TAZ DOWNREGULATES ANXA1 EXPRESSION TO MODULATE MYELOMA CELL INTERACTION WITH BONE MARROW MESENCHYMAL STROMAL CELLS.

We and others have previously shown that TAZ plays a tumor suppressive role in multiple myeloma. However, recent reports suggest that molecular crosstalk between the myeloma cells and bone marrow stromal components contributes to the myeloma cell survival and drug resistance. These reports further point to reciprocal interaction via adhesion molecules as the most prominent mechanism of intercellular crosstalk between myeloma cells and BM-MSCs. YAP/TAZ silencing/expression has been shown to correlate across all cancers with a set of adhesion/extracellular matrix proteins. Therefore, we hypothesized that TAZ may regulate myeloma cell interaction with BM stromal cells by influencing the expression of distinct cell adhesion signatures. We used previously established TAZ myeloma cell line models: DELTA47-pLENTI or TAZ knockout DELTA47 cells cocultured with or without BM-MSCs as our study models. Using RNA sequencing analysis, we performed the first comprehensive screen for cell adhesion-related transcriptional targets of TAZ in MM. In doing so, we uncovered an enrichment of cell adhesion-related genes in TAZ knockout DELTA47 cells relatively to pLENTI-DELTA47 cells, including 11 genes with log2 fold change>2 (P<0.05): ANXA1, ADGRL2, NCAM1, NCAM2, ADGRL3, CXADR, ALCAM, JAM2, KIRREL1, KIRREL2, and ADGRG7, suggesting possible relationship with TAZ. We validated ANXA1 as a bona fide target of TAZ in MM. We show that TAZ represses myeloma cell migration and interaction with BM-MSCs by transcriptionally downregulating ANXA1 expression via TEAD-dependent mechanism. Our data provide new insights into the understanding of the role of TAZ in the intercellular communication signals between myeloma cells and BM-MSCs. Our findings also suggest that ANXA1 represents a putative cell adhesion target to attenuate BM-MSC driven, tumour-promoting interaction with myeloma cells.

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