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Parthaprasad Chattopadhyay

Publications and source records attributed to Parthaprasad Chattopadhyay.

9 recordsLinked to original sources
PubMed2006

Identification and functional characterization of a novel unspliced transcript variant of HIC-1 in human cancer cells exposed to adverse growth conditions.

The wild-type p53 gene has been widely implicated in the regulation of hypermethylated in cancer-1 (HIC-1) transcription, a master growth regulatory gene with multiple promoters and, consequently, multiple alternatively spliced transcripts. We investigated the role of p53 (wild type and mutant, both endogenous and exogenous) in modulating the various HIC-1 transcripts. We discovered a novel unspliced HIC-1 transcript, identified as "f" in leukocytes and in the human cell lines U87MG (wild-type p53), U373MG (mutant p53), MCF-7 (wild-type p53), HeLa (p53 degraded by HPV18-E6 oncoprotein), and Saos-2 (p53 null). This transcript is initiated from a new transcription start site and has an intervening stop codon that would result in a possibly truncated 22-amino-acid polypeptide. When U87MG (wild-type p53) and MCF-7 cells (wild-type p53) were exposed to adverse growth conditions of serum starvation or treated with the chemotherapeutic agent cisplatin, cells underwent apoptosis and cell cycle arrest accompanied by increase in p53 and HIC-1 transcript levels. Although the increase of the HIC-1-spliced transcripts followed the increase of p53, increase in f transcript coincided with declining p53 and HIC-1 transcript and protein levels. Moreover, the levels of HIC-1 f transcript were not induced by exogenously transfected wild-type p53 in p53-mutated U373MG and p53-null Saos-2 cells, unlike the spliced transcripts that code for full-length HIC-1 protein. These findings suggest a working model wherein the status of f transcript, which is not under direct transcriptional control of wild-type p53, may influence the level of HIC-1 protein in cancer cells.

Amino Acid Sequence↗
PubMed2006

Modulation of CR1 transcript in systemic lupus erythematosus (SLE) by IFN-gamma and immune complex.

Reduced expression of Erythrocyte Complement Receptor 1 (E-CR1) is envisaged to contribute significantly to the pathophysiology of systemic lupus erythematosus (SLE). We determined the levels of CR1 transcript in the neutrophils from 25 untreated patients with active SLE and 25 normal healthy individuals and, studied the effect of interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and immune complexes (IC) on the same. The study revealed a marked decline in the levels of neutrophil CR1 (N-CR1) transcript in the patients with SLE, and differential pattern of IFN-gamma and IL-4 expression in the neutrophils from normals and patients. Opsonized immune complexes down regulated CR1 transcript in patients and IFN-gamma up regulated the same both in normals and patients. Immune complexes suppressed this effect of IFN-gamma. IL-4 also suppressed the effect of IFN-gamma but effect confined only to the normals. This is the first real-time RT-PCR data comparing the neutrophil CR1 expression in normals and patients with SLE and its modulation by IFN-gamma, IL-4 and immune complexes. IFN-gamma and immune complexes, respectively, emerged as the positive and negative modulators of neutrophil CR1 transcript in SLE.

Adult↗
PubMed2005

Inter-alu PCR detects high frequency of genetic alterations in glioma cells exposed to sub-lethal cisplatin.

Increased genomic instability contributes to higher frequency of secondary drug resistance and neoplastic progression in tumors as well as in cells exposed to sub-lethal concentrations of chemotherapeutic agents. We have used PCR based DNA fingerprinting techniques of randomly amplified polymorphic DNA (RAPD) and inter-alu PCR to study this phenomenon in the tumor genome. The choice of the primer, either random (for RAPD) or specific (inter-alu PCR) can determine the nature of alterations being assessed. We have compared the inter-alu PCR and RAPD profiles of U87MG glioblastoma cells exposed to sequentially increasing low doses of cisplatin for 24 passages to that of untreated controls. Inter-alu PCR, with 2 primers, demonstrated a number of alterations in the treated cells, in the form of loss / gain and changes in the intensity of bands. No changes were observed by RAPD analysis with 5 primers, however, indicating a preferential increase in the alu mediated recombination frequency in the treated cells (p = 1.866 x 10(-4)). The number of changes observed with respect to the corresponding leucocyte DNA in the inter-alu PCR profile of 26 primary tumors (Grade II = 13; Grade IV = 13), resected before chemotherapy, for the 2 inter-alu primers was very small. We present a novel application of the inter-alu PCR in detecting alterations in long term cultured cells at low dose exposure to a chemotherapeutic agent. Our results suggest that alu mediated recombination may be important in cells exposed to sub-lethal doses of cisplatin but not in the genesis of primary glioma.

Alu Elements↗
PubMed2004

Increased hMSH2 protein expression in glioblastoma multiforme.

hMSH2 and hMLH1 are the most commonly studied mismatch repair proteins and their absence is associated with microsatellite instability (MSI) especially in hereditary non-polyposis colorectal cancer, and also in some sporadic tumors. However, there are some tumors, namely, urothelial neoplasms and salivary gland tumors, where overexpression of the proteins has been reported, though the implications of these findings are not very clear. There is no report on the expression of these proteins in different grades of human astrocytic tumors. We have studied the expression pattern of hMSH2 and hMLHI in high (Grade IV, glioblastoma multiforme (GBM)) and low (Grade II, astrocytoma (AS)) grade primary human gliomas by immunohistochemistry. We observed that there was a significantly higher expression of hMSH2 protein in 28 GBM (mean 703.07 +/- 236.28) as compared with 27 AS (mean 307.03 +/- 204.71), p = 1.47 x 10(-8) by a two-tailed t-test of unpaired samples. However, for hMLH1 no such difference was observed, mean counts being 543.29 +/- 320.35 for 27 GBM and 505.92 +/- 342.37 for 26 AS, p = 0.67. A small proportion of tumors was observed to be immunonegative for either of the proteins in both high- and low-grade tumors. While MSI has been shown previously to be infrequent in human astrocytic tumors, the implications of the overexpression of hMSH2 in GBM are not clear.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Sensitizing glioma cells to cisplatin by abrogating the p53 response with antisense oligonucleotides.

Most gene therapy strategies related to p53 concentrate on the restoration of the activity of mutant p53, as several observations indicate that tumors and cell lines having the mutant gene are resistant to chemotherapy. However, as there is also some evidence to the contrary, we studied the relationship of the p53 status to the cellular response of glioma cells that were exposed to cisplatin. At a concentration of 2.5 microg/ml (which is about half the peak pharmacological blood level reached during chemotherapy), U373MG glioma cells, which had a mutant p53 gene, were more sensitive to the drug as compared to U87MG glioma cells (with normal p53). The U373MG cells responded with apoptosis while U87MG cells responded with a G2-M arrest. In U87MG cells, blocking the p53 response by antisense oligonucleotides also sensitized the cells to 2.5 microg/ml cisplatin, and shifted the cellular response from arrest to caspase 3-mediated apoptosis. A sensitive, p53-independent, mechanism for chemotherapy-induced apoptosis suggests that, in some cases, p53 abrogation by gene therapy or small molecule-based strategies could be a viable therapeutic strategy.

Antineoplastic Agents↗
PubMed2003

Loss of heterozygosity of a locus in the chromosomal region 17p13.3 is associated with increased cell proliferation in astrocytic tumors.

We had previously reported that loss of heterozygosity (LOH) of the D17S379 locus on 17p13.3 was significantly more frequent in high-grade gliomas (anaplastic astrocytoma, AA; glioblastoma multiforme, GBM) than in those of a low-grade diffuse astrocytoma (DA); however, this was independent of alterations at the TP53 locus, We also showed that LOH of D17S379 was associated with positive staining for p53 protein on immunohistochemistry, but LOH of the TP53 gene had no such association. In this work we show that cell proliferation as determined by MIB-1 labeling index (LI) was significantly higher in tumors with LOH of D17S379 than those with no LOH (NLOH). In accord with our previous results, p53 protein immunopositivity was also associated with increased MIB-1 LI; however, we observed no such association of LI with TP53 LOH. The results further confirm that alteration of one or more putative tumor suppressor loci at 17p13.3 is associated with increased proliferation in astrocytic tumors.

Adult↗
PubMed2003

Hydroxylamine potentiates the effect of low dose hydrogen peroxide in glioma cells independent of p53.

We had earlier shown that higher concentration of hydrogen peroxide (H(2)O(2)) induced p53-dependent apoptosis in glioma cell line with wild type p53 but had minimal effect on cells with mutated p53. Here we show a potentiating effect of hydroxylamine (HA), an inhibitor of catalase, on a nontoxic dose of H(2)O(2) in glioma cells. HA sensitized both p53 wild type and mutated glioma cells to 0.25 mM H(2)O(2). Potentiating effect of HA was independent of p53. Higher levels of reactive oxygen species (ROS) generation were observed in cells treated with HA+H(2)O(2) as compared to cells treated with each component alone in both the cell lines. Dimethyl sulfoxide (DMSO) protected cells. Cytosolic cytochrome c and activated caspase 3 were detected at 4h. The results suggest that higher levels of intracellular ROS, generated by HA+H(2)O(2) act as a molecular switch in activating a rapidly acting p53-independent mitochondrial apoptotic pathway.

Caspase 3↗
PubMed2002

p53 dependent apoptosis in glioma cell lines in response to hydrogen peroxide induced oxidative stress.

Generation of reactive oxygen species (ROS) is an important mode of action of many chemotherapeutic agents. Hydrogen peroxide (H(2)O(2)) is a model oxidant that has been used to study the response of cells to oxidative stress. The role of p53 in ROS induced cell death has not been consistent and has been shown to be cell type dependent. Study of cellular and molecular parameters and mechanisms involved in H(2)O(2) induced cell death in glioma cells will contribute to the understanding of response of these cells to oxidative stress. We investigated induction of cell death by H(2)O(2), and its relation to p53 in two human glial tumor derived cell lines U87MG (wild type p53) and U373MG (mutated p53). We observed that H(2)O(2) was able to induce apoptosis (as shown by morphology, flow cytometry and DNA fragmentation studies) in U87MG in a dose dependent manner. Dimethyl sulfoxide (DMSO), a known ROS scavenger, was protective to the cells. H(2)O(2) induced cell death was significantly reduced by antisense p53 oligonucleotide. Pretreatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of the redox sensitive transcription factor NF-kappa B, abrogated the increased expression of p53 protein in response to H(2)O(2), and enhanced cell survival. The U373MG cell line, having mutated p53, was comparatively resistant to H(2)O(2) induced cell death. We conclude from the study that p53, activated by NF-kappa B, is essential for H(2)O(2) induced apoptosis in glioma cells.

Antioxidants↗