Id Proteins Contribute to Tumor Development and Metastatic Colonization in a Model of Bladder Carcinogenesis

Inhibitor of DNA Binding 2 (ID2): A Novel Marker for Lymph Node Metastasis in Head and Neck Squamous Cell Carcinoma

BACKGROUND

Although aggressive invasion and sequential lymph node metastasis (LNM) significantly affect the prognosis of patients with head and neck squamous cell carcinoma (HNSCC), studies on identifying the factors that regulate this process remain scarce. This study found an inhibitor of DNA binding 2 (ID2) as a novel molecule involved in the regulation of invasion and LNM of HNSCC and further verified its functional role.

METHODS

The study examined the translational significance between ID2 expression levels and the presence of LNM as well as the prognosis for 119 patients with HNSCC after treatment. In addition, in vitro and in vivo experiments were performed using ID2 gene-modulated HNSCC cell lines to determine the functional role of ID2 in the invasion and LNM of HNSCC.

RESULTS

Elevated levels of ID2 expression were closely associated with the presence of LNM in 119 patients with HNSCC, resulting in a poor prognosis. Overexpression of ID2-induced invasion and LNM of HNSCC cells was observed in vitro and in vivo. By contrast, knockdown of the ID2 gene diminished invasion and LNM of HNSCC cells. In addition, the ID2 expression level increased the expression level of matrix metalloproteinase 1 (MMP1), a molecule downstream to ID2. Furthermore, silencing of MMP1 in ID2-overexpressed HNSCC cells rescued the elevated invasion and LNM capabilities of these cells, suggesting that ID2 enhances invasion and LNM partly via MMP1 activation.

CONCLUSION

In the invasion and LNM of HNSCC, ID2 plays an important role by modulating MMP1 expression, suggesting ID2-MMP1 axis to be a novel alternative therapeutic target for invasion and LNM of HNSCC.

Inhibitor of DNA binding proteins: implications in human cancer progression and metastasis

Inhibitor of DNA binding (ID) proteins are a class of helix-loop-helix (HLH) transcription regulatory factors that act as dominant-negative antagonists of other basic HLH proteins through the formation of non-functional heterodimers. These proteins have been shown to play critical roles in a wide range of tumor-associated processes, including cell differentiation, cell cycle progression, migration and invasion, epithelial-mesenchymal transition, angiogenesis, stemness, chemoresistance, tumorigenesis, and metastasis. The aberrant expression of ID proteins has not only been detected in many types of human cancers, but is also associated with advanced tumor stages and poor clinical outcome. In this review, we provide an overview of the key biological functions of ID proteins including affiliated signaling pathways. We also describe the regulation of ID proteins in cancer progression and metastasis, and elaborate on expression profiles in cancer and the implications for prognosis. Lastly, we outline strategies for the therapeutic targeting of ID proteins as a promising and effective approach for anticancer therapy.