Bmi1 Promotes Cholangiocarcinoma Progression And Correlates With Antitumor Immunity In An Exosome-Dependent Manner

Background: Cholangiocarcinoma (CCA) is a class of malignant tumors originating from bile duct epithelial cells. Due to difficult early diagnosis and limited treatment, the prognosis of CCA is extremely poor. Bmi1 is dysregulated in many human malignancies. However, the prognostic significance and oncogenic role of Bmi1 in cholangiocarcinoma (CCA) are not well elucidated. Methods: In the present study, we investigated its clinical importance and the potential mechanisms in the progression of CCA. We detected Bmi1 expression in a large CCA cohort. We demonstrated Bmi1 was substantially upregulated in CCA tissues and was identified as an independent prognostic biomarker of CCA. Moreover, overexpression of Bmi1 promoted CCA proliferation, migration, and invasion. And, Bmi1 knockdown could inhibit proliferation and metastases of CCA in vitro and in vitro/vivo validation. Interestingly, we found that CCA-derived exosomes contain Bmi1 proteins, which can transfer Bmi1 between CCA cells. The unique Bmi1-containing exosomes promote CCA proliferation and metastasis through autocrine/paracrine mechanisms. In addition, we demonstrated that Bmi1 inhibits CD8+T cell-recruiting chemokines by promoting repressive H2A ubiquitination in CCA cells. Conclusions: Bmi1 is an unfavorable prognostic biomarker of CCA. Our data demonstrate a novel function of Bmi1 in CCA tumorigenesis and metastasis mediated by exosomes. Besides, Bmi1 inhibition may augment immune checkpoint blockade to inhibit tumor progression by activating cell-intrinsic immunity of CCA

High BMI1 Expression with Low CD8+ and CD4+ T Cell Activity Could Promote Breast Cancer Cell Survival: A Machine Learning Approach

BMI1 is known to play a key role in the regulation of stem cell self-renewal in both endogenous and cancer stem cells. High BMI1 expression has been associated with poor prognosis in a variety of human tumors. The aim of this study was to reveal the correlations of BMI1 with survival rates, genetic alterations, and immune activities, and to validate the results using machine learning. We investigated the survival rates according to BMI1 expression in 389 and 789 breast cancer patients from Kangbuk Samsung Medical Center (KBSMC) and The Cancer Genome Atlas, respectively. We performed gene set enrichment analysis (GSEA) with pathway-based network analysis, investigated the immune response, and performed in vitro drug screening assays. The survival prediction model was evaluated through a gradient boosting machine (GBM) approach incorporating BMI1. High BMI1 expression was correlated with poor survival in patients with breast cancer. In GSEA and in in silico flow cytometry, high BMI1 expression was associated with factors indicating a weak immune response, such as decreased CD8+ T cell and CD4+ T cell counts. In pathway-based network analysis, BMI1 was directly linked to transcriptional regulation and indirectly linked to inflammatory response pathways, etc. The GBM model incorporating BMI1 showed improved prognostic performance compared with the model without BMI1. We identified telomerase inhibitor IX, a drug with potent activity against breast cancer cell lines with high BMI1 expression. We suggest that high BMI1 expression could be a therapeutic target in breast cancer. These results could contribute to the design of future experimental research and drug development programs for breast cancer.

Alantolactone inhibits cervical cancer progression by downregulating BMI1

Cervical cancer is the second most common cancer in women. Despite advances in cervical cancer therapy, tumor recurrence and metastasis remain the leading causes of mortality. High expression of BMI1 is significantly associated with poor tumor differentiation, high clinical grade, and poor prognosis of cervical cancer, and is an independent prognostic factor in cervical carcinoma. Alantolactone (AL), a sesquiterpene lactone, exhibits potent anti-inflammatory and anticancer activities. In this paper, we investigated the mechanism of AL in reducing the proliferation, migration, and invasion of HeLa and SiHa cervical cancer cells as well as its promotion of mitochondrial damage and autophagy. BMI1 silencing decreased epithelial-mesenchymal transformation-associated proteins and increased autophagy-associated proteins in HeLa cells. These effects were reversed by overexpression of BMI1 in HeLa cells. Thus, BMI1 expression is positively correlated with invasion and negatively correlated with autophagy in HeLa cells. Importantly, AL decreased the weight, volume, and BMI1 expression in HeLa xenograft tumors. Furthermore, the structure of BMI1 and target interaction of AL were virtually screened using the molecular docking program Autodock Vina; AL decreased the expression of N-cadherin, vimentin, and P62 and increased the expression of LC3B and Beclin-1 in xenograft tumors. Finally, expression of BMI1 increased the phosphorylation of STAT3, which is important for cell proliferation, survival, migration, and invasion. Therefore, we suggest that AL plays a pivotal role in inhibiting BMI1 in the tumorigenesis of cervical cancer and is a potential therapeutic agent for cervical cancer.

Combination of PKCδ Inhibition with Conventional TKI Treatment to Target CML Models†

Numerous combinations of signaling pathway blockades in association with tyrosine kinase inhibitor (TKI) treatment have been proposed for eradicating leukemic stem cells (LSCs) in chronic myeloid leukemia (CML), but none are currently clinically available. Because targeting protein kinase Cδ (PKCδ) was demonstrated to eliminate cancer stem cells (CSCs) in solid tumors, we evaluated the efficacy of PKCδ inhibition in combination with TKIs for CML cells. We observed that inhibition of PKCδ by a pharmacological inhibitor, by gene silencing, or by using K562 CML cells expressing dominant-negative (DN) or constitutively active (CA) PKCδ isoforms clearly points to PKCδ as a regulator of the expression of the stemness regulator BMI1. As a consequence, inhibition of PKCδ impaired clonogenicity and cell proliferation for leukemic cells. PKCδ targeting in K562 and LAMA-84 CML cell lines clearly enhanced the apoptotic response triggered by any TKI. A strong synergism was observed for apoptosis induction through an increase in caspase-9 and caspase-3 activation and significantly decreased expression of the Bcl-xL Bcl-2 family member. Inhibition of PKCδ did not modify BCR-ABL phosphorylation but acted downstream of the oncogene by downregulating BMI1 expression, decreasing clonogenicity. PKCδ inhibition interfered with the clonogenicity of primary CML CD34+ and BCR-ABL-transduced healthy CD34+ cells as efficiently as any TKI while it did not affect differentiation of healthy CD34+ cells. LTC-IC experiments pinpointed that PKCδ inhibition strongly decreased the progenitors/LSCs frequency. All together, these results demonstrate that targeting of PKCδ in combination with a conventional TKI could be a new therapeutic opportunity to affect for CML cells.

Activation of Wnt/β-catenin signaling to increase BMI1 by Licl attenuates the toxicity of cisplatin in the HEI-OC1 auditory cells

Cisplatin is a very effective anti-tumor drug; nonetheless, it can induce cochlear hair cell apoptosis and ototoxicity in large doses. WNT/β-catenin signaling is also closely related to aging, embryonic development, and apoptosis. We establish a cisplatin-induced HEI-OC1 auditory cells model. WNT/β-catenin was activated by GSK3 inhibitor Licl to detect the expression level of each component of the WNT pathway and BMI1. The expression of BMI1 in the hair cell line model of HEI-OC1 cells induced by cisplatin was significantly reduced, and cell apoptosis was significantly reduced by increasing the expression level of cell line BMI through activating WNT/β-catenin signaling. Activation of WNT/β-catenin signaling to increase BMI1 expression can reduce the apoptosis of cochlear hair cells induced by cisplatin. BMI1 also has a protective effect on the ototoxicity of cisplatin.

Role of microRNA-381 in bladder cancer growth and metastasis with the involvement of BMI1 and the Rho/ROCK axis

Background Emerging evidence has noted the important participation of microRNAs (miRNAs) in several human diseases including cancer. This research was launched to probe the function of miR-381 in bladder cancer (BCa) progression. Methods Twenty-eight patients with primary BCa were included in this study. Cancer tissues and the adjacent normal tissues were obtained. Aberrantly expressed miRNAs in BCa tissues were analyzed using miRNA microarrays. miR-381 expression in the bladder and paired tumor tissues, and in BCa and normal cell lines was determined. The target relationship between miR-381 and BMI1 was predicted online and validated through a luciferase assay. Gain-of-functions of miR-381 and BMI1 were performed to identify their functions on BCa cell behaviors as well as tumor growth in vivo. The involvement of the Rho/ROCK signaling was identified. Results miR-381 was poor regulated in BCa tissues and cells (all p < 0.05). A higher miR-381 level indicated a better prognosis of patients with BCa. Artificial up-regulation of miR-381 inhibited proliferation, invasion, migration, resistance to apoptosis, and tumor formation ability of BCa T24 and RT4 cells (all p < 0.05). miR-381 was found to directly bind to BMI1 and was negatively correlated with BMI1 expression. Overexpression of BMI1 partially blocked the tumor suppressing roles of miR-381 in cell malignancy and tumor growth (all p < 0.05). In addition, miR-381 led to decreased RhoA phosphorylation and ROCK2 activation, which were also reversed by BMI1 (all p < 0.05). Artificial inhibition of the Rho/ROCK signaling blocked the functions of BMI1 in cell growth and metastasis (all p < 0.05). Conclusion The study evidenced that miR-381 may act as a beneficiary biomarker in BCa patients. Up-regulation of miR-381 suppresses BCa development both in vivo and in vitro through BMI1 down-regulation and the Rho/ROCK inactivation.

EZH2 facilitates BMI1-dependent hepatocarcinogenesis through epigenetically silencing microRNA-200c

EZH2, a histone methyltransferase, has been shown to involve in cancer development and progression via epigenetic regulation of tumor suppressor microRNAs, whereas BMI1, a driver of hepatocellular carcinoma (HCC), is a downstream target of these microRNAs. However, it remains unclear whether EZH2 can epigenetically regulate microRNA expression to modulate BMI1-dependent hepatocarcinogenesis. Here, we established that high EZH2 expression correlated with enhanced tumor size, elevated metastasis, increased relapse, and poor prognosis in HCC patients. Further clinical studies revealed that EZH2 overexpression was positively correlated to its gene copy number gain/amplification in HCC. Mechanistically, EZH2 epigenetically suppressed miR-200c expression both in vitro and in vivo, and more importantly, miR-200c post-transcriptionally regulated BMI1 expression by binding to the 3′-UTR region of its mRNA. Furthermore, miR-200c overexpression inhibits the growth of HCC cells in vivo. Silencing miR-200c rescued the tumorigenicity of EZH2-depleted HCC cells, whereas knocking down BMI1 reduced the promoting effect of miR-200c depletion on HCC cell migration. Finally, combination treatment of EZH2 and BMI1 inhibitors further inhibited the viability of HCC cells compared with the cells treated with EZH2 or BMI1 inhibitor alone. Our findings demonstrated that alteration of EZH2 gene copy number status induced BMI1-mediated hepatocarcinogenesis via epigenetically silencing miR-200c, providing novel therapeutic targets for HCC treatment.

CSIG-12. HDACs-Sp1-BMI1 PATHWAY IS INVOLVED IN THE ATTENUATION OF STRESS- AND THERAPY-INDUCED DEATH IN GLIOMA

BMI-1 is a transcriptional repressor and overexpresses in various human cancer tissues, which is also known to involve in the maintenance of “stem cell” features in a cell sub-population within the tumor. Here, we investigate the roles of BMI1 oncogene in brain tumors, notably involving drug-resistant metabolism. Interestingly, microarray datasets in OMCOMINE indicated that BMI1 is not commonly increased in clinical brain tumors, and survival plots in PROGgeneV2 also showed that BMI1 expression is not statistically associated with glioma patients. However, stressful serum starvation and anchorage independence growth conditions enabled to induce upregulation of BMI1. Further investigation, we identified HDAC-Sp1 is a stress-responsive pathway, critically promoting BMI1 expression. HDAC inhibition via vorinostat treatment prevented the binding of Sp1 to BMI1 promoter, leading to decreased BMI1 expression and attenuated tumor growth of TMZ-resistant glioma xenografts. Importantly, increased expression of the HDAC-Sp1-BMI1 axis but not BMI1 alone showed an increased risk of death in both high- and low-grade glioma. Thus, the HDAC-Sp1-BMI1 axis is critical to attenuate stress- and therapy-induced death in glioma cells and the axis inhibition may prevent the recurrence of malignant cells persisting after primary therapy.