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 non-infected (n=15) subjects was analyzed by quantitative real-time PCR, western blot analysis, and immunohistochemisty. 15-PGDH DNA methylation was evaluated by methylation specific PCR and pyrosequencing. The expression of 15-PGDH, Snail, ERK1/2, TLR4 and MyD88 in response to H pylori infection was assessed by immunoblot analysis. Compared to 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 epidermal growth factor receptor (EGFR)-Snail. Inhibition of Snail and MyD88 reversed suppression of 15-PGDH expression and small interfering Myd88 reduced phosphorylated ERK1/2. Similarly, treatment with an ERK1/2 and EGFR inhibitor also restored 15-PGDH expression. Heliocobacter pylori appeared to promote gastric carcinogenesis by suppressing15-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.
Gastric cancer; Helicobacter pylori; 15-prostaglandin dehydrogenase
In current clinical practice, genetic testing to detect Lynch syndrome mutations ideally begins with diagnostic testing of an individual affected with cancer before offering predictive testing to at-risk relatives. An alternative strategy that warrants exploration involves screening unaffected individuals via demographic and family histories, and offering genetic testing to those individuals whose risks for carrying a mutation exceed a selected threshold. Whether this approach would improve health outcomes in a manner that is cost-effective relative to current standards of care has yet to be demonstrated. To do so, we developed a simulation framework that integrated models of colorectal and endometrial cancers with a 5-generation family history model to predict health and economic outcomes of 20 primary screening strategies (at a wide range of compliance levels) aimed at detecting individuals with mismatch repair gene mutations and their at-risk relatives. These strategies were characterized by (i) different screening ages for starting risk assessment and (ii) different risk thresholds above which to implement genetic testing. For each strategy, 100,000 simulated individuals, representative of the U.S. population, were followed from the age of 20, and the outcomes were compared with current practice. Findings indicated that risk assessment starting at ages 25, 30, or 35, followed by genetic testing of those with mutation risks exceeding 5%, reduced colorectal and endometrial cancer incidence in mutation carriers by approximately 12.4% and 8.8%, respectively. For a population of 100,000 individuals containing 392 mutation carriers, this strategy increased quality-adjusted life-years (QALY) by approximately 135 with an average cost-effectiveness ratio of $26,000 per QALY. The cost-effectiveness of screening for mismatch repair gene mutations is comparable to that of accepted cancer screening activities in the general population such as colorectal cancer screening, cervical cancer screening, and breast cancer screening. These results suggest that primary screening of individuals for mismatch repair gene mutations, starting with risk assessment between the ages of 25 and 35, followed by genetic testing of those whose risk exceeds 5%, is a strategy that could improve health outcomes in a cost-effective manner relative to current practice.
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 PPARγ 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.
A major barrier to oral cancer prevention has been the lack of validated risk predictors for oral premalignant lesions (OPLs). In 2000, we proposed a loss of heterozygosity (LOH) risk model in a retrospective study. This paper validated the previously reported LOH profiles as risk predictors and developed refined models via the largest longitudinal study to date of low-grade OPLs from a population-based patient group. Analysis involved a prospective cohort of 296 patients with primary mild/moderate oral dysplasia enrolled in the Oral Cancer Prediction Longitudinal Study. LOH status was determined in these OPLs. Patients were classified into high-risk or low-risk profiles to validate the 2000 model. Risk models were refined using recursive partitioning and Cox regression analyses. The prospective cohort validated that the high-risk lesions (3p &/or 9p LOH) had a 22·6 - fold increase in risk (P = 0·002) compared to low-risk lesions (3p & 9p retention). Addition of another two markers (loci on 4q/17p) further improved the risk prediction, with five-year progression rates of 3·1%, 16·3%, and 63·1% for the low-, intermediate-, and high-risk lesions, respectively. Compared to the low-risk group, intermediate- and high-risk groups had 11·6-fold and 52·1-fold increase in risk (P < 0·001). LOH profiles as risk predictors in the refined model were validated in the retrospective cohort. Multi-covariate analysis with clinical features showed LOH models to be the most significant predictors of progression. LOH profiles can reliably differentiate progression risk for OPLs. Potential uses include increasing surveillance for patients with elevated risk, improving target intervention for high-risk patients while sparing a large number of low-risk patients from needless screening and treatment.
The Western diet (WD) is associated with a higher incidence of colorectal cancer (CRC) than the Mediterranean diet. Polyphenols extracted from Annurca apple showed chemopreventive properties in CRC cells. A multifactorial, four-arm study by using wild-type (wt) and ApcMin/+ mice was carried out to evaluate the effect on polyp number and growth of APE treatment (60 μmol/L) ad libitum in drinking water combined with a WD or a balanced diet (BD) for 12 weeks. Compared with APE treatment, we found a significant drop in body weight (P < 0.0001), severe rectal bleeding (P = 0.0076), presence of extra-intestinal tumors, and poorer activity status (P = 0.0034) in water-drinking ApcMin/+ mice, more remarkably in the WD arm. In the BD and WD groups, APE reduced polyp number (35% and 42%, respectively, P < 0.001) and growth (60% and 52%, respectively, P < 0.0001) in both colon and small intestine. Increased antioxidant activity was found in wt animals fed both diets and in ApcMin/+ mice fed WD and drinking APE. Reduced lipid peroxidation was found in ApcMin/+ mice drinking APE fed both diets and in wt mice fed WD. In normal mucosa, mice drinking water had lower global levels of DNA methylation than mice drinking APE. APE treatment is highly effective in reducing polyps in ApcMin/+ mice and supports the concept that a mixture of phytochemicals, as they are naturally present in foods, represent a plausible chemopreventive agent for CRC, particularly in populations at high risk for colorectal neoplasia.
Serum autoantibodies, directed against oncogenic proteins, have been frequently detected in the sera of breast cancer patients. It is unknown whether serum antibodies that are identified in patients with established disease could also be detected in patients with newly diagnosed disease or even predate the diagnosis of breast cancer. Using sera collected at the time of treatment, at the time of diagnosis, or prior to the time of diagnosis, the current study aimed to address the temporal relationship between breast cancer development and serum antibody response. Starting from serum antibodies to eight known breast cancer antigens, we first identified four serum antibodies, HER-2/neu, p53, CEA, and cyclin B1, which are significantly increased in the sera collected from breast cancer patients at the time of treatment. These antibodies were also elevated in breast cancer sera collected at the time of diagnosis. Lastly, comparison of antibody responses in pre-diagnostic samples from women prior to the development of breast cancer and in controls demonstrated that antibodies to the HER-2/neu and p53 can be detected in sera that were collected on average more than 150 days before a breast cancer diagnosis. These results demonstrated that serum autoantibodies commonly reported in sera from patients with established disease can also be detected in pre-diagnostic sera and may be useful for the early detection of breast cancer.
serum antibody; breast cancer; early detection
Colorectal cancer (CRC) is the second leading cause of cancer-related death, and usually arises from colorectal polyps. Screening and removal of polyps reduce mortality from CRC. Colorectal polyps are known to aggregate in families; however the genetic determinants for risk of polyps are unknown. Additionally, it has been shown that nonsteroidal anti-inflammatory drug (NSAID) use decreases the risk of CRC and the incidence and size of polyps. In this study, we used data from the Tennessee Colorectal Polyp Study and the Tennessee-Indiana Adenoma Recurrence Study to evaluate selected genes from the prostaglandin metabolism and signaling pathways for association with risk of polyps and for interactions with NSAIDs. Our design consisted of discovery and replication phases for a total of 2,551 Caucasian polyp cases and 3,285 Caucasian controls. We performed multivariable logistic regression to test for association in both the discovery and replication phase and further examined the results with meta-analysis. We detected association signals in the genes prostaglandin E receptor 3 (PTGER3) and 15-hydroxyprostaglandin dehydrogenase (HPGD), both strong biological candidates for influence on polyp risk. We did not observe the previously reported effects and effect modification in prostaglandin-endoperoxide synthase 2 (PTGS2), prostaglandin E receptor 2 (PTGER2), or prostaglandin E receptor 4 (PTGER4), although we did observe a single nucleotide polymorphism in PTGER2 associated with risk of multiple adenomas. We also observed effect modification of the HPGD signal by NSAID exposure.
Colorectal adenoma; genetic association; prostaglandin signaling; prostaglandin metabolism; NSAIDs
APC/β-catenin pathway perturbation is a common early event in colorectal carcinogenesis and is affected by calcium and vitamin D in basic science studies. To assess the effects of calcium and vitamin D on APC, β-catenin, and E-cadherin expression in the normal appearing colorectal mucosa of sporadic colorectal adenoma patients, we conducted a randomized, double-blinded, placebo-controlled 2×2 factorial clinical trial. Pathology-confirmed colorectal adenoma cases were treated with 2 g/day elemental calcium and/or 800 IU/day vitamin D3 versus placebo over 6 months (N=92; 23/group). Overall APC, β-catenin, and E-cadherin expression and distributions in colon crypts in normal-appearing rectal mucosa biopsies were detected by standardized automated immunohistochemistry and quantified by image analysis. In the vitamin D3-supplemented group relative to placebo, the proportion of APC in the upper 40% of crypts (ϕh APC) increased 21% (p=0.01), β-catenin decreased 12% (p=0.18), E-cadherin increased 72% (p=0.03), and the ϕh APC/β-catenin ratio (APC/β-catenin score) increased 31% (p=0.02). In the calcium-supplemented group ϕh APC increased 10% (p=0.12), β-catenin decreased 15% (p=0.08), and the APC/β-catenin score increased 41% (p=0.01). In the calcium/vitamin D3 supplemented group β-catenin decreased 11% (p=0.20), E-cadherin increased 51% (p=0.08), and the APC/β-catenin score increased 16% (p=0.26). These results support 1) that calcium and vitamin D modify APC, β-catenin, and E-cadherin expression in humans in directions hypothesized to reduce risk for colorectal neoplasms, 2) calcium and vitamin D as potential chemopreventive agents against colorectal neoplasms, and 3) the potential of APC, β-catenin, and E-cadherin expression as modifiable, pre-neoplastic risk biomarkers for colorectal neoplasms.
calcium; vitamin D; colonic neoplasms; biomarkers; clinical trial
Obesity is a well-recognized risk factor for postmenopausal breast cancer. Although the underlying mechanisms are not clearly defined, aromatase is thought to play a pivotal role in connecting obesity-associated inflammation with postmenopausal breast cancer. It has been well established that both the pro-inflammatory prostaglandin E2 (PGE2) and the BRCA1 tumor-suppressor gene regulate aromatase expression. In this issue of the journal (beginning on page XXX), Subbaramaiah and colleagues improve our understanding of the molecular mechanisms by which peroxisome proliferator-activated receptor γ (PPARγ) inhibits aromatase expression. They found that pioglitazone, a PPARγ agonist, inhibited aromatase expression by inhibition of PGE2signaling and upregulation of BRCA1. Their findings provide potential targets for preventing or treating obesity-related breast cancer.
Obesity, an established risk factor for epithelial cancers, remains prevalent in the US and many other countries. In contrast to positive energy balance states (overweight, obesity), calorie restriction (CR) has been shown to act as a universal inhibitor of tumorigenesis in multiple animal models of human cancer. Unfortunately, the mechanisms underlying the enhancing effects of obesity or the inhibitory effects of CR on cancer etiology remain elusive. Here, we evaluated the impact of dietary energy balance manipulation on epithelial carcinogenesis and identified several potential mechanisms that may account for the differential effects of obesity and CR on cancer. Obesity enhanced tumor promotion during epithelial carcinogenesis, in part, due to altered IGF-1R/EGFR crosstalk and downstream signaling to effectors such as Akt/mTOR. Obesity-induced changes in cellular signaling subsequently led to altered levels of cell cycle proteins that favored enhanced epidermal proliferation during tumor promotion. In contrast, CR reduced susceptibility to tumor promotion, attenuated IGF-1R/EGFR crosstalk and downstream signaling and altered levels of cell cycle proteins that favored reduced epidermal proliferation during tumor promotion. Collectively, these findings suggest potential targets for the prevention of epithelial cancers, as well as for reversal of obesity-mediated cancer development and progression.
energy balance; epithelial carcinogenesis; IGF-1R/EGFR crosstalk; cell cycle; proliferation
Experimental and clinical data suggest that aspirin and other non-steroidal inflammatory drugs may delay the progression of prostate cancer through inhibition of the cyclooxygenase (COX) pathway and its effects on cellular proliferation, apoptosis and angiogenesis. Epidemiological data support a reduced risk of prostate cancer incidence with aspirin use, yet no evidence exists regarding whether aspirin after diagnosis influences progression or survival. We conducted a prospective study of 3,986 participants of the Health Professionals Follow-up Study, with a prostate cancer diagnosis between January 1, 1990 and December 31, 2005. We used Cox proportional hazards regression to evaluate the association between aspirin use after diagnosis and the development of metastases or fatal prostate cancer through January 31, 2008, adjusting for risk factors associated with incidence and mortality in this cohort, pre-diagnostic aspirin use, Gleason score, TNM stage and primary treatment. In total, 265 men developed bony or other organ metastases or fatal prostate cancer during the 18 years of follow-up. We observed no association between updated aspirin use after diagnosis and lethal prostate cancer (tablets/week: <2, HR=1.12, 95% CI: 0.72, 1.72; 2-5, HR=1.05, 95% CI: 0.62, 1.80, ≥ 6, HR=1.08, 95% CI: 0.76, 1.54; p-trend=0.99). The results remained unchanged when we examined aspirin use at baseline only (p-trend=0.70) or frequency of use (days/week, p-trend=0.35); or limited the outcome to fatal prostate cancer (p-trend = 0.63). There was no association between aspirin use after a prostate cancer diagnosis and lethal disease in this cohort of prostate cancer survivors.
Pancreatic cancer is the fourth leading cause of cancer-related deaths in the United States, which is, in part, due to intrinsic (de novo) and extrinsic (acquired) resistance to conventional therapeutics, suggesting that innovative treatment strategies are required for overcoming therapeutic resistance to improve overall survival of patients. Oral administration of metformin in patients with diabetes mellitus has been reported to be associated with reduced risk of pancreatic cancer and that metformin has been reported to kill cancer stem cells (CSC); however, the exact molecular mechanism(s) has not been fully elucidated. In the current study, we examined the effect of metformin on cell proliferation, cell migration and invasion, and self-renewal capacity of CSCs and further assessed the expression of CSC marker genes and microRNAs (miRNA) in human pancreatic cancer cells. We found that metformin significantly decreased cell survival, clonogenicity, wound-healing capacity, sphere-forming capacity (pancreatospheres), and increased disintegration of pancreatospheres in both gemcitabine-sensitive and gemcitabine-resistant pancreatic cancer cells. Metformin also decreased the expression of CSC markers, CD44, EpCAM, EZH2, Notch-1, Nanog and Oct4, and caused reexpression of miRNAs (let-7a, let-7b, miR-26a, miR-101, miR-200b, and miR-200c) that are typically lost in pancreatic cancer and especially in pancreatospheres. We also found that reexpression of miR-26a by transfection led to decreased expression of EZH2 and EpCAM in pancreatic cancer cells. These results clearly suggest that the biologic effects of metformin are mediated through reexpression of miRNAs and decreased expression of CSC-specific genes, suggesting that metformin could be useful for overcoming therapeutic resistance of pancreatic cancer cells.
There have been no controlled intervention studies to investigate the effects of green tea on circulating hormone levels, an established breast cancer risk factor. We conducted a randomized, double-blind, placebo-controlled intervention study to investigate the effect of the main green tea catechin, epigallocatechin gallate (EGCG), taken in a green tea extract, Polyphenon E (PPE). Postmenopausal women (n=103) were randomized into three arms: placebo, 400 mg EGCG as PPE, or 800 mg EGCG as PPE as capsules per day for 2 months. Urinary tea catechin and serum estrogen, androgen, lipid, glucose-related markers, adiponectin, and growth factor levels were measured at baseline and at the end of months 1 and 2 of intervention. Based on urinary tea catechin concentrations, compliance was excellent. Supplementation with PPE did not produce consistent patterns of changes in estradiol (E2), estrone (E1), or testosterone (T) levels. Low density lipoprotein (LDL)-cholesterol decreased significantly in both PPE groups but was unchanged in the placebo group; the change in LDL-cholesterol differed between the placebo and PPE groups (P=0.02). Glucose and insulin levels decreased nonsignificantly in the PPE groups but increased in the placebo group; statistically significant differences in changes in glucose (P=0.008) and insulin (P=0.01) were found. In summary, green tea (400 and 800 mg EGCG as PPE; ~5–10 cups) supplementation for 2 months had suggestive beneficial effects on LDL cholesterol concentrations and glucose-related markers.
green tea; hormones; lipids; glucose; intervention
Our previous work suggested that there was no significant association between plasma steroid hormone levels and prostate cancer (CaP) tumor grade at diagnosis. In this study, we systematically tested the hypothesis that inherited variations in the androgen and estrogen metabolic pathways may be associated with plasma levels of steroid hormones, or CaP aggressiveness at diagnosis.
Plasma hormone levels including total testosterone, total estradiol and sex hormone-binding globulin were measured in a cohort of 508 patients identified with localized CaP. D’Amico risk classification at diagnosis was also determined. 143 single nucleotide polymorphisms (SNPs) from 30 genes that are involved in androgen and estrogen metabolism were selected for analysis. The global association of genotypes with plasma hormone levels and CaP aggressiveness (D’Amico risk classification) was statistically analyzed. Q-values were estimated to account for multiple testing.
We observed significant associations between plasma testosterone level and SNPs in HSD17B2 (rs1424151), HSD17B3 (rs9409407) and HSD17B1 (rs12602084), with P values of 0.002, 0.006 and 0.006, respectively. We also observed borderline significant associations between prostate aggressiveness at diagnosis and SNPs in AKR1C1 (rs11252845; P = 0.005), UGT2B15 (rs2045100; P = 0.007) and HSD17B12 (rs7932905; P = 0.008). No individual SNP was associated with both clinical variables.
Genetic variants of genes in hormone metabolic pathways may influence plasma androgen levels or CaP aggressiveness. However, it appears that the inherited variations affecting plasma hormone levels differ from those affecting disease aggressiveness.
Prostate cancer; Hormone metabolism; Single-nucleotide Polymorphisms
Numerous dietary factors elevate serum levels of insulin and insulin-like growth factor I (IGF-I), both potent prostate cancer mitogens. We tested whether varying dietary carbohydrate and fat, without energy restriction relative to comparison diets, would slow tumor growth and reduce serum insulin, IGF-I, and other molecular mediators of prostate cancer in a xenograft model.
Individually caged male severe combined immunodeficient mice (n = 130) were randomly assigned to one of three diets (described as percent total calories): very high-fat/no-carbohydrate ketogenic diet (NCKD: 83% fat, 0% carbohydrate, 17% protein), low-fat/high-carbohydrate diet (LFD: 12% fat, 71% carbohydrate, 17% protein), or high-fat/moderate-carbohydrate diet (MCD: 40% fat, 43% carbohydrate, 17% protein). Mice were fed to maintain similar average body weights among groups. Following a preliminary feeding period, mice were injected with 1 × 106 LNCaP cells (day 0) and sacrificed when tumors were ≥1,000 mm3.
Two days before tumor injection, median NCKD body weight was 2.4 g (10%) and 2.1 g (8%) greater than the LFD and MCD groups, respectively (P < 0.0001). Diet was significantly associated with overall survival (log-rank P = 0.004). Relative to MCD, survival was significantly prolonged for the LFD (hazard ratio, 0.49; 95% confidence interval, 0.29–0.79; P = 0.004) and NCKD groups (hazard ratio, 0.59; 95% confidence interval, 0.37–0.93; P = 0.02). Median serum insulin, IGF-I, IGF-I/IGF binding protein-1 ratio, and IGF-I/IGF binding protein-3 ratio were significantly reduced in NCKD relative to MCD mice. Phospho-AKT/total AKT ratio and pathways associated with antiapoptosis, inflammation, insulin resistance, and obesity were also significantly reduced in NCKD relative to MCD tumors.
These results support further preclinical exploration of carbohydrate restriction in prostate cancer and possibly warrant pilot or feasibility testing in humans.
In addition to being causally linked to the formation of multiple tumor types, tobacco use has been associated with decreased efficacy of anticancer treatment and reduced survival time. A detailed understanding of the cellular mechanisms that are affected by tobacco smoke should facilitate the development of improved preventive and therapeutic strategies. We have investigated the effects of a tobacco smoke (TS) extract on the transcriptome of MSK-Leuk1 cells, a cellular model of oral leukoplakia. Using Affymetrix HGU133 Plus 2 arrays, 411 differentially expressed probesets were identified. The observed transcriptome changes were grouped according to functional information, and translated into molecular interaction network maps and signaling pathways. Pathways related to cellular proliferation, inflammation, apoptosis and tissue injury appeared to be perturbed. Analysis of networks connecting the affected genes identified specific modulated molecular interactions, hubs and key transcription regulators. Thus, TS was found to induce several EGFR ligands forming an EGFR-centered molecular interaction network, as well as several AhR-dependent genes, including the xenobiotic metabolizing enzymes CYP1A1 and CYP1B1. Notably, the latter findings in vitro are consistent with our parallel finding that levels of CYP1A1 and CYP1B1 were increased in oral mucosa of smokers. Collectively, these results offer insights into the mechanisms underlying the procarcinogenic effects of TS and raise the possibility that inhibitors of EGFR or AhR signaling will prevent or delay the development of tobacco smoke-related tumors. Moreover, the inductive effects of TS on xenobiotic metabolizing enzymes may help explain reduced efficacy of chemotherapy, and suggest targets for chemopreventive agents in smokers.
microarray; tobacco smoke; gene expression; oral; aryl hydrocarbon receptor
Skin cancer is the most common malignancy in organ transplant recipients, causing serious morbidity and mortality. Preventing and treating skin cancer in these individuals has been extraordinarily challenging. Following organ transplantation, cyclosporin A (CsA) has been used as an effective immunosuppressive to prevent rejection. Therefore immunosuppression has been widely assumed to be the major cause for increased skin carcinogenesis. However, the mechanism of skin carcinogenesis in organ transplant recipients has not been understood to date; specifically, it remains unknown whether these cancers are immunosuppression-dependent or -independent. Here, using both immunocompromised nude mice which are defective in mature T lymphocytes as an in vivo model and human keratinocytes as an in vitro model, we showed that CsA impairs genomic integrity in the response of keratinocytes to UVB. Following UVB radiation, CsA inhibited UVB-induced DNA damage repair by suppressing the transcription of the DNA repair factor xeroderma pigmentosum C (XPC). In addition, CsA compromised the UVB-induced checkpoint function by up-regulating the molecular chaperone protein cyclophilin A (CypA). XPC mRNA levels were lower, whereas CypA mRNA and protein levels were higher in human skin cancers than in normal skin. CsA-induced PI3K/AKT activation was required for both XPC suppression and CypA up-regulation. Blocking UVB damage or inhibiting the PI3K/AKT pathway prevented CsA-sensitized skin tumorigenesis. Our findings identified deregulation of XPC and CypA as key targets of CsA, and UVB damage and PI3K/AKT activation as two principal drivers for CsA-sensitized skin tumorigenesis, further supporting an immunosuppression-independent mechanism of CsA action on skin tumorigenesis.
XPC; CypA; Cyclosporin A; UVB; DNA repair; checkpoint
This perspective examines the report by Zhang et al. in this issue of the journal (beginning on page XiXiX) on the validation and refinement of a set of risk markers for oral premalignant lesion progression that incorporates loss of heterozygosity (LOH) markers. The perspective also discusses some of the challenges and opportunities of incorporating predictive biomarkers into monitoring and refined enrollment criteria for prevention studies.
Hepatocellular carcinoma (HCC) surveillance is underutilized among patients with cirrhosis. Understanding which steps in the surveillance process are not being performed is essential for designing effective interventions to improve surveillance rates. Our study's aim was to characterize reasons for failure in the HCC surveillance process among a cohort of cirrhotic patients with HCC. We conducted a retrospective cohort study of cirrhotic patients diagnosed with HCC at a large urban safety-net hospital between 2005–2011. Patients were characterized by receipt of HCC surveillance over a two-year period prior to HCC diagnosis. Among patients without HCC surveillance, we classified reasons for failure into four categories: failure to recognize liver disease, failure to recognize cirrhosis, failure to order surveillance, and failure to complete surveillance despite orders. Univariate and multivariate analyses were performed to identify predictors of failures. We identified 178 patients with HCC, of whom 20% had undergone surveillance. There were multiple points of failure- 20% had unrecognized liver disease, 19% had unrecognized cirrhosis, 38% lacked surveillance orders, and 3% failed to complete surveillance despite orders. Surveillance was more likely among patients seen by hepatologists (OR 6.11, 95%CI 2.5–14.8) and less likely in those with alcohol abuse (OR 0.14, 95%CI 0.03–0.65). Although a retrospective analysis in a safety-net hospital, our data suggest only one in five patients received surveillance prior to HCC diagnosis. There are multiple points of failure in the surveillance process, with the most common being failure to order surveillance in patients with known cirrhosis. Future interventions must target multiple failure points in the surveillance process to be highly effective.
Screening; underutilization; quality of care; liver cancer; cirrhosis
Skin cancer is one of the most commonly diagnosed cancers in United States. Taxifolin reportedly exerts multiple biological effects but the molecular mechanisms and direct target(s) of taxifolin in skin cancer chemoprevention are still unknown. In silico computer screening and kinase profiling results suggest that the epidermal growth factor receptor (EGFR), phosphatidyl inositol 3-kinase (PI3-K) and Src are potential targets for taxifolin. Pull-down assay results showed that EGFR, PI3-K and Src directly interacted with taxifolin in vitro, whereas taxifolin bound to EGFR and PI3-K but not to Src in cells. ATP-competition and in vitro kinase assay data revealed that taxifolin interacted with EGFR and PI3-K at the ATP binding pocket and inhibit their kinase activities. Western blot analysis showed that taxifolin suppressed UVB-induced phosphorylation of EGFR and Akt, and subsequently suppressed their signaling pathways in JB6 P+ mouse skin epidermal cells. Expression levels and promoter activity of COX-2 and prostaglandin E2 (PGE2) generation induced by UVB were also attenuated by taxifolin. The effect of taxifolin on UVB-induced signaling pathways and PGE2 generation was reduced in EGFR knockout murine embryonic fibroblasts (MEFs) compared with EGFR wildtype MEFs. Taxifolin also inhibited EGF-induced cell transformation. Importantly, topical treatment of taxifolin to the dorsal skin significantly suppressed tumor incidence, volume and multiplicity in a solar-UV (SUV)-induced skin carcinogenesis mouse model. Further analysis showed that the taxifolin-treated group had a substantial reduction in SUV-induced phosphorylation of EGFR and Akt in mouse skin. These results suggest that taxifolin exerts chemopreventive activity against UV-induced skin carcinogenesis by targeting EGFR and PI3-K.
taxifolin; EGFR; PI3-K; skin carcinogenesis
The interaction between the intestinal microbiota and host is much more complex than previously appreciated, and we are now learning that it can have an impact on extraintestinal human diseases. In this issue of the journal (beginning on page XXX), Lin et al present important data linking the microbiota, LPS, and TLR4 with hepatitis in a mouse model. These provocative results and those from other recent studies highlight the microbiota as a potential target for therapeutic intervention in several liver diseases.
Obesity is associated with increased risk of a number of cancers in humans, but the mechanism(s) responsible for these associations have not been established. It is estimated that 68% of adults are overweight or obese and that obesity may be causative in 4–7% of cancers in the United States. Several hypotheses have been put forward to explain the association between obesity and cancer including adipose-directed signaling (e.g. mTOR, AMPK), production of factors (e.g. insulin growth factor 1, fibroblast growth factor 1 (FGF1)) and/or chronic inflammation associated with obesity. Huffman and colleagues (beginning on page XXXX) used surgical methods to determine if visceral fat (VF) was causally related to intestinal tumorigenesis in the Apc1638/N+ mouse in a manner independent of confounding factors such as caloric restriction. They found that caloric restriction could extend survival in both male and female Apc1638/N+ mice but found that surgical removal of VF was only effective in reducing macroadenomas in females. The results of this study do not identify the specific mechanism of association between VF and intestinal carcinogenesis in female mice but do support the rationale for future cancer prevention trials that evaluate pharmacological and behavioral strategies to reduce abdominal obesity in humans.
Previous studies indicate that carbohydrate intake influences prostate cancer biology, as mice fed a no-carbohydrate ketogenic diet (NCKD) had significantly smaller xenograft tumors and longer survival than mice fed a Western diet. As it is nearly impossible for humans to consume and maintain NCKD, we determined whether diets containing 10% or 20% carbohydrate kcal showed similar tumor growth as NCKD. A total of 150 male severe combined immunodeficient mice were fed a Western diet ad libitum, injected with the human prostate cancer cell line LAPC-4, and then randomized 2 weeks later to one of three arms: NCKD, 10% carbohydrate, or 20% carbohydrate diets. Ten mice not injected were fed an ad libitum low-fat diet (12% fat kcal) serving as the reference in a modified-paired feeding protocol. Mice were sacrificed when tumors reached 1,000 mm3. Despite consuming extra calories, all mice receiving low-carbohydrate diets were significantly lighter than those receiving a low-fat diet (P < 0.04). Among the low-carbohydrate arms, NCKD-fed mice were significantly lighter than the 10% or 20% carbohydrate groups (P < 0.05). Tumors were significantly larger in the 10% carbohydrate group on days 52 and 59 (P < 0.05), but at no other point during the study. Diet did not affect survival (P = 0.34). There were no differences in serum insulin-like growth factor-I or insulin-like growth factor binding protein-3 at sacrifice among the low-carbohydrate arms (P = 0.07 and P = 0.55, respectively). Insulin was significantly lower in the 20% carbohydrate arm (P = 0.03). LAPC-4 xenograft mice fed a low-carbohydrate diet (10–20% carbohydrate kcal) had similar survival as mice consuming NCKD (0% carbohydrate kcal).
Barrett’s esophagus (BE) is the only known precursor to esophageal adenocarcinoma. As definitive diagnosis requires costly endoscopic investigation, we sought to develop a risk prediction model to aid in deciding which patients with gastroesophageal reflux (GER) symptoms to refer for endoscopic screening for BE.
The study included data from patients with incident nondysplastic BE (n=285) and endoscopy control patients with esophageal inflammatory changes without BE (“inflammation controls”, n=313). We used two phases of stepwise backwards logistic regression to identify the important predictors for BE in men and women separately: firstly including all significant covariates from univariate analyses; then fitting non-significant covariates from univariate analyses to identify those effects detectable only after adjusting for other factors. The final model pooled these predictors and was externally validated for discrimination and calibration using data from a BE study conducted in western Washington State, USA.
The final risk model included terms for age, sex, smoking status, body mass index, highest level of education, and frequency of use of acid suppressant medications (area under the ROC curve, 0.70, 95%CI 0.66–0.74). The model had moderate discrimination in the external dataset (area under the ROC curve, 0.61, 95%CI 0.56–0.66). The model was well calibrated (Hosmer-Lemeshow test, p=0.75), with predicted probability and observed risk highly correlated.
The prediction model performed reasonably well and has the potential to be an effective and useful clinical tool in selecting patients with GER symptoms to refer for endoscopic screening for BE.
Barrett’s esophagus; esophageal adenocarcinoma; risk; prediction; model
We have previously reported that the green tea polyphenol epigallocatechin-3-gallate (EGCG) and the epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) erlotinib had synergistic growth inhibitory effects in cell culture and a nude mouse xenograft model of squamous cell carcinoma of the head and neck (SCCHN). However, the mechanism of their anti-tumor synergism is not fully understood. In the current study, we investigate the mechanism of their synergistic growth inhibitory effects. The treatment of SCCHN cell lines with erlotinib time-dependently increased the expression of cell cycle regulatory proteins p21 and p27 and apoptosis regulatory protein Bim. EGCG alone had very little or no effect on the expression of these proteins among the cell lines. However, simultaneous treatment with EGCG and erlotinib strongly inhibited erlotinib-induced expression of p21 and p27 without affecting the expression of Bim. Moreover, erlotinib increased the expression of p53 protein, the ablation of which by shRNA strongly inhibited EGCG- and erlotinib-mediated growth inhibition and the expression of 21, p27 and Bim. In addition, combined treatment with erlotinib and EGCG inhibited the protein level of p65 subunit of NF-κB and its transcriptional target Bcl-2, but failed to do so in cells with ablated p53. Taken together our results, for the first time, suggest that erlotinib treatment activates p53, which plays a critical role in synergistic growth inhibition by erlotinib and EGCG via inhibiting NK-κB signaling pathway. Characterizing the underlying mechanisms of EGCG and erlotinib synergism will provide an important rationale for chemoprevention or treatment trials using this combination.
Chemoprevention; EGFR-TKI; molecular targets; p53