Loss of Transcription Factor KLF5 in the Context of p53 Ablation Drives Invasive Progression of Human Squamous Cell Cancer

Abstract

Squamous cell cancers account for more than half of all human cancers, and esophageal cancer is the sixth leading cause of cancer death worldwide. The majority of esophageal squamous cell carcinomas have identifiable p53 mutations, yet the same p53 mutations are found at comparable frequencies in pre-cancerous dysplasia, indicating that transformation requires additional somatic changes yet to be defined. Here we show that the zinc finger transcription factor KLF5 transactivates NOTCH1 in the context of p53 mutation or loss. KLF5 loss limited NOTCH1 activity and was sufficient on its own to transform primary human keratinocytes harboring mutant p53, leading to formation of invasive tumors. Restoration of NOTCH1 blocked transformation of KLF5-deficient and p53 mutant keratinocytes. While human dysplastic epithelia accumulated KLF5, KLF5 expression was lost concurrently with NOTCH1 in squamous cell cancers. Taken together, these results define KLF5 loss as a critical event in squamous cell transformation and invasion. Our findings suggest that KLF5 may be a useful diagnostic and therapeutic target in esophageal squamous carcinomas and possibly more generally in other cancers associated with p53 loss-of-function.

KLF5 Activates MicroRNA 200 Transcription To Maintain Epithelial Characteristics and Prevent Induced Epithelial-Mesenchymal Transition in Epithelial Cells

“…An earlier study suggested that EMT and the invasiveness induced by KLF5 knockdown depend on the mutation or ablation of p53 in esophageal squamous cell carcinoma (11). In HaCaT cells, both alleles of p53 are mutated, which extends the p53 half-life and disrupts its DNA binding activity (87).…”

“…Cellular migration, for example, appears to be regulated by KLF5 in a context-dependent manner (6,9,10), as KLF5 promotes cell migration in mouse primary esophageal keratinocytes by inducing the integrin-linked kinase (ILK) (10). Loss of Klf5 could drive invasive progression of human squamous cell cancer in the context of p53 ablation (11). The migratory ability of cells is often associated with epithelial-mesenchymal transition (EMT) during normal development and cancer progression (12), and KLF5 was predicted to be 1 of the 25 potential regulators of EMT predicted by a novel statistical method, NetworkProfiler, which predicts specific gene regulatory networks for a specific tumor characteristic on the basis of gene expression data (13).…”

KLF4 is downregulated but not mutated during human esophageal squamous cell carcinogenesis and has tumor stage-specific functions

“…11 Biotinylated species-specific secondary antibodies (Vector Laboratories) were added, and antibody binding was detected with the Vectastain Elite ABC Kit (Vector Laboratories) and DAB Peroxidase Substrate Kit (Vector Laboratories), followed by counterstaining with hematoxylin. KLF4 expression was scored using the following scale, as previously described 50 : 0, no staining; 1, very weak staining; 2, weak staining; 3, moderate staining; 4, strong staining; and 5, very strong staining. For each normal tissue, high-grade dysplasia, or invasive ESCC, 100 cells were scored.…”

Two Novel Variants on 13q22.1 Are Associated with Risk of Esophageal Squamous Cell Carcinoma

“…Considering ESCC, however, KLF5 might play a tumor suppressor role. Downregulation of KLF5 might reduce its limitation on NOTCH1 activity and is sufficient on its own to transform primary human keratinocytes to form invasive tumors in the context of P53 mutation or loss of function (41). KLF5 might also activate the JNK pathway and lead to apoptosis and reduced cell survival (42).…”