The metabolism and pharmacokinetics of phospho-sulindac (OXT-328) and the effect of difluoromethylornithine.

BACKGROUND AND PURPOSE: Phospho-sulindac (PS; OXT-328) prevents colon cancer in mice, especially when combined with difluoromethylornithine (DFMO). Here, we explored its metabolism and pharmacokinetics. EXPERIMENTAL APPROACH: PS metabolism was studied in cultured cells, liver microsomes and cytosol, intestinal microsomes and in mice. Pharmacokinetics and biodistribution of PS were studied in mice. KEY RESULTS: PS undergoes reduction and oxidation yielding PS sulphide and PS sulphone; is hydrolysed releasing sulindac, which generates sulindac sulphide (SSide) and sulindac sulphone (SSone), all of which are glucuronidated. Liver and intestinal microsomes metabolized PS extensively but cultured cells converted only 10% of it to PS sulphide and PS sulphone. In mice, oral PS is rapidly absorbed, metabolized and distributed to the blood and other tissues. PS survives only partially intact in blood; of its three major metabolites (sulindac, SSide and SSone), sulindac has the highest C(max) and SSone the highest t(1/2) ; their AUC(0-24h) are similar. Compared with conventional sulindac, PS generated more SSone but less SSide, which may contribute to the safety of PS. In the gastroduodenal wall of mice, 71% of PS was intact; sulindac, SSide and SSone together accounted for <30% of the total. This finding may explain the lack of gastrointestinal toxicity by PS. DFMO had no effect on PS metabolism but significantly reduced drug level in mouse plasma and other tissues. CONCLUSIONS AND IMPLICATIONS: Our findings establish the metabolism of PS define its pharmacokinetics and biodistribution, describe its interactions with DFMO and largely explain its gastrointestinal safety.

Phospho-ibuprofen (MDC-917) incorporated in nanocarriers: anti-cancer activity in vitro and in vivo.

BACKGROUND AND PURPOSE: Phospho-ibuprofen (P-I; MDC-917) inhibits the growth of colon cancer in mice. Here, we investigated the use of nanocarriers to improve its pharmacokinetics (PKs) and anti tumour efficacy. EXPERIMENTAL APPROACH: The cellular uptake and cytotoxicity of P-I encapsulated into liposomes and micelles, and its in vitro metabolic stability, were determined in cultures of human colon adenocarcinoma cells. The performance of liposomal P-I was further evaluated in PK studies in mice, and in a model of colon cancer xenografts in nude mice. KEY RESULTS: Liposomal P-I and micellar P-I showed significantly enhanced cellular uptake in the colon cancer cells. Liposomal P-I also demonstrated increased cytotoxicity in vitro. Free P-I was metabolized rapidly to ibuprofen in the presence of purified esterases. In contrast, liposomal P-I, and to a lesser extent micellar P-I, was resistant to esterase-mediated hydrolysis. In mice, liposomal P-I partially protected P-I from hydrolysis in the circulation, and improved the biodistribution of intact P-I and its metabolites compared to free P-I. Liposomal P-I was more effective at inhibiting the growth of human colon cancer xenografts in mice, which may be explained on the basis of its improved PK profile compared to free P-I. CONCLUSIONS AND IMPLICATIONS: Liposome encapsulation of P-I partially protected P-I from esterase-mediated hydrolysis in mice, enhanced the cytotoxicity and bioavailability of P-I and increased its efficacy at inhibiting the growth of human colon cancer xenografts. These results indicate that liposomes are suitable nanocarriers for the delivery of P-I, and that the anti-tumour potential of liposomal P-I merits further evaluation.

The novel phospho-non-steroidal anti-inflammatory drugs, OXT-328, MDC-22 and MDC-917, inhibit adjuvant-induced arthritis in rats.

BACKGROUND AND PURPOSE: The use of non-steroidal anti-inflammatory drugs (NSAIDs) in the treatment of rheumatoid arthritis (RA) is limited by their toxicity. We evaluated the anti-inflammatory efficacy and safety of three novel modified NSAIDs, phospho-aspirin, phospho-ibuprofen and phospho-sulindac. EXPERIMENTAL APPROACH: We determined the anti-inflammatory effects and gastrointestinal safety of the phospho-NSAIDs in the rat adjuvant arthritis model and studied their mechanism of action in cultured cells, Cytokines were measured with elisa and activation of nuclear factor-κB (NF-κB) by immunohistochemistry. KEY RESULTS: All three phospho-NSAIDs showed less gastrointestinal toxicity than their parent compounds and demonstrated strong anti-inflammatory effects, essentially reversing joint inflammation and oedema. They have a broad but not uniform effect on the expression of relevant cytokines, in general decreasing IL-6 and IL-1ß and increasing IL-10 levels in rat plasma and cultured cells. Phospho-sulindac and phospho-ibuprofen but not phospho-aspirin suppressed PGE(2) production in vitro, whereas phospho-aspirin (in contrast to aspirin) showed the same effect in vivo. In joint tissues, phospho-aspirin inhibited NF-κB activation, and suppressed inflammation and bone resorption. Phospho-aspirin also inhibited Jurkat T cell proliferation. In general, phospho-aspirin had greater efficacy but different effects upon inflammatory mediators compared with aspirin. The chemical modification of the parent NSAIDs seems crucial for their safety and efficacy. CONCLUSIONS AND IMPLICATIONS: Phospho-aspirin, phospho-ibuprofen and phospho-sulindac were safer than their parent NSAIDs, were highly effective in rat adjuvant arthritis and inhibited many key mediators in the pathophysiology of RA. These novel compounds are promising candidate drugs for the treatment of RA and merit further evaluation.

Induction of oxidative stress as a mechanism of action of chemopreventive agents against cancer.

Prevention is a promising option for the control of cancer. Cellular redox changes have emerged as a pivotal and proximal event in cancer. In this review, we provide a brief background on redox biochemistry, discuss the important distinction between redox signalling and oxidative stress, and outline the 'multiple biological personalities' of reactive oxygen and nitrogen species: at low concentrations they protect the cell; at higher concentrations they can damage many biological molecules, such as DNA, proteins, and lipids; and, as we argue here, they may also prevent cancer by initiating the death of the transformed cell. Nitric oxide-donating aspirin is discussed as an instructive example: it generates a state of oxidative stress through which it affects several redox-sensitive signalling pathways, leading ultimately to the elimination of the neoplastic cell via apoptosis or necrosis. As additional examples, we discuss the chemopreventive n-3 polyunsaturated fatty acids and conventional nonsteroidal anti-inflammatory drugs, which induce cell death through redox changes. We conclude that modulation of redox biochemistry represents a fruitful approach to cancer prevention.

Novel agents for cancer prevention based on nitric oxide.

NO (nitric oxide) biology has provided the impetus for the development of anticancer agents based on their ability to release NO. NO-NSAIDs (NO-donating non-steroidal anti-inflammatory drugs), consisting of a conventional NSAID to which an NO-releasing moiety is covalently attached, are promising chemopreventive agents against cancer. Compared with their parent compounds, NO-NSAIDs are up to several hundred times more potent in inhibiting the growth of cancer cell lines and prevent colon and pancreatic cancer in animal models. Their chemopreventive effect is due to inhibition of proliferation, induction of cell death and inhibition of cell-cycle-phase transitions. NO-ASA (NO-aspirin), the best-studied NO-NSAID, induces oxidative stress in target cells. Major downstream signalling effects involve the Wnt, NOS2 (nitric oxide synthase 2), MAPK (mitogen-activated protein kinase), NF-kappaB (nuclear factor kappaB) and Nrf2 (nuclear factor-erythroid 2 p45 subunit-related factor 2) pathways. NO-NSAIDs, particularly NO-ASA, appear to be safe compounds, as suggested by many animal and early human studies. An ongoing clinical trial is designed to determine whether NO-ASA can inhibit early stages of colon carcinogenesis in subjects at risk for colon cancer. It is clinical trials that will ultimately determine the role of NO-NSAIDs in cancer prevention and perhaps treatment.

Molecular targets of nitric-oxide-donating aspirin in cancer.

Nitric-oxide-donating aspirin (NO-ASA), consisting of ASA (aspirin) plus an -ONO2 moiety linked to it via a molecular spacer, is a new drug for cancer prevention. NO-ASA seems to overcome the low potency and toxicity of traditional ASA. The -ONO2 moiety is responsible for releasing NO, and it appears to be required for biological activity. In studies in vitro, NO-ASA inhibits the growth of colon, pancreatic, prostate, lung, skin, leukaemia and breast cancer cells, and is up to 6000-fold more potent than traditional ASA. This effect is owing to cell kinetics [inhibition of proliferation, induction of apoptosis (multiple criteria) and blocking the G1 to S cell-cycle transition] and cell signalling [inhibition of Wnt signalling (IC50=0.2 microM), inhibition of NF-kappaB (nuclear factor kappaB) activation (IC50=7.5 microM), inhibition of nitric oxide synthase-2 expression (IC50=48 microM), inhibition of MAPK (mitogen-activated protein kinase) signalling (IC50=10 microM) and induction of cyclo-oxygenase-2 at approx. 10 microM]. In studies in vivo, NO-ASA inhibits intestinal carcinogenesis in Min mice (tumour multiplicity was reduced by 59% after 3 weeks, with no effect in control animals and no side effects) and in the N-nitrosobis(2-oxopropyl)amine model of pancreatic cancer, where there was an 89% reduction in NO-ASA (3000 p.p.m. in the diet)-treated animals (P<0.001). There was no statistically significant effect by traditional ASA at equimolar doses. Our data indicate that NO-ASA is a highly promising agent for the prevention and/or treatment of cancer.

Is COX-2 a 'collateral' target in cancer prevention?

NSAIDs (non-steroidal anti-inflammatory drugs) prevent colon and other cancers. The fact that NSAIDs inhibit the eicosanoid pathway prompted mechanistic drug-developmental work focusing on COX (cyclo-oxygenase) and its products. The increased prostaglandin E2 levels and the overexpression of COX-2 in colon and many other cancers provided the rationale for clinical trials with COX-2 inhibitors for cancer prevention or treatment. However, one COX-2 inhibitor has been withdrawn from the market because of cardiovascular side effects, and there are concerns about a class effect. Evidence suggests that COX-2 may not be the only, or the ideal, target for cancer prevention; for example, COX-2 is not expressed in human aberrant crypt foci, the earliest recognizable pre-malignant lesion in the colon; COX-2 is expressed in less than half of the adenomas; in vitro data show that NSAIDs do not require the presence of COX-2 to prevent cancer; in familial adenomatous polyposis, the COX-2 inhibitor, celecoxib, had a modest effect, which was weaker than that of a traditional NSAID; and COX-2-specific inhibitors have several COX-2-independent activities, which may account for part of their cancer-preventive properties. The multiple COX-2-independent targets, and the limitations of COX-2 inhibitors, suggest the need to explore targets other than COX-2.

NO-NSAIDs and cancer: promising novel agents.

Three potential applications of NO-donating NSAIDs in human cancer include their use: as chemopreventive agents; against already developed cancers (chemotherapy); and for the control of cancer symptoms, notably cancer pain. The evidence to date of greater safety and enhanced efficacy of NO-donating NSAIDs underscores their potential to prevent colon cancer and overcome the limitations of traditional NSAIDs. NO-donating NSAIDs affect several pathways critical to colon carcinogenesis and this may explain in part their greater efficacy in colon cancer prevention as assessed in preclinical models.

Decreased expression of DNA-dependent protein kinase, a DNA repair protein, during human colon carcinogenesis.

DNA-dependent protein kinase (DNA-PK), consisting of a catalytic subunit (DNA-PKcs) and the Ku70 and Ku86 proteins, participates in the repair of DNA double-strand breaks (DSBs). We assessed its expression immunohistochemically in normal human colon tissue, colon adenomas, colon carcinomas, and normal tissue distant from carcinomas. Normal colonocytes expressed all DNA-PK proteins. Compared with the expression in normal tissue [176.62 +/- 18.56 (the intensity of expression x the percentage of cells expressing this protein), mean + SE], the expression of Ku70 was significantly reduced in adenomas (36.62 +/- 11.09; P < 0.001) and carcinomas (85.68 +/- 15.76; P < 0.01), as was the expression of Ku86 [(113.10 +/- 10.22 versus 41.66 +/- 14.71 in adenomas (P < 0.01) or versus 85.68 +/- 15.76 in carcinomas (P < 0.05)]. The expression of DNA-PKcs was not significantly changed. The marked underexpression of Ku70 and Ku86 starting at the adenoma stage may be crucial to the development of colon cancer.

Effect on treatment outcome of coinfection with SEN viruses in patients with hepatitis C.

The newly discovered SEN D and SEN H viruses are transmitted parenterally and can cause post-transfusion hepatitis. We assessed whether coinfection of patients with chronic hepatitis C and SEN D or SEN H correlates with the outcome of treatment with interferon and ribavirin. Of 31 patients with hepatitis C studied, six were positive for SEN D and seven for SEN H (one was positive for both). All of those positive for SEN D and five of those positive for SEN H failed to respond to therapy. Overall response (RNA titre and alanine aminotransferase concentration after treatment) was lower in SEN-infected patients than uninfected patients (p=0.025). We conclude that coinfection with SEN viruses is frequent in chronic hepatitis C patients and might adversely affect the outcome of treatment with interferon and ribavirin.

Nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NSAIDs) alter the kinetics of human colon cancer cell lines more effectively than traditional NSAIDs: implications for colon cancer chemoprevention.

Nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NO-NSAIDs), consisting of a known nonsteroidal anti-inflammatory drug (NSAID) and a nitric oxide (NO)-releasing group, are reported safer than NSAIDS: To assess their potential in colon cancer chemoprevention, we studied in vitro the effect of NO-aspirin, NO-sulindac, and NO-ibuprofen on colonocyte kinetics. These three NO-NSAIDs reduced the growth of cultured HT-29 colon adenocarcinoma cells much more effectively than the corresponding NSAIDs; e.g., at 24 h, their IC(50) values were as follows: (a) aspirin, >5000 microM; (b) NO-aspirin, 1 microM; (c) sulindac, 750 microM; (d) NO-sulindac, 150 microM; (e) ibuprofen, >1000 microM; and (f) NO-ibuprofen, 42 microM. This effect was due to inhibition of proliferation and induction of apoptosis and perhaps to the induction of novel cell changes, characterized by extensive DNA degradation. NO-NSAIDs also blocked the G(0)-G(1) to S cell cycle transition. Their superior effectiveness compared with traditional NSAIDs, combined with their reported safety, makes them promising candidates for chemopreventive agents against colon cancer.

The retinoid fenretinide inhibits proliferation and downregulates cyclooxygenase-2 gene expression in human colon adenocarcinoma cell lines.

Fenretinide [N-(4-Hydroxyphenyl)retinamide, 4-HPR] (10(-10)-10(-6) M) treatment of HT-29 human colon cancer cells for 24-72 h significantly inhibited their growth. Using HCT-15 cells, 4-HPR had limited inhibitory effects on cell proliferation over the same concentration range and time period. The inhibitory effects of 4-HPR on cell growth in HT-29 cells were markedly reduced in the presence of exogenously added prostaglandins (PGs), suggesting a possible role for inhibition of PG synthesis as a mechanism for 4-HPR's antiproliferative effects. Inhibition of PGE(2) production was caused by 4-HPR in a concentration-dependent manner and decreased COX-2 but not COX-1 mRNA levels; this is the first indication that 4-HPR selectively inhibits COX-2 gene expression. Our findings suggest a possible mechanism for the chemopreventive and anti-proliferative effects of 4-HPR.

Is inhibition of cyclooxygenase required for the chemopreventive effect of NSAIDs in colon cancer? A model reconciling the current contradiction.

NSAIDs are powerful chemopreventive agents for colon cancer, but their mechanism of action remains unknown. Their best recognized pharmacological property is inhibition of the enzyme cyclooxygenase (COX), which catalyzes the synthesis of prostaglandins; however, additional effects are well documented. Current studies on the mechanism of the chemopreventive effect of NSAIDs lead to two contradictory conclusions: NSAIDs prevent colon cancer either by inhibiting the activity of COX, or through mechanisms that do not require COX inhibition. To resolve this apparent conflict, after examining several alternatives, we propose a model, which assumes that both mechanisms are correct but that they exert their effect either on different steps of the multistep process of colon carcinogenesis or on different control mechanisms. This postulated dual action of NSAIDs may explain their remarkable effectiveness in colon cancer prevention. Unraveling these mechanistic details can be very rewarding for the design of more refined approaches to cancer chemoprevention and for a deeper understanding of colorectal carcinogenesis.

The effect of lithocholic acid on proliferation and apoptosis during the early stages of colon carcinogenesis: differential effect on apoptosis in the presence of a colon carcinogen.

Lithocholic acid (LCA) is implicated in human and experimental animal carcinogenesis. Its effect on apoptosis and proliferation of the colonic epithelium was studied in a 1,2-dimethylhydrazine (DMH)-induced murine carcinogenesis model. Four groups of mice, control, LCA, DMH and DMH+LCA, were studied for 4 weeks, a period corresponding to early stages of carcinogenesis. Apoptosis (AI) and proliferation (PI) indices in the colon were determined by immunohistochemistry. LCA stimulated apoptosis [AI = 1.2 +/- 0.3% (all values are the mean +/- SEM) versus control 0.5 +/- 0.1%, P < 0. 05], as did DMH (4.3 +/- 0.8%, P < 0.02). DMH increased apoptosis at the base of the crypt nearly 50-fold, with no effect at the lumenal third. In mice receiving DMH, LCA suppressed apoptosis almost completely (0.1 +/- 0.03%); this suppression was complete at the lower two-thirds of the crypt (AI = 0) and 60% at the lumenal third. LCA increased proliferation (PI = 22.2 +/- 4.6% versus 15.4 +/- 1% in controls), but this did not reach statistical significance. DMH increased proliferation (PI = 34.6 +/- 2.3%, P < 0.01). In mice receiving DMH, proliferation (41 +/- 2.9%) was about two-thirds of the additive effect. LCA affected proliferation, mainly in the middle third of the crypt; DMH's effect was similar in distribution, but more pronounced. In mice receiving DMH, LCA shifts proliferation upward, extending it to the lumenal third of the crypt. LCA's main cell kinetic effect in the colon is on apoptosis; this effect differs in normal (stimulation) and pre-malignant colon (nearly complete suppression). LCA does not significantly stimulate proliferation in either normal or pre-malignant colon. The differential effect of LCA on apoptosis in the presence of a carcinogen partially explains its effect as a promoter on colon carcinogenesis in animal models, and may have important implications for human carcinogenesis.

Infrared spectroscopic study of cervical smears in patients with HIV: implications for cervical carcinogenesis.

Patients with HIV have an increased incidence of cervical cancer, necessitating increased surveillance. Infrared spectroscopy (IRS) has the potential of aiding the diagnosis of cervical neoplasia and also of providing clues into its pathogenesis. We studied by IRS cervical scrapings from 22 HIV-infected and 23 control women; 8 of the former and none of the latter had dysplasia. The infrared spectra followed three patterns, designated pattern I (similar to that previously associated with normal cervical samples), pattern II (intermediate between patterns I and III), and pattern III (associated with cervical neoplasia). Compared with HIV-negative controls, HIV-infected women had a higher prevalence of pattern III and a lower prevalence of pattern II; these differences were statistically significant (P = .015 by chi2 analysis). Similar spectroscopic changes were present even when only the cytologically normal samples from HIV-positive and HIV-negative women were analyzed. We speculate that these changes may reflect early structural changes associated with cervical neoplasia that are not detectable cytologically. The infrared spectra in the region 950 to 1,300 cm(-1) could not differentiate cervical samples from HIV-infected and uninfected patients. The potential practical applications of IRS in HIV cervical disease are discussed.

Altered gastric epithelial cell kinetics in Helicobacter pylori-associated intestinal metaplasia: implications for gastric carcinogenesis.

We have compared apoptosis and proliferation in antral epithelium from individuals not infected with H. pylori (Hp), those with Hp-induced gastritis and those with Hp-induced gastritis containing areas of gastric intestinal metaplasia, the precursor lesion to gastric adenocarcinoma. Antral biopsies from 42 patients were assessed for evidence of Hp infection, severity of gastritis and intestinal metaplasia. Apoptosis was evaluated by the TUNEL assay and proliferation by Ki-67 immunohistochemistry and were expressed as apoptotic (AI) and proliferation (PI) indices. In the 31 Hp-positive (Hp(+)) patients, apoptosis and proliferation were increased compared with the 11 Hp-negative (Hp(-)) patients (AI = 1. 22 +/- 0.13% vs. 0.15 +/- 0.03%, p < 0.0001; PI = 24 +/- 1% vs. 13 +/- 2%, p < 0.0001). Increases were proportional to the severity of the inflammation. Within foci of intestinal metaplasia, in 9 of the Hp(+) patients, apoptosis was significantly reduced compared with surrounding gastritis (AI = 0.20 +/- 0.06% vs. 1.34 +/- 0.23%, p = 0. 0014), whereas proliferation was not altered (PI = 25.4 +/- 4% vs. 24.7 +/- 2%, p = 0.87), resulting in a lower AI/PI ratio in intestinal metaplasia than in surrounding gastritis (0.008 +/- 0.005 vs. 0.054 +/- 0.009, p < 0.02). Hp-induced gastritis is thus associated with increased epithelial apoptosis and proliferation compared with uninfected controls. In intestinal metaplasia, proliferation remains increased but apoptosis reverts to normal levels, and this perhaps contributes to Hp-associated gastric carcinogenesis.