Author(s)

Akihisa Takahashi, Hongyu Ma, Akiko Nakagawa, Yukari Yoshida, Tatsuaki Kanai, Tatsuya Ohno, Yoshikazu Kuwahara, Manabu Fukumoto, Takashi Nakano

Advanced Scientific Research Leaders Development Unit, Gunma University, Gunma, Japan.
Department of Pathology, IDAC, Tohoku University, Sendai, Japan.
Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
Gunma University Heavy Ion Medical Center, Gunma, Japan.

In order to see whether carbon ion (C-ion) beams have a biological advantage over X-rays, studies were designed to examine the effects of C-ion beams on radiosensitivity in X-ray resistant cells. Clinically relevant X-ray resistant SAS-R cells derived from human tongue cancer SAS cells were used. The cells were exposed to X-rays or Spread-Out Bragg peak (SOBP) beam C-ions. Cell survival was measured using a modified high-density survival assay. Cell survival signaling and cell death signaling were analyzed using flow cytometry. The cells were labeled with putative cancer stem cell markers such as CD44 and CD326. SAS-R cells were 1.6 times more radioresistant than SAS cells after exposure to X-rays. Cell survival was similar in each cell line after exposure to C-ion beams. SAS-R cells displayed enhanced cell survival signaling when compared to SAS cells under normal conditions. On the other hand, the phosphorylation of AKT-related proteins decreased and polycaspase activities were enhanced when cells were irradiated with C-ion beams in both cell lines. More CD44 and CD326 positive cells were seen in SAS-R cells than in SAS cells. Moreover, the marker positive cell numbers significantly decreased after exposure to C-ion beams when compared to X-rays at iso-survival doses in SAS-R cells. C-ion beams efficiently induced cell killing in X-ray resistant cells which displayed activated cell survival signaling and contained more numerous cancer stem-like cells. 

Carbon-Ion Beams, X-Ray Resistant Cells, Cell Survival and Death Signaling, Cancer Stem-Like Cells

Takahashi, A. , Ma, H. , Nakagawa, A. , Yoshida, Y. , Kanai, T. , Ohno, T. , Kuwahara, Y. , Fukumoto, M. and Nakano, T. (2014) Carbon-Ion Beams Efficiently Induce Cell Killing in X-Ray Resistant Human Squamous Tongue Cancer Cells. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 3, 133-142. doi: 10.4236/ijmpcero.2014.33019.