Cancer Control Research5R01CA142983-03
DISPARITIES IN CERVICAL CANCER PRECURSORS AND DEREGULATION OF IMPRINTED GENES
DESCRIPTION (provided by applicant): Although screening for uterine cervical intraepithelial lesions (CIN) and its aggressive treatment has resulted in decreased cervical cancer incidence and mortality, an estimated 11,000 cases of invasive cervical cancer (ICC) and 40,000 cases of carcinoma in situ (CIS) continue to be diagnosed every year in the United States. ICC incidence is 60% higher and mortality over two times higher in African Americans compared to whites. Such disparate rates in incidence and mortality are despite comparable screening rates to detect precursor lesions, comparable prevalence of 'high risk' human papillomavirus (HPV) infection, the etiologic agent, and co-factors such as cigarette smoking. Reasons for such disparities are largely unknown. A more detailed understanding of the etiology of lesions that progress will improve risk stratification to distinguish women with a low risk of progression from those likely to rapidly progress to invasive cancer. We posit that deregulation of genomically imprinted genes, a group of approximately 50 known growth-regulatory genes where only one allele is normally active, may predict progression to cervical cancer. We found that a substantial group of imprinted genes exhibit altered expression in ICC versus normal cervical epithelium. In addition, methylation analysis of two regulatory regions controlling IGF2 expression shows deviation from normal in specimens with CIN2-CIN3 classification and more profound deviation in invasive cancers. Together, these findings suggest that imprinted genes are deregulated in ICC and these features may improve detection of CIN cases likely to progress. Our central hypothesis is that deregulation at imprint regulatory elements of imprinted genes, likely influenced by environmental exposures, increases risk of progression to cervical cancer in women infected with 'high risk' HPV. We have already shown racial variation on the effect of environmental exposures on imprint deregulation, and thus, further hypothesize that higher risk in African Americans and Hispanics is due to race/ethnic differences in deregulation of these genes. Our specific aims are to: (1) determine if deregulation of imprint regulatory elements of known imprinted genes is associated with increased risk of progression of CIN1 to CIN2+, and whether this association varies by race/ethnicity; (2) determine whether aberrant methylation of imprint regulatory elements in cervical cells is similar to that found in peripheral blood cells, suggesting an early event; and associated with (i) transcriptional expression, and (ii) loss of imprinting; (3) evaluate whether deregulation of known imprinted genes in cervical cells can be used to discriminate women with CIN2+ among 500 Atypical Squamous Cells of Uncertain Significance (ASCUS) cases. To address the Aims, we will recruit and follow 1,500 women with CIN1 and 500 with ASCUS, and examine the association between aberrant methylation markers at imprinted regulatory elements of 12 genes and progression from CIN1 to CIN2+. We will then test the performance of these markers to identify CIN2+ cases from among 500 ASCUS cases. Data from the proposed study will improve triage decisions and reduce disparities in ICC morbidity and mortality. PUBLIC HEALTH RELEVANCE: Although screening for cervical intraepithelial lesions to prevent cervical cancer has resulted in decreased cancer incidence and mortality, an estimated 11,000 cases of invasive cervical cancer and 40,000 carcinomas in situ cases continue to be diagnosed every year in the United States with incidence 60% higher and mortality >2-times higher in African Americans compared to whites. We will recruit and follow 1,500 CIN1 and 500 cases of Atypical Squamous Cells of Uncertain Significance (ASCUS), and examine the association between aberrant methylation at imprinted regulatory elements of 12 genes and progression to CIN2 or worse and then test the performance of these markers in ASCUS cases, independent of known co-factors. Data from this study will elucidate the role of epigenetic deregulation in CIN2+ and inform triage decisions, reducing disparities in cervical cancer incidence and mortality.