Abstract 3246: Mapping of functional protein pathway modulations in non-sun exposed skin of healthy volunteers using solar simulated light: A new model for pharmacodynamic testing of skin cancer chemopreventive drugs
Authors: Stratton Steven P. , Curiel-Lewandrowski Clara , Einspahr Janine G. , Calvert Valerie , Hu Chengcheng , Bermudez Yira , Alberts David S. , Bowden George T. , Petricoin Emanuel F. 
Published: May 2015

Efficient secondary prevention methods for non-melanoma skin cancers are needed to supplement primary prevention in high-risk individuals. Pharmacologic effects in UV-induced keratinocyte signaling may predict efficacy of new drugs. In order to understand effects of solar light on signal transduction networks in human skin, we exposed buttocks skin of healthy volunteers to solar-simulated light (SSL) at doses 2x-3x of minimum erythemal dose (MED) using a Multiport UV Solar Simulator (Solar Light Co.). Punch biopsies (6 mm) were collected at baseline, 5 min, 1 hr, 5 hr, and 24 hr post-exposure. Biopsies were split with half fixed in formalin and half snap-frozen for Reverse Phase Protein Microarray (RPMA) analysis to identify relevant signaling networks activated by SSL exposure. 24 subjects ≥ 18 y.o. with Fitzpatrick skin type II or III, with no concurrent illness, cancer, or use of photosensitizing drugs were recruited. 12 were exposed to SSL at 2x MED, 6 at 2.5x MED, and 6 at 3x MED. The activation/phosphorylation or total levels of 128 key signaling proteins and drug targets were measured for each sample. Coordinate network-based analysis was performed on specific signaling pathways that included PI3k/Akt/mTOR, Ras/Raf/MEK/Erk, and Fyn/RSK2. Analyte levels were compared at baseline to those at 5 min, 1 hr, 5 hr, and 24 hr after SSL exposure. Unsupervised and supervised statistical analysis was used with Bonferroni multiple comparison adjustment (p &lt; 0.01). Pathway activation maps were constructed using p values to indicate time-dependence of pathway activation. Differences in MED did not significantly affect expression, so all 24 subjects were analyzed independent of SSL dose. Most pathway modulation occurred within the first 5 hr, with cell death and apoptosis-related endpoints maximal at 24 hr. Many kinases were activated within 5 min and activity increased at 1-5 hr before reversing to baseline or lower at 24 hr. Early and sustained activation of p38/SAPK/ ERK pathways started at 5 min, continued through 5 hr and was sustained at 24 hr. Systemic AKT-mTOR pathway activation was observed from 5 min-1 hr, sustained through 5 hr, and decreased at 24 hr. EGFR-HER3 activation followed a similar pattern. COX2 expression increased at 1 hr and was sustained through 24 hr. AMPK was activated early and sustained through 24 hr since LKB1, the dominant AMPK kinase was activated within 5 min-1hr and sustained. Correlation-based network maps were generated and revealed time-dependent SSL induced pathway activation linkages. This work shows that protein pathway activation mapping of phosphorylated proteins in relevant signaling pathways can be used in future studies to determine pharmacodynamic activity of selective topical agents administered in a test area exposed to SSL to determine drug-induced modification of skin carcinogenesis pathways.

Citation Format: Steven P. Stratton, Clara Curiel-Lewandrowski, Janine G. Einspahr, Valerie Calvert, Chengcheng Hu, Yira Bermudez, David S. Alberts, George T. Bowden, Emanuel F. Petricoin. Mapping of functional protein pathway modulations in non-sun exposed skin of healthy volunteers using solar simulated light: A new model for pharmacodynamic testing of skin cancer chemopreventive drugs. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3246. doi:10.1158/1538-7445.AM2014-3246