Prostaglandin production by murine tumors as a predictor for therapeutic response to indomethacin

We investigated whether there is a relationship between the production of eicosanoids by murine solid tumors and their response to the prostaglandin H (PGH) synthase inhibitor indomethacin. Three sarcomas, designated FSA, NFSA, and SA-NH, and two carcinomas, designated MCA-K and HCA-I, syngeneic to C3Hf/Kam mice were used. In general, FSA and NFSA produced more PGH synthase products than lipoxygenase products, whereas HCA-I produced both types of metabolites in large quantities. All three tumors responded well to indomethacin treatment by slowing their growth. In contrast, MCA-K and SA-NH tumors produced insignificant quantities of PGH synthase products, but substantial amounts of lipoxygenase products. Their growth was not affected by treatment with indomethacin. Indomethacin did not influence tumor cell survival either in vitro or in vivo, but it reduced the proportion of S-phase cells in the tumors. The antitumor effect of indomethacin was not reduced by immunosuppression of the tumor host and was independent of tumor immunogenicity, implying that indomethacin acted through nonimmunological mechanisms. Thus, the effectiveness of indomethacin was directly related to the ability of tumors to produce PGs. Consequently, the eicosanoid profile of tumors could serve as a valuable way to select patients likely to respond to indomethacin and other PGH synthase inhibiting agents.     

Detection of antigens associated with Epstein-Barr virus replication in extracts from biopsy specimens of nasopharyngeal carcinomas

By using monoclonal antibodies to different Epstein-Barr virus (EBV) polypeptides in combination with immunoblotting, we detected antigens associated with EBV replication in extracts from nasopharyngeal carcinoma (NPC) biopsy specimens. Major polypeptides associated with both the diffuse and the restricted components of the early antigen (EA) complex were found in extracts from nine of nine NPC biopsy specimens. Cells from an additional NPC biopsy specimen, passaged repeatedly in nude mice, were found to be positive for the major EA (restricted) polypeptide. This approach revealed that extracts from three of 14 biopsy specimens form other benign and malignant diseases also expressed these viral polypeptides. Therefore, for the first time, these results conclusively demonstrate the presence of EA polypeptides in extracts from NPC biopsy specimens. This finding provides at least a partial explanation for the reported prognostic value of antibodies to this antigen in patients with this disease.     

Relationship between Epstein-Barr virus genome number, amount of nuclear antigen, and early antigen inducibility in diploid and tetraploid lymphoma cells of related origin.

In a collection of near-diploid and near-tetraploid Raji sublines and somatic Raji/Raji hybrids a linear relationship was found between the number of Epstein-Barr virus (EBV) genome copies and the relative amount of EBV-determined nuclear antigen per cell. Inducibility of the viral cycle by iododeoxyuridine and by P3HR-1 virus superinfection coulb be related to the number of resident EBV genome copies per haploid target cell. The implications of these findings are discussed.     

Histamine release, an undesired effect of thrombin inhibitors with basic character, is mediated through direct activation of G(i) proteins

The common structural feature of LK direct thrombin inhibitors is a strong basic group attached to the azaphenylalanine scaffold, which is important for the appropriate interaction at the thrombin active site. Our previous results have shown that this basic group could be responsible for a reduction of tracheal air flow and a fall of mean arterial pressure in anaesthetized rats, an undesired effect of direct thrombin inhibitors which correlated with their ability to release histamine from mast cells. In the present study, we investigated the mechanism of LK direct thrombin inhibitors-induced histamine release from rat peritoneal mast cells. We demonstrated that thrombin inhibitors with basic character (LK-732, LK-639 and LK-6063) provoked release of histamine from mast cells, while less basic analogs (LK-658, LK-633 and LK-6062) had no effect. Histamine released by LK-732 and LK-639 was suppressed by removal of sialic acid residues by neuraminidase and by pertussis toxin, an inhibitor of G(i) protein activity. Additional demonstration that G proteins are the targets of LK-732 and LK-639 was provided by the increase of GTPgammaS binding rate to G proteins in rat brain cortical membranes. Our results indicate that basic direct thrombin inhibitors LK-732 and LK-639 provoke release of histamine from mast cells by direct activation of G(i) proteins through the similar biochemical pathway as basic secretagogues.     

Interferon production in multiple sclerosis

The interferon-synthesizing activity of the peripheral blood leukocytes and serum interferon in the blood of patients with multiple sclerosis were studied. A reverse relationship was found between antibody production (high titers of measles antibody) and the interferon-synthesizing activity of peripheral blood leukocytes in these patients. A 3-fold decline in serum interferon titers was observed in patients with multiple sclerosis as compared with the control group.     

Protective effects of WR-2721 against radiation-induced injury of murine gut, testis, lung, and lung tumor nodules

WR-2721 (S-2-(3 aminopropylamino) ethylphosphorothioic acid) has been investigated for its ability to protect gut, lung, and testis, as well as fibrosarcoma (FSa) tumor nodules, in the lungs of mice from gamma-radiation injury. This compound greatly protected jejunum and testis epithelial cells. FSa micrometastases in the lung were protected to a lesser extent than jejunum and testis. Conversely, WR-2721 was not able to protect the lung against radiation-induced enhancement of tumor metastases formation generated by intravenously injected FSa cells.     

Migration inhibition caused by EBV-specific 48K subcomponent of EBNA and the associated 53K cellular protein

Leukocytes from EBV-seropositive but not seronegative healthy donors responded with significant migration inhibition to the 48K subcomponent of the Epstein-Barr virus determined nuclear antigen (EBNA), known to carry the virally determined antigenic specificity. A concentration of 10 micrograms/ml was still effective while 5 micrograms/ml had no detectable effect. EBNA-associated cellular 53K protein had no effect by itself, but it potentiated the effect of 48K, even if the latter was added at the subliminal concentration of 5 micrograms/ml. The related 53K protein, isolated from EBV-negative human lymphoma cells, was also effective, whereas the corresponding murine-tumor-associated 53K had no potentiating effect. Immunization of mice with an extract of DNA-binding proteins from EBV-carrying Raji cells, known to contain both 48K and 53K, induced a significant macrophage migration inhibition response, to both human 48K and 53K. Murine 53K was ineffective, however. Human but not murine 53K increased the migration inhibitory activity of subliminal concentrations of 48K in the murine macrophage system as well. These findings suggest that human but not murine 53K may reconstitute with 48K (EBNA) to form a highly immunogenic complex.     

Humoral immune response to p53 correlates with clinical course in colorectal cancer patients during adjuvant chemotherapy

Background and aims Overexpression of p53 protein in malignancies induces an immune response in some cancer patients. We investigated whether production of serum antibodies against p53 (p53-Ab) is associated with pathohistological parameters of colorectal carcinoma and whether p53-Ab can serve as a tumor marker during cancer treatment.Patients and methods Serum samples from 220 colorectal cancer patients during surgery and adjuvant chemotherapy and 42 healthy controls were tested for the presence of p53-Ab by ELISA. Expression of p53 protein in tumors was determined using mouse anti-human p53-Ab.Results Serum p53-Ab were detected in 18% of patients while all controls were negative. A strong correlation between p53-Ab production and p53 protein expression was observed: 70% of p53-Ab positive cases had tumors positive for p53 vs. 52% of p53-Ab negative cases. There was also a significant predominance of p53-Ab positive cases in Dukes stages B and C over stage A. Although surgery alone reduced p53-Ab levels, decreases in p53-Ab titer became significant midterm through chemotherapy compared to both pre- and postoperative values and remained decreased until the completion of treatment.Conclusion The presence of p53-Ab in sera of patients with colorectal cancer indicates tumors in more advanced histopathologic stages (Dukes B, C). Due to low sensitivity (18%) p53-Ab are not recommendable as a preoperative marker for colorectal cancer. However, due to high specificity (100%), their monitoring after surgery and adjuvant chemotherapy has potential for early diagnosis of tumor relapse in p53-Ab positive cases.