Development and extensive analytical validation of deep amplicon sequencing for detecting KRAS and NRAS mutations in metastatic colorectal cancer samples.

The presence of wild-type RAS alleles, as determined by genotyping codons 12, 13, 59, 61, 117, and 146, is a prerequisite for personalized anti-EGFR treatment of metastatic colorectal cancer (mCRC) patients. Here we describe analytical validation of in-house developed massively parallel sequencing technology (MPS) in comparison to the in vitro diagnostics (IVD) certified qPCR method. DNA extracted from FFPE samples from CRC patients (n=703) and reference standards (n=33) were tested for KRAS and NRAS mutations in 6 codons of exons 2, 3, and 4 using deep amplicon sequencing (DAS) on a MiSeq benchtop sequencer (Illumina). Two different amplicon lengths and two different library preparation methods (long-RAS and short-RAS) were tested in order to evaluate their impact on DAS performance. In parallel, identical tumor DNA was tested by the following IVD assays: therascreen KRAS RGQ PCR Kit (Qiagen), cobas® KRAS Mutation Test (Roche Diagnostics), and SNaPshot assay (Thermo Fisher Scientific). Both DAS assays detected all the mutations present in reference standards and external quality control samples, except for the artificially generated KRAS codon 146 mutation. The DAS assays performed sufficient analytical specificity and sensitivity (≥0.95). The use of shorter amplicons prolonged the preparation steps but significantly improved the sequencing success rate of FFPE-derived DNA. RAS mutation frequencies in the Czech CRC patients were similar to previous reports, although rare mutations were also detected. DAS with short amplicons is a good strategy for routine assessment of somatic mutations in low-quality FFPE-derived DNA.

Precision medicine in medical oncology: hope, disappointment and reality.

During the past 20 years, targeted therapy based on the understanding of tumor biology has been complementing or even replacing cytotoxic agents that have dominated pharmacotherapy of cancer since the conception of medical oncology. Unfortunately, the fact that targeted therapies with potential to induce cure or at least substantially prolong survival are still not available for many common solid tumors results in skepticism or even nihilism. On the one hand, biomarker research is not keeping pace with the introduction of new agents, while on the other hand, effective drugs are still not available for many potential molecular targets associated with malignant transformation and tumor progression. However, targeted therapies have already transformed the natural history and clinical outcomes not only in patients with rare malignancies like gastrointestinal stromal tumor but also with many common tumors, e.g. breast cancer, malignant melanoma, non-small cell lung cancer or renal cell carcinoma. For further advances, a multidisciplinary effort is indispensible that should, above all, involve the collaboration of medical oncology and laboratory medicine.

From Tumor Immunology to Immunotherapy in Gastric and Esophageal Cancer.

Esophageal and gastric cancers represent tumors with poor prognosis. Unfortunately, radiotherapy, chemotherapy, and targeted therapy have made only limited progress in recent years in improving the generally disappointing outcome. Immunotherapy with checkpoint inhibitors is a novel treatment approach that quickly entered clinical practice in malignant melanoma and renal cell cancer, but the role in esophageal and gastric cancer is still poorly defined. The principal prognostic/predictive biomarkers for immunotherapy efficacy currently considered are PD-L1 expression along with defects in mismatch repair genes resulting in microsatellite instability (MSI-H) phenotype. The new molecular classification of gastric cancer also takes these factors into consideration. Available reports regarding PD-1, PD-L1, PD-L2 expression and MSI status in gastric and esophageal cancer are reviewed to summarize the clinical prognostic and predictive role together with potential clinical implications. The most important recently published clinical trials evaluating checkpoint inhibitor efficacy in these tumors are also summarized.

G12V and G12A KRAS mutations are associated with poor outcome in patients with metastatic colorectal cancer treated with bevacizumab.

The v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations are found in 35-45 % of colorectal cancer (CRC) cases. Although the association between the RAS signaling and angiogenesis is well known, the negative predictive value of KRAS mutation has not been established in patients treated with bevacizumab. The aim of this study was to evaluate the association between specific KRAS mutation types and outcome of patients with metastatic CRC treated with bevacizumab. The study included 404 patients with metastatic CRC (mCRC) treated with bevacizumab. Clinical data obtained from the clinical registry CORECT were retrospectively analyzed. The shortest survival was observed in patients with tumors harboring G12V or G12A KRAS mutation (G12V/A). The median progression-free survival (PFS) and overall survival (OS) for patients with tumors harboring G12V/A KRAS mutation was 6.6 and 16.8 compared to 11.6 and 26.3 months for patients with tumors harboring other KRAS mutation type (p < 0.001 and p < 0.001), while the survival of patients harboring other KRAS mutation types was comparable to those with tumors harboring wild-type KRAS gene. In the Cox multivariable analysis, KRAS G12V/A mutation type remains a significant factor predicting both PFS (HR = 2.18, p < 0.001) and OS (HR = 2.58, p < 0.001). In conclusion, the results of the present study indicate that there is a significant difference in biological behavior between tumors harboring G12V/A and other KRAS mutations. Moreover, comparison of the survival of patients with tumors harboring G12V/A KRAS mutations with those harboring wild-type KRAS gene revealed that G12V/A KRAS mutations are prognostic biomarker for inferior PFS and OS in patients with mCRC treated with bevacizumab in univariate as well as multivariable analyses.

Citrulline as a biomarker of gastrointestinal toxicity in patients with rectal carcinoma treated with chemoradiation.

BACKGROUND: Gastrointestinal toxicity is the principal toxicity of chemoradiation in the treatment of rectal carcinoma. The assessment of this toxicity still relies mostly on the symptoms reported by the patient. METHODS: Plasma citrulline, serum neopterin and urinary neopterin were followed weekly in 49 patients with rectal carcinoma during chemoradiation. RESULTS: Citrulline significantly (p<0.05) decreased while serum and urinary neopterin concentrations increased during therapy. Irradiated gut volume correlated significantly inversely with citrulline and positively with urinary neopterin. Statistically significant inverse correlations were also observed between urinary neopterin and plasma citrulline concentrations during the treatment. Urinary neopterin concentrations were significantly higher and citrulline concentrations were lower in patients who experienced grade ≥3 gastrointestinal toxicity. CONCLUSIONS: Citrulline represents a promising biomarker of gastrointestinal toxicity. Moreover, the volume of irradiated gut correlated with urinary neopterin concentrations and an association was observed between gastrointestinal toxicity evidenced by lower citrulline concentrations and systemic immune activation reflected in increased concentrations of urinary neopterin.

Neopterin as a biomarker of immune response in cancer patients.

With the advent of immunotherapy the topic of biomarkers of immune response is of high interest. Along with the expression of programmed death ligand 1 (PD-L1) or tumor infiltrating lymphocytes (TIL), biomarkers of macrophage activation could be of interest. Neopterin is a biomarker of immune activation increased in different disorders associated with immune activation, including cancer. Neopterin synthesis is induced by interferon-γ that also induces indoleamine 2,3-dioxygenase (IDO), an enzyme catalyzing catabolism of tryptophan to kynurenine. Increased urinary or serum concentrations of neopterin have been associated with poor prognosis across a spectrum of malignant disorders of different primary location. Neopterin concentration in peripheral blood as well as in the tumor microenvironment correlates with phenotypic and functional changes of lymphocytes, indicating immune dysfunction. Increased neopterin concentrations are also accompanied by increased rate of conversion of tryptophan to kynurenine. Increasing neopterin concentrations also accompany side effects of anticancer treatment and could predict subsequent complications. Although almost four decades have elapsed since the discovery of increased neopterin concentrations in cancer patients, the full potential of neopterin as a biomarker in this setting has not been so far realized.

Prognostic Significance of Serum and Urinary Neopterin Concentrations in Patients with Rectal Carcinoma Treated with Chemoradiation.

AIM: To analyze the prognostic significance of serum and urinary neopterin concentrations in patients with rectal adenocarcinoma treated with (chemo)radiation. PATIENTS AND METHODS: Urinary and serum neopterin and peripheral blood cell count were determined in 49 patients with rectal carcinoma before the start of (chemo)radiation. RESULTS: Neopterin concentrations exhibited a significant inverse correlation with hemoglobin and positive correlation with leukocyte count, platelet count and platelet-to-lymphocyte ratio. Increased serum neopterin concentration was associated with significantly inferior relapse-free survival (RFS) and overall survival. However, a significant association was observed only in 28 patients treated in the neoadjuvant setting. Although increased urinary neopterin was also associated with inferior RFS and overall survival, this was not statistically significant. The neutrophil-to-lymphocyte ratio was also associated with poor prognosis. CONCLUSION: The data presented herein indicate a prognostic significance of serum neopterin concentrations in patients with rectal cancer treated with neoadjuvant chemoradiation.