Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

1,072 records · Page 60Linked to original sources

PubMedDate not supplied

Effects of hyperthermia on natural killer cells: inhibition of lytic function and microtubule organization.

Cells with natural killer activity (NK) may play an important role in host defence against tumour cells. The lytic function of NK cells is very sensitive to hyperthermic inactivation. However, cells with NK activity isolated from rat spleen and exposed to 41-42.5 degrees C for 30 min could partially recover their cytotoxic activity after incubation at 37 degrees C. The recovered cytotoxicity was still NK-specific, as it only resulted in the lysis of YAC-1 sensitive targets, and could not lyse NK-resistant P815 mastocytoma cells. Conjugate formation assay using NK cells labelled with specific monoclonal antibody (mAb) 3.2.3 indicated that the binding of NK cells to targets was not significantly affected by heat treatment. Compared to controls, however, microtubule organizing centre (MTOC) reorientation towards the region of intercellular contact was reduced by 40% in heated effector cells. This was accompanied by a greater inhibition (62-77%) of NK lytic activity. Kinetic analysis indicated that MTOC reorientation capacity recovered following incubation at 37 degrees C. MTOC recovery was maximal 4 h after treatment whereas that of lytic activity peaked at 6 h. These data indicate that NK cells recover NK-specific lytic activity after heat inactivation. Moreover, our study demonstrates that hyperthermia interferes with post-binding MTOC reorientation, and further supports a role for microtubule in secretory processes involved in NK-mediated cytolysis.

Animals↗

PubMedDate not supplied

Cisplatin, hyperthermia and radiation treatment in human cisplatin-sensitive and resistant glioma cell lines.

In this study, the effects of mild protracted hyperthermia, combined with prolonged exposure to cisplatin and low dose-rate irradiation (LDRI), were examined in two human cell lines. The cell lines are human glioma parental and cisplatin-resistant variant cells. The results show that mild hyperthermia at 40 degrees C was able to sensitize both the parental and the variant cisplatin-resistant cells to cisplatin treatments (1 microgram/ml for up to 20 h) when the two treatments were given concurrently. When mild hyperthermia and cisplatin were given with LDRI concurrently, additional enhanced cell killing was observed in both the parental and the cisplatin-resistant variant cells. Further analysis of the results showed that when the effects of the trimodality treatment were normalized to the effects of the combined treatment of mild hyperthermia with cisplatin, the residual cell killing was still greater than that observed for radiation alone, indicating a synergistic interaction. This synergistic interaction was greater for the parental line compared to the cisplatin-resistant line. Thus, these data show that the concurrent application of mild hyperthermia, low concentration, long duration, cisplatin and low-dose rate irradiation may be an effective form of treatment in both normally responding and cisplatin-resistant variant human tumour cell lines.

Brain Neoplasms↗

PubMedDate not supplied

Regulation of signal transduction activity in normal and cancer cells.

UNLABELLED: The purpose of this investigation is to clarify critical aspects of the behavior and regulation of signal transduction activity in normal and cancer cells. MATERIALS AND METHODS: Signal transduction activity was determined by measuring the steady-state activity of the three synthetic enzymes involved in the conversion of 1-phosphatidylinositol to IP3, PI 4-kinase, PI 4-phosphate 5-kinase and phospholipase C. These enzymic activities were opposed by the activities of the degradative enzymes, 4-phosphatase and 5-phosphatase. RESULTS: We observed in hepatocellular carcinomas the operation of an integrated imbalance in signal transduction which was manifested in the up-regulation of the steady-state activities of the three synthetic enzymes and in the reduction of the activities of the two catabolic phosphatases. As a consequence of this enzyme imbalance there was an increase in the concentration of IP3 in hepatomas. Increased IP3 levels were also observed in numerous human carcinomas in clinical samples and in tissue culture cells. The signal transduction activity was subject to nutritional regulation and to drug action. The elevated signal transduction activity, as measured by the IP3 concentration, was down-regulated in a time- and dose-dependent fashion by the anticancer drug, tiazofurin, by the flavonoids, quercetin and genistein, and by the anti-estrogen receptor, tamoxifen. CONCLUSIONS: Our studies show that signal transduction activity is stringently linked with transformation and progression in rat and human carcinomas. Down-regulation of signal transduction activity by various drugs led to a marked reduction of IP3 concentration and then to apoptosis and induced differentiation.

Animals↗

PubMedDate not supplied

The genetic background of inflammatory bowel disease.

Available evidence indicates that genetic factors are essential in providing the susceptibility to the majority of the various forms of inflammatory bowel disease occurring in man. It is also clear that the genetic susceptibility to these diseases is complex, and that more than one gene may predispose (the concept of multilocus/oligogenic inheritance), and likely in different etiologic combinations (the concept of genetic heterogeneity). Paradigms are now available that should lead to the identification of a number of these predisposing genes. These paradigms include the candidate gene approach, systematic genome wide scans, and mouse human synteny. While genome wide scans are currently limited to multiplex family linkage studies, both candidate genes and mouse human synteny can be approached in either linkage or association paradigms. Eventually whole genome association studies will be available as well. Identification of inflammatory bowel disease predisposing genes should lead to their incorporation in studies of natural history, investigation of environmental risk factors, and especially utilization of genetic markers in clinical trials. This will allow us to identify the best therapy available for the individual patient based on their unique genetic constitution. With advances in molecular technology, the search for genes influencing traits and diseases with a complex genetic background, such as the inflammatory bowel diseases, has become a realistic task. Although exogenous or infectious agents may contribute to the pathogenesis or may trigger the onset of disease, and the immune system almost certainly mediates the tissue damage, it is clear from available data that genetic factors determine the susceptibility of a given individual to inflammatory bowel disease (reviewed below). Thus, genetic studies are essential for the delineation of the basic etiologies of the various forms of inflammatory bowel disease and thus can aid in the development of radically new and specific therapies. In this review, we will discuss the importance and complexity of genetic factors in inflammatory bowel disease, methods and problems in the genetic dissection of complex traits, and future directions of genetic studies in inflammatory bowel disease.

Animals↗

PubMedDate not supplied

Amplified increase in signal transduction activity in cancer cells.

AIM: To elucidate the behavior of 1 phosphatidylinositol 4,5 bisphosphate (PIP2) 5 phosphatase (PIP2 5-Pase, EC 3.1.3.36) and 1 phosphatidylinositol 4 phosphate (PIP) 4-phosphatase (PIP 4-Pase) in cancer cells, the steady state activities of PIP2 5-Pase and PIP 4-Pase were determined in the particulate fractions of rat liver and in a spectrum of rat hepatomas of different growth rates and malignancy. METHODS: A standard method was developed using exogenous PIP2 or PIP as substrates. RESULTS AND DISCUSSION: One half of the maximum activities was reached at about 0.3 mM of the substrates and at 0.1 to 0.2 mM magnesium chloride. The optimum concentrations of Triton X-100 and cetyltrimethyl ammonium bromide were 0.25% (w/v) and 1 mM, respectively. PIP2 5-Pase and PIP 4-Pase activities were linear with time for 20 min and proportional with protein concentrations up to 22 micrograms per 50 microliters reaction mixture. In rat liver the steady state activities of PIP2 5-Pase and PIP 4-Pase were 1849 to 1881 and 1394 to 1670 nmol/h/mg protein. In three rat hepatomas the enzyme activities decreased to 50-51% and 33-42%, respectively. These results and our earlier data showing increased 1 phosphatidylinositol 4 kinase (EC 2.7.1.67), PIP 5-kinase (EC 2.7.1.68) and phospholipase C, PIP2 phosphodiesterase (EC 3.1.4.11) activities provide evidence of a transformation linked amplified increased capacity in signal transduction activity in cancer cells. The discovery and documentation of this integrated imbalance in regulation in phosphoinositide metabolism in cancer cells are in line with our observations in cancer cells for enzymes of purine and pyrimidine metabolism. The amplified increase in signal transduction capacity in cancer cells provides novel targets for the development of anticancer drugs.

Animals↗

PubMedDate not supplied

Overexpression of human reticulon 3 (hRTN3) in astrocytoma.

Neuroendocrine-specific protein (NSP) reticulons (RTN) are endoplasmic reticulum-associated protein complexes, which are localized in the endoplasmic reticulum (ER) and identified as markers for neuroendocrine differentiation. At least 4 different RTN genes have been identified in mammals, but in most cases, the functions of the encoded proteins except mammalian RTN4-A and RTN4-B are still elusive. In the present study, the expression of human reticulon 3 (hRTN3) in a variety of tissues was investigated. Northern blotting hybridization revealed higher expression of hRTN3 in normal brain and some endocrine-related organs such as thyroid relative to other non-endocrine organs. Twelve surgical specimens meeting the histological criteria for astrocytoma grade II, III and IV were investigated by in situ hybridization and immunohistochemical analysis, which demonstrated the overexpression of hRTN3 in astrocytoma tumor cells, while in non-cancerous brain tissues hRTN3 was mainly expressed in neurons and almost no signals in glia cells could be detected. The differential expression of hRTN3 between astrocytoma and non-cancerous tissue may provide insight into the progress of astrocytoma.

Aged↗

PubMedDate not supplied

Comparative analysis of natural killer function in lung, spleen, and peripheral blood lymphocytes: evidence of differential characteristics.

Organ associated as well as systemic natural killer (NK) activity play an important role in host defense. It is likely that tissue NK cells exhibit some specific characteristics resulting from their local environment. The purpose of the present study was to compare NK cell function of rat lung to that of spleen and blood in terms of magnitude of NK activity, NK cell number, and response to biological response modifiers (BRM). Lung interstitial lymphocytes (LL) were found to display significant cytotoxicity which was selective for YAC-1 tumor cells and abolished by treatment with antiasialo GM-1 serum and L-leucine methyl ester. In addition, LL were more effective than peripheral blood lymphocytes (PBL) and spleen lymphocytes (SL), although LL contained the same proportion of NK 3.2.3 positive cells than the spleen. Furthermore, the in vitro response to BRM varied both with BRM used and effector cell origin. Human recombinant interleukin 2 (rIL-2) increased NK activity of LL and PBL to a similar extent, whereas SL were more responsive to such treatment. Interferon alpha/beta (IFN-alpha/beta) increased NK activity in all three compartments with PBL being less responsive. By contrast, rat recombinant interferon gamma (rIFN-gamma) failed to augment LL or SL NK activity but did result in a significant enhancement of PBL activity. Together these data indicate that the lung contains comparable numbers of NK cells to that of spleen but which display higher specific activity. Furthermore, NK cell response to BRM vary with tissue origin, suggesting that tissue specific response may be an important determinant for the effective use of BRM.

Animals↗

PubMedDate not supplied

Increased signal transduction activity and down-regulation in human cancer cells.

The purpose of this study was to elucidate the behavior of signal transduction activity in rat and human carcinoma cells. Signal transduction activity was measured by the steady-state activity of the three enzymes involved in the conversion of 1-phosphatidylinositol (PI) to IP3, PI 4-kinase, PI 4-phosphate 5-kinase, and phospholipase C activities were measured by our methods. The results indicate that the steady-state activities of the three signal transduction enzymes and the end-product, IP3, were up-regulated in a transformation- and progression-linked fashion. In rat liver PI kinase, PIP kinase and PLC activities were 0.4, O.04, and 800 nmol/hour/mg protein, respectively. PI and PIP kinase and PLC activities were increased 2- to 8-fold in five rat hepatomas and 29-, 45-, and 4-fold, respectively, in rapidly growing hepatoma 3924A. PI and PIP kinase activities as compared to normal ovary were elevated in human ovarian epithelial carcinomas (4- and 3-fold) and in OVCAR-5 cells in culture (31- and 11-fold). Compared to normal breast parenchymal cells, PI and PIP kinase activities were increased in human breast carcinoma cells (96- and 16-fold). When breast carcinoma cells were plated and expressed their neoplastic proliferative program. IP3 concentration increased 20-fold in early log phase: PI and PIP kinase activities increased 11-fold in mid log phase: PLC activity did not change throughout. PI and PIP kinase activities in bone marrow had short half-lives (t1/2 = 8 minutes) but PLC had a long one (t1/2 > 6 hours). The elevated signal transduction activity was down-regulated by the anti-cancer drug, tiazofurin, and also by quercetin, an inhibitor of PI kinase. The addition of these drugs to cultured carcinoma cells reduced the IP3 concentration, and the cells were killed. These integrated studies are the first showing that signal transduction activity is stringently linked with transformation and progression in rat and human solid tumors and carcinoma cells. Down-regulation (by tiazofurin) or inhibition of PI and PIP kinase activities (by quercetin) in human carcinoma cells led to a marked reduction of IP3 concentration and to cell death. Tiazofurin and quercetin may be useful in the treatment of carcinomas with increased signal transduction capacity.

1-Phosphatidylinositol 4-Kinase↗

PubMedDate not supplied

Phospholipase C (EC 3.1.4.11): a malignancy linked signal transduction enzyme.

AIM: To elucidate the relationship between phospholipase C, phosphatidylinositol-4,5-bisphosphate (PIP2) phosphodiesterase, EC 3.1.4.11 (PLC) and transformation, progression and proliferation, steady-state activity was determined in a spectrum of transplantable solid rat hepatomas of different growth rates, and in a variety of normal rat organs. METHODS: To measure PLC activity in the plasma membrane fraction a standard isotopic method was developed using exogenous PIP2 as substrate. PLC activity was linear with time for 2.5 min and proportional with protein concentrations over a range of 5 to 29 micrograms per 50 microliters reaction mixture. RESULTS: The apparent K(m) for PIP2 was 0.3 mM in both normal liver and rapidly growing hepatoma 3924A. PLC activity in adult rat liver was 747 and 986 nmol/h/mg protein; it increased 1.7- to 2.1-fold in hepatomas of slow and intermediate growth rates and 3.7-fold in rapidly growing hepatoma 3924A. By contrast, no significant difference was observed between 24 hours regenerating and sham-operated livers. PLC activity was high in thymus, spleen, testis, bone marrow, lung, brain, heart and renal cortex, but in the same range in skeletal muscle and liver. PLC has a relatively long half-life as there were no significant changes in PLC specific activity in bone marrow during the 9 hour period after intraperitoneal injection of the protein biosynthetic inhibitor, cycloheximide. PLC was subject to nutritional regulation because at 3 days' starvation the specific activity in rat bone marrow decreased to 78% of control values and recovered after 1-day refeeding. CONCLUSION: The results indicate that PLC is a transformation- and progression-linked signal transduction enzyme. This work and recent studies showing increased 1-phosphatidylinositol 4-kinase (EC 2.7.1.67) and 1-phosphatidylinositol 4-phosphate-5-kinase (EC 2. 7. 1. 68) provide evidence of a gain in function for a markedly elevated capacity of signal transduction sequence in transplantable rat hepatomas of different growth rates. Inhibition of the activities of kinases and PLC may provide sensitive targets for selective cancer therapy by down-regulating the up-regulated signal transduction cascade.

Animals↗

PubMedDate not supplied

Evaluation of apoptosis in four human tumour cell lines with differing sensitivities to cisplatin.

Four human tumour cell lines were evaluated for their ability to undergo apoptosis when subjected to cisplatin or hyperthermia treatment. In an ovarian carcinoma line (A2780s) and its derivative cisplatin resistant line (A2780cp) the variation in response was expressed for both the colony survival endpoint and the apoptosis endpoint. Apoptosis was measured by the number of floating cells, DNA agarose gels, and electron microscopy. In fact, cisplatin resistance was expressed to a higher level for apoptosis, than colony survival in the A2780cp cell line compared to the A2780s line. The melanoma cell line (Sk Mel-3) also showed induced apoptosis by cisplatin treatment while the glioma line (U87MG) showed little to no apoptosis in response to cisplatin treatment. Hyperthermia (43 degrees C for 1 hour) induced apoptosis in the human melanoma cell line but not in the glioma cell line. These data indicate that, while both cisplatin and hyperthermia can induce apoptosis in human tumour cell lines, the degree of induction is highly cell line dependent.

Antineoplastic Agents↗