Abhik Ray-Chaudhury

IFN-α-Induced Signal Transduction, Gene Expression, and Antitumor Activity of Immune Effector Cells Are Negatively Regulated by Suppressor of Cytokine Signaling Proteins

Proteins belonging to the suppressors of cytokine signaling (SOCS) family have been shown to regulate cytokine signal transduction in various cell types but their role in modulating the response of immune cells to IFN-α has not been fully explored. We hypothesized that SOCS proteins would inhibit the antitumor activity of IFN-α-stimulated immune cells. Transcripts for SOCS1, SOCS2, SOCS3, and cytokine-inducible Src homology 2-containing protein were identified in total human PBMC (PBMCs, NK cells, and T cells) within 1–2 h of stimulation with IFN-α (103–105 U/ml). Immunoblot analysis confirmed the expression of these factors at the protein level. Transcripts for SOCS proteins were rapidly but variably induced in PBMCs from patients with metastatic melanoma following the i.v. administration of IFN-α-2b (20 million units/m2). Overexpression of SOCS1 and SOCS3, but not SOCS2, in the Jurkat T cell line inhibited IFN-α-induced phosphorylated STAT1 and the transcription of IFN-stimulated genes. Conversely, small inhibitory RNA-mediated down-regulation of SOCS1 and SOCS3 in Jurkat cells and normal T cells enhanced the transcriptional response to IFN-α. Loss of SOCS1 or SOCS3 in murine immune effectors was associated with enhanced IFN-induced phosphorylated STAT1, transcription of IFN-stimulated genes, and antitumor activity. Of note, IFN-α treatment eliminated melanoma tumors in 70% of SOCS1-deficient mice, whereas IFN-treated SOCS-competent mice all died. The antitumor effects of IFN-α in tumor-bearing SOCS1-deficient mice were markedly inhibited following depletion of CD8+ T cells. These results indicate that the antitumor response of immune effector cells to exogenous IFN-α is regulated by SOCS proteins.

Increased expression of cholesterol 24S‐hydroxylase results in disruption of glial glutamate transporter EAAT2 association with lipid rafts: a potential role in Alzheimer’s disease

J. Neurochem. (2010) 113, 978–989.

CD24 on the resident cells of the central nervous system enhances experimental autoimmune encephalomyelitis.

CD24 is a cell surface glycoprotein that is expressed on both immune cells and cells of the CNS. We have previously shown that CD24 is required for the induction of experimental autoimmune encephalomyelitis (EAE), an experimental model for the human disease multiple sclerosis (MS). The development of EAE requires CD24 expression on both T cells and non-T host cells in the CNS. To understand the role of CD24 on the resident cells in the CNS during EAE development, we created CD24 bone marrow chimeras and transgenic mice in which CD24 expression was under the control of a glial fibrillary acidic protein promotor (AstroCD24TG mice). We showed that mice lacking CD24 expression on the CNS resident cells developed a mild form of EAE; in contrast, mice with overexpression of CD24 in the CNS developed severe EAE. Compared with nontransgenic mice, the CNS of AstroCD24TG mice had higher expression of cytokine genes such as IL-17 and demyelination-associated marker P8; the CNS of AstroCD24TG mice accumulated higher numbers of Th17 and total CD4+ T cells, whereas CD4+ T cells underwent more proliferation during EAE development. Expression of CD24 in CD24-deficient astrocytes also enhanced their costimulatory activity to myelin oligodendrocyte glycoprotein-specific, TCR-transgenic 2D2 T cells. Thus, CD24 on the resident cells in the CNS enhances EAE development via costimulation of encephalitogenic T cells. Because CD24 is increased drastically on resident cells in the CNS during EAE, our data have important implications for CD24-targeted therapy of MS.

Limits of 8-Tesla magnetic resonance imaging spatial resolution of the deoxygenated cerebral microvasculature.

To quantify the minimum magnetic resonance imaging (MRI) spatial resolution of the visible deoxygenated microscopic vessels of the human brain at 8 T.

Evidence of polyclonality in neurofibromatosis type 2-associated multilobulated vestibular schwannomas.

BACKGROUND Neurofibromatosis type 2 (NF2) is a tumor syndrome that results from mutation of the NF2 tumor suppressor gene. The hallmark of NF2 is the presence of bilateral vestibular schwannoma (VS). Though NF2-associated and sporadic VS share identical histopathologic findings and cytogenetic alterations, NF2-associated VS often appears multilobulated, is less responsive to radiosurgery, and has worse surgical outcomes. Temporal bone autopsy specimens and MRI of the inner ear performed on NF2 patients suggest that multiple discrete tumors may be present within the labyrinth and cerebellopontine angle. METHODS Treatment-naïve ears in patients enrolled in a prospective NF2 natural history study (NIH#08-N-0044) were included for MRI analysis. T2-weighted and postcontrast T1-weighted MRIs were evaluated for the presence of multiple discrete tumors or a multilobulated mass. Peripheral blood (germline) and regional samples of tumor tissue were procured from consecutive patients enrolled in this study undergoing resection of a multilobulated VS (MVS). Histopathologic evaluation and genetic analysis (single nucleotide polymorphism array analysis, NF2 sequencing) were performed on each specimen. RESULTS Over half of NF2 ears harbored either an MVS (60/139 ears) or multiple discrete masses (19/139 ears). For 4 successive MVSs, genetic analysis revealed an admixture of cell populations, each with its own somatic NF2 mutation or deletion. CONCLUSIONS These findings suggest that the majority of NF2-associated VSs are polyclonal, such that the tumor mass represents a collision of multiple, distinct tumor clones. This explains the characteristic lobulated gross appearance of NF2-associated VS, and may also explain the substantially different treatment outcomes compared with sporadic VS.

PP2A inhibition with LB100 enhances cisplatin cytotoxicity and overcomes cisplatin resistance in medulloblastoma cells.

The protein phosphatase 2A (PP2A) inhibitor, LB100, has been shown in pre-clinical studies to be an effective chemo- and radio-sensitizer for treatment of various cancers. We investigated effects associated with LB100 treatment alone and in combination with cisplatin for medulloblastoma (MB) in vitro and in vivo in an intracranial xenograft model. We demonstrated that LB100 had a potent effect on MB cells. By itself, LB100 inhibited proliferation and induced significant apoptosis in a range of pediatric MB cell lines. It also attenuated MB cell migration, a pre-requirement for invasion. When used in combination, LB100 enhanced cisplatin-mediated cytotoxic effects. Cell viability in the presence of 1 uM cisplatin alone was 61% (DAOY), 100% (D341), and 58% (D283), but decreased with the addition of 2 μM of LB100 to 26% (DAOY), 67% (D341), and 27% (D283), (p < 0.005). LB100 suppressed phosphorylation of the STAT3 protein and several STAT3 downstream targets. Also, LB100 directly increased cisplatin uptake and overcame cisplatin-resistance in vitro. Finally, LB100 exhibited potent in vivo anti-neoplastic activity in combination with cisplatin in an intracranial xenograft model.

Hemangioblastoma of the Cerebellopontine Angle

Tumors of the cerebellopontine angle (CPA) constitute 6% to 10% of all intracranial neoplasms. Most are vestibular schwannomas (VSs) and meningiomas, but as many as 1 in 5 CPA lesions are of other etiologies. 1,2 Hemangioblastomas (HMBs), which are highly vascular tumors of the central nervous system, represent up to 12% of infratentorial, intracranial tumors in adults and typically arise in the cerebellum, spinal cord, and brain-stem. 3 One in 4 HMBs is associated with von Hippel Lindau (VHL) disease. 4 A cerebellar HMB is found in 44% to 72% of patients with VHL disease 5 ; however, involvement of the CPA is uncommon. When present within the CPA, HMBs may mimic VSs because the 2 entities have similar magnetic resonance imaging (MRI) characteristics. Cystic changes are seen in 70% to 75% of all HMBs. 6,7 We report our experience with a large CPA HMB, which was initially thought to be an atypical cystic VS. Clinical and histologic findings of HMBs are discussed along with the potential for hearing preservation surgery when these lesions occur in the CPA.

Extradural dermoid tumor of the petrous apex

Dermoid cysts are rare, benign, congenital tumors. Most case series thus far have featured intradural tumors. The authors report on a case of an extradural dermoid tumor of the middle cranial fossa with osseous invasion, successfully removed using a left subtemporal extradural approach. The clinical presentation, histological features, radiological findings, and management of this unique case are described.

Spinal Myxopapillary Ependymoma Metastatic to Bilateral Internal Auditory Canals

Objectives We report a rare case of spinal myxopapillary ependymoma metastatic to both internal auditory canals (IACs) and its implications for diagnosing neurofibromatosis type 2 (NF2). Methods We present a detailed clinical history, magnetic resonance imaging (MRI), intraoperative photographs, and histopathologic findings from a patient with bilateral IAC lesions, and review the diagnostic criteria for NF2. Results An 11-year-old boy with surgically resected spinal myxopapillary ependymoma, treated with total spine irradiation for recurrence, later showed bilaterally enhancing IAC lesions on T1-weighted MRI with contrast. The diagnosis of NF2 with bilateral vestibular schwannomas was entertained. Close examination of T2-weighted MRI, however, demonstrated the masses to be isointense to cerebrospinal fluid. This finding raised the possibility of other, more unusual IAC lesions. The patient underwent sequential suboccipital craniotomies for tissue diagnosis, and both IAC lesions were found to be myxopapillary ependymomas. Conclusions This is the youngest reported patient with metastatic myxopapillary ependymoma. Although vestibular schwannomas account for the majority of contrast-enhancing T1-weighted IAC lesions, other uncommon lesions may present in a similar manner. A T2 fast-spin echo screening MRI would have missed this patients lesions. Therefore, both T1-weighted MRI with or without contrast and T2-weighted MRI may be necessary to distinguish vestibular schwannoma from other, more unusual IAC lesions.

Method for Novel Anti-Cancer Drug Development using Tumor Explants of Surgical Specimens

The current therapies for malignant glioma have only palliative effect. For therapeutic development, one hurdle is the discrepancy of efficacy determined by current drug efficacy tests and the efficacy on patients. Thus, novel and reliable methods for evaluating drug efficacy are warranted in pre-clinical phase. In vitro culture of tumor tissues, including cell lines, has substantial phenotypic, genetic, and epigenetic alterations of cancer cells caused by artificial environment of cell culture, which may not reflect the biology of original tumors in situ. Xenograft models with the immunodeficient mice also have limitations, i.e., the lack of immune system and interspecies genetic and epigenetic discrepancies in microenvironment. Here, we demonstrate a novel method using the surgical specimens of malignant glioma as undissociated tumor blocks to evaluate treatment effects. To validate this method, data with the current first-line chemotherapeutic agent, temozolomide (TMZ), are described. We used the freshly-removed surgical specimen of malignant glioma for our experiments. We performed intratumoral injection of TMZ or other drug candidates, followed by incubation and analysis on surgical specimens. Here, we sought to establish a tumor tissue explant method as a platform to determine the efficacy of novel anti-cancer therapies so that we may be able to overcome, at least, some of the current limitations and fill the existing gap between the current experimental data and the efficacy on an actual patients tumor. This method may have the potential to accelerate identifying novel chemotherapeutic agents for solid cancer treatment.