Non-major histocompatibility complex antigen class I-regulatory molecule for cytotoxicity by natural killer cells

The mechanism of the cytotoxicity by natural killer (NK) cells is not known. It is speculated that there exist several positively regulated and negatively regulated target molecules expressed on the target cell surface. Although one of the latter is considered to be major histocompatibility complex antigen (MHC) class I, in this study we described a novel non-MHC class I molecule that may negatively regulate the NK cytotoxicity. This antigen is defined by monoclonal antibody Cho-1 and is composed of noncovalently associated antigens that are 40 and 200 kilodaltons in molecular size. The expression of this antigen is reduced along with the cell growth induced by growth factors and/or oncogenes. Thus, Cho-1-defined antigen appears to be involved as one of the resistant molecules in the cytotoxic mechanism of NK cells.

Inhibition of natural killer cell cytotoxicity by cell growth-related molecules

Certain MHC class I molecules on target cells are known to inhibit the cytotoxic action of NK cells. By using monoclonal antibody (mAb) Cho-1, we have found inhibitory non-MHC class I cell surface molecules that are noncovalently-associated with 200 kDa and 40 kDa antigens. Poly I-C-induced rat NK cells were not cytotoxic to rat fetus-derived fibroblast WFB cell line. In contrast, NK cells were cytotoxic to H-ras oncogene-induced transformants of WFB, W14 and W31. FACS analysis indicated that mAb Cho-1 reacts with WFB, but not with W14 and W31 cells. Thus, this antigen may disappear concomitantly with cell growth and transformation. Cho-1 antigens were also expressed on other NK-resistant lines, such as mouse BALB3T3 fibroblast, EL-4 lymphoma and human fibroblast HEPM. However, they were not expressed on NK-sensitive mouse YAC-1 and H-ras transformant (Brash) of BALB3T3 cells. Furthermore, treatment of target cells with IFN-gamma clearly induced the cell surface expression of Cho-1 antigens, and conferred a resistance to NK cytolysis on target cells. These data strongly suggest that Cho-1 antigen expression may correlate with target cell susceptibility to NK cells. Indeed, treatment of NK-resistant WFB as well as HEPM cells with F(ab')2 fragments of mAb Cho-1 resulted in the acquisition of susceptibility to NK cytolysis. Cho-1 antigens may be novel molecules that regulate the NK resistance of cells.

Thermal response in murine L929 cells lacking alpha B-crystallin expression and alpha B-crystallin expressing L929 transfectants

We investigated the role of alpha B-crystallin expression in the development of thermotolerance in murine L929 cells. An initial heat-shock of 10 min at 45 degrees C induced thermotolerance in these cells to a heat challenge at 45 degrees C administered 24 h later. The thermotolerance ratio at 10(-1) isosurvival was 1.7. Expression of alpha B-crystallin gene was not detected during the 24 h incubation at 37 degrees C following heat shock by either northern or western blots. In contrast, inducible HSP70 synthesis was observed during this time period. Thus, this cell line provided an unique system in which to examine the effects of transfected alpha B-crystallin on thermoresistance and thermotolerance. Cells stably transfected with alpha B-crystallin under the control of an inducible promoter did not show a significant increase in the ability to develop thermotolerance. However, a stably transfected L929 clone expressing high levels of constitutive alpha B-crystallin exhibited an approximately 50% increase in thermal resistance over parental and control cells. Though expression of alpha B-crystallin is not requisite for the development of thermotolerance in L929 cells, overexpression of transfected alpha B-crystallin can contribute to increased thermoresistance.

Characterization of focal hepatic tumors. Value of two-phase scanning with spiral computed tomography

BACKGROUND

Spiral computed tomography (CT) allows imaging of the liver during the peak contrast material levels due to the capability of fast data acquisition. The objective of this study was to evaluate the usefulness of two-phase spiral CT in the differential diagnosis of focal hepatic tumors.

METHODS

One hundred two patients who had hepatic tumors (211 nodules; 149 hepatocellular carcinomas [HCCs], 36 metastases, and 26 hemangiomas) underwent two-phase spiral CT with 10-mm collimation at 10 mm/second table speed and 120 mL of contrast material injected at the rate of 3 mL/second. Computed tomography images of the hepatic arterial phase and late (equilibrium) phase were obtained at 35-second and 180-second delays, respectively. The enhancement patterns of tumors were divided into six types and were compared with the attenuation of surrounding liver parenchyma: totally high, peripherally high, centrally high, mixed, iso, and low.

RESULTS

The common enhancement patterns of HCC in two-phase spiral CT were totally high in the arterial phase and low (n = 63, 42%) or iso (n = 28, 19%) in the late phase. Metastasis showed peripherally nonnodular high attenuation (n = 9, 25%) or low attenuation (n = 9, 25%) in the arterial phase and low attenuation in the late phase, followed by totally high attenuation in the arterial phase and iso in the late phase (n = 6, 17%). Hemangiomas showed totally or peripherally nodular enhancement in the arterial and late phases (n = 23, 89%). In distinguishing hemangiomas from malignant tumors, totally high or peripherally nodular high attenuation in the late phase was the most useful contrast enhancement pattern (96% of hemangioma vs. 0% of malignant tumors). In distinguishing HCCs from metastases, a combination of contrast enhancement pattern of totally high attenuation in the arterial phase and low in the late phase was the most useful contrast enhancement pattern (42% of HCCs vs. 0% of metastases). The predictability of differentiation between hemangiomas and malignant tumors and between HCCs and metastases was 99% and 90% with spiral CT, respectively.

CONCLUSIONS

Two-phase spiral CT is useful in the differential diagnosis of focal hepatic tumors with evaluation of contrast enhancement patterns.

Differential effect of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) on alpha B-crystallin and hsp70 gene expression in murine cell lines

We studied the effect of isoquinolinesulfonamide derivatives (H-7, H-8, and HA1004) on the expression of two heat shock genes (alpha beta-crystallin and hsp70) in NIH 3T3 and Swiss 3T3 cells after heat shock at 45 degrees for 10 min. Western blots and northern blots showed that H-7 effectively suppressed the accumulation of HSP70 and alpha B-crystallin mRNA as well as the synthesis of their proteins. The degree of suppression was dependent upon the concentration of the drug. Moreover, the expression of the hsp genes was differentially suppressed by H-7. The expression of the alpha B-crystallin gene was more effectively inhibited than that of the hsp70 gene by H-7. Nuclear run-on assay demonstrates that this difference was due to the differential effect of H-7 on the elongation of transcription of different hsp genes.

Association of hepatitis C virus particles with immunoglobulin: a mechanism for persistent infection

The physical properties of hepatitis C virus (HCV) particles were determined by ultracentrifugation on 20-60% isopycnic sucrose density gradients. We report that (i) two populations of HCV particles were found in the sera of patients with chronic HCV infection [at high density (1.186-1.213 g/ml) and at low density (1.099-1.127 g/ml)], (ii) virus particles with high density values were associated with immunoglobulin, and (iii) virus particles with low density values accumulated base changes within a hypervariable region (HVR) of the E2 envelope domain of the RNA genome. The results indicate that base changes within the HVR of E2 lead to the accumulation of immunoglobulin-free virus particles. Therefore, these findings imply that persistent HCV infection is established as a consequence of sequence variation in the E2 envelope domain.

Heat-induced bFGF gene expression in the absence of heat shock element correlates with enhanced AP-1 binding activity

Basic fibroblast growth factor (bFGF) has been shown to be a potent mitogen and a promoter of angiogenesis. It has been hypothesized that the expression of the bFGF gene may be induced by stress of various types. To test that hypothesis, we investigated the expression of the bFGF gene during heat treatment in adriamycin-resistant (MCF-7/ADR) and -sensitive (MCF-7) human breast carcinoma cells. Under normal growth conditions, the bFGF mRNA was detected in MCF-7/ADR cells, while it was not detectable in MCF-7 cells by Northern blot analysis. During heating at 41 degrees C, the level of bFGF mRNA increased in MCF-7/ADR cells and the message became detectable in the MCF-7 cell line. However, after continuous heating at 41 degrees C for 24 h, the bFGF mRNA level decreased to control level in MCF-7/ADR cells. Interestingly, simultaneous treatment with heat and 60 micrograms/ml H-7 (1-(isoquinolinylsulfonyl)-2-methylpiperazine, a potent PKC inhibitor) decreased the level of bFGF mRNA in MCF-7/ADR cells. These results suggest that a protein kinase, likely PKC, is involved in the transcriptional regulation of the heat-enhanced bFGF gene expression in human breast carcinoma cells. Although no heat shock element can be identified in the promoter of the bFGF gene, we observed that the AP-1 binding activity to a TPA responsive element (TRE)-like sequence in the promoter of bFGF gene was enhanced by heat, as tested by mobility shift assay. Antibody developed against the c-Jun and c-Fos proteins inhibited the AP-1 binding activity to TRE. Therefore, the AP-1 complex appears to be responsible for the heat-enhanced binding to the TRE-like motif of the bFGF gene. Furthermore, the increased AP-1 binding activity does not require new protein synthesis but activation of the preexisting c-Jun proteins.

Predictive factors for beneficial response to interferon-alfa therapy in chronic hepatitis C

OBJECTIVES

Interferon is the only established treatment for chronic hepatitis C but the host-dependent or virus-related factors affecting the response rate to interferon therapy are not yet clear. The purpose of this study was to investigate the factors predictive of response to interferon-alfa therapy in chronic hepatitis C.

METHODS

Twenty-five consecutive patients with chronic hepatitis C were randomized to three regimens of interferon-alfa: group A (n = 7, 3 MU every day for 3 months), group B (n = 8, 3 MU every other day for 3 months) and group C (n = 10, 3 MU every other day for 6 months). We quantified serum HC RNA levels by competitive reverse transcription-polymerase chain reaction (RT-PCR) and performed HCV genotyping using type-specific primers deduced form the NS5 region of the HCV genome. We also attempted to identify which demographic, biochemical and histologic factors in addition to virus-related factors would significantly predict beneficial response to interferon by multivariate analysis.

RESULTS

Sustained responders were 8 (36.4%), nonsustained responders were 2 (9.1%) and nonresponders were 12 (54.5%) of 22 patients who had received complete therapy. The initial HCV RNA level (logarithmic transformed copy numbers per ml of serum) in sustained responders (5.75 +/- 0.39) was significantly lower than that of nonsustained responders (6.80 +/- 0.71) and nonresponders (6.70 +/- 0.52) (p < 0.05). In multivariate multiple logistic regression analysis, the serum HCV RNA level before therapy was only the independent predictor of a sustained response to interferon-alfa therapy (p = 0.001).

CONCLUSIONS

Serum HCV RNA level before therapy was the most useful predictor of a sustained response to interferon-alfa therapy for chronic hepatitis C.

Cystic peripheral cholangiocarcinoma: sonography and CT

A case of cystic peripheral cholangiocarcinoma is presented. Both sonography and computed tomography (CT) demonstrated a large intrahepatic cystic neoplasm containing an enhancing solid portion. Despite the very rare incidence of this tumor, we believe that cystic degeneration of peripheral cholangiocarcinoma should be considered with these radiologic findings.

The taste-active regions of monellin, a potently sweet protein

Monellin, a protein found in the berries of the West African plant Dioscoreophyllum cumminsii, is one of the most potently sweet compounds known. The native three-dimensional structure of monellin is required for sweetness, and this protein has been the subject of intense research in an attempt at understanding the structural basis for its taste activity. We have used structure-based site-directed mutagenesis to delineate the taste-active site(s) of monellin, and we present these results, along with similar work from M. Kohmura, Y. Ariyoshi and coworkers, in the light of the three-dimensional structure of this protein. The mutagenesis work suggests that at least four residues, located N-terminal to the alpha-helix, form part of a taste-active region of monellin. In addition, there is evidence that a second region, formed by residues in the fourth and fifth beta-strands, may also be contributing to monellin's activity.

Response of serum cytokines in patients undergoing laparoscopic cholecystectomy

The clinical observation that a laparoscopic cholecystectomy is a minimally invasive operation has not been demonstrated on a biochemical basis. Interleukin-6, a known endogenous pyrogen and hepatocyte-stimulating protein, correlates with the significance of surgical trauma. Utilizing the IL-6 immunoassay, we studied this biochemical parameter of trauma to compare its response in laparoscopic vs open cholecystectomy. Sixteen patients who underwent only laparoscopic cholecystectomy showed peak IL-6 concentrations of 51 pg/ml (22-86) vs a peak IL-6 concentration of 124 pg/ml (56-225) for open cholecystectomy. Six additional patients who underwent an ERCP followed by laparoscopic cholecystectomy showed a dramatic rise in peak IL-6 concentration to 315 pg/ml (15-634). These results biochemically confirm the true minimal invasiveness of laparoscopic cholecystectomy. The findings in the ERCP-followed-by-laparoscopic-cholecystectomy group support the theory that two invasive procedures in close proximity may prime the cytokine system in its response to surgical trauma.

Regulation of HSP70 and HSP28 gene expression: absence of compensatory interactions

We have previously reported the lack of HSP28 gene expression during acute and chronic thermotolerance development in L929 cells (J Cell Physiol 152: 118-125, 1992; Cancer Res 52: 5787, 1992). In contrast to HSP28, an extremely high level of inducible HSP70 synthesis was observed. These results led us to investigate the possibility of compensatory interactions between HSP70 and HSP28. To test the hypothesis, L929 cells were transfected with the human HSP28 gene contained in plasmid pCMV27. Data from Western blot and two-dimensional gel electrophoresis of [3H] leucine and [32P] orthophosphate-labeled proteins showed the synthesis and phosphorylation of HSP28 in transfected cells after heating at 45 degrees C for 10 min. However, the expression of constitutive and inducible HSP70 genes, along with the synthesis of their proteins, was not decreased after heat shock. These results suggest an independent regulation of HSP28 and HSP70 gene expression.

Mechanism of quercetin-induced suppression and delay of heat shock gene expression and thermotolerance development in HT-29 cells

Previous studies have shown that a combination of low pH and quercetin (QCT) treatment following heat shock markedly suppresses and delays the expression of heat shock protein genes, particularly the HSP70 gene (Lee et al., Biochem. Biophys. Res. Commun., 186:1121-1128, 1992). The possible mechanism for alteration of gene expression by treatment with QCT at low pH was investigated in human colon carcinoma cells. Cells were heated at 45 degrees C for 15 min and then incubated at 37 degrees C for various times (0-12 h) with QCT (0.05-0.2 mM) at pH 7.4 or 6.5. Gel mobility-shift analysis of whole cell extracts from heated cells showed the formation of the heat shock transcription factor (HSF)-heat shock element (HSE) complex. Dissociation of HSF from the HSE of the human HSP70 promotor occurred within 4 h under both pH conditions. The kinetics of recovery were not affected by treatment with 0.1% dimethyl sulfoxide (DMSO). However, the dissociation of HSF-HSE complex was markedly delayed during treatment with a combination of low pH and QCT. In addition, in vitro transcription assays showed a suppression of initiation and elongation of HSP70 mRNA. These results may explain why the combination of low pH and QCT treatment suppresses and delays the HSP70 gene expression as well as thermotolerance development.

Tyrosinase production in recombinant E. coli containing trp promoter and ubiquitin sequence

We have successfully expressed the active tyrosinase of Streptomyces antibioticus in Escherichia coli under the control of the trp promoter by fusing the sequence to the ORF438 gene. Because our attempt to connect the polycistronic gene of ORF438 and tyrosinase directly to the trp promoter of E. coli resulted in the expression of functionally inactive tyrosinase, we decided to fuse the COOH-terminus of ubiquitin sequence to the NH2-terminus of ORF438. Ubiquitin fusion has been shown to augment the yield of cloned gene products in E. coli by increasing the stability or translational efficiency of the fusion proteins. As a result, E. coli transformants harboring a plasmid pTRUBF that contains the ubiquitin-fused ORF438 and the tyrosinase gene produced the strong black pigment of melanin. About 300 units of tyrosinase per liter of batch culture were detected when cultivated in M9 medium containing casamino acids, L-tyrosine, and copper supplements. The black pigment, however, was not seen when grown in LB medium, suggesting that the trp promoter is well regulated. When recombinant E. coli cells grown in LB medium were transferred to a tryptophan-deficient minimal medium with phenol, we observed that phenol was removed from the solution, and the color of the medium turned black. This is due to the fact that the tyrosinase has polyphenol oxidase properties. We expect to use this recombinant E. coli for the waste treatment of phenolic compounds.

Homoharringtonine induces heat protection and facilitates dissociation of heat shock transcription factor and heat shock element complex

We investigated the effects of combined treatment with homoharringtonine (HHT) and hyperthermia on cytotoxicity and transcriptional regulation of heat shock genes in human colon carcinoma (HT-29) cells. The drug (100 ng/ml) which inhibited protein synthesis by 93% protected cells from killing at 43 degrees C. For example, treatment with HHT 2 hr before and during heating produced a 9-fold increase in survival from 3.7 x 10(-2) to 3.2 x 10(-1) after 10 hr at 43 degrees C. Little or no protection was observed if the drug was added only during heating. Interestingly, adding the drug (100 ng/ml) 2 hr before and during heat facilitated the dissociation of heat shock transcription factor-heat shock element (HSF-HSE) complex during continuous heating at 43 degrees C. These findings related to the literature suggest that the free pool of HSC70 is increased by inhibiting protein synthesis. An increase in the level of free HSC70 may more effectively protect or repair thermolabile targets and consequently affect regulation of heat shock response.

Two crystal structures of a potently sweet protein. Natural monellin at 2.75 A resolution and single-chain monellin at 1.7 A resolution

Two refined structures of the sweet-tasting protein monellin are presented. The structure of natural monellin has been refined at 2.75 A resolution. The final model consists of four monellin molecules in the asymmetric unit, encompassing 3136 non-hydrogen atoms. The crystallographic R-factor is 0.193 for the 8853 reflections between 6.0 A and 2.75 A resolution, and the root-mean-square deviations from ideality are 0.017 A for bond lengths and 3.6 degrees for bond angles. The refined structure generally confirms, with some difference in detail, the initial backbone model of monellin that was based on 3.0 A resolution data. Single-chain monellin (scm) was genetically engineered by fusing the two chains of monellin into a single 94-residue polypeptide. Using the refined monellin coordinates as a search model, the crystal structure of scm has been solved with the techniques of molecular replacement, and has been refined against data to 1.7 A resolution. The final model consists of two scm molecules per asymmetric unit, and includes 137 bound water molecules. The crystallographic R-factor for this model is 0.174 for the 15,053 reflections (magnitude of FO magnitude of > 2 sigma (FO)) between 6.0 A and 1.7 A resolution. The root-mean-square deviations from ideal bond lengths and angles are 0.015 A and 2.86 degrees, respectively, and the average coordinate error is approximately 0.2 A, as estimated from a Luzzati plot. The error in the model was also estimated by comparing the two molecules in the asymmetric unit. The most significant differences between the two molecules occur in loop regions and at the C terminus of the protein, and are generally correlated to differences in crystal packing contacts. Linking the two chains of monellin has not substantially altered the structure beyond the region immediately surrounding the new peptide bond. Like natural monellin, the conformation of scm is dominated by a 17-residue alpha-helix folded into the concave side of a twisted, five-strand anti-parallel beta-sheet. We expect that the availability of a high-resolution structure of scm, along with the convenience of producing site-specific mutants of this protein, will make scm a good model with which to probe the structural basis of sweetness.

Midkine that promotes survival of fetal human neurons is produced by fetal human astrocytes in culture

Midkine (MK), a retinoic acid responsive gene product, is a novel heparin-binding growth factor with an apparent molecular weight of 14-kDa. In fetal human neuron cultures, addition of recombinant human MK (10-100 ng/ml) resulted in a 3-fold increase in the number of surviving neurons under the serum-free culture condition. Production of MK was identified in the conditioned medium of astrocyte-enriched cultures by immunoblotting but not in the medium of neuron-enriched cultures. The level of MK production was not affected by treatment with retinoic acid. These results indicate that in the developing human central nervous system, astrocytes secrete MK that exhibits potent trophic activity to neurons.

Radiological findings of human fascioliasis

Fasciola hepatica is a trematode of herbivorous mammals. Humans are accidentally infected by the ingestion of water or raw aquatic vegetables contaminated with the metacercaria. Radiological findings of six patients with fascioliasis (five hepatic fascioliasis, one biliary fascioliasis) were analyzed. The diagnosis was based on serological testing and/or histopathologic findings of eosinophilic abscess in five patients and identification of the adult worm in one patient. The characteristic radiological features of hepatic fascioliasis were (1) cluster of microabscesses arranged in tract-like fashion (burrow tract), (2) subcapsular location of the hepatic lesions, and (3) very slow evolution of the lesion on follow-up examinations. In biliary fascioliasis, there were multiple conglomerated filling defects in the common bile duct. The authors believe that the demonstration of these features, together with peripheral eosinophilia or eosinophilic aspirate from the hepatic lesion, is very helpful in making the correct diagnosis.

Synergistic effects of cytokine and hyperthermia on cytotoxicity in HT-29 cells are not mediated by alteration of induced protein levels

In this study, we investigated the mechanism of synergistic effects of cytokine and hyperthermia on cytotoxicity in HT-29. When cells were heated at 42 degrees C in the presence of recombinant human tumor necrosis factor (rhTNF-alpha), recombinant interferon-gamma (rhIFN-gamma), or in a combination of both, a synergistic increase in the cytotoxic effects of the respective drugs was observed. We hypothesized that alteration of cytokine or heat-induced polypeptides synthesis was responsible for a synergistic interaction between heat and cytokine. Five heat shock proteins (HSPs, M(r) 110,000, 100,000, 90,000, 70,000, and 28,000) were preferentially synthesized during chronic heating at 42 degrees C. In contrast, the synthesis of two proteins (M(r) 60,000 and 29,000) was induced by treatment with rhIFN-gamma (1,000 U/ml). Although the combination of chronic hyperthermia (42 degrees C) with TNF-alpha, IFN-gamma, or TNF-alpha + IFN-gamma increased cytotoxicity, alteration/induction of polypeptides was not correlated with the synergistical cytotoxic effects of cytokine and heat. Thus, the synergistic effects of cytokine and hyperthermia are not mediated through an induction of polypeptides.

Calcified bladder tumors. CT features

CT scans of the pelvis in 132 patients with bladder tumor were reviewed. Calcifications in the bladder tumor were found in 11 men (8%) including transitional cell carcinoma (n = 6), mucinous adenocarcinoma (n = 4), and malignant mixed mesodermal tumor (n = 1). Calcifications in transitional cell carcinoma were located on the surface of the tumor in all 6 cases: they were nodular in 4 cases, nodular and arched in one, and plaque-like massive calcification in one. In mucinous adenocarcinoma multiple fine punctate calcifications were scattered within the mass in all 4 cases. The CT appearance of calcifications in bladder tumors may be helpful in predicting the histologic type of the tumor.

Development of monoclonal antibodies reacting against mycobacterial 65 kDa heat shock protein by using recombinant truncated products

A mycobacterial 65 kDa molecule is a member of the GroEL heat shock protein family. We developed mAbs reacting against recombinant 65 kDa protein by using a gene (pTB12) which encodes this protein. Three mAbs (B20, B97 and B167) reacted selectively with 65 kDa proteins of Mycobacterium tuberculosis, BCG and Mycobacterium leprae, although B20 and B167 may weakly react with a 15 kDa molecule of mammalian cells. One (B108) was obviously cross-reactive between mycobacterial 65 kDa and the mammalian intracytoplasmic protein. We also developed deletion mutants of pTB12. The localization of these mAb-defined epitopes was determined by using truncated proteins of the Mycobacterium tuberculosis 65 kDa molecule produced in E. coli. Immunohistochemical analysis showed that B20, B97 and B167 mAbs could detect this antigen in experimental granulomas induced by injection of BCG in the subcutaneous tissue of rats. These mAbs should be useful for analyzing the immunobiologic roles of mycobacterial 65 kDa molecules.

Tumor rejection antigens on BALB3T3 cells transformed by activated oncogenes

The clonal expression of tumor rejection Ag (TRA) was analyzed on nine different clones derived from parental BALB3T3 cells that were transfected with activated H-ras, polyoma middle T (PyMT), c-myc, and v-src oncogenes. It was shown that Bras-h clone, which is an activated H-ras oncogene-induced transformant, expressed TRA as assessed in the transplantation study using syngeneic BALB/c mice. This TRA was not detected on parental BALB3T3 nontransformed cells, suggesting that TRA could be expressed in the BALB3T3 cell transformation. Furthermore, the cross-protection experiments indicated that this TRA was also conferred on other BALB3T3 transformants with high anchorage-independent growth potential such as an activated H-ras transformant Bras-d, and PyMT transformants BMT-f, BnMT-11, BnMT-20, except in the case of one H-ras transformant Bnr-12. In contrast, this TRA was not expressed on the transfectants with little or no anchorage independent growth potential such as a PyMT transfectant BnMT-4, a c-myc transfectant Bmyc-7, and a v-src transfectant Bsrc-7. We developed the mAb BRH19 that could react with TRA+ clones but not with TRA- clones. This mAb makes an immunoprecipitate, which is composed of a 50-kDa single polypeptide chain from Bras-h cell lysate. An injection to mice with this antigen could confer the protection against Bras-h challenge. These data indicate that the 50-kDa putative TRA molecule could be expressed in close association with the cell transformation, irrespective of the introduced oncogenes, and there may exist some regulatory mechanisms rather than individually distinct manners for the expression of TRA.

Immunogenicity and involvement in the host's effector mechanisms of the oncogene--induced transformation--associated cell surface antigens

The clonal expression of oncogene-induced transformation-associated cell surface antigens (TAAs) of a WFB rat fetus fibroblast was analyzed by developing mAbs to TAAs. We identified four TAAs. Two out of four TAAs seemed to be involved in the cytotoxicity by NK cells. One is an hsp-like molecule. These TAAs may play an important role in the antitumor surveillance mechanism by the host immune system. By clarifying the molecular characteristics, it would be possible to apply the genes encoding these molecules in the immunotherapy of cancer.

Tumor rejection antigens on BALB3T3 cells transformed by activated oncogenes

The clonal expression of tumor rejection Ag (TRA) was analyzed on nine different clones derived from parental BALB3T3 cells that were transfected with activated H-ras, polyoma middle T (PyMT), c-myc, and v-src oncogenes. It was shown that Bras-h clone, which is an activated H-ras oncogene-induced transformant, expressed TRA as assessed in the transplantation study using syngeneic BALB/c mice. This TRA was not detected on parental BALB3T3 nontransformed cells, suggesting that TRA could be expressed in the BALB3T3 cell transformation. Furthermore, the cross-protection experiments indicated that this TRA was also conferred on other BALB3T3 transformants with high anchorage-independent growth potential such as an activated H-ras transformant Bras-d, and PyMT transformants BMT-f, BnMT-11, BnMT-20, except in the case of one H-ras transformant Bnr-12. In contrast, this TRA was not expressed on the transfectants with little or no anchorage independent growth potential such as a PyMT transfectant BnMT-4, a c-myc transfectant Bmyc-7, and a v-src transfectant Bsrc-7. We developed the mAb BRH19 that could react with TRA+ clones but not with TRA- clones. This mAb makes an immunoprecipitate, which is composed of a 50-kDa single polypeptide chain from Bras-h cell lysate. An injection to mice with this antigen could confer the protection against Bras-h challenge. These data indicate that the 50-kDa putative TRA molecule could be expressed in close association with the cell transformation, irrespective of the introduced oncogenes, and there may exist some regulatory mechanisms rather than individually distinct manners for the expression of TRA.