Targeting the inhibitor of Apoptosis Protein BIR3 binding domains

cIAP2 expression and clinical significance in pigmented villonodular synovitis

Pigmented villonodular synovitis (PVNS) is a rare hyperplasia disease of the synovium with a predilection for the knee in either a localized (LPVNS) or a diffuse form (DPVNS). But the exact cause is not clear. The aim of this study was to explore the relationship between the expression of cellular inhibitor of apoptosis 2 (cIAP2) and proliferation, apoptosis, invasive growth and postoperative recurrence in PVNS. Clinical significance of cIAP2 expression in synovium from 63 patients' knee joints with PVNS (40 DPVNS; 23 LPVNS) were investigated with 20 normal subjects acting as controls. The cIAP2 gene was screened by Human Cancer Pathway Finder PCR Array and real-time polymerase chain reaction (RT-PCR). We also used immunohistochemistry to detect cIAP2 and proliferating cell nuclear antigen (PCNA) protein expression and analyzed their relationship with PVNS type, invasive growth, and postoperative recurrence. The expression of cIAP2, PCNA, caspase-8, caspase-9 and caspase-3 protein was tested in Western blot. Screening results of Human Cancer Pathway Finder PCR array and RT-PCR showed significantly more cIAP2 mRNA in DPVNS synovium than in normal or LPVNS synovium (P < 0.05). Immunohistochemistry and western blot showed that the cIAP2 protein expression level in DPVNS was significantly higher than in LPVNS tissue (P < 0.01). As cIAP2 expression increased, the expression of PCNA increased (P < 0.05) and expression of cleaved caspase-3, -8, -9 decreased (P < 0.01). cIAP2 and PCNA overexpression were found to be related to ligament and bone erosion in PVNS and to disease recurrence (P < 0.05). This study suggested that cIAP2 overexpression plays an important role in the anti-apoptotic, proliferative and invasive growth of PVNS, which may account for the recurrence and poor prognosis of DPVNS.

Nrdp1 increases neuron apoptosis via downregulation of Bruce following intracerebral haemorrhage

Background

Neuregulin receptor degradation protein-1 (Nrdp1) is an E3 ubiquitin ligase that plays an important role in regulating cell growth, apoptosis and oxidative stress. However, the data regarding its expression and exact mechanism in neuronal injury following ICH has not been well identified.

Methods

In this study, primary cortical neurons from C57BL/6 mice were subjected to erythrocyte lysates. Nrdp1 expression, cell apoptosis, caspase-3 and BRUCE levels were detected. In addition, inflammatory response, brain edema, and neurological injury in ICH mice were also assessed.

Results

We found that the expression of Nrdp1 was significantly increased in neuron cells accompanied by up-regulation of active caspase-3 and decreased expression of BRUCE (an inhibitor of apoptosis protein). However, inhibiting Nrdp1 levels of neurons reduced caspase-3 activity but induced up-regulation of BRUCE. In vivo, inhibiting Nrdp1 levels increased pro-inflammatory cytokines, brain edema, and neurological injury following ICH.

Conclusions

Taken together, the data suggested that Nrdp1 might play a crucial role in neuronal apoptosis via inhibiting BRUCE following ICH.

Functional mismatch repair and inactive p53 drive sensitization of colorectal cancer cells to irinotecan via the IAP antagonist BV6

A common strategy to overcome acquired chemotherapy resistance is the combination of a specific anticancer drug (e.g., topoisomerase I inhibitor irinotecan) together with a putative sensitizer. The purpose of this study was to analyze the cytostatic/cytotoxic response of colorectal carcinoma (CRC) cells to irinotecan, depending on the mismatch repair (MMR) and p53 status and to examine the impact of BV6, a bivalent antagonist of inhibitors of apoptosis c-IAP1/c-IAP2, alone or combined with irinotecan. Therefore, several MSH2- or MSH6-deficient cell lines were complemented for MMR deficiency, or MSH6 was knocked out/down in MMR-proficient cells. Upon irinotecan, MMR-deficient/p53-mutated lines repaired DNA double-strand breaks by homologous recombination less efficiently than MMR-proficient/p53-mutated lines and underwent elevated caspase-9-dependent apoptosis. Opposite, BV6-mediated sensitization was achieved only in MMR-proficient/p53-mutated cells. In those cells, c-IAP1 and c-IAP2 were effectively degraded by BV6, caspase-8 was fully activated, and both canonical and non-canonical NF-κB signaling were triggered. The results were confirmed ex vivo in tumor organoids from CRC patients. Therefore, the particular MMR+/p53mt signature, often found in non-metastasizing (stage II) CRC might be used as a prognostic factor for an adjuvant therapy using low-dose irinotecan combined with a bivalent IAP antagonist.

Sanguinarine Induces Apoptosis Pathway in Multiple Myeloma Cell Lines via Inhibition of the JaK2/STAT3 Signaling

Sanguinarine (SNG), a benzophenanthridine alkaloid, has displayed various anticancer abilities in several vivo and in vitro studies. However, the anticancer potential of SNG is yet to be established in multiple myeloma (MM), a mostly incurable malignancy of plasma cells. In this study, we aimed to investigate the potential anti-proliferative and pro-apoptotic activities of SNG in a panel of MM cell lines (U266, IM9, MM1S, and RPMI-8226). SNG treatment of MM cells resulted in a dose-dependent decrease in cell viability through mitochondrial membrane potential loss and activation of caspase 3, 9, and cleavage of PARP. Pre-treatment of MM cells with a universal caspase inhibitor, Z-VAD-FMK, prevented SNG mediated loss of cell viability, apoptosis, and caspase activation, confirming that SNG-mediated apoptosis is caspase-dependent. The SNG-mediated apoptosis appears to be resulted from suppression of the constitutively active STAT3 with a concomitant increase in expression of protein tyrosine phosphatase (SHP-1). SNG treatment of MM cells leads to down-regulation of the anti-apoptotic proteins including cyclin D, Bcl-2, Bclxl, and XIAP. In addition, it also upregulates pro-apoptotic protein, Bax. SNG mediated cellular DNA damage in MM cell lines by induction of oxidative stress through the generation of reactive oxygen species and depletion of glutathione. Finally, the subtoxic concentration of SNG enhanced the cytotoxic effects of anticancer drugs bortezomib (BTZ) by suppressing the viability of MM cells via induction of caspase-mediated apoptosis. Altogether our findings demonstrate that SNG induces mitochondrial and caspase-dependent apoptosis, generates oxidative stress, and suppresses MM cell lines proliferation. In addition, co-treatment of MM cell lines with sub-toxic doses of SNG and BTZ potentiated the cytotoxic activity. These results would suggest that SNG could be developed into therapeutic agent either alone or in combination with other anticancer drugs in MM.

XIAP over-expression is an independent poor prognostic marker in Middle Eastern breast cancer and can be targeted to induce efficient apoptosis

Background

Breast cancer is the most common cancer in females and is ranked second in cancer-related deaths all over the world in women. Despite improvement in diagnosis, the survival rate of this disease has still not improved. X-linked Inhibitor of Apoptosis (XIAP) has been shown to be over-expressed in various cancers leading to poor overall survival. However, the role of XIAP in breast cancer from Middle Eastern region has not been fully explored.

Methods

We examined the expression of XIAP in more than 1000 Middle Eastern breast cancer cases by immunohistochemistry. Apoptosis was measured by flow cytometry. Protein expression was determined by western blotting. Finally, in vivo studies were performed on nude mice following xenografting and treatment with inhibitors.

Results

XIAP was found to be over-expressed in 29.5% of cases and directly associated with clinical parameters such as tumor size, extra nodal extension, triple negative breast cancer and poorly differentiated breast cancer subtype. In addition, XIAP over-expression was also significantly associated with PI3-kinase pathway protein; p-AKT, proliferative marker; Ki-67 and anti-apoptotic marker; PARP. XIAP over-expression in our cohort of breast cancer was an independent poor prognostic marker in multivariate analysis. Next, we investigated inhibition of XIAP using a specific inhibitor; embelin and found that embelin treatment led to inhibition of cell viability and induction of apoptosis in breast cancer cells. Finally, breast cancer cells treated with combination of embelin and PI3-kinase inhibitor; LY294002 synergistically induced apoptosis and caused tumor growth regression in vivo.

Conclusion

These data suggest that XIAP may be playing an important role in the pathogenesis of breast cancer and can be therapeutically targeted either alone or in combination with PI3-kinase inhibition to induce efficient apoptosis in breast cancer cells.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3627-4) contains supplementary material, which is available to authorized users.

Small molecule inhibitor of apoptosis proteins antagonists: a patent review

INTRODUCTION

The family of inhibitor of apoptosis proteins (IAPs) plays a key role in the suppression of proapoptotic signaling; hence, a small molecule that disrupts the binding of IAPs with their functional partner should restore apoptotic response to proapoptotic stimuli in cells. The continued publication of new patent applications of IAP antagonists over the past 4 years is a testament to the continued interest surrounding the IAP family of proteins.

AREAS COVERED

This review summarizes the IAP antagonist patent literature from 2010 to 2014. Monovalent and bivalent Smac mimetics will be covered as well as two new developments in the field: IAP antagonists coupled to or merged with other targeted agents and new BIR2 selective IAP antagonists.

EXPERT OPINION

In addition to the well-explored scaffolds for monovalent and bivalent Smac-mimetics, some companies have taken more drastic approaches to explore new chemical space - for example, fragment-based approaches and macrocyclic inhibitors. Furthermore, other companies have designed compounds with alternative biological profiles - tethering to known kinase binding structures, trying to target to the mitochondria or introducing selective binding to the BIR2 domain. An overview of the status for the four small molecule IAP antagonists being evaluated in active human clinical trials is also provided.