Mouse models of inflammatory bowel disease : insights into the mechanisms of inflammation-associated colorectal cancer

The association between chronic inflammation and cancer has been noted for at least a century but the exact molecular mechanisms of cancer initiation and promotion by such inflammation are still poorly understood. The gastrointestinal tract is a unique organ where maintaining a balance between the colonic epithelial cells, the immune system and a fine-tuned response to the resident microflora is crucial for preserving the gut homeostasis. A breakdown of the tight interdependent regulation of the epithelium-immunity-microbiota triangle leads to inflammatory bowel disorders and may promote cancer. This review focuses on inflammation-associated colorectal cancer in mouse models of the disease and highlights emerging research trends

Microsatellite instability in mouse models of colorectal cancer

Microsatellite instability (MSI) is caused by DNA mismatch repair deficiency and is an important prognostic and predictive biomarker in colorectal cancer but relatively few studies have exploited mouse models in the study of its clinical utility. Furthermore, most previous studies have looked at MSI in the small intestine rather than the colon of mismatch repair deficient Msh2-knockout (KO) mice. Here we compared Msh2-KO, p53-KO, and wild type (WT) mice that were treated with the carcinogen azoxymethane (AOM) and the nonsteroidal anti-inflammatory drug sulindac or received no treatment. The induced tumors and normal tissue specimens from the colon were analysed with a panel of five mononucleotide repeat markers. MSI was detected throughout the normal colon in untreated Msh2-KO mice and this involved contraction of the repeat sequences compared to WT. The markers with longer mononucleotide repeats (37-59) were the most sensitive for MSI while the markers with shorter repeats (24) showed only minor change. AOM exposure caused further contraction of the Bat37 and Bat59 repeats in the distal colon of Msh2-KO mice which was reversed by sulindac. Thus AOM-induced carcinogenesis is associated with increased instability of mononucleotide repeats in the colon of Msh2-KO mice but not in WT or p53-KO mice. Chemoprevention of these tumors by sulindac treatment reversed or prevented the increased MSI

Antibiotic exposure within six months before systemic therapy was associated with lower cancer survival

Objectives: The objective of the study was to quantify associations between cancer survival and antibiotic exposure before systemic anticancer therapy. Study Design and Setting: This population-based cohort study compares cause-specific survival according to antibiotic exposure before non–immune checkpoint inhibitor (ICI) systemic therapy in patients diagnosed with single primary cancers in New South Wales between 2013 and 2016. Proportional hazards regression was used to control for confounding, with no antibiotic exposure in the six months before non-ICI systemic therapy serving as the comparator. Results: After adjusting for tumour spread, cancer site, age, sex and comorbidity, people having antibiotic exposure within 180 days before non-ICI systemic therapy had poorer cancer survival (hazard ratios ranging from 1.21 [95% confidence interval: 1.06–1.39] to 1.58 [1.34–1.87]) for shorter periods since antibiotic exposure (P < .0001). Similarly, poorer survival trends applied for localized and metastatic cancer. Of six prevalent cancers studied, lung and breast primaries showed the strongest associations of lower survival with prior antibiotic exposure. Conclusion: Antibiotic exposure within 180 days before non-ICI systemic cancer treatment is associated with poorer survival. If confirmed in other studies, it provides another reason for vigilant antibiotic stewardship

The emerging role of the lung microbiome and its importance in non-small cell lung cancer diagnosis and treatment

Over the last 10 years, with the development of culture-free bacterial identification techniques, understanding of how the microbiome influences diseases has increased exponentially and has highlighted potential opportunities for its use as a diagnostic biomarker and interventional target in many diseases including malignancy. Initial research focused on the faecal microbiome since it contains the densest bacterial populations and many other mucosal sites, such as the lungs, were until recently thought to be sterile. However, in recent years, it has become clear that the lower airways are home to a dynamic bacterial population sustained by the migration and elimination of microbes from the gastrointestinal and upper airway tracts. As in the gut, the lung microbiome plays an important role in regulating mucosal immunity and maintaining the balance between immune tolerance and inflammation. Studies to date have all shown that the lung microbiome undergoes significant changes in the setting of pulmonary disease. In lung cancer, animal models and small patient cohort studies have suggested that microbiome dysbiosis may not only impact tumour progression and response to therapy, particularly immunotherapy, but also plays a key role in cancer pathogenesis by influencing early carcinogenic pathways. These early results have led to concerted efforts to identify microbiome signatures that represent diagnostic biomarkers of early-stage disease and to consider modulation of the lung microbiome as a potential therapeutic strategy. Lung microbiome research is in its infancy and studies to date have been small, single centre with significant methodological variation. Large, multicentre longitudinal studies are needed to establish the clinical potential of this exciting field

Fibroblast growth factor receptor 1 (FGFR1) copy number is an independent prognostic factor in non-small cell lung cancer

Fibroblast growth factor receptor 1 ( FGFR1) is an oncogene that can potentially be targeted by tyrosine kinase inhibitors. We aimed to investigate the prevalence and prognostic significance of alterations in FGFR1 copy number in non-small cell lung cancer (NSCLC). FGFR1 status was evaluated by chromogenic silver in situ hybridisation (ISH) in tissue microarray sections from a retrospective cohort of 304 surgically resected NSCLCs and results were correlated with the clinicopathological features and overall survival. High FGFR1 gene copy number (amplification or high-level polysomy) was significantly more frequent in squamous cell carcinomas (SCC) (24.8%) and large cell carcinomas (LCC) (25%) compared to adenocarcinomas (11.3%) ( p= 0.01 and p= 0.03 respectively). Among NSCLC there was no significant correlation between FGFR1-positive status and other clinicopathological features including age, gender, smoking history, tumour size, lymph node status, stage, grade, vascular, lymphatic or perineural invasion. FGFR1-positive patients showed a tendency to longer overall survival in univariate analysis ( p= 0.14). Multivariate survival analysis using Cox regression model confirmed FGFR1-positive patients had a significant reduction in the risk of death compared to FGFR1-negative patients (HR 0.6; p= 0.02). High. FGFR1 gene copy number is a common finding in SCC and LCC and is an independent favourable prognostic factor

HIF1α deficiency reduces inflammation in a mouse model of proximal colon cancer

Hypoxia-inducible factor 1α (HIF1α) is a transcription factor that regulates the adaptation of cells to hypoxic microenvironments, for example inside solid tumours. Stabilisation of HIF1α can also occur in normoxic conditions in inflamed tissue or as a result of inactivating mutations in negative regulators of HIF1α. Aberrant overexpression of HIF1α in many different cancers has led to intensive efforts to develop HIF1α-targeted therapies. However, the role of HIF1α is still poorly understood in chronic inflammation that predisposes the colon to carcinogenesis. We have previously reported that the transcription of HIF1α is upregulated and that the protein is stabilised in inflammatory lesions that are caused by the non-steroidal anti-inflammatory drug (NSAID) sulindac in the mouse proximal colon. Here, we exploited this side effect of long-term sulindac administration to analyse the role of HIF1α in colon inflammation using mice with a Villin-Cre-induced deletion of Hif1α exon 2 in the intestinal epithelium (Hif1αΔIEC). We also analysed the effect of sulindac sulfide on the aryl hydrocarbon receptor (AHR) pathway in vitro in colon cancer cells. Most sulindac-treated mice developed visible lesions, resembling the appearance of flat adenomas in the human colon, surrounded by macroscopically normal mucosa. Hif1αΔIEC mice still developed lesions but they were smaller than in the Hif1α-floxed siblings (Hif1αF/F). Microscopically, Hif1αΔ;IEC mice had significantly less severe colon inflammation than Hif1αF/F mice. Molecular analysis showed reduced MIF expression and increased E-cadherin mRNA expression in the colon of sulindac-treated Hif1αΔ;IEC mice. However, immunohistochemistry analysis revealed a defect of E-cadherin protein expression in sulindac-treated Hif1αΔIEC mice. Sulindac sulfide treatment in vitro upregulated Hif1α, c-JUN and IL8 expression through the AHR pathway. Taken together, HIF1α expression augments inflammation in the proximal colon of sulindac-treated mice, and AHR activation by sulindac might lead to the reduction of E-cadherin protein levels through the mitogen-activated protein kinase (MAPK) pathway

KRAS mutations and CDKN2A promoter methylation show an interactive adverse effect on survival and predict recurrence of rectal cancer

Colonic and rectal cancers differ in their clinicopathologic features and treatment strategies. Molecular markers such as gene methylation, microsatellite instability and KRAS mutations, are becoming increasingly important in guiding treatment decisions in colorectal cancer. However, their association with clinicopathologic variables and utility in the management of rectal cancer is still poorly understood. We analyzed CDKN2A gene methylation, CpG island methylator phenotype (CIMP), microsatellite instability and KRAS/BRAF mutations in a cohort of 381 rectal cancers with extensive clinical follow-up data. BRAF mutations (2%), CIMP-high (4%) and microsatellite instability-high (2%) were rare, whereas KRAS mutations (39%), CDKN2A methylation (20%) and CIMP-low (25%) were more common. Only CDKN2A methylation and KRAS mutations showed an association with poor overall survival but these did not remain significant when analyzed with other clinicopathologic factors. In contrast, this prognostic effect was strengthened by the joint presence of CDKN2A methylation and KRAS mutations, which independently predicted recurrence of cancer and was associated with poor overall and cancer-specific survival. This study has identified a subgroup of more aggressive rectal cancers that may arise through the KRAS-p16 pathway. It has been previously shown that an interaction of p16 deficiency and oncogenic KRAS promotes carcinogenesis in the mouse and is characterized by loss of oncogene-induced senescence. These findings may provide avenues for the discovery of new treatments in rectal cancer. What's new? Though the two are often considered together, rectal cancer and colon cancer behave differently and require different treatments. Fewer prognostic markers are available for rectal cancer, and indicators such as gene methylation, microsatellite instability, and KRAS mutations, which help inform treatment decisions, may be considered less often in rectal than colon cancer. The authors investigated these indicators in rectal cancers, and found that a combination of CDKN2A gene methylation and KRAS mutation may augur a poor outcome, thereby identifying a subgroup of more aggressive rectal cancers that may develop through the KRAS-p16 pathway

Alterations of MET gene copy number and protein expression in primary non-small-cell lung cancer and corresponding nodal metastases

Introduction: Mesenchymal epithelial transition factor (MET) is a promising therapeutic target in non-small-cell lung cancer (NSCLC) but there are limited data about MET alterations in treatment-naive NSCLC and whether or not these changes are consistent between primary tumors and metastases. We aimed to investigate concordance, clinicopathological correlations, and prognostic value of MET alterations in primary NSCLC and corresponding nodal metastases. Materials and Methods: MET gene copy number (GCN) status was evaluated using fluorescent in situ hybridization (FISH) and MET protein expression using immunohistochemistry (IHC) in tissue microarray sections from a retrospective cohort of 300 surgically resected NSCLCs including 93 cases with nodal metastases. Results: Primary NSCLCs were MET IHC positive in 28 (10.3%) of cases and MET FISH positive (high polysomy or amplification) in 22 (8.1%) but only 1 (0.4%) showed amplification. In metastases, high MET GCN (18.3%) and protein expression (21.3%) was more frequent compared with primary tumors. The status of MET in lymph nodes significantly correlated with MET status in the corresponding primary tumors. Squamous cell carcinomas showed lower MET overexpression compared with nonsquamous tumors but there were no other associations with clinicopathological characteristics. Patients with tumors that were either MET FISH positive or IHC positive had a significantly better overall survival in univariate and multivariate analyses. Conclusion: Alterations of MET are more commonly seen in nodal metastases than primary tumors and this might have implications for their utility as predictive biomarkers to select patients for MET inhibition. MET overexpression and MET high polysomy occur in a low proportion of primary NSCLCs and is associated with a good prognosis

Phosphorylated Akt expression is a prognostic marker in early-stage non-small cell lung cancer

Aims: To determine the prognostic significance of pAkt expression in order to identify high-risk stage IB patients with non-small cell lung cancer (NSCLC) in an exploratory study. Methods: We identified 471 consecutive patients with stage IB primary NSCLC according to the American Joint Commission on Cancer 6th edition tumour-node-metastasis (TNM) staging system, who underwent surgical resection between 1990 and 2008. Patients who received neoadjuvant or adjuvant treatments were excluded. Pathology reports were reviewed, and pathological characteristics were extracted. Expression of phosphorylated Akt (pAkt) in both cytoplasmic and nuclear locations was assessed by immunohistochemistry, and clinicopathological factors were analysed against 10-year overall survival using Kaplan-Meier and Cox proportional hazards model. Results: 455 (96.6%) cancers were adequate for pAkt immunohistochemical analysis. The prevalence of pAkt expression in the cytoplasm and nucleus of the cancers was 60.7% and 43.7%, respectively. Patients whose cancers expressed higher levels of cytoplasmic pAkt had a trend towards longer overall survival than those with lower levels (p=0.06). Conversely, patients whose cancers expressed higher levels of nuclear pAkt had a poorer prognosis than those with lower levels of expression (p=0.02). Combined low cytoplasmic/high nuclear expression of pAkt was an independent predictor of overall survival (HR=2.86 (95% CI 1.35 to 6.04); p=0.006) when modelled with age (HR=1.05 (95% CI 1.03 to 1.07); p0.05). Conclusions: Level of expression of pAkt in the cytoplasm and nucleus is an independent prognostic factor that may help to select patients with high-risk disease

Loss of special AT-rich binding protein 1 expression is a marker of poor survival in lung cancer

Introduction: Lung cancer is the leading cause of cancer-related mortality and requires more effective molecular markers of prognosis and therapeutic responsiveness. Special AT-rich binding protein 1 (SATB1) is a global genome organizer that recruits chromatin remodeling proteins to epigenetically regulate hundreds of genes in a tissue-specific manner. Initial studies suggest that SATB1 overexpression is a predictor of poor prognosis in breast cancer, but the prognostic significance of SATB1 expression has not been evaluated in lung cancer. Methods: A cohort of 257 lung cancers was evaluated by immunohistochemistry. Epigenetic silencing of SATB1 was examined in cell lines by 5-Aza 2-deoxycytidine and trichostatin A treatment, and chromatin immunoprecipitation. Results: Significant loss of SATB1 expression was found in squamous preinvasive lesions (p < 0.04) and in non-small cell lung cancers (p < 0.001) compared with matched normal bronchial epithelium. Loss of SATB1 independently predicted poor cancer-specific survival in squamous cell carcinomas (SCCs; hazard ratio: 2.06, 95% confidence interval: 1.2-3.7, p = 0.016). Treatment of lung cancer cell lines with the histone deacetylase inhibitor trichostatin A resulted in up-regulation of SATB1. SATB1 was associated with a decrease in the active chromatin mark acetylated histone H3K9 and an increase in the repressive polycomb mark trimethylated H3K27 in a SCC cell line relative to a normal bronchial epithelial cell line. Conclusions: This is the first study showing that SATB1 expression is lost in early preinvasive squamous lesions and that loss of SATB1 is associated with poor prognosis in lung SCC. We hypothesize that the SATB1 gene is epigenetically silenced through histone modifications