Arsenic trioxide and BIBR1532 synergistically inhibit breast cancer cell proliferation through attenuation of NF-κB signaling pathway.

AIMS: Despite the remarkable anti-proliferative effects of Arsenic trioxide (ATO) in breast cancer cells, the requirement of high, toxic concentrations to induce apoptosis may cause serious side effects in patients. In the present study, we aimed to use BIBR1532, an hTERT inhibitor, in combination with ATO to sensitize MCF7 and MDA-231 cells to lower concentrations of ATO. MAIN METHODS: Breast cancer cell lines MCF7 and MDA-231 were cultured and treated with different doses of ATO and BIBR1532 for 48 h and its effects on cell survival and proliferation were analyzed by MTT, crystal violet staining, colony formation assay, cell cycle, AnnexinV/PI and Real-time PCR tests. KEY FINDINGS: ATO and BIBR1532 synergistically inhibited proliferation and colony-forming ability of breast cancer cells. Besides, BIBR1532 augmented ATO-induced cytotoxic effects via triggering G1 cell cycle arrest and induction of apoptosis coupled with the down-regulation of NF-κB target genes that were involved in cell cycle progression (e.g. CCND1 and CDK6) and prevention of apoptosis such as Bcl-2, Bcl-xl, c-IAP2, and Survivin Respectively. Moreover, ATO-BIBR1532 significantly reduced the mRNA expression level of RELA, NFKB1, and several validated target genes of the NF-κB signaling pathway including NFKBIA, VEGFC, c-Myc, and hTERT. SIGNIFICANCE: The combination of ATO and BIBR1532 synergistically induced its anti-proliferative effect in breast cancer cells by targeting the two key cancer-related pathways, hTERT and NF-κB, and disrupting their feed-forward loop at the same time which result in the reduction of NF-κB transcriptional activity and subsequent down-regulation of its target genes.

Anti-tumor activity of cediranib, a pan-vascular endothelial growth factor receptor inhibitor, in pancreatic ductal adenocarcinoma cells.

PURPOSE: Pancreatic ductal adenocarcinoma (PDAC) is the most common and lethal subtype of pancreatic cancer, with a 5-year survival rate of < 3%. Early tumor dissemination, late diagnosis and insensitivity to conventional treatment are the major reasons for its high mortality rate. Members of the vascular endothelial growth factor (VEGF) family are overexpressed in PDAC and play important roles in its malignant progression, suggesting that VEGF-targeted therapies may interrupt the proliferation and motility of PDAC cells. Here, we evaluated the anti-tumor activity of cediranib, a pan-VEGF receptor inhibitor, on PDAC cells. METHODS: Anti-proliferative effects of cediranib were determined using cell proliferation and crystal violet staining assays. Annexin V/PI staining, radiation therapy, and cell migration and invasion assays were carried out to examine the effects of cediranib on apoptosis, radio-sensitivity and cell motility, respectively. Quantitative reverse transcription-PCR (qRT-PCR) and Western blot analyses were applied to elucidate the molecular mechanisms underlying the anti-tumor activity of cediranib. RESULTS: We found that cediranib decreased PDAC cell proliferation and clonogenic survival and induced apoptotic cell death through inhibition of the anti-apoptotic proteins cIAP1, XIAP, MCL-1 and survivin. Combination with cediranib synergistically increased the sensitivity of PDAC cells to chemotherapeutic agents such as gemcitabine and paclitaxel, and potentiated the effects of radiation therapy on PDAC cell growth inhibition and apoptosis induction. Furthermore, we found that treatment with cediranib impaired PDAC cell migration and invasion via expression reduction of the epithelial-to-mesenchymal transition (EMT) markers ZEB1, N-cadherin and Snail. CONCLUSIONS: Our data indicate that cediranib may exhibit anti-tumor activity in PDAC cells and provide a rationale for further investigation of the potential of VEGF receptor-targeted therapies for the treatment of PDAC.

Small molecule inhibitor of TLR4 inhibits ovarian cancer cell proliferation: new insight into the anticancer effect of TAK-242 (Resatorvid).

BACKGROUND: Despite all advances in the treatment of ovarian cancer (OC), it remains the most lethal gynecological malignancy worldwide. There are growing amounts of evidence indicating the role of inflammation in initiating chemoresistance. Therefore, Toll-like receptor 4 (TLR4), a mediator of inflammation in cancer cells, may be a proper anticancer target. METHODS: The effects of TLR4 activation by LPS was studied using MTT, colony formation, staining, scratch, and qRT-PCR assays as the first step. Then the same assays, in addition to anoikis resistance, cell cycle and annexin V/PI apoptosis tests, were used to investigate whether the inhibition of TLR4 using a small molecule inhibitor, TAK-242, could suppress the proliferation of various OC cell lines: A2780CP, 2008C13, SKOV3, and A2780S. RESULTS: The activation of TLR4 using LPS showed enhanced proliferation and invasion in the TLR4-expressing cell line (SKOV3). Next, treatment with the inhibitor revealed that TAK-242 suppressed the inflammatory condition of ovarian cancer cells, as evident by the down-regulation of IL-6 gene expression. We also found that TAK-242 halted cancer cell proliferation by inducing cell cycle arrest and apoptosis through the modulation of genes involved in these processes. Given the fact that the overexpression of TLR4 contributes to drug resistance, it was tempting to investigate the effect of TAK-242 in a combined-modality strategy. Interestingly, we found enhanced cytotoxicity when TAK-242 was used in combination with doxorubicin. CONCLUSION: TAK-242 serves as an appealing therapeutic strategy in the TLR4-expressing OC cells, either in the context of monotherapy or in combination with a chemotherapeutic drug.

Inhibition of bromodomain and extraterminal domain reduces growth and invasive characteristics of chemoresistant ovarian carcinoma cells.

Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy worldwide. Development of chemoresistance and peritoneal dissemination are the major reasons for low survival rate in the patients. The bromodomain and extraterminal domain (BET) proteins are known as epigenetic 'readers,' and their inhibitors are novel epigenetic strategies for cancer treatment. Accumulating body of evidence indicates that epigenetic modifications have critical roles in development of EOC, and overexpression of the BET family is a key step in the induction of important oncogenes. Here, we examined the mechanistic activity of I-BET151, a pan-inhibitor of the BET family, in therapy-resistant EOC cells. Our findings showed that I-BET151 diminished cell growth, clonogenic potential, and induced apoptosis. I-BET151 inhibited cell proliferation through down-modulation of FOXM1 and its targets aurora kinase B and cyclin B1. I-BET151 attenuated migration and invasion of the EOC cells by down-regulation of epithelial-mesenchymal transition markers fibronectin, ZEB2, and N-cadherin. I-BET151 synergistically enhanced cisplatin chemosensitivity by down-regulation of survivin and Bcl-2. Our data provide insights into the mechanistic activity of I-BET151 and suggest that BET inhibition has potential as a therapeutic strategy in therapy-resistant EOC. Further in vivo investigations on the therapeutic potential of I-BET151 in EOC are warranted.

Dacomitinib, a pan-inhibitor of ErbB receptors, suppresses growth and invasive capacity of chemoresistant ovarian carcinoma cells.

Epithelial ovarian cancer (EOC) is the most lethal gynaecological malignancy worldwide. Development of chemoresistance and peritoneal dissemination of EOC cells are the major reasons for low survival rate. Targeting signal transduction pathways which promote therapy resistance and metastatic dissemination is the key to successful treatment. Members of the ErbB family of receptors are over-expressed in EOC and play key roles in chemoresistance and invasiveness. Despite this, single-targeted ErbB inhibitors have demonstrated limited activity in chemoresistant EOC. In this report, we show that dacomitinib, a pan-ErbB receptor inhibitor, diminished growth, clonogenic potential, anoikis resistance and induced apoptotic cell death in therapy-resistant EOC cells. Dacominitib inhibited PLK1-FOXM1 signalling pathway and its down-stream targets Aurora kinase B and survivin. Moreover, dacomitinib attenuated migration and invasion of the EOC cells and reduced expression of epithelial-to-mesenchymal transition (EMT) markers ZEB1, ZEB2 and CDH2 (which encodes N-cadherin). Conversely, the anti-tumour activity of single-targeted ErbB agents including cetuximab (a ligand-blocking anti-EGFR mAb), transtuzumab (anti-HER2 mAb), H3.105.5 (anti-HER3 mAb) and erlotinib (EGFR small-molecule tyrosine kinase inhibitor) were marginal. Our results provide a rationale for further investigation on the therapeutic potential of dacomitinib in treatment of the chemoresistant EOC.

Significance of AZD1152 as a potential treatment against Aurora B overexpression in acute promyelocytic leukemia.

Aurora B kinase as a chromosomal passenger protein plays multiple roles in regulating mitosis and cytokinesis. The function of Aurora B in leukemic cells has made it an important treatment target. In this study, we explored the expressions of Aurora (A, B, and C) kinases in newly diagnosed acute promyelocytic leukemia (APL) patients. In addition, we investigated the effects of AZD1152 as a specific inhibitor of Aurora B on cell survival, DNA synthesis, nuclear morphology, apoptosis induction, cell cycle distribution, and gene expression in an APL-derived NB4 cell line. Our results showed that Aurora B was overexpressed in 88 % of APL patients. AZD1152 treatment of NB4 cells led to viability reduction and G2/M arrest followed by an increase in cell size and polyploidy induction. These giant cells showed morphological evidence of mitotic catastrophe. AZD1152 treatment induced activation of G2/M checkpoint which in turn led to transient G2/M arrest in a p21-independent manner. Lack of functional p53 in NB4 cells might provide an opportunity to escape from G2/M block and to endure repeated rounds of replication and polyploidy. Treated cells were probably eliminated via p73-mediated overexpression of BAX, PUMA, and APAF1 and downregulation of survivin and MCL-1. In summary, AZD1152 treatment led to endomitosis and polyploidy in TP53-mutated NB4 cells. These giant polyploid cells might undergo mitotic catastrophe and p73-mediated apoptosis. It seems that induction of polyploidy via AZD1152 could be a novel form of anti-cancer therapy for APL that may be clinically accessible in the near future.

Azidothymidine hinders arsenic trioxide-induced apoptosis in acute promyelocytic leukemia cells by induction of p21 and attenuation of G2/M arrest.

To enhance anticancer efficacy of the arsenic trioxide (ATO), the combination of ATO and azidothymidine (AZT), with convergence anti-telomerase activity, were examined on acute promyelocytic leukemia (APL) cell line, NB4. In spite of an induction of apoptosis by both drugs separately and a synergistic effect of them on hTERT down-regulation and telomerase inhibition, the ATO-induced cytotoxicity was reduced when it was used in combination with AZT. AZT attenuated the ATO effects on viability, metabolic activity, DNA synthesis, and apoptosis. These observations, despite the deflection from the main goal of this study, dedicate an especial opportunity to elucidate the importance of some of the mechanisms that have been suggested by which ATO induces apoptosis. Cell cycle distribution, ROS level, and caspase-3 activation analyses suggest that AZT reduced the ATO-induced cytotoxic effect possibly via relative induction and diminution of cells accumulated in (G1, S) and (G2/M) phase, respectively, as well as through attenuation of ROS generation and subsequent caspase-3 inhibition. QRT-PCR assay revealed that induction of p21expression by the combined AZT/ATO compared to ATO alone could be a reason for the relative decline of cells accumulation in G2/M and the increase of cells in G1 and S phases. Therefore, the G2/M arrest and ROS generation are likely principle mediators for the ATO-induced apoptosis and can be used as a guide to design rational combinatorial strategies involving ATO and agents with G2/M arrest or ROS generation capacity to intensify ATO-induced apoptosis.