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58HongKongMedJVol16No1#Supplement1#February2010Beta1subunit–dependentmodulationofBKchannelbymembranecholesterolWWu,CPLau,HFTse,GRLiDepartmentofMedicine,TheUniversityofHongKong,QueenMaryHospital,HongKongBackground:ThelargeconductanceCa2+-activatedK+(BKorMaxi-K)channelsareubiquitouslyexpressedindifferenttissueswithout(brain,liver,etc)orwith(smoothmuscleandheart)regulatorybeta-subunit,andplayanimportantroleinregulatingvariousphysiologicalprocessessuchascellexcitability,hormonesecretion,vascularactivity,etc.
RecentstudieshaveshownthatmembranecholesterolisamajorregulatorofseveralpotassiumchannelsincludingKirandKv1.
5channels.
However,theregulationofBKchannelsbycholesterolisnotfullyunderstood.
Methods:WholecellBKcurrentandBKsinglechannelcurrentwererecordedinwhole-cellpatchclampmodeandcell-attachedsinglechannelrecording,respectively,inHEK293cellsstablyexpressingMaxi-KgeneorMaxi-Kwithbeta1-subunit.
Results:Wefoundthatwhole-cellBKcurrentwassignificantlysuppressedwithcholesteroldepletionbymethyl-beta-cyclodextrin(MCD),whereascholesterol-saturated–MCDhadnoeffectonthecurrentamplitude.
SinglechannelrecordingshowedthatcholesteroldepletionsignificantlyreducedtheopenprobabilityofBKchannel,suggestingthatcholesteroldepletionlikelydecreasesthemembranechannelnumber.
Interestingly,incellsstablyexpressingSloandbeta1-subunit,depletionofmembranecholesterolincreasedBKcurrent,whilecholesterol-saturated–MCDreducedBKcurrent.
Conclusion:OurresultsdemonstratetheimportantevidencethatBKchannelsexhibitbeta1-subunit–dependentresponsestocholesterol.
TheenrichedcholesterolreducestheactivityofBKchannelsco-expressedwithMax-Kandbeta1-subunit,whichmayatleastinpartaccountsfortheoccurrenceofhypertensioninpatientswithhighplasmacholesterollevel,sincebeta-subunittranscriptsareabundantinvascularsmoothmuscle.
99PhaseI/IItrialofPTK787/ZK222584combinedwithintravenousdoxorubicinfortreatmentofpatientswithadvancedhepatocellularcarcinoma:implicationforanti-angiogenicapproachtohepatocellularcarcinomaTYau1,PChan1,KKNg2,STFan2,RTPoon21DepartmentofMedicine,TheUniversityofHongKong,QueenMaryHospital,HongKong2DepartmentofSurgery,TheUniversityofHongKong,QueenMaryHospital,HongKongBackground:ThisisaphaseI/IItrialaimingtoassesstheefficacyandtolerabilityofPTK787/ZK222584(PTK)incombinationwithintravenousdoxorubicinforthetreatmentofadvancedhepatocellularcarcinoma(HCC)patients.
Methods:InphaseI,advancedHCCpatientsreceivedPTKatescalatingdosestogetherwithdoxorubicin60mg/m2givenasanintravenousbolusevery3weekstoestablishthemaximumtolerateddose(MTD).
Subsequently,inphaseII,allpatientsreceivedthesameregimenwithoralPTKattheMTDdosetogetherwithdoxorubicin60mg/m2givenasanintravenousbolusevery3weeksforamaximumof6cycles.
Results:Ninepatientswererecruitedinphase1partwiththeMTDestablishedas750mgdaily.
Overall,27patientsreceivedtheregimenwithPTKat750mgdaily.
Themedianagewas52(range,23-73)yearsand63%ofpatientswerechronichepatitisBcarriers.
Notably,themajorityofpatientshadChildBcirrhosis.
Theoverallresponseratewas26.
0%withallpatientshavingpartialresponse,andanother20%ofpatientsachievedstablediseaseforatleast12weeks.
Themedianprogression-freesurvivalwas5.
4(0.
27-23.
6)monthsandoverallsurvivalwas7.
3(0.
8-23.
6)months.
Thecommonestgrade3or4non-haematologicaltoxicitiesweremucositis(11%)andalopecia(7%),respectively.
Grade3or4neutropeniawasobservedinseven(26%)patientswithtwohavingneutropenicsepsis.
Conclusion:ThecombinationofPTKwithintravenousdoxorubicinshowssynergisticactivityinadvancedHCCpatients.
Thus,theideaofcombininganti-angiogenicagenttogetherwithchemotherapymaywarrantfurtherevaluationinfutureclinicaltrialsofadvancedHCCpatients.
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