BACKGROUNDIt has been known that Kai1 is one of transmembrane 4 superfamily regulating cell proliferation, adhesion and mobility and its down-regulated expression is closely correlated with progression and prognosis of tumor. Fas ligand (FasL) is one of tumor necrosis factor/nerve growth factor family activating caspase-3, a key proteinase in cell apoptosis and leading immune escape in tumor cells. The aim of this study is to investigate the expression of Kai1 and FasL in non-small cell lung cancer (NSCLC) and to explore their roles and relationship in carcinogenesis and progression of NSCLC.

METHODSKai1 and FasL expressions were examined in 79 NSCLC tissues and their adjacent normal lung tissues by SP immunohistochemistry. Their expressions were compared with clinicopathological features of NSCLC. The relationship between Kai1 and FasL expressions was also analyzed in NSCLC.

RESULTSKai1 expression in NSCLC tissue was remarkably lower than that in their adjacent tissue (55.7% vs 82.6%, P < 0.05). However, it was the converse for FasL (73.4% vs 52.2%, P < 0.05). Kai1 expression was not correlated with age and gender of NSCLC patients, tumor location or histological classification (P > 0.05), but negatively with lymph node metastasis and clinicopathological staging and positively with differentiation degree (P < 0.05). FasL expression was not correlated with age and gender of the patients, tumor location or histological classification (P > 0.05), but positively with lymph node metastasis and negatively with differentiation degree (P < 0.05). Kai1 expression was closely correlated with FasL expression in NSCLC (P < 0.05).

CONCLUSIONSDown-regulation of Kai1 expression and up-regulation of FasL may play important roles in carcinogenesis and progression of NSCLC. Kai1 and FasL could be considered as molecular markers to reflect pathobiological behavior of NSCLC. Additionally, close correlation of FasL expression with Kai1 expression in NSCLC provides a novel insight into the regulatory effects of FasL expression on Kai1 expression.