HLI 373

IC50: N/A

HLI 373 is an inhibitor of Hdm2 ubiquitin ligase (E3).

Hdm2 ubiquitin ligase(E3) is a major regulator of p53 by promoting its ubiquitylation and proteasomal degradation. Therefore, blocking Hdm2-mediated activities may be a therapeutic approach for cancers expressing wild-type p53 [1].

In vitro: HLI373 effectively induces apoptosis of several tumor cells that are sensitive to DNA-damaging agents. HLI373-treated cells showed significantly more DNA retained on the filter, indicating that it does not induce single-strand break in U2OS cells. Having no discernable effect on gp78 or AO7, HLI373 seems prefer to inhibit the ubiquitin ligase activity of Hdm2. Treatment of U2OS cells with HLI373 at 10 Amol/L also leaded to a marked decrease in ubiquitylated species immunoprecipitated with anti-Hdm2, whereas the level of immunoprecipitated Hdm2 increased. Inhibition of Hdm2-mediated ubiquitylation in cells can trigger stabilization of both p53 and Hdm2 and preferential killing of tumor cells expressing wild-type p53. HLI373 increased p53 through inhibiting Hdm2-mediated ubiquitylation and not by inducing a DNA damage response in U2OS cells. HLI373 has high potency in stabilizing Hdm2 and p53. HLI373 inhibits the ubiquitin ligase activity of Hdm2 and induces a wild-type p53-dependent apoptosis in several tumor cells that are sensitive to DNA-damaging agents [1,2].

In vivo: So far, no study in vivo has been conducted.

Clinical trial: So far, no clinical study has been conducted.

References:
[1].  Kitagaki J, Agama KK, Pommier Y, et al. Targeting Tumor Cells Expressing p53 with a Water-soluble Inhibitor of Hdm2. Molecular Cancer Therapeutics, 2008; 7(8): 2445-1454.
[2]. Yang Y, Kitagaki J, Wang H, Hou DX, Perantoni AO. Targeting the Ubiquitin-proteasome System for Cancer Therapy. Cancer Science, 2009, 100(1): 24-28.

MDM2 promotes epithelial-mesenchymal transition and metastasis of ovarian cancer SKOV3 cells.[Pubmed:28817834]

Br J Cancer. 2017 Oct 10;117(8):1192-1201.

BACKGROUND: Metastasis accounts for the most lethal reason for the death of ovarian cancer patients, but remains largely untreated. Epithelial-mesenchymal transition (EMT) is critical for the conversion of early-stage ovarian tumours into metastatic malignancies. Thus the exploration of the signalling pathways promoting EMT would open potential opportunities for the treatment of metastatic ovarian cancer. Herein, the putative role of MDM2 in regulating EMT and metastasis of ovarian cancer SKOV3 cells was investigated. METHODS: The regulatory effects by MDM2 on cell motility was emulated by wound-healing and transwell assays. The effects on EMT transition and Smad pathway were studied by depicting the expression levels of epithelial marker E-cadherin as well as key components of Smad pathway. To evaluate the clinical relevance of our findings, the correlation of MDM2 expression levels with the stages of 104 ovarian cancer patients was investigated by immunohistochemistry assay. RESULTS: We demonstrate that MDM2 functions as a key factor to drive EMT and motility of ovarian SKOV3 cells, by facilitating the activation of TGF-beta-Smad pathway, which results in the increased transcription of snail/slug and the subsequent loss of E-cadherin levels. Such induction of EMT is sustained in either E3 ligase-depleted MDM2 or E3 ligase inhibitor HLI-373-treated cells, while being impaired by the N-terminal deletion of MDM2, which is also reflected by the inhibitory effects against EMT by Nutlin-3a, the N-terminal targeting agent. The expression levels of MDM2 is highly correlated with the stages of the ovarian cancer patients, and the higher expression of MDM2 together with TGFB are closely correlated with poor prognosis and predict a high risk of ovarian cancer patients. CONCLUSIONS: This study suggests that MDM2 activates Smad pathway to promote EMT in ovarian cancer metastasis, and targeting the N-terminal of MDM2 can reprogram EMT and impede the mobility of cancer cells.

Inhibitors of ubiquitin E3 ligase as potential new antimalarial drug leads.[Pubmed:28577368]

BMC Pharmacol Toxicol. 2017 Jun 2;18(1):40.

BACKGROUND: Protein ubiquitylation is an important post-translational regulation, which has been shown to be necessary for life cycle progression and survival of Plasmodium falciparum. Ubiquitin is a highly conserved 76 amino acid polypeptide, which attaches covalently to target proteins through combined action of three classes of enzymes namely, the ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2) and ubiquitin-protein ligase (E3). Ubiquitin E1 and E2 are highly conserved within eukaryotes. However, the P. falciparum E3 ligase is substantially variable and divergent compared to the homologs from other eukaryotes, which make the E3 ligase a parasite-specific target. METHODS: A set of selected E3 ubiquitin ligase inhibitors was tested in vitro against a chloroquine-sensitive P. falciparum D6 strain (PfD6) and a chloroquine-resistant P. falciparum W2 strain (PfW2). The inhibitors were also tested against Vero and transformed THP1 cells for cytotoxicity. The lead antimalarial E3 ubiquitin ligase inhibitors were further evaluated for the stage-specific antimalarial action and effects on cellular development of P. falciparum in vitro. Statistics analysis was done by two-way ANOVA followed by Tukey and Sidak multiple comparison test using GraphPad Prism 6. RESULTS: E3 ligase inhibitors namely, JNJ 26854165, HLI 373 and Nutlin 3 showed prominent antimalarial activity against PfD6 and PfW2. These inhibitors were considerably less cytotoxic to mammalian Vero cells. JNJ 26854165, HLI 373 and Nutlin 3 blocked the development of P. falciparum parasite at the trophozoite and schizont stages, resulting in accumulation of distorted trophozoites and immature schizonts. CONCLUSIONS: Interruption of trophozoites and schizont maturation by the antimalarial E3 ligase inhibitors suggest the role of ubiquitin/proteasome functions in the intraerythrocytic development of malaria parasite. The ubiquitin/proteasome functions may be critical for schizont maturation. Further investigations on the lead E3 ligase inhibitors shall provide better understanding regarding the importance of E3 ligase functions in the malaria parasite as a potential new antimalarial drug target and a new class of antimalarial drug leads.

Targeting tumor cells expressing p53 with a water-soluble inhibitor of Hdm2.[Pubmed:18723490]

Mol Cancer Ther. 2008 Aug;7(8):2445-54.

The tumor suppressor protein p53 is a potent inducer of apoptosis in transformed cells. Hdm2 is an ubiquitin ligase (E3) that acts as a major regulator of p53 by promoting its ubiquitylation and proteasomal degradation. For this reason, inhibiting the E3 activity of Hdm2 has been proposed as a therapeutic approach for cancers expressing wild-type p53. We previously identified a family of small molecules (HLI98s, 7-nitro-10-aryl-5-deazaflavins) that inhibit the E3 activity of Hdm2, increase cellular p53, and selectively kill transformed cells expressing wild-type p53. However, issues of both potency and solubility in aqueous solution limit the utility of the HLI98s. Here, we report that a highly soluble derivative of the HLI98s, which has a 5-dimethylaminopropylamino side chain but lacks the 10-aryl group (HLI373), has greater potency than the HLI98s in stabilizing Hdm2 and p53, activating p53-dependent transcription, and inducing cell death. Furthermore, we show that HLI373 is effective in inducing apoptosis of several tumor cells lines that are sensitive to DNA-damaging agents. These results suggest that HLI373 could serve as a potential lead for developing cancer therapeutics based on inhibition of the ubiquitin ligase activity of Hdm2.

Targeting the ubiquitin-proteasome system for cancer therapy.[Pubmed:19037995]

Cancer Sci. 2009 Jan;100(1):24-8.

The ubiquitin-proteasome system plays a critical role in controlling the level, activity and location of various cellular proteins. Significant progress has been made in investigating the molecular mechanisms of ubiquitination, particularly in understanding the structure of the ubiquitination machinery and identifying ubiquitin protein ligases, the primary specificity-determining enzymes. Therefore, it is now possible to target specific molecules involved in ubiquitination and proteasomal degradation to regulate many cellular processes such as signal transduction, proliferation and apoptosis. In particular, alterations in ubiquitination are observed in most, if not all, cancer cells. This is manifested by destabilization of tumor suppressors, such as p53, and overexpression of oncogenes such as c-Myc and c-Jun. In addition to the development and clinical validation of proteasome inhibitor, bortezomib, in myeloma therapy, recent studies have demonstrated that it is possible to develop inhibitors for specific ubiquitination and deubiquitination enzymes. With the help of structural studies, rational design and chemical synthesis, it is conceivable that we will be able to use 'druggable' inhibitors of the ubiquitin system to evaluate their effects in animal tumor models in the not-so-distant future.