Gibbs, Denise

Background Men of African ancestry experience higher burden from prostate cancer compared to men of other ancestral backgrounds. Limitations in the availability of high-quality biospecimens hinder the inclusion of this population in genetic studies of prostate cancer. The use of formalin-fixed paraffin-embedded (FFPE) tissues represent a potential rich source of genetic material particularly in some international settings, where fresh frozen tissue is difficult to obtain. In this study, we investigate the feasibility of using FFPE biospecimens acquired from various international sites for utility in next-generation sequencing. Methods A total of 976 FFPE blocks were collected between 2002 and 2017 from six international sites in Africa and the Caribbean representing three consortia: Prostate Cancer Transatlantic Consortium; African-Caribbean Cancer Consortium; and Men of African Descent and Carcinoma of the Prostate. Genomic DNA was checked for quality and quantity. Differences in mean quality control (QC) for pre-and-post pathology training were assessed using t-test. Pearson chi-square with trend analysis examined association between time-category and QC success status. Association of continuous DNA quality (Q129/Q41 ratio) and time of specimen collection was estimated with linear regression. Samples with a DNA quantity >0.2µg and a Q129/Q41 ratio >0.00225 were submitted for whole exome sequencing (WES). Results There was a positive relative percentage change in DNA quantity from 2002 to 2017 for Jamaica, Kenya and Senegal. There was a decline in DNA quantity over the same time period for Nigeria. There was a statistically significant improvement in quality of samples from Kenya ( P =0.032), Nigeria ( P <.001) and Senegal ( P =0.043). There was a significant improvement in the collected DNA sample quality over time with an R 2 of 0.12. Conclusions FFPE samples from low-resource settings could potentially provide sufficient DNA for WES. Improvements in biospecimen collection processing and storage for research are needed in some of these settings.

Mutations in the MEN1 gene are associated with the multiple endocrine neoplasia syndrome type 1 (MEN1), which is characterized by parathyroid hyperplasia and tumors of the pituitary and pancreatic islets. The mechanism by which MEN1 acts as a tumor suppressor is unclear. We have recently shown that menin, the MEN1 protein product, interacts with mixed lineage leukemia (MLL) family proteins in a histone methyltransferase complex including Ash2, Rbbp5, and WDR5. Here, we show that menin directly regulates expression of the cyclin-dependent kinase inhibitors p27 Kip1 and p18 Ink4c . Menin activates transcription by means of a mechanism involving recruitment of MLL to the p27 Kip1 and p18 Ink4c promoters and coding regions. Loss of function of either MLL or menin results in down-regulation of p27 Kip1 and p18 Ink4c expression and deregulated cell growth. These findings suggest that regulation of cyclin-dependent kinase inhibitor transcription by cooperative interaction between menin and MLL plays a central role in menin's activity as a tumor suppressor.