Abstract 1518: Microenvironment regulation of acute lymphoblastic leukemia miRNA profiles.

It is well established that the bone marrow microenvironment provides cues to hematopoietic tumors that initiate and progress in this unique anatomical site that likely mimics, to some degree, cell signaling that directs steady state hematopoiesis. We have previously documented diverse changes in gene and protein expression in acute lymphoblastic leukemia (ALL) cells in contact with either primary bone marrow stromal cells (BMSC obtained from consenting donors) or human derived osteoblasts (HOB); two components of the marrow stem cell niche (Wang 2007). Importantly, many of these changes are coincident with chemoresistance. In the current study we have expanded our investigation to include investigation of miRNA profile comparisons of the human Ph+ ALL cell line Sup-B15 (ATCC # CRL-1929) grown in media versus tumor cells grown in long term co-culture (greater than 3 months) with adherent BMSC or HOB. We have previously described the stem cell-like characteristics of Sup-B15, making it an intriguing cell line for continued study (Wang 2007). In addition, comparisons were completed for the cell lines Nalm-27 and Nalm-30 (Fujisaki Cancer Center, Okayama, Japan) for evaluation of tumors at diagnosis versus relapse of disease. Total RNA was isolated using Ambion miRVana RNA extraction kit and a microarray assay was performed using a service provider (LC Sciences, Houston TX) and μParafloTM MicroRNA Microarray Assays as described (Wei 2009). Preliminary observations identified over 15 different microRNAs expressed at baseline in all three lines evaluated which met the medium to high relative threshold according to the analysis. Profiles of Nalm-27 and Nalm-30 were highly conserved with the exception of miR-7-1-3p and miR-99b-5p which were upregulated and miR-142-3p, miR-1260b, and miR-19a-3p which were down regulated when the cell line established at relapse (Nalm-30) was compared to that from diagnosis (Nalm-27). Consistent with microRNAs as critical regulators of diverse cellular processes including proliferation, survival, and differentiation, several targets were noted to be significantly influenced by LTCC of Sup-B15 ALL cells with BMSC or HOB. Preliminary evaluation suggests miR-4254 expression was increased by BMSC and miR-4484, miR-34b-3p and miR-1237-5p were increased when tumor cells were provided continual access to HOB. In contrast, miR-221-3p, miR-222-3p, miR-4521, levels were decreased during BMSC co-culture as well as miR-221-3p, miR-222-3p, miR-199b-5p, miR-185-5p, miR-4521 during co-culture with HOB. Collectively these changes highlight the dynamic expression of microRNAs and emphasize their responsiveness to microenvironment derived signals. These observations will contribute to identification of novel pathways that include miRNAs that warrant consideration as therapeutic targets in efforts to eradicate residual disease in the setting of ALL. Citation Format: Blake Moses, Sriganesh G. Sharma, J. Michael Ruppert, Laura F. Gibson. Microenvironment regulation of acute lymphoblastic leukemia miRNA profiles. [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 1518. doi:10.1158/1538-7445.AM2013-1518