Finding effective therapies against cancers driven by mutant and/or overexpressed hyperactive G-proteins remains an area of active research. Polyisoprenylated cysteinyl amide inhibitors (PCAIs) are agents that mimic the essential posttranslational modifications of G-proteins. It is hypothesized that PCAIs work as anticancer agents by disrupting polyisoprenylation-dependent functional interactions of the G-Proteins. This study tested this hypothesis by determining the effect of the PCAIs on the levels of RAS and related monomeric G-proteins. Following 48 h exposure, we found significant decreases in the levels of KRAS, RHOA, RAC1, and CDC42 ranging within 20-66% after NSL-YHJ-2-27 (5 μM) treatment in all four cell lines tested, A549, NCI-H1299, MDA-MB-231, and MDA-MB-468. However, no significant difference was observed on the G-protein, RAB5A. Interestingly, 38 and 44% decreases in the levels of the farnesylated and acylated NRAS were observed in the two breast cancer cell lines, MDA-MB-231, and MDA-MB-468, respectively, while HRAS levels showed a 36% decrease only in MDA-MB-468 cells. Moreover, after PCAIs treatment, migration, and invasion of A549 cells were inhibited by 72 and 70%, respectively while the levels of vinculin and fascin dropped by 33 and 43%, respectively. These findings implicate the potential role of PCAIs as anticancer agents through their direct interaction with monomeric G-proteins.