Biomedical subjects

Susobhan Sarkar

Publications and source records attributed to Susobhan Sarkar.

10 recordsLinked to original sources

PubMed2006

Tenascin-C stimulates glioma cell invasion through matrix metalloproteinase-12.

The capacity of glioma cells to invade extensively within the central nervous system is a major cause of the high morbidity rate of primary malignant brain tumors. Glioma cell invasion involves the attachment of tumor cells to extracellular matrix (ECM), degradation of ECM components, and subsequent penetration into adjacent brain structures. These processes are accomplished in part by matrix metalloproteinases (MMP) within a three-dimensional milieu of the brain parenchyma. As the majority of studies have used a two-dimensional monolayer culture system, we have used a three-dimensional matrix of collagen type I gel to address glioma-secreted proteases, ECM, and invasiveness of glioma cells. We show that in a three-dimensional collagen type I matrix, the presence of tenascin-C, commonly elevated in high-grade gliomas, increased the invasiveness of glioma cells. The tenascin-C-mediated invasiveness was blocked by metalloproteinase inhibitors, but this did not involve the gelatinases (MMP-2 and MMP-9) commonly implicated in two-dimensional glioma growth. A thorough analysis of 21 MMPs and six members of a disintegrin and metalloproteinase domain showed that MMP-12 was increased in gliomas by tenascin-C in three-dimensional matrix. Furthermore, examinations of resected specimens revealed high MMP-12 levels in the high-grade glioblastoma multiforme tumors. Finally, a function-blocking antibody as well as small interfering RNA to MMP-12 attenuated the tenascin-C-stimulated glioma invasion. These results identify a new factor, MMP-12, in regulating glioma invasiveness through interaction with tenascin-C.

Brain Neoplasms↗

PubMed2005

The chemokine stromal cell derived factor-1 (CXCL12) promotes glioma invasiveness through MT2-matrix metalloproteinase.

Chemokines have been found to alter tumor growth and metastasis. We have described previously that a particular chemokine receptor, CXCR4, was predominantly expressed on various glioma cell lines and in resected glioblastoma specimens. Herein, we have tested the ligand of CXCR4, stromal cell derived factor-1alpha (SDF-1alpha, CXCL12), on the response of human glioma cells. We found that SDF-1alpha increased the expression of membrane type-2 matrix metalloproteinase (MT2-MMP), but not the other MT-MMPs, MMP-2 or MMP-9. The SDF-1alpha enhanced MT2-MMP expression was blocked by a CXCR4 antagonist, AMD3100. Functional invasion assays showed that SDF-1alpha stimulated glioma cells to invade through matrigel-coated chambers and this effect was inhibited in glioma cells by the stable downregulation of MT2-MMP expression using small interfering RNA (siRNA). In vivo and at asymptomatic stages following intracerebral implant of cells, mice harboring MT2-MMP siRNA downregulated clones had smaller and less invasive tumors compared with mice implanted with non-specific siRNA control cells. Analyses at symptomatic stages demonstrate that mice with MT2-MMP siRNA clones survive longer than mice harboring control cells. These results highlight MT2-MMP as an effector of CXCR4 signaling in glioma cells, and they reveal the novel role of MT2-MMP in modulating tumor activity.

Animals↗

PubMed2005

T11TS/S-LFA3 induces apoptosis of the brain tumor cells: a new approach to characterise the apoptosis associated genetic changes by arbitrarily primed-PCR.

Genetic alterations in ethyl nitrosourea (ENU) induced brain tumor model were analysed by simple PCR based technique with arbitrary primers. T11TS/SLFA3 was established previously as a potent immune stimulator with antineoplastic property in experimental glioma model. The goal of this study was to reveal whether T11TS induces apoptosis of the neural neoplastic cell and to decipher the DNA polymorphism level of the cells undergoing apoptosis. The results clearly establish the apoptogenic role of T11TS/S-LFA3 and along with the detection of cancer associated genomic instability, AP-PCR analysis is useful for the detection of DNA level fragmentation, a unique feature of apoptosis.

Animals↗

PubMed2005

Sheep erythrocyte demonstrated better effect than IL-2 and IFN-gamma as biological response modifier against glioma in experimental model.

The significant insights into the immunobiology of central nervous system (CNS) and brain tumor have opened up the feasibility of applying 'Immunotherapy' as an alternative to the poor prognosis of malignant brain tumor with conventional therapeutic approaches. Though cytokines like IL-2 and IFN-gamma used against glioma showed some favorable results by eliciting Th1 type immune response, a proper immunotherapeutic agent is still to be searched for. Sheep erythrocyte (SRBC), a corpuscular antigen showed a better therapeutic efficacy in terms of enhanced survival and augmentation of cell mediated immunity (CMI) in a glioma model developed by chemical carcinogen ethyl nitrosourea. Histological findings revealed most efficient glioma rejection in SRBC and combination biological response modifier (BRM) treated groups. Simultaneously E-rosetting, cytotoxicity of lymphocytes, phagocytosis and antigen presenting capacity of myeloid cells established the better therapeutic efficacy of SRBC alone than other BRMs viz. IL-2 and IFN-gamma. Even the effect of combination therapy of different BRMs showed marginal differences in facilitating glioma reduction than the single use of SRBC. These findings emphasized the application of SRBC as an exogenous BRM having the potential as a rational therapeutic adjunct against glioma.

Animals↗

PubMed2004

CD2-SLFA3/T11TS interaction facilitates immune activation and glioma regression by apoptosis.

OBJECTIVE: Exogenous application of T11TS/SLFA3 in glioma model had shown the regression of tumor load through immunopotentiation. The mechanistic module of this interaction on immunological synapse formation and resulting effect in glioma regression is searched for delineating immunotherapeutic efficacy of T11TS. METHODS: After purification of T11TS/SLFA3 from sheep erythrocytes the glycoprotein was characterized by SDS-PAGE analysis and glycoprotein staining. The modulatory effect of T11TS application on glioma animals were studied by CD2 and MHC class II expression on peripheral lymphocytes, PMN, macrophages and intracranial microglia by flowcytometric analysis. Finally apoptotic killing of brain cells were studied through annevin-V expression and measuring fragmented cytoplasmic DNA by ELISA. RESULTS: Compared to healthy normal counter-parts the CD2 receptor downregulation by ENU treatment in lymphocytes and PMN were upregulated with three consecutive doses of T11TS. Splenic antigen presenting macrophages and intracranial mocroglia had shown CD2 and MHC class II modulation simultaneously in their different subtypes. These receptor studies revealed significant boosting of the immune competent cells most effectively in second dose of T11TS whereas the third dose had some regulatory effect. Sharp increase of apoptosis in brain cells was found by phosphatidylserine externalization and presence of fragmented DNA in cytoplasm with application of T11TS in consecutive doses as a result of immune potentiation. CONCLUSION: Receptor studies revealed modulation of CD2 and MHC class II, two important constituents of immunological synapse successfully help to form the TCR-p-MHC complex and provide required co-stimulation for activation. Potentiated immune effector machinery was then directed to abrogate glioma by apoptosis signifying T11TS as an immunotherapeutic probe.

Animals↗

PubMed2004

Immunotherapeutic effects of T11TS/S-LFA3 against nitrosocompound mediated neural genotoxicity.

Nitrosocompounds formed by the interaction of nitrites and secondary amines are neurotoxic in human and different rodent species. Human exposure of nitrosocompounds are widespread affected by different modes like nitrite/nitrate preserved foods, beverages like beer, formed in the stomach following uptake of the precursors nitrates, nitrites and secondary amines. The productions of alkylating metabolites during the breakdown of nitrosocompounds are the causative agents for the neurotoxic changes of the neural cells. An attempt has been made in our lab to study the effect of nitrosocompound mediated toxicity and the gradual toxic effects of these neurotoxic agents to transform the normal glial cells to a neoplastic one. The present study indicated that a transmembrane glycopeptide of sheep red blood cell (SRBC), known as S-LFA3 or T11 target structure (T11TS) applied to nitrosocompound induced animals manifesting a full grown intracranial malignancy can revert back tumor-bearing condition to the normal physiological state. Young Druckray rat of both sexes aging 3-5 days were injected with N'-N'-ethyl nitrosourea (ENU) intraperitoneally (i.p.) at a single dose of 80 mg/kg body weight to simulate nitrosocompound mediated neurotoxicity. 2-,4-, 6-, 8-, and 10-month-old neonatal ENU induced animals were sacrificed for growth kinetics, functional immunological parameters and receptor studies to hint at the changes during tumor development. In order to determine the immunomodulatory role of T11TS, 7-month-old ENU induced animals were injected with T11TS at a dose of 0.41 mg/kg body weight, in three consecutive doses at an interval of 6 days maintaining normal control as untreated control and ENU induced animals of age-matched rats as tumor-bearing control. All the immunological parameters, growth kinetic study, receptor-based study by FACS directly established the immunomodulatory, anti-toxic and anti-tumor property of T11TS/S-LFA3. Finally, formation of DNA ladder along with the FACS-based apoptosis study clearly indicated that T11TS is a potent apoptotic inducer in neoplastic neural cells.

Adjuvants, Immunologic↗

PubMed2003

Brain tumor inhibition in experimental model by restorative immunotherapy with a corpuscular antigen.

In view of the advances in our understanding of anti-tumor immune response, it is now tempting to contemplate the development of immunotherapies for malignant brain tumors, for which no effective treatment exists. Immunotherapy, with agents known as biological response modifiers (BRMs) are thus gaining increasing interest as the fourth modality of treatment. A non-specific BRM, sheep erythrocytes (SRBC) when administered (ip, 7% PCV/V, 0.5 ml) in a group of animals at the end of seventh month of ethylnitrosourea administration, resulted in significant increase in the mean survival time (> 350 days). Studies conducted for growth kinetics pattern with proliferation index and fluorochrome (HO-33342) uptake techniques at the tissue culture level exhibited a regulatory inhibition of the cells isolated from tissue excised from the tumor susceptible area of brain of SRBC treated animals. Moreover, histological examination of brain from animals showed immunomodulatory role of SRBC in experimentally induced brain tumor. Further probe into the mechanisms involving immunological investigations at the cellular level in these animals indicated an augmented and potentiated cell mediated immune response (CMI) as evidenced by enhanced spontaneous rosette forming capacity and cytotoxic activity of lymphocytes and neutrophil (PMN) mediated phagocytosis respectively. The observations suggest that SRBC down regulate malignant growth pattern of experimental brain tumors either by an immunologically enhanced killing of tumor cells and/or by directly inhibiting the tumor growth possibly via a stimulated cytokine network. Thus, a corpuscular antigen, can potentiate CMI response in experimentally induced brain tumor animal model, in which response induced in the periphery are able to mediate anti-tumor effects in the brain.

Adjuvants, Immunologic↗

PubMed2002

Preclinical Changes in Immunoreactivity and Cellular Architecture during the Progressive Development of Intracranial Neoplasms and an Immunotherapeutic Schedule with a Novel Biological Response Modifier, the T11TS / S-LFA3.

Among neoplasms, brain tumors are particularly " difficult to treat" because of the partial immune privileged status of the brain and the presence of the blood brain barrier (Selmaj, 1996). Many details of progressive development of brain tumors remain unexplored and elucidation of consequent changes of the immune system with correlated cellular architecture and cell kinetics were the major objectives of the present course of investigations. Our studies have indicated that the primary resistance by the immune system to a growing tumor declines after a certain point, resulting in an immune suppressed state in a tumor bearing individual. The poor prognosis of malignant brain tumors with classical treatments like surgery, radiotherapy and chemotherapy has led to interest in immunotherapeutic protocols. In the present study, an attempt was made to determine the immunomodulatory and antitumor properties of a transmembrane glycopeptide of sheep red blood cells (SRBCs), known as S-LFA3 or T11TS. Young Druckray rat of both sexes aged 3-5 days were injected with N'-N'-ethyl nitrosourea (ENU) (i.p) to induce brain tumors and at 2,4,6,8 and 10 months of age were sacrificed for study of survival, tumor growth kinetics and immunological parameters like lymphocyte rosette formation, denoting CD2 - CD58 interactions and phagocytosis by peripheral macrophages and PMN hint at the changes during tumore development. In order to determine the immunomodulatory role of T11TS, 7 month old ENU induced animals and controls were injected with the compound (1 ml., i.p). The data obtained indicate that administration of T11TS results in increased survival of rats along with a decrease in growth kinetics of tumor cells to the normal level when compared to ENU induced animals of the same age. Pointers to mechanisms involving immunological investigations at the cellular level in these animals indicated improved lymphocyte function in terms of E-rosetting, augmented cytotoxicity and enhanced PMN and macrophage function in terms of phagocytosis. Finally histological examination showed complete reversal from the hyperplastic state to normal cellular homeostasis, indicating antitumor efficacy of T11TS, correlating very well with the data from survival and cell kinetic studies.

Journal Article↗

PubMedDate not supplied

Evaluation of anti-tumor property of specific and non-specific BRMs in experimental gioma by assessing the microglial cell functional and phenotypic modulations.

BACKGROUND: Microglial cells are considered to be the chief immunomodulatory cells of the brain. These cells play a crucial role against various neurodegenerative diseases. When modulated microglia have been shown to exert a potential anti-tumor immune response against brain neoplasms. Although several specific BRMs like IL-2, IFNgamma have been shown to modulate the microglia to get an effective anti-tumor immune response, associated toxicities and detrimental side effects have posed severe limitation in there use particularly for therapeutic purposes. OBJECTIVES: In the present study, attempts have been made to elicit the modulations of microglia cell function and phenotypic expression following specific (IL-2, IFNgamma and a novel nonspecific BRM (corpuscular antigen) in order to determine their anti-tumor property in experimental glioma model. MATERIALS AND METHODS: Brain was experimentally induced in young Druckray rats of both sexes with N-N-ethyl nitroso urea (ENU). These ENU treated animals were administered with both specific and nonspecific BRMs like IL-2, IFNgamma and SRBC either singly or in combination 5 months after ENU administration and after ascertaining its degree of malignancy. RESULTS: Microglial cells separated from different experimental groups were found to be positive for CD11b, MHC II, CD4 and negative for GFAP.FACS analysis demonstrated that different subtypes of microglial cell populations (CD25+, MHC II+ and CD25+MHC II+) in the brain tissue based on phenotypic expression, which were downregulated in tumor bearing animals, and subsequently restored with increased expression, particularly with SRBC administration. The Scanning Electron Microscopic (SEM) study also depicted modulation of cellular morphology of microglial cell predominantly with SRBC administration. Studies conducted ton evaluate immunological functions at the cellular level showed increased antigen presenting caopacity of microglial cell with SRBC administration, which was significantly greater then IL-2, IFNgamma and combined doses (E2_S). However phagocytic functions of microglial cells were found not to be significantly modulated with BRM treatment. CONCLUSION: The results suggest that the nonspecific BRM SRBC can exert greater modulatory effect on microglila cell function and phenotypic expression than the other BRMs used, and in doing so culminate in a potent anti tumor immune response in experimental glioma with compatible tolerance profile.

Animals↗

PubMedDate not supplied

The first cross sectional survey on intracranial malignancy in Kolkata, India: reflection of the state of the art in southern West Bengal.

Recent increase in the occurrence of intracranial malignancies and poor performance of therapeutic measures have established the disease as an important concern of medical sciences. The lack of information about the disease pattern throughout India creates problems for maintaining community health for prevention. The present study on the hospital population of Kolkata was conducted to determine the incidence pattern of the disease in the population of southern West Bengal, focusing on distribution with age, sex, occupation and religion in different districts of the region, and characterizing diagnostic and therapeutic measures. Among a total of 39,509 cancer patients from 21 health centers of Kolkata, 2.4% had brain cancers and among these more than 60% are gliomas. A cross-sectional study for a period of 3 years reported the occurrence of 15 types of intracranial malignancy, which demonstrated astrocytomas (36.8%), glioblastoma multiforme (GBM) (7.9%) and meningiomas (11.6%) to be predominant. Brain tumors occur more frequently in males with few exceptions and the incidence was found to be highest among the 40-49 year old group (20.2%). No specific trend for religion and occupation was apparent. However, the district wise distribution showed maximum incidences among industrial areas, namely, Kolkata (33.1%), North 24-Parganas (18.2%), Howrah (9.3%) and Hoogly (7.6%). Diagnosis of the disease was by CT scan, MRI and histological identification (pre and post operative). Therapeutic procedures rely mainly on surgery and radiotherapy, whereas chemotherapy was used as an adjuvant for about 10% of the cases. Evaluation of the scenario regarding intracranial malignancy in this region was a long awaited requirement which should ultimately serve an important function in pointing to risk zones within the population and allow better control measures to be introduced for the disease.

Adolescent↗