Sei Sai

Progesterone generates cancer stem cells through membrane progesterone receptor-triggered signaling in basal-like human mammary cells.

Ionizing radiation and cumulative exposure to steroid hormones are known risk factors for breast cancer. There is increasing evidence that breast tumors are driven by a subpopulation of tumor-initiating cancer stem cells (CSCs). In MCF10A non-cancerous basal-like PR(-) cells, progesterone treatment and X-rays generated ALDH(+) and CD44(+)/CD24(-) CSCs. Here, we report that in irradiated MCF10A cells, progesterone activated the PI3K/Akt pathway via membrane progesterone receptor (mPR). Inhibition of the PI3K/Akt pathway counteracted the generation of CSCs by progesterone and irradiation. The stimulation of PI3K/Akt via mPR resulted in the inactivation of FOXO transcriptional activity, the upregulation of snail and slug expression and a downregulation of miR-29 expression, which led to increased levels of KLF4, a transcription factor required for breast CSC maintenance. Stabilization of miR-29 expression impeded the generation of CSCs, while its inhibition alone was sufficient to generate CSCs. This study provides a new mechanistic basis for progesterone and radiation-induced breast cancer risk in basal cells. In addition, the elucidation of new pathways and miRNA regulations involved in CSC generation and maintenance may open the door to potential novel anti-CSC strategies.

Combination of Cancer Stem Cell Markers CD44 and CD24 Is Superior to ALDH1 as a Prognostic Indicator in Breast Cancer Patients with Distant Metastases.

The combination of CD44 and CD24, or aldehyde dehydrogenase 1 (ALDH1) alone, is a widely used cancer stem cell marker in breast cancer. However, no conclusion has yet been reached as to which marker is the best for characterizing cancer stemness. Immunohistochemical evaluation using cancer stem cell markers is clearly less common clinically than in basic experiments and how the expressions of these markers relate to patient outcomes remains controversial. To investigate whether combining these markers might improve the prediction of patient outcomes, we immunohistochemically examined clinical samples. Primary invasive breast cancer samples from 61 patients who eventually developed distant metastases after curative surgery were immunohistochemically examined. All patients were free of metastatic disease at the time of surgery and received standard adjuvant systemic treatments. CD44+/24- and ALDH1-positive rates in primary tumors differed according to intrinsic subtype. ER-positive patients with CD44+/24- tumors had significantly longer disease-free-survival than all other ER-positive patients (p = 0.0047). On the other hand, CD44+/24- tumors were associated with poor outcomes of ER-negative patients (p = 0.038). Finally, expression patterns of CD44 and ALDH1 in single tumors were strikingly different and there were virtually no individual double-stained cells. Thus, this combination does not allow evaluation of relationships with patient outcomes. Our results raise the possibility of CD44+/24- being a good prognostic marker, one which would allow treatment effects and outcomes to be predicted in patients with recurrent breast cancer.

Metformin enhances the radiosensitivity of human liver cancer cells to γ–rays and carbon ion beams

The purpose of this study was to investigate the effect of metformin on the responses of hepatocellular carcinoma (HCC) cells to γ–rays (low-linear energy transfer (LET) radiation) and carbon-ion beams (high-LET radiation). HCC cells were pretreated with metformin and exposed to a single dose of γ–rays or carbon ion beams. Metformin treatment increased radiation-induced clonogenic cell death, DNA damage, and apoptosis. Carbon ion beams combined with metformin were more effective than carbon ion beams or γ-rays alone at inducing subG1 and decreasing G2/M arrest, reducing the expression of vimentin, enhancing phospho-AMPK expression, and suppressing phospho-mTOR and phospho-Akt. Thus, metformin effectively enhanced the therapeutic effect of radiation with a wide range of LET, in particular carbon ion beams and it may be useful for increasing the clinical efficacy of carbon ion beams.

Effect of low- and high-linear energy transfer radiation on in vitro and orthotopic in vivo models of osteosarcoma by activation of caspase-3 and -9

Osteosarcoma (OS) is a malignant tumor of the bone derived from primitive transformed cells of the mesenchymal origin. Local low-linear energy transfer (LET) radiotherapy has limited benefits on OS owing to its radioresistance. Thus, this study aimed to investigate the effects of high-LET radiation on human OS. Therefore, the human OS cell lines, U2O2 and KHOS/NP, were examined in vitro, or an orthotopic mouse xenograft model was studied in vivo after treatment with low-LET (gamma-ray) and high-LET (neutron) radiation. Notably, OS cells were significantly more sensitive to high-LET radiation in vitro and in the orthotopic xenograft tumor model. Specifically, neutron radiation treatment increased the relative percentage of apoptotic sub-G1 phase cells via caspase-3/9 activation; increased intracellular reactive oxygen species, autophagy, and DNA damage; and decreased invasion and migration. Similarly, the mean size of gamma-irradiated (8 Gy) orthotopic KHOS/NP OS was 195 mm3 at 6 weeks after gamma-irradiation (8 Gy), but it was only 150 mm3 in mice treated with high-LET neutron radiotherapy. Significantly, our results provide a rationale for the use of high-LET radiotherapy to treat patients with OS.

Gold nanoparticles as a potent radiosensitizer in neutron therapy

The purpose of this study was to investigate the potential of gold nanoparticles as radiosensitizer for use in neutron therapy against hepatocellular carcinoma. The hepatocellular carcinoma cells lines Huh7 and HepG2 were irradiated with γ and neutron radiation in the presence or absence of gold nanoparticles. Effects were evaluated by transmission electron microscopy, cell survival, cell cycle, DNA damage, migration, and invasiveness. Gold nanoparticles significantly enhanced the radiosensitivity of Huh7 and HepG2 cells to γ-rays by 1.41- and 1.16-fold, respectively, and by 1.80- and 1.35-fold to neutron radiation, which has high linear energy transfer. Accordingly, exposure to neutron radiation in the presence of gold nanoparticles induced cell cycle arrest, DNA damage, and cell death to a significantly higher extent, and suppressed cell migration and invasiveness more robustly. These effects are presumably due to the ability of gold nanoparticles to amplify the effective dose from neutron radiation more efficiently. The data suggest that gold nanoparticles may be clinically useful in combination therapy against hepatocellular carcinoma by enhancing the toxicity of radiation with high linear energy transfer.

Effects of carbon ion beam alone or in combination with cisplatin on malignant mesothelioma cells in vitro

Malignant mesothelioma (MM) is extremely aggressive and a typical refractory cancer. In this study we investigated how effective on killing MM cells by carbon ion beam alone or in combination with cisplatin (CDDP) in vitro. Carbon ion beam (at the center of SOBP with 50 keV/µm of average LET) dose-independently suppressed MM cells MESO-1 and H226 cell viability and in combination with CDDP (25 μM) significantly enhanced its action. Relative biological effectiveness (RBE) values at 73 keV/μm and 13 keV/μm portion of carbon ion beam was estimated as 2.82-2.93 and 1.19-1.22 at D10 level relative to X-ray, respectively by using colony formation assay. Quantitative real time PCR analysis showed that expression of apoptosis-related BAX and autophagy-related Beclin1 and ATG7 was significantly enhanced by carbon ion beam alone or in combination with CDDP. Apoptosis analysis showed that caspase 3/7 activity and the percentage of apoptotic cells was dose-dependently increased after carbon ion beam and it was further increased when combined with CDDP. Spheroid formation ability of cancer stem like CD44+/CD26+ cells was significantly inhibited by carbon ion beam combined with CDDP. Besides, carbon ion beam combined with cisplatin significantly inhibited cell cycle progression (sub-G1 arrest) and induced more large number of γH2AX foci. In conclusion, carbon ion beam combined with CDDP has superior potential to kill MM cells including CSCs with enhanced apoptosis.

Abstract 1390: Combination of carbon ion beam and gemcitabine causes unrepairable DNA damage and death of radioresistant pancreatic cancer stem-like cells in vitro and in vivo

Purpose To elucidate whether carbon ion beam alone or in combination with gemcitabine has advantages over X-ray irradiation in targeting putative human pancreatic cancer stem cells (CSCs). Materials and Methods Human pancreatic CSCs sorted from PANC1 and PK45 cells were treated with carbon ion beam, X-ray alone or in combination with gemcitabine, and then colony, spheroid and tumor formation assays, RT Profiler PCR Array assay, immunofluorescence γH2AX foci assay as well as in vivo tumor control analysis were performed. Results The colony, spheroid formation as well as tumorigenicity assays confirmed that CD44+/ESA+ cells exactly have CSC properties compared to CD44-/ESA- cells. CSCs were more highly enriched after X-ray or gemcitabine compared to carbon ion beam alone, but extremely enhanced either X-ray or carbon ion beam in combination with gemcitabine. The number of colony and spheroid formed from CSCs after carbon ion beam was significantly reduced compared to that of X-ray, and it was extremely suppressed when combined with gemcitabine. The relative biological effectiveness (RBE) values for the carbon ion beam relative to X-ray at the D10 levels for CSCs were 2.13-2.78. RT Profiler PCR Array analysis showed that expressions of apoptosis-related genes (Bax, Cytochrome c), autophagy-related genes (LC3, p62), and senescence-related gene p21 were remarkably induced after carbon ion beam combined with gemcitabine compared to carbon ion beam alone or X-ray combined with gemcitabine. Immunofluorescence assay showed that not only the number but also the size of γH2AX foci in CSCs were lager 24 h after carbon ion beam combined with gemcitabine compared to carbon ion beam alone or X-ray combined with gemcitabine. Xenograft tumor control analysis showed that the tumors were not completely controlled even treated with 60 Gy of X-ray, but it was destroyed with 25 Gy of carbon ion beam combined with 50 mg/kg gemcitabine. Conclusions Carbon ion beam combined with gemcitabine has superior potential to kill pancreatic CSCs via unrepairable clustered DSB, and multiple cell death pathways at relatively lower doses compared to carbon ion alone or X-ray combined ith gemcitabine. Citation Format: Sei Sai, Toshifumi Wakai, Guillaumes Vares, Shigeru Yamada, Takehiko Kamijo, Eun Ho Kim, Tadashi Kamada, Toshiyuki Shirai. Combination of carbon ion beam and gemcitabine causes unrepairable DNA damage and death of radioresistant pancreatic cancer stem-like cells in vitro and in vivo. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1390. doi:10.1158/1538-7445.AM2015-1390

Abstract 3870: Effects of carbon ion beam, alone or in combination with cisplatin, on triple-negative breast cancer stem-like cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Aims To investigate whether a carbon ion beam alone or in combination with cisplatin has beneficial effects compared to X-ray by targeting putative triple negative (TN) breast cancer stem cells (CSCs). Materials and Methods Human breast CSCs sorted from MDA MB231 cells were treated with carbon ion or X-ray irradiation alone or in combination with cisplatin, and then colony, spheroid and tumor formation assays, RT-PCR Array analysis as well as immunofluorescence γH2AX foci assay were performed. Results The colony, spheroid formation as well as tumorigenicity assays confirmed that CD44+/CD24- and CD44+/ESA+ cells exactly have CSC properties compared to CD44-/CD24- and CD44-/ESA- cells. CSCs were more highly enriched after X-ray or cisplatin compared to carbon ion beam. Carbon ion beam combined with cisplatin significantly suppressed colony and spheroid formation compared to that of X-ray combined with cisplatin as well as carbon ion alone. RT-PCR Array analysis showed that expression of DNA repair, apoptosis and autophagy related genes were differently altered between carbon ion beam and X-ray irradiation alone or in combination with cisplatin, and carbon ion beam combined with cisplatin more highly induced apoptosis and autophagy compared to X-ray combined with cisplatin. Immunofluorescence assay showed that not only the number but also the size of γH2AX foci in CSCs were lager 24 h after carbon ion beam combined with cisplatin compared to that of X-ray combined with cisplatin as well as carbon ion alone. Conclusion Carbon ion beam combined with cisplatin has superior potential to kill TN breast CSCs with unrepairable severe DNA damage and enhanced apoptosis as well as autophagy. Citation Format: Sei Sai, Kumiko Karasawa, Guillaume Gueal Vares, Toshiyuki Shirai. Effects of carbon ion beam, alone or in combination with cisplatin, on triple-negative breast cancer stem-like cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3870. doi:10.1158/1538-7445.AM2014-3870