Gastric cancer (GC) is one of the most common cancer types worldwide. Adenocarcinoma is the most frequent type of tumor in GC. Southeast Mexico has the highest rate of comorbidities in all of Mexico. In clinical practice, diagnostic and prognostic biomarkers are scarce; hence, besides the great proportion of the underdiagnosed population, some affected subjects do not receive the correct treatment. The Human Epithelial Growth Factor Receptor 2 (HER2) is related to the invasion and progression of tumors, and its expression in GC is around 7-34%. Ki-67 is associated with cell proliferation and poor prognosis in patients with GC; Ki-67 is considered an excellent predictor of GC recurrence. Finally, the expression around 77% of Sialyl-Tn (sTn) is also considered a marker of low survival and high mortality in GC. Thus, the present study aims to determine the expression of HER2, Ki-67, and sTn expression as biomarkers of poor prognosis in patients with gastric adenocarcinoma who attended a reference hospital in Southeast Mexico.

221 patients with gastric adenocarcinoma were identified, but only 30 were selected after applying inclusion criteria. All selected patients had endoscopic or gastrectomy biopsies, showing 16 intestinal and 14 diffuse adenocarcinoma subtypes. Four slides with tumor tissue were obtained from each patient. An immunohistochemistry assay was performed to assess the expression of HER2, Ki-67, and sTn, and the staining of Hematoxylin & Eosin. One specialized pathologist determined the identification and the degree of differentiation.

In general, overexpression of the HER2 receptor in patients with gastric adenocarcinoma was 56.7%. Likewise, HER2 showed overexpression in the intestinal subtype (62.5%), even higher than diffuse adenocarcinoma. Ki-67 expression was predominantly expressed in the diffuse subtype (62.5%). Interestingly, all diffuse adenocarcinomas with Ki-67 expression showed poor differentiation in the tissue, most of them with advanced tumor stage and high phenotypic heterogeneity. Otherwise, sTn showed an expression of 73.3% in patients with gastric adenocarcinoma, and 72.7% of them had died. We observed that patients with sTn positive in diffuse adenocarcinoma increase 1.2-fold the risk of dying. Co-expression of three biomarkers increases 2.2-fold the risk of mortality. The expression of biomarkers was independent of the tumor stage.

The presence of three biomarkers in gastric adenocarcinoma indicated a poor prognosis. HER2 was overexpressed in intestinal adenocarcinoma. Ki-67 and sTn were predominantly expressed in diffuse adenocarcinoma poorly differentiated. Therefore, our findings suggest that the presence of sTn positive might be considered a mortality biomarker for patients with gastric adenocarcinoma in Southeast Mexico.