Esophageal Squamous Cell Dysplasia and Delayed Differentiation With Deletion of Krüppel-Like Factor 4 in Murine Esophagus

Abstract

Background & Aims Klf4 (Krüppel-like factor 4; GKLF) is a DNA-binding transcriptional regulator highly expressed in skin and gastrointestinal epithelia, specifically in regions of cellular differentiation. Homozygous null mice for Klf4 die shortly after birth from skin defects, precluding their analysis at later stages. The aim of this study was to analyze the function of Klf4 in keratinocyte biology and epithelial homeostasis in the adult by focusing on the squamous lined esophagus. Methods Using the ED-L2 promoter of Epstein-Barr virus to drive Cre, we obtained tissue specific ablation of Klf4 in the squamous epithelia of the tongue, esophagus, and forestomach. Results Mice with loss of Klf4 in esophageal epithelia survived to adulthood, bypassing the early lethality. Tissue-specific Klf4 knockout mice had increased basal cell proliferation and a delay in cellular maturation; these mice developed epithelial hypertrophy and subsequent dysplasia by 6 months of age. Moreover, loss of Klf4 in vivo was associated with increased expression of the pro-proliferative Klf5, and Klf4 downregulated Klf5 both transcriptionally and post-transcriptionally. Using gene expression profiling, we also showed decreased expression of critical late-stage differentiation factors and identified alterations of several genes important in cellular differentiation. Conclusions Klf4 is essential for squamous epithelial differentiation in vivo and interacts with Klf5 to maintain normal epithelial homeostasis.

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

“…Esophageal-specific deletion of Klf4 produces squamous cell dysplasia in mice, 13 and consistent with these mechanistic findings, KLF4 was markedly decreased in human esophageal dysplasia and in early stage ESCC compared to adjacent normal tissues (Fig. 2).…”

“…[10][11][12] In mice, Klf4 loss leads to the development of esophageal squamous cell dysplasia, and KLF4 is downregulated in human ESCC suggesting that KLF4 has tumor suppressive functions in ESCC. [13][14][15] Moreover, while Klf4 overexpression in murine esophagus leads to the development of inflammation-mediated ESCC, KLF4 is absent from these tumors, 16 suggesting that Klf4 silencing may be required for tumor formation. As such, KLF4 appears to be important for the development of ESCC, although the precise functions of KLF4 during ESCC development and progression and the mechanisms of KLF4 downregulation in ESCC are not well understood.…”

Esophageal development and epithelial homeostasis

“…Klf4 plays a critical role in normal esophageal epithelial differentiation. Klf4-deficient mice show impaired differentiation and hyperproliferation, resulting in epithelial dysplasia (84).…”

Krüppel-like Factor 4 Promotes Esophageal Squamous Cell Carcinoma Differentiation by Up-regulating Keratin 13 Expression

“…Mice homozygous for a null mutation in KLF4 die by postnatal day 1 and show selective perturbation of late stage differentiation structures in the epidermis (4). Squamous epithelium-specific KLF4 knock-out mice manifest an increased basal cell proliferation and a delayed cellular maturation, and this develops into epithelial hypertrophy and subsequent dysplasia, accompanying down-regulation of critical late stage differentiation factors, which show that KLF4 is essential for squamous epithelial differentiation and homeostasis maintenance (5). KLF4 knock-out mice exhibit a 90% decrease in the number of goblet cells and abnormal expression of the goblet cell-specific marker Muc2, which demonstrates that KLF4 is also required for terminal differentiation of goblet cells in the colon (6).…”