Using predictive biomarkers to select patients with advanced colorectal cancer for treatment with epidermal growth factor receptor antibodies

Exosomal microRNAs in regulation of tumor cells resistance to apoptosis

Exosomes are a type of extracellular vesicle that contains bioactive molecules that can be secreted by most cells. Nevertheless, the content of these cells differs depending on the cell from which they originate. The exosome plays a crucial role in modulating intercellular communication by conveying molecular messages to neighboring or distant cells. Cancer-derived exosomes can transfer several types of molecules into the tumor microenvironment, including high levels of microRNA (miRNA). These miRNAs significantly affect cell proliferation, angiogenesis, apoptosis resistance, metastasis, and immune evasion. Increasing evidence indicates that exosomal miRNAs (exomiRs) are crucial to regulating cancer resistance to apoptosis. In cancer cells, exomiRs orchestrate communication channels between them and their surrounding microenvironment, modulating gene expression and controlling apoptosis signaling pathways. This review presents an outline of present-day knowledge of the mechanisms that affect target cells and drive cancer resistance to apoptosis. Also, our study looks at the regulatory role of exomiRs in mediating intercellular communication between tumor cells and surrounding microenvironmental cells, specifically stromal and immune cells, to evade therapy-induced apoptosis.

Regulation of IFN-γ-mediated PD-L1 expression by MYC in colorectal cancer with wild-type KRAS and TP53 and its clinical implications

Introduction: In the tumor microenvironment, interferon gamma (IFN-γ) secreted by tumor infiltrating lymphocytes can upregulate programmed cell death 1 ligand 1 (PD-L1) expression in many cancers. The present study evaluated the expression of PD-L1 in selected colorectal cancer cell lines with IFN-γ treatment and explored the correlation between programmed cell death 1 ligand 1 expression and KRAS/TP53 mutation status. Methods: The selected colorectal cancer cell lines had known KRAS mutations or TP53 mutations. TCGA data analysis were used to investigate the correlation between overall survival of patient with anti-PD-1/PD-L1 immunotherapy and KRAS/TP53 mutation status. Besides, the correlation between PD-L1 expression and KRAS/TP53 mutation status were also investigated by using TCGA data analysis. In vitro experiments were used to explore the mechanism underlying KRAS- and TP53-related PD-L1 expression. Results: Firstly, TCGA data analysis for gene expression and overall survival and an in vitro study revealed that the wild-type KRAS/TP53 cell lines exhibited hyperresponsiveness to interferon gamma exposure and correlated with better survival in patients receiving anti-PD-1/PD-L1 treatment. Secondly, experimental data revealed that interferon gamma induced the upregulation of programmed cell death 1 ligand 1 mainly through regulating MYC in wild-type KRAS and TP53 colorectal cancers. Discussion: Our findings revealed that the response to anti-PD-1/PD-L1 cancer immunotherapy frequently happened in wild-type KRAS and TP53 colorectal cancers, which were also found to show higher programmed cell death 1 ligand 1 expression. Our results indicate that the wild-type KRAS/TP53 colorectal cancer cell lines may respond better to interferon gamma treatment, which causes increased programmed cell death 1 ligand 1 expression and may be a mechanism underlying the better responses to anti-PD-1/PD-L1 therapies in wild-type KRAS and wild-type TP53 colorectal cancer. Furthermore, the experimental results suggest that interferon gamma regulated programmed cell death 1 ligand 1 expression through the regulation of MYC, which may further affect the response to PD-1/PD-L1 cancer immunotherapy. These results suggest a novel potential treatment strategy for enhancing the efficacy of PD-1/PD-L1 blockade immunotherapy in most colorectal cancer patients.

Cutoff of 25% for Ki67 expression is a good classification tool for prognosis in colorectal cancer in the AJCC‑8 stratification

Ki‑67 expression has been widely used in clinical practice as an index to evaluate the proliferative activity of tumor cells. The cutoff for Ki67 expression in order to increase the prognostic value of Ki67 expression in colorectal cancer varies. The present study assessed the relationship between the 25% cutoff for Ki67 expression and prognosis in colorectal cancer in the AJCC‑8 (American Joint Committee on Cancer 8 edition) stratification. The current trial included 1,090 colorectal cancer patients enrolled from 2006 to 2012 at Huzhou Central Hospital. Ki67 expression was classified according to 25% intervals, dividing the patients into four groups. Measurement data were analyzed by ANOVA, and count data by Crosstabs. Bivariate correlation analysis was performed to assess clinicopathological indicators based on Ki67 expression. Disease‑free survival (DFS) and overall survival (OS) based on Ki67 levels were analyzed by the Kaplan‑Meier method. A total of 1,090 patients of the 2,080 enrolled CRC cases were evaluated (52.4%). Invasive depth, tumor differentiation, tumor size, AJCC‑8, positive number of lymph nodes and chemotherapy status showed significant differences in the various Ki67 expression groups (all P<0.05), with significant correlations (Spearman rho: 0.170, 0.456, 0.22, 0.195, 0.514 and ‑0.201, respectively, all P<0.001). DFS and OS for the different Ki67 level groups based on AJCC‑8 stratification were analyzed, and no significance was found in stage IV (P=0.334). DFS and OS survival rates were assessed at different Ki67 expression levels, and no significant differences were found (all P>0.05). Cox regression analysis showed that invasive depth, lymph node metastasis, tumor differentiation, AJCC‑8 and Ki67 were independent factors affecting colorectal cancer (P=0.030, all others P<0.001). In conclusion, a cutoff of 25% for Ki67 expression is a good classification tool. High Ki67 has a close association with poor prognosis in colorectal cancer and independently predicts prognosis in the AJCC‑8 stratification.

KRAS and NRAS mutational gene profile of metastatic colorectal cancer patients in Jordan

BACKGROUND

A constitutively active RAS protein in the absence of stimulation of the epidermal growth factor receptor (EGFR) is the result of mutations in KRAS and NRAS genes. Mutations in the KRAS exon 2 and outside exon 2 have been found to predict the resistance to anti-EGFR monoclonal therapy. A substantial proportion of metastatic colorectal cancer cases (mCRC) exhibit RAS mutations outside KRAS exon 2, particularly in KRAS exon 3 and 4 and NRAS exons 2 and 3. No data about RAS mutations outside KRAS exon 2 are available for Jordanian patients with mCRC. We aim to study the molecular spectrum, frequency, and distribution pattern of KRAS and NRAS mutations in Jordanian patients with mCRC.

METHODS

A cohort of 190 Jordanian metastatic colorectal cancer patients were enrolled in the trial. We detected mutations in exon 2 of the KRAS and NRAS gene as well as mutations outside of exon 2 using the StripAssay technique. The KRAS StripAssay covered 29 mutations and 22 NRAS mutations.

RESULTS

Mutations were observed in 92 (48.42%) cases, and KRAS exon 2 mutations accounted for 76 cases (83.69%). KRAS G12D was the most common mutation, occurring in 18 cases, followed by KRAS G12A in 16 cases, and G12T in 13 cases. Mutations outside of KRAS exon 2 represented 16.3% of the mutated cases. Among those, 6 cases (6.48%) carried mutations in NRAS exon 2 and 3, and 10 cases (10.87%) in KRAS exon 3 and 4.

CONCLUSION

The frequency of NRAS and KRAS mutations outside of exon 2 appears to be higher in Jordanian patients in comparison with patients from western countries. KRAS mutations outside of exon 2 should be tested routinely to identify patients who should not be treated with anti-EGFR antibodies.

Exosomal miRNA: Small Molecules, Big Impact in Colorectal Cancer

Colorectal cancer (CRC) is one of the major causes of cancer-related deaths worldwide. Tumor microenvironment (TME) contains many cell types including stromal cells, immune cells, and endothelial cells. The TME modulation explains the heterogeneity of response to therapy observed in patients. In this context, exosomes are emerging as major contributors in cancer biology. Indeed, exosomes are implicated in tumor proliferation, angiogenesis, invasion, and premetastatic niche formation. They contain bioactive molecules such as proteins, lipids, and RNAs. More recently, many studies on exosomes have focused on miRNAs, small noncoding RNA molecules able to influence protein expression. In this review, we describe miRNAs transported by exosomes in the context of CRC and discuss their influence on TME and their potential as circulating biomarkers. This overview underlines emerging roles for exosomal miRNAs in cancer research for the near future.

Discovery of A Novel EGFR-Targeting Antibody-Drug Conjugate, SHR-A1307, for the Treatment of Solid Tumors Resistant or Refractory to Anti-EGFR Therapies

Although inhibiting EGFR-mediated signaling proved to be effective in treating certain types of cancers, a quickly evolved mechanism that either restores the EGFR signaling or activates an alternative pathway for driving the proliferation and survival of malignant cells limits the efficacy and utility of the approach via suppressing the EGFR functionality. Given the fact that overexpression of EGFR is commonly seen in many cancers, an EGFR-targeting antibody-drug conjugate (ADC) can selectively kill cancer cells independently of blocking EGFR-mediated signaling. Herein, we describe SHR-A1307, a novel anti-EGFR ADC, generated from an anti-EGFR antibody with prolonged half-life, and conjugated with a proprietary toxin payload that has increased index of EGFR targeting-dependent versus EGFR targeting-independent cytotoxicity. SHR-A1307 demonstrated strong and sustained antitumor activities in EGFR-positive tumors harboring different oncogenic mutations on EGFR, KRAS, or PIK3CA. Antitumor efficacy of SHR-A1307 correlated with EGFR expression levels in vitro and in vivo, regardless of the mutation status of EGFR signaling mediators and a resultant resistance to EGFR signaling inhibitors. Cynomolgus monkey toxicology study showed that SHR-A1307 is well tolerated with a wide therapeutic index. SHR-A1307 is a promising therapeutic option for EGFR-expressing cancers, including those resistant or refractory to the EGFR pathway inhibitors.

L-Lactate dehydrogenase B may be a predictive marker for sensitivity to anti-EGFR monoclonal antibodies in colorectal cancer cell lines

Recently, proteins derived from cancer cells have been widely investigated as biomarkers for predicting the efficacy of chemotherapy. In this study, to identify a sensitive biomarker for the efficacy of anti-epidermal growth factor receptor monoclonal antibodies (anti-EGFR mAbs), proteins derived from 6 colorectal cancer (CRC) cell lines with different sensitivities to cetuximab, an anti-EGFR mAb, were analyzed. Cytoplasmic and membrane proteins extracted from each CRC cell line were digested using trypsin and analyzed comprehensively using mass spectrometry. As a result, 148 and 146 peaks from cytoplasmic proteins and 363 and 267 peaks from membrane proteins were extracted as specific peaks for cetuximab-resistant and -sensitive CRC cell lines, respectively. By analyzing the proteins identified from the peptide peaks, cytoplasmic L-lactate dehydrogenase B (LDHB) was detected as a marker of cetuximab sensitivity, and it was confirmed that LDHB expression was increased in cetuximab-resistant CRC cell lines. Furthermore, LDHB expression levels were significantly upregulated with the acquisition of resistance to cetuximab in cetuximab-sensitive CRC cell lines. In conclusion, LDHB was identified as an important factor affecting cetuximab sensitivity using comprehensive proteome analysis for the first time.

Molecular characterization and biomarker identification in colorectal cancer: Toward realization of the precision medicine dream

Colorectal cancer (CRC) is a major public health problem, both in the USA and globally. Over the past 20 years, significant advances have been made in the treatment of patients with metastatic CRC (mCRC). Recent efforts in the field of biomarkers have focused on the development of molecular diagnostics to define the subset of patients with mCRC that is likely to derive most benefit from anti-EGFR therapy. Herein, we review the recent advancements in molecular stratification of CRC and the role of current as well as emerging biomarkers in this disease. It is now clear that the presence of activating mutations in the KRAS and NRAS genes serves as reliable predictive markers for resistance to anti-EGFR therapy in mCRC. It is also clear that further improvements in the survival of mCRC patients will probably be made possible only with identification of new predictive molecular biomarkers and their evaluation using rational and innovative clinical trials. The recent advances in DNA sequencing technology and "omics"-based approaches have provided promising new strategies for the development of novel molecular biomarkers in this disease.

Diverse Long RNAs Are Differentially Sorted into Extracellular Vesicles Secreted by Colorectal Cancer Cells

The regulation and functional roles of secreted coding and long noncoding RNAs (lncRNAs; >200 nt) are largely unknown. We previously showed that mutant KRAS colorectal cancer (CRC) cells release extracellular vesicles (EVs) containing distinct proteomes, microRNAs (miRNAs), and circular RNAs. Here, we comprehensively identify diverse classes of CRC extracellular long RNAs secreted in EVs and demonstrate differential export of specific RNAs. Distinct noncoding RNAs, including antisense transcripts and transcripts derived from pseudogenes, are enriched in EVs compared to cellular profiles. We detected strong enrichment of Rab13 in mutant KRAS EVs and demonstrate functional delivery of Rab13 mRNA to recipient cells. To assay functional transfer of lncRNAs, we implemented a CRISPR/Cas9-based RNA-tracking system to monitor delivery to recipient cells. We show that gRNAs containing export signals from secreted RNAs can be transferred from donor to recipient cells. Our data support the existence of cellular mechanisms to selectively export diverse classes of RNA.

Noninvasive Biomarkers of Colorectal Cancer: Role in Diagnosis and Personalised Treatment Perspectives

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. It has been estimated that more than one-third of patients are diagnosed when CRC has already spread to the lymph nodes. One out of five patients is diagnosed with metastatic CRC. The stage of diagnosis influences treatment outcome and survival. Notwithstanding the recent advances in multidisciplinary management and treatment of CRC, patients are still reluctant to undergo screening tests because of the associated invasiveness and discomfort (e.g., colonoscopy with biopsies). Moreover, the serological markers currently used for diagnosis are not reliable and, even if they were useful to detect disease recurrence after treatment, they are not always detected in patients with CRC (e.g., CEA). Recently, translational research in CRC has produced a wide spectrum of potential biomarkers that could be useful for diagnosis, treatment, and follow-up of these patients. The aim of this review is to provide an overview of the newer noninvasive or minimally invasive biomarkers of CRC. Here, we discuss imaging and biomolecular diagnostics ranging from their potential usefulness to obtain early and less-invasive diagnosis to their potential implementation in the development of a bespoke treatment of CRC.

The effect of vascular endothelial growth factor-1 expression on survival of advanced colorectal cancer patients

Colorectal cancer is third leading cause of cancer mortality. About 60% of patients had already developed metastasis at the time of diagnosis. Vascular endothelial growth factor (VEGF) is crucial for the development of neovascularization and hence metastasis. This study aimed at investigating the relation between the expression of VEGF in biopsies from surgically dissected colon cancer and the survival of those patients. Biopsies were collected from 86 patients with advanced colon cancer and sections were stained by immunohistochemistry for VEGF. Patients received chemotherapy after the operation and were followed up for disease progression and survival. The clinical data were statistically analyzed with respect to the immunohistochemistry results. The survival of the patients was significantly longer in the patients for whom biopsies showed negative or weak expression of VEGF in comparison to those with moderate to high expression (p-value = 0.04). The expression of VEGF was more frequent in the patients who died as a consequence of the disease in comparison to the 10-year survivors. In conclusion, VEGF could be related to the survival of the patients with colorectal carcinoma and should be considered as a predictor of the prognosis.

Variations in transrenal DNA and comparison with plasma DNA as a diagnostic marker for colorectal cancer

BACKGROUND

Transrenal DNA can potentially be useful in the disease management of colorectal cancer (CRC) and has potential diagnostic utility. Our study aimed to conduct preoperative and postoperative analysis of KRAS-positive patients, using transrenal DNA compared with plasma DNA. This is critically needed for disease diagnostics and treatment response monitoring.

METHODS

CRC patients at different stages of the disease and with different molecular profiles were recruited for serial time-point analysis. Preoperative and postoperative urine specimens were extracted and compared with tumor tissues and plasma DNA.

RESULTS

Our analysis demonstrated that transrenal DNA offered comparable sensitivity and specificity to plasma DNA analysis. Collection of transrenal DNA, being noninvasive, is an attractive assay and easily allows serial monitoring of the disease. Results from preoperative detection showed a close correlation to tumor tissue profiling and demonstrated close associations to the disease. We also observed significant decreases in mutant KRAS DNA concentration after surgery, which confirmed transrenal DNA's sensitivity to treatment response.

CONCLUSIONS

The use of transrenal DNA offers a possible alternative method of disease profiling, detection and tracking. Our study is one of the first to systematically analyze a relatively large number of different CRC patients using transrenal DNA. The positive correlation with disease demonstrates the assay's viability in the clinical setting, and our method further opens up the possibility to use transrenal DNA for clinical intervention investigations.

Improved detection of BRAF V600E using allele-specific PCR coupled with external and internal controllers

Although traditional allele-specific PCR (tAS-PCR) is a common screening method for BRAF V600E mutations, its lower amplification specificity and mutation selectivity have limited its clinical applications. We hypothesize that these limitations are associated with the weaker specificities of allele-specific primers and the thermodynamic driving forces of DNA polymerase. We used three strategies to circumvent these limitations, namely, modifying allele-specific primers, introducing a competitive external allele-specific controller (i.e., cAS-PCR), and introducing a referenced internal positive controller in the cAS-PCR (i.e., rcAS-PCR). The amplification sensitivities and specificities were influenced by the position of the artificially introduced mismatched nucleotide in the allele-specific primers. Moreover, both cAS-PCR and rcAS-PCR could detect single-copy BRAF V600E alleles with higher mutation selectivity (0.1%) than tAS-PCR. In addition, cAS-PCR eliminated false-negative results caused by various PCR inhibitors that might be present in the DNA solutions. The rcAS-PCR could also be employed to avoid the false-negative results caused by low-abundance input templates in cAS-PCR. In conclusion, rcAS-PCR provides a rapid, simple, and low-cost method for detecting low levels of the mutated BRAF V600E gene.

Exploitation of Gene Expression and Cancer Biomarkers in Paving the Path to Era of Personalized Medicine

Cancer therapy agents have been used extensively as cytotoxic drugs against tissue or organ of a specific type of cancer. With the better understanding of molecular mechanisms underlying carcinogenesis and cellular events during cancer progression and metastasis, it is now possible to use targeted therapy for these molecular events. Targeted therapy is able to identify cancer patients with dissimilar genetic defects at cellular level for the same cancer type and consequently requires individualized approach for treatment. Cancer therapy begins to shift steadily from the traditional approach of “one regimen for all patients” to a more individualized approach, through which each patient will be treated specifically according to their specific genetic defects. Personalized medicine accordingly requires identification of indicators or markers that guide in the decision making of such therapy to the chosen patients for more effective therapy. Cancer biomarkers are frequently used in clinical practice for diagnosis and prognosis, as well as identification of responsive patients and prediction of treatment response of cancer patient. The rapid breakthrough and development of microarray and sequencing technologies is probably the main tool for paving the way toward “individualized biomarker-driven cancer therapy” or “personalized medicine”. In this review, we aim to provide an updated knowledge and overview of the current landscape of cancer biomarkers and their role in personalized medicine, emphasizing the impact of genomics on the implementation of new potential targeted therapies and development of novel cancer biomarkers in improving the outcome of cancer therapy.

Molecular genetics of microsatellite-unstable colorectal cancer for pathologists

Background

Microsatellite-unstable colorectal cancers (CRC) that are due to deficient DNA mismatch repair (dMMR) represent approximately 15% of all CRCs in the United States. These microsatellite-unstable CRCs represent a heterogenous group of diseases with distinct oncogenesis pathways. There are overlapping clinicopathologic features between some of these groups, but many important differences are present. Therefore, determination of the etiology for the dMMR is vital for proper patient management and follow-up.

Main body

Epigenetic inactivation of MLH1 MMR gene (sporadic microsatellite-unstable CRC) and germline mutation in an MMR gene (Lynch syndrome, LS) are the two most common mechanisms in the pathogenesis of microsatellite instability in CRC. However, in a subset of dMMR CRC cases that are identified by screening tests, no known LS-associated genetic alterations are appreciated by current genetic analysis. When the etiology for dMMR is unclear, it leads to patient anxiety and creates challenges for clinical management.

Conclusion

It is critical to distinguish LS patients from other patients with tumors due to dMMR, so that the proper screening protocol can be employed for the patients and their families, with the goal to save lives while avoiding unnecessary anxiety and costs. This review summarizes the major pathogenesis pathways of dMMR CRCs, their clinicopathologic features, and practical screening suggestions. In addition, we include frequently asked questions for MMR immunohistochemistry interpretation.

Colorectal Carcinoma: A General Overview and Future Perspectives in Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer-related death. Most cases of CRC are detected in Western countries, with its incidence increasing year by year. The probability of suffering from colorectal cancer is about 4%–5% and the risk for developing CRC is associated with personal features or habits such as age, chronic disease history and lifestyle. In this context, the gut microbiota has a relevant role, and dysbiosis situations can induce colonic carcinogenesis through a chronic inflammation mechanism. Some of the bacteria responsible for this multiphase process include Fusobacterium spp, Bacteroides fragilis and enteropathogenic Escherichia coli. CRC is caused by mutations that target oncogenes, tumour suppressor genes and genes related to DNA repair mechanisms. Depending on the origin of the mutation, colorectal carcinomas can be classified as sporadic (70%); inherited (5%) and familial (25%). The pathogenic mechanisms leading to this situation can be included in three types, namely chromosomal instability (CIN), microsatellite instability (MSI) and CpG island methylator phenotype (CIMP). Within these types of CRC, common mutations, chromosomal changes and translocations have been reported to affect important pathways (WNT, MAPK/PI3K, TGF-β, TP53), and mutations; in particular, genes such as c-MYC, KRAS, BRAF, PIK3CA, PTEN, SMAD2 and SMAD4 can be used as predictive markers for patient outcome. In addition to gene mutations, alterations in ncRNAs, such as lncRNA or miRNA, can also contribute to different steps of the carcinogenesis process and have a predictive value when used as biomarkers. In consequence, different panels of genes and mRNA are being developed to improve prognosis and treatment selection. The choice of first-line treatment in CRC follows a multimodal approach based on tumour-related characteristics and usually comprises surgical resection followed by chemotherapy combined with monoclonal antibodies or proteins against vascular endothelial growth factor (VEGF) and epidermal growth receptor (EGFR). Besides traditional chemotherapy, alternative therapies (such as agarose tumour macrobeads, anti-inflammatory drugs, probiotics, and gold-based drugs) are currently being studied to increase treatment effectiveness and reduce side effects.

Circular RNAs are down-regulated in KRAS mutant colon cancer cells and can be transferred to exosomes

Recent studies have shown that circular RNAs (circRNAs) are abundant, widely expressed in mammals, and can display cell-type specific expression. However, how production of circRNAs is regulated and their precise biological function remains largely unknown. To study how circRNAs might be regulated during colorectal cancer progression, we used three isogenic colon cancer cell lines that differ only in KRAS mutation status. Cellular RNAs from the parental DLD-1 cells that contain both wild-type and G13D mutant KRAS alleles and isogenically-matched derivative cell lines, DKO-1 (mutant KRAS allele only) and DKs-8 (wild-type KRAS allele only) were analyzed using RNA-Seq. We developed a bioinformatics pipeline to identify and evaluate circRNA candidates from RNA-Seq data. Hundreds of high-quality circRNA candidates were identified in each cell line. Remarkably, circRNAs were significantly down-regulated at a global level in DLD-1 and DKO-1 cells compared to DKs-8 cells, indicating a widespread effect of mutant KRAS on circRNA abundance. This finding was confirmed in two independent colon cancer cell lines HCT116 (KRAS mutant) and HKe3 (KRAS WT). In all three cell lines, circRNAs were also found in secreted extracellular-vesicles, and circRNAs were more abundant in exosomes than cells. Our results suggest that circRNAs may serve as promising cancer biomarkers.

Prognostic and predictive biomarkers in metastatic colorectal cancer anti-EGFR therapy

AIM: To reviewing genetic and epigenetic make-up of metastatic colorectal cancers (mCRCs) addicted to epidermal growth factor receptor (EGFR) signalling.

METHODS: The present study summarizes the potential value of prognostic and predictive biomarkers in selecting mCRC patients treated with anti-EGFR therapy. A meta-analysis was performed using a systematic search of PubMed, Medline and Web of Science to identify eligible papers until March 21^st, 2016 using these following terms: ‘‘colorectal cancer’’, “predictive biomarkers’’, “anti-EGFR therapy”, “KRAS”, “NRAS’’, “PIK3CA”, “TP53”, “PTEN”, ‘‘EGFR”, “MET”, “HER2”, “epiregulin”, “amphiregulin”, “prognostic biomarkers”, “BRAF”, “miRNA” and “antibody-dependent cell-mediated cytotoxicity (ADCC) activity”. Two investigators independently evaluated and extracted data from each identified studies based on selected criteria of inclusion and exclusion.

RESULTS: The introduction of agents targeting EGFR such as cetuximab and panitumumab increased overall survival of mCRCs. Nevertheless, it has firstly became evident that response rates to cetuximab regimens in unselected patient populations were typically lower than 30%. Clinical data confirmed the predictive value of RAS mutations for resistance to cetuximab and panitumumab leading to the license of these monoclonal antibodies exclusively for the management of patients with RAS-wild type colorectal cancers. So far the identification of predictive biomarkers have generated interesting, though preliminary and, at times, conflicting data on the importance of tumour mRNA levels of EGFR ligands, of activating mutations in other genes such as NRAS and PIK3CA. The prognostic value of selected microRNAs level and ADCC activity is under investigation, while the prognostic impact of BRAF status remains controversial.

CONCLUSION: This review focuses on the personalized treatment of mCRC and discusses the potential of new prognostic and predictive biomarkers in selecting patients treated with anti-EGFR therapy.

Precision Medicine and Non-Colorectal Cancer Liver Metastases: Fiction or Reality?

BACKGROUND

Non-colorectal liver metastases (nCRLM) constitute a variety of heterogeneous diseases and a considerable therapeutic challenge. Management is based on the primary tumor and the clinical course. In the era of precision medicine (PM) we know that cancer is heterogeneous within the tumor and across different sites.

METHODS

We give an overview of the path to PM through 'omics' beyond genomics. We refer to the experience gained to date from models such as colorectal cancer and we discuss the opportunity offered by PM for the management of nCRLM.

RESULTS

In order to best characterize and track tumor biological behaviors as well as to understand mechanisms of response to therapy and survival we suggest the application of novel clinical trial designs, a dynamic approach with serial monitoring involving evaluation of primary and metastatic sites. Quality and standardization of tissue acquisition and biobanking is a precondition for the reliability of this approach.

CONCLUSION

The application of PM is increasingly becoming a reality. Elucidating the mysteries of tumors in complex settings can only be achieved with the approach PM offers. nCRLM may serve as a model for the application of PM principles and techniques in understanding individual diseases and also cancer as an entity and therapeutic challenge.

RAS Mutations as Predictive Biomarkers in Clinical Management of Metastatic Colorectal Cancer

The use of anti-epidermal growth factor receptor (EGFR) monoclonal antibody therapies in patients with metastatic colorectal cancer is guided by the presence of activating point mutations in codons 12, 13, 59, 61, 117, and 146 of the KRAS and NRAS genes in the primary tumor. Although these mutations have been incorporated into the prescribing information for both cetuximab and panitumumab, highlighted in the National Comprehensive Cancer Network Guidelines, and routinely tested, a number of controversial issues and unanswered questions related to these mutations and their clinical significance remain. In the present review, we explored the contradictory data related to the prognostic value of KRAS mutations, the reported frequent discordance of KRAS mutations, and the reported nonequivalence of some of these mutations. We also considered the issues related to incorporating additional mutations into the already accredited and approved assays and the challenges created by changing an assay's analytical and clinical limits of detection. We also discuss the lack of biologic data supporting the pathogenicity of newly described clinically actionable mutations and explore the uncertainty regarding the clinical significance of low-frequency mutations, highlighting the importance of correcting allele frequencies for tumor purity. We also considered the importance of distinguishing the significance of low-frequency RAS mutations in tumors previously not treated or treated with anti-EGFR therapies and explore new technologies capable of detecting emerging polyclonal RAS mutations that appear to confer drug resistance.

KRAS-dependent sorting of miRNA to exosomes

Mutant KRAS colorectal cancer (CRC) cells release protein-laden exosomes that can alter the tumor microenvironment. To test whether exosomal RNAs also contribute to changes in gene expression in recipient cells, and whether mutant KRAS might regulate the composition of secreted microRNAs (miRNAs), we compared small RNAs of cells and matched exosomes from isogenic CRC cell lines differing only in KRAS status. We show that exosomal profiles are distinct from cellular profiles, and mutant exosomes cluster separately from wild-type KRAS exosomes. miR-10b was selectively increased in wild-type exosomes, while miR-100 was increased in mutant exosomes. Neutral sphingomyelinase inhibition caused accumulation of miR-100 only in mutant cells, suggesting KRAS-dependent miRNA export. In Transwell co-culture experiments, mutant donor cells conferred miR-100-mediated target repression in wild-type-recipient cells. These findings suggest that extracellular miRNAs can function in target cells and uncover a potential new mode of action for mutant KRAS in CRC.

KRAS-dependent sorting of miRNA to exosomes

Mutant KRAS colorectal cancer (CRC) cells release protein-laden exosomes that can alter the tumor microenvironment. To test whether exosomal RNAs also contribute to changes in gene expression in recipient cells, and whether mutant KRAS might regulate the composition of secreted microRNAs (miRNAs), we compared small RNAs of cells and matched exosomes from isogenic CRC cell lines differing only in KRAS status. We show that exosomal profiles are distinct from cellular profiles, and mutant exosomes cluster separately from wild-type KRAS exosomes. miR-10b was selectively increased in wild-type exosomes, while miR-100 was increased in mutant exosomes. Neutral sphingomyelinase inhibition caused accumulation of miR-100 only in mutant cells, suggesting KRAS-dependent miRNA export. In Transwell co-culture experiments, mutant donor cells conferred miR-100-mediated target repression in wild-type-recipient cells. These findings suggest that extracellular miRNAs can function in target cells and uncover a potential new mode of action for mutant KRAS in CRC.

Colorectal Cancer Biomarkers: Where Are We Now?

Colorectal cancer is one of the major causes of cancer-related death in the Western world. Patient survival is highly dependent on the tumor stage at the time of diagnosis. Reduced sensitivity to chemotherapy is still a major obstacle in effective treatment of advanced disease. Due to the fact that colorectal cancer is mostly asymptomatic until it progresses to advanced stages, the implementation of screening programs aimed at early detection is essential to reduce incidence and mortality rates. Current screening and diagnostic methods range from semi-invasive procedures such as colonoscopy to noninvasive stool-based tests. The combination of the absence of symptoms, the semi-invasive nature of currently used methods, and the suboptimal accuracy of fecal blood tests results in colorectal cancer diagnosis at advanced stages in a significant number of individuals. Alterations in gene expression leading to colorectal carcinogenesis are reflected in dysregulated levels of nucleic acids and proteins, which can be used for the development of novel, minimally invasive molecular biomarkers. The purpose of this review is to discuss the commercially available colorectal cancer molecular diagnostic methods as well as to highlight some of the new candidate predictive and prognostic molecular markers for tumor, stool, and blood samples.

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.

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.

Predictive biomarkers of response to anti-EGF receptor monoclonal antibody therapies

SUMMARY 

The EGF receptor (EGFR) pathway plays an important role in the progression of several carcinomas, including colorectal cancer (CRC). The EGFR has emerged as a candidate for targeted therapy for CRC. Two monoclonal antibodies used to inhibit the EGFR signaling pathway are cetuximab and panitumumab. Both these monoclonal antibodies inhibit tumor-promoting activities, such as tumor cell proliferation, survival, angiogenesis and metastasis. However, only a subpopulation of metastatic CRC patients responds to such therapy. Constitutive activation within the pathway gives rise to other aberrantly expressed biomarkers that are able to circumvent the anti-EGFR treatment and confer resistance. Mechanisms of resistance and the value of these emerging predictive biomarkers in the clinical setting are discussed in this review.

High-sensitivity PCR method for detecting BRAF V600E mutations in metastatic colorectal cancer using LNA/DNA chimeras to block wild-type alleles

The response to epidermal growth factor receptor (EGFR)-targeted therapy in metastatic colorectal cancer (mCRC) is variable because of intra-tumor heterogeneity at the genetic level, and consequently, it is important to develop sensitive and selective assays to predict patient responses to therapy. Low-abundance BRAF V600E mutations are associated with poor response to treatment with EGFR inhibitors. We developed a method for the detection of BRAF V600E mutations in mCRC using real-time wild-type blocking PCR (WTB-PCR), in which a chimera composed of locked nucleic acids and DNA is incorporated to amplify the mutant allele at high efficiency while simultaneously inhibiting the amplification of wild-type alleles. Mixing experiments showed that this method is exquisitely sensitive, with detection of the mutated allele at a mutant/wild-type ratio of 1:10,000. To demonstrate the applicability of this approach for mCRC patients, we assessed the V600E mutations in 50 clinical cases of mCRC by real-time WTB-PCR. The percentage of patients with V600E mutation as determined by WTB-PCR (16%, 8/50) was higher than by traditional PCR (10%, 5/50), suggesting an increased sensitivity for WTB-PCR. By calculating the ΔC q for real-time traditional PCR, which amplifies all BRAF alleles, versus WTB-PCR, which selectively amplifies mutant BRAF, we demonstrated that among the V600E-positive mCRC patient samples, the percentage of BRAF DNA with the V600E mutation ranged from 0.05 to 52.32%. In conclusion, WTB-PCR provides a rapid, simple, and low-cost method to detect trace amounts of mutated BRAF V600E gene.

Incidence and prognostic impact of KRAS and BRAF mutation in patients undergoing liver surgery for colorectal metastases

BACKGROUND

Molecular biomarkers offer the potential for refining prognostic determinants in patients undergoing cancer surgery. Among patients with colorectal cancer, KRAS and BRAF are important biomarkers, but their role in patients undergoing surgical therapy for liver metastases is unknown. In this study, the incidence and prognostic significance of KRAS and BRAF mutations were determined in patients undergoing surgical therapy of colorectal liver metastases (CRLM).

METHODS

KRAS and BRAF analysis was performed on 202 patients undergoing surgery for CRLM between 2003 and 2008. Tumor samples were analyzed for somatic mutations using sequencing analysis (KRAS, codon12/13, BRAF, V600E). The frequency of mutations was ascertained, and their impact on outcome was determined relative to other clinicopathologic factors.

RESULTS

KRAS gene mutations were detected in 58/202 patients (29%). In contrast, mutation in the BRAF gene was identified in very low frequency in this surgical cohort, found in only 4/202 (2%) patients. On multivariate analysis, KRAS mutation was associated with worse survival (hazard ratio [HR], 1.99; 95% confidence interval [CI], 1.21-3.26), as well as recurrence risk (HR, 1.68; 95% CI, 1.04-2.70). Although other clinicopathologic features, including tumor number, carcinoembryonic antigen, and primary stage were also associated with survival, KRAS status remained independently predictive of outcome. The low incidence of BRAF mutation limited assessment of its prognostic impact.

CONCLUSION

Whereas KRAS mutations were found in approximately one third of patients, BFAF mutations were found in only 2% of patients undergoing surgery for CRLM. KRAS status was an independent predictor of overall and recurrence-free survival. Molecular biomarkers such as KRAS may help to refine our prognostic assessment of patients undergoing surgical therapy for CRLM.

Targeted therapy in metastatic colorectal cancer -- an example of personalised medicine in action

In metastatic colorectal cancer (mCRC), an improved understanding of the underlying pathology and molecular biology has successfully merged with advances in diagnostic techniques and local/systemic therapies as well as improvements in the functioning of multidisciplinary teams, to enable tailored treatment regimens and optimized outcomes. Indeed, as a result of these advancements, median survival for patients with mCRC is now in the range of 20-24months, having approximately tripled in the last 20years. The identification of KRAS as a negative predictive marker for activity of epidermal growth factor receptor (EGFR)-targeted monoclonal antibodies (mAbs), such as panitumumab (Amgen, Thousand Oaks, USA) and cetuximab (ImClone, Branchburg, USA), has perhaps had the greatest impact on patient management. This meant that, for the first time, mCRC patients unlikely to respond to a targeted therapy could be defined ahead of treatment. Ongoing controversies such as whether patients with KRAS G13D- (or BRAF V600-) mutated tumours can still respond to EGFR-targeted mAbs and the potential impact of inter- and intra-tumour heterogeneity on tumour sampling show that the usefulness of KRAS as a biomarker has not yet been exhausted, and that other downstream biomarkers should be considered. Conversely, a predictive biomarker for anti-angiogenic agents such as bevacizumab (Genentech, San Francisco, USA) in the mCRC setting is still lacking. In this review we will discuss the discovery and ongoing investigation into predictive biomarkers for mCRC as well as how recent advances have impacted on clinical practice and ultimately the overall cost of treatment for these patients.

KRAS mutations and subtyping in colorectal cancer in Jordanian patients

Colorectal cancer (CRC) is one of the most common malignancies in the Western world and Jordan. v-Ki-ras2 Kirsten rat sarcoma (KRAS) mutations represent an early event in the development and progression of CRC. Previous studies have demonstrated that KRAS mutations serve as a predictor of response to EGFR-targeted therapies for patients with metastatic CRC. The aim of this study was to determine the portion of CRC patients with wildtype KRAS status and molecular subtypes of KRAS mutations in Jordan as compared with other countries. DNA was isolated from 100 consecutive colorectal carcinoma specimens from patients who underwent surgical resection or colonoscopic biopsies of colorectal tumors and had developed metastatic disease. KRAS mutations were detected by hybridization-based strip assay as well as RT-PCR-based assay and confirmed by standard Sanger sequencing of codon 12 and 13 of exon 1 of the KRAS gene. Among 100 tested patients, 56% had a wt-KRAS genotype and 44% had a mutated KRAS genotype. The pGly12Asp was the most commonly detected mutation (54.5%). KRAS mutations were independently associated with patient age, gender and tumoral variables. The ratio of mutated versus wt-KRAS patients in this study is similar to those reported in Western countries but contrasts to neighboring Middle Eastern countries. Colorectal carcinoma cases from Jordan had higher KRAS mutation frequencies compared with other Middle Eastern countries which is likely to reflect different molecular pathogenesis and environmental exposures.

Prognostic relevance of KRAS and BRAF mutations in Japanese patients with colorectal cancer

BACKGROUND

Mutations of the KRAS or BRAF genes are now recognized as prognostic markers for colorectal cancer (CRC). They are also important predictive markers for resistance to the monoclonal antibodies that target the epidermal growth factor receptor.

METHODS

In this retrospective study, KRAS and BRAF mutations were analyzed using a direct sequence method in 254 Japanese CRC patients, and the associations between KRAS or BRAF mutations and clinicopathological characteristics or outcome were evaluated.

RESULTS

KRAS and BRAF mutations were detected in 33.5 and 6.7 % of all patients, respectively. Consistent with previous reports, BRAF mutations were significantly correlated with the anatomical site of the tumor (P < 0.001), tumor grade (P = 0.001) and high frequency of microsatellite instability (P < 0.001). BRAF mutations were correlated with poor overall survival in the full patient cohort (P = 0.009). KRAS mutations were significantly correlated with poor recurrence-free survival (P = 0.03), particularly in patients with stage II CRC (P = 0.007). Cox regression analysis showed that KRAS mutations were a negative predictor of recurrence-free survival in patients with stage II CRC.

CONCLUSION

KRAS mutation status could be a novel biomarker for predicting disease recurrence in Japanese patients with stage II CRC.

Impact of STAT3 phosphorylation on the clinical effectiveness of anti-EGFR-based therapy in patients with metastatic colorectal cancer

Half of patients with KRAS wild-type colorectal cancer do not benefit from adding anti-epithelial growth factor receptor (EGFR) to standard chemotherapy regimens. This retrospective study was performed in 94 patients with metastatic colorectal cancer (mCRC) treated in the second line with cetuximab and chemotherapy. Signal transducer and activator of transcription 3 (STAT3) phosphorylation in tumor cells was correlated with decreased median progression-free survival and overall survival (OS). These results highlight the potential role of STAT3 as a molecular target to optimize anti-EGFR therapies.

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3) is involved in epithelial growth factor receptor (EGFR) signaling in a KRAS-independent manner. Phosphorylated STAT3 (pSTAT3) expression in patients with metastatic colorectal cancer (mCRC) treated with anti-EGFR-containing salvage chemotherapy has never been investigated.

PATIENTS AND METHODS

: The first endpoint of this retrospective study was to evaluate the impact of pSTAT3 on the time to progression (TTP) in 94 patients with mCRC treated with anti-EGFR-based therapies in the second- or third-line setting between July 2004 and November 2009. The influence of pSTAT3 on objective response rate and overall survival (OS) was also reported. Nuclear expression of pSTAT3 status was evaluated by immunohistochemical tests on formalin-fixed and paraffin-embedded tumor samples obtained before therapy.

RESULTS

Positive expression of pSTAT3 was observed in 24.5% of the tumor samples. The probability of achieving an objective response was 13% among patients with positive nuclear expression of pSTAT3 compared with 41% for patients displaying pSTAT3-negative tumors (P = .02). In a multivariate logistic regression model, high-grade skin rash, wild-type KRAS status, and negative pSTAT3 status significantly improved TTP and OS.

CONCLUSION

These results underscore an impact of pSTAT3 on the clinical efficacy of anti-EGFR-containing chemotherapy regimens and support the prospective assessment of this biomarker.

KRAS mutations and subtyping in colorectal cancer in Jordanian patients

Colorectal cancer (CRC) is one of the most common malignancies in the Western world and Jordan. v-Ki-ras2 Kirsten rat sarcoma (KRAS) mutations represent an early event in the development and progression of CRC. Previous studies have demonstrated that KRAS mutations serve as a predictor of response to EGFR-targeted therapies for patients with metastatic CRC. The aim of this study was to determine the portion of CRC patients with wildtype KRAS status and molecular subtypes of KRAS mutations in Jordan as compared with other countries. DNA was isolated from 100 consecutive colorectal carcinoma specimens from patients who underwent surgical resection or colonoscopic biopsies of colorectal tumors and had developed metastatic disease. KRAS mutations were detected by hybridization-based strip assay as well as RT-PCR-based assay and confirmed by standard Sanger sequencing of codon 12 and 13 of exon 1 of the KRAS gene. Among 100 tested patients, 56% had a wt-KRAS genotype and 44% had a mutated KRAS genotype. The pGly12Asp was the most commonly detected mutation (54.5%). KRAS mutations were independently associated with patient age, gender and tumoral variables. The ratio of mutated versus wt-KRAS patients in this study is similar to those reported in Western countries but contrasts to neighboring Middle Eastern countries. Colorectal carcinoma cases from Jordan had higher KRAS mutation frequencies compared with other Middle Eastern countries which is likely to reflect different molecular pathogenesis and environmental exposures.

Multidisciplinary approach of colorectal liver metastases

Colorectal cancer (CRC) is the second most common cause of cancer death in Spain. Fifty percent of patients will develop colorectal liver metastases (CLM) during the course of the disease. Less than 20% of patients with CLM are initially resectable and for them 5-year disease-free survival (DFS) is about 20-25%, with a high recurrence rate. CLM is a heterogeneous disease. From a clinical point of view, four main groups can be differentiated: initially resectable, not optimally resectable, unresectable that could be resectable and unresectable that never will be likely to be resected. Treatment of CLM must be established, always, in a multidisciplinary team discussion with an analysis of prognostic factors and resectability. For patients with resectable CLM, the EORTC trial 364 demonstrated that chemotherapy plus surgery is better than surgery alone. Consequently most patients should be treated with perioperative chemotherapy based on oxaliplatin, and if resection has been done without chemotherapy, they should receive adjuvant chemotherapy after R0 resection. Based on oncological factors, the 5-year survival rate after resection of CLM ranges from 60% to only 14% with a poor score. If a patient has more than one of the poor prognostic factors he should probably be referred for preoperative (induction) chemotherapy. Only a minority of patients with CLM are amenable to surgery; therefore, efforts have been made to increase the percentage of patients who could be candidates for resection. Studies, mostly retrospective, have confirmed the ability of neoadjuvant chemotherapy (conversion chemotherapy) to render some metastases resectable. The regimens we must use depend on the KRAS mutational status and the toxicity profiles of drugs in the context of each patient. In k-ras mutated tumours we can use bevacizumab combined with standard chemotherapy or concomitant administration of the three active agents (FOLFOXIRI) in suitable patients. In k-ras wild-type patients, the combination of cetuximab and FOLFIRI-FOLFOX improved response rates and resection rate in phase III-II trials. With a lower level of evidence, panitumumab is an alternative combined with FOLFOX. Bevacizumab is also an alternative as it does not depend on KRAS status. Radiotherapy is becoming an alternative in selected patients, where surgery is not an alternative. For the majority of patients, who will never be resectable, the continuum of care with chemotherapy will be the paradigm for their management.

Differences in the frequencies of K-ras c12-13 genotypes by gender and pathologic phenotypes in colorectal tumors measured using the allele discrimination method

The frequencies of different genotypes of the K-ras oncogene in colorectal cancer (CRC) reveal complex relationships among gender, age, and tumor aggression, however, differences among these studies could also be attributed to a lack of standardization of the detection methods used. We developed the allele discrimination assay, which uses dual-color real-time polymerase chain reaction (qPCR) as a fast K-ras genotyping method, and demonstrated higher sensitivity and specificity than DNA sequencing with formalin-fixed paraffin tissues. The assay detected K-ras mutations among 83 of 204 patients with CRC (40.7%); 20.6% of these mutations were G12D (GAT) mutations, 7.4% were G13D (GAC) and G12V (GTT), and 5.3% were other types. A higher proportion of females was observed overall in tumors with K-ras mutations (60.2%, P = 0.01), codon 12 mutations (63.2%, P = 0.005), and transversions (69.6%, P = 0.02), which reflected the higher prevalence of females among the well- to moderately differentiated tumors (29% in males vs. 53% in females; interaction P = 0.03). The opposite was observed for poorly differentiated tumors (47% in males vs. 35% in females). No significant influence of age was found on the prevalence of K-ras mutation. Males with pathological changes and females with poorly differentiated tumors displayed GAT as a less common genotype compared with most other prevalence studies. In conclusion, allele discrimination, with no additional amplification step, is a fast and reliable genotyping method for detecting K-ras c12-13 mutations. Using this method, we demonstrate differences in the frequencies of K-ras genotypes by gender and pathologic phenotypes of CRC.

Colonic vitamin D metabolism: implications for the pathogenesis of inflammatory bowel disease and colorectal cancer

In epidemiological studies serum levels below 30 nM of 25-OHD(3), the precursor of the active vitamin D metabolite 1,25-(OH)(2)D(3), were consistently associated with incidence of colorectal cancer. The active vitamin D metabolite possesses antimitotic, prodifferentiating and proapoptotic capacity in vivo and in vitro. The intestinal autocrine/paracrine vitamin D system, which is the main source of local 1,25-(OH)(2)D(3) plays a critical role in maintaining both mucosal immunity and normal growth of epithelial cells. It has been hypothesized that the VDR-mediated signaling antagonizing TNF-α and IL-6 receptor-activated pro-inflammatory and proliferative intracellular pathways, may prevent development of IBD and colitis-associated colorectal cancer. Conversely, any situation that impairs the efficiency of the 1,25-(OH)(2)D(3)/VDR signaling system at the level of the gut mucosa, e.g. vitamin D insufficiency, may increase risk for the development of IBD and colorectal cancer. Therefore, not only adequate serum levels of the precursor 25-OHD(3) are essential, but also optimal expression of the 1α-hydroxylating enzyme CYP27B1. The 1,25-(OH)(2)D(3) catabolizing hydroxylase CYP24A1 is increasingly expressed during colon cancer progression, indicating that colonocytes are released from normal growth control by the steroid hormone. Securing adequate levels of calcitriol by inhibition of catabolism and support of 1α-hydroxylation by calcium, phytoestrogens and folate could be a valid approach to control, at least in part, IBD and CRC pathogenesis.

Stem cell property epithelial-to-mesenchymal transition is a core transcriptional network for predicting cetuximab (Erbitux™) efficacy in KRAS wild-type tumor cells

Beyond a well-recognized effect of KRAS mutations in determining de novo inefficacy of cetuximab (CTX) in metastatic colorectal cancer, we urgently need a biomarker signature for predicting CTX efficacy in KRAS wild-type (WT) tumors. CTX-adapted EGFR gene-amplified KRAS WT tumor cell populations were induced by stepwise-chronic exposure of A431 epidermoid cancer cells to CTX. Genome-wide analyses of 44K Agilent's whole human arrays were bioinformatically evaluated by Gene Set Enrichment Analysis (GSEA)-based screening of the KEGG pathway database. Molecular functioning of CTX was found to depend on: (i) The occurrence of a positive feedback loop on Epidermal Growth Factor Receptor (EGFR) activation driven by genes coding for EGFR ligands (e.g., amphiregulin); (ii) the lack of a negative feedback on mitogen-activated protein kinase (MAPK) activation regulated by dual-specificity phosphatases (e.g., DUSP6) and; (iii) the transcriptional status of gene pathways controlling the epithelial-to-mesenchymal transition (EMT) and its reversal (MET) program (actin cytoskeleton and cell-cell communication-e.g., keratins-focal adhesion signaling-e.g., integrins-and EMT-inducing cytokines - e.g., transforming growth factor-β). Quantitative real-time PCR, high-content immunostaining, and flow-cytometry analyses confirmed that CTX efficacy depends on its ability to promote: (i) Stronger cell-cell contacts by up-regulating the expression of the epithelial markers E-cadherin and occludin; (ii) down-regulation of the epithelial transcriptional repressors Zeb, Snail, and Slug accompanied by restoration of cortical F-actin; and (iii) complete prevention of the CD44(pos)/CD24(neg/low) mesenchymal immunophenotype. The impact of EGFR ligands/MAPK phosphatases gene transcripts in predicting CTX efficacy in KRAS WT tumors may be tightly linked with the ability of CTX to concurrently reverse the EMT status, a pivotal property of migrating cancer stem cells.

The epidermal growth factor receptor conundrum

Soluble epidermal growth factor receptor (sEGFR), a cell surface and serum protein derived from an alternately spliced human EGFR transcript, is recognized by 2 therapeutic antibodies approved by the US Food and Drug Administration: cetuximab and panitumumab. Therefore, circulating sEGFR is an unanticipated first target for both of these therapeutic antibodies, adding a new level of complexity to the understanding of EGF receptor biology that should be considered in the design of future clinical studies.

KRAS, NRAS, PIK3CA exon 20, and BRAF genotypes in synchronous and metachronous primary colorectal cancers diagnostic and therapeutic implications

Targeted therapy of advanced colorectal carcinoma (CRC) necessitates KRAS genotyping. Because we were interested in diagnostic and therapeutic consequences, we studied the KRAS, NRAS, PIK3CA exon 20, and BRAF genotypes in synchronous and metachronous primary CRCs; in addition, we studied their available metastases. We studied 21 patients with 43 synchronous and 2 metachronous adenocarcinomas of the colorectum (n = 20) and stomach (n = 1). Five patients had liver metastases and one had a distant lymph node metastasis. Genomic DNA was extracted from microdissected tumor tissue. The DNA was analyzed by Sanger sequencing and pyrosequencing. Fifty-seven different neoplastic lesions were genotyped, showing 18 (31.6%) KRAS, 2 (3.5%) NRAS, and 7 (12.3%) BRAF mutations, distributed among 10 (47.6%), 1 (4.8%), and 5 (23.8%) of the patients. An identical genotype of all synchronous primary CRCs was found only in 7 (35%) of the patients; the remainder had dissimilar genotypes in various combinations. Interestingly, a single patient had an unknown KRAS genotype (c.37_39dupGGC). Six patients with 13 primary carcinomas had distant metastases. In three of these patients, the metastasis shared the genotype only with one of the primary tumors, because the other primary tumors had another genotype. Synchronous and metachronous primary CRCs of the same patient have variable KRAS, NRAS, and BRAF genotypes. When metastases occur in these patients, the genotype has diagnostic and therapeutic implications and should be determined from the simultaneous or metachronous distant metastases.

Predictive and prognostic biomarkers for targeted therapy in metastatic colorectal cancer

The use of targeted biologic agents in combination with chemotherapy has increased the overall survival (OS) of metastatic colorectal cancer (mCRC) to 23.5 months. With the assistance of Kirsten-ras (KRAS) mutational status, the subgroup population resistant to the inhibition of epidermal growth factor receptor (EGFR) by monoclonal antibodies (MoAbs) can be identified. However, only up to a third of the KRAS wild-type subpopulation respond to EGFR inhibition. Multiple factors, including relatively low response rates and high costs for targeted agents, are driving the search to identify further biomarkers within the EGFR/Ras/Raf/Mek/Erk and PTEN/PIP3/AKT signaling pathways. Vascular endothelial growth factor (VEGF) is a key player in tumor angiogenesis and the target for the MoAb bevacizumab, which is currently licensed for use in mCRC. Despite numerous studies, an equivalent predictive biomarker for bevacizumab has not been identified. Preclinical work indicates that inhibition of the insulin growth factor receptor (IGFR) pathway stops cellular transformation and tumor regression, thus identifying this pathway as a strong potential target for anticancer drug development and the identification of novel biomarkers. This review focuses on research relating to the roles of biomarkers within the EGF, VEGF, and IGF receptor pathways. The molecules KRAS, BRAF, NRAS, PTEN, PIP3, VEGF, IGF-1R, and IGF binding protein 3 are discussed. Currently, KRAS is the only biomarker used in clinical practice for mCRC. Pending the results of ongoing and future studies, additional biomarkers will be tested, tailoring our approach to targeted therapy in mCRC.

Method validation and application of protein biomarkers: basic similarities and differences from biotherapeutics

Protein drug development and biomarkers share common bioanalytical technologies that are applied for different purposes. A fit-for-purpose approach should be used for biomarker assays at various stages of novel biomarker development and their application to drug development. Biomarker quantifications can be absolute or relative, depending upon the characteristics of the standard curve, which include the reference standard, substituted matrix and parallelism. Appropriate method-validation experiments should be carried out on sample collection, relative accuracy and precision, range finding, parallelism, selectivity, specificity and stability in order to meet the need for exploratory or advanced application that is specified for a study. The interaction of a biotherapeutic with the target ligand or inter-related biomarkers should be taken into consideration for method platform choice and validation. Direct adoption of commercial diagnostic kits can produce confounding data. Therefore, kit comparison, modification and appropriate validation experiments are often carried out to meet the specific purpose for drug development. Multiplex assays and physicochemical methods can complement the single-analyte ligand-binding assay for protein drugs and biomarkers.

A multicentre study of capecitabine, oxaliplatin plus bevacizumab as perioperative treatment of patients with poor-risk colorectal liver-only metastases not selected for upfront resection

BACKGROUND

Perioperative chemotherapy improves outcome in resectable colorectal liver-only metastasis (CLM). This study aimed to evaluate perioperative CAPOX (capecitabine-oxaliplatin) plus bevacizumab in patients with poor-risk CLM not selected for upfront resection.

PATIENTS AND METHODS

Poor-risk CLM was defined as follows: more than four metastases, diameter >5 cm, R0 resection unlikely, inadequate viable liver function if undergoing upfront resection, inability to retain liver vascular supply, or synchronous colorectal primary presentation. Patients underwent baseline computed tomography, magnetic resonance imaging, and/or positron emission tomography (PET) for staging and received neoadjuvant CAPOX plus bevacizumab, with resectability assessed every four cycles. Primary end point was radiological objective response rate (ORR).

RESULTS

Forty-six patients were recruited, of which 91% underwent PET to ensure metastases confined to liver. Following neoadjuvant CAPOX plus bevacizumab, the ORR was 78% (95% confidence interval 63% to 89%). This allowed 12 of 30 (40%) patients with initial nonsynchronous unresectable CLM to be converted to resectability. In addition, 10 of 15 (67%) patients with synchronous resectable CLM underwent liver resection, with four additional patients being observed alone due to excellent response to neoadjuvant therapy. No grade 3-4 perioperative complications were seen.

CONCLUSION

Neoadjuvant CAPOX plus bevacizumab resulted in a high response rate for patients with CLMs with poor-risk features not selected for upfront resection and converted 40% of patients to resectability.

Impact of KRAS, BRAF, PIK3CA mutations, PTEN, AREG, EREG expression and skin rash in ≥ 2 line cetuximab-based therapy of colorectal cancer patients

Background

To investigate the predictive significance of KRAS, BRAF, PIK3CA mutational status, AREG- EREG mRNA expression, PTEN protein expression and skin rash in metastatic colorectal cancer (mCRC) patients treated with cetuximab containing salvage chemotherapy.

Methods

Primary tumors from 112 mCRC patients were analyzed. The worst skin toxicity during treatment was recorded.

Results

KRAS, BRAF and PIK3CA mutations were present in 37 (33%), 8 (7.2%) and 11 (9.8%) cases, respectively, PTEN was lost in 21 (19.8%) cases, AREG and EREG were overexpressed in 48 (45%) and 51 (49%) cases. In the whole study population, time to tumor progression (TTP) and overall survival (OS) was significantly lower in patients with KRAS (p = 0.001 and p = 0.026, respectively) or BRAF (p = 0.001 and p<0.0001, respectively) mutant tumors, downregulation of AREG (p = 0.018 and p = 0.013, respectively) or EREG (p = 0.002 and p = 0.004, respectively) and grade 0-1 skin rash (p<0.0001 and p<0.0001, respectively). In KRAS wt patients TTP and OS was significantly lower in patients with BRAF (p = 0.0001 and p<0.0001, respectively) mutant tumors, downregulation of AREG (p = 0.021 and p = 0.004, respectively) or EREG (p = 0.0001 and p<0.0001, respectively) and grade 0-1 skin rash (p<0.0001 and p<0.0001, respectively). TTP was significantly lower in patients with PIK3CA mutations (p = 0.01) or lost PTEN (p = 0.002). Multivariate analysis revealed KRAS (Hazard Ratio [HR] 4.3, p<0.0001), BRAF mutation (HR: 5.1, p<0.0001), EREG low expression (HR: 1.6, p = 0.021) and absence of severe/moderate skin rash (HR: 4.0, p<0.0001) as independent prognostic factors for decreased TTP. Similarly, KRAS (HR 2.9, p = 0.01), BRAF mutation (HR: 3.0, p = 0.001), EREG low expression (HR: 1.7, p = 0.021), absecence of severe/moderate skin rash (HR: 3.7, p<0.0001) and the presence of undifferantited tumours (HR: 2.2, p = 0.001) were revealed as independent prognostic factors for decreased OS.

Conclusions

These results underscore that KRAS-BRAF mutations and EREG expression can be used as biomarkers to further select patients undergoing anti-EGFR treatment.

Serum matrilysin correlates with poor survival independently of KRAS and BRAF status in refractory advanced colorectal cancer patients treated with irinotecan plus cetuximab

The purpose of the study was to prospectively explore the role of serum MMP-7 as a predictive and prognostic marker of anti-epidermal growth factor receptor (EGFR) therapy and irinotecan efficacy in third-line advanced colorectal cancer therapy. One hundred patients were recruited prospectively from six Spanish hospitals. Patients were treated with biweekly irinotecan 180 mg/m(2) and cetuximab 400 mg/m(2) (loading dose) and weekly cetuximab 250 mg/m(2) until progressive disease or unacceptable toxicity. Baseline MMP-7 was determined using a quantitative solid-phase sandwich ELISA. KRAS and BRAF mutational status were also assessed. The clinical endpoints examined were overall survival (OS), progression-free survival (PFS), and response rate. No association between serum MMP-7 and neither KRAS nor BRAF mutational status was found. The multivariate analysis revealed that MMP-7 predicts PFS both in wild-type (WT) KRAS patients (HR 1.03, 95% CI 1.00-1.06; p = 0.046) and in mutant KRAS patients (HR 1.18, 95% CI 1.01-1.35; p = 0.036). The presence of mutant BRAF was associated with shorter PFS (HR 8.49, 95% CI 2.88-25.0; p < 0.001) and worse OS (HR 3.55, 95% CI 1.39-9.09; p = 0.008) in the subset of WT KRAS patients. Serum MMP-7 is associated with PFS in colorectal patients treated with anti-EGFR therapy as third-line treatment independently of KRAS status.

BRAF mutation testing in colorectal cancer

Colorectal cancer is the second most common cause of cancer death in the United States. Understanding the biochemical pathways underlying carcinogenesis has paved the way for more effective treatments and better outcomes. BRAF mutation testing has a role in (1) differentiating sporadic colorectal cancer from Lynch syndrome, (2) identifying cancers lacking BRAF mutation that are more likely to respond to epidermal growth factor receptor inhibitor therapy, and (3) conferring worse prognosis in colorectal cancer that is microsatellite stable. Several analytic methods are available to reliably detect BRAF mutations. Real-time polymerase chain reaction identifies the most common BRAF mutation, V600E, in frozen or paraffin-embedded colorectal cancer tissue. Traditional DNA sequencing and the somewhat more-sensitive pyrosequencing method can detect multiple alternative BRAF mutations that are predicted to constitutively activate signaling through the MAPK pathway, promoting tumor growth and survival. Pathologists play an important role in assay validation as well as in consulting with clinicians about indications for testing, ensuring quality of testing, and interpreting results in conjunction with other clinicopathologic factors important in the management of affected patients.