Targeting the HER2-ELF3-KRAS axis: a novel therapeutic strategy for KRASG13D colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent cancers worldwide, with KRAS mutations playing a significant role in its tumorigenesis. Among the KRAS variants, the G13D mutation is associated with poor prognosis and distinctive biological behaviors. This study focuses on the role of HER2, a critical prognostic and predictive biomarker, in modulating the unique characteristics of KRASG13D-mutated CRCs. We identified a novel transcriptional regulatory network involving HER2, ELF3, and KRAS, with ELF3 acting as a key transcription factor (TF) that regulates KRAS expression under conditions of HER2 overexpression. Our findings reveal that this HER2-ELF3-KRAS axis is exclusively activated in KRASG13D, driving aggressive oncogenic features and conferring resistance to cetuximab (CTX) therapy. Through comprehensive analysis of gene expression profiles, we demonstrated that HER2 is a crucial therapeutic target specifically for KRASG13D CRCs. To explore this further, we introduced YK1, a small molecule inhibitor designed to disrupt the ELF3-MED23 interaction, leading to the transcriptional downregulation of HER2 and KRAS. This intervention significantly attenuated the HER2-ELF3-KRAS axis, sensitizing KRASG13D CRCs to CTX and reducing their tumorigenic potential by inhibiting the epithelial-to-mesenchymal transition process. Our study underscores the importance of HER2 as a key determinant in the unique biological characteristics of KRASG13D CRCs and highlights the therapeutic potential of targeting the HER2-ELF3-KRAS axis. By presenting YK1 as a novel pharmacological approach, we provide a promising strategy for developing tailored interventions for KRASG13D CRCs, contributing to the ongoing efforts in precision medicine for CRCs.

Platform combining statistical modeling and patient-derived organoids to facilitate personalized treatment of colorectal carcinoma

BACKGROUND

We propose a new approach for designing personalized treatment for colorectal cancer (CRC) patients, by combining ex vivo organoid efficacy testing with mathematical modeling of the results.

METHODS

The validated phenotypic approach called Therapeutically Guided Multidrug Optimization (TGMO) was used to identify four low-dose synergistic optimized drug combinations (ODC) in 3D human CRC models of cells that are either sensitive or resistant to first-line CRC chemotherapy (FOLFOXIRI). Our findings were obtained using second order linear regression and adaptive lasso.

RESULTS

The activity of all ODCs was validated on patient-derived organoids (PDO) from cases with either primary or metastatic CRC. The CRC material was molecularly characterized using whole-exome sequencing and RNAseq. In PDO from patients with liver metastases (stage IV) identified as CMS4/CRIS-A, our ODCs consisting of regorafenib [1 mM], vemurafenib [11 mM], palbociclib [1 mM] and lapatinib [0.5 mM] inhibited cell viability up to 88%, which significantly outperforms FOLFOXIRI administered at clinical doses. Furthermore, we identified patient-specific TGMO-based ODCs that outperform the efficacy of the current chemotherapy standard of care, FOLFOXIRI.

CONCLUSIONS

Our approach allows the optimization of patient-tailored synergistic multi-drug combinations within a clinically relevant timeframe.

Identification of RAS mutant biomarkers for EGFR inhibitor sensitivity using a systems biochemical approach

Mutations can be important biomarkers that influence the selection of specific cancer treatments. We recently combined mathematical modeling of RAS signaling network biochemistry with experimental cancer cell biology to determine why KRAS G13D is a biomarker for sensitivity to epidermal growth factor receptor (EGFR)-targeted therapies. The critical mechanistic difference between KRAS G13D and the other most common KRAS mutants is impaired binding to tumor suppressor Neurofibromin (NF1). Here, we hypothesize that impaired binding to NF1 is a "biophysical biomarker" that defines other RAS mutations that retain therapeutic sensitivity to EGFR inhibition. Both computational and experimental investigations support our hypothesis. By screening RAS mutations for this biophysical characteristic, we identify 10 additional RAS mutations that appear to be biomarkers for sensitivity to EGFR inhibition. Altogether, this work suggests that personalized medicine may benefit from migrating from gene-based and allele-based biomarker strategies to biomarkers based on biophysically defined subsets of mutations.

Discernment between candidate mechanisms for KRAS G13D colorectal cancer sensitivity to EGFR inhibitors

Phase three clinical trial evidence suggests that colorectal cancers with the KRAS G13D mutation may benefit from EGFR inhibitors, like cetuximab, in contrast to the other most common KRAS mutations. A mechanism to explain why this mutation behaves differently from other KRAS mutations had long been lacking. Two recent studies have reproduced KRAS G13D specific sensitivity to cetuximab in cellular models, and both have implicated the tumor suppressor NF1 as a critical variable in determining sensitivity and resistance. One study proposes a mechanism that focuses on the inhibition of active, GTP-bound wild-type RAS, which is proposed to occur to a greater extent in KRAS G13D tumors due to the inability of KRAS G13D to bind NF1 well. The other study suggests NF1 can convert GTP-bound KRAS G13D to inactive, GDP-bound KRAS G13D. Here, we report an inability to reproduce cellular and biophysical studies that suggested NF1 has strong GTPase activity on KRAS G13D. We also report additional data that further suggests only WT RAS-GTP levels are reduced with EGFR inhibition and that KRAS G13D is impaired in binding to NF1. These new experiments further support a mechanism in which cetuximab inhibits wild-type (HRAS and NRAS) signals in KRAS G13D colorectal cancers. Video Abstract.

A mechanism for the response of KRASG13D expressing colorectal cancers to EGFR inhibitors

Previous analysis of Phase 3 clinical trial data for colorectal cancer patients treated with cetuximab revealed that patients harboring a KRAS mutation did not benefit from treatment. This finding set the stage for one of the first examples of cancer personalized medicine. Confusingly, patients with a Glycine to Aspartic Acid mutation at amino acid 13 of KRAS (KRAS^G13D) appeared to respond positively to cetuximab, suggesting this mutation is an exception to the rule that KRAS mutations confer resistance to Epidermal Growth Factor Receptor (EGFR) inhibitors. Oncologists have stated that the mechanism that explains why the KRAS^G13D mutation is an exception should be identified before KRAS^G13D colorectal cancer patients should be treated differently. We have recently elucidated this mechanism using mathematical modeling of the KRAS biochemical system coupled with experimental biology. The mechanism we revealed involves a cetuximab-mediated reduction in HRAS and NRAS signaling within KRAS^G13D cancer cells, owing to impaired binding of KRAS^G13D to the tumor suppressor, Neurofibromin (NF1).

A systems mechanism for KRAS mutant allele-specific responses to targeted therapy

Cancer treatment decisions are increasingly guided by which specific genes are mutated within each patient's tumor. For example, agents inhibiting the epidermal growth factor receptor (EGFR) benefit many colorectal cancer (CRC) patients, with the general exception of those whose tumor includes a KRAS mutation. However, among the various KRAS mutations, that which encodes the G13D mutant protein (KRASG13D) behaves differently; for unknown reasons, KRASG13D CRC patients benefit from the EGFR-blocking antibody cetuximab. Controversy surrounds this observation, because it contradicts the well-established mechanisms of EGFR signaling with regard to RAS mutations. Here, we identified a systems-level, mechanistic explanation for why KRASG13D cancers respond to EGFR inhibition. A computational model of RAS signaling revealed that the biophysical differences between the three most common KRAS mutants were sufficient to generate different sensitivities to EGFR inhibition. Integrated computation with experimentation then revealed a nonintuitive, mutant-specific dependency of wild-type RAS activation by EGFR that is determined by the interaction strength between KRAS and the tumor suppressor neurofibromin (NF1). KRAS mutants that strongly interacted with and competitively inhibited NF1 drove wild-type RAS activation in an EGFR-independent manner, whereas KRASG13D weakly interacted with and could not competitively inhibit NF1 and, thus, KRASG13D cells remained dependent on EGFR for wild-type RAS activity. Overall, our work demonstrates how systems approaches enable mechanism-based inference in genomic medicine and can help identify patients for selective therapeutic strategies.

Intrinsic GTPase Activity of K-RAS Monitored by Native Mass Spectrometry

Mutations in RAS are associated with many different cancers and have been a therapeutic target for more than three decades. RAS cycles from an active to inactive state by both intrinsic and GTPase-activating protein (GAP)-stimulated hydrolysis. The activated enzyme interacts with downstream effectors, leading to tumor proliferation. Mutations in RAS associated with cancer are insensitive to GAP, and the rate of inactivation is limited to their intrinsic hydrolysis rate. Here, we use high-resolution native mass spectrometry (MS) to determine the kinetics and transition state thermodynamics of intrinsic hydrolysis for K-RAS and its oncogenic mutants. MS data reveal heterogeneity where both 2'-deoxy and 2'-hydroxy forms of GDP (guanosine diphosphate) and GTP (guanosine triphosphate) are bound to the recombinant enzyme. Intrinsic GTPase activity is directly monitored by the loss in mass of K-RAS bound to GTP, which corresponds to the release of phosphate. The rates determined from MS are in direct agreement with those measured using an established solution-based assay. Our results show that the transition state thermodynamics for the intrinsic GTPase activity of K-RAS is both enthalpically and entropically unfavorable. The oncogenic mutants G12C, Q61H, and G13D unexpectedly exhibit a 2'-deoxy GTP intrinsic hydrolysis rate higher than that for GTP.

K-ras oncogene mutation in pterygium

PurposePterygium is claimed to be a benign proliferation triggered by prolonged exposure to ultraviolet radiation. The frequency of K-ras oncogene mutation, which is among the initial mutations in tumorigenesis, is evaluated in this study.Patients and methodsIn this prospective randomized clinical, trial pterygium tissues and normal conjunctiva tissue specimens are obtained from the superotemporal quadrant of patients who underwent primary pterygium excision with autograft transplantation. DNA extraction from tissues was performed using the QIAamp DNA FFPE tissue kit. A PCR reaction was performed to amplify sequences containing codons 12, 13, and 61 of the K-ras gene in DNA. These PCR products then underwent the 'pyrosequencing' procedure for mutations at these codons.ResultsPterygium and normal conjunctival tissue samples of 25 patients (10 females, 15 males) were evaluated in the study. The mean age of the patients was 54.54±13.13 years. Genetic analysis revealed no K-ras mutations in normal conjunctival tissues, whereas pterygium tissues of the same cases demonstrated mutation at codon 12 in one case and mutations at codon 61 in seven cases, which was statistically significant (P<0.05). The point missense mutations at codon 61 were glutamine to arginine (Glu61Arg CAA>CGA) in four cases and glutamine to leucine (Glu61Leu CAA>CTA) in three cases.ConclusionThe significantly higher frequency of codon 61 mutation of the ras oncogene in primary and bilateral pterygium specimens compared with normal conjunctiva supports the tumoral origin of pterygium, and thus set the stage for research into a targeted therapy for pterygium with better outcomes than surgical excision.

Response to Cetuximab With or Without Irinotecan in Patients With Refractory Metastatic Colorectal Cancer Harboring the KRAS G13D Mutation: Australasian Gastro-Intestinal Trials Group ICECREAM Study

Purpose

RAS mutations predict lack of response to epidermal growth factor receptor monoclonal antibody therapy in patients with metastatic colorectal cancer (mCRC), but preclinical studies and retrospective clinical data suggest that patients with tumors harboring the exon 2 KRAS G13D mutation may benefit from cetuximab. We aimed to assess cetuximab monotherapy and cetuximab plus irinotecan in patients with molecularly selected (G13D mutation) chemotherapy-refractory mCRC in a randomized phase II trial of this rare molecular subtype.

Patients and Methods

Patients with chemotherapy-refractory KRAS G13D mutation–positive mCRC who had progressed within 6 months of irinotecan therapy were randomly assigned to cetuximab 400 mg/m2 loading dose and then 250 mg/m2 once per week with or without irinotecan 180 mg/m2 once every 2 weeks. The primary end point was 6-month progression-free survival; secondary end points were response rate, overall survival, quality of life, and toxicity.

Results

Fifty-one of 53 patients recruited over 2 years were eligible. The 6-month progression-free survival rate was 10% (95% CI, 2% to 26%) for cetuximab versus 23% (95% CI, 9% to 40%) for cetuximab plus irinotecan with a hazard ratio of 0.74 (95% CI, 0.42 to 1.32). Response and stable disease rates were 0% and 58% for monotherapy versus 9% and 70% for combination treatment, respectively. Overall survival and quality of life were similar; toxicities were higher with combination therapy.

Conclusion

In patients with G13D-mutated chemotherapy-refractory mCRC, there was no statistically significant improvement in disease control at 6 months with either cetuximab monotherapy or cetuximab plus irinotecan. No responses were seen with single-agent cetuximab. The responses observed with the combination of cetuximab and irinotecan may reflect true drug synergy or persistent irinotecan sensitivity. The ICECREAM (Irinotecan Cetuximab Evaluation and Cetuximab Response Evaluation Among Patients with a G13D Mutation) study demonstrates the need to prospectively evaluate hypotheses that were previously supported by retrospective analyses and exemplifies the value of international collaboration in trials of rare molecular subtypes.

ICECREAM: randomised phase II study of cetuximab alone or in combination with irinotecan in patients with metastatic colorectal cancer with either KRAS, NRAS, BRAF and PI3KCA wild type, or G13D mutated tumours

Background

Patients with metastatic colorectal cancer whose disease has progressed on oxaliplatin- and irinotecan-containing regimens may benefit from EGFR-inhibiting monoclonal antibodies if they do not contain mutations in the KRAS gene (are “wild type”). It is unknown whether these antibodies, such as cetuximab, are more efficacious in refractory metastatic colorectal cancer as monotherapy, or in combination with irinotecan. Lack of mutation in KRAS, BRAF and PIK3CA predicts response to EFGR-inhibitors. The ICECREAM trial examines the question of monotherapy versus combination with chemotherapy in two groups of patients: those with a “quadruple wild type” tumour genotype (no mutations in KRAS, NRAS, PI3KCA or BRAF genes) and those with the specific KRAS mutation in codon G13D, for whom possibly EGFR-inhibitor efficacy may be equivalent.

Methods and design

ICECREAM is a randomised, phase II, open-label, controlled trial comparing the efficacy of cetuximab alone or with irinotecan in patients with “quadruple wild type” or G13D-mutated metastatic colorectal cancer, whose disease has progressed on, or who are intolerant of oxaliplatin- and fluoropyrimidine-based chemotherapy. The primary endpoint is the 6-month progression-free survival benefit of the treatment regimen. Secondary endpoints are response rate, overall survival, and quality of life. The tertiary endpoint is prediction of outcome with further biological markers. International collaboration has facilitated recruitment in this prospective trial of treatment in these infrequently found molecular subsets of colorectal cancer.

Discussion

This unique trial will yield prospective information on the efficacy of cetuximab and whether this is further enhanced with chemotherapy in two distinct populations of patients with metastatic colorectal cancer: the “quadruple wild type”, which may ‘superselect’ for tumours sensitive to EGFR-inhibition, and the rare KRAS G13D mutated tumours, which are also postulated to be sensitive to the drug. The focus on establishing both positive and negative predictive factors for the response to targeted therapy is an attempt to improve outcomes, reduce toxicity and contain treatment costs. Tissue and blood will yield a resource for molecular studies. Recruitment, particularly of patients with the rare G13D mutation, will demonstrate the ability for international collaboration to run prospective trials in small colorectal cancer molecular subgroups.

Trial registration

Australian and New Zealand Clinical Trials Registry: ACTRN12612000901808, registered 16 August 2012.

Phosphoproteomic Analyses of NRAS(G12) and NRAS(Q61) Mutant Melanocytes Reveal Increased CK2α Kinase Levels in NRAS(Q61) Mutant Cells

In melanoma, mutant and thereby constantly active neuroblastoma rat sarcoma (NRAS) affects 15-20% of tumors, contributing to tumor initiation, growth, invasion, and metastasis. Recent therapeutic approaches aim to mimic RAS extinction by interfering with critical signaling pathways downstream of the mutant protein. This study investigates the phosphoproteome of primary human melanocytes bearing mutations in the two hot spots of NRAS, NRAS(G12) and NRAS(Q61). Stable isotope labeling by amino acids in cell culture followed by mass spectrometry identified 14,155 spectra of 3,371 unique phosphopeptides mapping to 1,159 proteins (false discovery rate < 2%). Data revealed pronounced PI3K/AKT signaling in NRAS(G12V) mutant cells and pronounced mitogen-activated protein kinase (MAPK) signaling in NRAS(Q61L) variants. Computer-based prediction models for kinases involved, revealed that CK2α is significantly overrepresented in primary human melanocytes bearing NRAS(Q61L) mutations. Similar differences were found in human NRAS(Q61) mutant melanoma cell lines that were also more sensitive to pharmacologic CK2α inhibition compared with NRAS(G12) mutant cells. Furthermore, CK2α levels were pronounced in patient samples of NRAS(Q61) mutant melanoma at the mRNA and protein level. The preclinical findings of this study reveal that codon 12 and 61 mutant NRAS cells have distinct signaling characteristics that could allow for the development of more effective, mutation-specific treatment modalities.

Prediction of response to anti-EGFR antibody-based therapies by multigene sequencing in colorectal cancer patients

BACKGROUND

The anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (moAbs) cetuximab or panitumumab are administered to colorectal cancer (CRC) patients who harbor wild-type RAS proto-oncogenes. However, a percentage of patients do not respond to this treatment. In addition to mutations in the RAS genes, mutations in other genes, such as BRAF, PI3KCA, or PTEN, could be involved in the resistance to anti-EGFR moAb therapy.

METHODS

In order to develop a comprehensive approach for the detection of mutations and to eventually identify other genes responsible for resistance to anti-EGFR moAbs, we investigated a panel of 21 genes by parallel sequencing on the Ion Torrent Personal Genome Machine platform. We sequenced 65 CRCs that were treated with cetuximab or panitumumab. Among these, 37 samples were responsive and 28 were resistant.

RESULTS

We confirmed that mutations in EGFR-pathway genes (KRAS, NRAS, BRAF, PI3KCA) were relevant for conferring resistance to therapy and could predict response (p = 0.001). After exclusion of KRAS, NRAS, BRAF and PI3KCA combined mutations could still significantly associate to resistant phenotype (p = 0.045, by Fisher exact test). In addition, mutations in FBXW7 and SMAD4 were prevalent in cases that were non-responsive to anti-EGFR moAb. After we combined the mutations of all genes (excluding KRAS), the ability to predict response to therapy improved significantly (p = 0.002, by Fisher exact test).

CONCLUSIONS

The combination of mutations at KRAS and at the five gene panel demonstrates the usefulness and feasibility of multigene sequencing to assess response to anti-EGFR moAbs. The application of parallel sequencing technology in clinical practice, in addition to its innate ability to simultaneously examine the genetic status of several cancer genes, proved to be more accurate and sensitive than the presently in use traditional approaches.

RAS testing of colorectal carcinoma—a guidance document from the Association of Clinical Pathologists Molecular Pathology and Diagnostics Group

Analysis of colorectal carcinoma (CRC) tissue for KRAS codon 12 or 13 mutations to guide use of anti-epidermal growth factor receptor (EGFR) therapy is now considered mandatory in the UK. The scope of this practice has been recently extended because of data indicating that NRAS mutations and additional KRAS mutations also predict for poor response to anti-EGFR therapy. The following document provides guidance on RAS (i.e., KRAS and NRAS) testing of CRC tissue in the setting of personalised medicine within the UK and particularly within the NHS. This guidance covers issues related to case selection, preanalytical aspects, analysis and interpretation of such RAS testing.

Differential in vivo tumorigenicity of diverse KRAS mutations in vertebrate pancreas: A comprehensive survey

Somatic activation of the KRAS proto-oncogene is evident in almost all pancreatic cancers, and appears to represent an initiating event. These mutations occur primarily at codon 12 and less frequently at codons 13 and 61. While some studies have suggested that different KRAS mutations may have variable oncogenic properties, to date there has been no comprehensive functional comparison of multiple KRAS mutations in an in vivo vertebrate tumorigenesis system. We generated a Gal4/UAS-based zebrafish model of pancreatic tumorigenesis in which the pancreatic expression of UAS-regulated oncogenes is driven by a ptf1a:Gal4-VP16 driver line. This system allowed us to rapidly compare the ability of 12 different KRAS mutations (G12A, G12C, G12D, G12F, G12R, G12S, G12V, G13C, G13D, Q61L, Q61R, and A146T) to drive pancreatic tumorigenesis in vivo. Among fish injected with one of five KRAS mutations reported in other tumor types but not in human pancreatic cancer, 2/79 (0.25%) developed pancreatic tumors, with both tumors arising in fish injected with A146T. In contrast, among fish injected with one of seven KRAS mutations known to occur in human pancreatic cancer, 22/106 (20.8%) developed pancreatic cancer. All eight tumorigenic KRAS mutations were associated with downstream MAPK/ERK pathway activation in preneoplastic pancreatic epithelium, while non-tumorigenic mutations were not. These results suggest that the spectrum of KRAS mutations observed in human pancreatic cancer reflects selection based upon variable tumorigenic capacities, including the ability to activate MAPK/ERK signaling.

Clinical relevance of KRAS mutations in codon 13: Where are we?

Recent advances in molecular diagnosis and the trend towards personalized medicine have made colorectal cancer one of the tumors where therapies have significantly improved patient survival after metastasis development. KRAS mutations in codon 12 and 13 are recognized biomarkers that are analyzed in clinic previously for anti-EGFR therapies administration. Since originally mutations in both codons were considered as a predictor of lack of response to cetuximab or panitumumab, the European Medicines Agency and the US Food and Drug Administration suggested that patients harboring any of those mutations should be excluded from the treatment. However, subsequent retrospective analysis has shown that mutations in codon 12 and codon 13 of KRAS gene could be different in their biological characteristics and as a result could confer variable effects in patients. In addition and increasing and sometimes contradictory number of solutions have been published demonstrating that patients with mutations in codon 13 could have worse outcome but could obtain a significant clinical benefit from anti-EGFR therapies. Here, we review and update the latest data on the biological role leading to a predictive outcome and benefit from anti-EGFR antibodies in patients with specific KRAS mutations in codon 13.

Phase II clinical study of modified FOLFOX7 (intermittent oxaliplatin administration) plus bevacizumab in patients with unresectable metastatic colorectal cancer-CRAFT study

PURPOSE

Continuous treatment with FOLFOX therapy is associated with peripheral nerve toxicity, and to improve this inconvenient side effect various methods of administration are being investigated. A regimen of intermittent oxaliplatin administration by continuous infusion therapy, i.e., modified FOLFOX7 (mFOLFOX7) + bevacizumab, was designed with the goal of alleviating severe peripheral nerve disorders and hematological toxicity. A phase II clinical study was conducted to evaluate the efficacy and safety of this regimen.

METHODS

Previously untreated patients were assigned to mFOLFOX7 (oxaliplatin 85 mg/m(2), levofolinate [l-LV] 200 mg/m(2), 5-fluorouracil [5-FU] 2400 mg/m(2)) + bevacizumab (5 mg/kg) administered every 2 weeks for 8 cycles, maintenance without oxaliplatin for 8 cycles, and reintroduction of mFOLFOX7 + bevacizumab for 8 cycles or until disease progression. Progression free survival (PFS) following the first dose (PFS 1) and following reintroduction of oxaliplatin (PFS 2) were used as indices for assessing the efficacy of intermittent administration.

RESULTS

Fifty-two patients were enrolled, with median age of 64 years (range, 36-74). Median PFS 1 was 11.8 months (95 % confidence interval [CI], 9.5 to 13.7), median time to treatment failure was 10.3 months (95 % CI, 5.6 to 12.1), percentage of patients with neutropenia of grade 3 or higher was 7.8 %, and percentage with peripheral nerve disorders was 3.9 %. Response rate was 50 %, and 84.4 % of patients who started modified simplified LV5FU2 + bevacizumab were reintroduced to oxaliplatin.

CONCLUSION

By excluding 5-FU bolus administration and administering bevacizumab continuously the mFOLFOX7 + bevacizumab regimen with preplanned withdrawal of oxaliplatin showed high tolerability and prevented severe peripheral neuropathy and neutropenia without reducing efficacy.

Sweating the small stuff: microRNAs and genetic changes define pancreatic cancer

MicroRNAs (miRNAs) are 18- to 22-nucleotide-long, single-stranded, noncoding RNAs that regulate important biological processes including differentiation, proliferation, and response to cellular stressors such as hypoxia, nutrient depletion, and traversion of the cell cycle by controlling protein expression within the cell. Many investigators have profiled cancer tissue and serum miRNAs to identify potential therapeutic targets, understand the pathways involved in tumorigenesis, and identify diagnostic tumor signatures. In the setting of pancreatic cancer, obtaining pancreatic tissue is invasive and impractical for early diagnosis. Several groups have profiled miRNAs that are present in the blood as a means to diagnose tumor progression and predict prognosis/survival or drug resistance. Several miRNA signatures found in pancreatic tissue and the peripheral blood, as well as the pathways that are associated with pancreatic cancer, are reviewed here in detail. Three miRNA biomarkers (miR-21, miR-155, and miR-200) have been repetitively identified in both pancreatic cancer tissue and patients' blood. Those miRNAs regulate and are regulated by the central genetic and epigenetic changes observed in pancreatic cancer including p53, transforming growth factor β, p16(INK4A), BRCA1/2, and Kras. These miRNAs are involved in DNA repair, cell cycle, and cell invasion and also play important roles in promoting metastases.

NMR-based functional profiling of RASopathies and oncogenic RAS mutations

Defects in the RAS small G protein or its associated network of regulatory proteins that disrupt GTPase cycling are a major cause of cancer and developmental RASopathy disorders. Lack of robust functional assays has been a major hurdle in RAS pathway-targeted drug development. We used NMR to obtain detailed mechanistic data on RAS cycling defects conferred by oncogenic mutations, or full-length RASopathy-derived regulatory proteins. By monitoring the conformation of wild-type and oncogenic RAS in real-time, we show that opposing properties integrate with regulators to hyperactivate oncogenic RAS mutants. Q61L and G13D exhibited rapid nucleotide exchange and an unexpected susceptibility to GAP-mediated hydrolysis, in direct contrast with G12V, indicating different approaches must be taken to inhibit these oncoproteins. An NMR methodology was established to directly monitor RAS cycling by intact, multidomain proteins encoded by RASopathy genes in mammalian cell extracts. By measuring GAP activity from tumor cells, we demonstrate how loss of neurofibromatosis type 1 (NF1) increases RAS-GTP levels in NF1-derived cells. We further applied this methodology to profile Noonan Syndrome (NS)-derived SOS1 mutants. Combining NMR with cell-based assays allowed us to differentiate defects in catalysis, allosteric regulation, and membrane targeting of individual mutants, while revealing a membrane-dependent compensatory effect that attenuates dramatic increases in RAS activation shown by Y337C, L550P, and I252T. Our NMR method presents a precise and robust measure of RAS activity, providing mechanistic insights that facilitate discovery of therapeutics targeted against the RAS signaling network.

Recommendations from the EGAPP Working Group: can testing of tumor tissue for mutations in EGFR pathway downstream effector genes in patients with metastatic colorectal cancer improve health outcomes by guiding decisions regarding anti-EGFR therapy?

SUMMARY OF RECOMMENDATIONS

The Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group (EWG) found that, for patients with metastatic colorectal cancer (mCRC) who are being considered for treatment with cetuximab or panitumumab, there is convincing evidence to recommend clinical use of KRAS mutation analysis to determine which patients are KRAS mutation positive and therefore unlikely to benefit from these agents before initiation of therapy. The level of certainty of the evidence was deemed high, and the magnitude of net health benefit from avoiding potentially ineffective and harmful treatment, along with promoting more immediate access to what could be the next most effective treatment, is at least moderate.The EWG found insufficient evidence to recommend for or against BRAF V600E testing for the same clinical scenario. The level of certainty for BRAF V600E testing to guide antiepidermal growth factor receptor (EGFR) therapy was deemed low. The EWG encourages further studies of the potential value of testing in patients with mCRC who were found to have tumors that are wild type (mutation negative) for KRAS to predict responsiveness to therapy.The EWG found insufficient evidence to recommend for or against testing for mutations in NRAS, or PIK3CA, and/or loss of expression of PTEN or AKT proteins. The level of certainty for this evidence was low. In the absence of supporting evidence, and with consideration of other contextual issues, the EWG discourages the use of these tests in guiding decisions on initiating anti-EGFR therapy with cetuximab or panitumumab unless further evidence supports improved clinical outcomes.

RATIONALE

It has been suggested that patients with mCRC whose tumors harbor certain mutations affecting EGFR pathway signaling are typically unresponsive to therapy with anti-EGFR antibodies (cetuximab and panitumumab). The EWG identified recent evidence reviews that have addressed this topic, and this recommendation statement is based on results of these reviews. In developing these recommendations the EWG considered evidence in the areas described below.

ANALYTIC VALIDITY

Although no research syntheses that have formally evaluated analytic validity of these tests were found, the EWG was able to draw the following conclusions from assessments included in the evidence reviews under consideration. There is adequate evidence that KRAS mutation analysis reliably and accurately detects common mutations (codons 12 and 13), whereas evidence was inadequate for less frequent KRAS mutations (e.g., codon 61). There is also adequate evidence that testing for BRAF V600E accurately and reliably detects the mutation. For common mutations in NRAS, PIK3CA, and expression of PTEN AKT, there is adequate evidence of accurate and reliable detection. However, much less data exist in support. Furthermore, in the specific context of mCRC, no evidence was found on the analytic validity of immunohistochemistry (IHC) assays for PTEN or AKT expression.

CLINICAL VALIDITY

For KRAS mutation analysis, the EWG found convincing evidence for association with treatment response to anti-EGFR therapy, independent of prognostic association. For BRAF V600E mutation testing, the EWG found insufficient evidence for association with treatment response to anti-EGFR therapy independent of prognostic association. The EWG found insufficient evidence for association of results of testing for mutations in NRAS or PIK3CA, and loss of expression of PTEN or ATK proteins, with treatment response to anti-EGFR therapy.

CLINICAL UTILITY

For KRAS mutation analysis, the EWG found adequate evidence that improved health outcomes are achieved by avoiding ineffective chemotherapy and potential side effects and expediting access to the next most effective treatment. Inadequate evidence was found regarding association of BRAF V600E mutation testing or loss of PTEN expression with improved health outcomes among patients with mCRC undergoing anti-EGFR therapy as compared with patients with tumors bearing wild-type BRAF sequence and PTEN expression levels, respectively. No evidence was found to support improved health outcomes associated with testing results for NRAS or PIK3CA variants, or AKT protein expression levels in this clinical scenario.

CONTEXTUAL ISSUES

CRC is an important and highly prevalent health problem. Improvements in mCRC outcomes associated with pharmacogenetic testing could have important clinical, and potentially public health, impacts. Adverse events related to cancer chemotherapy can be common and severe. Therefore, successfully optimizing treatment to maximize efficacy and minimize side effects is important for reducing mCRC-related morbidity and mortality.