Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor and bi-functional lipid and protein phosphatase. We report that the metabolic regulator pyruvate dehydrogenase kinase1 (PDHK1) is a synthetic-essential gene in PTEN-deficient cancer and normal cells. The PTEN protein phosphatase dephosphorylates nuclear factor κB (NF-κB)-activating protein (NKAP) and limits NFκB activation to suppress expression of PDHK1, a NF-κB target gene. Loss of the PTEN protein phosphatase upregulates PDHK1 to induce aerobic glycolysis and PDHK1 cellular dependence. PTEN-deficient human tumors harbor increased PDHK1, a biomarker of decreased patient survival. This study uncovers a PTEN-regulated signaling pathway and reveals PDHK1 as a potential target in PTEN-deficient cancers.

The success of targeted cancer therapy is limited by drug resistance that can result from tumor genetic heterogeneity. The current approach to address resistance typically involves initiating a new treatment after clinical/radiographic disease progression, ultimately resulting in futility in most patients. Towards a potential alternative solution, we developed a novel computational framework that uses human cancer profiling data to systematically identify dynamic, pre-emptive, and sometimes non-intuitive treatment strategies that can better control tumors in real-time. By studying lung adenocarcinoma clinical specimens and preclinical models, our computational analyses revealed that the best anti-cancer strategies addressed existing resistant subpopulations as they emerged dynamically during treatment. In some cases, the best computed treatment strategy used unconventional therapy switching while the bulk tumor was responding, a prediction we confirmed in vitro. The new framework presented here could guide the principled implementation of dynamic molecular monitoring and treatment strategies to improve cancer control.

The blood–brain barrier (BBB) is a biological firewall that carefully regulates the cerebral microenvironment by acting as a physical, metabolic and transport barrier. This selectively permeable interface was modelled using the immortalised human cerebral microvascular endothelial cell line (hCMEC/D3) to investigate interactions with the cationic amino acid (CAA) L-arginine, the precursor for nitric oxide (NO), and with asymmetric dimethylarginine (ADMA), an endogenously derived analogue of L-arginine that potently inhibits NO production. The transport mechanisms utilised by L-arginine are known but they are not fully understood for ADMA, particularly at the BBB. This is of clinical significance giving the emerging role of ADMA in many brain and cerebrovascular diseases and its potential as a therapeutic target. We discovered that high concentrations of ADMA could induce endothelial dysfunction in the hCMEC/D3s BBB permeability model, leading to an increase in paracellular permeability to the paracellular marker FITC-dextran (40kDa). We also investigated interactions of ADMA with a variety of transport mechanisms, comparing the data with L-arginine interactions. Both molecules are able to utilise the CAA transport system y+. Furthermore, the expression of CAT-1, the best known protein from this group, was confirmed in the hCMEC/D3s. It is likely that influx systems, such as y+L and b0,+, have an important physiological role in ADMA transport at the BBB. These data are not only important with regards to the brain, but apply to other microvascular endothelia where ADMA is a major area of investigation.

Phosphoinositide-3-kinase (PI3K)-α inhibitors have shown clinical activity in squamous cell carcinomas (SCCs) of head and neck (H&N) bearing PIK3CA mutations or amplification. Studying models of therapeutic resistance, we have observed that SCC cells that become refractory to PI3Kα inhibition maintain PI3K-independent activation of the mammalian target of rapamycin (mTOR). This persistent mTOR activation is mediated by the tyrosine kinase receptor AXL. AXL is overexpressed in resistant tumors from both laboratory models and patients treated with the PI3Kα inhibitor BYL719. AXL dimerizes with and phosphorylates epidermal growth factor receptor (EGFR), resulting in activation of phospholipase Cγ (PLCγ)-protein kinase C (PKC), which, in turn, activates mTOR. Combined treatment with PI3Kα and either EGFR, AXL, or PKC inhibitors reverts this resistance.

One strategy for combating cancer-drug resistance is to deploy rational polytherapy up front that suppresses the survival and emergence of resistant tumor cells. Here we demonstrate in models of lung adenocarcinoma harboring the oncogenic fusion of ALK and EML4 that the GTPase RAS-mitogen-activated protein kinase (MAPK) pathway, but not other known ALK effectors, is required for tumor-cell survival. EML4-ALK activated RAS-MAPK signaling by engaging all three major RAS isoforms through the HELP domain of EML4. Reactivation of the MAPK pathway via either a gain in the number of copies of the gene encoding wild-type K-RAS (KRAS(WT)) or decreased expression of the MAPK phosphatase DUSP6 promoted resistance to ALK inhibitors in vitro, and each was associated with resistance to ALK inhibitors in individuals with EML4-ALK-positive lung adenocarcinoma. Upfront inhibition of both ALK and the kinase MEK enhanced both the magnitude and duration of the initial response in preclinical models of EML4-ALK lung adenocarcinoma. Our findings identify RAS-MAPK dependence as a hallmark of EML4-ALK lung adenocarcinoma and provide a rationale for the upfront inhibition of both ALK and MEK to forestall resistance and improve patient outcomes.

Although oncogene-targeted therapy often elicits profound initial tumor responses in patients, responses are generally incomplete because some tumor cells survive initial therapy as residual disease that enables eventual acquired resistance. The mechanisms underlying tumor cell adaptation and survival during initial therapy are incompletely understood. Here, through the study of EGFR mutant lung adenocarcinoma, we show that NF-κB signaling is rapidly engaged upon initial EGFR inhibitor treatment to promote tumor cell survival and residual disease. EGFR oncogene inhibition induced an EGFR-TRAF2-RIP1-IKK complex that stimulated an NF-κB-mediated transcriptional survival program. The direct NF-κB inhibitor PBS-1086 suppressed this adaptive survival program and increased the magnitude and duration of initial EGFR inhibitor response in multiple NSCLC models, including a patient-derived xenograft. These findings unveil NF-κB activation as a critical adaptive survival mechanism engaged by EGFR oncogene inhibition and provide rationale for EGFR and NF-κB co-inhibition to eliminate residual disease and enhance patient responses.

Abstract Resistance to RAF-MEK targeted therapy is a major clinical challenge. RAF-MEK inhibitors are initially but only transiently effective in some but not all BRAF mutant patients, and largely ineffective in RAS mutant patients because of resistance. Through a genetic screen in BRAF mutant tumor cells, we show that the Hippo pathway effector YAP acts as a parallel survival input to promote resistance to RAF-MEK inhibitor therapy. Combined YAP and RAF-MEK inhibition was synthetically lethal not only in several BRAF mutant tumor types but also in RAS mutant tumors. Increased YAP in BRAFV600E patient tumors was a biomarker of worse initial response to RAF inhibition in patients, establishing the clinical relevance of our findings. Our data uncover YAP as a novel mechanism of resistance to RAF-MEK targeted therapy. The findings unveil the synthetic lethality of YAP and RAF-MEK co-suppression as a promising strategy to enhance response and patient survival. Citation Format: Luping Lin, Amit Sabnis, Elton Chan, Victor Olivas, Lindsay Cade, Evangelos Pazarentzos, Saurabh Asthana, Dana Neel, Jenny Jiacheng Yan, Xinyuan Lu, Luu Pham, Mingxue Wang, Niki Karachaliou, Maria G. Cao, Jose L. Manzano, Jose L. Ramirez, Jose M. Torres, Fiamma Buttitta, Charles M. Rudin, Eric A. Collisson, Alain Algazi, Eric Robinson, Iman Osman, Eva Munoz-Couselo, Javier Cortes, Dennie T. Frederick, Zachary A. Cooper, Martin McMahon, Antonio Marchetti, Rafael Rosell, Keith T. Flaherty, Jennifer A. Wargo, Trever G. Bivona. The Hippo effector YAP promotes resistance to RAF and MEK targeted therapies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-239. doi:10.1158/1538-7445.AM2015-LB-239

The identification of specific genetic alterations that drive the initiation and progression of cancer and the development of targeted drugs that act against these driver alterations has revolutionized the treatment of many human cancers. Although substantial progress has been achieved with the use of such targeted cancer therapies, resistance remains a major challenge that limits the overall clinical impact. Hence, despite progress, new strategies are needed to enhance response and eliminate resistance to targeted cancer therapies in order to achieve durable or curative responses in patients. To date, efforts to characterize mechanisms of resistance have primarily focused on molecular events that mediate primary or secondary resistance in patients. Less is known about the initial molecular response and adaptation that may occur in tumor cells early upon exposure to a targeted agent. Although understudied, emerging evidence indicates that the early adaptive changes by which tumor cells respond to the stress of a targeted therapy may be crucial for tumo r cell survival during treatment and the development of resistance. Here we review recent data illuminating the molecular architecture underlying adaptive stress signaling in tumor cells. We highlight how leveraging this knowledge could catalyze novel strategies to minimize or eliminate targeted therapy resistance, thereby unleashing the full potential of targeted therapies to transform many cancers from lethal to chronic or curable conditions.

Trever Bivona and colleagues show that the Hippo pathway effector YAP promotes resistance to RAF and MEK inhibitor therapy in multiple types of BRAF-mutant tumors. The findings suggest that combined suppression of YAP and RAF-MEK signaling might enhance treatment response and prevent drug resistance. Resistance to RAF- and MEK-targeted therapy is a major clinical challenge1,2,3,4. RAF and MEK inhibitors are initially but only transiently effective in some but not all patients with BRAF gene mutation and are largely ineffective in those with RAS gene mutation because of resistance5,6,7,8,9,10,11,12,13,14. Through a genetic screen in BRAF-mutant tumor cells, we show that the Hippo pathway effector YAP (encoded by YAP1) acts as a parallel survival input to promote resistance to RAF and MEK inhibitor therapy. Combined YAP and RAF or MEK inhibition was synthetically lethal not only in several BRAF-mutant tumor types but also in RAS-mutant tumors. Increased YAP in tumors harboring BRAF V600E was a biomarker of worse initial response to RAF and MEK inhibition in patients, establishing the clinical relevance of our findings. Our data identify YAP as a new mechanism of resistance to RAF- and MEK-targeted therapy. The findings unveil the synthetic lethality of combined suppression of YAP and RAF or MEK as a promising strategy to enhance treatment response and patient survival.

IκΒα (the protein product of NFKBIA gene) has widely been considered a pro- apoptotic factor due to its ability to inhibit the anti-apoptotic transcription factor NFκB. Our findings indicate that IκΒα also exerts a strong anti-apoptotic activity at the outer mitochondria membrane (OMM). This function we uncovered is distinct from its ability to sequester and inhibit NFκB. IκΒα instead binds to voltage dependent anion channel 1 (VDAC1) and Hexokinase 2 (HK2), stabilizes this complex and prevents mitochondria outer membrane permeabilisation (MOMP) and apoptosis.

Reference EPFL-ARTICLE-205309doi:10.1038/cdd.2014.196View record in Web of Science Record created on 2015-02-20, modified on 2016-08-09

Phosphoinositide-3-kinase (PI3K)-α inhibitors have shown clinical activity in squamous cell carcinomas (SCCs) of head and neck (H&N) bearing PIK3CA mutations or amplification. Studying models of therapeutic resistance, we have observed that SCC cells that become refractory to PI3Kα inhibition maintain PI3K-independent activation of the mammalian target of rapamycin (mTOR). This persistent mTOR activation is mediated by the tyrosine kinase receptor AXL. AXL is overexpressed in resistant tumors from both laboratory models and patients treated with the PI3Kα inhibitor BYL719. AXL dimerizes with and phosphorylates epidermal growth factor receptor (EGFR), resulting in activation of phospholipase Cγ (PLCγ)-protein kinase C (PKC), which, in turn, activates mTOR. Combined treatment with PI3Kα and either EGFR, AXL, or PKC inhibitors reverts this resistance.

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs widely in human cancers. Although somatic mutations in the PI3K pathway genes PIK3CA and PTEN are known to drive PI3K pathway activation and cancer growth, the significance of somatic mutations in other PI3K pathway genes is less clear. Here, we establish the signaling and oncogenic properties of a recurrent somatic mutation in the PI3K p110β isoform that resides within its kinase domain (PIK3CβD1067V). We initially observed PIK3CβD1067V by exome sequencing analysis of an EGFR-mutant non-small cell lung cancer (NSCLC) tumor biopsy from a patient with acquired erlotinib resistance. On the basis of this finding, we hypothesized that PIK3CβD1067V might function as a novel tumor-promoting genetic alteration, and potentially an oncogene, in certain cancers. Consistent with this hypothesis, analysis of additional tumor exome data sets revealed the presence of PIK3CβD1067V at low frequency in other patient tumor samples (including renal cell carcinoma, glioblastoma multiforme, head and neck squamous cell carcinoma, melanoma, thyroid carcinoma and endometrial carcinoma). Functional studies revealed that PIK3CβD1067V promoted PI3K pathway signaling, enhanced cell growth in vitro, and was sufficient for tumor formation in vivo. Pharmacologic inhibition of PIK3Cβ with TGX-221 (isoform-selective p110β inhibitor) specifically suppressed growth in patient-derived renal-cell carcinoma cells with endogenous PIK3CβD1067V and in NIH-3T3 and human EGFR-mutant lung adenocarcinoma cells engineered to express this mutant PI3K. In the EGFR-mutant lung adenocarcinoma cells, expression of PIK3CβD1067V also promoted erlotinib resistance. Our data establish a novel oncogenic form of PI3K, revealing the signaling and oncogenic properties of PIK3CβD1067V and its potential therapeutic relevance in cancer. Our findings provide new insight into the genetic mechanisms underlying PI3K pathway activation in human tumors and indicate that PIK3CβD1067V is a rational therapeutic target in certain cancers.

Abstract Recent advances in molecular profiling of many human tumor types has enabled the development and clinical use of molecularly-targeted therapies in patients. Many tumors exhibit inactivation of PTEN which is predicted to sensitize tumor cells to PI3 kinase or AKT inhibitor therapy. However, clinical responses to PI3 kinase or AKT inhibitors are variable and not curative. Furthermore, these responses in patients do not correlate uniformly with PTEN inactivation. Therefore, we investigated whether PTEN inactivation could lead to dependence on signaling pathways and components that function independently of PI3K or AKT and that could serve as novel therapeutic targets in PTEN deficient tumors. Using multiple human tumor models including lung adenocarcinoma, lung squamous, renal cell carcinoma, and prostate adenocarcinoma that express or lack PTEN and Gene Set Enrichment Analysis, we identified alterations in numerous metabolic regulatory genes in response to PTEN inactivation, including hexokinase 2 (HK2) and pyruvate dehydrogenase kinase 1 (PDK1). We found that in PTEN-deficient tumor cells HK2 is upregulated and selectively localizes to the mitochondria, where it enhances glycolytic flux and inhibits apoptosis. Furthermore, we found that PDK1 is also upregulated upon PTEN inactivation and suppresses oxidative phosphorylation, upregulating glycolysis and the production of lactate. Thus, we uncovered a novel role for HK2 and PDK1 in the metabolic reprogramming that occurs as a consequence of PTEN inactivation in tumor cells. Furthermore, we found that overexpression of either HK2 or PDK1 confers resistance to targeted therapies against PI3K and other oncogenic drivers more broadly. Conversely, genetic or pharmacological suppression of HK2 or PDK1 enhances response to targeted therapy in multiple tumor cell types. Together, our data identify HK2 and PDK1 as novel molecular biomarkers and promising therapeutic targets in multiple PTEN deficient tumor types. Citation Format: Evangelos Pazarentzos, Trever G. Bivona. PDK1 and hexokinase 2 are downstream effectors of PTEN loss and regulate response to targeted therapies in multiple tumor types. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1713. doi:10.1158/1538-7445.AM2014-1713

IB resides in the cytosol where it retains the inducible transcription factor NF-kappa B. We show that IB also localises to the outer mitochondrial membrane (OMM) to inhibit apoptosis. This effect is especially pronounced in tumour cells with constitutively active NF-B that accumulate high amounts of mitochondrial IB as a NF kappa-B target gene. 3T3 I kappa B alpha(-/-) cells also become protected from apoptosis when IB is specifically reconstituted at the OMM. Using various IB mutants, we demonstrate that apoptosis inhibition and NF-B inhibition can be functionally and structurally separated. At mitochondria, IB stabilises the complex of VDAC1 and hexokinase II (HKII), thereby preventing Bax recruitment to VDAC1 and the release of cytochrome c for apoptosis induction. When IB is reduced in tumour cells with constitutively active NF-kappa B, they show an enhanced response to anticancer treatment in an in vivo xenograft tumour model. Our results reveal the unexpected activity of IB in guarding the integrity of the OMM against apoptosis induction and open possibilities for more specific interference in tumours with deregulated NF-kappa B.

Gene therapy vectors are among the treatments currently used to treat malignant tumors. Gene therapy vectors use a specific therapeutic transgene that causes death in cancer cells. In early attempts at gene therapy, therapeutic transgenes were driven by non-specific vectors which induced toxicity to normal cells in addition to the cancer cells. Recently, novel cancer specific viral vectors have been developed that target cancer cells leaving normal cells unharmed. Here we review such cancer specific gene therapy systems currently used in the treatment of cancer and discuss the major challenges and future directions in this field.

Abstract The vast majority of patients with lung adenocarcinomas harboring activating mutation in EGFR respond to EGFR tyrosine inhibitors (TKI) (i.e. erlotinib). However, the magnitude of tumor regression is variable and responses are short-lived with a median duration of 9-12 months. We recently identified activation of the NF-κB (Nuclear Factor kappa-light-chain-enhancer of activated B cells) signaling pathway as a key mediator of de novo resistance to EGFR TKI therapy in cell lines and tumor xenograft models of lung adenocarcinoma. However, the role of NF-κB activation in mediating EGFR TKI acquired resistance in lung adenocarcinoma is not well defined. We have found that erlotinib treatment of EGFR TKI sensitive lung adenocarcinoma cell lines promotes the rapid phosphorylation and degradation of IκB (inhibitor of NF-κB) and subsequent activation of the NF-κB subunit RelA. RelA activation is accompanied by transcriptional activation of downstream NF-κB target genes, including IL6. Prolonged exposure of EGFR TKI sensitive lung adenocarcinoma cell lines to erlotinib leads to EGFR TKI acquired resistance that is accompanied by sustained NF-κB activation and IL6 expression. EGFR TKI acquired resistance can be overcome by treating cells with erlotinib in combination with PBS-1086 (rel∼MD, Inc.), a direct Rel inhibitor. Furthermore, concomitant treatment of EGFR TKI sensitive lung adenocarcinoma cells with erlotinib + PBS-1086 prevents the development of EGFR TKI acquired resistance. Together, these results demonstrate the molecular basis for the synthetic lethality of combined EGFR and NF-κB inhibition and provide mechanism-based rationale for polytherapies against both EGFR and NF-κB to enhance response in lung adenocarcinoma patients. Broadly, our findings provide novel insights into the biological and clinical consequences of the context-specific and dynamic functional interplay between EGFR and NF-κB signaling. Citation Format: Collin M. Blakely, Evangelos Pazarentzos, Saurabh Asthana, Victor Olivas, Irena Tan, Timothy Fouts, Jeffrey Meshulam, Trever G. Bivona. Erlotinib induces NF-kappa B dependence that promotes EGFR tyrosine kinase inhibitor resistance in lung adenocarcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1836. doi:10.1158/1538-7445.AM2014-1836

ORCTL3 is a member of a group of genes, the so-called anticancer genes, that cause tumour-specific cell death. We show that this activity is triggered in isogenic renal cells upon their transformation independently of the cells' proliferation status. For its cell death effect ORCTL3 targets the enzyme stearoyl-CoA desaturase-1 (SCD1) in fatty acid metabolism. This is caused by transmembrane domains 3 and 4, which are more efficacious in vitro than a low molecular weight drug against SCD1, and critically depend on their expression level. SCD1 is found upregulated upon renal cell transformation indicating that its activity, while not impacting proliferation, represents a critical bottleneck for tumourigenesis. An adenovirus expressing ORCTL3 leads to growth inhibition of renal tumours in vivo and to substantial destruction of patients' kidney tumour cells ex vivo. Our results indicate fatty acid metabolism as a target for tumour-specific apoptosis in renal tumours and suggest ORCTL3 as a means to accomplish this.