Rac1 plays a role in CXCL12 but not CCL3-induced chemotaxis and Rac1 GEF inhibitor NSC23766 has off target effects on CXCR4

Abstract

Cell migration towards a chemotactic stimulus relies on the re-arrangement of the cytoskeleton, which is triggered by activation of small G proteins RhoA, Rac1 and Cdc42, and leads to formation of lamellopodia and actin polymerisation amongst other effects. Here we show that Rac1 is important for CXCR4 induced chemotaxis but not for CCR1/CCR5 induced chemotaxis. For CXCL12-induced migration via CXCR4, breast cancer MCF-7 cells are reliant on Rac1, similarly to THP-1 monocytes and Jurkat T-cells. For CCL3-induced migration via CCR1 and/or CCR5, Rac1 signalling does not regulate cell migration in either suspension or adherent cells. We have confirmed the involvement of Rac1 with the use of a specific Rac1 blocking peptide. We also used a Rac1 inhibitor EHT 1864 and a Rac1-GEF inhibitor NSC23766 to probe the importance of Rac1 in chemotaxis. Both inhibitors did not block CCL3-induced chemotaxis, but they were able to block CXCL12-induced chemotaxis. This confirms that Rac1 activation is not essential for CCL3-induced migration, however NSC23766 might have secondary effects on CXCR4. This small molecule exhibits agonistic features in internalisation and cAMP assays, whereas it acts as an antagonist for CXCR4 in migration and calcium release assays. Our findings strongly suggest that Rac1 activation is not necessary for CCL3 signalling, and reveal that NSC23766 could be a novel CXCR4 receptor ligand.

Adenosine A2A receptor activation reduces brain metastasis via SDF‐1/CXCR4 axis and protecting blood‐brain barrier

“…The SDF‐1/CXCR4 signaling pathway participates in metastatic process in many cancer types such as liver cancer, colorectal cancer and breast cancer 35 . CXCR4 is widely expressed in CD43 + cancer stem cells and SDF‐1 is widely expressed in tumor endothelial cells 36 . Therefore, CXCR4 + tumor stem cells can migrate or invade along the SDF‐1 concentration gradient to seed in distant tissues or organs.…”

“…35 CXCR4 is widely expressed in CD43 + cancer stem cells and SDF-1 is widely expressed in tumor endothelial cells. 36 Therefore, CXCR4 + tumor stem cells can migrate or invade along the SDF-1 concentration gradient to seed in distant tissues or organs. CXCR4 has also been reported to promote the progression of tumors, and the overexpression of CXCR4 has been proved to correlated with poorer prognosis and shorter survival time.…”

Targeting Rac and Cdc42 GEFs in Metastatic Cancer

“…Recent studies have also demonstrated the potential of NSC23766 in combination therapy to overcome resistance to targeted as well as cytotoxic therapies (Karpel-Massler et al, 2017;Tian et al, 2018). Nonetheless, although the use of NSC23766 may look promising in some instances, the high effective concentrations (µM range) and the reported off-target effects in platelets, on alfa-1-adrenergic receptors and CXCR4 chemokine receptors, limits its therapeutic use (Dutting et al, 2015;Mills et al, 2018;Yu et al, 2019).…”

The Signaling Duo CXCL12 and CXCR4: Chemokine Fuel for Breast Cancer Tumorigenesis

“…This inhibitor shows dual secondary effects on the CXCR4 signaling. It acts as an activator in cAMP assays whereas it is inhibitory in migration and calcium release assays [ 101 ]. Another study showed that heregulin, a ligand for Erb3 and Erb4 receptors, sensitizes breast cancer cells for CXCL12 mediated Rac1 activation.…”