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Journal Articles

Generality assessment of a model considering heterogeneous cancer cells for predicting tumor control probability for stereotactic body radiotherapy against non-small cell lung cancer

Saga, Ryo*; Matsuya, Yusuke; Obara, Hideki*; Komai, Fumio*; Yoshino, Hironori*; Aoki, Masahiko*; Hosokawa, Yoichiro*

Advances in Radiation Oncology (Internet), 9 Pages, 2024/00

The curative effects after radiotherapy are evaluated by the index of tumor control probability (TCP), and the treatment regimen has been determined empirically based on clinical experiences. In recent years, in order to determine TCP for any treatment regimens based on cell experiments, it is necessary to consider the existence of radioresistant cancer stem cells, which are included in tumors at from a few to several tens of percent. Our previous study has proposed an integrated microdosimetric-kinetic (IMK) model that explicitly considers cancer stem cells, and successfully reproduced cancer cell death obtained from cell experiments and clinical TCP. However, the verification so far has been limited to comparison with the clinical data of Hirosaki University Hospital, and comparative verification with clinical data of other facilities has not been performed. In this study, we focused on the stereotactic radiotherapy against non-small cell lung cancer that prescribes a large dose at once, and compared the public data collected by meta-analysis with the IMK model. As a result, it was found that the IMK model considering cancer stem cells well reproduced the clinical TCP regardless of the observed facility type. This work would contribute to the development of technology for predicting curative effects of radiotherapy with high precision.

Journal Articles

Translational study for stereotactic body radiotherapy against non-small cell lung cancer, including oligometastases, considering cancer stem-like cells enable predicting clinical outcome from ${it in vitro}$ data

Saga, Ryo*; Matsuya, Yusuke; Sato, Hikari*; Hasegawa, Kazuki*; Obara, Hideki*; Komai, Fumio*; Yoshino, Hironori*; Aoki, Masahiko*; Hosokawa, Yoichiro*

Radiotherapy and Oncology, p.109444_1 - 109444_9, 2023/00

 Times Cited Count:0 Percentile:0(Oncology)

When treating non-small cell lung cancer (NSCLC), stereotactic body radiotherapy (SBRT) with high-dose irradiation is often utilized. The fractionation schemes and curative effects can be evaluated by mathematical models for predicting cell survival curve. Such model parameters can be determined from in vitro experiment, but they are empirically determined based on experiences in clinics. As such, there is a large gap between in vitro and clinical study. As such background, translational study between in vitro cell survival and clinical curative effects is necessary. In this study, explicitly considering existence of cancer stem-like cells (CSCs), we developed an all-in-one model for predicting both in vitro cell survival and clinical curative effects (integrated microdosimetric-kinetic (IMK) model) and performed retrospective evaluation of clinical outcomes following SBRT for NSCLC in Hirosaki University Hospital. As a result, the IMK model successfully reproduced both in vitro cell survival and the tumor control probability with various fractionation schemes (i.e., 6-10 Gy per fraction). The developed model would contribute on precisely understanding the impact of CSCs on curative effects after SBRT for NSCLC with high precision.

Journal Articles

Tumor radioresistance caused by radiation-induced changes of stem-like cell content and sub-lethal damage repair capability

Fukui, Roman*; Saga, Ryo*; Matsuya, Yusuke; Tomita, Kazuo*; Kuwahara, Yoshikazu*; Ouchi, Kentaro*; Sato, Tomoaki*; Okumura, Kazuhiko*; Date, Hiroyuki*; Fukumoto, Manabu*; et al.

Scientific Reports (Internet), 12(1), p.1056_1 - 1056_12, 2022/01

 Times Cited Count:6 Percentile:92.29(Multidisciplinary Sciences)

Alive cancer cells after fractionated irradiations with 2 Gy X-rays per day for more than 30 days show clinically relevant radioresistant. Such radioresistance is experimentally interpreted to attributed to the increment of stem-like cell content. However, only an experimental approach cannot clarify the cell responses (DNA damage and cell death induction) of cancer stem cells, so the radioresistant mechanisms remain uncertain. In addition to the conventional cell experiments using radio-resistant cell lines established after fractionated irradiations, in this study we developed a mathematical model (so called integrated microdosimetric-kinetic (IMK) model) explicitly considering cancer stem-like cell content and DNA damage responses and investigated radioresistant mechanisms acquired after fractionated irradiations. The IMK model analysis suggested that the changes of stem-like cell fraction and DNA repair efficiency play important roles of radioresisitance acquired after irradiations. Considering these into the IMK model, we successfully reproduced the experimental survival of various cell lines and various irradiation conditions. This work would contribute to not only the precise understanding of the radioresistant mechanisms induced after irradiation but also predicting curative effects with high precision.

Journal Articles

PSTEP: Project for solar-terrestrial environment prediction

Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.

Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12

 Times Cited Count:6 Percentile:52.8(Geosciences, Multidisciplinary)

The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

Journal Articles

4-Methylumbelliferone administration enhances radiosensitivity of human fibrosarcoma by intercellular communication

Saga, Ryo*; Matsuya, Yusuke; Takahashi, Rei*; Hasegawa, Kazuki*; Date, Hiroyuki*; Hosokawa, Yoichiro*

Scientific Reports (Internet), 11(1), p.8258_1 - 8258_10, 2021/04

 Times Cited Count:4 Percentile:48.97(Multidisciplinary Sciences)

Hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) is a candidate of radiosensitizers in X-ray therapy. The curative effects under such 4-MU administration have been investigated in vitro; however, the radiosensitizing mechanisms remain unclear. Here, we investigated the radiosensitizing effects under 4-MU treatment from cell experiments and model estimations. We generated experimental surviving fractions of human fibrosarcoma cells (HT1080) after 4-MU treatment combined with X-ray irradiation. Meanwhilst, we also modelled the pharmacological effects of 4-MU treatment and theoretically analyzed the synergetic effects between 4-MU treatment and X-ray irradiation. The results show that the enhancement of cell killing by 4-MU treatment is the greatest in the intermediate dose range of around 4 Gy, which indicates the involvement of intercellular communication. In addition, the oxidative stress level, which leads to DNA damage induction, significantly increased under 4-MU treatment, and the radiosensitization by 4-MU can be suppressed by the inhibitors for intercellular communication. These findings suggest that the synergetic effects between 4-MU treatment and irradiation are predominantly attributed to intercellular communication and provide more efficient tumour control than conventional X-ray therapy.

Journal Articles

Analysis of the high-dose-range radioresistance of prostate cancer cells, including cancer stem cells, based on a stochastic model

Saga, Ryo*; Matsuya, Yusuke; Takahashi, Rei*; Hasegawa, Kazuki*; Date, Hiroyuki*; Hosokawa, Yoichiro*

Journal of Radiation Research, 60(3), p.298 - 307, 2019/05

 Times Cited Count:21 Percentile:82.07(Biology)

In radiotherapy, it is recognized that cancer stem cells (CSCs) in tumor tissue shows radio-resistance. However, the relationship between content percentage of the CSCs and dose-response curve on cell survival remain unclear. In this study, we developed a stochastic model considering progeny cells and stem cells, and investigated the impact of stem cells on radio-sensitivity. From the flow-cytometric analysis (cell experiments), the content percentage of stem cells was 3.2% or less which agreed well with the model estimation from the cell survival curve. Based on the verification, it is suggested that cell survival in high-dose range is largely affected by the CSCs. In addition, regarding the sub-population of stem cells, the present model well reproduces the dose response on lethal lesions to DNA comparing with the conventional LQ model. This outcome indicates that the stem cells must be considered for describing the dose-response curve in wide dose range.

Oral presentation

Investigation of radiosensitivity enhanced by inflammatory responses after irradiation based on a cell-killing model considering non-targeted effects

Takahashi, Rei*; Saga, Ryo*; Matsuya, Yusuke; Hasegawa, Kazuki*; Fukui, Roman*; Hosokawa, Yoichiro*

no journal, , 

Inflammatory responses after irradiation induce antioxidant activity, leading to radioresistance in cancer cells. In our previous study, it was found that a hyaluronan synthesis inhibitor (4-MU) can suppress inflammatory responses, however the underlying mechanisms are still unknown. In this study, we aimed to clarify the radiosensitization mechanism induced by 4-MU in the application of cell-killing models. In terms of in vitro experiments, cultured human fibrosarcoma cells were exposed to X-rays in presence of 100 $$mu$$M 4-MU and scavenger of intercellular signalling (1% DMSO, 40 $$mu$$M c-PTIO), and we measured the relation between dose and cell viability by means of colony assay. The experimental results were also interpreted by using integrated cell-killing model which has been developed so as to consider non-targeted effects. From the experiments, it was found that a combination of 4-MU treatment and irradiation significantly reduced the cell survival. This reduced viability was suppressed in the presence of DMSO or c-TPIO. Meanwhile, the model analysis showed such an increase of cell-killing is predominantly attributed by non-targeted effects. These results suggest that the radiosensetization promoted by 4-MU treatment is predominantly attributed to the accumulation in non-targeted effects.

Oral presentation

Investigation of radioresistant mechanisms in oral squamous cell carcinoma cells in in hypoxic environment

Tosa, Nanami*; Saga, Ryo*; Matsuya, Yusuke; Hosokawa, Yoichiro*

no journal, , 

Cancer cells exposed to a hypoxic environment show malignant progression such resistant to both chemotherapy and radiotherapy. During fractionated radiotherapy (e.g., 2 Gy/fraction), due to broken fragile blood vessels, cancer cells near blood vessels are exposed to a hypoxic environment, leading to cancer stem-like cells (CSCs) niches and reduced radiosensitivity. However, the radioresistant mechanisms of cancer cells in hypoxia remain uncertain. In this study, we investigated the relationship between CSC fraction and radioresistance in hypoxia. The experimental results on surviving fraction of oral squamous cell carcinoma cells (HSC3 cells) shows that the radiosensitivity can be reduced as exposure time of hypoxia becomes longer. Meanwhile, using the integrated cell-killing model explicitly considering oxygen effects and CSC population (so called integrated microdosimetric-kinetic (IMK) model), the reduced radiosensitivity could be reproduced by reduced DNA damage yield and increased CSC fraction due to lack of oxygen. This work would contribute to the radioresistant mechanisms and the precise understanding of the therapeutic effects during fractionated radiotherapy.

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