Thompson, Patricia A.

Abstract Background: MicroRNAs (miRNA) are small, noncoding RNAs with important regulatory roles in tissue development, differentiation, proliferation, and when deregulated tumor formation. The goal of this study was to characterize the miRNA profile of normal breast tissue from carriers of either BRCA1 or BRCA2 mutations, with and without a prior history of cancer, for biomarker discovery for future prevention studies in high risk patient populations. Methods: MicroRNA profiling was conducted using a panel of breast candidate miRNAs and normal ‘non-cancerous’ tissue biopsy from 15 BRCA1 mutation carriers, 15 BRCA2 mutation carriers and 15 BRCA screened mutation negative subjects from high risk families. Results: While small differences were observed for any individual miRNA between groups, the most striking observation was the presence of a clear BRCA1 miRNA signature that was distinct from that in BRCA2 subjects or in the high-risk, non-mutation carriers. The BRCA1 pattern was present in normal appearing tissue biopsy independent of previous history of cancer, treatment for cancer, age, menopausal status or oophorectomy. BRCA2 carriers and high risk, mutation negative subjects showed an overall shared miRNA expression pattern. MicroRNA species that distinguished the groups included differences in the expressed levels of let-7a, let-7b, miR-125b, miR-145, miR-15b and members of the miR-181 family. Ongoing efforts include pathway modeling to gain insight on novel targets for prevention along with RT-PCR confirmation of differentiating microRNA species as well the potential downstream targets for example of miR-181b target genes including HOXA7, HOXA9, HOXA11 and PBX3. Conclusion: The presence of a distinctive miRNA profile in normal appearing tissue of BRCA1 mutation carriers suggest a major role of BRCA1 mutation status on the normal tissue not previously reported. If corroborated, miRNA profiling studies of normal breast tissue may prove useful in both risk assessment as well as providing insight on deregulated pathways for pharmacologic intervention for risk reduction in the BRCA carrier population. Citation Format: Sandhya Pruthi, Julie Buckmeier, Christina Preese, Vera J. Suman, Rachel M. Hurley, Patricia Thompson. microRNA expression profiling in normal breast epithelium of BRCA1 and BRCA2 carriers as prevention targets. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr C47.

498 Background: Prior study, demonstrating differential immunohistochemical EGFR expression between the primary colon cancer and the liver metastasis, suggested possible molecular differences between the two tumor sites. This questions the relevance of obtaining genomic information from the primary tumor to guide adjuvant treatment. In this study we examine whether there are genomic differences specific to metastatic nodes versus the paired colon primary samples. Methods: Using 30 primary and lymph node metastasis pairs (dissected for >80% tumor from paraffin embedded tissue), we obtained a dataset of copy number derived from the Affymetrix Oncoscan Molecular Inversion Probe platform. Using the Nexus Copy Number software for processing, we used the default automatic segmentation of the copy number data with a threshold for calling copy number gains/losses of 2.3/1.7. Subsequently we applied the Wilcoxon signed-rank test in order to find regions showing copy number imbalance that differ between the paired nodes and tumors correcting for multiple comparisons by performing permutation-based estimation of the false discovery rate permuting the samples 100 times. Results: Using 40 ng of total DNA from paraffin embedded tumor from primary and tumor in positive nodes, we obtained high quality, genome wide copy number data. Using FDR < 0.1, we identified four chromosomal segments that showed statistically significant increased likelihood of copy number gains in the primary tumor compared to the tumor-containing node. Thirty five percent of tumor-bearing lymph nodes were copy number normal at the EGFR locus whereas the corresponding primary tumor showed amplification at 7p11.2 (includes the EGFR gene). A similar pattern was observed for 8q24, 14q11.2, and 20q12-q13; regions associated with aggressive tumor behavior. Conclusions: Our results demonstrate four significant differences between the primary tumor and lymph node metastasis and in all cases the metastasis were copy number normal compared to the copy number gain observed in the primary tumor. These results support the importance to examine differences at the genome level between the metastatic tumor site and the primary.

Abstract COX inhibitors reduce colorectal adenoma recurrence by up to 45% and selenium supplementation may prevent colorectal cancer. Following colonoscopic adenoma resection, 1,600 men and women, ages 40 to 80 years, were randomized to celecoxib (400 mg daily), a selective COX-2 inhibitor, and/or selenium (200 μg daily as selenized yeast), or double placebo. The trial was initiated in November 2001. The primary trial endpoint is adenoma recurrence in each intervention group compared with placebo, as determined by surveillance colonoscopy conducted three to five years after baseline. Randomization was stratified by use of low-dose aspirin (81 mg) and clinic site. Following reports of cardiovascular toxicity associated with COX-2 inhibitors, the celecoxib arm was discontinued in December 2004 when 824 participants had been randomized. Accrual continued with randomization to selenium alone or placebo. Randomization of the originally planned cohort (n = 1,621) was completed in November 2008. A further 200 patients with one or more advanced adenomas (denoting increased risk for colorectal cancer) were accrued to enhance statistical power for determining intervention efficacy in this higher-risk subgroup. Accrual of the total cohort (n = 1,824) was completed in January 2011. Baseline cohort characteristics include: mean age 62.9 years; 65% male; body mass index (BMI) 29.1 ± 5.1; 47% taking low-dose aspirin while on trial; 20% with three or more adenomas; and 38% with advanced adenomas. Intervention effects on adenoma recurrence will be determined, and their modification by genetic background and baseline selenium level. The effect of selenium supplementation on risk for type II diabetes will also be reported. Cancer Prev Res; 5(12); 1381–93. ©2012 AACR.