This CHIR98014 in vitro confirms previous reports that UCH-L1 is highly expressed in NSCLC cell lines and primary tumours. UCH-L1 staining also correlates with histology as squamous cell carcinomas express the protein more frequently than adenocarcinomas. Although Sasaki et al [34] found no

such association, our results are in agreement with a previous study in which 72% squamous cell carcinoma tumours were positive for UCH-L1 in comparison to 41% in the adenocarcinoma subset [24]. The functional role of UCH-L1 in lung tumourigenesis however remains elusive, therefore following confirmation of high UCH-L1 expression we examined the phenotypic effects in NSCLC cell lines. The expression of UCH-L1 was reduced using siRNA in both squamous cell carcinoma (H157) and adenocarcinoma (H838) cell lines. Knockdown of UCH-L1 in H838 cells shows morphological differences indicative of apoptosis

AZD2171 price and cell death was confirmed by H&E staining, cell cycle analysis and the presence of PARP cleavage. Although other studies have not examined the effect of UCH-L1 specifically in H838 cells, UCH-L1 has been associated with apoptosis in several cases. In neuronal cells and testicular germ cells UCH-L1 is viewed as an apoptosis-promoting protein due to its role in balancing the levels of pro-apoptotic and anti-apoptotic proteins [9, 11, 12]. In contrast, the current investigation shows that UCH-L1 increases apoptotic EPZ015666 mw resistance, confirming a number of recent reports [15, 38]. Treatment of neuroblastoma cells with an UCH-L1 inhibitor was shown to cause apoptosis, mediated through decreased O-methylated flavonoid activity of the proteasome and accumulation of highly ubiquitinated proteins. This caused endoplasmic reticulum stress in the neuroblastoma cells which eventually led to the initiation of cell death [38]. Likewise, the up-regulation of UCH-L1 in human hepatoma cells following low dose UV irradiation was reported to be involved in the regulation of cell death

by inhibition of p53-mediated apoptosis; hence in both these cases UCH-L1 was demonstrated to be an “”apoptosis-evading protein”" [39], as in the present study. In contrast to H838 cells, our study reveals UCH-L1 knockdown causes no difference in morphology, apoptosis or proliferation in H157 cells but does reduce the capacity for cell migration. MLC2, a protein responsible for cell movement, is phosphorylated during cell invasion [40]. In this present study it was shown that reduced expression of UCH-L1 in H157 cells led to decreased phosphorylation of MLC2, suggesting that UCH-L1 may be involved in tumour cell migration. This challenges the findings of a recent study in which treatment of H157 cells with UCH-L1 siRNA resulted in increased apoptosis and inhibition of proliferation [33]. Conversely, we observed no morphological differences in H157 cells and no effect on proliferation (measured by Ki67 staining) when UCH-L1 expression was knocked down.