Overexpressed vs mutated Kras in murine fibroblasts: a molecular phenotyping study

Palmitoyl transferase ZDHHC20 promotes pancreatic cancer metastasis

Metastasis is one of the defining features of pancreatic ductal adenocarcinoma (PDAC) that contributes to poor prognosis. In this study, the palmitoyl transferase ZDHHC20 was identified in an in vivo short hairpin RNA (shRNA) screen as critical for metastatic outgrowth, with no effect on proliferation and migration in vitro or primary PDAC growth in mice. This phenotype is abrogated in immunocompromised animals and animals with depleted natural killer (NK) cells, indicating that ZDHHC20 affects the interaction of tumor cells and the innate immune system. Using a chemical genetics platform for ZDHHC20-specific substrate profiling, a number of substrates of this enzyme were identified. These results describe a role for palmitoylation in enabling distant metastasis that could not have been detected using in vitro screening approaches and identify potential effectors through which ZDHHC20 promotes metastasis of PDAC.

An integrated model for predicting KRAS dependency

The clinical approvals of KRAS G12C inhibitors have been a revolutionary advance in precision oncology, but response rates are often modest. To improve patient selection, we developed an integrated model to predict KRAS dependency. By integrating molecular profiles of a large panel of cell lines from the DEMETER2 dataset, we built a binary classifier to predict a tumor's KRAS dependency. Monte Carlo cross validation via ElasticNet within the training set was used to compare model performance and to tune parameters α and λ. The final model was then applied to the validation set. We validated the model with genetic depletion assays and an external dataset of lung cancer cells treated with a G12C inhibitor. We then applied the model to several Cancer Genome Atlas (TCGA) datasets. The final "K20" model contains 20 features, including expression of 19 genes and KRAS mutation status. In the validation cohort, K20 had an AUC of 0.94 and accurately predicted KRAS dependency in both mutant and KRAS wild-type cell lines following genetic depletion. It was also highly predictive across an external dataset of lung cancer lines treated with KRAS G12C inhibition. When applied to TCGA datasets, specific subpopulations such as the invasive subtype in colorectal cancer and copy number high pancreatic adenocarcinoma were predicted to have higher KRAS dependency. The K20 model has simple yet robust predictive capabilities that may provide a useful tool to select patients with KRAS mutant tumors that are most likely to respond to direct KRAS inhibitors.

Silencing effects of mutant RAS signalling on transcriptomes

Mutated genes of the RAS family encoding small GTP-binding proteins drive numerous cancers, including pancreatic, colon and lung tumors. Besides the numerous effects of mutant RAS gene expression on aberrant proliferation, transformed phenotypes, metabolism, and therapy resistance, the most striking consequences of chronic RAS activation are changes of the genetic program. By performing systematic gene expression studies in cellular models that allow comparisons of pre-neoplastic with RAS-transformed cells, we and others have estimated that 7 percent or more of all transcripts are altered in conjunction with the expression of the oncogene. In this context, the number of up-regulated transcripts approximates that of down-regulated transcripts. While up-regulated transcription factors such as MYC, FOSL1, and HMGA2 have been identified and characterized as RAS-responsive drivers of the altered transcriptome, the suppressed factors have been less well studied as potential regulators of the genetic program and transformed phenotype in the breadth of their occurrence. We therefore have collected information on downregulated RAS-responsive factors and discuss their potential role as tumor suppressors that are likely to antagonize active cancer drivers. To better understand the active mechanisms that entail anti-RAS function and those that lead to loss of tumor suppressor activity, we focus on the tumor suppressor HREV107 (alias PLAAT3 [Phospholipase A and acyltransferase 3], PLA2G16 [Phospholipase A2, group XVI] and HRASLS3 [HRAS-like suppressor 3]). Inactivating HREV107 mutations in tumors are extremely rare, hence epigenetic causes modulated by the RAS pathway are likely to lead to down-regulation and loss of function.

Transcriptome analysis reveals the molecular regulatory network of muscle development and meat quality in Sunit lamb supplemented with dietary probiotic

Supplementing animal feed with probiotic additives can promote muscle production and improve meat quality. The study aimed to explore the effects of dietary probiotics supplementation on the performance, meat quality and muscle transcriptome profile in Sunit lamb. Overall, feeding probiotics significantly increased the body length, LT area, pH24h and intramuscular fat (IMF) content, but decreased cooking loss and meat shear force compared to the control group (P < .05). A total of 651 differentially expressed genes (DEGs) were found in probiotic supplemented lambs. Pathway analysis revealed that DEGs were involved in multiple pathways related to muscle development and fat deposition, such as the ECM-receptor interactions, the MAPK signaling pathway and the FoxO signaling pathway. Therefore, dietary probiotic supplementation can improve muscle development and final meat quality in Sunit lambs by altering gene expression profiles associated with key pathways, providing unique insights into the molecular mechanisms by which dietary probiotics regulate muscle development in the lamb industry.

Mutant RAS and the tumor microenvironment as dual therapeutic targets for advanced colorectal cancer

RAS genes are the most frequently mutated oncogenes in cancer. These mutations occur in roughly half of the patients with colorectal cancer (CRC). RAS mutant tumors are resistant to therapy with anti-EGFR monoclonal antibodies. Therefore, patients with RAS mutant CRC currently have few effective therapy options. RAS mutations lead to constitutively active RAS GTPases, involved in multiple downstream signaling pathways. These alterations are associated with a tumor microenvironment (TME) that drives immune evasion and disease progression by mechanisms that remain incompletely understood. In this review, we focus on the available evidence in the literature explaining the potential effects of RAS mutations on the CRC microenvironment. Ongoing efforts to influence the TME by targeting mutant RAS and thereby sensitizing these tumors to immunotherapy will be discussed as well.

Fatty acid binding protein 5 regulates lipogenesis and tumor growth in lung adenocarcinoma

AIMS

Lung cancer is the leading cause of cancer-related death. Unfortunately, targeted-therapies have been unsuccessful for most patients with lung adenocarcinoma (LUAD). Thus, new early biomarkers and treatment options are a pressing need. Fatty acid binding protein 5 (FABP5) has been associated with various types of cancers. Its contribution to LUAD onset, progression and metabolic reprogramming is, however, not fully understood. In this study we assessed the importance of FABP5 in LUAD and its role in cancer lipid metabolism.

MAIN METHODS

By radioactive labeling and metabolite quantification, we studied the function of FABP5 in fatty acid metabolism using genetic/pharmacologic inhibition and overexpression models in LUAD cell lines. Flow cytometry, heterologous transplantation and bioinformatic analysis were used, in combination with other methodologies, to assess the importance of FABP5 for cellular proliferation in vitro and in vivo and in patient survival.

KEY FINDINGS

We show that high expression of FABP5 is associated with poor prognosis in patients with LUAD. FABP5 regulates lipid metabolism, diverting fatty acids towards complex lipid synthesis, whereas it does not affect their catabolism in vitro. Moreover, FABP5 is required for de novo fatty acid synthesis and regulates the expression of enzymes involved in the pathway (including FASN and SCD1). Consistently with the changes in lipid metabolism, FABP5 is required for cell cycle progression, migration and in vivo tumor growth.

SIGNIFICANCE

Our results suggest that FABP5 is a regulatory hub of lipid metabolism and tumor progression in LUAD, placing it as a new putative therapeutic target for this disease.

Biglycan as a potential regulator of tumorgenicity and immunogenicity in K-RAS-transformed cells

The extracellular matrix component biglycan (BGN) plays an essential role in various physiological and pathophysiological processes. A deficient BGN expression associated with reduced immunogenicity was found in HER-2/neu-overexpressing cells. To determine whether BGN is suppressed by oncogene-driven regulatory networks, the expression and function of BGN was analyzed in murine and human BGNlow/BGNhigh K-RASG12V-transformed model systems as well as in different patients' datasets of colorectal carcinoma (CRC) lesions. K-RAS-mutated CRC tissues expressed low BGN mRNA and protein levels when compared to normal colon epithelial cells, which was associated with a reduced patients' survival. Transfection of BGN in murine and human BGNlow K-RAS-expressing cells resulted in a reduced growth and migration of BGNhigh vs BGNlow K-RAS cells. In addition, increased MHC class I surface antigens as a consequence of an enhanced antigen processing machinery component expression was found upon restoration of BGN, which was confirmed by RNA-sequencing of BGNlow vs. BGNhigh K-RAS models. Furthermore, a reduced tumor formation of BGNhigh versus BGNlow K-RAS-transformed fibroblasts associated with an enhanced MHC class I expression and an increased frequency of tumor-infiltrating lymphocytes in tumor lesions was found. Our data provide for the first time an inverse link between BGN and K-RAS expression in murine and human K-RAS-overexpressing models and CRC lesions associated with altered growth properties, reduced immunogenicity and worse patients' outcome. Therefore, reversion of BGN might be a novel therapeutic option for K-RAS-associated malignancies.

KRAS mutant rectal cancer cells interact with surrounding fibroblasts to deplete the extracellular matrix

Somatic mutations in the KRAS oncogene are associated with poor outcomes in locally advanced rectal cancer but the underlying biologic mechanisms are not fully understood. We profiled mRNA in 76 locally advanced rectal adenocarcinomas from patients that were enrolled in a prospective clinical trial and investigated differences in gene expression between KRAS mutant (KRAS-mt) and KRAS-wild-type (KRAS-wt) patients. We found that KRAS-mt tumors display lower expression of genes related to the tumor stroma and remodeling of the extracellular matrix. We validated our findings using samples from The Cancer Genome Atlas (TCGA) and also by performing immunohistochemistry (IHC) and immunofluorescence (IF) in orthogonal cohorts. Using in vitro and in vivo models, we show that oncogenic KRAS signaling within the epithelial cancer cells modulates the activity of the surrounding fibroblasts in the tumor microenvironment.

Regulation of KRAS protein expression by miR-544a and KRAS-LCS6 polymorphism in wild-type KRAS sporadic colon adenocarcinoma

Colorectal carcinoma (CRC) results from the accumulation of genetic mutations and alterations in signaling pathways. KRAS is mutated in 40% of CRC cases and is involved in increased tumor cells proliferation and survival. Although KRAS mutations are a dominant event in CRC tumorigenesis, increased wild-type KRAS expression has a similar effect on accelerated tumor growth. In this study, we investigated the KRAS status in correlation with clinicopathological features in sporadic CRC and more importantly the role of let-7a-5p and miR-544a-3p in the regulation of wild-type KRAS protein expression in the tumor center (T1) and invasive tumor front (T2). Analysis showed that 39.1% of tumor samples had KRAS mutations. In wild-type KRAS tumors, 62.0% were positive for KRAS protein expression and there was a higher percentage of KRAS-positive tumor cells and a higher intensity of immunohistochemical reaction in T2 than in T1 samples. This could not be attributed to differences in KRAS mRNA levels, suggesting regulation via miR-544a-3p expression which was significantly decreased in T2 samples. Furthermore, we demonstrated that tumor samples carrying the KRAS-LCS6 variant allele had significantly higher protein expression of the wild-type KRAS. Our results suggest the role of the KRAS-LCS6 polymorphism and miR-544a-3p expression in the regulation of wild-type KRAS protein expression in sporadic CRC.

eVIP2: Expression-based variant impact phenotyping to predict the function of gene variants

While advancements in genome sequencing have identified millions of somatic mutations in cancer, their functional impact is poorly understood. We previously developed the expression-based variant impact phenotyping (eVIP) method to use gene expression data to characterize the function of gene variants. The eVIP method uses a decision tree-based algorithm to predict the functional impact of somatic variants by comparing gene expression signatures induced by introduction of wild-type (WT) versus mutant cDNAs in cell lines. The method distinguishes between variants that are gain-of-function, loss-of-function, change-of-function, or neutral. We present eVIP2, software that allows for pathway analysis (eVIP Pathways) and usage with RNA-seq data. To demonstrate the eVIP2 software and approach, we characterized two recurrent frameshift variants in RNF43, a negative regulator of Wnt signaling, frequently mutated in colorectal, gastric, and endometrial cancer. RNF43 WT, RNF43 R117fs, RNF43 G659fs, or GFP control cDNA were overexpressed in HEK293T cells. Analysis with eVIP2 predicted that the frameshift at position 117 was a loss-of-function mutation, as expected. The second frameshift at position 659 has been previously described as a passenger mutation that maintains the RNF43 WT function as a negative regulator of Wnt. Surprisingly, eVIP2 predicted G659fs to be a change-of-function mutation. Additional eVIP Pathways analysis of RNF43 G659fs predicted 10 pathways to be significantly altered, including TNF-α via NFκB signaling, KRAS signaling, and hypoxia, highlighting the benefit of a more comprehensive approach when determining the impact of gene variant function. To validate these predictions, we performed reporter assays and found that each pathway activated by expression of RNF43 G659fs, but not expression of RNF43 WT, was identified as impacted by eVIP2, supporting that RNF43 G659fs is a change-of-function mutation and its effect on the identified pathways. Pathway activation was further validated by Western blot analysis. Lastly, we show primary colon adenocarcinoma patient samples with R117fs and G659fs variants have transcriptional profiles similar to BRAF missense mutations with activated RAS/MAPK signaling, consistent with KRAS signaling pathways being GOF in both variants. The eVIP2 method is an important step towards overcoming the current challenge of variant interpretation in the implementation of precision medicine. eVIP2 is available at https://github.com/BrooksLabUCSC/eVIP2.

NRAS mutant E132K identified in young-onset sporadic colorectal cancer and the canonical mutants G12D and Q61K affect distinct oncogenic phenotypes

Recent data show a global increase in colorectal cancer (CRC) cases among younger demographics, which portends poorer prognosis. The cause of rising incidence is uncertain, and its mutational landscape remains largely unexplored, including those in genes of the epidermal growth factor receptor pathway. Among these are NRAS mutants where there is paucity of functional studies compared to KRAS. Here, the novel NRAS mutant E132K, identified in three tumor samples from Filipino young-onset, sporadic colorectal cancer patients, was investigated for its effects on different cancer hallmarks, alongside the NRAS canonical mutants G12D and Q61K which are yet poorly characterized in the context of CRC. The novel NRAS mutant E132K and the canonical G12D and Q61K mutants show resistance to apoptosis, cytoskeletal reorganization, and loss of adhesion. In contrast to activating KRAS mutations, including the analogous KRAS G12D and Q61K mutations, all three NRAS mutants have no apparent effect on cell proliferation and motility. The results highlight the need to characterize isoform- and mutation-specific oncogenic phenotypes which can have repercussions in disease management and choice of therapeutic intervention. Further analyses of young-onset versus late-onset CRC datasets are necessary to qualify NRAS E132K as a biomarker for the young-onset subtype.

From basic researches to new achievements in therapeutic strategies of KRAS-driven cancers

Among the numerous oncogenes involved in human cancers, KRAS represents the most studied and best characterized cancer-related genes. Several therapeutic strategies targeting oncogenic KRAS (KRAS onc ) signaling pathways have been suggested, including the inhibition of synthetic lethal interactions, direct inhibition of KRAS onc itself, blockade of downstream KRAS onc effectors, prevention of post-translational KRAS onc modifications, inhibition of the induced stem cell-like program, targeting of metabolic peculiarities, stimulation of the immune system, inhibition of inflammation, blockade of upstream signaling pathways, targeted RNA replacement, and oncogene-induced senescence. Despite intensive and continuous efforts, KRAS onc remains an elusive target for cancer therapy. To highlight the progress to date, this review covers a collection of studies on therapeutic strategies for KRAS published from 1995 to date. An overview of the path of progress from earlier to more recent insights highlight novel opportunities for clinical development towards KRASonc-signaling targeted therapeutics.

Phenotypic characterization of the novel, non-hotspot oncogenic KRAS mutants E31D and E63K

KRAS proto-oncogene, GTPase (KRAS) functions as a molecular switch at the apex of multiple signaling pathways controlling cell proliferation, differentiation, migration, and survival. Canonical KRAS mutants, such as those in codons 12 and 13, produce constitutively active oncoproteins that short-circuit epidermal growth factor receptor (EGFR)-initiated signaling, resulting in dysregulated downstream effectors associated with cellular transformation. Therefore, anti-EGFR therapy provides little to no clinical benefit to patients with activating KRAS mutations. Current genotyping procedures based on canonical mutation detection only account for ~40% of non-responders, highlighting the need to identify additional predictive biomarkers. In the present study, two novel non-hotspot KRAS mutations were functionally characterized in vitro: KRAS E31D was identified from a genetic screen of colorectal cancer specimens at the UP-National Institutes of Health. KRAS E63K is curated in the Catalogue of Somatic Mutations in Cancer database. Similar to the canonical mutants KRAS G12D and KRAS G13D, NIH3T3 cells overexpressing KRAS E31D and KRAS E63K showed altered morphology and were characteristically smaller, rounder, and highly refractile compared with their non-transformed counterparts. Filamentous actin staining also indicated cytoplasmic shrinkage, membrane ruffling, and formation of pseudopod protrusions. Further, they displayed higher proliferative rates and higher migratory rates in scratch wound assays compared with negative controls. These empirical findings suggest the activating impact of the novel KRAS mutations, which may contribute to resistance to anti-EGFR therapy. Complementary studies to elucidate the molecular mechanisms underlying the transforming effect of the rare mutants are required. In parallel, their oncogenic capacity in vivo should also be investigated.

KRAS induces lung tumorigenesis through microRNAs modulation

Oncogenic KRAS induces tumor onset and development by modulating gene expression via different molecular mechanisms. MicroRNAs (miRNAs) are small non-coding RNAs that have been established as main players in tumorigenesis. By overexpressing wild type or mutant KRAS (KRASG12D) and using inducible human and mouse cell lines, we analyzed KRAS-regulated microRNAs in non-small-cell lung cancer (NSCLC). We show that miR-30c and miR-21 are significantly upregulated by both KRAS isoforms and induce drug resistance and enhance cell migration/invasion via inhibiting crucial tumor suppressor genes, such as NF1, RASA1, BID, and RASSF8. MiR-30c and miR-21 levels were significantly elevated in tumors from patients that underwent surgical resection of early stages NSCLC compared to normal lung and in plasma from the same patients. Systemic delivery of LNA-anti-miR-21 in combination with cisplatin in vivo completely suppressed the development of lung tumors in a mouse model of lung cancer. Mechanistically, we demonstrated that ELK1 is responsible for miR-30c and miR-21 transcriptional activation by direct binding to the miRNA proximal promoter regions. In summary, our study defines that miR-30c and miR-21 may be valid biomarkers for early NSCLC detection and their silencing could be beneficial for therapeutic applications.

Oncogene mutation profile predicts tumor regression and survival in locally advanced rectal cancer patients treated with preoperative chemoradiotherapy and radical surgery

Tumor response to preoperative chemoradiotherapy and postoperative survival differs among patients with locally advanced rectal cancer. The objective was to find correlations of mutated oncogenes and clinical outcomes in locally advanced rectal cancer. A total of 70 patients with preoperative preoperative chemoradiotherapy followed by radical surgery at a single cancer center between 2006 and 2012 were enrolled. Pretreatment tumor biopsy samples were assayed for 238 mutation hotspots harboring 19 oncogenes by time-of-flight mass spectrometry and OncoCarta Array. Oncogene mutations were found in 48.6% of patients (34/70). KRAS was the most frequent driver mutation, found in 35.7% of patients (25/70), followed by PIK3CA (14.3%), NRAS (5.7%), FLT3 (2.9%), and BRAF (1.4%). Multiple gene mutations were observed in eight patients (11.4%). Tumors with KRAS mutations responded poorly to preoperative chemoradiotherapy (p = 0.044). Patients with oncogene mutations had worse 3-year disease-free survival than those without mutations (67.2% vs 94.2%, p = 0.010). Patients with KRAS or RAS mutations had lower 3-year disease-free survival (68% vs 88.3%, p = 0.016; 65.5% vs 92.3%, p = 0.004, respectively) and 3-year overall survival (88% vs 95.4%, p = 0.020; 89.7% vs 94.9%, p = 0.036, respectively) than those without KRAS or RAS mutations. Oncogene mutation status affected tumor response to treatment and long-term survival in locally advanced rectal cancer.

Aroclor 1254 causes atrophy of exocrine pancreas in mice and the mechanism involved

Polychlorinated biphenyls (PCBs) are a class of organic pollutants that have been linked to pancreatic disease. However, their role in affecting the exocrine function of pancreas and the underlying mechanism remains elusive. In the present study, male C57 mice were treated with Aroclor 1254, a commercially available PCBs mixture, at a dosage of 0.5, 5, 50, or 500 μg kg(-1) every 3 days by oral gavage. Decrease in pancreas/soma index and acinar atrophy were observed in the mice after exposure for 50 days. Aroclor 1254 exposure significantly decreased the PCNA-positive cells in the pancreatic acini in a dose-dependent manner. In addition, western blot analysis showed that PCNA expression was decreased in pancreas in the presence of Aroclor 1254, which suggests that Aroclor 1254 suppresses cell proliferation. TUNEL-positive apoptotic cells as well as the expression of Bcl2, BclXL, BAX, and Bad of exocrine pancreas did not show significant changes in the treated mice, indicating that Aroclor 1254 has no effect on apoptosis. We also found that phosphorylation of ERK1/2, P90RSK1 and Bad was increased in the treated groups; this compensatory activation of phosphorylation in ERK1/2-P90RSK1-Bad signaling cascade could protect cell from apoptosis to maintain the cell numbers and function of exocrine pancreas. Moreover, we found that the expression of Kras and TNFα was increased in the pancreas, indicating that Aroclor 1254 exposure could result in increased risk of inflammation and carcinoma. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 671-678, 2016.

Meta-analysis comparing the efficacy of anti-EGFR monoclonal antibody therapy between KRAS G13D and other KRAS mutant metastatic colorectal cancer tumours

BACKGROUND

Metastatic colorectal cancer (mCRC) tumours harbouring a RAS mutation are associated with a lack of treatment benefit from anti-EGFR monoclonal antibodies (mAbs). However, observational evidence has led to speculation that mCRC patients with KRAS G13D mutant (MT) tumours may derive a benefit from treatment with anti-EGFR mAbs.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate whether the efficacy of anti-EGFR mAbs for mCRC differs between tumours harbouring a KRAS G13D mutation (KRAS G13D) and KRAS mutations other than G13D (other KRAS MT).

RESULTS

Eight RCTs (n = 5967) met the inclusion criteria for assessment of both overall survival (OS) and progression-free survival (PFS). For other KRAS MT the hazard ratio for OS benefit with addition of anti-EGFR mAb therapy was 1.06 (95% confidence interval [CI]; 0.96, 1.17), compared to 1.08 (95% CI; 0.73, 1.60) for KRAS G13D [test for interaction p=0.99]. In contrast, the hazard ratio for KRAS wild-type (WT) tumours was 0.85 (95% CI; 0.76, 0.95). Regarding PFS benefit with anti-EGFR mAbs, the hazard ratio was 1.07 (95% CI; 0.92, 1.26) for other KRAS MT, 0.96 (95% CI; 0.73, 1.27) for KRAS G13D, and 0.68 (95% CI; 0.54, 0.85) for KRAS WT. Again, the test for interaction (p=0.46) demonstrated no significant difference in PFS benefit for anti-EGFR mAb therapy between KRAS G13D and other KRAS MT.

CONCLUSION

This meta-analysis demonstrates no significant difference between KRAS G13D and other KRAS MT tumours in terms of treatment benefit from anti-EGFR mAbs for mCRC.

Personalizing colon cancer therapeutics: targeting old and new mechanisms of action

The use of pharmaceuticals for colon cancer treatment has been increasingly personalized, in part due to the development of new molecular tools. In this review, we discuss the old and new colon cancer chemotherapeutics, and the parameters that have been shown to be predictive of efficacy and safety of these chemotherapeutics. In addition, we discuss how alternate pharmaceuticals have been developed in light of a potential lack of response or resistance to a particular chemotherapeutic.

PTTG acts as a STAT3 target gene for colorectal cancer cell growth and motility

Pituitary tumor transforming gene (PTTG), the index mammalian securin, is abundantly expressed in several tumors and regulates tumor growth and progression. Molecular mechanisms elucidating PTTG regulation and actions remain elusive. Here, we provide evidence that PTTG acts as a STAT3 target gene. Total STAT3 and Tyr705 phosphorylated STAT3 were concordantly expressed with PTTG in human colorectal tumors (n=97 and n=95 respectively, P<0.001). STAT3 specifically bound the human PTTG promoter and induced PTTG transcriptional activity (2-fold) as assessed by chromatin immunoprecipitation and luciferase reporter assays. STAT3 transfection increased PTTG mRNA and protein abundance 2-fold in HCT116 human colon cancer cells, and induction was further enhanced (3-fold) by constitutively active STAT3 (STAT3-C), while strongly abrogated by dominant negative STAT3 (STAT3-DN). Attenuating PTTG expression by siRNA in STAT3 HCT116 stable transfectants suppressed cell growth and colony formation in vitro, and PTTG cell knockout also constrained activated STAT3-induced explanted murine tumor growth in vivo. STAT3 increased HCT116 cell migration and invasion up to 5-fold, whereas cell mobility was abolished by STAT3-DN (>85%). Impairing PTTG expression by siRNA also strongly suppressed STAT3-faciliated cell migration and invasion by up to 90%. Knocking out PTTG in STAT3-C HCT116 stable transfectants strongly decreased tumor metastases in nude mice, indicating the requirement of PTTG for STAT3-promoted metastasis. These results elucidate a mechanism for tumor cell PTTG regulation, whereby STAT3 induces PTTG expression to facilitate tumor growth and metastasis; and further support the rationale for targeting PTTG to abrogate colorectal cancer growth.

Label-free quantitative proteomics and N-glycoproteomics analysis of KRAS-activated human bronchial epithelial cells

Mutational activation of KRAS promotes various malignancies, including lung adenocarcinoma. Knowledge of the molecular targets mediating the downstream effects of activated KRAS is limited. Here, we provide the KRAS target proteins and N-glycoproteins using human bronchial epithelial cells with and without the expression of activated KRAS (KRAS(V12)). Using an OFFGEL peptide fractionation and hydrazide method combined with subsequent LTQ-Orbitrap analysis, we identified 5713 proteins and 608 N-glycosites on 317 proteins in human bronchial epithelial cells. Label-free quantitation of 3058 proteins (≥2 peptides; coefficient of variation (CV) ≤ 20%) and 297 N-glycoproteins (CV ≤ 20%) revealed the differential regulation of 23 proteins and 14 N-glycoproteins caused by activated KRAS, including 84% novel ones. An informatics-assisted IPA-Biomarker® filter analysis prioritized some of the differentially regulated proteins (ALDH3A1, CA2, CTSD, DST, EPHA2, and VIM) and N-glycoproteins (ALCAM, ITGA3, and TIMP-1) as cancer biomarkers. Further, integrated in silico analysis of microarray repository data of lung adenocarcinoma clinical samples and cell lines containing KRAS mutations showed positive mRNA fold changes (p < 0.05) for 61% of the KRAS-regulated proteins, including biomarker proteins, CA2 and CTSD. The most significant discovery of the integrated validation is the down-regulation of FABP5 and PDCD4. A few validated proteins, including tumor suppressor PDCD4, were further confirmed as KRAS targets by shRNA-based knockdown experiments. Finally, the studies on KRAS-regulated N-glycoproteins revealed structural alterations in the core N-glycans of SEMA4B in KRAS-activated human bronchial epithelial cells and functional role of N-glycosylation of TIMP-1 in the regulation of lung adenocarcinoma A549 cell invasion. Together, our study represents the largest proteome and N-glycoproteome data sets for HBECs, which we used to identify several novel potential targets of activated KRAS that may provide insights into KRAS-induced adenocarcinoma and have implications for both lung cancer therapy and diagnosis.

Association of KRAS G13D tumor mutations with outcome in patients with metastatic colorectal cancer treated with first-line chemotherapy with or without cetuximab

PURPOSE

We investigated in the first-line setting our previous finding that patients with chemorefractory KRAS G13D-mutated metastatic colorectal cancer (mCRC) benefit from cetuximab treatment.

METHODS

Associations between tumor KRAS mutation status (wild-type, G13D, G12V, or other mutations) and progression-free survival (PFS), survival, and response were investigated in pooled data from 1,378 evaluable patients from the CRYSTAL and OPUS studies. Multivariate analysis correcting for differences in baseline prognostic factors was performed.

RESULTS

Of 533 patients (39%) with KRAS-mutant tumors, 83 (16%) had G13D, 125 (23%) had G12V, and 325 (61%) had other mutations. Significant variations in treatment effects were found for tumor response (P = .005) and PFS (P = .046) in patients with G13D-mutant tumors versus all other mutations (including G12V). Within KRAS mutation subgroups, cetuximab plus chemotherapy versus chemotherapy alone significantly improved PFS (median, 7.4 v 6.0 months; hazard ratio [HR], 0.47; P = .039) and tumor response (40.5% v 22.0%; odds ratio, 3.38; P = .042) but not survival (median, 15.4 v 14.7 months; HR, 0.89; P = .68) in patients with G13D-mutant tumors. Patients with G12V and other mutations did not benefit from this treatment combination. Patients with KRAS G13D-mutated tumors receiving chemotherapy alone experienced worse outcomes (response, 22.0% v 43.2%; odds ratio, 0.40; P = .032) than those with other mutations. Effects were similar in the separate CRYSTAL and OPUS studies.

CONCLUSION

The addition of cetuximab to first-line chemotherapy seems to benefit patients with KRAS G13D-mutant tumors. Relative treatment effects were similar to those in patients with KRAS wild-type tumors but with lower absolute values.

The molecular basis of chemoradiosensitivity in rectal cancer: implications for personalized therapies

Introduction

Preoperative chemoradiotherapy represents the standard treatment for patients with locally advanced rectal cancer. Unfortunately, the response of individual tumors to multimodal treatment is not uniform and ranges from complete response to complete resistance. This poses a particular problem for patients with a priori resistant tumors because they may be exposed to irradiation and chemotherapy, treatment regimens that are both expensive and at times toxic, without benefit. Accordingly, there is a strong need to establish molecular biomarkers that predict the response of an individual patient’s tumor to multimodal treatment and that indicate treatment-associated toxicities prior to therapy. Such biomarkers may guide clinicians in choosing the best possible treatment for each individual patient. In addition, these biomarkers could be used to identify novel molecular targets and thereby assist in implementing novel strategies to sensitize a priori resistant tumors to multimodal treatment regimens.

Objective

The aim of this review is to summarize recent findings about the molecular basis of treatment resistance and treatment toxicity in patients with rectal cancer. Whole-genome, as well as single-biomarker or multibiomarker, analyses and their potential implications will be highlighted. At the end, we will outline a future vision of rectal cancer treatment in the era of personalized medicine.

Mouse phenotyping

Model organisms like the mouse are important tools to learn more about gene function in man. Within the last 20 years many mutant mouse lines have been generated by different methods such as ENU mutagenesis, constitutive and conditional knock-out approaches, knock-down, introduction of human genes, and knock-in techniques, thus creating models which mimic human conditions. Due to pleiotropic effects, one gene may have different functions in different organ systems or time points during development. Therefore mutant mouse lines have to be phenotyped comprehensively in a highly standardized manner to enable the detection of phenotypes which might otherwise remain hidden. The German Mouse Clinic (GMC) has been established at the Helmholtz Zentrum München as a phenotyping platform with open access to the scientific community (www.mousclinic.de; [1]). The GMC is a member of the EUMODIC consortium which created the European standard workflow EMPReSSslim for the systemic phenotyping of mouse models (http://www.eumodic.org/[2]).