Microarray and biochemical analysis of lovastatin-induced apoptosis of squamous cell carcinomas.
We recently identified 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme of the mevalonate pathway, as a potential therapeutic target of the head and neck squamous cell carcinomas (HNSCC) and cervical carcinomas (CC). The products of this complex biochemical pathway, including de novo cholesterol, are vital for a variety of key cellular functions affecting membrane integrity, cell signaling, protein synthesis, and cell cycle progression. Lovastatin, a specific inhibitor of HMG-CoA reductase, induces a pronounced apoptotic response in a specific subset of tumor types, including HNSCC and CC. The mediators of this response are not well established. Identification of differentially expressed genes represents a feasible approach to delineate these mediators as lovastatin has the potential to modulate transcription indirectly by perturbing levels of sterols and other mevalonate metabolites. Expression analysis following treatment of the HNSCC cell lines SCC9 or SCC25 with 10 microM lovastatin for 1 day showed that less than 2% (9 cDNAs) of the 588 cDNAs on this microarray were affected in both cell lines. These included diazepam-binding inhibitor/acyl-CoA-binding protein, the activated transcription factor 4 and rhoA. Because the biosynthesis of mevalonate leads to its incorporation into more than a dozen classes of end products, their role in lovastatin-induced apoptosis was also evaluated. Addition of the metabolites of all the major branches of the mevalonate pathway indicated that only the nonsterol moiety, geranylgeranyl pyrophosphate (GGPP), significantly inhibited the apoptotic effects of lovastatin in HNSCC and CC cells. Because rhoA requires GGPP for its function, this links the microarray and biochemical data and identifies rhoA as a potential mediator of the anticancer properties of lovastatin. Our data suggest that the depletion of nonsterol mevalonate metabolites, particularly GGPP, can be potential mediators of lovastatin-induced apoptosis of HNSCC and CC cells.
Dimitroulakos
Jim
J
Department of Cellular and Molecular Biology, The University Health Network, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9.
Marhin
Wilson H
WH
Tokunaga
Jason
J
Irish
Jonathan
J
Gullane
Patrick
P
Penn
Linda Z
LZ
Kamel-Reid
Suzanne
S
D051696:Activating Transcription Factors; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001798:Blood Proteins / Q000378:metabolism; D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology; D019556:COS Cells / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002470:Cell Survival; D002522:Chlorocebus aethiops; D002784:Cholesterol / Q000378:metabolism; D003066:Coenzyme A Ligases / Q000502:physiology; D016384:Consensus Sequence; D016172:DNA Fingerprinting; D004268:DNA-Binding Proteins / Q000502:physiology; D026261:Diazepam Binding Inhibitor / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes / Q000032:analysis; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017930:Genes, Reporter; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000502:physiology; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D006904:Hydroxymethylglutaryl-CoA Synthase; D008148:Lovastatin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008156:Luciferases / Q000235:genetics; D008798:Mevalonic Acid / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D010590:Phalloidine / Q000032:analysis; D011106:Polyisoprenyl Phosphates / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics; D051780:Sterol Regulatory Element Binding Protein 1; D013261:Sterols / Q000378:metabolism; D013382:Subtraction Technique; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000473:pathology*; D020742:rhoA GTP-Binding Protein / Q000502:physiology
D051696:Activating Transcription Factors; D001798:Blood Proteins; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D026261:Diazepam Binding Inhibitor; D005456:Fluorescent Dyes; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D009363:Neoplasm Proteins; D011106:Polyisoprenyl Phosphates; D011993:Recombinant Fusion Proteins; C497387:SREBF1 protein, human; D051780:Sterol Regulatory Element Binding Protein 1; D013261:Sterols; D014157:Transcription Factors; D010590:Phalloidine; D002784:Cholesterol; D008148:Lovastatin; D006903:Hydroxymethylglutaryl CoA Reductases; D008156:Luciferases; D006904:Hydroxymethylglutaryl-CoA Synthase; D020742:rhoA GTP-Binding Protein; D003066:Coenzyme A Ligases; C002963:geranylgeranyl pyrophosphate; D008798:Mevalonic Acid