Coordinate direct input of both KRAS and IGF1 receptor to activation of PI3 kinase in KRAS-mutant lung cancer

Implication of PI3K/Akt pathway in pancreatic cancer: When PI3K isoforms matter?

Pancreatic cancer belongs to the incurable family of solid cancers. Despite of a recent better understanding its molecular biology, and an increased number of clinical trials, there is still a lack for innovative targeted therapies to fight this deadly malignancy. PI3K/Akt signalling is one of the most commonly deregulated signalling pathways in cancer, which explains the massive attention from many pharmaceutical companies over the ten past years on these signalling molecules. The already developed small molecule inhibitors are currently under clinical trial in various cancer types. Class I PI3Ks have 4 isoforms for which the role in physiology starts to be well described in the literature. Data are more unclear for their differential involvement in oncogenesis. In this review, we will discuss about the cognitive and therapeutic potential of targeting this signalling pathway and in particular Class I PI3K isoforms for pancreatic cancer treatment. Isoform-specificity of PI3K inhibitors are currently designed to achieve the same goal as pan-PI3K inhibitors but without potential adverse effects. We will discuss if such strategy is relevant in pancreatic adenocarcinoma.

Inhibition of IGF1R signaling abrogates resistance to afatinib (BIBW2992) in EGFR T790M mutant lung cancer cells

Non-small cell lung cancer (NSCLC) patients with an epidermal growth factor receptor (EGFR) mutation have benefited from treatment of reversible EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib. Acquisition of a secondary mutation in EGFR T790M is the most common mechanism of resistance to first generation EGFR TKIs, resulting in therapeutic failure. Afatinib is a second generation of EGFR TKI that showed great efficacy against tumors bearing the EGFR T790M mutation, but it failed to show the improvement on overall survival of lung cancer patients with EGFR mutations possibly because of novel acquired resistance mechanisms. Currently, there are no therapeutic options available for lung cancer patients who develop acquired resistance to afatinib. To identify novel resistance mechanism(s) to afatinib, we developed afatinib resistant cell lines from a parental human-derived NSCLC cell line, H1975, harboring both EGFR L858R and T790M mutations. We found that activation of the insulin-like growth factor 1 receptor (IGF1R) signaling pathway contributes to afatinib resistance in NSCLC cells harboring the T790M mutation. IGF1R knockdown not only significantly sensitizes resistant cells to afatinib, but also induces apoptosis in afatinib resistance cells. In addition, combination treatment with afatinib and linsitinib shows more than additive effects on tumor growth in in vivo H1975 xenograft. Therefore, these finding suggest that IGF1R inhibition or combination of EGFR-IGF1R inhibition strategies would be potential ways to prevent or potentiate the effects of current therapeutic options to lung cancer patients demonstrating resistance to either first or second generation EGFR TKIs.

RAS Synthetic Lethal Screens Revisited: Still Seeking the Elusive Prize?

The RAS genes are critical oncogenic drivers activated by point mutation in some 20% of human malignancies. However, no pharmacologic approaches to targeting RAS proteins directly have yet succeeded, leading to suggestions that these proteins may be "undruggable." This has led to two alternative indirect approaches to targeting RAS function in cancer. One has been to target RAS signaling pathways downstream at tractable enzymes such as kinases, particularly in combination. The other, which is the focus of this review, has been to seek targets that are essential in cells bearing an activated RAS oncogene, but not those without. This synthetic lethal approach, while rooted in ideas from invertebrate genetics, has been inspired most strongly by the successful use of PARP inhibitors, such as olaparib, in the clinic to treat BRCA defective cancers. Several large-scale screens have been carried out using RNA interference-mediated expression silencing to find genes that are uniquely essential to RAS-mutant but not wild-type cells. These screens have been notable for the low degree of overlap between their results, with the possible exception of proteasome components, and have yet to lead to successful new clinical approaches to the treatment of RAS-mutant cancers. Possible reasons for these disappointing results are discussed here, along with a reevaluation of the approaches taken. On the basis of experience to date, RAS synthetic lethality has so far fallen some way short of its original promise and remains unproven as an approach to finding effective new ways of tackling RAS-mutant cancers. Clin Cancer Res; 21(8); 1802-9. ©2015 AACR. See all articles in this CCR Focus section, "Targeting RAS-Driven Cancers."

Molecular histology of lung cancer: from targets to treatments

Lung cancer is the leading cause of cancer-related death worldwide with a 5-year survival rate of less than 15%, despite significant advances in both diagnostic and therapeutic approaches. Combined genomic and transcriptomic sequencing studies have identified numerous genetic driver mutations that are responsible for the development of lung cancer. In addition, molecular profiling studies identify gene products and their mutations which predict tumour responses to targeted therapies such as protein tyrosine kinase inhibitors and also can offer explanation for drug resistance mechanisms. The profiling of circulating micro-RNAs has also provided an ability to discriminate patients in terms of prognosis/diagnosis and high-throughput DNA sequencing strategies are beginning to elucidate cell signalling pathway mutations associated with oncogenesis, including potential stem cell associated pathways, offering the promise that future therapies may target this sub-population, preventing disease relapse post treatment and improving patient survival. This review provides an assessment of molecular profiling within lung cancer concerning molecular mechanisms, treatment options and disease-progression. Current areas of development within lung cancer profiling are discussed (i.e. profiling of circulating tumour cells) and future challenges for lung cancer treatment addressed such as detection of micro-metastases and cancer stem cells.

Phase I study of intermittent oral dosing of the insulin-like growth factor-1 and insulin receptors inhibitor OSI-906 in patients with advanced solid tumors

PURPOSE

We determined the maximum tolerated dose (MTD), safety, pharmacokinetics, pharmacodynamics, and preliminary activity of OSI-906, a potent, oral, dual inhibitor of insulin-like growth factor-1 receptor (IGF1R) and insulin receptor (IR), in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

This was a multicenter, open-label, dose escalation phase I study evaluating three intermittent dosing schedules of once-daily OSI-906 [schedule (S) 1, days 1-3 every 14 days; S2, days 1-5 every 14 days; S3, days 1-7 every 14 days]. A fed-fasting expansion cohort was included in the study.

RESULTS

Seventy-nine patients were enrolled: 62 in S1, 4 in S2, and 13 in S3. S2 was discontinued. Dose-limiting toxicity comprised grade 3-4 hyperglycemia, vomiting, fatigue, and prolonged QTc interval. The MTD and recommended phase II dose of OSI-906 was 600 mg for both S1 and S3 schedules. Other common adverse events were grade 1-2 nausea, vomiting, fatigue, and diarrhea. The pharmacokinetics of OSI-906 was dose linear, and the terminal half-life ranged between 2 and 6 hours. High-fat meals had a moderate effect on the pharmacokinetics of OSI-906. At the MTD, inhibition of IGF1R and IR was observed in peripheral blood mononuclear cells. An increase in plasma IGF1 concentrations, an indirect measure of IGF1R signaling inhibition, was seen at doses ≥ 450 mg. Two patients with adrenocortical carcinoma achieved partial responses.

CONCLUSION

The MTD of 600 mg was well tolerated and associated with preliminary antitumor activity. These data support further evaluation of OSI-906 in solid tumors.

The Role of the Insulin/IGF System in Cancer: Lessons Learned from Clinical Trials and the Energy Balance-Cancer Link

Numerous epidemiological and pre-clinical studies have demonstrated that the insulin/insulin-like growth factor (IGF) system plays a key role in the development and progression of several types of cancer. Insulin/IGF signaling, in cooperation with chronic low-grade inflammation, is also an important contributor to the cancer-promoting effects of obesity. However, clinical trials for drugs targeting different components of this system have produced largely disappointing results, possibly due to the lack of predictive biomarker use and problems with the design of combination therapy regimens. With careful attention to the identification of likely patient responders and optimal drug combinations, the outcome of future trials may be improved. Given that insulin/IGF signaling is known to contribute to obesity-associated cancer, further investigation regarding the efficacy of drugs targeting this system and its downstream effectors in the obese patient population is warranted.

IRS2 copy number gain, KRAS and BRAF mutation status as predictive biomarkers for response to the IGF-1R/IR inhibitor BMS-754807 in colorectal cancer cell lines

Insulin-like growth factor receptor 1 (IGF-1R)-targeting therapies are currently at an important crossroad given the low clinical response rates seen in unselected patients. Predictive biomarkers for patient selection are critical for improving clinical benefit. Coupling in vitro sensitivity testing of BMS-754807, a dual IGF-1R/IR inhibitor, with genomic interrogations in 60 human colorectal cancer cell lines, we identified biomarkers correlated with response to BMS-754807. The results showed that cell lines with BRAF(V600E) or KRAS(G13D) mutation were resistant, whereas cell lines with wild-type of both KRAS and BRAF were particularly sensitive to BMS-754807 if they have either higher RNA expression levels of IR-A or lower levels of IGFBP6. In addition, the cell lines with KRAS mutations, those with either insulin receptor substrate 2 (IRS2) copy number gain (CNG) or higher IGF-1R expression levels, were more sensitive to the drug. Furthermore, cell lines with IRS2 CNG had higher levels of ligand-stimulated activation of IGF-1R and AKT, suggesting that these cell lines with IGF-IR signaling pathways more actively coupled to AKT signaling are more responsive to IGF-1R/IR inhibition. IRS2 siRNA knockdown reduced IRS2 protein expression levels and decreased sensitivity to BMS-754807, providing evidence for the functional involvement of IRS2 in mediating the drug response. The prevalence of IRS2 CNG in colorectal cancer tumors as measured by qPCR-CNV is approximately 35%. In summary, we identified IRS2 CNG, IGF-1R, IR-A, and IGFBP6 RNA expression levels, and KRAS and BRAF mutational status as candidate predictive biomarkers for response to BMS-754807. This work proposed clinical development opportunities for BMS-754807 in colorectal cancer with patient selection to improve clinical benefit.

Novel oncogene and tumor suppressor mutations in KIT and PDGFRA wild type gastrointestinal stromal tumors revealed by next generation sequencing

Among gastrointestinal stromal tumors (GISTs) of 10-15% are negative for KIT and PDGFRA, and most of these cases are SDH deficient. Recent studies have provided data on additional molecular alterations such as KRAS in KIT mutant GISTs. We aimed to assess the frequency and spectrum of somatic mutations in common oncogenes as well as copy number variations in GISTs negative for KIT and PDGFRA mutations. GISTs with wild type KIT/PDGFRA were tested via next generation sequencing for somatic mutations in 341 genes. SDHB immunohistochemistry to evaluate for SDH deficiency was also performed. Of 267 GISTs tested for KIT and PDGFRA mutations, 15 were wild type, of which eight cases had material available for further testing. All eight cases had loss of SDHB expression and had various molecular alterations involving ARID1A, TP53, and other genes. One case had a KRAS G12V (c.35G>T) mutation in both the primary gastric tumor and a post-imatinib recurrence. This tumor had anaplastic features and was resistant to multiple tyrosine kinase inhibitors, ultimately resulting in cancer-related mortality within 2 years of diagnosis. In conclusion, KRAS mutations occur in rare GISTs with wild type KIT and PDGFRA. These tumors may display immunohistochemical positivity for KIT and primary resistance to tyrosine kinase inhibitors.

ASPP2 controls epithelial plasticity and inhibits metastasis through β-catenin-dependent regulation of ZEB1

Epithelial to mesenchymal transition (EMT), and the reverse mesenchymal to epithelial transition (MET), are known examples of epithelial plasticity that are important in kidney development and cancer metastasis. Here we identify ASPP2, a haploinsufficient tumour suppressor, p53 activator and PAR3 binding partner, as a molecular switch of MET and EMT. ASPP2 contributes to MET in mouse kidney in vivo. Mechanistically, ASPP2 induces MET through its PAR3-binding amino-terminus, independently of p53 binding. ASPP2 prevents β-catenin from transactivating ZEB1, directly by forming an ASPP2-β-catenin-E-cadherin ternary complex and indirectly by inhibiting β-catenin's N-terminal phosphorylation to stabilize the β-catenin-E-cadherin complex. ASPP2 limits the pro-invasive property of oncogenic RAS and inhibits tumour metastasis in vivo. Reduced ASPP2 expression results in EMT, and is associated with poor survival in hepatocellular carcinoma and breast cancer patients. Hence, ASPP2 is a key regulator of epithelial plasticity that connects cell polarity to the suppression of WNT signalling, EMT and tumour metastasis.

Dsh homolog DVL3 mediates resistance to IGFIR inhibition by regulating IGF-RAS signaling

Drugs that inhibit insulin-like growth factor 1 (IGFI) receptor IGFIR were encouraging in early trials, but predictive biomarkers were lacking and the drugs provided insufficient benefit in unselected patients. In this study, we used genetic screening and downstream validation to identify the WNT pathway element DVL3 as a mediator of resistance to IGFIR inhibition. Sensitivity to IGFIR inhibition was enhanced specifically in vitro and in vivo by genetic or pharmacologic blockade of DVL3. In breast and prostate cancer cells, sensitization tracked with enhanced MEK-ERK activation and relied upon MEK activity and DVL3 expression. Mechanistic investigations showed that DVL3 is present in an adaptor complex that links IGFIR to RAS, which includes Shc, growth factor receptor-bound-2 (Grb2), son-of-sevenless (SOS), and the tumor suppressor DAB2. Dual DVL and DAB2 blockade synergized in activating ERKs and sensitizing cells to IGFIR inhibition, suggesting a nonredundant role for DVL3 in the Shc-Grb2-SOS complex. Clinically, tumors that responded to IGFIR inhibition contained relatively lower levels of DVL3 protein than resistant tumors, and DVL3 levels in tumors correlated inversely with progression-free survival in patients treated with IGFIR antibodies. Because IGFIR does not contain activating mutations analogous to EGFR variants associated with response to EGFR inhibitors, we suggest that IGF signaling achieves an equivalent integration at the postreceptor level through adaptor protein complexes, influencing cellular dependence on the IGF axis and identifying a patient population with potential to benefit from IGFIR inhibition.

A phase I trial of vertical inhibition of IGF signalling using cixutumumab, an anti-IGF-1R antibody, and selumetinib, an MEK 1/2 inhibitor, in advanced solid tumours

BACKGROUND

We completed a phase I clinical trial to test the safety and toxicity of combined treatment with cixutumumab (anti-IGF-1R antibody) and selumetinib (MEK 1/2 inhibitor).

METHODS

Patients with advanced solid tumours, refractory to standard therapy received selumetinib hydrogen sulphate capsules orally twice daily, and cixutumumab intravenously on days 1 and 15 of each 28-day cycle. The study used a 3+3 design, with a dose-finding cohort followed by an expansion cohort at the maximally tolerated dose that included pharmacokinetic and pharmacodynamic correlative studies.

RESULTS

Thirty patients were enrolled, with 16 in the dose-finding cohort and 14 in the expansion cohort. Grade 3 or greater toxicities included nausea and vomiting, anaemia, CVA, hypertension, hyperglycaemia, and ophthalmic symptoms. The maximally tolerated combination dose was 50 mg twice daily of selumetinib and 12 mg kg(-1) every 2 weeks of cixutumumab. Two patients achieved a partial response (one unconfirmed), including a patient with BRAF wild-type thyroid carcinoma, and a patient with squamous cell carcinoma of the tongue, and six patients achieved time to progression of >6 months, including patients with thyroid carcinoma, colorectal carcinoma, and basal cell carcinoma. Comparison of pre- and on-treatment biopsies showed significant suppression of pERK and pS6 activity with treatment.

CONCLUSIONS

Our study of anti-IGF-1R antibody cixutumumab and MEK 1/2 inhibitor selumetinib showed that the combination is safe and well-tolerated at these doses, with preliminary evidence of clinical benefit and pharmacodynamic evidence of target inhibition.

Feedback and redundancy in receptor tyrosine kinase signaling: relevance to cancer therapies

Mammalian cells have multiple regulatory mechanisms to deal with perturbations in cellular homeostasis, including feedback loops and crosstalk between the major signaling pathways. While these mechanisms are critically required to help cells survive under dynamic physiological circumstances, they also pose an impediment to the effective treatment of cancer. In this review, we describe what has been learned about interactions between receptor tyrosine kinase-dependent signaling pathways, and how this knowledge can be used to design rational and more effective combination therapies for cancer.

Upregulation of IGF1R by mutant RAS in leukemia and potentiation of RAS signaling inhibitors by small-molecule inhibition of IGF1R

PURPOSE

Activating mutations in the RAS oncogene occur frequently in human leukemias. Direct targeting of RAS has proven to be challenging, although targeting of downstream RAS mediators, such as MEK, is currently being tested clinically. Given the complexity of RAS signaling, it is likely that combinations of targeted agents will be more effective than single agents.

EXPERIMENTAL DESIGN

A chemical screen using RAS-dependent leukemia cells was developed to identify compounds with unanticipated activity in the presence of an MEK inhibitor and led to identification of inhibitors of IGF1R. Results were validated using cell-based proliferation, apoptosis, cell-cycle, and gene knockdown assays; immunoprecipitation and immunoblotting; and a noninvasive in vivo bioluminescence model of acute myeloid leukemia (AML).

RESULTS

Mechanistically, IGF1R protein expression/activity was substantially increased in mutant RAS-expressing cells, and suppression of RAS led to decreases in IGF1R. Synergy between MEK and IGF1R inhibitors correlated with induction of apoptosis, inhibition of cell-cycle progression, and decreased phospho-S6 and phospho-4E-BP1. In vivo, NSG mice tail veins injected with OCI-AML3-luc+ cells showed significantly lower tumor burden following 1 week of daily oral administration of 50 mg/kg NVP-AEW541 (IGF1R inhibitor) combined with 25 mg/kg AZD6244 (MEK inhibitor), as compared with mice treated with either agent alone. Drug combination effects observed in cell-based assays were generalized to additional mutant RAS-positive neoplasms.

CONCLUSIONS

The finding that downstream inhibitors of RAS signaling and IGF1R inhibitors have synergistic activity warrants further clinical investigation of IGF1R and RAS signaling inhibition as a potential treatment strategy for RAS-driven malignancies.

Oncogenic KRAS signalling in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is almost universally fatal. The annual number of deaths equals the number of newly diagnosed cases, despite maximal treatment. The overall 5-year survival rate of <5% has remained stubbornly unchanged over the last 30 years, despite tremendous efforts in preclinical and clinical science. There is unquestionably an urgent need to further improve our understanding of pancreatic cancer biology, treatment response and relapse, and to identify novel therapeutic targets. Rigorous research in the field has uncovered genetic aberrations that occur during PDAC development and progression. In most cases, PDAC is initiated by oncogenic mutant KRAS, which has been shown to drive pancreatic neoplasia. However, all attempts to target KRAS directly have failed in the clinic and KRAS is widely assumed to be undruggable. This has led to intense efforts to identify druggable critical downstream targets and nodes orchestrated by mutationally activated KRAS. This includes context-specific KRAS effector pathways, synthetic lethal interaction partners and KRAS-driven metabolic changes. Here, we review recent advances in oncogenic KRAS signalling and discuss how these might benefit PDAC treatment in the future.

miR-375 suppresses IGF1R expression and contributes to inhibition of cell progression in laryngeal squamous cell carcinoma

MicroRNAs (miRNAs) are small noncoding RNA molecules which are involved in tumorigenesis and development. To investigate their role in primary laryngeal squamous cell carcinoma (LSCC), miRNA GeneChips were used to screen the differentially expressed miRNA, and then validated by real-time quantitative PCR in LSCC samples, we found that miR-375 was frequently downregulated in primary LSCC tissues. The tumor-suppressive effect of miR-375 was determined by in vitro assays; through gain-of-function studies we demonstrated that miR-375 can inhibit LSCC cell (SNU-48 and SNU-899) proliferation, motility, and invasion, and promote their apoptosis. In addition, bioinformatics tools TargetScan, PicTar, and Miranda were used to investigate the potential target of miR-375; bioinformatics analysis and dual-luciferase reporter assay indicated that IGF1R was a novel direct target of miR-375. Ectopic transfection of miR-375 led to a significant reduction in IGF1R and its downstream signaling molecule AKT at both the mRNA and protein levels in LSCC cells. Our results suggested that downregulation of miR-375 is one of the molecular mechanisms for the development and progression of LSCC by directly targeting IGF1R and affecting its downstream AKT signaling pathways. Furthermore, miR-375 and IGF1R may serve as a novel therapeutic target for LSCC.

Can we unlock the potential of IGF-1R inhibition in cancer therapy?

IGF-1R inhibitors arrived in the clinic accompanied by optimism based on preclinical activity of IGF-1R targeting, and recognition that low IGF bioactivity protects from cancer. This was tempered by concerns about toxicity to normal tissue IGF-1R and cross-reactivity with insulin receptor (InsR). In fact, toxicity is not a show-stopper; the key issue is efficacy. While IGF-1R inhibition induces responses as monotherapy in sarcomas and with chemotherapy or targeted agents in common cancers, negative Phase 2/3 trials in unselected patients prompted the cessation of several Pharma programs. Here, we review completed and on-going trials of IGF-1R antibodies, kinase inhibitors and ligand antibodies. We assess candidate biomarkers for patient selection, highlighting the potential predictive value of circulating IGFs/IGFBPs, the need for standardized assays for IGF-1R, and preclinical evidence that variant InsRs mediate resistance to IGF-1R antibodies. We review hypothesis-led and unbiased approaches to evaluate IGF-1R inhibitors with other agents, and stress the need to consider sequencing with chemotherapy. The last few years were a tough time for IGF-1R therapeutics, but also brought progress in understanding IGF biology. Even failed studies include patients who derived benefit; they should be investigated to identify features distinguishing the tumors and host environment of responders from non-responders. We emphasize the importance of incorporating biospecimen collection into trial design, and wording patient consents to allow post hoc analysis of trial material as new data become available. Such information represents the key to unlocking the potential of this approach, to inform the next generation of trials of IGF signalling inhibitors.

Non-small-cell lung cancers: a heterogeneous set of diseases

Non-small-cell lung cancers (NSCLCs), the most common lung cancers, are known to have diverse pathological features. During the past decade, in-depth analyses of lung cancer genomes and signalling pathways have further defined NSCLCs as a group of distinct diseases with genetic and cellular heterogeneity. Consequently, an impressive list of potential therapeutic targets was unveiled, drastically altering the clinical evaluation and treatment of patients. Many targeted therapies have been developed with compelling clinical proofs of concept; however, treatment responses are typically short-lived. Further studies of the tumour microenvironment have uncovered new possible avenues to control this deadly disease, including immunotherapy.

Non-small-cell lung cancers: a heterogeneous set of diseases

Non-small-cell lung cancers (NSCLCs), the most common lung cancers, are known to have diverse pathological features. During the past decade, in-depth analyses of lung cancer genomes and signalling pathways have further defined NSCLCs as a group of distinct diseases with genetic and cellular heterogeneity. Consequently, an impressive list of potential therapeutic targets was unveiled, drastically altering the clinical evaluation and treatment of patients. Many targeted therapies have been developed with compelling clinical proofs of concept; however, treatment responses are typically short-lived. Further studies of the tumour microenvironment have uncovered new possible avenues to control this deadly disease, including immunotherapy.

Genomic classification of the RAS network identifies a personalized treatment strategy for lung cancer

Better approaches are needed to evaluate a single patient's drug response at the genomic level. Targeted therapy for signaling pathways in cancer has met limited success in part due to the exceedingly interwoven nature of the pathways. In particular, the highly complex RAS network has been challenging to target. Effectively targeting the pathway requires development of techniques that measure global network activity to account for pathway complexity. For this purpose, we used a gene-expression-based biomarker for RAS network activity in non-small cell lung cancer (NSCLC) cells, and screened for drugs whose efficacy was significantly highly correlated to RAS network activity. Results identified EGFR and MEK co-inhibition as the most effective treatment for RAS-active NSCLC amongst a panel of over 360 compounds and fractions. RAS activity was identified in both RAS-mutant and wild-type lines, indicating broad characterization of RAS signaling inclusive of multiple mechanisms of RAS activity, and not solely based on mutation status. Mechanistic studies demonstrated that co-inhibition of EGFR and MEK induced apoptosis and blocked both EGFR-RAS-RAF-MEK-ERK and EGFR-PI3K-AKT-RPS6 nodes simultaneously in RAS-active, but not RAS-inactive NSCLC. These results provide a comprehensive strategy to personalize treatment of NSCLC based on RAS network dysregulation and provide proof-of-concept of a genomic approach to classify and target complex signaling networks.

Oncogenic KRAS signalling in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is almost universally fatal. The annual number of deaths equals the number of newly diagnosed cases, despite maximal treatment. The overall 5-year survival rate of <5% has remained stubbornly unchanged over the last 30 years, despite tremendous efforts in preclinical and clinical science. There is unquestionably an urgent need to further improve our understanding of pancreatic cancer biology, treatment response and relapse, and to identify novel therapeutic targets. Rigorous research in the field has uncovered genetic aberrations that occur during PDAC development and progression. In most cases, PDAC is initiated by oncogenic mutant KRAS, which has been shown to drive pancreatic neoplasia. However, all attempts to target KRAS directly have failed in the clinic and KRAS is widely assumed to be undruggable. This has led to intense efforts to identify druggable critical downstream targets and nodes orchestrated by mutationally activated KRAS. This includes context-specific KRAS effector pathways, synthetic lethal interaction partners and KRAS-driven metabolic changes. Here, we review recent advances in oncogenic KRAS signalling and discuss how these might benefit PDAC treatment in the future.

PI3K isoform dependence of PTEN-deficient tumors can be altered by the genetic context

There has been increasing interest in the use of isoform-selective inhibitors of phosphatidylinositide-3-kinase (PI3K) in cancer therapy. Using conditional deletion of the p110 catalytic isoforms of PI3K to predict sensitivity of cancer types to such inhibitors, we and others have demonstrated that tumors deficient of the phosphatase and tensin homolog (PTEN) are often dependent on the p110β isoform of PI3K. Because human cancers usually arise due to multiple genetic events, determining whether other genetic alterations might alter the p110 isoform requirements of PTEN-null tumors becomes a critical question. To investigate further the roles of p110 isoforms in PTEN-deficient tumors, we used a mouse model of ovarian endometrioid adenocarcinoma driven by concomitant activation of the rat sarcoma protein Kras, which is known to activate p110α, and loss of PTEN. In this model, ablation of p110β had no effect on tumor growth, whereas p110α ablation blocked tumor formation. Because ablation of PTEN alone is often p110β dependent, we wondered if the same held true in the ovary. Because PTEN loss alone in the ovary did not result in tumor formation, we tested PI3K isoform dependence in ovarian surface epithelium (OSE) cells deficient in both PTEN and p53. These cells were indeed p110β dependent, whereas OSEs expressing activated Kras with or without PTEN loss were p110α dependent. Furthermore, isoform-selective inhibitors showed a similar pattern of the isoform dependence in established Kras(G12D)/PTEN-deficient tumors. Taken together, our data suggest that, whereas in some tissues PTEN-null tumors appear to inherently depend on p110β, the p110 isoform reliance of PTEN-deficient tumors may be altered by concurrent mutations that activate p110α.

Molecular pathways and therapeutic targets in lung cancer

Lung cancer is still the leading cause of cancer death worldwide. Both histologically and molecularly lung cancer is heterogeneous. This review summarizes the current knowledge of the pathways involved in the various types of lung cancer with an emphasis on the clinical implications of the increasing number of actionable molecular targets. It describes the major pathways and molecular alterations implicated in the development and progression of non-small cell lung cancer (adenocarcinoma and squamous cancer), and of small cell carcinoma, emphasizing the molecular alterations comprising the specific blueprints in each group. The approved and investigational targeted therapies as well as the immune therapies, and clinical trials exploring the variety of targeted approaches to treatment of lung cancer are the main focus of this review.

Not just gRASping at flaws: finding vulnerabilities to develop novel therapies for treating KRAS mutant cancers

Mutations in Kirsten rat-sarcoma (KRAS) are well appreciated to be major drivers of human cancers through dysregulation of multiple growth and survival pathways. Similar to many other non-kinase oncogenes and tumor suppressors, efforts to directly target KRAS pharmaceutically have not yet materialized. As a result, there is broad interest in an alternative approach to develop therapies that induce synthetic lethality in cancers with mutant KRAS, therefore exposing the particular vulnerabilities of these cancers. Fueling these efforts is our increased understanding into the biology driving KRAS mutant cancers, in particular the important pathways that mutant KRAS governs to promote survival. In this mini-review, we summarize the latest approaches to treat KRAS mutant cancers and the rationale behind them.

Tales from the Jazz ASH: highlights from the 2013 American Society of Haematology meeting

The 55th annual ASH meeting was held in pleasant New Orleans and was the largest in its history, with 22,495 participants coming from 113 nations. A 'bench-to-bedside and back' attitude characterises haematology probably more than any other discipline in medicine and, as usual, this was reflected in the extremely wide breadth of the topics covered, including the last results from clinical trials and cutting-edge advancements in basic science. This year, the balance was arguably skewed: few truly clinical practice-changing results were presented. On the other hand, a great number of basic and translational studies significantly increased our understanding of the biology of numerous malignancies and heralded the coming of age of disruptive technologies. Namely, above all, next generation sequencing and T cell engineering-based cell therapy.

The end of KRAS, and other, cancers? A new way forward

Mutant KRAS, as well as other mutant driver genes and epidriver genes, is a dominant determinant of resistance to cancer therapeutics. The recent introduction of targeting therapies based on drugs that inhibit the kinase catalytic function of nodal points along the Ras/extracellular-signal-regulated kinase (ERK) and the phosphatidylinositol-3-kinase (PI3K)/Akt cascades is meeting with limited success. Against this background, recent evidence shows that the β-galactoside-binding protein (βGBP) molecule, a physiological PI3K inhibitor, is a potent inducer of apoptosis in KRAS-mutant cancer cells (along with other aggressive cancer cells of different genetic makeup) and that it is therapeutically effective in vivo. Absence of p53 or phosphatase and tensin homolog (PTEN) tumor suppressor function or added activating PI3K mutations does not affect βGBP function. In contrast to the concept of one drug against one target, βGBP operates through alternative physiological routes.

Requirement for interaction of PI3-kinase p110α with RAS in lung tumor maintenance

RAS proteins directly activate PI3-kinases. Mice bearing a germline mutation in the RAS binding domain of the p110α subunit of PI3-kinse are resistant to the development of RAS-driven tumors. However, it is unknown whether interaction of RAS with PI3-kinase is required in established tumors. The need for RAS interaction with p110α in the maintenance of mutant Kras-driven lung tumors was explored using an inducible mouse model. In established tumors, removal of the ability of p110α to interact with RAS causes long-term tumor stasis and partial regression. This is a tumor cell-autonomous effect, which is improved significantly by combination with MEK inhibition. Total removal of p110α expression or activity has comparable effects, albeit with greater toxicities.

Killing tumors by keeping ras and PI3' kinase apart

Ras proteins mediate PI3K activation through direct binding to p110 catalytic subunits. However, it is unclear when and where this interaction occurs. In this issue of Cancer Cell, Castellano and colleagues report that KRAS-driven lung cancers require the Ras-p110α interaction for full activation of PI3K and tumor maintenance.

The RalGEF/Ral pathway: evaluating an intervention opportunity for Ras cancers

Recognition that Ral guanine nucleotide exchange factors (RalGEFs) are direct Ras effectors and that Ral G-protein activation is a direct consequence of Ras activation has spurred focused efforts to establish the contribution of RalGEF/Ral signaling to oncogenic transformation. Here, we provide a broad-strokes overview of the mechanistic organization of the RalGEF/Ral signaling network, evaluate the evidence for participation of this network in tumorigenic regulatory milieus, consider targeting strategies, and discuss the challenges to and opportunities for clinical development of these targeting strategies.

Inhibiting the RAS-PI3K pathway in cancer therapy

The PI3K pathway is over-activated in the majority of human cancers. This may occur through oncogenic activation of upstream RAS isoforms and tyrosine kinase receptors, or by mutational activation of components of the PI3K pathway themselves. Stimulation of the PI3K pathway enhances growth, survival, and metabolism of cancer cells. Migration, invasion, and angiogenesis are also supported by PI3K signaling. Thus, the PI3K pathway is an attractive candidate for the therapeutic targeting of tumors. Multiple kinases within the PI3Ks, AKT, and mTOR pathway have been selected for inhibition, and dual inhibitors have also been produced. Recently, the development of kinase inhibitors with enhanced specificity and improved pharmacokinetics has facilitated the investigation of PI3K pathway inhibition in clinical trials. Initial reports are encouraging, with tolerable toxicity profiles reported. PI3K inhibitors have provided some benefit as single-agent treatments of advanced solid tumors and the possibilities for enhanced effect with combination treatments look promising. In this chapter, we describe the PI3K inhibitors currently under investigation for the treatment of cancer and discuss the opportunities and obstacles that have been revealed by the latest preclinical and clinical studies.

IGF-IR promotes prostate cancer growth by stabilizing α5β1 integrin protein levels

Dynamic crosstalk between growth factor receptors, cell adhesion molecules and extracellular matrix is essential for cancer cell migration and invasion. Integrins are transmembrane receptors that bind extracellular matrix proteins and enable cell adhesion and cytoskeletal organization. They also mediate signal transduction to regulate cell proliferation and survival. The type 1 insulin-like growth factor receptor (IGF-IR) mediates tumor cell growth, adhesion and inhibition of apoptosis in several types of cancer. We have previously demonstrated that β1 integrins regulate anchorage-independent growth of prostate cancer (PrCa) cells by regulating IGF-IR expression and androgen receptor-mediated transcriptional functions. Furthermore, we have recently reported that IGF-IR regulates the expression of β1 integrins in PrCa cells. We have dissected the mechanism through which IGF-IR regulates β1 integrin expression in PrCa. Here we report that IGF-IR is crucial for PrCa cell growth and that β1 integrins contribute to the regulation of proliferation by IGF-IR. We demonstrate that β1 integrin regulation by IGF-IR does not occur at the mRNA level. Exogenous expression of a CD4 - β1 integrin cytoplasmic domain chimera does not interfere with such regulation and fails to stabilize β1 integrin expression in the absence of IGF-IR. This appears to be due to the lack of interaction between the β1 cytoplasmic domain and IGF-IR. We demonstrate that IGF-IR stabilizes the β1 subunit by protecting it from proteasomal degradation. The α5 subunit, one of the binding partners of β1, is also downregulated along with β1 upon IGF-IR knockdown while no change is observed in the expression of the α2, α3, α4, α6 and α7 subunits. Our results reveal a crucial mechanistic role for the α5β1 integrin, downstream of IGF-IR, in regulating cancer growth.

Two is better than one: combining IGF1R and MEK blockade as a promising novel treatment strategy against KRAS-mutant lung cancer

A small-molecule inhibitor screen on a panel of human lung cancer cell lines has uncovered an unexpected sensitivity of cells expressing oncogenic KRAS toward insulin-like growth factor 1 receptor (IGF1R) inhibition. Combining IGF1R and MAP-ERK kinase blockade led to significant effects on viability in human non-small cell lung cancer (NSCLC) cell lines and in 2 mouse models of oncogenic KRAS-driven lung cancer. The mechanistic basis for this effect seems to be an increased baseline activation of IGF1R-mediated activation of AKT in cells that express oncogenic KRAS. The studies thus point to a novel approach for treatment of KRAS-driven NSCLC, a particularly difficult subset of patients to treat with existing approaches.

Genetics and biomarkers in personalisation of lung cancer treatment

Non-small-cell lung cancer is often diagnosed at the metastatic stage, with median survival of just 1 year. The identification of driver mutations in the epidermal growth factor receptor (EGFR) as the primary oncogenic event in a subset of lung adenocarcinomas led to a model of targeted treatment and genetic profiling of the disease. EGFR tyrosine kinase inhibitors confer remission in 60% of patients, but responses are short-lived. The pre-existing EGFR Thr790Met mutation could be a subclonal driver responsible for these transient responses. Overexpression of AXL and reduced MED12 function are hallmarks of resistance to tyrosine kinase inhibitors in EGFR-mutant non-small-cell lung cancer. Crosstalk between signalling pathways is another mechanism of resistance; therefore, identification of the molecular components involved could lead to the development of combination therapies cotargeting these molecules instead of EGFR tyrosine kinase inhibitor monotherapy. Additionally, novel biomarkers could be identified through deep sequencing analysis of serial rebiopsies before and during treatment.

Cytokines from the tumor microenvironment modulate sirtinol cytotoxicity in A549 lung carcinoma cells

Cytokines in tumor microenvironment play an important role in the success or failure of molecular targeted therapies. We have chosen tumor necrosis factor α (TNF-α), TNF related apoptosis inducing ligand (TRAIL), insulin-like growth factor 1 (IGF-1) and transforming growth factor β (TGF-β) as representative pro-inflammatory, pro-apoptotic, anti-apoptotic and anti-inflammatory tumor derived cytokines. Analysis of Oncomine database revealed the differential expression of these cytokines in a subset of cancer patients. The effects of these cytokines on cytotoxicity of FDA approved drugs - cisplatin and taxol and inhibitors of epidermal growth factor receptor - AG658, Janus kinase - AG490 and SIRT1 - sirtinol were assessed in A549 lung cancer cells. TRAIL augmented cytotoxicity of sirtinol and IGF-1 had a sparing effect. Since TRAIL and IGF-1 differentially modulated sirtinol cytotoxicity, further studies were carried out to identify the mechanisms. Sirtinol or knockdown of SIRT1 increased the expression of death receptors DR4 and DR5 and sensitized A549 cells to TRAIL. Increased cell death in presence of TRAIL and sirtinol was caspase independent and demonstrated classical features of necroptosis. Inhibition of iNOS increased caspase activity and switched the mode of cell death to caspase mediated apoptosis. Interestingly, sirtinol or SIRT1 knockdown did not increase IGF-1R expression. Instead, it abrogated ligand induced downregulation of IGF-1R and increased cell survival through PI3K-AKT pathway. In conclusion, these findings reveal that the tumor microenvironment contributes to modulation of cytotoxicity of drugs and that combination therapy, with agents that increase TRAIL signaling and suppress IGF-1 pathway may potentiate anticancer effect.

PI3K pathway dependencies in endometrioid endometrial cancer cell lines

PURPOSE

Endometrioid endometrial cancers (EEC) frequently harbor coexisting mutations in phosphoinositide 3-kinase (PI3K) pathway genes, including PTEN, PIK3CA, PIK3R1, and KRAS. We sought to define the genetic determinants of PI3K pathway inhibitor response in EEC cells, and whether PTEN-mutant EEC cell lines rely on p110β signaling for survival.

EXPERIMENTAL DESIGN

Twenty-four human EEC cell lines were characterized for their mutation profile and activation state of PI3K and mitogen-activated protein kinase (MAPK) signaling pathway proteins. Cells were treated with pan-class I PI3K, p110α, and p110β isoform-specific, allosteric mTOR, mTOR kinase, dual PI3K/mTOR, mitogen-activated protein/extracellular signal-regulated kinase (MEK), and RAF inhibitors. RNA interference (RNAi) was used to assess effects of KRAS silencing in EEC cells.

RESULTS

EEC cell lines harboring PIK3CA and PTEN mutations were selectively sensitive to the pan-class I PI3K inhibitor GDC-0941 and allosteric mTOR inhibitor temsirolimus, respectively. Subsets of EEC cells with concurrent PIK3CA and/or PTEN and KRAS mutations were sensitive to PI3K pathway inhibition, and only 2 of 6 KRAS-mutant cell lines showed response to MEK inhibition. KRAS RNAi silencing did not induce apoptosis in KRAS-mutant EEC cells. PTEN-mutant EEC cell lines were resistant to the p110β inhibitors GSK2636771 and AZD6482, and only in combination with the p110α selective inhibitor A66 was a decrease in cell viability observed.

CONCLUSIONS

Targeted pan-PI3K and mTOR inhibition in EEC cells may be most effective in PIK3CA- and PTEN-mutant tumors, respectively, even in a subset of EECs concurrently harboring KRAS mutations. Inhibition of p110β alone may not be sufficient to sensitize PTEN-mutant EEC cells and combination with other targeted agents may be required.