According to a study published on August 7, 2026, in Volume 17 of Oncotarget, treatment with the multi-kinase inhibitor K252a transiently delayed the growth of SK-ES-1 Ewing sarcoma tumor xenografts in immunodeficient mice. Led by researchers at the Federal University of Rio Grande do Sul and INCT BioOncoPed in Brazil, the team found that the tumor suppression correlated with reduced markers in the Trk, PI3K, and IGF1R signaling pathways.
Targeting Trk Receptors and Multi-Kinase Inhibition in Ewing Sarcoma
Ewing sarcoma is an aggressive cancer affecting children and adolescents in bone and soft tissue. While localized cases respond well to multimodal treatments, metastatic and relapsed forms have poor prognoses. To find new therapeutic targets, researchers focused on the tropomyosin receptor kinase (Trk) family. Encoded by NTRK1, NTRK2, and NTRK3 genes, these receptors regulate cell growth and survival.
Previous work by the group established that TrkA and TrkB are expressed in Ewing sarcoma cells. In this recent study, first author Bruna Almeida dos Santos and corresponding author Caroline Brunetto de Farias tested the non-specific multi-kinase inhibitor K252a on human SK-ES-1 cells grown in mice. When tumors reached 80 to 100 cubic millimeters, the research team administered daily intraperitoneal injections of 0.5 mg/kg of K252a or a vehicle for 18 days.
Did you know? Ewing sarcoma is an aggressive childhood tumor, driving intense scientific interest in identifying novel molecular targets like NTRK genes.
Tumor Xenograft Results and Signaling Pathway Analysis
According to the published findings, K252a treatment significantly slowed tumor growth between days 9 and 15 of the trial. However, the antitumor effect was temporary. By day 18, tumor volumes in the treated cohort returned to sizes comparable to the control group. Researchers noted no significant differences in body weight or serum biochemical markers between the mice.
Tissue analysis revealed that K252a reduced total and phosphorylated levels of TrkA, TrkB, phosphoinositide 3-kinase (PI3K), and insulin-like growth factor 1 receptor (IGF1R). Levels of TrkC remained unchanged. Because K252a targets multiple kinases, the authors cautioned that the tumor delay cannot be assigned to a single pathway. As stated in the study, “treatment with the multi-kinase inhibitor K252a is associated with inhibition of Trks, PI3K, and IGF1R and can transiently delay ES tumor growth.”
Combining Inhibitors and Exploring Patient Survival Datasets
To test whether dual-pathway interference yields stronger results, the team combined K252a with the selective IGF1R inhibitor NVP-ADW742 in cultured SK-ES-1 cells. While each compound caused small reductions in cell viability individually, combining them produced a significantly greater drop in viability.
Additionally, the researchers analyzed overall survival data using two independent gene-expression cohorts. Higher NTRK2 expression linked to shorter overall survival in the Children’s Oncology Group cohort, whereas higher NTRK1 expression associated with longer survival in the EuroEwing cohort. The authors emphasized that these cohort findings remain exploratory until validated in larger patient populations.
Frequently Asked Questions
What is K252a?
K252a is a non-specific multi-kinase inhibitor with activity against Trk receptors, PI3K, and IGF1R signaling pathways.
What did the animal study discover about tumor growth?
According to the Oncotarget study, K252a temporarily delayed Ewing sarcoma tumor growth in mice between days 9 and 15 before tumors caught up to control sizes by day 18.
Are NTRK genes reliable biomarkers for Ewing sarcoma yet?
Who led the research study?
The study was led by first author Bruna Almeida dos Santos and corresponding author Caroline Brunetto de Farias from the Federal University of Rio Grande do Sul and INCT BioOncoPed.