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Identification of miR-30e* regulation of Bmi1 expression mediated by tumor-associated macrophages in gastrointestinal cancer.

Sugihara H, Ishimoto T, Watanabe M, Sawayama H, Iwatsuki M, Baba Y, Komohara Y, Takeya M, Baba H - PLoS ONE (2013)

Bottom Line: On the other hand, tumor-associated macrophages (TAMs) contribute to tumor growth, invasion, and metastasis by producing various mediators in the tumor microenvironment.Luciferase assays using miR-30e* mimic revealed that Bmi1 was a direct target for miR-30e* by interactions with the putative miR-30e* binding sites in the Bmi1 3' untranslated region. qRT-PCR analysis of resected cancer specimens showed that miR-30e* expression was downregulated in tumor regions compared with non-tumor regions, and Bmi1 expression was inversely correlated with miR-30e* expression in gastric cancer tissues, but not in colon cancer tissues.Our findings suggest that TAMs may cause increased Bmi1 expression through miR-30e* suppression, leading to tumor progression.

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterological Surgery, Graduate School of Medical Science, Kumamoto University, Kumamoto, Japan.

ABSTRACT
Bmi1 is overexpressed in a variety of human cancers including gastrointestinal cancer. The high expression level of Bmi1 protein is associated with poor prognosis of gastrointestinal cancer patients. On the other hand, tumor-associated macrophages (TAMs) contribute to tumor growth, invasion, and metastasis by producing various mediators in the tumor microenvironment. The aim of this study was to investigate TAM-mediated regulation of Bmi1 expression in gastrointestinal cancer. The relationship between TAMs and Bmi1 expression was analyzed by immunohistochemistry and quantitative real-time PCR (qRT-PCR), and results showed a positive correlation with tumor-infiltrating macrophages (CD68 and CD163) and Bmi1 expression in cancer cells. Co-culture with TAMs triggered Bmi1 expression in cancer cell lines and enhanced sphere formation ability. miRNA microarray analysis of a gastric cancer cell line co-cultured with macrophages was conducted, and using in silico methods to analyze the results, we identified miR-30e* as a potential regulator of Bmi1 expression. Luciferase assays using miR-30e* mimic revealed that Bmi1 was a direct target for miR-30e* by interactions with the putative miR-30e* binding sites in the Bmi1 3' untranslated region. qRT-PCR analysis of resected cancer specimens showed that miR-30e* expression was downregulated in tumor regions compared with non-tumor regions, and Bmi1 expression was inversely correlated with miR-30e* expression in gastric cancer tissues, but not in colon cancer tissues. Our findings suggest that TAMs may cause increased Bmi1 expression through miR-30e* suppression, leading to tumor progression. The suppression of Bmi1 expression mediated by TAMs may thus represent a possible strategy as the treatment of gastrointestinal cancer.

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Relationship between the expression of Bmi1 and levels of TAMs.(A) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 83 gastric cancer tissues. Scale bars, 100um. (B) The percentage of CD68/163 positive specimens in high Bmi1 expressing gastric cancer. There was a significant correlation between Bmi1 expression and CD68/163 expression (*P < 0.05, ***P < 0.001, respectively). (C) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 49 colon cancer tissues. Scale bars, 100um. (D) The percentage of CD68/163 positive specimens in high Bmi1 expressing colon cancer. There was a significant correlation between these two groups (**P < 0.01, **P < 0.01, respectively).
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pone-0081839-g001: Relationship between the expression of Bmi1 and levels of TAMs.(A) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 83 gastric cancer tissues. Scale bars, 100um. (B) The percentage of CD68/163 positive specimens in high Bmi1 expressing gastric cancer. There was a significant correlation between Bmi1 expression and CD68/163 expression (*P < 0.05, ***P < 0.001, respectively). (C) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 49 colon cancer tissues. Scale bars, 100um. (D) The percentage of CD68/163 positive specimens in high Bmi1 expressing colon cancer. There was a significant correlation between these two groups (**P < 0.01, **P < 0.01, respectively).

Mentions: TAMs contribute to tumor growth, invasion, and metastasis in many cancers by producing various mediators[13-17]. To determine whether the expression of Bmi1 in cancer cells correlates with the levels of TAMs, we examined Bmi1, CD68, and CD163 expression in gastrointestinal cancer tissues using IHC. CD68 staining was used to detect pan-macrophages, and the M2 population was evaluated using CD163, as described previously[22]. Results showed a positive relationship with Bmi1 and CD68/CD163 expression in gastric cancer (Figure 1A, C) and in colon cancer (Figure 1B, D). These results suggest that macrophages in tumor stroma may be involved in Bmi1 expression in gastrointestinal cancer cells.


Identification of miR-30e* regulation of Bmi1 expression mediated by tumor-associated macrophages in gastrointestinal cancer.

Sugihara H, Ishimoto T, Watanabe M, Sawayama H, Iwatsuki M, Baba Y, Komohara Y, Takeya M, Baba H - PLoS ONE (2013)

Relationship between the expression of Bmi1 and levels of TAMs.(A) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 83 gastric cancer tissues. Scale bars, 100um. (B) The percentage of CD68/163 positive specimens in high Bmi1 expressing gastric cancer. There was a significant correlation between Bmi1 expression and CD68/163 expression (*P < 0.05, ***P < 0.001, respectively). (C) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 49 colon cancer tissues. Scale bars, 100um. (D) The percentage of CD68/163 positive specimens in high Bmi1 expressing colon cancer. There was a significant correlation between these two groups (**P < 0.01, **P < 0.01, respectively).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3842972&req=5

pone-0081839-g001: Relationship between the expression of Bmi1 and levels of TAMs.(A) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 83 gastric cancer tissues. Scale bars, 100um. (B) The percentage of CD68/163 positive specimens in high Bmi1 expressing gastric cancer. There was a significant correlation between Bmi1 expression and CD68/163 expression (*P < 0.05, ***P < 0.001, respectively). (C) Immunohistochemistry of Bmi1, CD68, and CD163 expression in 49 colon cancer tissues. Scale bars, 100um. (D) The percentage of CD68/163 positive specimens in high Bmi1 expressing colon cancer. There was a significant correlation between these two groups (**P < 0.01, **P < 0.01, respectively).
Mentions: TAMs contribute to tumor growth, invasion, and metastasis in many cancers by producing various mediators[13-17]. To determine whether the expression of Bmi1 in cancer cells correlates with the levels of TAMs, we examined Bmi1, CD68, and CD163 expression in gastrointestinal cancer tissues using IHC. CD68 staining was used to detect pan-macrophages, and the M2 population was evaluated using CD163, as described previously[22]. Results showed a positive relationship with Bmi1 and CD68/CD163 expression in gastric cancer (Figure 1A, C) and in colon cancer (Figure 1B, D). These results suggest that macrophages in tumor stroma may be involved in Bmi1 expression in gastrointestinal cancer cells.

Bottom Line: On the other hand, tumor-associated macrophages (TAMs) contribute to tumor growth, invasion, and metastasis by producing various mediators in the tumor microenvironment.Luciferase assays using miR-30e* mimic revealed that Bmi1 was a direct target for miR-30e* by interactions with the putative miR-30e* binding sites in the Bmi1 3' untranslated region. qRT-PCR analysis of resected cancer specimens showed that miR-30e* expression was downregulated in tumor regions compared with non-tumor regions, and Bmi1 expression was inversely correlated with miR-30e* expression in gastric cancer tissues, but not in colon cancer tissues.Our findings suggest that TAMs may cause increased Bmi1 expression through miR-30e* suppression, leading to tumor progression.

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterological Surgery, Graduate School of Medical Science, Kumamoto University, Kumamoto, Japan.

ABSTRACT
Bmi1 is overexpressed in a variety of human cancers including gastrointestinal cancer. The high expression level of Bmi1 protein is associated with poor prognosis of gastrointestinal cancer patients. On the other hand, tumor-associated macrophages (TAMs) contribute to tumor growth, invasion, and metastasis by producing various mediators in the tumor microenvironment. The aim of this study was to investigate TAM-mediated regulation of Bmi1 expression in gastrointestinal cancer. The relationship between TAMs and Bmi1 expression was analyzed by immunohistochemistry and quantitative real-time PCR (qRT-PCR), and results showed a positive correlation with tumor-infiltrating macrophages (CD68 and CD163) and Bmi1 expression in cancer cells. Co-culture with TAMs triggered Bmi1 expression in cancer cell lines and enhanced sphere formation ability. miRNA microarray analysis of a gastric cancer cell line co-cultured with macrophages was conducted, and using in silico methods to analyze the results, we identified miR-30e* as a potential regulator of Bmi1 expression. Luciferase assays using miR-30e* mimic revealed that Bmi1 was a direct target for miR-30e* by interactions with the putative miR-30e* binding sites in the Bmi1 3' untranslated region. qRT-PCR analysis of resected cancer specimens showed that miR-30e* expression was downregulated in tumor regions compared with non-tumor regions, and Bmi1 expression was inversely correlated with miR-30e* expression in gastric cancer tissues, but not in colon cancer tissues. Our findings suggest that TAMs may cause increased Bmi1 expression through miR-30e* suppression, leading to tumor progression. The suppression of Bmi1 expression mediated by TAMs may thus represent a possible strategy as the treatment of gastrointestinal cancer.

Show MeSH
Related in: MedlinePlus