Gastric cancer (GC) is the second leading cause of cancer-associated mortality 
worldwide. In advanced and metastatic GC, conventional chemotherapy results in 
limited efficacy and the average survival rate is currently approximately 10 
months. Dysregulated activation of numerous genes, including zinc finger, 
DHHC-type containing 14; caspase-associated recruitment domain-containing 
protein; and Ras association domain family member 10, have been implicated in 
GC. The tumor suppressor function of lactotransferrin (LTF) has been reported in 
a variety of tumors, including GC, nasopharyngeal carcinoma (NPC) and prostate 
cancer. However, the mechanism of the tumor suppressor function of LTF in GC 
remains unclear. In the present study, the expression levels of LTF in patient 
GC tissue samples were investigated using reverse transcription-quantitative 
polymerase chain reaction, and it was demonstrated that the LTF mRNA expression 
level in GC tissue samples was reduced by ~20-fold compared with the adjacent 
non-cancerous tissues (t=4.56, P<0.01). A similar trend in LTF protein 
expression was observed by western blot analysis. Furthermore, the present study 
demonstrated that the mitogen-activated protein kinase (MAPK) signaling pathway 
intermediates p38, c-Jun N-terminal kinase (JNK) and c-Jun were highly expressed 
in GC tissue samples, and indicated that LTF downregulation may be associated 
with the dysregulation of the MAPK signaling pathway in GC tissues. In addition, 
the present study indicated that LTF overexpression reduced the expression of 
p38, JNK2 and c-Jun in the GC cell line, SGC7901. The present study demonstrates 
that LTF expression is downregulated in GC tissues and that LTF may serve an 
important role in the dysregulation of the MAPK signaling pathway.