Leucin-rich repeat kinase 2 (LRRK2) plays an important role in the onset of sporadic as well as familial Parkinson’s disease. Pathogenic gain-of-function mutations of LRRK2 are associated with aberrant LRRK2 hyperactivity which results in neurotoxicity and protein aggregation caused by dysfunctional autophagy and vesicle trafficking. Thus, the development of LRRK2 inhibitors represents a promising strategy for the treatment of Parkinson’s disease. Interestingly LRRK2 mutations have also been reported to increase the risk for the onset of different types of cancer (e.g. breast, thyroid, lung). Several studies suggest that LRRK2 is involved in the regulation of different cancer-related pathways (e.g. ATM-p53-p21-pathway, JNK pathway). Deregulation of LRRK2 activity caused by mutations has been shown to interfere with these pathways thereby increasing the risk to develop certain types of cancer. Since anti-cancer treatments mostly target the same pathways, we hypothesized that LRRK2 inhibitors may affect anti-cancer treatments in specific cancer cell types. In this study we report on the analyses of various inhibitors (e.g. MLi-2 and PF-06447475) on LRRK2 autophosphorylation at S935 in a cellular phosphorylation assay using the non-small cell lung cancer cell line A549 in comparison to biochemical LRRK2 activity assays. Furthermore, we compare the direct LRRK2 inhibitor effect on the proliferation of 140 cell lines, as well as their potential combinatorial impact on the potency of chemotherapeutic agents (e.g. Adriamycin). The observed effects can help to understand the implications of pharmaceutical LRRK2 inhibition in the treatment of both Parkinson’s disease and cancer. Citation Format: Franziska Fimm-Todt, Joachim Lauterwasser, Eva-Maria Egenter, Christian Weber, Daniel Feger, Katharina Schaich, Sarah Ulrich, Oliver Siedentopf, Frank Totzke, Michael Kubbutat, Jan Erik Ehlert. Cytotoxic effects of LRRK2 inhibitors in combined treatment with chemotherapeutic agents on a large panel of cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4072.

The proto-oncogene KRas is a well-described small GTPase that functions as a molecular switch for major physiological signaling pathways involved in cell proliferation, differentiation and survival. It has been shown that activating mutations in KRas are among the most common oncogenic drivers of tumorigenesis. Missense mutations of KRas result in constitutive activation due to impaired hydrolysis of GTP which enhances tumor-promoting downstream signaling pathways. Most KRas mutations are located in exon 2 or 3 including the most frequently changed glycine 12 which is present in most pancreatic cancers as well as in colorectal cancers and lung adenocarcinomas. Although direct inhibition of KRas is challenging due to its small size, smooth surface and limited druggable pockets on its surface, first promising drug candidates for selected KRas mutants have been developed in recent years (e.g. Sotorasib, MRTX1133, BI-2852). It was the aim of this study to characterize the selective inhibitory effects of KRas inhibitors in a panel of cancer cell lines harboring different KRas mutations like G12C, G12V or G12D. So, we applied different cellular techniques including phosphorylation assays as well as 2D proliferation and 3D spheroid assays to screen KRas inhibitors for their effect on distinct KRas mutants. Firstly, inhibitors were tested in a cellular assay monitoring phosphorylation of the downstream target ERK at residues Thr202/Tyr204. Analysis applying the cellular pERK AlphaLisa assay showed a high selectivity of several inhibitors for specific KRas mutants, while RAF and MEK inhibitors showed no significant selectivity in the panel of cancer cell lines tested here. Next, KRas inhibitors were tested in a cellular 2D proliferation and a 3D spheroid assay to determine the inhibitory effect on cell growth in both settings. In line with published data, for some inhibitors we could observe a high selectivity for a specific KRas mutant which was even more pronounced in the 3D format as compared to the 2D setup. Most likely due to the fact that 3D growth assays mimic physiological conditions more closely than 2D settings. Interestingly, in the 2D and 3D assays we could not find such a clear inhibitory effect of the MEK and RAF inhibitors as compared to the cellular pERK assay. These results indicate that the described cellular pERK AlphaLisa assay established for selected cancer cell lines could be a useful tool to screen newly developed KRas inhibitors for their selective inhibition of specific KRas mutants. Additionally, the application of not only 2D proliferation but also 3D growth studies can further characterize the inhibitory potential of these KRas inhibitors. Citation Format: Franziska Fimm-Todt, Ezgi Dikici, Katharina Schaich, Oliver Siedentopf, Joachim Lauterwasser, Daniel Feger, Jan Erik Ehlert. Characterization of the selective inhibitory effect of KRas inhibitors in different cellular assay formats [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 549.