Pancreatic cancer has a dismal prognosis due to late detection and lack of efficient therapies.The Kirsten rat sarcoma virus(KRAS)oncogene is mutated in up to 90%of all pancreatic ductal adenocarcinomas(PDACs)and cons...Pancreatic cancer has a dismal prognosis due to late detection and lack of efficient therapies.The Kirsten rat sarcoma virus(KRAS)oncogene is mutated in up to 90%of all pancreatic ductal adenocarcinomas(PDACs)and constitutes an attractive target for therapy.However,the most common KRAS mutations in PDAC are G12D(44%),G12V(34%)and G12R(20%)that are not amenable to treatment by KRAS G12C-directed cysteine-reactive KRAS inhibitors such as Sotorasib and Adagrasib that exhibit clinical efficacy in lung cancer.KRAS G12C mutant pancreatic cancer has been treated with Sotorasib but this mutation is detected only in 2%–3%of PDAC.Recently,the KRAS G12D-directed MRTX1133 inhibitor has entered clinical trials and more of such inhibitors are in development.The other KRAS mutations may be targeted indirectly via inhibition of the cognate guanosine exchange factor(GEF)Son of Sevenless 1 that drives KRAS.These agents seem to provide the means to target the most frequent KRAS mutations in PDAC and to improve patient outcomes.展开更多
The Kirsten rat sarcoma virus—son of sevenless 1(KRAS-SOS1)axis drives tumor growth preferentially in pancreatic,colon,and lung cancer.Now,KRAS G12C mutated tumors can be successfully treated with inhibitors that cov...The Kirsten rat sarcoma virus—son of sevenless 1(KRAS-SOS1)axis drives tumor growth preferentially in pancreatic,colon,and lung cancer.Now,KRAS G12C mutated tumors can be successfully treated with inhibitors that covalently block the cysteine of the switch II binding pocket of KRAS.However,the range of other KRAS mutations is not amenable to treatment and the G12C-directed agents Sotorasib and Adragrasib show a response rate of only approximately 40%,lasting for a mean period of 8 months.One approach to increase the efficacy of inhibitors is their inclusion into proteolysis-targeting chimeras(PROTACs),which degrade the proteins of interest and exhibit much higher antitumor activity through multiple cycles of activity.Accordingly,PROTACs have been developed based on KRAS-or SOS1-directed inhibitors coupled to either von Hippel-Lindau(VHL)or Cereblon(CRBN)ligands that invoke the proteasomal degradation.Several of these PROTACs show increased activity in vitro and in vivo compared to their cognate inhibitors but their toxicity in normal tissues is not clear.The CRBN PROTACs containing thalidomide derivatives cannot be tested in experimental animals.Resistance to such PROTACS arises through downregulation or inactivation of CRBN or factors of the functional VHL E3 ubiquitin ligase.Although highly active KRAS and SOS1 PROTACs have been formulated their clinical application remains difficult.展开更多
Small cell lung cancer(SCLC)is frequently disseminated and has a dismal prognosis with survival times of approximately two years.This cancer responds well to initial chemotherapy but recurs within a short time as a gl...Small cell lung cancer(SCLC)is frequently disseminated and has a dismal prognosis with survival times of approximately two years.This cancer responds well to initial chemotherapy but recurs within a short time as a globally chemoresistant tumor.Circulating tumor cells(CTCs)are held responsible for metastasis,the extremely high numbers of these cells in advanced SCLC allowed us to establish several permanent CTC cell lines.These CTCs are distinguished by the spontaneous formation of large spheroids,termed tumorospheres,in regular tissue culture.These contain quiescent and hypoxic cells in their interior and are associated with high chemoresistance compared to single cell cultures.Nine CTC lines were compared for their expression of 84 proteins associated with cancer either as single cells or in the form of tumorospheres in Western blot arrays.With the exception of the UHGc5 line,all other CTC lines express EpCAM and lack a complete EpCAM-negative,vimentin-positive epithelial-mesenchymal transition(EMT)phenotype.Upon formation of tumorospheres the expression of EpCAM,that mediates cell-cell adhesion is markedly upregulated.Proteins such as E-Cadherin,p27 KIP1,Progranulin,BXclx,Galectin-3,and Survivin showed variable changes for the distinct CTC cell lines.In conclusion,EpCAM presents the most critical marker for individual SCLC CTCs and the assembly of highly chemoresistant tumorospheres.展开更多
文摘Pancreatic cancer has a dismal prognosis due to late detection and lack of efficient therapies.The Kirsten rat sarcoma virus(KRAS)oncogene is mutated in up to 90%of all pancreatic ductal adenocarcinomas(PDACs)and constitutes an attractive target for therapy.However,the most common KRAS mutations in PDAC are G12D(44%),G12V(34%)and G12R(20%)that are not amenable to treatment by KRAS G12C-directed cysteine-reactive KRAS inhibitors such as Sotorasib and Adagrasib that exhibit clinical efficacy in lung cancer.KRAS G12C mutant pancreatic cancer has been treated with Sotorasib but this mutation is detected only in 2%–3%of PDAC.Recently,the KRAS G12D-directed MRTX1133 inhibitor has entered clinical trials and more of such inhibitors are in development.The other KRAS mutations may be targeted indirectly via inhibition of the cognate guanosine exchange factor(GEF)Son of Sevenless 1 that drives KRAS.These agents seem to provide the means to target the most frequent KRAS mutations in PDAC and to improve patient outcomes.
文摘The Kirsten rat sarcoma virus—son of sevenless 1(KRAS-SOS1)axis drives tumor growth preferentially in pancreatic,colon,and lung cancer.Now,KRAS G12C mutated tumors can be successfully treated with inhibitors that covalently block the cysteine of the switch II binding pocket of KRAS.However,the range of other KRAS mutations is not amenable to treatment and the G12C-directed agents Sotorasib and Adragrasib show a response rate of only approximately 40%,lasting for a mean period of 8 months.One approach to increase the efficacy of inhibitors is their inclusion into proteolysis-targeting chimeras(PROTACs),which degrade the proteins of interest and exhibit much higher antitumor activity through multiple cycles of activity.Accordingly,PROTACs have been developed based on KRAS-or SOS1-directed inhibitors coupled to either von Hippel-Lindau(VHL)or Cereblon(CRBN)ligands that invoke the proteasomal degradation.Several of these PROTACs show increased activity in vitro and in vivo compared to their cognate inhibitors but their toxicity in normal tissues is not clear.The CRBN PROTACs containing thalidomide derivatives cannot be tested in experimental animals.Resistance to such PROTACS arises through downregulation or inactivation of CRBN or factors of the functional VHL E3 ubiquitin ligase.Although highly active KRAS and SOS1 PROTACs have been formulated their clinical application remains difficult.
基金partially funded by the“Medical Scientific Fund of the Mayor of the City of Vienna”,Grant Number 21040 to Dr.C.Lang.
文摘Small cell lung cancer(SCLC)is frequently disseminated and has a dismal prognosis with survival times of approximately two years.This cancer responds well to initial chemotherapy but recurs within a short time as a globally chemoresistant tumor.Circulating tumor cells(CTCs)are held responsible for metastasis,the extremely high numbers of these cells in advanced SCLC allowed us to establish several permanent CTC cell lines.These CTCs are distinguished by the spontaneous formation of large spheroids,termed tumorospheres,in regular tissue culture.These contain quiescent and hypoxic cells in their interior and are associated with high chemoresistance compared to single cell cultures.Nine CTC lines were compared for their expression of 84 proteins associated with cancer either as single cells or in the form of tumorospheres in Western blot arrays.With the exception of the UHGc5 line,all other CTC lines express EpCAM and lack a complete EpCAM-negative,vimentin-positive epithelial-mesenchymal transition(EMT)phenotype.Upon formation of tumorospheres the expression of EpCAM,that mediates cell-cell adhesion is markedly upregulated.Proteins such as E-Cadherin,p27 KIP1,Progranulin,BXclx,Galectin-3,and Survivin showed variable changes for the distinct CTC cell lines.In conclusion,EpCAM presents the most critical marker for individual SCLC CTCs and the assembly of highly chemoresistant tumorospheres.
