Novel Src/Abl tyrosine kinase inhibitor bosutinib suppresses neuroblastoma growth via inhibiting Src/Abl signaling

Integrative Analysis of Multi-Omics Data to Identify Deregulated Molecular Pathways and Druggable Targets in Chronic Lymphocytic Leukemia

Chronic Lymphocytic Leukemia (CLL) is the most common B-cell malignancy in the Western world, characterized by frequent relapses despite temporary remissions. Our study integrated publicly available proteomic, transcriptomic, and patient survival datasets to identify key differences between healthy and CLL samples. We exposed approximately 1000 proteins that differentiate healthy from cancerous cells, with 608 upregulated and 415 downregulated in CLL cases. Notable upregulated proteins include YEATS2 (an epigenetic regulator), PIGR (Polymeric immunoglobulin receptor), and SNRPA (a splicing factor), which may serve as prognostic biomarkers for this disease. Key pathways implicated in CLL progression involve RNA processing, stress resistance, and immune response deficits. Furthermore, we identified three existing drugs-Bosutinib, Vorinostat, and Panobinostat-for potential further investigation in drug repurposing in CLL. We also found limited correlation between transcriptomic and proteomic data, emphasizing the importance of proteomics in understanding gene expression regulation mechanisms. This generally known disparity highlights once again that mRNA levels do not accurately predict protein abundance due to many regulatory factors, such as protein degradation, post-transcriptional modifications, and differing rates of translation. These results demonstrate the value of integrating omics data to uncover deregulated proteins and pathways in cancer and suggest new therapeutic avenues for CLL.

Asciminib Maintains Antibody-Dependent Cellular Cytotoxicity against Leukemic Blasts

B cell acute lymphoblastic leukemia (B-ALL) is characterized by an accumulation of malignant precursor cells. Treatment consists of multiagent chemotherapy followed by allogeneic stem cell transplantation in high-risk patients. In addition, patients bearing the BCR-ABL1 fusion gene receive concomitant tyrosine kinase inhibitor (TKI) therapy. On the other hand, monoclonal antibody therapy is increasingly used in both clinical trials and real-world settings. The introduction of rituximab has improved the outcomes in CD20 positive cases. Other monoclonal antibodies, such as tafasitamab (anti-CD19), obinutuzumab (anti-CD20) and epratuzumab (anti-CD22) have been tested in trials (NCT05366218, NCT04920968, NCT00098839). The efficacy of monoclonal antibodies is based, at least in part, on their ability to induce antibody-dependent cellular cytotoxicity (ADCC). Combination treatments, e.g., chemotherapy and TKI, should therefore be screened for potential interference with ADCC. Here, we report on in vitro data using BCR-ABL1 positive and negative B-ALL cell lines treated with rituximab and TKI. NK cell activation, proliferation, degranulation, cytokine release and tumor cell lysis were analyzed. In contrast to ATP site inhibitors such as dasatinib and ponatinib, the novel first-in-class selective allosteric ABL myristoyl pocket (STAMP) inhibitor asciminib did not significantly impact ADCC in our settings. Our results suggest that asciminib should be considered in clinical trials.

The heterogeneity of signaling pathways and drug responses in intrahepatic cholangiocarcinoma with distinct genetic mutations

Intrahepatic cholangiocarcinoma (ICC) is the second most common malignancy among primary liver cancers, with an increasing overall incidence and poor prognosis. The intertumoral and intratumoral heterogeneity of ICC makes it difficult to find efficient drug therapies. Therefore, it is essential to identify tumor suppressor genes and oncogenes that induce ICC formation and progression. Here, we performed CRISPR/Cas9-mediated genome-wide screening in a liver-specific Smad4/Pten knockout mouse model (Smad4co/co;Ptenco/co;Alb-Cre, abbreviated as SPC), which normally generates ICC after 6 months, and detected that mutations in Trp53, Fbxw7, Inppl1, Tgfbr2, or Cul3 markedly accelerated ICC formation. To illustrate the potential mechanisms, we conducted transcriptome sequencing and found that multiple receptor tyrosine kinases were activated, which mainly upregulated the PI3K pathway to induce cell proliferation. Remarkably, the Cul3 mutation stimulated cancer progression mainly by altering the immune microenvironment, whereas other mutations promoted the cell cycle. Moreover, Fbxw7, Inppl1, Tgfbr2, and Trp53 also affect inflammatory responses, apelin signaling, mitotic spindles, ribosome biogenesis, and nucleocytoplasmic transport pathways, respectively. We further examined FDA-approved drugs for the treatment of liver cancer and performed high-throughput drug screening of the gene-mutant organoids. Different drug responses and promising drug therapies, including chemotherapy and targeted drugs, have been discovered for ICC.

Photoactivated Protein Degrader for Optical Control of Synaptic Function

Hundreds of proteins determine the function of synapses, and synapses define the neuronal circuits that subserve myriad brain, cognitive, and behavioral functions. It is thus necessary to precisely manipulate specific proteins at specific sub-cellular locations and times to elucidate the roles of particular proteins and synapses in brain function. We developed PHOtochemically TArgeting Chimeras (PHOTACs) as a strategy to optically degrade specific proteins with high spatial and temporal precision. PHOTACs are small molecules that, upon wavelength-selective illumination, catalyze ubiquitylation and degradation of target proteins through endogenous proteasomes. Here, we describe the design and chemical properties of a PHOTAC that targets Ca2+/calmodulin-dependent protein kinase II alpha (CaMKIIα), which is abundant and crucial for the baseline synaptic function of excitatory neurons. We validate the PHOTAC strategy, showing that the CaMKIIα-PHOTAC is effective in mouse brain tissue. Light activation of CaMKIIα-PHOTAC removed CaMKIIα from regions of the mouse hippocampus only within 25 μm of the illuminated brain surface. The optically controlled degradation decreases synaptic function within minutes of light activation, measured by the light-initiated attenuation of evoked field excitatory postsynaptic potential (fEPSP) responses to physiological stimulation. The PHOTACs methodology should be broadly applicable to other key proteins implicated in synaptic function, especially for evaluating their precise roles in the maintenance of long-term potentiation and memory within subcellular dendritic domains.

Bosutinib high density lipoprotein nanoformulation has potent tumour radiosensitisation effects

Disruption of the cell cycle is among the most effective approach to increase tumour cells' radio-sensitivity. However, the presence of dose-limiting side effects hampers the clinical use of tyrosine kinase inhibitors targeting the cell cycle. Towards addressing this challenge, we identified a bosutinib nanoformulation within high density lipoprotein nanoparticles (HDL NPs) as a promising radiosensitiser. Bosutinib is a kinase inhibitor clinically approved for the treatment of chronic myeloid leukemia that possesses radiosensitising properties through cell cycle checkpoint inhibition. We found that a remarkably high bosutinib loading (> 10%) within HDL NPs could be reliably achieved under optimal preparation conditions. The radiosensitisation activity of the bosutinib-HDL nanoformulation was first assessed in vitro in UM-SCC-1 head and neck squamous cell carcinoma (HNSCC) cells, which confirmed efficient disruption of the radiation induced G₂/M cell cycle arrest. Interestingly, the bosutinib nanoformulation out-performed free bosutinib, likely because of the specific affinity of HDL NPs with tumour cells. The combination of bosutinib-HDL NPs and radiotherapy significantly controlled tumour growth in an immunocompetent murine HNSCC model. The bosutinib-HDL nanoformulation also enhanced the radiation induced immune response through the polarisation of tumour associated macrophages towards proinflammatory phenotypes.

A Photoactivated Protein Degrader for Optical Control of Synaptic Function

Hundreds of proteins determine the function of synapses, and synapses define the neuronal circuits that subserve myriad brain, cognitive, and behavioral functions. It is thus necessary to precisely manipulate specific proteins at specific sub-cellular locations and times to elucidate the roles of particular proteins and synapses in brain function. We developed PHOtochemically TArgeting Chimeras (PHOTACs) as a strategy to optically degrade specific proteins with high spatial and temporal precision. PHOTACs are small molecules that, upon wavelength-selective illumination, catalyze ubiquitylation and degradation of target proteins through endogenous proteasomes. Here we describe the design and chemical properties of a PHOTAC that targets Ca 2+ /calmodulin-dependent protein kinase II alpha (CaMKIIα), which is abundant and crucial for baseline synaptic function of excitatory neurons. We validate the PHOTAC strategy, showing that the CaMKIIα-PHOTAC is effective in mouse brain tissue. Light activation of CaMKIIα-PHOTAC removed CaMKIIα from regions of the mouse hippocampus only within 25 μm of the illuminated brain surface. The optically-controlled degradation decreases synaptic function within minutes of light activation, measured by the light-initiated attenuation of evoked field excitatory postsynaptic potential (fEPSP) responses to physiological stimulation. The PHOTACs methodology should be broadly applicable to other key proteins implicated in synaptic function, especially for evaluating their precise roles in the maintenance of long-term potentiation and memory within subcellular dendritic domains.

YES1: a novel therapeutic target and biomarker in cancer

YES1 is a non-receptor tyrosine kinase that belongs to the SRC family of kinases (SFKs) and controls multiple cancer signaling pathways. YES1 is amplified and overexpressed in many tumor types, where it promotes cell proliferation, survival and invasiveness. Therefore, YES1 has been proposed as an emerging target in solid tumors. In addition, studies have shown that YES1 is a prognostic biomarker and a predictor of dasatinib activity. Several SFKs-targeting drugs have been developed and some of them have reached clinical trials. However, these drugs have encountered challenges to their utilization in the clinical practice in unselected patients due to toxicity and lack of efficacy. In the case of YES1, novel specific inhibitors have been developed and tested in preclinical models, with impressive antitumor effects. In this review, we summarize the structure and activation of YES1 and describe its role in cancer as a target and prognostic and companion biomarker. We also address the efficacy of SFKs inhibitors that are currently in clinical trials, highlighting the main hindrances for their clinical use. Current available information strongly suggests that inhibiting YES1 in tumors with high expression of this protein is a promising strategy against cancer.

Protein Tyrosine Phosphatases in Neuroblastoma: Emerging Roles as Biomarkers and Therapeutic Targets

Neuroblastoma is a type of cancer intimately related with early development and differentiation of neuroendocrine cells, and constitutes one of the pediatric cancers with higher incidence and mortality. Protein tyrosine phosphatases (PTPs) are key regulators of cell growth and differentiation by their direct effect on tyrosine dephosphorylation of specific protein substrates, exerting major functions in the modulation of intracellular signaling during neuron development in response to external cues driving cell proliferation, survival, and differentiation. We review here the current knowledge on the role of PTPs in neuroblastoma cell growth, survival, and differentiation. The potential of PTPs as biomarkers and molecular targets for inhibition in neuroblastoma therapies is discussed.

Protective effect of Bosutinib with caspase inhibitors on human K562 cells

Introduction

Cancer therapy has become increasingly focused on molecularly targeted medications. Despite the fact that multi-cytotoxic medication regimens have proven to be highly effective, many investigations in targeted treatments have focused on a single agent. The precise molecular mechanism of action of second-generation BCR–ABL tyrosine kinase inhibitors, which includes different targets and pathways, can help rationalize therapy in chronic myelogenous leukemia (CML) and other diseases affected by BCR–ABL tyrosine kinase inhibitors (TKIs).

Aim

The purpose of this study was to analyze if bosutinib (BOS) combined with Boc-D-FMK effectively suppressed proliferation and induced apoptosis in K562 cells to a lesser extent, implying that bosutinib is an effective leukemia treatment and that its combination with Boc-D-FMK is a mild chemotherapeutic agent against leukemia.

Methods

In this study, bosutinib was obtained together with other materials to perform a cell culture experiment with human cell lines, as well as additional drug treatment. Furthermore, cell viability (MTT assay) and flow cryometry such as viability and cell cycle assays are performed. The target profile of the dual SRC/ABL inhibitor bosutinib was studied in this study as a first kinase inhibitor to target K562 cells, which has recently been linked to the proliferation of myelogenous leukaemia cells, these results suggest the effectiveness of inhibitory activity on cell viability/proliferation, alone generated a potent value of 250 nM (39.27 ± 1.17) for 48 h as optimal dose.

Results

The cytotoxic effect of bosutinib on the K562 cell line was assessed in vitro using the MTT assay, and the cytotoxicity was further clarified using cell viability and cell cycle assays. Guava Cell Assay software validated the activation of apoptosis. Sub-G1, G0/G1, S, and G2/M phases are depicted. Cell cycle research revealed that K562 cells treated with bosutinib accumulated much more in the sub-G1 phase, which was later validated by a drop peak at the G2/M phase.

Conclusion

In conclusion, the nature of bosutinib's reduction of cancer cell growth may open the door to future research into the development of green synthesis medicines, particularly for cancer treatment.

Synthetic Heterocyclic Derivatives as Kinase Inhibitors Tested for the Treatment of Neuroblastoma

In the last few years, small molecules endowed with different heterocyclic scaffolds have been developed as kinase inhibitors. Some of them are being tested at preclinical or clinical levels for the potential treatment of neuroblastoma (NB). This disease is the most common extracranial solid tumor in childhood and is responsible for 10% to 15% of pediatric cancer deaths. Despite the availability of some treatments, including the use of very toxic cytotoxic chemotherapeutic agents, high-risk (HR)-NB patients still have a poor prognosis and a survival rate below 50%. For these reasons, new pharmacological options are urgently needed. This review focuses on synthetic heterocyclic compounds published in the last five years, which showed at least some activity on this severe disease and act as kinase inhibitors. The specific mechanism of action, selectivity, and biological activity of these drug candidates are described, when established. Moreover, the most remarkable clinical trials are reported. Importantly, kinase inhibitors approved for other diseases have shown to be active and endowed with lower toxicity compared to conventional cytotoxic agents. The data collected in this article can be particularly useful for the researchers working in this area.

Expression of claudin-8 is induced by aldosterone in renal collecting duct principal cells

Fine tuning of Na⁺ reabsorption takes place along the aldosterone-sensitive distal nephron, which includes the collecting duct (CD), where it is mainly regulated by aldosterone. In the CD, Na⁺ reabsorption is mediated by the epithelial Na⁺ channel and Na⁺ pump (Na⁺-K⁺-ATPase). Paracellular ion permeability is mainly dependent on tight junction permeability. Claudin-8 is one of the main tight junction proteins expressed along the aldosterone-sensitive distal nephron. We have previously shown a coupling between transcellular Na⁺ reabsorption and paracellular Na⁺ barrier. We hypothesized that aldosterone controls the expression levels of both transcellular Na⁺ transporters and paracellular claudin-8 in a coordinated manner. Here, we show that aldosterone increased mRNA and protein levels as well as lateral membrane localization of claudin-8 in cultured CD principal cells. The increase in claudin-8 mRNA levels in response to aldosterone was prevented by preincubation with 17-hydroxyprogesterone, a mineralocorticoid receptor antagonist, and by inhibition of transcription with actinomycin D. We also showed that a low-salt diet, which stimulated aldosterone secretion, was associated with increased claudin-8 abundance in the mouse kidney. Reciprocally, mice subjected to a high-salt diet, which inhibits aldosterone secretion, or treated with spironolactone, a mineralocorticoid receptor antagonist, displayed decreased claudin-8 expression. Inhibition of glycogen synthase kinase-3, Lyn, and Abl signaling pathways prevented the effect of aldosterone on claudin-8 mRNA and protein abundance, suggesting that signaling of protein kinases plays a permissive role on the transcriptional activity of the mineralocorticoid receptor. This study shows that signaling via multiple protein kinases working in concert mediates aldosterone-induced claudin-8 expression in the CD.NEW & NOTEWORTHY In this study, we showed that aldosterone modulates claudin-8 expression in cultured collecting duct principal cells and in the mouse kidney. The upregulation of claudin-8 expression in response to aldosterone is dependent on at least glycogen synthase kinase-3, Lyn, and Abl signaling pathways, indicating the participation of multiple protein kinases to the effect of aldosterone.

Translational Strategies for Repotrectinib in Neuroblastoma

Limited clinical data are available regarding the utility of multikinase inhibition in neuroblastoma. Repotrectinib (TPX-0005) is a multikinase inhibitor that targets ALK, TRK, JAK2/STAT, and Src/FAK, which have all been implicated in the pathogenesis of neuroblastoma. We evaluated the preclinical activity of repotrectinib monotherapy and in combination with chemotherapy as a potential therapeutic approach for relapsed/refractory neuroblastoma. In vitro sensitivity to repotrectinib, ensartinib, and cytotoxic chemotherapy was evaluated in neuroblastoma cell lines. In vivo antitumor effect of repotrectinib monotherapy, and in combination with chemotherapy, was evaluated using a genotypically diverse cohort of patient-derived xenograft (PDX) models of neuroblastoma. Repotrectinib had comparable cytotoxic activity across cell lines irrespective of ALK mutational status. Combination with chemotherapy demonstrated increased antiproliferative activity across several cell lines. Repotrectinib monotherapy had notable antitumor activity and prolonged event-free survival compared with vehicle and ensartinib in PDX models (P < 0.05). Repotrectinib plus chemotherapy was superior to chemotherapy alone in ALK-mutant and ALK wild-type PDX models. These results demonstrate that repotrectinib has antitumor activity in genotypically diverse neuroblastoma models, and that combination of a multikinase inhibitor with chemotherapy may be a promising treatment paradigm for translation to the clinic.

Bosutinib-induced osteonecrosis of the jaw in a patient with chronic myeloid leukemia: a case report

Medication-related osteonecrosis of the jaw (MRONJ) is an uncommon adverse drug reaction that can be induced by certain therapeutic drugs, including antiresorptive and antiangiogenic agents. Here, we describe the first case of ONJ induced by bosutinib, a tyrosine kinase inhibitor, in a patient with chronic myeloid leukemia (CML) who was not taking an antiresorptive agent. A 65-year-old male with no history of either antiresorptive treatment or dental surgery but diagnosed with CML had been undergoing treatment with bosutinib for 2 years. He developed right mandibular stage 2 osteonecrosis. The patient eventually underwent extensive surgery consisting of removal of the necrotic bone and infected soft tissue in combination with nasolabial flap reconstruction. He obtained complete resolution of MRONJ at 12 months postoperatively. As new cancer therapies become available, it is important that clinicians are aware of this novel case of bosutinib-induced ONJ in a patient undergoing CML treatment.

Bioinformatics Analysis of Neuroblastoma miRNA Based on GEO Data

Objective

To analyze the changes in downstream genes, signaling pathways, and proteins based on the difference of microRNA (miRNA) expression in neuroblastoma (NB).

Methods

GSE128004 second-generation sequencing expression data were downloaded from GEO, and Limma package of R language was used to analyze differential expression, and a volcano map and heat map were drawn; the target genes corresponding to the differential miRNA were found using the miWalk web tool, and GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) were performed. The key genes were identified and verified in the TCGA database.

Results

A total of 34 differentially expressed miRNAs were screened out. Among them, 22 up-regulated miRNAs predicted 1163 target genes and 12 down-regulated miRNAs predicted 1474 target genes. Target genes were enriched and analyzed by KEGG to find the FOXO signal pathway, mTOR signal pathway, AMPK signal pathway, and other signal pathways. After GO analysis, axon formation, regulation of chemical synaptic transmitters, regulation of nerve synapses, regulation of cross-synaptic signals, and other physiological processes were assessed. A total of 16 key genes were obtained by PPI analysis, and the survival analysis of TP53 and ATM genes verified in the TCGA database showed statistical significance.

Conclusion

The 34 differential miRNAs may be related to the occurrence and development of NB. TP53 and ATM are related to the prognosis of NB. The role and mechanism of TP53 and ATM in NB need to be further verified.

Targeting the Extra-Cellular Matrix-Tumor Cell Crosstalk for Anti-Cancer Therapy: Emerging Alternatives to Integrin Inhibitors

The extracellular matrix (ECM) is a complex network composed of a multitude of different macromolecules. ECM components typically provide a supportive structure to the tissue and engender positional information and crosstalk with neighboring cells in a dynamic reciprocal manner, thereby regulating tissue development and homeostasis. During tumor progression, tumor cells commonly modify and hijack the surrounding ECM to sustain anchorage-dependent growth and survival, guide migration, store pro-tumorigenic cell-derived molecules and present them to enhance receptor activation. Thereby, ECM potentially supports tumor progression at various steps from initiation, to local growth, invasion, and systemic dissemination and ECM-tumor cells interactions have long been considered promising targets for cancer therapy. Integrins represent key surface receptors for the tumor cell to sense and interact with the ECM. Yet, attempts to therapeutically impinge on these interactions using integrin inhibitors have failed to deliver anticipated results, and integrin inhibitors are still missing in the emerging arsenal of drugs for targeted therapies. This paradox situation should urge the field to reconsider the role of integrins in cancer and their targeting, but also to envisage alternative strategies. Here, we review the therapeutic targets implicated in tumor cell adhesion to the ECM, whose inhibitors are currently in clinical trials and may offer alternatives to integrin inhibition.

Tumor necrosis factor-α triggers opposing signals in head and neck squamous cell carcinoma and induces apoptosis via mitochondrial- and non-mitochondrial-dependent pathways

Head and neck squamous cell carcinoma (HNSCC) remains one of the most common malignancies worldwide. Although the treatment outcomes of HNSCC have improved in recent years, the prognosis of patients with advanced-stage disease remains poor. Current treatment strategies for HNSCC include surgery as a primary therapy, while radio-, chemo-, and biotherapeutics can be applied as second-line therapy. Although tumor necrosis factor-α (TNF-α) is a potent tumor suppressor cytokine, the stimulation of opposing signals impairs its clinical utility as an anticancer agent. The aim of this study was to elucidate the mechanisms regulating TNF-α‑induced opposing signals and their biological consequences in HNSCC cell lines. We determined the molecular mechanisms of TNF-α-induced opposing signals in HNSCC cells. Our in vitro analysis indicated that one of these signals triggers apoptosis, while the other induces both apoptosis and cell survival. The TNF-α-induced survival of HNSCC cells is mediated by the TNF receptor-associated factor 2 (TRAF2)/nuclear factor (NF)-κB-dependent pathway, while TNF-α-induced apoptosis is mediated by mitochondrial and non-mitochondrial-dependent mechanisms through FADD-caspase-8-caspase-3 and ASK-JNK-p53-Noxa pathways. The localization of Noxa protein to both the mitochondria and endoplasmic reticulum (ER) was found to cause mitochondrial dysregulation and ER stress, respectively. Using inhibitory experiments, we demonstrated that the FADD‑caspase-8‑caspase-3 pathway, together with mitochondrial dysregulation and ER stress-dependent pathways, are essential for the modulation of apoptosis, and the NF-κB pathway is essential for the modulation of anti-apoptotic effects/cell survival during the exposure of HNSCC cells to TNF-α. Our data provide insight into the mechanisms of TNF-α-induced opposing signals in HNSCC cells and may further help in the development of novel therapeutic approaches with which to minimize the systemic toxicity of TNF-α.

Silencing of COPB2 inhibits the proliferation of gastric cancer cells and induces apoptosis via suppression of the RTK signaling pathway

Emerging studies have reported that coatomer protein complex subunit β2 (COPB2) is overexpressed in several types of malignant tumor; however, to the best of our knowledge, no studies regarding COPB2 in gastric cancer have been published thus far. Therefore, the present study aimed to determine the significance and function of COPB2 in gastric cancer. COPB2 expression in gastric cancer cell lines was measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. In addition, lentivirus-short hairpin RNA (shRNA) COPB2 (Lv-shCOPB2) was generated and used to infect BGC-823 cells to analyze the effects of COPB2 on the cancerous phenotype. The effects of shRNA-mediated COPB2 knockdown on cell proliferation were detected using MTT, 5-bromo-2-deoxyuridine and colony formation assays. In addition, the effects of COPB2 knockdown on apoptosis were analyzed by flow cytometry. Nude mice and fluorescence imaging were used to characterize the regulation of tumor growth in vivo, and qPCR and immunohistochemistry were subsequently conducted to analyze COPB2 expression in xenograft tumor tissues. Furthermore, a receptor tyrosine kinase (RTK) signaling pathway antibody array was used to explore the relevant molecular mechanisms underlying the effects of COPB2 knockdown. The results revealed that COPB2 mRNA was abundantly overexpressed in gastric cancer cell lines, whereas knockdown of COPB2 significantly inhibited cell growth and colony formation ability, and led to increased cell apoptosis in vitro. The tumorigenicity assay revealed that knockdown of COPB2 reduced tumor growth in nude mice, and fluorescence imaging indicated that the total radiant efficiency of mice in the Lv-shCOPB2-infected group was markedly reduced compared with the mice in the Lv-shRNA control-infected group in vivo. The antibody array assay revealed that the levels of phosphorylation in 23 target RTKs were significantly reduced: In conclusion, COPB2 was highly expressed in gastric cancer cell lines, and knockdown suppressed colony formation and promoted cell apoptosis via inhibiting the RTK signaling and its downstream signaling cascade molecules. Therefore, COPB2 may present a valuable target for gene silencing strategy in gastric cancer.

Next-generation proteasome inhibitor oprozomib enhances sensitivity to doxorubicin in triple-negative breast cancer cells

Doxorubicin (DOX) is the most common chemotherapeutic drug for treatment of breast cancer but intrinsic and acquired resistance frequently occurs and severe side effects occur at high doses. DOX might induce activation of NF-κB causing this resistance, in which case proteasome inhibitors could inhibit activation of NF-κB by blocking inhibitory factor κB-alpha degradation. Triple-negative breast cancer (TNBC) is highly progressive and there are no established therapeutic targets against TNBC. Although some proteasome inhibitors have been shown to have antitumor effects in breast cancer, the effect of orally bioavailable proteasome inhibitor oprozomib on TNBC proliferation remains unclear. In the present study, we investigated the role of oprozomib in two TNBC lines, MDA-MB-231 and BT-549. Oprozomib had cytotoxic effects on TNBC cells and increased DOX-induced cytotoxic effects and apoptosis by enhancing DOX-induced JNK/p38 MAPK phosphorylation and inhibiting DOX-induced inhibitory factor êB alpha degradation. These results suggest that oprozomib has potent antitumor effects on TNBC in vitro and can sensitize TNBC cells to DOX treatment. The combination of DOX and oprozomib may be an effective and feasible therapeutic option for TNBC.

A Src/Abl kinase inhibitor, bosutinib, downregulates and inhibits PARP enzyme and sensitizes cells to the DNA damaging agents

Background:

Poly(ADP-ribosyl)ation (PARylation) catalyzed mainly by PARP1 is a highly regulated posttranslational modification associated with several pathways in cellular physiology and genotoxic deoxyribonucleic acid (DNA) damage response. PAR polymers and PARP enzyme function in DNA integrity maintenance and several PARP inhibitors have entered clinical phase studies for cancer therapies.

Material and methods:

The effect of bosutinib, a dual Src/Abl kinase inhibitor, on PARylation was fluorometrically measured. The cytotoxic and chemosensitizing effects were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The levels of DNA repair proteins and PARP enzyme were examined by immunoblotting.

Results:

In this study, bosutinib is characterized as a novel PARP inhibitor. Bosutinib inhibited oxidative stress-induced cellular PARylation and nuclear foci formation by downregulating PARP1 levels. Bosutinib was found to be more cytotoxic on Capan1 cells with BRCA2 mutation. Furthermore by acting as a chemosensitizer, bosutinib enhanced the cytotoxicity of doxorubicin (DOXO) and etoposide (ETP) by decreasing phosphorylation of DNA repair enzymes checkpoint kinase 1 (Chk1) and ataxia-telangiectasia mutated (ATM).

Conclusion:

By inhibition of both PARP and DNA damage checkpoint kinases, bosutinib increased the phospho-H2AX levels, an early indicator of DNA double strand breaks.

Small molecule inhibitor regorafenib inhibits RET signaling in neuroblastoma cells and effectively suppresses tumor growth in vivo

Neuroblastoma (NB), the most common extracranial pediatric solid tumor, continues to cause significant cancer-related morbidity and mortality in children. Dysregulation of oncogenic receptor tyrosine kinases (RTKs) has been shown to contribute to tumorigenesis in various human cancers and targeting these RTKs has had therapeutic benefit. RET is an RTK which is commonly expressed in NB, and high expression of RET correlates with poor outcomes in patients with NB. Herein we report that RET is required for NB cell proliferation and that the small molecule inhibitor regorafenib (BAY 73-4506) blocks glial cell derived neurotrophic factor (GDNF)-induced RET signaling in NB cells and inhibits NB growth both in vitro and in vivo. We found that regorafenib significantly inhibited cell proliferation and colony formation ability of NB cells. Moreover, regorafenib suppressed tumor growth in both an orthotopic xenograft NB mouse model and a TH-MYCN transgenic NB mouse model. Finally, regorafenib markedly improved the overall survival of TH-MYCN transgenic tumor-bearing mice. In summary, our study suggests that RET is a potential therapeutic target in NB, and that using a novel RET inhibitor, like regorafenib, should be investigated as a therapeutic treatment option for children with NB.