Systems-level immune profiling in children with solid tumors

<p dir="ltr">Childhood cancer is a leading cause of disease-related death in children, and despite major improvements in survival over the past decades, around 15% of affected children still do not survive. Those who do survive often experience long-term complications related to intensive treatment regimens. New therapies are therefore urgently needed, and immunotherapy, successful in many adult cancers both alone and combined with chemotherapy, offers a promising avenue. However, its success in pediatric solid tumors has been limited, in part because we still lack a detailed understanding of how the developing immune system in children interacts with cancer. The aim of this thesis is therefore to investigate the immune system of children with solid tumors, before and after chemotherapy, in order to pave the way for immunotherapy in pediatric cancer patients.</p><p dir="ltr">The general method used across all studies in this thesis is a systems-level immunomonitoring approach. Blood and tumor samples were collected from children aged 0-18 with solid tumors treated at Karolinska University Hospital. Samples were taken at diagnosis and after initial chemotherapy, and were analyzed for plasma protein levels, circulating immune cells, and tumor- infiltrating immune cells, providing a detailed characterization of each child's immune system.</p><p dir="ltr">Study I analyzed the immune system of 191 children with 34 different solid tumor types at diagnosis. We show that immune differences were largely driven by the child's age and tumor type, with some tumors showing similar immune patterns, suggesting shared biological features. We also found that childhood tumors generally had fewer mutations than adult tumors, and that in Wilms tumor (WT) and neuroblastoma, higher mutation levels were associated with increased CD8+ T cell infiltration. Overall, most pediatric solid tumors showed low T cell infiltration and limited systemic clonal expansion of CD8+ T cells. These findings indicate that spontaneous immune responses against pediatric solid tumors are rare, emphasizing the need for treatments that actively stimulate immunity, such as chemotherapy, which may prime the immune system for subsequent immunotherapy.</p><p dir="ltr">Study II focused on pediatric classical Hodgkin lymphoma (cHL), the most common cancer in adolescents. Although cure rates are high, a subset of patients experiences treatment failure or long-term toxicity, highlighting the need for improved risk stratification. By profiling immune responses in blood samples collected before and after chemotherapy, we identified distinct immune features in cHL compared with other childhood cancers. In particular, elevated plasma levels of CCL17 and MCP-4 distinguished cHL from other lymphomas and solid tumors and were associated with early treatment response. Chemotherapy induced consistent immune changes across patients, while low baseline levels of granzymes identified children at increased risk of neutropenic fever. Together, these findings demonstrate that systems-level immune profiling has the potential to improve diagnostic precision, inform early treatment decisions, and identify patients who require enhanced supportive care in pediatric cHL.</p><p dir="ltr">In study III we investigated how induction chemotherapy reshapes systemic and intratumoral immunity in children with high-risk neuroblastoma (HR-NBL) and WT, two cancers treated with markedly different chemotherapy intensities. Using patient-matched blood and tumor samples collected before and after treatment, we found that chemotherapy induced tumor-specific immune remodeling. Wilms tumors showed pronounced immune-stimulatory changes, whereas HR-NBL exhibited predominantly immunosuppressive patterns, although both cancers shared an increase of Th1-associated plasma proteins. Spatial analyses showed that most tumors were dominated by immune-desert or immune-sparse regions, however, lymphocyte-rich areas emerged after chemotherapy. Wilms tumors also displayed increased PD-L1 expression post- treatment, with PD-L1-enriched regions showing immune cell exclusion. Together, these findings demonstrate how chemotherapy can reshape systemic and local immunity and provide a rationale for personalized chemo- immunotherapy strategies in pediatric solid tumors.</p><p dir="ltr">In conclusion, this thesis demonstrates that systems-level immune profiling is a valuable complement to established molecular and clinical analyses in pediatric oncology. By revealing age- and tumor-specific immune heterogeneity, chemotherapy-induced immune remodeling and clinically relevant biomarkers across multiple cancer types, this work provides a framework for precision immuno-oncology. In line with the overarching aim of improving our understanding of immune responses in childhood cancer, these findings help pave the way for rational development of future immunotherapies and have the potential to guide treatment decisions, improve outcomes, and ultimately enhance survival and quality of life for children with cancer.</p><h3 dir="ltr">List of scientific papers</h3><p dir="ltr">I. Systems-level immunomonitoring in children with solid tumors to enable precision medicine Chen Q, Zhao B, Tan Z, <b>Hedberg G,</b> Wang J, Gonzalez L, Mugabo CH, Johnsson A, Negrini E, Paez LP, Rodriguez L, James A, Chen Y, Mikes J, Bernhardsson AK, Reitzner SM, von Walden F, O'Neill O, Barcenilla H, Wang C, Davis MM, Carlson L-M, Pal N, Blomgren K, Repsilber D, Herold N, Lakshmikanth T, Kogner P, Ljungblad L, Brodin P Cell, 2024, Volume 188, Issue 5, 1425-1440.e11 <a href="https://doi.org/10.1016/j.cell.2024.12.014" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.cell.2024.12.014</a></p><p dir="ltr">II. Systemic immune alterations in pediatric classical Hodgkin lymphoma with CCL17 and MCP-4 as diagnostic and predictive biomarkers <b>Hedberg G,</b> Chen Q, Lakshmikanth T, Herold N, Kogner P, Brodin P, Ljungblad L EJHaem, 2026 Jan 28; Volume 7, issue 1, e70228. <a href="https://doi.org/10.1002/jha2.70228" rel="noreferrer" target="_blank">https://doi.org/10.1002/jha2.70228</a></p><p dir="ltr">III. Effect of induction chemotherapy on the immune system in blood and tumor of children with high-risk neuroblastoma and Wilms tumor <b>Hedberg G,</b> Chen Q, Lakshmikanth T, Wessman S, Shirazi Fard S, Herold N, Ljungblad L, Brodin P, Kogner P [Manuscript]</p>