Increased survival of cancer-bearing mice treated with inhibitors of prostaglandin synthesis alone or with chemotherapy

COX inhibitors Indomethacin and Sulindac derivatives as antiproliferative agents: synthesis, biological evaluation, and mechanism investigation

Cyclooxygenase (COX) inhibitors Indomethacin and its structural analogs Sulindac exhibit cell growth inhibition and apoptosis inducing activities in various cancer cell lines via COX independent mechanisms. In this study, the molecular structures of Indomethacin and Sulindac were used as starting scaffolds to design novel analogs and their effects on the proliferation of human cancer cells were evaluated. Compared to Indomethacin and Sulindac inhibiting cancer cell proliferation with IC(50)s of more than 1 mM, the derivatives displayed significantly increased activities. Especially, one of the Indomethacin analogs inhibited the growth of a series of cancer cell lines with IC(50)s around 0.5 μM-3 μM. Mechanistic investigation revealed that the new analog was in fact a tubulin inhibitor, although the parental compound Indomethacin did not show any tubulin inhibitory activity. Tubulin polymerization assay indicated this compound inhibited tubulin assembly at high concentrations, but promoted this process at low concentrations which is a very unique mechanism. The binding mode of this compound in tubulin was predicted using the molecular docking simulation.

Activation of c-Jun-N-terminal-kinase is crucial for the induction of a cell cycle arrest in human colon carcinoma cells caused by flurbiprofen enantiomers

The unselective cyclooxygenase (COX) inhibitor S-flurbiprofen and its-in terms of COX-inhibition-"inactive" enantiomer R-flurbiprofen have been previously found to inhibit tumor development and growth in various animal models. The underlying mechanisms are unknown. Here, we show that both R- and S-flurbiprofen reduce survival of three colon cancer cell lines, which differ in the expression of COX-2 (HCT-15, no COX-2; Caco-2, inducible COX-2; and HT-29, constitutive COX-2). The IC50 for S- and R-flurbiprofen ranged from 250 to 450 microM. Both flurbiprofen enantiomers induced apoptosis in all three cell lines as indicated by DNA- and PARP-cleavage. In addition, R- and S-flurbiprofen caused a G1-cell cycle block. The latter was associated with an activation of c-Jun N-terminal kinase (JNK), an increase of the DNA binding activity of the transcription factor AP-1 and down-regulation of cyclin D1 expression. Western blot analysis, as well as supershift experiments, revealed that the AP-1 activation was associated with a change of AP-1 composition toward an increase of JunB. The JNK inhibitor SP600125 antagonized R- and S-flurbiprofen-induced AP-1 DNA binding, suppression of cyclin D1 expression, and the G1-cell cycle block. However, JNK inhibition had no effect on flurbiprofen-induced apoptosis. Hence, the cell cycle arrest is obviously mediated, at least in part, through JNK-activation, whereas R- and S-flurbiprofen-induced apoptosis is largely independent of JNK. Although in vitro effects of R- and S-flurbiprofen were indistinguishable, only R-flurbiprofen inhibited HCT-15 tumor growth in nude mice, suggesting the involvement of additional in vivo targets, which are differently affected by R- and S-flurbiprofen.

Synergistic effect of indomethacin with adriamycin and cisplatin on tumor growth

In this study, we have examined the antitumor effect of combined administrations of indomethacin (IND) with chemotherapeutic drugs on tumor growth. Colon 26 clone 20 (C20) cells and monocyte chemotactant protein-1 (MCP-1) transfected C20 cells (C20betaA-2-1) were used and these cells were inoculated into the footpad of BALB/c mice. At day 1 after tumor inoculation, treatment with 0.001% IND via the drinking water was commenced. At days 4, 6, and 8, adriamycin or cisplatin was administered intravenously at a dose of 5 mg/kg or intraperitoneally at a dose of 2 mg/kg, respectively. Although IND, adriamycin and cisplatin only partially reduced the growth of the C20 tumors after treatment with each drug on its own, a marked synergistic effect was observed when they were given in combination. A synergistic effect between IND and cisplatin on C20betaA-2-1 was also observed. However, IND itself showed no suppression of C20betaA-2-1 tumor growth. These results suggest that combination of indomethacin with chemotherapeutic drugs could be an effective form of cancer chemotherapy. The observed effects may be dependent on the expression of MCP-1.

Inhibitors of prostaglandin synthesis do not improve food intake or body weight of tumor-bearing rats

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) are immunoregulatory cytokines that mediate many aspects of the acute phase response to infection and injury. It has been hypothesized that these cytokines mediate the onset of the cachexia-anorexia syndrome with tumor growth. The anorexigenic effects of IL-1 are mediated in part by prostaglandins (PG). Therefore, the purpose of the present study was to determine if administration of ibuprofen (ibu) or indomethacin (indo), which inhibit PG synthesis, would affect the food intake and body weight of tumor-bearing rats. Rats were implanted with the Morris 7777 hepatoma, a tumor known to induce anorexia and weight loss in rats, and weight loss and leukocyte synthesis of IL-1 and TNF in mice. Treatment with indo or ibu did not improve food intake or body weight in the tumor-bearing rats. However, administration of ibu coincident with tumor implantation did result in smaller tumor mass compared to placebo-treated controls. The results of the present study suggest that PG synthesis is not a major factor in the onset of anorexia in this animal model of tumor-induced anorexia. However, further studies of the effects of inhibitors of PG synthesis on the kinetics of tumor growth are clearly indicated.

PGE2 production after angiotensin-converting enzyme inhibition

Using OKT3 monoclonal antibody driven T-lymphocyte proliferation, we investigated the effects of plasma 10, 20 and 30% in cell cultures on the proliferation ex vivo after exposure to captopril or enalapril taken orally by healthy volunteers. We also studied the effects of captopril, angiotensin II and bradykinin in vitro. We observed a plasma dependent dual effect of ACE inhibition both ex vivo and in vitro and of bradykinin in vitro being a stimulated proliferation at low (10% plasma) and a suppression of proliferation at high (30% plasma). The suppression was shown to be PGE2 mediated but the nature of the stimulatory signal is unknown. Proliferation was also suppressed by angiotensin II mediated by PGE2, but angiotensin II had no stimulatory effect. The results indicate that the effects of ACE inhibition on OKT3 mAb driven T-lymphocyte proliferation is plasma dependent, class specific for ACE inhibitors and mediated by both the ACE inhibitor itself and by bradykinin. Furthermore, it was shown that indomethacin in combination with an ACE inhibitor or bradykinin converted a suppressive response into proliferation indicating an immunostimulatory activity by indomethacin.

Enhancement of cytogenetic damage and of antineoplastic effect in lymphoid L1210 leukemia cells treated with prostaglandin E2 and cyclophosphamide in vivo

An enhanced frequency of sister-chromatid exchanges (SCEs) and increased cell division delays induced by cyclophosphamide (CP) were observed when lymphoid L1210 leukemia cells were post-treated in vivo with prostaglandin E2 (PGE2). CP gave a slight, non-significant increase in survival while PGE2 gave a slight, non-significant decrease in survival. However, PGE2 in combination with CP was found to have a non-significant potentiating effect on survival in comparison with mice treated with CP alone. In mice treated with the combined CP (5 micrograms/g b.w.) plus PGE2 (2 micrograms/g b.w.) treatment, a significant (P < 0.01) enhancement of survival time in comparison with the untreated controls was observed.

Do NSAIDs exert their colon cancer chemoprevention activities through the inhibition of mucosal prostaglandin synthetase?

Nonsteroidal antiinflammatory drugs (NSAIDs) have considerable potential as chemopreventive agents for colorectal cancer. Recent case-control drug surveillance and large cohort studies found that patients with regular aspirin use had a reduced incidence of colorectal cancer and/or decreased death rate from this disease. Several different NSAIDs reduce formation of both colon adenomatous polyps (the precursor lesion of colon cancer) and cancers in experimental animals given known carcinogens. Perhaps most convincing are reports that the NSAID sulindac promotes regression and inhibits recurrence of adenomatous colon polyps in patients with adenomatous polyposis coli. The best characterized pharmacologic effect of the NSAIDs is their reduction of prostaglandin synthesis by inhibiting prostaglandin synthetase PGE2, which catalyzes the formation of prostaglandin precursors from arachidonic acid. Several lines of evidence are contrary to the concept that inhibition of prostaglandin synthesis is central to the NSAIDs' chemopreventive effects. Relatively high levels of prostaglandins have been reported to inhibit tumor cell growth both in vivo and in vitro, and to inhibit differentiation in some tumor cell lines. We evaluated comparative chemopreventive effects on colon tumor formation in an azoxymethane (AOM)-induced colon carcinogenesis rat model using the NSAIDs piroxicam, sulindac, and sulindac sulfone, a metabolite of sulindac which lacks the anti-prostaglandin synthetase activity typically associated with NSAID-induced gastrointestinal toxicities. The results demonstrate that sulindac sulfone, a compound lacking anti-prostaglandin synthetase activity, inhibits AOM-induced colon cancer in rats. Substantial dose-dependent reductions in both tumor burden and tumor multiplicity were observed in the sulindac sulfone-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of antineoplastic effect and attenuation of sister chromatid exchanges by prostaglandin E2 in Ehrlich ascites tumour cells treated with cyclophosphamide in vivo

Reduced sister chromatid exchanges (SCE) frequency in response to cyclophosphamide (CP) was observed when Ehrlich ascites tumour (EAT) cells were exposed in vivo to 2 micrograms/g body weight of prostaglandin E2 (PGE2). 1 h before i.p. injection of 5-bromodeoxyuridine (BrdUrd) adsorbed to activated charcoal, EAT-bearing mice treated i.p. with CP appeared to have increased SCE rates and cell division delays. PGE2 had no effect on survival and in inhibiting tumour growth. CP had only a slight non-significant effect on survival and in inhibiting tumour growth. In mice treated with the combined CP (5 micrograms/g bd wt) plus PGE2 (2 micrograms/g bd wt) a significant enhancement (P < 0.01) of survival time was accompanied by inhibition of tumour growth (P < 0.01) in comparison with the untreated controls. These data imply that SCEs might result from errors in a repair process which might involve a PGE2 sensitive step.

The effects of cyclooxygenase inhibitors on tumor-induced anorexia in rats

BACKGROUND

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) are potent induces of prostaglandin (PG) synthesis and injection of PGE, IL-1, or TNF decreases food intake in healthy animals, whereas the anorexigenic effects of injected IL-1 and TNF are blocked by inhibitors of PG synthesis. It has been hypothesized that host secretion of IL-1 and TNF contribute to tumor-induced anorexia. This study was undertaken to determine whether administration of PG inhibitors alters food intake in anorectic rats implanted with Walker 256 carcinoma.

METHODS

Groups of six tumor-bearing rats were implanted with slow-release pellets containing ibuprofen, indomethacin, or acetylsalicylic acid. Food intake, tumor growth, and body temperature were monitored for 14 days and compared with control tumor-bearing animals implanted with placebo pellets.

RESULTS

Tumor growth was associated with anorexia, fever, weight loss, and increased leukocyte secretion of IL-1 and TNF. Indomethacin and ibuprofen retarded tumor growth 30-40% and lowered body temperature compared with controls, but had no effect on food intake or body weight of tumor-bearing animals.

CONCLUSIONS

Prostaglandins do not mediate tumor-induced anorexia.

Changes in tissue fatty acid composition in murine malignancy and following anticancer therapy

We studied the mouse NC tumour, a subcutaneously transplanted adenocarcinoma originally of mammary origin. Measurements per g tissue were made of 17 fatty acids (FAs), the combined amounts of n-3, n-6, saturated, unsaturated, and total FAs, and of various FA ratios in the tumour, mammary tissue, spleen, liver and plasma. Compared with mammary tissue from normal mice, tumours of vehicle-treated controls had less of seven of the FAs and more of two FAs. Mice bearing the NC tumour often had changed (usually decreased) amounts of FAs in the 'normal' spleen, liver and plasma, but not in mammary tissue. Treatment with methotrexate (MTX) was studied alone and with indomethacin which can potentiate MTX cytotoxicity. Indomethacin 1.25 mg kg-1 (INDO) increased the amounts of 3/17 tumours FAs and the unsaturated FAs, but reduced 9/17 FAs, the saturated and the unsaturated FAs in 'normal' mammary tissue, and usually had no effect on the FAs of other tissues. MTX 2 or 4 mg kg-1 (MTX 2 or 4 mg) +/- INDO in general partly restored (increased) the amounts of tumour FAs, and reduced the saturated/unsaturated FA ratio. In the 'normal' spleen and plasma also, but not in the liver, MTX 2 mg generally somewhat restored the FA composition. However, as in the liver, the spleen 20:4 and 22:6 (which form prostaglandins and lipid peroxides) did not increase in the presence of INDO. With MTX 4 mg, some of the plasma and liver FAs decreased, in contrast to the tumour. There was generally no evidence of MTX potentiation by INDO. These results are discussed in relation to carcinogenesis, cachexia, and the response to treatment.

Methotrexate alters the fatty acid composition of NC adenocarcinoma cells in culture

The effects of methotrexate and indomethacin alone and in combination have been examined on the fatty acid (FA) composition of total cellular lipids in cultured NC adenocarcinoma cells. These studies show that methotrexate can alter the lipid content of cancer cells. Methotrexate 16 ng/ml incubated with NC cells for 2 days increased the content of various FAs. When used alone, indomethacin 1 microgram/ml or methotrexate 8 ng/ml had no significant effect, but in combination caused FA increases, usually to about the same extent as with the higher concentration of methotrexate alone. No FA changes were seen up to 3 h with these drug concentrations or with methotrexate up to 10 micrograms/ml alone or with INDO 1 microgram/ml. These effects may explain previous findings that indomethacin potentiates methotrexate, an interaction which may be important in cancer therapy.

Effects of antiplatelet agents alone or in combinations on platelet aggregation and on liver metastases from a human pancreatic adenocarcinoma in the nude mouse

There is ample evidence to suggest that hematogenous metastasis may be related to the ability of tumor cells to promote aggregation of host platelets. Arachidonic acid metabolism in platelets and vessel walls may also contribute to the metastatic process. Several preliminary trials of platelet inhibitory agents have been performed. Ketoconazole (inhibitor of lipoxygenase and thromboxane synthetase), verapamil (calcium antagonist), forskolin (stimulator of platelet adenylate cyclase), and indomethacin (inhibitor of cyclooxygenase) were examined, alone and in combination, to investigate their effects on platelet aggregation and on hepatic metastases from human pancreatic tumor cells (RWP-2) in nude mice. The tumor cells were injected intrasplenically, and the animals were divided into control, single-drug and combination treatment groups. The agents were administered intraperitoneally 1 hr before and every 24 hr after the tumor cell injections for 6 days. Statistically significant differences were observed between the control and single-treatment groups on the reduction of liver tumor nodules (range P less than 0.001-0.032) and in the liver surface areas occupied by tumor (range P less than 0.001-0.013). Furthermore, when these agents were combined, similar reductions in liver tumor nodules were noted (range P less than 0.001-0.008), while even greater inhibitory effects were seen in the liver surface areas occupied by tumor (P less than 0.001) compared with the single-treatment groups. Also, the combination studies strongly inhibited RWP-2-induced platelet aggregation in human platelet-rich plasma.

The effect of nifedipine alone or combined with cytotoxic chemotherapy on the mouse NC carcinoma in-vitro and in-vivo

Effects of the calcium antagonist nifedipine on the response of the murine NC carcinoma has been examined alone and together with cytotoxic chemotherapy in-vitro and in-vivo. The cytotoxic drug combination of methotrexate and melphalan, or nifedipine alone (0.2-25 micrograms mL-1), caused a concentration-related reduction of NC cell growth in culture. At the lower concentrations, combination to the cytotoxic drugs with nifedipine resulted in an addition of the separate drug effects, but with drug concentrations that on their own approached maximal effectiveness the combined response was less than additive. NC tumours were excised from mice 14 days after inoculation s.c. with NC cells, weighed, and extracted for prostanoids. Mouse survival was determined up to day 121, and cancer spread was recorded postmortem. Nifedipine 1, 5 or 10 mg kg-1 had little or no effect on the tumour weight, tumour prostanoid content, metastasis to the lymph nodes or lungs, or on the increase of mouse longevity by the cytotoxic drugs.

The effect of indomethacin on food and water intake, motor activity and survival in tumour-bearing rats

This investigation has addressed the question whether food and water intake, motor activity and tumour growth are influenced by indomethacin in experimental cancer. Growing rats implanted with a methylcholanthrene-induced sarcoma were studied in metabolic cages connected to a computer. Food intake, water consumption and motor activity were continuously recorded over 30 days following tumour implantation. Treated tumour-bearing animals received indomethacin 1.0 mg/kg per day in drinking water. Food intake declined early in untreated tumour-bearing animals, but water intake was not affected. Motor activity decreased in untreated tumour-bearing animals from days 16-17 onward. Indomethacin treatment prolonged survival and 40% of these tumour-bearers were 'complete responders'. In some animals tumour growth was only marginally affected, but survival was still significantly improved ('partial responders'). Food intake was significantly improved in complete responders. Thus this positive effect seen in complete responders was secondary to less active tumour growth. Motor activity was also significantly higher in responders compared with non-responders.

Urinary excretion of prostacyclin and thromboxane degradation products in patients with ovarian malignancy: effect of cytostatic treatment

We studied the effect of ovarian cancer and its chemotherapy on the urinary excretion of prostacyclin (PGI2) and thromboxane A2 (TxA2) hydration and metabolic products. In six patients we measured 6-keto-PGF1 alpha and 2,3-dinor-6-keto-PGF1 alpha (PGI2 products) and thromboxane B2 (TxB2) and 2,3-dinor-TxB2 (TxA2 products) by HPLC followed by radioimmunoassay before, during and after the combined infusion of cisplatin, 4'epi-adriamycin and cyclophosphamide. Before the first cytostatic infusion, the urinary excretion of prostanoids was on average 4.4-5.8 times higher than in patients with ovarian endometriosis (n = 19). The infusion of cytostatics led to a 50-120% rise in the excretion of prostanoids during the first post-infusion 9 hours, but in the subsequent 10 hours their output was 25-45% below the initial value and remained low for at least 2 weeks. Following repetitive courses of cytostatics (2-4 per patient), prostanoid excretion tended to normalise. These data suggest that ovarian cancer is associated with increased production of PGI2 and TxA2, and that cytostatics suppress this production. This may be of biological significance in tumour behaviour and in the effect of cytostatics.

Anti-inflammation induced by counter-irritation or by treatment with non-steroidal agents inhibits the growth of a tumour of non-detected immunogenicity

Counter-irritation (CI) triggered by different non-specific irritant stimuli delayed the growth of a murine tumour of non-detected immunogenicity. The syngeneic LB tumour transplant by itself also induced CI and decreased the number of leukocytes migrating to a secondary s.c. irritant stimulus, e.g. sponge or carrageenan. On the other hand, partial inhibition of cell migration by treatment with either 0.5 mg kg-1 indomethacin or 0.3 mg kg-1 piroxicam retarded LB tumour growth, presumably by a mechanism unrelated to inhibition of immune responses by PGE2. It is suggested that CI may play a role in the early stages of concomitant resistance.

Prostaglandin synthesis by squamous carcinoma cells of head and neck, and its inhibition by non-steroidal anti-inflammatory drugs

The purpose of this study was to determine the nature and amounts of prostaglandins (PGs) produced by squamous carcinoma cells (SCC) and the sensitivity of these cells to non-steroidal anti-inflammatory drugs. SCC of four lines of the tongue and one line of facial epidermis of humans were incubated in phosphate buffer solution with 14C-arachidonic acid (AA). Radioactive metabolites in aqueous methanol were chromatographed on Sep-Pack C18 cartridges, separated and quantitated by means of TLC, autoradiography, and liquid scintillation counting. The results showed that cyclooxygenase products, PGs, were the major products formed by all cell lines, and PGE2 was predominant among the PGs detected. Two radioactive bands corresponding to PGF2 alpha and three unseparated standards of PGA2, 15-keto-PGE2, and 13,14-dihydro-15-keto-PGE2 were detected in lesser amounts. Very small amounts of the lipoxygenase products 12- and 15-HETE were found. The concentrations of indomethacin, ibuprofen and aspirin required to inhibit 50% of PGE2 synthesis (IC50) by SCC lines were .008-.080, .080-6.4 and 32-88 microM, respectively.

Studies on the mechanism by which indomethacin increases the anticancer effect of methotrexate

The effect of indomethacin on the response of the NC carcinoma to methotrexate has been examined in vivo and in vitro. Survival was prolonged in mice treated with indomethacin 1.25 mg kg-1 twice daily plus methotrexate 4 mg kg-1 daily, compared to mice given either drug alone or controls. Indomethacin 1 microgram ml-1 increased the killing of cultured NC cells by methotrexate. This was not due to displacement of methotrexate from binding sites on the serum proteins. Nor was it due (entirely) to inhibition of prostaglandin synthesis, since flurbiprofen did not mimic the effect. Inhibition of cyclic AMP phosphodiesterase seems unlikely to explain the effect of indomethacin since theophylline had little or no effect on NC cell killing by methotrexate. Indomethacin 1 microgram ml-1 increased the accumulation of tritium in NC cells incubated with [3H]-methotrexate. In contrast, with normal epithelial cells from human embryonic intestine, indomethacin 1 microgram ml-1 did not alter the cytotoxicity of methotrexate or the accumulation of tritium during incubation with [3H]-methotrexate. The beneficial interaction between indomethacin and methotrexate may have therapeutic potential in man.

Cancer in mice: effects of prednisolone or mepacrine alone and with cytotoxic drugs

WHT/Ht mice were transplanted s.c. with NC carcinoma, and the tumours were excised after 2 weeks. The mice were treated orally throughout the experiments with prednisolone 500 micrograms kg-1 or mepacrine 3.6 mg kg-1, starting the day after tumour transplantation or, with prednisolone, the day after tumour excision. In some experiments the mice were also treated with the cytotoxic drugs methotrexate 2 mg kg-1 and melphalan 1.4 mg kg-1. The excised tumours were weighed; some of them, and samples of serum, were extracted for prostanoids which were measured by radioimmunoassay. The chemotherapy lengthened the survival of the mice, but prednisolone or mepacrine had little or no effect on survival, metastasis, the response to chemotherapy, tumour size or the formation of tumour prostanoids.

Survival of mice with NC carcinoma is unchanged by drugs that are thought to inhibit thromboxane synthesis or increase prostacyclin formation

Mice transplanted with NC carcinoma were treated with the thromboxane synthetase inhibitor dazmegrel (UK38485) or with nafazatrom (BAY G 6575), a compound that is reported to increase prostacyclin formation. Some experiments included the cytotoxic drugs methotrexate and melphalan. The tumours were excised under anaesthesia on day 14 or day 21 after transplantation, and weighed; some were extracted for prostanoids which were measured by radioimmunoassay. Mouse survival time was determined up to day 121, and cancer spread was determined by postmortem examination. The survival was increased by methotrexate and melphalan but not by the other drugs. Nafazatrom-treated mice tended to have lighter tumours. Although dazmegrel reduced the formation of thromboxane B2 during clotting of blood from normal mice, it did not affect the tumour yields of prostanoids. Nafazatrom had no effect on serum or tumour prostanoids. There were no obvious effects of the treatments on the recurrence of tumour in the excision scar, lung metastasis or spread to lymph nodes.

Similar survival rates for rheumatoid and non-rheumatoid cancer patients

The survival rate for cancer patients with rheumatoid arthritis was compared with that for non-rheumatoid cancer patients. This was accomplished by linking two nationwide Finnish data registers, the Social Insurance Institution's Population Register and the Finnish Cancer Registry. For 2012 of the 2062 rheumatoid patients with cancer diagnosed after the diagnosis of rheumatoid arthritis, the Cancer Registry was successfully searched for a non-rheumatoid of diagnosis of control patient who matched with respect to sex, age, year of diagnosis of cancer and location of the tumour (and also, for leukaemia, with respect to cell type). The 5-year relative survival rate for male rheumatoid patients was 21.2% and, for the control cancer patients, 25.4%. In females, the corresponding rates were 38.2% for the rheumatoid patients and 41.2% for the control patients (p less than 0.05). At some sites, particularly with leukaemia, the rates for the rheumatoid patients were lower than those for the control patients. The difference, however, only reached a 5% significance level for colorectal cancer in males. Rheumatoid arthritis and its treatment do not seem to have any appreciable effect on the survival of cancer patients.

Treatment of mouse carcinoma in vivo with a prostaglandin E2 analogue and indomethacin

WHT/Ht mice transplanted s.c. with NC carcinoma were treated with 16,16-dimethyl prostaglandin E2 methyl ester (di-me-PGE2) and/or indomethacin. Each primary tumour was excised under anaesthesia 3 weeks after transplantation, weighed and extracted for prostaglandins. Mouse survival time and tumour recurrence were measured. Di-me-PGE2 10 micrograms, injected at the tumour site on alternate days from day 1 to 19, indomethacin 2.5 mg kg-1 daily by mouth, or both drugs together resulted in lighter tumours (respectively 45, 45 and 52% less, n = 18 to 20 per group, P less than 0.02) compared with vehicle-treated controls. Indomethacin reduced the tumour prostaglandin yield, but the biological activity in extracts of tumours from mice given di-me-PGE2 was high. The median survival time was longer in mice receiving indomethacin alone (61 days from tumour transplantation compared with 50 days in controls P less than 0.02). Di-me-PGE2 alone had little or no effect on survival (median 48 days) but counteracted the increase with indomethacin (di-me-PGE2 + indomethacin, 49 days median survival). There were no obvious effects of the treatments on tumour recurrence at the excision site, but there was a higher incidence of involved lymph nodes in mice given di-me-PGE2.

A new method for studying cell growth in suspension, and its use to show that indomethacin enhances cell killing by methotrexate

Microturbidimetry has been used to measure the growth of cells in suspension. Disaggregated mouse NC carcinoma cells in culture medium were added to the wells of a microtitre test plate and incubated. Absorbance of 600 nm light was measured daily for 4 days using a microplate reader. As the cells grew, light absorbance increased. Methotrexate 2-40 ng ml-1 reduced cell growth; this effect was increased by indomethacin 1 microgram ml-1, possibly by displacing methotrexate from its binding by serum protein or by enhancing cell uptake of methotrexate. Similar results were obtained by conventional clonogenic assays. The new technique offers simplicity, better reproducibility, and substantial savings in time and cost.

Rheumatoid arthritis and cancer studies based on linking nationwide registries in Finland

Two separate registries that cover the whole population of Finland have been linked in order to study the occurrence of cancer in patients with rheumatoid arthritis. The two registries involved were the Social Insurance Institution's Population Register, which collects information on medication for certain chronic diseases since 1967 including rheumatoid arthritis, and the Finnish Cancer Registry, which has data on all cancer patients in Finland since 1953. The 213,911 person-years' follow-up of 46,101 individuals with rheumatoid arthritis revealed 1,202 cases of cancer. The relative risk of cancer was 1.15 in males and 1.01 in females. The observed number of cases significantly exceeded that expected in Hodgkin's disease, non-Hodgkin's lymphomas, multiple myeloma, and leukemia. In general, the incidence of epithelial tumors was as expected. These findings were further supported by studying the occurrence of subsequent new primary cancers among patients with rheumatoid arthritis and cancer.

Multiple tumor incidence in patients with rheumatoid arthritis or allied disorders

The incidence of multiple malignant neoplasms in 55,279 patients with rheumatoid arthritis (RA) or allied disorders was studied by linking two separate nationwide data registers covering the whole Finnish population. The linking of the Social Insurance Institution's Population Register and the Finnish Cancer Registry resulted in 2106 cancer patients in whom both cancer (diagnosed in 1967-1978) and rheumatoid arthritis or allied disorders (diagnosed before cancer) were diagnosed. In 1974, the allied disorders (ankylosing spondylitis or systemic connective tissue diseases) accounted for 3.9% of all the diagnoses in the Social Insurance Institution's Population Register. The incidence of multiple neoplasms was slightly but not significantly higher in cancer patients with RA or allied disorders than in the general population or in all cancer patients taken together. The risk of leukemia was four times higher in the rheumatoid or allied disease cancer patients than in all the cancer patients. The results are consistent with previous results showing that the leukemia incidence in RA patients is higher than expected.

The cyclo-oxygenase and lipoxygenase pathways in human oral cancer tissue

This paper reports on the synthesis of prostaglandins in oral squamous epithelial carcinomas. Using radio-thin-layer chromatography, we observed the conversion of 14C-labelled arachidonic acid into the prostaglandins PGE2, PGF2 alpha, PGI2 and PGD2. We also observed an approximately equal production of hydroxy fatty acids. The role of the above-mentioned substances in the growth of malignant tumours and the process of metastasis is discussed.

Influence of various prostaglandin synthesis inhibitors on DMH-induced rat colon cancer

To evaluate the influence of inhibitors of prostaglandin synthesis on the incidence of DMH-induced colon cancer, 90 male Sprague-Dawley rats were randomly assigned to: indomethacin 20 mg per liter drinking water, meclofenamate 50 mg per liter drinking water, or normal drinking water (control group). Dimethylhydrazine was given by weekly subcutaneous injections (20 mg/kg body weight) during the first 20 weeks. Thirty-two weeks after the start of treatment and carcinogen exposure, the animals were killed and examined for the number, size, location, and spread of intestinal tumors. Colon cancer incidence was significantly lower in animals receiving indomethacin (56 per cent) compared with the control group (88 per cent) and with the meclofenamate group (90 per cent) (P less than 0.005). The corresponding figures for tumors in the small intestine were 31, 46, and 35 per cent, respectively. The tumors in indomethacin-treated animals did not differ in number, size, location, or spread from tumors of the other groups, suggesting that indomethacin might influence the carcinogenic process itself, rather than the natural course of the established disease. We conclude that indomethacin significantly reduces the incidence of large-bowel cancer in this animal model and that this observation may have some potential for future chemopreventive studies in human high-risk groups (e.g. ulcerative colitis, familial polyposis).

Growth inhibition of transplantable murine colon adenocarcinoma 38 by indomethacin

The anti-inflammatory drug indomethacin was tested for antitumor activity against transplantable mouse colon adenocarcinoma 38 (colon 38). Groups of BDF1 mice (C57BL/6 X DBA/2) were given intraperitoneal injections of this drug beginning on the 6th day after subcutaneous implantation of the tumor and continued for 4 to 8 days. In other groups of mice, identical treatment was delayed until the 16th day after implantation of the tumor. The higher antitumor activity against colon 38 was obtained with earlier initiation of treatment, indicated by decreased growth of the tumor and increased life span of the host. The later initiation of the treatment produced less antitumor activity. The antitumor activity was, however, less than that of 5-fluorouracil, which was used as a positive control drug. The two drugs in combination produced few advantages over 5-fluorouracil alone using the dose schedule designed in the present experiment. Indomethacin treatment significantly reduced prostaglandin E and F levels in the tumor tissue, but 5-fluorouracil did not. It seems likely that the inhibition of prostaglandin biosynthesis by indomethacin underlies the antitumor effect of this drug on colon 38.