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Epithelial-mesenchymal transition (EMT) is the phenotypic transition of epithelial cells to mesenchymal cells characterized by loss of epithelial markers, loss of intercellular adherence and acquirement of mesenchymal cell markers and increased locomotive ability. EMT is widely considered to be a gene regulated process necessary for cancer metastasis. Yet it is a highly controversial issue. We here propose that EMT is an environmentally induced cell behavior. It is the mimicry of their living environment. It is a survival strategy, a way of immune escape. We also propose here that the epithelial cell markers may functionally act as tumor antigens since in the mesenchymal surroundings there are no other structures bearing the same antigens as epithelial cells.

Aim: To investigate the relationship of solitary lymph node metastasis (SLNM) and age with patient survival in gastric cancer (GC)., Methods: The medical records databases of China's Beijing Cancer Hospital at the Peking University School of Oncology and Shanghai Tenth People's Hospital affiliated to Tongji University were searched retrospectively to identify patients with histologically proven GC and SLNM who underwent surgical resection between October 2003 and December 2012. Patients with distant metastasis or gastric stump carcinoma following resection for benign disease were excluded from the analysis. In total, 936 patients with GC + SLNM were selected for analysis and the recorded parameters of clinicopathological disease and follow-up (range: 13-2925 d) were collected. The Kaplan-Meier method was used to stratify patients by age (≤ 50 years-old, n = 198; 50-64 years-old, n = 321; ≥ 65 years-old, n = 446) and by metastatic lymph node ratio [MLR < 0.04 (1/25), n = 180; 0.04-0.06 (1/25-1/15), n = 687; ≥ 0.06 (1/15), n = 98] for 5-year survival analysis. The significance of intergroup differences between the survival curves was assessed by a log-rank test., Results: The 5-year survival rate of the entire GC + SLNM patient population was 49.9%. Stratification analysis showed significant differences in survival time (post-operative days) according to age: ≤ 50 years-old: 950.7 ± 79.0 vs 50-64 years-old: 1697.8 ± 65.9 vs ≥ 65 years-old: 1996.2 ± 57.6, all P < 0.05. In addition, younger age (≤ 50 years-old) correlated significantly with mean survival time (r = 0.367, P < 0.001). Stratification analysis also indicated an inverse relationship between increasing MLR and shorter survival time: < 0.04: 52.8% and 0.04-0.06: 51.1% vs ≥ 0.06: 40.5%, P < 0.05. The patients with the shortest survival times and rates were younger and had a high MLR (≥ 0.06): ≤ 50 years-old: 496.4 ± 133.0 and 0.0% vs 50-65 years-old: 1180.9 ± 201.8 and 21.4% vs ≥ 65 years-old: 1538.4 ± 72.4 and 37.3%, all P < 0.05. The same significant trend in shorter survival times and rates for younger patients was seen with the mid-range MLR group (0.04-0.06), but the difference between the two older groups was not significant. No significant differences were found between the age groups of patients with MLR < 0.04. Assessment of clinicopathological parameters identified age group, Borrmann type, histological type and tumor depth as the most important predictors of the survival rates and times observed for this study population., Conclusion: GC patients below 51 years of age with MLR of SLNM above 0.06 have shorter life expectancy than their older counterparts.