Synthesis and cytotoxicity studies of Hedgehog enzyme inhibitors SANT-1 and GANT-61 as anticancer agents

Understanding the Roles of the Hedgehog Signaling Pathway during T-Cell Lymphopoiesis and in T-Cell Acute Lymphoblastic Leukemia (T-ALL)

The Hedgehog (HH) signaling network is one of the main regulators of invertebrate and vertebrate embryonic development. Along with other networks, such as NOTCH and WNT, HH signaling specifies both the early patterning and the polarity events as well as the subsequent organ formation via the temporal and spatial regulation of cell proliferation and differentiation. However, aberrant activation of HH signaling has been identified in a broad range of malignant disorders, where it positively influences proliferation, survival, and therapeutic resistance of neoplastic cells. Inhibitors targeting the HH pathway have been tested in preclinical cancer models. The HH pathway is also overactive in other blood malignancies, including T-cell acute lymphoblastic leukemia (T-ALL). This review is intended to summarize our knowledge of the biological roles and pathophysiology of the HH pathway during normal T-cell lymphopoiesis and in T-ALL. In addition, we will discuss potential therapeutic strategies that might expand the clinical usefulness of drugs targeting the HH pathway in T-ALL.

A trans-Pt(II) hedgehog pathway inhibitor complex with cytotoxicity towards breast cancer stem cells and triple negative breast cancer cells

The first example of a Pt complex of GANT61, a hedgehog (Hh) pathway inhibitor is reported. Reaction of cis-[Pt(II)Cl₂(dmso)₂] with one equivalent of 4-pyridine carboxaldehyde (4-PCA, control ligand) or one equivalent of GANT61 (Hh pathway inhibitor) in acetone at rt for 30 minutes afforded trans-[Pt(II)Cl₂(dmso)(4-PCA)] (1) and trans-[Pt(II)Cl₂(dmso)(GANT61)] (2) respectively, where 4-PCA and GANT61 are N-donor ligands. The structures of 1 and 2 were fully characterised by elemental analysis, ¹H NMR, ¹³C NMR and IR spectroscopy and X-ray crystallography. 1 and 2 undergo isomerisation from trans- to cis-in solution and therefore the biological activity of 2 is also associated with the cis-configuration. The in vitro cytotoxicity data show that 2 is a potent inhibitor of the growth of breast CSC-depleted HMLER and breast CSC-enriched HMLER-shEcad cells. Furthermore 2 markedly reduced the size and viability and significantly reduced the number of CSC-enriched HMLER-shEcad mammospheres formed. 2 also induced apoptosis with low micromolar IC₅₀ values against two triple negative breast cancer lines, MDA-MB-231 (MDA231) and BT549. 2, which possesses the Hh pathway inhibitor GANT61 as an N donor ligand exhibits far superior anti-CSC activity including in the CSC-enriched mammosphere model and activity against TNBC cells as compared to its control analogue, the trans-Pt(II) 4-PCA complex 1. The trans-Pt GANT61 complex 2 has also been shown to cause DNA damage and inhibit the Hh pathway at the level of GLI.

Advances in glioma-associated oncogene (GLI) inhibitors for cancer therapy

The Hedgehog/Glioma-associated oncogene homolog (HH/GLI) signaling pathway regulates self-renewal of rare and highly malignant cancer stem cells, which have been shown to account for the initiation and maintenance of tumor growth as well as for drug resistance, metastatic spread and relapse. As an important component of the Hh signaling pathway, glioma-associated oncogene (GLI) acts as a key signal transmission hub for various signaling pathways in many tumors. Here, we review direct and indirect inhibitors of GLI; summarize the abundant active structurally diverse natural GLI inhibitors; and discuss how to better develop and utilize GLI inhibitors to solve the problem of drug resistance in tumors of interest. In summary, GLI inhibitors will be promising candidates for various cancer treatments.

Ni(II), Pd(II), and Pt(II) Complexes of the Hedgehog Pathway Inhibitor GANT61-D

GANT61-D is an important hedgehog pathway inhibitor and an interesting ligand candidate for metal coordination. The first examples of metal complexes of the potent hedgehog pathway inhibitor GANT61-D are described. The reaction of Ni(II), Pd(II), and Pt(II) precursors with the hedgehog pathway inhibitor GANT61-D gave [Ni^II(GANT61-D)(OH₂)₃(μ²-SO₄)(μ³-SO₄)] (1), [Pd^II(Cl)(GANT61-D)]Cl (2), [Pt^II(Cl)(GANT61-D)]Cl, and [Pt^II(CBDCA_-2H)(GANT61-D)]. X-ray crystal structure analysis revealed that GANT61-D is a versatile N-donor ligand that can act as a bidentate ligand via the diaminopropane (DAP) N atoms or a tridentate ligand via the DAP N atoms and one dimethylaniline N atom. Protonation constants of the GANT61-D ligand in water and in a 60:40 (w/w) dimethyl sulfoxide-water solvent mixture were determined. Potentiometric and spectroscopic data on the Ni^II(GANT61-D) system indicate the formation of octahedral 1:1 species with medium stability in solution. 1 and 2 exhibited noteworthy in vitro cytotoxicity against medulloblastoma cancer cells.

Design, synthesis and evaluation of some pyrazolo[3,4-d]pyrimidines as anti-inflammatory agents

New pyrazolo[3,4-d]pyrimidines substituted with various functionalities or attached to a substituted pyrazole ring through different linkages were synthesized. The synthesized compounds were evaluated for their anti-inflammatory activity using in vitro COX-1/COX-2 inhibition assay and in vivo formalin induced paw edema and cotton pellet-induced granuloma assays. Results revealed that compounds 17b and 18 possessed COX-1/COX-2 selectivity indices higher than diclofenac sodium and celecoxib. However, compounds 16a,b exhibited selectivity indices higher than diclofenac sodium and nearly equivalent to celecoxib, whereas, 9b displayed selectivity index comparable to diclofenac sodium. In vivo anti-inflammatory data showed that compounds 9b, 16a, 18 displayed anti-inflammatory activity higher than both references in the formalin induced paw edema model. On the other hand, the pyrazolyl derivatives 9b, 16b and 17b displayed anti-inflammatory activity about 2-2.5-fold that of diclofenac sodium and nearly 8-10.5-fold that of celecoxib in the cotton pellet-induced granuloma assay. The ulcerogenic effect of the active compounds was also investigated and results revealed that compounds 16a, 17a,b and 18 showed good gastrointestinal safety profile. Based on this, compounds 16a and 18 were considered as safe and effective leads in managing acute inflammation, while, 17b was prominent in controlling chronic inflammation.

Chemical, computational and functional insights into the chemical stability of the Hedgehog pathway inhibitor GANT61

This work aims at elucidating the mechanism and kinetics of hydrolysis of GANT61, the first and most-widely used inhibitor of the Hedgehog (Hh) signalling pathway that targets Glioma-associated oncogene homologue (Gli) proteins, and at confirming the chemical nature of its bioactive form. GANT61 is poorly stable under physiological conditions and rapidly hydrolyses into an aldehyde species (GANT61-A), which is devoid of the biological activity against Hh signalling, and a diamine derivative (GANT61-D), which has shown inhibition of Gli-mediated transcription. Here, we combined chemical synthesis, NMR spectroscopy, analytical studies, molecular modelling and functional cell assays to characterise the GANT61 hydrolysis pathway. Our results show that GANT61-D is the bioactive form of GANT61 in NIH3T3 Shh-Light II cells and SuFu^−/− mouse embryonic fibroblasts, and clarify the structural requirements for GANT61-D binding to Gli1. This study paves the way to the design of GANT61 derivatives with improved potency and chemical stability.

The Effect of SHH-Gli Signaling Pathway on the Synovial Fibroblast Proliferation in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by chronic synovitis. This study aims to investigate the role of sonic hedgehog (SHH)-Gli signaling pathway in synovial fibroblast proliferation in rheumatoid arthritis. The expression of serum SHH in RA patients group was significantly increased compared with the systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), and healthy subject (healthy control, HC) groups, respectively; serum SHH expression of RA patients was positively correlated with rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP Ab), while there was no significant correlation between SHH expression and erythrocyte sedimentation rate (ESR). SHH, Ptch, Smo, and Gli molecules were highly expressed in rat RA-synovial fibroblast (RA-SF); after blocking the SHH-Gli signaling pathway with a Gli specific inhibitor, Gli-antagonist 61 (GANT61), RA-SF proliferation was inhibited in a dose-dependent manner and the apoptosis rate of RA-SF was increased as well; the expression levels of fibroblast growth factor receptor 1 (FGFR1) and FGFR3 declined in SF cells after GANT61 treatment. Our results suggest that SHH-Gli pathway is involved in the pathogenesis of RA, and blocking SHH-Gli pathway inhibits RA-SF cell proliferation and increases cell apoptosis, which may shed light on developing new ideas for RA treatment.

Potential smoothened inhibitor from traditional Chinese medicine against the disease of diabetes, obesity, and cancer

Nowadays, obesity becomes a serious global problem, which can induce a series of diseases such as type 2 diabetes mellitus, cancer, cardiovascular disease, metabolic syndrome, and stoke. For the mechanisms of diseases, the hedgehog signaling pathway plays an important role in body patterning during embryogenesis. For this reason, smoothened homologue (Smo) protein had been indicated as the drug target. In addition, the small-molecule Smo inhibitor had also been used in oncology clinical trials. To improve drug development of TCM compounds, we aim to investigate the potent lead compounds as Smo inhibitor from the TCM compounds in TCM Database@Taiwan. The top three TCM compounds, precatorine, labiatic acid, and 2,2′-[benzene-1,4-diylbis(methanediyloxybenzene-4,1-diyl)]bis(oxoacetic acid), have displayed higher potent binding affinities than the positive control, LY2940680, in the docking simulation. After MD simulations, which can optimize the result of docking simulation and validate the stability of H-bonds between each ligand and Smo protein under dynamic conditions, top three TCM compounds maintain most of interactions with Smo protein, which keep the ligand binding stable in the binding domain. Hence, we propose precatorine, labiatic acid, and 2,2′-[benzene-1,4-diylbis(methanediyloxybenzene-4,1-diyl)]bis(oxoacetic acid) as potential lead compounds for further study in drug development process with the Smo protein.