Thapsigargin resistance in human prostate cancer cells.
BACKGROUND
Thapsigargin (TG) is a potent inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+ ATPases (SERCAs). TG-based prodrugs are being developed for the treatment of prostate cancer (PC). To develop optimal TG-based therapeutics it is important to understand the mechanisms of resistance to TG that may potentially occur in cancer cells.


METHODS
DU145/TG and PC3/TG cells were derived from human PC DU145 and PC3 cells, respectively, by incremental exposure to TG. Growth assays, Western blot analyses, cDNA microarrays, semiquantitative and real-time polymerase chain reaction (PCR), Northern blot analyses, and immunohistochemistry were used to study these cells.


RESULTS
DU145/TG cells are 1100-fold and PC3/TG cells are 1350-fold resistant to TG. Although expression of both SERCA and p-glycoprotein can mediate TG resistance in hamster cells, neither is modulated in DU145/TG cells. In contrast, in PC3/TG cells, SERCA, and not p-glycoprotein, is significantly overexpressed but cannot by itself account for the 1350-fold resistance to TG in these cells. Several genes not previously identified to be altered by TG selection are modulated in DU145/TG and PC3/TG cells. Furthermore, the spectrum of genes modulated in DU145/TG cells are distinct from that in PC3/TG cells, even though both cells are of prostate origin and share the same TG-resistant phenotype.


CONCLUSIONS
PC cells can adapt to SERCA inhibition by TG. However, they demonstrate cell type-specific plasticity with respect to gene expression upon TG selection. Further, previously not described mechanisms of resistance appear to be recruited in the TG-resistant PC cells, which provide a novel model to study mechanisms of resistance and adaptation in PC on TG-mediated dysregulation of Ca2+ homeostasis.
O'Neill
John P
JP
Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Velalar
Chidambaram Natesa
CN
Lee
Dong Ik
DI
Zhang
Bin
B
Nakanishi
Takeo
T
Tang
Yao
Y
Selaru
Florin
F
Ross
Douglas
D
Meltzer
Stephen J
SJ
Hussain
Arif
A
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D006224:Cricetinae; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019284:Thapsigargin / Q000494:pharmacology*; D015854:Up-Regulation
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004791:Enzyme Inhibitors; D019284:Thapsigargin