HKH40A downregulates GRP78/BiP expression in cancer cells.
HKH40A, the 8-methoxy analog of WMC79, is a synthetic agent with promising in vitro and in vivo antitumor activity, especially against solid tumors. However, molecular mechanisms underlying its antitumor effects are poorly understood. Here, we report that HKH40A markedly reduces the level of GRP78/BiP protein in cancer cell lines of various origin. In this study, we show that HKH40A not only downregulates transcription of GRP78 but also directly binds to the isolated protein and induces its proteosomal degradation. Knockdown of BiP increased the efficacy of the drug and overexpression of BiP diminished its activity. BiP is generally highly elevated in solid tumors having a pivotal role in cancer cell survival and chemoresistance, and has been suggested as a novel target for therapeutic intervention. We show that reduction of BiP level by HKH40A impairs its function and induces unfolded protein response as evidenced by the activation of IRE1α, ATF6 and PERK. This leads to a series of downstream events, including sustained eIF2α phosphorylation, increased abundance of spliced XBP1 mRNA and protein levels of ATF4 and CHOP. We also demonstrate that HKH40A inhibited tumor formation in an in vivo xenograft tumor model. Collectively, our data show that HKH40A reduces BiP levels and this could have an important role in the activity of HKH40A against cancer cells.
Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD, USA.
T
T
Kosakowska-Cholody
Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD, USA.
J
J
Lin
Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD, USA.
S M
SM
Srideshikan
Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD, USA.
L
L
Scheffer
Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, MD, USA.
N I
NI
Tarasova
Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD, USA.
J K
JK
Acharya
D054831:Acridones / Q000494:pharmacology*; D051702:Activating Transcription Factor 6 / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015536:Down-Regulation; D000091342:Endoplasmic Reticulum Chaperone BiP; D004722:Endoribonucleases / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D019073:HT29 Cells; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D053644:Naphthalimides / Q000494:pharmacology*; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D059748:Proteolysis; D034622:RNA Interference; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D047368:Tumor Burden / Q000187:drug effects; D056811:Unfolded Protein Response / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D019892:eIF-2 Kinase / Q000378:metabolism
C497111:ATF6 protein, human; D054831:Acridones; D051702:Activating Transcription Factor 6; D000970:Antineoplastic Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D053644:Naphthalimides; C525457:RTA 502; C460640:EIF2AK3 protein, human; C528229:ERN1 protein, human; D017346:Protein Serine-Threonine Kinases; D019892:eIF-2 Kinase; D004722:Endoribonucleases; D046988:Proteasome Endopeptidase Complex