SB202190 Predicts BRAF-Activating Mutations in Primary Colorectal Cancer Organoids via Erk1-2 Modulation

by Selleckchem | Jul 09 2023

The p38 inhibitor SB202190 is a necessary component of the medium used for normal colorectal mucosa cultures. Sato et al. suggested that the primary activity of SB202190 may be EGFR signaling stabilization, causing an increased phosphorylation of Erk1-2 sustaining organoid proliferation. However, the growth of some colorectal cancer (CRC)-derived organoid cultures is inhibited by this molecule via an unknown mechanism. We biochemically investigated SB202190 activity on a collection of 25 primary human CRC organoids, evaluating EGFR, Akt and Erk1-2 activation using Western blot. We found that Erk1-2 phosphorylation was induced by SB202190 in 20 organoid cultures and inhibited in 5 organoid cultures. A next-generation sequencing (NGS) analysis revealed that the inhibition of p-Erk1-2 signaling corresponded to the cultures with BRAF mutations (with four different hits, one being undescribed), while p-Erk1-2 induction was apparently unrelated to other mutations involving the EGFR pathway (Her2, KRAS and NRAS). We found that SB202190 mirrored the biochemical activity of the BRAF inhibitor Dabrafenib, known to induce the paradoxical activation of p-Erk1-2 signaling in BRAF wild-type cells. SB202190 was a more effective inhibitor of BRAF-mutated organoid growth in the long term than the specific BRAF inhibitors Dabrafenib and PLX8394. Overall, SB202190 can predict BRAF-activating mutations in patient-derived organoids, as well as allowing for the identification of new BRAF variants, preceding and enforcing NGS data.

Comments:

The study conducted by Sato et al. investigated the activity of the p38 inhibitor SB202190 in colorectal mucosa cultures and its effect on organoid proliferation. They found that SB202190 induced the phosphorylation of Erk1-2, a protein involved in cell signaling and proliferation, in most of the organoid cultures derived from normal colorectal mucosa. However, in some colorectal cancer (CRC)-derived organoid cultures, SB202190 inhibited the phosphorylation of Erk1-2, leading to growth inhibition. The underlying mechanism behind this differential response was not known at the time.

To further investigate this phenomenon, the researchers performed biochemical analyses using Western blotting to evaluate the activation of EGFR, Akt, and Erk1-2 in a collection of 25 primary human CRC organoids treated with SB202190. They observed that SB202190 induced Erk1-2 phosphorylation in 20 organoid cultures, while inhibiting it in 5 organoid cultures.

To understand the genetic basis of this differential response, the researchers performed next-generation sequencing (NGS) analysis on the organoid cultures. They found that the cultures in which SB202190 inhibited p-Erk1-2 signaling were characterized by BRAF mutations. Specifically, they identified four different hits, one of which was previously undescribed. On the other hand, the induction of p-Erk1-2 by SB202190 appeared to be unrelated to mutations involving the EGFR pathway, such as Her2, KRAS, and NRAS.

Further investigation revealed that the activity of SB202190 mirrored that of the BRAF inhibitor Dabrafenib, which is known to induce paradoxical activation of p-Erk1-2 signaling in BRAF wild-type cells. SB202190 was found to be a more effective inhibitor of BRAF-mutated organoid growth in the long term compared to specific BRAF inhibitors like Dabrafenib and PLX8394.

In summary, this study suggests that SB202190 can serve as a predictive tool for identifying BRAF-activating mutations in patient-derived organoids. Additionally, it may aid in the identification of new BRAF variants, complementing and preceding NGS data. The findings shed light on the complex interactions between p38 signaling, EGFR pathway, and BRAF mutations in colorectal cancer organoids, providing insights into potential therapeutic strategies for targeting specific molecular subtypes of CRC.