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Biomedical subjects

M S Lakshmi

Publications and source records attributed to M S Lakshmi.

At least 19 recordsLinked to original sources
PubMed1999

DNA ploidy and cell cycle distribution of breast cancer aspirate cells measured by image cytometry and analyzed by artificial neural networks for their prognostic significance.

Chromosomal abnormalities are commonly associated with cancer, and their importance in the pathogenesis of the disease has been well recognized. Also recognized in recent years is the possibility that, together with chromosomal abnormalities, DNA ploidy of breast cancer aspirate cells, measured by image cytometric techniques, may correlate with prognosis of the disease. Here, we have examined the use of an artificial neural network to predict: 1) subclinical metastatic disease in the regional lymph nodes and 2) histological assessment, through the analysis of data obtained by image cytometric techniques of fine needle aspirates of breast tumors. The cellular features considered were: 1) DNA ploidy measured in terms of nuclear DNA content as well as by cell cycle distribution; 2) size of the S-phase fraction; and 3) nuclear pleomorphism. A further objective of the study was to analyze individual markers in terms of impact significance on predicting outcome in both cases. DNA ploidy, indicated by cell cycle distribution, was found markedly to influence the prediction of nodal spread of breast cancer, and nuclear pleomorphism to a lesser degree. Furthermore, a comparison between histological assessment and artificial neural network prediction shows a closer correlation between the neural approach and the development of further metastases as indicated in subsequent follow-up, than does histological assessment. These data demonstrate that artificial neural networks are capable of providing powerful and reliable indicators of possible lymph node metastasis, using measurements of cellular features alone.

Breast Neoplasms↗
PubMed1998

Heat shock modulates the expression of the metastasis associated gene MTS1 and proliferation of murine and human cancer cells.

Mts1 is a metastasis-associated gene of the S-100 gene family and codes for a Ca2+-binding protein. It is highly expressed in murine and human cancers of high invasive and metastatic potential. Recent work has shown that the mts1 protein might be involved in cell cycle regulation. An upregulation of its expression drives cells into the S phase, together with an enhanced expression of p53 phosphoprotein, which has led to the suggestion that mtsl protein might be sequestering p53 thereby abrogating the G1-S checkpoint control normally exerted by p53. Preliminary studies showed that expression of mts1 is downregulated by hyperthermia. We present evidence that in murine BL6 melanoma cells and human HUT cells that hyperthermia downregulates the mts1 gene. It is also downregulated in heat-resistant variants of the B16 melanoma and HUT cells. In parallel, there is a decrease in the size of the S phase fraction and an increase in the doubling time of cells. Cell subjected to hyperthermia show an 2- to 3.5-fold increase in the expression of HSP28 which has been shown to possess a proliferation inhibitory action. It is postulated that a complete regulatory loop involving mtsl, p53, and HSP28 might be involved in cell proliferation.

Animals↗
PubMed1998

Expression of metastasis-associated genes h-mts1 (S100A4) and nm23 in carcinoma of breast is related to disease progression.

The murine 18A2/mts1 and its human homolog h-mts1 (S100A4), encoding a Ca2+-binding protein belonging to the S-100 family, are associated with high invasive and metastatic potentials of murine tumors, human tumor cell lines in vitro, and human tumors growing as xenografts. The nm23 is a putative metastasis-suppressor gene whose expression has been found to correlate inversely with the metastatic potential of some forms of human cancer. The products of both human genes alter cytoskeletal dynamics, with antagonistic effects. In view of the equivocal association of nm23 with the metastatic potential of human cancer, we suspected that the relative expression of h-mts1 and nm23 might reflect tumor progression more accurately than either of them alone. We describe here the expression of these genes in infiltrating ductal carcinomas of the breast and show that high h-mts1 expression is associated with metastatic spread to the regional lymph nodes. The expression of nm23 on its own did not show a statistically significant inverse correlation with nodal spread. However, the expression status of the two genes, taken together, correlated strongly with the occurrence of nodal metastases. Breast cancers with no detectable expression of h-mts1 were found to be estrogen and progesterone receptor positive. Expression of h-mts1 was not related to tumor differentiation. The clinical data, together with the state of expression of steroid receptors and the expression levels of h-mts1 and nm23 genes, were analyzed using artificial neural networks for accuracy in predicting nodal spread of the carcinomas. These analyses support the conclusion that, overall, h-mts1 expression appears to be associated with and indicative of more aggressive disease. Complemented with nm23, h-mts1 could provide a powerful marker of breast cancer prognosis.

Adult↗
PubMed1994

Induction of 18A2/mts1 gene expression and its effects on metastasis and cell cycle control.

The metastasis associated 18A2/mtsI gene was inserted into the mammalian expression vector pMAMneo placing it under the control of the dexamethasone-inducible MMTV promoter. The construct was transfected into dexamethasone receptor negative F1 and receptor positive F10 cells of the B16 murine melanoma. The transferred gene was switched on in two transfectant clones of F10, by exposure to 10(-6) M dexamethasone, but not in clones of the receptor negative F1 line. One of the F10 transfectant clones (F10-192/10) was characterized further. A 13.5-fold increase in 18A2/mts1 transcripts was found in this clone upon exposure to dexamethasone. There was also a seven-fold increase in lung colonization in an experimental metastasis assay, together with increased expression of depolymerized tubulin and enhanced detection of p53 protein. The number of cells in the S phase increased by 2.5-fold following dexamethasone treatment of the clone. These data suggest a direct involvement of the 18A2/mts1 gene in lung colonization by the tumor cells. The 18A2/mts1 protein promotes tubulin depolymerization, sequesters the p53 phosphoprotein, and induces the cells to enter the S phase, but the relevance of these in the metastatic process remains to be elucidated.

Animals↗
PubMed1994

Metastasis-associated mts1 gene expression correlates with increased p53 detection in the B16 murine melanoma.

MTS1 is a metastasis-associated gene highly expressed in high-metastasis tumors. Here we show that the expression of the suppressor gene p53 protein correlates with mts1 expression. In murine melanoma B16-F1 cells, alpha-melanocyte-stimulating hormone up-regulated mts1 and increased p53 positivity in immunohistochemical tests. In B16-ML8 cells, retinoic acid reduced mts1 expression together with a reduction of p53 positivity. The variation of p53 in association with mts1 gene expression suggests that the mts1 product might interact with and stabilize p53. Taxol-induced aneuploidy increased the proportion of G0G1 phase cells, increased p53 positivity, and down-regulated mts1. This suggests that mts1 transcription may have been negatively regulated, possibly on account of the stabilization of microtubules by taxol. We postulate that the control of G1-S transition by p53 could be due to p53 sequestration by mts1, leading to microtubule depolymerization and signaling entry, into the S phase. Thus, a coordinated function of mts1 and p53 may be involved not only in uncontrolled growth but also in cytoskeletal depolymerization that could lead to cancer invasion.

Calcium-Binding Proteins↗
PubMed1994

Metastasis-associated mts1 gene expression is down-regulated by heat shock in variant cell lines of the B16 murine melanoma.

Tumour cells are more heat sensitive than corresponding normal cells but the reasons for this are poorly understood. Here we report that induction of heat shock proteins was associated with a down-regulation of the metastasis associated mts1 gene in BL6-B16 murine melanoma cells, and the heat-resistant HTG variant of the BL6 line. Melanocyte stimulating hormone, which does not affect B16 cell proliferation but upregulates mts1 expression, only marginally enhanced heat shock protein expression in F1 cells as determined by immunohistochemical methods. Retinoic acid, which inhibits cell proliferation and down-regulates the mts1 gene, reduced heat shock protein expression in the ML8-B16 variant line. This suggests that the changes in the heat shock protein expression reported here may be cell proliferation related. Heat shock proteins are known to stabilize microtubules, whereas mts1 has been implicated in their depolymerization. Taxol, which stabilizes microtubules and arrests cells at the G1 phase of the cell cycle, down-regulated mts1 gene expression in both F1 and ML8 lines. Taxol also reduced heat shock protein expression in ML8 cells. These data suggest opposing functions of heat shock proteins and the mts1 gene in microtubule polymerization, and may provide a rationale for the use of hyperthermia as a treatment for tumours.

Animals↗
PubMed1992

Image processing for cell cycle analysis and discrimination in metastatic variant cell lines of the B16 murine melanoma.

Computer-based image analysis offers a wide range of techniques which can be used to make objective and reproducible detection and measurement of subvisual features of microscopic images of cells. We describe here a prototype imaging system for specimen analysis. Using this system, studies have been carried out on the low metastasis variant F1 and high metastasis variant BL6 of the B16 murine melanoma. Cell cycle analyses have been carried out based on the measurement of integrated nuclear density, nuclear area and nucleocytoplasmic ratio of cells stained using standard procedures. It has been possible to discriminate between the two cell populations on the basis of ploidy. The two cell lines had a similar proportion of cells in the S-phase.

Animals↗
PubMed1988

Spontaneous sister chromatid exchange in metastatic variants of the murine B16 melanoma and human astrocytomas in culture.

Three metastatic variants, BL6 (high metastasis), F1 (nonmalignant) and F10 (intermediate malignancy) of the B16 murine melanoma, and a pulmonary metastatic line BL6-ML8 of the BL6 primary tumour have been examined for spontaneous sister chromatid exchange (SCE). Two human astrocytoma cell lines were also examined. SCE was encountered in 29 and 13% of second division metaphases of BL6 and F10. In contrast, only 3% of second division metaphases of the F1 showed SCE. In BL6-ML8, 40% of the metaphases showed SCE. Approximately 2-4% of the human astrocytoma second division cells showed SCE. The variant lines were karyotypically heterogeneous. The pattern of cell distribution according to chromosome number showed an overall similar profile in the melanoma variants. However, the metastatic BL6-ML lines showed a marked shift to a hypertriploid state. SCEs occurred with higher frequency in this hypertriploid subpopulation of BL6 and F10 cells than in F1. SCE incidence in the hypertriploid subpopulation was twofold higher in the metastatic line than in the primary BL6 line. The number of SCEs per chromosome was twice as high in F10, BL6 and BL6-ML8 as in the F1 cells. This hypertriploid subpopulation showed a marked increase of SCEs on exposure to mitomycin C and ethyl methane sulphonate, indicating their mutability. It is suggested that the parallelism between SCE and metastatic potential may be relevant in the context of the generation of the metastatic phenotype.

Animals↗
PubMed1985

Antigenic heterogeneity of metastasizing and nonmetastasizing forms of hamster lymphosarcoma: comparison of primary tumor and spontaneous liver metastases.

Antisera were raised in rabbits against nonmetastasizing (NML) and metastasizing (ML) forms of hamster lymphosarcoma and were purified against normal hamster tissues. Immunoglobulins from the purified antisera were precipitated with 1.6 M ammonium sulfate, radioiodinated and IgG separated by Sephadex G-200 gel filtration. 125I-IgG preparations were analyzed by a direct cell binding assay and by a complement-dependent cytotoxicity test, employing single cell suspensions from primary lymphosarcoma. In some experiments, 125I-IgG was also tested against ML cells obtained from primary tumor (1 degree) and its liver metastasis (2 degrees). NML induced greater anti-tumor antibody production than ML, suggesting greater antigenicity of the non-metastasizing tumor. The two lymphosarcomas appeared to share some common tumor-associated antigens since antibody to one tumor type was either completely or partially absorbed by tumor cells of the other type. Anti-ML 125I-IgG proved up to 2-5 times more cytotoxic for ML 1 degree than 2 degrees cells. Although both tumors were highly tumorigenic in hamsters, only ML gave rise to distant metastases, predominantly in the liver.

Animals↗
PubMed1983

Isoelectric characteristics and the secondary structure of some nucleic acids.

The isoelectric characteristics of some nucleic acid preparations from rat liver have been examined. 10S and 4S RNA species and SV-DNA were found to have isoelectric points of 5.2, 6.0-6.7, and 4.35 respectively. The molecular charge ratios (net negative charge/nucleotide) were calculated. Using SV-DNA as a standard, these isoelectric characteristics and charge ratios have been interpreted as indicating that the 10S and 4S RNAs have 35 and 56% of the molecules involved in secondary structure.

DNA, Viral↗
PubMed1983

The membrane external proteins of human astrocytomas in culture.

The cell surface proteins of some human astrocytomas have been investigated. Cell cultures were initiated from the tumours and surface proteins labelled with radioiodine in monolayer cultures. Normal glial and astrocytoma cells were found to possess a common surface protein pattern. In the molecular weight (MW) range of 225,000-75,000 daltons, the protein profile contained 6 well-defined peaks. The 195,000-dalton component (pb) was found liable to resolve into pb and a forerunning component pb'. Component pd (130,000 daltons) similarly showed resolution into subcomponents in 5 out of 9 tumours. The remaining components appeared more homogeneous in electrophoresis. There were also significant quantitative changes in the expression of the various components of the astrocytomas as compared with the normal glial cell line. Component pa was found to be reduced by greater than 70% in 7 out of 9 astrocytomas. The levels of 225,000-dalton proteins were found to be directly proportional to the survival times of the patients. Components pc appeared to be amplified by a factor of 1.6-3.5 in all the astrocytomas as compared with the normal glial line. Increased incorporation of radioiodine was also seen in 7 out of 9 tumours in components with MW of less than 75,000 daltons. The possible significance of the differential expression of the surface components is discussed. It is suggested that some of these changes, especially in component pa, may be associated with the malignant state.

Astrocytoma↗
PubMed1982

Antigenic differences between a primary hamster lymphosarcoma and its liver metastases.

An antiserum was raised in rabbits against a primary metastasizing lymphosarcoma (ML) of the hamster. This was made tumor-specific by absorption with normal hamster tissue extracts. Immunoglobulin-G was prepared and tested for its cytotoxicity towards cells derived from the primary tumor and its liver metastases. The ML-specific IgG was found to be 2--5 times more cytotoxic for cells derived from the primary tumor compared to cells obtained from liver metastases.

Animals↗
PubMed1982

The role of cell surface proteins in the induction of histogenetic differentiative responses by some human breast tumours and hamster tumors implanted into chick embryos.

Cells of human breast tumours and fibrocystic hyperplasia grown in culture, and three hamster tumours were implanted between the cell layers of 18-hour-old chick blastoderm. Their ability to induce histogenetic responses in the ectodermal and endodermal embryonic tissues was investigated. The surface proteins of these tumour cells were labelled by lactoperoxidase-catalysed radioiodination. It is shown that the ability to induce the histogenetic effects may be related to the expression of 265K (K = 10(3) daltons) and 233K proteins on the surface of human tumour cells and of 115K proteins on the hamster tumour cells. The antiproteinase, aprotinin, inhibits the induction of the histogenetic responses by and apparently also prevents the deletion of 115K proteins from the hamster tumour cells. It is therefore suggested that cell surface proteins are involved in the complex processes of interaction between embryonic and tumour cells and in the recognition by the embryonic cells of the tumour cells implanted into their midst.

Animals↗
PubMed1981

Membrane surface properties of normal and malignant cells: partition in aqueous two-polymer phase systems.

The partition of normal and malignantly transformed fibroblast lines and cell lines initiated from malignant human astrocytomas and a benign ganglioneuroma has been examined in aqueous dextran-polyethylene glycol phase system containing phosphate buffer with a low phosphate/sodium chloride ratio. The malignant astrocytomas showed a significantly lower partition coefficient as compared with the benign ganglioneuroma. Treatment of astrocytoma cells with dexamethasone caused an increase in the partitioning of the cell population. No differences were found in the partition behaviour of normal BHK-21 cells and their malignant transformants, the TRES fibrosarcoma cells. Polyoma and simian virus-transformed 3T3 fibroblasts showed partition ratios similar to the untransformed cells. Dexamethasone pre-treatment had no effect on the partition behaviour of these cells. The significance of these observations has been discussed in relation to the surface hydrophobicity and the neoplastic state.

Animals↗
PubMed1979

Differences in the surface components of normal and SV-40 transformed 3T3 mouse fibroblasts.

The differences in the surface components of 3T3 mouse fibroblasts and those transformed by Simian virus 40 have been examined using the isoelectric equilibrium method. The net negative surface charge density of the transformed cells appears to be marginally lower than that of the untransformed cell. Chemical modification studies of the surface groups have indicated that about 30% more cationic groups are present on the transformed cells, suggesting the occurrence of some additional basic material not detectable on the surface of normal cells. These basic groups show a modulation of ionisation characteristics in the presence of carboxylic groups. This may indicate a distribution of the cationic extra material in the vicinity of acidic glycoprotein components of the surface. This investigation has also revealed the occurrence of unidentified anionic groups which ionise at high pH, which appear to be thiol groups.

Anions↗