Molecular modeling piloted analysis for semicarbazone derivative of curcumin as a potent Abl-kinase inhibitor targeting colon cancer

The human Abl kinases comprise a family of proteins that are known to be key stimulus drivers in the signaling pathways modulating cell growth, cell survival, cell adhesion, and apoptosis. Recent collative studies have indicated the role of activation of Abl and Abl-related genes in solid tumors; further terming the Abl kinases as molecular switches which promote proliferation, tumorigenesis, and metastasis. The up-regulated Abl-kinase expression in colorectal cancer (CRC) and the role of Abl tyrosine kinase activity in the Matrigel invasion of CRC cells have cemented its significance in CRC advancement. Therefore, the requisite of identifying small molecules which serve as Abl selective inhibitors and designing anti-Abl therapies, particularly for CRC tumors, has driven this study. Curcumin has been touted as an effective inhibitor of cancer cells; however, it is limited by its physicochemical inadequacies. Hence, we have studied the behavior of heterocyclic derivatives of curcumin via computational tools such as pharmacophore-based virtual screening, molecular docking, free-energy binding, and ADME profiling. The most actively docked molecule, 3,5-bis(4-hydroxy-3-methylstyryl)-1H-pyrazole-1-carboxamide, was comparatively evaluated against Curcumin via molecular dynamics simulation using Desmond, Schrödinger. The study exhibited the improved stability of the derivative as compared to Curcumin in the tested protein pocket and displayed the interaction bonds with the contacted key amino acids. To further establish the claim, the derivatives were synthesized via the mechanism of cyclization of Curcumin and screened in vitro using SRB assay against human CRC cell line, HCT 116. The active derivative indicated an IC50 value of 5.85 µM, which was sevenfold lower as compared to Curcumin’s IC50 of 35.40 µM. Hence, the results base the potential role of the curcumin derivative in modulating Abl-kinase activity and in turn may have potential therapeutic value as a lead for CRC therapy.

Inhibitors of Discoidin Domain Receptor (DDR) Kinases for Cancer and Inflammation

The discoidin domain receptor tyrosine kinases DDR1 and DDR2 are distinguished from other kinase enzymes by their extracellular domains, which interact with collagen rather than with peptidic growth factors, before initiating signaling via tyrosine phosphorylation. They share significant sequence and structural homology with both the c-Kit and Bcr-Abl kinases, and so many inhibitors of those kinases are also effective. Nevertheless, there has been an extensive research effort to develop potent and specific DDR inhibitors. A key interaction for many of these compounds is H-bonding to Met-704 in a hydrophobic pocket of the DDR enzyme. The most widespread use of DDR inhibitors has been for cancer therapy, but they have also shown effectiveness in animal models of inflammatory conditions such as Alzheimer’s and Parkinson’s diseases, and in chronic renal failure and glomerulonephritis.

Role of the ABL tyrosine kinases in the epithelial–mesenchymal transition and the metastatic cascade

The ABL kinases, ABL1 and ABL2, promote tumor progression and metastasis in various solid tumors. Recent reports have shown that ABL kinases have increased expression and/or activity in solid tumors and that ABL inactivation impairs metastasis. The therapeutic effects of ABL inactivation are due in part to ABL-dependent regulation of diverse cellular processes related to the epithelial to mesenchymal transition and subsequent steps in the metastatic cascade. ABL kinases target multiple signaling pathways required for promoting one or more steps in the metastatic cascade. These findings highlight the potential utility of specific ABL kinase inhibitors as a novel treatment paradigm for patients with advanced metastatic disease.

Abl kinase deficiency promotes AKT pathway activation and prostate cancer progression and metastasis

Abl family kinases function as proto-oncogenes in various leukemias, and pro-tumor functions have been discovered for Abl kinases in solid tumors as well. However, a growing body of evidence indicates that Abl kinases can function to suppress tumor cell proliferation, motility, and in vivo tumor growth in some settings. To investigate the role of Abl kinases in prostate cancer, we generated Abl-deficient cells in a pre-clinical model of spontaneously metastatic, androgen-indifferent prostate cancer. Loss of Abl family kinase expression resulted in a highly aggressive, metastatic phenotype in vivo that was associated with AKT pathway activation, increased growth on 3D collagen matrix, and enhanced cell motility in vitro. Treatment of Abl kinase-expressing cells with the Abl kinase inhibitor imatinib phenocopied the malignant phenotypes observed in Abl-deficient tumor cells. In addition, inhibiting AKT pathway signaling abolished the increased 3D growth of Abl-deficient cells. Our data reveal that Abl family kinases can function as suppressors of prostate cancer progression and metastasis by restraining AKT signaling, a signaling pathway known to be associated with emergence of metastatic castration-resistant prostate cancer.

Regulation of MT dynamics via direct binding of an Abl family kinase

Abl family kinases are essential regulators of cell shape and movement. Genetic studies revealed functional interactions between Abl kinases and microtubules (MTs), but the mechanism by which Abl family kinases regulate MTs remains unclear. Here, we report that Abl2 directly binds to MTs and regulates MT behaviors. Abl2 uses its C-terminal half to bind MTs, an interaction mediated in part through electrostatic binding to tubulin C-terminal tails. Using purified proteins, we found that Abl2 binds growing MTs and promotes MT polymerization and stability. In cells, knockout of Abl2 significantly impairs MT growth, and this defect can be rescued via reexpression of Abl2. Stable reexpression of an Abl2 fragment containing the MT-binding domain alone was sufficient to restore MT growth at the cell edge. These results show Abl2 uses its C-terminal half to bind MTs and directly regulate MT dynamics.

BSCI-22. IDENTIFICATION OF ACTIONABLE TYROSINE KINASE-REGULATED NETWORKS REQUIRED FOR LUNG AND BREAST CANCER BRAIN METASTASIS

Brain metastases are a common consequence of advanced lung and breast cancer resulting in functional impairment, cranial neuropathies, and decline in quality of life. Current therapies for brain metastasis, such as whole brain radiation therapy, can result in cognitive impairment, while targeted therapies and chemotherapy are largely ineffective due, in part, to the emergence of resistance and inability to reach effective concentrations in the central nervous system (CNS). We have uncovered a role for the Abelson (ABL) family of tyrosine kinases, ABL1 and ABL2, in lung and breast cancer metastasis to the brain. We show that cancer cells increase ABL expression upon colonization of the brain. Notably, we found that genetic inactivation or pharmacological inhibition of the ABL kinases suppressed lung and breast cancer metastasis to the brain. ABL allosteric inhibitors effectively cross the blood-brain barrier (BBB), inhibit ABL kinases and downstream targets in brain metastases, and markedly impair metastatic colonization of the brain. Further, treatment with an ABL allosteric inhibitor increased recruitment of Iba1+ macrophages/microglia to breast cancer brain metastases. Current studies are aimed at identifying the molecular mechanisms by which ABL kinase signaling regulates the crosstalk between cancer cells and macrophages/microglia, with the aim of disrupting metastatic colonization of the brain parenchyma. These data reveal, for the first time, a role for ABL kinases in promoting brain colonization by metastatic tumors, and demonstrate that ABL allosteric inhibitors efficiently penetrate the BBB and inhibit intracranial growth of breast and lung cancer metastases.