Differences in in vitro invasive capacity induced by differences in Ki-Ras protein mutations

The Impact of KRAS Mutation in Patients With Sporadic Nonampullary Duodenal Epithelial Tumors

INTRODUCTION

The genomic characterization of primary nonampullary duodenal adenocarcinoma indicates a genetic resemblance to gastric and colorectal cancers. However, a correlation between the clinical and molecular characteristics of these cancers has not been established. This study aimed to elucidate the clinicopathological features of sporadic nonampullary duodenal epithelial tumors, including their molecular characteristics and prognostic factors.

METHODS

One hundred forty-eight patients with sporadic nonampullary duodenal epithelial tumors were examined in this study. Patient sex, age, TNM stage, tumor location, treatment methods, histology, KRAS mutation, BRAF mutation, Fusobacterium nucleatum, mucin phenotype, and programmed death-ligand 1 (PD-L1) status were evaluated. KRAS and BRAF mutations, Fusobacterium nucleatum, mucin phenotype, and PD-L1 status were analyzed by direct sequencing, quantitative polymerase chain reaction, and immunochemical staining.

RESULTS

The median follow-up duration was 119.4 months. There were no deaths from duodenal adenoma (the primary disease). Kaplan-Meier analysis for duodenal adenocarcinoma showed a significant effect of TNM stage (P < 0.01). In univariate analysis of primary deaths from duodenal adenocarcinoma, TNM stage II or higher, undifferentiated, KRAS mutations, gastric phenotype, intestinal phenotype, and PD-L1 status were significant factors. In multivariate analysis, TNM stage II or higher (hazard ratio: 1.63 × 1010, 95% confidence interval: 18.66-6.69 × 1036) and KRAS mutation (hazard ratio: 3.49, confidence interval: 1.52-7.91) were significant factors.

DISCUSSION

Only KRAS mutation was a significant prognostic factor in primary sporadic nonampullary duodenal adenocarcinoma in cases in which TNM stage was considered.

Profiling tumour heterogeneity through circulating tumour DNA in patients with pancreatic cancer

The majority of pancreatic ductal adenocarcinomas (PDAC) are diagnosed late so that surgery is rarely curative. Earlier detection could significantly increase the likelihood of successful treatment and improve survival. The aim of the study was to provide proof of principle that point mutations in key cancer genes can be identified by sequencing circulating free DNA (cfDNA) and that this could be used to detect early PDACs and potentially, premalignant lesions, to help target early effective treatment. Targeted next generation sequencing (tNGS) analysis of mutation hotspots in 50 cancer genes was conducted in 26 patients with PDAC, 14 patients with chronic pancreatitis (CP) and 12 healthy controls with KRAS status validated by digital droplet PCR. A higher median level of total cfDNA was observed in patients with PDAC (585 ng/ml) compared to either patients with CP (300 ng/ml) or healthy controls (175 ng/ml). PDAC tissue showed wide mutational heterogeneity, whereas KRAS was the most commonly mutated gene in cfDNA of patients with PDAC and was significantly associated with a poor disease specific survival (p=0.018). This study demonstrates that tNGS of cfDNA is feasible to characterise the circulating genomic profile in PDAC and that driver mutations in KRAS have prognostic value but cannot currently be used to detect early emergence of disease. Importantly, monitoring total cfDNA levels may have utility in individuals "at risk" and warrants further investigation.

Prognostic impact of KRAS mutation subtypes in 677 patients with metastatic lung adenocarcinomas

BACKGROUND

We previously demonstrated that patients with metastatic KRAS mutant lung cancers have a shorter survival compared with patients with KRAS wild-type cancers. Recent reports have suggested different clinical outcomes and distinct activated signaling pathways depending on KRAS mutation subtype. To better understand the impact of KRAS mutation subtype, we analyzed data from 677 patients with KRAS mutant metastatic lung cancer.

METHODS

We reviewed all patients with metastatic or recurrent lung cancers found to have KRAS mutations over a 6-year time period. We evaluated the associations among KRAS mutation type, clinical factors, and overall survival in univariate and multivariate analyses. Any significant findings were validated in an external multi-institution patient dataset.

RESULTS

Among 677 patients with KRAS mutant lung cancers (53 at codon 13, 624 at codon 12), there was no difference in overall survival for patients when comparing KRAS transition versus transversion mutations (p = 0.99), smoking status (p = 0.33), or when comparing specific amino acid substitutions (p = 0.20). In our dataset, patients with KRAS codon 13 mutant tumors (n = 53) had shorter overall survival compared with patients with codon 12 mutant tumors (n = 624) (1.1 versus 1.3 years, respectively; p = 0.009), and the findings were confirmed in a multivariate Cox model controlling for age, sex, and smoking status (hazard ratio: 1.52, 95% confidence interval: 1.11-2.08; p = 0.008). In an independent validation set of tumors from 682 patients with stage IV KRAS mutant lung cancers, there was no difference in survival between patients with KRAS codon 13 versus codon 12 mutations (1.0 versus 1.1 years, respectively; p = 0.41).

CONCLUSIONS

Among individuals with KRAS mutant metastatic lung cancers treated with conventional therapy, there are no apparent differences in outcome based on KRAS mutation subtype.

Pooled Analysis of the Prognostic and Predictive Value of KRAS Mutation Status and Mutation Subtype in Patients with Non-Small Cell Lung Cancer Treated with Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

OBJECTIVES

This pooled analysis of four trials of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) versus placebo was conducted to clarify the prognostic and predictive roles of Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations (MUTs) and to explore the importance of MUT subtype.

METHODS

Data were pooled from four trials of EGFR TKIs versus placebo (National Cancer Institute of Canada Clinical Trials Group [NCIC CTG] trial BR.21, TOPICAL, NCIC CTG trial BR.26, and NCIC CTG trial BR.19). Analyses of the combined data were performed to determine relationships of MUT status/subtype to response and survival end points.

RESULTS

KRAS status was known for 1362 of 2624 patients (785 receiving EGFR TKIs and 577 receiving placebo); 275 (20%) had KRAS MUTs (248 at codon 12; 15 at codon 13; 12 at other codons). In the placebo arms there was no difference in overall survival (OS) for patients with KRAS MUTs or wild-type tumors (hazard ratio [HR] = 1.04, confidence interval [CI]: 0.81-1.33 for univariable analysis and HR = 1.09, CI: 0.85-1.41 for multivariable analysis). Patients with guanine-to-thymidine transversion MUTs had longer OS than did those with guanine-to-adenine transition MUTs or guanine-to-cytosine transversion MUTs (median OS 6.3, 1.8, and 3.9 months, respectively, p = 0.01). Patients with KRAS MUT tumors derived no benefit from EGFR TKIs (OS HR = 1.13, CI: 0.85-1.51; progression-free survival HR = 1.02, CI: 0.76-1.36). The interaction between KRAS status and EGFR TKI effect was significant for progression-free survival (p = 0.04) but not for OS (p = 0.17). For patients with G12V MUTs, EGFR TKI treatment was harmful (OS HR = 1.96, CI: 1.03-3.70, p = 0.04), whereas guanine-to-adenine transition MUTs were associated with an OS benefit from EGFR TKIs (HR = 0.49, CI: 0.24-1.00, p = 0.05).

CONCLUSIONS

Overall, KRAS MUT is neither prognostic nor predictive of benefit from EGFR TKIs. However, it appears that KRAS MUT subtypes are not homogeneous in terms of their prognostic and predictive effects. These observations require prospective validation.

Variant Profiling of Candidate Genes in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis. Variant profiling is crucial for developing personalized treatment and elucidating the etiology of this disease.

METHODS

Patients with PDAC undergoing surgery from 2007 to 2012 (n = 73) were followed from diagnosis until death or the end of the study. We applied an anchored multiplex PCR (AMP)-based next-generation sequencing (NGS) method to a panel of 65 selected genes and assessed analytical performance by sequencing a quantitative multiplex DNA reference standard. In clinical PDAC samples, detection of low-level KRAS (Kirsten rat sarcoma viral oncogene homolog) mutations was validated by allele-specific PCR and digital PCR. We compared overall survival of patients according to KRAS mutation status by log-rank test and applied logistic regression to evaluate the association between smoking and tumor variant types.

RESULTS

The AMP-based NGS method could detect variants with allele frequencies as low as 1% given sufficient sequencing depth (>1500×). Low-frequency KRAS G12 mutations (allele frequency 1%-5%) were all confirmed by allele-specific PCR and digital PCR. The most prevalent genetic alterations were in KRAS (78% of patients), TP53 (tumor protein p53) (25%), and SMAD4 (SMAD family member 4) (8%). Overall survival in T3-stage PDAC patients differed among KRAS mutation subtypes (P = 0.019). Transversion variants were more common in ever-smokers than in never-smokers (odds ratio 5.7; 95% CI 1.2-27.8).

CONCLUSIONS

The AMP-based NGS method is applicable for profiling tumor variants. Using this approach, we demonstrated that in PDAC patients, KRAS mutant subtype G12V is associated with poorer survival, and that transversion variants are more common among smokers.

Outcomes of patients with advanced cancer and KRAS mutations in phase I clinical trials

Background

KRAS mutation is common in human cancer. We assessed the clinical factors, including type of KRAS mutation and treatment, of patients with advanced cancer and tumor KRAS mutations and their association with treatment outcomes.

Methods

Patients referred to the Phase I Clinic for treatment who underwent testing for KRAS mutations were analyzed.

Results

Of 1,781 patients, 365 (21%) had a KRAS mutation. The G12D mutation was the most common mutation (29%). PIK3CA mutations were found in 24% and 10% of patients with and without KRAS mutations (p<0.0001). Of 223 patients with a KRAS mutation who were evaluable for response, 56 were treated with a MEK inhibitor-containing therapy and 167 with other therapies. The clinical benefit (partial response and stable disease lasting ≥ 6 months) rates were 23% and 9%, respectively, for the MEK inhibitor versus other therapies (p=0.005). The median progression-free survival (PFS) was 3.3 and 2.2 months, respectively (p=0.09). The respective median overall survival was 8.4 and 7.0 months (p=0.38). Of 66 patients with a KRAS mutation and additional alterations, higher rates of clinical benefit (p=0.04), PFS (p=0.045), and overall survival (p=0.02) were noted in patients treated with MEK inhibitor-containing therapy (n=9) compared to those treated with targeted therapy matched to the additional alterations (n=24) or other therapy (n=33).

Conclusions

MEK inhibitors in patients with KRAS-mutated advanced cancer were associated with higher clinical benefit rates compared to other therapies. Therapeutic strategies that include MEK inhibitors or novel agents combined with other targeted therapies or chemotherapy need further investigation.

Detection of K-ras gene mutation by liquid biopsy in patients with pancreatic cancer

BACKGROUND

Cell-free circulating tumor DNA (ctDNA) in serum has been considered to be a useful candidate for noninvasive cancer diagnosis. The current study was designed to estimate the clinical usefulness of genetic analysis for ctDNA by digital polymerase chain reaction in patients with pancreatic cancer.

METHODS

The authors compared K-ras mutations detected in endoscopic ultrasound-guided fine-needle aspiration biopsy tissue DNA and in ctDNA from 75 patients with pancreatic cancer. K-ras mutations in the serum of 66 independent, consecutive patients with pancreatic cancer were also analyzed and the authors compared the results with survival rates.

RESULTS

The frequencies of the mutations in tissue samples at G12V, G12D, and G12R in codon 12 were 28 of 75 samples (37.3%), 22 of 75 samples (29.3%), and 6 of 75 samples (8.0%), respectively. Conversely, the rates of the mutations in ctDNA were 26 of 75 samples (34.6%), 29 of 75 samples (38.6%), and 4 of 75 samples (5.3%), respectively. Overall, the K-ras mutation rates in tissue and ctDNA were 74.7% and 62.6%, respectively, and the concordance rate between them was 58 of 75 samples (77.3%). Survival did not appear to differ by the presence of K-ras mutations in tissue DNA, but the survival of patients with K-ras mutations in ctDNA was significantly shorter than that of patients without mutations in both a development set (P = .006) and an independent validation set (P = .002). The difference was especially evident in cases with a G12V mutation.

CONCLUSIONS

Analysis of ctDNA is a new useful procedure for detecting mutations in patients with pancreatic cancer. This noninvasive method may have great potential as a new strategy for the diagnosis of pancreatic cancer as well as for predicting survival.

Distinct Clinicopathological Patterns of Mismatch Repair Status in Colorectal Cancer Stratified by KRAS Mutations

In sporadic colorectal cancer (CRC), the BRAF^V600E mutation is associated with deficient mismatch repair (MMR) status and inversely associated with to KRAS mutations. In contrast to deficient MMR (dMMR) CRC, data on the presence of KRAS oncogenic mutations in proficient MMR (pMMR) CRC and their relationship with tumor progression are scarce. We therefore examined the MMR status in combination with KRAS mutations in 913 Chinese patients and correlated the findings obtained with clinical and pathological features. The MMR status was determined based on detection of MLH1, MSH2, MSH6 and PMS2 expression. KRAS mutation and dMMR status were detected in 36.9% and 7.5% of cases, respectively. Four subtypes were determined by MMR and KRAS mutation status: KRAS (+)/pMMR (34.0%), KRAS (+)/dMMR (2.9%), KRAS (-)/pMMR (58.5%) and KRAS (-)/dMMR (4.6%). A higher percentage of pMMR tumors with KRAS mutation were most likely to be female (49.0%), proximal located (45.5%), a mucinous histology (38.4%), and to have increased lymph node metastasis (60.3%), compared with pMMR tumors without BRAF^V600E and KRAS mutations (36.0%, 29.3%, 29.4% and 50.7%, respectively; all P < 0.01). To the contrary, compared with those with KRAS(-)/dMMR tumors, patients with KRAS(+)/dMMR tumors demonstrated no statistically significant differences in gender, tumor location, pT depth of invasion, lymph node metastasis, pTNM stage, and histologic grade. This study revealed that specific epidemiologic and clinicopathologic characteristics are associated with MMR status stratified by KRAS mutation. Knowledge of MMR and KRAS mutation status may enhance molecular pathologic staging of CRC patients and metastatic progression in CRC can be estimated based on the combination of these biomarkers.

KRAS (but not BRAF) mutations in ovarian serous borderline tumour are associated with recurrent low-grade serous carcinoma

BRAF and KRAS mutations in ovarian serous borderline tumours (OSBTs) and ovarian low-grade serous carcinomas (LGSCs) have been previously described. However, whether those OSBTs would progress to LGSCs or whether those LGSCs were developed from OSBT precursors in previous studies is unknown. Therefore, we assessed KRAS and BRAF mutations in tumour samples from 23 recurrent LGSC patients with a known initial diagnosis of OSBT. Paraffin blocks from both OSBT and LGSC samples were available for five patients, and either OSBTs or LGSCs were available for another 18 patients. Tumour cells from paraffin-embedded tissues were dissected out for mutation analysis by conventional polymerase chain reaction (PCR) and Sanger sequencing. Tumours that appeared to have wild-type KRAS by conventional PCR-Sanger sequencing were further analysed by full COLD (co-amplification at lower denaturation temperature)-PCR and deep sequencing. Full COLD-PCR was able to enrich the amplification of mutated alleles. Deep sequencing was performed with the Ion Torrent personal genome machine (PGM). By conventional PCR-Sanger sequencing, BRAF mutation was detected only in one patient and KRAS mutations were detected in ten patients. Full COLD-PCR deep sequencing detected low-abundance KRAS mutations in eight additional patients. Three of the five patients with both OSBT and LGSC samples available had the same KRAS mutations detected in both OSBT and LGSC samples. The remaining two patients had only KRAS mutations detected in their LGSC samples. For patients with either OSBT or LGSC samples available, KRAS mutations were detected in seven OSBT samples and six LGSC samples. Surprisingly, patients with the KRAS G12V mutation have shorter survival times. In summary, KRAS mutations are very common in recurrent LGSC, while BRAF mutations are rare. The findings indicate that recurrent LGSC can arise from proliferation of OSBT tumour cells with or without detectable KRAS mutations.

Molecular targeted therapies in metastatic melanoma

The advent of personalized medicine has ushered in a new era for cancer therapy with a significant impact on the management of advanced melanoma. Molecular targeted therapies have shown promise in the management of various malignancies, including melanoma, with lower toxicity profiles and better overall survival as compared with conventional therapy. The discovery of BRAF mutations in melanoma led to the development of BRAF inhibitors for the treatment of advanced melanoma. However, growing concerns over drug resistance to molecular targeted therapies including BRAF inhibitors, have spurred efforts to elucidate additional molecular targets for the treatment of advanced melanoma. In this review, we discuss the known molecular aberrations in melanoma, current and novel targeted approaches in its treatment, and drug resistance patterns.

The prevalence and prognostic significance of KRAS mutation in bladder cancer, chronic myeloid leukemia and colorectal cancer

Mutations in the KRAS gene have been shown to play a key role in the pathogenesis of a variety of human tumours. However the mutational spectrum of KRAS gene differs by organ site. In this study, we have analysed the mutational spectrum of KRAS exon 1 in bladder tumours, colorectal cancer (CRC) and chronic myeloid leukemia (CML). A total of 366 patients were included in the present study (234 bladder tumours, 48 CRC and 84 CML). The KRAS mutations are absent in BCR/ABL1 positive CML. This result suggests that BCR/ABL1 fusion gene and KRAS mutations were mutually exclusive. The frequency of KRAS mutations in bladder cancer was estimated at 4.27 %. All of mutations were found in codon 12 and 90 % of them were detected in advanced bladder tumours. However the correlation between KRAS mutations and tumour stage and grade does not report a statistical significant association. The KRAS mutations occur in 35.41 % of patients with CRC. The most frequent mutations were G12C, G12D and G13D. These mutations were significantly correlated with histological differentiation of CRC (p = 0.024). Although the high frequency of KRAS in CRC in comparison to bladder cancer, these two cancers appear to have the same mutational spectrum (p > 0.05).

Prognostic value of K-ras mutation status and subtypes in endoscopic ultrasound-guided fine-needle aspiration specimens from patients with unresectable pancreatic cancer

BACKGROUND

Although recent reports indicate that K-ras mutation status is a biomarker that acts as a prognostic factor, only a few analyses of K-ras mutation subtypes have been published. In addition, there are no reports that analyze overall survival and prognostic factors according to K-ras mutation status and subtypes in only unresectable pancreatic cancer (PC) determined from tissues obtained by endoscopic ultrasound-guided fine-needle aspiration.

METHODS

We retrospectively analyzed 242 patients who were diagnosed as having unresectable PC with available histological diagnosis. Clinical data collected included sex, age, Eastern Cooperative Oncology Group performance status, carbohydrate antigen (CA) 19-9, primary tumor location, stage (local or metastatic) according to TNM staging, first-line chemotherapy, K-ras mutation status and subtypes (G12D, G12V, and G12R), and overall survival. We analyzed the negative prognostic factors for reduced overall survival in unresectable PC patients using these data.

RESULTS

From multivariate analysis, CA19-9 ≥1000 U/ml (hazard ratio [HR] 1.78, 95 % confidence interval [CI] 1.28-2.46, P < 0.01), metastatic stage (HR 2.26, 95 % CI 1.58-3.24, P < 0.01), and mutant-K-ras (HR 1.76, 95 % CI 1.03-3.01, P = 0.04) were negative prognostic factors, indicating a reduced survival. Among the patients who had K-ras mutation subtypes, CA19-9 ≥1000 U/ml (HR 1.65, 95 % CI 1.12-2.37, P < 0.01), metastatic stage (HR 2.12, 95 % CI 1.44-3.14, P < 0.01), and the presence of the G12D or G12R mutations (HR 1.60, 95 % CI 1.11-2.28) were negative prognostic factors for overall survival.

CONCLUSIONS

K-ras mutation status and subtypes may be associated with survival duration in pancreatic cancer patients.

Targeted agents in non-small cell lung cancer therapy: What is there on the horizon?

Lung cancer is a heterogeneous group of diseases. There has been much research in lung cancer over the past decade which has advanced our ability to treat these patients with a more personalized approach. The scope of this paper is to review the literature and give a broad understanding of the current molecular targets for which we currently have therapies as well as other targets for which we may soon have therapies. Additionally, we will cover some of the issues of resistance with these targeted therapies. The molecular targets we intend to discuss are epidermal growth factor receptor (EGFR), Vascular endothelial growth factor (VEGF), anaplastic large-cell lymphoma kinase (ALK), KRAS, C-MET/RON, PIK3CA. ROS-1, RET Fibroblast growth factor receptor (FGFR). Ephrins and their receptors, BRAF, and immunotherapies/vaccines. This manuscript only summarizes the work which has been done to date and in no way is meant to be comprehensive.

KRAS mutation: should we test for it, and does it matter?

Lung cancer is the leading cause of cancer mortality in the United States and worldwide. Previously, lung cancer was simplistically divided into non-small-cell lung cancer (NSCLC) and small-cell lung cancer. However, in the last decade, we have gone from a simplistic binary system of classifying lung cancer to defining NSCLC on the basis of molecular subsets. KRAS mutations represent the most common molecular change in NSCLC. The presence of KRAS mutation has been shown to be associated with a poor prognosis in NSCLC, but this is of little clinical utility. More important is determining the clinical utility of KRAS mutational analysis for predicting benefit of chemotherapy, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), anti-EGFR monoclonal antibodies, or other novel therapeutics. Current data does not support the routine use of KRAS mutational analysis for predicting chemotherapy benefit. Additionally, there was significant interest in using KRAS status to select patients for EGFR TKI and anti-EGFR monoclonal antibodies. However, the EGFR mutational status has demonstrated significant predictive value in the selection of patients for EGFR TKI therapy and is now the preferred test. An association between KRAS mutational status and benefit of anti-EGFR monoclonal antibodies has not been demonstrated in NSCLC. Here we review, in the context of NSCLC, the underlying biology of KRAS mutations, the predictive value of KRAS mutations for therapeutic intervention, and the integration of KRAS mutational testing into our current clinical paradigms.

KRAS mutation and NF-κB activation indicates tolerance of chemotherapy and poor prognosis in colorectal cancer

BACKGROUND

Evidence shows a strong relationship between KRAS mutations and the NF-κB signaling pathway. In colorectal cancer, however, the study of this subject has been very limited and results are inconsistent.

AIMS

To examine the relationship between KRAS mutations and NF-κB activation and their effect on chemotherapy response and survival of colorectal cancer patients.

MATERIALS AND METHODS

NF-κB activation was analyzed by immunohistochemistry in 167 primary colorectal cancer specimens in which the KRAS mutation status was confirmed. Clinical and pathologic data were extracted from the medical records and reviewed.

RESULTS

Of 167 tumors screened, 63 (37.7 %) had NF-κB activation, 59 (35.3 %) had KRAS mutations, and 30 (18.0 %) had both NF-κB activation and KRAS mutations. The frequency of NF-κB activation in tumors with KRAS mutations was significantly higher than in tumors with wild type KRAS; 50.8 versus 30.6 %, P = 0.012. Patients with both KRAS mutations and NF-κB activation had a lower objective response to first-line chemotherapy than patients with other tumors, 23.8 versus 49.4 % (P = 0.035). Compared to patients with both KRAS mutations and NF-κB activation, overall survival of patients in other groups was significantly higher; median overall survival was 28.4 months (95 % CI 21.0-35.8) versus 46.3 months (95 % CI 39.4-53.2), hazard ratio 0.259 (95 % CI 0.125-0.538), P = 0.005.

CONCLUSIONS

NF-κB activation was associated with KRAS mutation, and both KRAS mutation and NF-κB activation were indicative of high tolerance of chemotherapy and poor prognosis for colorectal cancer patients. Tumors with KRAS mutations and NF-κB activation may be a unique subtype of colorectal cancer.

A subset of papillary thyroid carcinomas contain KRAS mutant subpopulations at levels above normal thyroid

The molecular pathogenesis of papillary thyroid carcinoma (PTC) is largely attributed to chromosomal rearrangements and point mutations in genes within the MAPK pathway (i.e., BRAF and RAS). Despite KRAS being the 6th most frequently mutated gene for all cancers, the reported frequency in thyroid cancer is only 2%. This may be due, in part, to the use of insensitive mutation detection methods such as DNA sequencing. Therefore, using the sensitive and quantitative ACB-PCR approach, we quantified KRAS codon 12 GGT → GAT and GGT → GTT mutant fraction (MF) in 20 normal thyroid tissues, 17 primary PTC, 2 metastatic PTC, and 1 anaplastic thyroid carcinoma. We observed measurable levels of KRAS codon 12 GAT or GTT mutation in all normal thyroid tissues. For PTCs, 29.4% and 35.3% had KRAS codon 12 GAT and GTT MF above the 95% upper confidence interval for the corresponding MFs in normal thyroid. The highest observed KRAS codon 12 GTT MFs were associated with tumors with follicular characteristics and relatively high levels of tumor necrosis. The results indicate KRAS mutant subpopulations are present in a large number of thyroid tumors, a fact previously unrecognized. The presence of KRAS mutation may indicate a tumor with an aggressive phenotype, thus directing the course of clinical treatment.

Genetic and biochemical alterations in non-small cell lung cancer

Despite significant advances in the detection and treatment of lung cancer, it causes the highest number of cancer-related mortality. Recent advances in the detection of genetic alterations in patient samples along with physiologically relevant animal models has yielded a new understanding of the molecular etiology of lung cancer. This has facilitated the development of potent and specific targeted therapies, based on the genetic and biochemical alterations present in the tumor, especially non-small-cell lung cancer (NSCLC). It is now clear that heterogeneous cell signaling pathways are disrupted to promote NSCLC, including mutations in critical growth regulatory proteins (K-Ras, EGFR, B-RAF, MEK-1, HER2, MET, EML-4-ALK, KIF5B-RET, and NKX2.1) and inactivation of growth inhibitory pathways (TP53, PTEN, p16, and LKB-1). How these pathways differ between smokers and non-smokers is also important for clinical treatment strategies and development of targeted therapies. This paper describes these molecular targets in NSCLC, and describes the biological significance of each mutation and their potential to act as a therapeutic target.

Personalized Medicine in Non–Small-Cell Lung Cancer: Is KRAS a Useful Marker in Selecting Patients for Epidermal Growth Factor Receptor–Targeted Therapy?

In patients with metastatic colorectal cancer, the predictive value of KRAS mutational status in the selection of patients for treatment with anti–epidermal growth factor (EGFR) monoclonal antibodies is established. In patients with non–small-cell lung cancer (NSCLC), the utility of determining KRAS mutational status to predict clinical benefit to anti-EGFR therapies remains unclear. This review will provide a brief description of Ras biology, provide an overview of aberrant Ras signaling in NSCLC, and summarize the clinical data for using KRAS mutational status as a negative predictive biomarker to anti-EGFR therapies. Retrospective investigations of KRAS mutational status as a negative predictor of clinical benefit from anti-EGFR therapies in NSCLC have been performed; however, small samples sizes as a result of low prevalence of KRAS mutations and the low rate of tumor sample collection have limited the strength of these analyses. Although an association between the presence of KRAS mutation and lack of response to EGFR tyrosine kinase inhibitors (TKIs) has been observed, it remains unclear whether there is an association between KRAS mutation and EGFR TKI progression-free and overall survival. Unlike colorectal cancer, KRAS mutations do not seem to identify patients who do not benefit from anti-EGFR monoclonal antibodies in NSCLC. The future value of testing for KRAS mutational status may be to exclude the possibility of an EGFR mutation or anaplastic lymphoma kinase translocation or to identify a molecular subset of patients with NSCLC in whom to pursue a drug development strategy that targets the KRAS pathway.

Gene expression deregulation by KRAS G12D and G12V in a BRAF V600E context

Background

KRAS and BRAF mutations appear of relevance in the genesis and progression of several solid tumor types but the co-occurrence and interaction of these mutations have not yet been fully elucidated. Using a microsatellite stable (MSS) colorectal cancer (CRC) cell line (Colo741) having mutated BRAF and KRAS^WT, we also aimed to investigate the KRAS-BRAF interaction. Gene expression profiles for control KRAS^WT, KRAS^G12V and KRAS^G12D transfected cells were obtained after cell clone selection and RT-PCR screening. Extensive qPCR was performed to confirm microarray data.

Results

We found that the KRAS^G12V state deregulated several genes associated to cell cycle, apoptosis and nitrogen metabolism. These findings indicated a reduced survival and proliferation with respect to the KRAS^WT state. The KRAS^G12D state was, instead, characterized by several other distinct functional changes as for example those related to chromatin organization and cell-cell adhesion without affecting apoptosis related genes.

Conclusion

These data predict that the G12D mutation may be more likely selected in a BRAF mutated context. At the same time, the presence of the KRAS^G12V mutation in the cells escaping apoptosis and inducing angiogenesis via IL8 may confer a more aggressive phenotype. The present results get along with the observations that CRCs with G12V are associated with a worse prognosis with respect to the WT and G12D states and may help identifying novel CRC pathways and biomarkers of clinical relevance.

Molecular detection (k-ras) of exfoliated tumour cells in the pelvis is a prognostic factor after resection of rectal cancer?

BACKGROUND

After total mesorectal excision (TME) for rectal cancer around 10% of patients develops local recurrences within the pelvis. One reason for recurrence might be spillage of cancer cells during surgery. This pilot study was conducted to investigate the incidence of remnant cancer cells in pelvic lavage after resection of rectal cancer. DNA from cells obtained by lavage, were analysed by denaturing capillary electrophoresis with respect to mutations in hotspots of the k-ras gene, which are frequently mutated in colorectal cancer.

RESULTS

Of the 237 rectal cancer patients analyzed, 19 had positive lavage fluid. There was a significant survival difference (p = 0.006) between patients with k-ras positive and negative lavage fluid.

CONCLUSION

Patients with k-ras mutated cells in the lavage immediately after surgery have a reduced life expectation. Detection of exfoliated cells in the abdominal cavity may be a useful diagnostic tool to improve the staging and eventually characterize patients who may benefit from aggressive multimodal treatment of rectal cancer.

Tumorigenesis of K-ras mutation in human endometrial carcinoma via upregulation of estrogen receptor

OBJECTIVE

To investigate the tumorigenesis of mutant [12Asp]-K-ras in endometrial carcinoma and its relationship with ER.

METHODS

We constructed pcDI-[12Asp]K-ras4B by inserting full-length [12Asp]K-ras4B from human endometrial carcinoma Hec-1A cells, into pcDI vector. Cell proliferation of NIH3T3 after transfection with pcDI-[12Asp]K-ras4B was measured by MTT assay. The cell transformation was determined by colony formation and tumor nodule development. [12Asp]-K-ras4B-NIH3T3 cells were transfected with constitutively active pCMV-RafCAAX and dominant-negative pCMV-RafS621A. Cell growth was measured by MTT assay and [3H]thymidine incorporation. After transfected with pcDI-[12Asp]K-ras4B or pCMV-RafS621A, the cells were harvested for Western blot and reporter assay to determine the expression and transcriptional activity of ERalpha and ERbeta, respectively.

RESULTS

[12Asp]-K-ras4B enhanced NIH3T3 cells proliferation after 48 h post-transfection (P < 0.05). More colonies were grown 10 days after incubating pcDI-[12Asp]-K-ras4B-NIH3T3 cells (13.48%) than pcDI-NIH3T3 (4.26%) or untreated NIH3T3 (2.33%). The pcDI-[12Asp]-K-ras4B-NIH3T3 cells injected to the nude mice Balb/C developed tumor nodules with poor-differentiated cells after 12 days. An increase of ERalpha and ERbeta was observed in pcDI-[12Asp]-K-ras4B-NIH3T3 cells. RafS621A downregulated ERalpha and ERbeta expression. Estrogen induced the ER transcriptional activity by 5-fold in pcDI-NIH3T3 cells, 13-fold in pcDI-[12Asp]K-ras4B-NIH3T3 and 19-fold in HEC-1A. RafS621A suppressed the ER transcriptional activity.

CONCLUSIONS

K-ras mutation induces tumorigenesis in endometrium, and this malignant transformation involves Raf signaling pathway and ER.

Mutant KRAS, chromosomal instability and prognosis in colorectal cancer

The RAS gene family provides a global effect on gene expression by encoding small GTP-binding proteins which act as molecular switches connecting extracellular signals with nuclear transcription factors. While wild type RAS proteins are switched off shortly after activation, mutant RAS proteins remain constitutively activated leading to complex interactions among their downstream effectors. For some human tumor types, these interactions were shown to contribute to cancer genesis and progression by inducing changes in cell survival, apoptosis, angiogenesis, invasion and metastasis. This review addresses the controversial link of KRAS mutations in colorectal cancer with chromosomal instability and patient prognosis.

Oncogenic Ras and its role in tumor cell invasion and metastasis

The processes by which cancer cells leave the tumor and enter adjacent tissue is known as invasion, whereas metastasis refers to secondary tumor colonization of tissue at a distance from the primary lesion. These two events are the most lethal of cancer phenomena and the signaling mechanisms that govern them are complex. The Ras signaling pathways are well represented in their involvement in tumor initiation, but considerably less is known about their contribution to invasion and metastasis. In this review, we discuss the current evidence for mutant Ras proteins as significant players in these aspects of cancer progression.