Krüppel-like factor 9 suppressed tumorigenicity of the pancreatic ductal adenocarcinoma by negatively regulating frizzled-5

Transcription factor KLF9 inhibits the proliferation, invasion, and migration of pancreatic cancer cells by repressing KIAA1522

AIM

Pancreatic cancer (PC) has a poor prognosis and high mortality. Kruppel-like factor 9 (KLF9), a transcription factor, is aberrantly expressed in various neoplasms. The current study sought to analyze the functional role of KLF9 in the proliferation, invasion, and migration of PC cells.

METHODS

The expression patterns of KLF9 and KIAA1522 in normal pancreatic cells (HPDE-C7) and PC cells (Panc 03.27, BxPc3, SW1990) were determined by real-time quantitative polymerase chain reaction and Western blot assay. After treatment of KLF9 overexpression, proliferation, invasion, and migration were evaluated by cell counting kit-8, 5-ethynyl-2'-deoxyuridine staining, and Transwell assays. The binding of KLF9 to the KIAA1522 promoter was analyzed by dual-luciferase assay and chromatin immunoprecipitation. The rescue experiment was conducted to analyze the role of KIAA1522.

RESULTS

KLF9 was downregulated, while KIAA1522 was upregulated in PC cells. KLF9 overexpression mitigated the proliferation, invasion, and migration of PC cells. Enrichment of KLF9 led to inhibition of the KIAA1522 promoter and repressed KIAA1522 expression. KIAA1522 overexpression neutralized the inhibitory role of KLF9 in PC cell functions.

CONCLUSION

KLF9 is enriched in the KIAA1522 promoter and negatively regulates KIAA1522 expression, thereby mitigating the proliferation, invasion, and migration of PC cells.

PAFAH1B3 is a KLF9 target gene that promotes proliferation and metastasis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies. Uncontrolled cell proliferation, invasion and migration of pancreatic cancer cells are the fundamental causes of death in PDAC patients. Our previous studies showed that KLF9 inhibits the proliferation, invasion and migration of pancreatic cancer cells. However, the underlying mechanisms are not fully understood. In this study, we found that platelet-activating factor acetylhydrolase IB3 (PAFAH1B3) is highly expressed in pancreatic cancer tissues and cells. In vitro and in vivo studies showed that overexpression of PAFAH1B3 promoted the proliferation and invasion of pancreatic cancer cells, while downregulation of PAFAH1B3 inhibited these processes. We found that KLF9 expression is negatively correlated with PAFAH1B3 expression in pancreatic cancer tissues and cells. Western blotting revealed that KLF9 negatively regulates the expression of PAFAH1B3 in pancreatic cancer tissues and cells. Rescue experiments showed that overexpression of PAFAH1B3 could partially attenuate the suppression of pancreatic cancer cell proliferation, invasion and migration induced by KLF9 overexpression. Finally, chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were carried out, and the results showed that KLF9 directly binds to the promoter of PAFAH1B3 and inhibits its transcriptional activity. In conclusion, our study indicated that KLF9 can inhibit the proliferation, invasion, migration and metastasis of pancreatic cancer cells by inhibiting PAFAH1B3.

Krüppel-like Factor-9 and Krüppel-like Factor-13: Highly Related, Multi-Functional, Transcriptional Repressors and Activators of Oncogenesis

Specificity Proteins/Krüppel-like Factors (SP/KLF family) are a conserved family of transcriptional regulators. These proteins share three highly conserved, contiguous zinc fingers in their carboxy-terminus, requisite for binding to cis elements in DNA. Each SP/KLF protein has unique primary sequence within its amino-terminal and carboxy-terminal regions, and it is these regions which interact with co-activators, co-repressors, and chromatin-modifying proteins to support the transcriptional activation and repression of target genes. Krüppel-like Factor 9 (KLF9) and Krüppel-like Factor 13 (KLF13) are two of the smallest members of the SP/KLF family, are paralogous, emerged early in metazoan evolution, and are highly conserved. Paradoxically, while most similar in primary sequence, KLF9 and KLF13 display many distinct roles in target cells. In this article, we summarize the work that has identified the roles of KLF9 (and to a lesser degree KLF13) in tumor suppression or promotion via unique effects on differentiation, pro- and anti-inflammatory pathways, oxidative stress, and tumor immune cell infiltration. We also highlight the great diversity of miRNAs, lncRNAs, and circular RNAs which provide mechanisms for the ubiquitous tumor-specific suppression of KLF9 mRNA and protein. Elucidation of KLF9 and KLF13 in cancer biology is likely to provide new inroads to the understanding of oncogenesis and its prevention and treatments.

The Role of Krüppel-like Factors in Pancreatic Physiology and Pathophysiology

Krüppel-like factors (KLFs) belong to the family of transcription factors with three highly conserved zinc finger domains in the C-terminus. They regulate homeostasis, development, and disease progression in many tissues. It has been shown that KLFs play an essential role in the endocrine and exocrine compartments of the pancreas. They are necessary to maintain glucose homeostasis and have been implicated in the development of diabetes. Furthermore, they can be a vital tool in enabling pancreas regeneration and disease modeling. Finally, the KLF family contains proteins that act as tumor suppressors and oncogenes. A subset of members has a biphasic function, being upregulated in the early stages of oncogenesis and stimulating its progression and downregulated in the late stages to allow for tumor dissemination. Here, we describe KLFs' function in pancreatic physiology and pathophysiology.

Krüppel-like factors in tumors: Key regulators and therapeutic avenues

Krüppel-like factors (KLFs) are a group of DNA-binding transcriptional regulators with multiple essential functions in various cellular processes, including proliferation, migration, inflammation, and angiogenesis. The aberrant expression of KLFs is often found in tumor tissues and is essential for tumor development. At the molecular level, KLFs regulate multiple signaling pathways and mediate crosstalk among them. Some KLFs may also be molecular switches for specific biological signals, driving their transition from tumor suppressors to promoters. At the histological level, the abnormal expression of KLFs is closely associated with tumor cell stemness, proliferation, apoptosis, and alterations in the tumor microenvironment. Notably, the role of each KLF in tumors varies according to tumor type and different stages of tumor development rather than being invariant. In this review, we focus on the advances in the molecular biology of KLFs, particularly the regulations of several classical signaling pathways by these factors, and the critical role of KLFs in tumor development. We also highlight their strong potential as molecular targets in tumor therapy and suggest potential directions for clinical translational research.

ID1 marks the tumorigenesis of pancreatic ductal adenocarcinoma in mouse and human

Pancreatic Ductal Adenocarcinoma (PDAC) is a deadly disease that has an increasing death rate but no effective treatment to now. Although biological and immunological hallmarks of PDAC have been frequently reported recently, early detection and the particularly aggressive biological features are the major challenges remaining unclear. In the current study, we retrieved multiple scRNA-seq datasets and illustrated the genetic programs of PDAC development in genetically modified mouse models. Notably, the transcription levels of Id1 were elevated specifically along with the PDAC development. Pseudotime trajectory analysis revealed that Id1 was closely correlated with the malignancy of PDAC. The gene expression patterns of human PDAC cells were determined by the comparative analysis of the scRNA-seq data on human PDAC and normal pancreas tissues. ID1 levels in human PDAC cancer cells were dramatically increased compared to normal epithelial cells. ID1 deficiency in vitro significantly blunt the invasive tumor-formation related phenotypes. IPA analysis on the differentially expressed genes suggested that EIF2 signaling was the core pathway regulating the development of PDAC. Blocking EFI2 signaling remarkably decreased the expression of ID1 and attenuated the tumor-formation related phenotypes. These observations confirmed that ID1 was regulated by EIF2 signaling and was the critical determinator of PDAC development and progression. This study suggests that ID1 is a potential malignant biomarker of PDAC in both mouse models and human and detecting and targeting ID1 may be a promising strategy to treat or even rescue PDAC.

Mxi1 participates in the progression of lung cancer via the microRNA-300/KLF9/GADD34 Axis

The purpose of the current study was to define the role of MAX interactor 1 (Mxi1) in the pathogenesis of lung cancer and its underlying molecular mechanism. Bioinformatics analysis was performed to identify important regulatory pathway related to lung cancer. Dual luciferase reporter and ChIP assays were adopted to validate the interaction among Mxi1, miR-300 and KLF9. Loss- and gain-of-function studies were conducted to determine the roles of Mxi1, miR-300, and KLF9 in cell proliferation, migration, and invasion in vitro and their effects on myeloid-derived suppressor cell (MDSC) recruitment in vivo. Mxi1 was poorly expressed in lung cancer tissues and cells and its poor expression was associated with poor prognosis. Mxi1 inhibited miR-300 by suppressing its transcription. miR-300 suppressed the expression of KLF9, and KLF9 negatively regulated GADD34 expression in lung cancer cells. Mxi1 or KLF9 elevation or miR-300 repression inhibited lung cancer cell proliferation, as evidenced by reduced Ki67 and PCNA expression, and lowered invasion and migration. In vivo findings revealed that silencing KLF9 induced tumor growth by enhancing MDSC-mediated immunosuppression through upregulation of GADD34. Collectively, these findings suggest that Mxi1 can inhibit lung cancer progression by regulating the miR-300/KLF9 axis and GADD34-mediated immunosuppression.

MiR-889 promotes cell growth in human non-small cell lung cancer by regulating KLF9

Currently, non-small cell lung cancer (NSCLC) is still the most common malignancy worldwide. Although miR-889 has been reported to play an important role in various malignancies, the physiological function of miR-889 in NSCLC remains unknown. This paper places emphasis on the influence of miR-889 on the development and progression of non-small cell lung cancer. To detect the expression level of miR-889 in NSCLC tissues and cell lines, quantitative real-time polymerase chain reaction (qRT-PCR) assay and In Situ Hybridization (ISH) were adopted in this study. Cell proliferation and colony forming ability were examined by Cell Counting Kit-8 (CCK-8) and colony formation assays. Furthermore, transwell experiments were conducted to determine the influence of miR-889 on migration. KLF9 expression was evaluated by qRT-PCR and Western blotting. First, miR-889 expression was increased in the cancer tissues of non-small cell lung cancer patients (n = 40) compared with adjacent tissues. Subsequently, knockdown of miR-889 significantly inhibited cell proliferation and migration, while overexpression of miR-889 had the opposite effect. KLF9 may be a potential target of miR-889. In addition, upregulation of miR-889 promotes tumorigenesis in vitro, and KLF9 protein levels are also reduced. The current study suggests that miR-889 may play a potential therapeutic role for NSCLC by targeting KLF9 to control NSCLC proliferation and migration.