SMAC Mimetic/IAP Inhibitor Birinapant Enhances Radiosensitivity of Glioblastoma Multiforme

Combinatorial screen with apoptosis pathway targeted agents alrizomadlin, pelcitoclax, and dasminapant in multi-cell type tumor spheroids

Apoptosis, or programmed cell death, plays a critical role in maintaining tissue homeostasis by eliminating damaged or abnormal cells. Dysregulation of apoptosis pathways is a hallmark of cancer, allowing malignant cells to evade cell death and proliferate uncontrollably. Targeting apoptosis pathways has emerged as a promising therapeutic strategy in cancer treatment, aiming to restore the balance between cell survival and death. The MDM2 inhibitor alrizomadlin, the Bcl-2/Bcl-xL inhibitor pelcitoclax, and the IAP family inhibitor dasminapant were evaluated both individually and in combinations with standard of care and investigational anticancer small molecules in a spheroid model of solid tumors. The multi-cell type tumor spheroids were grown from human endothelial cells and mesenchymal stem cells combined with human malignant cells that were either established or patient-derived cell lines from the NCI Patient-Derived Models Repository. The malignant cell lines were derived from a range of solid tumors including uterine carcinosarcoma, synovial sarcoma, rhabdomyosarcoma, soft tissue sarcoma, malignant fibrous histiocytoma, malignant peripheral nerve sheath tumor (MPNST), pancreas, ovary, colon, breast, and small cell lung cancer. Interactions were observed from combinations of the apoptosis pathway targeted agents. Additionally, interactions were observed from combinations of the apoptosis pathway targeted agents with other agents, including PARP inhibitors, the XPO1 inhibitor eltanexor, and the PI3K inhibitor copanlisib. Enhanced activity was also observed from combinations of the apoptosis pathway targeted agents with MAPK pathway targeted agents, including the MEK inhibitor cobimetinib as well as adagrasib and MRTX1133, which specifically target the KRAS G12C and G12D variants, respectively.

Cell death in glioblastoma and the central nervous system

Glioblastoma is the commonest and deadliest primary brain tumor. Glioblastoma is characterized by significant intra- and inter-tumoral heterogeneity, resistance to treatment and dismal prognoses despite decades of research in understanding its biological underpinnings. Encompassed within this heterogeneity and therapy resistance are severely dysregulated programmed cell death pathways. Glioblastomas recapitulate many neurodevelopmental and neural injury responses; in addition, glioblastoma cells are composed of multiple different transformed versions of CNS cell types. To obtain a greater understanding of the features underlying cell death regulation in glioblastoma, it is important to understand the control of cell death within the healthy CNS during homeostatic and neurodegenerative conditions. Herein, we review apoptotic control within neural stem cells, astrocytes, oligodendrocytes and neurons and compare them to glioblastoma apoptotic control. Specific focus is paid to the Inhibitor of Apoptosis proteins, which play key roles in neuroinflammation, CNS cell survival and gliomagenesis. This review will help in understanding glioblastoma as a transformed version of a heterogeneous organ composed of multiple varied cell types performing different functions and possessing different means of apoptotic control. Further, this review will help in developing more glioblastoma-specific treatment approaches and will better inform treatments looking at more direct brain delivery of therapeutic agents.

SMAC mimetic BV6 acts in synergy with mTOR inhibitor to increase cisplatin sensitivity in ovarian cancer

The objective of this study is to observe the antitumor efficacy of the second mitochondria-derived activator of caspases (SMAC) mimetic bivalent smac mimetic (BV6) in combination with target of rapamycin (mTOR) inhibitor on DDP (cisplatin) sensitivity. Ovarian cancer cells were exposed to cisplatin, BV6, DDP + BV6, and DDP + BV6 + mTOR inhibitor Rapamycin. Using proteomics and bioinformatics, protein expression profiles in ovarian cancer were determined. Bagg Albino color nude mice were treated with DDP or BV6 alone or in combination, or BV6 + DDP + Rapamycin. The effects of different treatments on ovarian cancer cells and tumor growth were evaluated in vivo and in vitro . Proteomics and bioinformatics analysis revealed significant changes of protein kinase (AKT)/mTOR pathway. Consistently, western blot data indicated that AKT/mTOR axis was gradually activated in BV6-treated ovarian cancer cells and attenuated the cytotoxic effect of BV6. Functional assays showed that DDP or BV6 treatment alone significantly enhanced the sensitivity and inhibited the migration of ovarian cancer cells, but without any synergistic effects. In addition, combination with BV6 and mTOR inhibitor Rapamycin significantly decreased cell viability and inhibited migration of ovarian cancer cells exposed to DDP. Consistently, the xenograft model showed that co-treatment with Rapamycin with BV6 had significantly suppressed tumor growth and metastasis. Our study demonstrated that SMAC analogue BV6 exhibits a strong anticancer effect on ovarian cancer in vitro and in vivo . Combination with Rapamycin overcomes the activation of mTOR pathway by BV6 and increases the chemosensitivity to DDP. These data suggest a potential application of triple combination with DDP + BV6 + Rapamycin in clinical management of ovarian cancer.

A Comprehensive Insight into Apoptosis: Molecular Mechanisms, Signaling Pathways, and Modulating Therapeutics

Apoptosis, or programmed cell death, is a fundamental biological process essential for maintaining tissue homeostasis. Dysregulation of apoptosis is implicated in a variety of diseases, including cancer, neurodegenerative disorders, and autoimmune conditions. This review provides an in-depth insight into the molecular mechanisms and signaling pathways that regulate apoptosis, highlighting both intrinsic and extrinsic pathways. Additionally, the review explains the tumor microenvironment's influence on apoptosis and its implications for cancer therapy resistance. Understanding the complex interplay between apoptotic signaling and cellular responses is crucial for developing targeted therapies that can effectively manage diseases associated with apoptosis dysregulation. The effects of conventional therapeutics and alternative substances with natural sources such as herbal compounds, alongside vitamins, minerals, and trace elements on cellular homeostasis and disease pathogenesis have been thoroughly investigated. Moreover, recent advances in therapeutic strategies aimed at modulating apoptosis are discussed, with a focus on novel interventions such as nutrition bio shield dietary supplement. These emerging approaches offer potential benefits beyond conventional treatments by selectively targeting apoptotic pathways to inhibit cancer progression and metastasis. By integrating insights from recent studies, this review aims to enhance our understanding of apoptosis and guide future research in developing innovative therapeutic approaches.

Astrocytes and the tumor microenvironment inflammatory state dictate the killing of glioblastoma cells by Smac mimetic compounds

Smac mimetic compounds (SMCs) are small molecule drugs that sensitize cancer cells to TNF-α-induced cell death and have multiple immunostimulatory effects through alterations in NF-κB signaling. The combination of SMCs with immunotherapies has been reported to result in durable cures of up to 40% in syngeneic, orthotopic murine glioblastoma (GBM) models. Herein, we find that SMC resistance is not due to a cell-intrinsic mechanism of resistance. We thus evaluated the contribution of GBM and brain stromal components to identify parameters leading to SMC efficacy and resistance. The common physiological features of GBM tumors, such as hypoxia, hyaluronic acid, and glucose deprivation were found not to play a significant role in SMC efficacy. SMCs induced the death of microglia and macrophages, which are the major immune infiltrates in the tumor microenvironment. This death of microglia and macrophages then enhances the ability of SMCs to induce GBM cell death. Conversely, astrocytes promoted GBM cell growth and abrogated the ability of SMCs to induce death of GBM cells. The astrocyte-mediated resistance can be overcome in the presence of exogenous TNF-α. Overall, our results highlight that SMCs can induce death of microglia and macrophages, which then provides a source of death ligands for GBM cells, and that the targeting of astrocytes is a potential mechanism for overcoming SMC resistance for the treatment of GBM.

Birinapant Reshapes the Tumor Immunopeptidome and Enhances Antigen Presentation

Birinapant, an antagonist of the inhibitor of apoptosis proteins, upregulates MHCs in tumor cells and displays a better tumoricidal effect when used in combination with immune checkpoint inhibitors, indicating that Birinapant may affect the antigen presentation pathway; however, the mechanism remains elusive. Based on high-resolution mass spectrometry and in vitro and in vivo models, we adopted integrated genomics, proteomics, and immunopeptidomics strategies to study the mechanism underlying the regulation of tumor immunity by Birinapant from the perspective of antigen presentation. Firstly, in HT29 and MCF7 cells, Birinapant increased the number and abundance of immunopeptides and source proteins. Secondly, a greater number of cancer/testis antigen peptides with increased abundance and more neoantigens were identified following Birinapant treatment. Moreover, we demonstrate the existence and immunogenicity of a neoantigen derived from insertion/deletion mutation. Thirdly, in HT29 cell-derived xenograft models, Birinapant administration also reshaped the immunopeptidome, and the tumor exhibited better immunogenicity. These data suggest that Birinapant can reshape the tumor immunopeptidome with respect to quality and quantity, which improves the presentation of CTA peptides and neoantigens, thus enhancing the immunogenicity of tumor cells. Such changes may be vital to the effectiveness of combination therapy, which can be further transferred to the clinic or aid in the development of new immunotherapeutic strategies to improve the anti-tumor immune response.

The SMAC mimetic birinapant alleviates lipopolysaccharide-induced acute lung injury by inhibiting MAPK signaling

The second mitochondria-derived activator of caspases (SMAC) mimetic birinapant attenuated liver injury by inhibited the degradation of tumor necrosis factor receptor-associated factor 3 (TRAF3) and activation of mitogen-activated protein kinase (MAPK) signaling pathway in liver macrophage, but its role in LPS induced acute lung injury (ALI) is not understood. The present study was to investigate the effects of birinapant on ALI and its possible mechanism. A dose of birinapant (30 mg/kg) or a vehicle was administered intravenously 24 hours before LPS (100 μg) stimulation in mice. The levels of TNF-α, IL-6 and IL-1β in bronchoalveolar lavage fluid (BALF) were measured by ELISA. The infiltrated macrophages and expression of monocyte chemoattractant protein-1 (MCP-1) was determined by immunohistochemistry staining in the lung tissues. The JNK and p38 MAPK activation, protein expression and K48-linked polyubiquitination of TRAF3 were determined in alveolar macrophage cell line (MH-S cells) after 1μg/ml LPS stimulation. The results showed that the birinapant down-regulated the levels of TNF-α, IL-6 and IL-1β in the BALF. In addition, birinapant markedly inhibited macrophages infiltration and MCP-1 protein expression in lung tissues. At last, birinapant suppressed the MAPKsignaling pathway and K48-linked ubiquitinated degradation of TRAF3 in MH-S cells after LPS administration. In conclusion, the results proved that birinapant protected against LPS-induced ALI through inhibiting MAPK activation and K48-linked ubiquitination of TRAF3 in alveolar macrophages.

Targeting Apoptosis in Cancer

PURPOSE OF REVIEW

Apoptosis is a major mechanism of cancer cell death. Thus, evasion of apoptosis results in therapy resistance. Here, we review apoptosis modulators in cancer and their recent developments, including MDM2 inhibitors and kinase inhibitors that can induce effective apoptosis.

RECENT FINDINGS

Both extrinsic pathways (external stimuli through cell surface death receptor) and intrinsic pathways (mitochondrial-mediated regulation upon genotoxic stress) regulate the complex process of apoptosis through orchestration of various proteins such as members of the BCL-2 family. Dysregulation within these complex steps can result in evasion of apoptosis. However, via the combined evolution of medicinal chemistry and molecular biology, omics assays have led to innovative inducers of apoptosis and inhibitors of anti-apoptotic regulators. Many of these agents are now being tested in cancer patients in early-phase trials. We believe that despite a sluggish speed of development, apoptosis targeting holds promise as a relevant strategy in cancer therapeutics.