DUSP1 is a novel target for enhancing pancreatic cancer cell sensitivity to gemcitabine
Authors: Fang Liu
Murray Korc
A Jesse Gore
Julie L Wilson
Journal: PLoS ONE (2014)
Discipline: Multidisciplinary
Keywords: Pancreatic ductal adenocarcinoma; PDAC; Dual specificity protein phosphatase 1; DUSP1; Chemoresistance
Affiliations: Departments of Medicine, Biochemistry and Molecular Biology, Indiana University School of Medicine, The Melvin and Bren Simon Cancer Center and the Center for Pancreatic Cancer Research, Indianapolis, Indiana, United States of America.

Abstract:  Pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer with a poor prognosis that is characterized by excessive mitogenic pathway activation and marked chemoresistance to a broad spectrum of chemotherapeutic drugs. Dual specificity protein phosphatase 1 (DUSP1) is a key negative regulator of mitogen activated protein kinases (MAPKs). Yet, DUSP1 is overexpressed in pancreatic cancer cells (PCCs) in PDAC where it paradoxically enhances colony formation in soft agar and promotes in vivo tumorigenicity. However, it is not known whether DUSP1 overexpression contributes to PDAC chemoresistance. Using BxPC3 and COLO-357 human PCCs, we show that gemcitabine activates c-JUN N-terminal kinase (JNK) and p38 mitogen activated protein kinase (p38 MAPK), key kinases in two major stress-activated signaling pathways. Gemcitabine-induced JNK and p38 MAPK activation mediates increased apoptosis, but also transcriptionally upregulates DUSP1, as evidenced by increased DUSP1 mRNA levels and RNA polymerase II loading at DUSP1 gene body. Conversely, shRNA-mediated inhibition of DUSP1 enhances JNK and p38 MAPK activation and gemcitabine chemosensitivity. Using doxycycline-inducible knockdown of DUSP1 in established orthotopic pancreatic tumors, we found that combining gemcitabine with DUSP1 inhibition improves animal survival, attenuates angiogenesis, and enhances apoptotic cell death, as compared with gemcitabine alone. Taken together, these results suggest that gemcitabine-mediated upregulation of DUSP1 contributes to a negative feedback loop that attenuates its beneficial actions on stress pathways and apoptosis, raising the possibility that targeting DUSP1 in PDAC may have the advantage of enhancing gemcitabine chemosensitivity while suppressing angiogenesis. 

Retracted: No

PubPeer comments:
 This work claims that they studied the proton transport in UiO-66-NH2 nanochannels before and after sulfonation. Figure 1 f-g shows the designed schematics of a UiO-66-(NH2)2 channel and UiO-66-(NH-SAG)2 channel so the structure of theses MOF channels should be homogeneous. But the real cross-sectional structure in MOF channels they fabricated are far from homogeneous, clearly shown in Figure S2 a-b, Figure S11 a-b and Figure S12 a-b. Take Figure S2 a for example, intuitively three different zones exist in the so-called UiO-66-(NH2)2 channel. i) the zone next to the polymer wall. ii) the zone in the center. iii) the gaps between the above two zones. When they tested ion conduction driven by voltage, what zones will be the ion pathway for the ions transfer dynamic-favorably? The gap zone rather than the MOF channels. In this way, the supposed Figure 1 f-g are not consistent with the experimental results. So all the conclusions in this work are open to doubt. The same issues also exist in their previous work in nature communications , 
 Issues: This work prohibitively calculate ion conductivity in MOF-filled polymer channels by wrongly deeming that MOF-modified polymer channels are solid. Contrariwise! they are hollow, not sub-1 nm MOF channels claimed. Proof: The Figure s2, Figure s11 and Figure s12 in Supporting Information explicitly show polymer channels are not totally filled by MOFs and there are interstices (about 100 nm in height ) in the center of MOF-modified polymer channel. These interstices have length of over half of the whole length ( about 10 micrometres ) of polymer channel. It is funnily enough that these gaps obviously present in the cross-section of MOF-modified polymer channels are overlooked. The authors recklessly thought MOF-modified polymer channels are solid, inferred from schematic diagrams of cross-section of MOF-modified polymer channels (Figure 1 f-g, Figure 4c ). Conclusion: The true fine structures of MOF-Polymer channels are overly simplified in this work. This cursoriness mistake compromises the validity of all ion conductance data for MOF-polymer channels ... ... , 
 #1 Thank you for your comments. I would like to answer your comments as follows: The gaps between the polymer substrate and the MOFSNC, and the inhomogeneity and hollows of MOFs grown inside the polymer nanochannels mainly occurred during the fabrication process of the cross-section fractures of the polymer-MOF membranes. The as-synthesized samples should not have such defects between the MOF and the polymer substrate since they have excellent proton sieving properties. If the as-synthesized have such big gaps and defects as you commented, all tested monovalent ions could transport through the PET-UiO-66 MOFSNCs. As a result, the samples should exhibit no ion selectivity. The SEM images of the tip and base sides of the nanochannels illustrated the nanochannels were fully filled by the intergrown MOF crystals. There were some defects found in the cross-section features of the polymer-MOF samples because their SEM samples were prepared by a complicated method, which should create new defects on the samples. As the polymer substrate is soft, it is very easy to be stretched when preparing fractures of the samples. To avoid residual strain in the fractured specimens, a special technique was used to render the polymer brittle before fracturing them. This technique is initially reported by Prof. Apel (please refer to Orelovich, O. L.; Apel, P. Y. Instrum. Exp. Tech. 2001, 44, 111) and we modified it in our previous works, so we did not describe it in detail in these two manuscripts. For instance, the as-prepared polymer-MOF samples were irradiated by UV light (310 nm, 3-5W) for at least 14 days. The UV-treated samples were wetted by water and then frozen by liquid nitrogen for at least 2 minutes. Subsequently, the frozen samples were fractured by two tweezers. The features of the samples were dried before preparing SEM samples for doing SEM characterization. As we know, MOF crystals are very brittle, the above-discussed processes could induce new cracks, gaps, or defects onto the samples especially when fracturing samples. Moreover, for each polymer-MOF membrane sample, two fractures could be observed. But the SEM images only showed one of the two fractures. The hollows caused by the missing MOF crystals on one fracture, such missing MOF crystals should be found on the other fracture. Finally, for the synthesis of MOF-based membranes, it is very difficult to make them defect-free. We only can conclude that there were no large and continuous defects in the polymer-MOF subnanochannels. But they may have some minor and isolated defects which do not impact their ion selectivity but may slightly increase the conductance of the samples. However, at the present stage, there is no relevant technique to do an in-situ measurement of the cross sections of the as-prepared polymer-MOF samples. We are trying to achieve this in our following works. Thank you again for your insightful comments. ,