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Background: Silibinin is a traditionally well-known drug for its hepatoprotective efficacy against various types of liver afflictions. In addition, it has recently been considered broadly as a potential chemopreventive agent against many types of cancers. The current study was designed to evaluate the restrictive effects of pharmacological doses of silibinin on SKBR3, an ErbB2-overexpressed and ER-negative human breast carcinoma cell line. Methods: Effect of silibinin on metabolic activity and proliferation of human breast carcinoma (SKBR3) cell line were evaluated by MTT and BrdU assays respectively. Furthermore, the proapoptotic effect of silibinin was investigated using flow cytometry. The NF-κB phosphorylation assay was also used to assess the effect of silibinin on NF-κB activation. The alkalizing effect of silibinin on SKBR3 cell line was evaluated by measuring pH of media of the silibinin-treated cells compared to control. Results: Our results indicate that silibinin inhibited metabolic activity and cell proliferation of SKBR3 cells in a dose-dependent manner. Moreover, silibinin significantly induced apoptosis in SKBR3 cells. On the other hand, silibinin significantly inhibited activation of NF-κB which is known to be highly active in this cell line. Alkalizing effect of silibinin was also observed. Conclusion: The results obtained here indicate that silibinin may be an efficacious therapeutic agent against ER-negative breast carcinomas with high inhibitory effect on NF-κB. [ABSTRACT FROM AUTHOR]

Abstract Telomerase-mediated immortalization and proliferation of tumor cells is a promising anti-cancer treatment strategy and development of potent telomerase inhibitors is believed to open new window of treatments in human malignancies. In the present study, we found that BIBR1532, a small molecule inhibitor of human telomerase, exerted cytotoxic effects on a panel of human cancer cells spanning from solid tumors to hematologic malignancies; however, as compared with solid tumors, leukemic cells were more sensitive to this inhibitor. This was independent of molecular status of p53 in the leukemic cells. The results of a miRNA PCR array revealed that BIBR1532-induced cytotoxic effects in NB4, the most sensitive cell line, was coupled with alteration in a substantial number of cancer-related miRNAs. Interestingly, most of these miRNAs were found to act as tumor suppressors with validated targets in cell cycle or nuclear factor (NF)-κB–mediated apoptosis. In accordance with a bioinformatics analysis, our experimental studies showed that BIBR1532-induced apoptosis is mediated, at least partly, by inhibition of NF-κB. Moreover, we found that the alteration in the expression of miRNAs was coupled with the alteration in the cell cycle progression. To sum up with, a straightforward interpretation of our results is that telomerase inhibition using BIBR1532 not only induced CDKN1A-mediated G1 arrest in NB4, but also resulted in a caspase-3-dependent apoptotic cell death mostly through suppression of NF-κB axis. [ABSTRACT FROM AUTHOR]

Abstract While a batch of efforts are fastened on synthesizing the novel targeted anti-cancer agents, recent investigations have achieved a breakthrough in identifying a favorable anti-tumor activity for some supportive drugs, which their safety have been confirmed thus far. The results of the present study highlighted the efficacy of Aprepitant, an oral antagonist of the neurokinin-1 receptor (NK1R), against both APL (NB4) and pre-B ALL (Nalm-6) cell lines; however, a differential sensitivity pattern was found in these cells. To the best of our knowledge, this is the first time that the molecular mechanisms of resistance to Aprepitant have been investigated and, herein, we proposed that the effectiveness of Aprepitant could be overshadowed, at least partially, through over-activated nuclear factor-κB in Nalm-6 pre-B ALL cells. In contrast to Nalm-6, the cytotoxic property of Aprepitant in NB4 was divulged at the lower concentrations. Of particular interest, we found that the cytotoxicity of the inhibitor became even more evident in the synergistic experiments, where an enhanced reduction in viability was noted after treatment of NB4 cells with ATO-plus-Aprepitant. The stimulatory effect of NK1R inhibition on ATO cytotoxicity is probably mediated through up-regulation of p73, which can subsequently engage p21 and NF-κB pathway via transcriptional suppression of c-Myc. Taken together, the present study suggests that inhibition of NK1R using Aprepitant, either alone or in combination with chemotherapeutic drugs, could be a novel therapeutic strategy for the treatment of acute leukemia, especially APL, that may be clinically accessible in the near future. [ABSTRACT FROM AUTHOR]

The intertwining between cancer pathogenesis and perturbation of multitude signaling pathways ushered the cancer therapeutic approaches into an unbounded route of targeted therapies. For the nonce and among the plethora of promising inhibitors, intense interest has focused on small molecules targeting different component of PI3K axis. Intrigued by the constant activation of PI3K in leukemia, this study aimed to investigate the effects of BKM120, as the excelled member of pan PI3K inhibitors, in a panel of hematologic malignant cell lines. The resulting data showed that BKM120 exerted a concentration-dependent growth suppressive effect; however, IC 50 values varied among the tested cells. Our results outlined that the blockage of PI3K in NB4, as the most sensitive cell line, resulted in a caspase-3-dependent apoptosis probably through NFκB-mediated suppression of c-Myc and hTERT. As far we are aware, to date, there have been no reports of BKM120 effect on enzymatic repression of telomerase, and this study represents for the first time that the anti-proliferative effect of the inhibitor on NB4 is mediated by down-regulation of telomerase; shedding new light on the novel mechanism of action of BKM120. [ABSTRACT FROM AUTHOR]

Complex interplay of intracellular signaling networks, spanning from the extracellular environment to the nucleus, orchestrate normal cell growth and survival. Dysregulation of such signals contributes to malignant transformation, thereby giving the cancer cells a survival advantage, but also could be exploited for new anticancer interventions. The aim of this study was to investigate the effects of pan class-I PI3K inhibitor NVP-BKM120 on two distinct acute leukemia cell lines, NB4 (with mutant p53) and Nalm-6 (with wild-type p53). Our data highlighted the efficacy of the inhibitor against APL and pre B ALL cell lines; however, we failed to find an obvious correlation between p53 status and the sensitivity of leukemic cells to NVP-BKM120. Real-time PCR analysis revealed a significant up-regulation of p53 target genes in Nalm-6 cells, indicating a p53-dependent mechanism involved in NVP-BKM120 cytotoxicity. On the other hand, cytotoxic effects in mutant p53-expressing NB4 cells seem to be mediated mostly by the inhibition of the PI3K/Akt/NF-κB axis. In conclusion, we suggest NVP-BKM120 induces apoptosis through p53-dependent and -independent mechanisms, indicating the potential application of the inhibitor in both wild-type and deficient p53-expressing leukemic cells. [ABSTRACT FROM AUTHOR]

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. 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. 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. 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. [ABSTRACT FROM AUTHOR]