Enzymatic Resolution and Decarboxylative Functionalization of α-Sulfinyl Esters.

α-Sulfinyl esters can be readily prepared through thiol substitution of α-bromo esters followed by oxidation to the sulfoxide. Enzymatic resolution with lipoprotein lipase provides both the unreacted esters and corresponding α-sulfinyl carboxylic acids in high yields and enantiomeric ratios. Subsequent decarboxylative halogenation, dihalogenation, trihalogenation and cross-coupling gives rise to functionalized sulfoxides. The method has been applied to the asymmetric synthesis of a potent inhibitor of 15-prostaglandin dehydrogenase.

Sulindac reversal of 15-PGDH-mediated resistance to colon tumor chemoprevention with NSAIDs.

Non-steroidal anti-inflammatory drugs prevent colorectal cancer by inhibiting cyclooxygenase (COX) enzymes that synthesize tumor-promoting prostaglandins. 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a tumor suppressor that degrades tumor-promoting prostaglandins. Murine knockout of 15-PGDH increases susceptibility to azoxymethane-induced colon tumors. It also renders these mice resistant to celecoxib, a selective inhibitor of inducible COX-2 during colon neoplasia. Similarly, humans with low colonic 15-PGDH are also resistant to colon adenoma prevention with celecoxib. Here, we used aspirin and sulindac, which inhibit both COX-1 and COX-2, in order to determine if these broader COX inhibitors can prevent colon tumors in 15-PGDH knockout (KO) mice. Unlike celecoxib, sulindac proved highly effective in colon tumor prevention of 15-PGDH KO mice. Significantly, however, aspirin demonstrated no effect on colon tumor incidence in either 15-PGDH wild-type or KO mice, despite a comparable reduction in colonic mucosal Prostaglandin E2 (PGE2) levels by both sulindac and aspirin. Notably, colon tumor prevention activity by sulindac was accompanied by a marked induction of lymphoid aggregates and proximal colonic inflammatory mass lesions, a side effect seen to a lesser degree with celecoxib, but not with aspirin. These findings suggest that sulindac may be the most effective agent for colon cancer prevention in humans with low 15-PGDH, but its use may also be associated with inflammatory lesions in the colon.

Colonic 15-PGDH levels are stable across distance and time and are not perturbed by aspirin intervention.

BACKGROUND AND AIMS: 15-Hydroxprostaglandin dehydrogenase (15-PGDH) mediates a colon neoplasia suppressor pathway, acting through metabolic antagonism of cyclooxygenase-mediated colon carcinogenesis. To determine whether the colon tumor prevention activity of 15-PGDH acts as a constant or variable effect among individuals, we determined whether 15-PGDH levels remain stable over subsite and time in the human colon, determined the extent of differences in 15-PGDH levels between different individuals, and determined whether 15-PGDH modulation mediates any part of the anti-colon tumor effect of aspirin. METHODS: Using real-time PCR, we measured 15-PGDH mRNA to determine the correlation of 15-PGDH level in replicate colon biopsies, in biopsies from throughout the length of the colon, in repeat biopsies taken 4 months apart, and in paired biopsies of individuals taken before and after aspirin treatment, and by Western-blot for 15-PGDH protein in mice. RESULTS: Colonic 15-PGDH levels varied 4.4-fold across the human population. Within individuals, 15-PGDH levels proved highly reproducible (r=0.81 in duplicate biopsies) and stable along the length of the colon, with average 15-PGDH levels deviating by only 17% from rectum to cecum. An individual's 15-PGDH levels are also highly stable over time, with a median coefficient of variation over a 4-month interval of only 12%. Last, colonic 15-PGDH levels proved resistant to alteration by aspirin, with only a 10% difference in 15-PGDH levels measured before and after aspirin treatment. CONCLUSIONS: 15-PGDH levels vary across the population in a stable and reproducible manner, and are resistant to alteration by aspirin. 15-PGDH represents an independent target for modulation by candidate colon tumor chemopreventive agents.

Small molecule inhibitors of 15-PGDH exploit a physiologic induced-fit closing system.

15-prostaglandin dehydrogenase (15-PGDH) is a negative regulator of tissue stem cells that acts via enzymatic activity of oxidizing and degrading PGE2, and related eicosanoids, that support stem cells during tissue repair. Indeed, inhibiting 15-PGDH markedly accelerates tissue repair in multiple organs. Here we have used cryo-electron microscopy to solve the solution structure of native 15-PGDH and of 15-PGDH individually complexed with two distinct chemical inhibitors. These structures identify key 15-PGDH residues that mediate binding to both classes of inhibitors. Moreover, we identify a dynamic 15-PGDH lid domain that closes around the inhibitors, and that is likely fundamental to the physiologic 15-PGDH enzymatic mechanism. We furthermore identify two key residues, F185 and Y217, that act as hinges to regulate lid closing, and which both inhibitors exploit to capture the lid in the closed conformation, thus explaining their sub-nanomolar binding affinities. These findings provide the basis for further development of 15-PGDH targeted drugs as therapeutics for regenerative medicine.

15-Hydroxyprostaglandin dehydrogenase inactivation as a mechanism of resistance to celecoxib chemoprevention of colon tumors.

Pharmacologic inhibitors of the prostaglandin-synthesizing COX-2 oncogene prevent the development of premalignant human colon adenomas. However, resistance to treatment is common. In this study, we show that the adenoma prevention activity of the COX-2 inhibitor celecoxib requires the concomitant presence of the 15-hydroxyprostaglandin dehydrogenase (15-PGDH) tumor suppressor gene, and that loss of 15-PGDH expression imparts resistance to celecoxib's anti-tumor effects. We first demonstrate that the adenoma-preventive activity of celecoxib is abrogated in mice genetically lacking 15-PGDH. In FVB mice, celecoxib prevents 85% of azoxymethane-induced tumors >1 mm in size, but is essentially inactive in preventing tumor induction in 15-PGDH-null animals. Indeed, celecoxib treated 15-PGDH null animals develop more tumors than do celecoxib naive WT mice. In parallel with the loss of tumor prevention activity, celecoxib-mediated suppression of colonic PGE(2) levels is also markedly attenuated in 15-PGDH-null versus WT mice. Finally, as predicted by the murine models, humans with low colonic 15-PGDH levels also exhibit celecoxib resistance. Specifically, in a colon adenoma prevention trial, in all cases tested, individuals who developed new adenomas while receiving celecoxib treatment were also found as having low colonic 15-PGDH levels.

15-hydroxyprostaglandin dehydrogenase is downregulated and exhibits tumor suppressor activity in gastric cancer.

We investigated the tumor suppressor activity and regulatory mechanism of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in gastric cancer; 15-PGDH expression was lost in 70.1% of malignant human gastric tissues, but was preserved in normal and metaplastic gastritis. KATO III and SNU-719 cells were transfected with pcDNA3.1-empty vector or an expression vector encoding wild-type 15-PGDH. In TUNEL assays apoptotic cell numbers were increased in KATO-PGDH-WT cells compared with control. We found that EGFR and ERK1/2 inhibitors clearly increased the expression of 15-PGDH in KATO III cells. Our findings demonstrate both downregulation and a tumor suppressor activity of 15-PGDH in gastric cancer.

A nonrandomized trial of vitamin D supplementation for Barrett's esophagus.

BACKGROUND: Vitamin D deficiency may increase esophageal cancer risk. Vitamin D affects genes regulating proliferation, apoptosis, and differentiation and induces the tumor suppressor 15-hydroxyprostaglandin dehydrogenase (PGDH) in other cancers. This nonrandomized interventional study assessed effects of vitamin D supplementation in Barrett's esophagus (BE). We hypothesized that vitamin D supplementation may have beneficial effects on gene expression including 15-PGDH in BE. METHODS: BE subjects with low grade or no dysplasia received vitamin D3 (cholecalciferol) 50,000 international units weekly plus a proton pump inhibitor for 12 weeks. Esophageal biopsies from normal plus metaplastic BE epithelium and blood samples were obtained before and after vitamin D supplementation. Serum 25-hydroxyvitamin D was measured to characterize vitamin D status. Esophageal gene expression was assessed using microarrays. RESULTS: 18 study subjects were evaluated. The baseline mean serum 25-hydroxyvitamin D level was 27 ng/mL (normal ≥30 ng/mL). After vitamin D supplementation, 25-hydroxyvitamin D levels rose significantly (median increase of 31.6 ng/mL, p<0.001). There were no significant changes in gene expression from esophageal squamous or Barrett's epithelium including 15-PGDH after supplementation. CONCLUSION: BE subjects were vitamin D insufficient. Despite improved vitamin D status with supplementation, no significant alterations in gene expression profiles were noted. If vitamin D supplementation benefits BE, a longer duration or higher dose of supplementation may be needed.

Molecular Imaging of Colorectal Tumors by Targeting Colon Cancer Secreted Protein-2 (CCSP-2).

A versatile biomarker for detecting colonic adenoma and colon cancer has yet to be developed. Colon cancer secreted protein-2 (CCSP-2) is a protein specifically expressed and secreted in colon adenomas and cancers. We developed a fluorescent imaging method based on CCSP-2 targeting for a more sensitive and specific detection of colorectal tumors. CCSP-2 expression was evaluated in human colon adenoma and colorectal specimens. Anti-CCSP-2 antibody was labeled with a near-infrared fluorescent dye, FPR-675, and molecular imaging of surgical human colorectal tumors was performed. Immunohistochemistry identified CCSP-2 expression in 87.0% of colorectal cancer specimens and 89.5% of colon adenoma specimens. Fluorescence imaging of surgical human colon specimens after spraying treatment with the probe permitted a clear distinction of cancer from paired normal colon tissue (target-to-background ratio, 4.09±0.42; P<.001). CCSP-2 targeting imaging was also evaluated in patient-derived colon cancer xenograft mouse and liver metastasis murine models. CCSP-2-positive colon cancer xenografts and liver metastases were visualized by near-infrared fluorescence imaging after intravenous injection of the probe, which showed significantly higher fluorescence. Our results show that CCSP-2 is a promising marker for colorectal tumor detection in clinical settings and that a CCSP-2-targeting molecular imaging strategy might improve the diagnosis of colorectal tumors in metastatic or recurrent cancers and aid in early colonoscopic detection of premalignant lesions.

Colon cancer secreted protein-2 (CCSP-2), a novel candidate serological marker of colon neoplasia.

Cancers of the colon and rectum are the second leading cause of cancer death among adult Americans. When detected at early stages, colon cancer is highly curable. Colonoscopy, an effective but invasive screening test, has been limited in its public acceptance. The goal of this study was to identify novel serum markers of colon cancers and precancerous colon adenomas as potential candidates for noninvasive detection of early colon neoplasms. Employing expression microarrays, we identified colon cancer secreted protein-2 (CCSP-2) as a novel transcript whose expression is generally absent in normal colon and other normal body tissues, but that is induced an average of 78-fold in Stage II, III, and IV colon cancers, as well as in colon adenomas and colon cancer cell lines. These findings were validated by real-time PCR analysis in an independent panel of colon cancer cases. Moreover, CCSP-2 was shown to encode a secreted protein that circulates stably and is detectable in the blood of mice bearing human cancer xenografts transfected with epitope-tagged CCSP-2. As a novel secreted protein that is markedly induced in colon adenomas and cancers, CCSP-2 is a novel candidate for development as a diagnostic serum marker of early stage colon cancer.

TGF-beta-induced nuclear localization of Smad2 and Smad3 in Smad4 null cancer cell lines.

Smad4 is a tumor suppressor gene that is commonly lost or mutated in colorectal and pancreatic cancers. The activated transforming growth factor-beta (TGF-beta) receptor phosphorylates Smad2 and Smad3, which then complex with Smad4 and translocate to the nucleus. Smad4 mutations when detected as present in some human cancers have been considered sufficient to inactivate TGF-beta signaling. In this work, we describe a colon cancer cell line, VACO-9M, that is Smad4 null when analysed by multiple assays. To study the role of Smad4 in TGF-beta-induced translocation of the receptor-activated Smads to the nucleus, we analysed by immunofluorescence the cellular localization of endogenous Smad2 and Smad3 after TGF-beta treatment of VACO-9M, plus four additional Smad4 null cell lines of breast (MDA-MB-468), or pancreatic (BxPC3, Hs766T, CFPAC-1) origin. In each cell line, TGF-beta treatment resulted in both Smad2 and Smad3 moving to the nucleus in a Smad4-independent fashion. Nuclear translocation of Smad2 and Smad3 was, however, not sufficient to activate reporters for TGF-beta-induced transcriptional responses, which were however restored by transient transfection of wild-type Smad4. We conclude that Smad4 is not required for nuclear translocation of Smad2 and Smad3, but is needed for activation of at least certain transcriptional responses.

Induction of KIAA1199/CEMIP is associated with colon cancer phenotype and poor patient survival.

Genes induced in colon cancer provide novel candidate biomarkers of tumor phenotype and aggressiveness. We originally identified KIAA1199 (now officially called CEMIP) as a transcript highly induced in colon cancer: initially designating the transcript as Colon Cancer Secreted Protein 1. We molecularly characterized CEMIP expression both at the mRNA and protein level and found it is a secreted protein induced an average of 54-fold in colon cancer. Knockout of CEMIPreduced the ability of human colon cancer cells to form xenograft tumors in athymic mice. Tumors that did grow had increased deposition of hyaluronan, linking CEMIP participation in hyaluronan degradation to the modulation of tumor phenotype. We find CEMIP mRNA overexpression correlates with poorer patient survival. In stage III only (n = 31) or in combined stage II plus stage III colon cancer cases (n = 73), 5-year overall survival was significantly better (p = 0.004 and p = 0.0003, respectively) among patients with low CEMIP expressing tumors than those with high CEMIP expressing tumors. These results demonstrate that CEMIP directly facilitates colon tumor growth, and high CEMIP expression correlates with poor outcome in stage III and in stages II+III combined cohorts. We present CEMIP as a candidate prognostic marker for colon cancer and a potential therapeutic target.

TISSUE REGENERATION. Inhibition of the prostaglandin-degrading enzyme 15-PGDH potentiates tissue regeneration.

Agents that promote tissue regeneration could be beneficial in a variety of clinical settings, such as stimulating recovery of the hematopoietic system after bone marrow transplantation. Prostaglandin PGE2, a lipid signaling molecule that supports expansion of several types of tissue stem cells, is a candidate therapeutic target for promoting tissue regeneration in vivo. Here, we show that inhibition of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a prostaglandin-degrading enzyme, potentiates tissue regeneration in multiple organs in mice. In a chemical screen, we identify a small-molecule inhibitor of 15-PGDH (SW033291) that increases prostaglandin PGE2 levels in bone marrow and other tissues. SW033291 accelerates hematopoietic recovery in mice receiving a bone marrow transplant. The same compound also promotes tissue regeneration in mouse models of colon and liver injury. Tissues from 15-PGDH knockout mice demonstrate similar increased regenerative capacity. Thus, 15-PGDH inhibition may be a valuable therapeutic strategy for tissue regeneration in diverse clinical contexts.

Aspirin and the risk of colorectal cancer in relation to the expression of 15-hydroxyprostaglandin dehydrogenase (HPGD).

Aspirin use reduces the risk of colorectal neoplasia, at least in part, through inhibition of prostaglandin-endoperoxide synthase 2 (PTGS2, cyclooxygenase 2)-related pathways. Hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (15-PGDH, HPGD) is down-regulated in colorectal cancers and functions as a metabolic antagonist of PTGS2. We hypothesized that the effect of aspirin may be antagonized by low 15-PGDH expression in the normal colon. In the Nurses' Health Study and the Health Professionals Follow-Up Study, we collected data on aspirin use every 2 years and followed up participants for diagnoses of colorectal cancer. Duplication-method Cox proportional, multivariable-adjusted, cause-specific hazards regression for competing risks data was used to compute hazard ratios (HRs) for incident colorectal cancer according to 15-PGDH mRNA expression level measured in normal mucosa from colorectal cancer resections. Among 127,865 participants, we documented 270 colorectal cancer cases from which we could assess 15-PGDH expression. Compared with nonuse, regular aspirin use was associated with lower risk of colorectal cancer that developed within a background of colonic mucosa with high 15-PGDH expression [multivariable HR, 0.49; 95% confidence interval (CI), 0.34 to 0.71], but not with low 15-PGDH expression (multivariable HR, 0.90; 95% CI, 0.63 to 1.27) (P for heterogeneity = 0.018). Regular aspirin use was associated with lower incidence of colorectal cancers arising in association with high 15-PGDH expression, but not with low 15-PGDH expression in normal colon mucosa. This suggests that 15-PGDH expression level in normal colon mucosa may serve as a biomarker that may predict stronger benefit from aspirin chemoprevention.

Inactivating mutation in the prostaglandin transporter gene, SLCO2A1, associated with familial digital clubbing, colon neoplasia, and NSAID resistance.

HPGDand SLCO2A1 genes encode components of the prostaglandin catabolic pathway, with HPGD encoding the degradative enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH), and SLCO2A1 encoding the prostaglandin transporter PGT that brings substrate to 15-PGDH. HPGD-null mice show increased prostaglandin E2 (PGE2), marked susceptibility to developing colon tumors, and resistance to colon tumor prevention by nonsteroidal anti-inflammatory drugs (NSAID). But in humans, HPGD and SLCO2A1 mutations have only been associated with familial digital clubbing. We, here, characterize a family with digital clubbing and early-onset colon neoplasia. Whole-exome sequencing identified a heterozygous nonsense mutation (G104X) in the SLCO2A1 gene segregating in 3 males with digital clubbing. Two of these males further demonstrated notably early-onset colon neoplasia, 1 with an early-onset colon cancer and another with an early-onset sessile serrated colon adenoma. Two females also carried the mutation, and both these women developed sessile serrated colon adenomas without any digital clubbing. Males with clubbing also showed marked elevations in the levels of urinary prostaglandin E2 metabolite, PGE-M, whereas, female mutation carriers were in the normal range. Furthermore, in the male proband, urinary PGE-M remained markedly elevated during NSAID treatment with either celecoxib or sulindac. Thus, in this human kindred, a null SLCO2A1 allele mimics the phenotype of the related HPGD-null mouse, with increased prostaglandin levels that cannot be normalized by NSAID therapy, plus with increased colon neoplasia. The development of early-onset colon neoplasia in male and female human SLCO2A1 mutation carriers suggests that disordered prostaglandin catabolism can mediate inherited susceptibility to colon neoplasia in man.

Genetic variation in 15-hydroxyprostaglandin dehydrogenase and colon cancer susceptibility.

BACKGROUND: 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is a metabolic antagonist of COX-2, catalyzing the degradation of inflammation mediator prostaglandin E2 (PGE2) and other prostanoids. Recent studies have established the 15-PGDH gene as a colon cancer suppressor. METHODS: We evaluated 15-PDGH as a colon cancer susceptibility locus in a three-stage design. We first genotyped 102 single-nucleotide polymorphisms (SNPs) in the 15-PGDH gene, spanning ∼50 kb up and down-stream of the coding region, in 464 colon cancer cases and 393 population controls. We then genotyped the same SNPs, and also assayed the expression levels of 15-PGDH in colon tissues from 69 independent patients for whom colon tissue and paired germline DNA samples were available. In the final stage 3, we genotyped the 9 most promising SNPs from stages 1 and 2 in an independent sample of 525 cases and 816 controls (stage 3). RESULTS: In the first two stages, three SNPs (rs1365611, rs6844282 and rs2332897) were statistically significant (p<0.05) in combined analysis of association with risk of colon cancer and of association with 15-PGDH expression, after adjustment for multiple testing. For one additional SNP, rs2555639, the T allele showed increased cancer risk and decreased 15-PGDH expression, but just missed statistical significance (p-adjusted = 0.063). In stage 3, rs2555639 alone showed evidence of association with an odds ratio (TT compared to CC) of 1.50 (95% CI = 1.05-2.15, p = 0.026). CONCLUSIONS: Our data suggest that the rs2555639 T allele is associated with increased risk of colon cancer, and that carriers of this risk allele exhibit decreased expression of 15-PGDH in the colon.

Inhibition of 15-hydroxyprostaglandin dehydrogenase by Helicobacter pylori in human gastric carcinogenesis.

Helicobacter pylori (H. pylori) infection induces a chronic inflammatory response, which promotes gastric carcinogenesis. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) plays a key role as a tumor suppressor in gastrointestinal cancers. The aim of this study was to elucidate the role of 15-PGDH in gastric carcinogenesis associated with H. pylori. 15-PGDH expression in gastric biopsies from H. pylori-infected (n = 25) and noninfected (n = 15) subjects was analyzed by quantitative real-time PCR, Western blot analysis, and immunohistochemistry. 15-PGDH DNA methylation was evaluated by methylation-specific PCR and pyrosequencing. The expression of 15-PGDH, Snail, extracellular signal-regulated kinase (ERK)1/2, TLR4, and MyD88 in response to H. pylori infection was assessed by immunoblot analysis. Compared with negative specimens, H. pylori-positive specimens had 2-fold lower 15-PGDH mRNA levels and significantly less 15-PGDH protein. In four H. pylori-infected subjects with longitudinal follow-up, the suppression of 15-PGDH expression was reversed by H. pylori eradication therapy. In parallel with suppressing 15-PGDH expression, H. pylori infection activated expression of TLR4 and MyD88 expression, increased levels of phospho-ERK1/2, and increased expression of EGF receptor (EGFR)-Snail. Inhibition of Snail and MyD88 reversed suppression of 15-PGDH expression, and siMyD88 reduced phosphorylated ERK1/2. Similarly, treatment with an ERK1/2 and EGFR inhibitor also restored 15-PGDH expression. H. pylori appeared to promote gastric carcinogenesis by suppressing 15-PGDH. This process is mediated by the TLR4/MyD88 pathway via ERK1/2 or EGFR-Snail transcriptional regulation. 15-PGDH may be a useful marker and a potential therapeutic target in H. pylori-induced gastric carcinogenesis.

Ugene, a newly identified protein that is commonly overexpressed in cancer and binds uracil DNA glycosylase.

Expression microarrays identified a novel transcript, designated as Ugene, whose expression is absent in normal colon and colon adenomas, but that is commonly induced in malignant colon cancers. These findings were validated by real-time PCR and Northern blot analysis in an independent panel of colon cancer cases. In addition, Ugene expression was found to be elevated in many other common cancer types, including breast, lung, uterus, and ovary. Immunofluorescence of V5-tagged Ugene revealed it to have a nuclear localization. In a pull-down assay, uracil DNA glycosylase 2 (UNG2), an important enzyme in the base excision repair (BER) pathway, was identified as a partner protein that binds to Ugene. Coimmunoprecipitation and Western blot analysis confirmed the binding between the endogenous Ugene and UNG2 proteins. Using deletion constructs, we find that Ugene binds to the first 25 amino acids of the UNG2 NH(2) terminus. We suggest that Ugene induction in cancer may contribute to the cancer phenotype by interacting with the BER pathway.