Death Of Human Breast Cancer Cells Research Articles

Upregulation of YPEL3 expression and induction of human breast cancer cell death by microRNAs

MicroRNAs (miRNAs), molecules comprising 18–22 nucleotides, regulate expression of genes post-transcriptionally at the 3′ untranslated region of target mRNAs. However, the biological roles and mechanisms of action of miRNAs in breast cancer remain unelucidated. Thus, in this study, we aimed to investigate the functions and possible mechanisms of action of miRNAs in breast cancer to suppress carcinogenesis. Using miRNA databases, we selected miR-34a and miR-605-5p to downregulate MDM4 and MDM2, respectively, because these ubiquitin E3 ligases degrade p53 and promote carcinogenesis. Results showed that miR-34a and miR-605-5p suppressed MDM4 and MDM2 expression, respectively. Moreover, they reduced the expression of yes‑associated protein 1 (YAP1), a well-known oncogene involved in Hippo signaling, but upregulated the mRNA and protein expression of yippee-like 3 (YPEL3). To elucidate whether these miRNAs promote cellular senescence and death through YPEL3 upregulation, we examined their effects on cellular proliferation, SA-β-gal activity, and mitochondrial activity in human breast cancer MCF-7 cells. Given their upregulating effect on YPEL3 expression, miR-34a and miR-605-5p increased the number of β-galactosidase-positive cells and depolarized live cells (by 10%–12%). These data suggest that miR-34a and miR-605-5p promote cellular senescence and cell death. Thus, they may act as tumor suppressors by inducing Hippo signaling and may serve as novel therapeutic agents in breast cancer treatment.

Human breast cancer cell death induced by BnSP-6, a Lys-49 PLA2 homologue from Bothrops pauloensis venom

This work shows the antitumoral effects of BnSP-6, a Lys 49 PLA2 isolated from Bothrops pauloensis venom, on human breast cancer MDA-MB-231 cells. BnSP-6 caused a dose-dependent cytotoxicity and inhibited cell adhesion. Interestingly, cytotoxic activity of BnSP-6 was significantly lower against MCF10A, a non-tumorigenic breast cell line, suggesting that this PLA2 presented a possible preference for targets in cancer cells. Analysis of cell death on MDA-MB-231 cells showed that BnSP-6 stimulated the autophagy process, as evidenced by labeling of autophagic vacuoles. Moreover, apoptosis assays showed that BnSP-6 induced both early and late apoptosis. Apoptosis of MDA-MB-231 cells was also confirmed by up-regulation of different genes related to the apoptosis pathway, such as TNF, TNFRSF10B, TNFRSF1A and CASP8 and decreased expression of anti-apoptotic genes (BCL2 and BCL2L). In addition, BnSP-6 caused a remarkable increase in gene expression of BRCA2 and TP53 tumor suppressors. Finally, BnSP-6 induced down-regulation of Angiopoetin 1 gene (potent pro-angiogenic factor) and inhibited adhesion and migration of MDA-MB-231 cells suggesting pharmaceutical applications of this PLA2 as an antiangiogenic and anti-metastatic agent. Taken together, our results show that the PLA2 BnSP-6 presents anticancer potential that can be exploited as prototype for the design of new therapies.

γ-Tocotrienol-induced endoplasmic reticulum stress and autophagy act concurrently to promote breast cancer cell death.

The anticancer effects of γ-tocotrienol are associated with the induction of autophagy and endoplasmic reticulum (ER) stress-mediated apoptosis, but a direct relationship between these events has not been established. Treatment with 40 μmol/L of γ-tocotrienol caused a time-dependent decrease in cancer cell viability that corresponds to a concurrent increase in autophagic and endoplasmic reticulum (ER) stress markers in MCF-7 and MDA-MB-231 human breast cancer cells. γ-Tocotrienol treatment was found to cause a time-dependent increase in early phase (Beclin-1, LC3B-II) and late phase (LAMP-1 and cathepsin-D) autophagy markers, and pretreatment with autophagy inhibitors Beclin-1 siRNA, 3-MA or Baf1 blocked these effects. Furthermore, blockage of γ-tocotrienol-induced autophagy with Beclin-1 siRNA, 3-MA, or Baf1 induced a modest, but significant, reduction in γ-tocotrienol-induced cytotoxicity. γ-Tocotrienol treatment was also found to cause a decrease in mitogenic Erk1/2 signaling, an increase in stress-dependent p38 and JNK1/2 signaling, as well as an increase in ER stress apoptotic markers, including phospho-PERK, phospho-eIF2α, Bip, IRE1α, ATF-4, CHOP, and TRB3. In summary, these finding demonstrate that γ-tocotrienol-induced ER stress and autophagy occur concurrently, and together act to promote human breast cancer cell death.

MAPK signaling mediates sinomenine hydrochloride-induced human breast cancer cell death via both reactive oxygen species-dependent and -independent pathways: an in vitro and in vivo study.

Sinomenine, the main alkaloid extracted from the medicinal plant Sinomenium acutum, is known for its anti-inflammatory effects. Recent studies have suggested its anti-cancer effect in synovial sarcoma, lung cancer and hepatic cancer. However, the underlying molecular mechanism for its anti-cancer effect still remains unclear. This study investigated the anti-tumor activity of sinomenine hydrochloride (SH), a hydrochloride form of sinomenine, in human breast cancer cells in vitro and in vivo. We found that SH potently inhibited cell viability of a broad panel of breast cancer cell lines. Two representative breast cancer cell lines, namely ER(−)/PR(−) MDA-MB-231 and ER(+)/PR(+) MCF-7, were used for further investigation. The results showed that SH induced G1/S cell cycle arrest, caused apoptosis and induced ATM/Chk2- and ATR/Chk1-mediated DNA-damage response in MDA-MB-231 and MCF-7. The anti-cancer effect of SH was regulated by increased expression levels of p-ERK, p-JNK and p-38 MAPK. Further studies showed that SH resulted in an increase in reactive oxygen species (ROS) and inhibition of ROS by N-acetyl-L-cysteine (NAC) almost blocked SH-induced DNA damage but only mitigated SH-induced MAPK expression changes, suggesting that both ROS-dependent and -independent pathways were involved in MAPK-mediated SH-induced breast cancer cell death. The in vivo study demonstrated that SH effectively inhibited tumor growth without showing significant toxicity. In conclusion, SH induced breast cancer cell death through ROS-dependent and -independent pathways with an upregulation of MAPKs, indicating that SH may be a potential anti-tumor drug for breast cancer treatment.

Abstract 853: Inhibition of the nuclear transport protein CRM1 induces human breast cancer cell death by regulating survivin degradation.

Abstract Survivin is a member of the inhibitor of apoptosis protein (IAP) family based on its N-terminal baculovirus IAP repeat (BIR) domain. The protein is largely undetectable in differentiated tissues, but is highly expressed in most human tumors. Its cytoplasmic expression in these tumors correlates with reduced tumor cell death, increased resistance to cancer therapy, and decreased patient survival. Survivin is actively exported into the cytoplasm exclusively by the chromosomal region maintenance 1 (CRM1/Exportin1) protein, one of seven known nuclear export proteins. CRM1 binds to the canonical nuclear export signal (NES) domain within the survivin protein. Inhibition of CRM1-mediated nuclear export has been suggested as a novel cancer therapeutic strategy that restores the tumor suppressor function of multiple nuclear proteins. Here, we investigated the anti-tumor mechanisms of two novel, drug-like CRM1 inhibitors, KPT-185 and KPT-276, in estrogen-receptor positive and triple negative breast cancer cell lines. Tumor and control cells were treated with varying doses of the KPT compounds over time. Cell proliferation and apoptosis were measured using standard assays. Survivin localization and expression in the presence and absence of the KPT drugs was assessed by immunofluorescence microscopy and cell fractionation. Breast cancer cell lines were engineered to express higher or lower levels of Survivin to determine the contribution of Survivin inhibition to the anti-tumor effects of the CRM1 inhibitors. Results showed that the KPT compounds have potent anti-proliferative properties and that they induce time- and dose-dependent apoptosis. KPT-185 and KPT-276 initially enhanced nuclear Survivin expression but produced a decrease in total cellular Survivin levels at later time points. Survivin protein degraded at a faster rate following KPT treatment, which was blocked by treatment with proteasome inhibitors. Knockdown of Survivin increased KPT-mediated cell apoptosis while exogenous expression of Survivin rescued cells from KPT-mediated apoptosis. In summary, our data demonstrate that inhibition of nuclear export by CRM1 inhibition suppresses breast tumor cell growth and enhances tumor cell death, in part through specific targeting of the Survivin-CRM1 complex. Citation Format: Yan Cheng, Michael Holloway, Kevin Nguyen, Michael Kauffman, Sharon Shacham, Rachel A. Altura. Inhibition of the nuclear transport protein CRM1 induces human breast cancer cell death by regulating survivin degradation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 853. doi:10.1158/1538-7445.AM2013-853

Ets2 Maintains hTERT Gene Expression and Breast Cancer Cell Proliferation by Interacting with c-Myc

Human telomerase reverse transcriptase (hTERT) underlies cancer cell immortalization, and the expression of hTERT is regulated strictly at the gene transcription. Here, we report that transcription factor Ets2 is required for hTERT gene expression and breast cancer cell proliferation. Silencing Ets2 induces a decrease of hTERT gene expression and increase in human breast cancer cell death. Reconstitution with recombinant hTERT rescues the apoptosis induced by Ets2 depression. In vitro and in vivo analyses show that Ets2 binds to the EtsA and EtsB DNA motifs on the hTERT gene promoter. Mutation of either Ets2 binding site reduces the hTERT promoter transcriptional activity. Moreover, Ets2 forms a complex with c-Myc as demonstrated by co-immunoprecipitation and glutathione S-transferase pulldown assays. Immunological depletion of Ets2, or mutation of the EtsA DNA motif, disables c-Myc binding to the E-box, whereas removal of c-Myc or mutation of the E-box also compromises Ets2 binding to EtsA. Thus, hTERT gene expression is maintained by a mechanism involving Ets2 interactions with the c-Myc transcription factor and the hTERT gene promoter, a protein-DNA complex critical for hTERT gene expression and breast cancer cell proliferation.

Ectopic Expression of Interferon Regulatory Factor-1 Promotes Human Breast Cancer Cell Death and Results in Reduced Expression of Survivin

The overexpression of the inhibitor of apoptosis protein, survivin, may provide tumor cells with a distinct survival advantage in situ; hence, therapeutic strategies have been designed to inhibit its expression. In this study, we ectopically expressed the interferon regulatory factor (IRF)-1 protein in the breast carcinoma cell lines MDA-MB-468 and SK-BR-3 using a recombinant adenovirus (Ad-IRF-1). By screening microarray analysis of cDNA from the human breast cancer cell line MDA-MB-468 infected with Ad-IRF-1, we observed a 15-fold down-regulation of the survivin gene when compared with uninfected cells. Consequently, we tested survivin expression in Ad-IRF-1-infected MDA-MB-468 and SK-BR-3 breast cancer cell lines. Immunoblotting analyses supported the contention that ectopic expression of the IRF-1 protein results in down-regulation of survivin protein expression that is independent of p53. In addition, Ad-IRF-1 infection of these human breast cancer cell lines induces the expression of p21. We also report that increased apoptosis is observed in tumor cells infected with Ad-IRF-1 compared with Ad-Psi5 mock-infected cells and that cell death is further augmented when the IRF-1-infected cells are cultured with Adriamycin. Moreover, in a xenogeneic mouse model of breast carcinoma, in vivo treatment of tumor-bearing mice with intratumoral Ad-IRF-1 injections results in tumor growth inhibition. In resected tumors from mice that had been treated with Ad-IRF-1, tumor cells that express the IRF-1 transgene have a predominant IRF-1-positive, survivin-negative phenotype. Collectively, these observations suggest that therapies designed to enhance IRF-1 expression within tumor cells may represent novel treatment strategies for breast cancer.

Effects of apoptosis-inducing nucleosides released from CD57+HLA-DRbright natural suppressor cell line on human breast cancer cell death and growth

The CD57+HLA-DRbright-natural suppressor (57.DR-NS) cell line induced apoptosis in estrogen-non-responsive human breast carcinoma MDA-MB-435 cells by apoptosis-inducing nucleosides (AINs) released into the cultures. We obtained six active AINs isolated by high performance liquid chromatography (HPLC) from 57.DR-NS cell cultures. Each AIN isolated from 57.DR-NS cell cultures induced apoptosis in MDA-MB-435 cells. We found the occurrence of DNA strand breaks followed by the activation of caspase-3 during AIN-induced apoptosis in MDA-MB-435 cells. The data obtained here indicated that 57.DR-NS cells could induce apoptosis in MDA-MB-435 cells mediated by AINs through DNA strand breaks and activation of caspase-3. Furthermore, the administration of AINs into MDA-MB-435 tumor-bearing SCID mice culminated in strong suppression of tumor growth with no change of body weight of experimental mice suggesting no side effects of AINs.

Bisphosphonates antagonise bone growth factors' effects on human breast cancer cells survival

Bone tissue constitutes a fertile ‘soil’ for metastatic tumours, notably breast cancer. High concentrations of growth factors in bone matrix favour cancer cell proliferation and survival, and a vicious cycle settles between bone matrix, osteoclasts and cancer cells. Classically, bisphosphonates interrupt this vicious cycle by inhibiting osteoclast-mediated bone resorption. We and others recently reported that bisphosphonates can also induce human breast cancer cell death in vitro, which could contribute to their beneficial clinical effects. We hypothesised that bisphosphonates could inhibit the favourable effects of ‘bone–derived’ growth factors, and indeed found that bisphosphonates reduced or abolished the stimulatory effects of growth factors (IGFs, FGF-2) on MCF-7 and T47D cell proliferation and inhibited their protective effects on apoptotic cell death in vitro under serum-free conditions. This could happen through an interaction with growth factors' intracellular phosphorylation transduction pathways, such as ERK1/2-MAPK. In conclusion, we report that bisphosphonates antagonised the stimulatory effects of growth factors on human breast cancer cell survival and reduced their protective effects against apoptotic cell death. Bisphosphonates and growth factors thus appear to be concurrent compounds for tumour cell growth and survival in bone tissue. This could represent a new mechanism of action of bisphosphonates in their protective effects against breast cancer-induced osteolysis.