Tumor xenograft animal models for esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is the predominant subtype of esophageal cancer worldwide and highly prevalent in less developed regions. Management of ESCC is challenging and involves multimodal treatments. Patient prognosis is generally poor especially for those diagnosed in advanced disease stage. One factor contributing to this clinical dismal is the incomplete understanding of disease mechanism, for which this situation is further compounded by the presence of other limiting factors for disease diagnosis, patient prognosis and treatments. Tumor xenograft animal models including subcutaneous tumor xenograft model, orthotopic tumor xenograft model and patient-derived tumor xenograft model are vital tools for ESCC research. Establishment of tumor xenograft models involves the implantation of human ESCC cells/xenografts/tissues into immunodeficient animals, in which mice are most commonly used. Different tumor xenograft models have their own advantages and limitations, and these features serve as key factors to determine the use of these models at different stages of research. Apart from their routine use on basic research to understand disease mechanism of ESCC, tumor xenograft models are actively employed for undertaking preclinical drug screening project and biomedical imaging research.

Preclinical Study of Novel Curcumin Analogue SSC-5 Using Orthotopic Tumor Xenograft Model for Esophageal Squamous Cell Carcinoma.

PURPOSE: Tumor xenograft model is an indispensable animal cancer model. In esophageal squamous cell carcinoma (ESCC) research, orthotopic tumor xenograft model establishes tumor xenograft in the animal esophagus, which allows the study of tumorigenesis in its native microenvironment. MATERIALS AND METHODS: In this study,we described two simple and reproducible methods to develop tumor xenograft at the cervical or the abdominal esophagus in nude mice by direct injection of ESCC cells in the esophageal wall. RESULTS: In comparing these two methods, the cervical one presented with more clinically relevant features, i.e., esophageal stricture, body weight loss and poor survival. In addition, the derived tumor xenografts accompanied a rapid growth rate and a high tendency to invade into the surrounding structures. This model was subsequently used to study the anti-tumor effect of curcumin, which is known for its potential therapeutic effects in various diseases including cancers, and its analogue SSC-5. SSC-5 was selected among the eight newly synthesized curcumin analogues based on its superior anti-tumor effect demonstrated in an MTT cell proliferation assay and its effects on apoptosis induction and cell cycle arrest in cultured ESCC cells. Treatment of orthotopic tumor-bearing mice with SSC-5 resulted in an inhibition in tumor growth and invasion. CONCLUSION: Taken together, we have established a clinically relevant orthotopic tumor xenograft model that can serve as a preclinical tool for screening new anti-tumor compounds, e.g., SSC-5, in ESCC.

14-3-3σ confers cisplatin resistance in esophageal squamous cell carcinoma cells via regulating DNA repair molecules.

Esophageal squamous cell carcinoma (ESCC) is the predominant type of esophageal cancer in Asia. Cisplatin is commonly used in chemoradiation for unresectable ESCC patients. However, the treatment efficacy is diminished in patients with established cisplatin resistance. To understand the mechanism leading to the development of cisplatin resistance in ESCC, we compared the proteomes from a cisplatin-resistant HKESC-2R cell line with its parental-sensitive counterpart HKESC-2 to identify key molecule involved in this process. Mass spectrometry analysis detected 14-3-3σ as the most abundant molecule expressed exclusively in HKESC-2R cells, while western blot result further validated it to be highly expressed in HKESC-2R cells when compared to HKESC-2 cells. Ectopic expression of 14-3-3σ increased cisplatin resistance in HKESC-2 cells, while its suppression sensitized SLMT-1 cells to cisplatin. Among the molecules involved in drug detoxification, drug transportation, and DNA repair, the examined DNA repair molecules HMGB1 and XPA were found to be highly expressed in HKESC-2R cells with high 14-3-3σ expression. Subsequent manipulation of 14-3-3σ by both overexpression and knockdown approaches concurrently altered the expression of HMGB1 and XPA. 14-3-3σ, HMGB1, and XPA were preferentially expressed in cisplatin-resistant SLMT-1 cells when compared to those more sensitive to cisplatin. In ESCC patients with poor response to cisplatin-based chemoradiation, their pre-treatment tumors expressed higher expression of HMGB1 than those with response to such treatment. In summary, our results demonstrate that 14-3-3σ induces cisplatin resistance in ESCC cells and that 14-3-3σ-mediated cisplatin resistance involves DNA repair molecules HMGB1 and XPA. Results from this study provide evidences for further work in researching the potential use of 14-3-3σ and DNA repair molecules HMGB1 and XPA as biomarkers and therapeutic targets for ESCC.

Oxygen carrier YQ23 can enhance the chemotherapeutic drug responses of chemoresistant esophageal tumor xenografts.

PURPOSE: Adjunct chemoradiation is offered to unresectable esophageal squamous cell carcinoma (ESCC) patients, while its use is limited in tumors with strong resistance. Oxygen carriers or anti-hypoxic drugs belong to an emerging class of regulators that can alleviate tumor hypoxia. METHODS: We investigate the potential use of a novel oxygen carrier YQ23 in sensitizing chemoresistant ESCC in a series of subcutaneous tumor xenograft models developed using ESCC cell lines with different strengths of chemosensitivities. RESULTS: Tumor xenografts were developed using SLMT-1 and HKESC-2 ESCC cell lines with different strengths of resistance to two chemotherapeutic drugs, 5-fluorouracil and cisplatin. More resistant SLMT-1 xenografts responded better to YQ23 treatment than HKESC-2, as reflected by the induced tumor oxygen level. YQ23 sensitized SLMT-1 xenografts toward 5-fluorouracil via its effect on reducing the level of a hypoxic marker HIF-1α. Furthermore, a derangement of tumor microvessel density and integrity was demonstrated with a concurrent decrease in the level of a tumor mesenchymal marker vimentin. Similar to the 5-fluorouracil sensitizing effect, YQ23 also enhanced the response of SLMT-1 xenografts toward cisplatin by reducing the tumor size and the number of animals with invasive tumors. Chemosensitive HKESC-2 xenografts were irresponsive to combined YQ23 and cisplatin treatment. CONCLUSIONS: In all, YQ23 functions selectively on chemoresistant ESCC xenografts, which implicates its potential use as a chemosensitizing agent for ESCC patients.

Overexpression of transferrin receptor CD71 and its tumorigenic properties in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is the predominant type of esophageal cancer in endemic Asian regions. In the present study, we investigated the clinical implication and role of transferrin receptor CD71 in ESCC. CD71 has a physiological role in cellular iron intake and is implicated in the carcinogenesis of various types of tumors. In our cohort, more than a 2-fold upregulation of the CD71 transcript was detected in 61.5% of patients using quantitative polymerase chain reaction. Immunohistochemical analysis also showed strong membranous and cytoplasmic localization of CD71 in paraffin-embedded tumors. Staining parallel tumor sections with the proliferative marker Ki-67 revealed that the pattern of Ki-67 staining was associated with CD71 expression. Analysis of clinicopathological data indicated that CD71 overexpression can be used as an indicator for advanced T4 stage (p=0.0307). These data suggested a strong link between CD71 and ESCC. Subsequent in vitro assays using short interfering RNA (siRNA) to suppress CD71 expression confirmed the tumorigenic properties of CD71 in ESCC; cell growth inhibition and cell cycle arrest at S phase were observed in CD71-suppressed cells. The underlying mechanism involved activation of the MEK/ERK pathway. In summary, the present study provides evidence showing the tumorigenic properties of CD71 in ESCC with clinical correlations and suggests targeting CD71 as a strategy for the treatment of ESCC.