Mutations In APC Gene Research Articles

A Role for the WNT Co-Receptor LRP6 in Pathogenesis and Therapy of Epithelial Cancers.

The WNT/β-catenin signaling pathway controls stem and progenitor cell proliferation, survival and differentiation in epithelial tissues. Aberrant stimulation of this pathway is therefore frequently observed in cancers from epithelial origin. For instance, colorectal and hepatic cancers display activating mutations in the CTNNB1 gene encoding β-catenin, or inactivating APC and AXIN gene mutations. However, these mutations are uncommon in breast and pancreatic cancers despite nuclear β-catenin localization, indicative of pathway activation. Notably, the low-density lipoprotein receptor-related protein 6 (LRP6), an indispensable co-receptor for WNT, is frequently overexpressed in colorectal, liver, breast and pancreatic adenocarcinomas in association with increased WNT/β -catenin signaling. Moreover, LRP6 is hyperphosphorylated in KRAS-mutated cells and in patient-derived colorectal tumours. Polymorphisms in the LRP6 gene are also associated with different susceptibility to developing specific types of lung, bladder and colorectal cancers. Additionally, recent observations suggest that LRP6 dysfunction may be involved in carcinogenesis. Indeed, reducing LRP6 expression and/or activity inhibits cancer cell proliferation and delays tumour growth in vivo. This review summarizes current knowledge regarding the biological function and regulation of LRP6 in the development of epithelial cancers—especially colorectal, liver, breast and pancreatic cancers.

Next-generation sequencing with comprehensive bioinformatics analysis facilitates somatic mosaic APC gene mutation detection in patients with familial adenomatous polyposis

BackgroundFamilial adenomatous polyposis (FAP) is an autosomal dominant colorectal tumor characterized by numerous adenomatous colonic polyps that often lead to colon cancer. Although most patients with FAP harbored germline mutations in APC gene, it was recently recognized that patients with clinical FAP, but without detectable pathogenic mutations, could be associated with somatic mosaic APC mutation.MethodsWe reanalyzed the nest-generation sequencing (NGS) gene panel testing results of patients who were diagnosed with FAP, but did not have APC mutations, at Yonsei Cancer Prevention Center between July 2016 and March 2018. We tested several variant calling algorithms to identify low level mosaic variants. In one patient with a low frequency APC mutation, NGS analysis was performed together with endoscopic biopsy. Variant calling tools HaplotypeCaller, MuTect2, VarScan2, and Pindel were used. We also used 3′-Modified Oligonucleotides (MEMO)-PCR or conventional PCR for confirmation.ResultsAmong 28 patients with clinical suspicion of FAP but no detectable pathogenic variants of colonic polyposis associated genes, somatic mosaic pathogenic variants were identified in seven patients. The variant allele frequency ranged from 0.3 to 7.7%. These variants were mostly detected through variant caller MuTect2 and Pindel, and were further confirmed using mutant enrichment with MEMO-PCR.ConclusionsThe NGS with an adequate combination of bioinformatics tools is effective to detect low level somatic variants in a single assay. Because mosaic APC mutations are more frequent than previously thought, the presence of mosaic mutations must be considered when analyzing genetic tests of patients with FAP.

Abstract 4287: Peroxiredoxin 2 has a crucial role in the survival of gastric cancer cells by regulating β-catenin and TNF signaling

Abstract Gastric cancer (GC) is globally the fifth most common cancer and third leading cause of cancer death. Functional activation of β-catenin is necessary for early events in gastric carcinogenesis and GC with mutation of APC gene, similar to colorectal tumorigenesis, occur during the early stages of gastric adenoma development. Mammalian 2-Cys peroxiredoxin (Prx) enzymes are overexpressed in most cancer tissues, but the effect of Prx2 expression on GC survival remains unclear. Here, we demonstrate that Prx2 deletion markedly reduces the active β-catenin levels and the expression of β-catenin target genes in GC cells. Furthermore, the TNF α-induced activation of ERK1/2 was inhibited and reciprocally, JNK phosphorylation and cleaved caspase3 was increased in Prx2-knockdown GC cells. Prx2 deletion also can suppress the viability, invasion and colony formation of GC cells. The proof-of-concept experiment using conoidinA as a Prx2 inhibitor shows it can significantly ablates the growth of 5-FU-resistant SNU620. Thus, our findings reveal that Prx2 is a key regulator of β-catenin and TNF signaling pathway in GC, and also suggest a pharmacologic strategy to effectively overcome drug-resistant GC. Note: This abstract was not presented at the meeting. Citation Format: Hee Sung Kim, Tae Hyeong Lee, Dong Hoon Kang, Peter Chang-Whan Lee, Byung Sik Kim. Peroxiredoxin 2 has a crucial role in the survival of gastric cancer cells by regulating β-catenin and TNF signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4287.

Abstract 4166: Hereditary cancer syndromes in Guatemalan population

Abstract BACKGROUND The majority of cancer are sporadic, only around 5 % are considered hereditary. Although it is a low percentage, the study of these cancers are of vital importance, since they require a special clinical monitoring and management. These kind of cancers are caused by the presence of an inherited gene mutation, which increase the risk of developing a tumor. The mutations associated with these tumors are germline mutations, this means that are present in all the patient's cells, including the egg cell an sperm; this is the reason why this type of cancer can transmit to the future generations. There are many syndromes that increase the risk of hereditary cancer development, the most frequent syndromes are: Familial Breast and Ovarian cancer (BRCA1 and BRCA2 gene mutations), Lynch syndrome (MSH2, MLH1, MSH6 and PMS2 mutations), Li-Fraumeni syndrome (TP53 gene mutations) and Familial adenomatous polyposis (APC gene mutations). The aim of this study is to screen the most common hereditary cancer syndromes in Guatemalan population. METHODS We analyzed 199 blood samples of patients with different types of tumors. We extracted DNA from the samples and then analyzed the gene mutations by next generation sequencing. RESULTS AND DISCUSSION We have included in the present study, 93 cases with Familial Breast cancer and 106 with another type of tumors. Of all cases, we have found 17 cases with hereditary cancer syndromes (8%). The most frequent is the Breast and Ovarian hereditary syndrome caused by BRCA1 and BRCA2 (12 patients). The other hereditary cancer syndromes are shown in Table 1. The detection of this germline mutations, have a large impact in the familial cases, because these patients and their families could be monitored and evaluated more frequently. This is the first report of these syndromes in our population. CONCLUSION We reported 6 different syndromes and 17 cases, related to hereditary cancer risk and predisposition in Guatemalan population. Frequency of hereditary cancer syndromesSYNDROMENUMBER OF PATIENTSCANCER TYPEAGESEXGENE MUTATIONBreast and ovarian hereditary syndrome7Breast cancer29-48FBRCA1Breast and ovarian hereditary syndrome5Breast cancer29-71FBRCA2Lynch syndrome1Breast cancer80FMSH6Li-Fraumeni syndrome1Breast cancer58FTP53Breast hereditary cancer1Breast cancer57FCDH1Peutz-Jeghers syndrome1Pancreatic cancer15FSTK11Familial adenomatous polyposis1Colorectal cancer13MAPC Citation Format: Claudia L. Carranza, Mariela Guerra, Claudia Osorio, Vanessa Zamora, Vivian Herrera, Jose Gil, Luis Alvarez. Hereditary cancer syndromes in Guatemalan population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4166.

P-128 - Circulating-free DNA analysis from long-term surviving metastatic colorectal cancer patients undergoing surgery for resectable disease

Abstract Background Liquid biopsies (LB) allow monitoring of genetically different and co-occurring cancer cell clones. In metastatic colorectal cancer (mCRC), circulating-free DNA (cfDNA) can be relevant for monitoring treatment and identification of molecular alterations resulting in disease relapse often earlier than radiological examinations. Methods Patients with mCRC at diagnosis and treated with chemotherapy (CT) in combination with antibodies (bevacizumab, cetuximab or panitumumab) before undergoing surgery for resectable disease were included. LB were collected before therapy start, every four weeks during treatment, within ten days of radiological disease evaluation, at radiological relapse and until two months after progression. Next generation sequencing based on plasma samples was performed (testing for mutations and copy number variations covering 77 genes). Results From February 2016 to October 2018, 14 patients having surgery after first line treatment were included herein; median follow-up was 21.5 months. Five of them had RAS wild-type disease and received CT plus anti-EGFR treatment, while nine RAS mutated mCRC patients received bevacizumab. Disease relapse happened in seven cases, with subsequent death in three cases. In six out of seven cases, gene alterations were already detected in the pre-operative cfDNA. In the seven cases without disease relapse, gene variants were detected even after the surgery in two patients despite receiving radical resection. Median number of gene variants was two. Beside the well-established mutations in TP53 gene, both APC and ROS1 gene mutations were frequent, while further evaluations are required for the other variants detected. Conclusions Evaluation of cfDNA mutations in LB from mCRC may be a useful tool for monitoring clinical response and predict treatment outcome. Moreover, this molecular analysis can help to subgroup patients with regard to risk of relapse after radical surgery. Indeed, cfDNA mutations present before surgery seem to be an indication for a higher risk of post-surgery disease relapse. Legal entity responsible for the study The authors. Funding MEDeA Onlus. Disclosure All authors have declared no conflicts of interest.

Clinical characterization and mutation spectrum in patients with familial adenomatous polyposis in China.

Familial adenomatous polyposis (FAP) is the most common adenomatous polyposis syndrome. Patients with FAP are screened for germline mutations of two genes, APC and MUTYH. However, limited data exist on the clinical characterization and genotypic spectrum of FAP in China. This study was aimed to determine APC and MUTYH mutational status in a small cohort of FAP probands in China and to characterize the genotype-phenotype correlation in mutated patients. Mutation screening of 46 unrelated probands was performed using multigene panels by next-generation sequencing. Clinical data of the index were used to assess genotype-phenotype correlations. Overall, 42 out of 46 (91.30%) unrelated probands found mutations, including 35 (76.09%) with APC mutations, 3 (6.52%) with MUTYH mutations, and 4 (8.70%) with both APC and MUTYH mutations. Ten APC genetic alterations variants were novel. The hereditary pattern of the family with both APC and MUTYH mutations was autosomal dominant inheritance. Upper gastrointestinal polyp was the most common extracolonic manifestations. The onset time for patients with both APC and MUTYH mutations was earlier than MUTYH mutation carriers and similar to APC mutation carriers. But the age of carcinogenesis for patients with both APC and MUTYH mutations was later than APC mutation carriers and similar to MUTYH mutation carriers. In this study, we show the importance of using multigene panels that allow for a parallel comprehensive screening. We suggest that genetic testing of patients with suspected adenomatous polyposis syndromes should include APC and MUTYH gene mutation analyses simultaneously.

CtDNA as a potential prognostic marker for locally advanced rectal cancer patients with ‘watch and wait’ approach.

3544 Background: ‘Watch and Wait’ policy has currently led to growing interest for organ-preservation after neoadjuvant chemoradiation (nCRT) to improve quality of life. However, how to predict and select patients who may achieve clinical complete response is still an unsolved issue. We conducted a pilot study to evaluate the potential role of ctDNA as a biomarker to predict treatment outcome and improve risk stratification in locally advanced rectal cancer (LARC). Methods: In this study, we recruited 119 patients with LARC receiving nCRT. 595 serial plasma samples were collected at d0, d15, d25 of radiotherapy as well before and 7 days post surgery. The level of ctDNA was calculated by dynamic monitoring the mutant allele frequency of somatic mutations in plasma. Plasma and tissue samples were subjected to targeted-NGS using a 422 cancer-related genes panel. We followed up patients with concomitant CT until disease progression or death. Results: Detected mutation of TP53 and APC gene in pre-treatment samples was negatively correlated with patients’ response to nCRT. Alterations in homologous recombination and adherens junction pathways were associated with a better response (P < 0.05). Detection of pre-treatment mutations in any time points during nCRT was significantly (P = 0.03) decreased from TRG3 to TRG0 group (33%, 29%, 22% and 4%, respectively); while detection of acquired mutations showed an opposite trend (P = 0.04). A predictive model based on support vector machine was developed for prediction of pCR achieving a mean AUC of 0.85 assessed by repeated cross validation. Further, detection of pre-treatment mutations after completion of nCRT was significantly associated with worse disease-free survival (DFS) (P < 0.05). Through tracking clonal extinction, persistence and emergence, patients were grouped into four evolutionary subtypes with distinct TRG and DFS. Conclusions: Our data showed the prognostic value of ctDNA on DFS. Dynamic monitoring of ctDNA can be used to predict TRG and prognosis in LARC patients receiving nCRT. ctDNA sequencing depicts the evolutionary trajectories of sensitive and resistant clones during nCRT in LARC. CtDNA could potentially be used to guide patient selection for W&W strategy.

Circulating-free DNA analysis from long-term surviving metastatic colorectal cancer patients undergoing surgery for resectable disease.

e14545 Background: Liquid biopsies (LB) allow monitoring of genetically different and co-occurring cancer cell clones present in primary tumor and all metastatic sites in parallel. In metastatic colorectal cancer (mCRC), circulating-free DNA (cfDNA) can be relevant for monitoring treatment and identification of molecular alterations resulting in disease relapse often earlier than radiological examinations. Methods: Patients with mCRC at diagnosis and treated with chemotherapy (CT) in combination with antibodies (bevacizumab, cetuximab or panitumumab) before undergoing surgery for resectable disease were included in this study. LB were collected before therapy start, every four weeks during treatment, within ten days of radiological disease evaluation, at radiological relapse and until two months after relapse. Next generation sequencing based on plasma samples was performed (testing for mutations and copy number variations covering 77 genes). Results: From February 2016 to October 2018, 14 patients having surgery after first line treatment were included herein; median follow-up was 21.5 months. Five of them had RAS wild-type disease and received CT plus anti-EGFR treatment, while nine RAS mutated mCRC patients received bevacizumab. Surgery was radical in 10 cases, with no further treatment. In four cases, surgery was not radical and required further treatment. Disease relapse happened in seven cases, with subsequent death in three cases. In six out of seven cases, gene alterations were already detected in the pre-operative cfDNA. In the seven cases without disease relapse, gene variants were detected even after the surgery in two patients despite receiving radical resection. Median number of gene variants was two. Beside the well-established mutations in TP53 gene, both APC and ROS1 gene mutations were frequent, while further evaluations are required for the other variants detected. Conclusions: Evaluation of cfDNA mutations in LB from mCRC may be a useful tool for monitoring clinical response and predict treatment outcome. Moreover, this molecular analysis can help to subgroup patients with regard to risk of relapse after radical surgery. Indeed, cfDNA mutations present before surgery seem to be an indication for a higher risk of post-surgery disease relapse.

The application of ApcMin/+ mouse model in colorectal tumor researches.

ApcMin/+ mouse is an excellent animal model bearing multiple intestinal neoplasia, used to simulate human familial adenomatous polyposis and colorectal tumors. The key point of this model is the mutation of Apc gene, which is a significant tumor-suppressor gene in the Wnt signaling pathway. There are also some other possible mechanisms responsible for the development of colorectal tumors in the ApcMin/+ mouse model, such as tumor-associated signaling pathways activation, the changes of tumor-related genes, and the involvement of some related proteins or molecules. The relevant literatures about ApcMin/+ mouse model from PUBMED databases are reviewed in this study. In recent years, increasing studies have focused on the application of ApcMin/+ mouse model in colorectal tumor, trying to find effective therapeutic targets for further use. This article will give a brief review on the related molecular mechanisms of the ApcMin/+ mouse model and its application in colorectal tumor researches.

Alteration of the tumor suppressor SARDH in sporadic colorectal cancer: A functional and transcriptome profiling-based study.

Sporadic colorectal cancer (sCRC) is one of the leading causes of cancer death worldwide. As a highly heterogeneous complex disease, the currently reported classical genetic markers for sCRC, including APC, KRAS, BRAF, and TP53 gene mutations and epigenetic alterations, can explain only some sCRC patients. Here, we first reported a deleterious c.551C>T mutation in SARDH in sCRC. SARDH was identified as a novel tumor suppressor gene and was abnormally decreased in sCRC at both the transcriptional and the translational level. SARDH mRNA levels were also down-regulated in oesophageal cancer, lung cancer, liver cancer, and pancreatic cancer in the TCGA database. SARDH overexpression inhibited the proliferation, migration, and invasion of CRC cell lines, whereas its depletion improved these processes. SARDH overexpression was down-regulated in multiple pathways, especially in the chemokine pathway. The SARDH transcript level was positively correlated with the methylation states of CXCL1 and CCL20. Therefore, we concluded that SARDH depletion is involved in the development of sCRC.

DNA damage response pathway mutations contribute to a high proportion of hereditary colorectal cancer in patients from the Republic of Macedonia.

512 Background: Hereditary factors are assumed to play а role in 35-45% of all colorectal cancers with 5%-10% associated with high penetrant disease-causing mutations in genes correlating to hereditary polyposis (HP) or hereditary nonpolyposis syndromes (HNPCC). Although inherited germline mismatch repair and APC gene mutations contribute significantly to CRC, still a genetic diagnosis cannot be obtained in > 50% of familial cases. Methods: We performed a targeted NGS sequencing of 103 probands with clinically diagnosed HP (39) or HNPCC (64) using a multigene panel on two different platforms (Illumina Cancer Panel and Ion Torrent custom panel) covering coding and exon/intron sequences of 100 genes implicated in hereditary cancers. Results: Overall, the molecular defect was identified in 60 (58%) index patients. As expected, a large percentage (82%) of these patients exhibited the presence of clearly pathogenic mutations in well-known genes associated with hCRC (APC, MUTYH, BMPR1A, NTHL1 in HP, MLH1, MSH2, PMS6, MSH6 in HNPCC). Surprisingly, all except one (FLCN c.1285dupC, detected in a family with classical FAP), of the remaining mutations were located in genes involved in the DNA damage response pathway, of which 3 in CHEK2 (c.1031delT; c.1229delC; c.599T>G), 2 in BRIP1 (c.2392C>T) and 1 in each of BLM (c.1642C>T), BRCA2 (c.4446_4451dupAACAGA), FANCM (c.2953delG), FH (c.1431_1433dupAAA) and ERCC2 (c.1403C>T). Clinically, six of these cases exhibited the HNPCC type X phenotype (mutations in BRCA2, BRIP1, FANCM and CHEK2) while the other four were classified as oligopolyposis (mutations in BLM, FH and CHEK2). Conclusions: Our data indicate a significant association of DNA damage response pathway deficiencies and carcinogenesis in patients with hCRC syndromes exhibiting either the HNPCC type X or oligopolyposis phenotype. No genetic defect was detected within the analyzed gene panel in 44 (42%) families, indicating the need of extended exome/whole genome analyses in a substantial portion of patients with this disease.

Genomic landscape of synchronous tubulovillous adenoma and multiple non-familial colon cancers from a single patient

Colorectal cancer (CRC) is one of the leading causes of cancer-related death. We analyzed genomic of non-familial tubulovillous adenoma (TVA) and two synchronous malignant colorectal adenocarcinomas from a single patient. The number of somatic mutations was higher in the tumor sample (especially, AV 50 cm adenocarcinoma sample) than TVA sample, and also the allele frequency of mutation was higher on colon adenocarcinoma samples than TVA. Although they were very low frequency of sharing same genomic alterations between the three lesions, APC gene mutation was present in all three lesions, which confirm that APC gene mutation was an early event in this patient. The genetic alterations of APC, KRAS and TP53, which play an important role in the development of carcinoma from TVA, were shown through whole exome sequencing data of each sample. Of note, of the two synchronous adenocarcinoma samples, one lesion was KRAS mutant while the other one was KRAS wild-type. Our findings implicate that KRAS mutation may need to be taken from every primary cancer in a patient with multiple primary sites since KRAS status may differ amongst synchronous cancer lesions.

Aldose Reductase Inhibitor, Fidarestat Prevents High-fat Diet-induced Intestinal Polyps in ApcMin/+ Mice

Recent epidemiological and experimental studies have shown that obesity is a major risk factor for Colorectal Cancer (CRC). Regular intake of high fat-containing diet can promote obesity and metabolic syndrome by increasing the insulin resistance and inflammatory response which contribute to carcinogenesis. Previously, we have shown that inhibition of polyol pathway enzyme aldose reductase (AR) prevents carcinogens- and inflammatory growth factorsinduced CRC. However, the effect of AR inhibition on a high-fat diet (HFD)-induced formation of intestinal polyps in Apc-deficient Min (multiple intestinal neoplasia; ApcMin/+) mice is not known. We examined the effect of AR inhibitor, fidarestat on the HFD-induced formation of preneoplastic intestinal polyps in ApcMin/+ mice which is an excellent model of colon cancer. APCMin/+ mice fed for 12 weeks of HFD caused a significant increase in the formation of polyps in the small and large intestines and fidarestat given along with the HFD prevented the number of intestinal polyps. Fidarestat also decreased the size of the polyps in the intestines of HFDtreated APC Min mice. Further, the expression levels of beta-catenin, PCNA, PKC-β2, P-AKT, Pp65, COX-2, and iNOS in the small and large intestines of HFD-treated mice significantly increased, and AR inhibitor prevented it. Our results thus suggest that fidarestat could be used as a potential chemopreventive drug for intestinal cancers due to APC gene mutations.

Peutz-Jeghers Phenotype Caused by an Unknown Variant APC Gene

Peutz-Jeghers syndrome is an autosomal dominant condition, characterized by hamartomatous polyps, mucocutanous pigmentation, and increased predisposition to both Gastrointestinal (GI) and Non-Gastrointestinal malignancies. Most cases are due to a mutation of the STK11 tumor suppressor gene. Diagnosis is based on clinical findings, while genetic studies are used to confirm the diagnosis. We present a rare case of Peutz-Jeghers phenotype with an APC gene mutation variant of unknown significance. A 56-year old male with significant past medical history of prior sigmoidectomy for a benign colon mass and hemorrhoidectomy, was evaluated for intermittent rectal bleeding. He described vague abdominal pain, and intermittent dark stools with concurrent bright red blood per rectum. Laboratory findings were consistent with iron deficiency anemia. Esophagogastroduodenoscopy revealed gastritis and a duodenal polyp, which on histology showed hamartomatous polyp with features of a Peutz-Jeghers polyp. Colonoscopy findings showed internal hemorrhoids. Retrospectively, on detailed physical examination, the patient was found to have brown pigmented macular lesions on his buccal mucosa. Molecular studies were performed for common hereditary cancer syndromes and revealed no STK11 mutation but showed an APC gene variant of unknown significance. Specifically, a c.2297C>T (P.Ala766Val) mutation. With the presence of classic Peutz-Jeghers polyp histology and mucocutaneous pigmentation, the patient was treated as a Peutz-Jeghers phenotype. He was discharged home on iron supplementation and is currently on an intensive surveillance regimen for cancers involving the thyroid, pancreas, colon, and testes. Hamartomatous polyps in Peutz-Jeghers syndrome can occur anywhere in the GI tract, yet they tend to have a strong predilection for the small intestine. Patients with Peutz-Jeghers are at an increased risk for cancers manifesting both within the intestinal tract and externally. Routine surveillance with endoscopy and polypectomy is indicated to screen for malignancy, and to help prevent polyp related complications including; bowel obstructions, intussusception, and bleeding. Genetically, STK11 mutation is present in between 50 to 80 percent of Peutz-Jeghers cases. We present a case of Peutz-Jeghers phenotype in the presence of an APC gene variant of unknown significance.

Dietary HNE and other lipid oxidation products in the development of colorectal carcinogenesis

Based on epidemiological studies and meta-analyses, the World Cancer Research Fund (WCRF) panel stated that red meat is a convincing cause of colorectal cancer. Recently, the IARC/WHO classified red meat consumption as “probably carcinogenic to humans” (Group 2A). Red meat contains high concentrations of heme iron that induces lipid peroxidation in the colon lumen and the subsequent formation of secondary lipid oxidation products such as 4-hydroxynonenal (HNE). HNE was found in foodstuffs in relatively high concentration, particularly in meat and processed meat. Moreover, HNE formation possibly occurs in the digestive tract when rats receive heme iron and a PUFA-rich oil at the same time. In vivo studies in rats show that the development of preneoplastic lesions is well correlated with heme-iron and HNE content of the diet, and also with the urinary excretion of the major metabolite of HNE, the mercapturic acid of 1,4-dihydroxynonene (DHN-MA). Secondary oxidation products of PUFA, and especially HNE, could be one of the missing links between heme iron, enhanced luminal lipid peroxidation and colon cancer development. In vitro studies in mouse epithelial colon immortalized cells show that the cells mutated on the Apc (Adenomatous polyposis coli) gene, an early and frequent mutation during the development of human colorectal cancer, were more resistant to HNE than non-mutated cells. This resistance is due to a better metabolization capacity of those cells towards HNE. The enzymes involved are under the transcriptional control of Nrf2/antioxidant responsive element (ARE) pathway, a pathway that is upregulated in Apc mutated cells. Nrf2 natural inducers, as curcumin, have a protective effect both in vitro and in vivo.

ANIMAL MODELS FOR COLORECTAL CANCER.

ABSTRACT Introduction: Colorectal cancer is a very frequent sort of neoplasm among the population, with a high mortality rate. It develops from an association of genetic and environmental factors, and it is related to multiple cell signaling pathways. Cell cultures and animal models are used in research to reproduce the process of disease development in humans. Of the existing animal models, the most commonly used are animals with tumors induced by chemical agents and genetically modified animals. Objective: To present and synthesize the main animal models of colorectal carcinogenesis used in the research, comparing its advantages and disadvantages. Method: This literature review was performed through the search for scientific articles over the last 18 years in PubMed and Science Direct databases, by using keywords such as “animal models”, “colorectal carcinogenesis” and “tumor induction”. Results: 1,2-dimethylhydrazine and azoxymethane are carcinogenic agents with high specificity for the small and large intestine regions. Therefore, the two substances are widely used. Concerning the genetically modified animal models, there is a larger number of studies concerning mutations of the APC, p53 and K-ras genes. Animals with the APC gene mutation develop colorectal neoplasms, whereas animals with p53 and K-ras genes mutations are able to potentiate the effects of the APC gene mutation as well as the chemical inducers. Conclusion: Each animal model has advantages and disadvantages, and some are individually efficient as to the induction of carcinogenesis, and in other cases the association of two forms of induction is the best way to obtain representative results of carcinogenesis in humans.

APC and MUTYH Analysis in FAP Patients: A Novel Mutation in APC Gene and Genotype-Phenotype Correlation.

APC and MUTYH genes are mutated in 70–90% and 10–30% of familial adenomatous polyposis cases (FAP) respectively. An association between mutation localization and FAP clinical phenotype is reported. The aims of this study were to determine APC and MUTYH mutational status in a small cohort of FAP patients and to evaluate the genotype-phenotype correlation in mutated patients. Here, we report the identification of a novel APC germline mutation, c.510_511insA. Overall, mutational analysis showed pathogenic mutations in 6/10 patients: 5/10 in APC and 1/10 in MUTYH. Additionally, we found three variants of unknown significance in MUTYH gene that showed no evidence of possible splicing defects by in silico analysis. Molecular analysis was also extended to family members of mutated patients. A genotype-phenotype correlation was observed for colonic signs whereas a variation of disease onset age was revealed for the same mutation. Moreover, we found an intrafamilial variability of FAP onset age. Regarding extracolonic manifestations, the development of desmoid tumors was related to surgery and not to mutation position, while a genotype-phenotype correspondence was observed for the onset of thyroid or gastric cancer. These findings can be useful in association to clinical data for early surveillance and suitable treatment of FAP patients.

Clinicopathologic and molecular features of cribriform morular variant of papillary thyroid carcinoma

Objective: To investigate the clinicopathologic and molecular features of the rare cribriform morular variant of papillary thyroid carcinoma (CMV-PTC). Methods: The clinicopathologic data of 10 patients with CMV-PTC were retrospectively reviewed. Immunohistochemical (IHC) staining was done using LSAB method. DNA sequencing for APC were applied using Sanger method. BRAF V600E mutation was examined using ARMS method. The cytological, morphological, IHC and molecular features were analyzed. Results: All patients were female at an average age of 27 years old. The tumors were mostly located in the right lobe of thyroid. Fine needle aspiration cytology was performed in three patients; two were diagnosed as suspicious for PTC and one as PTC. Nine tumors presented as solitary nodule and two as multiple nodules in both lobes. Infiltration was demonstrated in three cases. The average size was 2.6 cm. The neoplastic cells were arranged in papillary, cribriform, solid and glandular patterns, with rare or without colloid inside the lumen. The number of morula varied, ranging from zero to many. The neoplastic cells were variably enlarged, showing round, oval or spindle shape. Nuclear irregularity was identified as irregular membrane, nuclear grooves or pseudoinclusion, but no typical ground glass feature. Peculiar nuclear clearing could be observed in the morular cells. IHC staining showed the neoplastic cells were negative for thyroglobulin and p63, but positive for TTF1, cytokeratin 19 and estrogen receptor. Diffuse staining with cytokeratin was seen in the neoplastic cells and the morula. Specific cytoplasmic and nuclear staining of β-catenin was seen in the neoplastic cells but not the morula. Ki-67 proliferation index was 1%-30%. No recurrence or metastasis was observed. One patient was demonstrated to harbor both somatic and germline mutations of the APC gene, who was found to have adenomatous polyposis and her mother died of colonic carcinoma. No BRAF V600E mutation was detected. Conclusions: CMV-PTC is rare and shows atypical cytological and clinicopathological features, and it is easily misdiagnosed.TG, TTF1, ER and β-catenin are specific IHC markers for CMV-PTC. The morula is negative for cytokeratin 19, in contrast to squamous metaplasia. Although CMV-PTC has indolent clinical behavior, a definite diagnosis is necessary to rule out the possibility of APC gene mutation and related extra-thyroidal neoplasm, such as FAP and Gardner syndrome.

Cribriform-Morular Variant of Papillary Thyroid Carcinoma: Clinical and Pathological Features of 30 Cases.

Cribriform-morular variant of papillary thyroid carcinoma (CMV-PTC) is rare; it may occur in cases of familial adenomatous polyposis (FAP) or be sporadic. To clarify the clinicopathological features of CMV-PTC, the medical records of these patients were investigated retrospectively. Between 1979 and 2016, a total of 17,062 cases with PTC underwent initial surgery at Ito Hospital. Of these, 30 (0.2%) cases histologically diagnosed with CMV-PTC were reviewed. The patients were all women, with a mean age at the time of surgery of 24years. Seven (23%) cases were thought to have FAP because they had colonic polyposis or a family history of FAP or APC gene mutation. The remaining 23 (77%) were thought to be sporadic. Multiple tumors were detected in 6 cases, with a solitary tumor in 24. One patient had lung metastasis at diagnosis. Eleven patients underwent total thyroidectomy or subtotal thyroidectomy, and 19 underwent lobectomy. Twenty-six (87%) patients underwent neck lymph node dissection. Three patients had tumor metastasis in central lymph nodes, but these were incidentally detected metastatic classical PTC (cPTC) based on histological examination. In this series, there were no cases of LN metastases of CMV-PTC. During a mean follow-up of 15years, one patient had new cPTC in the remnant thyroid after initial surgery, and the other patients showed no signs of recurrence. CMV-PTC occurred in young women, their long-term prognosis was excellent. Total thyroidectomy is recommended for FAP-associated CMV-PTC, but modified neck lymph node dissection is not necessary.

The role of APC in WNT pathway activation in serrated neoplasia

Conventional adenomas are initiated by APC gene mutation that activates the WNT signal. Serrated neoplasia is commonly initiated by BRAF or KRAS mutation. WNT pathway activation may also occur, however, to what extent this is owing to APC mutation is unknown. We examined aberrant nuclear β-catenin immunolocalization as a surrogate for WNT pathway activation and analyzed the entire APC gene coding sequence in serrated and conventional pathway polyps and cancers. WNT pathway activation was a common event in conventional pathway lesions with aberrant nuclear immunolocalization of β-catenin and truncating APC mutations in 90% and 89% of conventional adenomas and 82% and 70% of BRAF wild-type cancers, respectively. WNT pathway activation was seen to a lesser extent in serrated pathway lesions. It occurred at the transition to dysplasia in serrated polyps with a significant increase in nuclear β-catenin labeling from sessile serrated adenomas (10%) to sessile serrated adenomas with dysplasia (55%) and traditional serrated adenomas (9%) to traditional serrated adenomas with dysplasia (39%) (P=0.0001). However, unlike the conventional pathway, truncating APC mutations were rare in the serrated pathway lesions especially sessile serrated adenomas even when dysplastic (15%) and in the BRAF mutant cancers with microsatellite instability that arise from them (8%). In contrast, APC missense mutations that were rare in conventional pathway adenomas and cancers (3% in BRAF wild-type cancers) were more frequent in BRAF mutant cancers with microsatellite instability (32%). We conclude that increased WNT signaling is important in the transition to malignancy in the serrated pathway but that APC mutation is less common and the spectrum of mutations is different than in conventional colorectal carcinogenesis. Moderate impact APC mutations and non-APC-related causes of increased WNT signaling may have a more important role in serrated neoplasia than the truncating APC mutations common in conventional adenomas.