Review article: Lynch Syndrome-a mechanistic and clinical management update.

BACKGROUND: Lynch syndrome (LS) is an autosomal dominant familial condition caused by a pathogenic variant (PV) in a DNA mismatch repair gene, which then predisposes carriers to various cancers. AIM: To review the pathogenesis, clinical presentation, differential diagnosis and clinical strategies for detection and management of LS. METHODS: A narrative review synthesising knowledge from published literature, as well as current National Comprehensive Cancer Network guidelines for management of LS was conducted. RESULTS: LS tumours are characterised by unique pathogenesis, ultimately resulting in hypermutation, microsatellite instability and high immunogenicity that has significant implications for cancer risk, clinical presentation, treatment and surveillance. LS is one of the most common hereditary causes of cancer, and about 1 in 279 individuals carry a PV in an LS gene that predisposes to associated cancers. Individuals with LS have increased risks for colorectal, endometrial and other cancers, with significant variation in lifetime risk by LS-associated gene. CONCLUSIONS: As genetic testing becomes more widespread, the number of individuals identified with LS is expected to increase in the population. Understanding the pathogenesis of LS informs current strategies for detection and clinical management, and also guides future areas for clinical innovation. Unravelling the mechanisms by which these tumours evolve may help to more precisely tailor management by the gene involved.

Selenium Supplementation for Prevention of Colorectal Adenomas and Risk of Associated Type 2 Diabetes.

BACKGROUND: Selenium supplementation may help to prevent colorectal cancer; as precursors of colorectal cancer, colorectal adenomas are a surrogate for colorectal cancer. Selenium supplementation may increase risk of type 2 diabetes (T2D). METHODS: The Selenium and Celecoxib (Sel/Cel) Trial was a randomized, placebo controlled trial of selenium 200 µg daily as selenized yeast and celecoxib 400 mg once daily, alone or together, for colorectal adenoma prevention. Men and women between age 40 and 80 years were eligible following colonoscopic removal of colorectal adenomas. The primary outcome was adenoma development. Celecoxib was suspended because of cardiovascular toxicity in other trials, but accrual continued to selenium and placebo. A total of 1621 participants were randomly assigned to selenium or placebo, of whom 1374 (84.8%) were available for analysis. All statistical tests were two-sided. RESULTS: In the respective placebo and selenium arms of 689 and 685 participants, adenoma detection after medians of 33.6 (range = 0.0-85.1 months) and 33.0 months (range = 0.0-82.6 months) were 42.8% and 44.1% (relative risk [RR] = 1.03, 95% confidence interval [CI] = 0.91 to 1.16, P = .68). In participants with baseline advanced adenomas, adenoma recurrence was reduced by 18% with selenium (RR = 0.82, 95% CI = 0.71 to 0.96, P = .01). In participants receiving selenium, the hazard ratio for new-onset T2D was 1.25 (95% CI = 0.74 to 2.11, P = .41), with a statistically significantly increased risk of selenium-associated T2D among older participants (RR = 2.21; 95% CI = 1.04 to 4.67, P = .03). CONCLUSIONS: Overall, selenium did not prevent colorectal adenomas and showed only modest benefit in patients with baseline advanced adenomas. With limited benefit and similar increases in T2D to other trials, selenium is not recommended for preventing colorectal adenomas in selenium-replete individuals.

Novel Evidence for Curcumin and Boswellic Acid-Induced Chemoprevention through Regulation of miR-34a and miR-27a in Colorectal Cancer.

Colorectal cancer is one of the most common causes of cancer-associated mortality worldwide, but it is truly a preventable disease. Both curcumin and boswellic acids are well-established dietary botanicals with potent antitumorigenic properties that have been shown to modulate multiple oncogenic pathways. Recent data suggest that the chemopreventive effects of these botanicals may, in part, be mediated through regulation of key cancer-related microRNAs (miRNA) and their downstream gene targets. Here, we investigated the antitumorigenic effects of curcumin and 3 acetyl-11-keto-ß-boswellic acid (AKBA) on modulation of specific cancer-related miRNAs in colorectal cancer cells and validated their protective effects in vivo using a xenograft mouse model. Both curcumin and AKBA inhibited cellular proliferation, induced apoptosis and cell-cycle arrest in colorectal cancer cell lines, and these effects were significantly enhanced with combined treatment. Gene-expression arrays revealed that curcumin and AKBA regulated distinct cancer signaling pathways, including key cell-cycle regulatory genes. Combined bioinformatics and in silico analysis identified apoptosis, proliferation, and cell-cycle regulatory signaling pathways as key modulators of curcumin and AKBA-induced anticancer effects. We discovered that curcumin and AKBA induced upregulation of tumor-suppressive miR-34a and downregulation of miR-27a in colorectal cancer cells. Furthermore, we demonstrated in a mouse xenograft model that both curcumin and AKBA treatments suppressed tumor growth, which corresponded with alterations in the expression of miR-34a and miR-27a, consistent with our in vitro findings. Herein, we provide novel mechanistic evidence for the chemopreventive effects of curcumin and AKBA through regulation of specific miRNAs in colorectal cancer.

Design and baseline characteristics of participants in a phase III randomized trial of celecoxib and selenium for colorectal adenoma prevention.

COX inhibitors reduce colorectal adenoma recurrence by up to 45% and selenium supplementation may prevent colorectal cancer. Following colonoscopic adenoma resection, 1,600 men and women, ages 40 to 80 years, were randomized to celecoxib (400 mg daily), a selective COX-2 inhibitor, and/or selenium (200 µg daily as selenized yeast), or double placebo. The trial was initiated in November 2001. The primary trial endpoint is adenoma recurrence in each intervention group compared with placebo, as determined by surveillance colonoscopy conducted three to five years after baseline. Randomization was stratified by use of low-dose aspirin (81 mg) and clinic site. Following reports of cardiovascular toxicity associated with COX-2 inhibitors, the celecoxib arm was discontinued in December 2004 when 824 participants had been randomized. Accrual continued with randomization to selenium alone or placebo. Randomization of the originally planned cohort (n = 1,621) was completed in November 2008. A further 200 patients with one or more advanced adenomas (denoting increased risk for colorectal cancer) were accrued to enhance statistical power for determining intervention efficacy in this higher-risk subgroup. Accrual of the total cohort (n = 1,824) was completed in January 2011. Baseline cohort characteristics include: mean age 62.9 years; 65% male; body mass index (BMI) 29.1 ± 5.1; 47% taking low-dose aspirin while on trial; 20% with three or more adenomas; and 38% with advanced adenomas. Intervention effects on adenoma recurrence will be determined, and their modification by genetic background and baseline selenium level. The effect of selenium supplementation on risk for type II diabetes will also be reported.

5-Fluorouracil adjuvant chemotherapy does not increase survival in patients with CpG island methylator phenotype colorectal cancer.

BACKGROUND & AIMS: 5-Fluorouracil (5-FU)-based adjuvant chemotherapy does not increase survival times of patients with colorectal tumors with microsatellite instability. We determined the response of patients with colorectal tumors with the CpG island methylator phenotype (CIMP) to 5-FU-based therapy. METHODS: We analyzed a population-based cohort of 302 patients with colorectal cancer (CRC) for a median follow-up time of 50.7 months. CIMP status was determined by analysis of the CACNAG1, SOCS1, RUNX3, NEUROG1, and MLH1 promoters; tumors were considered to be CIMP positive if at least 3 promoters were methylated. RESULTS: Tumors from 29.5% of patients (89/302) were CIMP positive; CIMP status did not influence disease-free survival (DFS; log-rank = 0.3). Of tumors of TNM stages II-III (n = 196), 32.7% were CIMP positive. Among patients with stages II-III CRC who did not receive adjuvant 5-FU chemotherapy, those with CIMP-positive tumors had longest times of DFS (log-rank = 0.04); In patients who received chemotherapy, those with CIMP-positive tumors had shorter times of DFS (log-rank = 0.02). In patients with CIMP-negative tumors, adjuvant 5-FU chemotherapy significantly increased time of DFS (log-rank = 0.00001). However, in patients with CIMP-positive tumors, adjuvant 5-FU chemotherapy did not affect time of DFS (log-rank = 0.7). Multivariate analysis showed a significant, independent interaction between 5-FU treatment and CIMP status (hazard ratio [HR], 0.6; 95% confidence interval [CI], 0.5-0.8). Among patients with CIMP-positive tumors, adjuvant chemotherapy was not an independent predictor of outcome (HR, 0.8; 95% CI, 0.3-2.0). In patients who did not receive adjuvant 5-FU chemotherapy, CIMP status was the only independent predictor of survival (HR, 2.0; 95% CI, 1.1-3.8). CONCLUSIONS: Patients with CIMP-positive colorectal tumors do not benefit from 5-FU-based adjuvant chemotherapy.

Regulation of colorectal cancer cell apoptosis by the n-3 polyunsaturated fatty acids Docosahexaenoic and Eicosapentaenoic.

Several studies have suggested that the n-3 fatty acids Docosahexaenoic (DHA) and Eicosapentaenoic (EPA) have an important protective effect on colorectal cancer, and this could be at least partly due to their proapoptotic activity. It is unclear, however, how this phenomenon is triggered and what mechanisms are implicated. Here, we show that both DHA and EPA have an important proapoptotic effect on colorectal cancer cells with different molecular phenotypes but not in noncancerous cells. Apoptosis is caspase dependent, and both intrinsic and extrinsic pathways are implicated. The dimerization of Bax and Bak, the depolarization of the mitochondrial membrane, and the subsequent release of cytochrome c and Smac/Diablo to the cytosol evidence the activation of the intrinsic pathway. The implication of the extrinsic pathway is shown by the activation of caspase-8, along with the down-regulation of FLIP. The timing of caspase-8 activation, and the oligomerization of Bid with Bax, suggest a cross-talk with the intrinsic pathway. None of the death receptors that commonly initiate the extrinsic pathway: FAS, TNF-R1, and TRAIL-R2 are found to be responsible for triggering the apoptosis cascade induced by DHA and EPA. Neither PPARgamma nor cyclooxygenase-2, two likely candidates to regulate this process, play a significant role. Our findings suggest that the down-regulation of two key regulatory elements of the extrinsic and intrinsic pathways, FLIP and XIAP, respectively, is determinant in the induction of apoptosis by DHA and EPA. These fatty acids could potentially be useful adjuvant anticancer agents in combination with other chemotherapeutic elements.

Chemopreventive properties of pinoresinol-rich olive oil involve a selective activation of the ATM-p53 cascade in colon cancer cell lines.

UNLABELLED: The Mediterranean diet is rich in extra virgin olive oil (EVOO) and associated with a lower incidence of colorectal cancer. EVOO contains phenolic extracts with potential anticarcinogenic activity. AIM: To assess the anticancer properties of EVOO phenolic extracts using in vitro models. METHODS: Phenolic profiles of two different EVOOs (A and B) were determined. RKO and HCT116 (both p53 proficient), SW480 (p53 mutant) and HCT116(p53-/-) (p53 knocked out) cell lines were treated with EVOO extracts and assessed for cell viability. Apoptosis was determined by terminal deoxynucleotidyl transferase nick end labeling (TUNEL) assay and changes in Bax transcript levels. Cell cycle analysis was determined by flow cytometry and western blots. To confirm the data, analysis of cell viability and cell cycle was performed with purified pinoresinol. RESULTS: Chemical characterization showed that pinoresinol is the main phenol in EVOO-A, and oleocanthal predominates in EVOO-B. Only EVOO-A affected cell viability, which was significantly more pronounced in p53-proficient cells. At a concentration of 200 nM, p53-proficient cells showed increased apoptosis and G(2)/M arrest. In p53-proficient cells, ataxia telangiectasia mutated (ATM) and its downstream-controlled proteins were upregulated after treatment, with a parallel decrease of cyclin B/cdc2. Identical results on cell viability and cell cycle were obtained with purified pinoresinol, but this required a higher concentration than in EVOO-A. CONCLUSION: Our results demonstrate that pinoresinol-rich EVOO extracts have potent chemopreventive properties and specifically upregulate the ATM-p53 cascade. This result was achieved at substantially lower concentrations in EVOO than with purified pinoresinol, indicating a possible synergic effect between the various polyphenols in olive oil.

Annurca apple polyphenols have potent demethylating activity and can reactivate silenced tumor suppressor genes in colorectal cancer cells.

The CpG island methylator phenotype is characterized by DNA hypermethylation in the promoters of tumor suppressor genes with silencing of transcription. Hypermethylation of the promoter of hMLH1 and subsequent microsatellite instability occurs in approximately 12% of sporadic colorectal cancers (CRC). Annurca apple, a variety of southern Italy, is rich in polyphenols that are associated with anticancer properties. Populations in southern Italy have lower incidences of CRC than elsewhere in the western world. We evaluated the mechanisms of putative anticancer effects of Annurca polyphenol extract (APE) in in vitro models of CRC. We extracted polyphenols from Annurca apples and treated RKO, SW48, and SW480 cells with APE and assessed the cell viability, apoptosis, and cell cycle. DNA methylation of selected tumor suppressor genes was evaluated after treatment with APE and was compared with the synthetic demethylating agent 5-aza-2'deoxycytidine (5-aza-2dC). DNA methyltransferase (DNMT)-1 and -3b levels were evaluated. Decreased cell viability and induction of apoptosis was evident after treatment. We found no significant changes in cell cycle dynamics. We observed significant increases of p53 protein expression in RKO after treatment. APE treatment strongly reduced DNA methylation in the promoters of hMLH1, p14(ARF), and p16(INK4a) with consequent restoration of normal expression. These effects were qualitatively comparable with those obtained with 5-aza-2dC. We observed a significant reduction in expression of DNMT proteins after treatment without changes in messenger RNA. In conclusion, APE have potent demethylating activity through the inhibition of DNMT proteins. The lack of toxicity in Annurca extracts makes them excellent candidates for the chemoprevention of CRC.

Use of 5-fluorouracil and survival in patients with microsatellite-unstable colorectal cancer.

BACKGROUND & AIMS: 5-Fluorouracil improves mortality in stage III colorectal cancer patients. In vitro studies suggest that microsatellite instability influences cell survival after 5-fluorouracil treatment. We investigated the survival influence of 5-fluorouracil in patients with microsatellite instability-high tumors. METHODS: We collected data and tumors on 204 consecutive stage II and III colorectal cancer patients from registries at the University of California and Veterans Administration hospitals in San Diego, California, from 1982 to 1999. Archival DNA was extracted, and microsatellite instability was assessed by National Cancer Institute-recommended markers. Cox proportional hazard modeling was used to determine survival associations for microsatellite instability and 5-fluorouracil treatment status. RESULTS: We identified 36 microsatellite instability-high (17.6%) and 168 non-microsatellite instability-high tumors (82.4%). Microsatellite instability-high tumors were significantly associated with proximal colon location, presence of mucin, and surrounding lymphoid reaction. Univariate and multivariate analyses showed no survival difference between microsatellite instability-high and non-microsatellite instability-high groups (hazard ratio, 1.04; P = 0.88). Dichotomized by use of 5-fluorouracil, there was increased risk of death in patients who received no adjuvant chemotherapy (hazard ratio, 2.02; P = 0.02). However, the benefit of 5-fluorouracil was different between microsatellite instability-high and non-microsatellite instability-high groups. Patients with non-microsatellite instability-high tumors who received 5-fluorouracil had better survival compared with patients who were not treated (P < 0.05). Conversely, patients with microsatellite instability-high tumors who were treated with 5-fluorouracil had no survival difference compared with patients without treatment (P = 0.52). CONCLUSIONS: There is improved survival in patients with non-microsatellite instability-high tumors after 5-fluorouracil-based chemotherapy that does not extend to patients with microsatellite instability-high tumors. The microsatellite instability status of a patient's colorectal cancer may indicate differences in 5-fluorouracil-based chemosensitivity; this is consistent with in vitro studies.