Activating mutations of BRAF have been identified in a variety of human cancers, most notably melanomas and papillary thyroid carcinomas (PTCs). The aim of the present study was to disclose the role of BRAF mutations in thyroid carcinoma development. Seventy-two thyroid tumors, including 60 PTCs, six follicular adenomas, five follicular carcinomas, and one anaplastic carcinoma, were studied. BRAF mutation screening focused on exon 15 and exon 11 of the gene by single-stranded conformational polymorphism and sequence analysis. Search of RET/PTC expression was conducted with the RT-PCR technique. The molecular genetic study of the BRAF gene showed the presence of a missense thymine to adenine transversion at nucleotide 1796, resulting in the V599E substitution, in 24 of 60 PTCs (40%), none of six follicular adenomas, and none of five follicular carcinomas or one anaplastic carcinoma. Moreover, nine of 60 PTCs (15%) presented RET/PTC expression. A genetico-clinical association analysis showed a statistically significant correlation between BRAF mutation and development of PTCs of the classic papillary histotype (P = 0.038). On the contrary, no link could be detected between expression of BRAF(V599E) and age at diagnosis, gender, dimension, and local invasiveness of the primary cancer, presence of lymph node metastases, tumor stage, and multifocality of the disease. These data clearly confirm that BRAF(V599E) is the more common genetic alteration found to date in adult sporadic PTCs, that it is unique for this thyroid cancer histotype, and that it might drive the development of PTCs of the classic papillary subtype.

Numerous biomolecular markers have been studied to improve the accuracy of fine needle aspiration biopsy (FNAB) in the diagnostic and prognostic evaluation of thyroid tumors, but none of them has yet become clinically useful. The recently discovered BRAF mutation, which occurs specifically in papillary thyroid cancers (PTC) with a high prevalence and is associated with poor clinicopathological outcomes, has the potential to be a useful diagnostic and prognostic marker for PTC. In the present study, we investigated whether detection of BRAF mutation on FNAB specimens was technically possible and could be used as an adjunct diagnostic tool with routine FNAB. Evaluation of a new colorimetric mutation detection method demonstrated 100% sensitivity and 100% specificity in comparison with conventional DNA sequencing as the "gold standard" in a large pool of DNA samples from various primary thyroid tumor specimens and cell lines. We found this novel technique even more sensitive in detecting BRAF mutation on FNAB specimens than conventional sequencing. In a series of 48 patients undergoing thyroidectomy, mostly for thyroid cancer or for suspicion of cancer, we performed preoperative FNAB and, using the colorimetric mutation detection method, identified BRAF mutation on the cytological specimens. Prospective analysis showed that 50% of the nodules that proved to be PTC on surgical histopathology were correctly diagnosed by BRAF mutation analysis on FNAB specimens; there were no false positive findings. Thus, we have demonstrated the usefulness of BRAF mutation detection on FNAB specimens that can help diagnose and identify those PTC patients who may need more aggressive surgical treatment and vigilant clinical monitoring.

In contrast to cutaneous melanoma, there is no evidence that BRAF mutations are involved in the activation of the mitogen-activated protein kinase (MAPK) pathway in uveal melanoma, although there is increasing evidence that this pathway is activated frequently in the latter tumours. In this study, we performed mutation analysis of the RAS and BRAF genes in a panel of 11 uveal melanoma cell lines and 19 primary uveal melanoma tumours. In addition, Western blot and immunohistochemical analyses were performed on downstream members of the MAPK pathway in order to assess the contribution of each of these components. No mutations were found in any of the three RAS gene family members and only one cell line carried a BRAF mutation (V599E). Despite this, mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK), ERK and ELK were constitutively activated in all samples. These data suggest that activation of the MAPK pathway is commonly involved in the development of uveal melanoma, but occurs through a mechanism different to that of cutaneous melanoma.

Sorafenib is the first and only p.o. administrated drug currently approved to treat advanced hepatocellular carcinoma (HCC). However, concerns have been raised about sorafenib therapy, including acquired drug resistance. This review provides an overview of sorafenib in the treatment of HCC on the basis of data obtained in the laboratory and in clinical studies. Three underlying mechanisms have been found to support sorafenib therapy. First, sorafenib blocks HCC cell proliferation by inhibiting BRaf and Raf1/c-Raf serine/threonine kinase phosphorylation in the mitogen-activated protein kinase pathway. Second, sorafenib induces apoptosis by reducing elF4E phosphorylation and downregulating Mcl-1 levels in tumor cells. Third, sorafenib prevents tumor-associated angiogenesis by inactivating vascular endothelial growth factor receptors (VEGFR-2 and -3) and the platelet-derived growth factor receptor-β. Clinical trials have demonstrated the effectiveness and relative safety of sorafenib, and thus the drug is used in unresectable HCC. However, many patients may develop acquired resistance to sorafenib, so their response to sorafenib is eventually lost. Sorafenib may induce autophagy, which leads to apoptosis. However, autophagy can also cause drug resistance. Many studies have combined sorafenib with other treatments in an effort to increase its effects, reduce the necessary dose or overcome resistance. It is urgent to study the mechanisms underlying how sorafenib interacts with cellular molecules and other drugs to increase its efficacy and reduce resistance in HCC patients.

CpG island methylator phenotype (CIMP) is a recently described subset of colorectal cancers (CRC) with widespread methylation of multiple promoter CpG islands. But the prognostic implication of CIMP in CRC has not been clarified. Thus, the aim of the present study was to differentiate the unique characteristics of CIMP from those of microsatellite instability (MSI)-high CRC, especially with regard to prognosis. CIMP, MSI, and mutations of KRAS codons 12 and 13 and of BRAF codon 600 were evaluated in 134 sporadic CRC. Patient survival and other clinicopathological variables were correlated with CIMP or genetic changes. High CIMP, high MSI, and mutations in KRAS or BRAF were detected in 31.3%, 14.2%, 33.6%, and 4.5% of overall CRC, respectively. High CIMP was closely associated with MSI and BRAF mutation but not with KRAS mutation. CIMP-high, microsatellite-stable (MSS) CRC were significantly associated with proximal location and nodal metastasis and had close but non-significant associations with liver metastasis. A worse clinical outcome was found for CIMP-high, MSS CRC with KRAS/BRAF mutation but not for those lacking KRAS/BRAF mutation. The findings support the contention that CIMP-high CRC have distinct clinicopathological and epidemiological features and suggest that the alleged poor clinical outcome of CIMP-high CRC patients is closely associated with the presence of KRAS/BRAF mutation.

Malignant melanoma is characterized by a propensity for early lymphatic and hematogenous spread. The hypoxia-inducible factor (HIF) family of transcription factors is upregulated in melanoma by key oncogenic drivers. HIFs promote the activation of genes involved in cancer initiation, progression, and metastases. Hypoxia has been shown to enhance the invasiveness and metastatic potential of tumor cells by regulating the genes involved in the breakdown of the ECM as well as genes that control motility and adhesion of tumor cells. Using a Pten-deficient, Braf-mutant genetically engineered mouse model of melanoma, we demonstrated that inactivation of HIF1α or HIF2α abrogates metastasis without affecting primary tumor formation. HIF1α and HIF2α drive melanoma invasion and invadopodia formation through PDGFRα and focal adhesion kinase-mediated (FAK-mediated) activation of SRC and by coordinating ECM degradation via MT1-MMP and MMP2 expression. These results establish the importance of HIFs in melanoma progression and demonstrate that HIF1α and HIF2α activate independent transcriptional programs that promote metastasis by coordinately regulating cell invasion and ECM remodeling.

Langerhans cell histiocytosis (LCH) represents a clonal proliferation of Langerhans cells. BRAF V600E mutations have been identified in approximately 50% of cases. To discover other genetic mechanisms underlying LCH pathogenesis, we studied 8 cases of LCH using a targeted next-generation sequencing platform. An E102_I103del mutation in MAP2K1 was identified in one BRAF wild-type case and confirmed by Sanger sequencing. Analysis of 32 additional cases using BRAF V600E allele-specific polymerase chain reaction and Sanger sequencing of MAP2K1 exons 2 and 3 revealed somatic, mutually exclusive BRAF and MAP2K1 mutations in 18 of 40 (45.0%) and 11 of 40 (27.5%) cases, respectively. This is the first report of MAP2K1 mutations in LCH that occur in 50% of BRAF wild-type cases. The mutually exclusive nature of MAP2K1 and BRAF mutations implicates a critical role of oncogenic MAPK signaling in LCH. This finding may also have implications in the use of BRAF and MEK inhibitor therapy.

MEK inhibitors are clinically active in BRAF(V600E) melanomas but only marginally so in KRAS mutant tumors. Here, we found that MEK inhibitors suppress ERK signaling more potently in BRAF(V600E), than in KRAS mutant tumors. To understand this, we performed an RNAi screen in a KRAS mutant model and found that CRAF knockdown enhanced MEK inhibition. MEK activated by CRAF was less susceptible to MEK inhibitors than when activated by BRAF(V600E). MEK inhibitors induced RAF-MEK complexes in KRAS mutant models, and disrupting such complexes enhanced inhibition of CRAF-dependent ERK signaling. Newer MEK inhibitors target MEK catalytic activity and also impair its reactivation by CRAF, either by disrupting RAF-MEK complexes or by interacting with Ser 222 to prevent MEK phosphorylation by RAF.

BACKGROUND

Clinical benefit from cytotoxic chemotherapy for metastatic papillary thyroid carcinoma (PTC) is disappointing, and effective therapeutic approaches for these patients are urgently needed. Because kinase-activating mutations in the BRAF proto-oncogene commonly occur in advanced PTC, and inhibition of BRAF(V600E) has shown promising clinical activity in melanoma, BRAF inhibitor therapy may be an effective strategy to treat metastatic PTC.

METHODS

The dose escalation portion of a first-in-human, phase I study of vemurafenib, a selective RAF inhibitor, included three patients with metastatic PTC harboring the BRAF(V600E) mutation. Vemurafenib was initially dosed at 240-360 mg twice a day, later escalated to 720 mg twice a day. Response evaluation was performed every 8 weeks per Response Evaluation Criteria in Solid Tumors (RECIST).

RESULTS

Among the three patients, one had a confirmed partial response with reduction of pulmonary target lesions by 31%, and the duration of response was 7.6 months before the disease progressed in the lungs and the bones. The time to progression was 11.7 months. The other two patients had stable disease, and the time to progression was 13.2 and 11.4 months, respectively.

CONCLUSIONS

Vemurafenib appears to have a promising clinical activity in patients with metastatic PTC, and our data suggest that the BRAF(V600E) mutant kinase is a relevant target for therapy in this patient population. Further investigation of inhibitors of mutated BRAF kinase in patients with PTC in a phase II study is warranted.

Repeat tumor biopsies to study genomic changes during therapy are difficult, invasive and data are confounded by tumoral heterogeneity. The analysis of circulating tumor DNA (ctDNA) can provide a non-invasive approach to assess prognosis and the genetic evolution of tumors in response to therapy. Mutation-specific droplet digital PCR was used to measure plasma concentrations of oncogenic BRAF and NRAS variants in 48 patients with advanced metastatic melanoma prior to treatment with targeted therapies (vemurafenib, dabrafenib or dabrafenib/trametinib combination) or immunotherapies (ipilimumab, nivolumab or pembrolizumab). Baseline ctDNA levels were evaluated relative to treatment response and progression-free survival (PFS). Tumor-associated ctDNA was detected in the plasma of 35/48 (73%) patients prior to treatment and lower ctDNA levels at this time point were significantly associated with response to treatment and prolonged PFS, irrespective of therapy type. Levels of ctDNA decreased significantly in patients treated with MAPK inhibitors (p < 0.001) in accordance with response to therapy, but this was not apparent in patients receiving immunotherapies. We show that circulating NRAS mutations, known to confer resistance to BRAF inhibitors, were detected in 3 of 7 (43%) patients progressing on kinase inhibitor therapy. Significantly, ctDNA rebound and circulating mutant NRAS preceded radiological detection of progressive disease. Our data demonstrate that ctDNA is a useful biomarker of response to kinase inhibitor therapy and can be used to monitor tumor evolution and detect the early appearance of resistance effectors.

OBJECTIVE

Our previous study revealed that 90% [47 of 52; 95% confidence interval (CI), 0.79-0.96] of Chinese never-smokers with lung adenocarcinoma harbor known oncogenic driver mutations in just four genes EGFR, ALK, HER2, and KRAS. Here, we examined the status of known driver mutations specifically in female never-smokers with lung adenocarcinoma.

METHODS

Tumors were genotyped for mutations in EGFR, KRAS, ALK, HER2, and BRAF. Data on age, stage, tumor differentiation, histologic subtypes, and molecular alterations were recorded from 349 resected lung adenocarcinomas from female never-smokers. We further compared the clinicopathologic parameters according to mutational status of these genes.

RESULTS

Two hundred and sixty-six (76.2%) tumors harbored EGFR mutations, 16 (4.6%) HER2 mutations, 15 (4.3%) EML4-ALK fusions, seven (2.0%) KRAS mutations, and two (0.6%) BRAF mutations. In univariate analysis, patients harboring EGFR mutations were significantly older (P < 0.001), whereas patients harboring HER2 mutations were significantly younger (P = 0.036). Higher prevalence of KRAS (P = 0.028) and HER2 (P = 0.021) mutations was found in invasive mucinous adenocarcinoma (IMA). The frequency of EGFR mutations was positively correlated with acinar predominant tumors (P = 0.002). Multivariate analysis revealed that older age at diagnosis (P = 0.013) and acinar predominant subtype (P = 0.005) were independent predictors of EGFR mutations. Independent predictors of HER2 mutations included younger age (P = 0.030) and IMA (P = 0.017). IMA (P = 0.006) and poor differentiation (P = 0.028) were independently associated with KRAS mutations.

CONCLUSIONS

The frequency of driver mutations in never-smoking female lung adenocarcinoma varies with histologic subtypes and age at diagnosis. These data have implications for both clinical trial design and therapeutic strategies.

BACKGROUND

Identifying predictive biomarkers is important to optimally treat patients. This analysis evaluated the association of K-ras, BRAF, and PIK3CA gene mutations with tumor resistance to panitumumab alone.

METHODS

From 3 phase II panitumumab metastatic colorectal cancer (mCRC) studies, 62 of 533 patient samples were available. Mutations were identified from genomic DNA by sequencing.

RESULTS

Of the 62 samples, 24 (38.7%) harbored a K-ras mutation, and 38 (61.3%) were wild type. In the wild-type K-ras group, 11% of patients had a partial response (PR), 53% had stable disease (SD), and 37% had progressive disease (PD). In the mutant K-ras group, 21% of patients had SD, and 79% of patients had PD; there were no responses. The absence of a K-ras mutation was associated with response to panitumumab (PR vs. SD vs. PD; P = .0028). The hazard ratio for wild-type versus mutant K-ras was 0.4 (95% CI, 0.2-0.7) for progression-free survival and 0.5 (95% CI, 0.3-0.9) for overall survival. Four patients had a V600E BRAF mutation, and 2 patients had a PIK3CA mutation.

CONCLUSIONS

These data suggest that patients with mCRC with activating K-ras mutations are less likely to respond to panitumumab alone. The small sample size limits us from defining a predictive role of PIK3CA and BRAF mutations for panitumumab treatment.

Patients suspected on clinical grounds to have hereditary non-polyposis colorectal cancer (HNPCC) may be offered laboratory testing in order to confirm the diagnosis and to facilitate screening of pre-symptomatic family members. Tumours from an affected family member are usually pre-screened for microsatellite instability (MSI) and/or loss of immunohistochemical expression of mismatch repair (MMR) genes prior to germline MMR gene mutation testing. The efficiency of this triage process is compromised by the more frequent occurrence of sporadic colorectal cancer (CRC) showing high levels of MSI (MSI-H) due to epigenetic loss of MLH1 expression. Somatic BRAF mutations, most frequently V600E, have been described in a significant proportion of sporadic MSI-H CRC but not in HNPCC-associated cancers. BRAF mutation testing has therefore been proposed as a means to more definitively identify and exclude sporadic MSI-H CRC cases from germline MMR gene testing. However, the clinical validity and utility of this approach have not been previously evaluated in a familial cancer clinic setting. Testing for the V600E mutation was performed on MSI-H CRC samples from 68 individuals referred for laboratory investigation of suspected HNPCC. The V600E mutation was identified in 17 of 40 (42%) tumours showing loss of MLH1 protein expression by immunohistochemistry but in none of the 28 tumours that exhibited loss of MSH2 expression (P < 0.001). The assay was negative in all patients with an identified germline MMR gene mutation. Although biased by the fact that germline testing was not pursued beyond direct sequencing in many cases lacking a high clinical index of suspicion of HNPCC, BRAF V600E detection was therefore considered to be 100% specific and 48% sensitive in detecting sporadic MSI-H CRC amongst those cases showing loss of MLH1 protein expression, in a population of patients with MSI-H CRC and clinical features suggestive of HNPCC. Accordingly, we recommend the incorporation of BRAF V600E mutation testing into the laboratory algorithm for pre-screening patients with suspected HNPCC, whose CRCs show loss of expression of MLH1. In such tumours, the presence of a BRAF V600E mutation indicates the tumour is not related to HNPCC and that germline testing of MLH1 in that individual is not warranted. We also recommend that in families where the clinical suspicion of HNPCC is high, germline testing should not be performed on an individual whose CRC harbours a somatic BRAF mutation, as this may compromise identification of the familial mutation.

Sézary syndrome is a leukemic and aggressive form of cutaneous T cell lymphoma (CTCL) resulting from the malignant transformation of skin-homing central memory CD4(+) T cells. Here we performed whole-exome sequencing of tumor-normal sample pairs from 25 patients with Sézary syndrome and 17 patients with other CTCLs. These analyses identified a distinctive pattern of somatic copy number alterations in Sézary syndrome, including highly prevalent chromosomal deletions involving the TP53, RB1, PTEN, DNMT3A and CDKN1B tumor suppressors. Mutation analysis identified a broad spectrum of somatic mutations in key genes involved in epigenetic regulation (TET2, CREBBP, KMT2D (MLL2), KMT2C (MLL3), BRD9, SMARCA4 and CHD3) and signaling, including MAPK1, BRAF, CARD11 and PRKG1 mutations driving increased MAPK, NF-κB and NFAT activity upon T cell receptor stimulation. Collectively, our findings provide new insights into the genetics of Sézary syndrome and CTCL and support the development of personalized therapies targeting key oncogenically activated signaling pathways for the treatment of these diseases.

OBJECTIVE

Aspirin use reduces the risk of colorectal carcinoma. Experimental evidence implicates a role of RAF kinases in up-regulation of prostaglandin-endoperoxide synthase 2 (PTGS2, cyclooxygenase 2), suggesting that BRAF-mutant colonic cells might be less sensitive to the antitumor effects of aspirin than BRAF-wild-type neoplastic cells.

OBJECTIVE

To examine whether the association of aspirin intake with colorectal cancer risk differs according to status of tumor BRAF oncogene mutation.

METHODS

We collected biennial questionnaire data on aspirin use and followed up participants in the Nurses' Health Study (from 1980) and the Health Professionals Follow-up Study (from 1986) until July 1, 2006, for cancer incidence and until January 1, 2012, for cancer mortality. Duplication-method Cox proportional cause-specific hazards regression for competing risks data was used to compute hazard ratios (HRs) for colorectal carcinoma incidence according to BRAF mutation status.

METHODS

Incidence of colorectal cancer cases according to tumor BRAF mutation status.

RESULTS

Among 127,865 individuals, with 3,165,985 person-years of follow-up, we identified 1226 incident rectal and colon cancers with available molecular data. Compared with nonuse, regular aspirin use was associated with lower BRAF-wild-type cancer risk (multivariable HR, 0.73; 95% CI, 0.64 to 0.83; age-adjusted incidence rate difference [RD], -9.7; 95% CI, -12.6 to -6.7 per 100,000 person-years). This association was observed irrespective of status of tumor PTGS2 expression or PIK3CA or KRAS mutation. In contrast, regular aspirin use was not associated with a lower risk of BRAF-mutated cancer (multivariable HR, 1.03; 95% CI, 0.76 to 1.38; age-adjusted, incidence RD, 0.7; 95% CI, -0.3 to 1.7 per 100,000 person-years: P for heterogeneity = .037, between BRAF-wild-type vs BRAF-mutated cancer risks). Compared with no aspirin use, aspirin use of more than 14 tablets per week was associated with a lower risk of BRAF-wild-type cancer (multivariable HR, 0.43; 95% CI, 0.25 to 0.75; age-adjusted incidence RD, -19.8; 95% CI, -26.3 to -13.3 per 100,000 person-years). The relationship between the number of aspirin tablets per week and colorectal cancer risk differed significantly by BRAF mutation status (P for heterogeneity = .005).

CONCLUSIONS

Regular aspirin use was associated with lower risk of BRAF-wild-type colorectal cancer but not with BRAF-mutated cancer risk. These findings suggest that BRAF-mutant colon tumor cells may be less sensitive to the effect of aspirin. Given the modest absolute risk difference, further investigations are necessary to determine clinical implications of our findings.

BACKGROUND

"Follicular lesion of undetermined significance/atypia of undetermined significance" is a heterogeneous category of cases that cannot be classified into 1 of the other established categories. The use of ancillary molecular studies has not been widely explored for this diagnosis.

METHODS

All thyroid cytology cases diagnosed as follicular lesion of undetermined significance/atypia of undetermined significance were retrieved from April 2007 to December 2008. During this time period, samples were collected routinely at the time of aspiration for cytologic and molecular studies. Analysis for BRAF and RAS gene mutations and RET/PTC and PAX8/PPARgamma gene rearrangements were performed and correlated with the cytologic features and surgical pathology outcome.

RESULTS

From a total of 513 follicular lesion of undetermined significance/atypia of undetermined significance cases identified, 455 had adequate molecular results. Of these, 117 cases had cytologic-histologic correlation. In this group, 35 (29.9%) cases had a neoplastic outcome and 20 (17.1%) cases from 19 patients were carcinoma. Positive molecular results were found in 12 cases, all of which were papillary carcinoma. There were no false-positive molecular results. In correlating the molecular results with surgical pathology outcome, we found that the cancer probability for follicular lesion of undetermined significance/atypia of undetermined significance cases with molecular alteration was 100%, while the probability for follicular lesion of undetermined significance/atypia of undetermined significance cases without molecular alteration was 7.6% (P < .001).

CONCLUSIONS

By cytomorphology alone, follicular lesion of undetermined significance/atypia of undetermined significance specimens represent cases that are intermediate in risk between the benign and "suspicious for follicular neoplasm" categories. Although not all papillary carcinoma cases are detected by molecular testing, a positive molecular test result is very helpful in refining follicular lesion of undetermined significance/atypia of undetermined significance cases into high-risk and low-risk categories.

Mutations of BRAF are found in ∼45% of papillary thyroid cancers and are enriched in tumors with more aggressive properties. We developed mice with a thyroid-specific knock-in of oncogenic Braf (LSL-Braf(V600E)/TPO-Cre) to explore the role of endogenous expression of this oncoprotein on tumor initiation and progression. In contrast to other Braf-induced mouse models of tumorigenesis (i.e., melanomas and lung), in which knock-in of Braf(V600E) induces mostly benign lesions, Braf-expressing thyrocytes become transformed and progress to invasive carcinomas with a very short latency, a process that is dampened by treatment with an allosteric MEK inhibitor. These mice also become profoundly hypothyroid due to deregulation of genes involved in thyroid hormone biosynthesis and consequently have high TSH levels. To determine whether TSH signaling cooperates with oncogenic Braf in this process, we first crossed LSL-Braf(V600E)/TPO-Cre with TshR knockout mice. Although oncogenic Braf was appropriately activated in thyroid follicular cells of these mice, they had a lower mitotic index and were not transformed. Thyroid-specific deletion of the Gsα gene in LSL-Braf(V600E)/TPO-Cre/Gnas-E1(fl/fl) mice also resulted in an attenuated cancer phenotype, indicating that the cooperation of TshR with oncogenic Braf is mediated in part by cAMP signaling. Once tumors were established in mice with wild-type TshR, suppression of TSH did not revert the phenotype. These data demonstrate the key role of TSH signaling in Braf-induced papillary thyroid cancer initiation and provide experimental support for recent observations in humans pointing to a strong association between TSH levels and thyroid cancer incidence.

BACKGROUND

Promoter mutations chr5:1,295,228C>T and chr5:1,295,250C>T (termed C228T and C250T, respectively) in the gene for telomerase reverse transcriptase (TERT) have been reported in various cancers and need to be further investigated in thyroid cancer.

OBJECTIVE

The aim of the study was to explore TERT promoter mutations in various thyroid tumors and examine their relationship with BRAF V600E mutation, iodine intake, and clinicopathological behaviors of thyroid cancer.

METHODS

TERT promoter and BRAF mutations were identified by sequencing genomic DNA of primary thyroid tumors from normal- and high-iodine regions in China, and clinicopathological correlation was analyzed.

RESULTS

The C228T mutation was found in 9.6% (39 of 408) of papillary thyroid cancer (PTC), C250T was found in 1.7% (7 of 408) of PTC, and they were collectively found in 11.3% (46 of 408) of PTC. C228T was found in 31.8% (7 of 22) and C250T in 4.6% (1 of 22) of follicular thyroid cancer (FTC), and they were collectively found in 36.4% (8 of 22) of FTC. No TERT mutation was found in 44 benign thyroid tumors. The two mutations occurred in 3.8% (6 of 158) of BRAF mutation-negative PTC vs 16.0% (40 of 250) of BRAF mutation-positive PTC (P = 5.87 × 10(-4)), demonstrating their association. Unlike BRAF mutation, TERT promoter mutations were not associated with high iodine intake, but they were associated with older patient age, larger tumor size, extrathyroidal invasion, and advanced stages III/IV of PTC. Coexisting TERT and BRAF mutations were even more commonly and more significantly associated with clinicopathological aggressiveness.

CONCLUSIONS

In this large cohort, we found TERT promoter mutations to be common, particularly in FTC and BRAF mutation-positive PTC, and associated with aggressive clinicopathological characteristics.

Phase II clinical trials of mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitors are ongoing and ERK1/2 activation is frequently used as a biomarker. In light of the mutational activation of BRAF and KRAS in colorectal cancer, inhibitors of the Raf-MEK-ERK mitogen-activated protein kinase are anticipated to be promising. Previous studies in pancreatic cancer have found little correlation between BRAF/KRAS mutation status and ERK1/2 activation, suggesting that identifying biomarkers of MEK inhibitor response may be more challenging than previously thought. The purpose of this study was to evaluate the effectiveness of MEK inhibitor therapy for colorectal cancer and BRAF/KRAS mutation status and ERK1/2 activation as biomarkers for MEK inhibitor therapy. First, we found that MEK inhibitor treatment impaired the anchorage-independent growth of nearly all KRAS/BRAF mutant, but not wild-type, colorectal cancer cells. There was a correlation between BRAF, but not KRAS, mutation status and ERK1/2 activation. Second, neither elevated ERK1/2 activation nor reduction of ERK1/2 activity correlated with MEK inhibition of anchorage-independent growth. Finally, we validated our cell line observations and found that ERK1/2 activation correlated with BRAF, but not KRAS, mutation status in 190 patient colorectal cancer tissues. Surprisingly, we also found that ERK activation was elevated in normal colonic epithelium, suggesting that normal cell toxicity may be a complication for colorectal cancer treatment. Our results suggest that although MEK inhibitors show promise in colorectal cancer, KRAS/BRAF mutation status, but not ERK activation as previously thought, may be useful biomarkers for MEK inhibitor sensitivity.

A high prevalence of the BRAF(V600E) somatic mutation was recently reported in several series of papillary thyroid carcinomas (PTC). This mutation appears to be particularly prevalent in PTC with a predominantly papillary architecture. Another BRAF mutation (K601E) was detected in a follicular adenoma and in some cases of the follicular variant of PTC. The few studies on record provided controversial data on the relationship between the occurrence of BRAF mutations and clinicopathologic parameters such as gender, age and tumour staging. In an attempt to clarify such controversies we decided to enlarge our previous series to 315 tumours or tumour-like lesions diagnosed in 280 patients, including a thorough analysis of several clinicopathologic features. The BRAF(V600E) mutation was exclusively detected in PTC with a papillary or mixed follicular/papillary architecture both of the conventional type (46%) and of other histotypes, such as microcarcinoma (43%), Warthin-like PTC (75%) and oncocytic variant of PTC (55%). The BRAF(K601E) mutation was detected in four of the 54 cases of the follicular variant of PTC (7%). The mean age of patients with conventional PTC harbouring BRAF(V600E) (46.7 years) was significantly higher (P<0.0001) than that of patients with conventional PTC without BRAF(V600E) (29.5 years). The BRAF (BRAF(V600E)) mutated PTC did not exhibit signs of higher aggressiveness (size, vascular invasion, extra-thyroid extension and nodal metastasis) and were in fact less often multicentric than PTC without the mutation.

Recent studies highlight the importance of BRAF alterations resulting in mitogen activated protein kinase (MAK/ERK) pathway activation in low-grade CNS tumors. We studied 106 low-grade CNS neoplasms in a cohort of primarily pediatric patients to identify the prevalence and clinicopathologic significance of these alterations. Polymerase chain reaction testing identified KIAA1549:BRAF fusions in 51 (48%) tumors overall, including 42 (60%) pilocytic astrocytomas, 4 (17%) unclassifiable low-grade gliomas, 4 (36%) low-grade glioneuronal/neuroepithelial tumors, 0 (of 5) pleomorphic xanthoastrocytomas, 0 (of 4) diffuse astrocytomas (World Health Organization grade II), and 1 (of 3, 33%) pilomyxoid astrocytoma. KIAA1549:BRAF gene fusions confirmed by sequencing included the previously reported ones involving exons 1-16/9-18 (49%), 1-15/9-18 (35%), and 1-16/11-18 (8%) and 2 fusions with novel breakpoints: 1-15/11-18 (6%) and 1-17/10-18 (1%). DNA sequencing identified BRAF mutations in 8% of tumors. BRAF mutations were absent. KIAA1549:BRAF fusions were significantly more frequent in infratentorial (57%) and optic pathway (59%) tumors versus supratentorial (19%) tumors (p = 0.001). We did not identify significantly improved progression-free survival in tumors with fusions. In summary, KIAA1549:BRAF fusions predominate in pilocytic astrocytomas but are also present in some low-grade unclassifiable gliomas and glioneuronal tumors. The prognostic and therapeutic significance of this alteration is unclear and merits further study.

BACKGROUND

There is conflicting literature regarding the association of the BRAF V600E mutation and aggressive clinicopathological features of papillary thyroid cancer (PTC). Nevertheless, some propose that BRAF status be incorporated into the management of patients with PTC, specifically recommendations regarding lymph node dissection. We therefore performed a meta-analysis to examine the relationship between BRAF and clinicopathological features of PTC.

METHODS

A literature search was performed within PubMed and EMBASE databases using the following Medical Subject Headings (MeSH) and keywords: "braf," "mutation," "thyroid," "neoplasm(s)," "tumor," "cancer," and "carcinoma." Individual study-specific odds ratios and confidence intervals were calculated, as were Mantel-Haenszel pooled odds ratios for the combined studies.

RESULTS

Thirty-two studies including 6372 patients were reviewed. BRAF mutation was associated with lymph node metastases (LNM), advanced stage, extrathyroidal extension, tumor size, male gender, multifocality, absence of capsule, classic PTC, and tall-cell variant PTC. There was no association with age or vascular invasion. Only two studies were prospective; nine included consecutive patients, whereas one included randomly selected patients; and only two included patients who had undergone routine central lymph node dissection and were thus evaluable for the presence of LNM.

CONCLUSIONS

Meta-analysis found that BRAF mutation is associated with LNM, stage, extrathyroidal extension, tumor size, male gender, multifocality, absence of capsule, classic PTC, and tall-cell variant PTC in PTC. However, almost all studies were retrospective and only two of 32 included patients who had undergone routine central lymph node dissection, emphasizing the need for well-designed studies to appropriately examine this association before making important clinical decisions.

OBJECTIVE

The association of deficient DNA mismatch repair (dMMR) with prognosis in patients with colon cancer treated with adjuvant fluorouracil, leucovorin, and oxaliplatin (FOLFOX) chemotherapy remains unknown.

METHODS

Resected, stage III colon carcinomas from patients (N = 2,686) randomly assigned to FOLFOX ± cetuximab (North Central Cancer Treatment Group N0147 trial) were analyzed for mismatch repair (MMR) protein expression and mutations in BRAF(V600E) (exon 15) and KRAS (codons 12 and 13). Association of biomarkers with disease-free survival (DFS) was determined using Cox models. A validation cohort (Cancer and Leukemia Group B 88903 trial) was used.

RESULTS

dMMR was detected in 314 (12%) of 2,580 tumors, of which 49.3% and 10.6% had BRAF(V600E) or KRAS mutations, respectively. MMR status was not prognostic overall (adjusted hazard ratio [HR], 0.82; 95% CI, 0.64 to 1.07; P = .14), yet significant interactions were found between MMR and primary tumor site (P(interaction) = .009) and lymph node category (N1 v N2; P(interaction) = .014). Favorable DFS was observed for dMMR versus proficient MMR proximal tumors (HR, 0.71; 95% CI, 0.53 to 0.94; P = .018) but not dMMR distal tumors (HR, 1.71; 95% CI, 0.99 to 2.95; P = .056), adjusting for mutations and covariates. Any survival benefit of dMMR was lost in N2 tumors. Mutations in BRAF(V600E) (HR, 1.37; 95% CI, 1.08 to 1.70; P = .009) or KRAS (HR, 1.44; 95% CI, 1.21 to 1.70; P < .001) were independently associated with worse DFS. The observed MMR by tumor site interaction was validated in an independent cohort of stage III colon cancers (P(interaction) = .037).

CONCLUSIONS

The prognostic impact of MMR depended on tumor site, and this interaction was validated in an independent cohort. Among dMMR cancers, proximal tumors had favorable outcome, whereas distal or N2 tumors had poor outcome. BRAF or KRAS mutations were independently associated with adverse outcome.

Uveal melanoma (UM) and cutaneous melanoma (CM) differ significantly in their epidemiological, clinical, immunophenotypical, and cytogenetic features, but the molecular basis for these differences has not been delineated. CMs frequently harbor an activating mutation in either NRAS or the RAS-regulated kinase BRAF, suggesting that either of these oncogenes may increase signaling through the mitogen-activated protein (MAP) kinase pathway and promote melanoma development. The aim of this study was to examine BRAF and NRAS gene mutations in UM. Genomic DNA from CM and UM was screened for mutations in BRAF exons 11 and 15 and NRAS exons 1 and 2 using a combination of denaturing high-performance liquid chromatography and direct sequencing. Mutations in BRAF exon 15 were detected in 16 (36.4%) of 44 CMs and 0 (0%) of 62 UMs. The most common mutation in CM was V599E, but a novel point mutation (L596Q) was identified in two cases and an in-frame deletion/insertion (VKSRWK599-604D) was discovered in one case. No BRAF exon 11 mutations were observed among seven CMs and nine UMs that were wild-type for exon 15. Mutation of NRAS exon 2 was rare in CM [1 (3.7%) of 27] and absent in UM [0 (0%) of 47]. No NRAS exon 1 mutations were detected in either type of melanoma. We conclude that UMs arise independent of oncogenic BRAF and NRAS mutations, an observation that may have implications for therapies targeted to the NRAS-BRAF pathway.