Rapamycin inhibition of polyposis and progression to dysplasia in a mouse model

Successful treatment of juvenile polyposis of infancy with sirolimus: a case report

BACKGROUND

Infantile Juvenile polyposis of infantile (JPI) is a rare and aggressive form of juvenile polyposis syndrome (JPS) typically diagnosed in the first year of life. It often carries a poor prognosis due to chronic gastrointestinal bleeding, protein-losing enteropathy, malnutrition and immune deficiency.

CASE PRESENTATION

We report a case of a girl initially presented with pallor at 7 months of age, which progressed to gastrointestinal bleeding and protein-losing enteropathy. Endoscopic examination, which included both upper gastrointestinal endoscopy and enteroscopy, showed diffuse polyposis. Histopathology results indicated the presence of juvenile polyps with no dysplasia in all removed polyps. Genetic testing identified a 2.1 Mb deletion on chromosome 10q23.2q23.31 involving the phosphatase and tensin homolog (PTEN) and bone morphogenetic protein receptor type IA (BMPR1A) genes. Treatment with sirolimus initiated at 10 months of age led to a reduction in the need for blood and albumin infusions, improved patient growth, and quality of life. While the frequency of endoscopic evaluations decreased with sirolimus, regular endoscopic polypectomy every 5 months remained necessary. However, discontinuation of sirolimus resulted in polyp recurrence after 2 months due to pneumonia.

CONCLUSION

This case highlights sirolimus treatment can alleviate many complications of JPI, it does not eliminate the need for aggressive polypectomy.

Interplay between WNT/PI3K-mTOR axis and the microbiota in APC-driven colorectal carcinogenesis: data from a pilot study and possible implications for CRC prevention

BACKGROUND

Wnt/β-catenin signalling impairment accounts for 85% of colorectal cancers (CRCs), including sporadic and familial adenomatous polyposis (FAP) settings. An altered PI3K/mTOR pathway and gut microbiota also contribute to CRC carcinogenesis. We studied the interplay between the two pathways and the microbiota composition within each step of CRC carcinogenesis.

METHODS

Proteins and target genes of both pathways were analysed by RT-qPCR and IHC in tissues from healthy faecal immunochemical test positive (FIT+, n = 17), FAP (n = 17) and CRC (n = 15) subjects. CRC-related mutations were analysed through NGS and Sanger. Oral, faecal and mucosal microbiota was profiled by 16 S rRNA-sequencing.

RESULTS

We found simultaneous hyperactivation of Wnt/β-catenin and PI3K/mTOR pathways in FAP-lesions compared to CRCs. Wnt/β-catenin molecular markers positively correlated with Clostridium_sensu_stricto_1 and negatively with Bacteroides in FAP faecal microbiota. Alistipes, Lachnospiraceae, and Ruminococcaceae were enriched in FAP stools and adenomas, the latter also showing an overabundance of Lachnoclostridium, which positively correlated with cMYC. In impaired-mTOR-mutated CRC tissues, p-S6R correlated with Fusobacterium and Dialister, the latter also confirmed in the faecal-ecosystem.

CONCLUSIONS

Our study reveals an interplay between Wnt/β-catenin and PI3K/mTOR, whose derangement correlates with specific microbiota signatures in FAP and CRC patients, and identifies new potential biomarkers and targets to improve CRC prevention, early adenoma detection and treatment.

Modulation of faecal miRNAs highlights the preventive effects of a Mediterranean low-inflammatory dietary intervention

BACKGROUND

Dietary interventions have been proposed as therapeutic approaches for several diseases, including cancer. A low-inflammatory Mediterranean dietary intervention, conducted as a pilot study in subjects with Familial Adenomatous Polyposis (FAP), reduced markers of local and systemic inflammation. We aim to determine whether this diet may modulate faecal microRNA (miRNA) and gene expression in the gut.

METHODS

Changes in the faecal miRNome were evaluated by small RNA sequencing at baseline (T0), after the three-month intervention (T1), and after an additional three months (T2). Changes in the transcriptome of healthy rectal mucosa and adenomas were evaluated by RNA sequencing at T0 and T2. The identification of validated miRNA-gene interactions and functional analysis of miRNA targets were performed using in silico approaches.

RESULTS

Twenty-seven subjects were included in this study. It was observed that the diet modulated 29 faecal miRNAs (p < 0.01; |log2 Fold Change|>1), and this modulation persisted for three months after the intervention. Levels of miR-3612-3p and miR-941 correlated with the adherence to the diet, miR-3670 and miR-4252-5p with faecal calprotectin, and miR-3670 and miR-6867 with serum calprotectin. Seventy genes were differentially expressed between adenoma and normal tissue, and most were different before the dietary intervention but reached similar levels after the diet. Functional enrichment analysis identified the proinflammatory ERK1/2, cell cycle regulation, and nutrient response pathways as commonly regulated by the modulated miRNAs and genes.

CONCLUSIONS

Faecal miRNAs modulated by the dietary intervention target genes that participate in inflammation. Changes in levels of miRNAs and genes with oncogenic and tumour suppressor functions further support the potential cancer-preventive effect of the low-inflammatory Mediterranean diet.

CLINICAL TRIAL NUMBER REGISTRATION

NCT04552405, Registered in ClinicalTrials.gov.

Endoscopic and chemopreventive management of familial adenomatous polyposis syndrome

Familial adenomatous polyposis (FAP) is an autosomal dominant syndrome predisposing affected individuals to gastrointestinal (GI) cancers through a high burden of polyposis. Colorectal cancer rates reach 100% by the age of 45, making early colectomy a mainstay of treatment. While most patients undergo colectomy at an early age, ongoing screening and surveillance of the upper gastrointestinal tract and rectal pouch must continue throughout adulthood. Endoscopic therapy of gastric, duodenal, ampullary and rectal pouch polyps is critical to reduce morbidity and cancer related mortality. Management of these lesions is not uniform, and is dependent on their location, size, histology, and risk of malignant potential. Medical therapies targeting pathways that reduce the malignant progression of pre-cancerous lesions have been studied for many years. While studies on the use of aspirin and non-steroidal anti-inflammatories (NSAIDs) in chemoprevention have shown encouraging results in Lynch syndrome and primary colorectal cancer, the potential benefits of these medications have not been duplicated in FAP cohorts. While data remains limited on chemoprevention in FAP, a number of randomized trials are currently underway examining targeted therapies with the potential to slow the progression of the disease. This review aims to provide an in-depth review of the literature on current endoscopic options and chemopreventive therapies targeting FAP. While the endoscopic management has robust data for its use, chemoprevention in FAP is still in its infancy. The complementary use of chemopreventive agents and endoscopic therapy for FAP patients is quickly becoming a growing and exciting area of research.

Advancing translational research for colorectal immuno-oncology

Colorectal cancer (CRC) is a common and deadly disease. Unfortunately, immune checkpoint inhibitors (ICIs) fail to elicit effective anti-tumour responses in the vast majority of CRC patients. Patients that are most likely to respond are those with DNA mismatch repair deficient (dMMR) and microsatellite instability (MSI) disease. However, reliable predictors of ICI response are lacking, even within the dMMR/MSI subtype. This, together with identification of novel mechanisms to increase response rates and prevent resistance, are ongoing and vitally important unmet needs. To address the current challenges with translation of early research findings into effective therapeutic strategies, this review summarises the present state of preclinical testing used to inform the development of immuno-regulatory treatment strategies for CRC. The shortfalls and advantages of commonly utilised mouse models of CRC, including chemically induced, transplant and transgenic approaches are highlighted. Appropriate use of existing models, incorporation of patient-derived data and development of cutting-edge models that recapitulate important features of human disease will be key to accelerating clinically relevant research in this area.

mTOR inhibition suppresses Myc-driven polyposis by inducing immunogenic cell death

Myc is a key driver of colorectal cancer initiation and progression, but remains a difficult drug target. In this study, we show that mTOR inhibition potently suppresses intestinal polyp formation, regresses established polyps, and prolongs lifespan of APC^Min/+ mice. Everolimus in diet strongly reduces p-4EBP1, p-S6, and Myc levels, and induces apoptosis of cells with activated β-catenin (p-S552) in the polyps on day 3. The cell death is accompanied by ER stress, activation of the extrinsic apoptotic pathway, innate immune cell recruitment, and followed by T-cell infiltration on day 14 persisting for months thereafter. These effects are absent in normal intestinal crypts with physiologic levels of Myc and a high rate of proliferation. Using normal human colonic epithelial cells, EIF4E S209A knockin and BID knockout mice, we found that local inflammation and antitumor efficacy of Everolimus requires Myc-dependent induction of ER stress and apoptosis. These findings demonstrate mTOR and deregulated Myc as a selective vulnerability of mutant APC-driven intestinal tumorigenesis, whose inhibition disrupts metabolic and immune adaptation and reactivates immune surveillance necessary for long-term tumor control.

Efficacy of Wholistic Turmeric Supplement on Adenomatous Polyps in Patients with Familial Adenomatous Polyposis-A Randomized, Double-Blinded, Placebo-Controlled Study

Several studies have demonstrated that curcumin can cause the regression of polyps in familial adenomatous polyposis (FAP), while others have shown negative results. Wholistic turmeric (WT) containing curcumin and additional bioactive compounds may contribute to this effect. We performed a double-blinded, randomized, controlled trial to assess the efficacy of WT in FAP patients. Ten FAP patients were randomly assigned to receive either WT or placebo for 6 months. Colonoscopies were performed at baseline and after 6 months. The polyp number and size, as well as the cumulative polyp burden, were assessed. No differences were noted between the groups in terms of changes from the baseline's polyp number, size, or burden. However, stratifying the data according to the right vs. left colon indicated a decrease in the median polyp number (from 5.5 to 1.5, p = 0.06) and polyp burden (from 24.25 mm to 11.5 mm, p = 0.028) in the left colon of the patients in the WT group. The adjusted left polyp number and burden in the WT arm were lower by 5.39 (p = 0.034) and 14.68 mm (p = 0.059), respectively. Whether WT can be used to reduce the polyp burden of patients with predominantly left-sided polyps remains to be seen; thus, further larger prospective trials are required.

Immunologic and dose dependent effects of rapamycin and its evolving role in chemoprevention

Rapamycin inhibits the mechanistic (formally mammalian) target of rapamycin (mTOR), an evolutionarily conserved intracellular kinase that influences activation of growth signaling pathways and immune responses to malignancy. Rapamycin has been found to have both immunosuppressant and immunostimulatory effects throughout the innate and adaptive responses based on the inhibition of mTOR signaling. While the immunosuppressant properties of rapamycin and mTOR inhibition explain rapamycin's success in the prevention of transplant rejection, the immunostimulatory characteristics are likely partially responsible for rapamycin's anti-neoplastic effects. The immunologic response to rapamycin is at least partially dependent on the dose and administration schedule, with lower doses inducing immunostimulation and intermittent dosing promoting immune function while limiting metabolic and immunosuppressant toxicities. In addition to its FDA-approved application in advanced malignancies, rapamycin may be effective as a chemopreventive agent, suspending progression of low-grade cancers, preventing invasive conversion of in situ malignancy, or delaying malignant transformation of established pre-malignant conditions.

Loss of aryl hydrocarbon receptor suppresses the response of colonic epithelial cells to IL22 signaling by upregulating SOCS3

IL22 signaling plays an important role in maintaining gastrointestinal epithelial barrier function, cell proliferation, and protection of intestinal stem cells from genotoxicants. Emerging studies indicate that the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, promotes production of IL22 in gut immune cells. However, it remains to be determined if AhR signaling can also affect the responsiveness of colonic epithelial cells to IL22. Here, we show that IL22 treatment induces the phosphorylation of STAT3, inhibits colonic organoid growth, and promotes colonic cell proliferation in vivo. Notably, intestinal cell-specific AhR knockout (KO) reduces responsiveness to IL22 and compromises DNA damage response after exposure to carcinogen, in part due to the enhancement of suppressor of cytokine signaling 3 (SOCS3) expression. Deletion of SOCS3 increases levels of pSTAT3 in AhR KO organoids, and phenocopies the effects of IL22 treatment on wild-type (WT) organoid growth. In addition, pSTAT3 levels are inversely associated with increased azoxymethane/dextran sulfate sodium (AOM/DSS)-induced colon tumorigenesis in AhR KO mice. These findings indicate that AhR function is required for optimal IL22 signaling in colonic epithelial cells and provide rationale for targeting AhR as a means of reducing colon cancer risk.NEW & NOTEWORTHY AhR is a key transcription factor controlling expression of IL22 in gut immune cells. In this study, we show for the first time that AhR signaling also regulates IL22 response in colonic epithelial cells by modulating SOCS3 expression.

Sirolimus for the Treatment of Juvenile Polyposis in Childhood

Juvenile polyposis syndrome (JPS) is a rare disease with an autosomal dominant inheritance pattern characterized by the development of multiple hamartomatous polyps in the gastrointestinal tract. The most frequent signs and symptoms are recurrent abdominal pain, rectal bleeding, anemia, and iron deficiency. The treatment of JPS is symptomatic, requiring serial endoscopic polypectomies or intestinal resections in the most severe cases. We describe the clinical case of a patient with JPS with a childhood juvenile polyposis phenotype because of a mutation on the SMAD4 gene, who received treatment with sirolimus successfully.

Adenomatous polyposis coli in cancer and therapeutic implications

Inactivating mutations of the adenomatous polyposis coli (APC) gene and consequential upregulation of the Wnt signaling pathway are critical initiators in the development of colorectal cancer (CRC), the third most common cancer in the United States for both men and women. Emerging evidence suggests APCmutations are also found in gastric, breast and other cancers. The APC gene, located on chromosome 5q, is responsible for negatively regulating the b-catenin/Wnt pathway by creating a destruction complex with Axin/Axin2, GSK-3b, and CK1. In the event of an APC mutation, b-catenin accumulates, translocates to the cell nucleus and increases the transcription of Wnt target genes that have carcinogenic consequences in gastrointestinal epithelial stem cells. A literature review was conducted to highlight carcinogenesis related to APC mutations, as well as preclinical and clinical studies for potential therapies that target steps in inflammatory pathways, including IL-6 transduction, and Wnt pathway signaling regulation. Although a range of molecular targets have been explored in murine models, relatively few pharmacological agents have led to substantial increases in survival for patients with colorectal cancer clinically. This article reviews a range of molecular targets that may be efficacious targets for tumors with APC mutations.

Updates in chemoprevention research for hereditary gastrointestinal and polyposis syndromes

PURPOSE OF REVIEW

To critically examine recently published research in the area of chemoprevention in hereditary polyposis and gastrointestinal cancers, and to briefly review several ongoing chemoprevention trials testing novel agents in this population.

RECENT FINDINGS

Four recent chemoprevention trials in patients with familial adenomatous polyposis (FAP) were identified and reviewed. In the FAPEST trial, the combination of erlotinib+sulindac (compared to placebo) met its primary outcome of decreased duodenal polyp burden. A secondary analysis of lower gastrointestinal tract outcomes also demonstrated significant benefits. Two randomized trials in FAP patients examining combination regimens (celecoxib+DFMO and sulindac+DFMO) failed to meet their primary endpoints. Benefits of further research into these combinations was suggested by efficacy signals seen in secondary and post-hoc analyses. Finally, a randomized trial found curcumin (vs placebo) to have no benefit in reducing colorectal polyp count or size in patients with FAP.

SUMMARY

Progress in developing new and more effective preventive options for patients with hereditary gastrointestinal syndromes continues to be made through the efforts of investigators conducting chemoprevention research.

Loss of Aryl Hydrocarbon Receptor Promotes Colon Tumorigenesis in ApcS580/+; KrasG12D/+ Mice

The mutational genetic landscape of colorectal cancer has been extensively characterized; however, the ability of "cooperation response genes" to modulate the function of cancer "driver" genes remains largely unknown. In this study, we investigate the role of aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, in modulating oncogenic cues in the colon. We show that intestinal epithelial cell-targeted AhR knockout (KO) promotes the expansion and clonogenic capacity of colonic stem/progenitor cells harboring Apc^S580/+; Kras^G12D/+ mutations by upregulating Wnt signaling. The loss of AhR in the gut epithelium increased cell proliferation, reduced mouse survival rate, and promoted cecum and colon tumorigenesis in mice. Mechanistically, the antagonism of Wnt signaling induced by Lgr5 haploinsufficiency attenuated the effects of AhR KO on cecum and colon tumorigenesis. IMPLICATIONS: Our findings reveal that AhR signaling plays a protective role in genetically induced colon tumorigenesis at least by suppressing Wnt signaling and provides rationale for the AhR as a therapeutic target for cancer prevention and treatment.

Chemoprevention in familial adenomatous polyposis: past, present and future

Familial adenomatous polyposis (FAP) is a hereditary colorectal cancer syndrome characterized by colorectal adenomas and a near 100% lifetime risk of colorectal cancer (CRC). Prophylactic colectomy, usually by age 40, is the gold-standard therapy to mitigate this risk. However, colectomy is associated with morbidity and fails to prevent extra-colonic disease manifestations, including gastric polyposis, duodenal polyposis and cancer, thyroid cancer, and desmoid disease. Substantial research has investigated chemoprevention medications in an aim to prevent disease progression, postponing the need for colectomy and temporizing the development of extracolonic disease. An ideal chemoprevention agent should have a biologically plausible mechanism of action, be safe and easily tolerated over a prolonged treatment period, and produce a durable and clinically meaningful effect. To date, no chemoprevention agent tested has fulfilled these criteria. New agents targeting novel pathways in FAP are needed. Substantial preclinical literature exists linking the molecular target of rapamycin (mTOR) pathway to FAP. A single case report of rapamycin, an mTOR inhibitor, used as chemoprevention in FAP patients exists, but no formal clinical studies have been conducted. Here, we review the prior literature on chemoprevention in FAP, discuss the rationale for rapamycin in FAP, and outline a proposed clinical trial testing rapamycin as a chemoprevention agent in patients with FAP.

Sirolimus for the treatment of polyposis of the rectal remnant and ileal pouch in four patients with familial adenomatous polyposis: a pilot study

Objective

After prophylactic colectomy, adenomas continue to develop in the remaining intestine of patients with familial adenomatous polyposis (FAP). There is a lack of standard clinical recommendation for chemoprevention in patients with FAP. Because of promising in vivo studies, the aim of this pilot study was to investigate the safety of sirolimus and its effect on progression of intestinal adenomas.

Design

Patients with FAP with InSiGHT Polyposis Staging System 3 of the retained rectum or pouch received sirolimus for 6 months, dosed at plasma concentration levels of 5–8 µg/L. Primary outcomes were safety and change in marked polyp size. Secondary outcomes were change in number of polyps and effect on proliferation and apoptosis assessed by immunohistochemistry.

Results

Each of the included four patients reported 4 to 18 adverse events (toxicity grades 1–3). One patient prematurely terminated the study because of adverse events. Marked polyp size decreased in 16 (80%)/20 and remained the same in 4 (20%)/20 patients. The number of polyps decreased in all patients (MD −25.75, p=0.13). Three out of four patients showed substantial induction of apoptosis or inhibition of proliferation.

Conclusion

Six months of sirolimus treatment in four patients with FAP showed promising effects especially on the number of polyps in the rectal remnant and ileal pouch, although at the cost of numerous adverse events.

Trial registration number

ClinicalTrials.gov ID NCT03095703.

Loss of aryl hydrocarbon receptor potentiates FoxM1 signaling to enhance self-renewal of colonic stem and progenitor cells

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that senses xenobiotics, diet, and gut microbial-derived metabolites, is increasingly recognized as a key regulator of intestinal biology. However, its effects on the function of colonic stem and progenitor cells remain largely unexplored. Here, we observed that inducible deletion of AhR in Lgr5⁺ stem cells increases the percentage of colonic stem cells and enhances organoid initiating capacity and growth of sorted stem and progenitor cells, while AhR activation has the opposite effect. Moreover, intestinal-specific AhR knockout increases basal stem cell and crypt injury-induced cell proliferation and promotes colon tumorigenesis in a preclinical colitis-associated tumor model by upregulating FoxM1 signaling. Mechanistically, AhR transcriptionally suppresses FoxM1 expression. Activation of AhR in human organoids recapitulates phenotypes observed in mice, such as reduction in the percentage of colonic stem cells, promotion of stem cell differentiation, and attenuation of FoxM1 signaling. These findings indicate that the AhR-FoxM1 axis, at least in part, mediates colonic stem/progenitor cell behavior.

Early-onset colorectal cancer: initial clues and current views

Over the past several decades, the incidence of early-onset colorectal cancer (EOCRC; in patients <50 years old) has increased at an alarming rate. Although robust and scientifically rigorous epidemiological studies have sifted out environmental elements linked to EOCRC, our knowledge of the causes and mechanisms of this disease is far from complete. Here, we highlight potential risk factors and putative mechanisms that drive EOCRC and suggest likely areas for fruitful research. In addition, we identify inconsistencies in the evidence implicating a strong effect of increased adiposity and suggest that certain behaviours (such as diet and stress) might place nonobese and otherwise healthy people at risk of this disease. Key risk factors are reviewed, including the global westernization of diets (usually involving a high intake of red and processed meats, high-fructose corn syrup and unhealthy cooking methods), stress, antibiotics, synthetic food dyes, monosodium glutamate, titanium dioxide, and physical inactivity and/or sedentary behaviour. The gut microbiota is probably at the crossroads of these risk factors and EOCRC. The time course of the disease and the fact that relevant exposures probably occur in childhood raise important methodological issues that are also discussed.

Are Wnt/β-Catenin and PI3K/AKT/mTORC1 Distinct Pathways in Colorectal Cancer?

Wnt/β-catenin and phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin complex 1 (PI3K/AKT/mTORC1) pathways both are critically involved in colorectal cancer (CRC) development, although they are implicated in the modulation of distinct oncogenic mechanisms. In homeostatic and pathologic conditions, these pathways show a fine regulation based mainly on feedback mechanisms, and are connected at multiple levels involving both upstream and downstream common effectors. The ability of the Wnt/β-catenin and PI3K/AKT/mTORC1 pathways to reciprocally control themselves represents one of the main resistance mechanisms to selective inhibitors in CRC, leading to the hypothesis that in specific settings, particularly in cancer driven by genetic alterations in Wnt/β-catenin signaling, the relationship between Wnt/β-catenin and PI3K/AKT/mTORC1 pathways could be so close that they should be considered as a unique therapeutic target. This review provides an update on the Wnt/β-catenin and PI3K/AKT/mTORC1 pathway interconnections in CRC, describing the main molecular players and the potential implications of combined inhibitors as an approach for CRC chemoprevention and treatment.

Successful Treatment of Juvenile Polyposis of Infancy With Sirolimus

Juvenile polyposis syndrome is a rare autosomal dominant condition characterized by multiple hamartomatous polyps throughout the gastrointestinal tract. Juvenile polyposis of infancy is a generalized severe form of juvenile polyposis syndrome associated with a poor prognosis. A 47-month-old female infant presented initially with gastrointestinal bleeding and protein-losing enteropathy at 4 months of age. At the age of 12 months, the condition worsened, requiring albumin infusions every 24 to 48 hours and red blood cell transfusions every 15 days. Upper gastrointestinal endoscopy, colonoscopy, and small-bowel enteroscopy revealed diffuse polyposis that was treated with multiple endoscopic polypectomies. Despite subtotal colectomy with ileorectal anastomosis, protein-losing enteropathy and bleeding persisted, requiring continued blood transfusions and albumin infusions. A chromosomal microarray revealed a single allele deletion in chromosome 10q23, involving both the PTEN and BMPR1A genes. Loss of PTEN function is associated with an increased activation of the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway involved in cell proliferation. Treatment with sirolimus, an mTOR inhibitor, was initiated with the aim of inhibiting polyp growth. Soon after initiation of treatment with sirolimus, blood and albumin infusions were no longer needed and resulted in improved patient growth and quality of life. This case represents the first detailed report of successful drug therapy for life-threatening juvenile polyposis of infancy.

Campylobacter jejuni promotes colorectal tumorigenesis through the action of cytolethal distending toxin

OBJECTIVE

Campylobacter jejuni produces a genotoxin, cytolethal distending toxin (CDT), which has DNAse activity and causes DNA double-strand breaks. Although C. jejuni infection has been shown to promote intestinal inflammation, the impact of this bacterium on carcinogenesis has never been examined.

DESIGN

Germ-free (GF) Apc^Min/+ mice, fed with 1% dextran sulfate sodium, were used to test tumorigenesis potential of CDT-producing C. jejuni. Cells and enteroids were exposed to bacterial lysates to determine DNA damage capacity via γH2AX immunofluorescence, comet assay and cell cycle assay. To examine the interplay of CDT-producing C. jejuni, gut microbiome and host in tumorigenesis, colonic RNA-sequencing and faecal 16S rDNA sequencing were performed. Rapamycin was administrated to investigate the prevention of CDT-producing C. jejuni-induced tumorigenesis.

RESULTS

GF Apc^Min/+ mice colonised with human clinical isolate C. jejuni81-176 developed significantly more and larger tumours when compared with uninfected mice. C. jejuni with a mutated cdtB subunit, mutcdtB, attenuated C. jejuni-induced tumorigenesis in vivo and decreased DNA damage response in cells and enteroids. C. jejuni infection induced expression of hundreds of colonic genes, with 22 genes dependent on the presence of cdtB. The C. jejuni-infected group had a significantly different microbial gene expression profile compared with the mutcdtB group as shown by metatranscriptomic data, and different microbial communities as measured by 16S rDNA sequencing. Finally, rapamycin could diminish the tumorigenic capability of C. jejuni.

CONCLUSION

Human clinical isolate C. jejuni 81-176 promotes colorectal cancer and induces changes in microbial composition and transcriptomic responses, a process dependent on CDT production.

Deptor Is a Novel Target of Wnt/β-Catenin/c-Myc and Contributes to Colorectal Cancer Cell Growth

Activation of the Wnt/β-catenin signaling pathway drives colorectal cancer growth by deregulating expression of downstream target genes, including the c-myc proto-oncogene. The critical targets that mediate the functions of oncogenic c-Myc in colorectal cancer have yet to be fully elucidated. Previously, we showed that activation of PI3K/Akt/mTOR contributes to colorectal cancer growth and metastasis. Here, we show that Deptor, a suppressor of mTOR, is a direct target of Wnt/β-catenin/c-Myc signaling in colorectal cancer cells. Inhibition of Wnt/β-catenin or knockdown of c-Myc decreased, while activation of Wnt/β-catenin or overexpression of c-Myc increased the expression of Deptor. c-Myc bound the promoter of Deptor and transcriptionally regulated Deptor expression. Inhibition of Wnt/β-catenin/c-Myc signaling increased mTOR activation, and the combination of Wnt and Akt/mTOR inhibitors enhanced inhibition of colorectal cancer cell growth in vitro and in vivo Deptor expression was increased in colorectal cancer cells; knockdown of Deptor induced differentiation, decreased expression of B lymphoma Mo-MLV insertion region 1 (Bmi1), and decreased proliferation in colorectal cancer cell lines and primary human colorectal cancer cells. Importantly, our work identifies Deptor as a downstream target of the Wnt/β-catenin/c-Myc signaling pathway, acting as a tumor promoter in colorectal cancer cells. Moreover, we provide a molecular basis for the synergistic combination of Wnt and mTOR inhibitors in treating colorectal cancer with elevated c-Myc.Significance: The mTOR inhibitor DEPTOR acts as a tumor promoter and could be a potential therapeutic target in colorectal cancer. Cancer Res; 78(12); 3163-75. ©2018 AACR.

Invasive mouse gastric adenocarcinomas arising from Lgr5+ stem cells are dependent on crosstalk between the Hedgehog/GLI2 and mTOR pathways

Gastric adenocarcinoma is the third most common cause of cancer-related death worldwide. Here we report a novel, highly-penetrant mouse model of invasive gastric cancer arising from deregulated Hedgehog/Gli2 signaling targeted to Lgr5-expressing stem cells in adult stomach. Tumor development progressed rapidly: three weeks after inducing the Hh pathway oncogene GLI2A, 65% of mice harbored in situ gastric cancer, and an additional 23% of mice had locally invasive tumors. Advanced mouse gastric tumors had multiple features in common with human gastric adenocarcinomas, including characteristic histological changes, expression of RNA and protein markers, and the presence of major inflammatory and stromal cell populations. A subset of tumor cells underwent epithelial-mesenchymal transition, likely mediated by focal activation of canonical Wnt signaling and Snail1 induction. Strikingly, mTOR pathway activation, based on pS6 expression, was robustly activated in mouse gastric adenocarcinomas from the earliest stages of tumor development, and treatment with rapamycin impaired tumor growth. GLI2A-expressing epithelial cells were detected transiently in intestine, which also contains Lgr5+ stem cells, but they did not give rise to epithelial tumors in this organ. These findings establish that deregulated activation of Hedgehog/Gli2 signaling in Lgr5-expressing stem cells is sufficient to drive gastric adenocarcinoma development in mice, identify a critical requirement for mTOR signaling in the pathogenesis of these tumors, and underscore the importance of tissue context in defining stem cell responsiveness to oncogenic stimuli.

Relationship Between Metformin Use and Recurrence and Survival in Patients With Resected Stage III Colon Cancer Receiving Adjuvant Chemotherapy: Results From North Central Cancer Treatment Group N0147 (Alliance)

BACKGROUND

Preclinical and epidemiological data suggest that metformin might have antineoplastic properties against colon cancer (CC). However, the effect of metformin use on patient survival in stage III CC after curative resection is unknown. The survival outcomes were comparable regardless of the duration of metformin use.

PATIENTS AND METHODS

Before randomization to FOLFOX (folinic acid, 5-fluorouracil, oxaliplatin) with or without cetuximab, 1,958 patients with stage III CC enrolled in the N0147 study completed a questionnaire with information on diabetes mellitus (DM) and metformin use. Cox models were used to assess the association between metformin use and disease-free survival (DFS), overall survival (OS), and the time to recurrence (TTR), adjusting for clinical and/or pathological factors.

RESULTS

Of the 1,958 patients, 1,691 (86%) reported no history of DM, 115 reported DM with metformin use (6%), and 152 reported DM without metformin use (8%). The adjuvant treatment arms were pooled, because metformin use showed homogeneous effects on outcomes across the two arms. Among the patients with DM (n = 267), DFS (adjusted hazard ratio [aHR], 0.90; 95% confidence interval [CI], 0.59-1.35; p = .60), OS (aHR, 0.99; 95% CI, 0.65-1.49; p = .95), and TTR (aHR, 0.87; 95% CI, 0.56-1.35; p = .53) were not different for the metformin users compared with the nonusers after adjusting for tumor and patient factors. The survival outcomes were comparable regardless of the duration of metformin use (<1, 1-5, 6-10, ≥11 years) before randomization (p_trend = .64 for DFS, p_trend = .84 for OS, and p_trend = .87 for TTR). No interaction effects were observed between metformin use and KRAS, BRAF mutation status, tumor site, T/N stage, gender, or age.

CONCLUSIONS

Patients with stage III CC undergoing adjuvant chemotherapy who used metformin before the diagnosis of CC experienced DFS, OS, and TTR similar to those for non-DM patients and DM patients without metformin use.

IMPLICATIONS FOR PRACTICE

The present study did not find any relationship between metformin use or its duration and disease-free survival, time to recurrence, and overall survival in a large cohort of patients with resected stage III colon cancer receiving adjuvant FOLFOX (folinic acid, fluorouracil, oxaliplatin)-based chemotherapy. This relationship was not modified by KRAS or BRAF mutation or DNA mismatch repair status. Metformin use did not increase or decrease the likelihood of chemotherapy-related grade 3 or higher adverse events.

Wnt Signaling in Normal and Malignant Stem Cells

Wnt signaling plays important roles in stem cell self-renewal and differentiation in adults as well as in embryonic development. Mutations that activate canonical Wnt/β-catenin signaling also initiate and maintain several cancer states, including colorectal cancer and leukemia, and hence Wnt inhibitors are currently being explored as therapeutic options. In this review, we summarize previous studies and update recent findings on canonical Wnt signaling and its components, as well as their roles in somatic stem cell homeostasis and maintenance of cancer initiating cells.

Generation of an inducible colon-specific Cre enzyme mouse line for colon cancer research

Current mouse models for colorectal cancer often differ significantly from human colon cancer, being largely restricted to the small intestine. Here, we aim to develop a colon-specific inducible mouse model that can faithfully recapitulate human colon cancer initiation and progression. Carbonic anhydrase I (Car1) is a gene expressed uniquely in colonic epithelial cells. We generated a colon-specific inducible Car1^CreER knock-in (KI) mouse with broad Cre activity in epithelial cells of the proximal colon and cecum. Deletion of the tumor suppressor gene Apc using the Car1^CreER KI caused tumor formation in the cecum but did not yield adenomas in the proximal colon. Mutation of both Apc and Kras yielded microadenomas in both the cecum and the proximal colon, which progressed to macroadenomas with significant morbidity. Aggressive carcinomas with some invasion into lymph nodes developed upon combined induction of oncogenic mutations of Apc, Kras, p53, and Smad4 Importantly, no adenomas were observed in the small intestine. Additionally, we observed tumors from differentiated Car1-expressing cells with Apc/Kras mutations, suggesting that a top-down model of intestinal tumorigenesis can occur with multiple mutations. Our results establish the Car1^CreER KI as a valuable mouse model to study colon-specific tumorigenesis and metastasis as well as cancer-cell-of-origin questions.

SOX9-regulated cell plasticity in colorectal metastasis is attenuated by rapamycin

The cancer stem cell (CSC) hypothesis proposes a hierarchical organization of tumors, in which stem-like cells sustain tumors and drive metastasis. The molecular mechanisms underlying the acquisition of CSCs and metastatic traits are not well understood. SOX9 is a transcription factor linked to stem cell maintenance and commonly overexpressed in solid cancers including colorectal cancer. In this study, we show that SOX9 levels are higher in metastatic (SW620) than in primary colorectal cancer cells (SW480) derived from the same patient. This elevated expression correlated with enhanced self-renewal activity. By gain and loss-of-function studies in SW480 and SW620 cells respectively, we reveal that SOX9 levels modulate tumorsphere formation and self-renewal ability in vitro and tumor initiation in vivo. Moreover, SOX9 regulates migration and invasion and triggers the transition between epithelial and mesenchymal states. These activities are partially dependent on SOX9 post-transcriptional modifications. Importantly, treatment with rapamycin inhibits self-renewal and tumor growth in a SOX9-dependent manner. These results identify a functional role for SOX9 in regulating colorectal cancer cell plasticity and metastasis, and provide a strong rationale for a rapamycin-based therapeutic strategy.

Lentivirus-mediated somatic recombination and development of a novel mouse model for sporadic colorectal cancer

In this study, we have developed a novel mouse model for sporadic colorectal cancer (CRC) by utilizing APC conditional knockout (Apc(CKO) ) mouse and lentivirus encoding Cre recombinase and a reporter gene (EGFP or LacZ). Lentiviral transduction of colonic crypt stem cells allowed for the long-term expression of reporter gene as well as excision of floxed Apc alleles, which resulted in tumor development. Tumors represented adenoma stages along with the nuclear accumulation of β-catenin. Loss of E-cadherin at the cellular junctions and strong expression of Vimentin suggested the sign of active epithelial-mesenchymal transition. Moreover, nuclear staining of Ki67 inside epithelial cells of aberrant crypts demonstrated their higher proliferative nature. Erratic downstream signaling of activated Wnt/β-catenin, AKT/mTOR, and Notch pathways provided strong evidence towards the higher proliferative index of epithelial cells inside the aberrant crypts. These results do recapitulate the findings of previous APC mutant mouse models. Our model represents sporadic CRC more precisely as (i) tumors result from somatic mutations but not from germline; (ii) tumors develop in colon not in small intestine; (iii) few tumors develop at the distal end of colons. Additionally, our model allows for the long-term expression of the gene(s), which get integrated into the host cell genome and provides an ability to track the tumor growth. © 2016 Wiley Periodicals, Inc.

Tumor suppressive role of sestrin2 during colitis and colon carcinogenesis

The mTOR complex 1 (mTORC1) and endoplasmic reticulum (ER) stress pathways are critical regulators of intestinal inflammation and colon cancer growth. Sestrins are stress-inducible proteins, which suppress both mTORC1 and ER stress; however, the role of Sestrins in colon physiology and tumorigenesis has been elusive due to the lack of studies in human tissues or in appropriate animal models. In this study, we show that human SESN2 expression is elevated in the colon of ulcerative colitis patients but is lost upon p53 inactivation during colon carcinogenesis. In mouse colon, Sestrin2 was critical for limiting ER stress and promoting the recovery of epithelial cells after inflammatory injury. During colitis-promoted tumorigenesis, Sestrin2 was shown to be an important mediator of p53's control over mTORC1 signaling and tumor cell growth. These results highlight Sestrin2 as a novel tumor suppressor, whose downregulation can accelerate both colitis and colon carcinogenesis.

Multistage vector delivery of sulindac and silymarin for prevention of colon cancer

Familial adenomatous polyposis (FAP) is an inherited condition secondary to germline mutations in the APC gene, thus resulting in the formation of hundreds of colonic adenomas that eventually progress into colon cancer. Surgical removal of the colon remains the only treatment option to avoid malignancy, as long-term exposure to chemopreventive agents such as sulindac (a non-steroidal anti-inflammatory drug) and silymarin (phytoestrogen) is not feasible. Here, we have developed a multistage silicon-based drug delivery platform for sulindac and silymarin that preferentially interacts with colon cancer cells as opposed to normal intestinal mucosa. Preferential binding and internalization of these drugs into colon cancer cells was obtained using a targeting strategy against the protein meprin A, which we demonstrate is overexpressed in human colon cancer cells and in the small intestine of Apc(Min/+) mice. We propose that this delivery system could potentially be used to reduce drug-induced side effects in FAP patients, thus enabling long-term prevention of adenoma formation.

Reserve stem cells: Differentiated cells reprogram to fuel repair, metaplasia, and neoplasia in the adult gastrointestinal tract

It has long been known that differentiated cells can switch fates, especially in vitro, but only recently has there been a critical mass of publications describing the mechanisms adult, postmitotic cells use in vivo to reverse their differentiation state. We propose that this sort of cellular reprogramming is a fundamental cellular process akin to apoptosis or mitosis. Because reprogramming can invoke regenerative cells from mature cells, it is critical to the long-term maintenance of tissues like the pancreas, which encounter large insults during adulthood but lack constitutively active adult stem cells to repair the damage. However, even in tissues with adult stem cells, like the stomach and intestine, reprogramming may allow mature cells to serve as reserve ("quiescent") stem cells when normal stem cells are compromised. We propose that the potential downside to reprogramming is that it increases risk for cancers that occur late in adulthood. Mature, long-lived cells may have years of exposure to mutagens. Mutations that affect the physiological function of differentiated, postmitotic cells may lead to apoptosis, but mutations in genes that govern proliferation might not be selected against. Hence, reprogramming with reentry into the cell cycle might unmask those mutations, causing an irreversible progenitor-like, proliferative state. We review recent evidence showing that reprogramming fuels irreversible metaplastic and precancerous proliferation in the stomach and pancreas. Finally, we illustrate how we think reprogrammed differentiated cells are likely candidates as cells of origin for cancers of the intestine.

TSC2/mTORC1 signaling controls Paneth and goblet cell differentiation in the intestinal epithelium

The intestinal mucosa undergoes a continual process of proliferation, differentiation and apoptosis, which is regulated by multiple signaling pathways. Notch signaling is critical for the control of intestinal stem cell maintenance and differentiation. However, the precise mechanisms involved in the regulation of differentiation are not fully understood. Previously, we have shown that tuberous sclerosis 2 (TSC2) positively regulates the expression of the goblet cell differentiation marker, MUC2, in intestinal cells. Using transgenic mice constitutively expressing a dominant negative TSC2 allele, we observed that TSC2 inactivation increased mTORC1 and Notch activities, and altered differentiation throughout the intestinal epithelium, with a marked decrease in the goblet and Paneth cell lineages. Conversely, treatment of mice with either Notch inhibitor dibenzazepine (DBZ) or mTORC1 inhibitor rapamycin significantly attenuated the reduction of goblet and Paneth cells. Accordingly, knockdown of TSC2 activated, whereas knockdown of mTOR or treatment with rapamycin decreased, the activity of Notch signaling in the intestinal cell line LS174T. Importantly, our findings demonstrate that TSC2/mTORC1 signaling contributes to the maintenance of intestinal epithelium homeostasis by regulating Notch activity.