Carbon ion beam combined with cisplatin effectively disrupts triple negative breast cancer stem-like cells in vitro.
OBJECTIVE
Although a relatively small proportion of all breast cancer (BC), triple negative (TN) BC is responsible for a relatively large proportion of BC deaths because of its worse clinical outcome. To investigate whether a carbon ion beam alone or in combination with cisplatin (CDDP) has a beneficial effect compared to X-rays, we target triple negative (TN) breast cancer stem-like cells (CSCs).


METHODS
Human breast CSCs sorted from MDA-MB-231 and MDA-MB-453 cells were treated with a carbon ion beam or X-ray irradiation alone or in combination with CDDP, and then colony, spheroid and tumor formation assays, RT-PCR Array analysis, and immunofluorescence γH2AX foci assay were performed.


RESULTS
The colony, spheroid formation, and tumorigenicity assays confirmed that CD44+/CD24- and ESA+/CD24- cells have CSC properties in MDA-MB-231 and MDA-MB-453 cells, respectively. The proportion of CSCs was more enriched after CDDP combination with either X-ray or carbon ion beam, however carbon ion beam combined with CDDP significantly suppressed colony and spheroid formation and more significantly inhibited cell cycle progression (sub-G1 arrest) compared to X-ray combined with CDDP or carbon ion beam alone. RT-PCR Array analysis showed that carbon ion beam combined with CDDP significantly induced apoptosis-related Cytochrome c, almost completely eliminated expression of the CSC markers CD44 and ESA, and significantly inhibited angiogenesis, and metastasis-related HIF1α and CD26 compared to carbon ion beam alone, X-ray alone, or X-ray combined with CDDP. The immunofluorescence assay showed that not only the number but also the size of γH2AX foci in CSCs were larger 24 h after carbon ion beam combined with CDDP compared to those of X-ray alone and X-ray combined with CDDP.


CONCLUSIONS
Carbon ion beam combined with CDDP has superior potential to kill TN breast CSCs with irreparable severe DNA damage and enhanced apoptosis.
Medical Physics Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa Inage-ku, Chiba, Chiba, 263-8555, Japan. saisei@nirs.go.jp.
Sei
S
Sai
Radiation Risk Reduction Research Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Chiba, Japan.
Guillaume
G
Vares
Division of Heavy Ion Clinical Research, Korea Institute of Radiological and Medical Sciences, 215-4 Gongneung-dong, Nowon-Gu, Seoul, 139-706, South Korea.
Eun Ho
EH
Kim
Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
Kumiko
K
Karasawa
Radiation Risk Reduction Research Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Chiba, Japan.
Bing
B
Wang
Radiation Risk Reduction Research Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Chiba, Japan.
Mitsuru
M
Nenoi
Department of Breast Oncology, Juntendo University School of Medicine, Tokyo, Japan.
Yoshiya
Y
Horimoto
Department of Breast Oncology, Tokyo Medical University Hachioji Medical Center, Tokyo, Japan.
Mitsuhiro
M
Hayashi
D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002945:Cisplatin / Q000008:administration & dosage*; D003131:Combined Modality Therapy; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D063193:Heavy Ion Radiotherapy; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000528:radiation effects; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D014965:X-Rays
D009363:Neoplasm Proteins; D002945:Cisplatin