X-linked inhibitor of apoptosis protein (XIAP) is constitutively expressed endogenous inhibitor of apoptosis, exhibit its antiapoptotic effect by inactivating key caspases such as caspase-3, caspase-7 and caspase-9 and also play pivotal role in rendering cancer chemoresistance. Our studies showed the coadministration of TQ and TAM resulting in a substantial increase in breast cancer cell apoptosis and marked inhibition of cell growth both in vitro and in vivo. Anti-angiogenic and anti-invasive potential of TQ and TAM was assessed through in vitro studies. This novel combinatorial regimen leads to regulation of multiple cell signaling targets including inactivation of Akt and XIAP degradation. At molecular level, TQ and TAM synergistically lowers XIAP expression resulting in binding and activation of caspase-9 in apoptotic cascade, and interfere with cell survival through PI3-K/Akt pathway by inhibiting Akt phosphorylation. Cleaved caspase-9 further processes other intracellular death substrates such as PARP thereby shifting the balance from survival to apoptosis, indicated by rise in the sub-G1 cell population. This combination also downregulates the expression of Akt-regulated downstream effectors such as Bcl-xL, Bcl-2 and induce expression of Bax, AIF, cytochrome C and p-27. Consistent with these results, overexpression studies further confirmed the involvement of XIAP and its regulatory action on Akt phosphorylation along with procaspase-9 and PARP cleavage in TQ-TAM coadministrated induced apoptosis. The ability of TQ and TAM in inhibiting XIAP was confirmed through siRNA-XIAP cotransfection studies. This novel modality may be a promising tool in breast cancer treatment.

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BackgroundTamoxifen (TAM) is widely used in the chemotherapy of breast cancer and as a preventive agent against recurrence after surgery. However, extended TAM administration for breast cancer induces increased VEGF levels in patients, promoting new blood vessel formation and thereby limiting its efficacy. Celecoxib (CXB), a selective COX-2 inhibitor, suppresses VEGF gene expression by targeting the VEGF promoter responsible for its inhibitory effect. For this study, we had selected CXB as non-steroidal anti-inflammatory drug in combination with TAM for suppressing VEGF expression and simultaneously reducing doses of both the drugs.MethodsThe effects of CXB combined with TAM were examined in two human breast cancer cell lines in culture, MCF7 and MDA-MB-231. Assays of proliferation, apoptosis, angiogenesis, metastasis, cell cycle distribution, and receptor signaling were performed.ResultsHere, we elucidated how the combination of TAM and CXB at nontoxic doses exerts anti-angiogenic effects by specifically targeting VEGF/VEGFR2 autocrine signaling through ROS generation. At the molecular level, TAM-CXB suppresses VHL-mediated HIF-1α activation, responsible for expression of COX-2, MMP-2 and VEGF. Besides low VEGF levels, TAM-CXB also suppresses VEGFR2 expression, confirmed through quantifying secreted VEGF levels, luciferase and RT-PCR studies. Interestingly, we observed that TAM-CXB was effective in blocking VEGFR2 promoter induced expression and further 2 fold decrease in VEGF levels was observed in combination than TAM alone in both cell lines. Secondly, TAM-CXB regulated VEGFR2 inhibits Src expression, responsible for tumor progression and metastasis. FACS and in vivo enzymatic studies showed significant increase in the reactive oxygen species upon TAM-CXB treatment.ConclusionsTaken together, our experimental results indicate that this additive combination shows promising outcome in anti-metastatic and apoptotic studies. In a line, our preclinical studies evidenced that this additive combination of TAM and CXB is a potential drug candidate for treatment of breast tumors expressing high levels of VEGF and VEGFR2. This ingenious combination might be a better tailored clinical regimen than TAM alone for breast cancer treatment.

Interleukin-6 (IL-6) signaling network has been implicated in oncogenic transformations making it attractive target for the discovery of novel cancer therapeutics. In this study, potent antiproliferative and apoptotic effect of diacerein were observed against breast cancer. In vitro apoptosis was induced by this drug in breast cancer cells as verified by increased sub-G1 population, LIVE/DEAD assay, cell cytotoxicity and presence of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, as well as downregulation of antiapoptotic proteins Bcl-2 and Bcl-xL and upregulation of apoptotic protein Bax. In addition, apoptosis induction was found to be caspase dependent. Further molecular investigations indicated that diacerein instigated apoptosis was associated with inhibition of IL-6/IL-6R autocrine signaling axis. Suppression of STAT3, MAPK and Akt pathways were also observed as a consequence of diacerein-mediated upstream inhibition of IL-6/IL-6R. Fluorescence study and western blot analysis revealed cytosolic accumulation of STAT3 in diacerein-treated cells. The docking study showed diacerein/IL-6R interaction that was further validated by competitive binding assay and isothermal titration calorimetry. Most interestingly, it was found that diacerein considerably suppressed tumor growth in MDA-MB-231 xenograft model. The in vivo antitumor effect was correlated with decreased proliferation (Ki-67), increased apoptosis (TUNEL) and inhibition of IL-6/IL-6R-mediated STAT3, MAPK and Akt pathway in tumor remnants. Taken together, diacerein offered a novel blueprint for cancer therapy by hampering IL-6/IL-6R/STAT3/MAPK/Akt network.

Recently, photoresponsive nanoparticles have received significant attention because of their ability to provide spatial and temporal control over the drug release. In the present work, we report for the first time photoresponsive multifunctional magnetic nanoparticles (MNPs) fabricated using coumarin-based phototrigger and Fe/Si MNPs for controlled delivery of anticancer drug chlorambucil. Further, newly fabricated photoresponsive multifunctional MNPs were also explored for cell luminescence imaging. In vitro biological studies revealed that coumarin tethered Fe/Si MNPs of ~9 nm size efficiently delivered the anticancer drug chlorambucil into cancer cells and thereby improving the drug action to kill the cancer cells upon irradiation. Such multifunctional MNPs with strong fluorescence, good biocompatibility and efficient photocontrolled drug release ability will be of great benefit in the construction of light-activated multifunctional nano drug delivery systems.