Downregulation of Bmi-1 is associated with suppressed tumorigenesis and induced apoptosis in CD44+ nasopharyngeal carcinoma cancer stem-like cells

Hairy gene homolog increases nasopharyngeal carcinoma cell stemness by upregulating Bmi-1

B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) is overexpressed in various cancer types. We found that Bmi-1 mRNA levels were elevated in nasopharyngeal carcinoma (NPC) cell lines. In immunohistochemical analyses, high Bmi-1 levels were observed in not only 5 of 38 non-cancerous nasopharyngeal squamous epithelial biopsies, but also in 66 of 98 NPC specimens (67.3%). High Bmi-1 levels were detected more frequently in T3-T4, N2-N3 and stage III-IV NPC biopsies than in T1-T2, N0-N1 and stage I-II NPC samples, indicating that Bmi-1 is upregulated in advanced NPC. In 5-8F and SUNE1 NPC cells, stable depletion of Bmi-1 using lentiviral RNA interference greatly suppressed cell proliferation, induced G1-phase cell cycle arrest, reduced cell stemness and suppressed cell migration and invasion. Likewise, knocking down Bmi-1 inhibited NPC cell growth in nude mice. Both chromatin immunoprecipitation and Western blotting assays demonstrated that Hairy gene homolog (HRY) upregulated Bmi-1 by binding to its promoter, thereby increasing the stemness of NPC cells. Immunohistochemistry and quantitative real-time PCR analyses revealed that HRY expression correlated positively with Bmi-1 expression in a cohort of NPC biopsies. These findings suggested that HRY promotes NPC cell stemness by upregulating Bmi-1, and that silencing Bmi-1 can suppress NPC progression.

Advances in targeted therapy mainly based on signal pathways for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant epithelial carcinoma of the head and neck region which mainly distributes in southern China and Southeast Asia and has a crucial association with the Epstein-Barr virus. Based on epidemiological data, both incidence and mortality of NPC have significantly declined in recent decades grounded on the improvement of living standard and medical level in an endemic region, in particular, with the clinical use of individualized chemotherapy and intensity-modulated radiotherapy (IMRT) which profoundly contributes to the cure rate of NPC patients. To tackle the challenges including local recurrence and distant metastasis in the current NPC treatment, we discussed the implication of using targeted therapy against critical molecules in various signal pathways, and how they synergize with chemoradiotherapy in the NPC treatment. Combination treatment including targeted therapy and IMRT or concurrent chemoradiotherapy is presumably to be future options, which may reduce radiation or chemotherapy toxicities and open new avenues for the improvement of the expected functional outcome for patients with advanced NPC.

Cancer stem cell markers in adenocarcinoma of the salivary glands - reliable prognostic markers?

Purpose

Adenocarcinoma of the salivary glands is of low incidence and a broad range of histopathological subtypes. Cancer stem cell markers (CSC) might serve as novel prognostic parameters. To date, only a few studies examined the expression of CSC in adenocarcinoma of the salivary glands with diverging results. To further investigate the reliability in terms of prognostic value, a histopathological analysis of CSCs on a cohort of patients with adenocarcinomas of the major salivary glands was performed.

Methods

Tumor samples of 40 consecutive patients with adenocarcinoma of the major salivary gland treated with curative intend at one tertiary center were stained with the CSCs ALDH1, BMI-1, CD44, Nanog, and SOX2. Expression of these markers was correlated with clinicopathological parameters and survival estimates.

Results

Correlation of high expression of ALDH1 with higher grading (p < 0.001) and high expression of CD44 with the localization of the neoplasm (p = 0.05), larger tumor size (p = 0.006), positive pN-category (p = 0.023), and advanced UICC stage (p = 0.002) was found. Furthermore, high expression of SOX2 correlated with a negative perineural invasion (p = 0.02). No significant correlation of any investigated marker with survival estimates was observed.

Conclusion

In conclusion, our study did not find a significant correlation of the investigated CSCs with survival estimates in adenocarcinoma of the major salivary glands. Recapitulating the results of our study in conjunction with data in the literature, the CSCs ALDH1, BMI-1, CD44, Nanog, and SOX2 do not seem to serve as reliable prognostic parameters in the treatment of adenocarcinoma of the salivary glands.

Electronic supplementary material

The online version of this article (10.1007/s00405-020-06389-7) contains supplementary material, which is available to authorized users.

Up-regulated long non-coding RNA ILF3-AS1 indicates poor prognosis of nasopharyngeal carcinoma and promoted cell metastasis

BACKGROUND

Long non-coding RNAs (lncRNAs) have been confirmed to participate in the regulation of nasopharyngeal carcinoma. Here, we endeavored to explore the character of lncRNA ILF3-AS1 in the nasopharyngeal carcinoma and its function.

METHODS

A total of 68 nasopharyngeal carcinoma tissues and adjacent normal nasopharyngeal tissues were collected. Expressions of lncRNA ILF3-AS1 in these tissues were detected using quantitative real-time polymerase chain reaction (qRT-PCR). The relationship between the expression level of lncRNA ILF3-AS1 and clinical pathological characteristics was analyzed. Inhibition of lncRNA ILF3-AS1 was done using small interference RNA.

RESULTS

lncRNA ILF3-AS1 expression was significantly up-regulated in the 68 nasopharyngeal carcinoma tissue samples compared to their adjacent normal tissue samples. Increased lncRNA ILF3-AS1 level was related to the advanced tumor node metastasis stage and the metastasis of nasopharyngeal carcinoma. Also, increased lncRNA ILF3-AS1 indicated poor prognosis of nasopharyngeal carcinoma patients. Inhibition of lncRNA ILF3-AS1 reduced proliferation, invasion and migration of nasopharyngeal carcinoma cells. MicroRNA-320a (miR-320a) was determined as a direct target for lncRNA ILF3-AS1 in nasopharyngeal carcinoma. Furthermore, lncRNA ILF3-AS1 could sponge miR-320a to promote BMI1 expression. The expression of BMI1 was significantly inhibited by the down-regulation of lncRNA ILF3-AS1.

CONCLUSIONS

For the first time, we demonstrated that lncRNA ILF3-AS1 was markedly over-expressed in nasopharyngeal carcinoma tissues and cells. Elevated lncRNA ILF3-AS1 expression was correlated with severe cancer stage and poor prognosis. lncRNA ILF3-AS1 could promote proliferation, invasion, and migration of cells, which might indicate a novel target site for the future diagnosis and therapy of nasopharyngeal carcinoma.

Effects of siRNA-mediated silencing of Bmi-1 gene expression on proliferation of gastric cancer cells

This study was designed to investigate the effects of siRNA-mediated silencing of Bmi-1 gene expression on proliferation of AGS gastric cancer cell. siRNA Bmi-1 was transfected into human AGS gastric cancer cells by liposome (as siRNA Bmi-1 group) with negative control (as control group); the expressions of Bmi-1 and apoptosis-related genes like P21, Bax, and Bcl-2 in AGS cells were determined by Western blot method; the apoptosis of AGS cells was detected by flow cytometry double staining and Hoechst staining; and cell cycle was measured by flow cytometry. Compared with the control group, the expression of Bmi-1 in the siRNA Bmi-1 group was significantly decreased ( P < 0.05), the apoptosis rate was increased ( P < 0.05), and cell cycles were arrested at G1 phase (P < 0.05); the expression level of P21 and Bax in cells was significantly up-regulated while that of Bcl-2 down-regulated ( P < 0.05). The down regulation of Bmi-1 can inhibit the proliferation of AGS gastric cancer cell and promote its apoptosis, which takes such effects mainly by up-regulating P21 as well as Bax and down-regulating Bcl-2.

Dynamism, Sensitivity, and Consequences of Mesenchymal and Stem-Like Phenotype of Cancer Cells

There are remarkable similarities in the description of cancer stem cells (CSCs) and cancer cells with mesenchymal phenotype. Both cell types are highly tumorigenic, resistant against common anticancer treatment, and thought to cause metastatic growth. Moreover, cancer cells are able to switch between CSC and non-CSC phenotypes and vice versa, to ensure the necessary balance within the tumor. Likewise, cancer cells can switch between epithelial and mesenchymal phenotypes via well-described transition (EMT/MET) that is thought to be crucial for tumor propagation. In this review, we discuss whether, and to which extend, the CSCs and mesenchymal cancer cells are overlapping phenomena in terms of mechanisms, origin, and implication for cancer treatment. As well, we describe the dynamism of both phenotypes and involvement of the tumor microenvironment in CSC reversion and in EMT.

Bmi‑1‑targeting suppresses osteosarcoma aggressiveness through the NF‑κB signaling pathway

Bone cancer is one of the most lethal malignancies and the specific causes of tumor initiation are not well understood. B‑cell‑specific Moloney murine leukemia virus integration site 1 protein (Bmi‑1) has been reported to be associated with the initiation and progression of osteosarcoma, and as a prognostic indicator in the clinic. In the current study, a full‑length antibody targeting Bmi‑1 (AbBmi‑1) was produced and the preclinical value of Bmi‑1‑targeted therapy was evaluated in bone carcinoma cells and tumor xenograft mice. The results indicated that the Bmi‑1 expression level was markedly upregulated in bone cancer cell lines, and inhibition of Bmi‑1 by AbBmi‑1 reduced the invasiveness and migration of osteosarcoma cells. Overexpression of Bmi‑1 promoted proliferation and angiogenesis, and increased apoptosis resistance induced by cisplatin via the nuclear factor‑κB (NF‑κB) signal pathway. In addition, AbBmi‑1 treatment inhibited the tumorigenicity of osteosarcoma cells in vivo. Furthermore, AbBmi‑1 blocked NF‑κB signaling and reduced MMP‑9 expression. Furthermore, Bmi‑1 promoted osteosarcoma tumor growth, whereas AbBmi‑1 significantly inhibited osteosarcoma tumor growth in vitro and in vivo. Notably, AbBmi‑1 decreased the percentages of Ki67‑positive cells and terminal deoxynucleotidyl transferase dUTP nick end labeling‑positive cells in tumors compared with Bmi‑1‑treated and PBS controls. Notably, MMP‑9 and NF‑κB expression were downregulated by treatment with AbBmi‑1 in MG‑63 osteosarcoma cells. In conclusion, the data provides evidence that AbBmi‑1 inhibited the progression of osteosarcoma, suggesting that AbBmi‑1 may be a novel anti‑cancer agent through the inhibition of Bmi‑1 via activating the NF‑κB pathway in osteosarcoma.

Downregulation of Bmi-1 suppresses epithelial‑mesenchymal transition in melanoma

Epithelial-mesenchymal transition (EMT) contributes to the invasion and metastasis of numerous malignant cancers, including melanoma. A significant higher expression of B-lymphoma Moloney murine leukemia virus insertion region-1 (Bmi-1) has been reported in cell lines from metastatic melanoma compared to cell lines from primary melanoma. There are studies that show that knockdown of Bmi-1 could induce E-cadherin expression in melanoma cells. However, the role of Bmi-1 in mediating EMT-like changes in melanoma has not yet been fully studied. In the present study, knockdown of Bmi-1 by shRNA transduction decreased the invasion properties of the cultured human melanoma cells A375 by a Matrigel invasion assay, along with alterations in EMT-related markers E-cadherin, α-catenin, vimentin and N-cadherin. The aforementioned altered expression of EMT markers was verified in BALB/c-nude mouse xenografts. Furthermore, to explore the underlying regulatory mechanism of EMT, we detected the significant downregulation of p-Akt/p‑NF-κB/MMP-2 and the upregulation of PTEN in Bmi-1-silenced A375 cells. The present study demonstrated that knockdown of Bmi-1 significantly inhibited the aggressive behavior of melanoma by reversing EMT-like changes via the PTEN/p-Akt/p‑NF-κB/MMP-2 pathway.