Long non‐coding RNA FTH1P3 activates paclitaxel resistance in breast cancer through miR‐206/ABCB1

Emerging evidence has indicated the important function of long non‐coding RNAs (lncRNAs) in tumour chemotherapy resistance. However, the underlying mechanism is still ambiguous. In this study, we investigate the physiopathologic role of lncRNA ferritin heavy chain 1 pseudogene 3 (FTH1P3) on the paclitaxel (PTX) resistance in breast cancer. Results showed that lncRNA FTH1P3 was up‐regulated in paclitaxel‐resistant breast cancer tissue and cells (MCF‐7/PTX and MDA‐MB‐231/PTX cells) compared with paclitaxel‐sensitive tissue and parental cell lines (MCF‐7, MDA‐MB‐231). Gain‐ and loss‐of‐function experiments revealed that FTH1P3 silencing decreased the 50% inhibitory concentration (IC50) value of paclitaxel and induced cell cycle arrest at G2/M phase, while FTH1P3‐enhanced expression exerted the opposite effects. In vivo, xenograft mice assay showed that FTH1P3 silencing suppressed the tumour growth of paclitaxel‐resistant breast cancer cells and ABCB1 protein expression. Bioinformatics tools and luciferase reporter assay validated that FTH1P3 promoted ABCB1 protein expression through targeting miR‐206, acting as a miRNA “sponge.” In summary, our results reveal the potential regulatory mechanism of FTH1P3 on breast cancer paclitaxel resistance through miR‐206/ABCB1, providing a novel insight for the breast cancer chemoresistance.     

miR‐516a‐3p inhibits breast cancer cell growth and EMT by blocking the Pygo2/Wnt signalling pathway

miR‐516a‐3p has been reported to play a suppressive role in several types of human tumours. However, the expression level, biological function and fundamental mechanisms of miR‐516a‐3p in breast cancer remain unclear. In the present study, we found that miR‐516a‐3p expression was down‐regulated and Pygopus2 (Pygo2) expression was up‐regulated in human breast cancer tissues and cells. Through analysing the clinicopathological characteristics, we demonstrated that low miR‐516a‐3p expression or positive Pygo2 expression was a predictor of poor prognosis for patients with breast cancer. The results of a dual luciferase reporter assay and Western blot analysis indicated that Pygo2 was a target gene of miR‐516a‐3p. Moreover, overexpression of miR‐516a‐3p inhibited cell growth, migration and invasion as well as epithelial‐mesenchymal transition (EMT) of breast cancer cells, whereas reduced miR‐516a‐3p expression promoted breast cancer cell growth, migration, invasion and EMT. Furthermore, we showed that miR‐516a‐3p suppressed cell proliferation, metastasis and EMT of breast cancer cells by inhibiting Pygo2 expression. We confirmed that miR‐516a‐3p exerted an anti‐tumour effect by inhibiting the activation of the Wnt/β‐catenin pathway. Finally, xenograft tumour models were used to show that miR‐516a‐3p inhibited breast cancer cell growth and EMT via suppressing the Pygo2/Wnt signalling pathway. Taken together, these results show that miR‐516a‐3p inhibits breast cancer cell growth, metastasis and EMT by blocking the Pygo2/ Wnt/β‐catenin pathway.     

miR‐4732‐5p promotes breast cancer progression by targeting TSPAN13

MiR‐4732‐5p was previously found to be dysregulated in nipple discharge of breast cancer. However, the expression and function of miR‐4732‐5p in breast cancer remain largely unknown. Here, the expression of miR‐4732‐5p was detected using quantitative real‐time PCR in breast cancer tissues and cell lines. Cell proliferation, apoptosis, migration and invasion assays were performed to examine the effects of miR‐4732‐5p in breast cancer. In addition, mRNA sequencing, bioinformatics analysis, Western blot and luciferase assays were performed to identify the target of miR‐4732‐5p. Overall, miR‐4732‐5p was significantly down‐regulated in breast cancer tissues, especially in lymph node metastasis (LNM)‐negative tissues, compared with adjacent normal tissues. However, it was more highly expressed in LNM‐positive breast cancer tissues, compared with LNM‐negative ones. Expression of miR‐4732‐5p was positively correlated with lymph node metastasis, larger tumour size, advanced clinical stage, high Ki‐67 levels and poor prognosis. MiR‐4732‐5p promoted cell proliferation, migration and invasion in breast cancer. MiR‐4732‐5p directly targeted the 3′‐UTR of tetraspanin 13 (TSPAN13) and suppressed TSPAN13 expression at the mRNA and protein levels. These results suggested that miR‐4732‐5p may serve as a tumour suppressor in the initiation of breast cancer, but as a tumour promoter in breast cancer progression by targeting TSPAN13.     

lncRNA NR2F1‐AS1 promotes breast cancer angiogenesis through activating IGF‐1/IGF‐1R/ERK pathway

Long non‐coding RNAs (lncRNAs) take various effects in cancer mostly through sponging with microRNAs (miRNAs). lncRNA NR2F1‐AS1 is found to promote tumour progression in hepatocellular carcinoma, endometrial cancer and thyroid cancer. However, the role of lncRNA NR2F1‐AS1 in breast cancer angiogenesis remains unknown. In this study, we found lncRNA NR2F1‐AS1 was positively related with CD31 and CD34 in breast cancer through Pearson's correlation analysis, while lncRNA NR2F1‐AS1 transfection promoted human umbilical vascular endothelial cell (HUVEC) tube formation. In breast cancer cells, lncRNA NR2F1‐AS1 enhanced the HUVEC proliferation, tube formation and migration ability through tumour‐conditioned medium (TCM). In zebrafish model, lncRNA NR2F1‐AS1 increased the breast cancer cell‐related neo‐vasculature and subsequently promoted the breast cancer cell metastasis. In mouse model, lncRNA NR2F1‐AS1 promoted the tumour vessel formation, increased the micro vessel density (MVD) and then induced the growth of primary tumour. Mechanically, lncRNA NR2F1‐AS1 increased insulin‐like growth factor‐1 (IGF‐1) expression through sponging miRNA‐338‐3p in breast cancer cells and then activated the receptor of IGF‐1 (IGF‐1R) and extracellular signal‐regulated kinase (ERK) pathway in HUVECs. These results indicated that lncRNA NR2F1‐AS1 could promote breast cancer angiogenesis through IGF‐1/IGF‐1R/ERK pathway.     

Long non‐coding RNA SNHG16 promotes proliferation and inhibits apoptosis of diffuse large B‐cell lymphoma cells by targeting miR‐497‐5p/PIM1 axis

The aberrant expression and dysfunction of long non‐coding RNAs (lncRNAs) have been identified as critical factors governing the initiation and progression of different human cancers, including diffuse large B‐cell lymphoma (DLBCL). LncRNA small nucleolar RNA host gene 16 (SNHG16) has been recognized as a tumour‐promoting factor in various types of cancer. However, the biological role of SNHG16 and its underlying mechanism are still unknown in DLBCL. Here we disclosed that SNHG16 was overexpressed in DLBCL tissues and the derived cell lines. SNHG16 knockdown significantly suppressed cell proliferation and cell cycle progression, and it induced apoptosis of DLBCL cells in vitro. Furthermore, silencing of SNHG16 markedly repressed in vivo growth of OCI‐LY7 cells. Mechanistically, SNHG16 directly interacted with miR‐497‐5p by acting as a competing endogenous RNA (ceRNA) and inversely regulated the abundance of miR‐497‐5p in DLBCL cells. Moreover, the proto‐oncogene proviral integration site for Moloney murine leukaemia virus 1 (PIM1) was identified as a novel direct target of miR‐497‐5p. SNHG16 overexpression rescued miR‐497‐5p‐induced down‐regulation of PIM1 in DLBCL cells. Importantly, restoration of PIM1 expression reversed SNHG16 knockdown‐induced inhibition of proliferation, G0/G1 phase arrest and apoptosis of OCI‐LY7 cells. Our study suggests that the SNHG16/miR‐497‐5p/PIM1 axis may provide promising therapeutic targets for DLBCL progression.     

Epigenetic silenced miR‐125a‐5p could be self‐activated through targeting Suv39H1 in gastric cancer

Emerging evidence suggests that microRNAs (miRNAs) serve an important role in tumorigenesis and development. Although the low expression of miR‐125a‐5p in gastric cancer has been reported, the underlying mechanism remains unknown. In the current study, the low expression of miR‐125a‐5p in gastric cancer was verified in paired cancer tissues and adjacent non‐tumour tissues. Furthermore, the GC islands in the miR‐125a‐5p region were hypermethylated in the tumour tissues. And the hypermethylation was negatively correlated with the miR‐125a‐5p expression. Target gene screening showed that the histone methyltransferase Suv39H1 was one of the potential target genes. In vitro studies showed that miR‐125a‐5p could directly suppress the Suv39H1 expression and decrease the H3K9me3 levels. On the other hand, the Suv39H1 could induce demethylation of miR‐125a‐5p, resulting in re‐activation of miR‐125a‐5p. What is more, overexpessing miR‐125a‐5p could also self‐activate the silenced miR‐125a‐5p in gastric cancer cells, which suppressed cell migration, invasion and proliferation in vitro and inhibited cancer progression in vivo. Thus, we uncovered here that the epigenetic silenced miR‐125a‐5p could be self‐activated through targeting Suv39H1 in gastric cancer, suggesting that miR‐125a‐5p might be not only the potential prognostic value as a tumour biomarker but also potential therapeutic targets in gastric cancer.     

Long non‐coding RNA NNT‐AS1 sponges miR‐424/E2F1 to promote the tumorigenesis and cell cycle progression of gastric cancer

Long non‐coding RNAs (lncRNAs) have been illustrated to function as important regulators in carcinogenesis and cancer progression. However, the roles of lncRNA NNT‐AS1 in gastric cancer remain unclear. In the present study, we investigate the biological role of NNT‐AS1 in gastric cancer tumorigenesis. Results revealed that NNT‐AS1 expression level was significantly up‐regulated in GC tissue and cell lines compared with adjacent normal tissue and normal cell lines. The ectopic overexpression of NNT‐AS1 indicated the poor prognosis of GC patients. In vitro experiments validated that NNT‐AS1 knockdown suppressed the proliferation and invasion ability and induced the GC cell cycle progression arrest at G0/G1 phase. In vivo xenograft assay, NNT‐AS1 silencing decreased the tumour growth of GC cells. Bioinformatics online program predicted that miR‐424 targeted the 3′‐UTR of NNT‐AS1. Luciferase reporter assay, RNA‐immunoprecipitation (RIP) and RNA pull‐down assay validated the molecular binding within NNT‐AS1 and miR‐424, therefore jointly forming the RNA‐induced silencing complex (RISC). Moreover, E2F1 was verified to act as the target gene of NNT‐AS1/miR‐424, indicating the NNT‐AS1/miR‐424/E2F1 axis. In conclusion, our study indicates that NNT‐AS1 sponges miR‐424/E2F1 to facilitate GC tumorigenesis and cycle progress, revealing the oncogenic role of NNT‐AS1 for GC.     

microRNA‐128‐3p overexpression inhibits breast cancer stem cell characteristics through suppression of Wnt signalling pathway by down‐regulating NEK2

Emerging evidence has reported that dysregulation of microRNAs (miRNAs) participated in the development of diverse types of cancers. Our initial microarray‐based analysis identified differentially expressed NEK2 related to breast cancer and predicted the regulatory microRNA‐128‐3p (miR‐128‐3p). Herein, this study aimed to characterize the tumour‐suppressive role of miR‐128‐3p in regulating the biological characteristics of breast cancer stem cells (BCSCs). CD44^＋CD24^?/low cells were selected for subsequent experiments. After verification of the target relationship between miR‐128‐3p and NEK2, the relationship among miR‐128‐3p, NEK2 and BCSCs was further investigated with the involvement of the Wnt signalling pathway. The regulatory effects of miR‐128‐3p on proliferation, migration, invasion and self‐renewal in vitro as well as tumorigenicity in vivo of BCSCs were examined via gain‐ and loss‐of‐function approaches. Highly expressed NEK2 was found in breast cancer based on GSE61304 expression profile. Breast cancer stem cells and breast cancer cells showed a down‐regulation of miR‐128‐3p. Overexpression of miR‐128‐3p was found to inhibit proliferation, migration, invasion, self‐renewal in vitro and tumorigenicity in vivo of BCSCs, which was further validated to be achieved through inhibition of Wnt signalling pathway by down‐regulating NEK2. In summary, this study indicates that miR‐128‐3p inhibits the stem‐like cell features of BCSCs via inhibition of the Wnt signalling pathway by down‐regulating NEK2, which provides a new target for breast cancer treatment.     

Endoplasmic reticulum stress‐induced exosomal miR‐27a‐3p promotes immune escape in breast cancer via regulating PD‐L1 expression in macrophages

Immune escape of breast cancer cells contributes to breast cancer pathogenesis. Tumour microenvironment stresses that disrupt protein homeostasis can produce endoplasmic reticulum (ER) stress. The miRNA‐mediated translational repression of mRNAs has been extensively studied in regulating immune escape and ER stress in human cancers. In this study, we identified a novel microRNA (miR)‐27a‐3p and investigated its mechanistic role in promoting immune evasion. The binding affinity between miR‐27a‐3p and MAGI2 was predicted using bioinformatic analysis and verified by dual‐luciferase reporter assay. Ectopic expression and inhibition of miR‐27a‐3p in breast cancer cells were achieved by transduction with mimics and inhibitors. Besides, artificial modulation of MAGI2 and PTEN was done to explore their function in ER stress and immune escape of cancer cells. Of note, exosomes were derived from cancer cells and co‐cultured with macrophages for mechanistic studies. The experimental data suggested that ER stress biomarkers including GRP78, PERK, ATF6, IRE1α and PD‐L1 were overexpressed in breast cancer tissues relative to paracancerous tissues. Endoplasmic reticulum stress promoted exosome secretion and elevated exosomal miR‐27a‐3p expression. Elevation of miR‐27a‐3p and PD‐L1 levels in macrophages was observed in response to exosomes‐overexpressing miR‐27a‐3p in vivo and in vitro. miR‐27a‐3p could target and negatively regulate MAGI2, while MAGI2 down‐regulated PD‐L1 by up‐regulating PTEN to inactivate PI3K/AKT signalling pathway. Less CD4⁺, CD8⁺ T cells and IL‐2, and T cells apoptosis were observed in response to co‐culture of macrophages and CD3⁺ T cells. Conjointly, exosomal miR‐27a‐3p promotes immune evasion by up‐regulating PD‐L1 via MAGI2/PTEN/PI3K axis in breast cancer.     

MicroRNA‐301b‐3p contributes to tumour growth of human hepatocellular carcinoma by repressing vestigial like family member 4

MicroRNAs (miRNAs) are key regulators in the tumour growth and metastasis of human hepatocellular carcinoma (HCC). Increasing evidence suggests that miR‐301b‐3p functions as a driver in various types of human cancer. However, the expression pattern of miR‐301b‐3p and its functional role as well as underlying molecular mechanism in HCC remain poorly known. Our study found that miR‐301b‐3p expression was significantly up‐regulated in HCC tissues compared to adjacent non‐tumour tissues. Clinical association analysis revealed that the high level of miR‐301b‐3p closely correlated with large tumour size and advanced tumour‐node‐metastasis stages. Importantly, the high miR‐301b‐3p level predicted a prominent poorer overall survival of HCC patients. Knockdown of miR‐301b‐3p suppressed cell proliferation, led to cell cycle arrest at G2/M phase and induced apoptosis of Huh7 and Hep3B cells. Furthermore, miR‐301b‐3p knockdown suppressed tumour growth of HCC in mice. Mechanistically, miR‐301b‐3p directly bond to 3′UTR of vestigial like family member 4 (VGLL4) and negatively regulated its expression. The expression of VGLL4 mRNA was down‐regulated and inversely correlated with miR‐301b‐3p level in HCC tissues. Notably, VGLL4 knockdown markedly repressed cell proliferation, resulted in G2/M phase arrest and promoted apoptosis of HCC cells. Accordingly, VGLL4 silencing rescued miR‐301b‐3p knockdown attenuated HCC cell proliferation, cell cycle progression and apoptosis resistance. Collectively, our results suggest that miR‐301b‐3p is highly expressed in HCC. miR‐301b‐3p facilitates cell proliferation, promotes cell cycle progression and inhibits apoptosis of HCC cells by repressing VGLL4.     

LncRNA MST1P2/miR‐133b axis affects the chemoresistance of bladder cancer to cisplatin‐based therapy via Sirt1/p53 signaling

Although bladder cancer is commonly chemosensitive to standard first‐line therapy, the acquisition of the resistance to cisplatin (DDP)‐based therapeutic regimens remains a huge challenge. Noncoding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs) and microRNAs, have been reported to play a critical role in cancer resistance to DDP. Here, we attempted to provide a novel mechanism by which the resistance of bladder cancer to DDP treatment could be modulated from the perspective of ncRNA regulation. We demonstrated that lncRNA MST1P2 (lnc‐MST1P2) expression was dramatically upregulated, whereas miR‐133b expression was downregulated in DDP‐resistant bladder cancer cell lines, SW 780/DDP and RT4/DDP. Lnc‐MST1P2 and miR‐133b negatively regulated each other via targeting miR‐133b. Both lnc‐MST1P2 silence and miR‐133b overexpression could resensitize DDP‐resistant bladder cancer cells to DDP treatment. More important, miR‐133b could directly target the Sirt1 3′‐untranslated region to inhibit its expression. Inc‐MST1P2/miR‐133b axis affected the resistance of bladder cancer cells to DDP via Sirt1/p53 signaling. In conclusion, MST1P2 serves as a competing endogenous RNA for miR‐133b to counteract miR‐133b‐induced suppression on Sirt1, therefore enhancing the resistance of bladder cancer cells to DDP. MST1P2/miR‐133b axis affects the resistance of bladder cancer cells to DDP via downstream Sirt1/p53 signaling.     

Long non‐coding RNA F11‐AS1 inhibits HBV‐related hepatocellular carcinoma progression by regulating NR1I3 via binding to microRNA‐211‐5p

Long non‐coding RNAs (lncRNAs) could regulate growth and metastasis of hepatocellular carcinoma (HCC). In this study, we aimed to investigate the mechanism of lncRNA F11‐AS1 in hepatitis B virus (HBV)–related HCC. The relation of lncRNA F11‐AS1 expression in HBV‐related HCC tissues to prognosis was analysed in silico. Stably HBV‐expressing HepG2.2.15 cells were established to explore the regulation of lncRNA F11‐AS1 by HBx protein, as well as to study the effects of overexpressed lncRNA F11‐AS1 on proliferation, migration, invasion and apoptosis in vitro. Subsequently, the underlying interactions and roles of lncRNA F11‐AS1/miR‐211‐5p/NR1I3 axis in HBV‐related HCC were investigated. Additionally, the influence of lncRNA F11‐AS1 and miR‐211‐5p on tumour growth and metastasis capacity of HepG2.2.15 cells were studied on tumour‐bearing nude mice. Poor expression of lncRNA F11‐AS1 was correlated with poor prognosis in patients with HBV‐related HCC, and its down‐regulation was caused by the HBx protein. lncRNA F11‐AS1 was proved to up‐regulate the NR1I3 expression by binding to miR‐211‐5p. Overexpression of lncRNA F11‐AS1 reduced the proliferation, migration and invasion, yet induced apoptosis of HepG2.2.15 cells in vitro, which could be abolished by overexpression of miR‐211‐5p. Additionally, either lncRNA F11‐AS1 overexpression or miR‐211‐5p inhibition attenuated the tumour growth and metastasis capacity of HepG2.2.15 cells in vivo. Collectively, lncRNA F11‐AS1 acted as a modulator of miR‐211‐5p to positively regulate the expression of NR1I3, and the lncRNA F11‐AS1/miR‐211‐5p/NR1I3 axis participated in HBV‐related HCC progression via interference with the cellular physiology of HCC.     

miR‐515‐5p controls cancer cell migration through MARK4 regulation

Here, we show that miR‐515‐5p inhibits cancer cell migration and metastasis. RNA‐seq analyses of both oestrogen receptor receptor‐positive and receptor‐negative breast cancer cells overexpressing miR‐515‐5p reveal down‐regulation of NRAS, FZD4, CDC42BPA, PIK3C2B and MARK4 mRNAs. We demonstrate that miR‐515‐5p inhibits MARK4 directly 3′ UTR interaction and that MARK4 knock‐down mimics the effect of miR‐515‐5p on breast and lung cancer cell migration. MARK4 overexpression rescues the inhibitory effects of miR‐515‐5p, suggesting miR‐515‐5p mediates this process through MARK4 down‐regulation. Furthermore, miR‐515‐5p expression is reduced in metastases compared to primary tumours derived from both in vivo xenografts and samples from patients with breast cancer. Conversely, miR‐515‐5p overexpression prevents tumour cell dissemination in a mouse metastatic model. Moreover, high miR‐515‐5p and low MARK4 expression correlate with increased breast and lung cancer patients' survival, respectively. Taken together, these data demonstrate the importance of miR‐515‐5p/MARK4 regulation in cell migration and metastasis across two common cancers.     

miR‐655 suppresses epithelial‐to‐mesenchymal transition by targeting Prrx1 in triple‐negative breast cancer

Triple‐negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. The epithelial‐to‐mesenchymal transition (EMT) is a key contributor in the metastatic process. In this study, we found that miR‐655 was down‐regulated in TNBC, and its expression levels were associated with molecular‐based classification and lymph node metastasis in breast cancer. These findings led us to hypothesize that miR‐655 overexpression may inhibit EMT and its associated traits of TNBC. Ectopic expression of miR‐655 not only induced the up‐regulation of cytokeratin and decreased vimentin expression but also suppressed migration and invasion of mesenchymal‐like cancer cells accompanied by a morphological shift towards the epithelial phenotype. In addition, we found that miR‐655 was negatively correlated with Prrx1 in cell lines and clinical samples. Overexpression of miR‐655 significantly suppressed Prrx1, as demonstrated by Prrx1 3′‐untranslated region luciferase report assay. Our study demonstrated that miR‐655 inhibits the acquisition of the EMT phenotype in TNBC by down‐regulating Prrx1, thereby inhibiting cell migration and invasion during cancer progression.     

Down‐regulated lncRNA SLC25A5‐AS1 facilitates cell growth and inhibits apoptosis via miR‐19a‐3p/PTEN/PI3K/AKT signalling pathway in gastric cancer

Mounting evidence has illustrated the vital roles of long non‐coding RNAs (lncRNAs in gastric cancer (GC). Nevertheless, the majority of their roles and mechanisms in GC are still largely unknown. In this study, we investigate the roles of lncRNA SLC25A5‐AS1 on tumourigenesis and explore its potential mechanisms in GC. The results showed that the expressions of SLC25A5‐AS1 in GC were significantly lower than that of adjacent normal tissues, which were significantly associated with tumour size, TNM stage and lymph node metastasis. Moreover, SLC25A5‐AS1 could inhibit GC cell proliferation, induce G1/G1 cell cycle arrest and cell apoptosis in vitro, as well as GC growth in vivo. Dual‐luciferase reporter assay confirmed the direct interaction between SLC25A5‐AS1 and miR‐19a‐3p, rescue experiment showed that co‐transfection miR‐19a‐3p mimics and pcDNA‐SLC25A5‐AS1 could partially restore the ability of GC cell proliferation and the inhibition of cell apoptosis. The mechanism analyses further found that SLC25A5‐AS1 might act as a competing endogenous RNAs (ceRNA), which was involved in the derepression of PTEN expression, a target gene of miR‐19a‐3p, and regulate malignant phenotype via PI3K/AKT signalling pathway in GC. Taken together, this study indicated that SLC25A5‐AS1 was down‐regulated in GC and functioned as a suppressor in the progression of GC. Moreover, it could act as a ceRNA to regulate cellular behaviours via miR‐19a‐3p/PTEN/PI3K/AKT signalling pathway. Thus, SLC25A5‐AS1 might be served as a potential target for cancer therapeutics in GC.     

Two new miR‐16 targets: caprin‐1 and HMGA1, proteins implicated in cell proliferation

Background information. miRNAs (microRNAs) are a class of non‐coding RNAs that inhibit gene expression by binding to recognition elements, mainly in the 3′ UTR (untranslated region) of mRNA. A single miRNA can target several hundred mRNAs, leading to a complex metabolic network. miR‐16 (miRNA‐16), located on chromosome 13q14, is involved in cell proliferation and apoptosis regulation; it may interfere with either oncogenic or tumour suppressor pathways, and is implicated in leukaemogenesis. These data prompted us to search for and validate novel targets of miR‐16. Results. In the present study, by using a combined bioinformatics and molecular approach, we identified two novel putative targets of miR‐16, caprin‐1 (cytoplasmic activation/proliferation‐associated protein‐1) and HMGA1 (high‐mobility group A1), and we also studied cyclin E which had been previously recognized as an miR‐16 target by bioinformatics database. Using luciferase activity assays, we demonstrated that miR‐16 interacts with the 3′ UTR of the three target mRNAs. We showed that miR‐16, in MCF‐7 and HeLa cell lines, down‐regulates the expression of caprin‐1, HMGA1a, HMGA1b and cyclin E at the protein level, and of cyclin E, HMGA1a and HMGA1b at the mRNA levels. Conclusions. Taken together, our data demonstrated that miR‐16 can negatively regulate two new targets, HMGA1 and caprin‐1, which are involved in cell proliferation. In addition, we also showed that the inhibition of cyclin E expression was due, at least in part, to a decrease in its mRNA stability.