TAZ downregulated ANXA1 expression to modulate myeloma cell interactions 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 bone marrow mesenchymal stromal cells (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, including 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 multiple myeloma (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), namely, 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, tumor-promoting interaction with myeloma cells.

TAZ upregulates MIR-224 to inhibit oxidative stress response in multiple myeloma.

BACKGROUND: Oxidative stress within the bone marrow niche of multiple myeloma contributes to disease progression and drug resistance. Recent studies have associated the Hippo pathway with miRNA biogenesis and oxidative stress in solid tumors. Oxidative stress and miRNA pathway inter-relates in several cancers. Our group recently showed that TAZ functions as a tumor suppressor in MM. However, the role of TAZ in oxidative stress in MM is unknown. AIMS: We sought to examine the role of TAZ in myeloma cells' response to BM oxidative stress. We postulated that TAZ might be associated with an oxidative stress phenotype and distinct miRNA signature in MM. METHODS AND RESULTS: Using human myeloma cell lines and clinical samples, we demonstrate that TAZ promotes myeloma cells' sensitivity to oxidative stress and anticancer-induced cytotoxicity by inducing miR-224 to repress the NRF2 antioxidant program in MM. We show that low expression of TAZ protein confers an oxidative stress-resistant phenotype in MM. Furthermore, we provide evidence that overexpression of miR-224 in myeloma cells expressing low amounts of TAZ protein inhibits cell growth and enhances sensitivity to anti-myeloma therapeutics. CONCLUSION: Our findings uncover a potential role for TAZ in oxidative stress response in MM via the miR-224-NRF2 molecular pathway. This provides the scientific ground to explore miR-224 as a potential molecular target to modify TAZ expression and enhance myeloma sensitivity to treatment.

An inflammatory environment containing TNFα favors Tet2-mutant clonal hematopoiesis.

Clonal hematopoiesis of aging and indeterminate potential (ARCH or CHIP), driven mainly by mutations in DNMT3A and TET2, is an emerging public health issue, affecting at least 10-15% of adults older than 65 years. CHIP is associated with increased risks of de novo and therapy-related hematological neoplasms and serves as a reservoir for leukemic relapse. CHIP is also associated with increased all-cause mortality and risk of cardio-metabolic disease. The latter association may be explained, at least in part, by the effects of inactivating mutations in TET2 on progeny macrophages. We and others have shown recently that TET2-deficient macrophages are hyperinflammatory and this may exacerbate processes such as atherosclerosis. We postulated an inflammatory state associated with TET2 inactivation and/or unhealthy aging may also favor TET2-mutant hematopoietic stem and progenitor cell (HSPC) expansion. Herein, we demonstrate a clonogenic advantage for Tet2-knockout murine and TET2-mutant human HSPCs in an in vitro environment that contains the proinflammatory cytokine tumor necrosis factor-alpha (TNFα). This phenotype emerges on chronic TNFα exposure and is associated with myeloid skewing and resistance to apoptosis. To our knowledge, this is the first evidence to suggest that TET2 mutations promote clonal dominance with aging by conferring TNFα resistance to sensitive bone marrow progenitors while also propagating such an inflammatory environment. Normalizing the immune environment may present a novel strategy to control or eradicate mutant CHIP clones.