Orthotopic Mouse Model Of Colorectal Cancer Research Articles

Abstract 478: Targeted combination nano-drug delivery system to enhance anti-cancer efficacy and reduce side effects

Abstract Background: Colorectal cancer (CRC) is a global health concern, with significant morbidity and mortality. Oxaliplatin (OXL) is a common treatment for CRC but its effectiveness is hampered by side effects, including gastrointestinal and neurotoxic effects. APX3330 exerts anti-angiogenic and neuroprotective effects. It is proposed that the combined use of OXL and APX3330-loaded nanoparticles (NPs) would improve drug delivery to cancer cells with enhanced therapeutic efficacy while reducing side effects of OXL. Methods: We developed dual-loaded NPs containing OXL and APX3330 linked to a cancer targeting monoclonal antibody (NPs+mAb). We characterized the physicochemical properties of the NPs and evaluated their cytotoxicity and drug release using CRC cell lines. In vivo, we assessed their therapeutic efficiency and side effects using an orthotopic CRC mouse model. Results: NPs exhibited an average size of 229±26 nm with a zeta potential of -24.1±2.1 mV. The drug loading and encapsulation efficiency were 3.3±0.2% and 71.9%, respectively. Morphological analysis via scanning electron microscopy confirmed NP structure. In vitro drug release studies showed a slower release profile from NPs compared to free OXL, with a cumulative release of 34% (w/w) after 48 hours. Notably, cytotoxicity evaluation on CT-26 cells revealed a significant reduction in the IC50 for NPs compared to free APX3330 and OXL. In vivo studies demonstrated a remarkable 31% reduction in tumor growth rate in animals treated with NPs+mAb compared to those receiving free forms of OXL and APX3330. Body weight for animals treated with NPs+mAb remained similar to the healthy group, indicating minimal systemic toxicity. Moreover, the length of the colon in healthy organs remained steady compared to animals treated with OXL, which experienced a reduction in colon length. Animals treated with the free form of OXL exhibited diarrhoea, while the stool water content for animals treated with NPs+mAb remained at a similar level as the healthy group, suggesting reduced gastrointestinal side effects. Conclusions: This study demonstrates the potential of NPs with improved retention and encapsulation efficiency for effective drug delivery. Our research validates our novel method for creating NPs with mAb conjugation, enhancing cytotoxicity against CRC cell lines. In conclusion, the designed NPs+mAb formulation improves OXL treatment efficacy, providing targeted delivery of anti-cancer drugs to the tumor site and reducing tumor size while minimizing side effects. Citation Format: Niloufar Rashidi, Majid Davidson, Vasso Apostolopoulos, Mark R. Kelley, Kulmira Nurgali. Targeted combination nano-drug delivery system to enhance anti-cancer efficacy and reduce side effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 478.

Design, Synthesis, and Evaluation of Glucose Transporter Inhibitor-SN38 Conjugates for Targeting Colorectal Cancer.

Irinotecan (1), a prodrug of SN38 (2) approved by the US Food and Drug Administration for treating colorectal cancer, lacks specificity and causes many side effects. To increase the selectivity and therapeutic efficacy of this drug, we designed and synthesized conjugates of SN38 and glucose transporter inhibitors (phlorizin (5) or phloretin (6)), which could be hydrolyzed by glutathione or cathepsin to release SN38 in the tumor microenvironment, as a proof of concept. These conjugates (8, 9, and 10) displayed better antitumor efficacy with lower systemic exposure to SN38 in an orthotopic colorectal cancer mouse model compared with irinotecan at the same dosage. Further, no major adverse effects of the conjugates were observed during treatment. Biodistribution studies showed that conjugate 10 could induce higher concentrations of free SN38 in tumor tissues than irinotecan at the same dosage. Thus, the developed conjugates exhibit potential for treating colorectal cancer.

Dual-targeting of artesunate and chloroquine to tumor cells and tumor-associated macrophages by a biomimetic PLGA nanoparticle for colorectal cancer treatment

The regimens on colorectal cancer (CRC) are clinically limited due to the ignorance of tumor-supportive microenvironments. To combine the therapeutic effects on both tumor cells growth and immunosuppressive tumor microenvironments (TME), we propose the artesunate (AS) and chloroquine (CQ) combination and develop a poly (d,l-lactide-co-glycolide) (PLGA)-based biomimetic nanoparticle for dual-targeting delivery of the drug combination. Hydroxymethyl phenylboronic acid conjugated PLGA (HPA) is synthesized to form a reactive oxygen species (ROS)-sensitive core of biomimetic nanoparticles. A mannose-modified erythrocyte membrane (Man-EM) obtained by a novel surface modification method is cloaked on the AS and CQ-loaded HPA core to receive a biomimetic nanoparticle-HPA/AS/CQ@Man-EM. It holds a strong promise in inhibiting the proliferation of CRC tumor cells and reversing the phenotypes of TAMs via targeting both tumor cells and M2-like tumor-associated macrophages (TAMs). Verifying in an orthotopic CRC mouse model, the biomimetic nanoparticles showed improved accumulation at tumor tissues and effectively suppressed the tumor growth via both inhibition of tumor cell growth and repolarization of TAMs. Notably, unbalanced distribution to the tumor cells and TAMs is the key to realize the remarkable anti-tumor effects. This work proposed an effective biomimetic nanocarrier for the CRC treatment.

RPL21 interacts with LAMP3 to promote colorectal cancer invasion and metastasis by regulating focal adhesion formation

BackgroundMetastasis is the leading cause of death among patients with colorectal cancer (CRC). Therefore, it is important to explore the molecular mechanisms of metastasis to develop effective therapeutic targets for CRC. In the present study, ribosomal protein L21 (RPL21) was considered as being involved in promoting CRC metastasis, yet the underlying mechanism requires further investigation.MethodsImmunohistochemistry, western blotting, and quantitative reverse transcription polymerase chain reaction were performed to measure the expression of RPL21 and lysosome-associated membrane protein 3 (LAMP3) in CRC tissues and cells. Wound healing, transwell migration, and invasion assays were performed to study the migration and invasion of cultured CRC cells. An orthotopic CRC mouse model was developed to investigate the metastatic ability of CRC. Transcriptome sequencing was conducted to identify the genes related to RPL21. The dual-luciferase reporter gene assay was performed to determine the transcriptional activity of transcription factor EB (TFEB). The GST/His pull-down assay was performed to investigate the specific binding sites of RPL21 and LAMP3. The cell adhesion assay was performed to determine the adhesion ability of CRC cells. Immunofluorescence staining was performed to observe focal adhesions (FAs).ResultsRPL21 was highly expressed in CRC, contributing to tumor invasiveness and poor patient prognosis. Functionally, RPL21 promoted the migration and invasion of CRC cells in vitro and tumor metastasis in vivo. Moreover, LAMP3 was identified as being highly related to RPL21 and was essential in promoting the migration and invasion of CRC cells. Mechanistically, RPL21 activated the transcriptional function of TFEB to upregulate LAMP3 expression. RPL21 directly bound to the aa 341–416 domain of LAMP3 via its aa 1–40 and aa 111–160 segments. The combination of RPL21 and LAMP3 enhanced the stability of the RPL21 protein by suppressing the degradation of the ubiquitin–proteasome system. Furthermore, RPL21 and LAMP3 promoted the formation of immature FAs by activating the FAK/paxillin/ERK signaling pathway.ConclusionsRPL21 promoted invasion and metastasis by regulating FA formation in a LAMP3-dependent manner during CRC progression. The interaction between RPL21 and LAMP3 may function as a potential therapeutic target against CRC.

Abstract 13: A non-surgical approach to develop an orthotopic colorectal cancer mouse model

Abstract Recapitulating physiologically relevant tumor microenvironment is an important yet a significant challenge in modeling colorectal cancer (CRC) for basic and translational studies. Cecal-wall injection is most widely used for orthotopic animal models of CRC. However, this procedure involves complicated surgical procedures, and its ectotopic nature is a major issue for therapeutic development. Here, we report a non-surgical procedure for establishing orthotopic CRC mouse models, reflecting the appropriate tumor microenvironment to better model the disease development and facilitate translational studies, including drug identification and validation. For this procedure, the mice are fasted overnight. The following day, anesthesia is induced in the study mice (Balb/c or C57BL/6) while placed on a thermostat-controlled heating blanket. Next, a specialized catheter is inserted and distended into the mouse colon to gently block the colon and ensure the localization for tumor development. Hereafter, the colonic epithelium is treated with proteases and mechanical abrasion to cause mild disruption. Following the local gut inflammation, the targeted colon region is incubated with tumor cells, leading to the adhesion of tumor cells (CT26 or MC38) to the colonic epithelium. Based on the animal background and the cell line used, the tumor is developed within 4-6 weeks. Pathological assessment on hematoxylin and eosin stained tumor tissues confirmed the stages of tumor development. Additional adaptations of this procedure include i) tumor development in different mouse strains, ii) local delivery of adeno-Cre in transgenic mice for CRC, and iii) transplantation of tumor organoids in the mouse colon. Overall, our non-surgical procedure overcomes the technical difficulties of surgery and offers several advantages like ease of handling, cost-effectiveness, pain-free with nearly no procedure-associated mortality, and adaptability to several strains. To conclude, this non-surgical procedure is a novel and promising alternative to conventional orthotopic CRC mouse models for translational studies. Citation Format: Samantha Sharma, Kevin Van der Jeught, Zhuolong Zhou, Xinna Zhang, Xiongbin Lu. A non-surgical approach to develop an orthotopic colorectal cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 13.

Rapamycin Liposomes Combined with 5-Fluorouracil Inhibits Angiogenesis and Tumor Growth of APC (Min/+) Mice and AOM/DSS-Induced Colorectal Cancer Mice.

Transgenic C57BL/6-APC(Min/+) spontaneous cancer mouse model and the Azoxymethane (AOM)/Dextran Sulfate Sodium (DSS) chemically induced orthotopic colorectal cancer mouse model represented distinct pathogenesis of colorectal cancers. Our previous study revealed that the combination of Rapamycin liposomes (Rapa/Lps) and 5-Fluorouracil (5-FU) has anti-colorectal cancer effects. However, the therapeutic efficacy of Rapa/Lps and 5-FU in other colorectal cancer mice models is yet to be thoroughly explored. The purpose of this study was to investigate the anti-tumor effect of Rapa/Lps combined with 5-FU in vivo and in vitro. In this study, we evaluated the effect of Rapa/Lps and 5-FU on APC (Min/+) mice and AOM/DSS-induced colorectal cancer mice. The small intestine, colorectum, serum, and plasma of mice in each group were collected following sacrifice to record the number of tumors. HE staining was utilized for observing pathological damage to intestine tissues. Tube formation assay, Transwell assay, wound healing assay, Western Blot were used to explore the anti-angiogenesis effect of drugs in HUVECs. As expected, Rapa/Lps and 5-FU significantly suppressed tumor formation, decreased the number of tumors, and tumor load both in two mouse models, and had no influence on mouse weight. Mechanically, the anti-tumor effect of the drug also was associated in inhibiting angiogenesis and proliferation. Furthermore, we found that Rapa/Lps obviously inhibited HUVECs tube formation and migration. Altogether, we revealed the Rapa/Lps synergism with 5-FU decreased colon and small intestinal tumorigenesis in AOM/DSS-treated and APC (Min/+) mice, respectively, and correlated with anti-angiogenesis.

A cyclodextrin-based nanoformulation achieves co-delivery of ginsenoside Rg3 and quercetin for chemo-immunotherapy in colorectal cancer

The immune checkpoint blockade therapy has profoundly revolutionized the field of cancer immunotherapy. However, despite great promise for a variety of cancers, the efficacy of immune checkpoint inhibitors is still low in colorectal cancer (CRC). This is mainly due to the immunosuppressive feature of the tumor microenvironment (TME). Emerging evidence reveals that certain chemotherapeutic drugs induce immunogenic cell death (ICD), demonstrating great potential for remodeling the immunosuppressive TME. In this study, the potential of ginsenoside Rg3 (Rg3) as an ICD inducer against CRC cells was confirmed using in vitro and in vivo experimental approaches. The ICD efficacy of Rg3 could be significantly enhanced by quercetin (QTN) that elicited reactive oxygen species (ROS). To ameliorate in vivo delivery barriers associated with chemotherapeutic drugs, a folate (FA)-targeted polyethylene glycol (PEG)-modified amphiphilic cyclodextrin nanoparticle (NP) was developed for co-encapsulation of Rg3 and QTN. The resultant nanoformulation (CD-PEG-FA.Rg3.QTN) significantly prolonged blood circulation and enhanced tumor targeting in an orthotopic CRC mouse model, resulting in the conversion of immunosuppressive TME. Furthermore, the CD-PEG-FA.Rg3.QTN achieved significantly longer survival of animals in combination with Anti-PD-L1. The study provides a promising strategy for the treatment of CRC.

Immunosuppressive Microenvironment Revealed by Immune Cell Landscape in Pre-metastatic Liver of Colorectal Cancer.

Background: Colorectal cancer, the fourth leading cause of cancer mortality, is prone to metastasis, especially to the liver. The pre-metastatic microenvironment comprising various resident stromal cells and immune cells is essential for metastasis. However, how the dynamic evolution of immune components facilitates pre-metastatic niche formation remains unclear.Methods: Utilizing RNA-seq data from our orthotopic colorectal cancer mouse model, we applied single sample gene set enrichment analysis and Cell type Identification By Estimating Relative Subsets Of RNA Transcripts to investigate the tumor microenvironment landscape of pre-metastatic liver, and define the exact role of myeloid-derived suppressor cells (MDSCs) acting in the regulation of infiltrating immune cells and gene pathways activation. Flow cytometry analysis was conducted to quantify the MDSCs levels in human and mice samples.Results: In the current work, based on the high-throughput transcriptome data, we depicted the immune cell infiltration pattern of pre-metastatic liver and highlighted MDSCs as the dominant altered cell type. Notably, flow cytometry analysis showed that high frequencies of MDSCs, was detected in the pre-metastatic liver of orthotopic colorectal cancer tumor-bearing mice, and in the peripheral blood of patients with stage I–III colorectal cancer. MDSCs accumulation in the liver drove immunosuppressive factors secretion and immune checkpoint score upregulation, consequently shaping the pre-metastatic niche with sustained immune suppression. Metabolic reprogramming such as upregulated glycolysis/gluconeogenesis and HIF-1 signaling pathways in the primary tumor was also demonstrated to correlate with MDSCs infiltration in the pre-metastatic liver. Some chemokines were identified as a potential mechanism for MDSCs recruitment.Conclusion: Collectively, our study elucidates the alterations of MDSCs during pre-metastatic niche transformation, and illuminates the latent biological mechanism by which primary tumors impact MDSC aggregation in the targeted liver.

Two nanoformulations induce reactive oxygen species and immunogenetic cell death for synergistic chemo-immunotherapy eradicating colorectal cancer and hepatocellular carcinoma

BackgroundFOLFOX is a combinational regimen of folinic acid (FnA, FOL), fluorouracil (5-Fu, F) and oxaliplatin (OxP, OX), and has been long considered as the standard treatment of colorectal cancer (CRC) and hepatocellular carcinoma (HCC). Recent developments of nano delivery systems have provided profound promise for improving anticancer efficacy and alleviating side effects of FOLFOX. Previously, a nanoformulation (termed Nano-Folox) containing OxP derivative and FnA was developed in our laboratory using nanoprecipitation technique. Nano-Folox induced OxP-mediated immunogenic cell death (ICD)-associated antitumor immunity, which significantly suppressed tumor growth in the orthotopic CRC mouse model when administrated in combination with free 5-Fu.MethodsA nanoformulation (termed Nano-FdUMP) containing FdUMP (5-Fu active metabolite) was newly developed using nanoprecipitation technique and used in combination with Nano-Folox for CRC and HCC therapies.ResultsSynergistic efficacy was achieved in orthotopic CRC and HCC mouse models. It resulted mainly from the fact that Nano-FdUMP mediated the formation of reactive oxygen species (ROS), which promoted the efficacy of ICD elicited by Nano-Folox. In addition, combination of Nano-Folox/Nano-FdUMP and anti-PD-L1 antibody significantly inhibited CRC liver metastasis, leading to long-term survival in mice.ConclusionThis study provides proof of concept that combination of two nano delivery systems can result in successful FOLFOX-associated CRC and HCC therapies. Further optimization in terms of dosing and timing will enhance clinical potential of this combination strategy for patients.Graphical abstract

Biological activities of siRNA-loaded lanthanum phosphate nanoparticles on colorectal cancer

Lanthanum can reduce absorption of phosphate by forming lanthanum phosphate complexes after oral administration of lanthanum carbonate tablets (FOSRENOL®) in patients. Based on the pH-responsive interaction of phosphate and lanthanum ions, the chitosan coated siRNA-loaded lanthanum phosphate nanoparticles (CS/LaP/siRNA NPs) were prepared for improving cancer treatment, in which polysaccharide chitosan was used as the outer shell to control the excessive growth of lanthanum phosphate complexes, and enable intestinal mucoadhesion. The CS/LaP/siEGFR NPs exhibited significant biological activities in human colorectal cancer HT-29 cells by the synergistic effects of siEGFRs and lanthanum ions, such as downregulation of EGFR and upregulation of miR-34a. Furthermore, significant tumor growth inhibition was observed in both transgenic C57BL/6-ApcMinC/Nju cancer mouse model and AOM/DSS chemically induced orthotopic colorectal cancer mouse model after intestinal instillation administration of CS/LaP/siEGFR NPs. Therefore, the lanthanum-based siRNA delivery system would provide a potential and efficient strategy for the treatment of colorectal cancers.

Nano Codelivery of Oxaliplatin and Folinic Acid Achieves Synergistic Chemo-Immunotherapy with 5-Fluorouracil for Colorectal Cancer and Liver Metastasis.

FOLFOX, the combinational strategy of folinic acid (FnA), 5-fluorouracil (5-Fu), and oxaliplatin (OxP), has been used as standard treatment of colorectal cancer (CRC) for decades. Despite the improved survival, patients still suffer from drawbacks such as low efficacy, high toxicity, and long course of treatment. New strategies to address these issues are needed to further clinical benefits. In this study, a nanoprecipitate (C26H35N9O7Pt) was formed by the active form of OxP ([Pt(DACH)(H2O)2]2+) and FnA, which was formulated into an aminoethyl anisamide targeted PEGylated lipid nanoparticle within microemulsions using nanoprecipitation technique. The resultant formulation (namely Nano-Folox) significantly promoted the blood circulation and tumor accumulation of platinum drug and FnA in an orthotopic CRC mouse model. Emerging evidence indicates that OxP can not only provide anticancer cytotoxic effects but also induce immunogenic cell death (a type of apoptosis that primes anticancer immune responses). Consequently, Nano-Folox demonstrated favorable chemo-immunotherapeutic activities in orthotopic CRC mice. In addition, when compared to FOLFOX the significantly stronger chemo-immunotherapeutic responses were achieved by the combination of Nano-Folox and 5-Fu without showing toxicity. Moreover, the anti-PD-L1 monoclonal antibody enhanced Nano-Folox/5-Fu for decreased liver metastases in mice. These results indicate the potential of Nano-Folox-based combination strategy for the treatment of CRC.

Magnetic Resonance Colonography Enables the Efficacy Assessment of Immune Checkpoint Inhibitors in an Orthotopic Colorectal Cancer Mouse Model

Immune checkpoint inhibitors (ICIs) have become an effective therapeutic option for colorectal cancer and studies on these drugs have therefore increased greatly. Efficacy assessments of ICIs in preclinical orthotopic colorectal cancer using MRI have not been reported however due to the difficulties in conducting colorectal imaging. The purpose of this present study was to investigate the feasibility of using magnetic resonance colonography (MRC) to evaluate the efficacy of an ICI, an anti-PD-L1 antibody, in an orthotopic colorectal cancer mouse model. The mouse model was generated by the engraftment of colorectal cancer cells into the submucosal layer of the colon. Anti-cancer efficacy was assessed by tumor volume and metastatic tumor number analyses, and these values were significantly lower in the PD-L1 antibody-treated group compared to the controls. Histological analyses using H&E and Ki-67 immunohistochemical staining confirmed a highly efficacious tumor growth inhibition and enhanced infiltration by CD4+ and CD8+ lymphocytes in the PD-L1 antibody-treated group. We conclude that MRC has the potential to be used for ICI efficacy assessments against orthotopic colorectal cancer mouse model.

Development of an Orthotopic Colorectal Cancer Mouse Model for Radiation Therapy Studies

Abstract Radiation is commonly used before surgery to reduce tumor burden in rectal cancer. It has been suggested that radiation therapy induces an immune response against the tumor. Previous work using mice ectopic models has shown a correlation between tumor regression and the production of IFN-g and the induction of cytotoxic T cells after radiotherapy. Ectopic models, such as the use of colon cell lines in leg muscle, provide us with some information about the response to radiation, but this response may differ if the tumor is grown orthotopically in the tissue from which it originates. To assess this difference in response, we have developed an orthotopic model to study the growth of colorectal cancer in mice and the response to radiation treatment. In our model, MC38 adenocarcinoma murine cells expressing luciferase are implanted in the rectal wall of C57BL/6 mice through the serous membrane. Tumor growth, assessed using IVIS, revealed tumor masses that steadily increase in size reaching approximately 1 gram 21 days post-injection of 50,000 cells. Importantly, tumor growth in most mice was limited to the site of injection, as mesenteric and omental sites were free of tumor burden. The cellular composition and the morphology of these tumors is being examined using flow cytometry and immunohistochemistry, respectively. Furthermore, studies are underway to determine the response of these tumors to fractionated radiation and to determine if there are differences from the ectopic models of colon cancer. This more clinically relevant model will improve our understanding of response to radiotherapy in colorectal cancer and help develop more effective treatments for this disease.

Characterization of an Orthotopic Colorectal Cancer Mouse Model and Its Feasibility for Accurate Quantification in Positron Emission Tomography.

Quantification in positron emission tomography (PET) imaging of an orthotopic mouse model of colorectal cancer (CRC) is challenging due to difficult tumor delineation. We aimed to establish a reproducible delineation approach, evaluate its feasibility for reliable PET quantification and compare its added translational value with its subcutaneous counterpart. A subcutaneous Colo205-luc2 tumor fragment harvested from a donor mouse was transplanted onto the caecum of nude mice, with (n=10) or without (n=10) the addition of an X-ray detectable thread. Animals underwent 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET imaging, complemented with X-ray computed tomography (CT) and magnetic resonance imaging (MRI, 7T). Animals without a thread underwent additional contrast enhanced (Exitron) CT imaging. Tumors were delineated on the MRI, μPET image or contrast enhanced μCT images and correlations between in vivo and ex vivo [18F]FDG tumor uptake as well as between image-derived and caliper-measured tumor volume were evaluated. Finally, cancer hallmarks were assessed immunohistochemically for the characterization of both models. Our results showed the strongest correlation between both in vivo and ex vivo uptake (r=0.84, p<0.0001) and image-derived and caliper-measured tumor volume (r=0.96, p<0.0001) when the tumor was delineated on the MR image. Orthotopic tumors displayed an abundance of stroma, higher levels of proliferation (p=0.0007), apoptosis (p=0.02), and necrosis (p<0.0001), a higher number of blood vessels (p<0.0001); yet lower tumor hypoxia (p<0.0001) as compared with subcutaneous tumors. This orthotopic mouse model proved to be a promising tool for the investigation of CRC through preclinical imaging studies provided the availability of anatomical MR images for accurate tumor delineation. Furthermore, the tumor microenvironment of the orthotopic tumor resembled more that of human CRC, increasing its likelihood to advance translational nuclear imaging studies of CRC.

Circulating tumor cells exhibit stem cell characteristics in an orthotopic mouse model of colorectal cancer.

The prognosis of colorectal cancer (CRC) is closely linked to the occurrence of distant metastases, which putatively develop from circulating tumor cells (CTCs) shed into circulation by the tumor. As far more CTCs are shed than eventually metastases develop, only a small subfraction of CTCs harbor full tumorigenic potential. The aim of this study was to further characterize CRC-derived CTCs to eventually identify the clinically relevant subfraction of CTCs.We established an orthotopic mouse model of CRC which reliably develops metastases and CTCs. We were able to culture the resulting CTCs in vitro, and demonstrated their tumor-forming capacity when re-injected into mice. The CTCs were then subjected to qPCR expression profiling, revealing downregulation of epithelial and proliferation markers. Genes associated with cell-cell adhesion (claudin-7, CD166) were significantly downregulated, indicating a more metastatic phenotype of CTCs compared to bulk tumor cells derived from hepatic metastases. The stem cell markers DLG7 and BMI1 were significantly upregulated in CTC, indicating a stem cell-like phenotype and increased capacity of tumor formation and self-renewal. In concert with their in vitro and in vivo tumorigenicity, these findings indicate stem cell properties of mouse-derived CTCs.In conclusion, we developed an orthotopic mouse model of CRC recapitulating the process of CRC dissemination. CTCs derived from this model exhibit stem-cell like characteristics and are able to form colonies in vitro and tumors in vivo. Our results provide new insight into the biology of CRC-derived CTCs and may provide new therapeutic targets in the metastatic cascade of CRC.

5-hydroxytryptamine receptor (5-HT1DR) promotes colorectal cancer metastasis by regulating Axin1/β-catenin/MMP-7 signaling pathway.

Overexpression of 5-hydroxytryptamine (5-HT) in human cancer contributes to tumor metastasis, but the role of 5-HT receptor family in cancer has not been thoroughly explored. Here, we report overexpression of 5-HT(1D) receptor (5-HT(1D)R) was associated with Wnt signaling pathway and advanced tumor stage. The underlying mechanism of 5-HT(1D)R-promoted tumor invasion was through its activation on the Axin1/β-catenin/MMP-7 pathway. In an orthotopic colorectal cancer mouse model, we demonstrated that a 5-HT(1D)R antagonist (GR127935) effectively inhibited tumor metastasis through targeting Axin1. Furthermore, in intestinal epithelium cells, we observed that 5-HT(1D)R played an important role in cell invasion via Axin1/β-catenin/MMP-7 pathway. Together, our findings reveal an essential role of the physiologic level of 5-HT(1D)R in pulmonary metastasis of colorectal cancer.

Near-Infrared Confocal Laser Endomicroscopy Detects Colorectal Cancer via an Integrin αvβ 3 Optical Probe.

Colorectal cancer (CRC) is one of the major causes of cancer-related deaths in industrialized countries. The identification of small polyps and neoplasms with non-polypoid morphology remains to be a serious challenge, as about a quarter of them are missed during routine colonoscopy. The aim of this study was to evaluate the application of an integrin αvβ3 optical probe in near-infrared fluorescence (NIRF) confocal laser endomicroscopy (CLE) for tumour detection in a rodent model. In a novel orthotopic CRC mouse model, tumour growth was monitored by bioluminescence imaging and by colonoscopy employing a rigid white-light endoscope, tumour development was scored by total number and size of tumours. Furthermore, NIRF CLE was established using a fibre probe attached to a confocal laser scanner operating at 660nm and an antagonistic small-molecule integrin αvβ3 NIRF contrast agent. Three CRC cell lines of different histological origin were successfully implanted in nude mice, proving the power of this new orthotopic model. Whole body NIRF images of tumour-bearing mice showed specific high accumulation of the integrin αvβ3 probe in regions of tumour growth, colocalizing with the bioluminescent signal. Molecular imaging by means of a CLE fibre probe allowed distinguishing normal mucosa structures from tumour tissue, as confirmed by quantitation of fluorescence intensities and histology. Targeting integrin αvβ3 in a molecular imaging approach was shown to be effective for CRC detection. Use of molecular guidance in near-infrared CLE represents a promising route to improving detection rates.

Abstract A32: Colorectal cancer stroma: Tumor cells in disguise

Abstract Background: Epithelial-to-mesenchymal transition (EMT) is thought to mediate cancer cell dissemination and metastasis. However, the role of EMT in the initial progression of human cancer remains unproven, since delaminating neoplastic cells have never been identified in the peritumoral stroma. Aim: To demonstrate the existence of EMT-neoplastic cells in mesenchymal disguise in the stroma of human colorectal cancer (CRC). Methods and Materials / Patients: In vitro, gene expression profile analysis of 18 CRC cells by microarray. Transfection/silencing of TWIST1 in CRC cells and invasion and migration assay. Immunohistochemistry for TWIST1 of 11 adenomas and of 201 CRC specimens. Combined TWIST1 immunofluorescence and in situ hybridization (iFISH) for CEP7 and 20 of 20 CRC specimens. In vivo, orthotopic graft of murine CRC cells CT26 in the rectal sub-mucosa of Balb/c mice. Results: TWIST1 was necessary to maintain mesenchymal phenotype and invasiveness of microsatellite-stable (MSS) cellular models of EMT, either spontaneous (CoLo741) or induced by transfection (SW480). TWIST1 mRNA was not translated in MSI CRC cells (HCT116). In an orthotopic mouse model of CRC, syngenic TWIST1-positive cells (CT26) acquired a mesenchymal phenotype when invading the peritumoral tissues. In human CRC tissues, the presence of TWIST1-positive cells within the stroma correlated with tumor MSS status (p=0.05), stage IV (p=0.02), and patient prognosis (DSS, p&amp;lt;0.01). Trisomies of chromosome 7 and/or chromosome 20 were detected within the tumor compartment of 17/20 CRC specimens. In each of these 17 tumors, TWIST1-positive cells with matching chromosomal gains were traceable in the peritumoral stroma (86 of 776 counted cells, 11.1%), whereas no trisomy was recognized in TWIST1-negative stromal cells (0 of 1249 cells; p&amp;lt;0.001). Conclusion: TWIST1 plays a crucial role in maintaining EMT in human CRC. By using TWIST1 as marker of EMT cells, we demonstrated that stromal cells, disguised as fibroblasts, are actually neoplastic. Targeting TWIST1+ stromal cells might open new scenarios for interfering with the metastatic cascade of CRC. Note: This abstract was not presented at the conference. Citation Format: Giuseppe Celesti, Giuseppe Di Caro, Paolo Bianchi, Fabio Grizzi, Gianluca Basso, Andrea Doni, Federica Marchesi, Giancarlo Marra, Massimo Roncalli, Alberto Mantovani, Alberto Malesci, Luigi Laghi. Colorectal cancer stroma: Tumor cells in disguise. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A32.