Lgr5 Protein Research Articles

Abstract 56: Preclinical in vivo characterization underpinning LGR5-targeting CAR-T cells as a cancer immunotherapy

Abstract Incidences of early-onset colorectal cancer (CRC) have been accelerating worldwide. To begin to address the lack of therapeutic options for CRC, we have developed a CAR-T cell therapy specific for leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5). LGR5 is known to potentiate Wnt/Β-catenin signaling and mark cells-of-origin in intestinal cancers. Extensive screening has demonstrated elevated expression of LGR5 in CRC, which is correlated with reduced patient survival. In CRC, LGR5 has been intimately linked with metastasis, cell survival and perturbation of chemotherapeutic interventions. We have developed a 9-day preclinical manufacturing method to generate LGR5-targeting CAR-T cells with a minimally differentiated T cell phenotype, which was concomitant with significant cytotoxic and activation marker expression. In human CRC xenograft mouse models, LGR5-targeting CAR-T cells eradicated tumors at doses as low as 800,000 CAR+ cells, and were capable of significantly inhibiting advanced tumor growth following delayed administration. Robust CAR-T cell-mediated immunological protection was observed in rechallenge experiments, in which secondary tumor growth was undetectable in mice which had tumors rejected following previous CAR-T cell administration. LGR5 protein and mRNA expression was also detected in a diverse range of cancer families, including ovarian, brain, liver and stomach, expanding upon the clinical indications with which LGR5-targeting CAR-T cells may be harnessed. These results contribute to a preclinical body of work that culminated in a Phase I/IIa clinical trial in metastatic colorectal cancer patients, which was approved for initiation by the FDA and commenced in 2023 (NCT05759728). Citation Format: Jade Foeng, Timona Tyllis, Caitlin Abbott, Dylan McPeake, Emma Thompson, Veronika Bandara, Batjargal Gundsambuu, Silvana Napoli, Claudine Bonder, Iain Comerford, Tim Sadlon, Simon Barry, Shaun McColl. Preclinical in vivo characterization underpinning LGR5-targeting CAR-T cells as a cancer immunotherapy [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 56.

Abstract 4552: EGFR inhibitors increase LGR5 expression and enhance potency of LGR5 antibody-drug conjugates targeting colorectal cancer stem cells

Abstract Colorectal cancer (CRC) is the second leading cause of cancer-associated deaths in the United States. One of the primary challenges in treating CRC is therapy resistance thought to be mediated by cancer stem cells (CSCs), a subpopulation of cancer cells with infinite replicative potential that can differentiate to drive tumorigenesis and disease relapse. Antibody-drug conjugates (ADCs) are amongst the fastest growing classes of anticancer drugs and utilize the specificity of monoclonal antibodies (mAbs) to hone cytotoxic payloads to cancer cells. We generated ADCs directed against leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), a well-defined biomarker of CSCs that is highly overexpressed in CRCs. LGR5 ADCs demonstrated high specificity and efficacy in CRC cells and xenograft models, though tumor relapse after treatment withdrawal was a major obstacle. Interestingly, FDA-approved therapy targeting epidermal growth factor receptor (EGFR) has been shown to increase LGR5 mRNA expression levels in patient-derived models of CRC. This study aims to determine the mechanism of EGFR-mediated regulation of LGR5 expression and evaluate the therapeutic efficacy of combination treatments targeting EGFR and LGR5 for the improved treatment of CRC. To first analyze the effect of EGFR inhibition on LGR5 expression, a panel of CRC cell lines of different KRAS and PI3CKA mutational statuses were treated with FDA-approved EGFR-targeted mAbs or small molecule inhibitors. LGR5 protein expression was shown to be upregulated by EGFR-targeted therapies in a dose- and time-dependent manner, independent of mutation status. Notably, treatment with EGF, MEK1/2 inhibitor trametinib, and EGFR-directed siRNA all resulted in concomitant reduction in EGFR and LGR5 protein levels, suggesting EGFR and LGR5 are co-degraded. Co-immunoprecipitation and immunocytochemistry experiments identified a novel EGFR-LGR5 interaction and co-internalization mechanism in CRC cells, respectively. Furthermore, we showed EGFR-LGR5 interaction is enhanced by treatment with the EGFR-targeting mAb, cetuximab (CTX). To evaluate efficacy of combination therapies targeting EGFR and LGR5, CRC cells were treated with LGR5 ADCs with or without CTX. Importantly, we showed CTX significantly enhanced the potency of LGR5 ADCs incorporating different classes of cytotoxic payloads. These results suggest combining LGR5 ADCs with EGFR inhibitors may be a more effective approach for the treatment of CRC and eliminating CSCs to overcome resistance and relapse. Citation Format: Peyton C. High, Zhengdong Liang, Kendra S. Carmon. EGFR inhibitors increase LGR5 expression and enhance potency of LGR5 antibody-drug conjugates targeting colorectal cancer stem cells [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 4552.

Krüppel-like factor 5 activates chick intestinal stem cell and promotes mucosal repair after impairment

ABSTRACTThe mucosal renewal, which depends on the intestinal stem cell (ISC) activity, is the foundation of mucosal repairment. Importantly, activation of reserve ISCs (rISCs) plays a vital role in initiating mucosal repair after injury. However, the underlying regulatory mechanism of rISCs activation in chickens remains unclear. In this study, immediately after lipopolysaccharide (LPS) challenge, mitochondrial morphological destruction and dysfunction appeared in the crypt, accompanied by decreased epithelial secretion (decreased Muc2 mRNA abundance and LYSOZYME protein level). However, immediately after mucosal injury, the mucosal renewal accelerated, as indicated by the increased BrdU positive rate, proliferating cell nuclear antigen (PCNA) protein level and mRNA abundance of cell cycle markers (Ccnd1, Cdk2). Concerning the ISCs activity, during the early period of injury, there appeared a reduction of active ISCs (aISCs) marker Lgr5 mRNA and protein, and an increasing of rISCs marker Hopx mRNA and protein. Strikingly, upon LPS challenge, increased mRNA transcriptional level of Krüppel-like factor 5 (Klf5) was detected in the crypt. Moreover, under LPS treatment in organoids, the KLF5 inhibitor (ML264) would decrease the mRNA and protein levels of Stat5a and Hopx, the STAT5A inhibitor (AC-4-130) would suppress the Lgr5 mRNA and protein levels. Furthermore, the Dual-Luciferase Reporter assay confirmed that, KLF5 would bind to Hopx promoter and activate the rISCs, STAT5A would trigger Lgr5 promoter and activate the aISCs. Collectively, KLF5 was upregulated during the early period of injury, further activate the rISCs directly and activate aISCs via STAT5A indirectly, thus initiate mucosal repair after injury.

Abstract 3199: Development of a flow cytometry-based assay for measuring specific CAR expression on LGR5-targeting CAR-T cells

Abstract The measurement of chimeric antigen receptor (CAR) expression is critical for the development, qualification and quantitation of CAR-T cells for clinical applications. There is a comprehensive range of tools commercially available for specifically measuring expression of the CAR on CD19-targeting CAR-T cells. However, with the rapidly expanding repertoire of CAR-T cells in development targeting a diverse range of tumour antigens, there is a paucity of readily implementable assays that specifically measure CAR expression, which is essential for translation into the clinic. We have developed several CARs targeting the cancer stem cell marker LGR5, one of which (CNA3103) is the lead candidate in an upcoming clinical trial in advanced metastatic colorectal cancer. Previously, the level of CNA3103 expression in this system has been determined indirectly by measuring expression of tEGFR on the CAR-T cell surface, taking advantage of co-expression of the CAR and tEGFR upon transduction with our lentiviral construct. tEGFR expression was found over many CAR-T cell manufacturing batches to report transduction efficiency reproducibly with high sensitivity. However, to specifically quantify expression of the CNA3103, an assay utilising an Fc-tagged recombinant human LGR5 protein, in combination with an anti-human IgG1 Fc-specific secondary antibody was developed. A number of optimisation steps including titration of multiple batches of rhLGR5-Fc, different anti-human IgG1 Fc-specific antibodies and a range of incubation parameters were tested. This resulted in development of an assay that yielded very similar reproducibility and sensitivity to that previously observed with the indirect tEGFR surrogate assay. Overall, the findings highlight the utility of using CAR-targeting recombinant proteins for evaluating CAR expression on CAR-T cells, providing a general flow cytometry-based staining strategy that may be adapted for assessing a diverse repertoire of CARs. Citation Format: Timona Tyllis, Caitlin Abbott, Dylan McPeake, Jade Foeng, Veronika Bandara, Batjargal Gundsambuu, Silvana Napoli, Stuart Mills, Emma Thompson, Lih Tan, Allison Cowin, Claudine Bonder, Timothy Sadlon, Simon Barry, Shaun McColl. Development of a flow cytometry-based assay for measuring specific CAR expression on LGR5-targeting CAR-T cells [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 3199.

Age-related glomerular histogenesis in inbred indigenous rabbit (Oryctolagus cuniculus): A morphological, morphometrical, and immunohistochemical study with emphasis on Lgr5-positive cells

Although the regeneration of renal glomeruli and nephrons after injuries especially in adult mammals is not possible, understanding normal glomerular histogenesis is important. Here, we sought to study the morphometrical and histological development of the normal renal glomeruli of rabbits from birth until postnatal day 40. Moreover, we immunohistochemically evaluated the extent and rate of the Lgr5 expression in the immature renal stem/progenitor cells. The untreated, clinically healthy inbred indigenous rabbits (from Duhok city of Iraqi Kurdistan) were sacrificed at postnatal days 1, 10, 15, 30, and 40. After being processed and embedded in paraffin, rabbit anti-human Lgr5 as a primary antibody and rabbit ImmunoCruz LSAB as a staining kit were used for the immunohistochemical detection of Lgr5+ve cells. For normal histology, hematoxylin and eosin were used. The peak generation and regression of renal corpuscles were at postnatal days 10, and 40, respectively, with 50% decrease. The glomeruli diameter significantly increased (1.3-fold, p = 0.001), whereas the Bowman’s space diameter decreased (50%, p < 0.0001) from postnatal day 1–40. The immature nephrons were seen only in one-day postnatal rabbits. While the superficial glomeruli were compact and small, the juxtamedullary glomeruli were larger and segmented. The formation and development of the juxtaglomerular apparatus were documented at postnatal days 30 and 40 only. Our data revealed highly expressed Lgr5 protein at postnatal day one, and the expression level decreased gradually with advancing age. It was moderately expressed on day 10 and mildly expressed on day 15, whereas no expression was recorded on days 30 and 40 postnatally. Our study provides evidence that the Lgr5 gene, within multipotent stem cells and their lineage progeny, was activated within newly formed glomeruli throughout the early postnatal stages of nephrogenesis.

Abstract 6328: GPR56 as a therapeutic target for the development of antibody-drug conjugates for the treatment of colorectal cancer

Abstract Cancer stem cell (CSC) marker LGR5 is highly expressed in colorectal cancer (CRC) and has been considered as a therapeutic target for the treatment of CRC. Previously, we and others showed that CRC tumors were eliminated by treatment with LGR5-targeted antibody-drug conjugates (ADCs). However, a fraction of tumors eventually recurred, likely due to CSC plasticity or the ability of LGR5-positive CSCs to interconvert into more drug resistant LGR5-negative cancer cells. Through our efforts to identify underlying mechanisms of drug resistance and plasticity and develop therapies to eliminate CRC, we showed that GPR56 expression is increased with loss of LGR5 protein expression. GPR56 is a member of the adhesion G-protein coupled receptor (GPCR) family which mediates diverse functions, including cell adhesion and tumorigenesis. GPR56 is also upregulated in CRC and increased expression levels correlate with poor patient survival. We recently showed GPR56 can promote tumor growth and drug resistance of CRC cells through upregulation of multidrug resistance proteins. These findings identify GPR56 as a potential therapeutic target for the treatment of CRC. Presently, we are focused on the development and characterization of anti-GPR56 ADCs that selectively bind GPR56-high CRC cells to deliver potent cytotoxic drugs and destroy them. We reported the generation of unique anti-GPR56 monoclonal antibodies (mAbs) and are currently developing and optimizing GPR56-targeted ADCs conjugated with different drugs. Cell-based binding assays show that our anti-GPR56 mAb binds with high affinity and specificity to 293T cells overexpressing recombinant GPR56 or GPR56-high CRC cells, with no detectable binding to GPR56-negative cells. Using cytotoxicity assays, we evaluated the in vitro efficacy of anti-GPR56 ADCs against several CRC lines with different levels of GPR56 expression and showed that the ADC is only effective against CRC cells expressing GPR56. Moreover, we evaluated the therapeutic efficacy of our anti-GPR56-ADC against CRC cell line and patient-derived tumor xenograft models in vivo and demonstrated significant inhibition of tumor growth. Altogether, these findings suggest that novel GPR56-targeted ADCs may be a promising therapeutic strategy to overcome resistance for the improved treatment of CRC. Citation Format: Liezl E. Francisco, Treena Chatterjee, Zhengdong Liang, Sheng Zhang, Kendra Carmon. GPR56 as a therapeutic target for the development of antibody-drug conjugates for the treatment of colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6328.

Canine Epithelial Skin Tumours: Expression of the Stem Cell Markers Lgr5, Lgr6 and Sox9 in Light of New Cancer Stem Cell Theories.

Evidence is accumulating that tumour development is driven by cancer stem cells (CSCs). In order to understand the presence and potential contribution of stem cells (SCs) as tumour-initiating cells in canine cutaneous tumours, we selected three putative SC markers (Lgr5, Lgr6 and Sox9) and investigated their expression pattern, level of protein and mRNA expression, in 43 canine hair follicle (HF) and 18 canine cutaneous epidermal tumours by immunohistochemistry and qRT-PCR, using normal skin samples as controls. Lgr5 protein expression was not detected in epidermal and HF tumours; however, Lgr5 mRNA overexpression was evident in some HF tumours. Sox9 was expressed in several tumour cases, both at the protein and mRNA level. The Lgr6 antibody tested was not suitable for formalin-fixed paraffin-embedded tissue samples, but Lgr6 gene showed higher expression in several samples of both HF and epidermal tumours compared with normal skin. Significantly higher mRNA expression levels of the three SC markers were found in trichoblastomas (TB) compared with basal cell carcinomas (BCC). The present results indicated that canine HF and epidermal tumours might have common tumour-initiating cells. The mRNA expression of the three selected SC markers, especially Lgr5, could be potentially useful in the distinction between canine TB and BCC.

The role of tumor budding in colorectal adenocarcinoma: Possible involvement of the intestinal cancer stem cell marker Lgr5.

Tumor budding (TB) is a promising prognostic factor in colorectal cancer (CRC) that is independent of tumor-node-metastasis (TNM) staging. Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) is a stem cell marker and a member of the canonical Wnt-signaling cascade. It is involved in colorectal carcinogenesis. However, its role in CRC progression and TB needs to be clarified. TB was assessed in both H and E and CK immunostained sections of 92 CRC cases. Associations between TB grade and different clinicopathological parameters were evaluated. Lgr5 expression in CRC cases and its association with TB grade and other clinicopathological features was also evaluated. H and E stained sections revealed low- and high-grade budding in 55 (59.8%) and 37 (40.2%) tumors, respectively, whereas Cytokeratin Immunohistochemistry (CK-IHC) showed low- and high-grade budding in 31 (33.7%) and 61 (66.3%) tumors, respectively. TB grade (in H and E and CK stained sections) was significantly associated with adverse pathological prognostic variables including vascular invasion (P = 0.03 and 0.001), lymph node metastasis (P = 0.001 and 0,001), advanced Dukes (P = 0.000 and 0.000), and TNM (P = 0.001 and 0.000) stages and inversely associated with Tumor infiltrating lymphocytes (TILS) (P = 0.02 and 0.0001) which is known to be a good prognostic indicator. Lgr5 protein was positively expressed in 52.2% (48/92) of the CRCs. Immunoreactivity of Lgr5 was significantly associated with histological grade (P = 0.01), lymph node metastasis (P = 0.002), vascular invasion (P = 0.02), TNM stage (P = 0.000), Dukes stage (P = 0.000), and TILS (P = 0.03). Furthermore, Lgr5 was found to be significantly associated with TB estimated in both H and E and CK stained tumors (P = 0.003 and 0.001 respectively). This study supported the relevance of TB in the assessment of CRC aggressiveness. It also revealed that Lgr5 expression is related to morphologic features in the invasive front of CRC. Lgr5 could have an important role in forming a morphologic feature at the invasive front associated with the aggressiveness of the tumor.

Expression of the leucinerich repeat containing G protein-coupled receptor 5 in locally advanced rectal cancer in response to neoadjuvant chemoradiotherapy

Objective To investigate changes in expression of the tumor stem cell marker Leucinerich repeat containing G protein-coupled receptor 5 (Lgr5) before and after neoadjuvant chemoradiotherapy and its predictive effect on neoadjuvant chemoradiotherapy. Methods A retrospective analysis was performed on the clinical data of 42 patients with locally mid-low advanced rectal cancer, who underwent neoadjuvant chemoradiotherapy followed by total mesorectal excision (TME) radical surgery. The patients were all given the test of Lgr5 level prior to and after the new adjuvant therapy. Results The univariate analysis showed that pre-chemoradiotherapy T stage (cT1-3) (P<0.05), pre-chemoradiotherapy N stage (P<0.05), pathological complete response (pCR) after neoadjuvant chemoradiotherapy (P<0.01) were associated with Lgr5 level before neoadjuvant chemoradiotherapy for locally mid-low advanced rectal cancer. In 42 patients, 11 (21.4%) achieved pCR after neoadjuvant chemoradiotherapy. The relationship between Lgr5 levels and pCR were assessed. The expression of Lgr5 protein was higher in the tissues with deeper infiltration or lymph node metastasis. The expression of Lgr5 protein before and after neoadjuvant chemoradiotherapy was 73.80% and 28.57% respectively. Conclusion The expression of Lgr5 is significantly correlated with invasion and lymph node metastasis, and may play an important role in the occurrence and development of epithelial rectal carcinoma. The expression of Lgr5 is related to the degree of tumor pathological remission after neoadjuvant chemoradiotherapy. Overexpression of Lgr5 provides an important implication of malignancy and prognosis in the local mid-low advanced rectal cancer. Key words: Leucinerich repeat containing G protein-coupled receptor 5; Neoadjuvant chemoradiotherapy; Rectal cancer

Expression of stem cell markers CD44 and Lgr5 in colorectal cancer and its relationship with lymph node and liver metastasis

Objective: To investigate the relationship between the expression of stem cell markers CD44 and Lgr5 and the clinicopathological features, lymph node and liver metastasis, and to analyse the value of both in evaluating the prognosis of colorectal cancer. Methods: A total of 90 cases of colorectal cancer, 20 cases of adjacent tissues, 30 cases of lymph node metastases, 28 cases of cancer nodules and 30 cases of liver metastasis of colorectal cancer were collected from Department of Pathology of the Second Hospital of Tianjin Medical University from January 2011 to June 2016. The expression of CD44 and Lgr5 protein was detected by immunohistochemistry, and the relationship between them and clinical pathological data, lymph node metastasis and liver metastasis were analyzed. Results: The positive expression rates of CD44 and Lgr5 in colorectal cancer tissues were 68.9% and 62.2%, which were significantly higher than 30.0% and 15.0% of adjacent tissues(P=0.001 and P<0.001). The expression of CD44 and Lgr5 in colorectal cancer was associated with histological differentiation, depth of tumor invasion, lymph node metastasis, soft tissue nodules, hepatic metastasis, and TNM staging(P=0.021, 0.032, 0.030, 0.011, 0.015, 0.007 and P=0.011, 0.027, 0.017, 0.008, 0.011, 0.021). The positive rates of CD44 and Lgr5 expression in lymph node metastases, cancer nodules and liver metastases (93.3%, 89.3%, 90.0%, and 83.3%, 89.3%, 86.7%) were higher than those in the primary lesions(68.9% and 62.2%)(P=0.007, 0.032, 0.022 and P=0.033, 0.007, 0.013). There is a positive correlation between the expression of CD44 and Lgr5 in colorectal cancer(r=0.615, P<0.001), and both positive expression of CD44 and Lgr5 is associated with histological differentiation, lymph node metastasis and cancer nodules, liver metastasis and TNM staging(P=0.005, 0.003, 0.003, 0.026, 0.014). The Kaplan-Meier survival curve showed that the survival rate of positive expression of CD44 and both positive expression of CD44 and Lgr5 in patients with colorectal cancer was low(P=0.030 and 0.001). Log-rank univariate survival analysis showed that histological differentiation, depth of invasion, lymph node metastasis, liver metastasis, and clinical stage were the influencing factors of postoperative survival time(P=0.035, 0.035, 0.018, 0.016, 0.004). Cox proportional hazards regression model multivariate analysis showed that both positive expression of CD44 and Lgr5, lymph node metastasis, liver metastasis, and clinical stage were independent factors affecting the prognosis of patients with colorectal cancer(P=0.004, 0.044, 0.031, 0.008). Conclusions: The expression of CD44 and Lgr5 is related to the malignant biological behavior of colorectal cancer, and they are important factors in promoting local and distant metastases. Both positive expression of them have a hint of bad prognosis.

Runx1-Stat3 signaling regulates the epithelial stem cells in continuously growing incisors

Rodent incisors grow permanently and the homeostasis of enamel production is maintained by a continuous supply of epithelial progenitors from putative stem cells in the cervical loop. We herein report that Runx1 regulates the Lgr5-expressing epithelial stem cells and their subsequent continuous differentiation into ameloblasts. Mice deficient in epithelial Runx1 demonstrate remarkable shortening of the incisors with underdevelopment of the cervical loop and enamel defects. In this mutant cervical loop, the proliferation of the dental epithelium was significantly disturbed and the expression of Lgr5 and enamel matrix proteins was remarkably downregulated. Interestingly, the expression of Socs3, an inhibitor of Stat3 signaling, was upregulated and Stat3 phosphorylation was suppressed specifically in the mutant cervical loop. The expression of Lgr5 and the enamel matrix protein in the wild-type incisor germs is disturbed by pharmaceutical Stat3 inhibition in vitro., of. Conversely, pharmaceutical activation of Stat3 rescues the defective phenotypes of the Runx1 mutant with upregulated Lgr5 and enamel matrix protein genes. The present results provide the first evidence of the role of Runx1 regulates the Lgr5-expressing epithelial stem cells and differentiation of ameloblast progenitors in the developing incisors. Our study also demonstrates that Stat3 modulates the Runx1-Lgr5 axis in the cervical loop.

Study on the Relationship between Expression of LGR5 and Clinicopathological Characteristics in Gastric Cancer Patients

The aim of the study was to clarify the role of LGR5 in the process of formation and development of gastric cancer. The expression of LGR5 in gastric cancer and corresponding non-cancerous gastric tissues of 52 gastric cancer patients was assessed with the real-time fluorescence quantitative polymerase chain reaction (RT-PCR) and immunohistochemistry. We also analyzed the relationship between the expression level and clinicopathological characteristics. LGR5 gene and protein expression in gastric cancer tissues was in both cases significantly higher than in corresponding non-cancerous gastric tissues (both P 0.05, respectively). Furthermore, LGR5 gene expression was markedly higher in gastric cancer tissues of Helicobacter pylori (HP)-positive patients than negative ones (P < 0.05). The result of the study showed that LGR5 might play a significant role in the process of formation and development of gastric cancer as an oncogene. Its effect might be strengthened by HP infection.

Effect of leucine-rich repeat-containing G-protein coupled receptor 5 gene silencing on biological behaviors of colon cancer stem cells

Objective To investigate the effect of leucine-rich repeat-containing G-protein coupled receptor 5 gene (LGR5) silencing on biological behaviors of colon cancer spheroid cells with stemness. Methods RNA interfering methods were used to knock down the LGR5 expression. Small interfering RNA (siRNA) targeting LGR5 and control siRNA were transfected into HT29 colon cancer spheroid cells by Lipofectamine RNAi MAX. Cells transfected with control siRNA or untransfected were used as negative control and blank control respectively. The expression of LGR5 mRNA and protein was detected by real-time quantitative polymerase chain reaction (Real-time PCR) and Western blotting. The proliferation of spheroid cells was detected by cell counting kit-8 (CCK-8) assay at 1st, 2nd, 3rd, and 4th day after transfection respectively. The self-renewal, invasion and cell cycle of spheroid cells were determined by sphere formation assay, Transwell assay and flow cytometry respectively at 48th h after transfection. Results At 48 h after transfection, the expression of LGR5 mRNA in experimental group (0.32±0.02) was remarkably lower than that in blank control group (1.00±0.16) and negative control group (0.99±0.12) (P=0.000). The expression of LGR5 protein in experimental group was also significantly down-regulated (P=0.000). CCK-8 assay showed that the absorbance (A) value in blank control group, negative control group and experimental group at 4th day was 0.540±0.010, 0.528±0.016 and 0.390±0.022, respectively (P=0.000). In addition, the experimental group (21.33±2.08) formed fewer secondary spheres than blank control group (72.33±3.06) and negative control group (70.67±2.52, P=0.000). Flow cytometry revealed that the cells in the experimental group were significantly arrested in G0/G1 phase (P=0.000). Furthermore, the number of cells passing through the Transwell membrane in experimental group (35.60±6.74) was remarkably decreased as compared with that in the blank control group (86.47±7.85) and negative control group (83.53±8.58, P=0.000). Conclusion LGR5 gene silencing markly inhibited the proliferation, self-renewal and invasion of HT29 spheroid cells, indicating that LGR5 may play an important role in manipulating the biological behaviors of colon cancer stem cells. Key words: Colon cancer; Cancer stem cells; Leucine-rich repeat-containing G-protein coupled receptor 5; Proliferation; Invasion

Research progress on Lgr5 protein

Research progress on Lgr5 protein

RNAi-mediated inhibition of Lgr5 leads to decreased angiogenesis in gastric cancer.

Leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) is a novel gastric cancer marker. However, it is unclear whether it can play roles in tumor angiogenesis. In this study, we aim to investigate the role of Lgr5 on gastric cancer angiogenesis. Lgr5, VEGF expression levels and microvessel density (MVD) were detected in tumor tissue. Then, Lgr5 mRNA was downregulated by small interference RNA technique. Western blotting and real-time quantitative PCR (qRT-PCR) were performed to detect the expression of Lgr5 and VEGF protein and mRNA in Lgr5 siRNA-transfected gastric cancer cells. The effect of silencing Lgr5 on angiogenesis was examined by assessing human umbilical vein endothelia cell (HUVEC) capillary tube formation. The results indicated that Lgr5 expression was upregulated in gastric cancer and positively correlated with VEGF (r=0.305, P=0.001) and MVD (r=0.312, P=0.001). Silencing of Lgr5 expression resulted in suppression of VEGF mRNA and protein (all P=0.001). Moreover, when HUVECs were stimulated with conditioned medium from Lgr5 siRNA-transfected gastric cancer cells, tube formation was significantly decreased (2.51 ± 0.19 mm/mm2) compared with the treatment with regular cell culture medium (DMEM) (7.34 ± 0.30 mm/mm2) or medium from control siRNA-transfected cells (7.18 ± 0.33 mm/mm2) (all P=0.001). In conclusion, Lgr5 plays important roles in angiogenesis. Lgr5-specific siRNA could be designed into an effective therapeutic agent to inhibit gastric cancer angiogenesis.

Abstract 1706: Evaluation of LGR5 protein expression in colon cancer stem cells

Abstract Cancer stem cells are a subpopulation of cancer cells responsible for cancer initiation, development and metastasis. A number of studies demonstrated that Leucine-rich repeat containing G-protein-coupled receptor 5 (LGR5) can drive cancer development through triggering canonical Wnt signaling and its downstream gene expression. LGR5 is an important biomarker specifically expressed on colon cancer stem cells. In this study, we have successfully developed an LGR5 antibody with high specificity to detect endogenous LGR5 expression in different immunoassay application. By screening multiple anti-LGR5 hybridoma clones, antibody generated by clone UMAB212 was proven to be highly specific on our high density protein microarray chip assay. Here our experimental data demonstrated that clone UMAB212 recognizes not only human LGR5 protein but also mouse LGR5 protein in both western blot and flow cytometry applications. No cross-reactivity was observed with the other two LGR family members, LGR4 and LGR6. Furthermore, this antibody also works great on immunohistochemistry application on FFPE tissue blocks. In summary, UMAB212 is great tool for us to study LGR5 protein in different immunoassay setting and it could also be a potential cancer diagnostic reagent. Citation Format: Wei Fu, Rachel Gonzalez, Kehu Yuan, Caiwei Chen, Haitao Wei, Hsiangmin Lu, Qi Ren, Evelin Logis, Sean Kelly, Wei-Wu He, Donghui Ma. Evaluation of LGR5 protein expression in colon cancer stem cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1706.

Isolation of Human Colon Stem Cells Using Surface Expression of PTK7.

SummaryInsertion of reporter cassettes into the Lgr5 locus has enabled the characterization of mouse intestinal stem cells (ISCs). However, low cell surface abundance of LGR5 protein and lack of high-affinity anti-LGR5 antibodies represent a roadblock to efficiently isolate human colonic stem cells (hCoSCs). We set out to identify stem cell markers that would allow for purification of hCoSCs. In an unbiased approach, membrane-enriched protein fractions derived from in vitro human colonic organoids were analyzed by quantitative mass spectrometry. Protein tyrosine pseudokinase PTK7 specified a cell population within human colonic organoids characterized by highest self-renewal and re-seeding capacity. Antibodies recognizing the extracellular domain of PTK7 allowed us to isolate and expand hCoSCs directly from patient-derived mucosa samples. Human PTK7+ cells display features of canonical Lgr5+ ISCs and include a fraction of cells that undergo differentiation toward enteroendocrine lineage that resemble crypt label retaining cells (LRCs).

Aberrant Expression of Markers of Cancer Stem Cells in Gastric Adenocarcinoma and their Relationship to Vasculogenic Mimicry.

Gastric cancer is the second leading cause of cancer-related death in Asia, and the majority type is gastric adenocarcinoma (GAC). Most GAC patients die of recurrence and metastasis. Cancer stem cells (CSCs) have been thought to be responsible for the initiation, development, metastasis, and ultimately recurrence of cancer. In this study, we aimed to investigate expression and clinical significance of CSCs markers, CD133 and Lgr5, and vasculogenic mimicry (VM) in primary GAC. Specimens from 261 Chinese patients with follow-up were analyzed for CD133, Lgr5 protein expression and VM by immunohistochemical and histochemical staining. The Pearson Chi's square test was used to assess the associations among the positive staining of these markers and clinicopathological characteristics. Postoperative overall survival time was were studied by univariate and multivariate analyses. In GAC tissues, positive rates of 49.0%, 38.7%, and 26.8% were obtained for CD133, Lgr5, and VM, respectively. The mean score of microvessel density (MVD) was 21.7±11.1 in GAC tissues. There was a significantly difference between the positive and negative groups. There was a positive relationship between the VM, the expression of CD133 and Lgr5, and the score of MVD and the grades of tumor, lymph node metastasis, TNM stages (all p<0.05). The overall mean survival time of the patients with CD133, Lgr5, VM, and MVD (≥22) positive expression was lower than that of patients with negative expression. The score of MVD, positive expression of CD133 and VM were independent prognostic factors of GAC (p<0.05). VM, and expression of CD133, Lgr5, and the score of MVD are related to grades of tumor, lymph node metastasis, TNM stages, and overall mean survival time. It is suggested that CSCs and VM could play an important role in the evolution of GAC.

Correlation of Musashi-1, Lgr5, and pEGFR expressions in human small intestinal adenocarcinomas.

Recent studies have revealed that Musashi-1 and Lgr5 (leucine-rich-repeat-containing G-protein-coupled receptor 5) were putative stem cell genes. The epidermal growth factor receptor (EGFR) has also been extensively studied; it was known as an oncogenic driver in cancers. Overexpressions of Musashi-1, EGFR, and Lgr5 have been reported in some tumor tissues and cell lines. In this study, we used immunohistochemical analysis to investigate the expression pattern of Musashi-1, Lgr5, and pEGFR in 38 small intestinal adenocarcinomas (SIAs) resection specimens, 20 matched normal specimens and tried to analyze the correlations among them. The positive rate of Musashi-1, Lgr5, and pEGFR in SIAs, respectively, was 71 % (27/38), 55 % (21/38), and 45 % (17/38). Compared with the adjacent normal small intestinal mucosa, Musashi-1, Lgr5, and pEGFR protein were overexpressed in SIAs (P< 0.05). Furthermore, Musashi-1 and Lgr5 expressions were significantly correlated with the depth of wall invasion (P = 0.0011, P = 0.0017, respectively). Musashi-1 expression was closely correlated with Lgr5 (P = 0.015, r = 0.392). However, pEGFR expression was not associated with age, gender, tumor size, differentiation, depth of invasion, lymphatic metastasis, TNM stage, and pEGFR expression was not correlated with Musashi-1 or Lgr5 (P > 0.05, r = 0.064; P > 0.05, r = 0.307, respectively). Thus, we suggest that Musashi-1, Lgr5, and pEGFR are overexpressed in human SIAs and may play roles in human SIA carcinogenesis and progression.

Nutrient stress alters the glycosylation status of LGR5 resulting in reduced protein stability and membrane localisation in colorectal tumour cells: implications for targeting cancer stem cells.

Background:LGR5 is an important marker of intestinal stem cells and performs its vital functions at the cell membrane. Despite the importance of LGR5 to both normal and cancer stem cell biology, it is not known how microenvironmental stress affects the expression and subcellular distribution of the protein.Methods:Nutrient stress was induced through glucose starvation. Glycosylation status was assessed using endoglycosidase or tunicamycin treatment. Flow cytometry and confocal microscopy were used to assess subcellular distribution of LGR5.Results:Glucose deprivation altered the glycosylation status of LGR5 resulting in reduced protein stability and cell surface expression. Furthermore, inhibiting LGR5 glycosylation resulted in depleted surface expression and reduced localisation in the cis-Golgi network.Conclusions:Nutrient stress within a tumour microenvironment has the capacity to alter LGR5 protein stability and membrane localisation through modulation of LGR5 glycosylation status. As LGR5 surface localisation is required for enhanced Wnt signalling, this is the first report to show a mechanism by which the microenvironment could affect LGR5 function.