title: A transcriptomic computational analysis of mastic oil-treated Lewis lung carcinomas reveals molecular mechanisms targeting tumor cell growth and survival.
abstract: BACKGROUND
  Mastic oil from Pistacia lentiscus variation chia, a blend of bioactive terpenes with recognized medicinal properties, has been recently shown to exert anti-tumor growth activity through inhibition of cancer cell proliferation, survival, angiogenesis and inflammatory response. However, no studies have addressed its mechanisms of action at genome-wide gene expression level.
  
  
  METHODS
  To investigate molecular mechanisms triggered by mastic oil, Lewis Lung Carcinoma cells were treated with mastic oil or DMSO and RNA was collected at five distinct time points (3-48 h). Microarray expression profiling was performed using Illumina mouse-6 v1 beadchips, followed by computational analysis. For a number of selected genes, RT-PCR validation was performed in LLC cells as well as in three human cancer cell lines of different origin (A549, HCT116, K562). PTEN specific inhibition by a bisperovanadium compound was applied to validate its contribution to mastic oil-mediated anti-tumor growth effects.
  
  
  RESULTS
  In this work we demonstrated that exposure of Lewis lung carcinomas to mastic oil caused a time-dependent alteration in the expression of 925 genes. GO analysis associated expression profiles with several biological processes and functions. Among them, modifications on cell cycle/proliferation, survival and NF-kappaB cascade in conjunction with concomitant regulation of genes encoding for PTEN, E2F7, HMOX1 (up-regulation) and NOD1 (down-regulation) indicated some important mechanistic links underlying the anti-proliferative, pro-apoptotic and anti-inflammatory effects of mastic oil. The expression profiles of Hmox1, Pten and E2f7 genes were similarly altered by mastic oil in the majority of test cancer cell lines. Inhibition of PTEN partially reversed mastic oil effects on tumor cell growth, indicating a multi-target mechanism of action. Finally, k-means clustering, organized the significant gene list in eight clusters demonstrating a similar expression profile. Promoter analysis in a representative cluster revealed shared putative cis-elements suggesting a common regulatory transcription mechanism.
  
  
  CONCLUSIONS
  Present results provide novel evidence on the molecular basis of tumor growth inhibition mediated by mastic oil and set a rational basis for application of genomics and bioinformatic methodologies in the screening of natural compounds with potential cancer chemopreventive activities.
authors.affiliation: Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, Athens, Greece. pmoulos@eie.gr
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Moulos
authors.forename: Olga
authors.initials: O
authors.lastname: Papadodima
authors.forename: Aristotelis
authors.initials: A
authors.lastname: Chatziioannou
authors.forename: Heleni
authors.initials: H
authors.lastname: Loutrari
authors.forename: Charis
authors.initials: C
authors.lastname: Roussos
authors.forename: Fragiskos N
authors.initials: FN
authors.lastname: Kolisis
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D018827:Carcinoma, Lewis Lung / Q000235:genetics* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D019295:Computational Biology; D020869:Gene Expression Profiling; D006801:Humans; D000069997:Mastic Resin; D051379:Mice; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D012116:Resins, Plant / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D000069997:Mastic Resin; D012116:Resins, Plant; D051059:PTEN Phosphohydrolase