PD-L1 expression in gastric and gastroesophageal junction cancer patients treated with perioperative chemotherapy.

BACKGROUND AND OBJECTIVES: The incidence, predictive, and prognostic impact of programmed cell death (PD-L1) expression in gastric (GC) and gastroesophageal junction tumors (GEJC) treated with perioperative chemotherapy is poorly understood. We aimed to assess PD-L1 expression by immunohistochemistry (IHC) in both pre and posttreatment specimens evaluating its impact on pathological response and survival outcomes. METHODS: Retrospective cohort of patients with GC and GEJ tumors treated in a single western cancer center between 2007 and 2017. PD-L1 expression was assessed by IHC before and after neoadjuvant chemotherapy, in surgical samples, and reported as combined positive score (CPS). CPS > 1% was tested for its association with pathological response and overall survival (OS). RESULTS: We were able to assess PD-L1 expression in at least one tissue sample from 155 subjects. PD-L1 positivity rate was 20%. In 74 paired samples, a 21% discordance between PD-L1 expression in biopsy sample and surgical specimen was observed. With a median follow-up period of 60.3 months, 5-years disease-free survival was 60.5% with a median OS not reached. PD-L1 expression was neither associated with pathological response or survival outcomes. CONCLUSIONS: PD-L1 expression in the setting of locally advanced GC tumors was relatively low and can vary considering the tissue sample analyzed. This expression had no association with survival or pathological response in this population.

Brazilian Group of Gastrointestinal Tumours' consensus guidelines for the management of oesophageal cancer.

Oesophageal cancer is among the ten most common types of cancer worldwide. More than 80% of the cases and deaths related to the disease occur in developing countries. Local socio-economic, epidemiologic and healthcare particularities led us to create a Brazilian guideline for the management of oesophageal and oesophagogastric junction (OGJ) carcinomas. The Brazilian Group of Gastrointestinal Tumours invited 50 physicians with different backgrounds, including radiology, pathology, endoscopy, nuclear medicine, genetics, oncological surgery, radiotherapy and clinical oncology, to collaborate. This document was prepared based on an extensive review of topics related to heredity, diagnosis, staging, pathology, endoscopy, surgery, radiation, systemic therapy (including checkpoint inhibitors) and follow-up, which was followed by presentation, discussion and voting by the panel members. It provides updated evidence-based recommendations to guide clinical management of oesophageal and OGJ carcinomas in several scenarios and clinical settings.

Brazilian Group of Gastrointestinal Tumours' consensus guidelines for the management of gastric cancer.

Gastric cancer is among the ten most common types of cancer worldwide. Most cases and deaths related to the disease occur in developing countries. Local socio-economic, epidemiologic and healthcare particularities led us to create a Brazilian guideline for the management of gastric carcinomas. The Brazilian Group of Gastrointestinal Tumors (GTG) invited 50 physicians with different backgrounds, including radiology, pathology, endoscopy, nuclear medicine, genetics, oncological surgery, radiotherapy and clinical oncology, to collaborate. This document was prepared based on an extensive review of topics related to heredity, diagnosis, staging, pathology, endoscopy, surgery, radiation, systemic therapy and follow-up, which was followed by presentation, discussion, and voting by the panel members. It provides updated evidence-based recommendations to guide clinical management of gastric carcinomas in several scenarios and clinical settings.

Comprehensive Analysis of DNA Methylation and Prediction of Response to NeoadjuvantTherapy in Locally Advanced Rectal Cancer.

The treatment for locally advanced rectal carcinomas (LARC) is based on neoadjuvant chemoradiotherapy (nCRT) and surgery, which results in pathological complete response (pCR) in up to 30% of patients. Since epigenetic changes may influence response to therapy, we aimed to identify DNA methylation markers predictive of pCR in LARC patients treated with nCRT. We used high-throughput DNA methylation analysis of 32 treatment-naïve LARC biopsies and five normal rectal tissues to explore the predictive value of differentially methylated (DM) CpGs. External validation was carried out with The Cancer Genome Atlas-Rectal Adenocarcinoma (TCGA-READ 99 cases). A classifier based on three-CpGs DM (linked to OBSL1, GPR1, and INSIG1 genes) was able to discriminate pCR from incomplete responders with high sensitivity and specificity. The methylation levels of the selected CpGs confirmed the predictive value of our classifier in 77 LARCs evaluated by bisulfite pyrosequencing. Evaluation of external datasets (TCGA-READ, GSE81006, GSE75546, and GSE39958) reproduced our results. As the three CpGs were mapped near to regulatory elements, we performed an integrative analysis in regions associated with predicted cis-regulatory elements. A positive and inverse correlation between DNA methylation and gene expression was found in two CpGs. We propose a novel predictive tool based on three CpGs potentially useful for pretreatment screening of LARC patients and guide the selection of treatment modality.

Case report of IgG4-related appendiceal disease: A challenging disease.

RATIONALE: Immunoglobulin G4 (IgG4)-related disease is an increasingly recognized immune-mediated entity that can affect virtually every organ system. Depending on the location of the disease, it can present a wide range of clinical manifestations and even mimic malignancies. Appendiceal involvement in patients with IgG4-related disease is particularly rare and very few cases are reported in the literature. PATIENT CONCERNS: We report a case of IgG4-related appendiceal disease in a 42-year-old woman who presents with a subacute onset of right lower quadrant abdominal pain. DIAGNOSIS: Abdominal computed tomography showed a markedly enlarged appendix, raising the concern of malignancy. The diagnosis of IgG4 appendiceal disease was confirmed by postoperative histopathologic and immunohistochemical examination. INTERVENTIONS: The patient underwent right hemicolectomy. OUTCOMES: After the surgery, the patient had an uneventful recovery and reported a resolution of her symptoms. The serum IgG4 was revaluated 5 days after surgery and returned to its normal values. At the 3-year follow up, the patient had no recurrence of symptoms and her imaging exams remain unremarkable. LESSONS: This study reports the fifth case of IgG4-related appendiceal disease. Increasing awareness of this condition may influence the management of these patients, once patients with IgG4-related disease should be monitored after treatment, due to the risk of recurrence or involvement of other organs.

Paradoxical interaction between cancer and long-term postsepsis disorder: impairment of de novo carcinogenesis versus favoring the growth of established tumors.

BACKGROUND: Previous data have reported that the growth of established tumors may be facilitated by postsepsis disorder through changes in the microenvironment and immune dysfunction. However, the influence of postsepsis disorder in initial carcinogenesis remains elusive. METHODS: In the present work, the effect of postsepsis on inflammation-induced early carcinogenesis was evaluated in an experimental model of colitis-associated colorectal cancer (CAC). We also analyzed the frequency and role of intestinal T regulatory cells (Treg) in CAC carcinogenesis. RESULTS: The colitis grade and the tumor development rate were evaluated postmortem or in vivo through serial colonoscopies. Sepsis-surviving mice (SSM) presented with a lower colonic DNA damage, polyp incidence, reduced tumor load, and milder colitis than their sham-operated counterparts. Ablating Treg led to restoration of the ability to develop colitis and tumor polyps in the SSM, in a similar fashion to that in the sham-operated mice. On the other hand, the growth of subcutaneously inoculated MC38luc colorectal cancer cells or previously established chemical CAC tumors was increased in SSM. CONCLUSION: Our results provide evidence that postsepsis disorder has a dual effect in cancer development, inhibiting inflammation-induced early carcinogenesis in a Treg-dependent manner, while increasing the growth of previously established tumors.

Primary Tumor Location Is a Predictor of Poor Prognosis in Patients with Locally Advanced Esophagogastric Cancer Treated with Perioperative Chemotherapy.

BACKGROUND: Esophagogastric cancer (EGC) is a leading neoplasm worldwide. Perioperative chemotherapy (periCT) is currently a standard of care for most patients (pts). Prevalence of esophagogastric junction (EGJ) tumors is increasing over the last years. METHODS: The aim of this study was to retrospectively search for prognostic factors in pts. with locally advanced EGC treated with periCT. Three-year overall survival (OS) and Event-Free Survival (EFS) were main end-points. HER-2 positive tumors were defined by immunohistochemistry or FISH. RESULTS: Between June/2007 and November/2015, 128 pts. started periCT for esophagogastric junction (EGJ) or gastric adenocarcinoma (GC). Median age was 59.5 y and 64% were male. Primary site was EGJ in 27% and 65% were cN+. Diffuse subtype was seen in 42%. Ninety-seven pts. were assessed for HER-2; 14 (14.4%) were positive. After median follow-up time of 45 m, 48 deaths occurred. The 3-year OS and EFS rate was 61.3% and 51.2%, respectively. Main prognostic factors were: AJCC ypT3-T4yN1-N3 (HR 6.75 p 0.002) and EGJ primary (HR 2.64, p 0.004). Overall HER-2 was not prognostic. Still, a difference in 3-year OS was observed for GC/HER2+ compared to EGJ/HER2+ (88.9% versus 20%, p = 0.002). This difference is greater for 3-year EFS with no patient with EGJ/HER2+ free-of-event against 62.5% for GC/HER+ (p = 0.011). CONCLUSION: In our analysis, pathological staging and primary site were main prognostic factors. Moreover, a small group of EGJ/HER2+ had very poor survival.

Predicting overall and major postoperative morbidity in gastric cancer patients.

BACKGROUND: Postoperative complications after gastric cancer resection vary in different series and they might have a significant impact in long-term outcomes. Our aim was to build a prediction rule on gastric cancer patients' overall and major morbidity risks. METHODS: This retrospective study included 1223 patients from a single center who were resected between 1992 and 2016. Overall and major morbidity predictors were identified through multiple logistic regression. Models' performances were assessed through discrimination, calibration, and cross-validation, and nomograms were constructed. RESULTS: The mean age was 61.3-year old and the male gender was more frequent (60%). The most common comorbidities were hypertension (HTN), diabetes, and chronic obstructive pulmonary disease (COPD). A D2-distal gastrectomy was the most frequent procedure and 87% of all lesions were located in the middle or distal third. Age, COPD, coronary heart disease, chronic liver disease, pancreatic resection, and operative time were independent predictors of overall and major morbidity. The extent of resection and splenectomy was associated with overall events and HTN with major ones. Both models were very effective in predicting events among patients at higher risk. CONCLUSIONS: The overall and major morbidity models and nomograms included clinical- and surgical-related data that were very effective in predicting events, especially for high-risk patients.

MicroRNA expression profiling provides novel insights into immune-related pathways involved in gastric cancer.

Gastric cancer is one of the most common cancers, and an increasing number of studies have found that microRNAs (miRNAs) play essential roles in gastric cancer progression; however, the roles of specific miRNAs involved in the immune response to this disease remain unclear. We compared the miRNA expression in tissues from primary gastric cancer patients and healthy controls to find miRNAs dysregulated in gastric cancer and used bioinformatics tools to determine potential roles of these miRNAs in the immune system. We evaluated 25 primary gastric cancer tissues and five healthy gastric tissues. Quantitative real-time polymerase chain reaction was performed for a set of miRNAs, followed by the prediction of their target genes and functional enrichment analysis of these targets. Analysis of a microarray dataset showed that the miRNA miR-196a-5p was significantly upregulated, while miR-374a-5p and miR-375 were downregulated in gastric cancer patients. In addition, miR-374-5p was significantly downregulated in patients with metastasis compared with its expression levels in non-metastatic patients (p = 0.03). Bioinformatics analysis suggested that the pathways regulated by these differentially expressed miRNAs were related to the immune response, cell adhesion, and cell migration. Most importantly, this study provides a new insight into the potential use of multiple miRNAs to find distinct pathways of immune regulation in gastric cancer.

Disparities in Epidemiological Profile of Gastric Adenocarcinoma in Selected Cities of Brazil

Background: Despite decreasing global incidence trends, gastric cancer is still among the five most incident cancers in the world and the third cancer-related cause of death. In Brazil, differences in incidence and mortality exist depending on the geographic region studied. Objective: To describe the incidence, mortality, trends and age-period-cohort of gastric cancer in three cities of Brazil (Sao Paulo, Belem and Fortaleza), in the period 1990-2012. Mortality for gastric cancer in Brazil overall and by region was described. Methods: 33,462 incident cases of gastric cancer were identified from the population-based cancer registries and 23,424 deaths from mortality information system in residents of the three cities and in Brazil were included in the study. Data for incident cases were extracted from the Population Based Cancer Registries from the National Cancer Institute (INCA). Mortality data on gastric cancer were extracted from Information Technology Department of Brazilian Public Health Care System/Health Ministry (DATASUS/MS). Mortality and incidence age standardized rates were calculated. For trends analysis the Joinpoint Regression and age-period-cohort model were applied. Results: Belem presented the highest incidence rates for gastric adenocarcinoma. Decreasing incidence trends were identified in Sao Paulo (-7.8% in men; -6.3% in women) and in Fortaleza (-1.2% in men). Increasing incidence trends were observed for women in Belem (1.8%) and Fortaleza (1.1%). In Belem (Amazon area), there was an increased risk for gastric cancer in women born after the 1960s. Overall in Brazil mortality for gastric cancer is decreasing. Mortality trends showed significant reduction, for both sexes, in the three Brazilian cities. Conclusion: Incidence of gastric cancer is increasing in women born in the sixties in Belem (Amazon region) and Fortaleza (Northeast region). In Brazil there was increase in mortality in Northeast region and decrease in others regions. More update data on incidence for Amazon and Northeast region is needed.

Locally advanced rectal cancer transcriptomic-based secretome analysis reveals novel biomarkers useful to identify patients according to neoadjuvant chemoradiotherapy response.

Most patients with locally advanced rectal cancer (LARC) present incomplete pathological response (pIR) to neoadjuvant chemoradiotherapy (nCRT). Despite the efforts to predict treatment response using tumor-molecular features, as differentially expressed genes, no molecule has proved to be a strong biomarker. The tumor secretome analysis is a promising strategy for biomarkers identification, which can be assessed using transcriptomic data. We performed transcriptomic-based secretome analysis to select potentially secreted proteins using an in silico approach. The tumor expression profile of 28 LARC biopsies collected before nCRT was compared with normal rectal tissues (NT). The expression profile showed no significant differences between complete (pCR) and incomplete responders to nCRT. Genes with increased expression (pCR = 106 and pIR = 357) were used for secretome analysis based on public databases (Vesiclepedia, Human Cancer Secretome, and Plasma Proteome). Seventeen potentially secreted candidates (pCR = 1, pIR = 13 and 3 in both groups) were further investigated in two independent datasets (TCGA and GSE68204) confirming their over-expression in LARC and association with nCRT response (GSE68204). The expression of circulating amphiregulin and cMET proteins was confirmed in serum from 14 LARC patients. Future studies in liquid biopsies could confirm the utility of these proteins for personalized treatment in LARC patients.

Impact of ypT, ypN, and Adjuvant Therapy on Survival in Gastric Cancer Patients Treated with Perioperative Chemotherapy and Radical Surgery.

BACKGROUND: Perioperative chemotherapy and surgery is the standard of care in advanced gastroesophageal cancer patients, but its impact among those treated with radical surgery still needs further assessment. We present the results of this multimodality treatment approach in a gastric cancer patients cohort treated with D2 lymphadenectomy. We aimed to identify prognostic factors associated with improved survival. PATIENTS AND METHODS: This retrospective cohort study enrolled patients treated with perioperative chemotherapy and resection in a single cancer center in Brazil between 2006 and 2016. Subjects presenting tumors of the gastric stump, esophageal tumors, or treated with intraperitoneal chemotherapy were excluded. Intention-to-treat survival analysis was performed for all subjects who started neoadjuvant chemotherapy, and prognostic factors were determined among those who had R0 resection. RESULTS: This study included 239 patients, of whom 198 had R0 resection. The mean age was 59.9 years, and most had clinical stage IIB or III disease (88%). Among the 239 patients who started neoadjuvant chemotherapy, 207 (86.6%) completed all neoadjuvant treatment cycles, and surgical resection was performed in 225 subjects (94.1%). Overall 60-day morbidity and mortality rates were 35.6% and 4.4%, respectively. For the entire cohort, median survival was 78 months and the 5-year survival rate was 55.3%. Factors associated with worse survival were ypT3-4 stage, ypN + stage, extended resection, and no adjuvant chemotherapy. CONCLUSIONS: Perioperative chemotherapy resulted in very good outcomes for patients treated with radical surgery, and downstaging after chemotherapy was shown to be a major determinant of prognosis.

Increased Levels of Genomic Instability and Mutations in Homologous Recombination Genes in Locally Advanced Rectal Carcinomas.

Pre-operative 5-fluoracil-based chemoradiotherapy (nCRT) is the standard treatment for patients with locally advanced rectal cancer (LARC). Patients with pathological complete response (pCR-0% of tumor cells in the surgical specimen after nCRT) have better overall survival and lower risk of recurrence in comparison with incomplete responders (pIR). Predictive biomarkers to be used for new therapeutic strategies and capable of stratifying patients to avoid overtreatment are needed. We evaluated the genomic profiles of 33 pre-treatment LARC biopsies using SNP array and targeted-next generation sequencing (tNGS). Based on the large number of identified genomic alterations, we calculated the genomic instability index (GII) and three homologous recombination deficiency (HRD) scores, which have been reported as impaired DNA repair markers. We observed high GII in our LARC cases, which was confirmed in 165 rectal cancer cases from TCGA. Patients with pCR presented higher GII compared with pIR. Moreover, a negative correlation between GII and the fraction of tumor cells remaining after surgery was observed (ρ = -0.382, P = 0.02). High HRD scores were detected in 61% of LARC, of which 70% were incomplete responders. Using tNGS (105 cancer-related genes, 13 involved in HR and 5 in mismatch repair pathways), we identified 23% of cases with mutations in HR genes, mostly in pIR cases (86% of mutated cases). In agreement, the analysis of the TCGA dataset (N = 145) revealed 21% of tumors with mutations in HR genes. The HRD scores were shown to be predictive of better response to PARP-inhibitors and platinum-based chemotherapy in breast and ovarian cancer. Our results suggest that the same strategy could be applied in a set of LARC patients with HRD. In conclusion, we identified high genomic instability in LARC, which was related to alterations in the HR pathway, especially in pIR. These findings suggest that patients with impaired HRD would clinically benefit from PARP-inhibitors and platinum-based therapy.

Rab5C enhances resistance to ionizing radiation in rectal cancer.

Rectal cancer represents one third of the colorectal cancers that are diagnosed. Neoadjuvant chemoradiation is a well-established protocol for rectal cancer treatment reducing the risk of local recurrence. However, a pathologic complete response is only achieved in 10-40% of cases and the mechanisms associated with resistance are poorly understood. To identify potential targets for preventing therapy resistance, a proteomic analysis of biopsy specimens collected from stage II and III rectal adenocarcinoma patients before neoadjuvant treatment was performed and compared with residual tumor tissues removed by surgery after neoadjuvant therapy. Three proteins, Ku70, Ku80, and Rab5C, exhibited a significant increase in expression after chemoradiation. To better understand the role of these proteins in therapy resistance, a rectal adenocarcinoma cell line was irradiated to generate a radiotherapy-resistant lineage. These cells overexpressed the same three proteins identified in the tissue samples. Furthermore, radiotherapy resistance in this in vitro model was found to involve modulation of epidermal growth factor receptor (EGFR) internalization by Rab5C in response to irradiation, affecting expression of the DNA repair proteins, Ku70 and Ku80, and cell resistance. Taken together, these findings indicate that EGFR and Rab5C are potential targets for the sensitization of rectal cancer cells and they should be further investigated. KEY MESSAGES: • Rab5C orchestrates a mechanism of radioresistance in rectal adenocarcinoma cell. • Rab5C modulates EGFR internalization and its relocalization to the nucleus. • In the nucleus, EGFR can modulate the expression of the DNA repair proteins, Ku70 and Ku80. • Rab5C, Ku70, and Ku80 are overexpressed in tumor tissues that contain tumor cells that are resistant to chemoradiation treatment.

The Potential Clinical Implications of Circulating Tumor Cells and Circulating Tumor Microemboli in Gastric Cancer.

BACKGROUND: Gastric adenocarcinoma (GAC) is the third deadliest malignant neoplasm worldwide, mostly because of late disease diagnosis, low chemotherapy response rates, and an overall lack of tumor biology understanding. Therefore, tools for prognosis and prediction of treatment response are needed. Quantification of circulating tumor cells (CTCs) and circulating tumor microemboli (CTM) and their expression of biomarkers has potential clinical relevance. Our aim was to evaluate CTCs and CTM and their expression of HER2 and plakoglobin in patients with nonmetastatic GAC, correlating the findings to clinicopathological data. MATERIALS AND METHODS: CTC enrichment was performed with isolation by size of epithelial tumor cells, and the analysis was performed with immunocytochemistry and microscopy. Two collections were made: one at diagnosis (55 samples before neoadjuvant treatment) and one after surgery and before adjuvant therapy (33 samples). RESULTS: A high detection rate of CTCs (90%) was observed at baseline. We evaluated HER2 expression in 45/55 biopsy samples and in 42/55 CTC samples, with an overlap of 36 subjects. Besides the good agreement observed for HER2 expression in primary tumors and paired CTCs for 36 cases (69.4%; κ = 0.272), the analysis of HER2 in CTCs showed higher positivity (43%) compared with primary tumors (11%); 3/5 patients with disease progression had HER2-negative primary tumors but HER2-positive CTCs. A significant CTC count drop in follow-up was seen for CTC-HER2-positive cases (4.45 to 1.0 CTCs per mL) compared with CTC-HER2-negative cases (2.6 to 1.0 CTCs per mL). The same was observed for CTC-plakoglobin-positive cases (2.9 to 1.25 CTCs per mL). CONCLUSION: CTC analysis, including their levels, plakoglobin, and HER2 expression, appears to be a promising tool in the understanding the biology and prognosis of GAC. IMPLICATIONS FOR PRACTICE: The analysis of circulating tumor cell levels from the blood of patients with gastric adenocarcinoma, before and after neoadjuvant treatment, is useful to better understand the behavior of the disease as well as the patients more likely to respond to treatment.

Oral ulcerative lesions in a post-liver-transplantation patient.

Oral involvement is rarely found in histoplasmosis, except in its disseminated form, which is mostly observed in the severely immunocompromised host. Herein, we presented the case of a 36-year-old female with a previous history of liver transplant, who was hospitalized due to fever, chills, night sweats, diarrhea, and painful oral lesions over the last 3 days. The oral examination revealed the presence of painful shallow ulcers lined by a pseudomembrane in the gingiva and the soft and hard palate. The initial working diagnosis comprised cytomegalovirus reactivation or herpes simplex virus infection. The diagnostic work-up included incisional biopsies of the gingiva and the sigmoid colon. Both biopsies confirmed the diagnosis of histoplasmosis. Intravenous itraconazole was administered with significant improvement after 7 days. Although oral involvement is rare, histoplasmosis should be included in the differential diagnosis of oral lesions, particularly when the patient is immunosuppressed. This study reports a rare presentation of histoplasmosis involving the mucosa of the oral cavity and the colon.

Oral ulcerative lesions in a post-liver-transplantation patient

Oral involvement is rarely found in histoplasmosis, except in its disseminated form, which is mostly observed in the severely immunocompromised host. Herein, we presented the case of a 36-year-old female with a previous history of liver transplant, who was hospitalized due to fever, chills, night sweats, diarrhea, and painful oral lesions over the last 3 days. The oral examination revealed the presence of painful shallow ulcers lined by a pseudomembrane in the gingiva and the soft and hard palate. The initial working diagnosis comprised cytomegalovirus reactivation or herpes simplex virus infection. The diagnostic work-up included incisional biopsies of the gingiva and the sigmoid colon. Both biopsies confirmed the diagnosis of histoplasmosis. Intravenous itraconazole was administered with significant improvement after 7 days. Although oral involvement is rare, histoplasmosis should be included in the differential diagnosis of oral lesions, particularly when the patient is immunosuppressed. This study reports a rare presentation of histoplasmosis involving the mucosa of the oral cavity and the colon.

Identification of DNA mutations in gastric washes from gastric adenocarcinoma patients: Possible implications for liquid biopsies and patient follow-up.

Whereas cancer patients have benefited from liquid biopsies, the scenario for gastric adenocarcinoma (GAC) is still dismal. We used next-generation deep sequencing of TP53-a highly mutated and informative gene in GAC-to assess mutations in tumor biopsies, plasma (PL) and stomach fluids (gastric wash-GW). We evaluated their potential to reveal tumor-derived mutations, useful for monitoring mutational dynamics at diagnosis, progression and treatment. Exon-capture libraries were constructed from 46 patients including tumor biopsies, GW and PL pre and post-treatment (196 samples), with high vertical coverage >8,000×. At diagnosis, we detected TP53 mutations in 15/46 biopsies (32.6%), 7/46 GW- (15.2%) and 6/46 PL-samples (13%). Biopsies and GW were concordant in 38/46 cases (82.6%) for the presence/absence of mutations and, furthermore, four GW-exclusive mutations were identified, suggesting tumor heterogeneity. Considering the combined analysis of GW and PL, TP53 mutations found in biopsies were also identified in 9/15 (60%) of cases, the highest detection level reported for GAC. Our study indicates that GW could be useful to track DNA alterations, especially if anchored to a comprehensive gene-panel designed for this malignancy.

Development of patient-derived orthotopic xenografts from metastatic colorectal cancer in nude mice.

Liver metastasis is the major cause of death for patients with colorectal cancer. Despite treatment with surgery and chemotherapy, patient outcomes are quite unfavourable. Thus, there is an urgent need to develop new treatment strategies with the associated establishment of good animal models. Metastatic disease can be modelled using patient-derived orthotopic xenografts, which accurately replicate intra-tumoral heterogeneity so that various chemotherapeutic agents can be tested on individual tumours to aid in clinical decision-making. The objective of this study was to develop metastatic colorectal tumours in athymic nude mice by implanting fresh tumour fragments into mouse liver parenchyma. Metastatic tumours were successfully propagated in mice following transplantation from human patients, then serially implanted in second and third-generation mice. Morphologic and immunohistochemical characteristics indicate that xenografts recreate the tumour architecture and mismatch repair gene expression for MLH1, MSH2, MSH1, and PMS2. After tumour implantation during the first passage, the time of tumour growth decreased without loss of tumour identity. Post-transplantation lymphoproliferative disease was observed in one case. This pilot study was successful in establishing the institutional PDX preclinical platform to study new therapeutic strategies, disease progression biomarkers, and treatment responsiveness.