Synergic activity of FGFR2 and MEK inhibitors in the treatment of FGFR2-amplified cancers of unknown primary

Patients with cancer of unknown primary (CUP) carry the double burden of an aggressive disease and reduced access to therapies. Experimental models summing up CUP features are pivotal for CUP biology investigation and drug testing. We derived two CUP cell lines (CUP#55 and #96), and corresponding patient-derived xenografts (PDXs), from ascites tumor cells. CUP cell lines and PDXs underwent histological, immune-phenotypical, molecular, and genomic characterization confirming the features of the original tumor. Genetic testing and FISH analysis identified FGFR2 amplification as therapeutic target in tumor tissues and patient-derived models. Drug-screening assays were performed to test the activity of FGFR2 targeting drug BGJ-398 (infigratinib) and the combination treatment with the MEK inhibitor trametinib, which proved to be synergic and exceptionally active, both in vitro and in vivo . This study brings personalized therapy closer to CUP patients and paves the way to future applications of personalized medicine for metastatic patients with adverse prognosis. ### Competing Interest Statement Francesco Gelsomino received personal fees from AstraZeneca and honoraria for advisory board participation from Eli-Lilly. ### Funding Statement Italian Association for Cancer Research (AIRC) IG 2021 ID 25789 project to Ferracin Manuela ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the local ethical committee (Comitato Etico Indipendente dell Azienda Ospedaliero-Universitaria di Bologna, Policlinico S.Orsola Malpighi) with protocol number EM435-2022_130/2016/U/Tess/AOUBo. All subjects provided a written informed consent to the study participation. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors