Genetic Predisposition to Colorectal Cancer: How Many and Which Genes to Test?

Colorectal cancer is one of the most common tumors, and genetic predisposition is one of the key risk factors in the development of this malignancy. Lynch syndrome and familial adenomatous polyposis are the best-known genetic diseases associated with hereditary colorectal cancer. However, some other genetic disorders confer an increased risk of colorectal cancer, such as Li-Fraumeni syndrome (TP53 gene), MUTYH-associated polyposis (MUTYH gene), Peutz-Jeghers syndrome (STK11 gene), Cowden syndrome (PTEN gene), and juvenile polyposis syndrome (BMPR1A and SMAD4 genes). Moreover, the recent advances in molecular techniques, in particular Next-Generation Sequencing, have led to the identification of many new genes involved in the predisposition to colorectal cancers, such as RPS20, POLE, POLD1, AXIN2, NTHL1, MSH3, RNF43 and GREM1. In this review, we summarized the past and more recent findings in the field of cancer predisposition genes, with insights into the role of the encoded proteins and into the associated genetic disorders. Furthermore, we discussed the possible clinical utility of genetic testing in terms of prevention protocols and therapeutic approaches.

Early Gastric Cancer: identification of molecular markers able to distinguish submucosa-penetrating lesions with different prognosis.

BACKGROUND: Early Gastric Cancer (EGC) reaches 25% of the gastric cancers surgically treated in some areas of Northeastern Italy and is usually characterized by a good prognosis. However, among EGCs classified according to Kodama's criteria, Pen A subgroup is characterized by extensive submucosal invasion, lymph node metastases and worse prognosis, whereas Pen B subgroup by better prognosis. The aim of the study was to characterize the differences between Pen A, Pen B and locally advanced gastric cancer (T3N0) in order to identify biomarkers involved in aggressiveness and clinical outcome. METHODS: We selected 33 Pen A, 34 Pen B and 20 T3N0 tumors and performed immunohistochemistry of mucins, copy number variation analysis of a gene panel, microsatellite instability (MSI), TP53 mutation and loss of heterozygosity (LOH) analyses. RESULTS: Pen A subgroup was characterized by MUC6 overexpression (p = 0.021). Otherwise, the Pen B subgroup was significantly associated with the amplification of GATA6 gene (p = 0.002). The higher percentage of MSI tumors was observed in T3N0 group (p = 0.002), but no significant differences between EGC types were found. Finally, TP53 gene analysis showed that 32.8% of Pen tumors have a mutation in exons 5-8 and 50.0% presented LOH. Co-occurrence of TP53 mutation and LOH mainly characterized Pen A tumors (p = 0.022). CONCLUSIONS: Our analyses revealed that clinico-pathological parameters, microsatellite status and frequency of TP53 mutations do not seem to distinguish Pen subgroups. Conversely, the amplification of GATA6 was associated with Pen B, as well as the overexpression of MUC6 and the TP53mut/LOH significantly characterized Pen A.

Prospective validation of VEGF and eNOS polymorphisms as predictors of first-line bevacizumab efficacy in patients with metastatic colorectal cancer.

Bevacizumab (Bev) plus chemotherapy is a standard first-line treatment in metastatic colorectal cancer (mCRC), however to date no predictive factors of response have been identified. Results of our previous analysis on patients enrolled in a randomized prospective phase III multicenter study (ITACa study) showed a predictive value of Vascular Endothelial Growth Factor (VEGF) polymorphism (VEGF + 936), a 27-nucleotide variable number tandem repeat (VNTR) of the endothelial nitric oxide synthase (eNOS) gene and eNOS + 894 polymorphism. mCRC patients, treated with Bev plus chemotherapy, were included in this prospective validation trial. eNOS + 894G > T was analyzed by Real time PCR, while the eNOS VNTR and VEGF + 936C > T were determined by standard PCR and direct sequencing analysis. These polymorphisms were assessed in relation to progression-free survival (PFS), overall survival (OS) and objective response rate (ORR). These three polymorphisms were not predictive of PFS (p 0.91, 0.59 and 0.09, respectively), and OS (p 0.95, 0.32 and 0.46, respectively). Moreover, the haplotype analyses did not confirm what was found in our previous study; patients bearing a specific haplotype of eNOS had not significantly improved outcomes. This prospective study failed to validate the predictive impact of eNOS and VEGF polymorphisms for response to Bev plus first-line chemotherapy in mCRC patients.

Dynamic Monitoring of Circulating Tumor DNA in Patients With Metastatic Colorectal Cancer.

PURPOSE: Plasma circulating tumor DNA (ctDNA) is a valuable resource for tumor characterization and for monitoring of residual disease during treatment; however, it is not yet introduced in metastatic colorectal cancer (mCRC) routine clinical practice. In this retrospective exploratory study, we evaluated the role of ctDNA in patients with mCRC treated with chemotherapy plus bevacizumab. MATERIALS AND METHODS: Fifty-three patients were characterized for RAS and BRAF status on tumor tissue before the start of treatment. Plasma was collected at baseline, at first clinical evaluation, and at disease progression. ctDNA analysis was performed using Oncomine Colon cfDNA Assay on the Ion S5 XL instrument. RESULTS: At baseline, from a plasma sample, RAS, BRAF, or PIK3CA mutations were detected in 44 patients. A high correspondence was observed between ctDNA and tumor tissue mutations (KRAS 100%, NRAS 97.9%, BRAF 97.9%, PIK3CA 90%). Low baseline variant allele frequency (VAF) was found to be associated with longer median progression-free survival (PFS) compared with those with high VAF (15.9 v 12.2 months, P = .02). A higher PFS {12.29 months (95% CI, 9.03 to 17.9) v 8.15 months (95% CI, 2.76 to not available [NA]), P = .04} and overall survival (34.1 months [95% CI, 21.68 to NA] v 11.1 months [95% CI, 3.71 to NA], P = .003) were observed in patients with large decline in VAF at first evaluation. CONCLUSION: ctDNA analysis is useful for molecular characterization and tumor response monitoring in patients with mCRC. Quantitative variations of released ctDNA are associated with clinical outcomes.

Inflammatory indices as prognostic markers in metastatic colorectal cancer patients treated with chemotherapy plus Bevacizumab.

Background: Validated predictors of sensitivity or resistance to Bevacizumab (Bev) are not available, and Inflammatory Indexes (IIs) has been reported to be useful prognostic factors in various malignant solid tumours, including metastatic colorectal cancer (mCRC). Objectives: To explore the prognostic value of IIs in mCRC patients treated with first-line chemotherapy plus Bev. Design: One hundred and eighty-two patients diagnosed with mCRC and treated with first line chemotherapy plus Bev were considered for this prospective non-pharmacological study. Neutrophil, lymphocyte, platelet, aspartate transaminase (AST) and lactate dehydrogenase (LDH) tests were carried out at baseline and before each treatment cycle, according to clinical practice. Methods: Pre-treatment Systemic Immune-inflammation Index (SII), Colon Inflammatory Index (CII) and Aspartate aminotransferase-Lymphocyte Ratio Index (ALRI) were evaluated to assess a correlation with progression-free survival (PFS) and overall survival (OS). Results: In the overall population, PFS and OS were lower in patients with high SII (HR 1.64, p = 0.006 and HR 1.75, p = 0.004, respectively) and high ALRI (HR 2.13, p = 0.001 and HR 1.76, p = 0.02, respectively), but no difference was detected according to CII value. The multivariate analysis confirmed both SII and ALRI as independent prognostic factors for PFS (HR 1.64 and 2.82, respectively) and OS (HR 1.65 and 2.12, respectively). Conclusion: Our results demonstrate and confirm that IIs, and in particular SII and ALRI, are easy to measure prognostic markers for patient candidates to first line chemotherapy plus Bev for mCRC.

Inflammatory Indexes can predict the efficacy of bevacizumab in metastatic colorectal cancer Bevacizumab (Bev) is a humanized monoclonal antibody with antiangiogenic activity, used in combination with chemotherapy as a standard first line treatment for many metastatic colorectal cancer patients. Validated predictors of sensitivity or resistance to Bevacizumab are not available, although several studies have investigated this issue in recent years. In this study, we investigated whether some selected baseline inflammatory indexes levels, namely Systemic Immune-inflammation Index (SII) and Aspartate aminotransferase-Lymphocyte Ratio Index (ALRI) could predict the survival in patients with metastatic colorectal cancer treated with Bevacizumab plus chemotherapy. We enrolled 182 patients diagnosed with mCRC and treated with first line chemotherapy plus Bev. For each patient we tested blood neutrophils, lymphocytes, platelets, aspartate transaminase (AST) and lactate dehydrogenase (LDH) before each treatment cycle, according to clinical practice. We calculated the SII value as platelet count × neutrophil count/lymphocyte count, and ALRI as AST/lymphocyte count. We found that patients with high SII and high ALRI values had lower survival as compared to those with low values. These parameters represent reproducible, inexpensive and easy to measure biomarkers to be used in both clinical practice and clinical trials, for patient selection.

Genetic and Epigenetic Alterations of CDH1 Regulatory Regions in Hereditary and Sporadic Gastric Cancer.

E-cadherin is a key player in gastric cancer (GC) and germline alterations of CDH1, its encoding gene, are responsible for Hereditary Diffuse Gastric Cancer (HDGC) syndrome. This study aimed at elucidating the role of genetic variants and DNA methylation of CDH1 promoter and enhancers in the regulation of gene expression. For this purpose, we analyzed genetic variants of the CDH1 gene through Next-Generation Sequencing (NGS) in a series of GC cell lines (NCI-N87, KATO-III, SNU-1, SNU-5, GK2, AKG, KKP) and the corresponding CDH1 expression levels. By bisulfite genomic sequencing, we analyzed the methylation status of CDH1 regulatory regions in 8 GC cell lines, in a series of 13 sporadic GC tissues and in a group of 20 HDGC CDH1-negative patients and 6 healthy controls. The NGS analysis on CDH1 coding and regulatory regions detected genetic alterations in 3 out of 5 GC cell lines lacking functional E-cadherin. CDH1 regulatory regions showed different methylation patterns in patients and controls, GC cell lines and GC tissues, expressing different E-cadherin levels. Our results showed that alterations in terms of genetic variants and DNA methylation patterns of both promoter and enhancers are associated with CDH1 expression levels and have a role in its regulation.