Prediction of tissue-of-origin of early stage cancers using serum miRNomes.

BACKGROUND: Noninvasive detection of early stage cancers with accurate prediction of tumor tissue-of-origin could improve patient prognosis. Because miRNA profiles differ between organs, circulating miRNomics represent a promising method for early detection of cancers, but this has not been shown conclusively. METHODS: A serum miRNA profile (miRNomes)-based classifier was evaluated for its ability to discriminate cancer types using advanced machine learning. The training set comprised 7931 serum samples from patients with 13 types of solid cancers and 5013 noncancer samples. The validation set consisted of 1990 cancer and 1256 noncancer samples. The contribution of each miRNA to the cancer-type classification was evaluated, and those with a high contribution were identified. RESULTS: Cancer type was predicted with an accuracy of 0.88 (95% confidence interval [CI] = 0.87 to 0.90) in all stages and an accuracy of 0.90 (95% CI = 0.88 to 0.91) in resectable stages (stages 0-II). The F1 score for the discrimination of the 13 cancer types was 0.93. Optimal classification performance was achieved with at least 100 miRNAs that contributed the strongest to accurate prediction of cancer type. Assessment of tissue expression patterns of these miRNAs suggested that miRNAs secreted from the tumor environment could be used to establish cancer type-specific serum miRNomes. CONCLUSIONS: This study demonstrates that large-scale serum miRNomics in combination with machine learning could lead to the development of a blood-based cancer classification system. Further investigations of the regulating mechanisms of the miRNAs that contributed strongly to accurate prediction of cancer type could pave the way for the clinical use of circulating miRNA diagnostics.

Fluoride-bridged dinuclear dysprosium complex showing single-molecule magnetic behavior: supramolecular approach to isolate magnetic molecules.

Using Na-encapsulated benzo[18]crown-6 (Na)(B18C6) as a counter cation, we successfully magnetically isolated a fluoride-bridging Dy dinuclear complex {[(PW11O39)Dy(H2O)2]2F} (Dy2POM) with lacunary Keggin ligands. (Na)(B18C6) formed two types of tetramers through C-H⋯O, π⋯π and C-H⋯π interactions, and each tetramer aligned in one dimension along the c-axis to form two types of channels. One channel was partially penetrated by a supramolecular cation from the ±a-axis direction, dividing the channel in the form of a "bamboo node". Dy2POM was spatially divided by this "bamboo node," which magnetically isolated one portion from the other. The temperature dependence of the magnetic susceptibility indicated a weak ferromagnetic interaction between the Dy ions bridged by fluoride. Dy2POM exhibited the magnetic relaxation characteristics of a single-molecule magnet, including the dependence of AC magnetic susceptibility on temperature and frequency. Magnetic relaxation can be described by the combination of thermally active Orbach and temperature-independent quantum tunneling processes. The application of a static magnetic field effectively suppressed the relaxation due to quantum tunneling.

Mechanical Thrombectomy for Bihemispheric Infarction Caused by Acute Unilateral Internal Carotid Artery Occlusion in a Patient with Contralateral Chronic Carotid Occlusion: A Case Report.

Objective: We report a patient with acute bihemispheric infarction who underwent mechanical thrombectomy. Case Presentation: A 76-year-old man suddenly developed coma and quadriplegia. Brain MRI and MRA revealed acute bihemispheric infarction due to occlusions of both the internal carotid arteries (ICAs). According to the DSA findings, we considered the left ICA as chronic occlusion and the right as acute. Mechanical thrombectomy for the right ICA occlusion was performed. Total recanalization was achieved using a stent retriever 181 minutes after onset. The left hemisphere was perfused by cross circulation through the anterior communicating artery, but the symptoms did not improve. MRI the day after thrombectomy showed extensive bihemispheric infarction. Recanalization for the bilateral hemispheres was maintained, although the left ICA remained occluded. He died 2 months later due to gastrointestinal bleeding. Conclusion: Acute bihemispheric infarction due to occlusions of both ICAs is a rare entity. The symptoms are very severe and the therapeutic time window is extremely short because of absent collateral pathways. We should consider pre-existing carotid occlusive disease, determine whether the occlusions are acute or chronic, and perform prompt therapy. Further investigation is warranted to obtain a better outcome.

Ultrasound image-guided gene delivery using three-dimensional diagnostic ultrasound and lipid-based microbubbles.

Gene therapy is a promising technology for genetic and intractable diseases. Drug delivery carriers or systems for genes and nucleic acids have been studied to improve transfection efficiency and achieve sufficient therapeutic effects. Ultrasound (US) and microbubbles have also been combined for use in gene delivery. To establish a clinically effective gene delivery system, exposing the target tissues to US is important. The three-dimensional (3D) diagnostic probe can three-dimensionally scan the tissue with mechanical regulation, and homogenous US exposure to the targeted tissue can be expected. However, the feasibility of therapeutically applying 3D probes has not been evaluated, especially gene delivery. In this study, we evaluated the characteristics of a 3D probe and lipid-based microbubbles (LB) for gene delivery and determined whether the 3D probe in the diagnostic US device could be used for efficient gene delivery to the targeted tissue using a mouse model. The 3D probe RSP6-16 with LB delivered plasmid DNA (pDNA) to the kidney after systemic injection with luciferase activity similar to that of probes used in previously studies. No toxicity was observed after treatment and, therefore, the combined 3D probe and LB would deliver genes to targeted tissue safely and efficiently.

[Surgical Case of Accidental Infantile Acute Subdural Hematoma Caused by Household Minor Head Trauma:Hyperperfusion during Postoperative Hemispheric Hypodensity, Namely "Big Black Brain"].

We experienced a case of an accidental infantile acute subdural hematoma caused by household minor head trauma(Nakamura type I intracranial hemorrhage)with postoperative hemispheric hypodensity lesion(Big Black Brain)whose pathophysiology was analyzed using perfusion MRI. A ten-month-old boy was admitted to our hospital in a comatose state. His mother revealed that the boy suffered a fall from a sofa bed. A CT scan indicated massive acute subdural hematoma in the left cerebral hemisphere. Emergency craniotomy and hematoma evacuation were performed. On postoperative day 3, CT revealed hemispheric hypodensity, and the boy suffered from status epilepticus. MRI on the following day showed widespread white matter hyperintensity in diffusion-weighted images, and MRA demonstrated dilation of the middle cerebral artery. Perfusion MRI using the dynamic susceptibility contrast method revealed a marked increase in cerebral blood flow in the left hemisphere. These abnormal MRI and MRA findings disappeared on postoperative day 13. Status epilepticus also improved upon administration of multi-antiepileptic drugs. Fundoscopy findings on postoperative day 3 showed small bilateral petechial or brush retinal hemorrhages. However, whole-body examination did not show any problems, and was consistent with the mother's account. Thus, we judged non-abusive head trauma. Although follow-up MRI showed diffuse atrophy of the left cerebral hemisphere, the boy aged well without obvious paresis or verbal developmental delay as judged by a follow-up more than a year later. Based on these results, we speculated that hyperperfusion caused by dilation of the cerebral artery was related to the postoperative hemispheric hypodensity, namely "Big Black Brain".

Overlapping Stents and Coil Embolization of Ruptured Anterior Cerebral Artery Dissecting Aneurysms in the Acute Phase.

Objective: To report a case of ruptured anterior cerebral artery dissection treated with stent-assisted coil embolization with overlapping stents. Case Presentation: A 51-year-old woman developed subarachnoid hemorrhage the day after transient left hemiparesis. Angiography revealed a ruptured anterior cerebral artery dissecting aneurysm. We conducted stent-assisted coil embolization with the overlapping stent technique on the day after the hemorrhage. She recovered steadily without rebleeding. Six months after embolization, no recurrence was found on angiography. Conclusion: Although an acceptable result was achieved in this case, the safety and efficacy of this procedure are unconfirmed. A larger number of cases should be accumulated.

A serum microRNA classifier for the diagnosis of sarcomas of various histological subtypes.

Due to their rarity and diversity, sarcomas are difficult to diagnose. Consequently, there is an urgent demand for a novel diagnostic test for these cancers. In this study, we investigated serum miRNA profiles from 1002 patients with bone and soft tissue tumors representing more than 43 histological subtypes, including sarcomas, intermediate tumors, and benign tumors, to determine whether serum miRNA profiles could be used to specifically detect sarcomas. Circulating serum miRNA profiles in sarcoma patients were clearly distinct from those in patients with other types of tumors. Using the serum levels of seven miRNAs, we developed a molecular detector, Index VI, that could distinguish sarcoma patients from benign and healthy controls with remarkably high sensitivity (90%) and specificity (95%), regardless of histological subtype. Index VI provides an approach to the early and precise detection of sarcomas, potentially leading to curative treatment and longer survival.

A Nucleolar Stress-Specific p53-miR-101 Molecular Circuit Functions as an Intrinsic Tumor-Suppressor Network.

BACKGROUND: Activation of intrinsic p53 tumor-suppressor (TS) pathways is an important principle underlying cancer chemotherapy. It is necessary to elucidate the precise regulatory mechanisms of these networks to create new treatment strategies. METHODS: Comprehensive analyses were carried out by microarray. Expression of miR-101 was analyzed by clinical samples of lung adenocarcinomas. FINDINGS: We discovered a functional link between p53 and miR-101, which form a molecular circuit in response to nucleolar stress. Inhibition of RNA polymerase I (Pol I) transcription resulted in the post-transcriptional activation of miR-101 in a p53-dependent manner. miR-101 induced G2 phase-specific feedback regulation of p53 through direct repression of its target, EG5, resulting in elevated phosphorylation of ATM. In lung cancer patients, low expression of miR-101 was associated with significantly poorer prognosis exclusively in p53 WT cases. miR-101 sensitized cancer cells to Pol I transcription inhibitors and strongly repressed xenograft growth in mice. Interestingly, the most downstream targets of this circuit included the inhibitor of apoptosis proteins (IAPs). Repression of cIAP1 by a selective inhibitor, birinapant, promoted activation of the apoptosis induced by Pol I transcription inhibitor in p53 WT cancer cells. INTERPRETATION: Our findings indicate that the p53-miR-101 circuit is a component of an intrinsic TS network formed by nucleolar stress, and that mimicking activation of this circuit represents a promising strategy for cancer therapy. FUND: National Institute of Biomedical Innovation, Ministry of Education, Culture, Sports & Technology of Japan, Japan Agency for Medical Research and Development.

[Bilateral Internal Carotid Artery Dissection Caused by Elongated Styloid Processes:A Case Report].

We report a case of bilateral internal carotid artery(ICA)dissection associated with bilateral elongated styloid processes(ESPs). A 46-year-old man presented with transient aphasia and left visual disturbance at a business meeting. He complained of a foreign body sensation in his throat during swallowing for two years. Magnetic resonance imaging(MRI)demonstrated fresh small infarcts in the left corona radiata. Magnetic resonance angiography(MRA)revealed string signs bilaterally in the cervical ICAs. The patient was diagnosed with bilateral idiopathic ICA dissection and was treated with ozagrel and clopidogrel. Three-dimensional computed tomographic angiogram(3DCTA)indicated bilateral ESPs and bilateral ICA stenosis. 3DCTA with the patient's head tilting and neck extension revealed that each ICA was compressed by the ipsilateral ESP. A follow-up MRA showed complete normalization of bilateral ICAs after neck rest and anti-platelet therapy, following which, clopidogrel was stopped. The patient wore a soft cervical collar until the operation, to avoid contact between the ESPs and ICAs due to changes in head position. Bilateral ESP resection was performed to prevent recurrence of cerebral ischemic events caused by ICA dissection. The patient was discharged one week after the surgery without any neurological deficit. There was no recurrence of symptoms during the next eight months after the operation.

An Integrated Prognostic Classifier for Stage I Lung Adenocarcinoma Based on mRNA, microRNA, and DNA Methylation Biomarkers.

INTRODUCTION: Up to 30% stage I lung cancer patients suffer recurrence within 5 years of curative surgery. We sought to improve existing protein-coding gene and microRNA expression prognostic classifiers by incorporating epigenetic biomarkers. METHODS: Genome-wide screening of DNA methylation and pyrosequencing analysis of HOXA9 promoter methylation were performed in two independently collected cohorts of stage I lung adenocarcinoma. The prognostic value of HOXA9 promoter methylation alone and in combination with mRNA and miRNA biomarkers was assessed by Cox regression and Kaplan-Meier survival analysis in both cohorts. RESULTS: Promoters of genes marked by polycomb in embryonic stem cells were methylated de novo in tumors and identified patients with poor prognosis. The HOXA9 locus was methylated de novo in stage I tumors (p < 0.0005). High HOXA9 promoter methylation was associated with worse cancer-specific survival (hazard ratio [HR], 2.6; p = 0.02) and recurrence-free survival (HR, 3.0; p = 0.01), and identified high-risk patients in stratified analysis of stages IA and IB. Four protein-coding gene (XPO1, BRCA1, HIF1α, and DLC1), miR-21 expression, and HOXA9 promoter methylation were each independently associated with outcome (HR, 2.8; p = 0.002; HR, 2.3; p = 0.01; and HR, 2.4; p = 0.005, respectively), and when combined, identified high-risk, therapy naive, stage I patients (HR, 10.2; p = 3 × 10). All associations were confirmed in two independently collected cohorts. CONCLUSION: A prognostic classifier comprising three types of genomic and epigenomic data may help guide the postoperative management of stage I lung cancer patients at high risk of recurrence.

Carbon-ion beam irradiation kills X-ray-resistant p53-null cancer cells by inducing mitotic catastrophe.

BACKGROUND AND PURPOSE: To understand the mechanisms involved in the strong killing effect of carbon-ion beam irradiation on cancer cells with TP53 tumor suppressor gene deficiencies. MATERIALS AND METHODS: DNA damage responses after carbon-ion beam or X-ray irradiation in isogenic HCT116 colorectal cancer cell lines with and without TP53 (p53+/+ and p53-/-, respectively) were analyzed as follows: cell survival by clonogenic assay, cell death modes by morphologic observation of DAPI-stained nuclei, DNA double-strand breaks (DSBs) by immunostaining of phosphorylated H2AX (γH2AX), and cell cycle by flow cytometry and immunostaining of Ser10-phosphorylated histone H3. RESULTS: The p53-/- cells were more resistant than the p53+/+ cells to X-ray irradiation, while the sensitivities of the p53+/+ and p53-/- cells to carbon-ion beam irradiation were comparable. X-ray and carbon-ion beam irradiations predominantly induced apoptosis of the p53+/+ cells but not the p53-/- cells. In the p53-/- cells, carbon-ion beam irradiation, but not X-ray irradiation, markedly induced mitotic catastrophe that was associated with premature mitotic entry with harboring long-retained DSBs at 24 h post-irradiation. CONCLUSIONS: Efficient induction of mitotic catastrophe in apoptosis-resistant p53-deficient cells implies a strong cancer cell-killing effect of carbon-ion beam irradiation that is independent of the p53 status, suggesting its biological advantage over X-ray treatment.

A three-microRNA signature predicts responses to platinum-based doublet chemotherapy in patients with lung adenocarcinoma.

PURPOSE: To examine the clinical utility of intratumor microRNAs (miRNA) as a biomarker for predicting responses to platinum-based doublet chemotherapy in patients with recurring lung adenocarcinoma (LADC). EXPERIMENTAL DESIGN: The expression of miRNAs was examined in LADC tissues surgically resected from patients treated with platinum-based doublet chemotherapy at the time of LADC recurrence. Microarray-based screening of 904 miRNAs followed by quantitative reverse transcription-PCR-based verification in 40 test cohort samples, including 16 (40.0%) responders, was performed to identify miRNAs that are differentially expressed in chemotherapy responders and nonresponders. Differential expression was confirmed in a validation cohort (n = 63 samples), including 18 (28.6%) responders. An miRNA signature that predicted responses to platinum-based doublet chemotherapy was identified and its accuracy was examined by principal component and support vector machine analyses. Genotype data for the TP53-Arg72Pro polymorphism, which is associated with responses to platinum-based doublet chemotherapy, were subsequently incorporated into the prediction analysis. RESULTS: A signature comprising three miRNAs (miR1290, miR196b, and miR135a*) enabled the prediction of a chemotherapeutic response (rather than progression-free and overall survival) with high accuracy in both the test and validation cohorts (82.5% and 77.8%). Examination of the latter was performed using miRNAs extracted from archived formalin-fixed paraffin-embedded tissues. Combining this miRNA signature with the TP53-Arg72Pro polymorphism genotype marginally improved the predictive power. CONCLUSION: The three-miRNA signature in surgically resected primary LADC tissues may by clinically useful for predicting responsiveness to platinum-based doublet chemotherapy in patients with LADC recurrence.

NEK9-dependent proliferation of cancer cells lacking functional p53.

Dysfunction of the p53 network is a major cause of cancer development, and selective elimination of p53-inactivated cancer cells therefore represents an ideal therapeutic strategy. In this study, we performed a microRNA target screen that identified NEK9 (NIMA-related kinase 9) as a crucial regulator of cell-cycle progression in p53-inactivated cancer cells. NEK9 depletion selectively inhibited proliferation in p53-deficient cancer cells both in vitro and in vivo. The resultant cell-cycle arrest occurred predominantly in G1 phase, and exhibited senescence-like features. Furthermore, NEK9 repression affected expression of a broad range of genes encoding cell-cycle regulators and factors involved in mRNA processing, suggesting a novel role for NEK9 in p53-deficient cells. Lung adenocarcinoma patients with positive staining for NEK9 and mutant p53 proteins exhibited significantly poorer prognoses, suggesting that expression of both proteins promotes tumor growth. Our findings demonstrate that a novel NEK9 network regulates the growth of cancer cells lacking functional p53.

Circulating exosomal microRNAs as biomarkers of colon cancer.

PURPOSE: Exosomal microRNAs (miRNAs) have been attracting major interest as potential diagnostic biomarkers of cancer. The aim of this study was to characterize the miRNA profiles of serum exosomes and to identify those that are altered in colorectal cancer (CRC). To evaluate their use as diagnostic biomarkers, the relationship between specific exosomal miRNA levels and pathological changes of patients, including disease stage and tumor resection, was examined. EXPERIMENTAL DESIGN: Microarray analyses of miRNAs in exosome-enriched fractions of serum samples from 88 primary CRC patients and 11 healthy controls were performed. The expression levels of miRNAs in the culture medium of five colon cancer cell lines were also compared with those in the culture medium of a normal colon-derived cell line. The expression profiles of miRNAs that were differentially expressed between CRC and control sample sets were verified using 29 paired samples from post-tumor resection patients. The sensitivities of selected miRNAs as biomarkers of CRC were evaluated and compared with those of known tumor markers (CA19-9 and CEA) using a receiver operating characteristic analysis. The expression levels of selected miRNAs were also validated by quantitative real-time RT-PCR analyses of an independent set of 13 CRC patients. RESULTS: The serum exosomal levels of seven miRNAs (let-7a, miR-1229, miR-1246, miR-150, miR-21, miR-223, and miR-23a) were significantly higher in primary CRC patients, even those with early stage disease, than in healthy controls, and were significantly down-regulated after surgical resection of tumors. These miRNAs were also secreted at significantly higher levels by colon cancer cell lines than by a normal colon-derived cell line. The high sensitivities of the seven selected exosomal miRNAs were confirmed by a receiver operating characteristic analysis. CONCLUSION: Exosomal miRNA signatures appear to mirror pathological changes of CRC patients and several miRNAs are promising biomarkers for non-invasive diagnosis of the disease.

Gene expression signature-based prognostic risk score in patients with glioblastoma.

The present study aimed to identify genes associated with patient survival to improve our understanding of the underlying biology of gliomas. We investigated whether the expression of genes selected using random survival forests models could be used to define glioma subgroups more objectively than standard pathology. The RNA from 32 non-treated grade 4 gliomas were analyzed using the GeneChip Human Genome U133 Plus 2.0 Expression array (which contains approximately 47 000 genes). Twenty-five genes whose expressions were strongly and consistently related to patient survival were identified. The prognosis prediction score of these genes was most significant among several variables and survival analyses. The prognosis prediction score of three genes and age classifiers also revealed a strong prognostic value among grade 4 gliomas. These results were validated in an independent samples set (n = 488). Our method was effective for objectively classifying grade 4 gliomas and was a more accurate prognosis predictor than histological grading.

Hyperpnoeic response independent of limb movements at exercise onset in mice.

We have shown that constant-load treadmill exercise in mice produces an abrupt ventilatory increase to a maximal level at exercise onset. We examined what caused this abrupt response. We measured ventilation during 30-min constant-load exercise on a treadmill, below the lactate threshold, in conscious mice. Video analysis showed that hyperpnoea started before locomotion began. Incremental changes in speed did not further increase ventilation during the early phase of exercise. Next, we measured ventilatory responses to a sudden movement of the treadmill belt on which the mice were kept in a stationary position by a mesh cover. Hyperpnoea started concurrently with the sudden belt movement. In the absence of locomotion, ventilation increased to the extent reached during exercise hyperpnoea. Finally, the abrupt response showed plasticity but was attenuated by experience. The present study shows the importance of factors independent of limb movements in the hyperpnoeic response during the early phase of treadmill exercise in mice.

Dopamine D1 receptors control exercise hyperpnoea in mice.

Previously, we undertook simultaneous recording of ventilation and pulmonary gas exchange in mice and revealed that dopamine D(2) receptors participate in exercise hyperpnoea via behavioural control of ventilation with unchanged pulmonary gas exchange. Here, we examined the hypothesis that D(1) receptors also contribute to exercise hyperpnoea using a D(1) receptor antagonist (SCH 23390; SCH) that crosses the blood-brain barrier, with the same recording technique and protocol as in the previous study. The respiratory responses of mice injected with saline or SCH (50 µg (kg body weight)(-1), i.p.) were compared during constant-load exercise at 6 m min(-1). Each mouse was set in an airtight treadmill chamber equipped with a differential pressure transducer and open-circuit system with a mass spectrometer. At rest, SCH-injected mice had significantly reduced respiratory frequency, minute ventilation and pulmonary gas exchange compared with saline-injected mice. Ventilation during hyperoxic gas inhalation and hypercapnic ventilatory responses between groups were similar. Abrupt increases and sequential declines to the steady-state level were produced by treadmill exercise in both groups of mice. Treatment with SCH lowered the increased levels of respiratory frequency, tidal volume and minute ventilation during the steady state, as well as reducing the O(2) uptake, CO(2) output and body temperature throughout treadmill exercise. These data suggest that D(1) receptors contribute to a resting ventilation level and exercise hyperpnoea during the steady state in parallel with metabolic changes. Notably, the metabolic control of D(1) receptors was important for maintenance of the steady state, and D(1) receptors in hypothalamic nuclei could be involved in this modulation.

Gene expression signature-based prognostic risk score in patients with primary central nervous system lymphoma.

PURPOSE: Better understanding of the underlying biology of primary central nervous system lymphomas (PCNSL) is critical for the development of early detection strategies, molecular markers, and new therapeutics. This study aimed to define genes associated with survival of patients with PCNSL. EXPERIMENTAL DESIGN: Expression profiling was conducted on 32 PCNSLs. A gene classifier was developed using the random survival forests model. On the basis of this, prognosis prediction score (PPS) using immunohistochemical analysis is also developed and validated in another data set with 43 PCNSLs. RESULTS: We identified 23 genes in which expressions were strongly and consistently related to patient survival. A PPS was developed for overall survival (OS) using a univariate Cox model. Survival analyses using the selected 23-gene classifiers revealed a prognostic value for high-dose methotrexate (HD-MTX) and HD-MTX-containing polychemotherapy regimen-treated patients. Patients predicted to have good outcomes by the PPS showed significantly longer survival than those with poor predicted outcomes (P < 0.0001). PPS using immunohistochemical analysis is also significant in test (P = 0.0004) and validation data set (P = 0.0281). The gene-based predictor was an independent prognostic factor in a multivariate model that included clinical risk stratification (P < 0.0001). Among the genes, BRCA1 protein expressions were most strongly associated with patient survival. CONCLUSION: We have identified gene expression signatures that can accurately predict survival in patients with PCNSL. These predictive genes should be useful as molecular biomarkers and they could provide novel targets for therapeutic interventions.

miR-493 induction during carcinogenesis blocks metastatic settlement of colon cancer cells in liver.

Liver metastasis is a major lethal complication associated with colon cancer, and post-intravasation steps of the metastasis are important for its clinical intervention. In order to identify inhibitory microRNAs (miRNAs) for these steps, we performed 'dropout' screens of a miRNA library in a mouse model of liver metastasis. Functional analyses showed that miR-493 and to a lesser extent miR-493(*) were capable of inhibiting liver metastasis. miR-493 inhibited retention of metastasized cells in liver parenchyma and induced their cell death. IGF1R was identified as a direct target of miR-493, and its inhibition partially phenocopied the anti-metastatic effects. High levels of miR-493 and miR-493(*), but not pri-miR-493, in primary colon cancer were inversely related to the presence of liver metastasis, and attributed to an increase of miR-493 expression during carcinogenesis. We propose that, in a subset of colon cancer, upregulation of miR-493 during carcinogenesis prevents liver metastasis via the induction of cell death of metastasized cells.