Gene expression changes associated with altered growth and differentiation in benzo[a]pyrene or arsenic exposed normal human epidermal keratinocytes

Both arsenic and benzo[a]pyrene (BaP) inhibit terminal differentiation and alter growth potential in normal human epidermal keratinocytes (NHEK) in vitro. To identify molecular alterations that may be involved in these cellular processes, microarray analysis was carried out on NHEK treated with BaP or arsenic. The gene expression microarray results measuring mRNA levels were as follows: (1) in total, the expression of 85 genes was induced and 17 genes was suppressed by 2.0 µm BaP. (2) Arsenic at an equitoxic dose (5.0 µm) induced the expression of 106 and suppressed 15 genes. Quantitative real‐time RT‐PCR was used subsequently to confirm microarray findings on selected genes involved in keratinocyte growth and differentiation pathways. These studies confirmed increased mRNA levels in NHEK by BaP of α‐integrin binding protein 63 (AIBP63) (2.48‐fold), retinoic acid‐ and interferon‐inducible protein (IFIT5) (2.74‐fold), interleukin‐1α (IL1A) (2.64‐fold), interleukin‐1β (IL1B) (2.84‐fold) and Ras guanyl releasing protein 1 (RASGRP1) (3.14‐fold). Real‐time RT‐PCR confirmed that arsenic increased mRNA levels of the following genes: retinoblastoma 1 (RB1) (5.4‐fold), retinoblastoma‐binding protein 1 (ARID4A) (6.8‐fold), transforming growth factor β‐stimulated protein (TSC22D1) (6.84‐fold), MAX binding protein (MNT) (2.44‐fold), and RAD50 (4.24‐fold). Collectively, these results indicate that these chemicals target different genes and molecular pathways involved in the regulatory processes controlling NHEK proliferation and differentiation. Mechanistic studies with a subset of genes may allow the correlation of alterations in these molecular markers with chemical‐specific blocks to differentiation in NHEK. Copyright © 2007 John Wiley & Sons, Ltd.