Page 215 - 2014 Printable Abstract Book
P. 215
(PS3-44) Radiation-induced, tumor-infiltrating neutrophils play an important role in the therapeutic
effect. Tsuguhide Takeshima; Debabrata Saha, Ph.D; Nathan Kim, MD, Ph.D; Jeffrey Meyer, MD; Ellen
Vitetta, Ph.D; and Raquibul Hannan, MD, Ph.D; University of Texas Southwestern Medical Center, Dallas,
TX
It is now becoming clear that the therapeutic response of radiation therapy (RT) is intricately
involved with the host’s immune system. Understanding the composition of the stromal cells in the tumor
microenvironment immediately after tumor irradiation may provide insights into the first steps in the
immunomodulation by RT. We report here the antitumor characteristics of neutrophil (CD11b+Gr-1+ cell)
which is recruited to the irradiated tumor. First, we harvested tumor mass at different times after a single
15 Gy dose of focused RT to the RM-9 (mouse prostate cancer cell line)- and LLC (lung cancer cell line)-
bearing C57BL/6 mice and 4T1 (breast cancer cell line)-bearing BALB/c mice. Subpopulations of
lymphocytes and granulocytes were analyzed in the harvested tissue by flow cytometry. We found that
an infiltration of CD11b+Gr-1+ neutrophils reached a peak within the tumor microenvironment at 24 h
after tumor RT while no significant changes in any other subpopulations were noted in all three tumor
models. To investigate the effect of neutrophils on tumor growth, we compared the tumor size in mice
treated with the neutrophil-depleting anti-Ly-6G mAb to those treated with an isotype-matched control
antibody. Interestingly, in all three tumor models, the therapeutic effect of RT was significantly attenuated
in the mice with depleted neutrophils (p=0.02, 0.03 and 0.04 in RM9, 4T1 and LLC respectively). Next,
CD11b+Gr-1+ cells were isolated from both 24h-post irradiated (RT-neut) and un-irradiated mice tumor
(Cont-neut) with a FACSAria cell sorter in order to measure their direct cytotoxicities against RM-9 cells in
vitro with 51Cr release assay. The RT-neut exhibited higher cytotoxicity (22.3 %, E/T ratio=10:1) than did
that of Cont-neut (4.7%, E/T ratio=10:1, p=0.006) To investigate the mechanism of increased tumor
cytotoxicity of RT-neut, the ROS production in both neutrophils were measured by flow cytometer after
staining with Dihydrorhodamine 123 (DHR 123). The mean fluorescence intensity of DHR 123 of RT-neut
(177) was higher than that of Cont-neut (141, p=0.02). This indicates that the increasing ROS production
by RT-neut may be involved in increasing the therapeutic effect of RT. These data support that radiation-
induced tumor-infiltrating neutrophils play an important role in the RT therapeutic effect.
(PS3-46) Dosimetric and biological response characterization of a novel image-guided precision proton
radiation platform (PPRP) for radiobiological experiments. Eric Ford; Robert Stewart; George Sandison;
Steven Bowen; and Jeffrey Schwartz; University of Washington, Seattle, WA
Purpose: We have developed a precision proton radiation platform (PPRP) that supports image-
guided proton irradiation of cell cultures, mice and rats. This tool is useful for comparative biological
response studies between proton and photon radiation. Methods: The PPRP employs a cyclotron to
generate a 50.5 MeV maximum energy proton beam. Various proton beam energies may be produced by
the cyclotron with collimated beam spot sizes (2mm here). This design integrates the proton beam with a
commercial image-guided X-ray irradiator to provide CT imaging along with proton or photon irradiation.
We performed dosimetric characterization of the PPRP using ion chambers and EBT3 film and compared
these measurements to the computational predictions of Geant4/TOPAS Monte Carlo simulations. We
also characterized the biological response to the PPRP proton beams with an in vitro for A459 lung cancer
cells, measuring chromosome breaks and cell survival at selected points along the penetration path of the
beams including the pristine Bragg peak. Results: Measurements and Monte Carlo simulations
213 | P a g e
effect. Tsuguhide Takeshima; Debabrata Saha, Ph.D; Nathan Kim, MD, Ph.D; Jeffrey Meyer, MD; Ellen
Vitetta, Ph.D; and Raquibul Hannan, MD, Ph.D; University of Texas Southwestern Medical Center, Dallas,
TX
It is now becoming clear that the therapeutic response of radiation therapy (RT) is intricately
involved with the host’s immune system. Understanding the composition of the stromal cells in the tumor
microenvironment immediately after tumor irradiation may provide insights into the first steps in the
immunomodulation by RT. We report here the antitumor characteristics of neutrophil (CD11b+Gr-1+ cell)
which is recruited to the irradiated tumor. First, we harvested tumor mass at different times after a single
15 Gy dose of focused RT to the RM-9 (mouse prostate cancer cell line)- and LLC (lung cancer cell line)-
bearing C57BL/6 mice and 4T1 (breast cancer cell line)-bearing BALB/c mice. Subpopulations of
lymphocytes and granulocytes were analyzed in the harvested tissue by flow cytometry. We found that
an infiltration of CD11b+Gr-1+ neutrophils reached a peak within the tumor microenvironment at 24 h
after tumor RT while no significant changes in any other subpopulations were noted in all three tumor
models. To investigate the effect of neutrophils on tumor growth, we compared the tumor size in mice
treated with the neutrophil-depleting anti-Ly-6G mAb to those treated with an isotype-matched control
antibody. Interestingly, in all three tumor models, the therapeutic effect of RT was significantly attenuated
in the mice with depleted neutrophils (p=0.02, 0.03 and 0.04 in RM9, 4T1 and LLC respectively). Next,
CD11b+Gr-1+ cells were isolated from both 24h-post irradiated (RT-neut) and un-irradiated mice tumor
(Cont-neut) with a FACSAria cell sorter in order to measure their direct cytotoxicities against RM-9 cells in
vitro with 51Cr release assay. The RT-neut exhibited higher cytotoxicity (22.3 %, E/T ratio=10:1) than did
that of Cont-neut (4.7%, E/T ratio=10:1, p=0.006) To investigate the mechanism of increased tumor
cytotoxicity of RT-neut, the ROS production in both neutrophils were measured by flow cytometer after
staining with Dihydrorhodamine 123 (DHR 123). The mean fluorescence intensity of DHR 123 of RT-neut
(177) was higher than that of Cont-neut (141, p=0.02). This indicates that the increasing ROS production
by RT-neut may be involved in increasing the therapeutic effect of RT. These data support that radiation-
induced tumor-infiltrating neutrophils play an important role in the RT therapeutic effect.
(PS3-46) Dosimetric and biological response characterization of a novel image-guided precision proton
radiation platform (PPRP) for radiobiological experiments. Eric Ford; Robert Stewart; George Sandison;
Steven Bowen; and Jeffrey Schwartz; University of Washington, Seattle, WA
Purpose: We have developed a precision proton radiation platform (PPRP) that supports image-
guided proton irradiation of cell cultures, mice and rats. This tool is useful for comparative biological
response studies between proton and photon radiation. Methods: The PPRP employs a cyclotron to
generate a 50.5 MeV maximum energy proton beam. Various proton beam energies may be produced by
the cyclotron with collimated beam spot sizes (2mm here). This design integrates the proton beam with a
commercial image-guided X-ray irradiator to provide CT imaging along with proton or photon irradiation.
We performed dosimetric characterization of the PPRP using ion chambers and EBT3 film and compared
these measurements to the computational predictions of Geant4/TOPAS Monte Carlo simulations. We
also characterized the biological response to the PPRP proton beams with an in vitro for A459 lung cancer
cells, measuring chromosome breaks and cell survival at selected points along the penetration path of the
beams including the pristine Bragg peak. Results: Measurements and Monte Carlo simulations
213 | P a g e
