DKK1 expression associates with tertiary lymphoid structure maturity in non-small cell lung cancer

Tertiary lymphoid structures (TLS) are organized lymphoid aggregates that form outside lymph nodes within the tumor microenvironment. They are linked to better prognosis and stronger antitumor immune responses. However, the key molecular factors that control TLS maturation in non-small cell lung cancer (NSCLC) are still not clear, and their prognostic value is not fully defined. We analyzed TLS-related genes to identify markers linked to prognosis. We used consensus clustering to define molecular subtypes with different survival outcomes. We then built a TLS risk score signature (TLSRS) using LASSO-Cox regression and tested it in independent meta-GEO cohorts. We also examined the association between DKK1 expression and TLS maturation by multiplex immunofluorescence in a clinical cohort. TLSRS separated patients into high- and low-risk groups in the training cohort (n = 503, P < 0.0001) and in the validation cohorts (n = 681, P < 0.0001). The time-dependent AUC values were 0.762, 0.710, and 0.708 at 1, 3, and 5 years. Multivariable analysis showed that TLSRS was an independent prognostic factor in all cohorts. Patients with low TLSRS showed higher immune cell infiltration and higher CCL19 expression, and they also showed stronger immune-related activity across cohorts. In an independent in-house cohort (n = 119), higher DKK1 expression was linked to worse overall survival. DKK1 expression was negatively correlated with the TLS maturity ratio, but it was not correlated with the number of TLS. We developed a prognostic TLSRS that captures key features of the immune microenvironment in NSCLC. We also found that DKK1 may act as a negative regulator of TLS maturation. These results help explain TLS biology and suggest that DKK1 could be a therapeutic target to improve antitumor immunity in NSCLC.