CD146 is a potential immunotarget for neuroblastoma

Neuroblastoma, the most common extracranial solid tumor of childhood, is thought to arise from neural crest-derived immature cells. The prognosis of patients with high-risk or recurrent/refractory neuroblastoma remains quite poor despite intensive multimodality therapy; therefore, novel therapeutic interventions are required. We examined the expression of a cell adhesion molecule CD146 (melanoma cell adhesion molecule [MCAM]) by neuroblastoma cell lines and in clinical samples and investigated the anti-tumor effects of CD146-targeting treatment for neuroblastoma cells both in vitro and in vivo. CD146 is expressed by 4 cell lines and by most of primary tumors at any stage. Short hairpin RNA-mediated knockdown of CD146, or treatment with an anti-CD146 polyclonal antibody, effectively inhibited growth of neuroblastoma cells both in vitro and in vivo, principally due to increased apoptosis via the focal adhesion kinase and/or nuclear factor-kappa B signaling pathway. Furthermore, the anti-CD146 polyclonal antibody markedly inhibited tumor growth in immunodeficient mice inoculated with primary neuroblastoma cells. In conclusion, CD146 represents a promising therapeutic target for neuroblastoma

Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I

We have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed no significant signals in 711 days of data. We obtain an upper limit for neutrino millicharge of 5.4 × 10−12e at 90% confidence level assuming all three species of neutrino have common millicharge. We also set flavor-dependent limits assuming the respective neutrino flavor is the only one carrying a millicharge, 7.3 × 10−12e for νe , 1.1 × 10−11e for νμ, and 1.1 × 10−11e for ντ . These limits are the most stringent yet obtained from direct measurements. We also obtain an upper limit for the neutrino magnetic moment of 1.8 × 10−10 Bohr magnetons. In addition, we obtain upper limits for the coupling constant of dark photons in the U(1)B−L model of 1.3 × 10−6 if the dark photon mass is 1 × 10−3 MeV/c2, and 8.8 × 10−5 if it is 10 MeV/c2

Search for dark matter in the form of hidden photons and axion-like particles in the XMASS detector

Hidden photons and axion-like particles are candidates for cold dark matter if they were produced non-thermally in the early universe. We conducted a search for both of these bosons using 800 live-days of data from the XMASS detector with 327 kg of liquid xenon in the fiducial volume. No significant signal was observed, and thus we set constraints on the α´/α parameter related to kinetic mixing of hidden photons and the coupling constant gAe of axion-like particles in the mass range from 40 to 120 keV/c2, resulting in α´/α < 6 × 10−26 and gAe < 4 × 10−13. These limits are the most stringent over this mass range derived from both direct and indirect searches to date

Direct dark matter search in XMASS-I

A search for dark matter using an underground single-phase liquid xenon detector was conducted at the Kamioka Observatory in Japan, particularly for Weakly Interacting Massive Particles (WIMPs). We have used 705.9 live days of data in a fiducial volume containing 97 kg of liquid xenon at the center of the detector. The event rate in the fiducial volume after the data reduction was (4.2 ± 0.2) × 10−3 day−1 kg−1 keVee−1 at 5 keVee, with a signal efficiency of 20%. All the remaining events are consistent with our background evaluation, mostly of the “mis-reconstructed events” originated from 210Pb in the copper plates lining the detector’s inner surface. The obtained upper limit on a spin-independent WIMP-nucleon cross section was 2.2 × 10−44 cm2 for a WIMP mass of 60 GeV/c2 at the 90% confidence level, which was the most stringent limit among results from single-phase liquid xenon detectors

Search for solar Kaluza–Klein axions by annual modulation with the XMASS-I detector

In theories with large extra dimensions beyond the standard 4-dimensional spacetime, axions could propagate in such extra dimensions, and acquire Kaluza–Klein (KK) excitations. These KK axions are produced in the Sun and could solve the unexplained heating of the solar corona. While most of the solar KK axions escape from the solar system, a small fraction are gravitationally trapped in orbits around the Sun. They would decay into 2 photons inside a terrestrial detector. The event rate is expected to modulate annually depending on the distance from the Sun. We have searched for the annual modulation signature using 832×359 kg⋅days of XMASS-I data. No significant event rate modulation is found, and hence we set the first experimental constraint on the KK axion–photon coupling of 4.8×10−12GeV−1 at the 90% confidence level for a KK axion number density of n¯a=4.07×1013m−3⁠, the total number of extra dimensions n=2⁠, and the number of extra dimensions δ=2 that axions can propagate in

Improved search for two-neutrino double electron capture on 124Xe and 126Xe using particle identification in XMASS-I

We conducted an improved search for the simultaneous capture of two K-shell electrons on the 124Xe and 126Xe nuclei with emission of two neutrinos using 800.0 days of data from the XMASS-I detector. A novel method to discriminate γ-ray/X-ray or double electron capture signals from β-ray background using scintillation time profiles was developed for this search. No significant signal was found when fitting the observed energy spectra with the expected signal and background. Therefore, we set the most stringent lower limits on the half-lives at 2.1×1022 and 1.9×1022 years for 124Xe and 126Xe, respectively, with 90% confidence level. These limits improve upon previously reported values by a factor of 4.5