already existent molecules and the design of novel promising anticancer drug candidates that target breast cancer mitochondria.

The interrelationship between HER2 and CASP3/8 with apoptosis in different cancer cell lines

HER2/ErbB2, a known proto-oncogene (also known as HER2, neu), is among the most practiced molecules in the cancer area. Human epidermal growth factor receptor 2 (HER2) is over expressed in approximately 20-30 % of breast cancer tumors and also in a lot of other human cancer types. It is known to be related to the aggressiveness of the disease, increased mortality and higher relapse ratio. The unusual HER2 overexpression is associated with more severe disease characteristics in several cancers. In recent past, there have been remarkable advances in understanding the role of the HER2 gene in cancers. Caspases are well renowned proteases that act as essential initiators and executioners of the apoptotic process. The primary function of HER2 is suppressing apoptosis to enhance cell survival and eventually giving rise to uncontrolled proliferation and tumor growth. The objective of this work was to study the expression levels of HER2 and apoptosis related factors CASP-3 and CASP-8 in several breast and other cancer cell lines and finally to find a meaningful correlation between all these. We summed up by obtaining an increase in expression of HER2 in all cancer cell lines as compared to that of CASP-3 and CASP-8. In summary we conclude that HER2 promotes cell survival by inhibiting apoptosis i.e. by downregulating CASP-3 and CASP-8. This is a novel study comprising the expression study of HER2 and different caspases in different cancer cell lines simultaneously. It is thus expected that this study will aid in better establishment of correlation between HER2 and caspases in different malignancies.

Chemoprevention of head and neck squamous cell carcinoma through inhibition of NF-κB signaling

Nuclear factor-kappa B (NF-κB) transcription factors regulate cellular processes such as inflammation and cell survival. The NF-κB pathway is often activated with development and progression of head and neck squamous cell carcinoma (HNSCC). As such, NF-κB represents an attractive target for chemoprevention. HNSCC involves progression of lesions from premalignant to malignant, providing a window of opportunity for intervention with chemopreventive agents. Appropriate chemopreventive agents should be inexpensive, nontoxic, and target important pathways involved in the development of HNSCC. Several such agents that inhibit the NF-κB pathway have been investigated in HNSCC. Retinoids have been studied most extensively but have shown limited potential in human trials. Epidermal growth factor receptor inhibitors and PI3K-mTOR inhibitors may benefit a subset of patients. Other agents such as green tea extract and curcumin are appealing because they are generally regarded as safe. In contrast, there is evidence that Vitamin E supplementation may actually increase mortality of cancer patients. Repurposed drugs such as cyclooxygenase (COX) inhibitors and antidiabetic drugs are an emerging area of interest. Future research to develop agents with lower toxicity and higher specificity for the NF-κB pathway, and to target these therapies to individual patient genetic signatures should help to increase the utility of chemoprevention in HSNCC.

Alteration of α-tocopherol-associated protein (TAP) expression in human breast epithelial cells during breast cancer development

Breast cancer is the most common malignancy among women and has an age-specific incidence profile. Over the last decade, many studies have demonstrated the anticancer activity of α-tocopherol, the main and most active form of natural vitamin E. α-Tocopherol-associated protein (TAP) was found to be one of the major α-tocopherol binding proteins in human serum and in liver, brain, and prostate tissues. In this study, we found that reduced TAP expression was significantly correlated with Her2/neu receptor expression, breast cancer stage and nodal stage in paired normal and cancerous breast tissue samples from 93 patients using real-time PCR analysis. A cell viability assay showed that α-tocopheryl succinate (α-TOS), a synthetic derivative of α-tocopherol, enhanced the cells' sensitivity to doxorubicin and resulted in a reduction in cell viability in breast cancers. Taken together, these data suggest that the use of vitamin E or its analogue as a dietary supplement may be beneficial for the treatment of cancer.

TRAIL and vitamins: opting for keys to castle of cancer proteome instead of open sesame

Cancer is a multifaceted molecular disorder that is modulated by a combination of genetic, metabolic and signal transduction aberrations, which severely impair the normal homeostasis of cell growth and death. Accumulating findings highlight the fact that different genetic alterations, such as mutations in tumor suppressor genes, might be related to distinct and differential sensitivity to targeted therapies. It is becoming increasingly apparent that a multipronged approach that addresses genetic milieu (alterations in upstream and/or parallel pathways) eventually determines the response of individual tumors to therapy. Cancerous cells often acquire the ability to evade death by attenuating cell death pathways that normally function to eliminate damaged and harmful cells. Therefore impaired cell death nanomachinery and withdrawal of death receptors from cell surface are some of major determinants for the development of chemotherapeutic resistance encountered during treatment. It is therefore essential to emphasize underlying factors which predispose cells to refractoriness against TRAIL mediated cell death pathway and the relevant regulatory components involved. We bring to limelight the strategies to re-sensitize TRAIL resistant cells via vitamins to induce apoptosis.

(+)α-Tocopheryl succinate inhibits the mitochondrial respiratory chain complex I and is as effective as arsenic trioxide or ATRA against acute promyelocytic leukemia in vivo

The vitamin E derivative (+)α-tocopheryl succinate (α-TOS) exerts pro-apoptotic effects in a wide range of tumors and is well tolerated by normal tissues. Previous studies point to a mitochondrial involvement in the action mechanism; however, the early steps have not been fully elucidated. In a model of acute promyelocytic leukemia (APL) derived from hCG-PML-RARα transgenic mice, we demonstrated that α-TOS is as effective as arsenic trioxide or all-trans retinoic acid, the current gold standards of therapy. We also demonstrated that α-TOS induces an early dissipation of the mitochondrial membrane potential in APL cells and studies with isolated mitochondria revealed that this action may result from the inhibition of mitochondrial respiratory chain complex I. Moreover, α-TOS promoted accumulation of reactive oxygen species hours before mitochondrial cytochrome c release and caspases activation. Therefore, an in vivo antileukemic action and a novel mitochondrial target were revealed for α-TOS, as well as mitochondrial respiratory complex I was highlighted as potential target for anticancer therapy.