Evaluation of Helium Ion Radiotherapy in Combination with Gemcitabine in Pancreatic Cancer In Vitro

Background: Pancreatic cancer is one of the most aggressive and lethal cancers. New treatment strategies are highly warranted. Particle radiotherapy could offer a way to overcome the radioresistant nature of pancreatic cancer because of its biological and physical characteristics. Within particles, helium ions represent an attractive therapy option to achieve the highest possible conformity while at the same time protecting the surrounding normal tissue. The aim of this study was to evaluate the cytotoxic efficacy of helium ion irradiation in pancreatic cancer in vitro. Methods: Human pancreatic cancer cell lines AsPC-1, BxPC-3 and Panc-1 were irradiated with photons and helium ions at various doses and treated with gemcitabine. Photon irradiation was performed with a biological cabin X-ray irradiator, and helium ion irradiation was performed with a spread-out Bragg peak using the raster scanning technique at the Heidelberg Ion Beam Therapy Center (HIT). The cytotoxic effect on pancreatic cancer cells was measured with clonogenic survival. The survival curves were compared to the predicted curves that were calculated via the modified microdosimetric kinetic model (mMKM). Results: The experimental relative biological effectiveness (RBE) of helium ion irradiation ranged from 1.0 to 1.7. The predicted survival curves obtained via mMKM calculations matched the experimental survival curves. Mainly additive cytotoxic effects were observed for the cell lines AsPC-1, BxPC-3 and Panc-1. Conclusion: Our results demonstrate the cytotoxic efficacy of helium ion radiotherapy in pancreatic cancer in vitro as well as the capability of mMKM calculation and its value for biological plan optimization in helium ion therapy for pancreatic cancer. A combined treatment of helium irradiation and chemotherapy with gemcitabine leads to mainly additive cytotoxic effects in pancreatic cancer cell lines. The data generated in this study may serve as the radiobiological basis for future experimental and clinical works using helium ion radiotherapy in pancreatic cancer treatment

Strength and anisotropy of hexagonal Fe-Si-C alloy in planetary cores

&amp;lt;div&amp;gt; &amp;lt;p class=&amp;quot;v1MsoNormal&amp;quot;&amp;gt;The observed density of planetary cores is lower than in pure iron-nickel alloy at corresponding conditions. Therefore, the cores of terrestrial planets should be composed of iron-nickel alloyed with some lighter elements. These elements should be abundant in the solar system, siderophile, and compatible with iron at high-pressure high-temperature conditions. Si and C comply with these requirements and could be planetary core constituents. Seismic observations of the Earth&amp;#039;s inner core revealed anisotropy of seismic wave propagation. For instance, compressional waves travel 1-3% faster along the polar axis compared to waves travelling in the equatorial plane. One of the hypotheses of the origin of the anisotropy is the plastic deformation and development of textures in inner-core materials under pressure. We employed Fe-Si-C alloy to study its yield strength and anisotropy at high-pressure high-temperature conditions to compare its properties with those observed in the Earth&amp;#039;s core. The experiments were conducted by radial X-ray diffraction coupled with resistively heated diamond anvil cells that acted as a deformation apparatus. We performed experiments up to 120 GPa pressure with temperatures exceeding 1100 K. The strength values of Fe-Si-C alloy are higher than the strength of pure Fe and Fe-Si alloys. Our results show lower anisotropy of sound-wave velocities in hexagonal Fe-Si-C alloy compared to the seismic observations. We detected the change in main texture orientation upon compression from [0001] to &amp;amp;#160;in Fe-Si-C alloy. In our presentation, we will discuss the dominant mechanisms of plastic deformation, responsible for these observations, and the overall effects of carbon and silicon on the strength and anisotropy of hexagonal iron alloys in planetary cores.&amp;amp;#160;&amp;lt;/p&amp;gt; &amp;lt;/div&amp;gt;</jats:p