Ionizing radiation-induced gene expression changes in TP53 proficient and deficient glioblastoma cell lines

Antitumoral Activity of the Universal Methyl Donor S-Adenosylmethionine in Glioblastoma Cells

Glioblastoma (GBM), the most frequent and lethal brain cancer in adults, is characterized by short survival times and high mortality rates. Due to the resistance of GBM cells to conventional therapeutic treatments, scientific interest is focusing on the search for alternative and efficient adjuvant treatments. S-Adenosylmethionine (AdoMet), the well-studied physiological methyl donor, has emerged as a promising anticancer compound and a modulator of multiple cancer-related signaling pathways. We report here for the first time that AdoMet selectively inhibited the viability and proliferation of U87MG, U343MG, and U251MG GBM cells. In these cell lines, AdoMet induced S and G2/M cell cycle arrest and apoptosis and downregulated the expression and activation of proteins involved in homologous recombination DNA repair, including RAD51, BRCA1, and Chk1. Furthermore, AdoMet was able to maintain DNA in a damaged state, as indicated by the increased γH2AX/H2AX ratio. AdoMet promoted mitotic catastrophe through inhibiting Aurora B kinase expression, phosphorylation, and localization causing GBM cells to undergo mitotic catastrophe-induced death. Finally, AdoMet inhibited DNA repair and induced cell cycle arrest, apoptosis, and mitotic catastrophe in patient-derived GBM cells. In light of these results, AdoMet could be considered a potential adjuvant in GBM therapy.

Dose-Dependent Transcriptional Response to Ionizing Radiation Is Orchestrated with DNA Repair within the Nuclear Space

Radiation therapy is commonly used to treat glioblastoma multiforme (GBM) brain tumors. Ionizing radiation (IR) induces dose-specific variations in transcriptional programs, implicating that they are tightly regulated and critical components in the tumor response and survival. Yet, our understanding of the downstream molecular events triggered by effective vs. non-effective IR doses is limited. Herein, we report that variations in the genetic programs are positively and functionally correlated with the exposure to effective or non-effective IR doses. Genome architecture analysis revealed that gene regulation is spatially and temporally coordinated with DNA repair kinetics. The radiation-activated genes were pre-positioned in active sub-nuclear compartments and were upregulated following the DNA damage response, while the DNA repair activity shifted to the inactive heterochromatic spatial compartments. The IR dose affected the levels of DNA damage repair and transcription modulation, but not the order of the events, which was linked to their spatial nuclear positioning. Thus, the distinct coordinated temporal dynamics of DNA damage repair and transcription reprogramming in the active and inactive sub-nuclear compartments highlight the importance of high-order genome organization in synchronizing the molecular events following IR.

Postsynaptic density radiation signature following space irradiation

Introduction: The response of the brain to space radiation is an important concern for astronauts during space missions. Therefore, we assessed the response of the brain to ²⁸Si ion irradiation (600 MeV/n), a heavy ion present in the space environment, on cognitive performance and whether the response is associated with altered DNA methylation in the hippocampus, a brain area important for cognitive performance. Methods: We determined the effects of ²⁸Si ion irradiation on object recognition, 6-month-old mice irradiated with ²⁸Si ions (600 MeV/n, 0.3, 0.6, and 0.9 Gy) and cognitively tested two weeks later. In addition, we determined if those effects were associated with alterations in hippocampal networks and/or hippocampal DNA methylation. Results: At 0.3 Gy, but not at 0.6 Gy or 0.9 Gy, ²⁸Si ion irradiation impaired cognition that correlated with altered gene expression and 5 hmC profiles that mapped to specific gene ontology pathways. Comparing hippocampal DNA hydroxymethylation following proton, ⁵⁶Fe ion, and ²⁸Si ion irradiation revealed a general space radiation synaptic signature with 45 genes that are associated with profound phenotypes. The most significant categories were glutamatergic synapse and postsynaptic density. Discussion: The brain's response to space irradiation involves novel excitatory synapse and postsynaptic remodeling.

The Molecular and Cellular Strategies of Glioblastoma and Non-Small-Cell Lung Cancer Cells Conferring Radioresistance

Ionizing radiation (IR) has been shown to play a crucial role in the treatment of glioblastoma (GBM; grade IV) and non-small-cell lung cancer (NSCLC). Nevertheless, recent studies have indicated that radiotherapy can offer only palliation owing to the radioresistance of GBM and NSCLC. Therefore, delineating the major radioresistance mechanisms may provide novel therapeutic approaches to sensitize these diseases to IR and improve patient outcomes. This review provides insights into the molecular and cellular mechanisms underlying GBM and NSCLC radioresistance, where it sheds light on the role played by cancer stem cells (CSCs), as well as discusses comprehensively how the cellular dormancy/non-proliferating state and polyploidy impact on their survival and relapse post-IR exposure.

The DNA Double-Strand Break Repair in Glioma: Molecular Players and Therapeutic Strategies

Gliomas are the most frequent type of tumor in the central nervous system, which exhibit properties that make their treatment difficult, such as cellular infiltration, heterogeneity, and the presence of stem-like cells responsible for tumor recurrence. The response of this type of tumor to chemoradiotherapy is poor, possibly due to a higher repair activity of the genetic material, among other causes. The DNA double-strand breaks are an important type of lesion to the genetic material, which have the potential to trigger processes of cell death or cause gene aberrations that could promote tumorigenesis. This review describes how the different cellular elements regulate the formation of DNA double-strand breaks and their repair in gliomas, discussing the therapeutic potential of the induction of this type of lesion and the suppression of its repair as a control mechanism of brain tumorigenesis.

Anti-Proliferative Effects of E2F1 Suppression in Glioblastoma Cells

Glioblastoma (GBM) is an aggressive malignant brain tumor; surgery, radiation, and temozolomide still remain the main treatments. There is evidence that E2F1 is overexpressed in various types of cancer, including GBM. E2F1 is a transcription factor that controls the cell cycle progression and regulates DNA damage responses and the proliferation of pluripotent and neural stem cells. To test the potentiality of E2F1 as molecular target for GBM treatment, we suppressed the E2F1 gene (siRNA) in the U87MG cell line, aiming to inhibit cellular proliferation and modulate the radioresistance of these cells. Following E2F1 suppression, associated or not with gamma-irradiation, several assays (cell proliferation, cell cycle analysis, neurosphere counting, and protein expression) were performed in U87MG cells grown as monolayer or neurospheres. We found that siE2F1-suppressed cells showed reduced cell proliferation and increased cell death (sub-G1 fraction) in monolayer cultures, and also a significant reduction in the number of neurospheres. In addition, in irradiated cells, E2F1 suppression caused similar effects, with reduction of the number of neurospheres and neurosphere cell numbers relative to controls; these results suggest that E2F1 plays a role in the maintenance of GBM stem cells, and our results obtained in neurospheres are relevant within the context of radiation resistance. Furthermore, E2F1 suppression inhibited or delayed GBM cell differentiation by maintaining a reasonable proportion of CD133+ cells when grown at differentiation condition. Therefore, E2F1 proved to be an interesting molecular target for therapeutic intervention in U87MG cells.

Genomic analyses of early responses to radiation inglioblastoma reveal new alterations at transcription,splicing, and translation levels

High-dose radiation is the main component of glioblastoma therapy. Unfortunately, radio-resistance is a common problem and a major contributor to tumor relapse. Understanding the molecular mechanisms driving response to radiation is critical for identifying regulatory routes that could be targeted to improve treatment response. We conducted an integrated analysis in the U251 and U343 glioblastoma cell lines to map early alterations in the expression of genes at three levels: transcription, splicing, and translation in response to ionizing radiation. Changes at the transcriptional level were the most prevalent response. Downregulated genes are strongly associated with cell cycle and DNA replication and linked to a coordinated module of expression. Alterations in this group are likely driven by decreased expression of the transcription factor FOXM1 and members of the E2F family. Genes involved in RNA regulatory mechanisms were affected at the mRNA, splicing, and translation levels, highlighting their importance in radiation-response. We identified a number of oncogenic factors, with an increased expression upon radiation exposure, including BCL6, RRM2B, IDO1, FTH1, APIP, and LRIG2 and lncRNAs NEAT1 and FTX. Several of these targets have been previously implicated in radio-resistance. Therefore, antagonizing their effects post-radiation could increase therapeutic efficacy. Our integrated analysis provides a comprehensive view of early response to radiation in glioblastoma. We identify new biological processes involved in altered expression of various oncogenic factors and suggest new target options to increase radiation sensitivity and prevent relapse.

Distinct TP53 Mutation Subtypes Differentially Influence Cellular Iron Metabolism

The most commonly mutated gene in all human cancers is the tumor suppressor gene TP53; however, in addition to the loss of tumor suppressor functions, mutations in TP53 can also promote cancer progression by altering cellular iron acquisition and metabolism. The primary objective of this work was to determine how TP53 mutation status influences the molecular control of iron homeostasis. The effect of TP53 mutation type on cellular iron homeostasis was examined using cell lines with inducible versions of either wild-type TP53 or a representative mutated TP53 gene from exemplary "hotspot" mutations in the DNA binding domain (R248, R273, and R175) as well as H193Y. The introduction of distinct TP53 mutation types alone was sufficient to disrupt cellular iron metabolism. These effects were mediated, at least in part, due to differences in the responsiveness of iron regulatory proteins (IRPs) to cellular iron availability. IRPs are considered the master regulators of intracellular iron homeostasis because they coordinate the expression of iron storage (ferritin) and iron uptake (transferrin receptor) genes. In response to changes in iron availability, cells harboring either a wild-type TP53 or R273H TP53 mutation displayed canonical IRP-mediated responses, but neither IRP1 RNA binding activity nor IRP2 protein levels were affected by changes in iron status in cells harboring the R175H mutation type. However, all mutation types exhibited robust changes in ferritin and transferrin receptor protein expression in response to iron loading and iron chelation, respectively. These findings suggest a novel, IRP-independent mode of iron regulation in cells expressing distinct TP53 mutations. As TP53 is mutated in nearly half of all human cancers, and iron is necessary for cancer cell growth and proliferation, the studies have implications for a wide range of clinically important cancers.

Inhibition of TAZ contributes radiation-induced senescence and growth arrest in glioma cells

Glioblastoma (GBM) is the most aggressive brain tumor and resistant to current available therapeutics, such as radiation. To improve the clinical efficacy, it is important to understand the cellular mechanisms underlying tumor responses to radiation. Here, we investigated long-term cellular responses of human GBM cells to ionizing radiation. Comparing to the initial response within 12 hours, gene expression modulation at 7 days after radiation is markedly different. While genes related to cell cycle arrest and DNA damage responses are mostly modulated at the initial stage; immune-related genes are specifically affected as the long-term effect. This later response is associated with increased cellular senescence and inhibition of transcriptional coactivator with PDZ-binding motif (TAZ). Mechanistically, TAZ inhibition does not depend on the canonical Hippo pathway, but relies on enhanced degradation mediated by the β-catenin destruction complex in the Wnt pathway. We further showed that depletion of TAZ by RNAi promotes radiation-induced senescence and growth arrest. Pharmacological activation of the β-catenin destruction complex is able to promote radiation-induced TAZ inhibition and growth arrest in these tumor cells. The correlation between senescence and reduced expression of TAZ as well as β-catenin also occurs in human gliomas treated by radiation. Collectively, these findings suggested that inhibition of TAZ is involved in radiation-induced senescence and might benefit GBM radiotherapy.

Oxidative stress and cell cycle arrest induced by short-term exposure to dustfall PM2.5 in A549 cells

It was reported that in vitro short-term exposure to PM_2.5 caused different lung diseases through inflammatory response, immune toxicity, oxidative stress, and genetic mutations. However, the complex molecular biological mechanism for its toxicity had not been fully elucidated. Therefore, the present study investigated the cytotoxicity, oxidative damage, mitochondria damage, apoptosis, and cell cycle arrest of NX and QH PM_2.5 in A549 cells. Further, cell cycle arrest-related gene levels in PM_2.5-induced A549 cells were also detected. Our results suggested that PM_2.5 reduced the cell viability in A549 cells. Simultaneously, excessive ROS decreased MMP levels and damaged mitochondrial membrane integrity and induced mitochondrial oxidative damage through the oxygen-dependent killer route, resulting in mitochondrial damage and cell apoptosis. Besides, the results also showed that PM_2.5 induced A549 cell cycle alteration in G2/M phase after co-culture for 24 h. G2/M phase arrest was induced by upregulation of p53 and p21 and downregulation of CDK1 mRNA expression. In addition, lncRNA Sox2ot might play an important role as the specific oncogenes and it participated in G2/M phase arrest by regulating the expression of EZH₂.

The Impact of Non-Lethal Single-Dose Radiation on Tumor Invasion and Cytoskeletal Properties

Irradiation is the standard therapy for glioblastoma multiforme. Glioblastoma are highly resistant to radiotherapy and the underlying mechanisms remain unclear. To better understand the biological effects of irradiation on glioblastoma cells, we tested whether nonlethal irradiation influences the invasiveness, cell stiffness, and actin cytoskeleton properties. Two different glioblastoma cell lines were irradiated with 2 Gy and changes in mechanical and migratory properties and alterations in the actin structure were measured. The invasiveness of cell lines was determined using a co-culture model with organotypic hippocampal slice cultures. Irradiation led to changes in motility and a less invasive phenotype in both investigated cell lines that were associated with an increase in a "generalized stiffness" and changes in the actin structure. In this study we demonstrate that irradiation can induce changes in the actin cytoskeleton and motility, which probably results in reduced invasiveness of glioblastoma cell lines. Furthermore, "generalized stiffness" was shown to be a profound marker of the invasiveness of a tumor cell population in our model.

E2F transcription factors associated with up-regulated genes in glioblastoma

BACKGROUND

Glioblastoma is considered to the most common and malignant brain tumor in adults. Patients have a median survival of approximately one year from diagnosis due to poor response to therapy.

OBJECTIVE

We applied bioinformatics approaches to predict transcription factors (TF) that are deregulated in glioblastoma in an attempt to point out molecular targets for therapy.

METHODS

Up-regulated genes in glioblastoma selected from public microarray data were submitted to two TF association analyses. Thereafter, the expression levels of TF obtained in the overlap of analyses were assessed by RT-qPCR carried out in seven glioblastoma cell lines (T98, U251, U138, U87, U343, M059J, and M059K).

RESULTS

E2F1 and E2F4 were highlighted in both TF analyses. However, only E2F1 was confirmed as significantly up-regulated in all glioblastoma cell lines in vitro.

CONCLUSION

E2F1 is a potential common regulator of differentially expressed genes in glioblastoma, despite the genetic heterogeneity of tumor cells.

HEB silencing induces anti-proliferative effects on U87MG cells cultured as neurospheres and monolayers

Glioblastoma multiforme (GBM) is a lethal tumor and novel strategies are required to overcome resistance. Transcription factor 12 (HEB) has been associated with neural and stem cell proliferation, is overexpressed in certain tumor types and is induced in irradiated U87MG cells. The present study aimed to determine whether HEB knockdown, with or without irradiation, may sensitize GBM cells. U87MG GBM and ACBRI‑371 primary human astrocytes were cultured in monolayers or neurospheres. Cell proliferation and death, cell cycle and sub‑G1 detection, and cluster of differentiation (CD) 133 immunofluorescence were analyzed by flow cytometry, whereas HEB protein expression was analyzed by immunocytochemistry and western blotting. Greater HEB protein expression was observed in U87MG neurospheres compared with ACBRI‑371, and the two cell lines exhibited nuclear HEB expression. HEB silencing in cells grown in monolayers induced a significant reduction in proliferation and decreased the proportion of cells in G0/G1 phase. In addition, HEB silencing reduced (two‑fold) the number of neurospheres compared with control scrambled (SCR) cells. HEB silencing combined with irradiation reduced U87MG cell proliferation when cultured in monolayers and reduced neurosphere cell number compared with the SCR irradiated group; however, not significantly. Differentiation of U87MG cells from neurospheres was reduced in HEB‑silenced cells, whereas in irradiated cells the proportion of CD133+ cells was similar in HEB‑silenced cells compared with the SCR control. These results suggest that HEB may contribute to the proliferation and maintenance of GBM cells. However, only limited effects were exerted by irradiation in HEB‑silenced cells. HEB may be a potential target to decrease proliferation in U87MG GBM cells, grown as monolayers or neurospheres, and may provide important information for the development of novel strategies for cancer therapy.

The regrowth kinetic of the surviving population is independent of acute and chronic responses to temozolomide in glioblastoma cell lines

Chemotherapy acts on cancer cells by producing multiple effects on a cell population including cell cycle arrest, necrosis, apoptosis and senescence. However, often a subpopulation of cells survives and the behavior of this subpopulation, which is responsible for cancer recurrence, remains obscure. Here we investigated the in vitro short- and long-term responses of six glioblastoma cell lines to clinically relevant doses of temozolomide for 5 days followed by 23 days of recovery, mimicking the standard schedule used in glioblastoma patient for this drug. These cells presented different profiles of sensitivity to temozolomide with varying levels of cell cycle arrest, autophagy and senescence, followed by a regrowth of the surviving cells. The initial reduction in cell number and the subsequent regrowth was analyzed with four new parameters applied to Cumulative Population Doubling (CPD) curves that describe the overall sensitivity of the population and the characteristic of the regrowth: the relative end point CPD (RendCPD); the relative Area Under Curve (rAUC); the Relative Time to Cross a Threshold (RTCT); and the Relative Proliferation Rate (RPR). Surprisingly, the kinetics of regrowth were not predicted by the mechanisms activated after treatment nor by the acute or overall sensitivity. With this study we added new parameters that describe key responses of glioblastoma cell populations to temozolomide treatment. These parameters can also be applied to other cell types and treatments and will help to understand the behavior of the surviving cancer cells after treatment and shed light on studies of cancer resistance and recurrence.

Combining PARP inhibitors with radiation therapy for the treatment of glioblastoma: Is PTEN predictive of response?

Glioblastoma (GBM) is fatal. The standard radiotherapy and chemotherapy (temozolomide) followed by an adjuvant phase of temozolomide provide patients with, on average, a 2.5 months benefit. New treatments that can improve sensitivity to the standard treatment are urgently needed. Herein, we review the mechanisms and utility of poly (ADP-ribose) polymerase inhibitors in combination with radiation therapy as a treatment option for GBM patients and the role of phosphatase and tensin homologue mutations as a biomarker of response.

Application of NMR Spectroscopy in the Assessment of Radiation Dose in Human Primary Cells

We employed the primary cell model system as a first step toward establishing a method to assess the influence of ionizing radiation by using a combination of common and abundant metabolites. We applied X-ray irradiation amounts of 0, 1, and 5 Gy to the cells that were harvested 24, 48, or 72 h later, and profiled metabolites by 2D-NMR spectroscopy to sort out candidate molecules that could be used to distinguish the samples under different irradiation conditions. We traced metabolites stemming from the input ¹³C-glucose, identified twelve of them from the cell extracts, and applied statistical analysis to find out that all the metabolites, including glycine, alanine, and gluatamic acid, increased upon irradiation. The combinatorial use of the selected metabolites showed promising results where the product of signal intensities of alanine and lactate could differentiate samples according to the dose of X-ray irradiation. We hope that this work can form a base for treating radiation-poisoned patients in the future.

Imaging Genomics of Glioblastoma: Biology, Biomarkers, and Breakthroughs

Glioblastoma is regarded as the most aggressive and most common primary malignant brain tumor in adults. Despite advancements in chemotherapy and radiotherapy, prognosis and overall survival of glioblastoma patients remain dismal. Recently, progresses in genetic profiling have increased our understanding of the underlying heterogenous molecular nature of this aggressive tumor. Several prognostic and predictive molecular biomarkers have been identified that have been linked to patient's survival and response to treatment, respectively. Imaging genomics represents a novel entity in clinical sciences that bidirectionally links imaging features with underlying molecular profile and thus can serve as a surrogate for noninvasive genomic correlation, prediction, and identification.

Microarray Analysis in Glioblastomas

Microarray analysis in glioblastomas is done using either cell lines or patient samples as starting material. A survey of the current literature points to transcript-based microarrays and immunohistochemistry (IHC)-based tissue microarrays as being the preferred methods of choice in cancers of neurological origin. Microarray analysis may be carried out for various purposes including the following: i. To correlate gene expression signatures of glioblastoma cell lines or tumors with response to chemotherapy (DeLay et al., Clin Cancer Res 18(10):2930-2942, 2012). ii. To correlate gene expression patterns with biological features like proliferation or invasiveness of the glioblastoma cells (Jiang et al., PLoS One 8(6):e66008, 2013). iii. To discover new tumor classificatory systems based on gene expression signature, and to correlate therapeutic response and prognosis with these signatures (Huse et al., Annu Rev Med 64(1):59-70, 2013; Verhaak et al., Cancer Cell 17(1):98-110, 2010). While investigators can sometimes use archived tumor gene expression data available from repositories such as the NCBI Gene Expression Omnibus to answer their questions, new arrays must often be run to adequately answer specific questions. Here, we provide a detailed description of microarray methodologies, how to select the appropriate methodology for a given question, and analytical strategies that can be used. Experimental methodology for protein microarrays is outside the scope of this chapter, but basic sample preparation techniques for transcript-based microarrays are included here.

Multimodal imaging based on MRI and PET reveals [(18)F]FLT PET as a specific and early indicator of treatment efficacy in a preclinical model of recurrent glioblastoma

PURPOSE

The primary objective of this study was to compare the ability of PET and MRI biomarkers to predict treatment efficacy in a preclinical model of recurrent glioblastoma multiforme.

METHODS

MRI (anatomical, diffusion, vasculature and oxygenation) and PET ([(18)F]FDG and [(18)F]FLT) parameters were obtained 3 days after the end of treatment and compared with late tumour growth and survival.

RESULTS

Early after tumour recurrence, no effect of treatment with temozolomide combined with bevacizumab was observed on tumour volume as assessed by T2-W MRI. At later times, the treatment decreased tumour volume and increased survival. Interestingly, at the earlier time, temozolomide + bevacizumab decreased [(18)F]FLT uptake, cerebral blood volume and oedema. [(18)F]FLT uptake, oedema and cerebral blood volume were correlated with overall survival but [(18)F]FLT uptake had the highest specificity and sensitivity for the early prediction of treatment efficacy.

CONCLUSION

The present investigation in a preclinical model of glioblastoma recurrence underscores the importance of multimodal imaging in the assessment of oedema, tumour vascular status and cell proliferation. Finally, [(18)F]FLT holds the greatest promise for the early assessment of treatment efficacy. These findings may translate clinically in that individualized treatment for recurrent glioma could be prescribed for patients selected after PET/MRI examinations.

APE1/REF-1 down-regulation enhances the cytotoxic effects of temozolomide in a resistant glioblastoma cell line

Temozolomide (TMZ) is widely used for patients with glioblastoma (GBM); however, tumor cells frequently exhibit drug-resistance. Base excision repair (BER) has been identified as a possible mediator of TMZ resistance, and an attractive approach to sensitizing cells to chemotherapy. Human apurinic/apyrimidinic endonuclease/redox factor-1 (APE1) is an essential enzyme with a role in the BER pathway by repairing abasic sites, and it also acts as a reduction factor, maintaining transcription factors in an active reduced state. Thus, we aimed to investigate whether the down-regulation of APE1 expression by siRNA can interfere with the resistance of GBM to TMZ, being evaluated by several cellular and molecular parameters. We demonstrated that APE1 knockdown associated with TMZ treatment efficiently reduced cell proliferation and clonogenic survival of resistant cells (T98G), which appears to be a consequence of increased DNA damage, S-phase arrest, and H2AX phosphorylation, resulting in apoptosis induction. On the contrary, for those assays, the sensitization effects of APE1 silencing plus TMZ treatment did not occur in the TMZ-sensitive cell line (U87MG). Interestingly, TMZ-treatment and APE1 knockdown significantly reduced cell invasion in both cell lines, but TMZ alone did not reduce the invasion capacity of U87MG cells, as observed for T98G. We also found that VEGF expression was down-regulated by TMZ treatment in T98G cells, regardless of APE1 knockdown, but U87MG showed a different response, since APE1 silencing counteracted VEGF induction promoted by TMZ, suggesting that the APE1-redox function may play an indirect role, depending on the cell line. The present results support the contribution of BER in the GBM resistance to TMZ, with a greater effect in TMZ-resistant, compared with TMZ-sensitive cells, emphasizing that APE1 can be a promising target for modifying TMZ tolerance. Furthermore, genetic characteristics of tumor cells should be considered as critical information to select an appropriate therapeutic strategy.

miR-30a suppresses breast cancer cell proliferation and migration by targeting Eya2

Eye absent (Eya) proteins are involved in cell fate determination in a broad spectrum of cells and tissues. Aberrant expression of Eya2 has been documented in a variety of cancers and correlates with clinical outcome. However, whether microRNAs (miRNAs) can regulate Eya2 expression remains unknown. Here, we show that miR-30a represses Eya2 expression by binding to the 3'-untranslated region of Eya2. Overexpression of Eya2 in miR-30a-transfected breast cancer cells effectively rescued the inhibition of cell proliferation and migration caused by miR-30a. Knockdown of Eya2 by small-interfering RNA (siRNA) in breast cancer cells mimicked the effect induced by miR-30a and abolished the ability of miR-30a to regulate breast cancer cell proliferation and migration. The miR-30a/Eya2 axis could regulate G1/S cell cycle progression, accompanied by the modulation of expression of cell cycle-related proteins, including cyclin A, cyclin D1, cyclin E, and c-Myc. Moreover, miR-30a expression was downregulated in breast cancer patients, and negatively correlated with Eya2, which was upregulated in breast cancer patients. These data suggest that the miR-30a/Eya2 axis may play an important role in breast cancer development and progression and that miR-30a activation or Eya2 inhibition may be a useful strategy for cancer treatment.