The complex interplay between Notch signaling and Snail1 transcription factor in the regulation of epithelial–mesenchymal transition (EMT): Notch and Snail1 in epithelial–mesenchymal transition (EMT)

The role of Notch ligand, Delta-like ligand 4 (DLL4), in cancer angiogenesis—implications for therapy

Background

It is generally accepted that angiogenesis is a complex and tightly regulated process characterized by the growth of blood vessels from existing vasculature. Activation of the Notch signalling pathway affects multiple aspects of vascular development. One of the components of the Notch signalling pathway, Delta-like ligand 4 (DLL4), has recently appeared as a critical regulator of tumour angiogenesis and thus as a promising therapeutic target.

Methods

This review article includes available data from peer-reviewed publications associated with the role of DLL4 in cancer angiogenesis. Searches were performed in PubMed, EMBASE, Google Scholar and Web of Science using the terms “tumour angiogenesis”, “DLL4”, “Notch signalling” and “anti-cancer therapy”.

Results

The survival curves of cancer patients revealed that the patients with high DLL4 expression levels had significantly shorter survival times than the patients with low DLL4 expression. Moreover, a positive correlation was also identified between DLL4 and VEGF receptorsʼ expression levels. It seems that inhibition of DLL4 may exert potent growth inhibitory effects on some tumours resistant to anti-VEGF therapies. A great number of blocking agents of DLL4/Notch signalling including anti-DLL4 antibodies, DNA vaccination, Notch antibodies and gamma-secretase inhibitors have been studied in preclinical tumour models.

Conclusion

DLL4 seems to be a promising target in anti-cancer therapy. Nevertheless, the careful evaluation of adverse effects on normal physiological processes in relation to therapeutic doses of anti-DLL4 drugs will be significant for advancement of DLL4 blocking agents in clinical oncology.

Notch and its oncogenic activity in human malignancies

BACKGROUND

Increasing evidence has demonstrated that Notch signaling is deregulated in human hematological malignancies and solid tumors. This signaling has a protumorigenic effect but may also act as a tumor suppressor. How induction of a single pathway gives rise to the opposite effects in different cell types is still unknown.

METHODS

This review article includes available data from peer-reviewed publications associated with the role of Notch signaling during cancer pathogenesis.

RESULTS

Numerous reports have indicated that alterations in Notch signaling and its oncogenic activity were originally associated with the pathogenesis of T‑cell acute lymphoblastic leukemia/lymphoma (T-ALL), an aggressive hematologic tumor affecting children and adolescents. The possibility that Notch could play a significant role in human breast cancer development comes from studies on mouse mammary tumor virus-induced cancer. Numerous findings over the past several years have indicated that alterations in Notch signaling are also responsible for ovarian cancer development. Mention should also be made of the connection between expression of Notch 3 and increased resistance to chemotherapy, which remains a major obstacle to successful treatment. Notch as an oncogenic factor is also involved in the development of colon cancer, lung carcinoma and Kaposi's sarcoma.

CONCLUSION

Notch is a binary cell fate determinant and its overexpression has been described as oncogenic in a wide array of human malignancies. This finding led to interest in therapeutically targeting this pathway, especially by the use of gamma-secretase inhibitors (GSIs) blocking the cleavage of Notch receptors at the cell membrane by the inhibition of Notch intracellular domain (NICD) releasing. Preclinical cancer models have revealed that GSIs suppress the growth of cancers such as pancreatic, breast and lung cancer.