3045 - Positive Feedback Activation of Notch Signal by Obesity Enhances Colorectal Tumorigenicity

Background

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Investigations revealed that the steep rise of CRC incidence was significantly linked to increased obesity rates. However, the molecular interactions of obesity with CRC are still not well understood. The Notch signaling pathway is critical for many cellular processes. It is also a key player in regulating body energy metabolism. Therefore, we aimed to investigate the potential interaction and mechanism of Notch signal between obesity and CRC tumorigenesis.

Methods

In the present study, we randomly recruited 968 cases of CRC specimens, 262 cases of colorectal intraepithelial neoplasia specimens and 185 cases of normal epithelium specimens. Target protein expression was investigated by immunohistochemistry. C57BL/6J mice were randomly allocated intogroups fed with standard rodent chow, high-fat diet (HFD), and HFD treated with DBZ or DAPT. Potential differentially expressed proteins were screened by iTRAQ, and these identified proteins were then analyzed.

Results

Notch1 intracellular domain and DLL4 was up-regulated in overweight participants compared with normal-weight ones. In overweight participants, Notch1 was increased from normal epithelium, intraepithelial neoplasia to CRC. Obesity was identified at week 5 in mice fed with HFD, which began to lead to upregulation of DLL4 and consequent increased Notch1 activity in colorectal tissues. While mice treated with DBZ and DAPT were almost resistant to HFD-induced obesity then. After 10 weeks, Notch1 activity in mice fed with HFD was significantly up-regulated compared with those fed with standard rodent chow. In addition, glucose tolerance and insulin sensitivity were also ameliorated by DBZ and DAPT treatment, through a PP2A-SHIP2 dependent manner.

Conclusions

Notch signaling activation is linked to obesity in both nonmalignant participants and CRC patients. Obesity induced by HFD can increase Notch activity by DLL4-Notch1 pathway. While inhibition of Notch signaling can attenuate high fat diet–induced obesity by improving insulin resistance.These results indicate that activation of Notch signaling by its positive feedback with obesity could be a molecular bridge that connecting obesity and CRC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Xian Jiaotong University.

Funding

National Nature Science Foundation of China.

Disclosure

All authors have declared no conflicts of interest.