To define differences in tumor microenvironment (TME) immune phenotypes between right and left colorectal cancers (CRCs) and explore their therapeutic implications. Gene expression profiling and clinical characteristics of patients with CRC were retrieved from The Cancer Genome Atlas data portal. Immune cell infiltration was estimated based on single-sample gene set enrichment analysis. CRCs tissue microarrays (TMAs) containing 90 consecutive cases of surgical samples were used for validation. Expression of CD8A and VEGFA was confirmed by immunohistochemistry (IHC) analysis with TMAs, and overall survival (OS) was analyzed. Expression profiling data demonstrated that CRC immune microenvironment from right side tumor was characterized as increased infiltration of immune cells with enhanced cytotoxic function, based on higher cytotoxic activity scores (CYT) and interferon-γ signatures. Expression of VEGFA, which could be neutralized by bevacizumab, was associated with decreased levels of activated CD8+ T-cells, Th1 cells, and PRF1 expression on the right side, but not on the left side. IHC analysis of TMAs further confirmed an inverse correlation between CD8A and VEGFA expression, and revealed a favorable OS for patients with CD8AHiVEGFALo disease among right-side CRCs. For the left side, higher CD56bright natural killer cell infiltration and active 4-1BB/IFN-ɑ signaling, which could providing a favorable condition for cetuximab-mediated antibody-dependent cell-mediated cytotoxicity effect, was present in a cohort with extended OS. In the TME, features of immune phenotype sidedness were identified, providing an implication for differential responses to bevacizumab/cetuximab treatment. In addition, a new avenue for innovative experimental design and combinational immunotherapy to treat CRC patients was suggested.

Terahertz (THz) radiation of layered molybdenum disulfide (MoS2) crystal under femtosecond laser irradiation was observed using THz surface emission spectroscopy under variable-angle transmission configuration. Although MoS2 demonstrates inversion symmetry, surface-symmetry breaking will introduce the resonant optical rectification, which is consistent with the incident polarization and azimuthal angle dependences of the THz radiation from MoS2. However, the surface depletion field induced THz radiation will make an important contribution under oblique incidence, which is consistent with the radiation saturation due to the electrostatic screening effect by photoexcited carriers. This pump-dependent saturable THz radiation can be fitted well by the calculation from Maxwell equations with electromagnetic boundary conditions. The maximum of the surface depletion field is estimated to be 1.45 × 104 V/cm with 130 nm in depth under −40° incidence. Interestingly, when the incident angle is tuned from −40° to 0°, the optical rectification contribution varies from 40% to 90%. In addition, MoS2 is diagnosed to be p-type from THz waveforms by comparison with GaAs(100). The results not only afford a comprehensive understanding of THz radiation from layered materials like MoS2 but also put forward THz emission spectroscopy for characterizing the surface and interface properties of two-dimensional materials.

Surfaces and interfaces are of particular importance for optoelectronic and photonic materials as they are involved in many physical and chemical processes such as carrier dynamics, charge transfer, chemical bonding, transformation reactions and so on. Terahertz (THz) emission spectroscopy provides a sensitive and nondestructive method for surface or interface analysis of advanced materials ranging from graphene to transition metal dichalcogenides, topological insulators, hybrid perovskites, and mixed-dimensional heterostructures based on 2D materials. In this review paper, we start with the THz radiation mechanisms under ultrafast laser excitation. Then we concentrate on the recent progresses of THz emission spectroscopy on the surface and interface properties of advanced materials, including transient surface photocurrents, surface nonlinear polarization, surface states, interface potential, and gas molecule adsorption/desorption processes. This novel spectroscopic method can not only promote the development of new and compact THz sources, but also provide a nondestructive optical method for surface and interface characterization of photocurrent and nonlinear polarization dynamics of materials.

No abstract