Development and validation of a novel lysosome-related LncRNA signature for predicting prognosis and the immune landscape features in colon cancer.

Lysosomes are essential components for managing tumor microenvironment and regulating tumor growth. Moreover, recent studies have also demonstrated that long non-coding RNAs could be used as a clinical biomarker for diagnosis and treatment of colorectal cancer. However, the influence of lysosome-related lncRNA (LRLs) on the progression of colon cancer is still unclear. This study aimed to identify a prognostic LRL signature in colon cancer and elucidated potential biological function. Herein, 10 differential expressed lysosome-related genes were obtained by the TCGA database and ultimately 4 prognostic LRLs for conducting a risk model were identified by the co-expression, univariate cox, least absolute shrinkage and selection operator analyses. Kaplan-Meier analysis, principal-component analysis, functional enrichment annotation, and nomogram were used to verify the risk model. Besides, the association between the prognostic model and immune infiltration, chemotherapeutic drugs sensitivity were also discussed in this study. This risk model based on the LRLs may be promising for potential clinical prognosis and immunotherapeutic responses related indicator in colon cancer patients.

Synthesis and evaluation of HIF-1α inhibitory activities of novel panaxadiol derivatives.

Hypoxia-inducible factor 1α (HIF-1α) is a known regulator of tumor cell proliferation, migration, and angiogenesis. The presence of a high concentration of HIF-1α is positively correlated with the severity of cancer. Therefore, the inhibition of this pathway represents an important therapeutic target for the treatment of various types of cancer. Here, we designed and synthesized 30 panaxadiol (PD) derivatives and evaluated their inhibitory activities against HIF-1α transcription. Of these, compound 3l exhibited the most promising inhibitory activity (IC50 = 3.7 µM) and showed significantly decreased cytotoxicity compared with PD. Compound 9e exhibited the strongest cytotoxic effect and may be considered for further preclinical development.

Noncoding RNAs in gastric cancer: implications for drug resistance.

Gastric cancer is the fourth most common malignancy and the third leading cause of cancer-related deaths worldwide. Advanced gastric cancer patients can notably benefit from chemotherapy including adriamycin, platinum drugs, 5-fluorouracil, vincristine, and paclitaxel as well as targeted therapy drugs. Nevertheless, primary drug resistance or acquisition drug resistance eventually lead to treatment failure and poor outcomes of the gastric cancer patients. The detailed mechanisms involved in gastric cancer drug resistance have been revealed. Interestingly, different noncoding RNAs (ncRNAs), such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), are critically involved in gastric cancer development. Multiple lines of evidences demonstrated that ncRNAs play a vital role in gastric cancer resistance to chemotherapy reagents and targeted therapy drugs. In this review, we systematically summarized the emerging role and detailed molecular mechanisms of ncRNAs impact drug resistance of gastric cancer. Additionally, we propose the potential clinical implications of ncRNAs as novel therapeutic targets and prognostic biomarkers for gastric cancer.

Correction: Tumor-associated macrophages promote tumor metastasis via the TGF-ß/SOX9 axis in non-small cell lung cancer.

[This corrects the article DOI: 10.18632/oncotarget.21068.].

SOX6 suppresses the development of lung adenocarcinoma by regulating expression of p53, p21CIPI , cyclin D1 and ß-catenin.

The Sry-related high-mobility group box6 (SOX6) has been implicated in the development of cancer, but its role in lung cancer is incompletely understood. Here, we report that SOX6 expression is frequently down-regulated in lung adenocarcinoma tissues. Moreover, SOX6 can inhibit the proliferation and invasion of lung adenocarcinoma cells, which may occur through cell cycle arrest at G1/S due to up-regulation of p53 and p21CIPI and down-regulation of cyclin D1 and ß-catenin. Univariate and multivariate analyses revealed that the expression of SOX6 is significantly associated with patient disease-related survival and is an independent prognostic factor for lung adenocarcinoma. These data suggest that SOX6 may act as a suppressor of lung adenocarcinoma.

The emerging role of microRNAs and long noncoding RNAs in drug resistance of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide and the second most lethal human cancer. A portion of patients with advanced HCC can significantly benefit from treatments with sorafenib, adriamycin, 5-fluorouracil and platinum drugs. However, most HCC patients eventually develop drug resistance, resulting in a poor prognosis. The mechanisms involved in HCC drug resistance are complex and inconclusive. Human transcripts without protein-coding potential are known as noncoding RNAs (ncRNAs), including microRNAs (miRNAs), small nucleolar RNAs (snoRNAs), long noncoding RNAs (lncRNAs) and circular RNA (circRNA). Accumulated evidences demonstrate that several deregulated miRNAs and lncRNAs are important regulators in the development of HCC drug resistance which elucidates their potential clinical implications. In this review, we summarized the detailed mechanisms by which miRNAs and lncRNAs affect HCC drug resistance. Multiple tumor-specific miRNAs and lncRNAs may serve as novel therapeutic targets and prognostic biomarkers for HCC.

The emerging role of noncoding RNAs in colorectal cancer chemoresistance.

BACKGROUND: Colorectal cancer (CRC) is the third most prevalent cancer in the world and one of the most lethal human malignancies. Chemotherapy with 5-fluorouracil, platinum, hydroxycamptothecin, vincristine, methotrexate, irinotecan, paclitaxel and/or cetuximab has significantly improved the survival of CRC patients. However, most CRC patients eventually develop chemoresistance, resulting in a poor prognosis. The mechanisms involved in CRC chemoresistance are complex and, as yet, inconclusive. Noncoding RNAs (ncRNAs), such as small nucleolar RNAs (snoRNAs), microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), represent transcripts without protein-coding potential. Accumulating evidence indicates that multiple deregulated ncRNAs, including miRNAs and lncRNAs, play pivotal roles in the development of chemoresistance in CRC. This notion has potential clinical implications. CONCLUSIONS: In this review, we highlight the emerging roles and the regulatory mechanisms by which miRNAs and lncRNAs affect CRC chemoresistance. Tumor-specific miRNAs and lncRNAs may serve as novel therapeutic targets and prognostic biomarkers for CRC.

Acylation of 25-hydroxyprotopanaxatriol with aromatic acids increases cytotoxicity.

20(R)-25-hydroxyprotopanaxadiol (25-OH-PPD) is a natural compound showing a variety of anti-tumor effects. In an attempt to search for a new anti-cancer compound with higher antitumor activities, we designed and synthesized a series of 25-OH-PPD derivatives. Cytotoxicity assay of these derivatives towards MCF-7, A549, U87, HO-8901, Hela cancer cell lines and normal IOSE144 cell lines were tested by MTT assay. Results showed that compared with compound 25-OH-PPD, Compounds 4, 5, 6, 10, 11 showed strong anticancer activity, and all compounds showed low toxicity or no toxicity for normal cells. In particular, compound 6 exhibited the best anti-tumor activity in all cancer cell lines (MCF-7, A549, U87, HO-8901, and Hela) with IC50 values of 5.04 µM, 1.36 µM, 3.24 µM, 3.47 µM, 4.57 µM, respectively. Among the five cell lines, all the compounds showed strong inhibition on A549 cells. Further studies showed that Compound 6 significantly inhibited the proliferation of A549 cells by inducing apoptosis. Our results indicate that Compound 6 is a potential anticancer inhibitor and provides a theoretical basis for further research.

lncRNA NEAT1 competes against let-7a to contribute to non-small cell lung cancer proliferation and metastasis.

Non-small cell lung cancer (NSCLC) accounts for >80% of diagnosed cases of lung cancer worldwide. Although multiple genes are altered in NSCLC, the precise mechanism of NSCLC requires further investigation. Nuclear paraspeckle assembly transcript (NEAT)1 is one of the long non-coding RNAs implicated in multiple types of cancer regulation. However, the role of NEAT1 in NSCLC is poorly understood. In this study, we investigated the function of NEAT1 in NSCLC and its related molecular mechanism. We demonstrated via real-time polymerase chain reaction that NEAT1 was significantly increased in NSCLC tissues and cell lines, suggesting a potential role of NEAT1 in NSCLC. CCK-8 assay and colony-formation assays showed that silencing of NEAT1 by siRNA pool inhibited NSCLC cell proliferation. An increased population of apoptotic cells was detected upon NEAT1 depletion by acridine orange/ethidium bromide staining compared to control cells. A549 cells depleted of NEAT1 exhibited reduced invasion and migration, characterized by wound healing assay and Transwell assay. To uncover the molecular mechanism of NEAT1 in lung cancer, we identified that NEAT1 could be a competing endogenous RNA against let-7a, and insulin-like growth factor (IGF)-2 could be a direct target of let-7a. These were characterized by reciprocal expression between NEAT1/IGF-2 and let-7a. Luciferase reporter assay validated direct binding of NEAT1/let-7a and let-7a/IGF-2. Exogenous IGF-2 expression reversed NEAT1-knockdown-induced growth inhibition assessed by CCK-8 assay and colony-formation assay. In conclusion, NEAT1 regulates lung cancer cell progression by competing endogenous RNA network of NEAT1/let-7a/IGF2. Our findings provide a novel insight into the biological function of NEAT1 in lung cancer and NEAT1 could be a potential therapeutic target for lung cancer.

Circulating tumor DNA measurement provides reliable mutation detection in mice with human lung cancer xenografts.

Genotype-directed targeted therapy has become one of the standard treatment options for non-small cell lung cancer (NSCLC). There have been numerous limitations associated with mutation analysis of tissue samples. Consequently, mutational profile analysis of circulating cell-free DNA (cfDNA) by highly sensitive droplet digital PCR (ddPCR) assay has been developed. Possibly due to differences in cfDNA concentrations, previous studies have shown numerous discrepancies in mutation detection consistency between tissue and cfDNA. In order to rigorously analyze the amount of cfDNA needed, we constructed 72 athymic nude mice xenografted with NCI-H1975 (harboring a EGFR T790M mutation) or NCI-H460 (harboring a KRAS Q61H mutation) human NSCLC. We thoroughly investigated the relationship between plasma cfDNA using Q-PCR targeting human long interspersed nuclear element-1 (LINE-1) retrotransposon and the mouse ACTB gene, and the accuracy of mutation detection by ddPCR at different times post-graft. Our results show that the concentration and fragmentation of human (tumor) derived cfDNA (hctDNA) were positively correlated with tumor weight, but not with mouse-derived cfDNA (mcfDNA). Quantification of cfDNA by Q-PCR depends on the amplified target length. Mutation copies in plasma of per milliliter were positively linked to tumor weight, hctDNA level and hctDNA/mcfDNA ratio, respectively. Furthermore, tumor weight, hctDNA level and ratio of hctDNA/mcfDNA were significantly higher in cfDNA mutation-positive mice than in negative mice. Also, our data indicate that when plasma hctDNA level and hctDNA/mcfDNA ratio reach a certain level in xenografted mice, plasma cfDNA mutation can be detected. In summary, the present study suggests that determination of ctDNA levels may be essential for reliable mutation detection by analysis of cfDNA.

Low-molecular-weight polysaccharides from Agaricus blazei Murrill modulate the Th1 response in cancer immunity.

To assess the effect of low-molecular-weight polysaccharides from Agaricus blazei Murrill (ABP-AW1) as an immunoadjuvant therapy for type 1 T-helper (Th1) responses in tumorigenesis, C57BL/6 mice were inoculated subcutaneously with ovalbumin (E.G7-OVA). After 3, 10 and 17 days, the mice were immunized with PBS, OVA alone, or OVA and ABP-AW1, at low (50 µg), intermediate (100 µg) or high (200 µg) doses. Tumor growth was examined and compared among the groups, as were the following parameters: Splenocyte viability/proliferation, peripheral blood CD4+/CD8+ T cell ratio, serum OVA-specific IgG1 and IgG2b, secretion of interleukin (IL)-2 and interferon (IFN)-γ, and IFN-γ production on a single cell level from cultured splenocytes. Tumor growth in mice treated with OVA and ABP-AW1 (100 or 200 µg) was significantly slower, compared with in the other groups at the same time-points. OVA with 100 or 200 µg ABP-AW1 was associated with a higher number of total splenocytes, a higher ratio of peripheral blood CD4+/CD8+ T-lymphocytes, higher serum levels of OVA-specific Th1-type antibody IgG2b and greater secretion of the Th1 cytokines IL-1 and IFN-γ from splenocytes. ABP-AW1 is a promising immunoadjuvant therapy candidate, due to its ability to boost the Th1 immune response when co-administered with a cancer vaccine intended to inhibit cancer progression.

Tumor-associated macrophages promote tumor metastasis via the TGF-ß/SOX9 axis in non-small cell lung cancer.

Tumor-associated macrophages (TAMs), most of which display the immunosuppressive M2 phenotype, affect the tumor microenvironment and promote progression and metastasis in lung carcinoma. In this study, we analyzed clinical non-small cell lung cancer (NSCLC) samples and found that high densities of TAMs were associated with a poor prognosis in NSCLC patients. Moreover, the number of TAMs present correlated positively with expression of sex determining region Y (SRY)-related high mobility group box 9 (SOX9) in NSCLC tissues. TAMs secreted TGF-ß, which increased SOX9 expression and promoted epithelial-to-mesenchymal transition (EMT) in lung cancer cells, thereby promoting tumor proliferation, migration, and invasion. SOX9 knockdown inhibited EMT, indicating that TGF-ß-mediated EMT is SOX9-dependent. TGF-ß induced SOX9 expression by upregulating the C-jun/SMAD3 pathway. These results indicate that TGF-ß secreted by TAMs promotes SOX9 expression via the C-jun/SMAD3 pathway, thereby promoting tumor metastasis. The TGF-ß/SOX9 axis may therefore be an effective target for the treatment of lung cancer.

Interleukin-22 promotes lung cancer cell proliferation and migration via the IL-22R1/STAT3 and IL-22R1/AKT signaling pathways.

Lung cancer continues to be an enormous burden on current health care systems throughout the world, with more than a million deaths every year. Previous studies have shown that interleukin-22 (IL-22) promotes survival and resistance to chemotherapy in human lung cancer cells. However, the association of IL-22 expression with recurrence of lung cancer is still unclear. In this study, we found that expression of IL-22 was upregulated in tumor tissues and serum from patients with recurrent non-small cell lung cancer (NSCLC) as compared to primary NSCLC samples. Treatment with IL-22 promoted cell proliferation and enhanced migration and invasion in A549 and H125 cell lines. Furthermore, we revealed that phosphorylation of STAT3 and AKT was highly induced by treatment with IL-22 via IL-22R1. IL-22R1 was also consistently overexpressed in recurrent NSCLC tissues. Finally, we found that siRNA-mediated depletion of IL-22R1 completely abrogated the effects of IL-22 treatment on cell proliferation and migration activity in NSCLC cell lines. Our findings indicate that IL-22 and IL-22R1 may be novel therapeutic targets for treatment of advanced NSCLC.

Twist may be associated with invasion and metastasis of hypoxic NSCLC cells.

Hypoxia promotes tumor invasion and metastasis via multiple mechanisms, including epithelial-mesenchymal transition (EMT). Twist, an EMT regulator, has been disclosed to associate with invasion and metastasis as well as poor prognosis of many malignancies. However, it remains undefined whether Twist is involved in invasion and metastasis of hypoxic non-small cell lung cancer (NSCLC). In this study, protein levels of Twist, hypoxia-inducible factor-1α (HIF-1α), and EMT markers (E-cadherin and vimentin) were examined by immunohistochemistry in 76 lung cancer tissues from NSCLC patients. Expression of Twist and its correlation with HIF-1α, E-cadherin, and vimentin were analyzed. Small interfering RNA (siRNA) against Twist was used to knockdown Twist expression in hypoxic NSCLC cells, A549 and NCI-H460. Cellular invasion and protein levels of Twist, E-cadherin, and vimentin were evaluated by matrigel invasion assay and Western blot, respectively. Our results showed that in clinical samples, there was a significant association between Twist expression and differentiation degree, lymph node metastasis, and TNM stage. Correlation analysis demonstrated that expression of Twist was negatively correlated with E-cadherin expression, but positively associated with HIF-1α and vimentin expression. In cultured NSCLC cells, Twist messenger RNA (mRNA) and protein levels were upregulated under hypoxia, while knockdown of Twist suppressed potentiated invasion and expression of mesenchymal marker vimentin induced by hypoxia. Protein level of increased epithelial marker E-cadherin was shown along with Twist downregulation. These findings suggest that Twist promoting hypoxic invasion and metastasis of NSCLC may be associated with altered expression of EMT markers. Inhibition of Twist may be of therapeutic significance.

Therapeutic effect of TMZ-POH on human nasopharyngeal carcinoma depends on reactive oxygen species accumulation.

Nasopharyngeal carcinoma (NPC) is a common head and neck malignancy without efficient chemotherapeutic agents for it. In our current study, we demonstrated the cytotoxicity effects of a newly patented compound temozolomide-perillyl alcohol (TMZ-POH) on NPC in vitro and in vivo, and the possible mechanisms involved. Human NPC cell lines CNE1, CNE2, HNE2, and SUME-α were treated with control (DMSO), TMZ, POH, TMZ plus POH, and TMZ-POH. Our data indicated that TMZ-POH could inhibit NPC cell proliferation, cause G2/M arrest and DNA damage. TMZ-POH triggered apoptosis in NPC cells via significant activation of caspase-3 and poly(ADP-ribose) polymerase (PARP). Importantly, TMZ-POH-induced cell death was found to be associated with (i) the loss of inner mitochondrial membrane potential (ΔΨm) and release of mitochondrial Cytochrome c, (ii) the increase in ROS generation, and (iii) the activation of stress-activated protein kinases (SAPK)/c-Jun N-terminal kinases (JNK) signaling pathway. The generation of ROS in response to TMZ-POH seems to play a crucial role in the cell death process since the blockage of ROS production using the antioxidant N-acetyl-L-cysteine or catalase reversed the TMZ-POH-induced JNK activation, DNA damage, and cancer cell apoptosis. These results provide the rationale for further research and preclinical investigation of the antitumor effect of TMZ-POH against human NPC.

miR-34c-3p functions as a tumour suppressor by inhibiting eIF4E expression in non-small cell lung cancer.

OBJECTIVES: MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate gene expression and mediate diverse physiological processes. In this study, we investigated functions of miRNA miR-34c-3p in non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: miR-34c-3p expression was evaluated by qPCR. Cell viability was examined by MTT and proliferation by cell cycle analysis. Cell migration and invasion were tested using Transwells with/without Matrigel coating. Western blot analysis was performed for eIF4E, c-Myc, Cyclin D1, survivin and Mcl-1 protein expression. RESULTS: miR-34c-3p expression was significantly reduced in tissues and serum samples from NSCLC patients and in NSCLC cell lines A549, H460, H23, H157 and H1299. Overexpression of miR-34c-3p in A549 and H157 cells reduced cell proliferation, migration and invasion, whereas transfection with miR-34c-3p inhibitor (miR-34c-3p-in) produced opposite effects. Target analysis using algorithms miRanda, TargetScan and DIANA identified eIF4E as a potential target of miR-34c-3p. Luciferase assay using the eIF4E 3'-UTR reporter carrying a putative miR-34c-3p target sequence revealed eIF4E to be a specific target of miR-34c-3p. Overexpression of miR-34c-3p in NSCLS cell lines led to significant reduction in mRNA and protein levels of eIF4E, whereas inhibition of miR-34c-3p resulted in significant increase in eIf4e protein levels, confirming eIF4E to be a direct target of miR-34c-3p in NSCLS. Overexpression of eIF4E in A549 cells promoted cell proliferation, migration and invasion, which were partially reversed by miR-34c-3p. CONCLUSION: miR-34c-3p directly targeted eIF4E and reduced miR-34c-3p expression in NSCLC, promoting cell cycle progression, proliferation, migration and invasion.

Knockdown of Med19 suppresses proliferation and enhances chemo-sensitivity to cisplatin in non-small cell lung cancer cells.

Mediator 19 (Med19) is a component of the mediator complex which is a coactivator for DNA-binding factors that activate transcription via RNA polymerase II. Accumulating evidence has shown that Med19 plays important roles in cancer cell proliferation and tumorigenesis. The involvement of Med19 in sensitivity to the chemotherapeutic agent cisplatin was here investigated. We employed RNA interference to reduce Med19 expression in human non-small cell lung cancer (NSCLC) cell lines and analyzed their phenotypic changes. The results showed that after Med19 siRNA transfection, expression of Med19 mRNA and protein was dramatically reduced (p<0.05). Meanwhile, impaired growth potential, arrested cell cycle at G0/G1 phase and enhanced sensitivity to cisplatin were exhibited. Apoptosis and caspase-3 activity were increased when cells were exposed to Med19 siRNA and/or cisplatin. The present findings suggest that Med19 facilitates tumorigenic properties of NSCLC cells and knockdown of Med19 may be a rational therapeutic tool for lung cancer cisplatin sensitization.

Lysyl oxidase may play a critical role in hypoxia-induced NSCLC cells invasion and migration.

Lysyl oxidase (LOX), a copper-dependent amine oxidase known to function both intracellularly and extracellularly, is implicated in promoting tumor progression and hypoxic metastasis in certain malignancies. Nonsmall cell lung cancer (NSCLC) is a highly aggressive cancer with poor prognosis worldwide. However, the role and molecular mechanism by which LOX involving in hypoxic NSCLC invasion and migration are poorly understood. This study explores the effect of LOX on invasion and migration of NSCLC cells under hypoxic conditions. Small interfering RNA (siRNA) targeting LOX was used to silence LOX expression of hypoxic NSCLC cells, SPCA1 and A549. Cellular invasive and migratory potentials were determined by matrigel invasion and migration assays. Expression of LOX, Src, Src activation (Tyr418 phosphorylation of Src), and Snail were evaluated by real-time PCR and western blot, respectively. The results showed that LOX mRNA and protein expression were upregulated under hypoxic conditions in NSCLC cells. Knockdown of LOX led to inhibition of hypoxia-induced invasion and migration. Phosphorylated Src (Tyr418) and Snail proteins were decreased along with LOX downregulation. Our data provide molecular evidences that LOX is mechanistically linked to increased invasion and migration of hypoxic NSCLC cells, and may serve as an antimetastasis target of human NSCLC.

Effect of chronic intermittent hypoxia on biological behavior and hypoxia-associated gene expression in lung cancer cells.

Hypoxia plays an important role in the development of solid tumors and is associated with their therapeutic resistance. There exist three major forms of hypoxia: acute, chronic, and intermittent hypoxia. Previous studies have shown that cancer cells could behave in the form of adaptation to hypoxia in tumor growth, which could result in their biological changes and determine their responses to the therapies. To investigate the tumor cells' adaptation to hypoxia, we recreated two models using two lung cancer cell lines in the presence of intermittent hypoxia, which is characterized by changes in oxygen pressure within the disorganized vascular network. We investigated biological behaviors such as cell cycle, proliferation, radiation sensitivity, apoptosis and migration, hypoxia signal pathway in the lung cancer cells treated with chronic intermittent hypoxia, as well as the role of hypoxia inducible factor 1 there, hypoxia-inducible genes analyzed by real-time RT-PCR chip in H446 cells treated with the model. The results indicated the changes of some hypoxia target gene expressions of those induced by hypoxia, some of which were confirmed by real-time RT-PCR. The cells mediated by irradiation induced resistance to radiation and apoptosis and increased metastasis in lung cancer cells. It was found that such changes were related to hypoxia inducible factor 1, alpha subunit (HIF-1α).

MicroRNA-21 regulates breast cancer invasion partly by targeting tissue inhibitor of metalloproteinase 3 expression.

BACKGROUND: MicroRNAs are non-coding RNA molecules that posttranscriptionally regulate expression of target genes and have been implicated in the progress of cancer proliferation, differentiation and apoptosis. The aim of this study was to determine whether microRNA-21 (miR-21), a specific microRNA implicated in multiple aspects of carcinogenesis, impacts breast cancer invasion by regulating the tissue inhibitor of metalloproteinase 3 (TIMP3) gene. METHODS: miR-21 expression was investigated in 32 matched breast cancer and normal breast tissues, and in four human breast cancer cell lines, by Taqman quantitative real-time PCR. Cell invasive ability was determined by matrigel invasion assay in vitro, in cells transfected with miR-21 or anti-miR-21 oligonucleotides. In addition, the regulation of tissue inhibitor of metalloproteinase 3 (TIMP3) by miR-21 was evaluated by western blotting and luciferase assays. RESULTS: Of the 32 paired samples analyzed, 25 breast cancer tissues displayed overexpression of miR-21 in comparison with matched normal breast epithelium. Additionally, incidence of lymph node metastasis closely correlated with miR-21 expression, suggesting a role for miR-21 in metastasis. Similarly, each of the four breast cancer cell lines analyzed overexpressed miR-21, to varied levels. Further, cells transfected with miR-21 showed significantly increased matrigel invasion compared with control cells, whereas transfection with anti-miR-21 significantly decreased cell invasion. Evaluation of TIMP3 protein levels, a peptidase involved in extarcellular matrix degredation, inversely correlated with miR-21 expression. CONCLUSION: As knockdown of miR-21 increased TIMP3 protein expression and luciferase reporter activity, our data suggests that miR-21 could promote invasion in breast cancer cells via its regulation of TIMP3.