In our study, overexpression of p-MEK and overexpression of p-ERK were observed in high proportions of tumours. Expression of p-ERK was slightly, but not significantly associated with survival, although p-MEK was not associated. The localization of p-ERK is an important factor in tumour progression, because activated ERK characteristically

accumulates in the nucleus and transports extracellular stimuli from the cell surface to the nucleus in intracellular Foretinib mw signal transducing pathways. MEK-catalysed ERK phosphorylation is necessary but not sufficient for the full nuclear localization response. Nuclear localization of phosphorylated ERK is affected by other proteins such as dual specificity phosphatase [25]. In colorectal cancer cells, the trafficking protein particle complex 4 (TRAPPC4) modulates the location of p-ERK to activate the relevant signaling pathway [26]. On the

other hand, other studies reported that MAPK activity is rather suppressed in human gastric adenocarcinoma [27, 28]. The complex multiple signaling MAPK pathway accepts many positive or negative stimuli, Salubrinal chemical structure including negative auto-feedback mechanisms, and ERK activation is inhibited by components of the network, such as protein tyrosine phosphatase (PTP) or other MAPK phosphatases activated by transcription factors [29]. Consequently, ERK might not necessarily be activated when the direct upstream regulator MEK is active. Raf/MEK/ERK Veliparib signaling pathway seems to be affected also by various regulators or negative feedback mechanisms. Therefore, the combined expression of upstream regulator and downstream effector may have an important impact on survival. In the present study, patients with negative RKIP expression had poorer survival (5-year RFS = 44%) than those with only positive RKIP expression (66%), patients with positive p-ERK expression had similar survival (49%) to those with negative p-ERK expression (75%), and patients with a combination of negative RKIP expression and positive p-ERK expression had poorer survival (33%) than those

with positive RKIP expression Morin Hydrate or negative p-ERK expression (69%). In addition, negative RKIP and positive p-ERK expression was observed in 18 (69%) of 26 metastatic lymph nodes obtained from patients with recurrent disease. Our findings suggest that combined expression might be an independent prognostic factor. ERK or MEK activation results from the sequential activation of a series of protein kinases, including Raf-1, and the up-regulating protein RAS. Approximately 30% of all human tumours have an activating mutation in a RAS gene. In particular, KRAS mutations are among the most common genetic abnormalities in several types of human cancer, including pancreatic cancer, colon cancer, and lung cancer [30].