Ryan Y Kim

University of California, San Diego, San Diego, California, United States

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Publications (22)48.43 Total impact

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    ABSTRACT: Analysis of extracellular vesicles (EVs) derived from plasma or cerebrospinal fluid (CSF) has emerged as a promising biomarker platform for therapeutic monitoring in glioblastoma patients. However, the contents of the various subpopulations of EVs in these clinical specimens remain poorly defined. Here we characterize the relative abundance of miRNA species in EVs derived from the serum and cerebrospinal fluid of glioblastoma patients. EVs were isolated from glioblastoma cell lines as well as the plasma and CSF of glioblastoma patients. The microvesicle subpopulation was isolated by pelleting at 10,000×g for 30 min after cellular debris was cleared by a 2000×g (20 min) spin. The exosome subpopulation was isolated by pelleting the microvesicle supernatant at 120,000×g (120 min). qRT-PCR was performed to examine the distribution of miR-21, miR-103, miR-24, and miR-125. Global miRNA profiling was performed in select glioblastoma CSF samples. In plasma and cell line derived EVs, the relative abundance of miRNAs in exosome and microvesicles were highly variable. In some specimens, the majority of the miRNA species were found in exosomes while in other, they were found in microvesicles. In contrast, CSF exosomes were enriched for miRNAs relative to CSF microvesicles. In CSF, there is an average of one molecule of miRNA per 150-25,000 EVs. Most EVs derived from clinical biofluids are devoid of miRNA content. The relative distribution of miRNA species in plasma exosomes or microvesicles is unpredictable. In contrast, CSF exosomes are the major EV compartment that harbor miRNAs.
    Journal of Neuro-Oncology 04/2015; DOI:10.1007/s11060-015-1784-3 · 2.79 Impact Factor
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    ABSTRACT: Glioblastoma cells secrete extra-cellular vesicles (EVs) containing microRNAs (miRNAs). Analysis of these EV miRNAs in the bio-fluids of afflicted patients represents a potential platform for biomarker development. However, the analytic algorithm for quantitative assessment of EV miRNA remains under-developed. Here, we demonstrate that the reference transcripts commonly used for quantitative PCR (including GAPDH, 18S rRNA, and hsa-miR-103) were unreliable for assessing EV miRNA. In this context, we quantitated EV miRNA in absolute terms and normalized this value to the input EV number. Using this method, we examined the abundance of miR-21, a highly over-expressed miRNA in glioblastomas, in EVs. In a panel of glioblastoma cell lines, the cellular levels of miR-21 correlated with EV miR-21 levels (p<0.05), suggesting that glioblastoma cells actively secrete EVs containing miR-21. Consistent with this hypothesis, the CSF EV miR-21 levels of glioblastoma patients (n=13) were, on average, ten-fold higher than levels in EVs isolated from the CSF of non-oncologic patients (n=13, p<0.001). Notably, none of the glioblastoma CSF harbored EV miR-21 level below 0.25 copies per EV in this cohort. Using this cut-off value, we were able to prospectively distinguish CSF derived from glioblastoma and non-oncologic patients in an independent cohort of twenty-nine patients (Sensitivity=87%; Specificity=93%; AUC=0.91, p<0.01). Our results suggest that CSF EV miRNA analysis of miR-21 may serve as a platform for glioblastoma biomarker development.
    PLoS ONE 10/2013; 8(10):e78115. DOI:10.1371/journal.pone.0078115 · 3.53 Impact Factor
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    ABSTRACT: Recent studies suggest both normal and cancerous cells secrete vesicles into the extracellular space. These extracellular vesicles (EVs) contain materials that mirror the genetic and proteomic content of the secreting cell. The identification of cancer-specific material in EVs isolated from the biofluids (e.g., serum, cerebrospinal fluid, urine) of cancer patients suggests EVs as an attractive platform for biomarker development. It is important to recognize that the EVs derived from clinical samples are likely highly heterogeneous in make-up and arose from diverse sets of biologic processes. This article aims to review the biologic processes that give rise to various types of EVs, including exosomes, microvesicles, retrovirus like particles, and apoptotic bodies. Clinical pertinence of these EVs to neuro-oncology will also be discussed.
    Journal of Neuro-Oncology 03/2013; 113(1). DOI:10.1007/s11060-013-1084-8 · 2.79 Impact Factor
  • Brain Pathology 03/2013; 23(2):223-4. DOI:10.1111/bpa.12033 · 4.35 Impact Factor
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    ABSTRACT: Object The object of this study was to determine the tolerability and activity of lacosamide in patients with brain tumors. Methods The authors reviewed the medical records at 5 US academic medical centers with tertiary brain tumor programs, seeking all patients in whom a primary brain tumor had been diagnosed and who were taking lacosamide. Results The authors identified 70 patients with primary brain tumors and reviewed seizure frequency and toxicities. The majority of the patients had gliomas (96%). Fifty-five (78%) had partial seizures only, and 12 (17%) had generalized seizures. Most of the patients (74%) were started on lacosamide because of recurrent seizures. Forty-six patients (66%) reported a decrease in seizure frequency, and 21 patients (30%) reported stable seizures. Most of the patients (54 [77%]) placed on lacosamide did not report any toxicities. Conclusions This retrospective analysis demonstrated that lacosamide was both well tolerated and active as an add-on antiepileptic drug (AED) in patients with brain tumors. Lacosamide's novel mechanism of action will allow for concurrent use with other AEDs, as documented by its activity across many different types of AEDs used in this patient population. Larger prospective studies are warranted.
    Journal of Neurosurgery 03/2013; 118(6). DOI:10.3171/2013.1.JNS12397 · 3.15 Impact Factor
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    ABSTRACT: The discovery that tumor-derived proteins and nucleic acids can be detected in nano-sized vesicles in the plasma and cerebrospinal fluid of patients afflicted with brain tumors has expanded opportunities for biomarker and therapeutic discovery. Through delivery of their contents to surrounding cells, exosomes, microvesicles and other nano-sized extra-cellular vesicles secreted by tumors modulate their environment as to promote tumor growth and survival. In this review, we discuss the biologic processes mediated by these extra-cellular vesicles as well as their applications in terms of brain tumor diagnosis, monitoring, and therapy. We review the normal physiology of these extra-cellular vesicles, their pertinence to tumor biology, and directions for research in this field.
    Neurosurgery 12/2012; DOI:10.1227/NEU.0b013e3182846e63 · 3.03 Impact Factor
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    ABSTRACT: An accurate, nonsurgical diagnostic test for brain tumors is currently unavailable, and the methods of monitoring disease progression are not fully reliable. MicroRNA profiling of biological fluids has recently emerged as a diagnostic tool for several pathologic conditions. Here we tested whether microRNA profiling of cerebrospinal fluid (CSF) enables detection of glioblastoma, discrimination between glioblastoma and metastatic brain tumors, and reflects disease activity. We determined CSF levels of several cancer-associated microRNAs for 118 patients diagnosed with different types of brain cancers and nonneoplastic neuropathologies by quantitative reverse transcription PCR analysis. The levels of miR-10b and miR-21 are found significantly increased in the CSF of patients with glioblastoma and brain metastasis of breast and lung cancer, compared with tumors in remission and a variety of nonneoplastic conditions. Members of the miR-200 family are highly elevated in the CSF of patients with brain metastases but not with any other pathologic conditions, allowing discrimination between glioblastoma and metastatic brain tumors. Quantification of as few as 7 microRNAs in CSF enables differential recognition of glioblastoma and metastatic brain cancer using computational machine learning tools (Support Vector Machine) with high accuracy (91%-99%) on a test set of samples. Furthermore, we show that disease activity and treatment response can be monitored by longitudinal microRNA profiles in the CSF of glioblastoma and non-small cell lung carcinoma patients. This study demonstrates that microRNA-based detection of brain malignancies can be reliably performed and that microRNAs in CSF can serve as biomarkers of treatment response in brain cancers.
    Neuro-Oncology 04/2012; 14(6):689-700. DOI:10.1093/neuonc/nos074 · 5.29 Impact Factor
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    ABSTRACT: With advances in genomic profiling and sequencing technology, we are beginning to understand the landscape of the genetic events that accumulated during the neoplastic process. The insights gleamed from these genomic profiling studies with regards to glioblastoma etiology has been particularly satisfying because it cemented the clinical pertinence of major concepts in cancer biology-concepts developed over the past three decades. This article will review how the glioblastoma genomic data set serves as an illustrative platform for the concepts put forward by Hanahan and Weinberg on the cancer phenotype. The picture emerging suggests that most glioblastomas evolve along a multitude of pathways rather than a single defined pathway. In this context, the article will further provide a discussion of the subtypes of glioblastoma as they relate to key principles of developmental neurobiology.
    Journal of Neuro-Oncology 03/2012; 107(1):1-12. DOI:10.1007/s11060-011-0714-2 · 2.79 Impact Factor
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    ABSTRACT: Paragangliomas are rare neuroendocrine tumors of neural crest origin. They are mostly benign, however; malignant tumors with aggressive behavior and distant metastasis can also occur. Intracranial involvement is extremely rare and has been sporadically reported in the literature. Here we report a case who presented with progressive neurologic deficits due to multiple intracranial lesions found to be metastasis from an occult retroperitoneal malignant paraganglioma.
    Neurological Sciences 12/2011; 33(5):1183-4. DOI:10.1007/s10072-011-0879-7 · 1.50 Impact Factor
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    ABSTRACT: A 45-year-old male presented with subacute onset of a right-sided hemiparesis, right homonymous hemianopsia, and slurred speech. The brain imaging revealed two separate intraparenchymal enhancing lesions. The cerebrospinal fluid rapid plasma reagin and venereal disease research laboratory test were positive and consistent with syphilitic gumma, and the patient responded dramatically to penicillin G. Despite, currently low incidence of syphilis; CNS gummas should be in the differential of mass lesions as they are eminently treatable.
    Neurological Sciences 12/2011; 33(5):1179-81. DOI:10.1007/s10072-011-0878-8 · 1.50 Impact Factor
  • Acta neurologica Belgica 12/2011; 111(4):373. · 0.60 Impact Factor
  • Ali Mahta, Ryan Y Kim, Santosh Kesari
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    ABSTRACT: A 45-year-old man with a new diagnosis of low grade glioma was started on an escalating dose of levetiracetam (Lev) for seizure management. He gradually developed intractable nausea/vomiting and a high creatinine concentration due to acute renal failure which was attributed to Lev-induced interstitial nephritis. The medication was changed and his renal function rapidly improved to his baseline.
    Journal of Clinical Neuroscience 11/2011; 19(1):177-8. DOI:10.1016/j.jocn.2011.08.007 · 1.32 Impact Factor
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    Ali Mahta, Ryan Y Kim, Santosh Kesari
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    ABSTRACT: No abstract available.
    European Neurology 09/2011; 66(4):242. DOI:10.1159/000331770 · 1.36 Impact Factor
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    ABSTRACT: Herein, we present an adult case of medulloblastoma who received chemotherapy, radiation therapy and stem cell transplantation, and underwent multiple surgical resections for what were thought to be recurrences; however pathology confirmed a diagnosis of relapsing tumefactive lesions. This phenomenon seems to be a consequence of stem cell transplantation rather than a simple radiation treatment effect.
    Pathology & Oncology Research 09/2011; 18(2):539-43. DOI:10.1007/s12253-011-9464-x · 1.81 Impact Factor
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    ABSTRACT: A 37-year-old female presented with medically intractable complex partial seizures with secondary generalization. She was found to have a dural-based lesion with radiologic features of meningioma. A gross total resection was performed and pathology confirmed a diagnosis of cavernous angioma and she became seizure free after the surgical resection. Cavernous angioma should be considered in differential diagnosis of a dural-based lesion manifesting with refractory seizures.
    Neurological Sciences 09/2011; 33(2):441-3. DOI:10.1007/s10072-011-0764-4 · 1.50 Impact Factor
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    Journal of Gastrointestinal Cancer 08/2011; 43(S1). DOI:10.1007/s12029-011-9312-y
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    Ryan Y. Kim, Ali Mahta, Santosh Kesari
    Cancer Stem Cells - The Cutting Edge, 08/2011; , ISBN: 978-953-307-580-8
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    ABSTRACT: Central nervous system (CNS) involvement is a rare complication of chronic lymphocytic leukemia (CLL) with varied outcomes. We contribute two additional cases of CLL with CNS involvement. The clinical course and response to treatment are described. All 78 previously reported cases of CLL with CNS involvement are presented in this comprehensive review of the literature. CNS involvement of CLL is a rare complication that does not seem to correlate with any evident risk factors. Resolution of CNS symptoms can often be accomplished with intrathecal chemotherapy or irradiation. Early detection and treatment may result in better outcomes in this rare complication.
    Journal of Neuro-Oncology 07/2011; 106(1):185-200. DOI:10.1007/s11060-011-0636-z · 2.79 Impact Factor
  • Ali Mahta, Ryan Y Kim, Santosh Kesari
    Medical Oncology 06/2011; 29(2):1285-6. DOI:10.1007/s12032-011-9994-9 · 2.06 Impact Factor
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    ABSTRACT: The severity of brain tumor associated seizures often mirror the growth of the underlying tumor, and may be intractable to conventional antiepileptic drugs. We present a patient with intractable seizures in the setting of a low grade glioma who responded dramatically to temozolomide despite minimal radiographic change in tumor size. Temozolomide is an effective treatment for seizure control in patients with brain tumors.
    Epilepsy research 05/2011; 95(3):270-2. DOI:10.1016/j.eplepsyres.2011.03.018 · 2.19 Impact Factor