Effects of protease, phytase and a Bacillus sp. direct-fed microbial on nutrient and energy digestibility, ileal brush border digestive enzyme activity and cecal short-chain fatty acid concentration in broiler chickens.

Two experiments were conducted to determine the effects of protease and phytase (PP) and a Bacillus sp. direct-fed microbial (DFM) on dietary energy and nutrient utilization in broiler chickens. In the first experiment, Ross 308 broiler chicks were fed diets supplemented with PP and DFM in a 2×2 factorial arrangement. The 4 diets (control (CON), CON + PP, CON + DFM, and CON + PP + DFM) were fed from 15-21 days of age. In Experiment 1, significant interaction (P≤0.01) between PP and DFM on the apparent ileal digestibility coefficient for starch, crude protein, and amino acid indicated that both additives increased the digestibility. Both additives increased the nitrogen retention coefficient with a significant interaction (P≤0.01). Although no interaction was observed, significant main effects (P≤0.01) for nitrogen-corrected apparent ME (AMEn) for PP or DFM indicated an additive response. In a follow-up experiment, Ross 308 broiler chicks were fed the same experimental diets from 1-21 days of age. Activities of ileal brush border maltase, sucrase, and L-alanine aminopeptidase were increased (P≤0.01) by PP addition, while a trend (P = 0.07) for increased sucrase activity was observed in chickens fed DFM, in Experiment 2. The proportion of cecal butyrate was increased (P≤0.01) by DFM addition. Increased nutrient utilization and nitrogen retention appear to involve separate but complementary mechanisms for PP and DFM, however AMEn responses appear to have separate and additive mechanisms.

DNA topoisomerase II enzymes as molecular targets for cancer chemotherapy.

DNA topoisomerase II enzymes regulate essential cellular processes by altering the topology of chromosomal DNA. These enzymes function by creating transient double-stranded breaks in the DNA molecule that allow the DNA strands to pass through each other and unwind or unknot tangled DNA. Because of the integral role of topoisomerases in regulating DNA metabolism, these enzymes are vital for cell survival. Several clinically active antitumor agents target these enzymes. Mammalian cells contain two topoisomerase II isozymes that are encoded by different genes: topoisomerase IIα and IIß. Although, both isozymes are homologous and exhibit similar catalytic activity, they are differentially regulated and are involved in distinct biological functions. The topoisomerase IIα and topoisomerase IIß enzymes are regulated by post-translational modifications, including sumoylation, ubiquitination and phosphorylation. These post-translational modifications influence the biologic and catalytic activity of the enzyme and affect sensitivity of cells to topoisomerase II-targeted drugs. In this review, we describe how the catalytic and biologic activity of the topoisomerase II enzyme is regulated and discuss the mechanisms by which chemotherapeutic agents that target these enzymes function. Given the potential importance of site-specific modifications, in particular phosphorylation, in regulating sensitivity to topoisomerase II-targeted drugs, we discuss the potential role of altered topoisomerase II phosphorylation in development of drug resistance, which is often a limiting factor in the treatment of cancer.

Downregulation of topoisomerase IIbeta in myeloid leukemia cell lines leads to activation of apoptosis following all-trans retinoic acid-induced differentiation/growth arrest.

Among the topoisomerase (topo) II isozymes (alpha and beta), topo IIbeta has been suggested to regulate differentiation. In this study, we examined the role of topo IIbeta in all-trans retinoic acid (ATRA)-induced differentiation of myeloid leukemia cell lines. Inhibition of topo IIbeta activity or downregulation of protein expression enhanced ATRA-induced differentiation/growth arrest and apoptosis. ATRA-induced apoptosis in topo IIbeta-deficient cells involved activation of the caspase cascade and was rescued by ectopic expression of topo IIbeta. Gene expression profiling led to the identification of peroxiredoxin 2 (PRDX2) as a candidate gene that was downregulated in topo IIbeta-deficient cells. Reduced expression of PRDX2 validated at the mRNA and protein level, in topo IIbeta-deficient cells correlated with increased accumulation of reactive oxygen species (ROS) following ATRA-induced differentiation. Overexpression of PRDX2 in topo IIbeta-deficient cells led to reduced accumulation of ROS and partially reversed ATRA-induced apoptosis. These results support a role for topo IIbeta in survival of ATRA-differentiated myeloid leukemia cells. Reduced expression of topo IIbeta induces apoptosis in part by impairing the anti-oxidant capacity of the cell owing to downregulation of PRDX2. Thus, suppression of topo IIbeta and/or PRDX2 levels in myeloid leukemia cells provides a novel approach for improving ATRA-based differentiation therapy.

Phase I trial of phenoxodiol delivered by continuous intravenous infusion in patients with solid cancer.

BACKGROUND: Phenoxodiol is a multi-pathway initiator of apoptosis with broad anti-tumor activity and high specificity for tumor cells. Its biochemical effects are particularly suited to reversal of chemo-resistance, and the drug is being developed as a chemo-sensitizer of standard chemotherapeutics in solid cancers. This phase I, single-center trial was conducted to test a continuous intravenous dosing regimen of phenoxodiol in patients with late-stage, solid tumors to determine toxicity, pharmacokinetics, and preliminary efficacy. METHODS: Phenoxodiol given by intravenous infusion continuously for 7 days on 14-day cycles was dose-escalated on an inter-patient basis at dosages of 0.65,1.3, 3.3, 20.0, and 27.0 mg/kg/day (three to four patients per stratum). Treatment cycles continued until disease progression. Toxicity was based on standard criteria; efficacy was based on changes in tumor burden (WHO); pharmacokinetic analysis was conducted on plasma samples at specified time points during treatment cycles. RESULTS: Nineteen heavily-pre-treated patients with solid tumors received a median of three cycles of treatment (range 1-13); two patients received >or= 12 cycles. No dose-limiting toxicities were encountered, with emesis and fatigue (one patient) and rash (one patient) the only significant toxicities. Stabilized disease was the best efficacy outcome, with one patient showing stable disease at 24 weeks. Pharmacokinetics suggested a linear relationship between dosage and mean steady-state plasma concentrations of phenoxodiol. CONCLUSION: A 7-day continuous infusion of phenoxodiol given every 2 weeks is well tolerated up to a dose of 27.0 mg/kg/day.

Enhanced etoposide sensitivity following adenovirus-mediated human topoisomerase IIalpha gene transfer is independent of topoisomerase IIbeta.

The roles that the alpha and beta isoforms of topoisomerase II (topo II) play in anticancer drug action were determined using MDA-VP etoposide-resistant human breast cancer cells and a newly constructed adenoviral vector containing the topo IIalpha gene (Ad-topo IIalpha). MDA-VP cells were more resistant to etoposide than to amsacrine and had more resistance to etoposide than did MDA-parental cells. MDA-VP cells also expressed lower topo IIalpha RNA and protein levels than parental cells but had comparable topo IIbeta levels. After infection with Ad-topo IIalpha, topo IIalpha, RNA and protein levels increased significantly, as did the cells' sensitivity to etoposide. In contrast, topo IIbeta levels remained constant with little alteration in the cells' sensitivity to amsacrine. Band-depletion immunoblotting assays indicated that topo IIalpha was depleted in etoposide-treated, Ad-topo IIalpha-transduced MDA-VP cells but not in amsacrine-treated cells. Topo IIbeta was depleted in amsacrine-treated, Ad-topo IIalpha-MDA-VP cells, with little change in the topo IIalpha levels. These results suggest that topo IIalpha gene transfer does not alter topo IIbeta expression and that enhanced sensitivity to etoposide is therefore secondary to change in topo IIalpha levels. These studies support the theory that etoposide preferentially targets topo IIalpha, while amsacrine targets topo IIbeta.

Topoisomerase II poisoning by ICRF-193.

Antineoplastic bis(dioxopiperazine)s, such as meso-2,3-bis(2,6-dioxopiperazin-4-yl)butane (ICRF-193), are widely believed to be only catalytic inhibitors of topoisomerase II. However, topoisomerase inhibitors have little or no antineoplastic activity unless they are topoisomerase poisons, a special subclass of topoisomerase-targeting drugs that stabilize topoisomerase-DNA strand passing intermediates and thus cause the topoisomerase to become a cytotoxic DNA-damaging agent. Here we report that ICRF-193 is a very significant topoisomerase II poison. Detection of topoisomerase II poisoning by ICRF-193 required the use of a chaotropic protein denaturant in the topoisomerase poisoning assays. ICRF-193 caused dose-dependent cross-linking of human topoisomerase IIbeta to DNA and stimulated topoisomerase IIbeta-mediated DNA cleavage at specific sites on (32)P-end-labeled DNA. Human topoisomerase IIalpha-mediated DNA cleavage was stimulated to a lesser extent by ICRF-193. In vivo experiments with MCF-7 cells also showed the requirement of a chaotropic protein denaturant in the assays and selectivity for the beta-isozyme of human topoisomerase II. Studies with two topoisomerase IIbeta-negative cell model systems confirmed significant topoisomerase II poisoning by ICRF-193 in the wild type cells and were consistent with beta-isozyme selectivity. Common use of only the detergent, SDS, in assays may have led to failure to detect topoisomerase II poisoning by ICRF-193 in earlier studies.

Cytotoxic mechanism of XK469: resistance of topoisomerase IIbeta knockout cells and inhibition of topoisomerase I.

Topoisomerase IIbeta knockout mouse cells (beta-/-) were found to have only slight resistance to m-AMSA, a dual topoisomerase IIalpha-IIbeta poison, as compared to wild-type cells (beta+/+) during 1 h or 3 day exposures to the drug. In contrast, the beta-/- cells were greater than threefold resistant to XK469, a selective topoisomerase IIbeta poison during three day drug exposures (beta+/+ IC(50) = 175 microM, beta-/- IC(50) = 581 microM). Short term (1 h) exposure to XK469 was not cytotoxic to either beta-/- or beta+/+ cells, suggesting that anticancer therapy with XK469 may be more efficacious if systemic levels can be prolonged. During studies on topoisomerase activity in nuclear extracts of the beta+/+ and beta-/- cells, we found evidence that XK469 is a weak topoisomerase I catalytic inhibitor. The high IC(50) for topoisomerase I inhibition (2 mM) suggests that topoisomerase I is not a significant target for XK469 cytotoxicity.

Cell cycle phase specificity in the potentiation of etoposide-induced DNA damage and apoptosis by KN-62, an inhibitor of calcium-calmodulin-dependent enzymes.

The cell cycle phase-dependent induction of DNA damage and apoptosis by etoposide (VP-16) and its modulation by 1-[N,O-bis(1, 5-isoquinolinesulfonyl)-N-methyl-l-tyrosyl]-4-piperazine (KN-62), an inhibitor of calcium-calmodulin-dependent enzymes, were examined in sensitive (HL-60/S) and VP-16-resistant (HL-60/DOX0.05) HL-60 cells. Cells from exponential-phase cultures were enriched by centrifugal elutriation into G(1), S, and G(2)+M fractions. Modulation of VP-16-induced apoptosis by KN-62 in HL-60/S cells was apparent only in the S phase at the IC(50) concentration. However, in the HL-60/DOX0.05 cells, significant (P < 0.001) potentiation of VP-16-induced apoptosis by a non-cytotoxic concentration of 2 microM KN-62 was apparent in cells in the G(1), S, and G(2)+M phases, as well as over the entire concentration range tested. VP-16-induced apoptosis and its potentiation by a non-cytotoxic concentration of 2 microM KN-62 were correlative with drug-stabilized DNA cleavable complex formation based on a band depletion assay. In agreement with the results on apoptosis in the resistant HL-60/DOX0.05 cells, the enhanced depletion of the alpha and beta isoforms of topoisomerase II by VP-16 + KN-62 was observed in G(1), S, and G(2)+M cells. Results suggest that the effects of KN-62 in reversing resistance are based on its role as a potent sensitizer of VP-16-induced DNA damage and apoptosis in a cell cycle phase-independent manner.

Roles of NF-kappaB and 26 S proteasome in apoptotic cell death induced by topoisomerase I and II poisons in human nonsmall cell lung carcinoma.

Activation of signaling pathways after DNA damage induced by topoisomerase (topo) poisons can lead to cell death by apoptosis. Treatment of human nonsmall cell lung carcinoma (NSCLC-3 or NSCLC-5) cells with the topo I poison SN-38 or the topo II poison etoposide (VP-16) leads to activation of NF-kappaB before induction of apoptosis. Inhibiting the degradation of IkappaBalpha by pretreatment with the proteasome inhibitor MG-132 significantly inhibited NF-kappaB activation and apoptosis but not DNA damage induced by SN-38 or VP-16. Transfection of NSCLC-3 or NSCLC-5 cells with dominant negative mutant IkappaBalpha (mIkappaBalpha) inhibited SN-38 or VP-16 induced transcription and DNA binding activity of NF-kappaB without altering drug-induced apoptosis. Regulation of apoptosis by mitochondrial release of cytochrome c and activation of pro-caspase 9 followed by cleavage of poly(ADP-ribose) polymerase by effector caspases 3 and 7 was similar in neo and mIkappaBalpha cells treated with SN-38 or VP-16. In contrast to pretreatment with MG-132, exposure to MG-132 after SN-38 or VP-16 treatment of neo or mIkappaBalpha cells decreased cell cycle arrest in the S/G2 + M fraction and enhanced apoptosis compared with drug alone. In summary, apoptosis induced by topoisomerase poisons in NSCLC cells is not mediated by NF-kappaB but can be manipulated by proteasome inhibitors.

Phase I trial of capecitabine in combination with interferon alpha in patients with metastatic renal cancer: toxicity and pharmacokinetics.

PURPOSE: The present study was designed to determine the toxicity and maximum tolerated doses of oral intermittent oral capecitabine and subcutaneous (s.c.) rHuIFNalpha2a in patients with metastatic renal cell carcinoma (RCC). The pharmacokinetics of capecitabine and its metabolites were also investigated. METHODS: A total of 27 patients were treated at four dose levels of capecitabine (825 or 1000 mg/m2 twice daily orally, days 1-14, 22-36) and rHuIFNalpha2a (1.5 or 3.0 MU/m2 s.c. three times weekly). Unchanged capecitabine and its metabolites were analyzed in plasma using liquid chroatography/mass spectrometry in ten patients. RESULTS: The toxicity of combined capecitabine and rHuIFNalpha2a was moderate. Patients experienced mild nausea/vomiting (70%) and diarrhea (63%). The hand-foot syndrome was seen in 67% of patients and was generally mild, as was hematologic toxicity. Dose-limiting toxicity included diarrhea, mucositis, neutropenia and the hand-foot syndrome. The dose level recommended for further trials included capecitabine 1000 mg/m2 twice daily and rHuIFNalpha2a 3.0 MU/m2 three times weekly. One patient had a partial response of a liver lesion (duration > 200 days). Pharmacokinetic parameters of capecitabine and its metabolites (5'-deoxy-5-fluorouridine, 5-fluorouracil and alpha-fluoro-beta-alanine) were similar to those reported by other authors. There was rapid conversion to 5'-deoxyuridine. The peak plasma concentrations of capecitabine occurred between 0.5 and 3.0 h. CONCLUSIONS: The combination of capecitabine and rHuIFNalpha2a was well tolerated. The recommended dose levels for phase II trials are: rHuIFNalpha2a 3.0 MU/m2 s.c. three times weekly and oral capecitabine 1000 mg/m2 twice daily for 2 weeks. No evidence of an effect of rHuIFNalpha2a on the pharmacokinetics of capecitabine or its metabolites was apparent. A phase II trial in untreated patients with metastatic RCC is planned.

A phase II pharmacodynamic study of pyrazoloacridine in patients with metastatic colorectal cancer.

PURPOSE: To perform a phase II trial of pyrazoloacridine (PZA), a novel DNA intercalator, in patients with metastatic colorectal carcinoma and no previous therapy. METHODS: PZA was administered at a dose of 750 mg/m2 intravenously over 3 h every 21 days. Pharmacokinetic studies to determine PZA plasma concentrations were performed. RESULTS: No responses were seen in 14 response-evaluable patients. Patients received a median of two cycles of PZA (range 1-6). Toxicity included neutropenia and neurologic side-effects, which were > or = grade III in 73% and 14%, respectively. High plasma concentrations of PZA (Cmax) correlated with low neutrophil counts (P = 0.04). CONCLUSIONS: PZA is inactive at this dose and schedule in colorectal cancer, and produces moderately severe toxicity.

Effect of extracellular magnesium on topoisomerase II activity and expression in human leukemia HL-60 cells.

Topoisomerase II (TopoII) is a Mg-dependent enzyme involved in topological modifications of DNA that are crucial to the regulation of cell proliferation and possibly differentiation. To investigate the role of Mg availability in the modulation of TopoII in whole cells, we studied enzyme activity and expression in HL-60 cells grown in the presence of decreasing amounts of extracellular Mg (0.5, 0.03, and 0.01 mM MgSO(4)). In comparison to cells grown in 0.5 mM Mg, cells grown in 0.03 mM Mg exhibited a decrease in TopoII activity, as evidenced by reduced induction of DNA/TopoII cleavable complexes and apoptosis by etoposide and teniposide. Enzyme activity was restored by the readdition of Mg (0.5 and 1.5 mM) in the incubation medium, confirming that this effect was indeed modulated by extracellular Mg. Restriction of Mg to 0.01 mM was associated with a dramatic decrease in TopoII activity resembling that observed in HL-60 cells differentiated by dimethyl sulfoxide treatment. The restriction of Mg, while decreasing enzyme activity, was found to upregulate TopoII protein expression, determined by Western blot analysis. The increase of TopoII protein levels was correlative with the degree of Mg deprivation. Collectively, these results indicate that extracellular levels of Mg may control availability of intracellular Mg, thus affecting the regulation of TopoII activity/expression and downstream processes of cell proliferation and/or differentiation.

Phase I trial of exisulind (sulindac sulfone, FGN-1) as a chemopreventive agent in patients with familial adenomatous polyposis.

Exisulind (sulindac sulfone; FGN-1), a metabolite of sulindac without known effects on prostaglandin synthesis, can promote apoptosis and inhibit tumorigenesis in preclinical systems. We performed a Phase I trial of this compound in patients with familial adenomatous polyposis (FAP) to examine the tolerability and safety of this drug in the cancer chemoprevention setting. Six patients each were treated with exisulind at doses of 200, 300, and 400 mg p.o. twice a day. Reversible hepatic dysfunction was noted in four of six patients treated at the 400-mg p.o., twice-a-day dose level, but in only one to two of six patients treated at each of the lower dose levels. The serum half-life of exisulind was 6-9 h; little drug accumulation was noted over time. A nonsignificant trend toward increased apoptosis in polyps was noted at the maximum tolerated dose, but no decrease in polyp numbers or significant effects on cellular proliferation was noted. After treatment, polyps tended to display a "halo" appearance grossly and mucinous differentiation histologically. The maximum safe dose of exisulind is 300 mg p.o. twice a day in patients with subtotal colectomies. Reversible hepatic dysfunction limits further dose escalation. A decrease in polyp numbers could not be demonstrated, but the trend toward increased apoptosis at the MTD and the observation of mucinous change histologically suggest that further investigation of drugs of this class might be warranted.

Altered drug interaction and regulation of topoisomerase IIbeta: potential mechanisms governing sensitivity of HL-60 cells to amsacrine and etoposide.

Topoisomerase II (topo II), an enzyme essential for cell viability, is present in mammalian cells as the alpha- and beta-isoforms. In human leukemia HL-60/S or HL-60/doxorubicin (DOX)0.05 cells, the levels of topo IIalpha- or beta-protein were similar in either asynchronous exponential or synchronized cultures. Although topo IIalpha was hypophosphorylated in HL-60/DOX0.05 compared with HL-60/S cells, both overall and site-specific hyperphosphorylation of topo IIbeta was apparent in HL-60/DOX0.05 compared with HL-60/S cells. The phosphorylation of topo IIalpha and not beta was enhanced in the S and G(2) + M phases of HL-60/S cells. In contrast, an increase in the phosphorylation of topo IIbeta compared with alpha was apparent in the G(1) and S phases of HL-60/DOX0.05 cells. The cytotoxicity and depletion of topo IIalpha or beta in cells treated with drug for 1 h revealed that mole-for-mole, amsacrine was 2-fold more effective than etoposide in killing HL-60/S or HL-60/DOX0.05 cells and in depleting the beta versus alpha topo II protein. Present results demonstrate that: 1) hyperphosphorylation of topo IIbeta in HL-60/DOX0.05 cells may be a compensatory consequence of the hypophosphorylation of topo IIalpha to maintain normal topo II function during proliferation, and 2) enhanced sensitivity of HL-60/S or HL-60/DOX0.05 cells to amsacrine may be due to the preferential interaction and depletion of topo IIbeta.

Gas chromatographic-mass spectrometric analysis of perillyl alcohol and metabolites in plasma.

Perillyl alcohol (POH), a metabolite of d-limonene and a component of the lavender oil, is currently in Phase I clinical trials both as a chemopreventative and chemotherapeutic agent. In vivo, POH is metabolized to less active perillic acid (PA) and cis- and trans-dihydroperillic acids [DHPA, 4-(1'-methylethenyl)-cyclohexane-1-carboxylic acid]. Previous pharmacokinetic studies using a GC-MS method detected POH metabolites but not POH itself; thus these studies lacked information on the parent drug. The present report describes a sensitive GC-MS method for the quantitation of POH and metabolites using stable-isotopically labeled internal standards. The residue obtained from CH2Cl2 extraction of a plasma sample was silylated. The products were separated on a capillary column and analyzed by an ion-trap GC-MS using NH3 chemical ionization. POH-d3 was used as the internal standard for POH while 13C-PA-d2 was used as the internal standards for the metabolites. The quantitation limits for POH, PA, cis- and trans-DPA were <10 ng/ml using 1-2 ml plasma. The assay was validated in rat and human plasma. The assay was linear from 2 to 2000 ng/ml for POH, 10 to 1000 ng/ml for PA and trans-DHPA, and 20 to 1000 ng/ml for cis-DHPA monitored. The within-run and between-run coefficients of variation were all <8%. Preliminary pharmacokinetic data from a rat following i.v. administration of POH at 23 mg/kg and from a patient receiving POH at 500 mg/m2 p.o. was also provided. Intact POH, PA, cis- and trans-DHPA were all detected in plasma in both cases. Two new major metabolites were found in human and one in the rat plasma.

Approaches to managing carboplatin-induced thrombocytopenia: focus on the role of amifostine.

Thrombocytopenia is a significant problem for patients receiving prolonged or aggressive chemotherapy for malignancy. For carboplatin, it is the predominant dose-limiting toxicity and it is cumulative in nature. A number of agents have been evaluated for efficacy in reducing the problem of thrombocytopenia. Some have proved valueless and have been discarded. Others (eg, recombinant thrombopoietin) are under current study, and one (interleukin-11 or oprelvekin) is now commercially available. In addition, the currently available cytoprotectant, amifostine (Ethyol; Alza Pharmaceuticals, Palo Alto, CA/US Bioscience, West Conshohocken, PA), has been shown to reduce the severity and duration of thrombocytopenia caused by carboplatin. Because of the short half-life of amifostine relative to that of carboplatin, multiple doses of amifostine have been administered in conjunction with carboplatin. The optimal dosing regimen with amifostine and carboplatin needs to be further evaluated in clinical studies. Future trials will also expand these observations to carboplatin-containing combination chemotherapy regimens and will further define the role of amifostine as a multilineage bone marrow protectant. The ability of amifostine to demonstrate multilineage bone marrow protection differentiates it from currently available growth factors and fulfills a medical need, including reducing the need for platelet transfusions and maintaining the desired chemotherapy dose intensity.

Sulindac sulfone induced regression of rectal polyps in patients with familial adenomatous polyposis.

Sulindac sulfone (Exisulind), a metabolite of the non-steroidal anti-inflammatory drug, sulindac, was evalauted for its effects on the development of rectal polyps in patients with familial adenomatous polyposis. Three cohorts of 6 patients each were given doses of 200, 300, or 400 mg Exisulind twice daily. Hepatotoxicity, shown by elevation in blood transaminase levels, was the dose-limiting toxicity and occurred at the 400 mg bid dose. Due to this toxicity, all patients treated with the 400 mg dose were subsequently reduced to the 200 mg dose level. Subsequently, 2 of the 6 patients were dose-escalated to 400 mg bid dose. The patients were treated with Exisulind for a period of six months. Sixteen of 18 patients had regression of small polyps (> or = 6 mm in diameter) characterized by a flattening of the polyps and a macular "halo" appearance. Histopathologic examination of the polyp biopsy specimens showed a marked increase in the proportion of mucin producing cells in the glands after treatment with Exisulind at all dose levels. Ki-67 staining, a measure of cell proliferation, was higher in the polyps than in normal mucosa. There was no significant change in the proliferation index between baseline and six month values in any of the groups treated with Exisulind or in normal tissues. The median apoptotic labeling index, as determined by the TUNEL technique, was higher in the polyps than in normal-appearing mucosa. Overall, there was no significant change in the apoptotic labeling index between base-line and 6 months in normal-appearing mucosa however, the index in polyps was increased. These results suggest that treatment of FAP patients with Exisulind for a period of six months may lead to regression of small polyps, and that the mechanisms of Exisulind--induced regression appear to be through stimulation of mucus differentiation and apoptosis in glandular epithelium.