PR55Œ± Subunit of Protein Phosphatase 2A Supports the Tumorigenic and Metastatic Potential of Pancreatic Cancer Cells by Sustaining Hyperactive Oncogenic Signaling
Authors: Yuri M Sheinin
Parthasarathy Seshacharyulu
Marc C Mumby
Surinder K Batra
Ying Yan
Moorthy P Ponnusamy
Satyanarayana Rachagani
Michel M Ouellette
Ashley L Hein
Journal: Cancer research (2016)
Discipline: CLINICAL MEDICINE
Keywords: PP2A; tumor suppressor; oncogenic signaling pathways; pancreatic cancer; PR55Œ±
Affiliations: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America., Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America., Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America., Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, United States of America., Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America.

Abstract:  The protein phosphatase 2 (PP2A) holoenzyme consists of a catalytic subunit, a scaffold subunit, and a regulatory subunit. Based on loss-of-function analysis using PP2A catalytic inhibitors or inhibition via tumor viral antigens, limited studies suggest that PP2A is a putative tumor suppressor. However, PP2A has also been shown to facilitate the activation of oncogenic signaling pathways when associated with specific regulatory subunits. In this study, we investigated the possible oncogenic role of PP2A in pancreatic cancer. We found a striking increase in the expression of PR55Œ± (PPP2R2A), a PP2A regulatory subunit, in pancreatic cancer cells compared with normal pancreatic epithelial cells. Consistently, PR55Œ± expression was markedly elevated in pancreatic ductal adenocarcinoma tissues compared with adjacent normal pancreatic tissues (P &lt; 0.0001) and correlated with poor survival of pancreatic cancer patients (P &lt; 0.0003). RNAi-mediated depletion of PR55Œ± in pancreatic cancer cell lines resulted in diminished phosphorylation of both AKT and ERK1/2 (MAPK3/1) and decreased protein levels of Œ≤-catenin (CTNNB1). Accordingly, pancreatic cancer cells with reduced PR55Œ± expression exhibited significantly impaired properties of transformation, including attenuated cell growth, clonogenicity, mobility, and anchorage-independent growth. Moreover, orthotopic implantation of PR55Œ±-depleted pancreatic cancer cells into nude mice resulted in markedly reduced tumorigenicity (P &lt; 0.001) and distant metastases. Together, these results suggest that PR55Œ± promotes pancreatic cancer development by sustaining hyperactivity of multiple oncogenic signaling pathways, including AKT, ERK, and Wnt. These studies also provide a basis for exploring PR55Œ± as a diagnostic or therapeutic target in pancreatic cancer. Cancer Res; 76(8); 2243-53. ¬©2016 AACR. 

Retracted: No

PubPeer comments:
 Figure 3A. * Marked with red arrows: Four lanes in the AKT panel appear to look very similar to each other. It is unexpected to see the same lanes multiple times within the same photo. Could the authors please check what happened?  , 
 Figure 3C. * Marked with blue arrows. Two lanes in the p-b-Catenin panel appear to look similar to each other. * Marked with aqua arrows. Two lanes in the b-Catenin panel appear to look similar to each other.  , 
 Figure 5B. Two colonies appear to be clonal. Shown with green boxes.  , 
 Figure 6 shows measurements of four groups of mice, with four mice per group. * Even though the lab appeared to have equipment to measure all 5 mice at the same time (as shown in e.g. #2 photos), the Control and #4 photo series appear to show mice at the same position. For example, in the Control row, 14th day, the third mouse appears to be at position 5, and mice 4 and 5 appear to be photographed at positions 1 and 2. There are certain markings and shadows that indicate they were photographed at a different position. Why were the mice not all photographed at the same time? * Lime green: In the photo representing group #4, 14th day, the same mouse appears to be shown twice.  , 
 #1 Dear Dr. Bik, in your comment 1#, you said the four lanes in AKT panel appear to look very similar to each other. However I found sort of similarity of shape between each other and inferred that the similarity was just the result of the similarity of (or the same of) the loading well. Actually there are different protuberances in the margin of the bands. , 
 #5 With all due respect I beg to differ, the same anomalies occur in all four bands which becomes clear when the colors on the gel are inverted, it is highly unlikely that the anomalies would repeat by random chance  , 
 Dear Dr. Bik, thank you for identifying these errors in our publication. We are sorry for the inconvenience to the readers. Below are our responses to your comments. Regarding the 3rd and 5th mouse in Fig 6A (14 days shRNA#4 group) In the 14 days shRNA#4 group of Fig 6A, mouse No. 3 was inadvertently reused as mouse No. 5. The error has been corrected in the revised Fig 6A attached below, which now includes a picture of the correct mouse No. 5. Also, for practical reasons, it is not always possible to get a family picture of all five mice in a group taken at once. Individual mice react differently to anesthesia, which sometimes forces us to image a mouse separately, albeit under the same exact conditions and within the hour. Regarding the mistakes made in Figs 3A, 3C, and 5B These three figures have in common that they were inadvertently taken from an early file made of preliminary results. Among these preliminary results were mock-up figures of expected results that were made to facilitate discussion and experimental planning. As experiments progressed, these mock-up figures were eventually populated with actual data to produce the final figures. However, in the case of the errors in Figs 3A, 3C and 5B, this substitution never took place. To rectify these mistakes, we are providing you with replacement figures made from the original data, as found in the research technologistu2019s notebook. Fig 3A: A scan of the original x-ray film for the correct AKT blot is attached below, which had previously been probed for the u201cBADu201d protein (arrows point to Bad and AKT). In the revised Fig 3A provided, the correct AKT panel is now shown. Fig 3C: The corrected Fig 3C is attached below, which now contains the actual data from the research technologistu2019s notebook. Scans of the original x-ray films used for the three panels of Fig 3C are provided below. Fig 5B: In the revised Fig 5B, the two photos are replaced with representative images of colonies as found in the technologistu2019s archive. Because it was plotted based on the actual data found in the archive, the bar graph of Fig 5B is correct and does not need to be replaced. Please take note that this experiment has been repeated many times, including in our most recent publication (Oncogenesis 2019 Oct 28;8(11):63. doi: 10.1038 s41389-019-0172-9; Figure 8C). The errors were not intentional and we regret the errors. We will submit the necessary corrections to the journal.           , 
 Please understand, it doesn t help to come up with new data when your first data was falsified. ,