Lack of an additive effect between the deletions of Klf5 and Nkx3-1 in mouse prostatic tumorigenesis

Klf5 deletion promotes Pten deletion-initiated luminal-type mouse prostate tumors through multiple oncogenic signaling pathways

Krüppel-like factor 5 (KLF5) regulates multiple biologic processes. Its function in tumorigenesis appears contradictory though, showing both tumor suppressor and tumor promoting activities. In this study, we examined whether and how Klf5 functions in prostatic tumorigenesis using mice with prostate-specific deletion of Klf5 and phosphatase and tensin homolog (Pten), both of which are frequently inactivated in human prostate cancer. Histologic analysis demonstrated that when one Pten allele was deleted, which causes mouse prostatic intraepithelial neoplasia (mPIN), Klf5 deletion accelerated the emergence and progression of mPIN. When both Pten alleles were deleted, which causes prostate cancer, Klf5 deletion promoted tumor growth, increased cell proliferation, and caused more severe morphologic and molecular alterations. Homozygous deletion of Klf5 was more effective than hemizygous deletion. Unexpectedly, while Pten deletion alone expanded basal cell population in a tumor as reported, Klf5 deletion in the Pten-null background clearly reduced basal cell population while expanding luminal cell population. Global gene expression profiling, pathway analysis, and experimental validation indicate that multiple mechanisms could mediate the tumor-promoting effect of Klf5 deletion, including the up-regulation of epidermal growth factor and its downstream signaling molecules AKT and ERK and the inactivation of the p15 cell cycle inhibitor. KLF5 also appears to cooperate with several transcription factors, including CREB1, Sp1, Myc, ER and AR, to regulate gene expression. These findings validate the tumor suppressor function of KLF5. They also yield a mouse model that shares two common genetic alterations with human prostate cancer—mutation/deletion of Pten and deletion of Klf5.

Krüppel-like factor 5: a novel biomarker for lymph node metastasis and recurrence in supraglottic squamous cell laryngeal carcinoma

Krüppel-like factor 5 (KLF5), a zinc finger-containing transcription factor, is involved in important biological processes including cell transformation, proliferation, and carcinogenesis. However, its clinical significance has remained largely unknown in laryngeal cancer. Here, specimens from 144 patients with laryngeal tumors were investigated by immunohistochemical staining for KLF5, integrin-linked kinase (ILK), and E-cadherin expressions. A clinicopathological study revealed that the KLF5 expression level in tumor cells was significantly correlated with lymph node metastasis (P < 0.05) and local recurrence (P < 0.05). In addition, KLF5, ILK, and E-cadherin (epithelial-mesenchymal transition (EMT) biomarker) expressions were correlated with each other. These findings suggest that KLF5 may be an epithelial-mesenchymal transition-associated biomarker in human laryngeal carcinomas and play important roles in the progression of laryngeal carcinomas. KLF5 immunoreactivity is therefore considered a potential lymph node metastasis and recurrence factor in human laryngeal cancers. In addition, the KLF5-mediated pathway is a potential target for elimination of laryngeal cancer in the future.