Kita-Kyushu Lung Cancer antigen-1 (KK-LC-1) is a cancer-testis antigen described as a potential target for adoptive immunotherapy using T-cell receptor (TCR) gene-engineered T cells. The study aimed to assess the utility of immunohistochemical detection of KK-LC-1 in resected lung adenocarcinoma specimens and to examine associations between KK-LC-1 positivity, pathological features, and clinical outcomes.
The investigators retrospectively reviewed medical records of 110 patients who underwent curative resection for lung adenocarcinoma. Immunohistochemical staining for KK-LC-1 employed the original monoclonal antibody Kmab34B3. Overall survival (OS) and recurrence-free survival (RFS) were compared by KK-LC-1 status and by EGFR mutation status where available. Cox regression analyses were used to identify prognostic factors. The abstract provides these core methods; additional methodological details such as scoring criteria for IHC positivity, follow-up duration, or extent of covariates entered into multivariate models were not reported in the abstract.
Among the 110 resected lung adenocarcinoma cases, 39 patients (35%) were immunohistochemically positive for KK-LC-1. KK-LC-1 positivity correlated significantly with several adverse pathological features: larger invasive tumor size, more advanced pathological stage, presence of lymphatic invasion, vascular invasion, and lymph node metastasis. These associations indicate that KK-LC-1–positive tumors were enriched for pathological high-grade characteristics in this cohort.
The 5-year overall survival (OS) did not reach a statistically significant difference between KK-LC-1–positive and KK-LC-1–negative patients (79.8% vs. 94.0%, p = 0.07). In contrast, recurrence-free survival (RFS) was significantly poorer among KK-LC-1–positive patients; 5-year RFS was 67.7% in the KK-LC-1–positive group versus 85.5% in the negative group (p = 0.020). These findings suggest KK-LC-1 positivity is associated with a higher risk of postoperative recurrence, although the effect on OS in the full cohort was not statistically significant in the reported analysis.
On multivariate Cox regression analysis reported in the abstract, KK-LC-1 positivity was not identified as an independent predictor of RFS (hazard ratio = 1.230, p = 0.63). The abstract does not list the other variables included in the multivariate model or their coefficients and significance levels; therefore, details about which covariates accounted for RFS risk and potential confounding factors are not available in the source summary.
EGFR mutation status was available for 89 patients; 45 of these (50.5%) harbored EGFR mutations. In the EGFR-mutant subgroup, KK-LC-1 positivity was associated with significantly worse OS: 5-year OS was 77.0% for KK-LC-1–positive patients versus 100% for KK-LC-1–negative patients (p = 0.026). For RFS in the EGFR-mutant subgroup, KK-LC-1–positive patients had a lower 5-year RFS (66.6% vs. 88.4%), but this difference did not meet statistical significance (p = 0.055). The abstract does not report whether interaction testing was performed or whether these subgroup results persisted after adjustment for other prognostic factors.
The authors conclude that immunohistochemical KK-LC-1 positivity is significantly associated with pathological high-grade features and with poorer RFS in patients undergoing resection for lung adenocarcinoma. Although KK-LC-1 was not an independent predictor of RFS in the reported multivariate analysis, its association with aggressive pathological characteristics and with worse outcomes in the EGFR-mutant subgroup supports the concept that KK-LC-1 may have prognostic relevance.
The study suggests that KK-LC-1–positive patients could be considered candidate populations for TCR reconstitution therapy targeting KK-LC-1. The source abstract does not provide data on response to TCR therapy, clinical trials, or validation of therapeutic efficacy; such therapeutic implications are presented as a rationale rather than demonstrated outcomes.
Limitations noted by omission: the abstract does not provide details on IHC scoring criteria, antibody validation beyond naming Kmab34B3, follow-up duration, the full list of variables in multivariate models, or external validation. These details would be necessary to assess reproducibility, independent prognostic value, and clinical applicability of KK-LC-1 testing as a biomarker.
Overall, the reported results from 110 patients indicate that KK-LC-1 expression marks tumors with high-grade pathological features and correlates with increased recurrence risk, and it may identify a subgroup—including some EGFR-mutant patients—who warrant further evaluation as candidates for KK-LC-1–directed immunotherapy.