We demonstrate a gain-switched thulium fiber laser that can be continuously tuned over 140 nm, while maintaining stable nanosecond single-pulse operation. To the best of our knowledge, this system represents the broadest tuning range for a gain-switched fiber laser. The system simplicity and wideband wavelength tunability combined with the ability to control the temporal characteristics of the gain-switched pulses mean this is a versatile source highly suited to a wide range of applications in the eye-safe region of the infrared, including spectroscopy, sensing and material processing, as well as being a practical seed source for pumping nonlinear processes.Sustained interest in the development of thuliumdoped fiber based technologies is motivated by the numerous applications that benefit from laser sources in the two micron spectral region.1,2 The strong absorption at ∼1.93 µm -corresponding to the first overtone vibration of the OH molecule 3 -can be exploited in the medical sector for laser surgery, 4,5 while an atmospheric transmission window in this region means highbrightness sources with coincident emission bands are attractive for range finding, remote sensing and free-space optical communications.6 To meet industrial demands, research efforts continue to focus on thulium-doped fiber for the development of both pulsed and continuous-wave two micron laser technologies due to its extremely broad emission band (approx. 1.8 µm -2.1 µm) that supports wideband tunable systems, 7-9 in addition to the intrinsic benefits of a fiber architecture including: excellent beam quality; thermal robustness; compact alignment free operation; and power scalability. 10-12Gain-switching of a laser -by fast modulation of the pump power 13,14 -is perhaps the simplest and most robust way to generate a train of short pulses and has been applied to fiber lasers operating across the near-infrared (1-2 µm). [15][16][17][18][19] By appropriate choice of the pump pulseenergy and duration, mutliple relaxation oscillations can be prevented, mitigating temporal instabilities and leading to the generation of stable Gaussian-like nanosecond pulses.17,18 As both the repetition rate and pulse duration can be controlled by the pump characteristics, gainswitched fiber lasers exhibit greater temporal flexibility compared to other pulse generation techniques, including Q-switching and mode-locking, where the dynamics of both the gain and an intra-cavity loss modulator, as well as dispersion of the laser cavity, play dominant contributions to pulse-shaping.20 Another desirable feature of gain-switched lasers is that they can be readily synchronized with an external reference source. Dea) Electronic mail: fwang@nju.edu.cn b) Electronic mail: edmund.kelleher08@imperial.ac.uk spite significant technical progress in recent years, including the demonstration of a pulse duration as short as ∼1.5 ns and peak powers in excess of 100 kW, 21,22 gain-switched thulium fiber lasers have typically adopted a design based on the use of fiber Bragg gratings (FBGs...
Id4 is one of the inhibitors of DNA-binding proteins (Id) and involved in the pathogenesis of numerous cancers. The specific mechanism underlying the Id4-mediated regulation of proliferation, invasion, and metastasis of colorectal cancer (CRC) cells is still largely unclear. In the present study, results showed CRC cells had a lower baseline Id4 expression than normal intestinal epithelial NCM460 cells. In order to explore the role of Id4 in the tumorigenicity, CRC HCT116 cells with stable Id4 expression were used, and results showed Id4 overexpression arrested the cell cycle at the G0/G1 phase, inhibited the cell proliferation and the colony formation, as well as suppressed the migration and invasion. In the in vivo model, Id4 overexpression inhibited the tumor growth and metastasis in the nude mice. Furthermore, Id4 overexpression upregulated the expression of proteins associated with cell proliferation, inhibited the PI3K/AKT pathway, and suppressed epithelial-mesenchymal transition (EMT) of HCT116 cells. Moreover, Id4 significantly decreased cytokeratin 18 (CK18) expression, but CK18 overexpression in Id4 expressing HCT116-Id4 cells rescued the activation of AKT, p-AKT, MMP2, MMP7, and E-cadherin. Collectively, our study indicated Id4 may inhibit CRC growth and metastasis through inhibiting the PI3K/AKT pathway in a CK18-dependent manner and suppressing EMT. Id4 may become a target for the treatment of CRC.
The efficacy of conventional treatments for pancreatic cancer remains unsatisfactory, and immunotherapy is an emerging option for adjuvant treatment of this highly deadly disorder. The tumor-associated antigen (TAA) MUC1 is expressed in a variety of human cancers and is overexpressed in more than 90% of pancreatic cancer, which makes it an attractive target for cancer immunotherapy. As a self-protein, MUC1shows a low immunogenicity because of immune tolerance, and the most effective approach to breaking immune tolerance is alteration of the antigen structure. In this study, the altered MUC1 1068-1076Y1 epitope (YLQRDISEM) by modification of amino acid residues in sequences presented a higher immunogenicity and elicited more CTLs relative to the wild-type (WT) MUC1 1068-1076 epitope (ELQRDISEM). In addition, the altered MUC1 1068-1076Y1 epitope was found to cross-recognize pancreatic cancer cells expressing WT MUC1 peptides in an HLA-A0201-restricted manner and trigger stronger immune responses against pancreatic cancer via the perforin/granzyme apoptosis pathway. As a potential HLA-A0201-restricted CTL epitope, the altered MUC1 1068-1076Y1 epitope is considered as a promising target for immunotherapy of pancreatic cancer. Alteration of epitope residues may be feasible to solve the problem of the low immunogenicity of TAA and break immune tolerance to induce immune responses against human cancers.
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