A153 PYCRL LACTYLATION AS A POTENTIAL REGULATOR OF CANCER STEM CELL METABOLISM IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA (ESCC)

Background

Patients with esophageal malignancy have a 5-year survival rate of only 14% in Canada. This high mortality rate is due to three factors: late diagnosis, difficulty in surgically removing the tumor because of its localization, and treatment resistance. Resistance can be developed after prolonged exposure to anti-cancer drugs and/or radiation. Indeed 30% of patients will not respond to treatment or will relapse. Resistance has been mainly ascribed to the presence of cancer stem cells (CSCs) inside the tumor. However, no treatment specifically directed against CSCs is available to patients.

Purpose

Thus, targeting CSCs is a promising strategy to improve the survival of patients with esophageal squamous cell carcinoma (ESCC), the most common type of esophageal cancer worldwide. Therefore, a better understanding of the molecular mechanisms occurring during long-term exposure to cancer treatments is imperative.

Method

Herein, we developed an unbiased approach to identify new players in chemotherapy and radiotherapy resistance development in ESCC. We established radio- (R), chemo- (C), and radiochemo-resistant (RC) human ESCC cell lines using prolonged exposure to radiation and/or chemotherapeutic agent 5-FU, respectively.

Result(s)

The enrichment in CSCs in all treated cell lines was demonstrated by an increase of ALDH1^high cells and CD24^high/CD44^high cells in flow cytometry. We then used a proteomic approach to identify new players in treatment resistance. Interestingly, pathway analysis pointed out to alterations in energy metabolism as well as amino acid metabolism. Seahorse assays showed that resistant cell lines have a lower respiration rate than control cells, while glycolysis remains unchanged. To further characterize these metabolic changes, we performed an unbiased metabolomic study and confirmed a decrease in amino acid levels such as proline, in resistant cell lines. Recently, metabolic regulation has been linked to a new post-translational modification, lactylation. Proteomic data were re-analyzed looking for lactylated protein and found, amongst others, PYCRL, an enzyme implicated in proline biosynthesis, as one of the most differentially lactylated proteins in treated cell lines compared to control. PYCRL lactylation was confirmed using immuno-fluorescence colocalization and immuno-precipitation. Lastly, using AlphaFold, preliminary results point toward the importance of PYCRL lactylation impairing PYCRL homomultimerization.

Conclusion(s)

To conclude, our results suggest an important role of proline metabolism following long-term treatment in ESCC. This study is a first step toward the identification of new targets to fight treatment resistance in ESCC patients.

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CAG, CIHR, Other

Please indicate your source of funding;

FRQ

Disclosure of Interest

None Declared

A10 OVEREXPRESSION OF ASCL2 ALTERS DIFFERENTIATION, CELL CYCLE AND RESISTANCE TO ANTI-CANCER TREATMENT IN ESOPHAGEAL ORGANOIDS

Background

The esophagus is in constant contact with the austere environment caused by food and gastric reflux. It is protected by a squamous epithelium which maintenance is provided by a rare subpopulation of basal cells: Keratin 15+ (Krt15+) stem cells. However, little is known about the mechanisms underlying the expansion and the function of these stem cells. It was shown that the transcription factor ASCL2 is strongly upregulated in Krt15+ cells compared to Krt15- cells. Interestingly, ASCL2 is a gene target of the Wnt/β-catenin pathway, which acts as a regulator of proliferation and maintenance of the stemness state.

Purpose

The ultimate goal of my research project is to determine the role of ASCL2 in the maintenance of esophageal stem cells. To do so, I will investigate the role of ASCL2 in esophageal epithelial biology.

Method

Lentiviral infection approach was used to obtain mouse esophageal organoids overexpressing ASCL2 (ASCL2^OE). Organoid culture, immunostaining (such as IF and H&E), qPCR, WB, mass spectrometry and proliferation assay were used to characterize the effect of ASCL2^OE on morphology, differentiation, proliferation, self-renewal, and gene expression.

Result(s)

ASCL2^OE severely altered the morphology of organoids, which were smaller and less differentiated. Defects in differentiation was investigated by IF which showed that some cells expressed both p63 and K13, respectively basal and suprabasal markers. Thus, cells seem to be blocked in an intermediate state of differentiation suggesting a default in cell fate decision. Mass spectrometry analysis confirmed a change in biological processes related to differentiation of keratinocytes and of epithelial cells. We also investigated the role of ASCL2 in self-renewal and observed that organoid formation rate (OFR) was reduced in ASCL2^OE organoids. Furthermore, proliferation was also reduced in WST-1 and EdU assays. We then observed significant changes in the cell cycle by flow cytometry: there is an increased in the number of cells in G0/G1 and a major decrease in G2/M cells, suggesting a blockade in G1. Interestingly, CDNK2a (p16INK4a), an inhibitor of cell cycle progression, was increased in our mass spectrometry results. Finally, ASCL2 could also play a role in radio and chemoresistance of Krt15+ stem cells, as ASCL2^OE organoids are less sensitive to radiation and chemotherapy agents than control.

Conclusion(s)

ASCL2 could play a role in orchestrating cell fate decision in the esophageal epithelium as ASCL2^OE organoids showed alteration in differentiation, proliferation, and cell cycle.

Please acknowledge all funding agencies by checking the applicable boxes below

Other

Please indicate your source of funding;

NSERC, Canada Research Chairs and CRCHUS scolarship

Disclosure of Interest

None Declared

A16 ESOPHAGEAL ORGANOID PROLIFERATION AND DIFFERENTIATION ARE ALTERED BY LOSS OF MSH2

Background

The stratified epithelium of the esophagus includes Krt15+ basal stem cells that display self-renewing and regenerative capacity, and multipotency. However, the mechanisms that specifically control their functions remain unknown. Interestingly, RNA sequencing and GSEA revealed an enrichment of a gene set associated with DNA repair in Krt15+ cells vs Krt15- cells. We also observed that Msh2 (DNA mismatch repair pathway) is the most significantly upregulated gene in Krt15+ stem cells.

Aims

To determine the effect of Msh2 loss on self-renewal and differentiation of esophageal organoids.

Methods

Esophageal epithelial cells were isolated from a wild-type mouse. Using flow cytometry, esophageal Krt15+ (GFP+) and Krt15- (GFP-) cells were sorted from Krt15-CrePR1 (R26^mT/mG) mice. All cell populations were grown as organoids and Msh2 was depleted using a CRISPR/Cas9 approach. Impact of Msh2 loss on self-renewal and differentiation in esophageal epithelial organoids was evaluated through organoid formation assays, WST-1 proliferation assays and histological analysis.

Results

At baseline, organoids depleted for Msh2 formed more poorly differentiated and less well-differentiated organoids than controls. Lower expression of differentiation gene Krt13 was also observed in Msh2-depleted organoids, confirming an altered differentiation pattern. Furthermore, these organoids showed a higher organoid formation rate and proliferation by WST-1 assay, suggesting that self-renewal capacity and viability are increased when Msh2 is depleted. Interestingly, following radiation, organoids depleted for Msh2 showed higher residual levels of p-H2AX (DNA damage marker), suggesting that their capacity to cope with DNA damages is altered. As mentioned above, we previously reported that Msh2 is the most upregulated gene in Krt15+ vs Krt15- cells. Therefore, to determine if Msh2 role is distinct in both populations, we depleted Msh2 in Krt15+ and Krt15- cells-derived organoids. Interestingly, our preliminary results suggest that Msh2 deletion led to increased p-H2AX and decreased Krt13 levels in Krt15+ organoids but not in Krt15- organoids.

Conclusions

Our results show that Msh2 is potentially a key contributor of esophageal stemness in homeostatic and injured conditions.

Funding Agencies

CIHRCanada Research Chair

A17 TRP53 REGULATES ESLF-RENEWAL AND CELL DIFFERENTIATION IN KRT15+ INTESTINAL STEM CELLS

Background

Different pools of stem cells assure the intestinal epithelium homeostasis and regeneration. We recently reported that Krt15+ intestinal cells harbor self-renewal, multipotent and regenerative capacities, characteristics consistent with a stem cell population. p53 has been associated with the development of various types of cancer, and recent studies suggested it also regulates adult stem cell behavior in some tissues. However, its role in the maintenance of intestinal stem cells has not been explicitly covered. Therefore, we hypothesize that Trp53 loss specifically in Krt15+ intestinal stem cells will perturb the epithelial homeostasis and differentiation.

Aims

Identify the role of Trp53 in the regulation of intestinal stem cell and intestinal homeostasis

Methods

To induce Trp53 loss specifically in Krt15+ cells, we generated Krt15 CrePR1;Trp53fl/fl ( Krt15△Trp53) mice and induced Cre recombination by injecting RU486 (PR agonist). Mice were euthanized after Cre recombination at different time points. Organoid cultures were established from control and experimental mice.

Results

Two-month post Cre recombination, we observed no major morphological changes in the intestinal epithelium. However, we observed that crypts isolated from Krt15△Trp53 mice died rapidly and had difficulties forming organoids. When hyperactivating the Wnt/beta-catenin pathway through CHIR treatment, we observed that budding capacity was maintained in experimental organoids while control organoids formed mainly cysts as expected. We also observed an increased in Paneth cell-specific genes, suggesting an enrichment in Paneth cells. Interestingly, the expression of EpHB2 receptor and its target genes was decreased in organoids derived from Krt15△Trp53 mice. Ephrin signaling plays a crucial role in intestinal homeostasis by regulating cell position and migration, and previous studies suggest that ephrin receptors are a target of p53. Indeed, twelve-month post Cre recombination, altered architecture of crypt and villi was noted in the small intestinal epithelium of Krt15△Trp53 mice. Differentiation towards secretory cell types, specifically Paneth, goblet, and tuft cells, are significantly increased in Krt15△Trp53 mice. Interestingly, we also observed crypt cells expressing both goblet and Paneth cell markers suggesting dysfunction in the cell fate decision. Finally, decreased Notch pathway activation was also observed supporting that Trp53 loss, specifically in Krt15+ cells, leads to a dysregulation of secretory cell fate.

Conclusions

Loss of Trp53 specifically in Krt15+ cells affects the small intestinal homeostasis and secretory cell differentiation. Decreased Notch and ephrin signaling support the possible role of Trp53 in cell fate decision and self-renewal.

Funding Agencies

None

A21 OVEREXPRESSION OF ASCL2 ALTERS DIFFERENTIATION IN ESOPHAGEAL ORGANOIDS

Background

The first population of stem cells in the esophageal epithelium was recently identified with the marker Keratin 15 ( Krt15). However, little is known about the mechanisms underlying the expansion and the function of these stem cells. It was shown that the transcription factor ASCL2 is upregulated in Krt15+ cells compared to Krt15- cells. Interestingly, ASCL2 is a gene target of the Wnt/β-catenin pathway, which acts as a regulator of proliferation and maintenance of the stemness state. The ultimate goal of my research project is to determine the role of ASCL2 in the maintenance of esophageal stem cells and to identify its binding partners.

Aims

Investigate the role of ASCL2 in esophageal epithelial biology.

Methods

Lentiviral infection approach was used to obtain mouse esophageal organoids overexpressing ASCL2. Organoid culture, immunostaining (such as IF and H&E), qPCR, WB and proliferation assay were used to characterize the effect of ASCL2 overexpression on morphology, differentiation, proliferation, self-renewal and gene expression.

Results

First, ASCL2 overexpression was confirmed by WB. Interestingly, the morphology of organoid overexpressing ASCL2 was severely altered: organoids were smaller and less differentiated. Defect in differentiation was investigated by qPCR and IF using relevant markers such as p63, Krt13, Wnt5a and NT5E. Indeed, we observed an increase in basal marker ( p63), a decrease in suprabasal markers ( Krt13, Wnt5a) and in a stem cell marker ( NT5E). We also investigated the role of ASCL2 in self-renewal and observed that organoid formation capacity was reduced in ASCL2-overexpressing organoids. Furthermore, proliferation was also reduced in WST-1 assays. We also observed lower expression of the gene Top2a, a recently identified marker of the proliferative basal cell population in the human esophagus. Finally, we observed significant changes in the expression of genes associated with quiescent stem cells (Clu, ZFP36L2 and Anxa1).

Conclusions

ASCL2 overexpression alters differentiation and proliferation in organoids. ASCL2 could play a role in orchestrating cell fate decision in the esophageal epithelium.

Funding Agencies

NSERC, Canada Research Chair

A3 TARGETING PROLINE METABOLISM TO OVERCOME TREATMENT RESISTANCE IN ESOPHAGEAL CANCER

Background

Patients with esophageal malignancy have a 5-year survival rate of only 14% in Canada. This high mortality rate is due to three factors: late diagnosis, difficulty to surgically remove the tumor due to its localization and treatment resistance. Treatment resistance has been ascribed to the presence of cancer stem cells (CSCs) inside the tumor. However, no treatment specifically directed against CSCs is available to patients. Therefore, targeting CSCs is a promising strategy to improve survival of patients with esophageal squamous cell carcinoma (ESCC), the most common type of esophageal cancer worldwide.

Aims

Herein, we developed an unbiased approach to identify new players in chemotherapy and radiotherapy resistance in ESCC.

Methods

We established radioresistant (RR), chemoresistant (CR) and radiochemoresistant (RCR) human ESCC cell lines using weekly radiation and/or continuous treatment with increasing doses of chemotherapeutic agent 5-FU. We validated that the process of resistance acquisition correlates with enrichment in CSCs as revealed by higher ALDH1 expression, and increased proportion of ALDH1^high cells and CD24^high/CD44^high cells in flow cytometry. We then used a proteomic approach to identify new players in treatment resistance.

Results

Interestingly, pathway analysis demonstrated enrichment in energy metabolism as well as amino acid metabolism. Seahorse assays showed a more quiescent metabolism in all three types of resistant cells compared to the control cell line. More precisely, resistant cell lines have a lower respiration rate than control cell line, while glycolysis remains unchanged. Surprisingly, our results show a metabolic rewiring very different from the well-known Warburg effect. To further characterise these metabolic changes, we performed an unbiased metabolomic pilot study and confirmed a decrease in amino acid levels such as proline, in resistant cell lines. Preliminary data show that when cultured in DMEM with proline addition, CD44^high/CD24^high cell proportion is decreased in control and RR cell lines suggesting that proline is a key regulator of CSC population in ESCC.

Conclusions

To conclude, our results suggest an important role of metabolism in ESCC treatment resistance. This study is a first step towards the identification of new targets to fight treatment resistance in ESCC patients.

Funding Agencies

CAG, CIHRCanada research chair TIER 2

Modeling Epithelial Homeostasis and Reactive Epithelial Changes in Human and Murine Three-Dimensional Esophageal Organoids

The homeostatic proliferation-differentiation gradient in the esophageal epithelium is perturbed under inflammatory disease conditions such as gastroesophageal reflux disease and eosinophilic esophagitis. Herein we describe the protocols for rapid generation (<14 days) and characterization of single-cell-derived, three-dimensional (3D) esophageal organoids from human subjects and mice with normal esophageal mucosa or inflammatory disease conditions. While 3D organoids recapitulate normal epithelial renewal, proliferation, and differentiation, non-cell autonomous reactive epithelial changes under inflammatory conditions are evaluated in the absence of the inflammatory milieu. Reactive epithelial changes are reconstituted upon exposure to exogenous recombinant cytokines. These changes are modulated pharmacologically or genetically ex vivo. Molecular, structural, and functional changes are characterized by morphology, flow cytometry, biochemistry, and gene expression analyses. Esophageal 3D organoids can be translated for the development of personalized medicine in assessment of individual cytokine sensitivity and molecularly targeted therapeutics in esophagitis patients © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Generation of esophageal organoids from biopsy or murine esophageal epithelial sheets Basic Protocol 2: Propagation and cryopreservation of esophageal organoids Basic Protocol 3: Harvesting of esophageal organoids for RNA isolation, immunohistochemistry, and evaluation of 3D architecture Basic Protocol 4: Modeling of reactive epithelium in esophageal organoids.

Generation and Characterization of Patient-Derived Head and Neck, Oral, and Esophageal Cancer Organoids

Esophageal cancers comprise adenocarcinoma and squamous cell carcinoma, two distinct histologic subtypes. Both are difficult to treat and among the deadliest human malignancies. We describe protocols to initiate, grow, passage, and characterize patient-derived organoids (PDO) of esophageal cancers, as well as squamous cell carcinomas of oral/head-and-neck and anal origin. Formed rapidly (<14 days) from a single-cell suspension embedded in basement membrane matrix, esophageal cancer PDO recapitulate the histology of the original tumors. Additionally, we provide guidelines for morphological analyses and drug testing coupled with functional assessment of cell response to conventional chemotherapeutics and other pharmacological agents in concert with emerging automated imaging platforms. Predicting drug sensitivity and potential therapy resistance mechanisms in a moderate-to-high throughput manner, esophageal cancer PDO are highly translatable in personalized medicine for customized esophageal cancer treatments. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Generation of esophageal cancer PDO Basic Protocol 2: Propagation and cryopreservation of esophageal cancer PDO Basic Protocol 3: Imaged-based monitoring of organoid size and growth kinetics Basic Protocol 4: Harvesting esophageal cancer PDO for histological analyses Basic Protocol 5: PDO content analysis by flow cytometry Basic Protocol 6: Evaluation of drug response with determination of the half-inhibitory concentration (IC₅₀ ) Support Protocol: Production of RN in HEK293T cell conditioned medium.

A2 KRT15+ TUMOR CELLS AS PUTATIVE CANCER STEM CELLS IN ESOPHAGEAL CANCER

Background

Esophageal cancer is a particularly deadly cancer with a 5-year survival rate of only 14% in Canada. Treatment resistance ascribed for at least 30% of the death. The acquisition of resistance to radio- and chemotherapy is mostly attributed to the presence of cancer stem cells (CSCs) and their persistence following classical treatments. CSCs are a subpopulation of tumor cells with high self-renewal and multipotent capacity which amongst others contribute to tumor heterogeneity. Our previous work identified Krt15+ esophageal cells as a rare and long-lived subpopulation of basal cells with higher self-renewal and multipotent capacities than other basal cells. Furthermore, preliminary observations suggest that Krt15+ cells could act as the cell-of-origin for ESCC, the most prevalent type of esophageal cancer worldwide. Though, we still ignore the role of Krt15+ cells in later stages of esophageal cancer such as treatment resistance and if therefore, they could act as CSC.

Aims

Determine if Krt15+ cells act as CSCs in ESCC patients and if they could contribute to treatment resistance.

Methods

To do so, we used Krt15-CrePR1;R26mT/mG mice treated with the carcinogen 4 Nitroquinoline-1-oxide (4NQO) in their drinking water for 16 weeks to induce ESCC. Twelve weeks following the beginning of 4NQO treatment, we induced Cre recombination with RU486, a PR1 agonist, leading to GFP expression specifically in Krt15+ cells. Following 4NQO treatment, mice were put back on normal water for 8 to 12 weeks allowing tumors to grow. At euthanasia, esophageal tumor cells were FACS sorted to isolate Krt15+ (GFP+) and Krt15- (GFP-) cells, which were then grown as tumoroids.

Results

We first validated that 4NQO successfully induced the formation of esophageal lesions in our model, which comprises Krt15+ and Krt15- tumor cells. Tumoroids were then successfully derived from these FACS-sorted cell populations. We demonstrated the increase of CSC-like cells within Krt15+ tumoroids compared to Krt15- tumoroids by measuring the presence of CD44highCD24high cells, two well-known CSC markers, by flow cytometry. Interestingly, Krt15+ and Krt15- tumoroids are histologically distinct. As observed for normal cells, Krt15+ tumoroids appeared as more multipotent and heterogenous than Krt15- tumoroids. Furthermore, Krt15+ tumoroids display higher hyperplasia than Krt15- tumoroids suggesting that Krt15+ tumor cells are functionally distinct from Krt15- tumor cells.

Conclusions

Krt15+ tumoroids display higher CSC content and hyperplastic capacity suggesting their potential role in esophageal cancer. With this project, we aim to highlight the role of Krt15+ cells in treatment resistance and put forward new targets to overcome this deadly issue in ESCC patients.

Funding Agencies

CAGCanada research chair TIER 2

A53 STUDYING THE ROLE OF ASCL2 IN THE ESOPHAGEAL EPITHELIUM USING ORGANOIDS

Background

The esophagus is lined with a stratified squamous epithelium that assure protection against the austere environment found in the esophageal lumen. The maintenance of this epithelium is ensured by a rare population of cells: stem cells. Those cells have increased capacity of self-renewal and multipotency, which is the capacity to give rise to every cell types of a tissue. The marker Krt15 was used to identify the first stem cell population in the esophagus. Krt15+ cells display an extended lifespan and they are radioresistant, multipotent and capable of self-renewal. Moreover, it was observed by RNA sequencing that the expression of the transcription factor ASCL2 is strongly increased in Krt15+ cells compared to Krt15- cells. Interestingly, ASCL2 is necessary to maintain the stemness of Lgr5+ intestinal stem cells. It is also a target of the Wnt/β-catenin pathway. The overall goal of this project is to determine the role of ACSL2 in the maintenance of esophageal stem cells and to identify its binding partners since ASCL2 needs to dimerize to efficiently bind DNA.

Aims

Confirm that esophageal organoids are adapted to study ASCL2 in the esophagus.

Methods

Esophageal organoids were established from esophageal epithelial cells from wildtype mice. Following this, organoids were treated with an inhibitor of the Notch pathway (DAPT) to induce hyperplasia or infected with lentiviruses to invalidate Ascl2 (CRISPR/Cas9 approach).

Results

To validate that Ascl2 plays an important role in esophageal cell proliferation, Notch pathway was inhibited through DAPT treatment in esophageal organoids to induce hyperplasia, which was confirmed by increased number of proliferative cells (Ki-67+). ASCL2 protein expression was also increased in DAPT-treated organoids supporting its role in proliferation and confirming that organoid is a good model to study ASCL2 role in esophageal epithelial cells. In this optic, organoids lines invalidated for Ascl2 (CRISPR/Cas9 approach) were established. Our preliminary results suggest that Ascl2 loss affects cell proliferation and organoid size under normal conditions.

Conclusions

The expression of ASCL2 correlates with hyperplasia which supports its role in esophageal epithelium homeostasis.

Funding Agencies

Canada research chair et NSERC

A27 MSH2 CONTRIBUTES TO SELF-RENEWAL OF ESOPHAGEAL ORGANOIDS

Background

The esophagus is lined by a stratified epithelium in which basal cells can proliferate and undergo differentiation while migrating towards the lumen. In the basal layer, we also find Krt15+ stem cells that are multipotent, self-renewing and that have regenerative capacity. However, mechanisms that specifically control their functions remain unknown. Interestingly, RNA sequencing and gene set enrichment analysis (GSEA) revealed an enrichment of a gene set associated with DNA repair in Krt15+ cells in comparison to Krt15- cells. We also observed that Msh2 (MutS homolog 2), a gene associated with the DNA mismatch repair (MMR) mechanism, is the most significantly upregulated gene in Krt15+ stem cells.

Aims

To determine the impact of Msh2 loss on self-renewal of esophageal organoids under normal and stress conditions.

Methods

Esophageal epithelial cells were isolated from a wild type mouse and grown as organoids, a 3D culture model that supports stem cell growth and morphologically reproduces the tissue of origin. To determine Msh2 role in esophageal epithelium, this gene was deleted through a CRISPR/Cas9 approach in mouse esophageal organoids. Invalidation was confirmed by Western Blot and immunofluorescence. Impact of Msh2 loss on self-renewal was measured under normal condition and following radiation.

Results

At baseline, loss of Msh2 decreases the organoid formation rate of esophageal organoids. Furthermore, following high-dose radiation, Msh2 deficient cells form less organoids than control cells. These results suggest that self-renewal capacity is reduced when Msh2 is depleted. Interestingly, following radiation, organoids depleted for Msh2 show higher residual levels of p-H2AX, a DNA damage marker, and p-ATM, a key kinase in DNA damage response, suggesting that their capacity to cope with DNA damages is reduced.

Conclusions

Our results suggest that Msh2 contributes to maintaining genomic integrity in esophageal cells and that contributes to maintaining self-renewal capacity of basal cells and possibly esophageal stem cells.

Funding Agencies

Canada Research Chair.

A149 TRP53 LOSS IN KRT15+ INTESTINAL STEM CELLS SEVERELY AFFECTS SECRETORY CELL FATE AND SELF-RENEWAL

Background

Intestinal epithelium homeostasis is maintained by two main populations of stem cells: Lgr5+ and reserve stem cells. Under injury, cell plasticity has been observed in progenitor and differentiated cells. We recently reported that Krt15+ cells are present in small intestinal and colon epithelia, and harbor self-renewal, multipotent and regenerative capacities. As in Lgr5+and reserve stem cells, hyperactivation of Wnt/b-catenin pathway in Krt15+ stem cells lead to tumor formation in the intestinal epithelium. While these intestinal stem cell populations can act as tumor-initiating cells in sporadic colon cancer, little is known about the cell-of-origin of colitis-associated colon cancer (CAC). TP53 alteration is reported as an early event in CAC. Therefore, we hypothesize that Trp53 loss specifically in Krt15+ stem cells will perturb the epithelial homeostasis and lead to tumor formation.

Aims

Identify if Krt15+ cells may act as the cell-of-origin in colitis-associated colorectal cancer

Methods

To induce Trp53 loss specifically in Krt15+ cells, we generated Krt15-CrePR1;Trp53fl/fl (Krt15△Trp53) mice, induced Cre recombination by injecting RU486 (PR agonist) and euthanized the mice at different time points following recombination.

Results

Results

Twelve-month following Cre recombination, adenoma formation was observed in a small proportion of Krt15△Trp53 mice. Though, Trp53 loss in Krt15+ cells severely perturbed the small intestinal morphology in every mouse studied. Increased crypt length and villi width was observed in Krt15△Trp53 vs control mice without any changes in cell proliferation. We also observed an increased number of Tuft cells and goblet cells in the villi of experimental mice. In the crypt, higher number of Paneth cells and aberrant presence of goblet cells were noted in Krt15△Trp53mice. Interestingly, we also observed crypt cells expressing goblet and Paneth cell markers and decreased Notch pathway activation suggesting dysregulation of secretory cell fate. Krt15△Trp53 mice display higher number of fibroblasts in the villi and the submucosa, as well as thickening of the muscularis layer. Interestingly, similar observations (accumulation of secretory cells and fibrosis) have been reported in IBD patients, supporting the possible role of Krt15+ cells in CAC. Furthermore, crypts isolated from Krt15△Trp53 mice rapidly die when seeded as organoids vs crypts from control mice, suggesting that the alterations observed in vivo in Paneth cells might interfere with the stem cell niche and therefore reduce self-renewal of Krt15+ cells.

Conclusions

Trp53 loss specifically in Krt15+ cells impaired cell fate decision, induced secretory cell hyperplasia, affected self-renewal ability, and initiated adenoma formation supporting the possible role of Krt15+ cells in gut inflammation and cancer.

Funding Agencies

Canada Research Chair, Cancer Research Society, CFI

A31 ALTERED SMALL INTESTINAL EPITHELIAL HOMEOSTASIS AND CELL FATE DECISION UPON LOSS OF TRP53 IN KRT15+ INTESTINAL STEM CELLS

Background

Intestinal homeostasis is mainly maintained by two groups of stem cells: Lgr5+ stem cells and reserve stem cells. Recently, we reported that Krt15+ cells are present in small intestinal and colon epithelia, and harbor self-renewal, multipotent and regenerative capacities. Initiation of sporadic colorectal cancer has been described in Krt15+ stem cells, Lgr5+ stem cells and reserve stem cells following the loss of Apc. While these intestinal stem cell (ISC) populations can act as tumor-initiating cells in sporadic colon cancer, little is known about the cell-of-origin of colitis-associated colon cancer. TP53 alteration is reported as an early event in colitis-associated colon cancer cases. Therefore, we hypothesize that Trp53 loss specifically in Krt15+ stem cells will perturb the epithelial homeostasis and lead to tumor formation

Aims

Identify if Krt15+ cells may act as the cell-of-origin in colitis-associated colorectal cancer.

Methods

To induce Trp53 loss specifically in Krt15+ cells, we generated Krt15-CrePR1;Trp53fl/fl (Krt15△Trp53) mice, induced Cre recombination by injecting RU486 (PR agonist) and euthanized the mice after 12 months following recombination. Histological analysis was performed on small intestinal tissues.

Results

Results: Trp53 loss in Krt15+ cells severely perturbed small intestinal morphology. Increased crypt (proliferative compartment) length correlated with no proliferation changes surprisingly but higher number of Paneth cells and abnormal presence of goblet cells. Interestingly, we also observed the presence of cells expressing both Paneth and goblet cells markers suggesting a deregulation of secretory cell fate decision. Decreased expression of Hes1 and increased β-catenin nuclear expression in the small intestinal crypt of Krt15△Trp53 mice suggest altered Notch and Wnt signaling. Furthermore, villi (differentiated compartment) were significantly wider and shorter, and showed accumulation of activated fibroblasts. Finally, we observed inflammatory lesions as well as adenomas in the small intestine of Krt15△Trp53 mice which remain to be further characterized

Conclusions

Conclusion: In summary, Trp53 loss specifically in Krt15+ cells impaired cell fate decision, induced inflammation and initiated tumor formation. Overall, these results suggest that Krt15+ cells could act as the cell-of-origin of colitis-associated colon cancer.

Funding Agencies

Cancer Research Society, CRC Tier 2

A7 DEVELOPING NEW TOOLS TO IDENTIFY NOVELS TARGETS TO OVERCOME TREATMENT RESISTANCE IN ESOPHAGEAL CANCER

Background

In Canada, patients with esophageal cancer have the 2nd worst 5-year survival rate (14%). Esophageal squamous cell carcinoma (ESCC) is the most common esophageal cancer type worldwide. Its high mortality rate is partly due to the treatment resistance acquired by patients, which has mostly been attributed to the presence of cancer stem cells (CSCs). Therefore, targeting CSCs is a promising strategy to improve treatment and survival of ESCC patients. CSCs are a subpopulation of tumor cells presenting high self-renewal and multipotent capacities, and therefore largely contribute to tumor heterogeneity in addition to treatment resistance.

Aims

In this study, we aim to establish human ESCC cell lines resistant to radiotherapy (TE15RR), chemotherapy (TE15CR) and both (TE15RCR), and study the relationship between resistance acquisition and CSC properties;

Methods

To do so, we exposed human ESCC cell line TE15 to chronic doses of radiotherapy (2 Gy/week for a total dose of 60 Gy) and/or increasing doses of chemotherapy (5-FU (1, 2, 5, 10 and 15mM)). We harvested samples at different time points to fully investigate resistance acquisition process. Then, we further validated resistance and properties of the resistant TE15 cell lines.

Results

We confirmed that TE15RR cells are less susceptible to radiation than control cells and showed that they are more proliferative at baseline using MTT assays. Moreover, we demonstrated that TE15RR cells comprise a higher proportion of CD24high/CD44high CSC population using flow cytometry. We also found that they express higher levels of ALDH1, another well-known CSC marker, by qPCR and Western Blot. Our preliminary observations also suggest a higher invasive phenotype in TE15RR cells in limited dilution spheroid assay than in control cells supporting that TE15RR cells display CSC-like properties. TE15CR and TE15RCR cell lines were validated using similar approaches. Finally, mass spectrometry was performed to compare the proteomic profile of the resistant cell lines to the control cell line in order to identify key players in treatment resistance acquisition.

Conclusions

Brief, we developed radioresistant, chemoresistant and radiochemoresistant human ESCC cell lines and demonstrated that resistance acquisition correlates with CSC enrichment. Mass spectrophotometry revealed significant proteomic differences between resistant and control cell lines, which should lead to the identification of novel targets to overcome resistance in ESCC patients.

Funding Agencies

Canada research chair TIER 2

Posttranscriptional regulation of colonic epithelial repair by RNA binding protein IMP1/IGF2BP1

RNA binding proteins, including IMP1/IGF2BP1, are essential regulators of intestinal development and cancer. Imp1 hypomorphic mice exhibit gastrointestinal growth defects, yet the specific role for IMP1 in colon epithelial repair is unclear. Our prior work revealed that intestinal epithelial cell-specific Imp1 deletion (Imp1 ^{Δ IEC} ) was associated with better regeneration in mice after irradiation. Here, we report increased IMP1 expression in patients with Crohn's disease and ulcerative colitis. We demonstrate that Imp1 ^{Δ IEC} mice exhibit enhanced recovery following dextran sodium sulfate (DSS)-mediated colonic injury. Imp1 ^{Δ IEC} mice exhibit Paneth cell granule changes, increased autophagy flux, and upregulation of Atg5. In silico and biochemical analyses revealed direct binding of IMP1 to MAP1LC3B, ATG3, and ATG5 transcripts. Genetic deletion of essential autophagy gene Atg7 in Imp1 ^{Δ IEC} mice revealed increased sensitivity of double-mutant mice to colonic injury compared to control or Atg7 single mutant mice, suggesting a compensatory relationship between Imp1 and the autophagy pathway. The present study defines a novel interplay between IMP1 and autophagy, where IMP1 may be transiently induced during damage to modulate colonic epithelial cell responses to damage.

Three-Dimensional Organoids Reveal Therapy Resistance of Esophageal and Oropharyngeal Squamous Cell Carcinoma Cells

BACKGROUND & AIMS

Oropharyngeal and esophageal squamous cell carcinomas, especially the latter, are a lethal disease, featuring intratumoral cancer cell heterogeneity and therapy resistance. To facilitate cancer therapy in personalized medicine, three-dimensional (3D) organoids may be useful for functional characterization of cancer cells ex vivo. We investigated the feasibility and the utility of patient-derived 3D organoids of esophageal and oropharyngeal squamous cell carcinomas.

METHODS

We generated 3D organoids from paired biopsies representing tumors and adjacent normal mucosa from therapy-naïve patients and cell lines. We evaluated growth and structures of 3D organoids treated with 5-fluorouracil ex vivo.

RESULTS

Tumor-derived 3D organoids were grown successfully from 15 out of 21 patients (71.4%) and passaged with recapitulation of the histopathology of the original tumors. Successful formation of tumor-derived 3D organoids was associated significantly with poor response to presurgical neoadjuvant chemotherapy or chemoradiation therapy in informative patients (P = 0.0357, progressive and stable diseases, n = 10 vs. partial response, n = 6). The 3D organoid formation capability and 5-fluorouracil resistance were accounted for by cancer cells with high CD44 expression and autophagy, respectively. Such cancer cells were found to be enriched in patient-derived 3D organoids surviving 5-fluorouracil treatment.

CONCLUSIONS

The single cell-based 3D organoid system may serve as a highly efficient platform to explore cancer therapeutics and therapy resistance mechanisms in conjunction with morphological and functional assays with implications for translation in personalized medicine.

The Esophageal Organoid System Reveals Functional Interplay Between Notch and Cytokines in Reactive Epithelial Changes

BACKGROUND & AIMS

Aberrations in the esophageal proliferation-differentiation gradient are histologic hallmarks in eosinophilic esophagitis (EoE) and gastroesophageal reflux disease. A reliable protocol to grow 3-dimensional (3D) esophageal organoids is needed to study esophageal epithelial homeostasis under physiological and pathologic conditions.

METHODS

We modified keratinocyte-serum free medium to grow 3D organoids from endoscopic esophageal biopsies, immortalized human esophageal epithelial cells, and murine esophagi. Morphologic and functional characterization of 3D organoids was performed following genetic and pharmacologic modifications or exposure to EoE-relevant cytokines. The Notch pathway was evaluated by transfection assays and by gene expression analyses in vitro and in biopsies.

RESULTS

Both murine and human esophageal 3D organoids displayed an explicit proliferation-differentiation gradient. Notch inhibition accumulated undifferentiated basal keratinocytes with deregulated squamous cell differentiation in organoids. EoE patient-derived 3D organoids displayed normal epithelial structure ex vivo in the absence of the EoE inflammatory milieu. Stimulation of esophageal 3D organoids with EoE-relevant cytokines resulted in a phenocopy of Notch inhibition in organoid 3D structures with recapitulation of reactive epithelial changes in EoE biopsies, where Notch3 expression was significantly decreased in EoE compared with control subjects.

CONCLUSIONS

Esophageal 3D organoids serve as a novel platform to investigate regulatory mechanisms in squamous epithelial homeostasis in the context of EoE and other diseases. Notch-mediated squamous cell differentiation is suppressed by cytokines known to be involved in EoE, suggesting that this may contribute to epithelial phenotypes associated with disease. Genetic and pharmacologic manipulations establish proof of concept for the utility of organoids for future studies and personalized medicine in EoE and other esophageal diseases.

Interplay between Notch1 and Notch3 promotes EMT and tumor initiation in squamous cell carcinoma

Notch1 transactivates Notch3 to drive terminal differentiation in stratified squamous epithelia. Notch1 and other Notch receptor paralogs cooperate to act as a tumor suppressor in squamous cell carcinomas (SCCs). However, Notch1 can be stochastically activated to promote carcinogenesis in murine models of SCC. Activated form of Notch1 promotes xenograft tumor growth when expressed ectopically. Here, we demonstrate that Notch1 activation and epithelial–mesenchymal transition (EMT) are coupled to promote SCC tumor initiation in concert with transforming growth factor (TGF)-β present in the tumor microenvironment. We find that TGFβ activates the transcription factor ZEB1 to repress Notch3, thereby limiting terminal differentiation. Concurrently, TGFβ drives Notch1-mediated EMT to generate tumor initiating cells characterized by high CD44 expression. Moreover, Notch1 is activated in a small subset of SCC cells at the invasive tumor front and predicts for poor prognosis of esophageal SCC, shedding light upon the tumor promoting oncogenic aspect of Notch1 in SCC.

Notch receptors can exert different roles in cancer. In this manuscript, the authors reveal that Notch1 activation and EMT promote tumor initiation and cancer cell heterogeneity in squamous cell carcinoma, while the repression of Notch3 by ZEB1 limits Notch1-induced differentiation, permitting Notch1-mediated EMT.

Metaplasia: tissue injury adaptation and a precursor to the dysplasia-cancer sequence

Metaplasia is the replacement of one differentiated somatic cell type with another differentiated somatic cell type in the same tissue. Typically, metaplasia is triggered by environmental stimuli, which may act in concert with the deleterious effects of microorganisms and inflammation. The cell of origin for intestinal metaplasia in the oesophagus and stomach and for pancreatic acinar-ductal metaplasia has been posited through genetic mouse models and lineage tracing but has not been identified in other types of metaplasia, such as squamous metaplasia. A hallmark of metaplasia is a change in cellular identity, and this process can be regulated by transcription factors that initiate and/or maintain cellular identity, perhaps in concert with epigenetic reprogramming. Universally, metaplasia is a precursor to low-grade dysplasia, which can culminate in high-grade dysplasia and carcinoma. Improved clinical screening for and surveillance of metaplasia might lead to better prevention or early detection of dysplasia and cancer.

Abstract 2578: Investigating the role of mutant p53 in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a highly aggressive cancer characterized by a high rate of metastasis, limited therapeutic options, and a poor prognosis. However, there is limited information regarding the molecular mechanisms underlying the metastatic properties of ESCC. p53 is one of the most commonly mutated genes in ESCC, and our group has shown that esophageal cells lines expressing a mutation in human p53 shows signs of malignancy and increased invasion in 3D organotypic culture. A mouse model of mutant p53 (R172H) in ESCC is lacking in the field. To elucidate the role of mutant p53 in ESCC we developed a novel mouse model utilizing a genetic and carcinogenic approach. L2cre;p53-/- and p53R172H/- mice were generated and treated with 4NQO in their drinking water for 16 weeks, which resulted in the development of ESCC. Compared to wildtype mice, p53R172H/- mice and p53-/- mice exhibited a decreased tumor latency time, increased tumor frequency and a more severe tumor diagnosis. However, p53R172H/- mice and p53-/- mice displayed similar tumorigenic properties. RNA-seq was performed on cell lines established from wildtype and p53 mouse models and reveled different gene expression profiles between wildtype, p53R172H/-, and p53-/- cells. p53R172H/- cells displayed an increase in mesenchymal and decrease in epithelial marker expression, supporting the idea that they are undergoing EMT. In addition, several endocytic recycling related genes, including Rab11-fip1, Rab25, and Myo5b were downregulated in mutant and null p53 compared to wildtype cells. Further examination of the differing genetic profiles in our mouse models can provide novel insight into the role of mutant p53 in ESCC tumorigenesis and lead to the identification of new therapeutic targets.

Citation Format: Ashley Lento, Apple Long, Veronique Giroux, Qiaosi Tang, Morgan Sammons, Andres Klein-Szanto, Shelly Berger, Anil Rustgi. Investigating the role of mutant p53 in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2578. doi:10.1158/1538-7445.AM2017-2578

Autophagy mediates epithelial cytoprotection in eosinophilic oesophagitis

OBJECTIVE

The influence of eosinophilic oesophagitis (EoE)-associated inflammation upon oesophageal epithelial biology remains poorly understood. We investigated the functional role of autophagy in oesophageal epithelial cells (keratinocytes) exposed to the inflammatory EoE milieu.

DESIGN

Functional consequences of genetic or pharmacological autophagy inhibition were assessed in endoscopic oesophageal biopsies, human oesophageal keratinocytes, single cell-derived ex vivo murine oesophageal organoids as well as a murine model recapitulating EoE-like inflammation and basal cell hyperplasia. Gene expression, morphological and functional characterisation of autophagy and oxidative stress were performed by transmission electron microscopy, immunostaining, immunoblotting, live cell imaging and flow cytometry.

RESULTS

EoE-relevant inflammatory conditions promoted autophagy and basal cell hyperplasia in three independent murine EoE models and oesophageal organoids. Inhibition of autophagic flux via chloroquine treatment augmented basal cell hyperplasia in these model systems. Oesophageal keratinocytes stimulated with EoE-relevant cytokines, including tumour necrosis factor-α and interleukin-13 exhibited activation of autophagic flux in a reactive oxygen species-dependent manner. Autophagy inhibition via chloroquine treatment or depletion of Beclin-1 or ATG-7, augmented oxidative stress induced by EoE-relevant stimuli in murine EoE, oesophageal organoids and human oesophageal keratinocytes. Oesophageal epithelia of paediatric EoE patients with active inflammation displayed increased autophagic vesicle content compared with normal and EoE remission subjects. Functional flow cytometric analysis revealed autophagic flux in human oesophageal biopsies.

CONCLUSIONS

Our findings reveal for the first time that autophagy may function as a cytoprotective mechanism to maintain epithelial redox balance and homeostasis under EoE inflammation-associated stress, providing mechanistic insights into the role of autophagy in EoE pathogenesis.

Loss of Stromal IMP1 Promotes a Tumorigenic Microenvironment in the Colon

The colon tumor microenvironment is becoming increasingly recognized as a complex but central player in the development of many cancers. Previously, we identified an oncogenic role for the mRNA-binding protein IMP1 (IGF2BP1) in the epithelium during colon tumorigenesis. In the current study, we reveal the contribution of stromal IMP1 in the context of colitis-associated colon tumorigenesis. Interestingly, stromal deletion of Imp1 (Dermo1Cre;Imp1(LoxP/LoxP), or Imp1(ΔMes)) in the azoxymethane/dextran sodium sulfate (AOM/DSS) model of colitis-associated cancer resulted in increased tumor numbers of larger size and more advanced histologic grade than controls. In addition, Imp1(ΔMes) mice exhibited a global increase in protumorigenic microenvironment factors, including enhanced inflammation and stromal components. Evaluation of purified mesenchyme from AOM/DSS-treated Imp1(ΔMes) mice demonstrated an increase in hepatocyte growth factor (HGF), which has not been associated with regulation via IMP1. Genetic knockdown of Imp1 in human primary fibroblasts confirmed an increase in HGF with Imp1 loss, demonstrating a specific, cell-autonomous role for Imp1 loss to increase HGF expression. Taken together, these data demonstrate a novel tumor-suppressive role for IMP1 in colon stromal cells and underscore an exquisite, context-specific function for mRNA-binding proteins, such as IMP1, in disease states.

IMPLICATIONS

The tumor-suppressive role of stromal IMP1 and its ability to modulate protumorigenic factors suggest that IMP1 status is important for the initiation and growth of epithelial tumors.

Abstract 1305: Alternative splicing of the metabolic regulator Estrogen-Related Receptor alpha (ERRα) in colon carcinogenesis

The nuclear receptor ERRα acts principally in pair with its coactivator PGC-1α as a regulator of metabolic processes particularly in tissues subjected to high-energy demand. Besides its implication in energy metabolism and mitochondrial biogenesis, ERRα was recently associated with tumorigenesis. Increased expression of ERRα was noted in different cancerous tissues as breast, ovary and colon. Also, a new form of ERRα lacking the exon5 (ERRα Δ5) was recently identified and suggested to be a dominant negative of ERRα and interestingly to be differently expressed in normal and cancerous tissues. Since a protumorigenic role is emerging for this metabolic regulator, we investigated the role of ERRα and its spliced form ERRα β5 in colon carcinogenesis. METHODS: shRNA-mediated silencing of ERRα and overexpression of ERRα β5 were performed by lentivirus infection in DLD1 and HCT116 human colon cancer cells. The interaction between both proteins was investigated as well as their respective roles in various tumorigenic processes. RESULTS: Silencing of ERRα by shRNA reduced proliferation of DLD1 and HCT116 cells as measured by growth kinetics and growth assays in soft agar and reduced tumor formation in NUDE mice. Furthermore, FACS-scan analysis revealed that ERRα silencing delays G1-S phase transition in colon cancer cells. Differential expression of a splice variant of ERRα (ERRα Δ5) in cancer vs normal tissues would support the importance of ERRα in colorectal carcinogenesis. This is the case at least for colon tumors as cancerous samples display lower amount of ERRα β5 and higher amount of ERRα compared to adjacent normal tissues. Also, the ERRα β5 expression is surprisingly regulated by proteosomal degradation in normal and colon cancer cell lines and this could explain the low abundance of the ERRα spliced form. Interaction between both variants has been characterized by immunoprecipitation assays, confirming the conserved dimerization potential of ERRα β5 variant with ERRα. Furthermore, luciferase assays revealed that ERRα β5 is transcriptionaly inactive and its expression inhibits the transcriptional activity of ERRα on its target genes, suggesting that this variant acts as a dominant negative for ERRα. Interestingly, the reexpression of ERRα β5 in colon cancer cells reduces soft agar colony formation. CONCLUSION: Strong ERRα expression is associated with cancerous tissues and is required for the intense proliferation of colon cancer cells. Interestingly, the poorly active splice variant ERRα β5 is lost in cancerous colon tissues and has antiproliferative properties when reintroduced in colon cancer cells. Since this splice variant could interact with ERRα and inhibit its activity, ERRα β5 reduction of expression in cancerous tissue could allow ERRα to fully promote colon cancer cell proliferation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1305. doi:1538-7445.AM2012-1305

Combined inhibition of PAK7, MAP3K7 and CK2alpha kinases inhibits the growth of MiaPaCa2 pancreatic cancer cell xenografts

A panel of kinases whose inhibition increased apoptosis of pancreatic adenocarcinoma cells in vitro was recently established. The aim of this work was to observe in a mouse xenograft model whether inhibition of these kinases would alter pancreatic tumor growth. Rate of apoptosis, caspase-3 activity and cell viability were assessed in two pancreatic cancer cell lines, MiaPaCa2 and BxPC3, after inhibiting selected kinases by transfection of specific siRNAs. For in vivo experiments, MiaPaCa2 cells were injected into the pancreas of nude mice, where they formed tumors. Inhibition of kinases was obtained by repeated intraperitoneal (i.p.) injections of modified O-Methyl (OMe) siRNAs specific for the selected kinases. Tumor volumes were assessed after 21 days. Among selected kinases, PAK7, MAP3K7 and CK2alpha were those whose inhibition increased apoptosis the most in vitro. Simultaneous inhibition of two of them increased apoptosis up to five times. Moreover, inhibiting these kinases had little effect on 10 non-pancreatic cell lines, suggesting pancreatic specificity. In vivo, OMe-siRNAs induced significant but incomplete inhibition of kinase expression (45-75%). Nevertheless, such inhibition resulted in a twofold increase in caspase-3 activity in tumors and a strong reduction in tumor volume (about 75%). In vivo inhibition by OMe-siRNAs of three survival kinases apparently specific for pancreatic cancer cells, PAK7, MAP3K7 and CK2alpha, decreases significantly the growth of xenografted MiaPaCa2 cells. This strategy is therefore of potential clinical interest.