Abstract:
Multiple myeloma (MM) is one of the most frequent hematological malignancies. The role of transcriptionally downregulated tumor suppressor genes has not been fully characterized in MM. As a transcription factor, SOX7 was characterized as a tumor suppressor gene in variety of cancer types. Based on previous and recent publications, SOX7 is underexpressed in MM due to a combination of genomic locus deletion and promoter hypermethylation. In this project, we directionally cloned human SOX7 coding sequence into pMIG, and ectopically expressed it in two SOX7-deficient MM cell lines. Two days post-transduction, GFP+ cells were sorted by flow cytometry, followed by ChIP-Seq and whole-transcriptome sequencing (WTS) using isolated DNA and total RNA samples. Selected transcriptionally regulated genes were cross-validated with qRT-PCR. Direct and indirect transcriptional targets of SOX7 were identified in KMS-18 and MM.1S cell lines by comparing SOX7-transduced cells with the empty vector-transduced cells. Based on ChIP-Seq, the number of SOX7 binding sites was markedly higher in MM.1S compared with those of KMS-18 cells. Of note, the proportion of genes common between WTS and ChIP-Seq was relatively low. Based on WTS, 189 protein coding genes were upregulated whereas 25 of them were downregulated in both cell lines. Pathway analysis of these transcriptionally regulated transcripts revealed Wnt and cadherinsignaling as the significant signaling pathways for both MM cell lines. Different than SOX7-regulated mRNAs, 17 and two lncRNAs were transcriptionally upregulated or downregulated, respectively.Consistent with the WTS data, CCND2 and DUSP6 were transcriptionally downregulated and upregulated in SOX7-transduced KMS-18 and MM.1S cell lines by qRT-PCR. Altogether, these observations suggest that several genes related to multiple myeloma development are transcriptionally regulated by SOX7 with implications in MM pathogenesis when it is underexpressed.
