Subtype-specific MEK-PI3 kinase feedback as a therapeutic target in pancreatic adenocarcinoma

Agrimoniin is a dual inhibitor of AKT and ERK pathways that inhibit pancreatic cancer cell proliferation

Molecular-targeted therapy has shown its effectiveness in pancreatic cancer, while single-targeted drug often cannot provide long-term benefit because of drug resistance. Fortunately, multitarget combination therapy can reverse drug resistance and achieve better efficacy. The typical treatment characteristics of traditional Chinese medicine monomer on tumor are multiple targets, with small side effects, low toxicity, and so forth. Agrimoniin has been reported to be effective on some cancers, while the mechanism still needs to be clarified. In this study, we used 5-ethynyl-2'-deoxyuridine, cell counting kit-8, flow cytometry, and western blot experiments to confirm that agrimoniin can significantly inhibit the proliferation of pancreatic cancer cell PANC-1 by inducing apoptosis and cell cycle arrest. In addition, by using SC79, LY294002 (the agonist or inhibitor of AKT pathway), and U0126 (the inhibitor of ERK pathway), we found that agrimoniin inhibited cell proliferation by simultaneously inhibiting AKT and ERK pathways. Moreover, agrimoniin could significantly increase the inhibitory effect of LY294002 and U0126 on pancreatic cancer cells. Meanwhile, in vivo experiments also supported the above results. In general, agrimoniin is a double-target inhibitor of AKT and ERK pathways in pancreatic cancer cells; it is expected to be used as a resistance reversal agent of targeted drugs or a synergistic drug of the inhibitor of AKT pathway or ERK pathway.

Tumor heterogeneity: An oncogenic driver of PDAC progression and therapy resistance under stress conditions

Pancreatic ductal adenocarcinoma (PDAC) is a clinically challenging disease usually diagnosed at advanced or metastasized stage. By this year end, there are an expected increase in 62,210 new cases and 49,830 deaths in the United States, with 90% corresponding to PDAC subtype alone. Despite advances in cancer therapy, one of the major challenges combating PDAC remains tumor heterogeneity between PDAC patients and within the primary and metastatic lesions of the same patient. This review describes the PDAC subtypes based on the genomic, transcriptional, epigenetic, and metabolic signatures observed among patients and within individual tumors. Recent studies in tumor biology suggest PDAC heterogeneity as a major driver of disease progression under conditions of stress including hypoxia and nutrient deprivation, leading to metabolic reprogramming. We therefore advance our understanding in identifying the underlying mechanisms that interfere with the crosstalk between the extracellular matrix components and tumor cells that define the mechanics of tumor growth and metastasis. The bilateral interaction between the heterogeneous tumor microenvironment and PDAC cells serves as another important contributor that characterizes the tumor-promoting or tumor-suppressing phenotypes providing an opportunity for an effective treatment regime. Furthermore, we highlight the dynamic reciprocating interplay between the stromal and immune cells that impact immune surveillance or immune evasion response and contribute towards a complex process of tumorigenesis. In summary, the review encapsulates the existing knowledge of the currently applied treatments for PDAC with emphasis on tumor heterogeneity, manifesting at multiple levels, impacting disease progression and therapy resistance under stress.

Recent advances in targeted therapy for pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PDAC) is a fatal disease with a 5-year survival rate of 8% and a median survival of 6 mo. In PDAC, several mutations in the genes are involved, with Kirsten rat sarcoma oncogene (90%), cyclin-dependent kinase inhibitor 2A (90%), and tumor suppressor 53 (75%–90%) being the most common. Mothers against decapentaplegic homolog 4 represents 50%. In addition, the self-preserving cancer stem cells, dense tumor microenvironment (fibrous accounting for 90% of the tumor volume), and suppressive and relatively depleted immune niche of PDAC are also constitutive and relevant elements of PDAC. Molecular targeted therapy is widely utilized and effective in several solid tumors. In PDAC, targeted therapy has been extensively evaluated; however, survival improvement of this aggressive disease using a targeted strategy has been minimal. There is currently only one United States Food and Drug Administration-approved targeted therapy for PDAC – erlotinib, but the absolute benefit of erlotinib in combination with gemcitabine is also minimal (2 wk). In this review, we summarize current targeted therapies and clinical trials targeting dysregulated signaling pathways and components of the PDAC oncogenic process, analyze possible reasons for the lack of positive results in clinical trials, and suggest ways to improve them. We also discuss emerging trends in targeted therapies for PDAC: combining targeted inhibitors of multiple pathways. The PubMed database and National Center for Biotechnology Information clinical trial website (www.clinicaltrials.gov) were queried to identify completed and published (PubMed) and ongoing (clinicaltrials.gov) clinical trials (from 2003-2022) using the keywords pancreatic cancer and targeted therapy. The PubMed database was also queried to search for information about the pathogenesis and molecular pathways of pancreatic cancer using the keywords pancreatic cancer and molecular pathways.

High-Throughput Functional Evaluation of MAP2K1 Variants in Cancer

Activating mutations in mitogen-activated protein kinase kinase 1 (MAP2K1) are involved in a variety of cancers and may be classified according to their RAF dependence. Sensitivity to combined BRAF and MEK treatments is associated with co-mutations of MAP2K1 and BRAF; however, the significance of less frequent MAP2K1 mutations is largely unknown. The transforming potential and drug sensitivity of 100 MAP2K1 variants were evaluated using individual assays and the mixed-all-nominated-in-one method. In addition, A375, a melanoma cell line harboring the BRAF V600E mutation, was used to evaluate the function of the MAP2K1 variants in combination with active RAF signaling. Among a total of 67 variants of unknown significance, 16 were evaluated as oncogenic or likely oncogenic. The drug sensitivity of the individual variants did not vary with respect to BRAF inhibitors, MEK inhibitors (MEKi), or their combination. Sensitivity to BRAF inhibitors was associated with the RAF dependency of the MAP2K1 variants, whereas resistance was higher in RAF-regulated or independent variants compared with RAF-dependent variants. Thus, the synergistic effect of BRAF and MEKis may be observed in RAF-regulated and RAF-dependent variants. MAP2K1 variants exhibit differential sensitivity to BRAF and MEKis, suggesting the importance of individual functional analysis for the selection of optimal treatments for each patient. This comprehensive evaluation reveals precise functional information and provides optimal combination treatment for individual MAP2K1 variants.

KRAS Mutation Variants and Co-occurring PI3K Pathway Alterations Impact Survival for Patients with Pancreatic Ductal Adenocarcinomas

BACKGROUND

KRAS variant alleles may have differential biological properties which impact prognosis and therapeutic options in pancreatic ductal adenocarcinomas (PDA).

MATERIALS AND METHODS

We retrospectively identified patients with advanced PDA who received first-line therapy and underwent blood and/or tumor genomic sequencing at the University of Washington between 2013 and 2020. We examined the incidence of KRAS mutation variants with and without co-occurring PI3K or other genomic alterations and evaluated the association of these mutations with clinicopathological characteristics and survival using a Cox proportional hazards model.

RESULTS

One hundred twenty-six patients had genomic sequencing data; KRAS mutations were identified in 111 PDA and included the following variants: G12D (43)/G12V (35)/G12R (23)/other (10). PI3K pathway mutations (26% vs. 8%) and homologous recombination DNA repair (HRR) defects (35% vs. 12.5%) were more common among KRAS G12R vs. non-G12R mutated cancers. Patients with KRAS G12R vs. non-G12R cancers had significantly longer overall survival (OS) (HR 0.55) and progression-free survival (PFS) (HR 0.58), adjusted for HRR pathway co-mutations among other covariates. Within the KRAS G12R group, co-occurring PI3K pathway mutations were associated with numerically shorter OS (HR 1.58), while no effect was observed on PFS.

CONCLUSIONS

Patients with PDA harboring KRAS G12R vs. non-G12R mutations have longer survival, but this advantage was offset by co-occurring PI3K alterations. The KRAS/PI3K genomic profile could inform therapeutic vulnerabilities in patients with PDA.

Moving Towards Dawn: KRas Signaling and Treatment in Pancreatic Ductal Adenocarcinoma

"Pancreatic ductal adenocarcinoma (PDAC)" is robust, nearly clueless, and all-around deadly among all tumors. Below 10 %, the general 5-year endurance period has remained adamantly unaltered in the last 30 years, regardless of enormous clinical and therapeutic endeavors. The yearly number of deaths is more than the number of recently analyzed cases. Not a classic one, but "Carbohydrate Antigen CA19- 9" remains the prevailing tool for diagnosis. MicroRNAs and non-invasive techniques are now incorporated for the effective prognosis of PDAC than just CA19-9. Mutated "Rat sarcoma virus Ras" conformation "V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog KRas" is 95 % accountable for PDAC, and its active (GTP-bound) formation activates signaling cascade comprising "Rapidly accelerated fibrosarcoma Raf"/"Mitogen-activated protein kinase MEK"/ "Extracellular signal-regulated kinase ERK" with "Phosphoinositide 3-kinase PI3K"/ "protein kinase B Akt"/ "mammalian target of rapamycin mTOR" pathways. KRas has acquired the label of 'undruggable' since the crosstalk in the nexus of pathways compensates for Raf and PI3K signaling cascade blocking. It is arduous to totally regulate KRascoordinated PDAC with traditional medicaments like "gemcitabine GEM" plus nabpaclitaxel/ FOLFIRINOX. For long-haul accomplishments aiming at KRas, future endeavors should be directed to combinatorial methodologies to adequately block KRas pathways at different standpoints. Currently they are contributing to healing PDAC. In this review article, we outline the function of KRas in carcinogenesis in PDAC, its signaling cascade, former techniques utilized in hindering Kras, current and future possibilities for targeting Kras.

Genomic Heterogeneity of Pancreatic Ductal Adenocarcinoma and Its Clinical Impact

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer death due to limited advances in recent years in early diagnosis and personalized therapy capable of overcoming tumor resistance to chemotherapy. In the last decades, significant advances have been achieved in the identification of recurrent genetic and molecular alterations of PDAC including those involving the KRAS, CDKN2A, SMAD4, and TP53 driver genes. Despite these common genetic traits, PDAC are highly heterogeneous tumors at both the inter- and intra-tumoral genomic level, which might contribute to distinct tumor behavior and response to therapy, with variable patient outcomes. Despite this, genetic and genomic data on PDAC has had a limited impact on the clinical management of patients. Integration of genomic data for classification of PDAC into clinically defined entities-i.e., classical vs. squamous subtypes of PDAC-leading to different treatment approaches has the potential for significantly improving patient outcomes. In this review, we summarize current knowledge about the most relevant genomic subtypes of PDAC including the impact of distinct patterns of intra-tumoral genomic heterogeneity on the classification and clinical and therapeutic management of PDAC.

Hacking Pancreatic Cancer: Present and Future of Personalized Medicine

Pancreatic cancer (PC) is a recalcitrant disease characterized by high incidence and poor prognosis. The extremely complex genomic landscape of PC has a deep influence on cultivating a tumor microenvironment, resulting in the promotion of tumor growth, drug resistance, and immune escape mechanisms. Despite outstanding progress in personalized medicine achieved for many types of cancer, chemotherapy still represents the mainstay of treatment for PC. Olaparib was the first agent to demonstrate a significant benefit in a biomarker-selected population, opening the doors for a personalized approach. Despite the failure of a large number of studies testing targeted agents or immunotherapy to demonstrate benefits over standard chemotherapy regimens, some interesting agents, alone or in combination with other drugs, have achieved promising results. A wide spectrum of therapeutic strategies, including immune-checkpoint inhibitors tyrosine kinase inhibitors and agents targeting metabolic pathways or the tumor microenvironment, is currently under investigation. In this review, we aim to provide a comprehensive overview of the current landscape and future directions of personalized medicine for patients affected by PC.

Pancreatitis initiated pancreatic ductal adenocarcinoma: Pathophysiology explaining clinical evidence

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant lethal disease due to its asymptomatic at its early lesion of the disease and drug resistance. Target therapy associated with molecular pathways so far seems not to produce reasonable outcomes. Understanding of the molecular mechanisms underlying inflammation-initiated tumorigenesis may be helpful for development of an effective therapy of the disease. A line of studies showed that pancreatic tumorigenesis was resulted from pancreatitis, which was caused synergistically by various pancreatic cells. This review focuses on those players and their possible clinic implications, such as exocrine acinar cells, ductal cells, and various stromal cells, including pancreatic stellate cells (PSCs), macrophages, lymphocytes, neutrophils, mast cells, adipocytes and endothelial cells, working together with each other in an inflammation-mediated microenvironment governed by a myriad of cellular signaling networks towards PDAC.

Modeling Adaptive Resistance of KRAS Mutant Colorectal Cancer to MAPK Pathway Inhibitors with a Three-Dimensional Tumor Model

Single-agent drug treatment of KRAS^mut colorectal cancers is often ineffective because the activation of compensatory signaling pathways leads to drug resistance. To mimic cyclic chemotherapy treatments of patients, we showed that intermittent treatments of 3D tumor spheroids of KRAS^mut colorectal cancer cells with inhibitors of mitogen-activated protein kinase (MAPK) signaling pathway temporarily suppressed growth of spheroids. However, the efficacy of successive single-agent treatments was significantly reduced. Molecular analysis showed compensatory activation of PI3K/AKT and STAT kinases and EGFR family proteins. To overcome the adaptation of cancer cells to MAPK pathway inhibitors, we treated tumor spheroids with a combination of MEK and EGFR inhibitors. This approach significantly blocked signaling of MAPK and PI3K/AKT pathways and prevented the growth of spheroids, but it was not effective against STAT signaling. Although the combination treatment blocked the matrix invasion of DLD1 cells, additional treatments with STAT inhibitors were necessary to prevent invasiveness of HCT116 cells. Overall, our drug resistance model elucidated the mechanisms of treatment-induced growth and invasiveness of cancer cells and allowed design-driven testing and identifying of effective treatments to suppress these phenotypes.

Developing effective combination therapy for pancreatic cancer: An overview

Pancreatic cancer is a fatal disease. The five-year survival for patients with all stages of this tumor type is less than 10%, with a majority of patients dying from drug resistant, metastatic disease. Gemcitabine has been a standard of care for the treatment of pancreatic cancer for over 20 years, but as a single agent gemcitabine is not curative. Since the only therapeutic option for the over 80 percent of pancreatic cancer patients ineligible for surgical resection is chemotherapy with or without radiation, the last few decades have seen a significant effort to develop effective therapy for this disease. This review addresses preclinical and clinical efforts to identify agents that target molecular characteristics common to pancreatic tumors and to develop mechanism-based combination approaches to therapy. Some of the most promising combinations include agents that inhibit transcription dependent on BET proteins (BET bromodomain inhibitors) or that inhibit DNA repair mediated by PARP (PARP inhibitors).

Preclinical Modelling of PDA: Is Organoid the New Black?

Pancreatic ductal adenocarcinoma (PDA) is a malignancy of the exocrine pancreas with the worst prognosis among all solid tumours, and soon to become the second leading cause of cancer-related deaths. A more comprehensive understanding of the molecular mechanisms underlying this disease is crucial to the development of diagnostic tools as well as to the identification of more effective therapies. High-frequency mutations in PDA occur in “undruggable” genes, and molecular subtyping based on bulk transcriptome analysis does not yet nominate valid therapeutic intervention strategies. Genome-wide sequencing studies have also demonstrated a considerable intra- and inter-patient’s genetic heterogeneity, which further complicate this dire scenario. More than in other malignancies, functionalization of the PDA genome and preclinical modelling at the individual patient level appear necessary to substantially improve survival rates for pancreatic cancer patients. Traditional human PDA models, including monolayer cell cultures and patient-derived xenografts, have certainly led to valuable biological insights in the past years. However, those model systems suffer from several limitations that have contributed to the lack of concordance between preclinical and clinical studies for PDA. Pancreatic ductal organoids have recently emerged as a reliable culture system to establish models from both normal and neoplastic pancreatic tissues. Pancreatic organoid cultures can be efficiently generated from small tissue biopsies, which opens up the possibility of longitudinal studies in individual patients. A proof-of-concept study has demonstrated that patient-derived PDA organoids are able to predict responses to conventional chemotherapy. The use of this three-dimensional culture system has already improved our understanding of PDA biology and promises to implement precision oncology by enabling the alignment of preclinical and clinical platforms to guide therapeutic intervention in PDA.

The significance of gene mutations across eight major cancer types

Mutations occur spontaneously, which can be induced by either chemicals (e.g. benzene) or biological factors (e.g. virus). Not all mutations cause noticeable changes in cellular functions. However, mutation in key cellular genes leads to developmental disorders. It is one of the main ways in which proto-oncogenes can be changed into their oncogenic state. The progressive accumulation of multiple mutations throughout life leads to cancer. In the past few decades, extensive research on cancer biology has discovered many genes and pathways having role in cancer development. In this review, we tried to summarize the current knowledge of mutational effect on different cancer types and its consequences in brief for future reference and guidance of researchers in cancer biology.

Cyclical Treatment of Colorectal Tumor Spheroids Induces Resistance to MEK Inhibitors

Adaptive drug resistance is a major obstacle to successful treatment of colorectal cancers. Physiologic tumor models of drug resistance are crucial to understand mechanisms of treatment failure and improve therapy by developing new therapeutics and treatment strategies. Using our aqueous two-phase system microtechnology, we developed colorectal tumor spheroids and periodically treated them with sub-lethal concentrations of three Mitogen Activated Kinase inhibitors (MEKi) used in clinical trials. We used long-term, periodic treatment and recovery of spheroids to mimic cycles of clinical chemotherapy and implemented a growth rate metric to quantitatively assess efficacy of the MEKi during treatment. Our results showed that efficacy of the MEKi significantly reduced with increased treatment cycles. Using a comprehensive molecular analysis, we established that resistance of colorectal tumor spheroids to the MEKi developed through activation of the PI3K/AKT/mTOR pathway. We also showed that other potential feedback mechanisms, such as STAT3 activation or amplified B-RAF, did not account for resistance to the MEKi. We combined each of the three MEKi with a PI3K/mTOR inhibitor and showed that the combination treatments synergistically blocked resistance to the MEKi. Importantly, and unlike the individual inhibitors, we demonstrated that synergistic concentrations of combinations of MEK and PI3K/mTOR inhibitors effectively inhibited growth of colorectal tumor spheroids in long-term treatments. This proof-of-concept study to model treatment-induced drug resistance of cancer cells using 3D cultures offers a unique approach to identify underlying molecular mechanisms and develop effective treatments.

Epithelial-mesenchymal-transition-inducing transcription factors: new targets for tackling chemoresistance in cancer?

Chemoresistance remains a major complication of cancer treatments. Recent data provide strong evidence that chemoresistance is linked to epithelial-mesenchymal transition (EMT), a latent developmental process, which is re-activated during cancer progression. EMT involves transcriptional reprogramming and is driven by specific EMT transcription factors (EMT-TFs). In this review, we provide support for the idea that EMT-TFs contribute to the development of resistance against cancer therapy and discuss how EMT-TFs might be targeted to advance novel therapeutic approaches to the treatment of cancer.

Molecular subtype specific efficacy of MEK inhibitors in pancreatic cancers

Pancreatic cancer is an increasing cause of cancer related death worldwide. KRAS is the dominant oncogene in this cancer type and molecular rationale would indicate, that inhibitors of the downstream target MEK could be appropriate targeted agents, but clinical trials have failed so far to achieve statistically significant benefit in unselected patients. We aimed to identify predictive molecular biomarkers that can help to define subgroups where MEK inhibitors might be beneficial alone or in combination. Next-generation sequencing data of 50 genes in three pancreatic cancer cell lines (MiaPaCa2, BxPC3 and Panc1) were analyzed and compared to the molecular profile of 138 clinical pancreatic cancer samples to identify the molecular subtypes of pancreatic cancer these cell lines represent. Luminescent cell viability assay was used to determine the sensitivity of cell lines to kinase inhibitors. Western blot was used to analyze the pathway activity of the examined cell lines. According to our cell viability and pathway activity data on these model cell lines only cells harboring the rare G12C KRAS mutation and low EGFR expression are sensitive to single MEK inhibitor (trametinib) treatment. The common G12D KRAS mutation leads to elevated baseline Akt activity, thus treatment with single MEK inhibitors fails. However, combination of MEK and Akt inhibitors are synergistic in this case. In case of wild-type KRAS and high EGFR expression MEK inhibitor induced Akt phosphorylation leads to trametinib resistance which necessitates for MEK and EGFR or Akt inhibitor combination treatment. In all we provide strong preclinical rational and possible molecular mechanism to revisit MEK inhibitor therapy in pancreatic cancer in both monotherapy and combination, based on molecular profile analysis of pancreatic cancer samples and cell lines. According to our most remarkable finding, a small subgroup of patients with G12C KRAS mutation may still benefit from MEK inhibitor monotherapy.

Deciphering the link between PI3K and PAK: An opportunity to target key pathways in pancreatic cancer?

The development of personalised therapies has ushered in a new and exciting era of cancer treatment for a variety of solid malignancies. Yet pancreatic ductal adenocarcinoma (PDAC) has failed to benefit from this paradigm shift, remaining notoriously refractory to targeted therapies. Chemotherapy is the cornerstone of management but can offer only modest survival benefits of a few months with 5-year survival rates rarely exceeding 3%. Despite these disappointing statistics, significant strides have been made towards understanding the complex biology of pancreatic cancer, with deep genomic sequencing identifying novel genetic aberrations and key signalling pathways. The PI3K-PDK1-AKT pathway has received great attention due to its prominence in carcinogenesis. However, efforts to target several components of this network have resulted in only a handful of drugs demonstrating any survival benefit in solid tumors; despite promising pre-clinical results. p-21 activated kinase 4 (PAK4) is a gene that is recurrently amplified or overexpressed in PDAC and both PAK4 and related family member PAK1, have been linked to aberrant RAS activity, a common feature in pancreatic cancer. As regulators of PI3K, PAKs have been highlighted as a potential prognostic marker and therapeutic target. In this review, we discuss the biology of pancreatic cancer and the close interaction between PAKs and the PI3K pathway. We also suggest proposals for future research that may see the development of effective targeted therapies that could finally improve outcomes for this disease.

Effect of Selumetinib and MK-2206 vs Oxaliplatin and Fluorouracil in Patients With Metastatic Pancreatic Cancer After Prior Therapy: SWOG S1115 Study Randomized Clinical Trial

IMPORTANCE

KRAS mutations are common in pancreatic cancer, but directly targeting the KRAS protein has thus far been unsuccessful. The aim of this trial was to block the MEK and PI3K/AKT pathways downstream of the KRAS protein as an alternate treatment strategy to slow cancer growth and prolong survival. This was the first cooperative group trial to evaluate this strategy using molecularly targeted oral combination therapy for the treatment of chemotherapy-refractory pancreatic cancer.

OBJECTIVE

To compare selumetinib and MK-2206 vs modified FOLFOX (mFOLFOX) in patients with metastatic pancreatic cancer for whom gemcitabine-based therapy had failed.

DESIGN, SETTING, AND PARTICIPANTS

SWOG S1115 was a randomized phase 2 clinical trial. Between September 2012 and May 2014, 137 patients with metastatic pancreatic adenocarcinoma for whom gemcitabine-based chemotherapy had failed were randomized to selumetinib plus MK-2206 or mFOLFOX. Patients were randomized in a 1:1 fashion and stratified according to duration of prior systemic therapy and presence of liver metastases.

INTERVENTIONS

Patients received selumetinib 100 mg orally per day plus MK-2206 135 mg orally once per week or mFOLFOX (oxaliplatin, 85 mg/m2 intravenous, and fluorouracil, 2400 mg/m2 intravenous infusion over 46-48 hours) on days 1 and 15 of a 28-day cycle.

MAIN OUTCOMES AND MEASURES

The primary end point of the study was overall survival. Secondary objectives included evaluating toxic effects, objective tumor response, and progression-free survival.

RESULTS

There were 58 patients in the selumetinib plus MK-2206 (experimental) arm (60% male; median [range] age, 69 [54-88] years) and 62 patients in the mFOLFOX arm (35% male; median [range] age, 65 [34-82] years). In the experimental arm, median overall survival was shorter (3.9 vs 6.7 months; HR, 1.37; 95% CI, 0.90-2.08; P = .15), as was median progression-free survival (1.9 vs 2.0 months; HR, 1.61; 95% CI, 1.07-2.43; P = .02). One vs 5 patients had a partial response and 12 vs 14 patients had stable disease in the experimental arm vs mFOLFOX arm. Grade 3 or higher toxic effects were observed in 39 patients treated with selumetinib and MK-2206 vs 23 patients treated with mFOLFOX. More patients in the experimental arm discontinued therapy due to adverse events (13 vs 7 patients).

CONCLUSIONS AND RELEVANCE

Dual targeting of the MEK and PI3K/AKT pathways downstream of KRAS by selumetinib plus MK-2206 did not improve overall survival in patients with metastatic pancreatic adenocarcinoma for whom gemcitabine-based chemotherapy had failed. This was the first randomized prospective evaluation of mFOLFOX in the US population that showed comparable results to CONKO-003 and PANCREOX.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01658943.

Co-clinical Assessment of Tumor Cellularity in Pancreatic Cancer

Purpose: Tumor heterogeneity is a hallmark of pancreatic ductal adenocarcinoma (PDAC). It determines tumor biology including tumor cellularity (i.e., amount of neoplastic cells and arrangement into clusters), which is related to the proliferative capacity and differentiation and the degree of desmoplasia among others. Given the close relation of tumor differentiation with differences in progression and therapy response or, e.g., the recently reported protective role of tumor stroma, we aimed at the noninvasive detection of PDAC groups, relevant for future personalized approaches. We hypothesized that histologic differences in PDAC tissue composition are detectable by the noninvasive diffusion weighted- (DW-) MRI-derived apparent diffusion coefficient (ADC) parameter.Experimental design: PDAC cellularity was quantified histologically and correlated with the ADC parameter and survival in genetically engineered mouse models and human patients.Results: Histologic analysis showed an inverse relationship of tumor cellularity and stroma content. Low tumor cellularity correlated with a significantly prolonged mean survival time (PDAC^low = 21.93 months vs. PDAC^med = 12.7 months; log-rank P < 0.001; HR = 2.23; CI, 1.41-3.53). Multivariate analysis using the Cox regression method confirmed tumor cellularity as an independent prognostic marker (P = 0.034; HR = 1.73; CI, 1.04-2.89). Tumor cellularity showed a strong negative correlation with the ADC parameter in murine (r = -0.84; CI, -0.90- -0.75) and human (r = -0.79; CI, -0.90 to -0.56) PDAC and high preoperative ADC values correlated with prolonged survival (ADC^high = 41.7 months; ADC^low = 14.77 months; log rank, P = 0.040) in PDAC patients.Conclusions: This study identifies high tumor cellularity as a negative prognostic factor in PDAC and supports the ADC parameter for the noninvasive identification of PDAC groups. Clin Cancer Res; 23(6); 1461-70. ©2016 AACR.

Molecular therapeutics in pancreas cancer

The emergence of the "precision-medicine" paradigm in oncology has ushered in tremendous improvements in patient outcomes in a wide variety of malignancies. However, pancreas ductal adenocarcinoma (PDAC) has remained an obstinate challenge to the oncology community and continues to be associated with a dismal prognosis with 5-year survival rates consistently less than 5%. Cytotoxic chemotherapy with gemcitabine-based regimens has been the cornerstone of treatment in PDAC especially because most patients present with inoperable disease. But in recent years remarkable basic science research has improved our understanding of the molecular and genetic basis of PDAC. Whole genomic analysis has exemplified the genetic heterogeneity of pancreas cancer and has led to ingenious efforts to target oncogenes and their downstream signaling cascades. Novel stromal depletion strategies have been devised based on our enhanced recognition of the complex architecture of the tumor stroma and the various mechanisms in the tumor microenvironment that sustain tumorigenesis. Immunotherapy using vaccines and immune checkpoint inhibitors has also risen to the forefront of therapeutic strategies against PDAC. Furthermore, adoptive T cell transfer and strategies to target epigenetic regulators are being explored with enthusiasm. This review will focus on the recent advances in molecularly targeted therapies in PDAC and offer future perspectives to tackle this lethal disease.

A Multicenter, Open-Label Phase II Clinical Trial of Combined MEK plus EGFR Inhibition for Chemotherapy-Refractory Advanced Pancreatic Adenocarcinoma

PURPOSE

On the basis of preclinical evidence of synergistic activity between MEK and EGFR inhibitors in pancreatic ductal adenocarcinoma (PDAC), we evaluated the safety and efficacy of selumetinib, a MEK1/2 inhibitor, plus erlotinib in patients with previously treated advanced PDAC.

EXPERIMENTAL DESIGN

In this single-arm phase II trial, eligible patients received the combination of erlotinib 100 mg plus selumetinib 100 mg daily in 3-week cycles. Study assessments included measurement of clinical outcomes, with a primary endpoint of overall survival, and exploration of potential molecular predictors of treatment benefit.

RESULTS

Forty-six patients were enrolled and received a median of two cycles (range, 1-7). Although no objective responses were observed, 19 patients (41%) showed evidence of stable disease for ≥6 weeks, and 13 of 34 patients (38%) had a CA19-9 decline ≥50%. Median progression-free survival was 1.9 months [95% confidence interval (CI), 1.4-3.3 months], with a median overall survival of 7.3 months (95% CI, 5.2-8.0 months). Common adverse events included rash, diarrhea, and nausea/vomiting. Patients with tumors exhibiting an epithelial phenotype (demonstrated by a high level of E-cadherin expression) were more likely to be sensitive to study treatment. Tumor-derived DNA was detectable in plasma from the majority of patients using next-generation digital DNA sequencing, and its relative abundance correlated with tumor burden.

CONCLUSIONS

A therapeutic strategy of dual targeted inhibition of the MEK and EGFR pathways shows modest antitumor activity in pancreatic cancer. Specific molecular subtypes may derive greatest benefit from this combination. Further exploration, both with more potent MEK inhibitors and in molecularly enriched patient subsets, is warranted.

MEK1 and MEK2 inhibitors and cancer therapy: the long and winding road

The role of the ERK signalling pathway in cancer is thought to be most prominent in tumours in which mutations in the receptor tyrosine kinases RAS, BRAF, CRAF, MEK1 or MEK2 drive growth factor-independent ERK1 and ERK2 activation and thence inappropriate cell proliferation and survival. New drugs that inhibit RAF or MEK1 and MEK2 have recently been approved or are currently undergoing late-stage clinical evaluation. In this Review, we consider the ERK pathway, focusing particularly on the role of MEK1 and MEK2, the 'gatekeepers' of ERK1/2 activity. We discuss their validation as drug targets, the merits of targeting MEK1 and MEK2 versus BRAF and the mechanisms of action of different inhibitors of MEK1 and MEK2. We also consider how some of the systems-level properties (intrapathway regulatory loops and wider signalling network connections) of the ERK pathway present a challenge for the success of MEK1 and MEK2 inhibitors, discuss mechanisms of resistance to these inhibitors, and review their clinical progress.

Pancreatic cancer: optimizing treatment options, new, and emerging targeted therapies

Pancreatic cancer is the fourth leading cause of cancer death in the US and is expected to become the second leading cause of cancer-related deaths in the next decade. Despite 5-fluorouracil/leucovorin with irinotecan and oxaliplatin (FOLFIRINOX) and gemcitabine/nab-paclitaxel significantly improving outcomes for metastatic cancer, refractory disease still poses significant challenges. Difficulties with early detection and the inherent chemo- and radio-resistant nature of this malignancy led to attempts to define the sequential biology of pancreatic cancer in order to improve survival outcomes. Pancreatic adenocarcinoma is characterized by several germline or acquired genetic mutations, the most common being KRAS (90%), CDK2NA (90%), TP53 (75%-90%), DPC4/SMAD4 (50%). In addition, the tumor microenvironment, chemoresistant cancer stem cells, and the desmoplastic stroma have been the target of some promising clinical investigations. Among the core pathways reproducibly shown to lead the development and progression of this disease, DNA repair, apoptosis, G1/S cell cycle transition, KRAS, Wnt, Notch, Hedgehog, TGF-beta, and other cell invasion pathways, have been the target of "precision therapeutics". No single molecularly targeted therapeutic though has been uniformly successful, probably due to the tumor heterogeneity, but biomarker research is evolving and it hopes to select more patients likely to benefit. Recent reports note activity with immunotherapies such as CD40 agonists, CCR2 inhibitors, cancer vaccines, and novel combinations against the immunosuppressive tumor milieu are ongoing. While many obstacles still exist, clearly we are making progress in deciphering the heterogeneity within pancreatic cancers. Integrating conventional and immunological targeting will be the key to effective treatment of this deadly disease.

Progress in the treatment of metastatic pancreatic cancer and the search for next opportunities

A growing number of therapeutic options are now available for patients with metastatic pancreatic cancer, informed by positive results from recently completed phase III clinical trials. These have led to modest, if not necessarily transformative, improvements in clinical outcomes. Although the standard of care for metastatic disease remains cytotoxic therapy, a variety of novel therapeutic approaches are currently under active investigation, several of which have already demonstrated encouraging results in phase I/II studies. The following three broad categories (with significant overlap among them) are highlighted here: stromal-depleting agents, immunotherapies, and signal transduction inhibitors. The mechanistic rationale, limitations, and promise of each of these strategies specific to pancreatic cancer are discussed, as are the aspects of this disease and this patient population that pose ongoing challenges in terms of both therapeutic management and biomarker-driven trial design.

Select biomarkers for tumors of the gastrointestinal tract: present and future

CONTEXT

Advances in molecular biomarkers of the gastrointestinal tract have contributed to a decline in the incidence of and mortality from diseases of the gastrointestinal tract. The discovery and clinical validation of new biomarkers are important to personalized cancer therapy, and numerous clinical trials are currently ongoing to help identify individualized therapy affecting these biomarkers and molecular mechanisms they represent. Distinct molecular pathways leading to cancers of the colorectum, esophagus, stomach, small bowel, and pancreas have been identified. Using biomarkers in these pathways to direct patient care, including selection of proper molecular testing for identification of actionable mutations and reporting the results of these biomarkers to guide clinicians and genetic counselors, is paramount.

OBJECTIVE

To examine and review select clinically actionable biomarkers of the colon, esophagus, stomach, small bowel, and pancreas, including present and future biomarkers with relevant clinical trials.

DATA SOURCES

Extensive literature review and practical and consultation experience of the authors.

CONCLUSIONS

Although numerous biomarkers have been identified and are currently guiding patient therapy, few have shown evidence of clinical utility in the management of patients with gastrointestinal cancers. Inconsistent results and discordant proposed algorithms for testing were identified throughout the literature; however, the potential for biomarkers to improve outcomes for patients with gastrointestinal cancer remains high. Continued advances through high-quality studies are needed.

Pathology of pancreatic ductal adenocarcinoma: Facts, challenges and future developments

Despite major improvements concerning its diagnosis and treatment, pancreatic ductal adenocarcinoma (PDAC) remains an aggressive disease with an extremely poor prognosis. Pathology, as interface discipline between basic and clinical medicine, has substantially contributed to the recent developments and has laid the basis for further progress. The definition and classification of precursor lesions of PDAC and their molecular characterization is a fundamental step for the potential identification of biomarkers and the development of imaging methods for early detection. In addition, by integrating findings in humans with the knowledge acquired through the investigation of transgenic mouse models for PDAC, a new model for pancreatic carcinogenesis has been proposed and partially validated in individuals with genetic predisposition for PDAC. The introduction and validation of a standardized system for pathology reporting based on the axial slicing technique has shown that most pancreatic cancer resections are R1 resections and that this is due to inherent anatomical and biological properties of PDAC. This standardized assessment of prognostic relevant parameters represents the basis for the successful conduction of multicentric studies and for the interpretation of their results. Finally, recent studies have shown that distinct molecular subtypes of PDAC exist and are associated with different prognosis and therapy response. The prospective validation of these results and the integration of molecular analyses in a comprehensive pathology report in the context of individualised cancer therapy represent a major challenge for the future.

Intrinsic and acquired resistance to MEK1/2 inhibitors in cancer

Recent clinical data with BRAF and MEK1/2 [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase 1/2] inhibitors have demonstrated the remarkable potential of targeting the RAF-MEK1/2-ERK1/2 signalling cascade for the treatment of certain cancers. Despite these advances, however, only a subset of patients respond to these agents in the first instance, and, of those that do, acquired resistance invariably develops after several months. Studies in vitro have identified various mechanisms that can underpin intrinsic and acquired resistance to MEK1/2 inhibitors, and these frequently recapitulate those observed clinically. In the present article, we review these mechanisms and also discuss recent advances in our understanding of how MEK1/2 inhibitor activity is influenced by pathway feedback.

Epithelial-to-mesenchymal transition (EMT) in intraductal papillary mucinous neoplasm (IPMN) is associated with high tumor grade and adverse outcomes

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is generally associated with increased tumor aggressiveness and poor prognosis. We evaluated EMT characteristics in intraductal papillary mucinous neoplasm (IPMN) tumor specimens and their potential role as biomarkers for malignancy, metastasis, and adverse patient outcomes.

METHODS

IPMN surgical specimens were identified and reviewed by two gastrointestinal pathologists. Immunohistochemical analysis of E-cadherin, vimentin, and ZEB-1 was performed. Samples were linked to clinicopathologic and outcome data for these patients. Western blot test was used to evaluate ZEB-1 expression in IPMN samples; 846 human miRNAs were profiled, and EMT-related differentially expressed miRNAs were validated using quantitative real-time polymerase chain reaction.

RESULTS

Fifty-eight IPMN specimens and five normal pancreatic tissue samples were immunohistochemically stained and scored. E-cadherin expression was significantly lower in malignant versus low-grade IPMN (p < 0.05). Vimentin expression was increased in malignant IPMN tumor samples (p < 0.05). EMT was associated with increased lymph node metastasis and decreased survival of malignant IPMN patients (p < 0.05). ZEB-1, an imperative EMT regulator, was exclusively expressed by malignant IPMN tumors. miRNA hierarchical clustering demonstrated grouping of two main IPMN subgroups: low-grade IPMN versus high-grade IPMN and carcinoma. Twenty-four miRNAs were differentially expressed (14 up-regulated, 10 down-regulated). The EMT-regulatory miRNAs, miR-200c and miR-141, were down-regulated (twofold and 1.8-fold decrease, respectively) in malignant versus low-grade IPMN (p < 0.05).

CONCLUSIONS

EMT may play a role in IPMN tumorigenesis and metastasis. EMT molecular deregulations could be utilized as potential novel biomarkers for the identification of high-risk IPMN patients.