Effect on tumor cells of blocking survival response to glucose deprivation.
BACKGROUND
Glucose deprivation, a feature of poorly vascularized solid tumors, activates the unfolded protein response (UPR), a stress-signaling pathway, in tumor cells. We recently isolated a novel macrocyclic compound, versipelostatin (VST), that inhibits transcription from the promoter of GRP78, a gene that is activated as part of the UPR. We examined the effect of VST on the UPR induced by glucose deprivation or other stressors and on tumor growth in vivo.


METHODS
Human colon cancer HT-29, fibrosarcoma HT1080, and stomach cancer MKN74 cells were cultured in the absence of glucose or in the presence of glucose and a UPR-inducing chemical stressor (the N-glycosylation inhibitor tunicamycin, the calcium ionophore A23187, or the hypoglycemia-mimicking agent 2-deoxyglucose [2DG]). The effect of VST on UPR induction was determined by reverse transcription-polymerase chain reaction and immunoblot analysis of the UPR target genes GRP78 and GRP94; by immunoblot analysis of the UPR transcriptional activators ATF6, XBP1, and ATF4; and by analyzing reporter gene expression in cells transiently transfected with a GRP78 promoter-reporter gene. Cell sensitivity to VST was examined with a colony formation assay and flow cytometry. In vivo antitumor activity of VST was assessed with an MKN74 xenograft model.


RESULTS
VST inhibited expression of UPR target genes in glucose-deprived or 2DG-treated cells but not in cells treated with tunicamycin or A23187. VST also inhibited the production of the UPR transcriptional activators XBP1 and ATF4 during glucose deprivation. The UPR-inhibitory action of VST was seen only in conditions of glucose deprivation and caused selective and massive killing of the glucose-deprived cells. VST alone and in combination with cisplatin statistically significantly (P =.004 and P<.001 for comparisons with untreated control, respectively) inhibited tumor growth of MKN74 xenografts.


CONCLUSIONS
Disruption of the UPR may provide a novel therapeutic approach to targeting glucose-deprived solid tumors.
Park
Hae-Ryong
HR
Laboratory of Chemical Biology, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Tomida
Akihiro
A
Sato
Shigeo
S
Tsukumo
Yoshinori
Y
Yun
Jisoo
J
Yamori
Takao
T
Hayakawa
Yoichi
Y
Tsuruo
Takashi
T
Shin-ya
Kazuo
K
D051701:Activating Transcription Factor 4; D051702:Activating Transcription Factor 6; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005354:Fibrosarcoma / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D018942:Macrolides / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D009844:Oligosaccharides / Q000494:pharmacology*; D010957:Plasmids; D017510:Protein Folding; D000071701:Regulatory Factor X Transcription Factors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000378:metabolism; D013306:Streptomycetaceae; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D000071717:X-Box Binding Protein 1
C497109:ATF4 protein, human; C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D000970:Antineoplastic Agents; C497112:Atf6 protein, mouse; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; D018942:Macrolides; D009687:Nuclear Proteins; D009844:Oligosaccharides; D000071701:Regulatory Factor X Transcription Factors; D015534:Trans-Activators; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605544:Xbp1 protein, mouse; C490154:versipelostatin; D051701:Activating Transcription Factor 4; D005947:Glucose