Transcriptional Regulation Of Id1 On Differentiation-associated Gene SPRR3

In our previous work of cDNA array, we identified 92 differentially expessed genes including 77 downregulated and 15 up-regulated genes in esophageal cancer tissues compaired with their adjacent normal counterparts. Among them, inhibitor of DNA binding or differentiation (Id1) is upregulated in esophageal squamous cancer and small proline-rich protein 3(SPRR3) is downregulated.We further analyzed the expression of Id1 and Id2 in esophageal cancer tissues and paired adjacent normal tissues using immunohistochemistry. Id1 and Id2 was significantly overexpressed in esophageal cancer tissues compared with their normal counterparts, moreover, strong expression of both genes was also found in the cytoplasm of vascular endothelium.SPRR3 was a differentiation-associated gene and downregulated in esophageal cancer, siRNA specific for Id1 was used to knockdown the expression of Id1 in KYSE450 esophageal cancer cell line and accordingly we detected the downregulated expression of SPRR3. To further confirm the function and possible mechanism of Id1 on SPRR3 transcription, a series of truncated vector of SPRR3 promoter were constructed to convey the dual luciferase reporter system assay. We found that Id1 and Ets1 can promote the transcriptional activity when co-transfected with one truncated region of SPRR3 promoter. Moreover, impaired capacity of KYSE450 esophageal cancer cell treated with Id1 siRNA suggested a role of Id1 in promoting cell invasion.