Jiazhi Li

MicroRNA-34a suppresses the breast cancer stem cell-like characteristics by downregulating Notch1 pathway

MicroRNAs play pivotal roles in cancer stem cell regulation. Previous studies have shown that microRNA‐34a (miR‐34a) is downregulated in human breast cancer. However, it is unknown whether and how miR‐34a regulates breast cancer stem cells. Notch signaling is one of the most important pathways in stem cell maintenance and function. In this study, we verified that miR‐34a directly and functionally targeted Notch1 in MCF‐7 cells. We reported that miR‐34a negatively regulated cell proliferation, migration, and invasion and breast cancer stem cell propagation by downregulating Notch1. The expression of miR‐34a was negatively correlated with tumor stages, metastasis, and Notch1 expression in breast cancer tissues. Furthermore, overexpression of miR‐34a increased chemosensitivity of breast cancer cells to paclitaxel (PTX) by downregulating the Notch1 pathway. Mammosphere formation and expression of the stemness factor ALDH1 were also reduced in the cells treated with miR‐34a and PTX compared to those treated with PTX alone. Taken together, our results indicate that miR‐34a inhibited breast cancer stemness and increased the chemosensitivity to PTX partially by downregulating the Notch1 pathway, suggesting that miR‐34a/Notch1 play an important role in regulating breast cancer stem cells. Thus miR‐34a is a potential target for prevention and therapy of breast cancer.

MicroRNA-138 modulates metastasis and EMT in breast cancer cells by targeting vimentin

Increasing evidence indicates that dysregulation of microRNAs (miRNAs) plays critical roles in malignant transformation and tumor progression. In this study, in order to investigate the association of miR-138 with breast cancer we investigated the role of miR-138 in breast cancer metastasis. Levels of miR-138 were determined by qRT-PCR in 45 breast cancer samples. Cell migration and invasion assays were performed in a stably expressing miRNA-138 breast cancer cell line established using a lentivirus expression system. Epithelial-mesenchymal transition (EMT) was evaluated using qRT-PCR and Western Blots to detect epithelial marker E-cadherin and mesenchymal marker, vimentin. Luciferase reporter assays were used to identify downstream targets and biological function of miR-138. Breast cancer tissues had significantly lower expression of miR-138 compared to non-tumor tissues. Low miR-138 levels were associated with lymph node metastasis and invasion. miR-138 overexpression inhibited metastasis of breast cancer cells. miR-138 overexpression also down-regulated vimentin expression and upregulated E-cadherin expression, suggesting that miR-138 inhibited EMT. Our results support the involvement of miR-138 in breast tumorigenesis, especially lymph node metastasis. We propose that miR-138 might be used as therapeutic agent for breast cancer.

Salinomycin exerts anticancer effects on human breast carcinoma MCF-7 cancer stem cells via modulation of Hedgehog signaling

Breast cancer tissue contains a small population of cells that have the ability to self-renew, these cells are known as breast cancer stem cells (BCSCs). The Hedgehog signal transduction pathway plays a central role in stem cell development, its aberrant activation has been shown to contribute to the development of breast cancer, making this pathway an attractive therapeutic target. Salinomycin (Sal) is a novel identified cancer stem cells (CSCs) killer, however, the molecular basis for its anticancer effects is not yet clear. In the current study, Sals ability to modulate the activity of key elements in the Hedgehog pathway was examined in the human breast cancer cell line MCF-7, as well as in a subpopulation of cancer stem cells identified within this cancer cell line. We show here that Sal inhibits proliferation, invasion, and migration while also inducing apoptosis in MCF-7 cells. Interestingly, in a subpopulation of MCF-7 cells with the CD44(+)/CD24(-) markers and high ALDH1 levels indicative of BCSCs, modulators of Hedgehog signaling Smo and Gli1 were significantly down-regulated upon treatment with Sal. These results demonstrate that Sal also inhibits proliferation and induces apoptosis of BCSCs, further establishing it as therapeutically relevant in the context of breast cancers and also indicating that modulation of Hedgehog signaling is one potential mechanism by which it exerts these anticancer effects.

miR-221/222 enhance the tumorigenicity of human breast cancer stem cells via modulation of PTEN/Akt pathway

BACKGROUND The miR-221/222 cluster has been discovered to function as oncogene in human malignancies including breast cancer. However, the role of miR-221/222 in the self-renewal of breast cancer stem cells (BCSCs) is not fully understood. In this study, we examined the impact and mechanism of miR-221/222 on the breast cancer cell viability, migration and invasion, and propagation of BCSCs. METHODS Human breast cancer cell line MCF-7 was transfected with miR-221/222 mimics or inhibitors to overexpress or knock down miR-221/222 respectively using Lipofactamine 2000. The biological effects of miR-221 and miR-222 were then assessed by cell proliferation assay, colony formation assay and transwell chamber assays. CD44/CD24 staining and mammosphere formation assay were performed to evaluate the ability of BCSCs self-renewal. Potential target gene phosphatase and tensin homolog (PTEN) and its downstream effector, phosphorylated Akt (p-Akt) were identified by Western blot and qRT-PCR methods. RESULTS PTEN, a tumor suppressor gene, was confirmed as a target of miR-221/222 in breast cancer cell line MCF-7. Downregulation of PTEN by miR-221/222 increased the phosphorylation of Akt. Enforced expression of miR-221/222 promoted breast cancer cell proliferation, migration and invasion via targeting PTEN/Akt pathway. Importantly, ectopic expression of miR-221/222 enriched the proportion of CD44(+)/CD24(-) BCSCs and improved the mammosphere formation capacity through targeting PTEN/Akt pathway. Blocking the endogenous miR-221/222 restored PTEN expression and subsequently decreased Akt phosphorylation, and thereby reversed this phenotype. CONCLUSIONS Our results suggested that miR-221/222 enhance breast cancer growth, migration and invasion, meanwhile propagate the self-renewal of BCSCs. This is achieved possibly through targeting PTEN/Akt pathway. miR-221/222 might be a novel therapeutic candidate for human breast cancer.

The mechanism between epithelial mesenchymal transition in breast cancer and hypoxia microenvironment

Hypoxia microenvironment widely exists in solid tumor tissues, which is mainly due to the rapid growth of cells within the tumor more than the speed of capillary in neoplasm, resulting in tumor tissue hypoxia. In hypoxia, hypoxia inducible factor 1 (HIF-1) is activated and regulate the expression of a series of hypoxia inducible genes, resulting in a series of hypoxia adaptation reaction. Researchs proved that, HIF-1 is closely related to the invasion, metastasis, prognosis of the tumor, and the expression of HIF-1 is higher in metastatic tissues compared with primary cancer tissues. In the evolution process of breast cancer, epithelial mesenchymal transition (EMT) define the characteristics of migration and invasion of breast cancer cells, which can also allow cancer cells to acquire the ability of self-renewing and stemness, so as to promote the generation of breast cancer stem cells. The incidence of EMT cancer stem cells are higher within the resistant to conventional treatment. This review focuses on breast cancer (stem cells), targeting the mechanism between hypoxia and EMT in tumor (stem cells), with the purpose of finding the new therapy to breast cancer.

Salinomycin suppresses TGF-β1-induced epithelial-to-mesenchymal transition in MCF-7 human breast cancer cells.

Epithelial-to-mesenchymal transition (EMT) is the major cause of breast cancer to initiate invasion and metastasis. Salinomycin (Sal) has been found as an effective chemical compound to kill breast cancer stem cells. However, the effect of Sal on invasion and metastasis of breast cancer is unclear. In the present study, we showed that Sal reversed transforming growth factor-β1 (TGF-β1) induced invasion and metastasis accompanied with down-regulation of MMP-2 by experiments on human breast cancer cell line MCF-7. Sal was able to inhibit TGF-β1-induced EMT phenotypic transition and the activation of key signaling molecules involved in Smad (p-Smad2/3,Snail1) and non-Smad (β-catenin, p-p38 MAPK) signals which cooperatively regulate the induction of EMT. Importantly, in a series of breast cancer specimens, we found strong correlation among E-cadherin expression, β-catenin expression, and the lymph node metastatic potential of breast cancer. Our research suggests that Sal is promised to be a chemotherapeutic drug by suppressing the metastasis of breast cancer.

microRNA -140-5p inhibits colorectal cancer invasion and metastasis by targeting ADAMTS5 and IGFBP5

BackgroundColorectal cancer (CRC) is one of the most common malignancies in the world. microRNA-140-5p (miR-140) has been shown to be involved in cartilage development and osteoarthritis (OA) pathogenesis. Some contradictions still exist concerning the role of miR-140 in tumor progression and metastasis, and the underlying mechanism is uncertain.MethodsImmunohistochemistry was performed to determine the expressions of ADAMTS5 and IGFBP5 in CRC tissues. Human CRC cell lines HCT116 and RKO were transfected with miR-140 mimic, inhibitor, or small interfering RNA (siRNA) against ADAMTS5 or IGFBP5, respectively, using oligofectamine or lipofectamine 2000. Scratch-wound assay and transwell migration and invasion assays were used to evaluate the effects of miR-140 on the capabilities of migration and invasion. The levels of miR-140 and ADAMTS5 and IGFBP5 mRNA were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to examine the expression of ADAMTS5 and IGFBP5 proteins.ResultsmiR-140 was significantly reduced, whereas ADAMTS5 and IGFBP5 were upregulated, in the human CRC tissues compared to the corresponding normal colorectal mucosa. miR-140 downregulation and ADAMTS5 or IGFBP5 overexpression were associated with the advanced TNM stage and distant metastasis of CRC. There was a reverse correlation between miR-140 levels and ADAMTS5 and IGFBP5 expression in CRC tissues. ADAMTS5 and IGFBP5 were downregulated by miR-140 at both the protein and mRNA levels in the CRC cell lines. The gain-of- and loss-of-function studies showed that miR-140 inhibited CRC cell migratory and invasive capacities at least partially via downregulating the expression of ADAMTS5 and IGFBP5.ConclusionsThese findings suggest that miR-140 suppresses CRC progression and metastasis, possibly through downregulating ADAMTS5 and IGFBP5. miR-140 might be a potential therapeutic candidate for the treatment of CRC.

MicroRNA-140 Inhibits the Epithelial-Mesenchymal Transition and Metastasis in Colorectal Cancer

MicroRNA-140, a cartilage-specific microRNA, has recently been implicated in the cancer progression. However, the comprehensive role of miR-140 in the invasion and metastasis of colorectal cancer (CRC) is still not fully understood. In this study, we confirmed that miR-140 downregulates SMAD family member 3 (Smad3), which is a key downstream effector of the TGF-β signaling pathway, at the translational level in the CRC cell lines. Ectopic expression of miR-140 inhibits the process of epithelial-mesenchymal transition (EMT), at least partially through targeting Smad3, and induces the suppression of migratory and invasive capacities of CRC cells in vitro. miR-140 also attenuates CRC cell proliferation possibly via downregulating Samd3. Furthermore, overexpression of miR-140 inhibits the tumor formation and metastasis of CRC in vivo, and silenced Smad3 has the similar effect. Additionally, miR-140 expression is decreased in the clinical primary CRC specimens and appears as a progressive reduction in the metastatic specimens, whereas Smad3 is overexpressed in the CRC samples. Taken together, our findings suggest that miR-140 might be a key suppressor of CRC progression and metastasis through inhibiting EMT process by targeting Smad3. miR-140 may represent a novel candidate for CRC treatment.

Protein tyrosine phosphatase receptor-type δ acts as a negative regulator suppressing breast cancer

Protein tyrosine phosphatase receptor-type δ (PTPRD) is frequently inactivated in human cancers. This study investigated the role of PTPRD in the regulation of stemness, epithelial-mesenchymal transition (EMT), and migration and invasion in breast cancer cells. In vitro, PTPRD silencing using siRNA enhanced the stem cell-like properties of breast cancer cells, including their mammosphere- and holoclone-forming abilities, and it promoted tumorigenicity in vivo. PTPRD knockdown also increased the CD44+/CD24− breast cancer stem cell (BCSC) population and the expression of the stem cell markers ALDH1 and OCT4. It also promoted migration and invasion by breast cancer cell, EMT, and activation of signal transducer and activator of transcription 3 (STAT3). BCSCs expressed low levels of PTPRD, displayed mesenchymal phenotypes, and were more sensitive to IL-6-mediated STAT3 activation than non-BCSCs. PTPRD expression was upregulated by IL-6 in breast cancer cells, thereby establishing a negative feedback circuit by which IL-6 induced canonical STAT3 phosphorylation and transiently upregulated PTPRD, which in turn dephosphorylated STAT3 and prevented downstream signaling via the IL-6/STAT3 cascade. These data suggest that therapies aimed at restoring or enhancing PTPRD expression may be effective in controlling breast cancer progression and metastasis.