Focal adhesion kinase (FAK) is a tyrosine kinase which is at the crossroad of extracellular signal-regulated kinase-1/2 (ERK1/2), PI3K/Akt, MAPK and JAK/STAT signaling pathways. We have previously reported that p-ERK1/2, p-Akt, p38MAPK and p-STAT3 are overexpressed in extramammary Paget's diseases (EMPD), this study aimed to examine the expression of phosphorylated (p)-FAK and p-ERK1/2 proteins in EMPD and to evaluate the relationships among them. Paraffin-embedded EMPD specimens (35 tissue samples from 33 patients with primary EMPD, including two samples of metastatic lymph nodes from two of the 33 patients) were subjected to immunohistochemical staining for p-FAK and p-ERK1/2. All of the 35 EMPD specimens, including all of six invasive EMPD and two metastatic lymph node specimens, showed cytoplasmic overexpression of p-FAK and nuclear overexpression of p-ERK1/2. The expression levels (% positive cells) of p-FAK and p-ERK1/2 (88.34 ± 14.66 and 91.26 ± 11.21%) in EMPD were significantly higher than those in normal skin (22.38 ± 2.13 and 29.00 ± 4.44%), respectively. The expression levels of p-FAK (95.38 ± 4.57%) and p-ERK1/2 (96.25 ± 5.01%) in the advanced EMPD showed slightly higher than that in the non-invasive EMPD (86.26 ± 15.99 and 89.78 ± 12.15%), respectively. There exhibited a significantly high positive correlation between expression levels of p-ERK1/2 and p-FAK in EMPD. The present study shows that the concordant overexpression of p-FAK and p-ERK1/2 in EMPD which is associated with the grade of malignancy of EMPD, indicating that p-FAK and p-ERK1/2 may play pivotal roles in the tumorigenesis and further malignant transduction of EMPD.
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