Glioblastoma multiforme therapy via telomerase reverse transcriptase (hTERT) down-regulation. Molecular chaperones redirect quadruplex folding to reverse the effect of hTERT gene promoter mutations.

Project Summary Overexpression of hTERT is a hallmark of cancer and is associated with oncogenesistumor maintenanceand resistance to conventional chemotherapyElongated telomeres at the ends of chromosomes are a hallmark for cancer in the early stage of tumorigenesis and are associated with genetic instabilityAs a consequencesuppressed telomerase in normal cells is highly activated to immortalize tumor cellsThere are several strategies to overcome activated telomerase for potential therapeutic treatmentincluding targeting the telomeric G quadruplex with small moleculesbut other strategies existwhich include targeting hTERT and hTR via gene therapyHoweveras yet no strategy for inhibition of telomerase has been successfully translated into a clinically useful agentAgents that target the telomeric G quadruplex mediate their effects by erosion of telomere lengthwhich can take several weeks or even monthsThis is a distinct disadvantage for cancer therapyOn the other handthe telomerase independent effects occur during a much more therapeutically relevant timeframeand this is the focus of this proposalSeveral groups have demonstrated recently that many different kinds of tumors have somatic mutations in the hTERT promoter regionandbases from the ATG start siteAs a possible explanation for the enhanced transcription of hTERTthe C T mutation in the sense strandor G A in the antisense strandis proposed to generate an ETS elementCCTT GGAAto increase binding of the ETS transcription factor for activation of hTERT transcriptionMore significantlythese mutations are also located in the G quadruplex with theloop configuration or in the corresponding C quadruplex forming regionWe have shown that mutations in the loop lead to misfolding of the G quadruplex that in turn leads to loss of hTERT silencer activityEighty one percent of adult GBM patients haveandmutants which are associated with the cooperative folding process and lead to misfolding of the silencer elementAnnually in the United Statesglioblastoma multiformeGBMafflicts nearlynew patientsWe have identified a small drug like pharmacological chaperonepharmacoperonemolecule that acts at an early step in the cooperative folding pathway to redirect the G quadruplex misfoldingwhich reinstates the correct folding pathway and reduces hTERT activityThis compoundTGdirectly decreases the transcription activity of the WT and theandmutants to a similar extent and suppresses the downstream gene BCLwhich activates caspaseand produces cell cycle arrestleading to cell deathFinallyTGsignificantly inhibits telomerase and shortens telomere length after five days of treatment and induces a senescence like phenotypeThe restoration of the silencer function of the WT Gquadruplex silencer element by drugs of this type has important applications in treating patients with cancers such as GBMwhere a significant number of the patient population carry these somatic mutations Project Narrative Evasion of programmed cell death is a hallmark of cancer and is associated with resistance to conventional chemotherapyTargeting the genes that support cancer cell survivalsuch as BCLvia hTERTwhich is commonly overexpressed in cancer cellsis an exciting new area of cancer drug discoveryWe have developed a highly innovative approach for inhibiting hTERT activity by directly targeting a DNA structure in the hTERT promoter of this gene and are seeking to develop a clinical stage drug