Kirsten ras mutations in patients with colorectal cancer: the 'RASCAL II' study

Can Serum be Used for Analyzing the KRAS Mutation Status in Patients with Advanced Colorectal Cancer?

Purpose

KRAS mutations have been used widely as prognostic or predictive marker in patients with advanced colorectal cancer (CRC). However, it may be difficult to obtain a tumor tissue for analyzing the status of KRAS mutation in large proportion of patients with advanced disease.

Materials and Methods

We obtained pairs of tumor and serum samples from 65 patients with advanced CRC, between March 2008 and July 2011. KRAS mutation status from the tumor samples was analyzed by genomic polymerase chain reaction and direct sequence, and KRASmutation status from the serum samples was determined by a genomic polymerase chain reaction–restriction fragment length polymorphism assay.

Results

KRAS mutations were detected in the serum samples of 26 patients and in the tumor samples of 31 patients. KRAS mutation status in the serum and tumor samples was consistent in 44 of the 65 pairs (67.7%). There was a significant correlation between the mutations detected in the serum sample and the mutations detected in the matched tumor sample (correlation index, 0.35; p < 0.004). Twenty-two of the 57 patients (38.5%) received anti-epidermal growth factor receptor therapy as any line therapy. There was no significant difference in the overall survival (OS) in accordance to the status of KRASmutations in both the serum and tumor samples (p > 0.05). In a multivariate analysis, liver metastasis and no cytoreductive operation were independent prognostic factors for decreased OS.

Conclusion

The serum sample might alternatively be used when it is difficult to obtain tumor tissues for analyzing the status of KRAS mutation in patients with advanced CRC.

Prognostic value of KRAS and BRAF mutations in curatively resected colorectal cancer

AIM: To investigate the prognostic role of KRAS and BRAF mutations after adjustment for microsatellite instability (MSI) status in Japanese colorectal cancer (CRC) population.

METHODS: We assessed KRAS and BRAF mutations and MSI status in 813 Japanese patients with curatively resected, stage I-III CRC and examined associations of these mutations with disease-free survival (DFS) and overall survival (OS) using uni- and multivariate Cox proportional hazards models.

RESULTS: KRAS and BRAF mutations were detected in 312 (38%) of 812 and 40 (5%) of 811 tumors, respectively. KRAS mutations occurred more frequently in females than in males (P = 0.02), while the presence of BRAF mutations was significantly associated with the female gender (P = 0.006), proximal tumor location (P < 0.001), mucinous or poorly differentiated histology (P < 0.001), and MSI-high tumors (P < 0.001). After adjusting for relevant variables, including MSI status, KRAS mutations were associated with poorer DFS (HR = 1.35; 95%CI: 1.03-1.75) and OS (HR = 1.46; 95%CI: 1.09-1.97). BRAF mutations were poor prognostic factors for DFS (HR = 2.20; 95%CI: 1.19-4.06) and OS (HR = 2.30; 95%CI: 1.15-4.71). Neither the BRAF by MSI interaction test nor the KRAS by MSI interaction test yielded statistically significant results for DFS and OS.

CONCLUSION: KRAS and BRAF mutations are associated with inferior survival, independent of MSI status, in Japanese patients with curatively resected CRC.

A specific KRAS codon 13 mutation is an independent predictor for colorectal cancer metachronous distant metastases

BACKGROUND

In colorectal cancer, there are significant differences between synchronous and metachronous distant metastases. However in recent studies, synchronous and metachronous metastases were always lumped together, neglecting their clinical and molecular differences. The mechanism of the latency of metachronous metastases is still unclear. We conducted this study to reveal the relationship between EGFR pathways and metachronous metastases, and try to find efficient predictors.

METHODS

PCRs and pyrosequencing were used to detect KRAS, BRAF, PIK3CA and PTEN mutations in primary tumor tissues in a total of 281 patients from 2002 to 2008. Patients were identified into three groups: no-metastases group, synchronous-metastases group and metachronous-metastases group. Clinical and survival data were collected from a prospective database.

RESULTS

KRAS codon 13 mutation was an independent predictor only for metachronous distant metastases (OR = 11.857, P < 0.001), but not for synchronous metastases. Male gender (OR = 2.233, P = 0.024), primary tumor located at rectum (OR = 0.404, P = 0.041), and primary pN2 stage (OR = 3.361, P = 0.01) were also independent predictors for metachronous distant metastases. Different SNPs in KRAS worked significantly different in determining synchronous or metachronous metastases. BRAF mutation (Univariate, OR = 11.5, P = 0.039) and > 200 ng/ml preoperative CEA (Univariate, OR = 41, P = 0.011) potentially predicted metastases within 6 months after primary tumor resection. After metachronous metastases, radical resection (HR = 0.280, P = 0.002) was the most important protective factor for long-term survival.

CONCLUSION

There were significant clinical and molecular differences between synchronous and metachronous metastases. As an independent predictor, KRAS codon 13 mutation might be the key to explain the mechanism of colorectal cancer metachronous distant metastases. Together with clinical characteristics, it could aid in the early detection of metachronous metastases.

Molecular markers identify subtypes of stage III colon cancer associated with patient outcomes

BACKGROUND & AIMS

Categorization of colon cancers into distinct subtypes using a combination of pathway-based biomarkers could provide insight into stage-independent variability in outcomes.

METHODS

We used a polymerase chain reaction-based assay to detect mutations in BRAF (V600E) and in KRAS in 2720 stage III cancer samples, collected prospectively from patients participating in an adjuvant chemotherapy trial (NCCTG N0147). Tumors deficient or proficient in DNA mismatch repair (MMR) were identified based on detection of MLH1, MSH2, and MSH6 proteins and methylation of the MLH1 promoter. Findings were validated using tumor samples from a separate set of patients with stage III cancer (n = 783). Association with 5-year disease-free survival was evaluated using Cox proportional hazards models.

RESULTS

Tumors were categorized into 5 subtypes based on MMR status and detection of BRAF or KRAS mutations which were mutually exclusive. Three subtypes were MMR proficient: those with mutations in BRAF (6.9% of samples), mutations in KRAS (35%), or tumors lacking either BRAF or KRAS mutations (49%). Two subtypes were MMR deficient: the sporadic type (6.8%) with BRAF mutation and/or or hypermethylation of MLH1 and the familial type (2.6%), which lacked BRAF(V600E) or hypermethylation of MLH1. A higher percentage of MMR-proficient tumors with BRAF(V600E) were proximal (76%), high-grade (44%), N2 stage (59%), and detected in women (59%), compared with MMR-proficient tumors without BRAF(V600E) or KRAS mutations (33%, 19%, 41%, and 42%, respectively; all P < .0001). A significantly lower proportion of patients with MMR-proficient tumors with mutant BRAF (hazard ratio = 1.43; 95% confidence interval: 1.11-1.85; Padjusted = .0065) or mutant KRAS (hazard ratio = 1.48; 95% confidence interval: 1.27-1.74; Padjusted < .0001) survived disease-free for 5 years compared with patients whose MMR-proficient tumors lacked mutations in either gene. Disease-free survival rates of patients with MMR-deficient sporadic or familial subtypes was similar to those of patients with MMR-proficient tumors without BRAF or KRAS mutations. The observed differences in survival rates of patients with different tumor subtypes were validated in an independent cohort.

CONCLUSIONS

We identified subtypes of stage III colon cancer, based on detection of mutations in BRAF (V600E) or KRAS, and MMR status that show differences in clinical and pathologic features and disease-free survival. Patients with MMR-proficient tumors and BRAF or KRAS mutations had statistically shorter survival times than patients whose tumors lacked these mutations. The tumor subtype found in nearly half of the study cohort (MMR-proficient without BRAF(V600E) or KRAS mutations) had similar outcomes to those of patients with MMR-deficient cancers.

Treatment of metastatic colorectal cancer: focus on panitumumab

Targeted agents are an important therapeutic option in the treatment of metastatic colorectal cancer (mCRC). Panitumumab is a recombinant, fully humanized, immunoglobulin G2 monoclonal antibody that targets the epidermal growth factor receptor (EGFR) with efficacy in mCRC as monotherapy and in combination with chemotherapy. Kirsten rat sarcoma (KRAS) mutation status has emerged as an important biomarker to predict response to anti-EGFR therapy. Optimal timing for panitumumab use in the mCRC treatment algorithm has not been established. This review discusses the mechanism of action, predictive biomarkers, and role of panitumumab in the treatment of mCRC.

KRAS mutation is associated with worse prognosis in stage III or high-risk stage II colon cancer patients treated with adjuvant FOLFOX

BACKGROUND

Although KRAS mutation has a predictive role in stage IV colorectal cancer (CRC) patients treated with anti-EGFR therapy, there have been controversies in the prognostic impact of KRAS mutation in stage II or III disease. The purpose of this study was to assess the prognostic impact of KRAS and BRAF mutation in patients treated with adjuvant 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX).

METHODS

KRAS exon 2 and BRAF codon 600 were analyzed in patients with stage II and III CRC who underwent curative resection followed by adjuvant FOLFOX. Clinicopathologic features and disease-free survival (DFS) were compared.

RESULTS

Among a total of 437 patients, mutational data of KRAS and BRAF were available in 388 and 433 patients, respectively. KRAS mutation (codon 12 and 13) and BRAF V600E mutation was found in 26.5 and 3.7 % of patients. DFS was significantly worse in the KRAS mutant patients compared to KRAS wild type patients (3-year DFS 79 and 92 %, p = 0.006). Multivariate analysis revealed KRAS mutation as an independent negative prognostic factor for DFS (adjusted hazard ratio 2.30, 95 % confidence interval 1.23-4.32). Among the various subtypes of KRAS mutation, G13D (3-year DFS 76 %, p = 0.008) was significantly associated with poor DFS, while G12D was not associated with prognosis (3-year DFS 86 %, p = 0.61). There was no association between BRAF mutation and DFS.

CONCLUSIONS

KRAS mutation has an adverse prognostic impact on stage II or III CRC treated with adjuvant FOLFOX.

Association between molecular subtypes of colorectal cancer and patient survival

BACKGROUND AND AIMS

Colorectal cancer (CRC) is a heterogeneous disease that can develop via several pathways. Different CRC subtypes, identified based on tumor markers, have been proposed to reflect these pathways. We evaluated the significance of these previously proposed classifications to survival.

METHODS

Participants in the population-based Seattle Colon Cancer Family Registry were diagnosed with invasive CRC from 1998 through 2007 in western Washington State (N = 2706), and followed for survival through 2012. Tumor samples were collected from 2050 participants and classified into 5 subtypes based on combinations of tumor markers: type 1 (microsatellite instability [MSI]-high, CpG island methylator phenotype [CIMP] -positive, positive for BRAF mutation, negative for KRAS mutation); type 2 (microsatellite stable [MSS] or MSI-low, CIMP-positive, positive for BRAF mutation, negative for KRAS mutation); type 3 (MSS or MSI low, non-CIMP, negative for BRAF mutation, positive for KRAS mutation); type 4 (MSS or MSI-low, non-CIMP, negative for mutations in BRAF and KRAS); and type 5 (MSI-high, non-CIMP, negative for mutations in BRAF and KRAS). Multiple imputation was used to impute tumor markers for those missing data on 1-3 markers. We used Cox regression to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations of subtypes with disease-specific and overall mortality, adjusting for age, sex, body mass, diagnosis year, and smoking history.

RESULTS

Compared with participants with type 4 tumors (the most predominant), participants with type 2 tumors had the highest disease-specific mortality (HR = 2.20, 95% CI: 1.47-3.31); subjects with type 3 tumors also had higher disease-specific mortality (HR = 1.32, 95% CI: 1.07-1.63). Subjects with type 5 tumors had the lowest disease-specific mortality (HR = 0.30, 95% CI: 0.14-0.66). Associations with overall mortality were similar to those with disease-specific mortality.

CONCLUSIONS

Based on a large, population-based study, CRC subtypes, defined by proposed etiologic pathways, are associated with marked differences in survival. These findings indicate the clinical importance of studies into the molecular heterogeneity of CRC.

Pyrosequencing evaluation of low-frequency KRAS mutant alleles for EGF receptor therapy selection in metastatic colorectal carcinoma

AIM

To evaluate whether pyrosequencing (PS) improves the KRAS mutational status predictive value.

PATIENTS & METHODS

A retrospective analysis of KRAS mutations by PS and direct sequencing (DS) in 192 metastatic colorectal carcinomas (mCRCs), subgrouped in 51 KRAS mutated at PS and 141 KRAS wild-type at DS.

RESULTS

DS failed to detect low-frequency KRAS mutations in four out of 51 mCRCs, whereas PS detected 12 additional low-frequency KRAS mutations in 141 mCRCs KRAS wild-type at DS. After reanalyzing by PS 97 KRAS wild-type tumors treated with anti-EGF receptor (EGFR) antibodies, nine additional mutations were revealed in nonresponders, whereas none of responders exhibited a KRAS-mutated genotype. Of note, KRAS-mutated tumors upon PS showed a worst progression-free survival after EGFR therapy. Finally, PS allowed the detection of additional NRAS, BRAF and exon 20 PIK3CA mutations mostly in KRAS wild-type mCRCs resistant to EGFR therapy.

CONCLUSION

PS detection of low-frequency mutations may improve the KRAS predictive value for EGFR therapy selection.

KRAS mutations in tumor tissue and plasma by different assays predict survival of patients with metastatic colorectal cancer

Background

The optimal laboratory assay for detecting KRAS mutations in different biospecimens from patients with metastatic colorectal cancer (mCRC), and the clinical relevance of these gene alterations is still in question. We analyzed the prognostic–predictive relevance of KRAS status, determined in tumor and plasma DNA by two different assays, in a large mono-institutional series of mCRC patients.

Methods

DNA sequencing and peptide-nucleic-acid-mediated-polymerase chain reaction clamping (PNA-PCR) were used to determine KRAS status in 416 tumor and 242 matched plasma DNA samples from mCRC patients who received chemotherapy only. Relationships with outcomes were analyzed with respect to the different assays and tissue types.

Results

PNA-PCR was significantly more sensitive in detecting KRAS mutations than sequencing (41% vs. 30%, p < 0.001). KRAS mutations were more frequent in tumor tissue than in plasma (sequencing, 38% vs. 17%, p < 0.001; PNA-PCR, 47% vs. 31%, p < 0.001). Median OS was consistently shorter in KRAS-mutated patients than KRAS wild-type patients, independent from the assay and tissue tested; the largest difference was in plasma samples analyzed by PNA-PCR (KRAS mutated vs. wild-type: 15.7 vs. 19.1 months, p = 0.009). No association was observed between KRAS status and other outcomes. When tumor and plasma results were considered together, median OS in patients categorized as tissue/plasma KRAS negative/negative, tissue/plasma KRAS discordant, and tissue/plasma KRAS positive/positive were 21.0, 16.9 and 15.4 months, respectively (p = 0.008).

Conclusions

KRAS mutation status is of prognostic relevance in patients with mCRC. KRAS mutations in both tumor tissue and plasma are a strong prognostic marker for poor outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-014-0104-7) contains supplementary material, which is available to authorized users.

KRAS mutation testing in clinical practice

Activating mutation of KRAS plays a significant role in the pathogenesis of common human malignancies and molecular testing of KRAS mutation has emerged as an essential biomarker in the current practice of clinical oncology. The presence of KRAS mutation is generally associated with clinical aggressiveness of the cancer and reduced survival of the patient. Therapeutically, KRAS mutation testing has maximum utility in stratifying metastatic colorectal carcinoma and lung cancer patients for treatment with targeted therapy. Diagnostically, KRAS mutation testing is useful in the workup of pancreaticobiliary and thyroid cancers, particularly using cytological specimens. In the era of precision medicine, the role of KRAS mutation testing is poised to expand, likely in a setting of combinatorial therapeutic strategy and requiring additional mutation testing of its upstream and/or downstream effectors.

RAS mutations affect pattern of metastatic spread and increase propensity for brain metastasis in colorectal cancer

BACKGROUND

RAS and PIK3CA mutations in metastatic colorectal cancer (mCRC) have been associated with worse survival. We sought to evaluate the impact of RAS and PIK3CA mutations on cumulative incidence of metastasis to potentially curable sites of liver and lung and other sites such as bone and brain.

METHODS

We performed a computerized search of the electronic medical record of our institution for mCRC cases genotyped for RAS or PIK3CA mutations from 2008 to 2012. Cases were reviewed for patient characteristics, survival, and site-specific metastasis.

RESULTS

Among the 918 patients identified, 477 cases were RAS wild type, and 441 cases had a RAS mutation (394 at KRAS exon 2, 29 at KRAS exon 3 or 4, and 18 in NRAS). RAS mutation was significantly associated with shorter median overall survival (OS) and on multivariate analysis independently predicted worse OS (HR, 1.6; P < .01). RAS mutant mCRC exhibited a significantly higher cumulative incidence of lung, bone, and brain metastasis and on multivariate analysis was an independent predictor of involvement of these sites (HR, 1.5, 1.6, and 3.7, respectively). PIK3CA mutations occurred in 10% of the 786 cases genotyped, did not predict for worse survival, and did not exhibit a site-specific pattern of metastatic spread.

CONCLUSIONS

The metastatic potential of CRC varies with the presence of RAS mutation. RAS mutation is associated with worse OS and increased incidence of lung, bone, and brain metastasis. An understanding of this site-specific pattern of spread may help to inform physicians' assessment of symptoms in patients with mCRC.

Mechanisms of resistance to EGFR inhibitors in colorectal cancers

SUMMARY 

The EGF receptor (EGFR) is important in the regulation of proliferation, apoptosis and angiogenesis in cancer. EGFR inhibitors have become a mainstay of treatment of metastatic colorectal cancer, in particular KRAS wild-type patients in 50–60% of patients. Despite this many patients do not respond to these agents. Over the last few years the molecular basis of resistance to EGFR inhibitors has been elucidated to a certain degree. Mutations in KRAS and the NRAS exon are unlikely to respond to EGFR inhibitors. Other mutations, such as BRAF, PI3KCA/AKT and MET, may also lead to resistance. A greater understanding of the molecular basis for resistance may lead to ways of overcoming this, leading to improvements in care for patients.

Differences in K-ras and mitochondrial DNA mutations and microsatellite instability between colorectal cancers of Vietnamese and Japanese patients

BACKGROUND

The incidence of early-onset (under 50 years of age) colorectal cancer (CRC) in the Vietnamese has been reported to be quite higher than that in the Japanese. To clarify the differences in genetic alterations between Vietnamese and Japanese CRCs, we investigated mutations in K-ras and mitochondrial DNA (mtDNA) and high-frequency microsatellite instability (MSI-H) in the CRCs of Vietnamese and Japanese patients.

METHODS

We enrolled 60 Vietnamese and 233 Japanese patients with invasive CRCs. DNA was extracted from formalin-fixed, paraffin-embedded tissue sections. K-ras mutations were examined with PCR-single-strand conformation polymorphism analysis. mtDNA mutations and MSI-H were examined with microsatellite analysis using D310 and BAT-26, respectively.

RESULTS

K-ras mutations were examined in 60 Vietnamese and 45 Japanese CRCs. The frequency of the mutations in the Vietnamese CRCs was significantly higher than that in the Japanese CRCs (8 of 24 [33%] vs 5 of 45 [11%], p =0.048). MSI-H was examined in 60 Vietnamese and 130 Japanese CRCs. The frequency of MSI-H in the Vietnamese CRCs was also significantly higher than that in the Japanese CRCs (6 of 27 [22%] vs 10 of 130 [8%], p =0.030). mtDNA mutations were examined in 60 Vietnamese and 138 Japanese CRCs. The frequency of mtDNA mutations in the Vietnamese CRCs was significantly higher than that in the Japanese CRCs (19 of 44 [43%] vs 11 of 133 [9%], p <0.001). There were no significant differences in clinicopathologic characteristics, such as age, sex, tumour location, and depth, in terms of tumours with/without each genetic alteration in the CRCs of the Vietnamese and Japanese patients.

CONCLUSIONS

These results indicate that the developmental pathways of CRCs in the Vietnamese may differ from those of CRCs in the Japanese.

Portrait of the PI3K/AKT pathway in colorectal cancer

PI3K/AKT signaling leads to reduced apoptosis, stimulates cell growth and increases proliferation. Under normal conditions, PI3K/AKT activation is tightly controlled and dependent on both extracellular growth signals and the availability of amino acids and glucose. Genetic aberrations leading to PI3K/AKT hyper-activation are observed at considerable frequency in all major nodes in most tumors. In colorectal cancer the most commonly observed pathway changes are IGF2 overexpression, PIK3CA mutations and PTEN mutations and deletions. Combined, these alterations are found in about 40% of large bowel tumors. In addition, but not mutually exclusive to these, KRAS mutations are observed at a similar frequency. There are however additional, less frequent and more poorly understood events that may also push the PI3K/AKT pathway into overdrive and thus promote malignant growth. Here we discuss aberrations of components at the genetic, epigenetic, transcriptional, post-transcriptional, translational and post-translational level where perturbations may drive excessive PI3K/AKT signaling. Integrating multiple molecular levels will advance our understanding of this cancer critical circuit and more importantly, improve our ability to pharmacologically target the pathway in view of clonal development, tumor heterogeneity and drug resistance mechanisms. In this review, we revisit the PI3K/AKT pathway cancer susceptibility syndromes, summarize the known aberrations at the different regulatory levels and the prognostic and predictive values of these alterations in colorectal cancer.

Cost estimates and economic implications of expanded RAS testing in metastatic colorectal cancer

BACKGROUND

In colorectal cancer (CRC), evidence shows that expanding RAS testing to analyze more mutations may better predict benefit from anti-EGFR therapy. The economic implications of expanding RAS testing for metastatic CRC were analyzed.

MATERIALS AND METHODS

Estimates of standard KRAS exon 2 testing were based on the Centers for Medicare and Medicaid Services (CMS) 2014 Diagnostic Laboratory Fee Schedule, and expanded RAS testing was estimated using a sensitivity analysis done with various potential cost scenarios (1, 2, 10, and 30 times the cost of the standard KRAS test). The cost estimates for cetuximab and panitumumab were based on the CMS payment allowance limits for Medicare Part B.

RESULTS

A total of 28,692 patients with metastatic CRC were estimated to be eligible annually for RAS testing. For cetuximab, the societal cost of standard KRAS testing plus the drug versus expanded testing plus the drug would be $1.16 billion versus $816 million if the cost of the tests were the same. If the cost of the expanded RAS test were 30 times the cost of the standard test, then the societal cost of standard KRAS testing plus the drug versus expanded testing plus the drug would be $1.16 billion versus $980 million, a continued savings of more than $184 million annually. Similar savings were seen with panitumumab.

CONCLUSION

The increased societal cost of expanded RAS testing versus standard approved KRAS exon 2 testing was inconsequential when compared with the amount of money saved by not treating the additional 18% of patients who harbor additional RAS mutations (beyond exon 2) with anti-EGFR therapy.

[In situ analyses of molecular mechanisms of colorectal carcinogenesis]

The main signaling pathways of colorectal carcinogenesis encompass the classical adenoma-carcinoma sequence and the serrated route. In the classical adenoma-carcinoma sequence there are initially frequent mutations of the APC gene which lead to an activation of the WNT signaling pathway. When the WNT signaling pathway is activated β-catenin mediates the transcription of diverse factors which cause migration, invasion and proliferation of cells. Although APC mutations occur in all tumor cells, a heterogeneous distribution pattern of β-catenin is found in tumors and β-catenin also represents an important prognostic marker. A similar picture is found for γ-catenin which is expressed independently from β-catenin. Clearly more homogeneous is the expression of TCF4 and LEF1 which are the main binding partners of β-catenin and γ-catenin and are likewise important prognostic markers. The TRAIL signaling pathway is therapeutically interesting and within this pathway loss of the main receptors TRAIL-R1 and TRAIL-R2 is frequently found. Furthermore, the membranous localization of both factors correlates with a better overall survival. These results might be therapeutically relevant with respect to therapy with recombinant TRAIL molecules binding to TRAIL-R1 and TRAIL-R2. In the serrated route oncogen-induced senescence caused by mutations of the KRAS and BRAF oncogenes initially plays an important role. This senescence blockade is overcome by hypermethylation of the p16(INK4a) promoter and leads to the development of invasive tumors. The SIRT1 and c-Myc genes also contribute to progression of lesions in the serrated route and are activated through the RAS/RAF/MAPK-kinase signaling pathway as well as the WNT/β-catenin signaling pathway.

BRAF V600E mutation and KRAS codon 13 mutations predict poor survival in Chinese colorectal cancer patients

Background

Mutations in KRAS, BRAF and PIK3CA are the most common somatic alterations found in the colorectal cancer (CRC) patients from Western countries; but their prevalence and prognostic value have not been adequately assessed in Asian patients. The aim of this study was to determine the mutation frequencies of these genes in Chinese CRC patients and to investigate their impact on prognosis.

Methods

The sequences of exon 2 of KRAS, exon 15 of BRAF and exons 9 and 20 of PIK3CA were evaluated by PCR and direct sequencing using DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues from primary CRC tumors of 214 patients (colon/rectum: 126/88).

Results

KRAS, BRAF and PIK3CA mutations were identified in 44.9% (96/214), 4.2% (9/214) and 12.3% (26/212) CRCs, respectively. The most frequent mutations in KRAS, BRAF and PIK3CA were G12D, V600E and H1047R, respectively. All BRAF and 80.8% PIK3CA mutations were from colon cancer patients. BRAF V600E was associated with advanced TNM (P < 0.001), more distant metastases (P = 0.025), and worse overall survival (OS, P < 0.001; multivariate HR = 4.2, P = 0.004) in colon cancer patients. Compared with KRAS wt/BRAF wt CRC patients (N = 109), those with KRAS codon 13 mutations (N = 25) had significantly worse OS (P = 0.016; multivariate HR = 2.7, P = 0.011), whereas KRAS codon 12-mutated cases were not significantly associated with survival. Among the three most common KRAS mutations, G13D (N = 23) showed significant association with poor OS (P = 0.024; multivariate HR = 2.6, P = 0.016) compared with KRAS wt/BRAF wt patients.

Conclusion

Our findings indicate that PI3K/RAS-RAF signaling pathway genes are frequently mutated in Chinese CRC patients, but have different characteristics than found in Western patients. BRAF V600E is an independent prognostic factor for Chinese patients. Our finding that KRAS codon 13 mutations (in particular G13D) are associated with inferior survival in BRAF wild-type CRCs in Chinese patients was not reported thus far. Our data emphasizes the importance of prospective evaluation of molecular features in CRC patients, because a single mutation type may represent a distinct biologic effect and clinical implication.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-802) contains supplementary material, which is available to authorized users.

The BRAF mutation is associated with the prognosis in colorectal cancer

BACKGROUND

Two members of the Ras/Raf signaling pathway, KRAS and B-raf, are suspected to be involved in the stepwise progression of colorectal cancer (CRC) tumorigenesis.

OBJECTIVE

We compared the KRAS and BRAF mutation status of CRC patients with their clinicopathological characteristics and examined the effect of mutation status on survival rates.

METHODS

DNA was extracted from 164 samples, and the mutation statuses of KRAS and BRAF were assessed using peptide PNA clamp real-time PCR method. The presences of mutation were compared with clinicopathological factors and 5-year survival rate.

RESULTS

Among the 164 CRC cases, KRAS mutation as detected in 71 cases (43.3 %), respectively, with no relationship with clinicopathological factors of the patients. On Kaplan-Meier survival analysis, KRAS mutation was not significantly associated with survival (p = 0.971). BRAF mutation was detected in 26 cases (15.9 %) and not associated with clinicopathological factors of the patients. However, the 5-year survival rate of BRAF mutations was significantly decreased (p = 0.02).

CONCLUSIONS

The presence of KRAS mutation did not correlate with the various clinicopathological factors of CRC patients or the survival rate. However, the survival rate was reduced in BRAF-mutated CRC patients. Therefore, BRAF mutation could be an important prognostic factor in CRC patients.

Higher metastatic efficiency of KRas G12V than KRas G13D in a colorectal cancer model

Although all KRas (protein that in humans is encoded by the KRas gene) point mutants are considered to have a similar prognostic capacity, their transformation and tumorigenic capacities vary widely. We compared the metastatic efficiency of KRas G12V (Kirsten rat sarcoma viral oncogene homolog with valine mutation at codon 12) and KRas G13D (Kirsten rat sarcoma viral oncogene homolog with aspartic mutation at codon 13) oncogenes in an orthotopic colorectal cancer (CRC) model. Following subcutaneous preconditioning, recombinant clones of the SW48 CRC cell line [Kras wild-type (Kras WT)] expressing the KRas G12V or KRas G13D allele were microinjected in the mouse cecum. The percentage of animals developing lymph node metastasis was higher in KRas G12V than in KRas G13D mice. Microscopic, macroscopic, and visible lymphatic foci were 1.5- to 3.0-fold larger in KRas G12V than in KRas G13D mice (P < 0.05). In the lung, only microfoci were developed in both groups. KRas G12V primary tumors had lower apoptosis (7.0 ± 1.2 vs. 7.4 ± 1.0 per field, P = 0.02), higher tumor budding at the invasion front (1.2 ± 0.2 vs. 0.6 ± 0.1, P = 0.04), and a higher percentage of C-X-C chemokine receptor type 4 (CXCR4)-overexpressing intravasated tumor emboli (49.8 ± 9.4% vs. 12.8 ± 4.4%, P < 0.001) than KRas G13D tumors. KRas G12V primary tumors showed Akt activation, and β5 integrin, vascular endothelial growth factor A (VEGFA), and Serpine-1 overexpression, whereas KRas G13D tumors showed integrin β1 and angiopoietin 2 (Angpt2) overexpression. The increased cell survival, invasion, intravasation, and specific molecular regulation observed in KRas G12V tumors is consistent with the higher aggressiveness observed in patients with CRC expressing this oncogene.

Association between specific KRAS mutations and the clinicopathological characteristics of colorectal tumors

The aim of this study was to investigate the clinicopathological characteristics and distribution by tumor localization of KRAS point mutations in metastatic colorectal cancer. A total of 189 patients diagnosed with colorectal cancer between 2007 and 2014, who were either metastatic at the time of diagnosis or developed metastasis subsequently, were included in this study. KRAS mutation analysis was performed in the primary tumor tissues and KRAS mutations were identified in 47.6% of the patients. There was a high frequency of the p.G13D point mutation in left-colon tumors (P=0.011), while the p.G12D point mutation was more frequent in right-colon tumors (P=0.004). KRAS wild-type frequency (P=0.02) was higher among patients aged <40 years. A comparison of codon 12 and 13 mutations revealed that codon 12 mutations were more common in the >50-year-old group (P=0.03) and codon 13 mutations were more common in the <70-year-old group (P=0.04). KRAS wild-type tumors were localized in the right colon (P=0.005) and tumors with the p.G13D point mutation (P=0.018) were diagnosed at non-metastatic stages. In conclusion, KRAS point mutations in colorectal cancer exhibited a heterogeneous distribution in terms of tumor localization. In addition, the p.G13D point mutation was found to differ from other mutations in several aspects.

The prevalent KRAS exon 2 c.35 G>A mutation in metastatic colorectal cancer patients: A biomarker of worse prognosis and potential benefit of bevacizumab-containing intensive regimens?

Bevacizumab-containing chemotherapy differently predict increased efficacy in KRAS exon 2 mutant and wild-type metastatic colorectal cancer (MCRC) patients. Mutant compared to wild-type status did not significantly affect progression-free survival (PFS) and overall survival (OS) in patients fit for first line bevacizumab-containing FIr-B/FOx regimen, and after progression. In patients unfit for intensive regimens, mutant status significantly affected PFS, while not OS. Codon 12 KRAS mutations differentially affect GTPase function, and confer worse clinical behaviour. Prognostic relevance of the prevalent c.35 G>A KRAS mutation was retrospectively evaluated. Fit c.35 G>A mutant patients showed significantly worse OS compared to wild-type and to other mutant. After progression and in unfit patients, c.35 G>A mutation affected significantly worse PFS and OS. c.35 G>A mutant status does not significantly affect worse PFS in patients fit for first line FIr-B/FOx, and it may depend upon effectiveness of anti-VEGF-containing intensive regimen.

Molecular markers for colon diagnosis, prognosis and targeted therapy

Colorectal adenocarcinoma (CRC), the second leading cancer-related death in the United States, remains a global public health issue. Sporadic CRC is considered the result of sequential mucosal changes from normal colonic mucosa to adenocarcinoma. Efforts in understanding the molecular pathways leading to CRC tumorigenesis may lead to identifying novel, individually tailored therapeutic targets for patients. In this review, we focus on well-published prognostic and predictive markers in CRC and examine their role in clinical practice.

Prognostic value of KRAS mutations in stage III colon cancer: post hoc analysis of the PETACC8 phase III trial dataset

BACKGROUND

The prognostic value of KRAS mutations in colon adenocarcinoma is controversial. We examined this question as an ancillary study of the PETACC8 phase III trial.

PATIENTS AND METHODS

We analyzed the prognostic impact of KRAS exon 2 mutations in stage III colon cancer patients (n = 1657) receiving adjuvant FOLFOX ± cetuximab therapy included in the PETACC8 trial. Patients with BRAF-mutated cancers were excluded and, as no difference was found for time to recurrence (TTR) and disease-free survival (DFS) between treatment arms, both were pooled for analysis. Associations with TTR and DFS were analyzed using a Cox proportional hazards model.

RESULTS

KRAS mutations were found in 638 of 1657 tumors and linked to shorter TTR (P < 0.001). However, when specific mutations were compared with wild-type, codon 12 mutations [hazard ratio (HR) 1.67, 95% confidence interval (CI) 1.35-2.04; P < 0.001] but not codon 13 (HR 1.23, 95% CI 0.85-1.79; P = 0.26) were significantly associated with shorter TTR, independently of other covariates. The interaction test showed that, regarding tumor location (distal versus proximal), KRAS genotype affects differently on recurrence (P = 0.02) and DFS (P = 0.042). Subgroup analysis showed that KRAS only affected TTR and DFS in distal tumors (n = 1043; 692 wild type; 351 mutated), with an increased risk of relapse (HR 1.96, 95% CI 1.51-2.56; P < 0.0001) for KRAS codon 12 mutations and a borderline significance for codon 13 mutations (HR 1.59, 95% CI 1.00-2.56; P = 0.051).

CONCLUSION

KRAS exon 2 mutations are independent predictors of shorter TTR in patients with resected stage III distal colon cancers receiving adjuvant therapy. Future clinical trials in the adjuvant setting should consider both the tumor location and KRAS mutations as important stratification factors.

CLINICAL TRIAL NUMBER

This is an ancillary study of the PETACC8 trial: EUDRACT 2005-003463-23.

Ganetespib, a novel Hsp90 inhibitor in patients with KRAS mutated and wild type, refractory metastatic colorectal cancer

BACKGROUND

Heat shock protein 90 (Hsp90) is a cellular chaperone that is required for the maturation and stability of a variety of proteins that play key roles in colon cancer initiation and progression. The primary objective of the current study was to define the safety and efficacy of ganetespib, a novel, selective small-molecule Hsp90 inhibitor, in patients with refractory metastatic colorectal cancer.

PATIENTS AND METHODS

The study was a single-arm, Simon 2-stage, phase II trial for patients with chemotherapy-refractory, metastatic colorectal cancer. Patients received ganetespib 200 mg/m(2) intravenously. Tumor tissue was collected before treatment and 48 hours after treatment for changes in expression of Hsp90 client proteins and other potential pharmacodynamics markers. V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), v-Raf murine sarcoma viral oncogene homolog B, and phosphatidylinositol-4, 5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutational status was also determined.

RESULTS

Seventeen patients were treated (median age, 58; range, 44-79 years). No patients demonstrated objective regression of disease. Two patients had stable disease of 6.8 and 5.1 months duration. Serious adverse events that were potentially attributable to ganetespib included diarrhea (12%, n = 2), fatigue (17%, n = 3), and increased aspartate aminotransferase/alanine aminotransferase (12%, n = 2) and alkaline phosphatase (6%, n = 1) levels. Of the 17 evaluable patients, 9 (53%) including patients with stable disease as best response, had KRAS-mutant tumors.

CONCLUSION

In this first phase II investigation of an Hsp90 inhibitor in colorectal cancer, ganetespib as a single agent did not demonstrate activity in chemotherapy-refractory metastatic colorectal cancer. However, on the basis of the drug's promising preclinical combination data and the relatively mild toxicity profile, further clinical investigation of this agent in combination with standard cytotoxic agents is planned.

[Clinical relevance of the K-ras oncogene in colorectal cancer: experience in a Mexican population]

BACKGROUND

Colorectal cancer is frequent in the developed countries, with a cancer-specific mortality rate of 33%. Different biomarkers are associated with overall survival and the prediction of monoclonal treatment effectiveness. The presence of mutations in the K-ras oncogene alters the response to target therapy with cetuximab and could be an independent prognostic factor.

AIMS

To analyze the difference in survival between patients with mutated K-ras and those with K-ras wild-type status.

METHODS

Thirty-one clinical records were retrospectively analyzed of patients presenting with colorectal cancer that underwent K-ras sequencing through real-time polymerase chain reaction within the time frame of 2009 to 2012 at the Hospital de Alta Especialidad de Veracruz of the Instituto para la Salud y Seguridad Social de los Trabajadores del Estado (HAEV-ISSSTE). Survival analysis for patients with and without K-ras mutation was performed using the Kaplan Meier method. Contrast of covariates was performed using logarithmic transformations.

RESULTS

No statistically significant difference was found in relation to survival in the patients with mutated K-ras vs. those with K-ras wild-type (P=.416), nor were significant differences found when analyzing the covariants and survival in the patients with mutated K-ras: ECOG scale (P=.221); age (less than, equal to or greater than 65years, P=.441); clinical stage according to the AJCC (P=.057), and primary lesion site (P=.614).

CONCLUSIONS

No relation was found between the K-ras oncogene mutation and reduced survival, in contrast to what has been established in the international medical literature. Further studies that include both a larger number of patients and those receiving monoclonal treatment, need to be conducted. There were only 5 patients in the present study that received cetuximab, resulting in a misleading analysis.

KRAS mutation influences recurrence patterns in patients undergoing hepatic resection of colorectal metastases

BACKGROUND

The validity of the KRAS mutation as a predictor of recurrence-free survival (RFS) or overall survival (OS) is unclear. The current study investigated whether the presence of the KRAS mutation decreased RFS or OS in patients with colorectal cancer who underwent liver resection.

METHODS

Patients with resected colorectal liver metastases who received adjuvant hepatic arterial infusion plus systemic therapy and for whom KRAS data was available were evaluated. Correlation between KRAS and clinical factors was done using the Fisher exact test. Kaplan-Meier methods were used to estimate the median RFS and OS.

RESULTS

A total of 169 patients were evaluated, 118 of whom had KRAS wild-type (WT) and 51 had KRAS mutated (MUT) tumors. The 3-year RFS rate was 46% for patients with KRAS WT (95% confidence interval [95% CI], 35%-56%) and 30% (95% CI, 16%-44%) for patients with KRAS MUT (P =.005). The 3-year OS rate was 95% (95% CI, 87%-98%) and 81% (95% CI, 62%-95%), respectively, for patients with KRAS WT and KRAS MUT (P =.07). On multivariate analysis, KRAS remained a significant predictor of RFS (hazard ratio, 1.9). The 3-year cumulative recurrence rate by site of metastases was as follows: 2% versus 13.4% for bone (P≤.01), 2% versus 14.5% for brain (P =.05), 33.2% versus 58% for lung (P≤.01), and 30% versus 47% for liver (P =.10) in patients with KRAS WT versus KRAS MUT.

CONCLUSIONS

In the current study, among patients with resected colorectal liver metastases who were treated with adjuvant hepatic arterial infusion plus systemic therapy, patients with KRAS MUT were found to have a significantly worse 3-year RFS (30%) compared with KRAS WT (46%) p=.005. The cumulative incidence of bone, brain, and lung metastases was significantly higher for patients with KRAS MUT compared with those with KRAS WT.

Adjuvant systemic chemotherapy with or without bevacizumab in patients with resected pulmonary metastases from colorectal cancer

INTRODUCTION

We investigated the impact of modern chemotherapy regimens and bevacizumab following pulmonary metastasectomy (PM) from metastatic colorectal cancer (CRC).

METHODS

A total of 122 consecutive patients who were curatively resected for pulmonary metastases of CRC in twelve oncology centers were retrospectively analysed between January 2000 and April 2012.

RESULTS

Of 122 patients, 14 did not receive any treatment following PM. The remaining 108 patients received fluoropyrimidine-based (n = 12), irinotecan-based (n = 56) and oxaliplatin-based (n = 40) chemotherapy combinations. Among these, 52 patients received bevacizumab (BEV) while 56 did not (NoBEV). Median recurrence-free survival (RFS) was 17 months and median overall survival (OS) has not been reached at a median follow-up of 25 months after PM. Three and five-year OS rates were 66% and 53%, respectively. RFS and OS were similar, irrespective of the chemotherapy regimen or BEV use. Positive pulmonary margin, KRAS mutation status, and previous liver metastasectomy were negative independent prognostic factors for RFS, while pathologically confirmed thoracic lymph node involvement was the only negative independent prognostic for OS in multivariate analysis.

CONCLUSIONS

No significant RFS or OS difference was observed in respect to chemotherapy regimens with or without BEV in patients with pulmonary metastases of CRC following curative resection.

Beyond KRAS: Predictive factors of the efficacy of anti-EGFR monoclonal antibodies in the treatment of metastatic colorectal cancer

Systematic analysis of the epidermal growth factor receptor (EGFR) pathway revealed that biomarkers could be used to predict the response to and outcome of anti-EGFR therapies in patients affected by metastatic colorectal cancer. We have conducted a review on the most recent findings and advances on this topic. To this aim, we searched the PubMed database for articles devoted to predictive and prognostic biomarkers for patients administered cetuximab- and panitumumab-based therapies. Here we review the state of the art and the controversies about the molecular factors known to be predictors of the efficacy of anti-EGFR therapy, namely, KRAS, BRAF, NRAS, PI3KCA and PTEN, and we discuss their prognostic value in colorectal cancer patients.

Clinical impact of c-MET expression and genetic mutational status in colorectal cancer patients after liver resection

c-MET is implicated in the pathogenesis and growth of a wide variety of human malignancies, including colorectal cancer (CRC). The aim of the present study was to clarify the association between c-MET expression and tumor recurrence in CRC patients after curative liver resection, and to evaluate concordance in c-MET expression and various mutations of KRAS, BRAF and PIK3CA between primary CRC and paired liver metastases. A cohort of patients was tested for c-MET immunoreactivity (i.e. immunohistochemistry [IHC]) and KRAS, BRAF and PIK3CA mutations. Analyses were performed both on primary tumors and paired liver metastases, and the association between IHC and mutations results were assessed. A total of 108 patients were eligible. A total of 53% of patients underwent simultaneous resection of primary tumors and metastases, and the others underwent metachronous resection. Levels of concordance between primary tumors and metastases were 65.7%, 87.7%, 100% and 95.2% for c-MET, KRAS, BRAF and PIK3CA, respectively. High levels of c-MET expression (c-MET-high) in the primary tumors were observed in 52% of patients. Relapse-free survival was significantly shorter for patients with c-MET-high primary tumors (9.7 months) than for those with c-MET-low primary tumors (21.1 months) (P = 0.013). These results suggest that a high level of genetic concordance in KRAS, BRAF and PIK3CA between primary tumors and liver metastases, and c-MET-high in the primary tumors were associated with shorter relapse-free survival after hepatic metastasectomy.

Molecular diagnostics in colorectal carcinoma

Molecular pathogenesis and classification of colorectal carcinoma are based on the adenoma-carcinoma sequence in the Vogelstein model, serrated polyp pathway, and microsatellite instability. The genetic basis for hereditary nonpolyposis colorectal cancer is based on detection of genetic mutations. Genetic testing for Lynch syndrome includes microsatellite instability, methylator phenotyping, BRAF mutation, and molecular testing. Molecular makers include quantitative multigene reverse transcriptase-polymerase chain reaction assay and KRAS and BRAF mutation analysis. Potential biomarkers include one-step nucleic acid amplification and epigenetic inactivation of endothelin 2 and endothelin 3 in colon cancer. Molecular screening approaches in colorectal cancer using stool DNA are under investigation.

Prognostic Impact of Deficient DNA Mismatch Repair and Mutations in KRAS, and BRAFV600E in Patients with Lymph Node-Positive Colon Cancer

While tumor stage remains the key determinant of colorectal cancer (CRC) prognosis and treatment, there is considerable stage-independent variability in clinical outcome. Molecular markers hold promise for explaining variations in clinical behavior, and may identify patient subsets with differential efficacy and survival after adjuvant chemotherapy which is standard of care for patients with lymph node-positive, i.e., stage III, colon cancer. An increased understanding of the molecular evolution and progression of CRC has identified two major pathways of tumorigenesis that are characterized by chromosomal instability or microsatellite instability (MSI). MSI is a consequence of deficient DNA mismatch repair (MMR) that is generally due to epigenetic inactivation of MLH1 in tumors that often carry mutations in oncogenic BRAF^V600E . Activating BRAF^V600E and KRAS mutations are mutually exclusive and in this article, we review the current status of these mutations and MMR status as prognostic biomarkers in stage III colon cancers.

Phase II trial of cetuximab plus irinotecan for oxaliplatin- and irinotecan-based chemotherapy-refractory patients with advanced and/or metastatic colorectal cancer: evaluation of efficacy and safety based on KRAS mutation status (T-CORE0801)

BACKGROUND

Mutations in the KRAS gene have been identified as negative predictors of response to anti-epidermal growth factor receptor (EGFR) monoclonal antibody therapy by patients with metastatic colorectal cancer (mCRC). However, it has been based on the study of mainly Caucasian mCRC patients. This prospective study investigated the relationship between the mutation status of EGFR-related genes including KRAS and the response rate (RR) to cetuximab plus irinotecan therapy in Japanese mCRC patients.

METHODS

Samples taken from 43 chemotherapy-refractory mCRC patients who had undergone cetuximab plus irinotecan therapy at 11 medical centers in Japan were subjected to direct DNA sequencing to determine the KRAS, BRAF, PIK3CA, NRAS, and AKT1 mutation status. The clinical outcome after the treatment was evaluated for each mutation status.

RESULTS

KRAS mutations were detected in 31.7% of 41 eligible patients. The RR to cetuximab plus irinotecan therapy was found to be 17.9 and 0% in the KRAS wild-type and mutant subgroups, respectively.

CONCLUSION

Despite the identification of a lower-than-expected RR to treatment by the KRAS wild-type subgroup, KRAS mutation status appears to be a useful predictive marker of response to cetuximab plus irinotecan therapy in Japanese mCRC patients.

Prevalence of germline MUTYH mutations among Lynch-like syndrome patients

BACKGROUND AND AIMS

Individuals with tumours showing mismatch repair (MMR) deficiency not linked to germline mutations or somatic methylation of MMR genes have been recently referred as having 'Lynch-like syndrome' (LLS). The genetic basis of these LLS cases is unknown. MUTYH-associated polyposis patients show some phenotypic similarities to Lynch syndrome patients. The aim of this study was to investigate the prevalence of germline MUTYH mutations in a large series of LLS patients.

METHODS

Two hundred and twenty-five probands fulfilling LLS criteria were included in this study. Screening of MUTYH recurrent mutations, whole coding sequencing and a large rearrangement analysis were undertaken. Age, sex, clinical, pathological and molecular characteristics of tumours including KRAS mutations were assessed.

RESULTS

We found a prevalence of 3.1% of MAP syndrome in the whole series of LLS (7/225) and 3.9% when only cases fulfilling clinical criteria were considered (7/178). Patients with MUTYH biallelic mutations had more adenomas than monoallelic (P=0.02) and wildtype patients (P<0.0001). Six out of nine analysed tumours from six biallelic MUTYH carriers harboured KRAS-p.G12C mutation. This mutation was found to be associated with biallelic MUTYH germline mutation when compared with reported series of unselected colorectal cancer cohorts (P<0.0001).

CONCLUSIONS

A proportion of unexplained LLS cases is caused by biallelic MUTYH mutations. The obtained results further justify the inclusion of MUTYH in the diagnostic strategy for Lynch syndrome-suspected patients.

Genomic profiling of intrahepatic cholangiocarcinoma: refining prognosis and identifying therapeutic targets

BACKGROUND

The molecular alterations that drive tumorigenesis in intrahepatic cholangiocarcinoma (ICC) remain poorly defined. We sought to determine the incidence and prognostic significance of mutations associated with ICC among patients undergoing surgical resection.

METHODS

Multiplexed mutational profiling was performed using nucleic acids that were extracted from 200 resected ICC tumor specimens from 7 centers. The frequency of mutations was ascertained and the effect on outcome was determined.

RESULTS

The majority of patients (61.5 %) had no genetic mutation identified. Among the 77 patients (38.5 %) with a genetic mutation, only a small number of gene mutations were identified with a frequency of >5 %: IDH1 (15.5 %) and KRAS (8.6 %). Other genetic mutations were identified in very low frequency: BRAF (4.9 %), IDH2 (4.5 %), PIK3CA (4.3 %), NRAS (3.1 %), TP53 (2.5 %), MAP2K1 (1.9 %), CTNNB1 (0.6 %), and PTEN (0.6 %). Among patients with an IDH1-mutant tumor, approximately 7 % were associated with a concurrent PIK3CA gene mutation or a mutation in MAP2K1 (4 %). No concurrent mutations in IDH1 and KRAS were noted. Compared with ICC tumors that had no identified mutation, IDH1-mutant tumors were more often bilateral (odds ratio 2.75), while KRAS-mutant tumors were more likely to be associated with R1 margin (odds ratio 6.51) (both P < 0.05). Although clinicopathological features such as tumor number and nodal status were associated with survival, no specific mutation was associated with prognosis.

CONCLUSIONS

Most somatic mutations in resected ICC tissue are found at low frequency, supporting a need for broad-based mutational profiling in these patients. IDH1 and KRAS were the most common mutations noted. Although certain mutations were associated with ICC clinicopathological features, mutational status did not seemingly affect long-term prognosis.

Molecular pathways: targeting NRAS in melanoma and acute myelogenous leukemia

Successful targeting of specific oncogenic "driver" mutations with small-molecule inhibitors has represented a major advance in cancer therapeutics over the past 10 to 15 years. The most common activating oncogene in human malignancy, RAS (rat sarcoma), has proved to be an elusive target. Activating mutations in RAS induce mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase-AKT pathway signaling and drive malignant progression in up to 30% of cancers. Oncogenic NRAS mutations occur in several cancer types, notably melanoma, acute myelogenous leukemia (AML), and less commonly, colon adenocarcinoma, thyroid carcinoma, and other hematologic malignancies. Although NRAS-mutant tumors have been recalcitrant to targeted therapeutic strategies historically, newer agents targeting MAP/ERK kinase 1 (MEK1)/2 have recently shown signs of clinical efficacy as monotherapy. Combination strategies of MEK inhibitors with other targeted agents have strong preclinical support and are being evaluated in clinical trials. This review discusses the recent preclinical and clinical studies about the role of NRAS in cancer, with a focus on melanoma and AML.

KRAS codon 12 and 13 mutations in relation to disease-free survival in BRAF-wild-type stage III colon cancers from an adjuvant chemotherapy trial (N0147 alliance)

PURPOSE

We examined the prognostic impact of specific KRAS mutations in patients with stage III colon adenocarcinoma receiving adjuvant FOLFOX alone or combined with cetuximab in a phase III trial (N0147). Analysis was restricted to BRAF-wild-type tumors, because BRAF mutation was associated with poor prognosis, and BRAF and KRAS mutations are mutually exclusive.

EXPERIMENTAL DESIGN

The seven most common KRAS mutations in codon 12 and codon 13 were examined in 2,478 BRAF-wild-type tumors. Because KRAS mutations in codon 12 (n = 779) or 13 (n = 220) were not predictive of adjuvant cetuximab benefit, study arms were pooled for analysis. Disease-free survival (DFS) was evaluated by HRs using Cox models.

RESULTS

KRAS mutations in codon 12 (multivariate HR, 1.52; 95% confidence interval, CI, 1.28-1.80; P < 0.0001) or codon 13 (multivariate HR, 1.36; 95% CI, 1.04-1.77; P = 0.0248) were significantly associated with shorter DFS compared with patients with wild-type KRAS/BRAF tumors, independent of covariates. KRAS codon 12 mutations were independently associated with proficient mismatch repair (P < 0.0001), proximal tumor site (P < 0.0001), low grade, age, and sex, whereas codon 13 mutations were associated with proximal site (P < 0.0001).

CONCLUSION

KRAS mutations in either codon 12 or 13 are associated with inferior survival in patients with resected stage III colon cancer. These data highlight the importance of accurate molecular characterization and the significant role of KRAS mutations in both codons in the progression of this malignancy in the adjuvant setting. Clin Cancer Res; 20(11); 3033-43. ©2014 AACR.

Differential survival trends of stage II colorectal cancer patients relate to promoter methylation status of PCDH10, SPARC, and UCHL1

Surgical excision of colorectal cancer at early clinical stages is highly effective, but 20-30% of patients relapse. Therefore, it is of clinical relevance to identify patients at high risk for recurrence, who would benefit from adjuvant chemotherapy. The objective of this study was to identify prognostic and/or predictive methylation markers in stage II colorectal cancer patients. Therefore, we selected six gene promoters (FZD9, PCDH10 (protocadherin 10), SFRP2, SPARC (secreted protein acidic and rich in cysteine), UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), and WIF1) for methylation analysis in formalin-fixed, paraffin-embedded primary tumor samples of colorectal cancer patients (n=143) who were enrolled in a prospective randomized phase III trial of the Austrian Breast and Colorectal cancer Study Group. Patients were randomized to adjuvant chemotherapy with 5-fluorouracil and leucovorin or surveillance only. Survival analyses revealed that combined evaluation of three promoters (PCDH10, SPARC, and UCHL1) showed differential effects with regard to disease-free survival and overall survival in the two treatment groups (significance level 0.007). In the chemotherapy arm, a statistically insignificant trend for patients without methylation toward longer survival was observed (P=0.069 for disease-free survival and P=0.139 for overall survival). Contrary, patients in the surveillance arm without methylation in their gene promoters had shorter disease-free survival and overall survival (P=0.031 for disease-free survival and P=0.003 for overall survival), indicating a prognostic effect of methylation in this group (test for interaction, P=0.006 for disease-free survival and P=0.018 for overall survival). These results indicate that promoter methylation status of PCDH10, SPARC, and UCHL1 may be used both as prognostic and predictive molecular marker for colorectal cancer patients and, therefore, may facilitate treatment decisions for stage II colorectal cancer.

Analyses of clinicopathological, molecular, and prognostic associations of KRAS codon 61 and codon 146 mutations in colorectal cancer: cohort study and literature review

Background

KRAS mutations in codons 12 and 13 are established predictive biomarkers for anti-EGFR therapy in colorectal cancer. Previous studies suggest that KRAS codon 61 and 146 mutations may also predict resistance to anti-EGFR therapy in colorectal cancer. However, clinicopathological, molecular, and prognostic features of colorectal carcinoma with KRAS codon 61 or 146 mutation remain unclear.

Methods

We utilized a molecular pathological epidemiology database of 1267 colon and rectal cancers in the Nurse’s Health Study and the Health Professionals Follow-up Study. We examined KRAS mutations in codons 12, 13, 61 and 146 (assessed by pyrosequencing), in relation to clinicopathological features, and tumor molecular markers, including BRAF and PIK3CA mutations, CpG island methylator phenotype (CIMP), LINE-1 methylation, and microsatellite instability (MSI). Survival analyses were performed in 1067 BRAF-wild-type cancers to avoid confounding by BRAF mutation. Cox proportional hazards models were used to compute mortality hazard ratio, adjusting for potential confounders, including disease stage, PIK3CA mutation, CIMP, LINE-1 hypomethylation, and MSI.

Results

KRAS codon 61 mutations were detected in 19 cases (1.5%), and codon 146 mutations in 40 cases (3.2%). Overall KRAS mutation prevalence in colorectal cancers was 40% (=505/1267). Of interest, compared to KRAS-wild-type, overall, KRAS-mutated cancers more frequently exhibited cecal location (24% vs. 12% in KRAS-wild-type; P < 0.0001), CIMP-low (49% vs. 32% in KRAS-wild-type; P < 0.0001), and PIK3CA mutations (24% vs. 11% in KRAS-wild-type; P < 0.0001). These trends were evident irrespective of mutated codon, though statistical power was limited for codon 61 mutants. Neither KRAS codon 61 nor codon 146 mutation was significantly associated with clinical outcome or prognosis in univariate or multivariate analysis [colorectal cancer-specific mortality hazard ratio (HR) = 0.81, 95% confidence interval (CI) = 0.29-2.26 for codon 61 mutation; colorectal cancer-specific mortality HR = 0.86, 95% CI = 0.42-1.78 for codon 146 mutation].

Conclusions

Tumors with KRAS mutations in codons 61 and 146 account for an appreciable proportion (approximately 5%) of colorectal cancers, and their clinicopathological and molecular features appear generally similar to KRAS codon 12 or 13 mutated cancers. To further assess clinical utility of KRAS codon 61 and 146 testing, large-scale trials are warranted.

Role of NRAS mutations as prognostic and predictive markers in metastatic colorectal cancer

NRAS mutations occur in 3-5% of colorectal cancer. Differently from KRAS and BRAF mutations, the role of NRAS mutations as prognostic and predictive markers in metastatic colorectal cancer (mCRC) has been investigated to a lesser extent. A retrospective series suggested the role of NRAS mutations as predictors of resistance to anti-EGFR monoclonal antibodies (MoAbs) in chemo-refractory patients with mCRC. In our study, KRAS codons 12, 13, 61 and BRAF codon 600 mutational status were evaluated in mCRCs referred to our Institution from 2009 to 2012. NRAS codons 12, 13 and 61 mutational status was analyzed in KRAS/BRAF wt patients. We collected pathological and clinical features in the overall population and outcome data in a subset of NRAS mutated chemo-refractory patients treated with anti-EGFR MoAbs in advanced lines. NRAS was mutated in 47/786 (6%) mCRCs. NRAS and KRAS mutated tumors did not show significant differences in terms of clinical and pathological characteristics, except for a lower prevalence of mucinous histology (p = 0.012) and lung metastases (p = 0.012) among NRAS mutated tumors. In the uni- and multivariate model, NRAS mutations were associated with shorter overall survival (OS) compared to all wt patients (median OS 25.6 vs 42.7 months; univ: HR = 1.91, 95% CI 1.39-3.86, p = 0.0013; multiv: HR = 1.75, 95% CI 1.1.3-2.72, p = 0.013). None of the chemo-refractory NRAS mutated patients evaluable for response to anti-EGFRs achieved response. In conclusion, NRAS mutations have a relevant incidence in patients with mCRC and showed an association with specific clinical and pathological features. NRAS mutations affect mCRC patients' prognosis and predict lack of response to anti-EGFRs.

Molecular patterns in deficient mismatch repair colorectal tumours: results from a French prospective multicentric biological and genetic study

Background:

To test the prognostic value of tumour protein and genetic markers in colorectal cancer (CRC) and examine whether deficient mismatch repair (dMMR) tumours had a distinct profile relative to proficient mismatch repair (pMMR) tumours.

Methods:

This prospective multicentric study involved 251 stage I–III CRC patients. Analysed biomarkers were EGFR (binding assay), VEGFA, thymidylate synthase (TS), thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) expressions, MMR status, mutations of KRAS (codons 12–13), BRAF (V600E), PIK3CA (exons 9 and 20), APC (exon 15) and P53 (exons 4–9), CpG island methylation phenotype status, ploidy, S-phase, LOH.

Results:

The only significant predictor of relapse-free survival (RFS) was tumour staging. Analyses restricted to stage III showed a trend towards a shorter RFS in KRAS-mutated (P=0.005), BRAF wt (P=0.009) and pMMR tumours (P=0.036). Deficient mismatch repair tumours significantly demonstrated higher TS (median 3.1 vs 1.4) and TP (median 5.8 vs 3.5) expression relative to pMMR (P<0.001) and show higher DPD expression (median 14.9 vs 7.9, P=0.027) and EGFR content (median 69 vs 38, P=0.037) relative to pMMR.

Conclusions:

Present data suggesting that both TS and DPD are overexpressed in dMMR tumours as compared with pMMR tumours provide a strong rationale that may explain the resistance of dMMR tumours to 5FU-based therapy.

The role of antiangiogenic agents in the treatment of patients with advanced colorectal cancer according to K-RAS status

Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer worldwide. Recently, it has been found that about 40 % of patients with CRC have mutations in the K-RAS gene. Several clinical trials have showed that patients with metastatic colorectal cancer (mCRC) who present tumour-promoting mutations in signalling pathways involving the epidermal growth factor receptor (EGFR), which includes activating K-RAS mutations, do not respond to anti-EGFR drugs such as panitumumab and cetuximab. Hence, K-RAS status is now considered an important negative predictive factor for response to anti-EGFR drugs. Moreover, K-RAS status seems to have also a prognostic role in CRC, but this fact is somewhat controversial. Activity of antiangiogenic agents seems not to be influenced by K-RAS gene status. Tumour angiogenesis has attracted interest in attempts to improve the management of mCRC. The vascular endothelial growth factor (VEGF) pathway is fundamental to the regulation of angiogenesis, and research has focused on developing agents that selectively target it. In this way, the anti-VEGF antibody bevacizumab in combination with chemotherapy has provided important clinical benefits in terms of response rate, progression-free survival and overall survival to patients with mCRC. Efficacy data of bevacizumab in K-RAS wild-type patients seem to be comparable with the efficacy data observed with anti-EGFR therapies in a cross-trial comparison. Although there is a lack of prospective and randomized data in this setting, the combination of chemotherapy plus antiangiogenic agents could be considered as an effective alternative for the treatment of mCRC with independence of K-RAS gene status. Here, we review the available data we have in the literature of the use of antiangiogenic strategies in the treatment of mCRC nowadays.

Implication of K-ras and p53 in colorectal cancer carcinogenesis in Tunisian population cohort

According to the multistep route of genetic alterations in the colorectal adenoma-carcinoma sequence, the complex K-ras/p53 mutation is one of the first alterations to occur and represent an important genetic event in colorectal cancer (CRC). An evaluation of the mutation spectra in K-ras and p53 gene was effected in 167 Tunisian patients with sporadic CRC to determine whether our populations have similar pattern of genetic alteration as in Maghrebin's population. Mutation patterns of codon 12-13 of K-ras and exon 5-8 of p53 were analyzed by immunohistochemistry and PCR-SSCP and confirmed by sequencing. Mutations in the K-ras gene were detected in 31.13 % and affect the women more than the men (p = 0.008). Immunostaining showed that expression of p21 ras was correlated with the advanced age (p = 0.004), whereas loss of signal was associated with mucinous histotype (p = 0.003). Kaplan-Meier survival curve found that patients with the K-ras mutation had a shorter survival compared with patients without mutation (p = 0.005). Alteration in p53 was seen in 17.4 % of patients and affects three hot spot codons such as 175, 245, and 248. Overexpression of p53 was seen in 34.1 % and correlated with tumor node metastasis (TNM) advanced stage (p = 0.037) and mucinous histotype (p = 0.001). A high concordance between p53 expression and alteration (p<0.005) was shown. Concomitant mutations in K-ras and p53 gene were detected in only 4 % of tumors. K-ras and p53 undergo separate pathways in colorectal tumorogenesis. Interestingly, mutations in the K-ras gene might be considered a valuable prognostic factor correlated to poor outcome. p53 gene alterations were rather low in our set, and methylation pattern of p53 is required to elucidate the molecular basis of this protein in CRC.

BRAF mutation predicts for poor outcomes after metastasectomy in patients with metastatic colorectal cancer

BACKGROUND

BRAF mutations occur in 5% to 11% of patients with metastatic colorectal cancer (mCRC) and have been associated with poor prognosis. The current study was undertaken to determine the clinicopathologic characteristics, PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha) mutation frequency, and outcomes after metastasectomy in patients with BRAF-mutant mCRC.

METHODS

Data from 1941 consecutive patients with mCRC who underwent KRAS/BRAF mutation testing between 2009 and 2012 at a single institution were identified to identify BRAF-mutant mCRC cases (92 cases). BRAF wild-type mCRC cases from 2011 (423 cases) served as a control group.

RESULTS

BRAF-mutated mCRC was found to be significantly associated with older age at diagnosis, female sex, right-sided location, poorly differentiated morphology, and mucinous histology compared with wild-type cases. BRAF-mutant cases more frequently progressed from stage III disease (32% vs 17%; P = .003) and among those patients with stage III disease, T4 disease was more common (48% vs 27%; P = .05). PIK3CA was found to be co-mutated in 5% of BRAF-mutant tumors versus 17% of KRAS-mutant tumors (P < .01) and 4% of BRAF/KRAS wild-type cases. Patients with BRAF-mutated mCRC presented more frequently with peritoneal involvement (26% vs 14%; P < 0.01) and less frequently with liver-limited metastases (41% vs 63%; P < .01). Patients with BRAF-mutated mCRC were less likely to undergo metastasectomy (41% vs 26% at 2 years from diagnosis of metastatic disease; P < .01) and were found to have lower overall survival (P < .01) after metastasectomy.

CONCLUSIONS

BRAF-mutant mCRC is associated with worse clinical outcome. Patients with BRAF-mutant tumors more commonly develop peritoneal metastases, less frequently present with disease limited to the liver, and have shorter survival after metastasectomy compared with patients with BRAF wild-type tumors.

Predictive and prognostic biomarkers with therapeutic targets in advanced colorectal cancer

Colorectal cancer (CRC) is one of the most common human malignant diseases and the second leading cause of cancer-related deaths worldwide. The treatment of advanced CRC has improved significantly in recent years. With the emergence of two targeted antibodies, cetuximab (Erbitux), an anti-epidermal growth factor receptor monoclonal antibody and bevacizumab (Avastin), a vascular endothelial growth factor monoclonal antibody, the treatment of metastatic CRC has entered the era of personalized therapy. Predictive and prognostic biomarkers have, and will continue to, facilitate the selection of suitable patients and the personalization of treatment for metastatic CRC (mCRC). In this review, we will focus primarily on the important progresses made in the personalized treatment of mCRC and discuss the potentially novel predictive and prognostic biomarkers for improved selection of patients for anti-cancer treatment in the future.

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.

KRAS mutations: variable incidences in a Brazilian cohort of 8,234 metastatic colorectal cancer patients

BACKGROUND

KRAS mutations are frequently found in colorectal cancer (CRC) indicating the importance of its genotyping in the study of the molecular mechanisms behind this disease. Although major advances have occurred over the past decade, there are still important gaps in our understanding of CRC carcinogenesis, particularly whether sex-linked factors play any role.

METHODS

The profile of KRAS mutations in the Brazilian population was analyzed by conducting direct sequencing of KRAS codons 12 and 13 belonging to 8,234 metastatic CRC patient samples. DNA was extracted from paraffin-embedded tissue, exon 1 was amplified by PCR and submitted to direct sequencing. The data obtained was analysed comparing different geographical regions, gender and age.

RESULTS

The median age was 59 years and the overall percentage of wild-type and mutated KRAS was 62.8% and 31.9%, respectively. Interestingly, different percentages of mutated KRAS patients were observed between male and female patients (32.5% versus 34.8%, respectively; p = 0.03). KRAS Gly12Asp mutation was the most prevalent for both genders and for most regions, with the exception of the North where Gly12Val was the most frequent mutation found.

CONCLUSIONS

To the best of our knowledge this is one of the largest cohorts of KRAS genotyping in CRC patients and the largest to indicate a higher incidence of KRAS mutation in females compared to males in Brazil. Nevertheless, further research is required to better address the impact of gender differences in colorectal cancer.