Reverse phase
protein microarray analysis was used to identify cell signaling derangements in
squamous cell carcinoma (SCC) compared with
actinic keratosis (AK) and upper inner arm (UIA). We analyzed two independent tissue sets with isolation and enrichment of epithelial cells by
laser capture microdissection. Set 1 served as a pilot and a means to identify
protein pathway activation alterations that could be further validated in a second independent set. Set 1 was comprised of 4 AK, 13 SCC, and 20 UIA. Set 2 included 15 AK, 9 SCCs, and 20 UIAs. Activation of 51 signaling
proteins, known to be involved in
tumorigenesis, were assessed for set 1 and showed that the
MEK-ERK [
mitogen-activated
protein (MAP)/extracellular signal-regulated (ERK;
MEK)] pathway was activated in SCC compared with AK and UIA, and that
epidermal growth factor receptor (EGFR) and mTOR pathways were aberrantly activated in SCC. Unsupervised two-way hierarchical clustering revealed that AK and UIA shared a common signaling network activation architecture while SCC was dramatically different. Statistical analysis found that prosurvival signaling through phosphorylation of ASK and 4EBP1 as well as increased Bax and Bak expression was higher in AK compared with UIA. We expanded pathway network activation mapping in set 2 to 101 key signaling
proteins, which corroborated activation of
MEK-ERK, EGFR, and mTOR pathways through discovery of a number of upstream and downstream signaling molecules within these pathways to conclude that SCC is indeed a pathway activation-driven disease. Pathway activation mapping of SCC compared with AK revealed several interconnected networks that could be targeted with
drug therapy for potential
chemoprevention and therapeutic applications.