Sialosyl-Tn, a
mucin-associated
carbohydrate antigen, is not expressed by normal mucus-producing cells of the stomach but becomes expressed in metaplastic, pre-malignant and malignant gastric tissues. Reports vary as to the frequency of STn expression and its prognostic role in
gastric cancer. To determine whether these differences might be due to inter-country variations in
gastric cancer biology, we immunohistochemically analyzed 340
gastric cancers from 2 countries at high-risk (high incidence) for
gastric cancer (Japan and Chile), one with intermediate risk (Brazil) and one with low-risk (USA). Expression of STn was correlated with clinico-pathological features of the
tumors and with
cancer-related survival. Regardless of country, the frequency of STn-positive
tumors was lower in non-invasive ("early") than in advanced
gastric cancer. Consequently, high-risk countries where early
gastric cancer is more common demonstrated a lower overall frequency of STn-positive
tumors. In all 4 countries, STn expression directly correlated with depth of invasion, stage, and lymph node involvement. In addition, STn expression correlated with a poor prognosis in all 4 countries, but the effect of STn on survival was not independent of
tumor stage. Our findings indicate the need to consider the inherent
gastric cancer risk and prevalence of early
gastric cancer in the study population when reporting frequency of STn expression in
gastric cancer. Regardless of country, however, STn expression is a marker of
gastric cancer progression suggesting that
cancer-associated
mucins play a role in the malignant behavior of this
tumor.