Two Sides of the Same Coin: The Roles of KLF6 in Physiology and Pathophysiology.

The Krüppel-like factors (KLFs) family of proteins control several key biological processes that include proliferation, differentiation, metabolism, apoptosis and inflammation. Dysregulation of KLF functions have been shown to disrupt cellular homeostasis and contribute to disease development. KLF6 is a relevant example; a range of functional and expression assays suggested that the dysregulation of KLF6 contributes to the onset of cancer, inflammation-associated diseases as well as cardiovascular diseases. KLF6 expression is either suppressed or elevated depending on the disease, and this is largely due to alternative splicing events producing KLF6 isoforms with specialised functions. Hence, the aim of this review is to discuss the known aspects of KLF6 biology that covers the gene and protein architecture, gene regulation, post-translational modifications and functions of KLF6 in health and diseases. We put special emphasis on the equivocal roles of its full-length and spliced variants. We also deliberate on the therapeutic strategies of KLF6 and its associated signalling pathways. Finally, we provide compelling basic and clinical questions to enhance the knowledge and research on elucidating the roles of KLF6 in physiological and pathophysiological processes.

LncRNA CASC11 promotes the development of esophageal carcinoma by regulating KLF6.

OBJECTIVE: The aim of this study was to investigate the expression level of long non-coding RNA (lncRNA) CASC11 in esophageal carcinoma (ECa), and to further explore its relationship with clinical progression, pathological parameters, and prognosis of ECa patients. PATIENTS AND METHODS: Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was used to examine the level of lncRNA CASC11 in 45 pairs of ECa tissues and adjacent normal tissues. The relationship between the lncRNA CASC11 level and clinical progression, pathological parameters, and prognosis of ECa patients was analyzed. Meanwhile, the level of lncRNA CASC11 in the ECa cell lines was verified by qPCR as well. In addition, lncRNA CASC11 knockdown model was constructed using lentiviral transfection in ECa cell lines. Subsequently, the cell counting kit-8 (CCK8), colony formation assay, and flow cytometry were used to explore the effect of lncRNA CASC11 on the biological functions of the ECa cells. Finally, the Western Blot and the recovery experiments were used to explore the potential mechanism. RESULTS: In this work, the qPCR results showed that the expression level of lncRNA CASC11 in the ECa tissues was remarkably higher than that of the adjacent normal tissues, and the difference was statistically significant (p<0.05). Compared with patients with a low level of lncRNA CASC11, the pathological stage of patients with high expression was significantly higher, while the overall survival rate was lower (p<0.05). Compared with negative control (NC) group, the proliferation ability of the cells in the lncRNA CASC11 knockdown group CASC11 significantly decreased, whereas cell apoptosis remarkably increased (p<0.05). The Western Blot results revealed that protein expression of KLF6 was remarkably up-regulated after lncRNA CASC11 knockdown. In addition, the recovery experiments found that lncRNA CASC11 and KLF6 had mutual regulation, thereby promoting the malignant progression of ECa. CONCLUSIONS: LncRNA CASC11 expression was remarkably up-regulated in ECa, which was associated with the pathological stage and poor prognosis of ECa. In addition, lncRNA CASC11 could promote the malignant progression of ECa by mutual regulation of KLF6.

MicroRNA 148a-3p promotes Thrombospondin-4 expression and enhances angiogenesis during tendinopathy development by inhibiting Krüppel-like factor 6.

Tendinopathy is a common musculoskeletal disorder with characteristic hypervascularity. The mechanism of angiogenesis in tendinopathy remains unclear. The present study aimed to investigate the roles of miR-148a-3p in angiogenesis development of tendinopathy. In this study, we demonstrated that miR-148a-3p expression was increased in tendinopathy tissues and positively correlated with CD34 levels which is a specific marker for angiogenesis. We identified Krüppel-like factor 6 (KLF6) as a direct target gene of miR-148a-3p in tenocytes. Furthermore, reduced levels of KLF6 in tendinopathy tissues was showed using qRT-PCR and immunohistochemical analysis, compared with controls. A negative correlation between the levels of KLF6 mRNA and miR-148a-3p was observed. Then, we verified that miR-148a-3p could regulate Tsp-4 expression by targeting KLF6 in tenocyte and was positively correlated with Tsp-4 levels in tendinopathy tissues. In a coculture system of tenocytes with endothelial cells (ECs), we observed that transfection of Lv-miR-148a-3p markedly upregulated EC angiogenesis. In summary, our data establish a novel molecular mechanism by which miR-148a-3p upregulates Tsp-4 expression in tenocytes to promote EC angiogenesis by targeting KLF6, which could be helpful for the treatment of tendinopathy in the future.

Autologous T cells expressing the oncogenic transcription factor KLF6-SV1 prevent apoptosis of chronic lymphocytic leukemia cells.

Crosstalk between leukemic cells and the tumor microenvironment is of importance in chronic lymphocytic leukemia (CLL). T cells seem to sustain the survival of CLL cells by various mechanisms. The Krüppel-like family of transcription factors (KLFs) are identified as regulators of proliferation and cell death. In the present study, we analyzed the expression of the wild type (WT) gene KLF6 and the oncogenic splice variant 1 (KLF6-SV1) at the mRNA level in subsets of T cells from CLL patients (n = 29), multiple myeloma patients (n = 6) and normal donors (n = 10). RNA Silencing was used for wtKLF6 and KLF6-SV1. Tumor cell apoptosis was measured. A significant overexpression of wtKLF6 and KLF6-SV1 in T cells of CLL patients compared to normal donors and myeloma patients was noted (p<0.002). Western blot showed that both wtKLF6 and KLF6-SV1 were expressed in purified T cells from CLL patients. KLF6-SV1 siRNA transfection induced a significant down-regulation of KLF6-SV1 in CLL T cells, which lost the capability to sustain the growth of leukemic cells. However, no such a significant effect was seen after wtKLF6 transfection of the autologous T cells. The results suggest that KLF6-SV1 may play a role in the regulation of survival CLL cells.

MicroRNA-543 promotes the proliferation and invasion of clear cell renal cell carcinoma cells by targeting Krüppel-like factor 6.

MicroRNA-543 (miR-543) has been suggested as an important regulator of the development and progression of various cancer types. However, the role and biological function of miR-543 in clear cell renal cell carcinoma (ccRCC) remains unclear. Here, we found that miR-543 expression was significantly increased in tumor tissues from ccRCC patients and ccRCC cell lines. We found that overexpression of miR-543 markedly promoted the proliferation and invasion of ccRCC cells, whereas suppression of miR-543 had the opposite effects. Krüppel-like factor 6 (KLF6) was identified as a target gene of miR-543. Furthermore, we found that miR-543 negatively regulates the expression of KLF6 and p21 in ccRCC cells. Overexpression of KLF6 markedly attenuated the oncogenic effect of miR-543 overexpression. Moreover, knockdown of KLF6 significantly reversed the antitumor effect of miR-543 inhibition. Overall, our results demonstrate that miR-543 promotes the proliferation and invasion of ccRCC cells by targeting KLF6 and suggest that miR-543 may serve as a potential therapeutic target for treatment of ccRCC.

KLF6 inhibited oral cancer migration and invasion via downregulation of mesenchymal markers and inhibition of MMP-9 activities.

Krüppel-like factors can bind to specific DNA motifs and regulate various cellular functions, such as metabolism, cell proliferation, and differentiation. Krüppel-like factor 6 (KLF6), a member of this family, is downregulated in human cancers. Oral cancer is a highly prevalent type in Taiwan. Although KLF6 overexpression in human cancer cells inhibits cell proliferation, induces apoptosis, and attenuates cell migration, the effects of KLF6 on oral cancer remains poorly elucidated. This study investigated the role of KLF6 in oral cancer tumorigenesis. Immunohistochemical staining revealed that nuclear KLF6 level was significantly and inversely associated with tumor size and stages. KLF6 overexpression attenuated the migration and invasion of oral cancer SAS cells. Zymography assay demonstrated that KLF6 inhibited the activities of matrix metalloproteinase 9 (MMP-9) and weakened the expression of mesenchymal markers, such as snail, slug, and vimentin. Our study is the first to provide demonstrate that KLF6 functions as a tumor suppressor gene and prevents the metastasis of oral cancer cells.