Poster Presentation 37th Lorne Cancer Conference 2025

Phosphoproteomic analysis identifies casein kinase II and MAPK signaling inhibition as a therapeutic strategy for metastatic colorectal cancer (#202)

Mattia Marinucci 1 2 , Gina Faye Boot 1 2 , Elenia Toccafondi 1 2 , Daniela Liberati 1 2 , Mairene Coto Llerena 1 2 , Lara Zaidi 2 , Cinzia Esposito 1 2 , Andrej Benjak 3 , Luigi Maria Terracciano 4 5 , Raoul A. Droser 6 , Savas D. Soysal 7 , Otto Kollmar 8 , Charlotte K. Y. Ng 3 5 , Salvatore Piscuoglio 1 5
  1. Department of Biomedicine, Visceral Surgery and Precision Medicine Research Laboratory, Department of Biomedicine, University of Basel, Basel, Basel-Stadt, Switzerland
  2. Institute of Medical Genetics and Pathology, University Hospital Basel, University of Basel, Basel, Basel-Stadt, Switzerland
  3. Department for BioMedical Research (DBMR), Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
  4. Department of Biomedical Science, Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090 Pieve Emanuele, MIlan, Italy
  5. IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089 Rozzano, MIlan, Italy
  6. Faculty of Medicine, University of Basel, Klingelbergstrasse 61, 4056, Basel, Basel-Stadt, Switzerland
  7. Department of Visceral Surgery, Clarunis, Department of Visceral Surgery, University Centre for Gastrointestinal and Liver Diseases, St. Clara Hospital and University Hospital Basel, Basel, Basel-Stadt, Switzerland
  8. Kantonsspital Baselland, 4410 Liestal, Switzerland, Liestal, Baselland, Switzerland

Aberrant regulation of proteomic networks is implicated in cancer development and progression and the understanding of these processes opens new opportunities for therapeutic interventions. In this study, we performed phosphoproteomic analysis and ex-vivo drug testing on a cohort of ten metastatic colorectal cancer (mCRC) tissues and matched patient-derived organoids (PDO) to identify new potential druggable biomarkers. Besides the upregulation of well-known tumor-sustaining pathways, such as MYC and mTORC1 signaling, our data highlighted increased casein kinase II (CKII) activity, an important regulator of cell cycle progression. 

Ex-vivo drug treatment on mCRC PDOs demonstrated that silmitasertib-mediated CKII inhibition exerted anti-tumoral activity and induced PARP cleavage and DNA damage. On the other hand, no cytotoxic effects were noticed on PDOs derived from normal colon tissues. Our phosphoproteomics dataset also revealed that the heterogeneous sensitivity of PDOs to clinically relevant concentrations of silmitasertib was correlated with increased EGFR and mTORC1 signaling activities. Accordingly, molecular analysis confirmed that failure to reduce CKII activity and PDO viability correlated with sustained ERK1/2 and S6 signaling, suggesting potential resistance mechanisms.

Complementing CKII blockade with targeted MAPK or mTORC1 signaling inhibition, we observed additive/synergistic interactions that resulted in an enhanced antitumor activity. In particular, the combination between silmitasertib and trametinib, a selective inhibitor of MEK1/2, induced a simultaneous reduction of mTORC1, MAPK and CKII signaling compared to either drug alone. KRAS-mutant PDOs showed the greatest benefit from the combinatorial treatment. Importantly, no major cytotoxic effects were observed in normal colon PDOs. Additionally, the dual therapy significantly reduced active β-catenin levels and decreased the pool of CD44/CD133 double-positive cancer stem cells, which are critical in therapy resistance.

Taken together, our findings highlight the potential of phosphoproteomic analysis to strategically inform and advance cancer therapy and propose a promising new therapeutic opportunity for mCRC patients, warranting further preclinical and clinical investigations.