Pathways In Cancer Development Research Articles

Abstract B12: Associations between invasive breast cancer with and without a DCIS component and breast cancer risk factors in African American and European American women

Abstract Introduction: Breast cancer presents as several clinically distinct forms, including invasive ductal carcinoma (IDC) with an associated ductal carcinoma in situ (DCIS) component, and pure IDC. The absence of concomitant DCIS was previously associated with a significantly worse prognosis for IDC, even after adjustment for stage and tumor size. Evidence from gene expression studies suggests that the absence of a DCIS component is associated with an altered tumor microenvironment, which may involve a distinct pathway of cancer development, with unique risk factors and prognoses. The absence of a DCIS component in IDC has not previously been examined in relation to the breast cancer disparities between African-American (AA) and European-American (EA) women. Methods: IDC breast cancer patients with or without a DCIS component were identified by examining pathological reports from the Women's Circle of Health Study, an on-going case-control study examining racial disparities in women diagnosed with breast cancer in NYC and NJ. Through in-person interviews information was collected on known and suspected breast cancer risk factors. In this case-case analysis, we examined these factors in relation to IDC with and without a DCIS component, adjusting for self-reported race and also stratified by race. Interactions were assessed with the Wald Chi-square. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived to estimate the odds of having pure IDC compared to patients with a DCIS component. Results: Of 729 women with IDC, 19.5% were confirmed to have pure IDC and 80.5% IDC with a DCIS component. EA women were less likely than AA women to present with pure IDC without a DCIS component (OR=0.66; 95% CI 0.43–0.99). Women who breastfed were less likely to have pure IDC than IDC with a DCIS component (OR=0.65; 95% CI 0.40–1.04). Stratified analyses by race did not reveal major differences from unstratified analyses for breastfeeding (OR=0.64; 95% CI 0.35–1.16, OR=0.68; 95% CI 0.28–1.64 in AA and EA women, respectively). AA women with a body mass index (BMI) ≥30 compared to a BMI <25 were less likely to have pure IDC than IDC with DCIS (OR=0.52; 95% CI 0.25–0.97), whereas EA women with a high BMI were more likely to have pure IDC (OR=1.36; 95% CI 0.67–2.76, p for interaction=0.01). Pure IDC was directly and inversely associated with family history of breast cancer in EA and AA women, respectively (OR=1.89; 95% CI 1.01–3.55, OR=0.84; 95% CI 0.42–1.67, respectively, p for interaction=0.09). Conclusion: Compared to EA women, AA women are more likely to present with pure IDC without a DCIS component. Stratified analyses suggest that risk factors associated with pure IDC may be significantly different between AA and EA women. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B12.

Abstract C24: LRpath analysis reveals common pathways dysregulated via DNA methylation across cancer types

Abstract Since the introduction of the Illumina HumanMethylation27 BeadArray platform, which assesses the % methylation of over 27,000 sites across the genome, several studies have been published testing for genes with aberrant methylation in their promoter regions. Interestingly, a majority of these publicly available datasets are studying cancer, making the time ripe to perform an integrative analysis of these results. Our hypothesis is that during the pathogenesis of cancer, certain pathways or biological gene groups are commonly dysregulated via DNA methylation across cancer types. The ability of our logistic regression-based gene set enrichment method (LRpath) to implicate important biological pathways and groupings has previously been demonstrated and published. Recently, we developed a web-based application for LRpath with greatly expanded and novel gene set annotations, including transcription factor and microRNA target sets not yet published, and clustering analysis functionality, allowing one to identify and compare biological concept signatures across multiple studies. We employed LRpath and clustering analysis to unravel the commonly altered pathways and other biological concepts across multiple cancer studies using DNA methylation data profiled using the Illumina Infinium HumanMethylation27 BeadArray. Using six independent cancer datasets (five solid tumors including breast, colorectal, glioblastoma, lung, and prostate, and one myeloma), we identified genes harboring abberant promoter methylation between normal and cancer samples using an empirical Bayes method. Each gene was assigned a p-value and change in % methylation indicating the level of hyper- or hypomethylation. The gene list in each study was then subjected to LRpath enrichment analysis using multiple annotation databases. To identify the biological concepts commonly altered across various types of cancer, concepts satisfying defined significance criteria were subjected to the clustering analysis using Euclidean distance matrix and ward linkage method. Clustering analysis performed on the results of LRpath identified tightly clustered hypermethylated concepts involved in neurogenesis and epidermis development. It has been previously reported that the group of genes regulating early development is occupied by polycomb repressive complex 2 subunit SUZ12 in human embryonic stem cells. Another tightly clustered group involves voltage-gated potassium channels, which play a role in cell proliferation processes. This result supports previously reported promoter DNA methylation events in breast and pancreas adenocarcinomas. The majority of hypomethylated concepts identified across various cancer studies were related to immune response concepts identified by GO terms and KEGG pathways. These immune-related concepts range from chemokine and cytokine activity, responses to stimulus and inflammation, to receptor binding activities. The DNA hypomethylation events often result in gene upregulation. Thus, this result suggests elevated immune responses as a commonly affected mechanism across multiple cancer types. Interestingly, cell cycle activity, one of the most commonly affected pathways in cancer development, was found to be significantly depleted in both hyper- and hypomethylation across cancer types. Based on this observation, we speculate that genes involved in cell cycle tend to be dysregulated by alternative mechanisms such as genomic aberrations, mutations, and histone modifications, rather than DNA methylation. Here, we performed an integrative analysis of commonly affected biological concepts across six different cancer types. We were able to clearly identify concepts that are affected in cancer regardless of its type and further support biologically important findings. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr C24.

Abstract 325: Mutation analysis of PIK3CA, KRAS, BRAF and Corresponding EGFR status in head and neck squamous cell carcinoma

Abstract Background: KRAS, BRAF, PIK3CA activate protein kinase signaling and an important pathway in cancer development. Recent reports show that these downstream signaling molecules are mutated in a number of cancers. However, in head and neck squamous cell carcinoma (HNSCC), the frequency and positions of these molecules mutations are not clear. In this study we detected mutations from the clinical specimens of HNSCC by High-Throughput sequencing KRAS, BRAF, PIK3CA. Next we also intended to discover whether these mutations in downstream signaling molecules of EGFR are corresponding with EGFR status. Patients and Method: The ninety-six tumors for this study were obtained from HNSCC patients surgically treated at the Department of head and neck surgery, Jikei University School of Medicine, Tokyo. The hot-spot regions in exons 1 and 2 of K-RAS, exon 15 of BRAF, exon 9 and 20 of PIK3CA were amplified by PCR and sequenced directly using DNA from samples. Next, we analyzed expression and phosphorylation of the EGFR protein by Western blotting as well as mutations encoding the hot-spot regions in exons 18 to 21. Results: We identified mutations in 6 of the 96 patients (6.2%). 3 mutations (G12A) were found in exon 1 of K-RAS. In PIK3CA, 2 mutations were found in exon 9 (E545K) and one was in exon 20(H1047R). No other mutation was found in BRAF. Overexpression of EGFR protein was observed in all clinical samples with these mutations. On the other hand, hyper-phospholyation of EGFR was confirmed in only one sample. Finally, we tried to elucidate associations between these molecular status and patient characteristics and disease-free survival to asses the prognostic values of these molecules factors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 325. doi:10.1158/1538-7445.AM2011-325

Aberrant expression of DNA damage response proteins is associated with breast cancer subtype and clinical features

Landmark studies of the status of DNA damage checkpoints and associated repair functions in preneoplastic and neoplastic cells has focused attention on importance of these pathways in cancer development, and inhibitors of repair pathways are in clinical trials for treatment of triple negative breast cancer. Cancer heterogeneity suggests that specific cancer subtypes will have distinct mechanisms of DNA damage survival, dependent on biological context. In this study, status of DNA damage response (DDR)-associated proteins was examined in breast cancer subtypes in association with clinical features; 479 breast cancers were examined for expression of DDR proteins γH2AX, BRCA1, pChk2, and p53, DNA damage-sensitive tumor suppressors Fhit and Wwox, and Wwox-interacting proteins Ap2α, Ap2γ, ErbB4, and correlations among proteins, tumor subtypes, and clinical features were assessed. In a multivariable model, triple negative cancers showed significantly reduced Fhit and Wwox, increased p53 and Ap2γ protein expression, and were significantly more likely than other subtype tumors to exhibit aberrant expression of two or more DDR-associated proteins. Disease-free survival was associated with subtype, Fhit and membrane ErbB4 expression level and aberrant expression of multiple DDR-associated proteins. These results suggest that definition of specific DNA repair and checkpoint defects in subgroups of triple negative cancer might identify new treatment targets. Expression of Wwox and its interactor, ErbB4, was highly significantly reduced in metastatic tissues vs. matched primary tissues, suggesting that Wwox signal pathway loss contributes to lymph node metastasis, perhaps by allowing survival of tumor cells that have detached from basement membranes, as proposed for the role of Wwox in ovarian cancer spread.

Sp1 acetylation is associated with loss of DNA binding at promoters associated with cell cycle arrest and cell death in a colon cell line.

Butyrate, a known histone deacetylase inhibitor (HDACi) and product of fibre fermentation, is postulated to mediate the protective effect of dietary fibre against colon cancer. The transcription factor Sp1 is a target of acetylation and is known to be associated with class I HDACs, including HDAC1. Sp1 is a ubiquitous transcription factor and Sp1-regulated genes include those involved in cell cycle regulation, apoptosis and lipogenesis: all major pathways in cancer development. The only known acetylated residue of Sp1 is lysine703 which resides in the DNA binding domain. Here we show that acetylated Sp1 loses p21- and bak-promoter -binding function in vitro. Furthermore treatment with a panel of HDAC inhibitors showed clustering of activities for a subset of inhibitors, causing G2 cell cycle arrest, Sp1 acetylation, p21 and Bak over-expression, all with very similar EC50 concentrations. These HDACi activities were not distributed according to the molecular class of compound. In order to mimic loss of binding, an siRNA strategy was used to reduce Sp1 expression. This resulted in altered expression of multiple elements of the p53/p21 pathway. Taken together our data suggest a mechanistic model for the chemopreventive actions of butyrate in colon epithelial cells, and provide new insight into the differential activities some classes of HDAC inhibitors.

Population genetics meets cancer genomics

There is a broad consensus that genetic alterations of normal body cells are the basis of cancer progression. Throughout the lifetime of an individual, her or his cells have to divide often, which is associated with occasional genetic changes. Some of the changes lead to uncontrolled cell proliferation and, at later stages of cancer progression, to blood vessel formation in the tumor tissue and distribution of tumor tissue across the body. The molecular genetics of cancer is a very advanced field: Many genetic alterations that predispose an individual to a certain cancer have been identified, and specific genetic pathways of cancer development have been elucidated (1). More recently, studies have been conducted on the scale of the entire genome to identify cancer-associated mutations (2–5). However, our understanding of the population genetic aspects of cancer development, that is, those aspects that relate to the dynamics of cancer cell replication, survival, and evolution, have not yet caught up with the advances in molecular genetics. A study by Bozic et al. (6) in PNAS brings the understanding of the population genetics of cancer cells closer to the edge defined by recent studies of the molecular genetics and genomics of various cancers.

RelB Enhances Prostate Cancer Growth and Resistance to Radiation Therapy: Implications for Cancer Detection and Treatment

The NF-κB classical pathway is thought to be critical for tumorigenesis, but little is known about the role of the NF-κB alternative pathway in cancer development and sensitivity to radiation therapy. High constitutive nuclear levels of RelB have been observed in human prostate cancer specimens with high Gleason scores. We investigated the role of RelB on tumorgenicity and sensitivity of prostate cancer to radiation.

Abstract LB-403: Levels of nitric oxide and prostate cancer development in healthy US men enrolled in the Health Professionals Follow-up Study

Abstract Nitric oxide (NO) has a strong impact on cancer development. Experimental studies have reported that, depending on levels, NO has either tumoricidal or tumor-promoting effects. In addition, NO is strongly associated with oxidative and inflammatory pathways, which have been implicated in prostate cancer. In general, maintaining normal-range levels of NO is important for physiological function and may actually have tumoricidal effects. Furthermore, extremely high levels of NO have been found to stimulate prostate tumor growth in rats. However, the relationship between plasma NO level and risk of prostate cancer (PCa) development has not been assessed. NO is difficult to measure directly in large epidemiologic studies. This barrier has hampered the identification of NO-related pathways in cancer development. We have found that plasma levels of nitrite/nitrate, measured as a surrogate marker of NO, are both stable and reproducible within individuals over time. Using a prospective nested case-control design, we identified 600 PCa cases and 600 matched controls from 2000-2004 among men who provided a blood sample in 1993-1995. This study is nested within a blood cohort in the Health Professionals Follow-up Study. We have already measured baseline plasma levels of nitrite/nitrate in 170 cases and 170 controls. The multivariate-adjusted odds ratio of nitrite/nitrate from quintile 2-quintile 4 as compared to quintile 1 are 0.71 (95%CI, 0.24-2.75), 0.20 (95%CI, 0.05-0.75), 0.81 (95%CI, 0.30-2.91), and 1.12 (95%CI, 0.65-2.78), respectively. Our preliminary data suggest that medium levels of nitrite/nitrate maximally reduce the risk of prostate cancer, and that men with high or low levels of nitrite/nitrate may be at elevated risk of prostate cancer. Confirming our results in our remaining samples and other populations may have important implications for prevention of prostate cancer. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-403.

Convergence between Wnt-β-catenin and EGFR signaling in cancer

Wnt and EGFR signaling play key roles in embryonic development and cell proliferation. It is well documented that dysregulation of these two pathways often leads to tumorigenesis with poor prognosis. However, the possible crosstalk between the two pathways in cancer development is largely unknown. Although some reports show that EGFR might antagonize Wnt signaling during development in Drosophila, an increasing body of evidence indicates that Wnt and EGFR signaling crosstalk and transactivate one another in development and cancer. This review summarizes recent studies on the crosstalk between Wnt and EGFR signaling in cancers and points out several possible convergence points. Wnt ligands can activate EGFR signaling through their 7-transmembrane domain receptor Frizzled while EGFR can activate β-catenin via receptor tyrosine kinase-PI3K/Akt pathway; EGFR has been shown to form a complex with β-catenin and increase the invasion and metastasis of cancer cells. NKD2, a Wnt antagonist by interacting with Dishevelled, also escorts TGFα-containing exocytic vesicles to the basolateral membrane of polarized epithelial cells. Down-regulation of NKD2 causes Wnt activation and TGFα misdelivery, suggesting its functions in cell homeostasis and prevention of tumorigenesis.

Cancer Metabolism and the Warburg Effect As Anabolic Process Outcomes of Oncogene Operation

Having considered the results of early works by other authors, their assumption was developed using modern knowledge that made it possible to propose the concept of a Warburg effect mechanism in cancer metabolism. This concept accents the high prevalence of anabolic processes in cancer metabolism, taking into account oncogene operation. The explanation of the Warburg effect mechanism alone has been provided considering the mechanism of energy shift to an anabolic pathway of cancer development. On the basis of previous experiments, the concept has also detected the point of bifurcation of the pathways of anabolic and catabolic processes, which have made it possible to ascertain the consumption of acetyl-CoA for anabolic processes and the lack of acetyl-CoA for catabolic processes. Thus, the results of other authors' experiments were explained using the proposed concept. The mechanism of surviving cancer cells (apoptosis resistance) was also explained using this concept. In addition to using the Theorell formula and the proposed concept, an explanation has also been given from the physical chemistry point of view of the mechanism of the phenomenon regarding the absence of contact inhibition of proliferating cells in malignant tumors. Thus, this made it possible to explain other cancer phenomena mechanisms, including metastasis, nonhealing ulcers, and irrepressible growth mechanisms. In addition, this concept has made it possible to also explain experimental results that early and modern authors could not explain. Lastly, the distinction between mechanisms of the Pasteur effect and the Warburg effect was explained using the proposed concept.

Signal integration by JNK and p38 MAPK pathways in cancer development

Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) family members function in a cell context-specific and cell type-specific manner to integrate signals that affect proliferation, differentiation, survival and migration. Consistent with the importance of these events in tumorigenesis, JNK and p38 MAPK signalling is associated with cancers in humans and mice. Studies in mouse models have been essential to better understand how these MAPKs control cancer development, and these models are expected to provide new strategies for the design of improved therapeutic approaches. In this Review we highlight the recent progress made in defining the functions of the JNK and p38 MAPK pathways in different cancers.

The Rb Pathway and Cancer Therapeutics

The retinoblastoma gene, Rb, was originally identified as the tumor suppressor gene mutated in a rare childhood cancer called retinoblastoma (reviewed in [1]). Subsequent studies showed that Rb functions in a pathway that is often functionally inactivated in a large majority of human cancers. Interestingly, recent studies showed that in certain types of cancers, Rb function is actually required for cancer development. The intimate link between the Rb pathway and cancer development suggests that the status of Rb activity can potentially be used to develop targeted therapy. However, a prerequisite will be to understand the role of Rb and its interaction with other signaling pathways in cancer development. In this review, we will discuss the roles of Rb in proliferation, apoptosis and differentiation by reviewing the recent findings in both mammalian systems and different model organisms. In addition, we will discuss strategies that can be employed that specifically target cancer cells based on the status of the Rb pathway.

RelB Enhances Prostate Cancer Growth: Implications for the Role of the Nuclear Factor-κB Alternative Pathway in Tumorigenicity

The nuclear factor-kappaB (NF-kappaB) classic pathway is thought to be critical for tumorigenesis, but little is known about the role of the NF-kappaB alternative pathway in cancer development. Recently, high constitutive nuclear levels of RelB have been observed in human prostate cancer specimens with high Gleason scores. Here, we used four complementary approaches to test whether RelB contributes to tumorigenicity of prostate cancer. Inhibiting RelB in aggressive androgen-independent PC-3 cells by stable or conditional expression of a dominant-negative p100 mutant significantly reduced the incidence and growth rate of tumors. The decrease in tumorigenicity coincided with a reduction in the NF-kappaB target interleukin-8 (IL-8). Consistently, down-regulation of RelB by small interfering RNA targeting also reduced tumor growth and decreased levels of IL-8. Conversely, stable expression of RelB in androgen-responsive LNCaP tumors increased the circulating IL-8 levels. Taken together, these results reveal a tumor-supportive role of RelB, implicate the NF-kappaB alternative pathway as a potential target for preventing prostate cancer, and suggest the use of IL-8 as a marker for prostate cancer prognosis.

No Incidence of BRAF Mutations in Salivary Gland Carcinomas—Implications for Anti‐EGFR Therapies

BRAF is the main effector of KRAS in the RAS-RAF-MAPK axis, a signaling pathway downstream of EGFR. The activation of this cascade is an important pathway in cancer development and is considered a key pathway for therapeutic molecules. Recent studies in metastatic colorectal cancer found that an oncogenic activation of BRAF by a point mutation in exon 15 (V600E) could bypass the EGFR-initiated signaling cascade with the effect that patients bearing the mutant BRAF allele are not likely to benefit from EGFR-targeted therapies. We designed an allele-specific PCR and screened 65 salivary gland carcinoma (SGC) of the main histopathological types for the BRAF V600E mutation. All 65 SGC in this cohort (100%) presented the BRAF wildtype. In a previous study, we found a KRAS wildtype in 98.5% of SGC. These findings imply that SGC rarely acquires mutations that result in a constitutive activation of the signaling cascade downstream of EGFR and this pleads in favor of further therapeutic trials with EGFR-targeting monoclonal antibodies.

Organotypic modelling as a means of investigating epithelial-stromal interactions during tumourigenesis

The advent of co-culture approaches has allowed researchers to more accurately model the behaviour of epithelial cells in cell culture studies. The initial work on epidermal modelling allowed the development of reconstituted epidermis, growing keratinocytes on top of fibroblasts seeded in a collagen gel at an air-liquid interface to generate terminally differentiated 'skin equivalents'. In addition to developing ex vivo skin sheets for the treatment of burns victims, such cultures have also been used as a means of investigating both the development and repair of the epidermis, in more relevant conditions than simple two-dimensional culture, but without the use of animals. More recently, by varying the cell types used and adjusting the composition of the matrix components, this physiological system can be adapted to allow the study of interactions between tumour cells and their surrounding stroma, particularly with regards to how such interactions regulate invasion. Here we provide a summary of the major themes involved in tumour progression and consider the evolution of the approaches used to study cancer cell behaviour. Finally, we review how organotypic models have facilitated the study of several key pathways in cancer development and invasion, and speculate on the exciting future roles for these models in cancer research.

Expression and mutation analysis of epidermal growth factor receptor in head and neck squamous cell carcinoma

The epidermal growth factor receptor (EGFR)-RAS-RAF-mitogen-activated protein kinase signaling cascade is an important pathway in cancer development and recent reports show that EGFR and its downstream signaling molecules are mutated in a number of cancers. We have analyzed 91 Japanese head and neck squamous cell carcinomas (HNSCC) and 12 HNSCC cell lines for mutations in EGFR, ErbB2, and K-ras. Exons encoding the hot-spot regions in the tyrosine kinase domain of both EGFR (exons 18, 19, and 21) and ErbB2 (exons 18-23), as well as exons 1 and 2 of K-ras were amplified by polymerase chain reaction and sequenced directly. EGFR expression was also analyzed in 65 HNSCC patients using immunohistochemistry. Only one silent mutation, C836T, was found in exon 21 of EGFR in the UT-SCC-16A cell line and its corresponding metastasic cell line UT-SCC-16B. No other mutation was found in EGFR, ErbB2, or K-ras. All tumors showed EGFR expression. In 21 (32%) tumors, EGFR was expressed weakly (+1). In 27 (42%) tumors it was expressed (+2) moderately, and in 17 (26%) tumors high expression (+3) was detected. Overexpression (+2, +3) was found in 44 tumors (68%). A worse tumor differentiation and a positive nodal stage were significantly associated with EGFR overexpression (P = 0.02, P = 0.032, respectively). Similar to patients from western ethnicity, mutations are absent or rare in Japanese HNSCC. Protein overexpression rather than mutation might be responsible for activation of the EGFR pathway in HNSCC.

Hedgehog signaling overrides p53-mediated tumor suppression by activating Mdm2

The hedgehog (Hh) signaling pathway regulates the development of many organs in mammals, and activation of this pathway is widely observed in human cancers. Although it is known that Hh signaling activates the expression of genes involved in cell growth, the precise role of the Hh pathway in cancer development is still unclear. Here, we show that constitutively activated mutants of Smoothened (Smo), a transducer of the Hh signaling pathway, inhibit the accumulation of the tumor suppressor protein p53. This inhibition was also observed in the presence of Hh ligand or with the overexpression of the transcription factors Gli1 and Gli2, downstream effectors of Smo, indicating that this inhibition is specific for the Hh pathway. We also report that Smo mutants augment p53 binding to the E3 ubiquitin-protein ligase Mdm2 and promote p53 ubiquitination. Furthermore, Hh signaling induced the phosphorylation of human Mdm2 protein on serines 166 and 186, which are activating phosphorylation sites of Mdm2. Smo mutants enhanced the proliferation of mouse embryonic fibroblasts (MEFs) while inducing a DNA-damage response. Moreover, Smo partially inhibited p53-dependent apoptosis and cell growth inhibition in oncogene-expressing MEFs. We also found that accumulation of p53 is inhibited by Hh signaling in several human cancer cell lines. Therefore, the Hh pathway may be a powerful accelerator of oncogenesis by activating cell proliferation and inhibiting the p53-mediated anti-cancer barrier induced by oncogenic stress.

Activated neutrophils induce an hMSH2-dependent G2/M checkpoint arrest and replication errors at a (CA)13-repeat in colon epithelial cells

Objective: Chronic inflammation in ulcerative colitis is associated with increased risk for colorectal cancer. Its molecular pathway of cancer development is poorly understood. We investigated the role of neutrophil-derived cellular...

Demethylation of (Cytosine-5-C-methyl) DNA and regulation of transcription in the epigenetic pathways of cancer development

Cancer cells and tissues exhibit genome wide hypomethylation and regional hypermethylation. CpG-methylation of DNA ((Me)CpG-DNA) is defined as the formation of a C-C covalent bond between the 5'-C of cytosine and the -CH(3) group of S-adenosylmethionine. Removal of the sole -CH(3) group from the methylated cytosine of DNA is one of the many ways of DNA-demethylation, which contributes to activation of transcription. The mechanism of demethylation, the candidate enzyme(s) exhibiting direct demethylase activity and associated cofactors are not firmly established. Genome-wide hypomethylation can be obtained in several ways by inactivation of DNMT enzyme activity, including covalent trapping of DNMT by cytosine base analogues. Removal of methyl layer could also be occurred by excision of the 5-methyl cytosine base by DNA glycosylases. The importance of truly chemically defined direct demethylation of intact DNA in regulation of gene expression, development, cell differentiation and transformation are discussed in this contribution.

Differential expression of α-methylacyl-coenzyme A racemase in colorectal carcinoma bears clinical and pathologic significance

alpha-methylacyl-coenzyme A racemase (AMACR) is a recently discovered biomarker that is shown to be overexpressed in some prostatic carcinomas and associated with prostatic cancer progression. Given that AMACR plays an important role in peroxisomal beta-oxidation of branched-chain fatty acids from red meat and dairy products, and that consumption of red meat may increase risk of developing colon cancer as suggested by epidemiological studies, it is plausible to explore the function of AMACR in colorectal carcinoma. A few previous studies have indeed observed overexpression of AMACR in 45% to 69% of the colorectal carcinomas. However, the clinical and pathologic characteristics of such AMACR expressers have not been investigated. In this study, the immunohistochemical expression pattern of AMACR of 163 patients with primary colorectal carcinoma treated primarily with surgical resection was analyzed and correlated with tumor pathologic features (tumor location, histologic type, grade, pathologic stage, lymph node and distant metastasis) and patient outcome (disease-specific survival). The results showed variable positive staining for AMACR in 123 (75%) of 163 tumors, and moderate to strong staining in 63 (39%) of 163. Lack of staining or low-intensity staining appeared to correlate significantly with mucinous histology (P < .001), poor tumor differentiation (P = .021), and presence of lymphovascular invasion (P = .032). Patients whose tumors showed lack of staining or low-intensity staining also had a significantly worse 5-year disease-specific survival (P < .012), as did patients whose tumors had lymphovascular invasion, or were of high American Joint Committee on Cancer (AJCC) stage. On multivariate analysis, AMACR staining and AJCC staging remained independent predictors for patient outcome. Thus, our data suggest that AMACR expression in colorectal carcinoma correlates with certain tumor pathologic characteristics (histologic type, differentiation, and lymphovascular invasion) and patient outcome. Additional confirmatory studies are needed to establish the significance of AMACR as a prognostic marker for colorectal carcinoma. Further investigation on interaction between AMACR and other known colorectal cancer development pathways may provide new insights on colorectal carcinogenesis.