Oncogene addiction: pathways of therapeutic response, resistance, and road maps toward a cure

Androgen receptor enhancer amplification in matched patient-derived xenografts of primary and castrate-resistant prostate cancer

Amplifications of the androgen receptor (AR) occur in up to 80% of men with castration-resistant prostate cancer (CRPC). Recent studies highlighted that these amplifications not only span the AR gene but usually encompass a distal enhancer. This represents a newly recognised, non-coding mechanism of resistance to AR-directed therapies, including enzalutamide. To study disease progression before and after AR amplification, we used tumour samples from a castrate-sensitive primary tumour and castrate-resistant metastasis of the same patient. For subsequent functional and genomic studies, we established serially transplantable patient-derived xenografts (PDXs). Whole genome sequencing showed that alterations associated with poor prognosis, such as TP53 and PTEN loss, existed before androgen deprivation therapy, followed by co-amplification of the AR gene and enhancer after the development of metastatic CRPC. The PDX of the primary tumour, without the AR amplification, was sensitive to AR-directed treatments, including castration, enzalutamide, and apalutamide. The PDX of the metastasis, with the AR amplification, had higher AR and AR-V7 expression in castrate conditions, and was resistant to castration, apalutamide, and enzalutamide in vivo. Treatment with a BET inhibitor outperformed the AR-directed therapies for the metastasis, resulting in tumour regression for some, but not all, grafts. Therefore, this study provides novel matched PDXs to test potential treatments that target the overabundance of AR in tumours with AR enhancer amplifications. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

TNF receptor-associated factor 3 restrains B-cell receptor signaling in normal and malignant B cells

TRAF3 has diverse signaling functions, which vary by cell type. Uniquely in B lymphocytes, TRAF3 inhibits homeostatic survival. Highlighting the role of TRAF3 as a tumor suppressor, loss-of-function TRAF3 mutations are associated with human B-cell malignancies, while B-cell-specific deletion of TRAF3 in mice leads to autoimmunity and lymphoma development. The role of TRAF3 in inhibiting noncanonical NF-κB activation, CD40 and BAFF-R signaling to B cells is well documented. In contrast, TRAF3 enhances many T-cell effector functions, through associating with and enhancing signaling by the T-cell receptor (TCR)-CD28 complex. The present study was designed to determine the role of TRAF3 in signaling via the B-cell antigen receptor (BCR). The BCR is crucial for antigen recognition, survival, proliferation, and antibody production, and defects in BCR signaling can promote abnormal survival of malignant B cells. Here, we show that TRAF3 is associated with both CD79B and the BCR-activated kinases Syk and Btk following BCR stimulation. BCR-induced phosphorylation of Syk and additional downstream kinases was increased in TRAF3^−/− B cells, with regulation observed in both follicular and marginal zone B-cell subsets. BCR stimulation of TRAF3^−/− B cells resulted in increased surface expression of MHC-II, CD80, and CD86 molecules. Interestingly, increased survival of TRAF3^−/− primary B cells was resistant to inhibition of Btk, while TRAF3-deficient malignant B-cell lines showed enhanced sensitivity. TRAF3 serves to restrain normal and malignant BCR signaling, with important implications for its role in normal B-cell biology and abnormal survival of malignant B cells.

Targeting ubiquitin conjugating enzyme UbcH5b by a triterpenoid PC3-15 from Schisandra plants sensitizes triple-negative breast cancer cells to lapatinib

Increasing evidence suggested that a number of ubiquitin enzymes, including ubiquitin-activating enzymes, ubiquitin-conjugating enzymes, E3 ubiquitin ligases and deubiquitination enzymes contribute to therapeutic resistance in triple-negative breast cancer (TNBC) cells. Inhibition of these enzymes with small molecule inhibitors may restore therapeutic sensitivity. Here, we demonstrated ubiquitin conjugating enzyme UbcH5b strongly supports HECTD3 auto-ubiquitination in vitro. Based on this, we developed a Fluorescence Resonance Energy Transfer (FRET) assay and identified three Schisandraceae triterpenoids, including PC3-15, to block HECTD3/UbcH5b auto-ubiquitination. Furthermore, we revealed that PC3-15 directly binds to UbcH5b and also inhibits UbcH5b-mediated p62 ubiquitination. We found that the UbcH5b-p62 axis confers TNBC cells resistance to lapatinib by promoting autophagy. Consistently, PC3-15 inhibits lapatinib-induced autophagy and increases lapatinib sensitivity in TNBC in vitro and in mouse xenografts. These findings suggest that the UbcH5b-p62 axis provides potential therapeutic targets and that Schisandraceae triterpenoids may be used for TNBC treatment in combination with lapatinib.

Potential of enhancer of zeste homolog 2 inhibitors for the treatment of SWI/SNF mutant cancers and tumor microenvironment modulation

Enhancer of zeste homolog 2 (EZH2), a catalytic component of polycomb repressive complex 2 (PRC2), is commonly overexpressed or mutated in many cancer types, both of hematological and solid nature. Till now, plenty of EZH2 small molecule inhibitors have been developed and some of them have already been tested in clinical trials. Most of these inhibitors, however, are effective only in limited cases in the context of EZH2 gain-of-function mutated tumors such as lymphomas. Other cancer types with aberrant EZH2 expression and function require alternative approaches for successful treatment. One possibility is to exploit synthetic lethal strategy, which is based on the phenomenon that concurrent loss of two genes is detrimental but the deletion of either of them leaves cell viable. In the context of EZH2/PRC2, the most promising synthetic lethal target seems to be SWItch/Sucrose Non-Fermentable chromatin remodeling complex (SWI/SNF), which is known to counteract PRC2 functions. SWI/SNF is heavily involved in carcinogenesis and its subunits have been found mutated in approximately 20% of tumors of different kinds. In the current review, we summarize the existing knowledge of synthetic lethal relationships between EZH2/PRC2 and components of the SWI/SNF complex and discuss in detail the potential application of existing EZH2 inhibitors in cancer patients harboring mutations in SWI/SNF proteins. We also highlight recent discoveries of EZH2 involvement in tumor microenvironment regulation and consequences for future therapies. Although clinical studies are limited, the fundamental research might help to understand which patients are most likely to benefit from therapies using EZH2 inhibitors.

Integrin ανβ6 Protein Expression and Prognosis in Solid Tumors: A Meta-Analysis

BACKGROUND AND OBJECTIVE

Integrins are a family of adhesion receptor proteins that provide signaling from the extracellular matrix to the cytoplasm. They have been associated with cancer by promoting migration, invasion, metastasis, and survival. ανβ6 integrin is upregulated in several tumors. Here, we evaluate the prognostic impact of ανβ6 integrin protein expression in solid tumors.

METHODS

A systematic search of electronic databases identified publications exploring the effect of ανβ6 integrin on overall survival (OS). Hazard ratios (HRs) were pooled in a meta-analysis using generic inverse variance and random effects modeling. Subgroup analyses were conducted based on tumor site, tumor stage, antibody used for immunohistochemistry (IHC) and method for extraction of the HR. A meta-regression explored the influence of clinical variables on the magnitude of effect of ανβ6 integrins on OS.

RESULTS

Seventeen studies comprising 5795 patients met the inclusion criteria. High ανβ6 integrin expression in tumors was associated with worse OS (HR 1.65, 95% confidence interval [CI] 1.32-2.06; Cochran's Q p < 0.001, I² = 81%). Adverse outcomes were similar in all tumor sites (subgroup difference p = 0.10), with the strongest association between ανβ6 integrins and OS in gastric cancer (HR 2.20, 95% CI 1.71-2.83) and the lowest in head and neck cancer (HR 1.21, 95% CI 0.79-1.83). There was no significant difference between early-stage and metastatic cancer, type of IHC antibodies, and analysis methods.

CONCLUSIONS

High expression of ανβ6 integrins is associated with adverse survival outcome in several tumors. Prospective studies evaluating the prognostic impact of ανβ6 integrin and its role as a therapeutic target are warranted.

Transcriptional coregualtor NUPR1 maintains tamoxifen resistance in breast cancer cells

To support cellular homeostasis and mitigate chemotherapeutic stress, cancer cells must gain a series of adaptive intracellular processes. Here we identify that NUPR1, a tamoxifen (Tam)-induced transcriptional coregulator, is necessary for the maintenance of Tam resistance through physical interaction with ESR1 in breast cancers. Mechanistically, NUPR1 binds to the promoter regions of several genes involved in autophagy process and drug resistance such as BECN1, GREB1, RAB31, PGR, CYP1B1, and regulates their transcription. In Tam-resistant ESR1 breast cancer cells, NUPR1 depletion results in premature senescence in vitro and tumor suppression in vivo. Moreover, enforced-autophagic flux augments cytoplasmic vacuolization in NUPR1-depleted Tam resistant cells, which facilitates the transition from autophagic survival to premature senescence. Collectively, these findings suggest a critical role for NUPR1 as a transcriptional coregulator in enabling endocrine persistence of breast cancers, thus providing a vulnerable diagnostic and/or therapeutic target for endocrine resistance.

Integrated molecular characterisation of the MAPK pathways in human cancers reveals pharmacologically vulnerable mutations and gene dependencies

The mitogen-activated protein kinase (MAPK) pathways are crucial regulators of the cellular processes that fuel the malignant transformation of normal cells. The molecular aberrations which lead to cancer involve mutations in, and transcription variations of, various MAPK pathway genes. Here, we examine the genome sequences of 40,848 patient-derived tumours representing 101 distinct human cancers to identify cancer-associated mutations in MAPK signalling pathway genes. We show that patients with tumours that have mutations within genes of the ERK-1/2 pathway, the p38 pathways, or multiple MAPK pathway modules, tend to have worse disease outcomes than patients with tumours that have no mutations within the MAPK pathways genes. Furthermore, by integrating information extracted from various large-scale molecular datasets, we expose the relationship between the fitness of cancer cells after CRISPR mediated gene knockout of MAPK pathway genes, and their dose-responses to MAPK pathway inhibitors. Besides providing new insights into MAPK pathways, we unearth vulnerabilities in specific pathway genes that are reflected in the re sponses of cancer cells to MAPK targeting drugs: a revelation with great potential for guiding the development of innovative therapies.

The intracellular domain of UNC5B facilities proliferation and metastasis of bladder cancer cells

The intracellular domain of UNC5B contains both death domain and caspase‐3 cleavage site, and is regarded as a functional domain that mediates apoptosis. However, in our previous studies, we found that the death domain of UNC5B in bladder cancer cells could not be activated to promote apoptosis. In this study, different UNC5B truncates (residue 399‐945, residue 412‐945) were created to explore whether the caspase‐3 cleavage site (site 412), as another potential functional domain of its intracellular portion, could be activated to induce apoptosis in bladder cancer cells. Using mass spectrometry, we acquired a comprehensive and detailed identification of differentially expressed proteins by overexpressing UNC5B and its truncates. Protein‐protein‐interaction (PPI) network analysis was also applied to investigate the aggregation of related proteins and predict the functional changes. EDU assay, apoptosis, xenograft tumour implantation, migration, invasion and tumour metastasis were performed to comprehensively identify the effects of UNC5B truncates on bladder cancer cells. We demonstrate that the intracellular domain of UNC5B promotes cell proliferation in vitro and tumour formation in vivo, by binding to a large number of ribosomal proteins. The overexpression of intracellular domain also facilitates cells to migrate, invade and metastasize by interacting with fibronectin, beta‐catenin and vimentin. In addition, we reveal that overexpressing the intracellular domain of UNC5B cannot bind or activate cleaved caspase‐3 to trigger apoptosis in bladder cancer cells.

Synthetic Lethality through the Lens of Medicinal Chemistry

Personalized medicine and therapies represent the goal of modern medicine, as drug discovery strives to move away from one-cure-for-all and makes use of the various targets and biomarkers within differing disease areas. This approach, especially in oncology, is often undermined when the cells make use of alternative survival pathways. As such, acquired resistance is unfortunately common. In order to combat this phenomenon, synthetic lethality is being investigated, making use of existing genetic fragilities within the cancer cell. This Perspective highlights exciting targets within synthetic lethality, (PARP, ATR, ATM, DNA-PKcs, WEE1, CDK12, RAD51, RAD52, and PD-1) and discusses the medicinal chemistry programs being used to interrogate them, the challenges these programs face, and what the future holds for this promising field.

Functional proteomic analysis reveals roles for PKCδ in regulation of cell survival and cell death: Implications for cancer pathogenesis and therapy

Protein Kinase C-δ (PKCδ), regulates a broad group of biological functions and disease processes, including well-defined roles in immune function, cell survival and apoptosis. PKCδ primarily regulates apoptosis in normal tissues and non-transformed cells, and genetic disruption of the PRKCD gene in mice is protective in many diseases and tissue damage models. However pro-survival/pro-proliferative functions have also been described in some transformed cells and in mouse models of cancer. Recent evidence suggests that the contribution of PKCδ to specific cancers may depend in part on the oncogenic context of the tumor, consistent with its paradoxical role in cell survival and cell death. Here we will discuss what is currently known about biological functions of PKCδ and potential paradigms for PKCδ function in cancer. To further understand mechanisms of regulation by PKCδ, and to gain insight into the plasticity of PKCδ signaling, we have used functional proteomics to identify pathways that are dependent on PKCδ. Understanding how these distinct functions of PKCδ are regulated will be critical for the logical design of therapeutics to target this pathway.

Checkpoint Kinase 1 Pharmacological Inhibition Synergizes with DNA-Damaging Agents and Overcomes Platinum Resistance in Basal-Like Breast Cancer

Basal-like breast cancer is an incurable disease with limited therapeutic options, mainly due to the frequent development of anti-cancer drug resistance. Therefore, identification of druggable targets to improve current therapies and overcome these resistances is a major goal. Targeting DNA repair mechanisms has reached the clinical setting and several strategies, like the inhibition of the CHK1 kinase, are currently in clinical development. Here, using a panel of basal-like cancer cell lines, we explored the synergistic interactions of CHK1 inhibitors (rabusertib and SAR020106) with approved therapies in breast cancer and evaluated their potential to overcome resistance. We identified a synergistic action of these inhibitors with agents that produce DNA damage, like platinum compounds, gemcitabine, and the PARP inhibitor olaparib. Our results demonstrated that the combination of rabusertib with these chemotherapies also has a synergistic impact on tumor initiation, invasion capabilities, and apoptosis in vitro. We also revealed a biochemical effect on DNA damage and caspase-dependent apoptosis pathways through the phosphorylation of H2AX, the degradation of full-length PARP, and the increase of caspases 3 and 8 activity. This agent also demonstrated synergistic activity in a platinum-resistant cell line, inducing an increase in cell death in response to cisplatin only when combined with rabusertib, while no toxic effect was found on non-tumorigenic breast tissue-derived cell lines. Lastly, the combination of CHK1 inhibitor with cisplatin and gemcitabine resulted in more activity than single or double combinations, leading to a higher apoptotic effect. In conclusion, in our study we identify therapeutic options for the clinical development of CHK1 inhibitors, and confirm that the inhibition of this kinase can overcome acquired resistance to cisplatin.

ELP-dependent expression of MCL1 promotes resistance to EGFR inhibition in triple-negative breast cancer cells

Targeted therapeutics for cancer generally exploit "oncogene addiction," a phenomenon in which the growth and survival of tumor cells depend on the activity of a particular protein. However, the efficacy of oncogene-targeted therapies varies substantially. For instance, targeting epidermal growth factor receptor (EGFR) signaling is effective in some non-small cell lung cancer (NSCLC) but not in triple-negative breast cancer (TNBC), although these cancers show a similar degree of increase in EGFR activity. Using a genome-wide CRISPR-Cas9 genetic knockout screen, we found that the Elongator (ELP) complex mediates insensitivity to the EGFR inhibitor erlotinib in TNBC cells by promoting the synthesis of the antiapoptotic protein Mcl-1. Depleting ELP proteins promoted apoptotic cell death in an EGFR inhibition-dependent manner. Pharmacological inhibition of Mcl-1 synergized with EGFR inhibition in a panel of genetically diverse TNBC cells. The findings indicate that TNBC "addiction" to EGFR signaling is masked by the ELP complex and that resistance to EGFR inhibitors in TNBC might be overcome by cotargeting Mcl-1.

Breast Cancer Heterogeneity and Response to Novel Therapeutics

Simple Summary

Breast cancer is a heterogeneous disease that is driven by genetic, epigenetic and phenotypic modifications and is also affected by the microenvironment and the metabolism. In this article we review genetic and non-genetic causes of tumor heterogeneity focusing on the impact that heterogeneity has on resistance to therapy. We will provide examples of personalized medicines and their translation to the clinic.

Abstract

Targeted cancer therapies against oncogenic drivers are actively being developed and tested in clinical trials. Targeting an oncogenic driver may only prove effective if the mutation is present in most tumoral cells. Therefore, highly heterogeneous tumors may be refractory to these therapies. This makes tumor heterogeneity a major challenge in cancer therapy. Although heterogeneity has traditionally been attributed to genetic diversity within cancer cell populations, it is now widely recognized that human cancers are heterogeneous in almost all distinguishable phenotypic characteristics. Understanding the genetic variability and also the non-genetic influences of tumor heterogeneity will provide novel insights into how to reverse therapeutic resistance and improve cancer therapy.

Natural and Semisynthetic Chalcones as Dual FLT3 and Microtubule Polymerization Inhibitors

Activating mutations in FLT3 receptor tyrosine kinase are found in a third of acute myeloid leukemia (AML) patients and are associated with disease relapse and a poor prognosis. The majority of these mutations are internal tandem duplications (ITDs) in the juxtamembrane domain of FLT3, which have been validated as a therapeutic target. The clinical success of selective inhibitors targeting oncogenic FLT3, however, has been limited due to the acquisition of drug resistance. Herein the identification of a dual FLT3/microtubule polymerization inhibitor, chalcone 4 (2'-allyloxy-4,4'-dimethoxychalcone), is reported through screening of 15 related chalcones for differential antiproliferative activity in leukemia cell lines dependent on FLT3-ITD (MV-4-11) or BCR-ABL (K562) oncogenes and by subsequent screening for mitotic inducers in the HCT116 cell line. Three natural chalcones (1-3) were found to be differentially more potent toward the MV-4-11 (FLT3-ITD) cell line compared to the K562 (BCR-ABL) cell line. Notably, the new semisynthetic chalcone 4, which is a 2'-O-allyl analogue of the natural chalcone 3, was found to be more potent toward the FLT3-ITD+ cell line and inhibited FLT3 signaling in FLT3-dependent cells. An in vitro kinase assay confirmed that chalcone 4 directly inhibited FLT3. Moreover, chalcone 4 induced mitotic arrest in these cells and inhibited tubulin polymerization in both cellular and biochemical assays. Treatment of MV-4-11 cells with this inhibitor for 24 and 48 h resulted in apoptotic cell death. Finally, chalcone 4 was able to overcome TKD mutation-mediated acquired resistance to FLT3 inhibitors in a MOLM-13 cell line expressing FLT3-ITD with the D835Y mutation. Chalcone 4 is, therefore, a promising lead for the discovery of dual-target FLT3 inhibitors.

Targeted Molecular Therapies in the Treatment of Esophageal Adenocarcinoma, Are We There Yet?

Esophageal adenocarcinoma is one of the leading causes of cancer-related deaths worldwide. The incidence of esophageal adenocarcinoma has increased at an alarming rate in the Western world and long-term survival remains poor. Current treatment approaches involve a combination of surgery, chemotherapy, and radiotherapy. Unfortunately, standard first-line approaches are met with high rates of recurrence and metastasis. More recent investigations into the distinct molecular composition of these tumors have uncovered key genetic and epigenetic alterations involved in tumorigenesis and progression. These discoveries have driven the development of targeted therapeutic agents in esophageal adenocarcinoma. While many agents have been studied, therapeutics targeting the human epidermal growth factor receptor (HER2) and vascular endothelial growth factor (VEGF) pathways have demonstrated improved survival. More recent advances in immunotherapies have also demonstrated survival advantages with monoclonal antibodies targeting the programmed death ligand 1 (PD-L1). In this review we highlight recent advances of targeted therapies, specifically agents targeting receptor tyrosine kinases, small molecule kinase inhibitors, and immune checkpoint inhibitors. While targeted therapeutics and immunotherapies have significantly improved survival, the benefits are limited to patients whose tumors express biomarkers such as PD-L1 and HER2. Survival remains poor for the remainder of patients with esophageal adenocarcinoma, underscoring the critical need for development of novel treatment strategies.

Development of synthetic lethality in cancer: molecular and cellular classification

Recently, genetically targeted cancer therapies have been a topic of great interest. Synthetic lethality provides a new approach for the treatment of mutated genes that were previously considered unable to be targeted in traditional genotype-targeted treatments. The increasing researches and applications in the clinical setting made synthetic lethality a promising anticancer treatment option. However, the current understandings on different conditions of synthetic lethality have not been systematically assessed and the application of synthetic lethality in clinical practice still faces many challenges. Here, we propose a novel and systematic classification of synthetic lethality divided into gene level, pathway level, organelle level, and conditional synthetic lethality, according to the degree of specificity into its biological mechanism. Multiple preclinical findings of synthetic lethality in recent years will be reviewed and classified under these different categories. Moreover, synthetic lethality targeted drugs in clinical practice will be briefly discussed. Finally, we will explore the essential implications of this classification as well as its prospects in eliminating existing challenges and the future directions of synthetic lethality.

Overexpression of wild type or a Q311E mutant MB21D2 promotes a pro-oncogenic phenotype in HNSCC

Cadherin‐mediated cell–cell contacts regulated by intracellular binders play critical roles in tissue homeostasis and tumorigenesis. Here, we screened mutational profiles of 312 annotated genes involved in cadherin binding in human squamous cell carcinomas and found MB21D2 to carry a unique recurrent Q311E mutation. MB21D2 overexpression was also frequently found in head and neck cancer (HNSCC) and was associated with poor clinical outcomes. Cell‐based characterizations revealed pro‐oncogenic roles for MB21D2 wild‐type (WT) and its Q311E mutant (Q311E) in cell proliferation, colony formation, sphere growth, and migration/invasion by promoting epithelial–mesenchymal transition. Conversely, MB21D2 knockdown in MB21D2‐overexpressing cells resulted in cell growth arrest and apoptosis. Xenograft tumor models with Q311E‐expressing cells formed larger and more aggressive lesions, compared to models with WT‐MB21D2‐expressing cells or an empty vector. Transcriptome and protein interactome analyses revealed enrichment of KRAS signaling by MB21D2 expression. Immunoblotting confirmed RAS elevation, along with upregulation/phosphorylation of PI3K, AKT, and CREB. Blocking RAS signaling in MB21D2‐expressing cells by manumycin significantly reduced cell growth and survival. Our study thus defined RAS signaling‐dependent pro‐oncogenic roles for MB21D2 overexpression and Q311E MB21D2 expression in HNSCC development.

Proteolysis targeting chimeras (PROTACs) in cancer therapy

Exploitation of the protein degradation machinery as a therapeutic strategy to degrade oncogenic proteins is experiencing revolutionary advances with the development of proteolysis targeting chimeras (PROTACs). PROTACs are heterobifunctional structures consisting of a ligand that binds a protein to be degraded and a ligand for an E3 ubiquitin ligase. The bridging between the protein of interest and the E3 ligase mediated by the PROTAC facilitates ubiquitination of the protein and its proteasomal degradation. In this review we discuss the molecular medicine behind PROTAC mechanism of action, with special emphasis on recent developments and their potential translation to the clinical setting.

PLCɛ maintains the functionality of AR signaling in prostate cancer via an autophagy-dependent mechanism

Androgen receptor (AR) signaling is a major driver of prostate cancer (CaP). Although most therapies targeting AR are initially effective in CaP patients, drug resistance is inevitable, mainly because of the inappropriate re-activation of AR pathway. However, the underlying mechanisms remain largely unknown. Here, we found that phospholipase C epsilon (PLCɛ) was highly expressed in CaP samples, and was closely associated with AR signaling activities. PLCɛ depletion triggered enhanced autophagic activities via AMPK/ULK1 pathway, causing autophagy-mediated AR degradation and inhibition of AR nuclear translocation. This subsequently reduced AR signals in CaP and inhibited AR-driven cell migration/invasion. Furthermore, a positive correlation between PLCɛ and AR signaling activity was also observed in bicalutamide-resistant CaP samples and in AR-antagonist-resistant CaP cell models. PLCɛ depletion resulted in the failure to establish AR-antagonist-resistant CaP cell lines, and hindered the metastatic prowess of already established ones. These findings suggest that PLCɛ-mediated autophagic activity alteration is indispensible for the functionality of AR signaling and for CaP development.

Role of Poly [ADP-ribose] Polymerase 1 in Activating the Kirsten ras (KRAS) Gene in Response to Oxidative Stress

In pancreatic Panc-1 cancer cells, an increase of oxidative stress enhances the level of 7,8-dihydro-8-oxoguanine (8OG) more in the KRAS promoter region containing G4 motifs than in non-G4 motif G-rich genomic regions. We found that H₂O₂ stimulates the recruitment to the KRAS promoter of poly [ADP-ribose] polymerase 1 (PARP-1), which efficiently binds to local G4 structures. Upon binding to G4 DNA, PARP-1 undergoes auto PARylation and thus becomes negatively charged. In our view this should favor the recruitment to the KRAS promoter of MAZ and hnRNP A1, as these two nuclear factors, because of their isoelectric points >7, are cationic in nature under physiological conditions. This is indeed supported by pulldown assays which showed that PARP-1, MAZ, and hnRNP A1 form a multiprotein complex with an oligonucleotide mimicking the KRAS G4 structure. Our data suggest that an increase of oxidative stress in Panc-1 cells activates a ROS-G4-PARP-1 axis that stimulates the transcription of KRAS. This mechanism is confirmed by the finding that when PARP-1 is silenced by siRNA or auto PARylation is inhibited by Veliparib, the expression of KRAS is downregulated. When Panc-1 cells are treated with H₂O₂ instead, a strong up-regulation of KRAS transcription is observed.

Oncogenic ERBB2 aberrations and KRAS mutations cooperate to promote pancreatic ductal adenocarcinoma progression

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with few therapeutic options, representing one of the great challenges in oncology. Activating KRAS mutation, occurring in >90% PDACs, is present in pancreatic intraepithelial neoplasia lesions, the precursor ductal lesions of PDAC, indicating additional genetic alterations contribute to the pathogenesis of PDAC. PDAC sequencing projects identify recurrent genomic ERBB2 alterations, mutations and amplifications, in 8.5% of PDAC patients, ranking as the top hit among the 100 receptor tyrosine kinases-encoding genes. Introduction of the ERBB2 mutations encoding protein variants S310F, S423R, R678Q, Q679L, E717D, L755S, V777L and V842I into human pancreatic epithelial cells causes oncogenic transformation, increasing ERBB2 signaling, anchorage-independent cell growth and tumor xenograft growth in nude mice, demonstrating that they are activating mutations. Interestingly, in many PDACs, mutations in ERBB2 and KRAS occur together. ERBB2 activating mutants facilitate KRAS-driven oncogenic properties. Introduction of ERBB2 mutations into KRAS-mutant PDAC cells activates ERBB2 signaling, promotes tumor growth and attenuates KRAS dependency. In contrast, a CRISPR-mediated knockout (KO) of ERBB2 in ERBB2-amplified PDAC cells inhibits ERBB2 signaling, colony formation, anchorage-independent growth and tumor xenograft formation. Finally, oncogenic ERBB2 aberrations can be abrogated by treatment with small-molecule inhibitors. ERBB2 and KRAS inhibition cooperate to suppress PDAC cell growth in vitro and to promote tumor regression in nude mice, providing a rationale for testing an anti-ERBB2 drug in combination with a KRAS inhibitor in ERBB2-mutant PDAC patients that are currently untreatable.

Identification of UBE2T as an independent prognostic biomarker for gallbladder cancer

Gallbladder cancer is the most common biliary tract malignant tumor, with unfavorable patient outcomes. The present study aimed to identify potential diagnostic or prognostic biomarkers for gallbladder cancer. To do so, differentially expressed genes in the gallbladder walls and tumor tissues of patients with gallbladder cancer were analyzed via microarray. Furthermore, a protein-protein interaction network was constructed and genes with a degree score >10 were selected as hub genes. As ubiquitin conjugating enzyme E2T (UBE2T) was considered to be a hub gene, its expression was assessed via reverse transcription-quantitative (RT-q)PCR and immunohistochemistry (IHC). In addition, the association between UBE2T expression and the clinicopathological characteristics of patients with gallbladder cancer was analyzed using the χ² test. Furthermore, all patients were divided into high- and low groups based on UBE2T expression level and overall survival analysis was performed. Univariate and multivariate Cox regression analyses were performed to determine whether UBE2T may serve as an independent risk factor for gallbladder cancer. The results demonstrated that UBE2T expression was upregulated in the gallbladder walls and tumor tissues of patients with gallbladder cancer. Furthermore, UBE2T expression level was confirmed to be upregulated following RT-qPCR, and results from IHC demonstrated that UBE2T was predominantly expressed in the cytoplasm of gallbladder cancer cells. In addition, high UBE2T expression level was associated with clinical stage, T classification, N classification and M classification. The results from Univariate and multivariate analyses indicated that UBE2T expression level may be considered as an independent risk factor for gallbladder cancer. Taken together, the findings from this study suggested that high UBE2T expression level may contribute to the poor prognosis of patients with gallbladder cancer, and that UBE2T may act as an independent prognostic biomarker for these patients.

Challenges and Opportunities in Cancer Drug Resistance

There has been huge progress in the discovery of targeted cancer therapies in recent years. However, even for the most successful and impactful cancer drugs which have been approved, both innate and acquired mechanisms of resistance are commonplace. These emerging mechanisms of resistance have been studied intensively, which has enabled drug discovery scientists to learn how it may be possible to overcome such resistance in subsequent generations of treatments. In some cases, novel drug candidates have been able to supersede previously approved agents; in other cases they have been used sequentially or in combinations with existing treatments. This review summarizes the current field in terms of the challenges and opportunities that cancer resistance presents to drug discovery scientists, with a focus on small molecule therapeutics. As part of this review, common themes and approaches have been identified which have been utilized to successfully target emerging mechanisms of resistance. This includes the increase in target potency and selectivity, alternative chemical scaffolds, change of mechanism of action (covalents, PROTACs), increases in blood-brain barrier permeability (BBBP), and the targeting of allosteric pockets. Finally, wider approaches are covered such as monoclonal antibodies (mAbs), bispecific antibodies, antibody drug conjugates (ADCs), and combination therapies.

The Role of the Curcumin for Inducing Apoptosis in Acute Lymphoblastic Leukemia Cells: A Systematic Review

Acute lymphoblastic leukemia (ALL) is a hematological malignancy of lymphoid progenitor cells associated with excessive proliferation of lymphocytes. Curcumin, a polyphenolic compound, is known to possess anticancer activity. However, the mechanism of apoptosis induction differs in cancers. In this study, we discuss the potential apoptosis and anticancer effect of curcumin on the ALL. After choosing Medical Subject Headings (MeSH) keywords, including "Curcumin", "acute lymphoblastic leukemia", "apoptosis", as well as searching Medline/PubMed, Scopus, Sciencedirect. hand searching in key journals, list of references of selected articles and gray literature, without time and language limitation, articles up to December 2017 were entered into this review. In this review, 244 articles were acquired at the primary search. Study selection and quality assessment processes were done based on Cochrane library guidelines. According to six articles that were selected, curcumin could enhance the antitumor activity of chemotherapy drugs such as L-asparaginase. Curcumin induces apoptosis in Pre B- ALL and T- ALL cells by decreased NF-kB levels, increased p53 levels, PARP-1 cleavage. Also, the induction of growth-arrest and apoptosis in association with the blockade of constitutively active JAK-STAT pathway suggests this be a mechanism by curcumin. Curcumin could be used for the treatment of cancer like ALL.

UNC5B mediates G2/M phase arrest of bladder cancer cells by binding to CDC14A and P53

UNC5B is a known tumor suppressor gene in a variety of cancers. As a transmembrane protein, UNC5B also induces apoptosis in a P53-dependent manner. In this study, we demonstrate that UNC5B inhibits proliferation through G2/M phase arrest by mass spectrometry and bioinformatics analysis in bladder cancer cells. By combing with CDC14A and P53, UNC5B dephosphorylated P53 at Ser-315 site. This dephosphorylation facilitated G2/M phase arrest by reducing the expression of cyclin B1 and increasing the expression of p-CDK1, thus inhibiting tumor proliferation. Knockdown of CDC14A suppressed the G2/M phase arrest induced by UNC5B in vitro, and eliminated the inhibitory effect of UNC5B on tumor proliferation in vivo. Our results show that UNC5B-mediated cell cycle arrest may act as a potential treatment for bladder cancer.

Targeted therapy and drug resistance in triple-negative breast cancer: the EGFR axis

Targeting of estrogen receptor is commonly used as a first-line treatment for hormone-positive breast cancer patients, and is considered as a keystone of systemic cancer therapy. Likewise, HER2-targeted therapy significantly improved the survival of HER2-positive breast cancer patients, indicating that targeted therapy is a powerful therapeutic strategy for breast cancer. However, for triple-negative breast cancer (TNBC), an aggressive breast cancer subtype, there are no clinically approved targeted therapies, and thus, an urgent need to identify potent, highly effective therapeutic targets. In this mini-review, we describe general strategies to inhibit tumor growth by targeted therapies and briefly discuss emerging resistance mechanisms. Particularly, we focus on therapeutic targets for TNBC and discuss combination therapies targeting the epidermal growth factor receptor (EGFR) and associated resistance mechanisms.

Advances in Targeting RET-Dependent Cancers

RET alterations have been characterized as oncogenic drivers in multiple cancers. The clinical validation of highly selective RET inhibitors demonstrates the utility of specific targeting of aberrantly activated RET in patients with cancers such as medullary thyroid cancer or non-small cell lung cancer. The remarkable responses observed have opened the field of RET-targeted inhibitors. In this review, we seek to focus on the impact of therapeutic RET targeting in cancers. SIGNIFICANCE: Successful clinical translation of selective RET inhibitors is poised to alter the therapeutic landscape of altered cancers. Questions that clearly need to be addressed relate to the ability to maintain long-term inhibition of tumor cell growth, how to prepare for the potential mechanisms of acquired resistance, and the development of next-generation selective RET inhibitors.

MET targeting: time for a rematch

MET, the receptor tyrosine kinase (RTK) for hepatocyte growth factor, is a proto-oncogene involved in embryonic development and throughout life in homeostasis and tissue regeneration. Deregulation of MET signaling has been reported in numerous malignancies, prompting great interest in MET targeting for cancer therapy. The present review offers a summary of the biology of MET and its known functions in normal physiology and carcinogenesis, followed by an overview of the most relevant MET-targeting strategies and corresponding clinical trials, highlighting both past setbacks and promising future prospects. By placing their efforts on a more precise stratification strategy through the genetic analysis of tumors, modern trials such as the NCI-MATCH trial could revive the past enthusiasm for MET-targeted therapy.

Thermal Proteome Profiling Identifies Oxidative-Dependent Inhibition of the Transcription of Major Oncogenes as a New Therapeutic Mechanism for Select Anticancer Compounds

Identification of the molecular mechanism of action (MoA) of bioactive compounds is a crucial step for drug development but remains a challenging task despite recent advances in technology. In this study, we applied multidimensional proteomics, sensitivity correlation analysis, and transcriptomics to identify a common MoA for the anticancer compounds RITA, aminoflavone (AF), and oncrasin-1 (Onc-1). Global thermal proteome profiling revealed that the three compounds target mRNA processing and transcription, thereby attacking a cancer vulnerability, transcriptional addiction. This led to the preferential loss of expression of oncogenes involved in PDGF, EGFR, VEGF, insulin/IGF/MAPKK, FGF, Hedgehog, TGFβ, and PI3K signaling pathways. Increased reactive oxygen species level in cancer cells was a prerequisite for targeting the mRNA transcription machinery, thus conferring cancer selectivity to these compounds. Furthermore, DNA repair factors involved in homologous recombination were among the most prominently repressed proteins. In cancer patient samples, RITA, AF, and Onc-1 sensitized to poly(ADP-ribose) polymerase inhibitors both in vitro and ex vivo These findings might pave a way for new synthetic lethal combination therapies.Significance: These findings highlight agents that target transcriptional addiction in cancer cells and suggest combination treatments that target RNA processing and DNA repair pathways simultaneously as effective cancer therapies.

OT-82, a novel anticancer drug candidate that targets the strong dependence of hematological malignancies on NAD biosynthesis

Effective treatment of some types of cancer can be achieved by modulating cell lineage-specific rather than tumor-specific targets. We conducted a systematic search for novel agents selectively toxic to cells of hematopoietic origin. Chemical library screenings followed by hit-to-lead optimization identified OT-82, a small molecule with strong efficacy against hematopoietic malignancies including acute myeloblastic and lymphoblastic adult and pediatric leukemias, erythroleukemia, multiple myeloma, and Burkitt's lymphoma in vitro and in mouse xenograft models. OT-82 was also more toxic towards patients-derived leukemic cells versus healthy bone marrow-derived hematopoietic precursors. OT-82 was shown to induce cell death by inhibiting nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the salvage pathway of NAD synthesis. In mice, optimization of OT-82 dosing and dietary niacin further expanded the compound's therapeutic index. In toxicological studies conducted in mice and nonhuman primates, OT-82 showed no cardiac, neurological or retinal toxicities observed with other NAMPT inhibitors and had no effect on mouse aging or longevity. Hematopoietic and lymphoid organs were identified as the primary targets for dose limiting toxicity of OT-82 in both species. These results reveal strong dependence of neoplastic cells of hematopoietic origin on NAMPT and introduce OT-82 as a promising candidate for the treatment of hematological malignancies.

Specific targeting of PDGFRβ in the stroma inhibits growth and angiogenesis in tumors with high PDGF-BB expression

PDGF-BB/PDGFRβ signaling plays an important role during vascularization by mediating pericyte recruitment to the vasculature, promoting the integrity and function of vessels. Until now it has not been possible to assess the specific role of PDGFRβ signaling in tumor progression and angiogenesis due to lack of appropriate animal models and molecular tools.

Methods: In the present study, we used a transgenic knock-in mouse strain carrying a silent mutation in the PDGFRβ ATP binding site that allows specific targeting of PDGFRβ using the compound 1-NaPP1. To evaluate the impact of selective PDGFRβ inhibition of stromal cells on tumor growth we investigated four tumor cell lines with no or low PDGFRβ expression, i.e. Lewis lung carcinoma (LLC), EO771 breast carcinoma, B16 melanoma and a version of B16 that had been engineered to overexpress PDGF-BB (B16/PDGF-BB).

Results: We found that specific impairment of PDGFRβ kinase activity by 1-NaPP1 treatment efficiently suppressed growth in tumors with high expression of PDGF-BB, i.e. LLC and B16/PDGF-BB, while the clinically used PDGFRβ kinase inhibitor imatinib did not suppress tumor growth. Notably, tumors with low levels of PDGF-BB, i.e. EO771 and B16, neither responded to 1-NaPP1 nor to imatinib treatment. Inhibition of PDGFRβ by either drug impaired tumor vascularization and also affected pericyte coverage; however, specific targeting of PDGFRβ by 1-NaPP1 resulted in a more pronounced decrease in vessel function with increased vessel apoptosis in high PDGF-BB expressing tumors, compared to treatment with imatinib. In vitro analysis of PDGFRβ ASKA mouse embryo fibroblasts and the mesenchymal progenitor cell line 10T1/2 revealed that PDGF-BB induced NG2 expression, consistent with the in vivo data.

Conclusion: Specific targeting of PDGFRβ signaling significantly inhibits tumor progression and angiogenesis depending on PDGF-BB expression. Our data suggest that targeting PDGFRβ in the tumor stroma could have therapeutic value in patients with high tumor PDGF-BB expression.

A solid-phase transfection platform for arrayed CRISPR screens

Arrayed CRISPR-based screens emerge as a powerful alternative to pooled screens making it possible to investigate a wide range of cellular phenotypes that are typically not amenable to pooled screens. Here, we describe a solid-phase transfection platform that enables CRISPR-based genetic screens in arrayed format with flexible readouts. We demonstrate efficient gene knockout upon delivery of guide RNAs and Cas9/guide RNA ribonucleoprotein complexes into untransformed and cancer cell lines. In addition, we provide evidence that our platform can be easily adapted to high-throughput screens and we use this approach to study oncogene addiction in tumor cells. Finally demonstrating that the human primary cells can also be edited using this method, we pave the way for rapid testing of potential targeted therapies.

Network-based Biased Tree Ensembles (NetBiTE) for Drug Sensitivity Prediction and Drug Sensitivity Biomarker Identification in Cancer

We present the Network-based Biased Tree Ensembles (NetBiTE) method for drug sensitivity prediction and drug sensitivity biomarker identification in cancer using a combination of prior knowledge and gene expression data. Our devised method consists of a biased tree ensemble that is built according to a probabilistic bias weight distribution. The bias weight distribution is obtained from the assignment of high weights to the drug targets and propagating the assigned weights over a protein-protein interaction network such as STRING. The propagation of weights, defines neighborhoods of influence around the drug targets and as such simulates the spread of perturbations within the cell, following drug administration. Using a synthetic dataset, we showcase how application of biased tree ensembles (BiTE) results in significant accuracy gains at a much lower computational cost compared to the unbiased random forests (RF) algorithm. We then apply NetBiTE to the Genomics of Drug Sensitivity in Cancer (GDSC) dataset and demonstrate that NetBiTE outperforms RF in predicting IC50 drug sensitivity, only for drugs that target membrane receptor pathways (MRPs): RTK, EGFR and IGFR signaling pathways. We propose based on the NetBiTE results, that for drugs that inhibit MRPs, the expression of target genes prior to drug administration is a biomarker for IC50 drug sensitivity following drug administration. We further verify and reinforce this proposition through control studies on, PI3K/MTOR signaling pathway inhibitors, a drug category that does not target MRPs, and through assignment of dummy targets to MRP inhibiting drugs and investigating the variation in NetBiTE accuracy.

SL-BioDP: Multi-Cancer Interactive Tool for Prediction of Synthetic Lethality and Response to Cancer Treatment

Synthetic lethality exploits the phenomenon that a mutation in a cancer gene is often associated with new vulnerability which can be uniquely targeted therapeutically, leading to a significant increase in favorable outcome. DNA damage and survival pathways are among the most commonly mutated networks in human cancers. Recent data suggest that synthetic lethal interactions between a tumor defect and a DNA repair pathway can be used to preferentially kill tumor cells. We recently published a method, DiscoverSL, using multi-omic cancer data, that can predict synthetic lethal interactions of potential clinical relevance. Here, we apply the generality of our models in a comprehensive web tool called Synthetic Lethality Bio Discovery Portal (SL-BioDP) and extend the cancer types to 18 cancer genome atlas cohorts. SL-BioDP enables a data-driven computational approach to predict synthetic lethal interactions from hallmark cancer pathways by mining cancer’s genomic and chemical interactions. Our tool provides queries and visualizations for exploring potentially targetable synthetic lethal interactions, shows Kaplan–Meier plots of clinical relevance, and provides in silico validation using short hairpin RNA (shRNA) and drug efficacy data. Our method would thus shed light on mechanisms of synthetic lethal interactions and lead to the discovery of novel anticancer drugs.

The ROS-KRAS-Nrf2 axis in the control of the redox homeostasis and the intersection with survival-apoptosis pathways: Implications for photodynamic therapy

In highly proliferating cancer cells oncogenic mutations reprogram the metabolism and increase the production of reactive oxygen species (ROS). Cancer cells prevent ROS accumulation by upregulating antioxidant systems. Here we show that an increase of oxidative stress (ROS and singlet oxygen), generated by photoactivated TMPyP4, results in the upregulation of KRAS and Nrf2, the major regulator of the redox homeostasis. In agreement with a previous observation, the ectopic expression of KRAS G12D or G12 V is found to stimulate Nrf2. This suggests that ROS, KRAS and Nrf2 establish a molecular axis controlling the redox homeostasis in cancer cells. We found that this axis also modulates the function of the NF-kB/Snail/RKIP circuitry, regulating the survival and apoptosis pathways. Our data show that low ROS levels, obtained when Nrf2 is activated by KRAS, results in the upregulation of prosurvival Snail and simultaneous downregulation of proapoptotic RKIP: an expression pattern favouring cell proliferation. By contrast, high ROS levels, obtained when Nrf2 is inhibited by a small molecule (luteolin), favour apoptosis by upregulating proapoptotic RKIP and downregulating prosurvival Snail. The results of this study are useful to design efficient photodynamic therapy (PDT) against cancer. We hypothesize that cancer cells can be sensitized to PDT when the photosensitizer is used in the presence of an inhibitor of Nrf2 (adjuvant). To test this hypothesis, we used luteolin (3',4',5,7-tetrahydroflavone) as Nrf2 inhibitor, since it reduces the expression of Nrf2 and increases intracellular ROS. By means of colony formation and viability assays we found that when Nrf2 is inhibited, PDT shows an increase of efficiency up to 45%.

COL6A6 interacted with P4HA3 to suppress the growth and metastasis of pituitary adenoma via blocking PI3K-Akt pathway

The role and mechanism of collagen type VI alpha 6 (COL6A6) on tumor growth and metastasis in pituitary adenoma (PA) was determined. COL6A6 was downregulated in PA tissues and cell lines, which was negatively associated with the expression of prolyl-4-hydroxylase alpha polypeptide III (P4HA3) in the progression of PA. Overexpression of COL6A6 significantly suppressed tumor growth and metastasis capacity in PA. In addition, P4HA3 worked as the upstream of the PI3K-Akt pathway to alleviate the antitumor activity of COL6A6 on the growth and metastasis of both AtT-20 and HP75 cells. Furthermore, the inhibitory effect of COL6A6 on cell proliferation, migration and invasion, and epithelial-mesenchymal transition (EMT) was reversed by P4HA3 overexpression or activation of the PI3K-Akt pathway induced by IGF-1 addition, which provided a new biomarker for clinical PA treatment.

Computer-aided drug repurposing for cancer therapy: Approaches and opportunities to challenge anticancer targets

Despite huge efforts made in academic and pharmaceutical worldwide research, current anticancer therapies achieve effective treatment in a limited number of neoplasia cases only. Oncology terms such as big killers - to identify tumours with yet a high mortality rate - or undruggable cancer targets, and chemoresistance, represent the current therapeutic debacle of cancer treatments. In addition, metastases, tumour microenvironments, tumour heterogeneity, metabolic adaptations, and immunotherapy resistance are essential features controlling tumour response to therapies, but still, lack effective therapeutics or modulators. In this scenario, where the pharmaceutical productivity and drug efficacy in oncology seem to have reached a plateau, the so-called drug repurposing - i.e. the use of old drugs, already in clinical use, for a different therapeutic indication - is an appealing strategy to improve cancer therapy. Opportunities for drug repurposing are often based on occasional observations or on time-consuming pre-clinical drug screenings that are often not hypothesis-driven. In contrast, in-silico drug repurposing is an emerging, hypothesis-driven approach that takes advantage of the use of big-data. Indeed, the extensive use of -omics technologies, improved data storage, data meaning, machine learning algorithms, and computational modeling all offer unprecedented knowledge of the biological mechanisms of cancers and drugs' modes of action, providing extensive availability for both disease-related data and drugs-related data. This offers the opportunity to generate, with time and cost-effective approaches, computational drug networks to predict, in-silico, the efficacy of approved drugs against relevant cancer targets, as well as to select better responder patients or disease' biomarkers. Here, we will review selected disease-related data together with computational tools to be exploited for the in-silico repurposing of drugs against validated targets in cancer therapies, focusing on the oncogenic signaling pathways activation in cancer. We will discuss how in-silico drug repurposing has the promise to shortly improve our arsenal of anticancer drugs and, likely, overcome certain limitations of modern cancer therapies against old and new therapeutic targets in oncology.

RITA induces apoptosis in p53-null K562 leukemia cells by inhibiting STAT5, Akt, and NF-κB signaling pathways

Targeting oncogenic signaling pathways by small molecules has emerged as a potential treatment strategy for cancer. reactivation of p53 and induction of tumor cell apoptosis (RITA) is a promising anticancer small molecule that reactivates p53 and induces exclusive apoptosis in tumor cells. Less well appreciated was the possible effect of small molecule RITA on p53-null leukemia cells. In this study, we demonstrated that RITA has potent antileukemic properties against p53-null chronic myeloid leukemia (CML)-derived K562 cells. RITA triggered apoptosis through caspase-9 and caspase-3 activation and poly (ADP-ribose) polymerase cleavage. RITA decreased STAT5 tyrosine phosphorylation, although it did not inhibit phosphorylation of the direct BCR-ABL substrate CrkL. Real-time PCR analysis showed that RITA downregulates antiapoptotic STAT5 target genes Bcl-xL and MCL-1. The downregulation of nuclear factor-κB (NF-κB), as evidenced by inhibition of IκB-α phosphorylation and its degradation, was associated with inhibition of Akt phosphorylation in RITA-treated cells. Furthermore, consistent with the decrease of mRNA levels, protein levels of the nuclear factor-κB-regulated antiapoptotic (cIAP1, XIAP, and Bcl-2) and proliferative (c-Myc) genes were downregulated by RITA in K562 cells. In conclusion, the ability of RITA to inhibit prosurvival signaling pathways in CML cells suggests a potential application of RITA in CML therapeutic protocols.

TRAF3 regulates the oncogenic proteins Pim2 and c-Myc to restrain survival in normal and malignant B cells

TRAF3 is a versatile intracellular adapter protein with multiple context-specific roles. Uniquely in B cells, TRAF3 deficiency enhances survival and increases the risk of transformation, as loss of TRAF3 is observed in several types of B cell cancers. Here, we report a new mechanism for TRAF3 in the restraint of B cell survival. We found that TRAF3 deficiency was associated with induction of the pro-survival kinase Pim2 in mouse primary B cells and human malignant B cell lines. The increase in Pim2 was independent of NF-κB2 activation but was ameliorated with inhibition of STAT3 expression or function. TRAF3 deficiency also led to a Pim2-dependent increase in c-Myc protein levels and was associated with reduced c-Myc ubiquitination. TRAF3-deficient primary B cells were less sensitive to cell death induced by the Pim inhibitors SGI-1776 and TP-3654. Interestingly, human malignant B cell lines with low expression of TRAF3 were more sensitive to Pim inhibition-induced cell death. Combination treatment of TRAF3-deficient B cells and B cell tumor lines with c-Myc inhibitors enhanced their sensitivity to Pim inhibition, suggesting a possible therapeutic strategy. TRAF3 thus suppresses a Pim2-mediated B cell survival axis, which can be a potential target for treatment of B cell malignancies.

Multiple roles and regulatory mechanisms of the transcription factor GATA6 in human cancers

Cancer is a common type of non-communicable disease, and its morbidity and mortality are rapidly increasing. It is expected to become the largest obstacle to the promotion of global human health in the future. Some transcription factors that play important regulatory roles in embryogenesis and subsequent tissue maintenance can be selectively amplified during tumorigenesis. Due to its high expression in the embryonic endoderm and mesoderm, GATA6 plays a crucial role in the normal development of early human heart, lung, digestive system, adrenal glands, breasts, ovaries, retina, skin, and nervous system. Up to now, overexpression of the GATA6 gene has been shown to play an important role in several cancers, including lung cancer, digestive system tumors, breast cancer, and ovarian cancer. However, the human body is a complex organism, which causes the transcription factor GATA6 to have multiple roles in cancer. In this review, we summarize the multiple roles of transcription factor GATA6 in various cancers and its regulatory mechanisms. The aim is to better understand the relationship between GATA6 gene expression and cancer development and to provide new insights for exploring potential therapeutic targets.

YES1 Is a Targetable Oncogene in Cancers Harboring YES1 Gene Amplification

Targeting genetic alterations of oncogenes by molecular-targeted agents (MTA) is an effective approach for treating cancer. However, there are still no clinical MTA options for many cancers, including esophageal cancer. We used a short hairpin RNA library to screen for a new oncogene in the esophageal cancer cell line KYSE70 and identified YES proto-oncogene 1 (YES1) as having a significant impact on tumor growth. An analysis of clinical samples showed that YES1 gene amplification existed not only in esophageal cancer but also in lung, head and neck, bladder, and other cancers, indicating that YES1 would be an attractive target for a cancer drug. Because there is no effective YES1 inhibitor so far, we generated a YES1 kinase inhibitor, CH6953755. YES1 kinase inhibition by CH6953755 led to antitumor activity against YES1-amplified cancers in vitro and in vivo. Yes-associated protein 1 (YAP1) played a role downstream of YES1 and contributed to the growth of YES1-amplified cancers. YES1 regulated YAP1 transcription activity by controlling its nuclear translocation and serine phosphorylation. These findings indicate that the regulation of YAP1 by YES1 plays an important role in YES1-amplified cancers and that CH6953755 has therapeutic potential in such cancers. SIGNIFICANCE: These findings identify the SRC family kinase YES1 as a targetable oncogene in esophageal cancer and describe a new inhibitor for YES1 that has potential for clinical utility.See related commentary by Rai, p. 5702.

Oral MEK 1/2 Inhibitor Trametinib in Combination With AKT Inhibitor GSK2141795 in Patients With Acute Myeloid Leukemia With RAS Mutations: A Phase II Study

BACKGROUND

With proven single-agent activity and favorable toxicity profile of MEK-1/2 inhibition in advanced leukemia, investigation into combination strategies to overcome proposed resistance pathways is warranted. Resistance to MEK inhibition is secondary to upstream hyperactivation of RAS/RAF or activation of the PI3K/PTEN/AKT/mTOR pathway. This phase II multi-institution Cancer Therapy Evaluation Program-sponsored study was conducted to determine efficacy and safety of the combination of the ATP-competitive pan-AKT inhibitor GSK2141795, targeting the PI3K/AKT pathway, and the MEK inhibitor trametinib in RAS-mutated relapsed/refractory acute myeloid leukemia (AML).

PATIENTS AND METHODS

The primary objective was to determine the proportion of patients achieving a complete remission. Secondary objectives included assessment of toxicity profile and biologic effects of this combination. Twenty-three patients with RAS-mutated AML received the combination. Two dose levels were explored (dose level 1: 2 mg trametinib, 25 mg GSK2141795 and dose level 2: 1.5 mg trametinib, 50 mg GSK2141795).

RESULTS

Dose level 1 was identified as the recommended phase II dose. No complete remissions were identified in either cohort. Minor responses were recognized in 5 (22%) patients. The most common drug-related toxicities included rash and diarrhea, with dose-limiting toxicities of mucositis and colitis. Longitudinal correlative assessment of the modulation of MEK and AKT pathways using reverse phase protein array and phospho-flow analysis revealed significant and near significant down-modulation of pERK and pS6, respectively. Combined MEK and AKT inhibition had no clinical activity in patients with RAS-mutated AML.

CONCLUSION

Further investigation is required to explore the discrepancy between the activity of this combination on leukemia cells and the lack of clinical efficacy.

Identification of survival‑associated key genes and long non‑coding RNAs in glioblastoma multiforme by weighted gene co‑expression network analysis

Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumour. However, the causes of GBM are not clear, and the prognosis remains poor. The aim of the present study was to elucidate the key coding genes and long non‑coding RNAs (lncRNAs) associated with the survival time of GBM patients by obtaining the RNA expression profiles from the Chinese Glioma Genome Atlas database and conducting weighted gene co‑expression network analysis. Modules associated with overall survival (OS) were identified, and Gene Ontology and pathway enrichment analyses were performed. The hub genes of these modules were validated via survival analysis, while the biological functions of crucial lncRNAs were also analysed in the publicly available data. The results identified a survival‑associated module with 195 key genes. Among them, 33 key genes were demonstrated to be associated with OS, and the majority of these were involved in extracellular matrix‑associated and tyrosine kinase receptor signalling pathways. Furthermore, LOC541471 was identified as an OS‑associated lncRNA, and was reported to be involved in the oxidative phosphorylation of GBM with pleckstrin‑2. These findings may significantly enhance our understanding on the aetiology and underlying molecular events of GBM, while the identified candidate genes may serve as novel prognostic markers and potential therapeutic targets for GBM.

Road map for fibrolamellar carcinoma: progress and goals of a diversified approach

Fibrolamellar carcinoma is a rare liver cancer, which primarily afflicts adolescents and young adults worldwide and is frequently lethal. Given the rarity of this disease, patient recruitment for clinical trials remains a challenge. In November 2017, the Second Fibrolamellar Cancer Foundation Scientific Summit (Stamford, CT, USA) provided an opportunity for investigators to discuss recent advances in the characterization of the disease and its surrounding liver and immune context. The Fibrolamellar Cancer Foundation has thus set out a road map to identify and test therapeutic targets in the most efficient possible manner.

Principles of Resistance to Targeted Cancer Therapy: Lessons from Basic and Translational Cancer Biology

Identification of the genomic drivers of cancer has led to the clinical development of targeted therapies that strike at the heart of many malignancies. Nonetheless, many cancers outsmart such precision-medicine efforts, and thus therapeutic resistance contributes significantly to cancer mortality. Attempts to understand the basis for resistance in patient samples and laboratory models has yielded two major benefits: one, more effective chemical inhibitors and rational combination therapies are now employed to prevent or circumvent resistance pathways; and two, our understanding of how oncogenic mutations drive cancer cell survival and oncogene addiction is deeper and broader, highlighting downstream or parallel cellular programs that shape these phenotypes. This review discusses emerging principles of resistance to therapies targeted against key oncogenic drivers.

The Oncogene Addiction Switch from NOTCH to PI3K Requires Simultaneous Targeting of NOTCH and PI3K Pathway Inhibition in Glioblastoma

The NOTCH pathway regulates neural stem cells and glioma initiating cells (GICs). However, blocking NOTCH activity with γ-secretase inhibitors (GSIs) fails to alter the growth of GICs, as GSIs seem to be active in only a fraction of GICs lines with constitutive NOTCH activity. Here we report loss of PTEN function as a critical event leading to resistance to NOTCH inhibition, which causes the transfer of oncogene addiction from the NOTCH pathway to the PI3K pathway. Drug cytotoxicity testing of eight GICs showed a differential growth response to GSI, and the GICs were thus stratified into two groups: sensitive and resistant. In the sensitive group, GICs with loss of PTEN function appeared less sensitive to GSI treatment. Here we show that NOTCH regulates PTEN expression and the activity of the PI3K pathway in GICs, as treatment with GSI attenuated the NOTCH pathway and increased PTEN expression. NOTCH regulates PTEN expression via Hes-1, as knockdown of Notch or Hes1 increased expression of PTEN. This novel observation suggests that both pathways must be simultaneously inhibited in order to improve therapeutic efficacy in human glioblastomas (GBMs).