Preclinical Efficacy and Toxicology Evaluation of RAC1 Inhibitor 1A-116 in Human Glioblastoma Models.

Malignant gliomas are the most common primary central nervous system tumor in adults. Despite current therapeutics, these tumors are associated with poor prognosis and a median survival of 16 to 19 months. This highlights the need for innovative treatments for this incurable disease. Rac1 has long been associated with tumor progression and plays a key role in glioma's infiltrative and invasive nature. The aim of this study is to evaluate the 1A-116 molecule, a Rac1 inhibitor, as targeted therapy for this aggressive disease. We found that targeting Rac1 inhibits cell proliferation and cell cycle progression using different in vitro human glioblastoma models. Additionally, we evaluated 1A-116 in vivo, showing a favorable toxicological profile. Using in silico tools, 1A-116 is also predicted to penetrate the blood-brain barrier and present a favorable metabolic fate. In line with these results, 1A-116 i.p daily treatment resulted in a dose-dependent antitumor effect in an orthotopic IDH-wt glioma model. Altogether, our study provides a strong potential for clinical translation of 1A-116 as a signal transduction-based precision therapy for glioma and also increases the evidence of Rac1 as a key molecular target.

In silico repurposing the Rac1 inhibitor NSC23766 for treating PTTG1-high expressing clear cell renal carcinoma.

The pituitary tumor-transforming gene 1 (PTTG1), also known as Securin, is considered an oncogene. This study aimed to investigate the role of PTTG1 in clear cell renal cell carcinoma (ccRCC) using in silico bioinformatics approaches. A pan-cancer analysis using The Cancer Genome Atlas (TCGA) data indicated that among all cancer types copy number amplification of PTTG1 gene was most frequently found in ccRCC. However, amplification of PTTG1 gene copy number did not correlate with the increase of mRNA level in ccRCC, and did not predict the patients' overall survival. Instead, ccRCC was correlated with overexpression of PTTG1 mRNA, and its expression level was stage-dependent increased in cancer patients. An outlier analysis using the Oncomine database suggested that PTTG1 mRNA expression served as a good biomarker for ccRCC. Pathway analysis for upregulated genes enriched in PTTG1-high expressing ccRCC patients found that PTTG1 overexpression was associated with mitotic defects. Mining drug sensitivity data using the Cancer Therapeutics Response Portal (CTRP) discovered that PTTG1-high expressing ccRCC cell lines were susceptible to a Rac1 (Ras-related C3 botulinum toxin substrate 1) inhibitor NSC23766. Therefore, this study provides an in silico insight into the role of PTTG1 in ccRCC, and repurposes the Rac1 inhibitor NSC23766 for treating PTTG1-high expressing ccRCC.

Design, synthesis and biological evaluation of new carbazole derivatives as anti-cancer and anti-migratory agents.

Based on the efficacy of EHop-016 as an inhibitor of migration and Rac1 activation, a new series of carbazole derivatives has been synthesized. Cytotoxic and anti-migratory effects of these compounds were evaluated in MCF-7 and MDA-MB-231 breast cancer cell lines. Preliminary investigations of their anticancer activity demonstrated that several compounds have moderate antiproliferative effects on cancer cell lines with GI50 values in the range of 13-50 µM. Furthermore, compounds 3b and 11b inhibit migration activity of metastatic cell line MDA-MB-231 by 32% and 34%, respectively. Compound 11b was shown to inhibit activation of the Rho GTPase Rac1 by 55% at 250 nM in both MDA-MB-231 and MDA-MB-435 cell lines. Compared with the IC50 of Rac1 inhibition by lead compound EHop-016 of 1.1 µM, compound 11b demonstrates 4X improved in vitro efficacy.

Pharmacological Rescue of Hippocampal Fear Learning Deficits in Fragile X Syndrome.

Fragile X Syndrome (FXS) is the leading cause of autism spectrum disorder and intellectual disability and results from loss of Fragile X mental retardation protein (FMRP). In neurons, FMRP controls the translation of synaptic plasticity proteins that are implicated in learning and memory. FMRP also regulates development- and experience-dependent actin cytoskeleton remodeling within dendritic spines through the small Rho GTPase Rac1. Modulation of Rac1 activity is critical during synaptic plasticity as well as learning and memory. We have previously shown that FXS mouse models exhibit learning and memory deficits as well as hyperactive Rac1 in the hippocampus. To determine whether pharmacological inhibition of Rac1 in FXS improves cognitive impairment, FXS mice were treated with the specific Rac1 inhibitor NSC23766, followed by fear conditioning. Whereas non-cognitive functions were unaffected, hippocampus-related memory improved in FXS mice treated with the Rac1 inhibitor. Furthermore, long-term potentiation in hippocampal slices from FXS mice was increased after incubation with the Rac1 inhibitor. Together, these observations indicate that modulation of Rac1 may provide a novel therapeutic target in the treatment of cognitive impairment in FXS.

Rhein inhibits the movement and invasion of human ovarian carcinoma cells through Rac1/LIMK1/cofilin signaling pathway / 中国药理学通报

Aim To investigate the effect of Rhein on the movement and invasiveness of human ovarian carci-noma cells with directional high lymphatic metastasis SKOV3-PM4 cells and explore the role of Rac1/LIMK1/cofilin signaling pathway. Methods Migration assay and invasion assay were used to observe the effect of Rhein on the metastatic and invasive ability of SK-OV3-PM4 cells in vitro. The effect of Rhein on the morphology and cytoskeleton ultrastructure of ovarian cancer cells was observed by laser scanning confocal microscope and scanning electron microscope. The protein expression level of Rac1,LIMK1,PAK1 and co-filin were detected by Western blot, respectively. Re-sults Rhein inhibited the abilities of cell invasion and migration of SKOV3-PM4 cells,and the inhibitory rate increased along with the increase of the concentration and treatment duration. After treated with 8. 80 μmol· L-1 ,17. 60 μmol · L-1 , 26. 40 μmol · L-1 of Rhein for 24 h,the abilities of migration and invasion of SK-OV3-PM4 cells were inhibited ( P <0. 05 ); the mor-phology and cytoskeleton ultrastructure of SKOV3-PM4 cells were changed, cellular pseudopod reduced, cell microfilament fractured and its distribution disordered, plasma membrane was uneven and cell gap widened . After treatment of Rhein and Rac1 inhibitor , Rac1 protein expression and the expression of P-LIMK1 , P-PAK1 and P-cofilin notably decreased in a dose-de-pendent manner compared with the control group ( P<0. 05 ) . After Rhein and Rhein plus Rac1 inhibitor treatment ,P-LIMK1, P-cofilin, P-PAK1 protein levels of SKOV3-PM4 cells significantly decreased compared with the control group , and the group of Rac1 inhibi-tor plus Rhein treatment, the phosphorylated protein decreased more significantly ( P <0. 05 ) . After Rac1 activator plus Rhein treatment, phosphorylated protein expression of P-LIMK1 ,P-PAK1 and P-cofilin upregu-lated significantly ( P <0. 05 ) . Conclusions Rhein may be a potential inhibitor of Rac1 and can inhibit the migrating and invasive capabilities of directional high lymphatic metastasis SKOV3-PM4 cells through down-regulating the phosphorylation of Rac1/LIMK1 /cofilin pathway associated protein.

Akt and Rac1 signaling are jointly required for insulin-stimulated glucose uptake in skeletal muscle and downregulated in insulin resistance.

Skeletal muscle plays a major role in regulating whole body glucose metabolism. Akt and Rac1 are important regulators of insulin-stimulated glucose uptake in skeletal muscle. However the relative role of each pathway and how they interact are not understood. Here we delineate how Akt and Rac1 pathways signal to increase glucose transport independently of each other and are simultaneously downregulated in insulin resistant muscle. Pharmacological inhibition of Rac1 and Akt signaling was used to determine the contribution of each pathway to insulin-stimulated glucose uptake in mouse muscles. The actin filament-depolymerizing agent LatrunculinB was combined with pharmacological inhibition of Rac1 or Akt, to examine whether either pathway mediates its effect via the actin cytoskeleton. Akt and Rac1 signaling were investigated under each condition, as well as upon Akt2 knockout and in ob/ob mice, to uncover whether Akt and Rac1 signaling are independent and whether they are affected by genetically-induced insulin resistance. While individual inhibition of Rac1 or Akt partially decreased insulin-stimulated glucose transport by ~40% and ~60%, respectively, their simultaneous inhibition completely blocked insulin-stimulated glucose transport. LatrunculinB plus Akt inhibition blocked insulin-stimulated glucose uptake, while LatrunculinB had no additive effect on Rac1 inhibition. In muscles from severely insulin-resistant ob/ob mice, Rac1 and Akt signaling were severely dysregulated and the increment in response to insulin reduced by 100% and 90%, respectively. These findings suggest that Rac1 and Akt regulate insulin-stimulated glucose uptake via distinct parallel pathways, and that insulin-induced Rac1 and Akt signaling are both dysfunctional in insulin resistant muscle. There may thus be multiple treatment targets for improving insulin sensitivity in muscle.