Chemoprevention of colorectal neoplasia: the potential for personalized medicine

Cancer-associated fibroblasts in neoadjuvant setting for solid cancers

Therapeutic approaches for cancer have become increasingly diverse in recent times. A comprehensive understanding of the tumor microenvironment (TME) holds great potential for enhancing the precision of tumor therapies. Neoadjuvant therapy offers the possibility of alleviating patient symptoms and improving overall quality of life. Additionally, it may facilitate the reduction of inoperable tumors and prevent potential preoperative micrometastases. Within the TME, cancer-associated fibroblasts (CAFs) play a prominent role as they generate various elements that contribute to tumor progression. Particularly, extracellular matrix (ECM) produced by CAFs prevents immune cell infiltration into the TME, hampers drug penetration, and diminishes therapeutic efficacy. Therefore, this review provides a summary of the heterogeneity and interactions of CAFs within the TME, with a specific focus on the influence of neoadjuvant therapy on the microenvironment, particularly CAFs. Finally, we propose several potential and promising therapeutic strategies targeting CAFs, which may efficiently eliminate CAFs to decrease stroma density and impair their functions.

Colorectal Cancer Chemoprevention: A Dream Coming True?

Colorectal cancer (CRC) is one of the deadliest forms of cancer worldwide. CRC development occurs mainly through the adenoma-carcinoma sequence, which can last decades, giving the opportunity for primary prevention and early detection. CRC prevention involves different approaches, ranging from fecal occult blood testing and colonoscopy screening to chemoprevention. In this review, we discuss the main findings gathered in the field of CRC chemoprevention, focusing on different target populations and on various precancerous lesions that can be used as efficacy evaluation endpoints for chemoprevention. The ideal chemopreventive agent should be well tolerated and easy to administer, with low side effects. Moreover, it should be readily available at a low cost. These properties are crucial because these compounds are meant to be used for a long time in populations with different CRC risk profiles. Several agents have been investigated so far, some of which are currently used in clinical practice. However, further investigation is needed to devise a comprehensive and effective chemoprevention strategy for CRC.

Efficacy of Wholistic Turmeric Supplement on Adenomatous Polyps in Patients with Familial Adenomatous Polyposis-A Randomized, Double-Blinded, Placebo-Controlled Study

Several studies have demonstrated that curcumin can cause the regression of polyps in familial adenomatous polyposis (FAP), while others have shown negative results. Wholistic turmeric (WT) containing curcumin and additional bioactive compounds may contribute to this effect. We performed a double-blinded, randomized, controlled trial to assess the efficacy of WT in FAP patients. Ten FAP patients were randomly assigned to receive either WT or placebo for 6 months. Colonoscopies were performed at baseline and after 6 months. The polyp number and size, as well as the cumulative polyp burden, were assessed. No differences were noted between the groups in terms of changes from the baseline's polyp number, size, or burden. However, stratifying the data according to the right vs. left colon indicated a decrease in the median polyp number (from 5.5 to 1.5, p = 0.06) and polyp burden (from 24.25 mm to 11.5 mm, p = 0.028) in the left colon of the patients in the WT group. The adjusted left polyp number and burden in the WT arm were lower by 5.39 (p = 0.034) and 14.68 mm (p = 0.059), respectively. Whether WT can be used to reduce the polyp burden of patients with predominantly left-sided polyps remains to be seen; thus, further larger prospective trials are required.

Precision Medicine and Triple-Negative Breast Cancer: Current Landscape and Future Directions

Simple Summary

The implementation of precision medicine will revolutionize cancer treatment paradigms. Notably, this goal is not far from reality: genetically similar cancers can be treated similarly. The heterogeneous nature of triple-negative breast cancer (TNBC) made it a suitable candidate to practice precision medicine. Using TNBC molecular subtyping and genomic profiling, a precision medicine-based clinical trial is ongoing. This review summarizes the current landscape and future directions of precision medicine and TNBC.

Abstract

Triple-negative breast cancer (TNBC) is an aggressive and heterogeneous subtype of breast cancer associated with a high recurrence and metastasis rate that affects African-American women disproportionately. The recent approval of targeted therapies for small subgroups of TNBC patients by the US ‘Food and Drug Administration’ is a promising development. The advancement of next-generation sequencing, particularly somatic exome panels, has raised hopes for more individualized treatment plans. However, the use of precision medicine for TNBC is a work in progress. This review will discuss the potential benefits and challenges of precision medicine for TNBC. A recent clinical trial designed to target TNBC patients based on their subtype-specific classification shows promise. Yet, tumor heterogeneity and sub-clonal evolution in primary and metastatic TNBC remain a challenge for oncologists to design adaptive precision medicine-based treatment plans.

Kinome-wide analysis of the effect of statins in colorectal cancer

BACKGROUND

Epidemiological studies and meta-analyses show an association between statin use and a reduced incidence of colorectal cancer (CRC). We have shown that statins act on CRC through bone morphogenetic protein (BMP) signalling, but the exact cellular targets and underlying mechanism of statin action remain elusive. In this study, we set out to assess the influence of statins on global cancer cell signalling by performing an array-based kinase assay using immobilised kinase substrates spanning the entire human kinome.

METHODS

CRC cells with or without Lovastatin treatment were used for kinome analysis. Findings on kinome arrays were further confirmed by immunoblotting with activity-specific antibodies. Experiments in different CRC cell lines using immunoblotting, siRNA-mediated knockdown and treatment with specific BMP inhibitor Noggin were performed. The relevance of in vitro findings was confirmed in xenografts and in CRC patients treated with Simvastatin.

RESULTS

Kinome analysis can distinguish between non-specific, toxic effects caused by 10 µM of Lovastatin and specific effects on cell signalling caused by 2 µM Lovastatin. Statins induce upregulation of PTEN activity leading to downregulation of the PI3K/Akt/mTOR signalling. Treatment of cells with the specific BMP inhibitor Noggin as well as PTEN knockdown and transfection of cells with a constitutively active form of AKT abolishes the effect of Lovastatin on mTOR phosphorylation. Experiments in xenografts and in patients treated with Simvastatin confirm statin-mediated BMP pathway activation, activation of PTEN and downregulation of mTOR signalling.

CONCLUSIONS

Statins induce BMP-specific activation of PTEN and inhibition of PI3K/Akt/mTOR signalling in CRC.

Heterogeneity of Colorectal Cancer Progression: Molecular Gas and Brakes

The review begins with molecular genetics, which hit the field unveiling the involvement of oncogenes and tumor suppressor genes in the pathogenesis of colorectal cancer (CRC) and uncovering genetic predispositions. Then the notion of molecular phenotypes with different clinical behaviors was introduced and translated in the clinical arena, paving the way to next-generation sequencing that captured previously unrecognized heterogeneity. Among other molecular regulators of CRC progression, the extent of host immune response within the tumor micro-environment has a critical position. Translational sciences deeply investigated the field, accelerating the pace toward clinical transition, due to its strong association with outcomes. While the perturbation of gut homeostasis occurring in inflammatory bowel diseases can fuel carcinogenesis, micronutrients like vitamin D and calcium can act as brakes, and we discuss underlying molecular mechanisms. Among the components of gut microbiota, Fusobacterium nucleatum is over-represented in CRC, and may worsen patient outcome. However, any translational knowledge tracing the multifaceted evolution of CRC should be interpreted according to the prognostic and predictive frame of the TNM-staging system in a perspective of clinical actionability. Eventually, we examine challenges and promises of pharmacological interventions aimed to restrain disease progression at different disease stages.

Recent advances in clinical practice: colorectal cancer chemoprevention in the average-risk population

Colorectal cancer (CRC) is one of the most common and lethal malignancies in Western countries. Its development is a multistep process that spans more than 15 years, thereby providing an opportunity for prevention and early detection. The high incidence and mortality rates emphasise the need for prevention and screening. Many countries have therefore introduced CRC screening programmes. It is expected, and preliminary evidence in some countries suggests, that this screening effort will decrease CRC-related mortality rates. CRC prevention involves a healthy lifestyle and chemoprevention-more specifically, oral chemoprevention that can interfere with progression from a normal colonic mucosa to adenocarcinoma. This preventive effect is important for individuals with a genetic predisposition, but also in the general population. The ideal chemopreventive agent, or combination of agents, remains unknown, especially when considering safety during long-term use. This review evaluates the evidence across 80 meta-analyses of interventional and observational studies of CRC prevention using medications, vitamins, supplements and dietary factors. This review suggests that the following factors are associated with a decreased incidence of CRC: aspirin, non-steroidal anti-inflammatory drugs, magnesium, folate, a high consumption of fruits and vegetables, fibre and dairy products. An increased incidence of CRC was observed with frequent alcohol or meat consumption. No evidence of a protective effect for tea, coffee, garlic, fish and soy products was found. The level of evidence is moderate for aspirin, β-carotene and selenium, but is low or very low for all other exposures or interventions.

Diacerein treatment prevents colitis-associated cancer in mice

BACKGROUND

Inflammation is a well-established enabling factor for cancer development and provides a framework for the high prevalence of colon cancer in inflammatory bowel disease. In accordance, chronic inflammation has recently been implicated in the development of cancer stem cells (CSCs). However, the mechanism whereby anti-inflammatory drugs act in the prevention of colitis-associated cancer (CAC) is only partially understood.

AIM

To evaluate the role of diacerein (DAR), an anti-inflammatory drug that mainly acts through the inhibition of interleukin (IL)-1β expression in the development of CSCs and CAC.

METHODS

The effects of DAR on colon inflammation in mice with CAC were evaluated by inflammatory index, reverse real-time transcription polymerase chain reaction and western blot. Cytokine levels were measured by enzyme-linked immunosorbent assay. Cells assays evaluated the effects of DAR on CSCs. Immunohistochemistry and apoptosis assays were also used to evaluate the effects of DAR on tumorigenesis associated with inflammation.

RESULTS

DAR treatment reduced colon inflammation as well as the number and size of tumors in azoxymethane plus dextran sulphate sodium-treated animals. Accordingly, DAR treatment was associated with reduced intracellular signals of inflammation (inhibitor of nuclear factor kappa B kinase and c-Jun N-terminal kinase phosphorylation) in the colon. In addition, DAR treatment was associated with a decrease in colon CSC formation, suggesting that besides reducing colonic inflammation, DAR has a direct effect on the inhibition of colon carcinogenesis.

CONCLUSION

Together, these data indicate that DAR-mediated IL-1β suppression attenuates inflammation-induced colon cancer and CSC formation, highlighting DAR as a potential candidate for the chemoprevention of CAC.

Chemoprevention of Colorectal Cancer

Although colorectal cancer (CRC) screening has reduced the incidence of and mortality from CRC, chemoprevention strategies have the potential to further reduce CRC incidence and mortality. Chemoprevention agents might be used for average-risk as well as high-risk groups, and to prevent CRC recurrence after therapy. CRC chemoprevention agents that have been studied include aspirin, nonaspirin nonsteroidal anti-inflammatory drugs, statins, agents that target metabolic pathways, and vitamins and minerals. We review the prospect of chemoprevention of CRC, results from preclinical and human studies, challenges, and future directions.

Bufalin, a Traditional Chinese Medicine Compound, Prevents Tumor Formation in Two Murine Models of Colorectal Cancer

Chemoprevention is cost-effective for colorectal cancer when targeted at intermediate- or high-risk populations. Bufalin is a cardiac glycoside extracted from the traditional Chinese medicine (TCM) "Chan Su," which has been used as an anticancer agent. On the basis of the relative safety of bufalin, we investigated whether bufalin could act as a chemoprophylactic agent to prevent colon tumorigenesis in two murine models, namely colitis-associated colorectal cancer and Apc germline mutation-developed colorectal cancer. Our results revealed that long-term (12-16 weeks) administration of low-dose bufalin (0.5 mg/kg) effectively suppressed tumorigenesis in both colorectal cancer models, accompanied by attenuated epithelial cell proliferation (reduced bromodeoxyuridine incorporation, lower levels of cyclin A, cyclin D1, cyclin E, and cyclin-dependent kinases-2/4, and higher levels of p21 and p27) and promoted apoptosis (increased TUNEL positivity and caspase-3/9 cleavages, reduced levels of Bcl-2, Bcl-xL and survivin, and increased levels of Bax and Bak). Bufalin also suppressed the expression of proinflammatory mediators [reduced levels of cyclooxygenase-2, tumor TNFα, IL1β, IL6, C-X-C motif chemokine ligand (CXCL)-1, CXCL-2, and CXCL-5] in the colitis-associated colorectal cancer model. These effects were associated with the inhibition of oncogenic NF-κB and PI3K/Akt pathways. Our findings unveil a novel chemoprophylactic action of bufalin in colorectal cancer in vivo and provided efficacy data and mechanistic evidence for further clinical evaluation of this TCM compound for colorectal cancer chemoprevention in individuals at risk of colorectal cancer.

Resorting the function of the colorectal cancer gatekeeper adenomatous polyposis coli

As a large number of cancers are caused by nonsense mutations in key genes, read-through of these mutations to restore full-length protein expression is a potential therapeutic strategy. Mutations in the adenomatous polyposis coli (APC) gene initiate the majority of both sporadic and hereditary colorectal cancers (CRC) and around 30% of these mutations are nonsense mutations. Our goal was to test the feasibility and effectiveness of APC nonsense mutation read-through as a potential chemo-preventive therapy in Familial Adenomatous Polyposis (FAP), an inherited CRC syndrome patients. Ten FAP patients harboring APC nonsense mutations were treated with the read-through inducing antibiotic erythromycin for 4 months. Endoscopic assessment of the adenomas was performed at baseline, after 4 and after 12 months. Adenoma burden was documented in terms of adenoma number, maximal polyp size and cumulative polyp size per procedure. Tissue samples were collected and subjected to molecular and genetic analyses. Our results show that in the majority of patients the treatment led to a decrease in cumulative adenoma burden, median reduction in cumulative adenoma size and median reduction in adenoma number. Molecular and genetic analyses of the adenomas revealed that the treatment led to a reduced number of somatic APC mutations, reduced cellular proliferation and restoration of APC tumor-suppressing activity. Together, our findings show that induced read-through of APC nonsense mutations leads to promising clinical results and should be further investigated to establish its therapeutic potential in FAP and sporadic CRCs harboring nonsense APC mutations.

Angiogenin and the MMP9-TIMP2 axis are up-regulated in proangiogenic, decidual NK-like cells from patients with colorectal cancer

NK cells are effector lymphocytes involved in tumor immunosurveillance; however, in patients with solid malignancies, NK cells have compromised functions. We have previously reported that lung tumor-associated NK cells (TANKs; peripheral blood) and tumor-infiltrating NK cells (TINKs) show proangiogenic, decidual NK-like (dNK) phenotype. In this study, we functionally and molecularly investigated TINKs and TANKs from blood and tissue samples of patients with colorectal cancer (CRC), a neoplasm in which inflammation and angiogenesis have clinical relevance, and compared them to NK cells from controls and patients with nononcologic inflammatory bowel disease. CRC TINKs/TANKs showed decreased expression for the activatory marker NKG2D, impaired degranulation activity, a decidual-like NK polarization toward the CD56^brightCD16^dim/-CD9⁺CD49⁺ subset. TINKs and TANKs secreted cytokines with proangiogenic activities, and induce endothelial cell proliferation, migration, adhesion, and the formation of capillary-like structures in vitro. dNK cells release specific proangiogenic factors; among which, angiogenin and invasion-associated enzymes related to the MMP9-TIMP1/2 axis. Here, we describe, for the first time, to our knowledge, the expression of angiogenin, MMP2/9, and TIMP by TANKs in patients with CRC. This phenotype could be relevant to the invasive capabilities and proangiogenic functions of CRC-NK cells and become a novel biomarker. STAT3/STAT5 activation was observed in CRC-TANKs, and treatment with pimozide, a STAT5 inhibitor, reduced endothelial cell capability to form capillary-like networks, inhibiting VEGF and angiogenin production without affecting the levels of TIMP1, TIMP2, and MMP9, indicating that STAT5 is involved in cytokine modulation but not invasion-associated molecules. Combination of Stat5 or MMP inhibitors with immunotherapy could help repolarize CRC TINKs and TANKs to anti-tumor antimetastatic ones.-Bruno, A., Bassani, B., D'Urso, D. G., Pitaku, I., Cassinotti, E., Pelosi, G., Boni, L., Dominioni, L., Noonan, D. M., Mortara, L., Albini, A. Angiogenin and the MMP9-TIMP2 axis are up-regulated in proangiogenic, decidual NK-like cells from patients with colorectal cancer.

Codonopis bulleynana Forest ex Diels inhibits autophagy and induces apoptosis of colon cancer cells by activating the NF-κB signaling pathway

Despite its favorable clinical efficacy, oxaliplatin-based chemotherapy frequently results in treatment withdrawal and induces liver damage in colon cancer. Therefore, it is important to develop novel drugs, which can safely and effectively complement or replace the therapeutic effects of oxaliplatin. Codonopis bulleynana Forest ex Diels (cbFeD) has wide range of pharmacological effects, including anticancer effects. In the present study, the anticancer activity of cbFeD and its potential molecular mechanisms were investigated. In vitro, cell counting kit-8 assays and flow cytometry were used to assess the anti-proliferation and apoptosis-promoting activities of cbFeD. Transmission electron microscopy was used to monitor the autophagic vesicles. Immunofluorescence staining was performed to observe the nuclear translocation of p65 and the fluorescence of microtubule-associated protein 1 light chain 3 (LC3) B-II. The protein expression levels of p65, inhibitor of nuclear factor (NF)-κB (IκB) a, LC3B-I, LC3B-II and Beclin-1 were detected using western blot analysis. In vivo, the antitumor effect of cbFeD was assessed in colon cancer-bearing nude mice as a model. H&E staining and immunohistochemistry (IHC) were performed, with oxaliplatin set as a positive control. The results showed that cbFeD inhibited cell proliferation and promoted cell apoptosis in a dose-dependent manner. The effects of a high dose of cbFeD on colon cancer cells were similar to those of oxaliplatin. In HCT116 and SW480 cells, cbFeD inhibited the expression of IκBα, LC3B-I/II and Beclin-1, and the results of western blot analysis and immunofluorescence showed that, in the cells treated with cbFeD, p65 gradually entered nuclei in a dose-dependent manner, and the expression of LC3B-II was gradually reduced. The results of the acridine orangestaining and electron microscopy demonstrated fewer autophagic vesicles in the high-dose cbFeD group and the oxaliplatin group. The high dose of cbFeD reversed the effect of pyrrolidine dithiocarbamate, a p65-inhibitor, on the expression of p65, LC3B-I, LC3B-II and Beclin-1, and on the production of autophagic vacuoles. The high dose of cbFeD and oxaliplatin also suppressed tumorigenicity in vivo. The results of the H&E and IHC staining confirmed the inhibition of autophagy (LC3 and Beclin-1) and activation of p65 by treatment with the high dose of cbFeD and oxaliplatin. Taken together, cbFeD exhibited an antitumor effect in colon cancer cells by inhibiting autophagy through activation of the NF-κB pathway. Therefore, cbFeD may be a promising Chinese herbal compound for development for use in cancer therapy.

Influence of NSAID Use Among Colorectal Cancer Survivors on Cancer Outcomes

PURPOSE

Colorectal cancer (CRC) is the third most common cancer diagnosed in men and women in the United States. Given the availability of effective screening, most tumors are found early enough to offer patients substantial long-term survival. Thus there is a resulting significant population of CRC survivors for whom modifiable risk factors for recurrence and survival would be of interest.

METHODS

We conducted a population-based retrospective cohort study among patients enrolled in 2 large Midwestern health plans for which claims data, including pharmacy fill data, and medical record data were available. Men and women who were 40 years of age or older at the time of CRC diagnosis with disease less than stage IV and no history of Crohn disease, ulcerative colitis, and irritable bowel syndrome were included. CRC cases diagnosed between January 1, 1990 and December 31, 2000 were included if they met the inclusion criteria. Adjusted Cox proportional hazard models were used with exposure modeled as a time-dependent covariate. We assessed progression-free survival, defined as an aggressive polyp or invasive disease, and overall survival.

RESULTS

After adjustment for age at diagnosis, sex, race, body mass index, stage, side of initial tumor, and tumor histology, we found that current users of nonsteroidal anti-inflammatory drugs had a 3-fold decreased risk of recurrence and a >7-fold decreased risk of death. Our results are statistically significant with P-values <0.05.

CONCLUSIONS

Our results suggest that current use of nonsteroidal anti-inflammatory drugs provides significant improvements in CRC outcomes.

Paracrine cyclooxygenase-2 activity by macrophages drives colorectal adenoma progression in the Apc Min/+ mouse model of intestinal tumorigenesis

Genetic deletion or pharmacological inhibition of cyclooxygenase (COX)-2 abrogates intestinal adenoma development at early stages of colorectal carcinogenesis. COX-2 is localised to stromal cells (predominantly macrophages) in human and mouse intestinal adenomas. Therefore, we tested the hypothesis that paracrine Cox-2-mediated signalling from macrophages drives adenoma growth and progression in vivo in the Apc^Min/+ mouse model of intestinal tumorigenesis. Using a transgenic C57Bl/6 mouse model of Cox-2 over-expression driven by the chicken lysozyme locus (cLys-Cox-2), which directs integration site-independent, copy number-dependent transgene expression restricted to macrophages, we demonstrated that stromal macrophage Cox-2 in colorectal (but not small intestinal) adenomas from cLys-Cox-2 x Apc^Min/+ mice was associated with significantly increased tumour size (P = 0.025) and multiplicity (P = 0.025), compared with control Apc^Min/+ mice. Transgenic macrophage Cox-2 expression was associated with increased dysplasia, epithelial cell Cox-2 expression and submucosal tumour invasion, as well as increased nuclear β-catenin translocation in dysplastic epithelial cells. In vitro studies confirmed that paracrine macrophage Cox-2 signalling drives catenin-related transcription in intestinal epithelial cells. Paracrine macrophage Cox-2 activity drives growth and progression of Apc^Min/+ mouse colonic adenomas, linked to increased epithelial cell β-catenin dysregulation. Stromal cell (macrophage) gene regulation and signalling represent valid targets for chemoprevention of colorectal cancer.

Calcium remodeling in colorectal cancer

Colorectal cancer (CRC) is the third most frequent form of cancer and the fourth leading cause of cancer-related death in the world. Basic and clinical data indicate that aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) may prevent colon cancer but mechanisms remain unknown. Aspirin metabolite salicylate and other NSAIDs may inhibit tumor cell growth acting on store-operated Ca²⁺ entry (SOCE), suggesting an important role for this pathway in CRC. Consistently, SOCE is emerging as a novel player in different forms of cancer, including CRC. SOCE and store-operated currents (SOCs) are dramatically enhanced in CRC while Ca²⁺ stores are partially empty in CRC cells. These features may contribute to CRC hallmarks including enhanced cell proliferation, migration, invasion and survival. At the molecular level, enhanced SOCE and depleted stores are mediated by overexpression of Orai1, Stromal interaction protein 1 (STIM1) and Transient receptor protein channel 1 (TRPC1) and downregulation of STIM2. In normal colonic cells, SOCE is mediated by Ca²⁺-release activated Ca²⁺ channels made of STIM1, STIM2 and Orai1. In CRC cells, SOCE is mediated by different store-operated currents (SOCs) driven by STIM1, Orai1 and TRPC1. Loss of STIM2 contributes to depletion of Ca²⁺ stores and enhanced resistance to cell death in CRC cells. Thus, SOCE is a novel key player in CRC and inhibition by salicylate and other NSAIDs may contribute to explain chemoprevention activity.

SUMMARY

Colorectal cancer (CRC) is the third most frequent form of cancer worldwide. Recent evidence suggests that intracellular Ca²⁺ remodeling may contribute to cancer hallmarks. In addition, aspirin and other NSAIDs might prevent CRC acting on remodeled Ca²⁺ entry pathways. In this review, we will briefly describe 1) the players involved in intracellular Ca²⁺ homeostasis with a particular emphasis on the mechanisms involved in SOCE activation and inactivation, 2) the evidence that aspirin metabolite salicylate and other NSAIDs inhibits tumor cell growth acting on SOCE, 3) evidences on the remodeling of intracellular Ca²⁺ in cancer with a particular emphasis in SOCE, 4) the remodeling of SOCE and Ca²⁺ store content in CRC and, finally, 5) the molecular basis of Ca²⁺ remodeling in CRC. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Prevention of Colorectal Neoplasia

Colorectal cancer (CRC) is one of the leading causes of cancer-related morbidity and mortality worldwide. There are well-established screening protocols involving fecal testing, radiographic, and endoscopic evaluations that have led to decreased incidence and mortality of CRC in the United States. In addition to screening for CRC, there is interest in preventing colorectal neoplasia by targeting the signaling pathways that have been identified in the pathway of dysplasia progressing to carcinoma. This review will detail the efficacy of multiple potential preventative strategies including lifestyle changes (physical activity, alcohol use, smoking cessation, and obesity); dietary factors (dietary patterns, calcium, vitamin D, fiber, folate, and antioxidants and micronutrients); and chemopreventive agents (nonsteroidal anti-inflammatory drugs, statins, metformin, bisphosphonates, and postmenopausal hormonal therapy).

Manipulation of DNA Repair Proficiency in Mouse Models of Colorectal Cancer

Technical and biological innovations have enabled the development of more sophisticated and focused murine models that increasingly recapitulate the complex pathologies of human diseases, in particular cancer. Mouse models provide excellent in vivo systems for deciphering the intricacies of cancer biology within the context of precise experimental settings. They present biologically relevant, adaptable platforms that are amenable to continual improvement and refinement. We discuss how recent advances in our understanding of tumorigenesis and the underlying deficiencies of DNA repair mechanisms that drive it have been informed by using genetically engineered mice to create defined, well-characterized models of human colorectal cancer. In particular, we focus on how mechanisms of DNA repair can be manipulated precisely to create in vivo models whereby the underlying processes of tumorigenesis are accelerated or attenuated, dependent on the composite alleles carried by the mouse model. Such models have evolved to the stage where they now reflect the initiation and progression of sporadic cancers. The review is focused on mouse models of colorectal cancer and how insights from these models have been instrumental in shaping our understanding of the processes and potential therapies for this disease.

Colorectal Cancer Screening in Inflammatory Bowel Disease

Patients with long-standing ulcerative colitis (UC) or Crohn's colitis are at increased risk of developing colorectal cancer (CRC). Given that most cases of CRC are thought to arise from dysplasia, previous guidelines have recommended endoscopic surveillance with random biopsies obtained from all segments of the colon involved by endoscopic or microscopic inflammation. However, recent evidence has suggested that the majority of dysplastic lesions in patients with inflammatory disease (IBD) are visible, and data have been supportive of chromoendoscopy with targeted biopsies of visible lesions versus traditional random biopsies. This review article will discuss the risk of colon cancer in patients with IBD, as well as current recommendations for CRC screening and surveillance in patients with UC or Crohn's colitis.

Sulindac, 3,3'-diindolylmethane and curcumin reduce carcinogenesis in the Pirc rat, an Apc-driven model of colon carcinogenesis

Background

Recently, we showed that Sulindac (SU; 320 ppm) reduces precancerous lesions in the colon of Pirc rats, mutated in the Apc gene. Surprisingly, previous data in Apc-mutated mice showed that SU, with reported efficacy in Familial Adenomatous Polyposis (FAP), increases colon carcinogenesis. Therefore, we assessed the effect of SU 320 ppm in a long-term carcinogenesis experiment in Pirc rats. Moreover, since side effects of SU hamper its chronic use and a combination of drugs could be more effective and less toxic than single agents, we also studied whether two natural compounds, 3,3’-diindolylmethane (DIM; 250 ppm) and curcumin (CUR; 2000 ppm), with or without lower doses of SU could affect carcinogenesis

Methods

Pirc rats were fed an AIN76 diet containing SU, DIM and CUR and sacrificed at 8 months of age to measure intestinal tumours. Apoptosis and proliferation in the normal colon mucosa, as well as gene expression profile were studied

Results

Colon tumours were significantly reduced by SU 320 ppm (62 % reduction over Controls), by DIM and CUR without or with SU 80 and 160 ppm (50, 53 and 58 % reduction, respectively) but not by SU 80 ppm alone. Total tumours (colon and small intestine) were reduced by SU (80 and 320 ppm) and by DIM and CUR. Apoptosis in the normal mucosa was significantly increased by SU 320 ppm, and slightly increased by DIM and CUR with or without SU. A slight reduction in Survivin-Birc5 expression was observed with all the treatments compared to Controls. Proliferative activity was not varied

Conclusions

The results on SU reinforce the validity of Pirc rats to identify chemopreventive products. Moreover, the efficacy of the DIM and CUR combination to lower colon tumours, suggests an alternative strategy to be exploited in patients at risk.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1627-9) contains supplementary material, which is available to authorized users.

Non-cell autonomous effects of targeting inducible PGE2 synthesis during inflammation-associated colon carcinogenesis

Microsomal PGE2 synthase-1 (mPGES-1), the terminal enzyme in the formation of inducible PGE2, represents a potential target for cancer chemoprevention. We have previously shown that genetic abrogation of mPGES-1 significantly suppresses tumorigenesis in two preclinical models of intestinal cancer. In this study, we examined the role of mPGES-1 during colon tumorigenesis in the presence of dextran sulfate sodium (DSS)-induced inflammatory microenvironment. Using Apc (Δ14/+) in which the mPGES-1 gene is either wild-type (D14:WT) or deleted (D14:KO), we report that mPGES-1 deficiency enhances sensitivity to acute mucosal injury. As a result of the increased epithelial damage, protection against adenoma formation is unexpectedly compromised in the D14:KO mice. Examining the DSS-induced acute injury, cryptal structures are formed within inflamed areas of colonic mucosa of both genotypes that display the hallmarks of early neoplasia. When acute epithelial injury is balanced by titration of DSS exposures, however, these small cryptal lesions progress rapidly to adenomas in the D14:WT mice. Given that mPGES-1 is highly expressed within the intestinal stroma under the inflammatory conditions of DSS-induced ulceration, we propose a complex and dual role for inducible PGE2 synthesis within the colonic mucosa. Our data suggest that inducible PGE2 is critical for the maintenance of an intact colonic epithelial barrier, while promoting epithelial regeneration. This function is exploited during neoplastic transformation in Apc (Δ14/+) mice as PGE2 contributes to the growth and expansion of the early initiated cryptal structures. Taken together, inducible PGE2 plays a complex role in inflammation-associated cancers that requires further analysis. Inducible PGE2 production by mPGES-1 is critical for the colonic mucosal homeostasis. This function is exploited in the presence of the neoplastic transformation in Apc (Δ14/+) mice as PGE2 contributes to the growth and expansion of the early cryptal structures.

The risk of cancer in patients with rheumatoid arthritis taking tumor necrosis factor antagonists: a nationwide cohort study

Introduction

The association between cancer and use of biologic therapy among rheumatoid arthritis (RA) patients remains controversial. We aimed to compare the relative risk of cancer development between RA patients taking tumor necrosis factor α (TNFα) antagonists and those taking nonbiologic disease-modifying anti-rheumatic drugs (nbDMARDs).

Methods

We conducted a nationwide cohort study between 1997 and 2011 using the Taiwan National Health Insurance Research Database. The risk of newly diagnosed cancer was compared between patients starting TNF-α antagonists (biologics cohort) and matched subjects taking nbDMARDs only (nbDMARDs cohort). Cumulative incidences and hazard ratios (HR) were calculated after adjusting for competing mortality. Standardized incidence ratio (SIR) was calculated for cancer risk. Multivariate analyses were performed using Cox proportional hazards model.

Results

We compared 4426 new users of TNF-α antagonists and 17704 users of nbDMARDs with similar baseline covariate characteristics. The incidence rates of cancer among biologics and nbDMARDs cohorts were 5.35 (95% confidence interval (CI) 4.23 to 6.46) and 7.41 (95% CI 6.75 to 8.07) per 1000 person-years, respectively. On modified Cox proportional hazards analysis, the risk of cancer was significantly reduced in subjects in biologics cohort (adjusted HR 0.63, 95% CI 0.49 to 0.80, P < .001), after adjusting for age, gender, disease duration, major co-morbidities, and prior use of DMARDs and corticosteroids. However, there was an increased risk for hematologic cancers in biologics cohort, yet without statistical significance. The effect of biologics was consistent across all multivariate stratified analyses and the association between biologics use and cancer risk was independent of dosage of concomitant nbDMARDs.

Conclusion

These findings suggested that RA patients taking TNF-α antagonist are associated with a lower risk of cancer, but not for hematologic cancers, than RA patients taking nbDMARDs alone.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0449-5) contains supplementary material, which is available to authorized users.

Colorectal cancer in inflammatory bowel disease: The risk, pathogenesis, prevention and diagnosis

Patients with inflammatory bowel disease (IBD) are at increased risk for developing colorectal cancer (CRC), although the overall incidence of IBD-associated CRC has been diminishing in recent decades in western countries. As demonstrated in previous studies, the risk of CRC in IBD increases with longer duration, extent of colitis, a familial history of CRC, coexistent primary sclerosing cholangitis, and the degree of inflammation. The pathogenesis of CRC in IBD is poorly understood. Similar to sporadic CRC, IBD-associated CRC is a consequence of sequential episodes of genomic alteration. Multiple inter-related pathways, including immune response by mucosal inflammatory mediators, oxidative stress, and intestinal microbiota, are also involved the pathogenesis of IBD-associated CRC. Continuing colonic inflammation appears to be a factor in the development of CRC; therefore, anti-inflammatory agents such as 5-aminosalicylate compounds and immune modulators have been considered as potential chemopreventive agents. Colonoscopic surveillance is widely accepted as being effective in reducing the risk of IBD-associated CRC, although no clear evidence has confirmed that surveillance colonoscopy prolongs survival in patients with extensive colitis. The traditional recommendation has been quadrantic random biopsies throughout the entire colon; however, several guidelines now have endorsed chromoendoscopy with a target biopsy because of increasing diagnostic yields and reduced workloads for endoscopists and pathologists. New technologies such as narrow band imaging, confocal endomicroscopy, and autofluorescence imaging have not yet been confirmed as surveillance strategies in IBD.

Personalised cancer medicine

The evolving field of personalised medicine is playing an increasingly important role in cancer prevention, diagnosis, prognosis and therapeutics. Its importance in clinical management is demonstrated by the recent introduction into routine clinical practice of various individualised, molecularly targeted therapies with increased efficacy and/or reduced toxicity. The identification of cancer predisposition genes, such as the BRCA genes in breast cancer, permits screening programmes to identify patients "at-risk" of developing cancer and helps them make decisions on individual risk-modification behaviours. Personalised medicine also plays an increasingly important role in cancer treatment. It is increasingly clear that there are molecularly distinct subtypes of various common cancers, with different therapeutic approaches required for each subtype, for example, the use of the monoclonal antibodies (trastuzumab and cetuximab) in HER2-positive breast cancer and wild-type KRAS colorectal cancer; tyrosine kinase inhibitors (imatinib, gefitinib, erlotinib and crizotinib) in chronic myeloid leukaemia, gastrointestinal stromal tumours and non-small-cell lung cancer and intracellular agents (vemurafenib and olaparib) in metastatic malignant melanoma and ovarian, breast and prostate cancer. The efficacy of various targeted therapies in such disparate tumours suggests that we are entering an era in which treatment decisions will be based on tumour molecular abnormality profile or "signature," rather than tumour tissue type or anatomical site of origin, improving patient prognosis and quality of life. This mini review focuses on the role of personalised medicine in cancer prevention and treatment as well as its future direction in oncology.

Increased risk of colorectal cancer after obesity surgery

OBJECTIVE

The purpose was to determine whether obesity surgery is associated with a long-term increased risk of colorectal cancer.

BACKGROUND

Long-term cancer risk after obesity surgery is not well characterized. Preliminary epidemiological observations and human tissue biomarker studies recently suggested an increased risk of colorectal cancer after obesity surgery.

METHODS

A nationwide retrospective register-based cohort study in Sweden was conducted in 1980-2009. The long-term risk of colorectal cancer in patients who underwent obesity surgery, and in an obese no surgery cohort, was compared with that of the age-, sex- and calendar year-matched general background population between 1980 and 2009. Obese individuals were stratified into an obesity surgery cohort and an obese no surgery cohort. The standardized incidence ratio (SIR), with 95% confidence interval (CI), was calculated.

RESULTS

Of 77,111 obese patients, 15,095 constituted the obesity surgery cohort and 62,016 constituted the obese no surgery cohort. In the obesity surgery cohort, we observed 70 patients with colorectal cancer, rendering an overall SIR of 1.60 (95% CI 1.25-2.02). The SIR for colorectal cancer increased with length of time after surgery, with a SIR of 2.00 (95% CI 1.48-2.64) after 10 years or more. In contrast, the overall SIR in the obese no surgery cohort (containing 373 colorectal cancers) was 1.26 (95% CI 1.14-1.40) and remained stable with increasing follow-up time.

CONCLUSIONS

Obesity surgery seems to be associated with an increased risk of colorectal cancer over time. These findings would prompt evaluation of colonoscopy surveillance for the increasingly large population who undergo obesity surgery.

Use of thiopurines and risk of colorectal neoplasia in patients with inflammatory bowel diseases: a meta-analysis

OBJECTIVE

Inflammatory bowel disease (IBD) is commonly treated with thiopurines such as azathioprine and mercaptopurine for the maintenance of remission. Studies examining chemopreventive of these medications on colorectal neoplasm in IBD patients have yielded conflicting results. We performed a meta-analysis to assess the role of thiopurines for this indication.

METHODS

We performed a systematic search of PubMed, Web of Science, EMBASE and Cochrane to identify studies reporting colorectal neoplasm from IBD patients treated with thiopurines and conducted a meta-analysis of pooled relative risk (RR) using the random effects model.

RESULTS

Nine case-control and ten cohort studies fulfilled the inclusion criteria. The use of thiopurines was associated with a statistically significant decreased incidence of colorectal neoplasm (summary RR=0.71, 95% CI=0.54-0.94, p=0.017), even after adjustment for duration and extent of the disease, but there was high heterogeneity among studies (I(2)=68.0%, p<0.001). The RR of advanced neoplasm (high-grade dysplasia and cancer) was 0.72 (95%CI=0.50-1.03, p=0.070) and that of cancer was 0.70 (95% CI=0.46-1.09, p=0.111) for thiopurine-treated patients. Heterogeneity of the studies was affected by the sample size (

CONCLUSION

The current meta-analysis revealed that thiopurines had a chemopreventive effect of colorectal neoplasms and a tendency of reducing advanced colorectal neoplasms in IBD. Due to the heterogeneity of included studies, these results should be interpreted with caution.

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Key Words Collapse

MESH Headings

• Azathioprine/adverse effects
• Azathioprine/therapeutic use
• Colorectal Neoplasms/chemically induced
• Humans
• Inflammatory Bowel Diseases/drug therapy
• Mercaptopurine/adverse effects
• Mercaptopurine/therapeutic use
• Risk

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Grants Collapse

Affiliation(s)

Jianfeng Gong Department of General Surgery, Jinling hospital, Medical School of Nanjing University, Nanjing, PR China
Lijing Zhu Department of Oncology, Drum Tower hospital, Medical school of Nanjing University, Nanjing, PR China
Zhen Guo Department of General Surgery, Jinling hospital, Medical School of Nanjing University, Nanjing, PR China
Yi Li Department of General Surgery, Jinling hospital, Medical School of Nanjing University, Nanjing, PR China
Weiming Zhu Department of General Surgery, Jinling hospital, Medical School of Nanjing University, Nanjing, PR China
Ning Li Department of General Surgery, Jinling hospital, Medical School of Nanjing University, Nanjing, PR China
Jieshou Li Department of General Surgery, Jinling hospital, Medical School of Nanjing University, Nanjing, PR China

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Chemoprevention of gastrointestinal neoplasia

Cancer chemoprevention is defined as the pharmacologic intervention, by drugs or nutrient-components, with the process of carcinogenesis, in order to prevent the development of invasive malignant neoplasms. This preventive attempt is particularly challenging in cancer types, which have a long subclinical developmental phase, because of their low cellular proliferation rate and their slow pre-clinical evolution, until they become clinically detectable and therapeutically as well as prognostically relevant. Therefore, only certain specific cancer types are presently in the focus of clinical chemoprevention. Among the GI tract cancer, colorectal (CRC) as well as esophageal cancer have raised the most attention over the past decades, as they both share a long precancerous stage (the adenoma in CRC and Barrett's esophagus in the case of esophageal adenocarcinoma) which provides a window of opportunity to intervene and prevent development of cancer.In this review, we will focus on both CRC as well as esophageal adenocarcinoma (EAC).

A randomized controlled trial of eicosapentaenoic acid and/or aspirin for colorectal adenoma prevention during colonoscopic surveillance in the NHS Bowel Cancer Screening Programme (The seAFOod Polyp Prevention Trial): study protocol for a randomized controlled trial

Background

The naturally-occurring omega (ω)-3 polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA) reduces colorectal adenoma (polyp) number and size in patients with familial adenomatous polyposis. The safety profile and potential cardiovascular benefits associated with ω-3 PUFAs make EPA a strong candidate for colorectal cancer (CRC) chemoprevention, alone or in combination with aspirin, which itself has recognized anti-CRC activity. Colorectal adenoma number and size are recognized as biomarkers of future CRC risk and are established as surrogate end-points in CRC chemoprevention trials.

Design

The seAFOod Polyp Prevention Trial is a randomized, double-blind, placebo-controlled, 2 × 2 factorial ‘efficacy’ study, which will determine whether EPA prevents colorectal adenomas, either alone or in combination with aspirin. Participants are 55–73 year-old patients, who have been identified as ‘high risk’ (detection of ≥5 small adenomas or ≥3 adenomas with at least one being ≥10 mm in diameter) at screening colonoscopy in the English Bowel Cancer Screening Programme (BCSP). Exclusion criteria include the need for more than one repeat endoscopy within the three-month BCSP screening period, malignant change in an adenoma, regular use of aspirin or non-aspirin non-steroidal anti-inflammatory drugs, regular use of fish oil supplements and concomitant warfarin or anti-platelet agent therapy. Patients are randomized to either EPA-free fatty acid 1 g twice daily or identical placebo AND aspirin 300 mg once daily or identical placebo, for approximately 12 months. The primary end-point is the number of participants with one or more adenomas detected at routine one-year BCSP surveillance colonoscopy. Secondary end-points include the number of adenomas (total and ‘advanced’) per patient, the location (left versus right colon) of colorectal adenomas and the number of participants re-classified as ‘intermediate risk’ for future surveillance. Exploratory end-points include levels of bioactive lipid mediators such as ω-3 PUFAs, resolvin E1 and PGE-M in plasma, urine, erythrocytes and rectal mucosa in order to gain insights into the mechanism(s) of action of EPA and aspirin, alone and in combination, as well as to discover predictive biomarkers of chemopreventive efficacy. The recruitment target is 904 patients.

Trial Registration

Current Controlled Trials ISRCTN05926847

Associations between urinary soy isoflavonoids and two inflammatory markers in adults in the United States in 2005-2008

PURPOSE

The aim of this study was to determine the association between urinary isoflavonoid (genistein, daidzein, and the daidzein metabolites O-desmethylangolensin (O-DMA) and equol) excretion and markers of inflammation in adults in the United States in National Health and Nutrition Examination Survey (NHANES) 2005-2008.

METHODS

The NHANES is a cross-sectional study conducted by the National Center for Health Statistics to study the health and nutritional status of people living in the United States. The analysis included 1,683 participants from study years 2005-2008 for whom urinary isoflavonoids were measured and who met inclusion criteria. Urinary isoflavonoids were measured by HPLC-APPI-MS/MS. Serum C-reactive protein (CRP) was measured by latex-based nephelometry. White blood cell (WBC) count was measured by Coulter counting. Multivariable linear regression was used to calculate the geometric mean values of the markers, and multivariable logistic regression was used to estimate the odds of high CRP (≥3 mg/L) and of high WBC count (≥7,900/μL) by quartile of urinary isoflavonoid (nmol/mg creatinine).

RESULTS

The highest quartile of genistein (OR = 0.62; 95 % CI 0.39-0.99) was associated with significantly decreased odds of high CRP compared with the lowest quartile. The sum of daidzein and its metabolites was significantly inversely associated with serum CRP concentration (p-trend = 0.017). Equol was inversely associated with WBC count (p-trend < 0.0001). O-DMA was the only isoflavonoid whose excretion was significantly associated with a decrease in both CRP (p-trend = 0.024) and WBC count (p-trend < 0.0001).

CONCLUSIONS

Though no clear pattern emerged, higher excretion of certain soy isoflavonoids was associated with decreased CRP concentration and WBC counts, suggesting a possible inverse association between soy intake and inflammation.

Treatment with Jian-pi-qing-re-huo-xue detection regulates SW480 cell apoptosis by altering Wnt/β-catenin expression

AIM: To investigate the effect of treatment with Jian-pi-qing-re-huo-xue decoction on SW480 cell proliferation and apoptosis and the expression of β-catenin, TCF-4, c-myc and cyclin D1.

METHODS: SW480 cells were divided into a blank group, an intervention group and a control group, which were incubated with fetal calf serum, different concentrations of serum containing Jian-pi-qing-re-huo-xue decoction, or serum containing mesalamine for 24 h, respectively. The proliferation and apoptosis of SW480 cells were detected by MMT assay and flow cytometry, respectively. The mRNA and protein expression of β-catenin, TCF-4, c-myc, and cyclin D1 was assayed by real-time PCR and Western blot.

RESULTS: Compared to the blank group, the survival of SW480 cells was reduced in the intervention group (P < 0.05). When the dilution concentration of Jian-pi-qing-re-huo-xue decoction was 5%, 10%, 15%, 20% and 30%, the reduced rate of cell growth was 28%, 44.58%, 65.86%, 57.86% and 49.89%, respectively. However, this inhibitory effect was not concentration-dependent (P > 0.05). Intervention with Jian-pi-qing-re-huo-xue decoction significantly increased the percentage of cells at S phase and decreased that of cells at G1 in a concentration-dependent manner compared to the control group (both P < 0.05). β-catenin was more abundantly expressed in the nucleus in the blank group. In the intervention group, the ectopic expression of β-catenin in the cytoplasm and nucleus declined, and membrane expression increased (P < 0.05). Treatment with Jian-pi-qing-re-huo-xue decoction induced cell apoptosis and down-regulated the expression of β-catenin, TCF-4, c-myc, and cyclin D1 compared to the blank group (P < 0.01), and the effect was more significant when middle concentration of serum containing the decoction was used.

CONCLUSION: Jian-pi-qing-re-huo-xue decoction exerts a distinct preventive and therapeutic effect on colon cancer possibly by altering the expression of Wnt/β-catenin, affecting cell cycle progression and inducing cell apoptosis.

Chemoprevention utility of silibinin and Cdk4 pathway inhibition in Apc(-/+) mice

Background

Colorectal cancer (CRC) is the second leading cause of death from cancer in the United States. Colorectal cancers have a prolonged latency following initiation that may span decades providing ample time for implementing a chemoprevention strategy that could block or reverse the progression to CRC. Cdk4 pathway alterations have been linked to a number of cancers including CRC. In these experiments we focused on the Cdk4 pathway and its role in intestinal tumorigenesis as a possible target in chemoprevention strategies.

Methods

We evaluated the effect of Cdk4 blockade on the prevention of intestinal tumor formation by crossing Cdk4^−/− mice to Apc^−/+ mice. In addition, we tested the effect of the dietary compound silibinin on the Cdk4 pathway in Apc^−/+ mice and HT-29 colon cancer cells in culture.

Results

Cdk4^−/− mice backcrossed to Apc^−/+ mice reduced intestinal adenoma formation compared to Apc^−/+ controls. Silibinin effectively targeted the Cdk4 pathway causing hypophosphorylation of the retinoblastoma protein, inhibited cell growth, and induced apoptosis. As a result silibinin blocked the development of intestinal adenomas by 52% in this genetic model (Apc^−/+ mice) of early events in colorectal cancer formation. No toxic abnormalities were detected in mice which received silibinin.

Conclusions

Modification of the Cdk4 pathway using a natural plant-derived compound such as silibinin may be a useful chemopreventive strategy for colorectal carcinomas.

COX-2 active agents in the chemoprevention of colorectal cancer

Chemopreventive strategies for colorectal cancer (CRC) have been extensively studied to prevent the recurrence of adenomas and/or delay their development in the gastrointestinal tract. The non-steroidal anti-inflammatory drugs (NSAIDs) and selective cyclooxygenase (COX)-2 inhibitors have been proven as promising and the most attractive candidates for CRC clinical chemoprevention. The preventive efficacy of these agents is supported by a large number of animal and epidemiological studies which have clearly demonstrated that NSAID consumption prevents adenoma formation and decreases the incidence of, and mortality from CRC. On the basis of these studies, aspirin chemoprevention may be effective in preventing CRC within the general population, while aspirin and celecoxib may be effective in preventing adenomas in patients after polypectomy. Nevertheless, the consumption of NSAID and COX-2 inhibitors is not toxic free. Well-known serious adverse events to the gastrointestinal, renal and cardiovascular systems have been reported. These reports have led to some promising studies related to the use of lower doses and in combination with other chemopreventive agents and shown efficacy. In the intriguing jigsaw puzzle of cancer prevention, we now have a definite positive answer for the basic question "if", but several other parts of the equation-proper patient selection, the ultimate drug, optimal dosage and duration are still missing.

Mechanistic and pharmacological issues of aspirin as an anticancer agent

Recent findings have shown that aspirin, taken for several years, reduces the long-term risk of some cancers, particularly colorectal cancer. The result that aspirin benefit is detectable at daily low-doses (at least 75mg), the same used for the prevention of cardiovascular disease, positions the antiplatelet action of aspirin at the center of its antitumor efficacy. At low-doses given every 24 h, aspirin is acting by a complete and persistent inhibition of cyclooxygenase (COX)-1 in platelets (in the pre-systemic circulation) while causing a limited and rapidly reversible inhibitory effect on COX-2 and/or COX-1 expressed in nucleated cells. Aspirin has a short half-life in human circulation (approximately 20 min); nucleated cells have the ability to resynthesize the acetylated COX-isozymes within a few hours, while platelets do not. COX-independent mechanisms of aspirin, such as the inhibition of Wnt/ β-catenin and NF-kB signaling and the acetylation of extra-COX proteins, have been suggested to play a role in its chemo-preventive effects, but their relevance remains to be demonstrated in vivo at clinical doses. In conclusion, the results of clinical pharmacology and the analysis of randomized and epidemiological studies suggest that colorectal cancer and atherothrombosis share a common mechanism of disease, i.e. enhanced platelet activation in response to injury at distinct sites.

Cholesterol metabolism and colorectal cancers

Colorectal cancer (CRC) is primarily a lifestyle disease of the western world. As such it can be likened to cardiovascular disease and indeed it shares many of the same risk factors. It is therefore perhaps unsurprising that cholesterol metabolism and colorectal cancer are also intricately linked. Many of the initial studies suggesting a link between dietary cholesterol, blood cholesterol levels and cholesterol lowering drugs were performed more than a decade ago. The most recent insights in this field are the result of meta-analyses, advances in pharmacogenetics and the new field of molecular pathological epidemiology. This review summarises the current evidence linking cholesterol metabolism with colorectal cancer including the suggested underlying molecular causes and the implications for colorectal cancer prevention.

Epigenetic deregulation of the COX pathway in cancer

Inflammation is a major cause of cancer and may condition its progression. The deregulation of the cyclooxygenase (COX) pathway is implicated in several pathophysiological processes, including inflammation and cancer. Although, its targeting with nonsteroidal antiinflammatory drugs (NSAIDs) and COX-2 selective inhibitors has been investigated for years with promising results at both preventive and therapeutic levels, undesirable side effects and the limited understanding of the regulation and functionalities of the COX pathway compromise a more extensive application of these drugs. Epigenetics is bringing additional levels of complexity to the understanding of basic biological and pathological processes. The deregulation of signaling and biosynthetic pathways by epigenetic mechanisms may account for new molecular targets in cancer therapeutics. Genes of the COX pathway are seldom mutated in neoplastic cells, but a large proportion of them show aberrant expression in different types of cancer. A growing body of evidence indicates that epigenetic alterations play a critical role in the deregulation of the genes of the COX pathway. This review summarizes the current knowledge on the contribution of epigenetic processes to the deregulation of the COX pathway in cancer, getting insights into how these alterations may be relevant for the clinical management of patients.

Aspirin and the prevention of colorectal cancer

A large body of evidence from basic science, epidemiologic observations and population-based studies demonstrates that aspirin, as well as other non-steroidal anti-inflammatory drugs, has a chemopreventive effect on several cancer types and, more specifically, in CRC. This protective effect includes prevention of adenoma recurrence and reduction of CRC incidence and mortality. Although the protective effect appears to depend on the dose and the drug, the most important factor is the duration of exposure. However, the lowest effective dose, treatment duration, specific target populations, and effects on survival have not been defined yet. More important, data on the risk-benefit profile for cancer prevention are insufficient and, accordingly, no definitive recommendation can be made at present. In this article, besides reviewing current knowledge of the mechanisms involved in aspirin-based CRC chemoprevention, we will be focused on randomized controlled studies assessing its efficacy in high-, moderate- and average-risk populations.

Exposure to bisphosphonates and risk of colorectal cancer: a population-based nested case-control study

BACKGROUND

Chemoprevention is a potentially attractive strategy for decreasing the burden of colorectal cancer (CRC). Preclinical studies suggest that bisphosphonates (BPs) may have direct antitumour effects against CRC. The objective of this study was to determine the effect of exposure to BPs on the incidence of CRC.

METHODS

The Manitoba Cancer Registry was used to identify patients who were diagnosed with CRC from 2000 to 2009 who had been living in Manitoba for at least 5 years before diagnosis (cases). Each case was matched to 10 controls of similar age, sex, and duration of residence in Manitoba using incidence density sampling. Exposure to BPs was determined using the provincial Drug Program Information Network database. Conditional logistic regression analysis was performed to determine the effect of exposure to BPs on CRC incidence with adjustment for health care use, medical procedures (including lower gastrointestinal endoscopy), socioeconomic status, and pre-existing health conditions.

RESULTS

In total, 5425 patients with CRC were matched to 54,242 controls. In the multivariate analysis, exposure to BPs was associated with a reduction in the risk of CRC (2-13 BP prescriptions over ≥5 years: odds ratio [OR] 0.84; 95% confidence interval [CI], 0.71-1.00; ≥14 BP prescriptions over ≥5 years: OR, 0.78; 95% CI, 0.65-0.94). When the effect of specific BP agents was evaluated, the effect was significant only for exposure to risedronic acid (OR, 0.50; 95% CI, 0.30-0.85). There was no significant effect of increasing duration or cumulative dose of alendronic acid.

CONCLUSIONS

The results from this study suggested that exposure to BPs, especially risedronic acid, may be associated with a decreased risk of developing CRC.

Chemoprevention of colorectal cancer in inflammatory bowel disease

The risk of developing colorectal cancer is increased in patients with inflammatory bowel disease (IBD). Surveillance colonoscopy has not been shown to prolong survival and rates of interval cancer are reported to be high. Various chemopreventive agents have been clearly shown to reduce the risk of colorectal adenoma and cancer in the general population and the problems associated with colonoscopic surveillance have led to increasing interest in utilising chemopreventive strategies to reduce the risk of colorectal cancer in patients with inflammatory bowel disease as well. Continuing colonic inflammation has been shown to be important in the development of colorectal cancer and therefore anti-inflammatory agents have been considered potential chemopreventive agents. As present no agents have been shown to have indisputable chemopreventive activity in IBD but 5-ASAs and thiopurine analogues by reducing inflammation are likely to have some chemopreventive activity and will often be indicated for disease control. More studies are needed using agents such as aspirin and calcium which have been shown to be chemopreventive in sporadic colorectal neoplasia.

Chemoprevention for advanced CR neoplasia

Colorectal cancer (CRC) is a major health concern worldwide. In 2011 1,200,000 new cases are predicted and half of them are going to die from the disease. CRC carcinogenesis is a multi-step process that spans over 10-20 years, providing a window of opportunity for effective intervention. CRC can be prevented by life style modification and screening program. However, although these strategies are standard clinical practice, their impact is limited due to low adherence. The number of deaths due to CRC remains alarming high, and makes CRC prevention a paramount. Chemoprevention interferes with the carcinogenesis process by targeting key molecular pathways. It involves the use of a variety of natural or chemical compounds that can delay, prevent or even reverse the adenoma to carcinoma sequence. Numerous chemopreventive agents have been studied but the most efficient are the NSAID group of agents. Much of their efficacy and toxicity has been attributed to their potent inhibition of the cyclooxygenase (COX) enzymes. Chemoprevention has the potential to represent a cost-effective intervention, particularly when targeted at intermediate-risk populations, ages 61-70, following polypectomy. Chemoprevention in this setting is as very important as polyp recurrence in this population can be as high as 50%, even with surveillance colonoscopy every 1-3 years. The most challenging task is to find the proper place for these interventions in the entire effort of general wellbeing. Subjects are likely to be more adherent to prescribed regimens if cancer prevention may be combined with a cardiovascular and Alzheimer prophylaxis. Subjects with a normal colon or non advanced adenomas can be safely monitored with surveillance colonoscopy every 5-10 years. The ideal chemopreventive agent remains to be discovered with great emphasis on the need not to harm. Possibly, combinations of agents will maximize effectiveness while limiting drug toxicity. Finally, personalized approaches would include the ability to predict risk, as well as benefit for a specific individual based on specific SNP's or other genetic profiles.

Coxibs and other nonsteroidal anti-inflammatory drugs in animal models of cancer chemoprevention

Coxibs, including celecoxib, and other nonsteroidal anti-inflammatory drugs (NSAID), including aspirin, are among the most promising cancer chemopreventive agents in development today. This article examines the data on the efficacy of these agents in animal model studies of cancer prevention carried out by the authors. The studies evaluated here are restricted to our rodent models of colon/intestinal, bladder, and nonmelanoma skin cancer, in which celecoxib and other NSAIDs were administered as either cancer preventive or therapeutic agents. These studies may shed light on several questions. Is celecoxib unique compared with other NSAIDs, and if so, what implications would this have for human use? Are standard NSAIDs (which inhibit both COX-1 and COX-2) as effective as celecoxib in animal studies? Is the efficacy of celecoxib in particular or NSAIDs in general due to their off-target effects or to their effects on COX-1 and COX-2? What is the likely efficacy of low-dose aspirin? Some questions raised by human trials and epidemiology are discussed and related to our observations in animal model studies. We also discuss the problem of cardiovascular (CV) events associated with coxibs and certain other NSAIDs and whether results in animal models are predictive of efficacy in humans. On the basis of epidemiologic studies and its CV profile, aspirin seems to be the most promising NSAID for preventing human colorectal, bladder, and skin cancer, although the animal data for aspirin are less clear. A comprehensive understanding of the results of coxibs and other NSAIDs in animal studies may help inform and shape human trials of these commonly employed, relatively inexpensive, and highly effective compounds.

Protein nitration and nitrosylation by NO-donating aspirin in colon cancer cells: Relevance to its mechanism of action

Nitric oxide-donating aspirin (NO-ASA) is a promising agent for cancer prevention. Although studied extensively, its molecular targets and mechanism of action are still unclear. S-nitrosylation of signaling proteins is emerging as an important regulatory mechanism by NO. Here, we examined whether S-nitrosylation of the NF-κB, p53, and Wnt signaling proteins by NO-ASA might explain, in part, its mechanism of action in colon cancer. NO-ASA releases significant amounts of NO detected intracellularly in HCT116 and HT-29 colon cells. Using a modified biotin switch assay we demonstrated that NO-ASA S-nitrosylates the signaling proteins p53, β-catenin, and NF-κB, in colon cancer cells in a time- and concentration-dependent manner. NO-ASA suppresses NF-κB binding to its cognate DNA oligonucleotide, which occurs without changes in the nuclear levels of the NF-κB subunits p65 and p50 and is reversed by dithiothreitol that reduces -S-NO to -SH. In addition to S-nitrosylation, we documented both in vitro and in vivo widespread nitration of tyrosine residues of cellular proteins in response to NO-ASA. Our results suggest that the increased intracellular NO levels following treatment with NO-ASA modulate cell signaling by chemically modifying key protein members of signaling cascades. We speculate that S-nitrosylation and tyrosine nitration are responsible, at least in part, for the inhibitory growth effect of NO-ASA on cancer cell growth and that this may represent a general mechanism of action of NO-releasing agents.

Five-year analysis of the prevention of colorectal sporadic adenomatous polyps trial

OBJECTIVES

Subjects in the Prevention of Colorectal Sporadic Adenomatous Polyps (PreSAP) trial (PRESAP/NCT00141193/www.clinicaltrials.gov) were studied to determine efficacy and safety at a year 5 assessment.

METHODS

In this randomized, placebo-controlled, double-blind trial, 1,561 subjects with diagnosed colorectal adenomas removed within 3 months of the study's initiation were assessed after ~ 3 years on celecoxib followed by 2 years off. Studied in 107 primary and secondary care settings, subjects were stratified by cardioprotective aspirin use and randomized to receive orally 400 ng celecoxib (933 subjects) or placebo (628 subjects) once daily. Efficacy was measured by colonoscopy at years 1, 3, and 5, and safety was measured by investigators for the on-treatment period and collected by subject self-report over 2 years post-treatment.

RESULTS

At year 5, the primary outcome measure was the rate of new adenomas measured cumulatively from baseline. This rate was statistically significantly lower in the celecoxib group (51.4%) than in the placebo group (57.5%; P<0.001). Similarly, the cumulative rate of new advanced adenomas was significantly lower in the celecoxib group (10.0%) than in the placebo group (13.8%; P=0.007). However, the year 5 interval measure, which was not cumulative and did not take the rates of previous years into account, showed that after 2 years off treatment, the celecoxib group (27.0%) was 1.66 times more likely to have new adenomas than the placebo group (16.3%; P<0.0001). Similarly, the percentage of patients with new advanced adenomas was significantly higher in the celecoxib group (5.0%) than in the placebo group (3.8%) (P=0.0072). The evaluation of safety from baseline through year 5 indicated that the risks of serious cardiac disorders (relative risk (RR) 1.66; 95% confidence interval (CI) 1.01-2.73), selected renal/hypertension events (RR 1.35; 95% CI 1.09-1.68), and general vascular (RR 1.34; 95% CI 1.08-1.68) and cardiac disorders (RR 1.59; 95% CI 1.12-2.26) were higher in those taking celecoxib than in those on placebo.

CONCLUSIONS

The year 5 cumulative measures of the incidence of new and advanced adenomas were significantly lower in the celecoxib group than in the placebo group, but the year 5 interval rates of these measures were significantly lower in the placebo group than the celecoxib group, perhaps suggesting a release of cyclooxygenase-2 inhibition. Consistent with what has been previously reported, increased risk of renal/hypertension events and cardiac disorders associated with celecoxib therapy mandates caution in patient selection.