RalA ELISA.

This assay used J82 human bladder cancer cells that stably expressed Flag-tagged RalA. The Flag epitope tag greatly increased the sensitivity and dynamic range of the assay compared with using Ral-specific antibodies for detection. Cells were treated with each of the 88 compounds (tested at 50 mM), and then extracts were prepared. The binding of Flag–RalA to recombinant RALBP1 that had been immobilized in 96-well plates was quantified. In this assay, RalA binding reflects Ral’s GTP loading and capacity for effector activation.

Cell lines

Human lung cancer cell lines (H2122, H358)

Preparation method

Soluble in DMSO >10 mM. General tips for obtaining a higher concentration: Please warm the tube at 37 ℃ for 10 minutes and/or shake it in the ultrasonic bath for a while. Stock solution can be stored below -20℃ for several months.

Reaction Conditions

2-4 weeks at 37oC

Applications

BQU57 acts specifically through the GDP-bound form of Ral proteins. Ral-dependent lines H2122 and H358 are sensitive to treatment with BQU57. BQU57 treatment exhibits no further inhibition of colony formation after RAL knockdown.

Animal models

H2122 tumor xenografts (median size, 250 mm3)

Dosage form

Single intraperitoneal injection of BQU57 (10, 20 and 50 mg per kg body weight)

Applications

BQU57 shows a dose-dependent (10, 20 and 50 mg per kg body weight per day) growth inhibition in the mice. Both RalA and RalB were blocked by BQU57.

Other notes

Please test the solubility of all compounds indoor, and the actual solubility may slightly differ with the theoretical value. This is caused by an experimental system error and it is normal.

BQU57 is a derivative of RBC8. It show selectivity for Ral relative to the GTPases Ras and RhoA and inhibit tumour xenograft growth. The binding of BQU57 to RalB–GDP was with a dissociation constant (Kd) of 7.760.6 mM by using isothermal titration calorimetry (ITC). It was similar to the results from surface plasmon resonance (SPR), which had a Kd value of 4.761.5 mM¹.

RBC8 or BQU57 can effectively inhibited the colony formation in soft agar of the Ral-dependent lines H2122 and H358, but not H460 or Calu-6. The IC50 value of RBC8 was 3.5 mM in H2122 cells and 3.4 mM in H358 cells; and the IC50 value of BQU57 was 2.0 mM in H2122 cells and 1.3 mM in H358 cells. RBC8 or BQU57 treatment showed no further inhibition of colony formation after RAL knockdown¹.

RBC8 and BQU57 acted specifically through the GDP-bound form of Ral proteins. RBC8 and BQU57 inhibited both Ral A and Ral B activation in both the H2122 and H358 cell lines by a Ral pull-down assay using RALBP1-bound agarose beads¹.

The inhibition of Ral activity and tumour growth by these compounds were evaluated in human lung cancer xenografts in mice. RBC8 and BQU57 showed good properties in vivo. RBC8 and BQU57 entry into tumour tissue 3 h after dosing, and were detectable in tumour tissue¹. BQU57 (10, 20 and 50mg per kg bodyweight) was intraperitoneal injected into H2122 tumour xenografts, and the activation of Ral in tumour extracts was analysed in RALBP1 pull-down assays. Both RalA and RalB were inhibited by RBC8 and BQU57. But no inhibition of Ras or RhoA activity was happened¹.

References:
1. Yan C, Liu D, Li L et al. Discovery and characterization of small molecules that target the GTPase Ral. Nature. 2014 Nov 20;515(7527):443-7.