Immunomodulatory drugs reorganize cytoskeleton by modulating Rho GTPases

Abstract

IMiDs immunomodulatory drugs, including lenalidomide and pomalidomide represent a novel class of small molecule anticancer and anti-inflammatory drugs with broad biologic activities. However, the molecular mechanism through which these drugs exert their effects is largely undefined. Using pomalidomide and primary human monocytes, we report that pomalidomide rapidly and selectively activated RhoA and Rac1, but not Cdc42 or Ras, in the absence of any costimulation.Consistent with the activation of Rho GTPases, we found that pomalidomide enhanced F-actin formation, stabilized microtubules, and increased cell migration, all of which were blocked by selective inhibitors of ROCK1 and Rac1. Further, we showed that in Swiss 3T3 cells, pomalidomide only activated RhoA, not Rac1 or Cdc42, and potently induced stress fiber formation. The pomalidomide effect on actin cytoskeleton was blocked by the ROCK1 inhibitor, but not Rac1 inhibitor.Finally, we demonstrated that pomalidomide was able to regulate the activity of Rho GTPases and the formation of Factin in primary human T cells as it did in monocytes and showed that the activation of RhoA was essential for pomalidomide-induced interleukin-2 expression in T cells. IntroductionIMiDs immunomodulatory drugs were originally characterized for their ability to inhibit lipopolysaccharide (LPS)-induced tumor necrosis factor-␣ (TNF-␣) production in peripheral blood mononuclear cells (PBMCs) and to enhance interleukin-2 (IL-2) and interferon-␥ (IFN-␥) expression in activated T cells. 1,2 Broad biologic and pharmacologic activities have been demonstrated in a variety of in vitro and in vivo systems. [3][4][5] One of the IMiDs drugs, lenalidomide, has been approved for the treatment of 5qϪ myelodysplasia (MDS) and for multiple myeloma (MM). 6,7 Clinical studies on lenalidomide have also demonstrated its efficacy in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). [8][9][10][11] Pomalidomide, another potent IMiDs drug, is currently in clinical trials for several indications including MM, myelofibrosis, sickle cell anemia, and solid tumors. 3 In vitro, immunomodulatory, proapoptotic, antiangiogenic, and antiproliferative activities have been demonstrated for IMiDs drugs in different cellular models. 4,5,12,13 While each of these activities has been implicated to the anticancer activities observed clinically, a unifying molecular mechanism has not been demonstrated, if indeed one exists to explain the apparently diverse functional effects of these drugs. We have been particularly interested in IMiDs drug effects in the enhancement of T-cell and natural killer (NK) cell immune activity and the possibility that this is crucial for therapeutic response seen clinically in MM, CLL, and NHL patients. For example, IMiDs compounds were found to induce proliferation of T cells from healthy volunteers and MM patients in vitro after CD3 activation. 2,14 Both lenalidomide and pomalidomide have been demonstrated to increase IL-2 and IFN-␥ production in activated T cells, to activat...

The monocytic population in chronic lymphocytic leukemia shows altered composition and deregulation of genes involved in phagocytosis and inflammation

“…Immunomodulatory drugs rapidly regulate cytoskeleton reorganization in monocytes and T cells through selective activation of Rho family GTPases, inducing increase in F-actin formation, microtubule stabilization and synapse formation. 32 In the light of our findings, the normalization of leukemia-derived impairment of actin cytoskeleton in both T cells and monocytes by immunomodulatory drugs could be a key mechanism of immune activation described in CLL patients treated with immunomodulatory drugs. Furthermore, impairment of IgG-mediated phagocytosis may be considered a potential mechanism of rituximabresistance in CLL patients.…”

Ribosomopathies: human disorders of ribosome dysfunction

“…28 Lenalidomide has many biologic activities, including the promotion of erythropoiesis, modulation of cytokine production, inhibition of 2 phosphatases on 5q (CDC25C, and PP2A) and the activation of Rac1 and RhoA. [28][29][30][31][32] RPS14 was identified as a 5qϪ syndrome gene in an RNA interference screen of each gene within the 5qϪ syndrome common deleted region. 3,33 In patients with the 5qϪ syndrome, 1 allele of RPS14 is deleted, 3 and haploinsufficient expression of RPS14 has been confirmed in patient samples.…”

Lenalidomide interferes with tumor-promoting properties of nurse-like cells in chronic lymphocytic leukemia

“…IMiDs were shown to increase migration of normal monocytes and to repair motility dysfunction of T cells from CLL patients. 16,24 Conversely, IMiDs impaired migration capability of CLL cells and endothelial cells. 17,25 To…”

“…24 To evaluate whether lenalidomide could affect actin cytoskeleton in monocytes from CLL patients, we treated purified CD14 + monocytes (n=9) with lenalidomide for 20 min at doses ranging from 0.5 mM to 10 mM and measured the F-actin content. Lenalidomide stimulated actin polymerization at the clinically relevant doses of 0.5 mM and 1 mM ( Figure 1A).…”