Growth of Theileria annulata and Theileria parva macroschizont-infected bovine cells in immunodeficient mice: effect of irradiation and tumour load on lymphocyte subsets.

Bovine cells infected with macroschizonts of the protozoan parasites Theileria annulata and Theileria parva formed solid tumours when injected into irradiated Balb/c and irradiated Balb/c nude mice. T. annulata tumours grew more vigorously than T. parva tumours, when initiated with similar doses of infected cells in mice exposed to the same doses of gamma-irradiation. In irradiated Balb/c mice, tumours of both species of parasites began to regress 2-3 weeks after injection of cells but grew without regression in irradiated Balb/c nude mice. Haemorrhage and necrosis of tumours, induced by macrophages and neutrophils, were seen in both mouse strains but were insufficient to cause regression in Balb/c nude mice. Theileria-infected bovine cells failed to establish in C57 beige mice, which lack functional natural killer (NK) cells. Flow cytometry, using monoclonal antibodies to murine leukocyte/lymphocyte antigens, showed that the radiation dose required to allow establishment of T. annulata tumours in Balb/c mice caused a severe depletion of splenic lymphocytes. B cells, helper T and cytotoxic T cells showed differing levels of susceptibility to irradiation. The presence of a tumour promoted the recovery of lymphocyte populations: this recovery was accompanied by destruction of the tumour.     

Effects of omeprazole on cell kinetics of carcinogen-induced colon tumours in rats

This study was designed to evaluate the effects of hypergastrinaemia induced via suppression of gastric acid by omeprazole on carcinogen-induced colon cancer in rats. The carcinogen methylazoxymethanol (MAM), 30 mg/kg, was administered intraperitoneally at 6-weekly intervals to Sprague-Dawley rats. Four weeks after the last MAM injection, the first daily dose of omeprazole, 40 mg/kg, was given by gastric gavage to one group of rats, and the rest were given buffered methylcellulose vehicle. After 10 weeks of daily omeprazole or vehicle, the rats were anaesthetized with ether, blood samples obtained, and animals sacrificed. Gastrin levels in serum from omeprazole-treated rats were elevated nearly six-fold. DNA and RNA levels in gastric mucosa were unchanged by omeprazole, but protein content was somewhat reduced. No biochemical or histological changes related to omeprazole treatment were observed in normal colon. The number of tumours, tumour volumes, and total tumour burden were not significantly different in colons of vehicle- or omeprazole-treated rats. Analysis by flow cytometry revealed that the S phase fraction was lower in tumour cells from omeprazole-treated animals; and that the frequency of DNA aneuploidy was also reduced. The results indicate that while omeprazole-induced suppression of stomach acid in rats elevates levels of gastrin in serum, it does not substantially alter the biochemical or cellular characteristics of carcinogen-induced colon tumours.     

Correlation of Zn2+ content with aflatoxin content of corn.

Forty-nine samples from the 1983 Virginia corn harvest were analyzed for aflatoxin, zinc, copper, iron, and manganese content. Values (mean +/- standard deviation) were as follows: aflatoxin, 117 +/- 360 micrograms/kg; zinc, 22.5 +/- 3.4 mg/kg; copper, 2.27 +/- 0.56 mg/kg; iron, 40.8 +/- 18.7 mg/kg; and manganese, 5.1 +/- 1.1 mg/kg. Aflatoxin levels positively correlated with zinc (Spearman correlation coefficient, 0.385; P less than 0.006) and copper levels (Spearman correlation coefficient, 0.573; P less than 0.0001). Based on biochemical data in the literature, we believe that the correlation with zinc is important and that there may be a cause-and-effect relationship between zinc levels in corn and aflatoxin levels which are produced upon infection with Aspergillus flavus or A. parasiticus. Control of aflatoxin contamination in field corn by decreasing the zinc levels may be feasible, but no methods to decrease zinc levels are currently available.     

Correlation of Zn2+ content with aflatoxin content of corn

Forty-nine samples from the 1983 Virginia corn harvest were analyzed for aflatoxin, zinc, copper, iron, and manganese content. Values (mean +/- standard deviation) were as follows: aflatoxin, 117 +/- 360 micrograms/kg; zinc, 22.5 +/- 3.4 mg/kg; copper, 2.27 +/- 0.56 mg/kg; iron, 40.8 +/- 18.7 mg/kg; and manganese, 5.1 +/- 1.1 mg/kg. Aflatoxin levels positively correlated with zinc (Spearman correlation coefficient, 0.385; P less than 0.006) and copper levels (Spearman correlation coefficient, 0.573; P less than 0.0001). Based on biochemical data in the literature, we believe that the correlation with zinc is important and that there may be a cause-and-effect relationship between zinc levels in corn and aflatoxin levels which are produced upon infection with Aspergillus flavus or A. parasiticus. Control of aflatoxin contamination in field corn by decreasing the zinc levels may be feasible, but no methods to decrease zinc levels are currently available.     

Effect of local interleukin-2 treatment on spontaneous tumours of different immunogenic strength

Transplantable tumour lines established from spontaneous tumours of BALB/c, CBA, and DBA/2 mice displayed different immunogenic strength. This report describes tumour susceptibility to interleukin-2 (IL-2) therapy in relation to tumour immunogenicity. The following tumour lines were used: X5, X6, and X9 mammary tumours of DBA/2, BALB/c, and CBA origin respectively, X7 carcinoma of BALB/c and X18 papilloma of CBA mice. Two spontaneous tumours of long transplantation history, SL2 lymphoma (SL2) of DBA/2 and Madison lung carcinoma M109 (M109) of BALB/c origin, were used as control systems. Experimental mice were transplanted with different inocula of tumour cells at day 0; treatment with IL-2 was initiated on days 1–3 or delayed until day 10 and consisted of daily injections of low doses of 5000 or 20 000 U/mouse given five times a week for a period of 3 weeks. Treatment of SL2 (2 × 10⁴ cells injected i.p.) consisted of i.p. injections of 5000 or 20 000 U IL-2/mouse given on days 10–14 after tumour transplantation. IL-2 therapy of SL2-bearing DBA/2JIco mice resulted in a significant proportion of cures; however, no response to IL-2 treatment was achieved in SL2-bearing DBA/2CrIiw mice. BALB/c mice with the i.p. transplant of M109 responded to IL-2 treatment with 40% increase in lifespan. The low-dose IL-2 therapy of the five spontaneous tumours resulted, in general, in transient growth inhibition of the i.m. transplants of lines X5, X6, and X7 provided that IL-2 was administered locally. The therapeutic effect depended on the number of transplanted tumour cells, the best results being achieved at cell numbers close to the dose-inducing tumour growth in 50% of animals. We found that the spontaneously arising tumours responding to IL-2 treatment were all slowly growing and immunogenic (X6 and X7) or might have viral association (X5) and, as such, might express foreign antigens. The data suggest a correlation between tumour immunogenicity and the therapeutic effect. However, IL-2 can still exert some effect against tumours with negligible immunogenicity. Received: 16 July 1998 / Accepted: 5 October 1998     

Delayed cell cycle progression in human lymphoblastoid cells after exposure to high-LET radiation correlates with extremely localized DNA damage

To compare the genotoxic effects of high-LET ionizing radiation to those of low-LET radiation, we investigated the responses of human lymphoblastoid cells to DNA damage TK6 after treatment with either low-LET X rays or high-LET iron ions (1000 keV/microm). A highly localized distribution of gammaH2AX/RAD51 foci was observed in the nuclei of cells irradiated with iron ions, in sharp contrast to cells exposed to X rays, where the distribution of foci was much more uniform. This implied the occurrence of a relatively high frequency of closely spaced double-strand breaks, i.e. clustered DNA damage, after iron-ion exposure. Despite the well-established notion that clustered DNA damage is refractory to repair compared to isolated DNA lesions, there were no significant differences in the levels of clonogenic survival and apoptosis between cells treated with iron ions or X rays. Strikingly, however, cells accumulated in G(2)/M phase to a much lesser extent after iron-ion exposure than after X-ray exposure. This differential accumulation could be attributed to a much slower evacuation of the S-phase compartment in the case of cells irradiated with iron ions. Taken together, our results indicate that, relative to the situation for low-LET X rays, exposure to high-LET iron ions results in a substantially greater inhibition of S-phase progression as a result of a higher frequency of DNA replication-blocking clustered DNA damage.     

The binding of SSB-proteins with DNA in chromatin of Ehrlich ascites carcinoma cells]

Using UV-induced cross-linking between proteins and DNA, the contacts between single-stranded DNA-binding proteins (SSB proteins) and chromatin DNA have been demonstrated. Ehrlich ascites tumour DNA was labeled in vivo by inoculation of tumour-bearing mice with 3H-thymidine. The cells were irradiated with the UV light dose of 3000 J/m2, destroyed in a Triton X-100-containing hypotonic medium, and separated by centrifugation into the extrachromatin fraction and chromatin. Chromatin DNA was digested with DNAase 1, and the chromatin proteins were extracted with 2 M NaCl-polyethyleneglycol. SSB proteins from the extrachromatin fraction and chromatin were purified. Only SSB proteins from UV-irradiated cell chromatin appeared to possess a high specific radioactivity which exceeded 7.5-fold that of non-irradiated cells. There were no differences between chromatin SSB proteins in control and irradiated cells as could be evidenced from SDS electrophoresis data. It is assumed that in irradiated cells SSB proteins of DNA-digested chromatin are covalently cross-linked with DNA fragments.     

DNA adducts in relation to lung tumour outcome are not markers of susceptibility following a single dose treatment of SWR, BALB/c and C57BL/6J mice with N-nitrosodiethylamine

The formation of DNA adducts by the covalent binding of genotoxic chemicals to DNA represents a valuable marker for assessing exposure to carcinogens but as yet the role of DNA adducts as a biomarker of carcinogenic susceptibility still needs to be clearly ascertained. To address this question an animal study was instigated using mice (SWR (high), BALB/c (intermediate) and C57BL/6J (low)) varying in their susceptibility to lung carcinogenesis. Groups of animals from each strain were dosed with a single intraperitoneal injection of saline or N -nitrosodiethylamine (NDEA) at 15 or 90 mg kg^-1 body weight. Lung and liver tissues were removed at different time points following dosing. Further groups of mice dosed with the same regime had urine samples collected 24 h post dosing and were then left up to 18 months to allow for the development of tumours. Immunoslot-blot analysis was used for the determination of N-7 ethylguanine (N-7EtG) and O⁶ ethylguanine (O⁶EtG) adduct levels in the DNA from the tissues and gas chromatography-mass spectrometry (GC-MS) was used to determine N-3 ethyladenine (N-3EtA) adduct levels in the urine samples. Levels of alkyltransferase (ATase) were also determined in the tissues. The results showed that the DNA adduct levels and persistence were similar across the three strains of mice following dosing with 15 and 90 mg kg^-1 NDEA. High levels of adducts were observed in the urine of the BALB/c strain, implying an increased metabolic or repair capacity in this strain. However there were no differences in the levels of ATase in the lung and liver of the three strains of mice following dosing with 15 mg kg^-1 NDEA. The incidence of tumours in C57BL/6J mice was lower compared with the other two strains and showed a dose dependent increase. The results from this study show that the differences in susceptibility to lung carcinogenesis between the three strains of mice do not appear to be linked to the formation of the two adducts detected. These results imply that dosing with NDEA resulted in toxicity which may have led to cell death and induction of tumours by compensatory cell proliferation. Although these results do not allow decisive conclusions to be drawn concerning the relationship between total levels of DNA adducts and differences in carcinogenic susceptibility for the three strains of mice it is clear that the increased presence of a DNA adduct in the target tissue increases the likelihood of tumour development.     

Excision of O6-methylguanine from DNA of various mouse tissues following a single injection of N-methyl-N-nitrosourea

The persistence of O⁶-methylguanine produced by a single dose of N-methyl-N-nitrosourea (MNU) was determined in DNA of various murine tissues and compared with the location of tumours induced by MNU and related alkylating carcinogens in this species. A/J and C3HeB/FeJ mice received a single intravenous injection of MNU (10 mg/kg) and were killed at different time intervals ranging from 4 h to 7 days.The rate of loss of O⁶-methylguanine from brain DNA was considerably slower than from liver DNA; tumours have been found in both organs after administration of MNU and other alkylnitrosoureas. There was no difference in the rate of excision from cerebral DNA of A/J and C3HeB/FeJ mice, although these strains differ significantly in their susceptibility to the neurooncogenic effect of MNU and related carcinogens. Excision of O⁶-methylguanine from hepatic DNA was significantly slower in A/J than in C3HeB/FeJ mice; both strains have been found to develop hepatic carcinomas following MNU administration. Seven days after the injection of ³H-MNU, O⁶-methylguanine concentrations were highest in brain and lung DNA, lowest in the liver, and intermediate in kidney, spleen, small intestine and stomach. The lung is a principal target organ for tumour induction by MNU and other carcinogens in mice; however, neural tumours are usually induced at a low incidence.The results obtained do not contradict the hypothesis that O⁶-alkylation of guanine in DNA is a critical event in the initiation of tumour induction by alkylating agents. However, the location of tumours produced in mice does not seem to depend solely on the formation and persistence of O⁶-alkylguanine in DNA.     

'Iron-saturated' lactoferrin is a potent natural adjuvant for augmenting cancer chemotherapy

Bovine lactoferrin (bLf), an iron-containing natural defence protein found in bodily secretions, has been reported to inhibit carcinogenesis and the growth of tumours. Here, we investigated whether natural bLf and iron-saturated forms of bLf differ in their ability to augment cancer chemotherapy. bLf was supplemented into the diet of C57BL/6 mice that were subsequently challenged subcutaneously with tumour cells, and treated by chemotherapy. Chemotherapy eradicated large (0.6 cm diameter) EL-4 lymphomas in mice that had been fed iron-saturated bLf (here designated Lf(+)) for 6 weeks prior to chemotherapy, but surprisingly not in mice that were fed lesser iron-saturated forms of bLf, including apo-bLf (4% iron saturated), natural bLf (approximately 15% iron saturated) and 50% iron-saturated bLf. Lf(+)-fed mice bearing either EL-4, Lewis lung carcinoma or B16 melanoma tumours completely rejected their tumours within 3 weeks following a single injection of either paclitaxel, doxorubicin, epirubicin or fluorouracil, whereas mice fed the control diet were resistant to chemotherapy. Lf(+) had to be fed to mice for more than 2 weeks prior to chemotherapy to be wholly effective in eradicating tumours from all mice, suggesting that it acts as a competence factor. It significantly reduced tumour vascularity and blood flow, and increased antitumour cytotoxicity, tumour apoptosis and the infiltration of tumours by leukocytes. Lf(+) bound to the intestinal epithelium and was preferentially taken up within Peyer's patches. It increased the production of Th1 and Th2 cytokines within the intestine and tumour, including TNF, IFN-gamma, as well as nitric oxide that have been reported to sensitize tumours to chemotherapy. Importantly, it restored both red and white peripheral blood cell numbers depleted by chemotherapy, potentially fortifying the mice against cancer. In summary, bLf is a potent natural adjuvant and fortifying agent for augmenting cancer chemotherapy, but needs to be saturated with iron to be effective.     

Requirement for Protein Synthesis in rec-Dependent Repair of Deoxyribonucleic Acid in Escherichia coli after Ultraviolet or X Irradiation

Deprivation of amino acids required for growth or treatment with chloramphenicol or puromycin after irradiation reduced the survival of Rec(+) cells of Escherichia coli K-12 which had been exposed to either ultraviolet (UV) or X radiation. In contrast, these treatments caused little or no reduction in the survival of irradiated recA or recB mutants. The effect of chloramphenicol on the survival of X-irradiated cells was correlated with an inhibition of repair of single-strand breaks in irradiated deoxyribonucleic acid (DNA), previously shown to be controlled by recA and recB. In UV-irradiated cells no effect of chloramphenicol was detected on the repair of single-strand discontinuities in DNA replicated from UV-damaged templates, a process controlled by recA but not by recB. From this we concluded that inhibiting protein synthesis in UV or X-irradiated cells may interfere with some biochemical step in repair dependent upon the recB gene. When irradiated Rec(+) cells were cultured for a sufficient period of time in minimal growth medium before chloramphenicol treatment their survival was no longer decreased by the drug. After X irradiation this occurred in less than one generation time of the unirradiated control cells. After UV irradiation it occurred more slowly and was only complete after several generation times of the unirradiated controls. These observations indicated that replication of the entire irradiated genome was probably not required for rec-dependent repair of X-irradiated cells, although it might be required for rec-dependent repair of UV-irradiated cells.     

DNA adducts in relation to lung tumour outcome are not markers of susceptibility following a single dose treatment of SWR,BALB/c and C57BL/6J mice with N-nitrosodiethylamine

The formation of DNA adducts by the covalent binding of genotoxic chemicals to DNA represents a valuable marker for assessing exposure to carcinogens but as yet the role of DNA adducts as a biomarker of carcinogenic susceptibility still needs to be clearly ascertained. To address this question an animal study was instigated using mice (SWR (high), BALB/c (intermediate) and C57BL/6J (low)) varying in their susceptibility to lung carcinogenesis. Groups of animals from each strain were dosed with a single intraperitoneal injection of saline or N -nitrosodiethylamine (NDEA) at 15 or 90 mg kg^-1 body weight. Lung and liver tissues were removed at different time points following dosing. Further groups of mice dosed with the same regime had urine samples collected 24 h post dosing and were then left up to 18 months to allow for the development of tumours. Immunoslot-blot analysis was used for the determination of N-7 ethylguanine (N-7EtG) and O⁶ ethylguanine (O⁶EtG) adduct levels in the DNA from the tissues and gas chromatography-mass spectrometry (GC-MS) was used to determine N-3 ethyladenine (N-3EtA) adduct levels in the urine samples. Levels of alkyltransferase (ATase) were also determined in the tissues. The results showed that the DNA adduct levels and persistence were similar across the three strains of mice following dosing with 15 and 90 mg kg^-1 NDEA. High levels of adducts were observed in the urine of the BALB/c strain, implying an increased metabolic or repair capacity in this strain. However there were no differences in the levels of ATase in the lung and liver of the three strains of mice following dosing with 15 mg kg^-1 NDEA. The incidence of tumours in C57BL/6J mice was lower compared with the other two strains and showed a dose dependent increase. The results from this study show that the differences in susceptibility to lung carcinogenesis between the three strains of mice do not appear to be linked to the formation of the two adducts detected. These results imply that dosing with NDEA resulted in toxicity which may have led to cell death and induction of tumours by compensatory cell proliferation. Although these results do not allow decisive conclusions to be drawn concerning the relationship between total levels of DNA adducts and differences in carcinogenic susceptibility for the three strains of mice it is clear that the increased presence of a DNA adduct in the target tissue increases the likelihood of tumour development.     

Chromogranin A as a determinant of midgut carcinoid tumour volume

Neuroendocrine (NE) tumours are characterized by their capacity to synthesize, store and release hormonal products. These substances are stored in neurosecretory vesicles together with chromogranin A (CgA). The concentration of plasma CgA in patients with NE tumours is thought to reflect the degree of NE differentiation, total tumour burden and effect of medical treatment. The aim of this study was to analyse the correlation between tumour weight and plasma CgA levels as well as the influence of treatment with a long-acting somatostatin analogue (octreotide) using nude mice with xenografted human ileal carcinoid tumours. There was a correlation between tumour weight and plasma CgA levels in all animals (p<0.00001). In octreotide-treated mice, plasma CgA levels were significantly reduced versus untreated animals (p=0.037).

In conclusion, this study demonstrates that plasma CgA levels are closely correlated to tumour burden, and that plasma CgA is well suited for monitoring the clinical course and outcome of treatment in patients with NE tumours.     

Topical thymidine dinucleotide application protects against UVB-induced skin cancer in mice with DNA repair gene (Ercc1)-deficient skin

Topical application of thymidine dinucleotides (pTpT) provides some protection against the effects of UV on the skin, however, many details of the protective mechanism have yet to be elucidated. We have used mice with an epidermis-specific knockout for the nucleotide excision repair gene, Ercc1, to investigate the mechanisms of protection. pTpT offered no protection against the pronounced UV-induced short-term erythema and skin thickening responses that are characteristic of DNA repair-deficient skin. It also had no effect on UV-induced apoptosis in Ercc1-deficient cultured keratinocytes. However, in these short-term experiments in both skin and keratinocyte culture pTpT did cause a slight reduction in proliferation. pTpT application during a chronic UV irradiation protocol provided some protection from UVB-induced skin carcinogenesis in epidermis-specific Ercc1 knockout mice. The median tumour free survival time was increased in the pTpT-treated group and treated animals had fewer tumours. In addition, pTpT-treated animals developed fewer large inwardly growing skin lesions than untreated animals. Furthermore, the proliferation response was reduced in chronically irradiated, non-lesional pTpT-treated skin. We conclude that cancer protection by pTpT in our mice is not modulated by an upregulation of DNA repair, as protection appears to be independent of a functional nucleotide excision repair pathway. We hypothesise instead that protection by pTpT is due to a reduction in epidermal proliferation.     

Hormone-independent polyamine metabolism of squamous cell carcinoma of the prostate

The levels of polyamines and their synthesizing enzymes in squamous cell carcinoma of prostate implanted in intact as well as castrated male rats were determined after certain hormonal manipulations. The tumour was found to grow with an identical rate in non-castrated and castrated rats. Polyamine content and activities of polyamine synthesizing enzymes in the tumour were found to be much lower compared to their values in ventral prostate. Moreover, the levels of these parameters were comparable in tumours whether implanted in non-castrated or gonadectomized animals. The sequential analyses of putrescine and spermidine and activities of L-ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase of tumours at different time intervals showed a significant reduction in their levels at 30 days compared to 10 days post implantation in non-castrated as well as castrated rats. Daily intramuscular administration of tumour-bearing intact or castrated animals with testosterone (50 micrograms/g), beta-estradiol (2 micrograms/g) or cyproterone (12.5 micrograms/g) for 10 days did not influence polyamine metabolism in tumour tissue. However, either beta-estradiol and cyproterone treatments or castration were found to decrease polyamine synthesis in ventral prostate. At the same time, the testosterone replacement therapy did not allow polyamine levels or activities of polyamine synthesizing enzymes to decline in the ventral prostate of castrated rats. Our results demonstrated that contrary to ventral prostate, the polyamine metabolism in squamous cell carcinoma of prostate is independent of hormonal control. The loss of hormonal sensitivity of polyamine metabolism in the prostatic tumour could be the result of qualitative changes that occurred during transformation.     

Biochemical states of zinc incorporated in the liver of mice treated with a radioelement after irradiation with a sublethal dose of gamma-rays

Radioresistance has been observed in mice which have received an inorganic zinc 24 hours prior to gamma irradiation with a sublethal dose. In order to elucidate the mechanism of radioresistance, the biochemical states of the metal in filtrate extracted from the homogenated liver of the animal which have received an injection of zinc under the form of 65Zn as tracer 24 hours post irradiation, were analyzed and compared with those of non-irradiated (control) mice. Two peaks of radioactivity: P-1 and P-2, having molecular weight of about 45,000 and 20,000-25,000 respectively, were revealed by Sephadex G-75 separation. The radioactivity of P-2 (39%) from the irradiated mice is lower than that from the controls (46%). Chromatography of P-2 from control animals through DEAE-Sephadex A-50 revealed the existence of a large radioactive peak (P-U). Chromatography of P-2 from irradiated animals did not show any P-U peak. This P-U peak is composed principally from 2 to 3 proteins with a molecular weight of 12,000 to 26,000. Proteins of the P-U peak provoke a protection effect against the lethal effect of gamma-rays when they are injected into mice after irradiation.     

Effect of hypothermia on radiosensitization

Hypothermia reduces metabolism and oxygen utilization by tissues. If the blood supply to a solid tumour can be maintained at a sufficient level, the hypoxic fraction of tumour cells may be reduced and radiosensitivity increased. This may be achieved if hyperbaric oxygen is used in combination with the hypothermia. The blood supply and oxygen tension have been measured in C3H mouse mammary tumours under hypothermia and hyperbaric oxygen, and the enhancement of radiosensitivity by hyperbaric oxygen has been estimated in mice irradiated at different temperatures with and without anaesthesia. Measurement of xenon-133 clearance showed that the blood supply of a tumour tended to increase when anaesthetized mice became hypothermic. Oxygen cathode data showed that the oxygen tension tended to be relatively higher in tumours and lower in subcutaneous tissue when mice exposed to hyperbaric oxygen became hypothermic under anaesthesia. Hyperbaric oxygen enhanced the radiation response of the tumour in terms of an increase in regrowth delay by a factor of 1.7 when the mice had been anaesthetized, whether or not they became hypothermic. A lower factor of 1.4 was obtained without anaesthesia although induced hypothermia increased the response to a small extent. We conclude that anaesthesia and hypothermia affect oxygen metabolism in tumours by different mechanisms.     

Cytokine profiles in mice tissues after irradiation of the thymus projection area with femtosecond laser

The effects of pulsed femtosecond laser irradiation in the near ultraviolet region on the levels of cytokines in the thymus, blood, and skin of irradiated mice have been studied. Irradiation of the thymus projection area with low-intensity laser radiation in the near UV region of the spectrum showed significant changes in cytokine levels in the skin and thymus and, to a lesser extent, in the blood of irradiated mice. Laser irradiation with a power density of 20 mW/cm² affects the cytokine profile in the thymus: IFN-γ, IL-3, IL-4, IL-5, eotaxin, GM-CSF, and chemokine KC–factors that can affect differentiation and proliferation of the cells of the immune system in the gland. Conclusions: It is assumed that changes in the expression of cytokines in the thymus after laser irradiation are explained by the rearrangement of biochemical processes possibly associated with the maturation of cells in the gland.     

Effect of monoclonal antibodies to early pregnancy factor (EPF) on the in vivo growth of transplantable murine tumours

Summary Neutralisation studies with monoclonal antibodies (mAbs) specific for early pregnancy factor (EPF) have shown it to be essential for the continuation of pregnancy in mice and the growth of some tumour cells in vitro. These studies report that the mAbs are also able to limit the growth of two murine tumour lines transplanted s. c. The development of MCA-2 tumours in CBA mice was unaffected by the injection of 1 mg anti-EPF IgM at the time of tumour cell inoculation. However, four doses of 500 µg anti-EPF, injected one dose per day for 4 days after tumour cell inoculation, significantly retarded tumour development such that no tumours were palpable on day 13. A similar dose regimen of control IgM had no effect on tumour size. Dose/response studies revealed that lower doses of anti-EPF administered after tumour cell inoculation were effective in retarding the growth of the MCA-2 tumours. The effect of anti-EPF mAb administration on the growth rate of palpable B16 tumours established s. c. in C57BL/6 mice was also determined. Tumours injected with 6 mg anti-EPF 5/341 or anti-EPF 5/333 mAbs showed significant decrease in the uptake of [³H]thymidine into tumour tissue, measured 16 h after injection. Furthermore, titration of sera for active EPF showed that a significant reduction in the EPF titre was associated with a significant inhibition of tumour DNA synthesis. Thus it appears that neutralisation of EPF retards tumour growth both in vitro and in vivo. In vitro the effects must be due to anti-EPF mAb interfering with a direct mechanism that contributes to the maintenance of cells in the active growing phase. However, in vivo host immunological mechanism that are modified to allow tumour survival may also be affected. The presence of EPF-induced suppressor factors curculating in the serum of tumour-bearing mice has been confirmed and the contribution of such factors to tumour progression must now be investigated.     

Tumour bed effect: hypoxic fraction of tumours growing in preirradiated beds

The reduction in tumour growth rate seen when tumours are implanted into preirradiated sites, the tumour bed effect (TBE), is believed to be due to radiation damage to vascular stroma, leading to defective angiogenesis in the tumour. The present work examined whether or not the functional inadequacy of irradiated stroma was accompanied by an increased hypoxic fraction in tumours growing in irradiated beds. Mouse flank skin was given 0 or 20 Gy X-rays and RIF-1 fibrosarcoma cells were implanted i.d. into the centre of the treatment field one week later. Tumours of 200 mm3 were irradiated under clamped or unclamped conditions and the hypoxic fraction measured from the displacement of the corresponding survival curves, assayed in vitro. Results indicated a small increase in the hypoxic fraction. Averaging values from three independent experiments, the percentage of hypoxic cells increased from 2.5 per cent for cells in tumours growing in unirradiated beds to 4.6 per cent for those from tumours in beds given 20 Gy. Thus an irradiated vascular bed is still to some extent able to maintain the proportion of oxic: hypoxic tumour cells found in tumours growing in unirradiated beds, despite manifest changes in tumour necrosis and growth rate.