Journal of Chromatography B, 931 (2013) 90–96 Contents lists available at SciVerse ScienceDirect Journal of Chromatography B j ourna l h o mepa ge: www.elsevier.com/locate/chromb Volatile biomarkers from human melanoma cells Jae Kwak a , Michelle Gallagher a , Mehmet Hakan Ozdener a , Charles J. Wysocki a,b , Brett R. Goldsmith c , Amaka Isamah a , Adam Faranda a , Steven S. Fakharzadeh d , Meenhard Herlyn e , A.T. Charlie Johnson c , George Preti a,d,∗ a Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA b Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA c Department of Astronomy and Physics, University of Pennsylvania, Philadelphia, PA 19104, USA d Department of Dermatology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA e Wistar Institute, Philadelphia, PA 19104, USA a r t i c l e i n f o Article history: Received 3 December 2012 Accepted 13 May 2013 Available online xxx Keywords: Volatile organic compounds Gas chromatography–mass spectrometry Melanoma Carbon nanotubes Volatile metabolome a b s t r a c t Dogs can identify, by olfaction, melanoma on the skin of patients or melanoma samples hidden on healthy subjects, suggesting that volatile organic compounds (VOCs) from melanoma differ from those of normal skin. Studies employing gas chromatography–mass spectrometry (GC–MS) and gas sensors reported that melanoma-related VOCs differed from VOCs from normal skin sources. However, the identities of the VOCs that discriminate melanoma from normal skin were either unknown or likely derived from exogenous sources. We employed solid-phase micro-extraction, GC–MS and single-stranded DNA-coated nanotube (DNACNT) sensors to examine VOCs from melanoma and normal melanocytes. GC–MS revealed dozens of VOCs, but further analyses focused on compounds most likely of endogenous origin. Several compounds differed between cancer and normal cells, e.g., isoamyl alcohol was higher in melanoma cells than in normal melanocytes but isovaleric acid was lower in melanoma cells. These two compounds share the same precursor, viz., leucine. Melanoma cells produce dimethyldi- and trisulfide, compounds not detected in VOCs from normal melanocytes. Furthermore, analyses of the total volatile metabolome from both melanoma cells and normal melanocytes by DNACNT sensors, coupled with the GC–MS results, demonstrate clear differences between these cell systems. Consequently, monitoring of melanoma VOCs has potential as a useful screening methodology. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Skin cancer is the most common form of cancer in the United States, and it is divided into 3 types: basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma [1]. BCC is the most frequent skin cancer and rarely spreads (“metastasizes”) to other parts of the body. BCC accounts for about 80% of all diagnosed skin cancers, followed by SCC, which accounts for about 16% of skin can- cers [2]. SCC requires early treatment to prevent metastasis. More than 2 million cases of BCC and SCC occur annually in the United States alone [3]. Melanoma is the deadliest form of skin cancer Abbreviations: VOCs, volatile organic compounds; GC–MS, gas chromatography– mass spectrometry; DNACNT, DNA-coated nanotube; BCC, basal cell carcinoma; SCC, squamous cell carcinoma; SPME, solid phase micro-extraction; e-nose, electronic nose; CNT, carbon nanotube; CNT FET, carbon nanotube field effect transistors; ss- DNA, single strand DNA; RGP, radial growth phase; VGP, vertical growth phase; Mm, metastatic melanoma; TIC, total ion chromatogram. ∗ Corresponding author at: Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA. Tel.: +1 267 519 4920; fax: +1 215 898 2084. E-mail addresses: preti@monell.org, preti@pobox.upenn.edu (G. Preti). because it can rapidly spread to other parts of the body. In the United States, it is estimated that more than 76,000 people will be diagnosed with, and about 9000 patients will die from, melanoma in 2012 [4]. Skin cancer is highly curable when detected early and treated properly. Melanoma is also highly curable if limited to the outermost layers of the skin. Thus, early detection of skin carci- noma is critical and various diagnostic imaging techniques have been proposed [5]. Currently, early detection of skin carcinoma is accomplished primarily through a visual exam, imaging techniques and biopsy of any suspected areas. Biopsy is invasive and usually requires examination by a pathologist. A recent review cites the large increase in the use of reflectance confocal microscopy and dermoscopy in situ for diagnosis of primary melanoma and other skin diseases [6]. Sophisticated imaging technologies such as these provide spatial and diagnostic information that will aid the spe- cialist (dermatologist, cosmetic surgeon) in surgery. In addition, the most recent sophisticated versions of these techniques, which have been practiced for many years, are still “emerging” and even after they do mature to a role in the clinic, they may be too expen- sive and require specialized training for general screening use, such as by primary care physicians or nursing home physicians. 1570-0232/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jchromb.2013.05.007