Overestimation of clinical N-staging in microsatellite instable gastric cancers is associated with VEGF-C signaling and CD8+ T-cell dynamics.

[BACKGROUND] Microsatellite instable (MSI) gastric cancers exhibit reduced lymph node (LN) metastasis and improved survival compared to microsatellite stable (MSS) counterparts. However, to our longstanding observation, clinical N-staging (cN) is frequently overestimated in MSI cases. The clinical implications and underlying mechanisms of this discrepancy warrant further investigation.

[MATERIALS AND METHODS] We conducted a comprehensive review of clinicopathological data from a 141 MSI and 1119 MSS gastric cancer patients. Expression of vascular endothelial growth factor-C (VEGF-C) and its receptor VEGFR-3 were assessed using qPCR and immunohistochemistry. High-parameter flow cytometry was employed to analyze subsets of CD8+ T cells within the tumors.

[RESULTS] Multivariate analysis revealed that MSI status was an independent prognostic factor, alongside the LN ratio and AJCC8 pathology staging. MSI gastric cancers exhibited a reduced LN ratio, particularly at advanced T-staging, compared to MSS counterparts, while maintaining an equivalent LN yield. Overestimation of cN by computed tomography preoperatively was frequent in MSI gastric cancers but was more commonly underestimated in MSS counterparts. VEGF-C and VEGFR-3 expression were lower in MSI tumors. MSI gastric cancers showed an increased total number of CD8+ T cells, albeit with a lower proportion of effector memory cells expressing CD45RA (EMRA) and CD8+ CXCR4+ T cells, compared to MSS counterparts.

[CONCLUSION] Frequent overestimation of clinical N-staging in MSI gastric cancers is associated with VEGF-C signaling and CD8+ T-cell dynamics and should be cautiously interpreted, as it might misguide therapeutic options.