A Novel Naphthoquinone-Coumarin Hybrid That Inhibits BCR-ABL1-STAT5 Oncogenic Pathway and Reduces Survival in Imatinib-Resistant Chronic Myelogenous Leukemia Cells

1,2,3-Triazole-totarol conjugates as potent PIP5K1α lipid kinase inhibitors

The human phosphatidylinositol 4-phosphate 5-kinase type I α (hPIP5K1α) plays a key role in the development of prostate cancer. In this work, seventeen derivatives of the natural diterpene totarol were prepared by copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction of the correspondingO-propargylated totarol with aryl or alkyl azides and screened for their inhibitory activities toward hPIP5K1α. Five compounds, 3a, 3e, 3f, 3i, and 3r, strongly inhibited the enzyme activity with IC50 values of 1.44, 0.46, 1.02, 0.79, and 3.65 µM, respectively, with the most potent inhibitor 3e 13-[(1-(3-nitrophenyl)triazol-4yl)methoxy]-totara-8,11,13-triene). These compounds were evaluated on their antiproliferative effects in a panel of prostate cancer cell lines. Compound 3r inhibited the proliferation of LNCaP, PC3 and DU145 cells at 20 µM, strongly, but also has strong cytotoxic effects on all tested cells.

Targeting integrated stress response with ISRIB combined with imatinib treatment attenuates RAS/RAF/MAPK and STAT5 signaling and eradicates chronic myeloid leukemia cells

The integrated stress response (ISR) facilitates cellular adaptation to unfavorable conditions by reprogramming the cellular response. ISR activation was reported in neurological disorders and solid tumors; however, the function of ISR and its role as a possible therapeutic target in hematological malignancies still remain largely unexplored. Previously, we showed that the ISR is activated in chronic myeloid leukemia (CML) cells and correlates with blastic transformation and tyrosine kinase inhibitor (TKI) resistance. Moreover, the ISR was additionally activated in response to imatinib as a type of protective internal signaling. Here, we show that ISR inhibition combined with imatinib treatment sensitized and more effectively eradicated leukemic cells both in vitro and in vivo compared to treatment with single agents. The combined treatment specifically inhibited the STAT5 and RAS/RAF/MEK/ERK pathways, which are recognized as drivers of resistance. Mechanistically, this drug combination attenuated both interacting signaling networks, leading to BCR-ABL1- and ISR-dependent STAT5 activation. Consequently, leukemia engraftment in patient-derived xenograft mice bearing CD34+ TKI-resistant CML blasts carrying PTPN11 mutation responsible for hyperactivation of the RAS/RAF/MAPK and JAK/STAT5 pathways was decreased upon double treatment. This correlated with the downregulation of genes related to the RAS/RAF/MAPK, JAK/STAT5 and stress response pathways and was associated with lower expression of STAT5-target genes regulating proliferation, viability and the stress response. Collectively, these findings highlight the effect of imatinib plus ISRIB in the eradication of leukemic cells resistant to TKIs and suggest potential clinical benefits for leukemia patients with TKI resistance related to RAS/RAF/MAPK or STAT5 signaling. We propose that personalized treatment based on the genetic selection of patients carrying mutations that cause overactivation of the targeted pathways and therefore make their sensitivity to such treatment probable should be considered as a possible future direction in leukemia treatment.

Hybrid Molecules Containing Naphthoquinone and Quinolinedione Scaffolds as Antineoplastic Agents

In recent decades, molecular hybridization has proven to be an efficient tool for obtaining new synthetic molecules to treat different diseases. Based on the core idea of covalently combining at least two pharmacophore fragments present in different drugs and/or bioactive molecules, the new hybrids have shown advantages when compared with the compounds of origin. Hybridization could be successfully applied to anticancer drug discovery, where efforts are underway to develop novel therapeutics which are safer and more effective than those currently in use. Molecules presenting naphthoquinone moieties are involved in redox processes and in other molecular mechanisms affecting cancer cells. Naphthoquinones have been shown to inhibit cancer cell growth and are considered privileged structures and useful templates in the design of hybrids. The present work aims at summarizing the current knowledge on antitumor hybrids built using 1,4- and 1,2-naphthoquinone (present in natural compounds as lawsone, napabucasin, plumbagin, lapachol, α-lapachone, and β -lapachone), and the related quinolone- and isoquinolinedione scaffolds reported in the literature up to 2021. In detail, the design and synthetic approaches adopted to produce the reported compounds are highlighted, the structural fragments considered in hybridization and their biological activities are described, and the structure–activity relationships and the computational analyses applied are underlined.

JKST6, a novel multikinase modulator of the BCR-ABL1/STAT5 signaling pathway that potentiates direct BCR-ABL1 inhibition and overcomes imatinib resistance in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a hematological malignancy that highly depends on the BCR-ABL1/STAT5 signaling pathway for cell survival. First-line treatments for CML consist of tyrosine kinase inhibitors that efficiently target BCR-ABL1 activity. However, drug resistance and intolerance are still therapeutic limitations in Ph+ cells. Therefore, the development of new anti-CML drugs that exhibit alternative mechanisms to overcome these limitations is a desirable goal. In this work, the antitumoral activity of JKST6, a naphthoquinone-pyrone hybrid, was assessed in imatinib-sensitive and imatinib-resistant human CML cells. Live-cell imaging analysis revealed JKST6 potent antiproliferative activity in 2D and 3D CML cultures. JKST6 provoked cell increase in the subG1 phase along with a reduction in the G0/G1 phase and altered the expression of key proteins involved in the control of mitosis and DNA damage. Rapid increases in Annexin V staining and activation/cleavage of caspases 8, 9 and 3 were observed after JKST6 treatment in CML cells. Of interest, JKST6 inhibited BCR-ABL1/STAT5 signaling through oncokinase downregulation that was preceded by rapid polyubiquitination. In addition, JKST6 caused a transient increase in JNK and AKT phosphorylation, whereas the phosphorylation of P38-MAPK and Src was reduced. Combinatory treatment unveiled synergistic effects between imatinib and JKST6. Notably, JKST6 maintained its antitumor efficacy in BCR-ABL1-T315I-positive cells and CML cells that overexpress BCR-ABL and even restored imatinib efficacy after a short exposure time. These findings, together with the observed low toxicity of JKST6, reveal a novel multikinase modulator that might overcome the limitations of BCR-ABL1 inhibitors in CML therapy.

Therapeutic inhibition of FcγRIIb signaling targets leukemic stem cells in chronic myeloid leukemia

Despite the successes achieved with molecular targeted inhibition of the oncogenic driver Bcr-Abl in chronic myeloid leukemia (CML), the majority of patients still require lifelong tyrosine kinase inhibitor (TKI) therapy. This is primarily caused by resisting leukemic stem cells (LSCs), which prevent achievement of treatment-free remission in all patients. Here we describe the ITIM (immunoreceptor tyrosine-based inhibition motif)-containing Fc gamma receptor IIb (FcγRIIb, CD32b) for being critical in LSC resistance and show that targeting FcγRIIb downstream signaling, by using a Food and Drug Administration-approved BTK inhibitor, provides a successful therapeutic approach. First, we identified FcγRIIb upregulation in primary CML stem cells. FcγRIIb depletion caused reduced serial re-plaiting efficiency and cell proliferation in malignant cells. FcγRIIb targeting in both a transgenic and retroviral CML mouse model provided in vivo evidence for successful LSC reduction. Subsequently, we identified BTK as a main downstream mediator and targeting the Bcr-Abl-FcγRIIb-BTK axis in primary CML CD34⁺ cells using ibrutinib, in combination with standard TKI therapy, significantly increased apoptosis in quiescent CML stem cells thereby contributing to the eradication of LSCs.. As a potential curative therapeutic approach, we therefore suggest combining Bcr-Abl TKI therapy along with BTK inhibition.

Redox cycling of copper by coumarin-di(2-picolyl)amine hybrid molecule leads to ROS-mediated modulation of redox scavengers, DNA damage and cell death in diethylnitrosamine induced hepatocellular carcinoma

Targeted therapy is a new strategy for cancer treatment that targets chemical entities specific to cancer cells than normal ones. One of the features associated with malignancy is the elevated copper which plays an integral role in angiogenesis. Work is in progress in our lab to identify new copper chelators to target elevated copper under targeted therapy for the killing of cancer cells. Recently, a coumarin-based copper chelator, di(2-picolyl)amine-3(bromoacetyl)coumarin hybrid molecule (ligand-L) has been synthesized by us, and also studied its copper-dependent macromolecular damage response in copper overloaded lymphocytes. The present study investigates the anticancer activity of ligand-L and its mode of action in rat model of diethylnitrosamine (DEN) induced hepatocellular carcinoma. It has been found that liver tissue has a marked increase in copper levels in DEN induced hepatocellular carcinoma. Ex vivo results showed that ligand-L inhibited cell viability, induced reactive oxygen species (ROS) generation, DNA damage, loss of mitochondrial membrane potential and caspase-3 activation in isolated hepatocellular carcinoma cells (HCC). All these effects induced by ligand-L were abrogated by neocuproine and N-acetylcysteine (ROS scavenger). Further, ligand-L treatment of animals bearing hepatocellular carcinoma results in an increment in the cellular redox scavengers, lipid peroxidation and DNA breakage in malignant hepatocytes. In vivo studies using ligand-L also showed that ligand-L possesses anticancer properties as evidenced by improvement in liver marker enzymes and liver surface morphology, and reduced alpha-fetoprotein in the treated group compared to untreated cancer-induced group. Overall, this study suggests that copper-ligand-L interaction leads to ROS generation which caused DNA damage and apoptosis in malignant cells. This study provides enough support to establish ligand-L as a clinically relevant lead molecule for the treatment of different malignancies.