Browsing by Author "Zhang, Xin"

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    OncomiR-10b hijacks the small molecule inhibitor linifanib in human cancers
    (Springer Nature, 2018) Monroig-Bosque, Paloma del C.; Shah, Maitri Y.; Fu, Xiao; Fuentes-Mattei, Enrique; Ling, Hui; Ivan, Cristina; Nouraee, Nazila; Huang, Beibei; Chen, Lu; Pileczki, Valentina; Redis, Roxana S.; Jung, Eun-Jung; Zhang, Xin; Lehrer, Michael; Nagvekar, Rahul; Mafra, Ana Carolina P.; Monroig-Bosque, Maria del Mar; Irimie, Alexandra; Rivera, Carlos; Dumitru, Calin Dan; Berindan-Neagoe, Ioana; Nikonowicz, Edward P.; Zhang, Shuxing; Calin, George A.
    The pervasive role of microRNAs (miRNAs) in cancer pathobiology drives the introduction of new drug development approaches such as miRNA inhibition. In order to advance miRNA-therapeutics, meticulous screening strategies addressing specific tumor targets are needed. Small molecule inhibitors represent an attractive goal for these strategies. In this study, we devised a strategy to screen for small molecule inhibitors that specifically inhibit, directly or indirectly, miR-10b (SMIRs) which is overexpressed in metastatic tumors. We found that the multi-tyrosine kinase inhibitor linifanib could significantly inhibit miR-10b and reverse its oncogenic function in breast cancer and liver cancer both in vitro and in vivo. In addition, we showed that the efficacy of linifanib to inhibit tyrosine kinases was reduced by high miR-10b levels. When the level of miR-10b is high, it can "hijack" the linifanib and reduce its kinase inhibitory effects in cancer resulting in reduced anti-tumor efficacy. In conclusion, our study describes an effective strategy to screen for small molecule inhibitors of miRNAs. We further propose that miR-10b expression levels, due to the newly described "hijacking" effect, may be used as a biomarker to select patients for linifanib treatment.
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    Xanthone-based solvatochromic fluorophores for quantifying micropolarity of protein aggregates
    (Royal Society of Chemistry, 2022) Wang, Lushun; Hsiung, Chia-Heng; Liu, Xiaojing; Wang, Shichao; Loredo, Axel; Zhang, Xin; Xiao, Han
    Proper three-dimensional structures are essential for maintaining the functionality of proteins and for avoiding pathological consequences of improper folding. Misfolding and aggregation of proteins have been both associated with neurodegenerative disease. Therefore, a variety of fluorogenic tools that respond to both polarity and viscosity have been developed to detect protein aggregation. However, the rational design of highly sensitive fluorophores that respond solely to polarity has remained elusive. In this work, we demonstrate that electron-withdrawing heteroatoms with (d–p)–π* conjugation can stabilize lowest unoccupied molecular orbital (LUMO) energy levels and promote bathochromic shifts. Guided by computational analyses, we have devised a novel series of xanthone-based solvatochromic fluorophores that have rarely been systematically studied. The resulting probes exhibit superior sensitivity to polarity but are insensitive to viscosity. As proof of concept, we have synthesized protein targeting probes for live-cell confocal imaging intended to quantify the polarity of misfolded and aggregated proteins. Interestingly, our results reveal several layers of protein aggregates in a way that we had not anticipated. First, microenvironments with reduced polarity were validated in the misfolding and aggregation of folded globular proteins. Second, granular aggregates of AgHalo displayed a less polar environment than aggregates formed by folded globular protein represented by Htt–polyQ. Third, our studies reveal that granular protein aggregates formed in response to different types of stressors exhibit significant polarity differences. These results show that the solvatochromic fluorophores solely responsive to polarity represent a new class of indicators that can be widely used for detecting protein aggregation in live cells, thus paving the way for elucidating cellular mechanisms of protein aggregation as well as therapeutic approaches to managing intracellular aggregates.