Improved xenograft efficiency of esophageal adenocarcinoma cell lines through in vivo selection

Spontaneous and Induced Animal Models for Cancer Research

Considering the complexity of the current framework in oncology, the relevance of animal models in biomedical research is critical in light of the capacity to produce valuable data with clinical translation. The laboratory mouse is the most common animal model used in cancer research due to its high adaptation to different environments, genetic variability, and physiological similarities with humans. Beginning with spontaneous mutations arising in mice colonies that allow for pursuing studies of specific pathological conditions, this area of in vivo research has significantly evolved, now capable of generating humanized mice models encompassing the human immune system in biological correlation with human tumor xenografts. Moreover, the era of genetic engineering, especially of the hijacking CRISPR/Cas9 technique, offers powerful tools in designing and developing various mouse strains. Within this article, we will cover the principal mouse models used in oncology research, beginning with behavioral science of animals vs. humans, and continuing on with genetically engineered mice, microsurgical-induced cancer models, and avatar mouse models for personalized cancer therapy. Moreover, the area of spontaneous large animal models for cancer research will be briefly presented.

Genetic and pharmacological inhibition of eIF4E effectively targets esophageal cancer cells and augments 5-FU's efficacy

Background

Aberrant activation of eIF4E is critically involved in the progression and chemoresistance of various cancers. Elevated expression of eIF4E has also been documented in human cancerous esophageal tissues. However, the role of eIF4E in esophageal cancer is unclear.

Methods

We analysed the levels of eIF4E expression and eIF4E function in a number of normal and cancerous esophageal cancer cell lines, and studied its underlying mechanism.

Results

We observed that eIF4E expression varies in different esophageal cancer cell lines but was significantly elevated in all tested esophageal cell lines as compared to the control cell lines. We demonstrated that eIF4E inhibition via genetic and pharmacological approaches inhibits cancer cell growth and survival. This inhibition also augments 5-flurouracil's (5-FU's) efficacy as demonstrated with both the in vitro esophageal cancer culture system and our in vivo xenograft mouse model. Of note, the sensitivity of esophageal cancer cells to ribavirin or eIF4E knockdown correlates well with the expression levels of eIF4E, demonstrating that esophageal cells with higher eIF4E expression are more sensitive to eIF4E inhibition. We further confirmed that the mechanism of action of ribavirin on esophageal cancer cells was through suppressing the Akt/mTOR/eIF4E and eIF4E-regulated pathways.

Conclusions

To our knowledge, our work is the first to demonstrate the multiple roles of eIF4E in esophageal cancer. eIF4E was shown to promote cancer cell growth and survival, and protected the cells from chemotherapy. Our work also demonstrated that ribavirin is an attractive candidate for the treatment of esophageal cancer.

Hypoxia imaging with 18F-FAZA PET/CT predicts radiotherapy response in esophageal adenocarcinoma xenografts

Background

Esophageal cancer is an aggressive disease with poor survival rates. A more patient-tailored approach based on predictive biomarkers could improve outcome. We aimed to predict radiotherapy (RT) response by imaging tumor hypoxia with ¹⁸F-FAZA PET/CT in an esophageal adenocarcinoma (EAC) mouse model. Additionally, we investigated the radiosensitizing effect of the hypoxia modifier nimorazole in vitro and in vivo.

Methods

In vitro MTS cell proliferation assays (OACM5 1.C SC1, human EAC cell line) were performed under normoxic and hypoxic (< 1%) conditions: control (100 μL PBS), nimorazole, irradiation (5, 10 or 20 Gy) with or without nimorazole. In vivo, subcutaneous xenografts were induced in nude mice (OACM5 1.C SC1). Treatment was given daily for 5 consecutive days: (A) control (600 μl NaCl 0.9% intraperitoneally (IP)) (N = 5, n = 7), (B) RT (5 Gy/d) (N = 11, n = 20), (C) combination (nimorazole (200 mg/kg/d IP) 30 min before RT) (N = 13, n = 21). N = number of mice, n = number of tumors. ¹⁸F-FAZA PET/CT was performed before treatment and tumor to background (T/B) ratios were calculated. Relative tumor growth was calculated and tumor sections were examined histologically (hypoxia, proliferation).

Results

A T/B ≥ 3.59 on pre-treatment ¹⁸F-FAZA PET/CT was predictive for worse RT response (sensitivity 92.3%, specificity 71.4%). Radiation was less effective in hypoxic tumors (T/B ≥ 3.59) compared to normoxic tumors (T/B < 3.59) (P = 0.0025). In vitro, pre-treatment with nimorazole significantly decreased hypoxic radioresistance (P < 0.01) while in vivo, nimorazole enhanced the efficacy of RT to suppress cancer cell proliferation in hypoxic tumor areas (Ki67, P = 0.064), but did not affect macroscopic tumor growth.

Conclusions

Tumor tissue hypoxia as measured with ¹⁸F-FAZA PET/CT is predictive for RT response in an EAC xenograft model. The radiosensitizing effect of nimorazole was questionable and requires further investigation.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-0984-3) contains supplementary material, which is available to authorized users.