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interface ( 3 ). A stronger compression was
realized by replacing the liquid subphase
of ethylene glycol with diethylene glycol,
which provided higher aliphatic hydropho-
bicity and increased the interfacial surface
energy between the solvent (i.e., cyclohex-
ane for dispersing the semiconductor NCs)
and the substrate (i.e., diethylene glycol).
This change led to a smaller receding angle
at the solidification front of assembled NCs.
Thus, the assembled NCs lacked space to ex-
tend vertically and were firmly squeezed by
the liquid surface to form 2D superlattices
of hexagonal symmetry. However, the use
of ethylene glycol as the substrate created a
higher receding angle and provided sufficient
space for selective facet-to-facet alignment of
the semiconductor tetrahedrons and the cor-
responding QC superlattices.
The flexible polygon tiling rule, facilitated
by both the anisotropic patchiness of sur-
face chemistry and the appropriate pairing
of solvent and liquid substrate used in the
self-assembly process, led to the successful
formation of QC tessellation of tetrahedral
NCs. Although self-assembly of nanopar-
ticles into dodecagonal (12-fold) QC orders
had been demonstrated from the mixtures
of spherical nanoparticles of two different
types and sizes ( 7 ), the 10 - fold QC order of
tetrahedral NCs reported by Nagaoka et al.
had been neither observed experimentally
nor predicted in any simulated QC models.
This success demonstrates that control-
ling the geometrical and chemical anisotropy(in addition to size) of nanoparticle building
blocks can enable their assembly into highly
complicated (or even unexpected) super-
lattice symmetries. Unlike the commonly
observed entropy maximization process,
anisotropic patchiness favors directional
enthalpic driving forces to promote the for-
mation of new QC superlattices. The work of
Nagaoka et al. will drive a wave of attention
from matter assembly researchers, including
the synthesis and use of different types of
anisotropic building blocks to create uncon-
ventional superlattices and complex struc-
tures. Because the tessellation of tetrahedral
and pyramidal shapes is a fascinating and
challenging research topic in many research
fields, including mathematics and computer
simulation, this experimental discovery will
likely stimulate other follow-up studies. j
REFERENCES
1. A. Haji-Akbari et al., Nature 462 , 773 ( 2009 ).
2. D. Shechtman, I. Blech, D. Gratias, J. W. Cahn, Phys. Rev.
Lett. 53 , 1951 (1 984 ).
3. Y. Nagaoka, H. Zhu, D. Eggert, O. Chen, Science 362 , 1 396
( 201 8).
4. Y. Nagaoka et al., Nature 561 , 378 ( 201 8).
5. M. Engel, H.-R. Trebin, Phys. Rev. Lett. 98 , 22550 5 ( 2007 ).
6. S. Torquato, Y. Jiao, Phys. Rev. E 80 , 041104 ( 2009 ).
7. D. V. Talapin et al., Nature 461 , 964 (2 009 ).10. 1126 /science. aav8 597Packing nanosized tetrahedrons. Self-assembly
of tetrahedral semiconductor nanoparticles normally
forms a regular periodic Bragg lattice (this page).
Nagaoka et al. show that packing at a liquid-air interface
can create a quasicrystalline lattice (preceding page).CANCER IMMUNOTHERAPYChemotherapy
and tumor
immunity
By Stéphanie Cornen^1 and Eric Vivier1,2,^3A
large increase in the incidence of can-
cers has been predicted for the com-
ing years, with the number of cases
worldwide rising from 15 million to
24 million between 2015 and 2035
( 1 ). The current revolution in can-
cer treatment—cancer immunotherapy—is
based on the mobilization of the immune
system to target cancer cells and is opening
new avenues for achieving cancer control.
However, evidence suggests that immuno-
therapies in many cancers are most effec-
tive when combined with other treatments,
such as surgery, radiotherapy, and chemo-
therapy. On page 1416 of this issue, Ruscetti
et al. ( 2 ) show that a combination of che-
motherapy drugs inhibiting MEK (mitogen-
activated protein kinase kinase) and CDKs
(cyclin-dependent kinases) induces tumor
cell senescence, a type of cell growth arrest,
that alerts the innate immune system by ac-
tivating natural killer (NK) cells, leading to
immune control of the cancer.
Therapies that enhance the development
of an immune response against tumor cells
are of high interest because the absence of
antitumor immunity prior to treatment ap-
pears to be a major factor of resistance to
immunotherapy. MEK and CDK inhibitors
target the Ras-Raf-MEK-ERK (extracellular
signal–regulated kinase) pathway, which is
a key pathway in many cancers. CDKs act
downstream from ERK to control the cell
cycle, and hence their activity can promote
tumor cell division. BRAF inhibitors, such
as dabrafenib, have potent antitumor activ-
ity, particularly when combined with MEK
inhibitors, such as trametinib, in the treat-
ment of melanoma and non–small cell lungInducing senescence
in tumor cells stimulates
antitumor innate
immune responses(^1) Innate Pharma, Marseille, France. 2 Aix Marseille Université,
INSERM, CNRS, Centre d’Immunologie de Marseille-Luminy,
Marseille, France. 3 Service d’Immunologie, Marseille
Immunopole, Hôpital de la Timone, Assistance
Publique-Hôpitaux de Marseille, Marseille, France.
Email: [email protected]
21 DECEMBER 2018 • VOL 362 ISSUE 6421 1355
Published by AAAS
on December 20, 2018^
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