TGFβ1 inhibition increases the radiosensitivity of breast cancer cells in vitro and promotes tumor control by radiation in vivo.
OBJECTIVE
To determine whether inhibition of TGFβ signaling prior to irradiation sensitizes human and murine cancer cells in vitro and in vivo.


METHODS
TGFβ-mediated growth and Smad phosphorylation of MCF7, Hs578T, MDA-MB-231, and T47D human breast cancer cell lines were examined and correlated with clonogenic survival following graded radiation doses with and without pretreatment with LY364947, a small molecule inhibitor of the TGFβ type I receptor kinase. The DNA damage response was assessed in irradiated MDA-MB-231 cells pretreated with LY364947 in vitro and LY2109761, a pharmacokinetically stable inhibitor of TGFβ signaling, in vivo. The in vitro response of a syngeneic murine tumor, 4T1, was tested using a TGFβ neutralizing antibody, 1D11, with single or fractionated radiation doses in vivo.


RESULTS
Human breast cancer cell lines pretreated with TGFβ small molecule inhibitor were radiosensitized, irrespective of sensitivity to TGFβ growth inhibition. Consistent with increased clonogenic cell death, radiation-induced phosphorylation of H2AX and p53 was significantly reduced in MDA-MB-231 triple-negative breast cancer cells when pretreated in vitro or in vivo with a TGFβ type I receptor kinase inhibitor. Moreover, TGFβ neutralizing antibodies increased radiation sensitivity, blocked γH2AX foci formation, and significantly increased tumor growth delay in 4T1 murine mammary tumors in response to single and fractionated radiation exposures.


CONCLUSIONS
These results show that TGFβ inhibition prior to radiation attenuated DNA damage responses, increased clonogenic cell death, and promoted tumor growth delay, and thus may be an effective adjunct in cancer radiotherapy.
Department of Radiation Oncology, New York University School of Medicine, New York, New York 10016, USA.
Fanny
F
Bouquet
Anupama
A
Pal
Karsten A
KA
Pilones
Sandra
S
Demaria
Byron
B
Hann
Rosemary J
RJ
Akhurst
Jim S
JS
Babb
Scott M
SM
Lonning
J Keith
JK
DeWyngaert
Silvia C
SC
Formenti
Mary Helen
MH
Barcellos-Hoff
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D048708:Cell Growth Processes / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology*; D011758:Pyrroles / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014966:Xanthenes / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
D000596:Amino Acids; C530108:LY2109761; C479758:LY366457; D011720:Pyrazoles; D011758:Pyrroles; D011838:Radiation-Sensitizing Agents; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014966:Xanthenes; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I