Identification of Micro RNAs within Chromosome 1p Minimal Deletion Region Associated Adverse Outcomes in Multiple Myeloma
Yijun Yang, Yi Ning, Hong Chang. Univesity Health Network, Toronto, Canada; University of Maryland, Baltimore
Background: Chromosome 1p deletion is detected in nearly 20 % of patients diagnosed with multiple myeloma (MM) and confers a significantly shorter survival. A region of minimal deletion 1p12-1p21 was identified using SNAP based arrays and karyotype analysis. Since microRNAs play an important role in cancer related cellular functions, such as proliferation, differentiation and apoptosis, to pursue our search for potential tumor suppressor gene(s) in the 1p21 deletion region, we searched for miRNA genes that are mapped to the minimal deletion region (1p12-1p21).
Design: We used NCBI MapViewer to identify potential miRNAs within the 1p21-1p21 region, and USCS Genome Browser to find BAC clones for FISH probes. Interphase FISH was performed in MM cell lines and primary MM samples to evaluate these miRNAs deletion status as well as their correlations with the patients outcomes. qRT-PCR with specific primers of miRNAs, miR137, miR553, were used to validate their expressions in MM cells with or without 1p21 deletions.
Results: According to NCBI MapViewer, minimal deletion region is located between nucleotides 94,500,000 to 124,300,000. Defining these nucleotides as start- and end- locations in miRBase search lists identifies a total of five miRNAs: miR-553 and miR-137 are located in 1p21, others are located in 1p13 region, which is closer to centromere. A number of clones were found from human BAC series RP11. To confirm miRNA deletion status in MM, we performed FISH experiments on 20 primary MM samples (12 with 1p21 deletion, 8 without deletion) and 10 MM cell lines (4 with 1p21 deletion, 6 without deletion) to assess their miR-553, miR-137 deletion status using the Bac clone probes. We found that miR-553 and miR-137 were deleted in all 12 MM cases and 4 MM cell lines harboring del(1p21). This was further validated by qRT-PCR demonstrating significant low expressions of miR-553 and miR-137 in myeloma cells showing hemizygous 1p21 deletions in comparison to those without such deletions. Importantly, deletions/lower expressions of miR-553 and miR-137 were associated with significantly shorter survivals in an independent cohort of MM undergoing autologous stem cells transplantations.
Conclusions: We have validated 2 microRNAs miR-553 and miR-137 within 1p21 region that were frequently deleted in MM and associated with adverse clinical outcomes. Further functional studies are ongoing to identify their gene targets and elucidate the role in the pathogenesis /disease progression of MM.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 217, Wednesday Afternoon