The lymphangiogenic factor SOX 18: a key indicator to stage gastric tumor progression.

SOX group F genes are important regulators of angiogenesis and lymphangiogenesis. The aim of the present study was to examine the relationships between Sox group F expression and clinicopathological factors in gastric cancer. Three hundred and fifteen gastric cancer tissues and the corresponding normal gastric tissue were obtained from the tumor bank at the National Cancer Center, Korea. SOX group F mRNA levels in these tissues were evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). The serum levels of SOX 18 proteins in 219 gastric cancer patients and in 30 healthy volunteers were also measured by enzyme-linked immunosorbent assay. Furthermore, immunohistochemistry (IHC) was performed on 679 gastric cancer tissues and the clinicopathological characteristics, as well as the survival rates of SOX 18 positive and negative gastric cancers were compared. RT-PCR showed that SOX group F mRNA was increased in the gastric cancer tissues compared to the normal gastric tissues (p < 0.001, respectively). The serum levels of SOX 18 protein were also increased in gastric cancer patients compared to healthy volunteers. IHC showed that of the 679 gastric cancer cases, 177 (26.1%) were positive for SOX 18 expression in their tumor stroma, and the frequencies of both lymphovascular invasion and lymph node metastases were higher in the SOX 18 positive than in the negative group. Both the 5-year survival and the recurrence-free survival were shorter for SOX 18 positive tumors (p = 0.023 and 0.012, respectively). SOX 18 expression might be a prognostic tumor marker and a potential therapeutic target in gastric cancer.