Downregulation of PAX6 by shRNA inhibits proliferation and cell cycle progression of human non-small cell lung cancer cell lines

Mechanism of PAX6 overexpression in inhibiting the growth of hepatocellular carcinoma cells and promoting the killing ability of the natural killer cells

OBJECTIVES

Paired box gene 6 (PAX6) plays a major role in the regulation of embryonic development. Abnormal expression of PAX6 is associated with the development of various tumors. PAX6 can play a role in promoting or suppressing cancer in different tumors. This study aim to observe the effect of overexpression of PAX6 on the growth of hepatocellular carcinoma cells, and the killing of hepatocellular carcinoma cells via natural killer (NK) cell and the possible mechanism.

METHODS

The protein levels of PAX6, soluble major histocompatibility complex class I-like protein A (sMICA) and soluble UL16 binding protein 2 (sULBP2) in peripheral blood from 68 cases of hepatocellular carcinoma (HCC) patients and 10 healthy volunteers were detected by ELISA. Hepatocellular carcinoma cell line (HepG2, LM3) and human normal liver cells (LO2) were cultured at 37 ℃ and 5% CO2 condition in vitro. The PAX6 overexpressed plasmid (PAX6-OE) and empty vector (NC) were transferred into HepG2 and LM3 cells to construct stable cell lines. The mRNA and protein expression levels of PAX6 in HepG2 and LM3 cells were detected by real-time PCR, Western blotting and immunofluorescence, respectively. PAX6 was overexpressed in HepG2 and LM3 cells, the cell growth and migration ability were detected by CCK-8 method and cell scratch assay, and the levels of sMICA and sULBP2 in the supernatant were detected by ELISA. Matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9) and disintegrin and metalloproteinase 10 (ADAM10) in HepG2 and LM3 cells were detected by Western blotting. The killing ability of NK cells against these 2 HCC cells was detected by flow cytometry.

RESULTS

Compared with the healthy volunteers, the expressions of PAX6 in the HCC patients were significantly decreased (P=0.002), while the expression of sMICA and sULBP2 were significantly increased (P=0.004 and P<0.001, respectively). Real-time PCR and Western blotting results showed that compared with LO2 cells, mRNA and protein expressions of PAX6 in HepG2 and LM3 cells were significantly decreased (all P<0.05). Immunofluorescence results also showed that the expressions of PAX6 in HepG2 and LM3 were lower than those of LO2 cells. Compared with the NC group, the ability of proliferation and migration of HepG2 and LM3 cells were decreased (both P<0.05). The protein expressions of MMP2, MMP9 and ADAM10 in HepG2 and LM3 cells in the PAX6-OE group were significantly decreased, and the levels of sMICA and sULBP2 in superneant of HepG2 and LM3 cells in the PAX6-OE group were significantly lower than those in the NC group (all P<0.05). Flow cytometry results showed that compared with the NC group, the proportion of NK cells killing HepG2 and LM3 cells in PAX6-OE group was significantly increased (both P<0.05).

CONCLUSIONS

The expression of PAX6 is decreased in serum of HCC patients and hepatocellular carcinoma cell lines. Overexpression of PAX6 can inhibit the growth of hepatocellular carcinoma cells, enhance the killing efficiency of NK cells against hepatoma cells. The mechanism is related to the inhibition of the expression of metalloproteinase via PAX6 and the decrease of the secretion levels of sMICA and sULBP2.

TNFRSF9 Suppressed the Progression of Breast Cancer via the p38MAPK/PAX6 Signaling Pathway

Worldwide, breast cancer is the most common cancer in females. Endocrine therapy can effectively treat 85% of breast cancer patients, but 15% of patients could only be treated with chemotherapy and surgery, and the prognosis is much worse. Immunotherapy is the novel treatment for breast cancer, where PD-1 and CTLA-4 antibodies have shown evidence of immune modulation in breast cancer drug trials. In this study, we report that TNFRSF9 regulates the cell proliferation, invasion, and apoptosis of breast cancer cells through regulating the phosphorylation of p38, thus further regulating the expression of PAX6. In both breast cancer tissues and cell lines, the levels of TNFRSF9 are significantly decreased, and breast cancer cell development will be promoted with knockdown of TNFRSF9. Moreover, we identify that downregulation of TNFRSF9 can upregulate the phosphorylated p38 (p-p38) and PAX6. We further elucidate that p-p38 is essential for PAX6 expression as p38 phosphorylation inhibitor can reverse the upregulation of PAX6 and suppress cell proliferation and invasion and promote apoptosis in breast cancer cells. In summary, this study proposed a novel TNFRSF9/p38/PAX6 axis that contributes to tumor suppression, which suggests a potential immunotherapy target for breast cancer.

Elevation of microRNA-365 impedes malignant behaviors of gastric cancer cells by inhibiting PAX6

MicroRNA-365 (miR-365) has been revealed to be a vital regulator in tumorigenesis of multiple cancers, while there is a large gap in the knowledge about miR-365 expression and gastric cancer (GC). This research focused on the effects of miR-365 and paired box 6 (PAX6) on GC development. Levels of miR-365 and PAX6 in GC tissues and cell lines were determined, followed by the screening of the AGS and NCI-N87 cells. Gain- or loss-of-function assays were used to analyze the effect of miR-365, PAX6 on AGS and NCI-N87 cell behaviors. The effects of altered miR-365 and PAX6 on animal models were observed. Moreover, to assess the interaction between miR-365 and PAX6, we implemented the bioinformatic method and dual luciferase reporter gene assay. MiR-365 was decreased while PAX6 was increased in GC tissues and cell lines. There existed a negative association between miR-365 and PAX6. The promoted miR-365 could repress oncogenicity in vivo and malignant transformation in vitro of GC. PAX6 was the target gene of miR-365. Overexpression of PAX6 reversed the inhibitory effect of up-regulated miR-365 on malignant behavior of gastric cancer cells. Our research displays that the amplification of miR-365 could suppress the malignant behaviors of GC cells via inhibiting PAX6, which may be helpful for GC treatment.

Upstream ORF frameshift variants in the PAX6 5'UTR cause congenital aniridia

Congenital aniridia (AN) is a severe autosomal dominant panocular disorder associated with pathogenic variants in the PAX6 gene. Previously, we performed a molecular genetic study of a large cohort of Russian patients with AN and revealed four noncoding nucleotide variants in the PAX6 5'UTR. 14 additional PAX6-5'UTR variants were also reported in the literature, but the mechanism of their pathogenicity remained unclear. In the present study, we experimentally analyze five patient-derived PAX6 5'UTR-variants: four variants that we identified in Russian patients (c.-128-2delA, c.-125dupG, c.-122dupG, c.-118_-117del) and one previously reported (c.-52+5G>C). We show that the variants lead to a decrease in the protein translation efficiency, while mRNA expression level is not significantly reduced. Two of these variants also affect splicing. Furthermore, we predict and experimentally validate the presence of an evolutionarily conserved small uORF in the PAX6 5'UTR. All studied variants lead to the frameshift of the uORF, resulting in its extension. This extended out-of-frame uORF overlaps with the downstream CDS and thereby reduces its translation efficiency. We conclude that the uORF frameshift may be the main mechanism of pathogenicity for at least 15 out of 18 known PAX6 5'UTR variants. Moreover, we predict additional uORFs in the PAX6 5'UTR.

Nuclear P38: Roles in Physiological and Pathological Processes and Regulation of Nuclear Translocation

The p38 mitogen-activated protein kinase (p38MAPK, termed here p38) cascade is a central signaling pathway that transmits stress and other signals to various intracellular targets in the cytoplasm and nucleus. More than 150 substrates of p38α/β have been identified, and this number is likely to increase. The phosphorylation of these substrates initiates or regulates a large number of cellular processes including transcription, translation, RNA processing and cell cycle progression, as well as degradation and the nuclear translocation of various proteins. Being such a central signaling cascade, its dysregulation is associated with many pathologies, particularly inflammation and cancer. One of the hallmarks of p38α/β signaling is its stimulated nuclear translocation, which occurs shortly after extracellular stimulation. Although p38α/β do not contain nuclear localization or nuclear export signals, they rapidly and robustly translocate to the nucleus, and they are exported back to the cytoplasm within minutes to hours. Here, we describe the physiological and pathological roles of p38α/β phosphorylation, concentrating mainly on the ill-reviewed regulation of p38α/β substrate degradation and nuclear translocation. In addition, we provide information on the p38α/β ’s substrates, concentrating mainly on the nuclear targets and their role in p38α/β functions. Finally, we also provide information on the mechanisms of nuclear p38α/β translocation and its use as a therapeutic target for p38α/β-dependent diseases.

The PAX6-ZEB2 axis promotes metastasis and cisplatin resistance in non-small cell lung cancer through PI3K/AKT signaling

Paired-box 6 (PAX6) is an important transcription factor required for the function of human neuroectodermal epithelial tissues. Previous studies have suggested that it is also expressed in several types of tumors and has an oncogenic role. However, little is known about its role in non-small cell lung cancer (NSCLC). Here, we found that PAX6 expression levels were upregulated in human lung cancer tissues and correlated with poor clinical outcomes. PAX6 overexpression significantly promoted NSCLC epithelial-to-mesenchymal transition (EMT) and metastasis, whereas its knockdown inhibited these processes. PAX6 is commonly correlated with EMT-mediated stem cell transformation, thereby inducing cisplatin resistance. Using the RT² Profiler PCR Array, we found that WNT5A, EGFR, and ZEB2 were differentially regulated in response to PAX6 modulation. In addition, PAX6 directly bound to the promoter region of ZEB2. ZEB2 knockdown significantly reduced the expression and function of PAX6. ZEB2 was upregulated upon PAX6 overexpression and downregulated upon PAX6 knockdown, whereas E-cadherin expression negatively correlated with PAX6 levels. Moreover, p-PI3K and p-AKT were significantly enhanced by PAX6, which was reversed by the addition of the PI3K-AKT inhibitor, LY294002. These data suggest that PAX6 can mediate E-cadherin downregulation through the PI3K/AKT signaling pathway by directly binding the promoter region of ZEB2, thereby mediating cell migration, stem cell transformation, and cisplatin resistance; and ultimately, affecting survival in NSCLC patients.

MicroRNA-664 targets paired box protein 6 to inhibit the oncogenicity of pancreatic ductal adenocarcinoma

The abnormal expression of microRNAs (miRNAs or miRs) with oncogenic or tumor‑suppressive roles in pancreatic ductal adenocarcinoma (PDAC) has been widely reported in recent years, and these dysregulated miRNAs are implicated in the formation and progression of PDAC. Therefore, an investigation into the functional roles of miRNAs in PDAC may facilitate the identification of effective therapeutic targets. miRNA‑664 (miR‑664) has been found to be aberrantly expressed and to play crucial roles in several human cancer types. However, the expression pattern and functional roles of miR‑664 in the malignant capacity of PDAC have yet to be elucidated. In this study, the results revealed that miR‑664 was clearly downregulated in PDAC tissues and cell lines. The low miR‑664 expression was strongly associated with pathological T stage and lymph node metastasis of the patients with PDAC. Patients with PDAC with a low miR‑664 expression had a poorer overall survival and a worse disease‑free survival than those patients with a high miR‑664 level. Functional experiments suggested that exogenous miR‑664 expression suppressed the growth and metastasis of PDAC cells in vitro, whereas miR‑664 downregulation exerted the opposite effects. In addition, miR‑664 suppressed the tumor growth of PDAC cells in vivo. Mechanistically, paired box protein 6 (PAX6) was identified as a direct target gene of miR‑664 in PDAC cells. Furthermore, PAX6 was upregulated in PDAC tissues, and its upregulation inversely correlated with miR‑664 levels. Moreover, the silencing of PAX6 mimicked the effects of miR‑664 upregulation in PDAC cells, and the recovered expression of PAX6 eliminated the effects of miR‑664 on PDAC cells. Notably, miR‑664 could inhibit the activation of PI3K/Akt pathway in PDAC cells in vitro and in vivo. Cumulatively, these results indicate an important role of the miR‑664/PAX6 pathway in suppressing the aggressiveness of PDAC cells, suggesting that miR‑664 may be an attractive therapeutic target for the treatment of patients with this fatal disease.

Investigating the mechanism by which SMAD3 induces PAX6 transcription to promote the development of non-small cell lung cancer

Background

This study investigated the function of SMAD3 (SMAD family member 3) in regulating PAX6 (paired box 6) in non-small cell lung cancer.

Methods

First, qRT-PCR was employed to detect SMAD3 expression in cancer tissues along with normal tissues and four cell lines, including BEAS-2B, H125, HCC827 and A549 cells. SMAD3 was knocked down by small interference RNA (siRNA), and then its expression was determined via qRT-PCR and Western blot analysis. The correlation between SMAD3 and PAX6 was determined by double luciferase reporter experiments and chromatin immunoprecipitation (ChIP) assay. Cell viability was evaluated by CCK-8 and colony forming assays, while cell migration and invasion were detected by Transwell analysis.

Results

SMAD3 and PAX6 were upregulated in lung cancer tissues and cancer cells. Knocking down SMAD3 and PAX6 by transfection with siRNAs specifically suppressed the expression of SMAD3 and PAX6 mRNA and protein levels. SMAD3 could promote PAX6 transcriptional activity by binding to its promoter. Reduced expression of SMAD3 led to the downregulation of PAX6 mRNA and protein levels along with decreased cell migration, invasion, proliferation and viability in A549 and HCC827 cells. PAX6 overexpression altered the si-SMAD3-induced inhibition of cell migration, invasion, proliferation and viability in A549 and HCC827 cells. Additionally, PAX6 knockdown alone also repressed the cell migration, invasion, proliferation and viability of the cell lines.

Conclusions

SMAD3 promotes the progression of non-small cell lung cancer by upregulating PAX6 expression.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0948-z) contains supplementary material, which is available to authorized users.

MicroRNA‑509 targets PAX6 to inhibit cell proliferation and invasion in papillary thyroid carcinoma

MicroRNAs (miRNAs/miRs) negatively regulate the expression of numerous genes and therefore contribute to the occurrence and development of papillary thyroid carcinoma (PTC). Hence, further investigation into the specific roles of miRNAs in PTC is valuable for developing effective therapeutic methods for patients with this disease. MiRNA‑509 is dysregulated and serves pivotal roles in several types of human cancer; however, the expression and roles of miR‑509 in PTC and its underlying mechanism require further investigation. In the present study, the expression of miR‑509 in PTC tissues and cell lines was detected and the specific functions of miR‑509 in the progression of PTC were investigated. Additionally, the molecular mechanisms underlying the action of miR‑509 in PTC were determined. The present study demonstrated that miR‑509 was significantly downregulated in PTC tissues and cell lines. MiR‑509 upregulation inhibited the PTC cell proliferation and invasion. Mechanistically, paired box 6 (PAX6) was identified as a novel target of miR‑509 in PTC cells. In clinical PTC samples, miR‑509 was significantly overexpressed and inversely correlated with PAX6 expression. PAX6 restoration effectively reversed the inhibitory effects of miR‑509 overexpression on PTC cell proliferation and invasion. These results demonstrated that miR‑509 may act as a tumor suppressor in PTC by directly targeting PAX6. Thus, miR‑509 may be a potential therapeutic target for the treatment of patients with PTC.

Epigenetically regulated PAX6 drives cancer cells toward a stem-like state via GLI-SOX2 signaling axis in lung adenocarcinoma

It remains unclear whether PAX6 acts as a crucial transcription factor for lung cancer stem cell (CSC) traits. We demonstrate that PAX6 acts as an oncogene responsible for induction of cancer stemness properties in lung adenocarcinoma (LUAD). Mechanistically, PAX6 promotes GLI transcription, resulting in SOX2 upregulation directly by the binding of GLI to the proximal promoter region of the SOX2 gene. The overexpressed SOX2 enhances the expression of key pluripotent factors (OCT4 and NANOG) and suppresses differentiation lineage factors (HOPX and NKX2-1), driving cancer cells toward a stem-like state. In contrast, in the differentiated non-CSCs, PAX6 is transcriptionally silenced by its promoter methylation. In human lung cancer tissues, the positive linear correlations of PAX6 expression with GLI and SOX2 expression and its negative correlations with HOPX and NKX2-1 expression were observed. Therapeutically, the blockade of the PAX6-GLI-SOX2 signaling axis elicits a long-lasting therapeutic efficacy by limiting CSC expansion following chemotherapy. Furthermore, a methylation panel including the PAX6 gene yielded a sensitivity of 79.1% and specificity of 83.3% for cancer detection using serum DNA from stage IA LUAD. Our findings provide a rationale for targeting the PAX6-GLI-SOX2 signaling axis with chemotherapy as an effective therapeutic strategy and support the clinical utility of PAX6 gene promoter methylation as a biomarker for early lung cancer detection.

PAX6 Promoter Methylation Correlates with MDA-MB-231 Cell Migration, and Expression of MMP2 and MMP9

Objective: Breast cancer is a heterogeneous disease characterized by an accumulation of genetic and epigenetic alterations that lead tumor cells to acquire characteristics like the capacity for invasion and metastasis. Metastasis remains a major challenge in cancer management and understanding of its molecular basis should result in improved prevention, diagnosis, and treatment of breast cancer patients. The aim of this study was to investigate how promoter DNA methylation regulates PAX6 gene expression and influences breast carcinoma cell migration. Methods: PAX6 promoter methylation was detected by Methyl Specific-Multiplex Ligation Probe Amplification (MS-MLPA). Gene expression was evaluated using qRT-PCR, while the effect of PAX6 on migration was ssessed by wound healing assay. In addition, MMP2 and MMP9 genes were studied using different bioinformatic tools. Results: The PAX6 promoter is methylated in breast cancer cell lines and methylation in this region impacts on its expression. Migration assays revealed that PAX6 overexpression promotes cell migration, while PAX6 inhibition decreases it. More importantly, we found that migration is affected by PAX6 methylation status. Employing bioinformatic analysis, binding sites for PAX6 on the regulatory regions of the MMP2 and MMP9 genes were established, PAX6 overexpression increasing MMP2 and MMP9 expression at the mRNA level. Conclusion: Our study provides novel insights into epigenetic events that regulate PAX6 expression and molecular mechanisms by which PAX6 modifies the migration capacity of breast cancer cells.

Protecting Pax6 3' UTR from MicroRNA-7 Partially Restores PAX6 in Islets from an Aniridia Mouse Model

Aniridia is a rare congenital syndrome that is associated with reduced visual acuity and progressive loss of vision. Aniridia patients may also develop systemic health issues associated with defects in the pancreas, digestive, and central nervous systems. The spectrum of symptoms associated with aniridia is due to haploinsufficiency of the paired box 6 gene (PAX6) and its role in the development and maintenance of the affected tissues. Here, we isolated pancreatic islets from mice heterozygous for Pax6 to test whether a Pax6-specific miRNA suppression (target protector) strategy can restore PAX6 protein levels. We show that miR-7 and miR-375 target specific sites within the Pax6 3' UTR in a mouse pancreatic β-insulinoma cell line. Tough decoys (Tuds) against miR-7 and miR-375 increase expression of a mouse Pax6 3' UTR luciferase reporter and increase PAX6 protein levels in these cells. Finally, we demonstrate that the shielding of the miR-7 binding site with a target protector restores PAX6 protein levels in the Pax6 heterozygous islets. The data presented here represent a proof of concept for RNA-based therapy for the progressive defects associated with aniridia and suggest the target protector approach may be a useful therapeutic strategy for other haploinsufficiency diseases.

Estradiol and the Development of the Cerebral Cortex: An Unexpected Role?

The cerebral cortex undergoes rapid folding in an "inside-outside" manner during embryonic development resulting in the establishment of six discrete cortical layers. This unique cytoarchitecture occurs via the coordinated processes of neurogenesis and cell migration. In addition, these processes are fine-tuned by a number of extracellular cues, which exert their effects by regulating intracellular signaling pathways. Interestingly, multiple brain regions have been shown to develop in a sexually dimorphic manner. In many cases, estrogens have been demonstrated to play an integral role in mediating these sexual dimorphisms in both males and females. Indeed, 17β-estradiol, the main biologically active estrogen, plays a critical organizational role during early brain development and has been shown to be pivotal in the sexually dimorphic development and regulation of the neural circuitry underlying sex-typical and socio-aggressive behaviors in males and females. However, whether and how estrogens, and 17β-estradiol in particular, regulate the development of the cerebral cortex is less well understood. In this review, we outline the evidence that estrogens are not only present but are engaged and regulate molecular machinery required for the fine-tuning of processes central to the cortex. We discuss how estrogens are thought to regulate the function of key molecular players and signaling pathways involved in corticogenesis, and where possible, highlight if these processes are sexually dimorphic. Collectively, we hope this review highlights the need to consider how estrogens may influence the development of brain regions directly involved in the sex-typical and socio-aggressive behaviors as well as development of sexually dimorphic regions such as the cerebral cortex.

MicroRNA‑874 inhibits proliferation and invasion of pancreatic ductal adenocarcinoma cells by directly targeting paired box 6

Studies have demonstrated that a number of microRNAs (miRNAs) are dysregulated in pancreatic ductal adenocarcinoma (PDAC), and alterations in their expression may affect the onset and progression of PDAC. Therefore, the expression patterns, biological functions and associated molecular mechanisms of miRNAs in PDAC should be elucidated for the development of novel therapeutic methods. Previous studies reported significant miRNA‑874 (miR‑874) dysregulation in multiple types of human cancer. However, the expression pattern, possible roles and underlying mechanisms of miR‑874 in PDAC remain to be elucidated. This study evaluated miR‑874 expression in PDAC and examined its biological functions and underlying mechanism of action in PDAC progression. miR‑874 expression was downregulated in PDAC tissues and cell lines. Functional experiments demonstrated that upregulation of miR‑874 inhibited cell proliferation and invasion in PDAC. Additionally, paired box 6 (PAX6) was predicted as a putative target of miR‑874 using bioinformatics analysis. Further experiments demonstrated that PAX6 may be the direct target gene of miR‑874 in PDAC. PAX6 knockdown exhibited similar inhibitory effects to miR‑874 overexpression in PDAC cells. In addition, restored PAX6 expression may reverse the suppressive roles of miR‑874 overexpression in PDAC cells. The results demonstrated that miR‑874 may serve tumor suppressive roles in PDAC by directly targeting PAX6. Therefore, miR‑874 may exhibit potential applications for treatment of patients with PDAC.

Generation of a PAX6 knockout glioblastoma cell line with changes in cell cycle distribution and sensitivity to oxidative stress

BACKGROUND

The transcription factor PAX6 is expressed in various cancers. In anaplastic astrocytic glioma, PAX6 expression is inversely related to tumor grade, resulting in low PAX6 expression in Glioblastoma, the highest-grade astrocytic glioma. The aim of the present study was to develop a PAX6 knock out cell line as a tool for molecular studies of the roles PAX6 have in attenuating glioblastoma tumor progression.

METHODS

The CRISPR-Cas9 technique was used to knock out PAX6 in U251 N cells. Viral transduction of a doxycycline inducible EGFP-PAX6 expression vector was used to re-introduce (rescue) PAX6 expression in the PAX6 knock out cells. The knock out and rescued cells were rigorously characterized by analyzing morphology, proliferation, colony forming abilities and responses to oxidative stress and chemotherapeutic agents.

RESULTS

The knock out cells had increased proliferation and colony forming abilities compared to wild type cells, consistent with clinical observations indicating that PAX6 functions as a tumor-suppressor. Cell cycle distribution and sensitivity to H₂O₂ induced oxidative stress were further studied, as well as the effect of different chemotherapeutic agents. For the PAX6 knock out cells, the percentage of cells in G2/M phase increased compared to PAX6 control cells, indicating that PAX6 keeps U251 N cells in the G1 phase of the cell cycle. Interestingly, PAX6 knock out cells were more resilient to H₂O₂ induced oxidative stress than wild type cells. Chemotherapy treatment is known to generate oxidative stress, hence the effect of several chemotherapeutic agents were tested. We discovered interesting differences in the sensitivity to chemotherapeutic drugs (Temozolomide, Withaferin A and Sulforaphane) between the PAX6 expressing and non-expressing cells.

CONCLUSIONS

The U251 N PAX6 knock out cell lines generated can be used as a tool to study the molecular functions and mechanisms of PAX6 as a tumor suppressor with regard to tumor progression and treatment of glioblastoma.

Transcription factor PAX6 as a novel prognostic factor and putative tumour suppressor in non-small cell lung cancer

Lung cancer is the leading cause of cancer deaths. Novel predictive biomarkers are needed to improve treatment selection and more accurate prognostication. PAX6 is a transcription factor with a proposed tumour suppressor function. Immunohistochemical staining was performed on tissue microarrays from 335 non-small cell lung cancer (NSCLC) patients for PAX6. Multivariate analyses of clinico-pathological variables and disease-specific survival (DSS) was carried out, and phenotypic changes of two NSCLC cell lines with knockdown of PAX6 were characterized. While PAX6 expression was only associated with a trend of better disease-specific survival (DSS) (p = 0.10), the pN+ subgroup (N = 103) showed significant correlation between high PAX6 expression and longer DSS (p = 0.022). Median survival for pN + patients with high PAX6 expression was 127.4 months, versus 22.9 months for patients with low PAX6 expression. In NCI-H661 cells, knockdown of PAX6 strongly activated serum-stimulated migration. In NCI-H460 cells, PAX6 knockdown activated anchorage-independent growth. We did not observe any significant effect of PAX6 on proliferation in either of cell lines. Our findings strongly support the proposition of PAX6 as a valid and positive prognostic marker in NSCLC in node-positive patients. There is a need for further studies, which should provide mechanistical explanation for the role of PAX6 in NSCLC.

MicroRNA-19 contributes to the malignant phenotypes of osteosarcoma in vitro by targeting Pax6

This study was conducted to detect the expression of miR-19 and Pax6 (Paired box protein 6) in human osteosarcoma cells and the effects on biological characteristics of osteosarcoma cells. Quantitative real-time polymerase chain reaction was used to detect the expression of Pax6 and miR-19 in normal human osteoblasts (hFOB 1.19) and osteosarcoma cell lines (U2OS, Saos-2, and MG-63). Results showed that miR-19 was significantly upregulated in osteosarcoma cell lines compared with that in hFOB 1.19 cells, while the expression of Pax6 messenger RNA was significantly downregulated. Pax6 was defined as the target gene of miR-19 which was validated by luciferase reporter gene analysis. Results indicated that miR-19 had an interaction with Pax6 3'-untranslated region. At the same time, the protein expression of Pax6 was significantly decreased in the MG-63 cells transfected with miR-19 mimic and was notably enhanced in osteosarcoma MG-63 cells transfected with miR-19 inhibitor. These data suggested that Pax6 was a target of miR-19 in osteosarcoma MG-63 cells. The effects of miR-19 on the biological behavior of MG-63 cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry, and Transwell assay. Results showed that the downregulation of miR-19 inhibited cell viability, reduced the percentage of cells in S phase and the number of cells passing through the Transwell chamber, and increased the number of apoptotic cells. Western blot analysis showed that the inhibition of miR-19 significantly increased the expression of epithelial proteins (E-cadherin and β-catenin) and decreased the expression of mesenchymal protein (Vimentin), extracellular signal-regulated kinase, and phosphorylated extracellular signal-regulated kinase in MG-63 cells. MiR-19 inhibitor and Pax6 small interfering RNA were simultaneously transfected into MG-63 cells. Results from 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry, and Transwell assay demonstrated that the inhibition of Pax6 expression in MG-63 cells could reverse the cell biological effects induced by the inhibition of miR-19 expression. Based on these findings, it was suggested that miR-19, upregulated in osteosarcoma cells, negatively regulated the expression of Pax6, which can promote the malignant phenotypes of osteosarcoma cells via activation of the extracellular signal-regulated kinase signaling pathways. Therefore, miR-19/Pax6 may offer potential for use as a target for the treatment of osteosarcoma.

[Construction of a lentiviral vector carrying short?hairpin RNA targeting PAX6 and its effect on proliferation of glioma U251 cells in vitro]

OBJECTIVE

To construct a lentiviral vector for delivering short hairpin RNA (shRNA) targeting PAX6 and investigate its effect on the proliferation of glioma U251 cells in vitro.

METHODS

Two small interfering RNA sequences targeting PAX6 gene were designed based on the reported sequence of PAX6 and annealed to form a double?stranded chain, which was inserted into a lentiviral vector to construct the recombinant lentiviral vector shRNA?PAX6. The recombinant vector was infected into U251 cells, and the expression of PAX6 mRNA and protein in the cells was detected by real?time PCR and Western blotting, respectively. The changes in the proliferation of U251 cells after the infection was assessed using MTT assay.

RESULTS

Double enzyme digestion of the lentiviral vector pLKD?CMV?G&NR?U6?shRNA yielded an 8208?bp fragment, and colony PCR and sequencing analysis confirmed successful construction of the lentiviral vector shRNA?PAX6. Infection of the cells with shRNA?PAX6 caused a significant reduction of the expressions of PAX6 mRNA and protein (P<0.05) and resulted in obviously increased proliferation of U251 cells (P<0.05).

CONCLUSION

We successfully constructed the recombinant vector shRNA?PAX6 for silencing PAX6 gene. PAX6 gene silencing results in increased proliferation of U251 cells in vitro.

Autophagy mediates cell cycle response by regulating nucleocytoplasmic transport of PAX6 in limbal stem cells under ultraviolet-A stress

Limbal stem cells (LSC) account for homeostasis and regeneration of corneal epithelium. Solar ultraviolet A (UVA) is the major source causing oxidative damage in the ocular surface. Autophagy, a lysosomal degradation mechanism, is essential for physiologic function and stress defense of stem cells. PAX6, a master transcription factor governing corneal homeostasis by regulating cell cycle and cell fate of LSC, responds to oxidative stress by nucleocytoplasmic shuttling. Impaired autophagy and deregulated PAX6 have been reported in oxidative stress-related ocular surface disorders. We hypothesize a functional role for autophagy and PAX6 in LSC’s stress response to UVA. Therefore, human LSC colonies were irradiated with a sub-lethal dose of UVA and autophagic activity and intracellular reactive oxygen species (ROS) were measured by CYTO-ID assay and CM-H₂DCFDA live staining, respectively. Following UVA irradiation, the percentage of autophagic cells significantly increased in LSC colonies while intracellular ROS levels remained unaffected. siRNA-mediated knockdown (KD) of ATG7 abolished UVA-induced autophagy and led to an excessive accumulation of ROS. Upon UVA exposure, LSCs displayed nuclear-to-cytoplasmic translocation of PAX6, while ATG7KD or antioxidant pretreatment largely attenuated the intracellular trafficking event. Immunofluorescence showing downregulation of proliferative marker PCNA and induction of cell cycle regulator p21 indicates cell cycle arrest in UVA-irradiated LSC. Abolishing autophagy, adenoviral-assisted restoration of nuclear PAX6 or antioxidant pretreatment abrogated the UVA-induced cell cycle arrest. Adenoviral expression of an ectopic PAX gene, PAX7, did not affect UVA cell cycle response. Furthermore, knocking down PAX6 attenuated the cell cycle progression of irradiated ATG7KD LSC by de-repressing p21 expression. Collectively, our data suggest a crosstalk between autophagy and PAX6 in regulating cell cycle response of ocular progenitors under UVA stress. Autophagy deficiency leads to impaired intracellular trafficking of PAX6, perturbed redox balance and uncurbed cell cycle progression in UVA-stressed LSCs. The coupling of autophagic machinery and PAX6 in cell cycle regulation represents an attractive therapeutic target for hyperproliferative ocular surface disorders associated with solar radiation.

Clinical Value and Prospective Pathway Signaling of MicroRNA-375 in Lung Adenocarcinoma: A Study Based on the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and Bioinformatics Analysis

BACKGROUND Lung adenocarcinoma (LUAD) is the most frequent lung cancer. MicroRNAs (miRNAs) are believed to have fundamental roles in tumorigenesis of LUAD. Although miRNAs are broadly recognized in LUAD, the role of microRNA-375 in LUAD is still not fully elucidated. MATERIAL AND METHODS We evaluated the significance of miR-375 expression in LUAD by using analysis of a public dataset from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database and a literature review. Furthermore, we investigated the biological function of miR-375 by gene ontology enrichment and target prediction analysis. RESULTS MiR-375 expression was significantly higher in LUAD by TCGA data compared to normal lung tissue (p<0.0001). In addition, a common pattern of upregulation for miR-375 in LUAD was found in our review of the literature. A total of 682 genes, both LUAD-related and miR-375-related, were obtained from the analytical integration. Critical pathways were unveiled in the network analysis of the overlaps, such as pentose and glucuronate interconversions, ascorbate and aldarate metabolism, and starch and sucrose metabolism. Furthermore, we identified covert miR-375 associated genes that might participate in LUAD by network analysis, such as FGF2 (fibroblast growth factor 2), PAX6 (paired box 6), and RHOJ. The expression of these three genes were all downregulated in LUAD. Finally, FGF2 was revealed to be negatively correlated with miR-375 in LUAD (r=-0.1821, p=0.0001). CONCLUSIONS Overall, our study provides evidence that miR-375 is essential for the progression of LUAD.

Quantitative methylation analysis reveals distinct association between PAX6 methylation and clinical characteristics with different viral infections in hepatocellular carcinoma

Background

Related to genetic alteration, frequent promoter hypermethylation is also a contributing factor in the development of human cancers. Recently, we discovered numerous novel genes that were aberrantly methylated in hepatocellular carcinoma (HCC) by using Infinium HumanMethylation27 BeadChip array. We utilized a quantitative methylation-specific PCR (Q-MSP) system for the evaluation of PAX6 methylation in 29 normal controls and 160 paired HCC tissues and their adjacent non-tumor tissues. We verified the correlation between the methylation status of PAX6 and clinical characteristics with different viral status.

Results

Paired-box 6 promoter methylation was observed in 39.4 %, 15.6 %, and 3.4 % in primary HCCs, adjacent non-tumors, and normal control tissues, respectively. Methylation of the PAX6 promoter region in HCCs significantly increased compared with control tissues. PAX6 was frequently methylated in HCV-positive HCC tissues (61.3 %) and rarely methylated in HBV-positive (22.1 %) and double-negative HCC tissues (33.3 %).

Conclusions

Our data suggests that promoter hypermethylation of PAX6 is a common event in HCCs and the association of PAX6 methylation in clinicopathological features is divergent with different viral status.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0208-3) contains supplementary material, which is available to authorized users.

SOX4, SOX11 and PAX6 mRNA expression was identified as a (prognostic) marker for the aggressiveness of neuroendocrine tumors of the lung by using next-generation expression analysis (NanoString)

BACKGROUND

Neuroendocrine tumors of the lung (NELC) account for 25% of all lung cancer cases and transcription factors may drive dedifferentiation of these tumors. This study was conducted to identify supportive diagnostic and prognostic biomarkers.

MATERIALS & METHODS

A total of 16 TC, 13 AC, 16 large cell neuroendocrine carcinomas and 15 small cell lung cancer were investigated for the mRNA expression of 11 transcription factors and related genes (MYB, MYBBP1A, OCT4, PAX6, PCDHB, RBP1, SDCBP, SOX2, SOX4, SOX11, TEAD2).

RESULTS

SOX4 (p = 0.0002), SOX11 (p < 0.0001) and PAX6 (p = 0.0002) were significant for tumor type. Elevated PAX6 and SOX11 expression correlated with poor outcome in large cell neuroendocrine carcinomas and small cell lung cancer (p < 0.0001 and p = 0.0232, respectively) based on survival data of 34 patients (57%).

CONCLUSION

Aggressiveness of NELC correlated with increasing expression of transcription factors. SOX11 seems to be a highly valuable diagnostic and prognostic marker for aggressive NELC.

miR-488 acts as a tumor suppressor gene in gastric cancer

MicroRNAs (miRNAs) are small, non-coding RNAs that modulate development, cell proliferation, and apoptosis. The deregulated expression of microRNAs is found in carcinogenesis including gastric cancer (GC). In this study, we showed that the expression levels of miR-488 were downregulated in GC tissues compared to in non-tumor tissues. In addition, the expression of miR-488 was also lower in GC cell lines in contrast with the gastric epithelial cell line (GES). In addition, the expression level of miR-488 was negatively correlated with the TNM stage in GC patients, and lower miR-488 expression was found in tumors with advanced TNM stage. The ectopic expression of miR-488 suppressed the GC cell proliferation, cell cycle, colony information, and migration. PAX6 was identified as a direct target gene of miR-488 in HGC-27. Moreover, we found that the expression level of PAX6 was upregulated in the GC tissues compared with the non-tumor tissues. The PAX6 expression level was correlated with the cancer TNM stage, and higher PAX6 expression was found in tumors with advanced TNM stage. Furthermore, there was an inverse correlation between PAX6 and miR-488 expression levels in GC tissues. Therefore, these studies demonstrated that miR-488 might act as a tumor suppressor miRNA in the development of GC.

Ret finger protein-like 3 promotes tumor cell growth by activating telomerase reverse transcriptase expression in human lung cancer cells

In this study, we identified ret finger protein-like 3 (RFPL3) as a hTERT promoter binding protein in lung cancer cells. The high hTERT promoter-binding activity of RFPL3 was detected in lung cancer cells compared to normal cells. Chromatin immunoprecipitation confirmed RFPL3 as a tumor-specific hTERT promoter binding protein. Overexpression of RFPL3 activated hTERT promoter and up-regulated hTERT expression and telomerase activity. Inhibition of RFPL3 expression by siRNA suppressed hTERT promoter activation and telomerase activity. Inhibition of RFPL3 by siRNA or shRNA also significantly inhibited tumor cell growth in vitro and in a xenograft mouse model in vivo. Immunohistochemical analysis of 181 human lung adenocarcinomas specimens showed a significant correlation between RFPL3 and hTERT expression. The overexpression of RFPL3 was also associated significantly with lymph node metastasis. Univariate and multivariate Cox model analyses of NSCLC clinical specimens revealed a strong correlation between RFPL3 expression and overall survival. These results demonstrate that RFPL3 is an important cellular factor which promotes lung cancer growth by activating hTERT expression and may be a potential novel therapeutic target for lung cancer.

Down-regulation of PAX6 by promoter methylation is associated with poor prognosis in non small cell lung cancer

BACKGROUND

Promoter methylation is an alternative mechanism of gene silencing in human tumorigenesis. Although a number of methylated genes have been found in non small cell lung cancer (NSCLC), useful methylation markers for early prognostic evaluation of NSCLC remain largely unknown.

METHODS

Using methylation-specific PCR (MSP), we examined promoter methylation status of PAX6 gene, and explored their association with clinical features in NSCLC via chi-square test. NSCLC patient survival was assessed by Kaplan-Meier analyses and a Cox proportional hazard model was employed for multivariate analyses.

RESULTS

The methylation level of PAX6 gene was higher in tumor tissues than that in normal tissues. In addition, PAX6 promoter methylation showed a very significant correlation with differentiation (P = 0.002), distant metastasis (P = 0.024), and TNM stage (P = 0.002). PAX6 gene promoter hyper-methylation was found to be significantly associated with poor overall survival (P = 0.018) and to serve as an independent marker for prognosis using multivariate Cox regression analysis (HR: 2.254, 95% CI: 1.088-4.667, P = 0.029).

CONCLUSION

We found that PAX6 gene was specifically methylated in NSCLC, and demonstrated the effect of promoter methylation of PAX6 gene on clinical outcome in NSCLC, indicating the methylated PAX6 may be useful biomarkers for prognostic evaluation in NSCLC.

Identification of protein expression alterations in gefitinib-resistant human lung adenocarcinoma: PCNT and mPR play key roles in the development of gefitinib-associated resistance

Gefitinib is the first-line chemotherapeutic drug for treating non-small cell lung cancer (NSCLC), which comprises nearly 85% of all lung cancer cases worldwide. However, most patients eventually develop drug resistance after 12-18 months of treatment. Hence, investigating the drug resistance mechanism and resistance-associated biomarkers is necessary. Two lung adenocarcinoma cell lines, PC9 and gefitinib-resistant PC9/Gef, were established for examining resistance mechanisms and identifying potential therapeutic targets. Two-dimensional differential gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry were used for examining global protein expression changes between PC9 and PC9/Gef. The results revealed that 164 identified proteins were associated with the formation of gefitinib resistance in PC9 cells. Additional studies using RNA interference showed that progesterone receptor membrane component 1 and pericentrin proteins have major roles in gefitinib resistance. In conclusion, the proteomic approach enabled identifying of numerous proteins involved in gefitinib resistance. The results provide useful diagnostic markers and therapeutic candidates for treating gefitinib-resistant NSCLC.

Epigenetic variations in breast cancer progression to lymph node metastasis

Breast cancer is a heterogeneous disease characterized by the accumulation of genetic and epigenetic alterations that contribute to the development of regional and distant metastases. Lymph node metastasis (LNM) status is the single most important prognostic factor. Metastatic cancer cells share common molecular alterations with those of the primary tumor, but in addition, they develop distinct changes that allow the cancer to progress. There is an urgent need for molecular studies which focus on identifying genomic and epigenomic markers that can predict the progression to metastasis. The objective of this study was to identify epigenetic similarities and differences between paired primary breast tumor (PBT) and LNM. We employed Methylation-Specific-MLPA (Multiplex ligation-dependent probe amplification) to assess the methylation status of 33 cancer-related genes in a cohort of 50 paired PBT and LNM specimens. We found that the methylation index, which represents the degree of aberrantly methylated genes in a specimen, was maintained during the progression to LNM. However, some genes presented differential methylation profiles. Interestingly, PAX6 presented a significant negative correlation between paired PBT and LNM (p = 0.03), which indicated a switch from methylated to unmethylated status in the progression from PBT to LNM. We further identified that the methylation status of PAX6 on the identified CpG site functionally affected the expression of PAX6 at the mRNA level. Our study unraveled significant epigenetic changes during the progression from PBT to LNM, which may contribute to improved prognosis, prediction and therapeutic management of metastatic breast cancer patients.

Regulation of Human PAX6 Expression by miR-7

The paired box gene 6 (PAX6) is a powerful mediator of eye and brain organogenesis whose spatiotemporal expression is exquisitely controlled by multiple mechanisms, including post-transcriptional regulation by microRNAs (miRNAs). In the present study, we use bioinformatic predictions to identify three candidate microRNA-7 (miR-7) target sites in the human PAX6 3′ untranslated region (3′-UTR) and demonstrate that two of them are functionally active in a human cell line. Furthermore, transient transfection of cells with synthetic miR-7 inhibits PAX6 protein expression but does not alter levels of PAX6 mRNA, suggesting that miR-7 induces translational repression of PAX6. Finally, a comparison of PAX6 3′-UTRs across species reveals that one of the functional miR-7 target sites is conserved, whereas the second functional target site is found only in primates. Thus, the interaction between PAX6 and miR-7 appears to be highly conserved; however, the precise number of sites through which this interaction occurs may have expanded throughout evolution.