Hypoxia-Independent Gene Expression Mediated by SOX9 Promotes Aggressive Pancreatic Tumor Biology

Pancreatic cancer aggressiveness is characterized by its high capacity for local invasion, ability to promote angiogenesis, and potential to metastasize. Hypoxia is known to represent a crucial step in the development of aggressive malignant features of many human cancers. However, micrometastatic tumors are not typically subjectedtohypoxiceventsduringearlystagesofdissemination;therefore,itisunclearhowthesetumorsareableto maintain their aggressive phenotype. Thus, the identification of regulators of hypoxia-related genes in aggressive/ metastatictumorsrepresentsafundamentalstepforthedesignoffuturetherapiestotreatpancreaticcancer.Tothis end, transcriptomic profileswere compared between thenonmetastaticpancreatic cancercellline FG(LMET)and itsangiogenic/metastaticderivateL3.6pl(HMET)undernormoxicorhypoxicconditions.Clusteranalysisrevealed a number of transcripts that were induced by hypoxia in nonmetastatic cancer cells. Strikingly, this cluster was determined to be constitutively activated under normoxia in the metastatic cancer cells and could not be further inducedbyhypoxia.Asubsetofthesetranscriptswere regulatedbythetranscriptionfactorSOX9intheaggressivemetastatic cells, but driven by hypoxia-inducible factor-1a (HIF-1a) in the parental nonmetastatic cell line. Moreover, these transcripts were enriched in cancer-related networks including: WNT, CXCR4, retinoic acid, and (FAK)focaladhesionkinase,genePTK2signalingpathways.Infunctionalassays,inhibitionofSOX9expressionin HMETcellsledtoincreasedapoptosisandreducedmigrationinvitroanda significantreduction inprimary tumor growth,angiogenesis,andmetastasisfollowingorthotopictumorcellinjection.Atthemolecularlevel,thecontrolof SOX9 expression was associated with changes in the methylation status of the SOX9 promoter. Finally, SOX9 upregulation was verified in a series of tumor specimens of patients with pancreatic carcinoma. Implications:SOX9representsanoveltargetforpancreaticcancertherapy.MolCancerRes;12(3);421–32. � 2013 AACR.