Identification of miR-30e* Regulation of Bmi1 Expression Mediated by Tumor-Associated Macrophages in Gastrointestinal Cancer

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.

Downregulation of 15‐hydroxyprostaglandin dehydrogenase by interleukin‐1β from activated macrophages leads to poor prognosis in pancreatic cancer

“…The average intensity of positively stained cells was given an intensity score from 0 to 3: 0, absent; 1, weak; 2, moderate; and 3, strong expression). The two scores were multiplied to characterize 15-PGDH expression as low (0-7) or high (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). CD163-positive cells were counted in four randomly selected area of a high-power field (9200) of a microscope.…”

“…8,9 Solid tumors are composed of cancer cells and diverse types of stromal cells, including cancer-associated fibroblasts and TAMs. [10][11][12][13] Thus, tumor progression depends on not only the aggressive characteristics of cancer cells themselves but also on their interactions with stromal cells. A previous study reported that prostaglandin signal activation caused by TAMs promoted tumor metastasis.…”

PLD4 promotes M1 macrophages to perform antitumor effects in colon cancer cells

“…HT-29, HCT116 and SW620 colon cells were plated at 10 4 cells/well in a 96-well plate that contained 100 µl RPMI-1640 supplement with 10% fBS for 24 h (19). Then, the culture medium was replaced by PLD4-siRNA (20 nM) group, control-group cell supernatant of M1 macrophages for another 24 h. For cell proliferation assay, the cells were quantified using a Cell Counting kit-8 (CCK-8; Nanjing KeyGen Biotech, Co., Ltd., Nanjing, China).…”

Function and significance of MicroRNAs in benign and malignant human stem cells

“…During cancer progression, molecular changes arise in the tumor as well as in the neighbouring tissue stroma, with substantial experimental evidence indicating that the stroma contributes significantly to cancer progression (124) (130,131). In another study, collagen remodeling was associated with suppression of M a n u s c r i p t the tumor-suppressive let-7 miRNA in pancreatic ductal adenocarcinomas (132).…”