Role of lumican in cancer cells and adjacent stromal tissues in human pancreatic cancer

Lumican is a member of a small leucine-rich proteoglycan family and its overexpression has been reported in carcinoid tumor, breast, colorectal, neuroendocrine cell, uterine cervical and pancreatic cancers. The expression of lumican in stromal tissues in breast cancer is associated with a high tumor grade, a low estrogen receptor expression level and young age. Lumican expression in the cytoplasm in advanced colorectal cancer is correlated with a poor prognosis. Lumican expression was previously reported in pancreatic cancer, but the role of lumican in pancreatic cancer is still not well understood. In this study, we aimed to clarify the role of lumican in pancreatic cancer. Reverse-transcription polymerase chain reaction and Western blot analyses revealed lumican mRNA and protein expression in six pancreatic ductal adenocarcinoma cell lines (i.e. PANC-1, MIA PaCa-2, KLM-1, Capan-1, PK-1 and PK-8). On the basis of its immunoreactivity, lumican was found to be localized in islet cells of normal pancreatic tissues, but not in exocrine cells. In pancreatic cancer tissues, lumican was predominantly localized in the cytoplasm of cancer cells in 30 out of 53 (56.6%) cancer patients, whereas lumican was detected in stromal tissues in 36 out of 53 (67.9%) cancer patients. Lumican expression in pancreatic cancer cells did not correlate with clinicopathological factors, whereas lumican expression in stromal tissues correlated with the female gender, advanced stage, retroperitoneal and duodenal invasion and residual tumor (p=0.030, 0.038, 0.049, 0.049 and 0.048, respectively). Patients with lumican-positive cancer cells tended to survive longer than those with lumican-negative cancer cells (p=0.286), but patients with lumican-positive stromal tissues had shorter survival than those with lumican-negative stromal tissues (p=0.062). These results suggest that lumican in stromal tissues plays an important role in the growth and invasion of pancreatic cancer.