Establishment of a colorectal cancer nude mouse visualization model of HIF-1α overexpression

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Band 3 ectopic expression in colorectal cancer induces an increase in erythrocyte membrane-bound IgG and may cause immune-related anemia

Autoimmune hemolytic anemia (AIHA) is a rare comorbidity in colorectal cancer (CRC) and has an unknown etiology. Previously, we described an AIHA case secondary to CRC with ectopic band 3 expression. Herein, we investigated ectopic band 3 expression and erythrocyte membrane-bound IgG in a CRC cohort. Between September 2016 and August 2018, 50 patients with CRC and 26 healthy controls were enrolled in the present study. The expression of band 3 and SLC4A1 mRNA was observed in 97% of CRC surgical specimens. Although clinical AIHA was not observed in any patient with CRC, a direct antiglobulin test was positive in 10 of the patients in the CRC group (p = 0.01). Flow cytometry revealed significantly increased erythrocyte membrane-bound IgG among patients with CRC compared to healthy controls (mean ± standard deviation; 38.8 ± 4.7 vs. 29.9 ± 15.6, p = 0.012). Normocytic anemia was observed, including in cases negative for fecal occult blood, suggesting a shortened erythrocyte life-span due to increased membrane-bound IgG. Immunoprecipitation revealed increased anti-band 3 autoantibodies in patients' sera. Mouse experiments recapitulated this phenomenon. We also confirmed that band 3 expression is controlled by 5'AMP-activated protein kinase under hypoxic conditions. These findings increase our understanding of the etiology of cancer-related anemia.

An insertion/deletion polymorphism within the promoter of EGLN2 is associated with susceptibility to colorectal cancer

OBJECTIVE

To investigate the association between susceptibility to colorectal cancer (CRC) and a 4-bp insertion/deletion polymorphism (rs10680577) in the proximal promoter of the EGLN2 gene.

METHOD

The first step in genotyping EGLN2 was PCR, then the PCR products were separated using 7% nondenaturing polyacrylamide gel electrophoresis and visualized by silver staining according to the final product band location and quantity to determine the genotype of the sample. The final count was done by two different pathologists.

RESULT

In the codominant model, compared with the ins/ins genotype, subjects with the heterozygous ins/del or homozygous del/del genotype had a significantly increased risk of CRC (adjusted OR = 1.45, p<0.0001 and OR = 2.44, p = 0.0001, respectively). Each additional copy of the 4-bp deletion allele conferred a significantly increased risk of CRC (OR = 1.47, 95% CI 1.28-1.66, p<0.0001). In the stratification analysis, we further proved that the association was more prominent in TNM stage III and IV cancer compared with stage I and II (adjusted OR = 1.43, 95% CI 1.07-1.93, p for heterogeneity = 0.02).

CONCLUSIONS

Our study provided initial evidence that the insertion/deletion polymorphism rs10680577 may play a functional role in the development of CRC in the Chinese population.

Hypoxic behavior in cells under controlled microfluidic environment

BACKGROUND

Depleted oxygen levels, known as hypoxia, causes considerable changes in the cellular metabolism. Hypoxia-inducible factors (HIF) act as the major protagonist in orchestrating manifold hypoxic responses by escaping cellular degradation mechanisms. These complex and dynamic intracellular responses are significantly dependent on the extracellular environment. In this study, we present a detailed model of a hypoxic cellular microenvironment in a microfluidic setting involving HIF hydroxylation.

METHODS

We have modeled the induction of hypoxia in a microfluidic chip by an unsteady permeation of oxygen from the microchannel through a porous polydimethylsiloxane channel wall. Extracellular and intracellular interactions were modeled with two different mathematical descriptions. Intracellular space is directly coupled to the extracellular environment through uptake and consumption of oxygen and ascorbate similar to cells in vivo.

RESULTS

Our results indicate a sharp switch in HIF hydroxylation behavior with changing prolyl hydroxylase levels from 0.1 to 4.0μM. Furthermore, we studied the effects of extracellular ascorbate concentration, using a new model, to predict its accumulation inside the cell over a relevant physiological range. In different hypoxic conditions, the cellular environment showed a significant dependence on oxygen levels in resulting intracellular response.

CONCLUSIONS

Change in hydroxylation behavior and nutrient supplementation can have significant potential in designing novel therapeutic interventions in cancer and ischemia/reperfusion injuries.

GENERAL SIGNIFICANCE

The hybrid mathematical model can effectively predict intracellular behavior due to external influences providing valuable directions in designing future experiments.