Antitumor activity of new pyrazolo[3,4-d]pyrimidine SRC kinase inhibitors in Burkitt lymphoma cell lines and its enhancement by WEE1 inhibition

Integration of transcriptomics, proteomics and loss-of-function screening reveals WEE1 as a target for combination with dasatinib against proneural glioblastoma

Glioblastoma is characterized by a pronounced resistance to therapy with dismal prognosis. Transcriptomics classify glioblastoma into proneural (PN), mesenchymal (MES) and classical (CL) subtypes that show differential resistance to targeted therapies. The aim of this study was to provide a viable approach for identifying combination therapies in glioblastoma subtypes. Proteomics and phosphoproteomics were performed on dasatinib inhibited glioblastoma stem cells (GSCs) and complemented by an shRNA loss-of-function screen to identify genes whose knockdown sensitizes GSCs to dasatinib. Proteomics and screen data were computationally integrated with transcriptomic data using the SamNet 2.0 algorithm for network flow learning to reveal potential combination therapies in PN GSCs. In vitro viability assays and tumor spheroid models were used to verify the synergy of identified therapy. Further in vitro and TCGA RNA-Seq data analyses were utilized to provide a mechanistic explanation of these effects. Integration of data revealed the cell cycle protein WEE1 as a potential combination therapy target for PN GSCs. Validation experiments showed a robust synergistic effect through combination of dasatinib and the WEE1 inhibitor, MK-1775, in PN GSCs. Combined inhibition using dasatinib and MK-1775 propagated DNA damage in PN GCSs, with GCSs showing a differential subtype-driven pattern of expression of cell cycle genes in TCGA RNA-Seq data. The integration of proteomics, loss-of-function screens and transcriptomics confirmed WEE1 as a target for combination with dasatinib against PN GSCs. Utilizing this integrative approach could be of interest for studying resistance mechanisms and revealing combination therapy targets in further tumor entities.

Pyrazolo - Pyrimidines as Targeted Anticancer Scaffolds - A Comprehensive Review

BACKGROUND

Globally, cancer is the leading cause of death, which causes 10 million deaths yearly. Clinically, several drugs are used in treatment but due to drug resistance and multidrug resistance, there occurs a failure in the cancer treatment.

OBJECTIVES

The present review article is a comprehensive review of pyrazole and pyrimidine hybrids as potential anticancer agents.

METHODS

The review comprises more than 60 research works done in this field. The efficiency of the reported pyrazolopyrimidine fused heterocyclic with their biological data and the influence of the structural aspects of the molecule have been discussed.

RESULTS

This review highlighted pyrazolo-pyrimidines as targeted anticancer agents with effect on multiple targets.

CONCLUSION

The review will be helpful for the researchers involved in targeted drugs for cancer therapy for designing new scaffolds with pyrazolo-pyrimidine moieties.

Biological Evaluation and In Vitro Characterization of ADME Profile of In-House Pyrazolo[3,4-d]pyrimidines as Dual Tyrosine Kinase Inhibitors Active against Glioblastoma Multiforme

The therapeutic use of tyrosine kinase inhibitors (TKIs) represents one of the successful strategies for the treatment of glioblastoma (GBM). Pyrazolo[3,4-d]pyrimidines have already been reported as promising small molecules active as c-Src/Abl dual inhibitors. Herein, we present a series of pyrazolo[3,4-d]pyrimidine derivatives, selected from our in-house library, to identify a promising candidate active against GBM. The inhibitory activity against c-Src and Abl was investigated, and the antiproliferative profile against four GBM cell lines was studied. For the most active compounds endowed with antiproliferative efficacy in the low-micromolar range, the effects toward nontumoral, healthy cell lines (fibroblasts FIBRO 2-93 and keratinocytes HaCaT) was investigated. Lastly, the in silico and in vitro ADME properties of all compounds were also assessed. Among the tested compounds, the promising inhibitory activity against c-Src and Abl (K_i 3.14 µM and 0.44 µM, respectively), the irreversible, apoptotic-mediated death toward U-87, LN18, LN229, and DBTRG GBM cell lines (IC₅₀ 6.8 µM, 10.8 µM, 6.9 µM, and 8.5 µM, respectively), the significant reduction in GBM cell migration, the safe profile toward FIBRO 2-93 and HaCaT healthy cell lines (CC₅₀ 91.7 µM and 126.5 µM, respectively), the high metabolic stability, and the excellent passive permeability across gastrointestinal and blood-brain barriers led us to select compound 5 for further in vivo assays.

The Androgen Receptor and Its Crosstalk With the Src Kinase During Castrate-Resistant Prostate Cancer Progression

While the androgen receptor (AR) signalling is the mainstay therapeutic target for metastatic prostate cancers, these tumours will inevitably develop therapy resistance to AR pathway inhibitors suggesting that prostate tumour cells possess the capability to develop mechanisms to bypass their dependency on androgens and/or AR to survive and progress. In many studies, protein kinases such as Src are reported to promote prostate tumour progression. Specifically, the pro-oncogene tyrosine Src kinase regulates prostate cancer cell proliferation, adhesion, invasion, and metastasis. Not only can Src be activated under androgen depletion, low androgen, and supraphysiological androgen conditions, but also through crosstalk with other oncogenic pathways. Reciprocal activations between Src and AR proteins had also been reported. These findings rationalize Src inhibitors to be used to treat castrate-resistant prostate tumours. Although several Src inhibitors had advanced to clinical trials, the failure to observe patient benefits from these studies suggests that further evaluation of the roles of Src in prostate tumours is required. Here, we summarize the interplay between Src and AR signalling during castrate-resistant prostate cancer progression to provide insights on possible approaches to treat prostate cancer patients.

Targeting Wee1 kinase as a therapeutic approach in Hematological Malignancies

Hematologic malignancies include various diseases that develop from hematopoietic stem cells of bone marrow or lymphatic organs. Currently, conventional DNA-damage-based chemotherapy drugs are approved as standard therapeutic regimens for these malignancies. Although many improvements have been made, patients with relapsed or refractory hematological malignancies have a poor prognosis. Therefore, novel and practical therapeutic approaches are required for the treatment of these diseases. Interestingly several studies have shown that targeting Wee1 kinase in the Hematological malignancies, including AML, ALL, CML, CLL, DLBCL, BL, MCL, etc., can be an effective therapeutic strategy. It plays an essential role in regulating the cell cycle process by abrogating the G2-M cell-cycle checkpoint, which provides time for DNA damage repair before mitotic entry. Consistently, Wee1 overexpression is observed in various Hematological malignancies. Also, in healthy normal cells, repairing DNA damages occurs due to G1-S checkpoint function; however, in the cancer cells, which have an impaired G1-S checkpoint, the damaged DNA repair process depends on the G2-M checkpoint function. Thus, Wee1 inhibition could be a promising target in the presence of DNA damage in order to potentiate multiple therapeutic drugs. This review summarized the potentials and challenges of Wee1 inhibition combined with other therapies as a novel effective therapeutic strategy in Hematological malignancies.

New Therapeutic Strategy for Overcoming Multidrug Resistance in Cancer Cells with Pyrazolo[3,4-d]pyrimidine Tyrosine Kinase Inhibitors

Simple Summary

P-glycoprotein (P-gp) is an ATP-binding cassette transporter whose overexpression in cancer cells is one of the main causes of multidrug resistance (MDR). Tyrosine kinase inhibitors (TKIs) have been reported to interact with ABC transporters and in some cases, increase the susceptibility of cancer cells to chemotherapy. We investigated the potential of novel TKI pyrazolo[3,4-d] pyrimidines and their prodrugs to inhibit P-gp in two MDR cancer cell lines with P-gp overexpression. The tested compounds were able to suppress P-gp by inhibiting its ATPase activity. Interestingly, prodrugs displayed a stronger potential to modulate P-gp and showed higher interaction energies in the docking simulations compared to their parent drugs. Furthermore, prodrugs showed significant potential to inhibit P-gp activity even in prolonged treatment and therefore to enhance the efficacy of doxorubicin and paclitaxel in MDR cancer cells. All of these characteristics imply that the new TKIs could be considered a valuable strategy for combating resistant cancers, especially in combination with other chemotherapeutics.

Abstract

Tyrosine kinase inhibitors (TKIs) often interact with the multidrug resistant (MDR) phenotype of cancer cells. In some cases, TKIs increase the susceptibility of MDR cancer cells to chemotherapy. As the overexpression of membrane transporter P-glycoprotein (P-gp) is the most common alteration in MDR cancer cells, we investigated the effects of TKI pyrazolo[3,4-d]pyrimidines on P-gp inhibition in two cellular models comprising sensitive and corresponding MDR cancer cells (human non-small cell lung carcinoma and colorectal adenocarcinoma). Tested TKIs showed collateral sensitivity by inducing stronger inhibition of MDR cancer cell line viability. Moreover, TKIs directly interacted with P-gp and inhibited its ATPase activity. Their potential P-gp binding site was proposed by molecular docking simulations. TKIs reversed resistance to doxorubicin and paclitaxel in a concentration-dependent manner. The expression studies excluded the indirect effect of TKIs on P-gp through regulation of its expression. A kinetics study showed that TKIs decreased P-gp activity and this effect was sustained for seven days in both MDR models. Therefore, pyrazolo[3,4-d]pyrimidines with potential for reversing P-gp-mediated MDR even in prolonged treatments can be considered a new therapeutic strategy for overcoming cancer MDR.

High Iodine Induces the Proliferation of Papillary and Anaplastic Thyroid Cancer Cells via AKT/Wee1/CDK1 Axis

High iodine can alter the proliferative activity of thyroid cancer cells, but the underlying mechanism has not been fully elucidated. Here, the role of high iodine in the proliferation of thyroid cancer cells was studied. In this study, we demonstrated that high iodine induced the proliferation of BCPAP and 8305C cells via accelerating cell cycle progression. The transcriptome analysis showed that there were 295 differentially expressed genes (DEGs) in BCPAP and 8305C cells induced by high iodine, among which CDK1 expression associated with the proliferation of thyroid cancer cells induced by high iodine. Moreover, the western blot analysis revealed that cells exposed to high iodine enhanced the phosphorylation activation of AKT and the expression of phospho-Wee1 (Ser642), while decreasing the expression of phospho-CDK1 (Tyr15). Importantly, the inhibition of AKT phosphorylation revered the expression of CDK1 induced by high iodine and arrested the cell cycle in the G₁ phase, decreasing the proliferation of thyroid cancer cells induced by high iodine. Taken together, these findings suggested that high iodine induced the proliferation of thyroid cancer cells through AKT-mediated Wee1/CDK1 axis, which provided new insights into the regulation of proliferation of thyroid cancer cells by iodine.

Activation of bovine oocytes by protein synthesis inhibitors: new findings on the role of MPF/MAPKs†

The present study evaluated the mechanism by which protein synthesis inhibitors activate bovine oocytes. The aim was to analyze the dynamics of MPF and MAPKs. MII oocytes were activated with ionomycin (Io), ionomycin+anisomycin (ANY) and ionomycin+cycloheximide (CHX) and by in vitro fertilization (IVF). The expression of cyclin B1, p-CDK1, p-ERK1/2, p-JNK, and p-P38 were evaluated by immunodetection and the kinase activity of ERK1/2 was measured by enzyme assay. Evaluations at 1, 4, and 15 hours postactivation (hpa) showed that the expression of cyclin B1 was not modified by the treatments. ANY inactivated MPF by p-CDK1Thr14-Tyr15 at 4 hpa (P < 0.05), CHX increased pre-MPF (p-CDK1Thr161 and p-CDK1Thr14-Tyr15) at 1 hpa and IVF increased p-CDK1Thr14-Tyr15 at 17 hours postfertilization (hpf) (P < 0.05). ANY and CHX reduced the levels of p-ERK1/2 at 4 hpa (P < 0.05) and its activity at 4 and 1 hpa, respectively (P < 0.05). Meanwhile, IVF increased p-ERK1/2 at 6 hpf (P < 0.05); however, its kinase activity decreased at 6 hpf (P < 0.05). p-JNK in ANY, CHX, and IVF oocytes decreased at 4 hpa (P < 0.05). p-P38 was only observed at 1 hpa, with no differences between treatments. In conclusion, activation of bovine oocytes by ANY, CHX, and IVF inactivates MPF by CDK1-dependent specific phosphorylation without cyclin B1 degradation. ANY or CHX promoted this inactivation, which seemed to be more delayed in the physiological activation (IVF). Both inhibitors modulated MPF activity via an ERK1/2-independent pathway, whereas IVF activated the bovine oocytes via an ERK1/2-dependent pathway. Finally, ANY does not activate the JNK and P38 kinase pathways.

Pharmacological Inhibition of WEE1 Potentiates the Antitumoral Effect of the dl922-947 Oncolytic Virus in Malignant Mesothelioma Cell Lines

Malignant mesothelioma (MM) is a very aggressive asbestos-related cancer, for which no therapy proves to be effective. We have recently shown that the oncolytic adenovirus dl922-947 had antitumor effects in MM cell lines and murine xenografts. Previous studies demonstrated that dl922-947-induced host cell cycle checkpoint deregulation and consequent DNA lesions associated with the virus efficacy. However, the cellular DNA damage response (DDR) can counteract this virus action. Therefore, we assessed whether AZD1775, an inhibitor of the G2/M DNA damage checkpoint kinase WEE1, could enhance MM cell sensitivity to dl922-947. Through cell viability assays, we found that AZD1775 synergized with dl922-947 selectively in MM cell lines and increased dl922-947-induced cell death, which showed hallmarks of apoptosis (annexinV-positivity, caspase-dependency, BCL-XL decrease, chromatin condensation). Predictably, dl922-947 and/or AZD1775 activated the DDR, as indicated by increased levels of three main DDR players: phosphorylated histone H2AX (γ-H2AX), phospho-replication protein A (RPA)32, phospho-checkpoint kinase 1 (CHK1). Dl922-947 also increased inactive Tyr-15-phosphorylated cyclin-dependent kinase 1 (CDK1), a key WEE1 substrate, which is indicative of G2/M checkpoint activation. This increase in phospho-CDK1 was effectively suppressed by AZD1775, thus suggesting that this compound could, indeed, abrogate the dl922-947-induced DNA damage checkpoint in MM cells. Overall, our data suggest that the dl922-947-AZD1775 combination could be a feasible strategy against MM.

Targeting SRC Family Kinases in Mesothelioma: Time to Upgrade

Malignant mesothelioma (MM) is a deadly tumor mainly caused by exposure to asbestos. Unfortunately, no current treatment is able to change significantly the natural history of the disease, which has a poor prognosis in the majority of patients. The non-receptor tyrosine kinase SRC and other SRC family kinase (SFK) members are frequently hyperactivated in many cancer types, including MM. Several works have indeed suggested that SFKs underlie MM cell proliferation, survival, motility, and invasion, overall affecting multiple oncogenic pathways. Consistently, SFK inhibitors effectively counteracted MM cancerous features at the preclinical level. Dasatinib, a multi-kinase inhibitor targeting SFKs, was also assessed in clinical trials either as second-line treatment for patients with unresectable MM or, more recently, as a neoadjuvant agent in patients with resectable MM. Here, we provide an overview of the molecular mechanisms implicating SFKs in MM progression and discuss possible strategies for a more successful clinical application of SFK inhibitors. Our aim is to stimulate discussion and further consideration of these agents in better designed preclinical and clinical studies to make the most of another class of powerful antitumoral drugs, which too often are lost in translation when applied to MM.

Src Inhibitors Pyrazolo[3,4-d]pyrimidines, Si306 and Pro-Si306, Inhibit Focal Adhesion Kinase and Suppress Human Glioblastoma Invasion In Vitro and In Vivo

Glioblastoma (GBM), as the most aggressive brain tumor, displays a high expression of Src tyrosine kinase, which is involved in the survival, migration, and invasiveness of tumor cells. Thus, Src emerged as a potential target for GBM therapy. The effects of Src inhibitors pyrazolo[3,4-d]pyrimidines, Si306 and its prodrug pro-Si306 were investigated in human GBM cell lines (U87 and U87-TxR) and three primary GBM cell cultures. Primary GBM cells were more resistant to Si306 and pro-Si306 according to the 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. However, the ability of all GBM cells to degrade the extracellular matrix was considerably compromised after Si306 and pro-Si306 applications. Besides reducing the phosphorylation of Src and its downstream signaling pathway components, both compounds decreased the phosphorylated form of focal adhesion kinase (FAK) and epidermal growth factor receptor (EGFR) expression, showing the potential to suppress the aggressiveness of GBM. In vivo, Si306 and pro-Si306 displayed an anti-invasive effect against U87 xenografts in the zebrafish embryo model. Considering that Si306 and pro-Si306 are able to cross the blood–brain barrier and suppress the spread of GBM cells, we anticipate their clinical testing in the near future. Moreover, the prodrug showed similar efficacy to the drug, implying the rationality of its use in clinical settings.

The therapeutic effectiveness of 177Lu-lilotomab in B-cell non-Hodgkin lymphoma involves modulation of G2/M cell cycle arrest

Some patients with B-cell non-Hodkin lymphoma Lymphoma (NHL) become refractory to rituximab (anti-CD20 antibody) therapy associated with chemotherapy. Here, the effect of the anti-CD37 antibody-radionuclide conjugate lutetium-177 (¹⁷⁷Lu)-lilotomab (Betalutin^®) was investigated in preclinical models of NHL. In SCID mice bearing DOHH2 (transformed follicular lymphoma, FL) cell xenografts, ¹⁷⁷Lu-lilotomab significantly delayed tumor growth, even at low activity (100 MBq/kg). In athymic mice bearing OCI-Ly8 (diffuse large B-cell lymphoma, DLBCL) or Ramos (Burkitt’s lymphoma) cell xenografts, ¹⁷⁷Lu-lilotomab activity had to be increased to 500 MBq/kg to show a significant tumor growth delay. Clonogenic and proliferation assays showed that DOHH2 cells were highly sensitive to ¹⁷⁷Lu-lilotomab, while Ramos cells were the least sensitive, and U2932 (DLBCL), OCI-Ly8, and Rec-1 (mantle cell lymphoma) cells displayed intermediate sensitivity. The strong ¹⁷⁷Lu-lilotomab cytotoxicity observed in DOHH2 cells correlated with reduced G2/M cell cycle arrest, lower WEE-1- and MYT-1-mediated phosphorylation of cyclin-dependent kinase-1 (CDK1), and higher apoptosis. In agreement, ¹⁷⁷Lu-lilotomab efficacy in vitro, in vivo, and in patient samples was increased when combined with G2/M cell cycle arrest inhibitors (MK-1775 and PD-166285). These results indicate that ¹⁷⁷Lu-lilotomab is particularly efficient in treating tumors with reduced inhibitory CDK1 phosphorylation, such as transformed FL.

Dual Inhibition of GLUT1 and the ATR/CHK1 Kinase Axis Displays Synergistic Cytotoxicity in KRAS-Mutant Cancer Cells

The advent of molecularly targeted therapeutic agents has opened a new era in cancer therapy. However, many tumors rely on nondruggable cancer-driving lesions. In addition, long-lasting clinical benefits from single-agent therapies rarely occur, as most of the tumors acquire resistance over time. The identification of targeted combination regimens interfering with signaling through oncogenically rewired pathways provides a promising approach to enhance efficacy of single-agent-targeted treatments. Moreover, combination drug therapies might overcome the emergence of drug resistance. Here, we performed a focused flow cytometry-based drug synergy screen and identified a novel synergistic interaction between GLUT1-mediated glucose transport and the cell-cycle checkpoint kinases ATR and CHK1. Combined inhibition of CHK1/GLUT1 or ATR/GLUT1 robustly induced apoptosis, particularly in RAS-mutant cancer cells. Mechanistically, combined inhibition of ATR/CHK1 and GLUT1 arrested sensitive cells in S-phase and led to the accumulation of genotoxic damage, particularly in S-phase. In vivo, simultaneous inhibition of ATR and GLUT1 significantly reduced tumor volume gain in an autochthonous mouse model of Kras^G12D -driven soft tissue sarcoma. Taken together, these findings pave the way for combined inhibition of GLUT1 and ATR/CHK1 as a therapeutic approach for KRAS-driven cancers. SIGNIFICANCE: Dual targeting of the DNA damage response and glucose transport synergistically induces apoptosis in KRAS-mutant cancer, suggesting this combination treatment for clinical validation in KRAS-stratified tumor patients.

A New Strategy for Glioblastoma Treatment: In Vitro and In Vivo Preclinical Characterization of Si306, a Pyrazolo[3,4-d]Pyrimidine Dual Src/P-Glycoprotein Inhibitor

Overexpression of P-glycoprotein (P-gp) and other ATP-binding cassette (ABC) transporters in multidrug resistant (MDR) cancer cells is responsible for the reduction of intracellular drug accumulation, thus decreasing the efficacy of chemotherapeutics. P-gp is also found at endothelial cells' membrane of the blood-brain barrier, where it limits drug delivery to central nervous system (CNS) tumors. We have previously developed a set of pyrazolo[3,4-d]pyrimidines and their prodrugs as novel Src tyrosine kinase inhibitors (TKIs), showing a significant activity against CNS tumors in in vivo. Here we investigated the interaction of the most promising pair of drug/prodrug with P-gp at the cellular level. The tested compounds were found to increase the intracellular accumulation of Rho 123, and to enhance the efficacy of paclitaxel in P-gp overexpressing cells. Encouraging pharmacokinetics properties and tolerability in vivo were also observed. Our findings revealed a novel role of pyrazolo[3,4-d]pyrimidines which may be useful for developing a new effective therapy in MDR cancer treatment, particularly against glioblastoma.

Prodrugs of Pyrazolo[3,4-d]pyrimidines: From Library Synthesis to Evaluation as Potential Anticancer Agents in an Orthotopic Glioblastoma Model

Pyrazolo[3,4-d]pyrimidines are potent protein kinase inhibitors with promising antitumor activity but suboptimal aqueous solubility, consequently worth being further optimized. Herein, we present the one-pot two-step procedure for the synthesis of a set of pyrazolo[3,4-d]pyrimidine prodrugs (1a-8a and 9a-e) with higher aqueous solubility and enhanced pharmacokinetic and therapeutic properties. ADME studies demonstrated for the most promising prodrugs a better aqueous solubility, a favorable hydrolysis in human and murine serum, and an increased ability to cross cell membranes with respect to the parental drugs, explaining their better 24 h in vitro cytotoxicity against human glioblastoma U87 cell line. Finally, the 4-4a couple of drug/prodrug was also evaluated in vivo, revealing a profitable pharmacokinetic profile of the prodrug associated with a good efficacy. The application of the prodrug approach demonstrated to be a successful strategy for improving aqueous solubility of the parental drugs, determining a positive impact also in their biological efficacy.

A Pyrazolo[3,4-d]pyrimidine Compound Reduces Cell Viability and Induces Apoptosis in Different Hematological Malignancies

Molecular targeted therapies are based upon drugs acting on tumors by interfering with specific targets involved in growth and spread of cancer. Many targeted therapies were approved by Food and Drug Administration as standard treatment, others were introduced into preclinical or clinical studies on hematological malignancies (HMs). The development of drug-resistance in some HMs and the lack of effective treatments in other ones emphasized the need for searching new molecular targets and therapeutic agents. The aim of this study was to evaluate the effects of 4c pyrazolo[3,4-d]pyrimidine compound, a Src inhibitor, on lymphoid and myeloid neoplasms. Here, we demonstrated its ability to reduce cell viability, induce apoptosis and cell cycle arrest in lymphoid cell lines such as Jurkat, SKMM1, Derl-2/7, and myeloid cell lines, such as Jurl-MK1. Moreover, we reported a high expression of a Src kinase, Fyn, in these cell lines compared to healthy subjects. This study was a starting point to investigate 4c pyrazolo[3,4-d]pyrimidine compound as a drug for HMs and Src kinases as its potential molecular targets.

RETRACTED: Design, synthesis, structure-activity relationship and kinase inhibitory activity of substituted 3-methyl-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4-ones

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the author who confirmed that the purity of some of the described compounds is below acceptable standards and thus the biochemical results reported in the paper have no validity.

SRC Family Kinase Inhibition in Ewing Sarcoma Cells Induces p38 MAP Kinase-Mediated Cytotoxicity and Reduces Cell Migration

Ewing sarcoma (ES) is a highly aggressive bone and soft tissue cancer, representing the second most common primary malignant bone tumor in children and adolescents. Although the development of a multimodal therapy, including both local control (surgery and/or radiation) and systemic multidrug chemotherapy, has determined a significant improvement in survival, patients with metastatic and recurrent disease still face a poor prognosis. Moreover, considering that ES primarily affects young patients, there are concerns about long-term adverse effects of the therapy. Therefore, more rational strategies, targeting specific molecular alterations underlying ES, are required. Recent studies suggest that SRC family kinases (SFKs), which are aberrantly activated in most cancer types, could represent key therapeutic targets also for ES. Here, we challenged ES cell lines with a recently developed selective SFK inhibitor (a pyrazolo[3,4-d]pyrimidine derivative, called SI221), which was previously shown to be a valuable proapoptotic agent in other tumor types while not affecting normal cells. We observed that SI221 significantly reduced ES cell viability and proved to be more effective than the well-known SFK inhibitor PP2. SI221 was able to induce apoptosis in ES cells and also reduced ES cell clonogenic potential. Furthermore, SI221 was also able to reduce ES cell migration. At the molecular level, our data suggest that SFK inhibition through SI221 could reduce ES cell viability at least in part by hindering an SFK-NOTCH1 receptor-p38 mitogen-activated protein kinase (MAPK) axis. Overall, our study suggests a potential application of specific SFK inhibition in ES therapy. J. Cell. Physiol. 232: 129-135, 2017. © 2016 Wiley Periodicals, Inc.

Combined inhibition of Chk1 and Wee1 as a new therapeutic strategy for mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive, incurable disease, characterized by a deregulated cell cycle. Chk1 and Wee1 are main regulators of cell cycle progression and recent data on solid tumors suggest that simultaneous inhibition of these proteins has a strong synergistic cytotoxic effect. The effects of a Chk1 inhibitor (PF-00477736) and a Wee1 inhibitor (MK-1775) have been herein investigated in a large panel of mature B-cell lymphoma cell lines. We found that MCL cells were the most sensitive to the Chk1 inhibitor PF-00477736 and Wee1 inhibitor MK-1775 as single agents. Possible involvement of the translocation t(11;14) in Chk1 inhibitor sensitivity was hypothesized. The combined inhibition of Chk1 and Wee1 was strongly synergistic in MCL cells, leading to deregulation of the cell cycle, with increased activity of CDK2 and CDK1, and activation of apoptosis. In vivo treatment with the drug combination of mice bearing JeKo-1 xenografts (MCL) had a marked antitumor effect with tumor regressions observed at non-toxic doses (best T/C%=0.54%). Gene expression profiling suggested effect on genes involved in apoptosis. The strong synergism observed by combining Chk1 and Wee1 inhibitors in preclinical models of MCL provides the rationale for testing this combination in the clinical setting.

SRC family kinase (SFK) inhibition reduces rhabdomyosarcoma cell growth in vitro and in vivo and triggers p38 MAP kinase-mediated differentiation

Recent data suggest that SRC family kinases (SFKs) could represent potential therapeutic targets for rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children. Here, we assessed the effect of a recently developed selective SFK inhibitor (a pyrazolo[3,4-d]pyrimidine derivative, called SI221) on RMS cell lines. SI221, which showed to be mainly effective against the SFK member YES, significantly reduced cell viability and induced apoptosis, without affecting non-tumor cells, such as primary human skin fibroblasts and differentiated C2C12 cells. Moreover, SI221 decreased in vitro cell migration and invasion and reduced tumor growth in a RMS xenograft model. SFK inhibition also induced muscle differentiation in RMS cells by affecting the NOTCH3 receptor-p38 mitogen-activated protein kinase (MAPK) axis, which regulates the balance between proliferation and differentiation. Overall, our findings suggest that SFK inhibition, besides reducing RMS cell growth and invasive potential, could also represent a differentiation therapeutic strategy for RMS.

SRC family kinase inhibition through a new pyrazolo[3,4-d]pyrimidine derivative as a feasible approach for glioblastoma treatment

Glioblastoma (GB) is the most common and aggressive primary tumor of the central nervous system. The current standard of care for GB consists of surgical resection, followed by radiotherapy combined with temozolomide chemotherapy. However, despite this intensive treatment, the prognosis remains extremely poor. Therefore, more effective therapies are urgently required. Recent studies indicate that SRC family kinases (SFKs) could represent promising molecular targets for GB therapy. Here, we challenged four GB cell lines with a new selective pyrazolo[3,4-d]pyrimidine derivative SFK inhibitor, called SI221. This compound exerted a significant cytotoxic effect on GB cells, without significantly affecting non-tumor cells (primary human skin fibroblasts), as evaluated by MTS assay. We also observed that SI221 was more effective than the well-known SFK inhibitor PP2 in GB cells. Notably, despite the high intrinsic resistance to apoptosis of GB cells, SI221 was able to induce this cell death process in all the GB cell lines, as observed through cytofluorimetric analysis and caspase-3 assay. SI221 also exerted a long-term inhibition of GB cell growth and was able to reduce GB cell migration, as shown by clonogenic assay and scratch test, respectively. Moreover, through in vitro pharmacokinetic assays, SI221 proved to have a high metabolic stability and a good potential to cross the blood brain barrier, which is an essential requirement for a drug intended to treat brain tumors. Therefore, despite the need of developing strategies to improve SI221 solubility, our results suggest a potential application of this selective SFK inhibitor in GB therapy.

Studies on the ATP Binding Site of Fyn Kinase for the Identification of New Inhibitors and Their Evaluation as Potential Agents against Tauopathies and Tumors

Fyn is a member of the Src-family of nonreceptor protein-tyrosine kinases. Its abnormal activity has been shown to be related to various human cancers as well as to severe pathologies, such as Alzheimer's and Parkinson's diseases. Herein, a structure-based drug design protocol was employed aimed at identifying novel Fyn inhibitors. Two hits from commercial sources (1, 2) were found active against Fyn with K(i) of about 2 μM, while derivative 4a, derived from our internal library, showed a K(i) of 0.9 μM. A hit-to-lead optimization effort was then initiated on derivative 4a to improve its potency. Slightly modifications rapidly determine an increase in the binding affinity, with the best inhibitors 4c and 4d having K(i)s of 70 and 95 nM, respectively. Both compounds were found able to inhibit the phosphorylation of the protein Tau in an Alzheimer's model cell line and showed antiproliferative activities against different cancer cell lines.

Flow sorting and exome sequencing reveal the oncogenome of primary Hodgkin and Reed-Sternberg cells

Classical Hodgkin lymphoma (cHL) is characterized by sparsely distributed Hodgkin and Reed-Sternberg (HRS) cells amid reactive host background, complicating the acquisition of neoplastic DNA without extensive background contamination. We overcame this limitation by using flow-sorted HRS and intratumor T cells and optimized low-input exome sequencing of 10 patient samples to reveal alterations in genes involved in antigen presentation, chromosome integrity, transcriptional regulation, and ubiquitination. β-2-microglobulin (B2M) is the most commonly altered gene in HRS cells, with 7 of 10 cases having inactivating mutations that lead to loss of major histocompatibility complex class I (MHC-I) expression. Enforced wild-type B2M expression in a cHL cell line restored MHC-I expression. In an extended cohort of 145 patients, the absence of B2M protein in the HRS cells was associated with lower stage of disease, younger age at diagnosis, and better overall and progression-free survival. B2M-deficient cases encompassed most of the nodular sclerosis subtype cases and only a minority of mixed cellularity cases, suggesting that B2M deficiency determines the tumor microenvironment and may define a major subset of cHL that has more uniform clinical and morphologic features. In addition, we report previously unknown genetic alterations that may render selected patients sensitive to specific targeted therapies.

Abrogating G₂/M checkpoint through WEE1 inhibition in combination with chemotherapy as a promising therapeutic approach for mesothelioma

Malignant mesothelioma (MM) is a very aggressive asbestos-related neoplasm of the serous membranes, whose incidence is increasing worldwide. Although the introduction of new drug combinations, such as cisplatin plus pemetrexed/gemcitabine, has determined an improvement in the patient quality of life, MM remains a universally fatal disease. The observation that key G 1/S checkpoint regulators are often functionally inactivated in MM prompted us to test whether the use of G 2/M checkpoint inhibitors, able to sensitize G 1/S checkpoint-defective cancer cells to DNA-damaging agents, could be successful in MM. We treated six MM cell lines, representative of different histotypes (epithelioid, biphasic, and sarcomatoid), with cisplatin in combination with MK-1775, an inhibitor of the G 2/M checkpoint kinase WEE1. We observed that MK-1775 enhanced the cisplatin cytotoxic effect in all MM cell lines, except the sarcomatoid cell line, which is representative of the most aggressive histotype. As expected, the enhancement in cisplatin toxicity was accompanied by a decrease in the inactive phosphorylated form of cyclin-dependent kinase 1 (CDK1), a key substrate of WEE1, which is indicative of G 2/M checkpoint inactivation. Consistently, we also observed a decrease in G 2/M accumulation and an increase in mitotic entry of DNA-damaged cells and apoptosis, probably due to the loss of the cell ability to arrest cell cycle in response to DNA damage, irrespectively of p53 mutational status. Notably, this treatment did not increase cisplatin cytotoxicity on normal cells, thus suggesting a possible use of MK-1775 in combination with cisplatin for a safe and efficient treatment of epithelioid and biphasic MM.

Erlotinib antagonizes ABC transporters in acute myeloid leukemia

Erlotinib was originally developed as an epidermal growth factor receptor (EGFR)-specific inhibitor for the treatment of solid malignancies, yet also exerts significant EGFR-independent antileukemic effects in vitro and in vivo. The molecular mechanisms underlying the clinical antileukemic activity of erlotinib as a standalone agent have not yet been precisely elucidated. Conversely, in preclinical settings, erlotinib has been shown to inhibit the constitutive activation of SRC kinases and mTOR, as well as to synergize with the DNA methyltransferase inhibitor azacytidine (a reference therapeutic for a subset of leukemia patients) by promoting its intracellular accumulation. Here, we show that both erlotinib and gefitinib (another EGFR inhibitor) inhibit transmembrane transporters of the ATP-binding cassette (ABC) family, including P-glycoprotein (P-gp), multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP), also in acute myeloid leukemia (AML) cells that do not overexpress these pumps. Thus, inhibition of drug efflux by erlotinib and gefitinib selectively exacerbated (in a synergistic or additive fashion) the cytotoxic response of KG-1 cells to chemotherapeutic agents that are normally extruded by ABC transporters (e.g., doxorubicin and etoposide). Erlotinib limited drug export via ABC transporters by multiple mechanisms, including the downregulation of surface-exposed pumps and the modulation of their ATPase activity. The effects of erlotinib on drug efflux and its chemosensitization profile persisted in patient-derived CD34+ cells, suggesting that erlotinib might be particularly efficient in antagonizing leukemic (stem cell) subpopulations, irrespective of whether they exhibit or not increased drug efflux via ABC transporters.