The Pan-Cancer Analysis Uncovers the Prognostic and Immunotherapeutic Significance of CD19 as an Immune Marker in Tumor.

Background: The specific cytotoxic effects of anti-CD19 chimeric antigen receptor (CAR) T-cell therapy have led to impressive outcomes in individuals previously treated for B-cell malignancies. However, the specific biological role of CD19(+) target cells, which exert antitumor immunity against some solid tumors, remains to be elucidated.

Methods: We collected information regarding the level of CD19 mRNA and protein expression from various databases including The Cancer Genome Atlas (TCGA), Tumor Immune Estimation Resource (TIMER), Genotype-Tissue Expression (GTEx), and Human Protein Atlas (HPA) for both tumor and normal samples. To evaluate the patient's prognosis according to CD19 expression, a Kaplan-Meier (KM) analysis and univariate Cox regression were performed. Furthermore, using the Estimation of Stromal and Immune Cells in Malignant Tumor Tissues Using the Expression Data (ESTIMATE) algorithm, we estimated the ratio of immune cells infiltrating malignant tumor tissues. Afterward, the GSCALite repository was employed to evaluate the vulnerability of tumors expressing CD19 to drugs used in chemotherapy. To validate the results in clinical samples of certain cancer types, immunohistochemistry was then performed.

Results: Most tumor types exhibited CD19 expression differently, apart from colon adenocarcinoma (COAD). The early diagnostic value of CD19 has been demonstrated in 9 different tumor types, and the overexpression of CD19 has the potential to extend the survival duration of patients. Multiple tumors showed a positive correlation between CD19 expression and tumor mutation burden (TMB), microsatellite instability (MSI), and ESTIMATE score. Furthermore, a direct association was discovered between the expression of CD19 and the infiltration of immune cells, particularly in cases of breast invasive carcinoma (BRCA). Moreover, CD19 is highly sensitive to a variety of chemotherapy drugs.

Conclusion: The study reveals the potential of CD19 as both a predictive biomarker and a target for different cancer immunotherapies.