Steven P. Stratton

Chemoprevention of human skin cancer.

The incidence of skin cancer has been rising in recent years with significant effects on public health. Primary prevention has proven inadequate in impacting the incidence of skin cancer, thus stimulating the development of chemopreventive strategies. The majority of skin cancer chemoprevention studies focus on occurrence of new nonmelanoma skin cancers (NMSC) in individuals with a previous NMSC, or on reduction in the number of premalignant skin lesions such as actinic keratoses (AK). Dysplastic nevi, a likely precursor of melanoma, are also potential targets for chemoprevention strategies. Premalignant lesions are especially attractive as endpoints since they are more common than frank cancer, resulting in reduced sample size, length, and cost of clinical trials. Development of new agents that affect the pathogenesis of skin cancer will be discussed, from elucidation of molecular targets to implementation of trials designed to determine the effects of chemopreventive interventions on human skin cancer.

The state-of-the-art in chemoprevention of skin cancer

The incidence of skin cancer (both melanoma and non-melanoma) continues to grow at an alarming rate. Our chemoprevention strategies include the development of novel agents evaluated by (1) preclinical mechanistic studies in models of ultraviolet (UV) radiation-induced skin carcinogenesis; (2) clinical studies of immunohistochemical surrogate endpoint biomarkers in high-risk patients; and (3) randomised, placebo-controlled phase I, II and III clinical chemoprevention trials. Recent clinical results validate this development model. Molecular targets of chemopreventive strategies for melanoma and non-melanoma skin cancers include the ras and activator protein-1 (AP-1) signal transduction pathways. A transgenic murine melanoma model has been developed for evaluating potential agents in vivo. Agents at various stages of study include the green tea catechin epigallocatechin gallate (EGCG), the limonene derivative perillyl alcohol, the ornithine decarboxylase inhibitor alpha-difluoromethylornithine (DFMO), selenium, retinoids and salicylates. New chemopreventive agents that can be used to complement sunscreens may result in decreased incidence, morbidity and mortality of skin cancer.

Gemcitabine plus celecoxib in patients with advanced or metastatic pancreatic adenocarcinoma: results of a phase II trial.

Objectives:Cycloxygenase-2 (COX-2) is overexpressed in pancreatic tumors where it may be involved in inflammation, carcinogenesis, and the regulation of neoangiogenesis. The purpose of this trial was to evaluate the combination of intravenous gemcitabine with selective COX-2 inhibitor, celecoxib for effect on survival, disease progression, and tolerability in patients with advanced pancreatic cancer. In addition, limited pharmacokinetic and pharmacodynamic analyses were preformed. Materials and Methods:Eligible patients included those with locally advanced or metastatic pancreatic cancer with no prior chemotherapy and ECOG performance status 0–2. The treatment consisted of intravenous gemcitabine 1000 mg/m2 weekly × 7 weeks and concurrent daily oral celecoxib 400 mg orally twice a day. Daily oral low-dose aspirin 81 mg was administered throughout the study as a precaution for increased risk of thrombotic events. Those with stable or responsive disease were continued on intravenous gemcitabine 1000 mg/m2 weekly × 3 weeks and concurrent oral celecoxib. Results:Twenty five patients have been enrolled at 3 centers. Five patients had locally advanced cancer; 20 had metastatic disease. The most common grade 3/4 hematological toxicities were neutropenia (32%) and anemia (20%). Four patients (17%) had partial response and 7 (35%) demonstrated stable disease. The estimated 12-month survival rate was 15%, which did not reach the predetermined efficacy end point. There was a trend suggestive of correlation between a decrease in serum vascular endothelial growth factor and patient survival. Conclusion:The addition of celecoxib to gemcitabine therapy did not demonstrate significant improvement in measured clinical outcomes, in patients with advanced pancreatic cancer. Higher doses of celecoxib may be needed to observe significant antitumor activity.

A Phase I Pharmacokinetic and Pharmacodynamic Study of PX-12, a Novel Inhibitor of Thioredoxin-1, in Patients with Advanced Solid Tumors

Purpose: Thioredoxin-1 (Trx-1) is a cellular redox protein that promotes tumor growth, inhibits apoptosis, and up-regulates hypoxia-inducible factor-1α and vascular endothelial growth factor. Objectives of this study were to determine safety, tolerability, pharmacodynamics, and pharmacokinetics of PX-12, a small-molecule inhibitor of Trx-1. Experimental Design: Thirty-eight patients with advanced solid tumors received PX-12 at doses of 9 to 300 mg/m2, as a 1- or 3-h i.v. infusion on days 1 to 5, repeated every 3 weeks. Results: At the 300 mg/m2 dose level, one patient experienced a reversible episode of pneumonitis during the first cycle, and a second patient developed pneumonitis after the second cycle. Doses up to 226 mg/m2 were well tolerated, and grade 3/4 events were uncommon (<3% of patients). The limiting factor on this dosing schedule was pungent odor caused by expired drug metabolite, 2-butanethiol. The best response was stable disease in seven patients (126-332 days). Whereas PX-12 was not detectable following the infusion, the Cmax of its inactive metabolite, 2-mercaptoimidazole, increased linearly with dose. PX-12 treatment lowered plasma Trx-1 concentrations in a dose-dependent manner. Conclusions: PX-12, the first Trx-1 inhibitor to enter clinical trials, was tolerated up to a dose of 226 mg/m2 by a 3-h infusion. Based on pharmacodynamic and pharmacokinetic data, a trial of prolonged infusion schedule of PX-12 has been initiated.

Phase 3 clinical trial investigating the effect of selenium supplementation in men at high‐risk for prostate cancer

This study was conducted to investigate the effect of Se supplementation on prostate cancer incidence in men at high risk for prostate cancer.

Functional protein pathway activation mapping of the progression of normal skin to squamous cell carcinoma.

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. Cancer Prev Res; 5(3); 403–13. ©2012 AACR.

A Phase 2a Study of Topical Perillyl Alcohol Cream for Chemoprevention of Skin Cancer

The chemopreventive and antitumor properties of perillyl alcohol (POH) that were studied preclinically indicate that topical POH inhibits both UVB-induced murine skin carcinogenesis (squamous cell tumor models) and 7,12-dimethylbenz(a)anthracene–induced murine melanoma (transgenic models involving tyrosinase-driven Ras). A previous phase 1 clinical trial in participants with normal-appearing skin showed that topical POH cream was well tolerated at a dose of 0.76% (w/w). Here, we performed a 3-month, double-blind, randomized, placebo-controlled phase 2a trial of two different doses of topical POH in individuals with sun-damaged skin. Participants applied POH cream twice daily to each dorsal forearm. Baseline and end-of-study biopsies were taken from each participant to evaluate whether the topical application of POH was effective in reversing actinic damage as evidenced by normalization of quantitative skin histopathologic scores and change in nuclear chromatin pattern as measured by karyometric analysis. There was a borderline reduction in the histopathologic score of the lower-dose POH group compared with the placebo (P = 0.1), but this was not observed in the high-dose group. However, in the high-dose group, a statistically significant reduction in the proportion of nuclei deviating from normal was observed by the use of karyometric analysis (P < 0.01). There was no statistical significance shown in the lower-dose group. No changes were observed in p53 expression, cellular proliferation (by proliferating cell nuclear antigen expression), or apoptosis in either treatment group compared with the placebo group. These results suggest that whereas our karyometric analyses can detect a modest effect of POH in sun-damaged skin, improved delivery into the epidermis may be necessary. Cancer Prev Res; 3(2); 160–9

Oral Selenium Supplementation Has No Effect on Prostate- Specific Antigen Velocity in Men Undergoing Active Surveillance for Localized Prostate Cancer

The Nutritional Prevention of Cancer trial showed a 52% lower incidence of prostate cancer in men supplemented with selenium. As a result, our study was designed to assess whether selenium supplementation attenuates the progression of prostate cancer. A phase 2 randomized, double-blind, placebo-controlled clinical trial was conducted in men with localized nonmetastatic prostate cancer who had elected to forgo active treatment and be followed by active surveillance. A total of 140 men were randomized to placebo (n = 46), 200 μg/d (n = 47), or 800 μg/d (n = 47) selenium p.o. (as selenized yeast) and followed every 3 months for up to 5 years. Prostate-specific antigen (PSA) velocity was used as a marker of prostate cancer progression and was estimated using mixed-effects regression. Adjusting for age, body mass index, baseline selenium, smoking, baseline PSA, race, PSA method, and Gleason score, PSA velocities for the 200 μg/d and 800 μg/d treatment groups were not statistically significantly different from placebo (P = 0.32 and P = 0.61, respectively). In the highest quartile of baseline selenium, men supplemented with 800 μg selenium showed statistically significantly higher PSA velocity as compared with placebo (P = 0.018). Selenium supplementation did not show a protective effect on PSA velocity in subjects with localized prostate cancer. On the contrary, supplementation with high-dose selenium was observed to be a risk factor for increased PSA velocity in men with high baseline plasma selenium concentrations. Cancer Prev Res; 3(8); 1035–43. ©2010 AACR.

Cross-validation of Murine UV Signal Transduction Pathways in Human Skin

Acute UVB irradiation of mouse skin results in activation of phospatidyinositol‐3 (PI‐3) kinase and mitogen‐activated protein kinase (MAPK) pathways leading to altered protein phosphorylation and downstream transcription of genes. We determined whether activation of these pathways also occurs in human skin exposed to 4× minimal erythemic dose of UVB in 23 volunteers. Biopsies were taken prior to, at 30 min, 1 and 24 h post‐UVB. In agreement with mouse studies, the earliest UV‐induced changes in epidermis were seen in phospho‐CREB (two‐ and five‐fold at 30 min and 1 h) and in phospho‐MAPKAPK‐2 (three‐fold at both 30 min and 1 h). At 1 h, phospho‐c‐JUN and phospho‐p38 were increased five‐ and two‐fold, respectively. Moreover, phospho‐c‐JUN and phospho‐p38 were further increased at 24 h (12‐ and six‐fold, respectively). Phospho‐GSK‐3β was similarly increased at all time points. Increases in phospho‐p53 (12‐fold), COX‐2 (four‐fold), c‐FOS (14‐fold) and apoptosis were not seen until 24 h. Our data suggest that UVB acts through MAPK p38 and PI‐3 kinase with phosphorylation of MAPKAPK‐2, CREB, c‐JUN, p38, GSK‐3β and p53 leading to marked increases in c‐FOS, COX‐2 and apoptosis. Validation of murine models in human skin will aid in development of effective skin cancer chemoprevention and prevention strategies.

Effect of aspirin, other NSAIDs, and statins on PSA and PSA velocity.

Aspirin, other non‐steroidal anti‐inflammatory drugs (NSAIDs), and statins have been associated with lower risk of prostate cancer and its progression, though results have been inconsistent.