Expression of the proto-oncogene Pokemon in colorectal cancer--inhibitory effects of an siRNA

Pokemon inhibits Bim transcription to promote the proliferation, anti-anoikis, invasion, histological grade, and dukes stage of colorectal neoplasms

PURPOSE

This study aims to determine whether Pokemon regulates Bim activity in colorectal carcinoma (CRC) carcinogenesis.

METHODS

Clinical tissue samples were analyzed to detect the expression and clinicopathological significance of Pokemon and Bim in CRC. Proliferation, apoptosis, and invasion assays were conducted to identify the regulatory effect of Pokemon on Bim. The combined treatment effects of Pokemon knockdown and diamminedichloroplatinum (DDP) were also examined.

RESULTS

Immunohistochemical analysis of 80 samples of colorectal epithelia (CRE), 80 cases of colorectal adenoma (CRA), and 160 of CRC samples revealed protein expression rates of 23.8%, 38.8%, and 70.6% for Pokemon, and 88.8%, 73.8%, and 31.9% for Bim, respectively. A significant negative correlation was observed between Pokemon and Bim expression across the CRE, CRA, and CRC lesion stages. In CRC, higher Pokemon and lower Bim expression correlated with higher histological grades, advanced Dukes stages, and increased cancer invasion. In both LoVo and HCT116 cells, overexpression of Pokemon significantly reduced Bim expression, leading to increased proliferation, resistance to anoikis, and cell invasion. Additionally, Pokemon overexpression significantly decreased DDP-induced Bim expression, reduction of anti-apoptosis and invasion, whereas Pokemon knockdown resulted in the opposite effects.

CONCLUSION

These findings suggest that Pokemon inhibits Bim transcription, thereby promoting CRC proliferation, resistance to apoptosis, invasion, and advancing histological grade and Dukes staging. Pokemon knockdown enhances the therapeutic efficacy of DDP in the treatment of CRC.

ZBTB7A functioned as an oncogene in colorectal cancer

Background

Despite zinc finger and BTB domain-containing 7A (ZBTB7A) documented importance in multiple tumors, the function and clinical value in Colorectal cancer (CRC) remain elusive. The aim of this study was to evaluate the functional roles and the clinical value of ZBTB7A in CRC progression.

Methods

The level of ZBTB7A was detected in a large cohort of CRC patients (n = 189) by immunohistochemistry (IHC), and we analyzed the diagnostic and prognostic value of the protein. In addition, the functional roles of ZBTB7A on CRC were explored in vitro and in vivo.

Results

Survival analyses indicated that patients with high ZBTB7A expression made the prognosis worse (P = 0.024). Functionally, knockdown of ZBTB7A could markedly inhibit tumor proliferation in vitro and in vivo, whereas ZBTB7A overexpression displayed the opposite results.

Conclusions

ZBTB7A was associated with poor survival outcomes and functioned as an oncogene in CRC patients, indicating that it is a potential prognostic biomarker and therapeutic target for CRC patients.

Emerging role of ZBTB7A as an oncogenic driver and transcriptional repressor

ZBTB7A is a member of the POK family of transcription factors that possesses a POZ-domain at the N-terminus and Krüppel-like zinc-finger at the c-terminus. ZBTB7A was initially isolated as a protein that binds to the inducer of the short transcript of HIV-1 virus TAT gene promoter. The protein forms a homodimer through protein-protein interaction via the N-terminus POZ-domains. ZBTB7A typically binds to the DNA elements through its zinc-finger domains and represses transcription both by modification of the chromatin organization and through the direct recruitment of transcription factors to gene regulatory regions. ZBTB7A is involved in several fundamental biological processes including cell proliferation, differentiation, and development. It also participates in hematopoiesis, adipogenesis, chondrogenesis, cellular metabolism and alternative splicing of BCLXL, DNA repair, development of oligodendrocytes, osteoclast and unfolded protein response. Aberrant ZBTB7A expression promotes oncogenic transformation and tumor progression, but also maintains a tumor suppressive role depending on the type and genetic context of cancer. In this comprehensive review we provide information about the structure, function, targets, and regulators of ZBTB7A and its role as an oncogenic driver and transcriptional repressor in various human diseases.

ZBTB7 evokes 5-fluorouracil resistance in colorectal cancer through the NF‑κB signaling pathway

Zinc finger and BTB domain containing 7A (ZBTB7), a POZ/BTB and Krüppel erythroid myeloid oncogenic factor, is critical for the tumorigenicity and progression of various cancer types. ZBTB7 has been reported to promote the cell proliferation of colorectal cancers (CRC). However, the function of ZBTB7 to 5-fluorouracil (5‑FU) resistance has not yet been studied. In the current study, ZBTB7 expression and function in 5‑FU resistance in CRC were investigated using with multidisciplinary approaches, including western blot analysis, Transwell assay, CCK8 and a tumor xenograft model. Overexpression of ZBTB7 was increased the level of proteins associated with cell invasion and epithelial-mesenchymal transition. ZBTB7 inhibition attenuated the invasion and enhanced the apoptosis of CRC cells. IC50 values and cell viability were significantly reduced in cells with short hairpin RNA (shRNA)-mediated ZBTB7 depletion compared with the control group. 5‑FU administration decreased viability to a greater extent in the ZBTB7-shRNA group compared with the control, which was dose- and time-dependent. Analysis of gene expression omnibus data demonstrated that ZBTB7 mediated 5‑FU resistance, potentially through nuclear factor (NF)-κB signaling. NF‑κB inhibitor SN50 reversed ZBTB7-induced resistance in CRC. Collectively, the findings demonstrated that ZBTB7 mediated 5‑FU resistance in CRC cells through NF‑κB signaling. Thus, targeting ZBTB7 and NF‑κB signaling may be an effective strategy to reverse 5‑FU resistance in CRC.

The expression and clinical significance of ZBTB7 in transitional cell carcinoma of the bladder

Zinc finger and BTB domain containing 7A (ZBTB7) is a ZBTB protein family member of transcriptional repressors that serves a critical role in cell transformation and malignancy. However, the association between ZBTB7 expression in bladder cancer tissues and the prognosis of patients remains unclear. The aim of the current study was to detect the expression of ZBTB7 in transitional cell carcinoma (TCC) of the bladder and normal bladder mucous tissues to evaluate the diagnostic and prognostic value of ZBTB7 in TCC of the bladder. A total of 100 TCC specimens were analyzed and the expression of ZBTB7 mRNA was examined via reverse transcription-quantitative polymerase chain reaction. The expression of ZBTB7 protein was examined by western blotting and immunohistochemistry. The association between ZBTB7 expression and the clinical prognosis of patients from the TCGA database was analyzed. High expression of ZBTB7 mRNA and protein in TCC tissue was detected and TCC expression was significantly higher in TCC tissue than in normal bladder mucous tissues (P<0.05). Furthermore, ZBTB7 expression was associated with recurrence, a larger tumor size and higher tumor grade. In terms of overall and recurrence-free survival, the group expressing high levels of ZBTB7 exhibited lower overall and recurrence-free survival compared with the low ZBTB7 expression group, although these differences were not statistically significant. Therefore, ZBTB7 may be important in the initiation and progression of TCC.

Differences in Zbtb7a expression cause heterogeneous changes in human nasopharyngeal carcinoma CNE3 sublines

The present study aimed to determine the association between changes in Zbtb7a expression levels and heterogeneity of nasopharyngeal carcinoma (NPC) CNE3 sublines. CNE3 sublines were established by screening of serial dilution and continuous passage. Proliferative ability and tumorigenicity of the sublines were analyzed separately by soft-agar colony formation and mouse studies. The NPC tissues from mice were analyzed by histological evaluation and immunohistochemistry. The expression levels of Zbtb7a mRNA and protein were analyzed separately by quantitative reverse transcription polymerase chain reaction and western blotting. According to findings from the soft-agar colony formation and mouse studies, two sublines with increased tumorigenicity compared with other sublines were transfected transiently with Zbtb7a short hairpin RNA (shRNA) recombinant plasmid. The changes in viability, migration and invasion abilities were evaluated separately by MTT, colorimetric focus-formation, Transwell migration and invasion assays. The sublines CNE3-GX6 and CNE3-GX11 were selected for subsequent study due to increased tumorigenicity and increased Zbtb7a expression levels compared with the other sublines. High metastatic potency was not observed in all of the sublines. Zbtb7a expression levels were positively associated with tumorigenic degree of the sublines. The growth, migration and invasion abilities of the sublines transfected with Zbtb7a shRNA plasmid were decreased compared with the cells transfected with empty vector in the negative control group. The findings suggest Zbtb7a expression levels may be associated with heterogeneity of CNE3 sublines. Therefore, Zbtb7a may have an important role in the regulatory mechanism of NPC heterogeneity.

Pretreatment Pokemon Level as a Predictor of Response to Cisplatin and Paclitaxel in Patients with Unresectable Non-Small Cell Lung Cancer

BACKGROUND

We firstly investigated the expression of Pokemon in patients with non-small cell lung cancer (NSCLC), then characterized the role of Pokemon in evaluating the response to combined cisplatin and paclitaxel chemotherapy and prognosis.

PATIENTS AND METHODS

In this study, 61 patients with previously untreated locally advanced or metastatic NSCLC were treated with a combination chemotherapy comprising cisplatin and paclitaxel. The correlation between serum expression of Pokemon and effectiveness of chemotherapy was assessed.

RESULTS

The expression level of Pokemon in NSCLC patients was higher than that in healthy controls (p = 0.000), and was correlated with tumor size and TNM stage (p < 0.05). Kaplan-Meier analysis and Cox proportional hazard model demonstrated a poor response and shorter survival time in patients with pretreatment Pokemon levels in excess of 135.09 ng/ml compared to those with Pokemon levels below 135.09 ng/ml (p = 0.013). Pokemon ≥ 135.09 ng/ml was an independent risk factor for survival time in NSCLC patients undergoing combination chemotherapy (p = 0.018).

CONCLUSION

The serum level of Pokemon correlated with efficacy of cisplatin and paclitaxel combination chemotherapy and survival time, which indicated that Pokemon may be a potentially useful biomarker for predicting treatment effectiveness of first-line chemotherapy and prognosis in NSCLC.

Cooperation of the BTB-Zinc finger protein, Abrupt, with cytoskeletal regulators in Drosophila epithelial tumorigenesis

The deregulation of cell polarity or cytoskeletal regulators is a common occurrence in human epithelial cancers. Moreover, there is accumulating evidence in human epithelial cancer that BTB-ZF genes, such as Bcl6 and ZBTB7A, are oncogenic. From our previous studies in the vinegar fly, Drosophila melanogaster, we have identified a cooperative interaction between a mutation in the apico-basal cell polarity regulator Scribble (Scrib) and overexpression of the BTB-ZF protein Abrupt (Ab). Herein, we show that co-expression of ab with actin cytoskeletal regulators, RhoGEF2 or Src64B, in the developing eye-antennal epithelial tissue results in the formation of overgrown amorphous tumours, whereas ab and DRac1 co-expression leads to non-cell autonomous overgrowth. Together with ab, these genes affect the expression of differentiation genes, resulting in tumours locked in a progenitor cell fate. Finally, we show that the expression of two mammalian genes related to ab, Bcl6 and ZBTB7A, which are oncogenes in mammalian epithelial cancers, significantly correlate with the upregulation of cytoskeletal genes or downregulation of apico-basal cell polarity neoplastic tumour suppressor genes in colorectal, lung and other human epithelial cancers. Altogether, this analysis has revealed that upregulation of cytoskeletal regulators cooperate with Abrupt in Drosophila epithelial tumorigenesis, and that high expression of human BTB-ZF genes, Bcl6 and ZBTB7A, shows significant correlations with cytoskeletal and cell polarity gene expression in specific epithelial tumour types. This highlights the need for further investigation of the cooperation between these genes in mammalian systems.

The effect of Pokemon on bladder cancer epithelial-mesenchymal transition

OBJECTIVE

This study aimed at detecting Pokemon expression in bladder cancer cell and investigating the relationship between Pokemon and epithelial-mesenchymal transition. Furthermore, we investigated the functions of Pokemon in the carcinogenesis and development of bladder cancer. This study was also designed to observe the inhibitory effects of siRNA expression vector on Pokemon in bladder cancer cell.

METHODS

The siRNA expression vectors which were constructed to express a short hairpin RNA against Pokemon were transfected to the bladder cancer cells T24 with a liposome. Levels of Pokemon, E-cadherin and β-catenin mRNA and protein were examined by real-time quantitative-fluorescent PCR and Western blot analysis, respectively. The effects of Pokemon silencing on epithelial-mesenchymal transition of T24 cells were evaluated with wound-healing assay.

RESULTS

Pokemon was strongly inhibited by siRNA treatment, especially siRNA3 treatment group, as it was reflected by Western blot and real-time PCR. The gene and protein of E-cadherin expression level showed increased markedly after Pokemon was inhibited by RNA interference. While there were no differences in the levels of gene and protein of β-catenin among five groups. The bladder cancer cell after Pokemon siRNA interference showed a significantly reduced wound-closing efficiency at 6, 12 and 24h.

CONCLUSIONS

Our findings suggest Pokemon may inhibit the expression of E-cadherin. The low expression of E-cadherin lead to increasing the phenotype and apical-base polarity of epithelial cells. These changes of cells may result in the recurrence and progression of bladder cancer at last.