TY - JOUR
T1 - Abrogation of signal transducer and activator of transcription 3 reactivation after Src kinase inhibition results in synergistic antitumor effects
AU - Johnson, Faye M.
AU - Saigal, Babita
AU - Tran, Hai
AU - Donato, Nicholas J.
PY - 2007/7/15
Y1 - 2007/7/15
N2 - Purpose: The Src family of kinases (SFKs) regulate multiple signal transduction cascades and influence proliferation, motility, survival, and angiogenesis. Dasatinib inhibits SFKs, which leads to cytotoxicity, cell cycle arrest, apoptosis, and decreased invasion of cancer cells. Signal transducer and activator of transcription 3 (STAT3) is a latent transcription factor that regulates survival and proliferation. Dasatinib results in rapid and durable inhibition of c-Src, whereas STAT3 undergoes only transient inactivation. We hypothesized that the reactivation of STAT3 after dasatinib treatment represents the engagement of a compensatory signal for cell survival that blocks the antitumor effects of SFK inhibition. Experimental Design: The effects of upstream inhibitors on STAT3 activation were assessed with western blotting and a quantitative bioplex phosphoprotein assay. We used the 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to determine the cytotoxicity and propidium iodine/annexin V staining with flourescence-activated cell sorting (FACS) analysis to evaluate cell cycle change and apoptosis. The combination index was calculated by the Chou-Talalay equation. Cytokines were quantitated using a multiplexed, particle-based FACS analysis. Results: C-Src and several downstream molecules were rapidly and durably inhibited by dasatinib. However, STAT3 was reactivated by 24 h. The addition of JAK inhibitors during dasatinib incubation resulted in sustained inhibition of STAT3, although JAK activation by dasatinib was not shown. Combined SFK and JAK inhibition resulted in synergistic cytotoxicity due to increased apoptosis. Conclusions: The reactivation of STAT3 during dasatinib treatment is caused by the engagement of a compensatory pathway that suppresses the antitumor effects of SFK inhibition and allows cancer cell survival. Abrogation of this pathway resulted in synergistic cytotoxicity. Given that STAT3 reactivation occurred in 14 of 15 solid tumor cell lines, dasatinib combined with Janus-activated kinase inhibitors may have widespread application in cancer treatment.
AB - Purpose: The Src family of kinases (SFKs) regulate multiple signal transduction cascades and influence proliferation, motility, survival, and angiogenesis. Dasatinib inhibits SFKs, which leads to cytotoxicity, cell cycle arrest, apoptosis, and decreased invasion of cancer cells. Signal transducer and activator of transcription 3 (STAT3) is a latent transcription factor that regulates survival and proliferation. Dasatinib results in rapid and durable inhibition of c-Src, whereas STAT3 undergoes only transient inactivation. We hypothesized that the reactivation of STAT3 after dasatinib treatment represents the engagement of a compensatory signal for cell survival that blocks the antitumor effects of SFK inhibition. Experimental Design: The effects of upstream inhibitors on STAT3 activation were assessed with western blotting and a quantitative bioplex phosphoprotein assay. We used the 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to determine the cytotoxicity and propidium iodine/annexin V staining with flourescence-activated cell sorting (FACS) analysis to evaluate cell cycle change and apoptosis. The combination index was calculated by the Chou-Talalay equation. Cytokines were quantitated using a multiplexed, particle-based FACS analysis. Results: C-Src and several downstream molecules were rapidly and durably inhibited by dasatinib. However, STAT3 was reactivated by 24 h. The addition of JAK inhibitors during dasatinib incubation resulted in sustained inhibition of STAT3, although JAK activation by dasatinib was not shown. Combined SFK and JAK inhibition resulted in synergistic cytotoxicity due to increased apoptosis. Conclusions: The reactivation of STAT3 during dasatinib treatment is caused by the engagement of a compensatory pathway that suppresses the antitumor effects of SFK inhibition and allows cancer cell survival. Abrogation of this pathway resulted in synergistic cytotoxicity. Given that STAT3 reactivation occurred in 14 of 15 solid tumor cell lines, dasatinib combined with Janus-activated kinase inhibitors may have widespread application in cancer treatment.
UR - http://www.scopus.com/inward/record.url?scp=34547125964&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34547125964&partnerID=8YFLogxK
U2 - 10.1158/1078-0432.CCR-06-2981
DO - 10.1158/1078-0432.CCR-06-2981
M3 - Article
C2 - 17634553
AN - SCOPUS:34547125964
SN - 1078-0432
VL - 13
SP - 4233
EP - 4244
JO - Clinical Cancer Research
JF - Clinical Cancer Research
IS - 14
ER -