Antitumor Activity and Pharmacodynamic Biomarkers of a Novel and Orally Available Small-Molecule Antagonist of Inhibitor of Apoptosis Proteins

Screening of Anti-carcinogenic Properties of Phytocompounds from Allium ascalonicum for Treating Breast Cancer Through In Silico and In Vitro Approaches

Plants, rich in phytocompounds, have been in usage since time immemorial for treating various diseases, namely, cancer. One such plant species, Allium ascalonicum (Shallot) belonging to Amaryllidaceae family is being studied here for its anti-carcinogenic properties against breast cancer. GC-MS characterization of A. ascalonicum exhibited 48 phytocompounds containing five peak phytocompounds and 13 phytocompounds with anti-carcinogenic properties. These 13 anti-carcinogenic phytocompounds were docked with three hormonal receptors involved in breast cancer malignancy, namely, ERα, PR, and human EGFR with tamoxifen as standard for in silico analysis. The results exhibited three phytocompounds that had better binding scores compared to that of the standard drug, tamoxifen. Lyophilized powder of aqueous A. ascalonicum extract, also referred as ASE, was used for in vitro approaches. Antioxidant study using DPPH assay revealed that the highest percentage of FRSA in ASE, nearly 51%, was observed at 50 µg/ml concentration. Cytotoxicity study on MCF-7 cell line using MTT assay demonstrated IC₅₀ value at 1400 µg/ml and anti-proliferative study using Trypan blue assay for the determination of percentage viability of MCF-7 cells at IC₅₀ concentration was observed to be 49%. Anti-mitotic activity using Vigna radiata seed germination assay revealed clear morphological differences in a dose-dependent manner between the seeds grown at various concentrations of ASE with nearly 56.5% growth inhibition observed at 1500 µg/ml concentration. Hence, this research work proves that Allium ascalonicum has very good anti-carcinogenic properties and this can be confirmed further through in vivo animal model studies and it can also be formulated as a promising drug to treat breast cancer. GC-MS characterization of Allium ascalonicum demonstrated the presence of five peak compounds and thirteen anti-carcinogenic compounds. The thirteen anti-carcinogenic compounds were docked with three target proteins (in silico analysis) involved in breast cancer malignancy and identified the presence of three potential phytocompounds that can be used for treating breast cancer. In vitro approaches also confirmed the presence of anti-carcinogenic properties such as antioxidative potential, cytotoxic, anti-proliferative, and anti-mitotic effects. Hence, Allium ascalonicum can be taken further to in vivo studies so that it can be formulated to treat breast cancer.

Therapeutics Targeting the Core Apoptotic Machinery

Simple Summary

Cancer develops when the balance between cell death and cell division in tissues is dysregulated. A key focus of cancer drug discovery is identifying therapeutic agents which will selectively kill and eliminate cancer cells from the body. A number of proteins can prevent the death of cancer cells and developing inhibitors against these proteins to promote cancer cell death is a focus of recent drug discovery efforts. This review aims to summarize the key targets being explored, the drug development approaches being adopted, and the success or limitations of agents currently approved or in clinical development.

Abstract

Therapeutic targeting of the apoptotic pathways for the treatment of cancer is emerging as a valid and exciting approach in anti-cancer therapeutics. Accumulating evidence demonstrates that cancer cells are typically “addicted” to a small number of anti-apoptotic proteins for their survival, and direct targeting of these proteins could provide valuable approaches for directly killing cancer cells. Several approaches and agents are in clinical development targeting either the intrinsic mitochondrial apoptotic pathway or the extrinsic death receptor mediated pathways. In this review, we discuss the main apoptosis pathways and the key molecular targets which are the subject of several drug development approaches, the clinical development of these agents and the emerging resistance factors and combinatorial treatment approaches for this class of agents with existing and emerging novel targeted anti-cancer therapeutics.

Advances in Cancer Treatment by Targeting the Neddylation Pathway

Developmental down-regulation protein 8 (NEDD8), expressed by neural progenitors, is a ubiquitin-like protein that conjugates to and regulates the biological function of its substrates. The main target of NEDD8 is cullin-RING E3 ligases. Upregulation of the neddylation pathway is closely associated with the progression of various tumors, and MLN4924, which inhibits NEDD8-activating enzyme (NAE), is a promising new antitumor compound for combination therapy. Here, we summarize the latest progress in anticancer strategies targeting the neddylation pathway and their combined applications, providing a theoretical reference for developing antitumor drugs and combination therapies.

The Multiple Roles of the IAP Super-family in cancer

The Inhibitor of Apoptosis proteins (IAPs) are a family of proteins that are mainly known for their anti-apoptotic activity and ability to directly bind and inhibit caspases. Recent research has however revealed that they have extensive roles in governing numerous other cellular processes. IAPs are known to modulate ubiquitin (Ub)-dependent signaling pathways through their E3 ligase activity and influence activation of nuclear factor κB (NF-κB). In this review, we discuss the involvement of IAPs in individual hallmarks of cancer and the current status of therapies targeting these critical proteins.

Impact of P-Glycoprotein on Intestinal Absorption of an Inhibitor of Apoptosis Protein Antagonist in Rats: Mechanisms of Nonlinear Pharmacokinetics and Food Effects

PURPOSE

This study was designed to investigate the effects of P-glycoprotein (P-gp) expressed in the intestine on the nonlinear pharmacokinetics (PK) of T-3256336, an inhibitor of apoptosis protein inhibitor, and food effects on its bioavailability in rats.

METHODS

To investigate the factors that contribute to nonlinear PK of T-3256336 in the intestine and liver, rats double-cannulated in the portal vein and femoral artery (PS rats) were used. F_aF_g (F_a, absorption ratio; F_g, intestinal availability) and hepatic availability (F_h) were simultaneously evaluated based on the difference between the portal and systemic blood area under the concentration-time curve (AUC). Elacridar was used as a P-gp inhibitor to assess the impact of P-gp on the intestinal absorption.

RESULTS

After oral administration of T-3256336 to PS rats at 3 and 30 mg/kg, F_aF_g value increased with dose escalation, whereas F_h value was nearly constant. Moreover, co-administration of elacridar resulted in a 5-fold increase in the F_aF_g value at 3 mg/kg. The AUC value of T-3256336 under fed conditions was 3-fold lower than that under fasted conditions. This food effect on the oral bioavailability (BA) was reduced by concomitant administration of elacridar.

CONCLUSION

P-gp expressed in the intestine would cause nonlinear PK and a food effect on BA of T-3256336 in rats.

An inhibitor of apoptosis protein antagonist T-3256336 potentiates the antitumor efficacy of the Nedd8-activating enzyme inhibitor pevonedistat (TAK-924/MLN4924)

Inhibitors of apoptosis proteins (IAPs) are antiapoptotic regulators that block cell death, and are frequently overexpressed in several human cancers, where they facilitate evasion of apoptosis and promote cell survival. IAP antagonists are also known as second mitochondria-derived activator of caspase (SMAC)-mimetics, and have recently been considered as novel therapeutic agents for inducing apoptosis, alone and in combination with other anticancer drugs. In this study, we showed that T-3256336, the orally available IAP antagonist has synergistically enhances the antiproliferative effects of the NEDD8-activating enzyme (NAE) inhibitor pevonedistat (TAK-924/MLN4924), and these effects were attenuated by a TNFα-neutralizing antibody. In the present mechanistic analyses, pevonedistat induced TNFα mRNA and triggered IAP antagonist-dependent extrinsic apoptotic cell death in cancer cell lines. Furthermore, synergistic effects of the combination of T-3256336 and pevonedistat were demonstrated in a HL-60 mouse xenograft model. Our findings provide mechanistic evidence of the effects of IAP antagonists in combination with NAE inhibitors, and demonstrate the potential of a new combination therapy for cancer.

T-3256336, a novel and orally available small molecule IAP antagonist, induced tumor cell death via induction of systemic TNF alpha production

Inhibitors of apoptosis proteins (IAPs) are a family of antiapoptotic regulators that have attracted attention as potential targets for cancer therapeutics. Although recent studies have revealed that small-molecule IAP antagonists induce tumor selective cell death in an autocrine tumor necrosis factor (TNF)α-dependent manner, the single-agent efficacy of IAP antagonists is restricted to a small subset of cancer cells. In this study, we showed that the single-agent activity of T-3256336 was limited to a few cancer cell lines in vitro, and these cell lines were defined by relatively high levels of TNFα mRNA expression. However, some other cancer cells, including PANC-1 cells, become drastically sensitive to T-3256336 when costimulated with exogenous TNFα. In PANC-1 mouse xenograft models, the administration of T-3256336 increased levels of several cytokines including TNFα and lead to tumor regression as a single agent, which was attenuated by the neutralization of circulating mouse TNFα with an antibody. These results suggest dual roles of IAP antagonists, increase systemic cytokines including TNFα, and sensitization of tumors to IAP antagonist-induced death.

The suppression of torulene and torularhodin treatment on the growth of PC-3 xenograft prostate tumors

Torulene and torularhodin are two of the principal carotenoids in Sporidiobolus pararoseus and have a similar structure to that of lycopene. The present study was to elucidate the anti-cancer activity of torulene and torularhodin in vivo with lycopene as a control. Nude mice were orally supplemented every day with a low or high dose [9 or 18 mg/kg body weight (BW)] of lycopene, torularhodin or torulene. Two weeks after the supplementation, mice were injected once with hormone-independent prostatic carcinoma PC-3 cells. When the tumor of the control group load exceeded 200 mm(3), mice were killed and the study was terminated. Compared with the controls, high-carotenoid supplementation lowered the mean number of tumors from 248.13 ± 28.74 to 50.83 ± 7.63, 70.34 ± 6.77, and 60.53 ± 6.78 mm(3) (P < 0.05, n = 8) by, respectively. Histological examination showed tumor degeneration, apoptosis and necrosis presented at the end of the experiment. Quantitative polymerase chain reaction and immunohistochemistry results showed Bcl-2 expression of the control group was higher than that of the carotenoid-treated group while the expression of Bax was lower than the carotenoid-treated group. High-carotenoid supplementation also increased the mRNA expressions of caspase-3, 8 and 9 in tumor tissues. These results show that both torulene and torularhodin supplementation inhibit the growth of prostate cancer in nude mice and suggest that such an action is associated the apoptosis of tumor cells.

A novel antagonist to the inhibitors of apoptosis (IAPs) potentiates cell death in EGFR-overexpressing non-small-cell lung cancer cells

In the effort to develop an efficient chemotherapy drug for the treatment of non-small-cell lung cancer (NSCLC), we analyzed the anti-tumorigenic effects of a novel small molecule targeting the inhibitor of apoptosis (IAPs), HM90822B, on NSCLC cells. HM90822B efficiently decreased IAP expression, especially that of XIAP and survivin, in several NSCLC cells. Interestingly, cells overexpressing epidermal growth factor receptor (EGFR) due to the mutations were more sensitive to HM90822B, undergoing cell cycle arrest and apoptosis when treated. In xenograft experiments, inoculated EGFR-overexpressing NSCLC cells showed tumor regression when treated with the inhibitor, demonstrating the chemotherapeutic potential of this agent. Mechanistically, decreased levels of EGFR, Akt and phospho-MAPKs were observed in inhibitor-treated PC-9 cells on phosphorylation array and western blotting analysis, indicating that the reagent inhibited cell growth by preventing critical cell survival signaling pathways. In addition, gene-specific knockdown studies against XIAP and/or EGFR further uncovered the involvement of Akt and MAPK pathways in HM90822B-mediated downregulation of NSCLC cell growth. Together, these results support that HM90822B is a promising candidate to be developed as lung tumor chemotherapeutics by targeting oncogenic activities of IAP together with inhibiting cell survival signaling pathways.

Design, stereoselective synthesis, and biological evaluation of novel tri-cyclic compounds as inhibitor of apoptosis proteins (IAP) antagonists

We recently reported the discovery of octahydropyrrolo[1,2-a]pyrazine A as a lead compound for an inhibitor of apoptosis proteins (IAP) antagonist. To develop IAP antagonists with favorable PK profiles, we designed novel tri-cyclic compounds, octahydro-1H-cyclopropa[4,5]pyrrolo[1,2-a]pyrazines 1 and 2 based on co-crystal structural analysis of A with cellular IAP-1 (cIAP-1). The additional cyclopropane moiety was used to block the predicted metabolic site of compound A without detriment to the binding affinity for cIAP. Compounds 1 and 2 were stereoselectively synthesized via intermediates 4a and 5b', which were obtained by Simmons-Smith cyclopropanation of ethylester 3a and silyl ether 3b'. Compounds 1 and 2 showed strong growth inhibition in MDA-MB-231 breast cancer cells and improved metabolic stability in comparison to A. Compound 2 exhibited significant in vivo PD effects to increase tumor necrosis factor-alpha mRNA in a dose dependent manner.