Inhibitor of Differentiation 1 (Id1) in Cancer and Cancer Therapy.

The inhibitor of DNA binding (Id) proteins are regulators of cell cycle and cell differentiation. Of all Id family proteins, Id1 is mostly linked to tumorigenesis, cellular senescence as well as cell proliferation and survival. Id1 is a stem cell-like gene more than a classical oncogene. Id1 is overexpressed in numerous types of cancers and exerts its promotion effect to these tumors through different pathways. Briefly, Id1 was found significantly correlated with EMT-related proteins, K-Ras signaling, EGFR signaling, BMP signaling, PI3K/Akt signaling, WNT and SHH signaling, c-Myc signaling, STAT3 signaling, RK1/2 MAPK/Egr1 pathway and TGF-ß pathway, etc. Id1 has potent effect on facilitating tumorous angiogenesis and metastasis. Moreover, high expression of Id1 plays a facilitating role in the development of drug resistance, including chemoresistance, radiation resistance and resistance to drugs targeting angiogenesis. However, controversial results were also obtained. Overall, Id1 represent a promising target of anti-tumor therapeutics based on its potent promotion effect to cancer. Numerous drugs were found exerting their anti-tumor function through Id1-related signaling pathways, such as fucoidan, berberine, tetramethylpyrazine, crizotinib, cannabidiol and vinblastine.

Suppression of ID1 expression in colon cancer cells increases sensitivity to 5-fluorouracil.

Adjuvant chemotherapy with 5-fluorouracil remains the basic treatment for patients with advanced colorectal carcinoma. The major obstacle in successful treatment is the ability of CRC cells to acquire chemoresistance. Here we examined the impact of ID1 silencing on the sensitivity of CRC cells to 5-FU. To suppress ID1 expression in HT-29 and HCT-116 cells the cells were transduced with a lentiviral vector carrying the ID1 silencing sequence. Cells with silenced ID1 showed altered expression of epithelial and mesenchymal markers and exhibited increased proliferation rate compared to the parental cells. HCT-116 cells with suppressed ID1 became sensitized to 5-FU and this was not observed in HT-29 cells. Silencing ID1 resulted in altered expression of genes encoding enzymes metabolizing 5-FU. HT-29 cells with suppressed ID1 had significantly reduced mRNA level for thymidine phosphorylase, uridine-cytydine kinase 2 and dihydropyrimidine dehydrogenase. ID1 suppression in HCT-116 cells resulted in an increase of mRNA level for thymidine phosphorylase, thymidine kinase and uridine-cytydine kinase 2 with concurrent drop of dihydropyrimidine dehydrogenase and thymidylate synthetase mRNA levels. In conclusion, ID1 expression impacts the sensitivity of colon cancer cells to 5-FU and may be considered as a potential predictive marker in CRC treatment.

Inhibition of Id proteins by a peptide aptamer induces cell-cycle arrest and apoptosis in ovarian cancer cells.

BACKGROUND: Inhibitors of DNA-binding proteins (Id1-4), lacking the basic DNA-binding domain, function as dominant inhibitors of cell-cycle regulators. Overexpression of Id proteins promotes cancer cell proliferation and resistance against apoptosis. Level of Id protein expression, especially of Id1, correlates with poor differentiation, enhanced malignant potential and more aggressive clinical behaviour of ovarian tumours. Although overexpression of Ids has been found and shown to correlate with poor clinical outcome, their inhibition at protein level has never been studied. METHODS: A peptide aptamer, Id1/3-PA7, targeting Id1 and Id3, was isolated from a randomised combinatorial expression library using yeast and mammalian two-hybrid systems. Id1/3-PA7 was fused, expressed and purified with a cell-penetrating protein transduction domain. RESULTS: Intracellular-delivered Id1/3-PA7 colocalised to Id1 and Id3. It induced cell-cycle arrest and apoptosis in ovarian cancer cells ES-2 and PA-1. It activated the E-box promoter and increased the expression level of cyclin-dependent kinase inhibitor (CDKN2A) in a dose-dependent manner that is paralleled by the cleavage of poly-ADP ribose polymerase. These effects were counteracted by ectopically overexpressed Id1 and Id3. CONCLUSION: Id1/3-PA7 could represent an exogenous anti-tumour agent that can significantly trigger cell-cycle arrest and apoptosis in ovarian cancer.