A study by the Molecular Oncology Research Center (CPOM) at the Hospital de Amor in Barretos, Brazil, has uncovered unique immune signatures in pediatric germ cell tumors (GCTs) that could pave the way for more targeted and less toxic therapies. The research, published in Frontiers in Immunology, analyzed the expression of around 800 immune-related genes and characterized the types and behavior of immune cells in different GCT subtypes. 0
Germ cell tumors, which arise from primordial germ cells, can occur in the ovaries, testes, central nervous system, or retroperitoneum and account for only about three percent of all tumors in children. Due to their rarity and heterogeneity, they are difficult to study. Standard treatment includes surgical removal followed by platinum-based chemotherapy, which, however, is variably effective depending on the subtype and causes long-term side effects in children.
The researchers investigated the tumor's immune microenvironment, i.e., the interaction between the patient's immune system and the tumor cells. Different histotypes showed distinct differences: Ovarian dysgerminomas exhibited an immunoactive environment, with high proportions of cytotoxic CD8+ T cells and increased expression of immune checkpoint molecules such as CTLA4, TIGIT, and IDO1. These molecules inhibit the immune response and are suitable targets for inhibitors that could release antitumor immunity. Such tumors are considered less aggressive and well-responsive to therapy, which is explained by the active defense mechanisms.
In contrast, yolk sac tumors (YSTs) presented an immunosuppressive profile: T cells recognized the tumor but could not trigger an effective response. High expression of CD24 and PVR, associated with immune evasion and chemotherapy resistance, explains the aggressiveness of this subtype. Similarly, embryonal carcinomas showed increased CD24 levels. Blocking CD24 could enhance the efficacy of cisplatin, a standard chemotherapeutic agent, and sensitize resistant cases. PVR, particularly prominent in YSTs, promotes the suppression of natural killer cells and correlates with poorer prognoses in other cancer types.
A comparison with adult GCT datasets revealed age-specific differences: molecules such as IDO1 and CD24 were elevated in both groups, while CTLA4 and PVR varied. This underscores the need for pediatric-adapted therapeutic approaches to enable personalized, more effective, and less harmful treatments.
The results lay the groundwork for biomarker-based diagnostics and subtype-specific protocols. Next steps include validation in larger multicenter studies and clinical trials for immunotherapies against CD24, CTLA4, IDO1, and PVR. The findings could advance immunotherapy in pediatrics and contribute to a more accurate characterization of aggressive tumors.
