Colorectal Cancer In African Americans Research Articles

Abstract A75: Excess of proximal microsatellite-stable colorectal cancer in African Americans from a multiethnic study

Abstract Background: African Americans (AAs) have the highest incidence of colorectal cancer (CRC) compared to other US populations and more proximal CRCs. The objective is to elucidate the basis of these cancer disparities. Methods: 566 AA and 328 Non-Hispanic White (NHW) CRCs were ascertained in five Chicago hospitals. Clinical and exposure data were collected. Microsatellite instability and BRAF (V600E) and KRAS mutations were tested. Statistical significance of categorical variables was tested by Fisher's exact test or logistic regression and age by Mann-Whitney U test. Results: Over a ten-year period, the median age at diagnosis significantly decreased for both AAs (68 to 61; P<0.01) and NHWs (64.5 to 62; P=0.04); more AA patients were diagnosed before age 50 than NHWs (22% vs 15%; P=0.01). AAs had more proximal CRC than NHWs (49.5% vs. 33.7%; P<0.01), but overall frequencies of microsatellite instability, BRAF and KRAS mutations were not different nor were they different by location in the colon. Proximal CRCs often presented with lymphocytic infiltrate (P<0.01) and were diagnosed at older ages (P=0.02). Smoking, drinking, and obesity were less common in this group, but results were not statistically significant. Conclusions: Patients with CRC have gotten progressively younger. The excess of CRC in AAs predominantly consists of more proximal, microsatellite stable tumors, commonly presenting lymphocytic infiltrate and less often associated with toxic exposures or a higher BMI. Younger AAs had more distal CRCs than older ones. These data suggest two different mechanisms driving younger age and proximal location of CRCs in AAs. Citation Format: Rosa Xicola, The Chicago Colorectal Cancer Consortium, Sonia Kupfer, Carol Braunschweig, Nathan Ellis, Xavier Llor. Excess of proximal microsatellite-stable colorectal cancer in African Americans from a multiethnic study. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr A75.

Higher prevalence of proximal colon polyps and villous histology in African-Americans undergoing colonoscopy at a single equal access center.

In the United States, African Americans (AA) have the highest incidence and mortality from colorectal cancer (CRC) of any racial group. Few studies have evaluated if AA who undergo colonoscopy are more likely to have aggressive neoplasia (polyp) tumor biology compared to Caucasians (C). The primary aim of the study was to compare polyp characteristics between AA and C undergoing outpatient colonoscopy. A single center retrospective cohort study was performed at a single Veteran Administration (VA) health care system. The charts of 4,038 veterans undergoing colonoscopy from 2005 to 2008 were reviewed. After applying exclusion criteria, data was analyzed for 1,388 persons. Categorical variables were compared using the chi-square test and data were expressed as percentages. Continuous variables were compared using student's t-test and the data were expressed as mean with standard deviation. A total of 37% of AA had proximal polyps compared to 21% of C (P<0.0001). Twenty-four percent of AA had polyps with villous histology compared to 16% of C (P=0.01). Twelve percent of AA had hyperplastic polyps compared to 20% of C (P=0.02). There was no difference in the overall prevalence of tubular adenomas, adenomatous polyps with high-grade dysplasia, number, size or polyp morphology between groups. In an equal access healthcare system and under varying indications, AA have more proximal polyps and polyps with more aggressive histology compared to C. This could partially explain the higher incidence of CRC in AA, and the increased likelihood for AA to develop advanced proximal neoplasia.

Mutation Spectrum and Risk of Colorectal Cancer in African American Families with Lynch Syndrome

African Americans (AAs) have the highest incidence of and mortality resulting from colorectal cancer (CRC) in the United States. Few data are available on genetic and nongenetic risk factors for CRC among AAs. Little is known about cancer risks and mutations in mismatch repair (MMR) genes in AAs with the most common inherited CRC condition, Lynch syndrome. We aimed to characterize phenotype, mutation spectrum, and risk of CRC in AAs with Lynch syndrome. We performed a retrospective study of AAs with mutations in MMR genes (MLH1, MSH2, MSH6, and PMS2) using databases from 13 US referral centers. We analyzed data on personal and family histories of cancer. Modified segregation analysis conditioned on ascertainment criteria was used to estimate age- and sex-specific CRC cumulative risk, studying members of the mutation-carrying families. We identified 51 AA families with deleterious mutations that disrupt function of the MMR gene product: 31 in MLH1 (61%), 11 in MSH2 (21%), 3 in MSH6 (6%), and 6 in PMS2 (12%); 8 mutations were detected in more than 1 individual, and 11 have not been previously reported. In the 920 members of the 51 families with deleterious mutations, the cumulative risks of CRC at 80 years of age were estimated to be 36.2% (95% confidence interval [CI], 10.5%-83.9%) for men and 29.7% (95% CI, 8.31%-76.1%) for women. CRC risk was significantly higher among individuals with mutations in MLH1or MSH2 (hazard ratio, 13.9; 95% CI, 3.44-56.5). We estimate the cumulative risk for CRC in AAs with MMR gene mutations to be similar to that of individuals of European descent with Lynch syndrome. Two-thirds of mutations were found in MLH1, some of which were found in multiple individuals and some that have not been previously reported. Differences in mutation spectrum are likely to reflect the genetic diversity of this population.

ENVE: a novel computational framework characterizes copy-number mutational landscapes in colorectal cancers from African American patients.

Reliable detection of somatic copy-number alterations (sCNAs) in tumors using whole-exome sequencing (WES) remains challenging owing to technical (inherent noise) and sample-associated variability in WES data. We present a novel computational framework, ENVE, which models inherent noise in any WES dataset, enabling robust detection of sCNAs across WES platforms. ENVE achieved high concordance with orthogonal sCNA assessments across two colorectal cancer (CRC) WES datasets, and consistently outperformed a best-in-class algorithm, Control-FREEC. We subsequently used ENVE to characterize global sCNA landscapes in African American CRCs, identifying genomic aberrations potentially associated with CRC pathogenesis in this population. ENVE is downloadable at https://github.com/ENVE-Tools/ENVE.Electronic supplementary materialThe online version of this article (doi:10.1186/s13073-015-0192-9) contains supplementary material, which is available to authorized users.

African Americans should be screened at an earlier age for colorectal cancer

African Americans (AAs) have been shown to exhibit a higher incidence of colorectal cancer and experience lower survival compared with whites. There is disagreement regarding the age at which to initiate screening in AAs. To calculate the age-specific incidence in AAs compared with whites while controlling for differences in socioeconomic status (SES) and to calculate the joinpoint at which the incidence begins to increase in each race. Retrospective database review. Surveillance, Epidemiology, and End Results database. All patients with adenocarcinoma of the colon or rectum from 2000 through 2011 in the SEER 18 database. We calculated the joinpoint of the upward trend of the age-adjusted incidence rate to determine the age at which the slope of the incidence curve began to increase in each race, while controlling for differences in SES by using a composite socioeconomic index. Age-adjusted incidence of colon and rectal cancer. The age-specific incidence of colorectal cancer (cases per 100,000 population) was 0.3 versus 0.4 in whites compared with AAs at 20 years of age. At 50 years of age, the incidence was 44.2 compared with 62.6 in whites compared with AAs. The model indicated a joinpoint at 47 years of age for whites (95% confidence interval, 45-49) and 43 for AAs (95% confidence interval, 42-45) (P< .001.) When SES was considered in stratification, joinpoints for whites were 48, 47, and 46 at high, middle, and low SES, respectively. Conversely, joinpoints of 43, 44, and 42 in the corresponding SES for AAs were noted (P≤ .001). There was no intervention, and we cannot conclude that changing screening policy would affect this disparity. There is a disparity in the age-specific incidence of colorectal cancer in AAs compared with whites beginning at 45 years of age. These differences persist across socioeconomic strata.

Dual role of TGFBR1 as a modifier of colorectal cancer risk.

600 Background: Experimental and clinical evidence suggests that constitutively decreased Transforming Growth Factor Beta type I receptor (TGFBR1) signaling predisposes to colorectal cancer (CRC) development. However, associations between TGFBR1 variants and CRC risk in case-control studies have been inconsistent. Methods: We utilized 1,043 CRC cases and their 1,627 unaffected sibling controls obtained from the Colon Cancer Family Registry (C-CFR). Individuals were genotyped for twelve TGFBR1 haplotype tagging SNPs. SNPs associated with CRC risk were validated in 261 CRC cases and 531 controls of African American ancestry and 990 CRC cases and 3,427 controls of Han Chinese ancestry. Validated SNPs were functionally characterized with respect to TGFBR1 expression and TGF-β signaling. Results: The TGFBR1 rs7034462-TT genotype was associated with CRC risk in C-CFR participants (OR 3.80[1.46-9.85]) and African Americans (OR 8.16[2.07-32.08]) (see Table). The TT genotype was associated with stage III and stage IV at diagnosis in C-CFR participants (OR 2.99[1.15-7.81] and OR 9.38[1.54-57.28]) and African Americans (OR 5.89[1.15-30.02] and OR 12.75[1.88-86.33]), respectively. The rs7034462-CT genotype was associated with decreased risk for CRC in African Americans (OR 0.55[0.31-0.99]) and Han Chinese (OR 0.67[0.48-0.95]) (see table). Cells carrying the rs7034462-TT genotype exhibited decreased constitutive TGFBR1 expression, increased SMAD7 expression, and decreased TGF-β signaling. Conclusions: The TGFBR1 rs7034462-T allele has dual, opposite roles with respect to CRC risk. The rare rs7034462-TT genotype is a moderate penetrance genotype associated with risk for CRC and advanced stage disease at diagnosis. In contrast, the common rs7034462-CT genotype is associated with decreased CRC risk. [Table: see text]

Screening for colorectal cancer in African Americans: determinants and rationale for an earlier age to commence screening.

Colorectal cancer (CRC) screening is a cost-effective approach to reduce morbidity, mortality, and prevalence of CRC in populations. Current recommendations for asymptomatic populations begin screening at age 50 years, after which ~95% of cancers occur. Determinants that modify timing and frequency for screening include: personal/family history of adenomas or CRC, age of onset of lesions, and presence or potential to harbor high-risk conditions like inflammatory bowel disease (IBD), familial adenomatous polyposis (FAP), or Lynch syndrome. Although race, like family history, is heritable, it has not engendered inclusion in systematic screening recommendations despite multiple studies demonstrating disparity in the incidence and mortality from CRC, and the potential for targeted screening to reduce disparity. African Americans, when compared to Caucasians, have lower CRC screening utilization, younger presentation for CRC, higher CRC prevalence at all ages, and higher proportion of CRCs before age 50 years (~11 vs. 5%); are less likely to transmit personal/family history of adenomas or CRC that may change screening age; show excess of high-risk proximal adenomas, matched with 7-15% excess right-sided CRCs that lack microsatellite instability; show higher frequencies of high-risk adenomas for every age decile; and demonstrate genetic biomarkers associated with metastasis. These epidemiological and biological parameters put African Americans at higher risk from CRC irrespective of socioeconomic issues, like IBD, FAP, and Lynch patients. Including race as a factor in national CRC screening guidelines and commencing screening at an age earlier than 50 years seems rational based on the natural history and aggressive behavior in this population.

Race Matters: Analyzing the Relationship between Colorectal Cancer Mortality Rates and Various Factors within Respective Racial Groups.

Colorectal cancer (CRC) is the third leading cause of mortality due to cancer (with over 50,000 deaths annually), representing 9% of all cancer deaths in the United States (1). In particular, the African-American CRC mortality rate is among the highest reported for any race/ethnic group. Meanwhile, the CRC mortality rate for Hispanics is 15–19% lower than that for non-Hispanic Caucasians (2). While factors such as obesity, age, and socio-economic status are known to associate with CRC mortality, do these and other potential factors correlate with CRC death in the same way across races? This research linked CRC mortality data obtained from the National Cancer Institute with data from the United States Census Bureau, the Centers for Disease Control and Prevention, and the National Solar Radiation Database to examine geographic and racial/ethnic differences, and develop a spatial regression model that adjusted for several factors that may attribute to health disparities among ethnic/racial groups. This analysis showed that sunlight, obesity, and socio-economic status were significant predictors of CRC mortality. The study is significant because it not only verifies known factors associated with the risk of CRC death but, more importantly, demonstrates how these factors vary within different racial groups. Accordingly, education on reducing risk factors for CRC should be directed at specific racial groups above and beyond creating a generalized education plan.

Abstract C61: Genetic alterations in the TP53 genomic region of African American and Caucasian colorectal cancers

Abstract Purpose: In the US, colorectal cancer (CRC) is the second leading cause of cancer-related deaths and the third most common cancer in both men and women. CRC affects African Americans (AAs) disproportionately, relative to non-Hispanic Caucasians (CAs). Data from our prior studies indicate that the p53 codon 72 polymorphism is disproportionately higher in AAs compared to CAs [Clin Cancer Res; 15(14); 2406–-2416. 2009]. It is also evident that genetic human diversity is due not only to single nucleotide polymorphisms (SNPs), but also to structural variants or retrotransposons. Retrotransposons induce mutations, near or within genes by several mechanisms: insertions, deletions, duplications, copy number variants, inversions, or translocations, all of which expand human diversity and possibly alter cancer susceptibility. Thus, our objectives are to establish genomic profiles of the p53 tumor suppressor (TP53) region of CRCs of AA and CA patients to identify race/ethnic-specific alterations that are associated with ancestry, and to develop a DNA sequencing protocol to delineate AA and CA patient profiles using this complex genomic region (∼19 Kb). Methods: Genomic DNA was extracted from 4 frozen tissue samples (2 CRCs and their corresponding normal pairs) and 4 (2 CRCs/normal pairs) formalin-fixed, paraffin-embedded (FFPE) tissues. For the DNA of two CRC patients (one tumor/normal pair each of AA and CA patients), the complete TP53 gene (∼19 Kb, including exons and introns) was amplified by PCR in two halves, followed by Illumina next-generation sequencing and comparison to the human genome 19 reference sequence. For each patient, paired normal (benign/control) and tumor tissue DNAs were compared. Results: TheTP53 gene was amplified from DNA extracted from all 4 frozen CRC tissues, but not from the 4 FFPE tissues. Sequence comparisons of normal versus tumor DNA revealed 80 single nucleotide polymorphisms (SNPs). Most (96%, n=77) located within introns. Of these, 34 were shared by AA and CA patients. In contrast, 8 SNPs were detected only in a CA patient, and 13 others were present only in an AA patient. Two SNPs found in our AA patient were absent in our CA patient and in the publicly available HapMap database of CAs, suggesting that these SNPs reflect African ancestry. Also, 22 SNPs were exclusively present in the CA tumor, whereas only 3 SNPs were unique to the AA tumor. These findings deserve further investigation. Conclusions: We developed PCR protocols that should allow us to conduct a comprehensive mutational profiling of coding and non-coding regions of the TP53 genomic region in DNA isolated from frozen tissues. Comparison of genetic alteration profiles of TP53 in AAs and CAs will aid in determining the race/ethnicity of CRC patients. These studies were supported by a Charles Barkley Foundation grant though the UAB MHRC and a pre-pilot project of the UAB/TU/MSM Partnership grant, U54-CA 118948. Citation Format: Jesus F. Salazar-Gonzalez, Maria G. Salazar, Balananda Dhurjati Kumar Putcha, Edward E. Partridge, Mona N. Fouad, Manne Upender. Genetic alterations in the TP53 genomic region of African American and Caucasian colorectal cancers. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C61. doi:10.1158/1538-7755.DISP13-C61

Abstract C56: The role of BetaB2-crystallin in progression of colorectal and breast cancers in African Americans

Abstract Purpose: African-American (AA) breast cancer (BC) and colorectal cancer (CRC) patients experience higher mortality rates than Non-Hispanic Caucasian (CA) patients. These disparities are thought to be due to race/ethnicity-specific tumor molecular biology. Our initial gene expression investigations have identified a Beta B2-Crystallin (CRYBB2) gene that is preferentially over-expressed in CRC of AA patients. However, the precise role of CRYBB2 in aggressiveness of CRC and BC has not been examined. Therefore, we hypothesize that biological mechanism linked to CRYBB2 could contribute to the disparate progression of CRC and BC in AA patients. Experimental Design: Gene expression studies were performed using Affymetrix Human Genome U133 Plus 2.0 arrays and mRNA samples extracted from 10 fresh frozen Stage III CRCs (5 from AA and 5 from CA) that were previously analyzed for the microsatellite instability (MS) status. Established CRC (HT29 and SW480) and BC (MBA-MD 231) cell lines were used to examine the phenotypic expression of CRYBB2. Also, paired lesions of human CRC (hCRC) and human mice CRC (hmCRC) xenograft were assessed for CRYBB2 by western blot and immunofluorescence (IF). To study the involvement of CRYBB2 in CRC and BC biology, siRNA mediated gene silencing was used to inhibit CRYBB2 expression. The apoptosis of CRC and BC cells after knockdown of CRYBB2 was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The epithelial-mesenchymal transition (EMT) of CRC and BC cells was analyzed by western blot for E-cadherin, MM9 and vimentin expression. Western blot analysis was performed on lysates of CRC and BC cells to assess the effect of CRYBB2 knockdown for expression/ activation of the AKT, and mitogen-activated protein kinase pathway proteins. Results: Our microarray analyses have suggested that several key genes involved in tumor metastasis (CRYBB2, VSNL-1and PFN2) are up-regulated in MS-CRCs of AA but down regulated in MS-CRCs of CA patients. The phenotypic expression of CRYBB2 was found to be higher in CRC tissues as compared to matching normal tissues. Over-expression of CRYBB2 correlated with metastatic CRC and N-cadherin expression and the expression of CRYBB2 was substantially increased in metastatic lesion of CRC and BC xenografts as compared to the primary tumors. Knockdown of CRYBB2 induced apoptosis in CRC and BC cells. In addition, Knockdown of CRYBB2 suppressed EMT signatures, such as decreasing the expression of MMP9, vimentin (mesenchymal markers) and increasing the expression of E-cadherin (epithelial marker). Furthermore, depletion of CRYBB2 decreased the phosphorylation of AKT (p-AKT) in CRC and BC cells. CRYBB2 was mainly localized in cytoplasm of BC and CRC cells. Conclusions: Our data suggest that CRYBB2 inhibits apoptosis, activates EMT process and AKT phosphorylation by which it contributes the aggressiveness of CRC and BC. It may serve as a promising biomarker for identifying CRC and BC patients at high risk for metastases. It may also be useful as a therapeutic target to inhibit the growth and metastasis of CRC and BC. These studies are supported by NIH/NCI funds (R21-CA171251 and U54- CA 118948). Citation Format: Harvey L. Bumpers, Venkat Katkoori, Dongquan Chen, Upender Manne. The role of BetaB2-crystallin in progression of colorectal and breast cancers in African Americans. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C56. doi:10.1158/1538-7755.DISP13-C56

Abstract A20: Wii Can: Merging technology and support from community health advisors

Abstract Introduction and Purpose: Despite the benefits of physical activity, many cancer survivors fail to meet activity recommendations. Moreover, African American cancer survivors are less active than other survivor racial/ethnic groups. To address this disparity, we designed an intervention (Wii Can). Wii Can combines the appeal of emerging technology (Nintendo Wii) with the strength of social support from community health advisors (CHAs). The purpose of the current abstract is to describe the recruitment and retention of CHAs and African American cancer survivors to Wii Can. Methods: CHAs from the NCI-funded Deep South Network (DSN) for Cancer Control were identified and recruited to participate. CHAs completed training to deliver a 12 week intervention to increase physical activity in survivors. The intervention was based on Self Determination Theory. African American colorectal cancer survivors 45 to 75 years old who were not physically active, were recruited primarily through a hospital registry. Results: 10 CHAs were successfully recruited and trained as interventionists. Their mean age was 59.9 ± 3.9 years, 70% were female, 40% had some college, 40% had BA or BS, 20% had associate degrees. On average, they had been a DSN CHA for 3.1 ± 0.99 years. Reasons for deciding to participate in our study as a Wii Can CHA included: Family or friend with cancer; believe physical activity is important in general or for cancer survivors; helping others and being a role model; and encourage black people to participate in studies. All CHAs trained for the study have been retained. 170 letters were mailed to African American CRC survivors to invite their participation in the study. We were able to reach and screen 40 survivors. Incorrect mailing address, deceased, disconnected/incorrect telephone, or lack of interest were some of the reasons we were unable to screen a larger number. Of those screened, 25 were eligible. Of this group, 6 withdrew prior to enrollment (most common reason was lack of time to participate), 16 have received medical clearance to participate in the study (13 of these have enrolled and have been randomized; mean age of enrollees is 61 years). Three participants remain in the recruitment pipeline. The most common reason for ineligibility was currently receiving treatment. Only 2 individuals were ineligible due to already being too physically active. Study participants have been 100% adherent with baseline and follow-up assessments in addition to 100% adherent to receiving the planned intervention sessions (home visits and phone calls). Conclusions: A technology-based physical activity intervention is both acceptable to community health advisors who were trained to deliver the intervention and to African American CRC survivors. Challenges remain for some, as almost one quarter of those interested and eligible later determined that lack of time for the study was a barrier. Further, lack of accurate contact information provided by a hospital registry precluded optimal recruitment. Researchers need to identify efficient ways to engage African American survivors in health promotion interventions if we are to significantly impact the burden of this disease. Funding Acknowledgement: NCI: 1U54CA153719 Citation Format: Michelle Y. Martin, Hon Yuen, Claudia M. Hardy, Maria Pisu. Wii Can: Merging technology and support from community health advisors. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr A20. doi:10.1158/1538-7755.DISP13-A20

Abstract C22: Overexpression of miR-181b and underlying molecular mechanisms in aggressive progression of African American colorectal cancers

Abstract Background: MicroRNAs (miRs) are 19 to 24 nucleotide sequences that regulate cell proliferation, differentiation, and apoptosis. mir-181b is involved in tumor initiation and progression of several human malignancies, including colorectal cancers (CRCs). Our recent study of CRCs has demonstrated that increased expression of miR-181b is an indicator of poor patient prognosis, especially for African American patients with Stage III CRCs [Clin Cancer Res; 19(14); 1–11. 2013]. In the current study, we investigated molecular mechanisms of miR-181b over-expression in aggressive progression of CRCs. Methods: The effects of miR-181b over-expression on cell migration, apoptosis, and the cell cycle were analyzed. Putative molecular targets of miR-181b were identified by in silico analysis. miR-181b mediated, post-transcriptional regulation of these targets was assessed in CRC cell lines (HCT116wt/wt, HCT116 p53-/- and SW480 p53mut/mut) subjected to transient transfection. The targets were validated by measuring their mRNA expression levels, by qRT-PCR, in Stage III CRC tissues (n=18), which exhibited elevated levels of miR-181b. Further, luciferase assays were performed to assess a direct interaction between miR-181b and the 3′UTR of its target genes. Results: Transfection studies indicated that, in CRC cells, over-expression of miR-181b enhanced the rate of migration, diminished apoptosis, and shifted CRC cells from the G1 to the G2/M phase in a p53-dependent manner. Fourteen putative molecular targets of miR-181b were identified by in silico analysis, and miR-181b mediated post-transcriptional regulation of these targets was validated in CRC cell lines by qRT-PCR. Upon over-expression of miR-181b, integrin alpha-3 (cell surface adhesion molecule that mediates cell-adhesion to extra cellular matrix) was up-regulated, and BCL2L11 (apoptosis facilitator) and TNF-alpha (cytokine that has been implicated in tumor regression and also causes apoptosis) were down-regulated. Also, these targets were validated in human CRC tissues that exhibited elevated miR-181b levels (n=8). Finally, the direct interaction of miR-181b with the target gene 3′UTRs was confirmed by luciferase assays. Conclusions: These results demonstrate that, in CRCs, miR-181b post-transcriptionally regulates expression of integrin alpha-3, BCL2L11, and TNF-alpha and also regulates the cell cycle, migration, and apoptosis. This study was funded in part by the National Cancer Institute of the National Institute of Health UAB/TU/MSM Partnership grant (U54 CA118948). Citation Format: Balananda-Dhurjati Kumar Putcha, Brittany Michelle Holt, Liselle Bovell, Trafina Jadhav, Upender Manne. Overexpression of miR-181b and underlying molecular mechanisms in aggressive progression of African American colorectal cancers. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C22. doi:10.1158/1538-7755.DISP13-C22

Abstract 1279: Association between vitamin D levels and colorectal cancer in African Americans

Abstract Background. Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer in the world and there is a sizeable disparity in CRC incidence and mortality between African Americans (AAs) and all other US racial groups that remains unexplained. Associations between vitamin D levels and CRC have been widely reported in many populations, but there are few studies in AAs. We hypothesized that vitamin D levels are lower in AAs with CRC. Methods. 401 subjects were prospectively ascertained in endoscopy clinics in the Illinois Medical District: 130 healthy controls, 136 individuals with adenomatous polyps, and 130 individuals with CRC; 270 of 401 subjects were AA. Clinical data included age, gender, and BMI (kg/m2); smoking and drinking status; anti-inflammatory medication use; education and income levels; physical exercise level. Levels of serum 25-(OH) vitamin D2 and D3 were measured by Quest Diagnostics using liquid chromatography and tandem mass spectroscopy. Thirty nine potentially functional SNPs from eight vitamin D-related genes (CYP2R1, CYP24A1, CYP27A1, CYP27B1, CYP3A4, DHCR7, GC, and VDR) were genotyped using the Sequenom MassARRAY platform. We tested associations between vitamin D and CRC using logistic regression models, adjusting for age, gender, and time of year of blood collection, and we tested each clinical covariate in the model. In addition, we tested associations between SNPs and vitamin D levels using logistic regression, adjusting for age, gender, and time of collection. Results. Levels of total vitamin D (D2 + D3) and of vitamin D3 were statistically significantly lower in AAs compared to Non-Hispanic Whites (NHW). Approximately 15% of AAs exhibited detectable levels of vitamin D2, which was evidence of supplementation; only 8% of NHWs supplemented. Supplementation was significantly associated with older ages, female gender, less alcohol use and less exercise. Vitamin D3 levels were 22% lower in AA CRC cases compared to AA controls (18.5 ng/ml vs 23.7 ng/ml; P &amp;lt;0.03); vitamin D3 levels were not significantly different in NHW CRC cases compared to controls (29.8 ng/ml vs. 28.2 ng/ml). Vitamin D3 levels in adenoma cases were not significantly different compared to controls in either group (23.5 ng/ml in AA adenoma cases and 27.3 ng/ml in NHW adenoma cases). The SNP rs1544410 in VDR and rs3829251 in DHCR7 had the smallest p values (0.008 and 0.013, respectively). The minor allele of rs16847024 in GC was associated with lower vitamin D3 levels; this same SNP was associated with left-sided CRC in AAs in a larger case-control study performed by our group. rs3829251 in DHCR7 has been previously associated with serum vitamin D levels in Han Chinese. Conclusion. These data demonstrated that vitamin D levels are associated with protection against CRC in AAs. SNPs in vitamin D-related genes may modulate vitamin D levels and risk of CRC. Citation Format: Sariya Siddiqi, Fabio Pibiri, Rosa Munoz Xicola, Rick A. Kittles, Xavier Llor, Sonia S. Kupfer, Nathan A. Ellis. Association between vitamin D levels and colorectal cancer in African Americans. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1279. doi:10.1158/1538-7445.AM2014-1279

Abstract 2191: Identification of functional risk alleles in colorectal cancer-associated regions in African Americans

Abstract Background. There are disparities in both colorectal cancer (CRC) incidence and survival between African Americans (AAs) and Non-Hispanic Whites (NHWs). Genetic susceptibility factors are believed to contribute to CRC development but have been inadequately studied in AAs. Our previous work showed both shared and independent CRC-associated risk alleles are present in some gene regions identified in genome-wide association studies (GWAS) in NHWs. In the present work, using a functional bioinformatics approach, we searched for risk alleles in these regions in AAs. Methods. 10 chromosomal regions (8q23.3, 8q24.21, 10p14, 11q23.1, 14q22.2, 15q13.3, 16q22.1, 18q21.1, 19q13.11, 20p12) from COGENT consortium meta-analysis were selected for DNA sequencing. Three additional high-interest regions were included. The region surrounding each associated SNP was analyzed using r2 plots, based on European-ancestry genotype data from HapMap Phase 3. DNAs from 63 individuals (25 AA CRC cases and 38 AA controls) were sequenced using Agilent SureSelect enrichment arrays and Illumina HiSeq platform technology. Variants from the targeted sequencing were combined with 1000 genomes variant data for a total of 16,193 variants. Potentially functional variants were identified based on the following criteria: the variant is (i) in a coding region, (ii) an expression quantitative trait locus (eQTL) or a DNAseI eQTL (DsQTL), (iii) in a miRNA binding site, and (iv) in a transcription factor binding site. Golden Helix software was used to process the data. Using the Sequenom Massarray platform, we genotyped variants in discovery and replication sets for a total of 1177 AA CRC cases and 1264 AA controls. We calculated odds ratios (OR) and 95% confidence intervals using logistic regression, assuming an additive genetic model and adjusting for age, sex, and African ancestry. Results. We identified 81 variants in coding sequences, 82 eQTLs, 5 dsQTLs, 38 variants in putative microRNA binding sites, 33 variants in possible transcription factor binding sites, and 6 variants that are in two or more of the preceding categories, for a total of 245 variants. After assay development and quality control, 163 SNPs were available for genetic analysis. Nominal associations (p&amp;lt;0.05) were detected between CRC and 17 variants. We have completed genetic analysis in the replication set for 8 of the 17 SNPs. The SNPs rs1862748 (OR, 0.73; P = 0.001) in the CDH1 region and 16888699 (OR, 1.39; P = 0.0006) in the EIF3H region were statistically significant in both the discovery and replication series. rs1862748 has previously been associated with AA CRC and was identified as a eQTL for ZFP90. rs16888699 was identified as an eQTL for UTP23. Conclusion. Our results suggest that rs1862748 and rs16888699 are CRC risk alleles, validating the bioinformatics approach. Functional studies will are now needed to characterize the genetic mechanisms underlying risk. Citation Format: Fabio Pibiri, Ricky Rechenmacher, Rosa Xicola, Rick Kittles, Robert Sandler, Temitope Keku, Xavier Llor, John Carpten, Sonia Kupfer, Nathan Ellis. Identification of functional risk alleles in colorectal cancer-associated regions in African Americans. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2191. doi:10.1158/1538-7445.AM2014-2191

Abstract 3853: Predictive and prognostic analysis of KRAS and MSI markers in treatment of urban African American colorectal cancer patients

Abstract Background: Advancement of molecular analytic techniques has led to the discovery of a number of genetic biomarkers thought to be associated with prognosis and treatment outcomes in colorectal cancer (CRC). Aim: To analyze response to treatment in a group of CRC patients as a function of their genetic background. Method: A retrospective chart review of patients diagnosed with CRC from 2010- 2012 at Howard University Hospital was undertaken. African American (AA) patients diagnosed with CRC, the majority of whom received 5-Fluorouracil based chemotherapy, were selected. Data was collected from in-patient and out-patient records. Response to treatment was determined by Response Evaluation Criteria In Solid Tumors (RECIST) criteria from prior radiological investigations. The data was analyzed using Kaplan-Meier survival estimate and log rank test to compare the disease free survival (DFS) in correlation with clinical and genetic markers. Results: There were 30 AA patients with CRC who received chemotherapy. The average age of the cohort was 59 years, 53 % (n=16) were females and 80% (n=24) of the CRCs were distal. There were 10% (n=3), 23% (n=7), 37% (n=11), and 30% (n=9) patients at stage I, II, III, and IV, respectively. After three years of follow-up, disease free survival was 0.37 (95%CI: 0.14-0.60). Patients with MSI-H (n=3) had worse DFS. Patients with wild-type (WT) KRAS (n=16) had better DFS than mutant KRAS (n=10). The type of chemotherapy received did not affect response. Conclusions: DFS was worse in patients with a higher stage at the time of diagnosis, as well as, in patients with MSI-H versus MSS. Further study is warranted in AA since CRC patients with MSI-H historically have a better prognosis. DFS was found to be better in patients with WT KRAS, independent of chemotherapeutic regimen. These findings confirm that KRAS mutations negatively affected the prognosis in our study population. Table 1Characteristics of Responders vs Non-respondersCharacteristicsResponderNon-responderP-valueGenderMale770.4Female106Age&amp;lt; 60 years750.9≥60 years108StageI300.026II52III74IV27LocationLeft1590.3Right24MSIMSS157&amp;lt;0.0001(n=25)MSI-H03KRASmutant280.022(n=26)WT1245FUyes7120.1no101Oxaliplatinyes990.4no84Cetuximabyes100.6no1613Irinotectanyes020.05no1711 Citation Format: Priya Gopie, Maryam Yazdy, Bashira Giwa, Sanjeev Solomon, Gladys Onojobi, Seyed-Mehdi Nouraie, Bonnie Davis, Kamyar Sartip, Shokrani Babak, Lee Edward, Hassan Brim, Hassan Ashktorab. Predictive and prognostic analysis of KRAS and MSI markers in treatment of urban African American colorectal cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3853. doi:10.1158/1538-7445.AM2014-3853

Identification of novel mutations by exome sequencing in African American colorectal cancer patients.

The purpose of this study was to identify genome-wide single nucleotide variants and mutations in African American patients with colorectal cancer (CRC). There is a need of such studies in African Americans, because they display a higher incidence of aggressive CRC tumors. We performed whole exome sequencing (WES) on DNA from 12 normal/tumor pairs of African American CRC patient tissues. Data analysis was performed using the software package GATK (Genome Analysis Tool Kit). Normative population databases (eg, 1000 Genomes SNP database, dbSNP, and HapMap) were used for comparison. Variants were annotated using analysis of variance and were validated via Sanger sequencing. We identified somatic mutations in genes that are known targets in CRC such as APC, BRAF, KRAS, and PIK3CA. We detected novel alterations in the Wnt pathway gene, APC, within its exon 15, of which mutations are highly associated with CRC. This WES study in African American patients with CRC provides insight into the identification of novel somatic mutations in APC. Our data suggest an association between specific mutations in the Wnt signaling pathway and an increased risk of CRC. The analysis of the pathogenicity of these novel variants may shed light on the aggressive nature of CRC in African Americans.

Excess of proximal microsatellite-stable colorectal cancer in African Americans from a multiethnic study.

African Americans (AA) have the highest incidence of colorectal cancer compared with other U.S. populations and more proximal colorectal cancers. The objective is to elucidate the basis of these cancer disparities. Of note, 566 AA and 328 non-Hispanic White (NHW) colorectal cancers were ascertained in five Chicago hospitals. Clinical and exposure data were collected. Microsatellite instability (MSI) and BRAF (V600E) and KRAS mutations were tested. Statistical significance of categorical variables was tested by the Fisher exact test or logistic regression and age by the Mann-Whitney U test. Over a 10-year period, the median age at diagnosis significantly decreased for both AAs (68-61; P < 0.01) and NHWs (64.5- 62; P = 0.04); more AA patients were diagnosed before age 50 than NHWs (22% vs. 15%; P = 0.01). AAs had more proximal colorectal cancer than NHWs (49.5% vs. 33.7%; P < 0.01), but overall frequencies of MSI, BRAF and KRAS mutations were not different nor were they different by location in the colon. Proximal colorectal cancers often presented with lymphocytic infiltrate (P < 0.01) and were diagnosed at older ages (P = 0.02). Smoking, drinking, and obesity were less common in this group, but results were not statistically significant. Patients with colorectal cancer have gotten progressively younger. The excess of colorectal cancer in AAs predominantly consists of more proximal, microsatellite stable tumors, commonly presenting lymphocytic infiltrate and less often associated with toxic exposures or a higher BMI. Younger AAs had more distal colorectal cancers than older ones. These data suggest two different mechanisms driving younger age and proximal location of colorectal cancers in AAs.

Mo1152 The Role of Cancer Stem Cells in the Increased Risk of Colorectal Cancer in African-Americans

Background: Epidemiological studies have demonstrated that African-Americans (AAs) have a higher incidence of colorectal cancer (CRC) and greater mortality from this disease than Caucasians (CAs). The underlyingmechanisms for this increased risk are not well understood. We hypothesize that differences in the number and characteristics of a small subset of selfrenewing cancer stem/stem-like cells (CSCs) present within the colonic mucosa are responsible for the higher incidence of CRC in AAs. We also postulate that microRNAs (miRs), specifically miR-21, up-regulated in CRC and miR-145, which is down-regulated in CRC, play pivotal roles in regulating colon CSCs. Methods: Biopsies were obtained through a standardized protocol from normal-appearing colonic mucosa at the time of routine colonoscopy. Biopsies were subjected to collagenase/hyaluronidase digestion for isolation of CSCs (AJP:GI 302:G655-'63, 2012) and subsequently analyzed for CD44+CD166colon CSC phenotype, which we have previously found to be significantly higher in colonic mucosa of patients with tubular adenomas than those without adenomas (Dig. Dis. Sci. 57:2334'39, 2012). We also determined the expression of miR-21 and miR-145. In addition, the relative abundance of EGFR and β-catenin, that are known to be dysregulated in CRC, was examined by immunohistochemistry. Results: The current cohort includes 48 subjects, of which 63% were found to have adenomas. We have observed a 44.7% higher proportion of CD44+/CD166CSC phenotype in normal appearing colonic mucosa in AAs (27.12%; n=10) than CAs (18.74%; n=8). Likewise, the levels of miR-21 were 70% higher in the colonic mucosa of AAs with adenomas than CAs. In contrast, miR-145 levels were downregulated by 45% in AAs over the CA patients. The relative abundance of both EGFR and β-catenin in the colonic crypt of AAs was found to be 80% and 5-fold higher, respectively in AAs with adenomas than their CA counterparts. Conclusion: The increased risk for CRC in AAs might be explained by the increase CSCs in their colonic mucosa. miR-21 and miR-145, which also regulate EGFR, are thought to be involved in regulating CSCs in the colonic mucosa of AAs.

Mo1154 3D Reconstruction of Stomach Using Endoscopy for Endoluminal Bariatric Treatment

Background: Epidemiological studies have demonstrated that African-Americans (AAs) have a higher incidence of colorectal cancer (CRC) and greater mortality from this disease than Caucasians (CAs). The underlyingmechanisms for this increased risk are not well understood. We hypothesize that differences in the number and characteristics of a small subset of selfrenewing cancer stem/stem-like cells (CSCs) present within the colonic mucosa are responsible for the higher incidence of CRC in AAs. We also postulate that microRNAs (miRs), specifically miR-21, up-regulated in CRC and miR-145, which is down-regulated in CRC, play pivotal roles in regulating colon CSCs. Methods: Biopsies were obtained through a standardized protocol from normal-appearing colonic mucosa at the time of routine colonoscopy. Biopsies were subjected to collagenase/hyaluronidase digestion for isolation of CSCs (AJP:GI 302:G655-'63, 2012) and subsequently analyzed for CD44+CD166colon CSC phenotype, which we have previously found to be significantly higher in colonic mucosa of patients with tubular adenomas than those without adenomas (Dig. Dis. Sci. 57:2334'39, 2012). We also determined the expression of miR-21 and miR-145. In addition, the relative abundance of EGFR and β-catenin, that are known to be dysregulated in CRC, was examined by immunohistochemistry. Results: The current cohort includes 48 subjects, of which 63% were found to have adenomas. We have observed a 44.7% higher proportion of CD44+/CD166CSC phenotype in normal appearing colonic mucosa in AAs (27.12%; n=10) than CAs (18.74%; n=8). Likewise, the levels of miR-21 were 70% higher in the colonic mucosa of AAs with adenomas than CAs. In contrast, miR-145 levels were downregulated by 45% in AAs over the CA patients. The relative abundance of both EGFR and β-catenin in the colonic crypt of AAs was found to be 80% and 5-fold higher, respectively in AAs with adenomas than their CA counterparts. Conclusion: The increased risk for CRC in AAs might be explained by the increase CSCs in their colonic mucosa. miR-21 and miR-145, which also regulate EGFR, are thought to be involved in regulating CSCs in the colonic mucosa of AAs.

Sa1892 Dabigatran -Risk Factor of Severe Bleeding in Distal Esophagus in Elderly Women

Background: Several driver mutations have been discovered in colorectal cancer (CRC) progression including KRAS and BRAF that have practical significant therapeutic and prognostic implications. Whole Exome sequencing (WES) is revolutionizing the screening for pathologic single nucleotide variants (SNV) in complex disorders such as CRC. Little or no studies have comprehensively examined the association between somatic genetic variants in signaling pathways and risk of CRC in African Americans (AA). Aim: To determine somatic variants that drive colorectal carcinogenesis in AA. Methods: WES was carried out on DNA from 12 normal-tumor pairs of frozen biopsies from AA CRC patients. Base call quality recalibration, realignment validation around Indels, SNV calling and variants' call recalibration were carried out using GATK (Genome Analysis Tool Kit), and normative population databases (e.g. 1000Genomes SNP database, dbSNP, andHapMap) that provide the capability to filter genetic variants from putative mutations. Variants were then annotated using Annova. Sanger sequencing was used for SNVs' validation. Results: WES uncovered somatic mutations in many genes that are known targets in CRC including APC, BRAF, KRAS, Notch1, PIK3CA, and NDRG4. We discovered a number of novel SNVs in EID3, RGS3, HNRNPF, GNAS and APC. We detected several rare and unique alterations in the known WNT pathway gene: APC. These SNPs included, NM_001127511.2:c.4378_4384del (APC4378), NM_ 001127511.2:c.4401delT (APC4401), NM_001127511.2:c.648_657del (APC648), and NM_001127511.2:c.3418A>T (APC3418) which consist of a, frame shift deletions for the first three SNPs, and one stop codon mutation for the fourth SNP. Three of these novel variants, namely APC4378, APC4401 and APC3418, are located in exon 15, the exon of which the mutations are highly associated with CRC risk. Conclusion: This first WES from