Aim: to investigate the events involved in the progression of myxoid liposarcoma (MLS).
Gene expression profiling and immunohistochemical/biochemical analyses were applied to specimens representative of the opposite ends of the MLS spectrum: pure myxoid (ML) and pure round cell (RC) liposarcomas.
The analyses revealed the involvement of both coding and non coding RNAs (SNORDs located in DLK1-DIO3 region) and support a model of stepwise progression mainly driven by epigenetic changes involving tumour vascular supply and tumoral cellular component. In this model, a switch in the vascular landscape from a normal to a pro-angiogenic signature and the silencing of DLK1-DIO3 region mark the progression from ML to RC in concert with the acquisition by the latter of the over-expression of YY1/C-MYC/HDAC2, together with over-expression of genes involved in cell proliferation and stemness: MKNK2, MSX1 and TRIM71.
Taken together, these findings strongly suggest that to progress from ML to RC liposarcoma the cells have to overcome the epigenetic silencing restriction point in order to reset their new stem-like differentiation signature. Our findings provide a first attempt at identifying the missing links between ML and RC liposarcomas, that may also have broader applications in other clinico-pathological settings characterised by a spectrum of progression.
myxoid liposarcoma; progression to round cell; gene expression array; epigenetic deregulation; stemness related genes; fast cell cycle related genes
Microarray technology was used to profile miRNA expression in primary tumor and stromal tissue from paraffin embedded material of 51 patients with colorectal cancer. 26 miRNAs resulted differentially expressed with at least 2-fold change in tumor tissue with respect to stroma (16 more expressed in the tumor and 10 more expressed in the stroma). 10/26 were confirmed as differentially expressed at qRTPCR: miR-200c-3p, miR-141-3p, miR-200b-3p, miR-200a-3p, miR-1246, miR-92a-3p, miR-194-5p, miR-192-5p, miR-3651-5p, and miR-574-3p. No significant association was found between miRNA expressions and stage at diagnosis, site of primary tumor, first site of metastasis, progression-free, or overall survival.
The production rate of gene expression data is nothing less than astounding. However, with the benefit of hindsight we can assert that, since we completely ignored the non-coding part of the transcriptome, we spent the last decade to study cell mechanisms having few data in our hands. In this scenario, microRNAs, which are key post-trascriptional regulators, deserve special attention. Given the state of knowledge about their biogenesis, mechanisms of action and the numerous experimentally validated target genes, miRNAs are also gradually appearing in the formal pathway representations such as KEGG and Reactome maps. However, the number of miRNAs annotated in pathway maps are very few and pathway analyses exploiting this new regulatory layer are still lacking. To fill these gaps, we present ‘micrographite’ a new pipeline to perform topological pathway analysis integrating gene and miRNA expression profiles. Here, micrographite is used to study and dissect the epithelial ovarian cancer gene and miRNA transcriptome defining and validating a new regulatory circuit related to ovarian cancer histotype specificity.
The prevailing paradigm states that cancer cells acquire multiple genetic mutations in oncogenes or tumor suppressor genes whose respective activation/up-regulation or loss of function serve to impart aberrant properties, such as hyperproliferation or inhibition of cell death. However, a tumor is now considered as an organ-like structure, a complex system composed of multiple cell types (e.g., tumor cells, inflammatory cells, endothelial cells, fibroblasts, etc.) all embedded in an inflammatory stroma. All these components influence each other in a complex and dynamic cross-talk, leading to tumor cell survival and progression. As the microenvironment has such a crucial role in tumor pathophysiology, it represents an attractive target for cancer therapy. In this review, we describe the mechanism of action of trabectedin and plitidepsin as an example of how these specific drugs of marine origin elicit their antitumor activity not only by targeting tumor cells but also the tumor microenvironment.
trabectedin; plitidepsin; tumor-associated macrophages; tumor microenvironment
Quadruplexes DNA are present in telomeric DNA as well as in several cancer-related gene promoters and hence affect gene expression and subsequent biological processes. The conformations of G4 provide selective recognition sites for small molecules and thus these structures have become important drug-design targets for cancer treatment.
The DNA G-quadruplex binding pentacyclic acridinium salt RHPS4 (1) has many pharmacological attributes of an ideal telomere-targeting agent but has undesirable off-target liabilities. Notably a cardiovascular effect was evident in a guinea pig model, manifested by a marked and sustained increase in QTcB interval. In accordance with this, significant interaction with the human recombinant β2 adrenergic receptor, and M1, M2 and M3 muscarinic receptors was observed, together with a high inhibition of the hERG tail current tested in a patch clamp assay.
Two related pentacyclic structures, the acetylamines (2) and (3), both show a modest interaction with β2 adrenergic receptor, and do not significatively inhibit the hERG tail current while demonstrating potent telomere on-target properties comparing closely with 1. Of the two isomers, the 2-acetyl-aminopentacycle (2) more closely mimics the overall biological profile of 1 and this information will be used to guide further synthetic efforts to identify novel variants of this chemotype, to maximize on-target and minimize off-target activities.
Consequently, the improvement of toxicological profile of these compounds could therefore lead to the obtainment of suitable molecules for clinical development offering new pharmacological strategies in cancer treatment.
Telomere targeting agents; G-quadruplex; Anti-cancer therapy
A sensitive, simple and reproducible protocol for nanoparticle-assisted laser desorption/ionization mass spectrometry imaging technique is described. The use of commercially available TiO2 nanoparticles abolishes heterogeneous crystallization, matrix background interferences and enhances signal detection, especially in the low mass range. Molecular image normalization was based on internal standard deposition on tissues, allowing direct comparison of drug penetration and distribution between different organs and tissues. The method was applied to analyze the distribution of the anticancer drug paclitaxel, inside normal and neoplastic mouse tissue sections. Spatial resolution was good, with a linear response between different in vivo treatments and molecular imaging intensity using therapeutic drug doses. This technique distinguishes the different intensity of paclitaxel distribution in control organs of mice, such as liver and kidney, in relation to the dose. Animals treated with 30 mg/kg of paclitaxel had half of the concentration of those treated with 60 mg/kg. We investigated the spatial distribution of paclitaxel in human melanoma mouse xenografts, following different dosage schedules and found a more homogeneous drug distribution in tumors of mice given repeated doses (5×8 mg/kg) plus a 60 mg/kg dose than in those assigned only a single 60 mg/kg dose. The protocol can be readily applied to investigate anticancer drug distribution in neoplastic lesions and to develop strategies to optimize and enhance drug penetration through different tumor tissues.
Tumor-associated macrophages (TAMs) and other myeloid cells that infiltrate neoplastic lesions promote tumor progression and are associated with poor patient prognosis. We have recently demonstrated that trabectedin, a licensed and commercially available anticancer agent, is selectively cytotoxic for TAMs and their circulating precursors (monocytes). The macrophage-depleting effect of trabectedin is a key component of its antitumor activity.
tumor-associated macrophages; chemotherapy; micro-environment; angiogenesis; marine drug
Pyriplatin (cis-diammine(pyridine)chloroplatinum(II) or cDPCP), a platinum-based antitumor drug candidate, is a cationic compound with anticancer properties in mice and is a substrate for the organic cation transporters, hOCT1 and hOCT2, which facilitate oxaliplatin uptake. Unlike cisplatin and oxaliplatin, which form DNA cross-links, pyriplatin binds DNA in a monofunctional manner. The antiproliferative effects of pyriplatin, as well as combintions of pyriplatin with known anticancer drugs (paclitaxel, gemcitabine, SN38, cisplatin or 5-fluorouracil), were evaluated in a panel of epithelial cancer cell lines, with direct comparison to cisplatin and oxaliplatin. The effects of pyriplatin on gene expression and platinum-DNA adduct formation were also investigated. Pyriplatin exhibited cytotoxic effects against human cell lines after 24 h (IC50: 171 – 443 μM), with maximum cytotoxicity in HOP-62 non-small cell lung cancer cells after 72 h (IC50: 24 μM). Pyriplatin caused a G2/M block of cell cycle similar to that induced by cisplatin and oxaliplatin. Apoptotic cell death was supported by Annexin-V analysis and detection of phosphorylated H2AX and Chk2. Treatment with pyriplatin caused an increase in CDKN1/p21 and decrease in ERCC1 mRNA expression. On a platinum-per-nucleotide basis, pyriplatin adducts resulted in less cytotoxicity than cisplatin- and oxaliplatin-DNA adducts. The mRNA levels of several genes implicated in drug transport and repair of DNA damage, including MSH2 and GSTP1, correlate with pyriplatin cellular activity in our panel of cell lines. Synergy was observed in combinations of pyriplatin with paclitaxel. Because it has a different spectrum of activitythan that of cisplatin or oxaliplatin, pyriplatin may be regarded as a lead compound for the development of other drug candidates with cytotoxicity profiles that differ from those of the drugs currently in use.
cisplatin; pyriplatin; cytotoxicity; apoptosis; cell cycle; anticancer activity; DNA adducts
Trabectedin, a new antitumor compound originally derived from a marine tunicate, is clinically effective in soft tissue sarcoma. The drug has shown a high selectivity for myxoid liposarcoma, characterized by the translocation t(12;16)(q13; p11) leading to the expression of FUS-CHOP fusion gene. Trabectedin appears to act interfering with mechanisms of transcription regulation. In particular, the transactivating activity of FUS-CHOP was found to be impaired by trabectedin treatment. Even after prolonged response resistance occurs and thus it is important to elucidate the mechanisms of resistance to trabectedin. To this end we developed and characterized a myxoid liposarcoma cell line resistant to trabectedin (402-91/ET), obtained by exposing the parental 402-91 cell line to stepwise increases in drug concentration. The aim of this study was to compare mRNAs, miRNAs and proteins profiles of 402-91 and 402-91/ET cells through a systems biology approach. We identified 3,083 genes, 47 miRNAs and 336 proteins differentially expressed between 402-91 and 402-91/ET cell lines. Interestingly three miRNAs among those differentially expressed, miR-130a, miR-21 and miR-7, harbored CHOP binding sites in their promoter region. We used computational approaches to integrate the three regulatory layers and to generate a molecular map describing the altered circuits in sensitive and resistant cell lines. By combining transcriptomic and proteomic data, we reconstructed two different networks, i.e. apoptosis and cell cycle regulation, that could play a key role in modulating trabectedin resistance. This approach highlights the central role of genes such as CCDN1, RB1, E2F4, TNF, CDKN1C and ABL1 in both pre- and post-transcriptional regulatory network. The validation of these results in in vivo models might be clinically relevant to stratify myxoid liposarcoma patients with different sensitivity to trabectedin treatment.
This analysis determined the incidence of serious rhabdomyolysis events reported during trabectedin treatment since the first phase I clinical trial in April 1996 up to September 2010.
Search was done in the Yondelis® Pharmacovigilance and Clinical Trials databases using a list of terms according to the Medical Dictionary for Regulatory Activities (MedDRA, v. 13.1), followed by a medical review of all cases retrieved. Total estimated sample was 10,841 patients: 2,789 from clinical trials; 3,926 from compassionate use programs; and 4,126 treated in the marketplace. Two groups were identified: (1) rhabdomyolysis and (2) clinically relevant creatine phosphokinase (CPK) increases without acute renal failure (ARF). Descriptive analysis included demographic, clinical/laboratory data, and contributing/confounding factors. Potential predictive factors were evaluated by multivariate stepwise logistic regression analysis. Possible changes of pharmacokinetics (PK) in patients with rhabdomyolysis were explored using a population PK model.
The global incidence of rhabdomyolysis was 0.7 %, and most cases occurred in Cycle 2 of treatment. The incidence of fatal cases was 0.3 %. None of the variables evaluated to detect potential risk factors of rhabdomyolysis were predictive. Additionally, CPK increases (without ARF) were detected in 0.4 % of patients as an incidental finding with good prognosis.
Rhabdomyolysis is an uncommon event during trabectedin treatment. Multivariate analyses did not show any potential factor that could be predictive or represent a significantly higher risk of developing rhabdomyolysis. Nevertheless, close patient monitoring and adherence to drug administration guidelines may help to limit the incidence of this event.
Trabectedin; Rhabdomyolysis; Creatine phosphokinase
RNA-Seq allows a theoretically unbiased analysis of both genome-wide transcription levels and mutation status of a tumor. Using this technique we sought to identify novel candidate therapeutic targets expressed in epithelial ovarian cancer (EOC).
Specifically, we sought candidate invasion/migration targets based on expression levels across all tumors, novelty of expression in EOC, and known function. RNA-Seq analysis revealed the high expression of CD151, a transmembrane protein, across all stages of EOC. Expression was confirmed at both the mRNA and protein levels using RT-PCR and immunohistochemical staining, respectively.
In both EOC tumors and normal ovarian surface epithelial cells we demonstrated CD151 to be localized to the membrane and cell-cell junctions in patient-derived and established EOC cell lines. We next evaluated its role in EOC dissemination using two ovarian cancer-derived cell lines with differential levels of CD151 expression. Targeted antibody-mediated and siRNA inhibition or loss of CD151 in SKOV3 and OVCAR5 cell lines effectively inhibited their migration and invasion.
Taken together, these findings provide the first proof-of-principle demonstration for a next generation sequencing approach to identifying candidate therapeutic targets and reveal CD151 to play a role in EOC dissemination.
CD151; Epithelial Ovarian Cancer; Invasion; Migration; Metastasis; RNA-Seq
We sought to identify candidate serum biomarkers for the detection and surveillance of EOC. Based on RNA-Seq transcriptome analysis of patient-derived tumors, highly expressed secreted proteins were identified using a bioinformatic approach.
RNA-Seq was used to quantify papillary serous ovarian cancer transcriptomes. Paired end sequencing of 22 flash frozen tumors was performed. Sequence alignments were processed with the program ELAND, expression levels with ERANGE and then bioinformatically screened for secreted protein signatures. Serum samples from women with benign and malignant pelvic masses and serial samples from women during chemotherapy regimens were measured for IGFBP-4 by ELISA. Student's t Test, ANOVA, and ROC curves were used for statistical analysis.
Insulin-like growth factor binding protein (IGFBP-4) was consistently present in the top 7.5% of all expressed genes in all tumor samples. We then screened serum samples to determine if increased tumor expression correlated with serum expression. In an initial discovery set of 21 samples, IGFBP-4 levels were found to be elevated in patients, including those with early stage disease and normal CA125 levels. In a larger and independent validation set (82 controls, 78 cases), IGFBP-4 levels were significantly increased (p < 5 × 10-5). IGFBP-4 levels were ~3× greater in women with malignant pelvic masses compared to women with benign masses. ROC sensitivity was 73% at 93% specificity (AUC 0.816). In women receiving chemotherapy, average IGFBP-4 levels were below the ROC-determined threshold and lower in NED patients compared to AWD patients.
This study, the first to our knowledge to use RNA-Seq for biomarker discovery, identified IGFBP-4 as overexpressed in ovarian cancer patients. Beyond this, these studies identified two additional intriguing findings. First, IGFBP-4 can be elevated in early stage disease without elevated CA125. Second, IGFBP-4 levels are significantly elevated with malignant versus benign disease. These findings provide the rationale for future validation studies.
IGFBP-4; epithelial ovarian cancer; serum biomarker; RNA-Seq; transcriptome
Mesenchymal and amoeboid movements are two important mechanisms adopted by cancer cells to invade the surrounding environment. Mesenchymal movement depends on extracellular matrix protease activity, amoeboid movement on the RhoA-dependent kinase ROCK. Cancer cells can switch from one mechanism to the other in response to different stimuli, limiting the efficacy of antimetastatic therapies.
Methodology and Principal Findings
We investigated the acquisition and molecular regulation of the invasion capacity of neoplastically transformed human fibroblasts, which were able to induce sarcomas and metastases when injected into immunocompromised mice. We found that neoplastic transformation was associated with a change in cell morphology (from fibroblastic to polygonal), a reorganization of the actin cytoskeleton, a decrease in the expression of several matrix metalloproteases and increases in cell motility and invasiveness. In a three-dimensional environment, sarcomagenic cells showed a spherical morphology with cortical actin rings, suggesting a switch from mesenchymal to amoeboid movement. Accordingly, cell invasion decreased after treatment with the ROCK inhibitor Y27632, but not with the matrix protease inhibitor Ro 28-2653. The increased invasiveness of tumorigenic cells was associated with reduced expression of Rnd3 (also known as RhoE), a cellular inhibitor of ROCK. Indeed, ectopic Rnd3 expression reduced their invasive ability in vitro and their metastatic potential in vivo.
These results indicate that, during neoplastic transformation, cells of mesenchymal origin can switch from a mesenchymal mode of movement to an amoeboid one. In addition, they point to Rnd3 as a possible regulator of mesenchymal tumor cell invasion and to ROCK as a potential therapeutic target for sarcomas.
This study was designed to determine the effects of vandetanib, a small-molecule receptor tyrosine kinase inhibitor of vascular endothelial growth factor and epidermal growth factor receptor, on paclitaxel (PTX) tumor distribution and antitumor activity in xenograft models of human ovarian carcinoma. Nude mice bearing A2780-1A9 xenografts received daily (5, 10, or 15 days) doses of vandetanib (50 mg/kg per os), combined with PTX (20 mg/kg intravenously). Morphologic and functional modifications associated with the tumor vasculature (CD31 and α-smooth muscle actin staining and Hoechst 33342 perfusion) and PTX concentrations in plasma and tumor tissues were analyzed. Activity was evaluated as inhibition of tumor growth subcutaneously and spreading into the peritoneal cavity. Vandetanib treatment produced no significant change in tumor vessel density, although a reduced number of large vessels, an increased percentage of mature vessels, and diminished tumor perfusion were evident. Pretreatment with vandetanib led to decreased tumor PTX levels within 1 hour of PTX injection, although 24 hours later, tumor PTX levels were comparable with controls. In efficacy studies, the combination of vandetanib plus PTX improved antitumor activity compared with vandetanib or PTX alone, with greater effects being obtained when PTX was administered before vandetanib. The combination of PTX plus vandetanib reduced tumor burden in the peritoneal cavity of mice and significantly increased their survival. Analysis of vascular changes and PTX tumor uptake in vandetanib-treated tumors may help to guide the scheduling of vandetanib plus PTX combinations and may have implications for the design of clinical trials with these drugs.
Functional telomeres are required to maintain the replicative ability of cancer cells and represent putative targets for G-quadruplex (G4) ligands. Here, we show that the pentacyclic acridinium salt RHPS4, one of the most effective and selective G4 ligands, triggers damages in cells traversing S phase by interfering with telomere replication. Indeed, we found that RHPS4 markedly reduced BrdU incorporation at telomeres and altered the dynamic association of the telomeric proteins TRF1, TRF2 and POT1, leading to chromosome aberrations such as telomere fusions and telomere doublets. Analysis of the molecular damage pathway revealed that RHPS4 induced an ATR-dependent ATM signaling that plays a functional role in the cellular response to RHPS4 treatment. We propose that RHPS4, by stabilizing G4 DNA at telomeres, impairs fork progression and/or telomere processing resulting in telomere dysfunction and activation of a replication stress response pathway. The detailed understanding of the molecular mode of action of this class of compounds makes them attractive tools to understand telomere biology and provides the basis for a rational use of G4 ligands for the therapy of cancer.
Functional telomeres are required for the replicability of cancer cells. The G-rich strand of telomeric DNA can fold into a 4-stranded structure known as the G-quadruplex (G4), whose stabilization alters telomere function limiting cancer cell growth. Therefore, the G4 ligand RHPS4 may possess antitumor activity. Here, we show that RHPS4 triggers a rapid and potent DNA damage response at telomeres in human transformed fibroblasts and melanoma cells, characterized by the formation of several telomeric foci containing phosphorylated DNA damage response factors γ-H2AX, RAD17, and 53BP1. This was dependent on DNA repair enzyme ATR, correlated with delocalization of the protective telomeric DNA–binding protein POT1, and was antagonized by overexpression of POT1 or TRF2. In mice, RHPS4 exerted its antitumor effect on xenografts of human tumor cells of different histotype by telomere injury and tumor cell apoptosis. Tumor inhibition was accompanied by a strong DNA damage response, and tumors overexpressing POT1 or TRF2 were resistant to RHPS4 treatment. These data provide evidence that RHPS4 is a telomere damage inducer and that telomere disruption selectively triggered in malignant cells results in a high therapeutic index in mice. They also define a functional link between telomere damage and antitumor activity and reveal the key role of telomere-protective factors TRF2 and POT1 in response to this anti-telomere strategy.
Posttranslational modifications of p53 induced by two widely used anticancer agents, cisplatinum (DDP) and taxol were investigated in two human cancer cell lines. Although both drugs were able to induce phosphorylation at serine 20 (Ser20), only DDP treatment induced p53 phosphorylation at serine 15 (Ser15). Moreover, both drug treatments were able to increase p53 levels and consequently the transcription of waf1 and mdm-2 genes, although DDP treatment resulted in a stronger inducer of both genes. Using two ataxia telangiectasia mutated (ATM) cell lines, the role of ATM in drug-induced p53 phosphorylations was investigated. No differences in drug-induced p53 phosphorylation could be observed, indicating that ATM is not the kinase involved in these phosphorylation events. In addition, inhibition of DNA-dependent protein kinase activity by wortmannin did not abolish p53 phosphorylation at Ser15 and Ser20, again indicating that DNA-PK is unlikely to be the kinase involved. After both taxol and DDP treatments, an activation of hCHK2 was found and this is likely to be responsible for phosphorylation at Ser20. In contrast, only DDP was able to activate ATR, which is the candidate kinase for phosphorylation of Ser15 by this drug. This data clearly suggests that differential mechanisms are involved in phosphorylation and activation of p53 depending on the drug type.
phosphorylation; cell cycle; checkpoints; anticancer agents; p53
The proapoptotic gene bax is one of the downstream effectors of p53. The p53 binding site in the bax promoter is less responsive to p53 than the one in the growth arrest mediating gene p21. We introduced the bax gene under the control of 13 copies of a strong p53 responsive element into two ovarian cancer cell lines. The clones expressing bax under the control of p53 obtained from the wild-type (wt) p53-expressing cell line A2780 were much more sensitive (500- to 1000-fold) to the anticancer agent taxol than the parent cell line, with a higher percentage of cells undergoing apoptosis after drug treatment that was clearly p53-dependent and bax-mediated. Xenografts established in nude mice from one selected clone (A2780/C3) were more responsive to taxol than the parental line and the apoptotic response of A2780/C3 tumors was also increased after treatment. Introduction of the same plasmid into the p53 null SKOV3 cell line did not alter the sensitivity to taxol or the induction of apoptosis. In conclusion, driving the p53 response (after taxol treatment) by activating the bax gene rather than the p21 gene results in induction of massive apoptosis, in vitro and in vivo, and greatly enhances sensitivity to the drug.
apoptosis; p53; anticancer agents; tumor xenografts; transcription
The transcriptional activity of the p53 tumor suppressor protein is crucial for the regulation of cell growth, apoptosis and tumor progression. The first identified p53 relative, p73, was reported to be monoallelically expressed in normal tissues. In some tumors, loss of heterozygosity was associated with overexpression of the silent allele. Human p73α was transfected into the wild-type p53-expressing human ovarian carcinoma cell line A2780. Unlike human osteosarcoma Saos-2 cells, A2780 cells could tolerate hyperexpression of p73α and clones overexpressing p73α could be isolated. No p53–p73 protein–protein interaction was found in these clones in co-immunoprecipitation experiments. Endogenous p53 transcriptional activity was markedly decreased both when p73 was integrated into the genome and in transient transfections using a reporter plasmid containing the p53 binding site linked to luciferase. Transient transfection of p73 with a mutation in the DNA-binding domain did not show these effects. The competition for p53 DNA binding by p73α was also evident in gel shift experiments. The results suggest that p73 can modulate p53 function by inhibiting its DNA binding and that overexpression of p73 in tumors might be a novel mechanism of inactivation of p53.
Ovarian cancer is a leading cause of cancer deaths among women. Effective targets to treat advanced epithelial ovarian cancer (EOC) and biomarkers to predict treatment response are still lacking because of the complexity of pathways involved in ovarian cancer progression. Here we show that miR-181a promotes TGF-β-mediated epithelial-to-mesenchymal transition via repression of its functional target, Smad7. miR-181a and phosphorylated Smad2 are enriched in recurrent compared with matched-primary ovarian tumours and their expression is associated with shorter time to recurrence and poor outcome in patients with EOC. Furthermore, ectopic expression of miR-181a results in increased cellular survival, migration, invasion, drug resistance and in vivo tumour burden and dissemination. In contrast, miR-181a inhibition via decoy vector suppression and Smad7 re-expression results in significant reversion of these phenotypes. Combined, our findings highlight an unappreciated role for miR-181a, Smad7, and the TGF-β signalling pathway in high-grade serous ovarian cancer.
Ovarian cancer is often diagnosed at a late stage when metastasis has already occurred. In this study, Parikh et al. show that mir-181a is involved in mediating the epithelial-to-mesenchymal transition in ovarian cancer, leading to activation of the TGF-β signalling pathway and metastasis.