Abstract 1834: Noncoding RNAs of the 8q24 locus: Consequences of the over-expression or suppression of miR-1204 and PVT1 in developing B cells.

Immortalized models of the mouse B lymphocyte lineage have proven to be valuable resources for a wide variety of B cell neoplasms and for the study of normal B cell differentiation. Whether these models have been engineered in mice (in vivo) or in cell culture (in vitro), there are distinct advantages and disadvantages to both. Homogeneity and ease of accessibility can be considered a benefit of working with cultured cells, whereas the contribution from accessory or stromal cells can be an important element not readily available in the in vitro model system. We originally used immortalized Burkitt9s Lymphoma (BL) cells to discover a cluster of microRNAs, miR-1204∼1208, that map within the noncoding PVT1 locus in the region of human 8q24 region down-stream of MYC. The BL cell lines allowed us to isolate a large amount of RNA from a homogeneous resource that enhanced discovery of low-level transcripts. Using probes for mouse miR-1204∼1208 to examine expression in a panel of mouse cell lines representing different stages of B cell development, we were able to show that expression of miR-1204∼1208 appeared to arise at the small B cell stage and that these higher levels of expression continued through to the mature plasma cell. This suggested that the pre-B cell or naive small B cell stages may be most illuminating in assigning targets and function to miR-1204∼1208 or PVT1. To determine if over-expression of one of these miRNAs, miR-1204, influences the latency and/or type of B cell malignancy we used two mouse transgenic (TG) models of B cell malignancy, H2-L d -hu-IL6 and iMyc, lentiviral expression of miR-1204 reduced the latency of tumor development in both models and in the case of iMyc-TG, there was also a shift in tumor type from late stage plasmacytoma to the earlier stage of large B cell lymphoma. However, further interpretation of these results was confounded by heterogeneity of lentiviral integration and expression among tumors. Thus, we turned to several human and mouse in vitro models of B cell development, representing pro-B, pre-B, small B, mature B and plasma cell stages to address the effects of modulating the expression of miR-1204 and its host noncoding transcript, PVT1. Over-expression of miR-1204 has been achieved through the use of lentiviruses or synthetic mimics and suppressed expression has been achieved through application of synthetic inhibitors. We also over-expressed PVT1 using a lentiviral vector and suppressed PVT1 expression through the use of siRNA corresponding to various exons of PVT1. Resultant changes in growth and morphology of these cell lines hint that microarray expression analyses will reveal functional targets of miR-1204 in normal and malignant lymphoid development. It will also be of interest to examine whether over-expression or inhibition of miR-1204 plays an additional role in maturation of the normal B cell. Citation Format: Konrad Huppi, Oliver L. Ou, Jason J. Pitt, Brady Wahlberg, Tamara L. Jones, Vishala Neppalli, Siegfried Janz, Natasha J. Caplen. Noncoding RNAs of the 8q24 locus: Consequences of the over-expression or suppression of miR-1204 and PVT1 in developing B cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1834. doi:10.1158/1538-7445.AM2013-1834