Rat fibroblasts transfected with the human 70-kDa heat shock gene exhibit altered translation and eukaryotic initiation factor 2 alpha phosphorylation following heat shock

Heat shock inhibits translation in a wide variety of cells. After heating, eukaryotic initiation factor 2-alpha (eIF-2 alpha) becomes phosphorylated which prevents the binding of Met-tRNA to the 40s ribosomal subunit inhibiting initiation of translation. Thermotolerant cells demonstrate resistance to inhibition of translation by additional heating suggesting that heat shock proteins may help to maintain translational integrity following thermal stress. Here we have examined the effects of increased intracellular levels of hsp70 protein on translation and eIF-2 alpha phosphorylation using rat fibroblasts stably transfected with a cloned human hsp70 gene. We observed a decrease in the rate of translational inhibition following heat shock in both hsp70-transfected and thermotolerant cells. Upon recovery at 37 degrees C, both hsp70-transfected and thermotolerant cells exhibit a faster rate of translational recovery. Utilizing slab gel isoelectric focusing coupled with immunoblotting we demonstrate that 45 degrees C heat shock leads to a rapid 4-5-fold increase in eIF-2 alpha phosphorylation, with little difference seen between control cells and hsp70-transfected cells. However, dephosphorylation of eIF-2 alpha occurs faster in the hsp70-transfected cells. These results suggest that hsp70 may play a role in facilitating the dephosphorylation of eIF-2 alpha as well as reversing the inhibition of translation following heat shock.

HSP 70 synthesis in clinical hyperthermia patients: preliminary results of a new technique

PURPOSE

Although thermotolerance may be an important variable in clinical hyperthermia, few means have been described to measure its effect or duration in the clinical setting. This study was undertaken to determine if heat shock protein 70 could be used as an assay to predict the presence of retained thermotolerance in human tumors.

METHODS AND MATERIALS

Tissue samples were obtained from patients undergoing hyperthermia and assayed for heat shock protein 70 synthesis. Eight patients having advanced, persistent, or recurrent malignant tumors had open-ended thermometry catheters placed into the lesion being heated. Through these catheters, tissue samples were obtained using a fine needle aspiration technique. Attempts were made to obtain samples before and after the first three heat treatments. Some samples were labeled immediately with radioactive methionine (35S) at 37 degrees C for 4-8 hr, others were given a test heat dose in vitro and then labeled. Protein synthesis profiles were analyzed by gel electrophoresis and autoradiography.

RESULTS

Preliminary results show that it is possible to obtain tissue from hyperthermia patients in a safe and practical manner, that the rate of heat shock protein 70 synthesis can be measured in a variety of tumors, and that the persistence of thermotolerance in the clinical setting can be shown by the inability to reinduce heat shock protein 70 synthesis.

CONCLUSION

The measurement of heat shock protein 70 using the described technique may provide an assay for retained thermotolerance in clinical hyperthermia. Technical difficulties which need to be addressed include obtaining sufficient tissue in all patients, confirming the presence of tumor in the obtained tissue, and obtaining tissue at more frequent intervals to best determine the kinetics of thermotolerance.

Thermal response of yeast cells overexpressing hsp70 genes

We have performed experiments to examine whether the overexpression of different members of the hsp70 family (SSA1, SSA2 and SSA4) in yeast Saccharomyces cerevisiae protects cells from thermal stress. Yeast cells were transformed with plasmids containing the SSA1 or SSA4 gene which was placed under the control of a galactose-inducible GAL1 promoter. In galactose, transformed yeast cells successfully overexpressed these hsp70 proteins at 23 degrees C, their normal growth temperature. When cell survival after heat shock at 50 or 56 degrees C was examined, our results showed that overexpression of SSA1 or SSA4 protein did not protect yeast cells against thermal stress, nor affect the cells' ability to develop thermotolerance. In contrast, thermal sensitivity was modified significantly by growing cells in galactose. Cellular survival of these cells after a 50 degrees C, 30-min heat treatment was 10(4)-fold higher than that of the same strains grown in glucose. In order to study the effects of overexpression of hsp70 on the thermal response of yeast cells independent of the carbon source, we eliminated the glucose-galactose-associated differences in thermal sensitivity by cloning the aforementioned hsp70 genes under the control of a glyceraldehyde phosphatase GAP promoter. S. cerevisiae transformed with these plasmids overexpressed the appropriate hsp70 gene in glucose as well as in galactose at 23 degrees C. Again, the overexpression of hsp70 neither protected cells from thermal stress, nor had a significant effect on the development of thermotolerance.

[Inhibitory effects of protein kinase C inhibitor and calmodulin antagonist on tumor necrosis factor production by mouse macrophages]

Mouse peritoneal macrophages were primed with calcium ionophore calcimycin 1 mumol.L-1 for 8 h and then elicited by lipopolysaccharides (LPS, 10 ng.ml-1) for 6 h to induce tumor necrosis factor (TNF), measured by crystal violet staining assay using murine fibroblast L929 cells. Protein kinase C (PKC) inhibitor, 1-(5-isoquinolinesulphonyl)-2-methylpiperazine (H-7) and calmodulin (CaM) antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) were studied on LPS-induced TNF production by macrophages. Addition of H-7 (0.31-50 micrograms.ml-1) and W-7 (10-4000 ng.ml-1) simultaneously with LPS to the culture medium suppressed LPS-induced TNF production in a concentration-dependent manner. When macrophages were pretreated with W-7 (10 ng.ml-1), LPS-induced TNF production was completely inhibited at 8 h. These results suggest that TNF production by macrophages may be dependent on the PKC and CaM.

Cellular resistance to oxidative stress is accompanied by resistance to cisplatin: the significance of increased catalase activity and total glutathione in hydrogen peroxide-resistant fibroblasts

Studies designed to better understand the involvement of cellular resistance to oxidative stress in mechanisms of cellular resistance to cisplatin were undertaken using H2O2-resistant variants of the HA1 Chinese hamster fibroblast cell line. H2O2-resistant cell lines were resistant to clonogenic inactivation mediated by cisplatin with dose modifying factors at 10% survival of 1.5-3.0, relative to HA1 cells. The most cisplatin resistant of these cell lines (OC5) also demonstrated fewer DNA-DNA crosslinks induced by cisplatin, relative to HA1. Since H2O2-resistant cells contained increased catalase activity as well as total glutathione (GSH) content, the involvement of these cellular antioxidants in the resistance to cisplatin toxicity was evaluated. Treatment of HA1 and H2O2-resistant cell lines (OC5, OC14) with 9 mM aminotriazole reduced catalase activity by 60-65% but had no effect on the cytotoxicity of cisplatin. In contrast, treatment with 5 mM buthionine sulfoximine reduced total GSH by 90% and sensitized the cells to cisplatin cytotoxicity. Furthermore, extracellular reaction of GSH with cisplatin prior to treating HA1 cells reduced the toxicity of the compound, indicating that this reaction is capable of participating in the detoxification of cisplatin. These results indicate that cellular adaptation to oxidative stress renders cells resistant to DNA damage as well as to cytotoxicity associated with cisplatin treatment. Furthermore, increases in total GSH content (but not catalase activity) appear to partially account for cisplatin resistance demonstrated by H2O2-resistant cells.

Dual control of heat shock response: involvement of a constitutive heat shock element-binding factor

Heat shock factor (HSF) has been implicated as the key regulatory protein in the heat shock response. Our studies on the response of rodent cells to heat shock or sodium arsenite indicate that a high level of HSF-DNA-binding activity, by itself, is not sufficient for the induction of hsp70 mRNA synthesis; furthermore, a high level of HSF binding is also not necessary for this induction. Analysis of the binding of protein factors to the heat shock element (HSE) in extracts of stressed rodent cells indicates that the regulation of heat shock response involves the heat-inducible HSF and a constitutive HSE-binding factor. Our results also suggest that overexpression of human hsp70 may decrease the level of heat-induced HSF-HSE-binding activity in rat cells.

Effect of amino acid analogs on the development of thermotolerance and on thermotolerant cells

Exposure of HA-1 Chinese hamster fibroblasts to amino acid analogs has been shown to have a heat-sensitizing effect as well as inducing the heat shock response (Li and Laszlo, 1985a). In this study, we have examined the effect of amino acid analogs on the development of thermotolerance after a brief heat shock or exposure to sodium arsenite and the effect of amino acid analogs on cells that are already thermotolerant. Exposure of HA-1 cells to amino acid analogs inhibited the development of thermotolerance following a mild heat shock or treatment with sodium arsenite. However, cells that were already thermotolerant were resistant to the sensitizing action of amino acid analogs. The refractoriness of thermotolerant cells to amino acid analog treatment developed in parallel with thermotolerance. The uptake of the arginine analog, canavanine, and its incorporation into proteins was not altered in the thermotolerant cells. Furthermore, another biological consequence of exposure to amino acid analogs, sensitization to ionizing radiation, also was not altered in the thermotolerant cells. The inhibition of the development of thermotolerance by amino acid analogs and the refractoriness of thermotolerant cells to the heat-sensitizing action of amino acid analogs lend further support the role of heat-shock proteins in the phenomenon of thermotolerance.

Major heat shock protein hsp70 protects tumor cells from tumor necrosis factor cytotoxicity

Heat treatment and various other stresses render tumor cells resistant to cytotoxicity mediated by tumor necrosis factors (TNFs). Here, we elucidate the molecular basis of this phenomenon by demonstrating that the major heat shock protein, hsp70, protects tumor cells from TNF cytotoxicity even in the absence of stress. The human hsp70 gene was stably introduced into highly TNF-sensitive WEHI-S tumor cells both in the sense and antisense orientation. All clones constitutively expressing the exogenous human hsp70 gene were protected from TNF-mediated killing approximately 1000-fold. Remarkably, the growth of one clone was actually stimulated by low concentrations of TNF. Moreover, a clone expressing antisense hsp70 RNA was rendered extremely sensitive to TNFs. Hsp70-mediated protection from TNF cytotoxicity was confirmed in transient expression experiments employing retroviral vectors. Changes in cellular sensitivity to TNF were not associated with alterations in the binding of TNF to its receptors. Neither the transfection procedure itself nor overexpression of the low molecular weight heat shock protein, hsp27, had any effect on cellular susceptibility to TNFs. Our data suggest that hsp70 may increase the oncogenic potential of some tumor cells by providing them with an escape mechanism from immunological defense.

Expression of human hsp70 in rat fibroblasts enhances cell survival and facilitates recovery from translational and transcriptional inhibition following heat shock

We report here our studies on the inhibitional effect of 45 degrees C heat shock on transcriptional and translational activity and their subsequent recovery at 37 degrees C in Rat-1 cells, thermotolerant Rat-1 cells (TT Rat-1), and Rat-1 cells transfected with human hsp70 gene (HR24, M21). Specifically, we ask whether overexpression of hsp70 protects cells from heat-induced inhibition in RNA and protein synthesis, and/or facilitates cells' ability to recover from translational or transcriptional inhibition after heat shock treatment. Our data demonstrate that the constitutive expression of human hsp70, by itself, confers thermal resistance as expressed in enhanced survival and translational tolerance, but not transcriptional tolerance. In addition, the expression of human hsp70 in Rat-1 cells facilitates cells' ability to recover from heat-induced inhibition in protein and RNA synthesis. After healing at 45 degrees C for 25 min, the time required for RNA and protein synthesis to recover is considerably shorter in HR24, M21, and TT Rat-1 cells than that in control Rat-1 cells. These results provide strong evidence for a direct link between the expression of a functional form of mammalian hsp70, and cells' translational tolerance, as well as their ability to recover from translational and transcriptional inhibition after heat shock.

Heat shock protein hsp70 protects cells from thermal stress even after deletion of its ATP-binding domain

Retroviral-mediated gene transfer experiments show that rodent cells become heat resistant when stably and constitutively expressing a cloned human gene encoding an intact human 70-kDa heat shock protein (hsp70). Cells expressing higher levels of the hsp70 protein generally tolerate thermal stress better, whereas cells expressing either of two mutated hsp70-encoding genes, one with a 4-base pair out-of-frame deletion and one with an in-frame deletion of codons 438-618, are heat sensitive. These results provide strong evidence that expression of hsp70 leads directly to thermal tolerance. Surprisingly, cells expressing a mutant hsp70 of a human gene missing codons 120-428 are, nevertheless, heat resistant. Because the deleted region of this mutant contains the ATP-binding domain of human hsp70, this domain appears dispensable in the hsp70-mediated protection of cells from thermal stress.

Identification of human hsp-70 expression in stably transfected rodent cells by isoelectrofocus immunoblots

The major heat-shock protein, hsp-70, is synthesized by cells from a wide variety of organisms in response to heat shock or other stresses. It is assumed that hsp-70 may have an important thermal protective function. To test this hypothesis directly, we have transfected rat fibroblast cells with appropriate expression plasmids containing a cloned human hsp-70 gene. Stable transfectants expressing the human hsp-70 gene product were identified by Western blot analysis. During the course of selecting successful transfectants, we found that when standard methods of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunostaining were employed with the monoclonal antibody raised against the human hsp-70 antigen, we were unable to differentiate the human hsp-70 from the heat-inducible rat hsp-70. This was because the monoclonal antibody cross-reacts with the human and rat proteins, which have the same mobility in SDS-PAGE, and it is difficult to determine which protein is expressed. To improve the resolution of the Western blot technique, we performed additional immunoblot analysis of cellular proteins separated by slab gel isoelectrofocusing. Our study shows that the isoelectrofocusing technique, when combined with antibodies against hsp-70, gave a better resolution for the separation of exogenous human hsp-70 and the endogenous rat hsp-70 than the commonly used SDS-PAGE Western blot analysis. It provides a rapid and specific method to identify positive colonies that express the human hsp-70 gene in transfected rodent cells.

Thermal response of rat fibroblasts stably transfected with the human 70-kDa heat shock protein-encoding gene

The major heat shock protein hsp70 is synthesized by cells of a wide variety of organisms in response to heat shock or other environmental stresses and is assumed to play an important role in protecting cells from thermal stress. We have tested this hypothesis directly by transfecting a constitutively expressed recombinant human hsp70-encoding gene into rat fibroblasts and examining the relationship between the levels of human hsp70 expressed and thermal resistance of the stably transfected rat cells. Successful transfection and expression of the gene for human hsp70 were characterized by RNA hybridization analysis, two-dimensional gel electrophoresis, and immunoblot analysis. When individual cloned cell lines were exposed to 45 degrees C and their thermal survivals were determined by colony-formation assay, we found that the expression of human hsp70 conferred heat resistance to the rat cells. These results reinforce the hypothesis that hsp70 has a protective function against thermal stress.

Alterations in specific and general protein synthesis after heat shock in heat-sensitive mutants of CHO cells and their wild-type counterparts

The rates of general and specific protein synthesis were studied in two heat-sensitive strains of CHO cells (Harvey and Bedford, Radiat. Res. 113, 526-542, 1988), both of which show a reduced ability to develop thermotolerance following an initial 45 degrees C heat shock. After various labeling periods with [35S]methionine, wild-type and mutant labeled proteins were separated by one- and two-dimensional polyacrylamide gel electrophoresis. Autoradiograms showed differences in levels of synthesis of several proteins after a 45 degrees C heat shock. In particular, these were in the hsp-70 group referred to as hsp-70a, b, and c, having molecular weights of 76, 73, and 72 kDa and isoelectric focusing pH values of 5.7, 5.5, and 5.7, respectively. Of particular note were changes in the hsp-70c region of the autoradiograms. We found that there was perhaps a low level of synthesis of hsp-70c in unheated wild-type cells but none was detectable in the mutant lines. After an isosurvival (approximately 10%) pulse of 45 degrees C heat there was a gradual increase in the synthesis of hsp-70c for wild-type but a smaller increase for the heat-sensitive strain 36 (HS-36) cells. In contrast, for HS-23 cells there was a very large initial increase by 5 to 7 h after the heat pulse and then a rapid decrease to undetectable levels by 11 to 13 h. The inhibition and recovery of general protein synthesis for both mutant and wild-type cells was also measured following various heat treatments at 45 degrees C. We observed that inhibition and resumption to a "normal" rate of protein synthesis for HS-23 cells paralleled the same response observed for the wild-type 10B2 cells. In sharp contrast, the time for recovery from the inhibition of protein synthesis for HS-36 cells was severely reduced for all heating times tested. Our results show that the period of delay before resumption of protein synthesis after heating does not always correlate with heat sensitivity or the degree of thermotolerance development. Several explanations for these observations are possible. One is that while synthesis of certain heat-shock proteins may indeed be responsible for the development of thermotolerance, the timing of the synthesis of these proteins in relation to the period of inhibition of general protein synthesis is crucial to such development.(ABSTRACT TRUNCATED AT 400 WORDS)

Myocardial protection with preconditioning

Myocardial preconditioning with brief coronary artery occlusions before a sustained ischemic period is reported to reduce infarct size. To determine the number of occlusive episodes required to produce the preconditioning effect, we performed single or multiple occlusions of the left circumflex coronary artery (LCx) followed by a sustained occlusion (60 minutes) of the LCx. Anesthetized dogs underwent one (P1), six (P6), or 12 (P12) 5-minute occlusions of the LCx. Each occlusion period was followed by a 10-minute reperfusion period. A 60-minute occlusion of the LCx followed the preconditioning sequences. A control group received a 60-minute occlusion of the LCx without preconditioning. All groups were subjected to 6 hours of reperfusion after which the heart was removed for calculating infarct size (IS), area at risk (AR), and left ventricular mass (LV). The IS/AR ratio for the control group was 29.8 +/- 4.4% (n = 17), which was substantially greater (p less than 0.001) than that of the preconditioned groups: P1, 3.9 +/- 1.3% (n = 14); P6, 0.4 +/- 0.3% (n = 5); and P12, 2.9 +/- 2.8% (n = 5). There were no significant differences in the IS/AR ratio among the three preconditioned groups. The AR/LV ratio was comparable among all groups and did not differ statistically: control, 40.4 +/- 1.3%; P1, 36.2 +/- 1.7%; P6, 36.1 +/- 1.7%; and P12, 37.3 +/- 2.1%. Collateral blood flow to the inner two thirds of the risk region determined with radiolabeled microspheres during ischemia did not differ significantly between the control group (0.03 +/- 0.01 ml/min/g, n = 8) and single occlusion group (0.06 +/- 0.02 ml/min/g, n = 8), indicating that the marked disparity in infarct size could not be attributed to differences in collateral blood flow. The data indicate that preconditioning with one brief ischemic interval is as effective as preconditioning with multiple ischemic periods.

Thermal response of oncogene-transfected rat cells

Rat embryo cells or Rat-1 fibroblasts were transfected with either an activated c-myc or a c-Ha-ras from the T24/EJ bladder carcinoma, or they were cotransfected with both. A gene conferring neomycin or hygromycin resistance was also cotransfected so that independent cell lines could be selected by growth in medium containing the antibiotic. Certain isolates from cells transfected with only one type of oncogene were further transformed by exposure to 600 cGy of 250-kVp X-rays. Successful transfection and transformation were characterized by altered morphology, increased plating efficiency, shorter doubling time, longer life span, foci formation, anchorage-independent growth, and Southern and Northern hybridization analysis. The thermal response of these cells at different stages of oncogenic transformation was examined by exposing exponentially growing cells to 45 degrees C for 0 to 45 min and measuring cellular survivals using colony formation assay. We found that cells transfected with myc oncogene, singly or in combination with ras, were more sensitive to thermal stress. Aside from that, the cells' thermal sensitivity was not affected by the degree or the nature of transformation.

Heat sensitivity, thermotolerance and protein synthesis of granulocyte and macrophage progenitors from mice and from long-term bone marrow cultures

Ex-vivo purging of leukaemic cells by single or fractionated heating during bone marrow transplantation for acute myeloid or lymphoblastic leukaemias may be possible since many leukaemic cells may be more sensitive to killing by heat than normal bone marrow colony-forming unit-granulocyte and macrophage (CFU-GM). In these studies we have compared heat response, thermotolerance response and heat shock protein (HSP) synthesis of bone marrow progenitors from intact mice or bone marrow obtained from 37 degrees C or 33 degrees C long-term bone marrow cultures (LTBMCs). Such studies were done to examine whether CFU-GM responses to heat are influenced by in vitro growth conditions. In terms of heat response CFU-GM progenitors from LTBMCs showed increased heat sensitivity when compared to CFU-GM from mice, with CFU-GM from 33 degrees C cultures being more heat-sensitive than those from 37 degrees C cultures. The kinetics of thermotolerance development and decay in CFU-GM were similar from all three systems. Thermotolerance was maximum at 3-9 h, began to decay by 24 h and was absent by 48 h from cells obtained from mice and LTBMCs grown at 37 degrees C. However, CFU-GM from 33 degrees C LTBMCs showed a delay in decay of thermotolerance. The kinetics of the development and decay of thermotolerance remained as above and was independent of incubation conditions whether bone marrow was left in situ or incubated in vitro in medium containing various colony-stimulating factors (CSF) or medium containing no CSF. The synthesis of HSPs was measured by one- and two-dimensional gel electrophoresis. Synthesis of HSP-70 kd was detected following a triggering dose of heat at 0-3 h for bone marrow heated in vivo and 0-6 h for bone marrow from LTBMCs. These studies indicate that CFU-GM heat and thermotolerance response was influenced by the temperature at which the cultures were maintained but not by other differences present in their microenvironment.

Heat-induced cytotoxicity in H2O2-resistant Chinese hamster fibroblasts

Hydrogen-peroxide-resistant Chinese hamster fibroblasts, derived from the HA-1 cell line, were isolated following continuous culturing in the presence of progressively increasing concentrations of hydrogen peroxide. The hydrogen-peroxide-resistant phenotype has been stable for over 360 days following removal from H2O2 stress. These H2O2-resistant cell lines demonstrate increased resistance to hyperthermic cell killing mediated by continuous heating at 43 degrees C but not 45 degrees C. The relationship between mammalian cellular adaptation to oxidative stress mediated by H2O2 and resistance to 43 degrees C hyperthermia is discussed.

Relationship between changes in ploidy and stable cellular resistance to hydrogen peroxide

Stable hydrogen peroxide (H2O2)-resistant variants of the Chinese hamster ovary HA-1 line have been isolated by culturing cells in progressively increasing concentrations of H2O2 (greater than 200 days, in 50-800 microM H2O2). Increases in catalase activity in these variant cell lines were shown to correlate with increased H2O2 resistance. Stable (greater than 240 days) H2O2-resistant cell lines, seven quasidiploid (21-22 chromosomes/cell) and six quasitetraploid (40-44 chromosomes/cell) were clonally isolated from the 800 microM adapted H2O2-resistant variants which were heterogeneous with respect to ploidy. The H2O2 dose-modifying factors (DMFs) were 3, 5, 8, 13, 15, 26, and 27 for the seven quasidiploid cell lines, and 21, 32, 38, 40, 42, and 49 for the six quasitetraploid cell lines. The mean DMF was 14 +/- 10 for the former and 37 +/- 10 for the latter. Our data show that on the average the quasitetraploid cell lines were significantly more resistant to H2O2-mediated cell killing than the quasidiploid cell lines derived from the same mixed population of 800 microM H2O2-adapted cells. When catalase activities (k units/cell) of the HA-1 cells and three of the clonally derived cell lines (two quasidiploid and one quasitetraploid) were determined and plotted vs. H2O2-DMF, a positive linear correlation was obtained (correlation coefficient = 0.99). This result was further confirmed when immunoreactive catalase protein/cell was detected by Western blots. Our data show that chronic exposure of cells to H2O2 stress (800 microM) was accompanied by increases in quasitetraploid cells within the population. Quasitetraploid cell lines derived from this population demonstrated increased stable H2O2-resistance which may be related to stable increases in the expression of catalase.

Will heat-stable proteins nonspecifically protect cells from thermal stress?

In cell-free systems, stress-resistant proteins nonspecifically stabilize stress-susceptible proteins. This mechanism has been suggested to contribute to thermotolerance in cells (Minton et al.: Proc. Natl. Acad. Sci. USA, 79: 7107-7117, 1982). To test this hypothesis, red-blood-cell-mediated microinjection was used to transfer macromolecules into monolayers of CHO cells. We introduced the heat-stable proteins fetuin and ovomucoid into RBCs during hypotonic hemolysis and then fused the RBCs to CHO cells with polyethylene glycol as fusogen. Fetuin and ovomucoid were successfully transferred into 36-55% of the CHO cells as demonstrated by fluorescence of FITC-conjugated proteins. The plating efficiency of these CHO cells after fusion ranged from 35% to 60%. Three hours after fusion, CHO cells microinjected with fetuin or ovomucoid were exposed to 43 degrees C for 0-180 min or 45 degrees C for 0-40 min, and thermal survival was determined. There was no difference in cell survival between control untreated cells, control cells fused with nonloaded RBCs, and cells fused with RBCs loaded with fetuin or ovomucoid. While our results do not support the hypothesis that heat-stable proteins nonspecifically protect cells from thermal stress, several possible explanations are provided for this observation.

Re-induction of hsp70 synthesis: an assay for thermotolerance

Of the many heat shock proteins (HSPs), hsp70 appears to correlate best with heat resistance, either permanent or transient. We have investigated various approaches to quantify the concentration of hsp 70, and examined the relationship between hsp70 and cells' thermal sensitivity during the development and decay of thermotolerance in model systems. Here, experiments were performed to determine the possibility of using the rate of synthesis of hsp70 after a second test heat shock to predict the kinetics of thermotolerance. Specifically, we studied the relationship between the retained thermotolerance in a murine tumor cell line SQ-1 and a human tumor cell line, HCT-8, after fractionated heat doses and the cells' ability to re-initiate synthesis of hsp70 in response to an additional test heat dose in vitro. Monolayers of cells were exposed to a first heat treatment (e.g., 41 degrees C, 4 h) and then incubated at 37 degrees C for 0-72 h. At various times after the first heat treatment, cells were either challenged with a 45 degrees C, 45 min heat shock to assess the residual thermotolerance by colony formation, or labelled with [35S]methionine before or after an additional test heat dose (e.g. 43.5 degrees C, 15 min). We found that the cells' ability to re-initiate hsp70 synthesis in response to the test heat shock inversely correlated with retained thermotolerance. Our data suggest the level of hsp70 in thermotolerant cells regulates the rate of synthesis of additional hsp70 in response to the subsequent heat challenge. Furthermore, the results showed that the rate of re-induction of hsp70 synthesis after a test shock can be used as a rapid measure of retained thermotolerance. This study suggests an approach for quantifying the level of retained thermotolerance during a course of fractionated hyperthermia.

Characterization of a heat-resistant strain of Tilapia ovary cells

Tilapia ovary cells (TO-2) cease to proliferate when moved from normal growth temperature of 31 degrees C to 37 degrees C, and arrest in G1 and G2 phases of the cell cycle. The ability of the arrested cells to re-enter the cell cycle when restored to 31 degrees C decreases inversely with time spent at 37 degrees C. A heat-resistant strain, TO-37c, cloned from the surviving fraction of TO-2 after heat treatment, has been found to re-enter the cell cycle with greater facility and to have a higher rate of survival. TO-37c cells have a smaller cell volume than TO-2 and show a distinct morphology at 37 degrees C. Most of the heat-shock proteins (hsps) induced on temperature change were similar, but in TO-37c the decline in the synthesis of a 27 X 10(3) Mr hsp was faster and a 37 degrees C-specific 60 X 10(3) Mr hsp was missing. Ultraviolet (u.v.) sensitivity was slightly affected if heat treatment was given after irradiation. However, when cells were preheated and then u.v. irradiated, the u.v. sensitivity increased sharply for TO-2 cells but not for TO-37c.

Effect of irradiation on thermal sensitivity of bone marrow progenitors

The heat sensitivity of murine CFU-GM and CFU-E following 2.5 Gy of total body irradiation (TBI) was studied. C3H f/Sed female mice were treated with 2.5 Gy TBI and femoral bone marrow was heated in vitro at 43 degrees C. CFU-GM show heat radiosensitization when bone marrow was heated immediately following irradiation. There was a brief decline in heat and radiation interaction when cells were heated 3 hours following 2.5 Gy of TBI, but heat radiosensitization returned to its maximum from 1 to 2 days following irradiation and remained significantly different from the control on days 5 and 7 following irradiation. The heat and radiation interaction disappeared by 30 days. CFU-E shows significant heat radiosensitization only on day 2 following 2.5 Gy of TBI. Total nucleated cells per femur showed a decrease by 70 per cent in days 1 to 2 following TBI, recovered to control values by day 5, and did not correlate with the changes in heat radiosensitization. Cell cycle analysis of CFU-GM using hydroxyurea showed no significant changes in cell cycle parameters on days 1 and 2 following 2.5 Gy, when maximum heat sensitization was observed. It is concluded that bone marrow progenitors may respond in a different way from other normal tissues to heat and irradiation sequencing, and that these differences must be considered when designing clinical trials.

Stable H2O2-resistant variants of Chinese hamster fibroblasts demonstrate increases in catalase activity

Hydrogen peroxide (H2O2)-resistant variants of the Chinese hamster ovary HA-1 line have been derived by culturing cells in progressively higher concentrations of H2O2 (greater than 200 days, in 50-800 microM H2O2). The H2O2-resistant phenotype has been stable for over 60 passages (240 days) following removal from the H2O2 stress. The resistant cells demonstrate both increased capacity to deplete exogenously added H2O2 from the growth medium and increased catalase activity. H2O2 resistance correlates well with catalase activity. An increase in chromosome number occurred in the cells adapted to 200-800 microM H2O2, but increases in aneuploidy and tetraploidy were not necessary for resistance. These results suggest that adaptation to chronic oxidative stress mediated by H2O2 in mammalian cells is accompanied by a stable heritable change in expression of catalase activity.

[Surgical treatment of breast cancer in elderly women--analysis of 244 patients]

From April 1964 to December 1981, 244 patients, women over 60 years old, with unilateral breast cancer were treated by surgery in our hospital. In this series, 15 patients (6.1%) had Stage I, 131 (53.6%) Stage II, 82 (33.6%) Stage III and 16 (6.6%) unstaged lesions. Of these patients, 3 were treated by extended radical mastectomy (ERM), 140 by standard radical mastectomy (SRM), 49 by modified radical mastectomy (MRM) and 52 by total mastectomy (TM). Except 52 cases by TM, axillary lymph node metastasis rate in 192 patients of this series was 49.3%. The 5- and 10-year survival rates were 33.3% in ERM group, 53.4% and 39.5% in SRM group, 70.8% and 48.5% in MRM group, and 73.4% and 55.3% in TM group, respectively. The overall 5-and 10-year survival rates were 62.1% and 45.6%. In Stage I, II patients, the 5-and 10-year survival rates of TM group were much higher than those of SRM and MRM groups (P less than 0.01), but in Stage III, the 5- and 10-year survival rates of MRM group were higher than those of other groups (P less than 0.05). Noticeably, the 5- and 10-year survival rates of SRM group in Stage I approximately III were not satisfactory. Our data show that the postoperative radiotherapy or chemotherapy was ineffective in elderly patients with breast cancer.