ROCK Inhibition Induces Terminal Adipocyte Differentiation and Suppresses Tumorigenesis in Chemoresistant Osteosarcoma Cells

Abstract

Tumors comprise heterogeneous cell types including cancer stem cells (CSC), progenitor cells, and differentiated cells. Chemoresistance is a potential cause of relapse and a key characteristic of CSC, but the development of novel therapeutic approaches for targeting these cells has been limited. We previously established osteosarcoma-initiating (OSi) cells by introducing the gene for c-Myc into bone marrow stromal cells of Ink4a/Arf knockout mice. These OSi cells are composed of two distinct clones: highly tumorigenic cells (AX cells), similar to bipotent committed osteochondral progenitor cells, and tripotent cells of low tumorigenicity (AO cells), similar to mesenchymal stem cells. Here we show that depolymerization of the actin cytoskeleton induces terminal adipocyte differentiation and suppresses tumorigenesis in chemoresistant OSi cells. In contrast to AX cells, AO cells were highly resistant to conventional chemotherapeutic agents such as doxorubicin and were thus identified as chemoresistant cells. Inhibition of Rho-associated coiled-coil containing protein kinase (ROCK) elicited terminal adipocyte differentiation in chemoresistant AO cells through negative regulation of the transcriptional coactivator megakaryoblastic leukemia 1 associated with actin depolymerization. The clinically administered ROCK inhibitor fasudil significantly suppressed growth in vitro and tumorigenicity in vivo of chemoresistant AO cells as well as of OSi cells. Our findings thus suggest a new therapeutic strategy based on the induction of trans-terminal differentiation via modulation of actin cytoskeleton dynamics for therapyresistant osteosarcoma stem cells. Significance: These findings suggest that induction of trans-terminal differentiation through regulation of actin dynamics is a potential novel therapeutic approach for targeting chemoresistant stem-like tumor cells.

KD025, an anti‑adipocyte differentiation drug, enhances the efficacy of conventional chemotherapeutic drugs in ABCG2‑overexpressing leukemia cells

“…The present study indicated that KD025 treatment may be an effective inhibitor for reversing MDR in leukemia cell lines. These results were consistent with other previous studies on the ROCK signaling pathway in leukemia (41,45). However, the reversal efficiency and mechanism of KD025 treatment in ABCG2-mediated MDR remains unclear.…”

“…Furthermore, the ROCK pathway was also discovered to serve an important role in physiological conditions and the abnormal activation of myeloproliferative diseases (40). A previous study demonstrated that ROCK inhibition effectively reduced leukemic cell proliferation (41). Therefore, the deregulation of ROCK signaling is emerging as a potential key target in leukemia.…”

Cancer Stem Cells in Soft-Tissue Sarcomas

“…Another differentiation approach has been described in osteosarcoma. Inhibition of Rho-associated coiled-coil containing protein kinase (ROCK) by fasudil caused terminal adipocyte differentiation in chemotherapy-resistant OS CSCs [120]. This approach takes advantage of the pluripotency of CSCs to induce their trans-differentiation into another lineage; however, its therapeutic value is still unknown in STS.…”

The insulin‐PI3K‐Rac1 axis contributes to terminal adipocyte differentiation through regulation of actin cytoskeleton dynamics

“…The inhibitory effect of NSC23766 on terminal adipogenesis might therefore have been due to the activation of RhoA. We previously showed that treatment with Y‐27632 or fasudil as specific inhibitors of the downstream RhoA effector ROCK drives adipogenesis in DFAT cells, 3T3‐L1 preadipocytes, or osteosarcoma cells through negative regulation of MKL1 associated with F‐actin depolymerization, similar to the effect of LatA (Nobusue et al, ; Takahashi et al, ). We therefore next examined the effects of both ROCK and Rac1 inhibitors on adipogenesis in DFAT cells.…”