Targeted delivery of a colchicine analogue provides synergy with ATR inhibition in cancer cells

Hypoxia-Responsive Prodrug of ATR Inhibitor, AZD6738, Selectively Eradicates Treatment-Resistant Cancer Cells

Targeted therapy remains the future of anti-cancer drug development, owing to the lack of specificity of current treatments which lead to damage in healthy normal tissues. ATR inhibitors have in recent times demonstrated promising clinical potential, and are currently being evaluated in the clinic. However, despite the considerable optimism for clinical success of these inhibitors, reports of associated normal tissues toxicities remain a concern and can compromise their utility. Here, ICT10336 is reported, a newly developed hypoxia-responsive prodrug of ATR inhibitor, AZD6738, which is hypoxia-activated and specifically releases AZD6738 only in hypoxic conditions, in vitro. This hypoxia-selective release of AZD6738 inhibited ATR activation (T1989 and S428 phosphorylation) and subsequently abrogated HIF1a-mediated adaptation of hypoxic cancers cells, thus selectively inducing cell death in 2D and 3D cancer models. Importantly, in normal tissues, ICT10336 is demonstrated to be metabolically stable and less toxic to normal cells than its active parent agent, AZD6738. In addition, ICT10336 exhibited a superior and efficient multicellular penetration ability in 3D tumor models, and selectively eradicated cells at the hypoxic core compared to AZD6738. In summary, the preclinical data demonstrate a new strategy of tumor-targeted delivery of ATR inhibitors with significant potential of enhancing the therapeutic index.

Cancer-specific glycosylation of CD13 impacts its detection and activity in preclinical cancer tissues

Harnessing the differences between cancer and non-cancer tissues presents new opportunities for selective targeting by anti-cancer drugs. CD13, a heavily glycosylated protein, is one example with significant unmet clinical potential in cancer drug discovery. Despite its high expression and activity in cancers, CD13 is also expressed in many normal tissues. Here, we report differential tissue glycosylation of CD13 across tissues and demonstrate for the first time that the nature and pattern of glycosylation of CD13 in preclinical cancer tissues are distinct compared to normal tissues. We identify cancer-specific O-glycosylation of CD13, which selectively blocks its detection in cancer models but not in normal tissues. In addition, the metabolism activity of cancer-expressed CD13 was observed to be critically dependent on its unique glycosylation. Thus, our data demonstrate the existence of discrete cancer-specific CD13 glycoforms and propose cancer-specific CD13 glycoforms as a clinically useful target for effective cancer-targeted therapy.

Screening MT1-MMP Activity and Inhibition in Three-Dimensional Tumor Spheroids

Membrane type 1 matrix metalloproteinase (MT1-MMP) has been shown to be crucial for tumor angiogenesis, invasion, and metastasis, and thus MT1-MMP is a high priority target for potential cancer therapies. To properly evaluate MT1-MMP inhibitors, a screening protocol is desired by which enzyme activity can be quantified in a tumor microenvironment-like model system. In the present study, we applied a fluorogenic, collagen model triple-helical substrate to quantify MT1-MMP activity for tumor spheroids embedded in a collagen hydrogel. The substrate was designed to be MT1-MMP selective and to possess fluorescent properties compatible with cell-based assays. The proteolysis of the substrate correlated to glioma spheroid invasion. In turn, the application of either small molecule or protein-based MMP inhibitors reduced proteolytic activity and glioma spheroid invasion. The presence of MT1-MMP in glioma spheroids was confirmed by western blotting. Thus, spheroid invasion was dependent on MT1-MMP activity, and inhibitors of MT1-MMP and invasion could be conveniently screened in a high-throughput format. The combination of the fluorogenic, triple-helical substrate, the three-dimensional tumor spheroids embedded in collagen, and Hit-Pick software resulted in an easily adaptable in vivo-like tumor microenvironment for rapidly processing inhibitor potential for anti-cancer use.

AZD6738 Inhibits fibrotic response of conjunctival fibroblasts by regulating checkpoint kinase 1/P53 and PI3K/AKT pathways

Trabeculectomy can effectively reduce intraocular pressure (IOP) in glaucoma patients, the long-term surgical failure is due to the excessive proliferation and fibrotic response of conjunctival fibroblasts which causes the subconjunctival scar and non-functional filtering bleb. In this study, we demonstrated that AZD6738 (Ceralasertib), a novel potent ataxia telangiectasia and Rad3-related (ATR) kinase inhibitor, can inhibit the fibrotic response of conjunctival fibroblasts for the first time. Our in vitro study demonstrated that AZD6738 inhibited the level and the phosphorylation of checkpoint kinase 1 (CHK1), reduced TGF-β1-induced cell proliferation and migration, and induced apoptosis of human conjunctival fibroblasts (HConFs) in the high-dose group (5 μM). Low-dose AZD6738 (0.1 μM) inhibited the phosphorylation of CHK1 and reduce fibrotic response but did not promote apoptosis of HConFs. Further molecular research indicated that AZD6738 regulates survival and apoptosis of HConFs by balancing the CHK1/P53 and PI3K/AKT pathways, and inhibiting TGF-β1-induced fibrotic response including myofibroblast activation and relative extracellular matrix (ECM) protein synthesis such as fibronectin (FN), collagen Ⅰ (COL1) and collagen Ⅳ (COL4) through a dual pharmacological mechanism. Hence, our results show that AZD6738 inhibits fibrotic responses in cultured HConFs in vitro and may become a potential therapeutic option for anti-subconjunctival scarring after trabeculectomy.