Two-dimensional monolayer transition metal dichalcogenide semiconductors are ideal building blocks for atomically thin, flexible optoelectronic and catalytic devices. Although challenging for two-dimensional systems, sub-diffraction optical microscopy provides a nanoscale material understanding that is vital for optimizing their optoelectronic properties. Here we use the ‘Campanile' nano-optical probe to spectroscopically image exciton recombination within monolayer MoS2 with sub-wavelength resolution (60 nm), at the length scale relevant to many critical optoelectronic processes. Synthetic monolayer MoS2 is found to be composed of two distinct optoelectronic regions: an interior, locally ordered but mesoscopically heterogeneous two-dimensional quantum well and an unexpected ∼300-nm wide, energetically disordered edge region. Further, grain boundaries are imaged with sufficient resolution to quantify local exciton-quenching phenomena, and complimentary nano-Auger microscopy reveals that the optically defective grain boundary and edge regions are sulfur deficient. The nanoscale structure–property relationships established here are critical for the interpretation of edge- and boundary-related phenomena and the development of next-generation two-dimensional optoelectronic devices.
Summary
Accumulating evidence suggests that co-deletion of tumor suppressor genes Pten and p53 plays a crucial role in the development of castration-resistant prostate cancer in vivo. However, the molecular mechanism underlying Pten/p53-deficiency driven prostate tumorigenesis remains incompletely understood. Building upon insights gained from our studies with Pten/p53-deficient mouse embryonic fibroblasts (MEFs), we report here that hexokinase 2 (HK2) is selectively upregulated by the combined loss of Pten and p53 in prostate cancer cells. Mechanistically, Pten deletion increases HK2 mRNA translation through activation of the AKT-mTORC1-4EBP1 axis and p53 loss enhances HK2 mRNA stability through inhibition of miR143 biogenesis. Genetic studies demonstrate that HK2-mediated aerobic glycolysis, known as the Warburg effect, is required for Pten/p53-deficiency driven tumor growth in xenograft mouse models of prostate cancer. Our findings suggest that HK2 might be a therapeutic target for prostate cancer patients carrying Pten and p53 mutations.
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