MEK inhibitor PD0325901 significantly reduces the growth of papillary thyroid carcinoma cells in vitro and in vivo

OSI-027 as a Potential Drug Candidate Targeting Upregulated Hub Protein TAF1 in Potential Mechanism of Sinonasal Squamous Cell Carcinoma: Insights from Proteomics and Molecular Docking

Sinonasal squamous cell carcinoma (SNSCC) is a rare tumor with high mortality and recurrence rates. However, SNSCC carcinogenesis mechanisms and potential therapeutic drugs have not been fully elucidated. This study investigated the key molecular mechanisms and hub proteins involved in SNSCC carcinogenesis using proteomics and bioinformatic analysis. Dysregulated proteins were validated by RT-qPCR in SNSCC and nasal polyp (NP) tissues. Proteomic analysis revealed that differentially expressed proteins were clustered using MCODE scores ≥ 4 into three modules. The specific hub proteins in each module were analyzed in carcinogenesis pathways using STRING, highlighting potential mechanisms of histone modification and spliceosome dysregulation. Spliceosome components SNRNP200 and SF3A3 were significantly downregulated in SNSCC by RT-qPCR. Web-based applications L1000CDS2 and iLINCS were applied to identify 10 potential repurposable drugs that could reverse the gene expression pattern associated with SNSCC. Docking studies of TAF1, a protein in histone modification, with these 10 small molecule inhibitors indicated OSI-027 to be the most promising due to its strong binding interactions with key residues. These findings suggest that hub proteins involved in the underlying mechanism of SNSCC carcinogenesis may serve as valuable targets for drug development, with OSI-027 emerging as a novel candidate against TAF1 in SNSCC.

Versatile Split-and-Mix Liposome PROTAC Platform for Efficient Degradation of Target Protein In Vivo

PROTAC (Proteolysis TArgeting Chimeras) is a promising therapeutic approach for targeted protein degradation that recruits an E3 ubiquitin ligase to a specific protein of interest (POI), leading to its degradation by the proteasome. Recently, we developed a novel split-and-mix PROTAC system based on liposome self-assembly (LipoSM-PROTAC) which could achieve target protein degradation at comparable concentrations comparable to small molecules. In this study, we expanded protein targets based on the LipoSM-PROTAC platform and further examined its therapeutic effects in vivo. Notably, this platform could efficiently degrade the protein level of MEK1/2 in A375 cells or Alk in NCI-H2228 cells and display obvious tumor inhibition (60-70% inhibition rate) with negligible toxicity. This study further proved the LipoSM-PROTAC's application potentials.

E-cadherin interacts with EGFR resulting in hyper-activation of ERK in multiple models of breast cancer

The loss of intercellular adhesion molecule E-cadherin is a hallmark of the epithelial-mesenchymal transition (EMT), during which tumor cells transition into an invasive phenotype. Accordingly, E-cadherin has long been considered a tumor suppressor gene; however, E-cadherin expression is paradoxically correlated with breast cancer survival rates. Using novel multi-compartment organoids and multiple in vivo models, we show that E-cadherin promotes a hyper-proliferative phenotype in breast cancer cells via interaction with the transmembrane receptor EGFR. The E-cad and EGFR interaction results in activation of the MEK/ERK signaling pathway, leading to a significant increase in proliferation via activation of transcription factors, including c-Fos. Pharmacological inhibition of MEK activity in E-cadherin positive breast cancer significantly decreases both tumor growth and macro-metastasis in vivo. This work provides evidence for a novel role of E-cadherin in breast tumor progression and identifies a new target to treat hyper-proliferative E-cadherin-positive breast tumors, thus providing the foundation to utilize E-cadherin as a biomarker for specific therapeutic success.

Hsp Inhibitor is Affective Against Adenocarcinomic Human Alveolar Basal Epithelial Cells Through Modulating ERK/MAPK Signaling Pathway

The extracellular signal-regulated kinase (ERK) - mitogen-activated protein kinase (MAPK) pathway regulates cell proliferation, differentiation, and apoptosis. Heat Shock Protein 90 (HSP90) is required to activate proto-oncogenic protein kinases and promotes tumor growth through anti-apoptotic effects on A549-non-small cell lung cancer (NSCLC). Therefore, deregulation of the ERK-MAPK pathway and abnormal expression of HSP90 are reasonably frequent events in NSCLC. In this study, novel perimidine-pyrazole compounds employed to block ERK-MAPK deregulation through inhibiting HSP dependent cancer cell survival mechanisms. A set of perimidine-pyrazole derivatives effects was monitored on NSCLC cell line. Array experiments performed to understand the effect of the compounds on signaling pathways and results were analyzed by gene enrichment analysis. Further, senescence and apoptosis experiments were performed to support the enrichment results along with in silico methods to determine perimidine-pyrazole/HSP interactions. Treatment of NSCLC cells with perimidine-pyrazole derivatives displayed cancer-inhibitory, pro-senescent and pro-apoptotic effects on NSCLC cells through ERK/MAPK pathway and these compounds are promising templates for designing anticancer drugs.

Establishment and characterization of patient-derived xenograft of a rare pediatric anaplastic pleomorphic xanthoastrocytoma (PXA) bearing a CDC42SE2-BRAF fusion

Pleomorphic xanthoastrocytoma (PXA) is a rare subset of primary pediatric glioma with 70% 5-year disease free survival. However, up to 20% of cases present with local recurrence and malignant transformation into more aggressive type anaplastic PXA (AXPA) or glioblastoma. The understanding of disease etiology and mechanisms driving PXA and APXA are limited, and there is no standard of care. Therefore, development of relevant preclinical models to investigate molecular underpinnings of disease and to guide novel therapeutic approaches are of interest. Here, for the first time we established, and characterized a patient-derived xenograft (PDX) from a leptomeningeal spread of a patient with recurrent APXA bearing a novel CDC42SE2-BRAF fusion. An integrated -omics analysis was conducted to assess model fidelity of the genomic, transcriptomic, and proteomic/phosphoproteomic landscapes. A stable xenoline was derived directly from the patient recurrent tumor and maintained in 2D and 3D culture systems. Conserved histology features between the PDX and matched APXA specimen were maintained through serial passages. Whole exome sequencing (WES) demonstrated a high degree of conservation in the genomic landscape between PDX and matched human tumor, including small variants (Pearson's r = 0.794-0.839) and tumor mutational burden (~ 3 mutations/MB). Large chromosomal variations including chromosomal gains and losses were preserved in PDX. Notably, chromosomal gain in chromosomes 4-9, 17 and 18 and loss in the short arm of chromosome 9 associated with homozygous 9p21.3 deletion involving CDKN2A/B locus were identified in both patient tumor and PDX sample. Moreover, chromosomal rearrangement involving 7q34 fusion; CDC42SE-BRAF t (5;7) (q31.1, q34) (5:130,721,239, 7:140,482,820) was identified in the PDX tumor, xenoline and matched human tumor. Transcriptomic profile of the patient's tumor was retained in PDX (Pearson r = 0.88) and in xenoline (Pearson r = 0.63) as well as preservation of enriched signaling pathways (FDR Adjusted P < 0.05) including MAPK, EGFR and PI3K/AKT pathways. The multi-omics data of (WES, transcriptome, and reverse phase protein array (RPPA) was integrated to deduce potential actionable pathways for treatment (FDR < 0.05) including KEGG01521, KEGG05202, and KEGG05200. Both xenoline and PDX were resistant to the MEK inhibitors trametinib or mirdametinib at clinically relevant doses, recapitulating the patient's resistance to such treatment in the clinic. This set of APXA models will serve as a preclinical resource for developing novel therapeutic regimens for rare anaplastic PXAs and pediatric high-grade gliomas bearing BRAF fusions.

Bioinformatics and cheminformatics approaches to identify pathways, molecular mechanisms and drug substances related to genetic basis of cervical cancer

Cervical cancer (CC) is a global threat to women and our knowledge is frighteningly little about its underlying genomic contributors. Our research aimed to understand the underlying molecular and genetic mechanisms of CC by integrating bioinformatics and network-based study. Transcriptomic analyses of three microarray datasets identified 218 common differentially expressed genes (DEGs) within control samples and CC specimens. KEGG pathway analysis revealed pathways in cell cycle, drug metabolism, DNA replication and the significant GO terms were cornification, proteolysis, cell division and DNA replication. Protein-protein interaction (PPI) network analysis identified 20 hub genes and survival analyses validated CDC45, MCM2, PCNA and TOP2A as CC biomarkers. Subsequently, 10 transcriptional factors (TFs) and 10 post-transcriptional regulators were detected through TFs-DEGs and miRNAs-DEGs regulatory network assessment. Finally, the CC biomarkers were subjected to a drug-gene relationship analysis to find the best target inhibitors. Standard cheminformatics method including in silico ADMET and molecular docking study substantiated PD0325901 and Selumetinib as the most potent candidate-drug for CC treatment. Overall, this meticulous study holds promises for further in vitro and in vivo research on CC diagnosis, prognosis and therapies. Communicated by Ramaswamy H. Sarma.

The FGFR1 Signaling Pathway Upregulates the Oncogenic Transcription Factor FOXQ1 to Promote Breast Cancer Cell Growth

FGFR1 is a receptor tyrosine kinase deregulated in certain breast cancers (BCs) with a poor prognosis. Although FGFR1-activated phosphorylation cascades have been mapped, the key genes regulated by FGFR1 in BC are largely unclear. FOXQ1 is an oncogenic transcription factor. Although we found that activation of FGFR1 robustly upregulated FOXQ1 mRNA, how FGFR1 regulates FOXQ1 gene expression and whether FOXQ1 is essential for FGFR1-stimulated cell proliferation are unknown. Herein, we confirmed that activation of FGFR1 robustly upregulated FOXQ1 mRNA and protein in BC cells. Knockdown of FOXQ1 blocked the FGFR1 signaling-stimulated BC cell proliferation, colony formation, and xenograft tumor growth. Inhibition of MEK or ERK1/2 activities, or knockout of ERK2 but not ERK1 suppressed the FGFR1 signaling-promoted FOXQ1 gene expression. Inhibition of ERK2 in ERK1 knockout cells blocked, while ectopic expression of FOXQ1 in ERK2 knockout cells rescued the FGFR1-signaling-promoted cell growth. Mechanistically, c-FOS, an early response transcription factor upregulated by the FGFR1-MEK-ERK2 pathway, bound to the FOXQ1 promoter to mediate the FGFR1 signaling-promoted FOXQ1 expression. These results indicate that the FGFR1-ERK2-c-FOS-FOXQ1 regulatory axis plays an essential role in the FGFR1 signaling-promoted BC growth. Targeting ERK2 and FOXQ1 should block BC growth caused by a deregulated FGFR1 signaling.

Identification of Zinc-Binding Inhibitors of Matrix Metalloproteinase-9 to Prevent Cancer Through Deep Learning and Molecular Dynamics Simulation Approach

The overexpression of matrix metalloproteinase-9 (MMP-9) is associated with tumor development and angiogenesis, and hence, it has been considered an attractive drug target for anticancer therapy. To assist in drug design endeavors for MMP-9 targets, an in silico study was presented to investigate whether our compounds inhibit MMP-9 by binding to the catalytic domain, similar to their inhibitor or not. For that, in the initial stage, a deep-learning algorithm was used for the predictive modeling of the CHEMBL321 dataset of MMP-9 inhibitors. Several regression models were built and evaluated based on R2, MAE MSE, RMSE, and Loss. The best model was utilized to screen the drug bank database containing 9,102 compounds to seek novel compounds as MMP-9 inhibitors. Then top high score compounds were selected for molecular docking based on the comparison between the score of the reference molecule. Furthermore, molecules having the highest docking scores were selected, and interaction mechanisms with respect to S1 pocket and catalytic zinc ion of these compounds were also discussed. Those compounds, involving binding to the catalytic zinc ion and the S1 pocket of MMP-9, were considered preferentially for molecular dynamics studies (100 ns) and an MM-PBSA (last 30 ns) analysis. Based on the results, we proposed several novel compounds as potential candidates for MMP-9 inhibition and investigated their binding properties with MMP-9. The findings suggested that these compounds may be useful in the design and development of MMP-9 inhibitors in the future.

SEMCM: A Self-Expressive Matrix Completion Model for Anti-cancer Drug Sensitivity Prediction

Background:

Genomic data sets generated by several recent large scale high-throughput screening efforts pose a thorny computational challenge for anticancer drug sensitivity prediction.

Objective:

We aimed to design an algorithm model that would predict missing elements in incomplete matrices and could be applicable to drug response prediction programs.

Method:

We developed a novel self-expressive matrix completion model to improve the predictive performance of drug response prediction problems. The model is based on the idea of subspace clustering and as a convex problem, it can be solved by alternating direction method of multipliers. The original incomplete matrix can be filled through model training and parameters updated iteratively.

Results:

We applied SEMCM to Genomics of Drug Sensitivity in Cancer (GDSC) and Cancer Cell Line Encyclopedia (CCLE) datasets to predict unknown response values. A large number of experiments have proved that the algorithm has good prediction results and stability, which are better than several existing advanced drug sensitivity prediction and matrix completion algorithms. Without modeling mutation information, SEMCM could correctly predict cell line-drug associations for mutated cell lines and wild cell lines. SEMCM can also be used for drug repositioning. The newly predicted drug responses of GDSC dataset suggest that BL-41 was highly sensitive to Bortezomib. Moreover, the sensitivity of A172 and NCI-H1437 to Paclitaxel was roughly the same.

Conclusion:

We report an efficient anticancer drug sensitivity prediction algorithm which is open-source and can predict the unknown responses of cancer cell lines to drugs. Experimental results prove that our method can not only improve the prediction accuracy but also can be applied to drug repositioning.

SIRT2 regulates mitochondrial dynamics and reprogramming via MEK1-ERK-DRP1 and AKT1-DRP1 axes

During somatic reprogramming, cellular energy metabolism fundamentally switches from predominantly mitochondrial oxidative phosphorylation toward glycolysis. This metabolic reprogramming, also called the Warburg effect, is critical for the induction of pluripotency, but its molecular mechanisms remain poorly defined. Notably, SIRT2 is consistently downregulated during the reprogramming process and regulates glycolytic switch. Here, we report that downregulation of SIRT2 increases acetylation of mitogen-activated protein kinase (MAPK) kinase-1 (MEK1) at Lys175, resulting in activation of extracellular signal-regulated kinases (ERKs) and subsequent activation of the pro-fission factor dynamin-related protein 1 (DRP1). In parallel, downregulation of SIRT2 hyperacetylates the serine/threonine protein kinase AKT1 at Lys20 in a non-canonical way, activating DRP1 and metabolic reprogramming. Together, our study identified two axes, SIRT2-MEK1-ERK-DRP1 and SIRT2-AKT1-DRP1, that critically link mitochondrial dynamics and oxidative phosphorylation to the somatic reprogramming process. These upstream signals, together with SIRT2’s role in glycolytic switching, may underlie the Warburg effect observed in human somatic cell reprogramming.

Mitochondrial remodeling has critical roles for the somatic cell reprogramming process. Cha et al. report the functional role of SIRT2 in mitochondrial dynamics and remodeling during the human somatic cell reprogramming process. They identify two axes, SIRT2-MEK1-ERK-DRP1 and SIRT2-AKT1-DRP1, that link SIRT2 downregulation to mitochondrial remodeling and somatic cell reprogramming.

AKAP13 couples GPCR signaling to mTORC1 inhibition

The mammalian target of rapamycin complex 1 (mTORC1) senses multiple stimuli to regulate anabolic and catabolic processes. mTORC1 is typically hyperactivated in multiple human diseases such as cancer and type 2 diabetes. Extensive research has focused on signaling pathways that can activate mTORC1 such as growth factors and amino acids. However, less is known about signaling cues that can directly inhibit mTORC1 activity. Here, we identify A-kinase anchoring protein 13 (AKAP13) as an mTORC1 binding protein, and a crucial regulator of mTORC1 inhibition by G-protein coupled receptor (GPCR) signaling. GPCRs paired to Gα_s proteins increase cyclic adenosine 3’5’ monophosphate (cAMP) to activate protein kinase A (PKA). Mechanistically, AKAP13 acts as a scaffold for PKA and mTORC1, where PKA inhibits mTORC1 through the phosphorylation of Raptor on Ser 791. Importantly, AKAP13 mediates mTORC1-induced cell proliferation, cell size, and colony formation. AKAP13 expression correlates with mTORC1 activation and overall lung adenocarcinoma patient survival, as well as lung cancer tumor growth in vivo. Our study identifies AKAP13 as an important player in mTORC1 inhibition by GPCRs, and targeting this pathway may be beneficial for human diseases with hyperactivated mTORC1.

The mammalian target of rapamycin complex 1 (mTORC1) can sense multiple upstream stimuli to regulate cell growth and metabolism. Increased mTORC1 activation results in many human diseases such as cancer. Small molecules like rapamycin that target and inhibit mTORC1, are available in the clinic with limited success. Thus, decoding the mechanisms involved in mTORC1 regulation is crucial. Most of the research has focused on stimuli that activate mTORC1. Less is known about signaling pathways that can directly inhibit mTORC1 activity. G-protein coupled receptors (GPCRs) coupled to Gα_s proteins signal to and potently inhibit mTORC1. In this study, we have identified AKAP13 to play a crucial role in mTORC1 inhibition by GPCR signaling. Importantly, GPCRs are the largest family of drug targets with many approved FDA compounds. Targeting this signaling pathway may be beneficial for human diseases with hyperactivated mTORC1.

RASAL2 Confers Collateral MEK/EGFR Dependency in Chemoresistant Triple-Negative Breast Cancer

PURPOSE

While chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC), identifying and managing chemoresistant tumors has proven elusive. We sought to discover hallmarks and therapeutically actionable features of refractory TNBC through molecular analysis of primary chemoresistant TNBC specimens.

EXPERIMENTAL DESIGN

We performed transcriptional profiling of tumors from a phase II clinical trial of platinum chemotherapy for advanced TNBC (TBCRC-009), revealing a gene expression signature that identified de novo chemorefractory tumors. We then employed pharmacogenomic data mining, proteomic and other molecular studies to define the therapeutic vulnerabilities of these tumors.

RESULTS

We reveal the RAS-GTPase-activating protein (RAS-GAP) RASAL2 as an upregulated factor that mediates chemotherapy resistance but also an exquisite collateral sensitivity to combination MAP kinase kinase (MEK1/2) and EGFR inhibitors in TNBC. Mechanistically, RASAL2 GAP activity is required to confer kinase inhibitor sensitivity, as RASAL2-high TNBCs sustain basal RAS activity through suppression of negative feedback regulators SPRY1/2, together with EGFR upregulation. Consequently, RASAL2 expression results in failed feedback compensation upon co-inhibition of MEK1/2 and EGFR that induces synergistic apoptosis in vitro and in vivo. In patients with TNBC, high RASAL2 levels predict clinical chemotherapy response and long-term outcomes, and are associated via direct transcriptional regulation with activated oncogenic Yes-Associated Protein (YAP). Accordingly, chemorefractory patient-derived TNBC models exhibit YAP activation, high RASAL2 expression, and tumor regression in response to MEK/EGFR inhibitor combinations despite well-tolerated intermittent dosing.

CONCLUSIONS

These findings identify RASAL2 as a mediator of TNBC chemoresistance that rewires MAPK feedback and cross-talk to confer profound collateral sensitivity to combination MEK1/2 and EGFR inhibitors.

Characterization of Biological Pathways Regulating Acute Cold Resistance of Zebrafish

Low temperature stress represents a major threat to the lives of both farmed and wild fish species. However, biological pathways determining the development of cold resistance in fish remain largely unknown. Zebrafish larvae at 96 hpf were exposed to lethal cold stress (10 °C) for different time periods to evaluate the adverse effects at organism, tissue and cell levels. Time series RNA sequencing (RNA-seq) experiments were performed to delineate the transcriptomic landscape of zebrafish larvae under cold stress and during the subsequent rewarming phase. The genes regulated by cold stress were characterized by progressively enhanced or decreased expression, whereas the genes associated with rewarming were characterized by rapid upregulation upon return to normal temperature (28 °C). Genes such as trib3, dusp5 and otud1 were identified as the representative molecular markers of cold-induced damages through network analysis. Biological pathways involved in cold stress responses were mined from the transcriptomic data and their functions in regulating cold resistance were validated using specific inhibitors. The autophagy, FoxO and MAPK (mitogen-activated protein kinase) signaling pathways were revealed to be survival pathways for enhancing cold resistance, while apoptosis and necroptosis were the death pathways responsible for cold-induced mortality. Functional mechanisms of the survival-enhancing factors Foxo1, ERK (extracellular signal-regulated kinase) and p38 MAPK were further characterized by inhibiting their activities upon cold stress and analyzing gene expression though RNA-seq. These factors were demonstrated to determine the cold resistance of zebrafish through regulating apoptosis and p53 signaling pathway. These findings have provided novel insights into the stress responses elicited by lethal cold and shed new light on the molecular mechanisms underlying cold resistance of fish.

Role of CK2 inhibitor CX-4945 in anti-cancer combination therapy - potential clinical relevance

BACKGROUND

Protein kinase CK2 inhibition has long been considered as an attractive anti-cancer strategy based on the following considerations: CK2 is a pro-survival kinase, it is frequently over-expressed in human tumours and its over-expression correlates with a worse prognosis. Preclinical evidence strongly supports the feasibility of this target and, although dozens of CK2 inhibitors have been described in the literature so far, CX-4945 (silmitasertib) was the first that entered into clinical trials for the treatment of both human haematological and solid tumours. However, kinase inhibitor monotherapies turned out to be effective only in a limited number of malignancies, probably due to the multifaceted causes that underlie them, supporting the emerging view that multi-targeted approaches to treat human tumours could be more effective.

CONCLUSIONS

In this review, we will address combined anti-cancer therapeutic strategies described so far which involve the use of CX-4945. Data from preclinical studies clearly show the ability of CX-4945 to synergistically cooperate with different classes of anti-neoplastic agents, thereby contributing to an orchestrated anti-tumour action against multiple targets. Overall, these promising outcomes support the translation of CX-4945 combined therapies into clinical anti-cancer applications.

AXL Inhibition Enhances MEK Inhibitor Sensitivity in Malignant Peripheral Nerve Sheath Tumors

Dysregulation of the receptor tyrosine kinase AXL is known to promote cancer cell growth and survival in many sarcomas, including the rare subtype, malignant peripheral nerve sheath tumors (MPNST). MPNSTs are largely chemoresistant and carry a poor prognosis. AXL is an attractive potential therapeutic target, as it is aberrantly expressed, and its activation may be an early event in MPNST. However, the effect of AXL inhibition on MPNST development and progression is not known. Here, we investigated the role of AXL in MPNST development and the effects of AXL and MEK1/2 co-inhibition on MPNSTs. We used western blotting to examine AXL expression and activation in MPNST cell lines. We analyzed the effects of exogenous growth arrest-specific 6 (GAS6) expression on downstream signaling and the proliferation, migration, and invasion of MPNST cells. The effect of AXL knockdown with or without mitogen-activated protein kinase (MAPK) inhibition on downstream signal transduction and tumorigenesis was also examined in vivo and in vitro. We found that AXL knockdown increased MAPK pathway signaling. This compensation, in turn, abrogated the antitumorigenic effects linked to AXL knockdown in vivo. AXL knockdown, combined with pharmacological MEK inhibition, reduced the proliferation and increased the apoptosis of MPNST cells both in vitro and in vivo. The pharmacological co-inhibition of AXL and MEK1/2 reduced MPNST volumes. Together these findings suggest that AXL inhibition enhances the sensitivity of MPNST to other small molecule inhibitors. We conclude that combination therapy with AXL inhibitor may be a therapeutic option for MPNST.

Emerging role of phytochemicals in targeting predictive, prognostic, and diagnostic biomarkers of lung cancer

Lung-cancer is the foremost cause of cancer in humans worldwide, of which 80-85% cases are composed of non-small cell lung carcinoma. All treatment decisions depend on the pattern of biomarkers selection to enhance the response to the targeted therapies. Although advanced treatments are available for lung-cancer, the disease treatment remains not adequate. There are several synthetic chemotherapeutic agents available for the treatment of lung cancer. However, due to their toxic effect, survival rate is still 15-18%. Besides, medicinal plants are a huge reservoir of natural products that provide protective effects against lung cancer. Likewise, successful studies of potential phytochemicals in targeting lung-cancer biomarkers have created a novel paradigm for the discovery of potent drugs against lung-cancer. Hence, to defeat severe toxicity and resistance towards the synthetic drugs, detailed studies are required regarding the available phytochemicals and targets responsible for the treatment of lung-cancer. The present review provides a comprehensive information about the lung-cancer biomarkers under the classification of predictive, prognostic, and diagnostic type. Moreover, it discusses and enlists the phytochemicals with mode of action against different biomarkers, effective doses in in vitro, in vivo, and clinical studies, the limitations associated with usage of phytochemicals as a drug to prevent/cure lung-cancer and the latest techniques employed to overcome such issues.

Mutant BRAF and MEK Inhibitors Regulate the Tumor Immune Microenvironment via Pyroptosis

Combinations of BRAF inhibitors and MEK inhibitors (BRAFi + MEKi) are FDA-approved to treat BRAF V600E/K-mutant melanoma. Efficacy of BRAFi + MEKi associates with cancer cell death and alterations in the tumor immune microenvironment; however, the links are poorly understood. We show that BRAFi + MEKi caused durable melanoma regression in an immune-mediated manner. BRAFi + MEKi treatment promoted cleavage of gasdermin E (GSDME) and release of HMGB1, markers of pyroptotic cell death. GSDME-deficient melanoma showed defective HMGB1 release, reduced tumor-associated T cell and activated dendritic cell infiltrates in response to BRAFi + MEKi, and more frequent tumor regrowth after drug removal. Importantly, BRAFi + MEKi-resistant disease lacked pyroptosis markers and showed decreased intratumoral T-cell infiltration but was sensitive to pyroptosis-inducing chemotherapy. These data implicate BRAFi + MEKi-induced pyroptosis in antitumor immune responses and highlight new therapeutic strategies for resistant melanoma. SIGNIFICANCE: Targeted inhibitors and immune checkpoint agents have advanced the care of patients with melanoma; however, detailed knowledge of the intersection between these two research areas is lacking. We describe a molecular mechanism of targeted inhibitor regulation of an immune-stimulatory form of cell death and provide a proof-of-principle salvage therapy concept for inhibitor-resistant melanoma.See related commentary by Smalley, p. 176.This article is highlighted in the In This Issue feature, p. 161.

Mitogen-Activated Protein Kinase Pathway Inhibition for Redifferentiation of Radioiodine Refractory Differentiated Thyroid Cancer: An Evolving Protocol

Background: Some patients with metastatic differentiated thyroid cancer (DTC) lack iodine avidity and are therefore unsuitable for radioactive iodine (RAI) therapy. Limited experience suggests that single-agent selective mitogen-activated protein kinase (MAPK) pathway inhibitors can restore expression of the sodium-iodide symporter rendering RAI refractory (RAIR) DTC patients amenable to RAI therapy. The aim of this study was to assess the feasibility of mutation-guided MAPK-pathway blockade combined with thyroid hormone withdrawal (THW) for redifferentiation. Methods: This is a retrospective review of metastatic RAIR DTC and driver mutation in MAPK pathway, treated on a redifferentiation protocol. All patients had metastatic disease that had never been RAI-avid and/or imaging and biochemical progression despite treatment with RAI within the past 12 months. Patients with tumors harboring an NRAS mutation were treated with an MEK inhibitor (trametinib), and tumors with a BRAF^V600E mutation with combined BRAF and MEK inhibition (dabrafenib and trametinib; or vemurafenib and cobimetinib) for four weeks. Thyrotropin stimulation was performed by THW for four weeks. Restoration of RAI uptake was determined by ¹²⁴I positron emission tomography/computed tomography imaging. The response was assessed at least three months post-RAI. Results: From 2015 to 2017, six patients (age 45-70, four females) received redifferentiation therapy. Three patients had an NRAS mutation; two with follicular thyroid carcinoma (FTC) and one with a poorly differentiated thyroid carcinoma (PDTC); and three patients had a BRAF^V600E mutation and papillary thyroid carcinoma (PTC). One NRAS and all BRAF^V600E mutation cases demonstrated restoration of RAI uptake and proceeded to RAI therapy with a median follow-up of 16.6 months (range 13.5-42.3 months). The patient with an NRAS mutation and two of three patients with a BRAF^V600E demonstrated partial imaging response beyond a three-month follow-up. Grade 3 adverse events (acneiform rash) were observed in two patients with NRAS mutations. Conclusions: Mutation-guided MAPK pathway inhibition with MEK inhibitor or a combination of BRAF inhibitor and MEK inhibitor under concurrent THW is a feasible and a promising strategy to redifferentiate RAIR DTC, thereby rendering them suitable for RAI therapy with satisfactory retention following treatment.

Mouse models of thyroid cancer: Bridging pathogenesis and novel therapeutics

Due to a global increase in the incidence of thyroid cancer, numerous novel mouse models were established to reveal thyroid cancer pathogenesis and test promising therapeutic strategies, necessitating a comprehensive review of translational medicine that covers (i) the role of mouse models in the research of thyroid cancer pathogenesis, and (ii) preclinical testing of potential anti-thyroid cancer therapeutics. The present review article aims to: (i) describe the current approaches for mouse modeling of thyroid cancer, (ii) provide insight into the biology and genetics of thyroid cancers, and (iii) offer guidance on the use of mouse models for testing potential therapeutics in preclinical settings. Based on research with mouse models of thyroid cancer pathogenesis involving the RTK, RAS/RAF/MEK/ERK, PI3K/AKT/mTOR, SRC, and JAK-STAT signaling pathways, inhibitors of VEGFR, MEK, mTOR, SRC, and STAT3 have been developed as anti-thyroid cancer drugs for "bench-to-bedside" translation. In the future, mouse models of thyroid cancer will be designed to be ''humanized" and "patient-like," offering opportunities to: (i) investigate the pathogenesis of thyroid cancer through target screening based on the CRISPR/Cas system, (ii) test drugs based on new mouse models, and (iii) explore the underlying mechanisms based on multi-omics.

Identification of an ERK Inhibitor as a Therapeutic Drug Against Tau Aggregation in a New Cell-Based Assay

Formation of Tau aggregates is a common pathological feature of tauopathies and their accumulation directly correlates with cytotoxicity and neuronal degeneration. Great efforts have been made to understand Tau aggregation and to find therapeutics halting or reversing the process, however, progress has been slowed due to the lack of a suitable method for monitoring Tau aggregation. We developed a cell-based assay allowing to detect and quantify Tau aggregation in living cells. The system is based on the FRET biosensor CST able to monitor the molecular dynamic of Tau aggregation in different cellular conditions. We probed candidate compounds that could block Tau hyperphosphorylation. In particular, to foster the drug discovery process, we tested kinase inhibitors approved for the treatment of other diseases. We identified the ERK inhibitor PD-901 as a promising therapeutic molecule since it reduces and prevents Tau aggregation. This evidence establishes the CST cell-based aggregation assay as a reliable tool for drug discovery and suggests that PD-901 might be a promising compound to be tested for further preclinical studies on AD.

PLATYPUS: A Multiple-View Learning Predictive Framework for Cancer Drug Sensitivity Prediction

Cancer is a complex collection of diseases that are to some degree unique to each patient. Precision oncology aims to identify the best drug treatment regime using molecular data on tumor samples. While omics-level data is becoming more widely available for tumor specimens, the datasets upon which computational learning methods can be trained vary in coverage from sample to sample and from data type to data type. Methods that can 'connect the dots' to leverage more of the information provided by these studies could offer major advantages for maximizing predictive potential. We introduce a multi-view machinelearning strategy called PLATYPUS that builds 'views' from multiple data sources that are all used as features for predicting patient outcomes. We show that a learning strategy that finds agreement across the views on unlabeled data increases the performance of the learning methods over any single view. We illustrate the power of the approach by deriving signatures for drug sensitivity in a large cancer cell line database. Code and additional information are available from the PLATYPUS website https://sysbiowiki.soe.ucsc.edu/platypus.

A NUMB-EFA6B-ARF6 recycling route controls apically restricted cell protrusions and mesenchymal motility

The endocytic protein NUMB has been implicated in the control of various polarized cellular processes, including the acquisition of mesenchymal migratory traits through molecular mechanisms that have only been partially defined. Here, we report that NUMB is a negative regulator of a specialized set of understudied, apically restricted, actin-based protrusions, the circular dorsal ruffles (CDRs), induced by either PDGF or HGF stimulation. Through its PTB domain, NUMB binds directly to an N-terminal NPLF motif of the ARF6 guanine nucleotide exchange factor, EFA6B, and promotes its exchange activity in vitro. In cells, a NUMB-EFA6B-ARF6 axis regulates the recycling of the actin regulatory cargo RAC1 and is critical for the formation of CDRs that mark the acquisition of a mesenchymal mode of motility. Consistently, loss of NUMB promotes HGF-induced cell migration and invasion. Thus, NUMB negatively controls membrane protrusions and the acquisition of mesenchymal migratory traits by modulating EFA6B-ARF6 activity.

Signaling cascades in thyroid cancer: Increasing the armory of archers to hit bullseye

Thyroid cancer is a multifaceted and therapeutically challenging disease and rapidly accumulating experimentally verified findings have considerably improve our understanding of the molecular mechanisms which underlie its development. Substantial fraction of information has been added into existing landscape of molecular oncology and we have started to develop a sharper understanding of the underlying mechanisms of thyroid cancer. Wealth of information demystified different intracellular signaling cascades which are frequently deregulated in thyroid cancer. In vitro assays and xenografted mice based studies have helped us to identify drug targets and different synthetic and natural products are currently being tested to effectively treat thyroid cancer. Cabozantinib and vandetanib have been approved to treat medullary thyroid cancer (MTC) and two agents (lenvatinib and sorafenib) are also being used to treat radioactive-iodine refractory differentiated thyroid cancer. This review comprehensively summarizes most recent advancements in our knowledge related to dysregulated intracellular signaling cascades in thyroid cancer and how different proteins can be therapeutically exploited. (1) We discuss how loss of TRAIL mediated apoptosis occurred in thyroid cancer cells and how different strategies can be used to restore apoptosis in resistant cancer cells; (2) We provide detailed account of seemingly opposite roles of NOTCH signaling in thyroid cancers; (3) TGF/SMAD mediated signaling also needs detailed research because of context dependent role in thyroid cancer. Researchers have only begun to scratch the surface of how TGF signaling works in thyroid cancer and metastasis; and (4) Role of SHH signaling in thyroid cancer stem cells is also well appreciated and targeting of SHH pathway will be an important aspect in treatment of thyroid cancer. Better concepts and improved knowledge will be helpful for clinicians in getting a step closer to individualized medicine.

Pathological processes and therapeutic advances in radioiodide refractory thyroid cancer

While in most patients with non-medullary thyroid cancer (TC), disease remission is achieved by thyroidectomy and ablation of tumor remnants by radioactive iodide (RAI), a substantial subgroup of patients with metastatic disease present tumor lesions that have acquired RAI resistance as a result of dedifferentiation. Although oncogenic mutations in BRAF, TERT promoter and TP53 are associated with an increased propensity for induction of dedifferentiation, the role of genetic and epigenetic aberrations and their effects on important intracellular signaling pathways is not yet fully elucidated. Also immune, metabolic, stemness and microRNA pathways have emerged as important determinants of TC dedifferentiation and RAI resistance. These signaling pathways have major clinical implications since their targeting could inhibit TC progression and could enable redifferentiation to restore RAI sensitivity. In this review, we discuss the current insights into the pathological processes conferring dedifferentiation and RAI resistance in TC and elaborate on novel advances in diagnostics and therapy to improve the clinical outcome of RAI-refractory TC patients.

The impact of P-glycoprotein and breast cancer resistance protein on the brain pharmacokinetics and pharmacodynamics of a panel of MEK inhibitors

Mitogen/extracellular signal-regulated kinase (MEK) inhibitors have been tested in clinical trials for treatment of intracranial neoplasms, including glioblastoma (GBM), but efficacy of these drugs has not yet been demonstrated. The blood-brain barrier (BBB) is a major impediment to adequate delivery of drugs into the brain and may thereby also limit the successful implementation of MEK inhibitors against intracranial malignancies. The BBB is equipped with a range of ATP-dependent efflux transport proteins, of which P-gp (ABCB1) and BCRP (ABCG2) are the two most dominant for drug efflux from the brain. We investigated their impact on the pharmacokinetics and target engagement of a panel of clinically applied MEK inhibitors, in order to select the most promising candidate for brain cancers in the context of clinical pharmacokinetics and inhibitor characteristics. To this end, we used in vitro drug transport assays and conducted pharmacokinetic and pharmacodynamic studies in wildtype and ABC-transporter knockout mice. PD0325901 displayed more promising characteristics than trametinib (GSK1120212), binimetinib (MEK162), selumetinib (AZD6244), and pimasertib (AS703026): PD0325901 was the weakest substrate of P-gp and BCRP in vitro, its brain penetration was only marginally higher in Abcb1a/b;Abcg2^-/- mice, and efficient target inhibition in the brain could be achieved at clinically relevant plasma levels. Notably, target inhibition could also be demonstrated for selumetinib, but only at plasma levels far above levels in patients receiving the maximum tolerated dose. In summary, our study recommends further development of PD0325901 for the treatment of intracranial neoplasms.

Discovering novel pharmacogenomic biomarkers by imputing drug response in cancer patients from large genomics studies

Obtaining accurate drug response data in large cohorts of cancer patients is very challenging; thus, most cancer pharmacogenomics discovery is conducted in preclinical studies, typically using cell lines and mouse models. However, these platforms suffer from serious limitations, including small sample sizes. Here, we have developed a novel computational method that allows us to impute drug response in very large clinical cancer genomics data sets, such as The Cancer Genome Atlas (TCGA). The approach works by creating statistical models relating gene expression to drug response in large panels of cancer cell lines and applying these models to tumor gene expression data in the clinical data sets (e.g., TCGA). This yields an imputed drug response for every drug in each patient. These imputed drug response data are then associated with somatic genetic variants measured in the clinical cohort, such as copy number changes or mutations in protein coding genes. These analyses recapitulated drug associations for known clinically actionable somatic genetic alterations and identified new predictive biomarkers for existing drugs.

Deciphering KRAS and NRAS mutated clone dynamics in MLL-AF4 paediatric leukaemia by ultra deep sequencing analysis

To induce and sustain the leukaemogenic process, MLL-AF4+ leukaemia seems to require very few genetic alterations in addition to the fusion gene itself. Studies of infant and paediatric patients with MLL-AF4+ B cell precursor acute lymphoblastic leukaemia (BCP-ALL) have reported mutations in KRAS and NRAS with incidences ranging from 25 to 50%. Whereas previous studies employed Sanger sequencing, here we used next generation amplicon deep sequencing for in depth evaluation of RAS mutations in 36 paediatric patients at diagnosis of MLL-AF4+ leukaemia. RAS mutations including those in small sub-clones were detected in 63.9% of patients. Furthermore, the mutational analysis of 17 paired samples at diagnosis and relapse revealed complex RAS clone dynamics and showed that the mutated clones present at relapse were almost all originated from clones that were already detectable at diagnosis and survived to the initial therapy. Finally, we showed that mutated patients were indeed characterized by a RAS related signature at both transcriptional and protein levels and that the targeting of the RAS pathway could be of beneficial for treatment of MLL-AF4+ BCP-ALL clones carrying somatic RAS mutations.

Combinatorial treatment using targeted MEK and SRC inhibitors synergistically abrogates tumor cell growth and induces mesenchymal-epithelial transition in non-small-cell lung carcinoma

Oncogenesis in non-small cell lung cancer (NSCLC) is regulated by a complex signal transduction network. Single-agent targeted therapy fails frequently due to treatment insensitivity and acquired resistance. In this study, we demonstrate that co-inhibition of the MAPK and SRC pathways using a PD0325901 and Saracatinib kinase inhibitor combination can abrogate tumor growth in NSCLC. PD0325901/Saracatinib at 0.25:1 combination was screened against a panel of 28 NSCLC cell lines and 68% of cell lines were found to be sensitive (IC₅₀ < 2 μM) to this combination. In Snail1 positive NSCLC lines, the drug combination complementarily enhanced mesenchymal-epithelial transition (MET), increasing both E-cadherin and Plakoglobin expression, and reducing Snail1, FAK and PXN expression. In addition, the drug combination abrogated cell migration and matrigel invasion. The co-inhibition of MAPK and SRC induced strong G1/G0 cell cycle arrest in the NSCLC lines, inhibited anchorage independent growth and delayed tumor growth in H460 and H358 mouse xenografts. These data provide rationale for further investigating the combination of MAPK and SRC pathway inhibitors in advanced stage NSCLC.

Inhibition of acquired-resistance hepatocellular carcinoma cell growth by combining sorafenib with phosphoinositide 3-kinase and rat sarcoma inhibitor

BACKGROUND

To provide support for combined usage of phosphoinositide 3-kinase (PI3K) inhibitors or mitogen-activated protein kinase pathway inhibitors together with sorafenib in treatment of sorafenib-resistant hepatocellular carcinoma.

MATERIALS AND METHODS

The sorafenib-resistant cell lines were established to evaluate the effects of MK-2206 2HCL, a dual PI3K/mammalian target of rapamycin (mTOR) inhibitor, and PD0325901, an rat sarcoma (RAS) and/or extracellular signal-regulated kinase (ERK) inhibitor, on cell proliferation and apoptosis, as both single and combined treatments with sorafenib. In addition, multidrug resistance 1 gene expression, mutation status of key members in PI3K/mTOR, and RAS/ERK pathways and pathway activation were analyzed to identify predictors of drug response.

RESULTS

Molecular studies reveal that combining MK-2206 2HCL or PD0325901 with sorafenib not only has a synergistic effect, in suppressing PI3K/protein kinase B/mTOR and RAS/MEK/ERK signaling more effectively than either treatment alone, but also prevents the cross activation of the other pathway that occurs with single treatments in both sorafenib sensitive and resistant lines. PD0325901 exhibited a stronger synergic effect with sorafenib than MK-2206 2HCL. Sorafenib-resistant cell lines were characterized by activation of both of the two pathways, as indicated by multidrug resistance 1 gene expression profiles and pathway activity analysis.

CONCLUSIONS

Our studies have showed that both inhibitors of PI3K/mTOR and RAS/ERK signaling are potentially effective antihepatocellular carcinoma drugs especially in treating sorafenib-resistant hepatocellular carcinoma.

Allosteric modulators of MEK1: drug design and discovery

Mitogen-activated protein kinase kinase (MAPKK, MEK) mediates signal transduction, controlling cell proliferation and survival. MEK occupies a key downstream position in the Ras-Raf-MEK-ERK signaling pathway, implying that inhibition of MEK will potently suppress tumor cell growth, with potential applications in cancer therapy. Based on the promising therapeutic effects of MEK modulators, continued efforts have been made in this class. Here, we review the discovery and development of MEK1 allosteric modulators, classifying them into four structural groups. The allosteric mechanisms and recent clinical progress involving these modulators are also reviewed.

Pluripotency markers are differentially induced by MEK inhibition in thyroid and melanoma BRAFV600E cell lines

Oncogenic mutations in BRAF are common in melanoma and thyroid carcinoma and drive constitutive activation of the MAPK pathway. Molecularly targeted therapies of this pathway improves survival compared to chemotherapy; however, responses tend to be short-lived as resistance invariably occursCell line models of melanoma and thyroid carcinoma, +/− BRAF^V600E activating mutation, were treated with the MEK inhibitor PD0325901. Treated and naive samples were assayed for expression of key members of the MAPK pathway. Global microRNA expression profiling of naive and resistant cells was performed via next generation sequencingand indicated pluripotency pathways in resistance. Parental cell lines were progressed to holoclones to confirm the miRNA stemness profileMembers of the MIR302/373/374/520 family of embryonic stem cell specific cell cycle regulating (ESCC) microRNAs were identified as differentially expressed between resistant BRAF^V600E melanoma and thyroid cell lines. Upregulated expression of gene and protein stemness markers, upregulated expression of MAPK pathway genes and downregulation of the ESCC MIR302 cluster in BRAF^V600E melanoma indicated an increased stem-like phenotype in resistant BRAF^V600E melanoma. Conversely, downregulated expression of gene and protein stemness markers, downregulated expression of MAPK pathway genes, upregulation of the ESCC MIR520 cluster, reeexpression of cell surface receptors, and induced differentiation-associated morphology in resistant BRAF^V600E indicate a differentiated phenotype associated with MEK inhibitor resistance in BRAF^V600E thyroid cellsThe differential patterns of resistance observed between BRAF^V600E melanoma and thyroid cell lines may reflect tissue type or de novo differentiation, but could have significant impact on the response of primary and metastatic cells to MEK inhibitor treatment. This study provides a basis for the investigation of the cellular differentiation/self-renewal access and its role in resistance to MEK inhibition.

Targeting of proangiogenic signalling pathways in chronic inflammation

Angiogenesis is de novo capillary outgrowth from pre-existing blood vessels. This process not only is crucial for normal development, but also has an important role in supplying oxygen and nutrients to inflamed tissues, as well as in facilitating the migration of inflammatory cells to the synovium in rheumatoid arthritis, spondyloarthritis and other systemic autoimmune diseases. Neovascularization is dependent on the balance of proangiogenic and antiangiogenic mediators, including growth factors, cytokines, chemokines, cell adhesion molecules and matrix metalloproteinases. This Review describes the various intracellular signalling pathways that govern these angiogenic processes and discusses potential approaches to interfere with pathological angiogenesis, and thereby ameliorate inflammatory disease, by targeting these pathways.

Adenosine triphosphate prevents serum deprivation-induced apoptosis in human mesenchymal stem cells via activation of the MAPK signaling pathways

Human mesenchymal stem cells (hMSC) are multipotent cells derived from various sources including adipose and placental tissues as well as bone marrow. Owing to their regenerative and immunomodulatory properties, their use as a potential therapeutic tool is being extensively tested. However, one of the major hurdles in using cell-based therapy is the use of fetal bovine serum that can trigger immune responses, viral and prion diseases. The development of a culture medium devoid of serum while preserving cell viability is therefore a major challenge. In this study, we demonstrated that adenosine triphosphate (ATP) restrained serum deprivation-induced cell death in hMSC by preventing caspases 3/7 activation and modulating ERK1/2 and p38 MAPK signaling pathways. We also showed that serum deprivation conditions triggered dephosphorylation of the proapoptotic protein Bad leading to cell death. Adjunction of ATP restored the phosphorylation state of Bad. Furthermore, ATP significantly modulated the expression of proapoptopic and antiapoptotic genes, in favor of an antiapoptotic profile expression. Finally, we established that hMSC released a high amount of ATP in the extracellular medium when cultured in a serum-free medium. Collectively, our results demonstrate that ATP favors hMSC viability in serum deprivation conditions. Moreover, they shed light on the cardinal role of the MAPK pathways, ERK1/2 and p38 MAPK, in promoting hMSC survival.

Characterization of thyroid cancer cell lines in murine orthotopic and intracardiac metastasis models

Thyroid cancer incidence has been increasing over time, and it is estimated that ∼1950 advanced thyroid cancer patients will die of their disease in 2015. To combat this disease, an enhanced understanding of thyroid cancer development and progression as well as the development of efficacious, targeted therapies are needed. In vitro and in vivo studies utilizing thyroid cancer cell lines and animal models are critically important to these research efforts. In this report, we detail our studies with a panel of authenticated human anaplastic and papillary thyroid cancer (ATC and PTC) cell lines engineered to express firefly luciferase in two in vivo murine cancer models-an orthotopic thyroid cancer model as well as an intracardiac injection metastasis model. In these models, primary tumor growth in the orthotopic model and the establishment and growth of metastases in the intracardiac injection model are followed in vivo using an IVIS imaging system. In the orthotopic model, the ATC cell lines 8505C and T238 and the PTC cell lines K1/GLAG-66 and BCPAP had take rates >90 % with final tumor volumes ranging 84-214 mm(3) over 4-5 weeks. In the intracardiac model, metastasis establishment was successful in the ATC cell lines HTh74, HTh7, 8505C, THJ-16T, and Cal62 with take rates ≥70 %. Only one of the PTC cell lines tested (BCPAP) was successful in the intracardiac model with a take rate of 30 %. These data will be beneficial to inform the choice of cell line and model system for the design of future thyroid cancer studies.

New therapies for dedifferentiated papillary thyroid cancer

The number of thyroid cancers is increasing. Standard treatment usually includes primary surgery, thyroid-stimulating hormone suppressive therapy, and ablation of the thyroid remnant with radioactive iodine (RAI). Despite the generally good prognosis of thyroid carcinoma, about 5% of patients will develop metastatic disease, which fails to respond to RAI, exhibiting a more aggressive behavior. The lack of specific, effective and well-tolerated drugs, the scarcity of data about the association of multi-targeting drugs, and the limited role of radioiodine for dedifferentiated thyroid cancer, call for further efforts in the field of new drugs development. Rearranged during transfection (RET)/papillary thyroid carcinoma gene rearrangements, BRAF (B-RAF proto-oncogene, serine/threonine kinase) gene mutations, RAS (rat sarcoma) mutations, and vascular endothelial growth factor receptor 2 angiogenesis pathways are some of the known pathways playing a crucial role in the development of thyroid cancer. Targeted novel compounds have been demonstrated to induce clinical responses and stabilization of disease. Sorafenib has been approved for differentiated thyroid cancer refractory to RAI.

MEK inhibitor PD-0325901 overcomes resistance to CK2 inhibitor CX-4945 and exhibits anti-tumor activity in head and neck cancer

The serine-threonine kinase CK2 exhibits genomic alterations and aberrant overexpression in human head and neck squamous cell carcinomas (HNSCC). Here, we investigated the effects of CK2 inhibitor CX-4945 in human HNSCC cell lines and xenograft models. The IC_50's of CX-4945 for 9 UM-SCC cell lines measured by MTT assay ranged from 3.4-11.9 μM. CX-4945 induced cell cycle arrest and cell death measured by DNA flow cytometry, and inhibited prosurvival mediators phospho-AKT and p-S6 in UM-SCC1 and UM-SCC46 cells. CX-4945 decreased NF-κB and Bcl-XL reporter gene activities in both cell lines, but upregulated proapoptotic TP53 and p21 reporter activities, and induced phospho-ERK, AP-1, and IL-8 activity in UM-SCC1 cells. CX-4945 exhibited modest anti-tumor activity in UM-SCC1 xenografts. Tumor immunostaining revealed significant inhibition of PI3K-Akt-mTOR pathway and increased apoptosis marker TUNEL, but also induced p-ERK, c-JUN, JUNB, FOSL1 and proliferation (Ki67) markers, as a possible resistance mechanism. To overcome the drug resistance, we tested MEK inhibitor PD-0325901 (PD-901), which inhibited ERK-AP-1 activation alone and in combination with CX-4945. PD-901 alone displayed significant anti-tumor effects in vivo, and the combination of PD-901 and CX-4945 slightly enhanced anti-tumor activity when compared with PD-901 alone. Immunostaining of tumor specimens after treatment revealed inhibition of p-AKT S129 and p-AKT T308 by CX-4945, and inhibition of p-ERK T202/204 and AP-1 family member FOSL-1 by PD-901. Our study reveals a drug resistance mechanism mediated by the MEK-ERK-AP-1 pathway in HNSCC. MEK inhibitor PD-0325901 is active in HNSCC resistant to CX-4945, meriting further clinical investigation.

Development and characterization of six new human papillary thyroid carcinoma cell lines

CONTEXT

Cell lines are a widely used tool in cancer research. However, despite the relatively high incidence of papillary thyroid carcinoma (PTC), there are only four PTC cell lines available for international research audience.

OBJECTIVE

The objective of this study was to establish and characterize new PTC cell lines that represent primary tumor biology. Surgical specimens were obtained to generate PTC cell lines. Short tandem repeat profiling was used to confirm the uniqueness of the cell lines against databases of known cell lines and mutations were assessed using Sequenom. The expression of thyroid-specific genes was examined using real-time PCR. Tumorigenicity was determined using an orthotopic thyroid xenograft tumor mouse model.

RESULTS

Six PTC cell lines (five conventional PTCs and one follicular variant of PTC) were generated and found to be unique when compared by short tandem repeat profiling against databases of all existing cell lines. The five conventional PTC cell lines carry the BRAF V600E mutation and the follicular variant of PTC cell line had an NRAS mutation. Five of the six cell lines had a mutation in the promoter of the human telomerase reverse transcriptase gene. None of the cell lines have RET/PTC rearrangements. Three cell lines were tumorigenic in the orthotopic thyroid xenograft tumor mouse model.

CONCLUSIONS

These five characterized conventional PTC cell lines and the unique follicular variant of PTC cell line should be valuable reagents for thyroid cancer research. The three tumorigenic cell lines can be used for in vivo testing of targeted therapeutic and novel agents.

BRAF inhibitor dabrafenib in patients with metastatic BRAF-mutant thyroid cancer

BACKGROUND

Mutations of v-raf murine sarcoma viral oncogene homolog B (BRAF) are commonly identified in papillary and anaplastic thyroid carcinoma and are associated with worse prognosis compared with the wild type. BRAF inhibition in papillary thyroid carcinoma cell lines and xenografts inhibits proliferation and decreases downstream phosphorylation. Our objectives were to analyze safety and efficacy of the selective BRAF inhibitor dabrafenib in patients with metastatic BRAF-mutant thyroid carcinoma.

METHODS

We present the subset of patients with BRAF-mutant thyroid carcinoma enrolled in a larger phase 1 study, the main results of which are reported elsewhere.

RESULTS

Fourteen patients with BRAF(V600E)-mutant thyroid carcinoma were enrolled, of whom 13 (93%) had received prior radioactive iodine. The median duration on treatment was 8.4 months, and seven (50%) patients received treatment for ≥10 months. The most common treatment-related adverse events were skin papillomas (n=8, 57%), hyperkeratosis (n=5, 36%), and alopecia (n=4, 29%), all of which were grade 1. Treatment-related adverse events grade ≥3 included grade 4 elevated lipase and grade 3 elevated amylase, fatigue, febrile neutropenia, and cutaneous squamous cell carcinoma (n=1 for each). Four (29%) partial responses were observed, and nine (64%) patients achieved at least 10% decrease. Only one responder progressed while on the study drug after a response duration of 9.3 months. The other three responders had not progressed, with response duration of 4.6+, 10.4+, and 21.4+ months. With seven (50%) patients showing no progression at the time of study completion, the median progression-free survival was 11.3 months.

CONCLUSIONS

Dabrafenib was well tolerated and resulted in durable responses in BRAF-mutant differentiated thyroid carcinoma patients.

A preclinical orthotopic model for glioblastoma recapitulates key features of human tumors and demonstrates sensitivity to a combination of MEK and PI3K pathway inhibitors

Current therapies for glioblastoma multiforme (GBM), the highest grade malignant brain tumor, are mostly ineffective, and better preclinical model systems are needed to increase the successful translation of drug discovery efforts into the clinic. Previous work describes a genetically engineered mouse (GEM) model that contains perturbations in the most frequently dysregulated networks in GBM (driven by RB, KRAS and/or PI3K signaling and PTEN) that induce development of Grade IV astrocytoma with properties of the human disease. Here, we developed and characterized an orthotopic mouse model derived from the GEM that retains the features of the GEM model in an immunocompetent background; however, this model is also tractable and efficient for preclinical evaluation of candidate therapeutic regimens. Orthotopic brain tumors are highly proliferative, invasive and vascular, and express histology markers characteristic of human GBM. Primary tumor cells were examined for sensitivity to chemotherapeutics and targeted drugs. PI3K and MAPK pathway inhibitors, when used as single agents, inhibited cell proliferation but did not result in significant apoptosis. However, in combination, these inhibitors resulted in a substantial increase in cell death. Moreover, these findings translated into the in vivo orthotopic model: PI3K or MAPK inhibitor treatment regimens resulted in incomplete pathway suppression and feedback loops, whereas dual treatment delayed tumor growth through increased apoptosis and decreased tumor cell proliferation. Analysis of downstream pathway components revealed a cooperative effect on target downregulation. These concordant results, together with the morphologic similarities to the human GBM disease characteristics of the model, validate it as a new platform for the evaluation of GBM treatment.

Establishment of genetically diverse patient-derived xenografts of colorectal cancer

Preclinical compounds tested in animal models often show limited efficacy when transitioned into human clinical trials. As a result, many patients are stratified into treatment regimens that have little impact on their disease. In order to create preclinical models that can more accurately predict tumor responses, we established patient-derived xenograft (PDX) models of colorectal cancer (CRC). Surgically resected tumor specimens from colorectal cancer patients were implanted subcutaneously into athymic nude mice. Following successful establishment, fourteen models underwent further evaluation to determine whether these models exhibit heterogeneity, both at the cellular and genetic level. Histological review revealed properties not found in CRC cell lines, most notably in overall architecture (predominantly columnar epithelium with evidence of gland formation) and the presence of mucin-producing cells. Custom CRC gene panels identified somatic driver mutations in each model, and therapeutic efficacy studies in tumor-bearing mice were designed to determine how models with known mutations respond to PI3K, mTOR, or MAPK inhibitors. Interestingly, MAPK pathway inhibition drove tumor responses across most models tested. Noteworthy, the MAPK inhibitor PD0325901 alone did not significantly mediate tumor response in the context of a KRAS(G12D) model, and improved tumor responses resulted when combined with mTOR inhibition. As a result, these genetically diverse models represent a valuable resource for preclinical efficacy and drug discovery studies.

MEK1 is associated with carboplatin resistance and is a prognostic biomarker in epithelial ovarian cancer

BACKGROUND

Primary systemic treatment for ovarian cancer is surgery, followed by platinum based chemotherapy. Platinum resistant cancers progress/recur in approximately 25% of cases within six months. We aimed to identify clinically useful biomarkers of platinum resistance.

METHODS

A database of ovarian cancer transcriptomic datasets including treatment and response information was set up by mining the GEO and TCGA repositories. Receiver operator characteristics (ROC) analysis was performed in R for each gene and these were then ranked using their achieved area under the curve (AUC) values. The most significant candidates were selected and in vitro functionally evaluated in four epithelial ovarian cancer cell lines (SKOV-3-, CAOV-3, ES-2 and OVCAR-3), using gene silencing combined with drug treatment in viability and apoptosis assays. We collected 94 tumor samples and the strongest candidate was validated by IHC and qRT-PCR in these.

RESULTS

All together 1,452 eligible patients were identified. Based on the ROC analysis the eight most significant genes were JRK, CNOT8, RTF1, CCT3, NFAT2CIP, MEK1, FUBP1 and CSDE1. Silencing of MEK1, CSDE1, CNOT8 and RTF1, and pharmacological inhibition of MEK1 caused significant sensitization in the cell lines. Of the eight genes, JRK (p = 3.2E-05), MEK1 (p = 0.0078), FUBP1 (p = 0.014) and CNOT8 (p = 0.00022) also correlated to progression free survival. The correlation between the best biomarker candidate MEK1 and survival was validated in two independent cohorts by qRT-PCR (n = 34, HR = 5.8, p = 0.003) and IHC (n = 59, HR = 4.3, p = 0.033).

CONCLUSION

We identified MEK1 as a promising prognostic biomarker candidate correlated to response to platinum based chemotherapy in ovarian cancer.

Dual pharmacological targeting of the MAP kinase and PI3K/mTOR pathway in preclinical models of colorectal cancer

BACKGROUND

The activation of the MAPK and PI3K/AKT/mTOR pathways is implicated in the majority of cancers. Activating mutations in both of these pathways has been described in colorectal cancer (CRC), thus indicating their potential as therapeutic targets. This study evaluated the combination of a PI3K/mTOR inhibitor (PF-04691502/PF-502) in combination with a MEK inhibitor (PD-0325901/PD-901) in CRC cell lines and patient-derived CRC tumor xenograft models (PDTX).

MATERIALS AND METHODS

The anti-proliferative effects of PF-502 and PD-901 were assessed as single agents and in combination against a panel of CRC cell lines with various molecular backgrounds. Synergy was evaluated using the Bliss Additivity method. In selected cell lines, we investigated the combination effects on downstream effectors by immunoblotting. The combination was then evaluated in several fully genetically annotated CRC PDTX models.

RESULTS

The in vitro experiments demonstrated a wide range of IC50 values for both agents against a cell line panel. The combination of PF-502 and PD-901 demonstrated synergistic anti-proliferative activity with Bliss values in the additive range. As expected, p-AKT and p-ERK were downregulated by PF-502 and PD-901, respectively. In PDTX models, following a 30-day exposure to PF-502, PD-901 or the combination, the combination demonstrated enhanced reduction in tumor growth as compared to either single agent regardless of KRAS or PI3K mutational status.

CONCLUSIONS

The combination of a PI3K/mTOR and a MEK inhibitor demonstrated enhanced anti-proliferative effects against CRC cell lines and PDTX models.

MEK inhibitor for gastric cancer with MEK1 gene mutations

The prognosis for patients with unresectable advanced or recurrent gastric cancer remains poor. The identification of additional oncogenes with influences similar to those of epidermal growth factor receptor gene mutations, upon which the growth of cancer cells is dependent, is needed. In this study, we evaluated sensitivity to MEK inhibitors (GSK1120212 and PD0325901) in several gastric cancer cell lines in vitro and found three poorly differentiated gastric cancer cell lines that were hypersensitive to the inhibitors. The sequence analyses in these three cell lines revealed that one cell line had a novel MEK1 mutation, while the other two had previously reported KRAS and MEK1 mutations, respectively; the gene statuses of the other resistant cell lines were all wild-type. Experiments using MEK1 expression vectors demonstrated that the MEK1 mutations induced the phosphorylation of ERK1/2 and had a transforming potential, enhancing the tumorigenicity. The MEK inhibitor dramatically reduced the phosphorylation of ERK1/2 and induced apoptosis in the cell lines with MEK1 mutations. In vivo, tumor growth was also dramatically decreased by an inhibitor. One of the 46 gastric cancer clinical samples that were examined had a MEK1 mutation; this tumor had a poorly differentiated histology. Considering the addiction of cancer cells to active MEK1 mutations for proliferation, gastric cancer with such oncogenic MEK1 mutations might be suitable for targeted therapy with MEK inhibitors.

Prospects for MEK inhibitors for treating cancer

INTRODUCTION

The MAPK pathway is a signaling network that plays a key role in many normal cellular processes and in a large number of human malignancies. One of its effectors, MEK, is essential for the carcinogenesis of different tumors. In recent years, several drugs able to inhibit MEK have been assessed in clinical trials. Trametinib has recently become the first MEK inhibitor licensed for cancer treatment (advanced melanoma).

AREAS COVERED

We comprehensively review the safety and clinical efficacy of the family of MEK inhibitors, either alone or in combination with other drugs. We discuss data ranging from the Phase III trial of trametinib in melanoma to the most recent drugs with early signs of antitumor activity. In addition, we explain the reasons for the unsuccessful results of the early trials with MEK inhibitors and provide a view of their role in cancer treatment in forthcoming years.

EXPERT OPINION

MEK inhibitors are a potentially safe and active treatment option for the treatment of many human malignancies. The information provided by a large series of studies currently ongoing will be very valuable in order to optimize their use. Adequate selection of patients is crucial for achieving successful results with these compounds.

Modulation of endochondral ossification by MEK inhibitors PD0325901 and AZD6244 (Selumetinib)

MEK inhibitors (MEKi) PD0325901 and AZD6244 (Selumetinib) are drugs currently under clinical investigation for cancer treatment, however the Ras-MAPK pathway is also an important mediator of normal bone cell differentiation and function. In this study we examined the effects of these compounds on endochondral processes using both in vitro and in vivo models. Treatment with PD0325901 or AZD6244 significantly increased Runx2 and Alkaline phosphate gene expression in calvarial osteoblasts and decreased TRAP+ cells in induced osteoclast cultures. To test the effects of these drugs on bone healing, C57/Bl6 mice underwent a closed tibial fracture and were treated with PD0325901 or AZD6244 at 10mg/kg/day. Animals were culled at day 10 and at day 21 post-fracture for analysis of the fracture callus and the femoral growth plate in the contralateral leg. MEKi treatment markedly increased cartilage volume in the soft callus at day 10 post-fracture (+60% PD0325901, +20% AZD6244) and continued treatment led to a delay in cartilage remodeling. At the growth plate, we observed an increase in the height of the hypertrophic zone relative to the proliferative zone of +78% in PD0325901 treated mice. Osteoclast surface was significantly decreased both at the terminal end of the growth plate and within the fracture calluses of MEKi treated animals. The mechanistic effects of MEKi on genes encoding cartilage matrix proteins and catabolic enzymes were examined in articular chondrocyte cultures. PD0325901 or AZD6244 led to increased matrix protein expression (Col2a1 and Acan) and decreased expression of catabolic factors (Mmp13 and Adamts-5). Taken together, these data support the hypothesis that MEKi treatment can impact chondrocyte hypertrophy, matrix resorption, and fracture healing. These compounds can also affect bone architecture by expanding the hypertrophic zone of the growth plate and reducing osteoclast surface systemically.