RACIAL DIFFERENCES IN HEPATOCYTE GROWTH FACTOR GENE SIGNATURE EXPRESSION BY BREAST CANCER SUBTYPE AND ITS ASSOCIATION WITH SURVIVAL OUTCOMES

In the United States, African American women have a 41% higher mortality rate from breast cancer compared to Caucasian women. This disparity is believed to be partially caused by higher prevalence rates of triple negative and basal-like breast cancers among African American women. The triple negative/basal like subtype account for 22% of the breast cancers diagnosed in African American women, but only 10% of the breast cancers in white women. However, even within a given subtype, there may be other biological factors or tumor microenvironment features that affect outcomes. One possible biologic mechanism that may help to explain heterogeneity of survival within an intrinsic subtype is Hepatocyte growth factor (HGF), a protein in a signaling pathway that has been implicated in tumor progression and metastasis of breast cancer. HGF is a stroma derived factor that can indicate an activated stromal microenvironment that may be conducive for tumor promotion. The aims of this dissertation are: (1) to describe the patient and clinical characteristics associated with the HGF positive tumor phenotype, including distribution by intrinsic subtypes and race. (2) to assess if differential expression of the HGF genetic signature affects breast-cancer specific survival or disease-free survival among breast cancer patients, overall or stratified on subtype. HGF will be assessed using gene expression data based on Nanostring technology from invasive breast cancer cases in the Carolina Breast Cancer Study (CBCS, Phases 1-3, recruited from 1993-2013). Patients were followed up prospectively for survival via medical records or National Death Index through 2009. HGF genetic signature and intrinsic subtypes have been measured in 1,957 tumors. The study results will provide insights into the role of stromal microenvironment in breast cancer heterogeneity and survival. HGF signaling is also targetable, and therefore, results may suggest novel treatment strategies for breast cancer.Doctor of Philosoph

Modulation of the Intestinal Microbiota Alters Colitis-Associated Colorectal Cancer Susceptibility

It is well established that the intestinal microbiota plays a key role in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) collectively referred to as inflammatory bowel disease (IBD). Epidemiological studies have provided strong evidence that IBD patients bear increased risk for the development of colorectal cancer (CRC). However, the impact of the microbiota on the development of colitis-associated cancer (CAC) remains largely unknown. In this study, we established a new model of CAC using azoxymethane (AOM)-exposed, conventionalized-Il10−/− mice and have explored the contribution of the host intestinal microbiota and MyD88 signaling to the development of CAC. We show that 8/13 (62%) of AOM-Il10−/− mice developed colon tumors compared to only 3/15 (20%) of AOM- wild-type (WT) mice. Conventionalized AOM-Il10−/− mice developed spontaneous colitis and colorectal carcinomas while AOM-WT mice were colitis-free and developed only rare adenomas. Importantly, tumor multiplicity directly correlated with the presence of colitis. Il10−/− mice mono-associated with the mildly colitogenic bacterium Bacteroides vulgatus displayed significantly reduced colitis and colorectal tumor multiplicity compared to Il10−/− mice. Germ-free AOM-treated Il10−/− mice showed normal colon histology and were devoid of tumors. Il10−/−; Myd88−/− mice treated with AOM displayed reduced expression of Il12p40 and Tnfα mRNA and showed no signs of tumor development. We present the first direct demonstration that manipulation of the intestinal microbiota alters the development of CAC. The TLR/MyD88 pathway is essential for microbiota-induced development of CAC. Unlike findings obtained using the AOM/DSS model, we demonstrate that the severity of chronic colitis directly correlates to colorectal tumor development and that bacterial-induced inflammation drives progression from adenoma to invasive carcinoma

Modulation of the Intestinal Microbiota Alters Colitis-Associated Colorectal Cancer Susceptibility

It is well established that the intestinal microbiota plays a key role in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) collectively referred to as inflammatory bowel disease (IBD). Epidemiological studies have provided strong evidence that IBD patients bear increased risk for the development of colorectal cancer (CRC). However, the impact of the microbiota on the development of colitis-associated cancer (CAC) remains largely unknown. In this study, we established a new model of CAC using azoxymethane (AOM)-exposed, conventionalized-Il10−/− mice and have explored the contribution of the host intestinal microbiota and MyD88 signaling to the development of CAC. We show that 8/13 (62%) of AOM-Il10−/− mice developed colon tumors compared to only 3/15 (20%) of AOM- wild-type (WT) mice. Conventionalized AOM-Il10−/− mice developed spontaneous colitis and colorectal carcinomas while AOM-WT mice were colitis-free and developed only rare adenomas. Importantly, tumor multiplicity directly correlated with the presence of colitis. Il10−/− mice mono-associated with the mildly colitogenic bacterium Bacteroides vulgatus displayed significantly reduced colitis and colorectal tumor multiplicity compared to Il10−/− mice. Germ-free AOM-treated Il10−/− mice showed normal colon histology and were devoid of tumors. Il10−/−; Myd88−/− mice treated with AOM displayed reduced expression of Il12p40 and Tnfα mRNA and showed no signs of tumor development. We present the first direct demonstration that manipulation of the intestinal microbiota alters the development of CAC. The TLR/MyD88 pathway is essential for microbiota-induced development of CAC. Unlike findings obtained using the AOM/DSS model, we demonstrate that the severity of chronic colitis directly correlates to colorectal tumor development and that bacterial-induced inflammation drives progression from adenoma to invasive carcinoma

Prevalence of HPV Infection in Racial-Ethnic Subgroups of Head and Neck Cancer Patients

The landscape of HPV infection in racial/ethnic subgroups of head and neck cancer (HNC) patients has not been evaluated carefully. In this study, a meta-analysis examined the prevalence of HPV in HNC patients of African ancestry. Additionally, a pooled analysis of subject-level data was also performed to investigate HPV prevalence and patterns of p16 (CDNK2A) expression amongst different racial groups. Eighteen publications (N = 798 Black HNC patients) were examined in the meta-analysis, and the pooled analysis included 29 datasets comprised of 3,129 HNC patients of diverse racial/ethnic background. The meta-analysis revealed that the prevalence of HPV16 was higher among Blacks with oropharyngeal cancer than Blacks with non-oropharyngeal cancer. However, there was great heterogeneity observed among studies (Q test P<0.0001). In the pooled analysis, after adjusting for each study, year of diagnosis, age, gender and smoking status, the prevalence of HPV16/18 in oropharyngeal cancer patients was highest in Whites (61.1%), followed by 58.0% in Blacks and 25.2% in Asians (P<0.0001). There was no statistically significant difference in HPV16/18 prevalence in non-oropharyngeal cancer by race (P=0.682). With regard to the pattern of HPV16/18 status and p16 expression, White patients had the highest proportion of HPV16/18+/p16+ oropharyngeal cancer (52.3%), while Asians and Blacks had significantly lower proportions (23.0% and 22.6%, respectively) [P <0.0001]. Our findings suggest that the pattern of HPV16/18 status and p16 expression in oropharyngeal cancer appears to differ by race and this may contribute to survival disparities

Prevalence of HPV infection in racial–ethnic subgroups of head and neck cancer patients

The landscape of human papillomavirus (HPV) infection in racial/ethnic subgroups of head and neck cancer (HNC) patients has not been evaluated carefully. In this study, a meta-analysis examined the prevalence of HPV in HNC patients of African ancestry. Additionally, a pooled analysis of subject-level data was also performed to investigate HPV prevalence and patterns of p16 (CDNK2A) expression amongst different racial groups. Eighteen publications (N=798 Black HNC patients) were examined in the meta-analysis, and the pooled analysis included 29 datasets comprised of 3129 HNC patients of diverse racial/ethnic background. The meta-analysis revealed that the prevalence of HPV16 was higher among Blacks with oropharyngeal cancer than Blacks with non-oropharyngeal cancer. However, there was great heterogeneity observed among studies (Q test P<0.0001). In the pooled analysis, after adjusting for each study, year of diagnosis, age, gender and smoking status, the prevalence of HPV16,18 in oropharyngeal cancer patients was highest in Whites (61.1%), followed by 58.0% in Blacks and 25.2% in Asians (P<0.0001). There was no statistically significant difference in HPV16,18 prevalence in non-oropharyngeal cancer by race (P=0.682). With regard to the pattern of HPV16,18 status and p16 expression, White patients had the highest proportion of HPV16,18+/p16+ oropharyngeal cancer (52.3%), while Asians and Blacks had significantly lower proportions (23.0 and 22.6%, respectively) [P<0.0001]. Our findings suggest that the pattern of HPV16,18 status and p16 expression in oropharyngeal cancer appears to differ by race and this may contribute to survival disparities

<i>Il10^−/−</i> mice exhibit accelerated tumor progression.

<p>A. Percent of tumor-bearing WT and <i>Il10^−/−</i> mice with high-grade or invasive carcinoma (upper panel). Representative low-grade adenoma observed in WT mice (middle panel). Representative invasive carcinoma observed in <i>Il10^−/−</i> mice (lower panel).</p

<i>Il10^−/−</i>; <i>Myd88^−/−</i> mice show decreased tumor multiplicity and expression of <i>Il12p40</i> and <i>Tnfα</i> mRNA.

<p>A. Representative histology observed in <i>Il10^−/−</i> and <i>Il10^−/−</i>; <i>Myd88^−/−</i> mice treated with AOM. B. Tumor multiplicity in <i>Il10^−/−</i> and <i>Il10^−/−</i>; <i>Myd88^−/−</i> mice treated with AOM. C. Relative expression of <i>Il12p40</i> and <i>Tnfα</i> mRNA in the distal colons of <i>Il10^−/−</i> and <i>Il10^−/−</i>; <i>Myd88^−/−</i> mice.</p