When does “overlap” become plagiarism? Here’s what PLOS ONE decided

Consider this: Fragments of a PLOS ONE paper overlap with pieces of other publications. The authors used them without credit and without quotation marks.

This sounds an awful lot like plagiarism — using PLOS‘s own standards, even. But the journal isn’t calling it plagiarism. They’ve labeled this an instance of “text overlap,” a spokesperson told us, based on the amount of material that the paper shares with others.

The last author — Carlo Croce, who has two retractions under his belt — denies that he plagiarized, and says that his university has cleared him of a plagiarism charge from an anonymous whistleblower.

PLOS fixed this case last year with a correction notice — not the common course of action for a case of confirmed plagiarism. Take a look at the notice for yourself:

After the publication of the article [MiR-34a/c-Dependent PDGFR-α/β Downregulation Inhibits Tumorigenesis and Enhances TRAIL-Induced Apoptosis in Lung Cancer], it was noticed that fragments of text in this article overlap with that from previous publications. The overlap in the text relates to the Introduction, Results and Discussion sections, where sentences were reproduced without quotation marks. We would like to acknowledge this and include the relevant references. It should be noted that no concerns have been raised regarding the originality of the work reported in the article and that this has no bearing on the results and conclusions of the study.

In the Introduction section there is some overlap in text with that from the following publications:

McDermott U, Ames RY, Iafrate AJ, Maheswaran S, Stubbs H, Greninger P, et al. Ligand-dependent platelet-derived growth factor receptor (PDGFR)-alpha activation sensitizes rare lung cancer and sarcoma cells to PDGFR kinase inhibitors. Cancer Res. 2009 May 1;69(9):3937–46. doi: 10.1158/0008-5472.CAN-08-432

Hermeking H. The miR-34 family in cancer and apoptosis. Cell Death Differ. 2010 Feb;17(2):193–9. doi: 10.1038/cdd.2009.56.

Raica M, and Cimpean AM. Platelet-Derived Growth Factor (PDGF)/PDGF Receptors (PDGFR) Axis as Target for Antitumor and Antiangiogenic Therapy. Pharmaceuticals (Basel). 2010 Mar; 3(3): 572–599. doi: 10.3390/ph3030572

In the Results section there is some overlap in text with that from the following article:

Tanaka N, Toyooka S, Soh J, Kubo T, Yamamoto H, Maki Y, et al. Frequent methylation and oncogenic role of microRNA-34b/c in small-cell lung cancer. Lung Cancer. 2012 Apr;76(1):32–8. doi: 10.1016/j.lungcan.2011.10.002.

In the Discussion section there is some overlap in text with that from the following publications:

Zhang H, Bajraszewski N, Wu E, Wang H, Moseman AP, Dabora SL, Griffin JD, and Kwiatkowski DJ. PDGFRs are critical for PI3K/Akt activation and negatively regulated by mTOR. J Clin Invest. 2007 Mar;117(3):730-8.doi:10.1172/JCI28984.

West KA, Castillo SS and Dennis PA. Activation of the PI3K/Akt pathway and chemotherapeutic resistance. Drug Resist Updat. 2002 Dec;5(6):234–48

The 2013 paper has been cited 40 times, according to Thomson Reuters Web of Science.

We find the wording in this notice strange, so we asked a spokesperson for PLOS ONE why the journal isn’t calling this plagiarism. He said:

The journal office was alerted to instances of overlap in the text of the article with that from other publications. Upon follow up with the authors and evaluation of the level of text overlap, the editors considered that the most appropriate step was to issue a Correction to make readers aware of the instances of overlap in text with the sources listed.

It’s not clear exactly how much of the text appears to overlap with the other publications — the spokesperson told us “the overlap involved sentences.” In one example, here’s what we believe is the sum total of the text shared by the PLOS ONE paper and the Pharmaceuticals paper mentioned in the notice:

All members of the PDGF family display potent angiogenic activity in vivo, and from this point of view, PDGF-B/PDGFRβ axis was the most extensive evaluated.

Virginia Barbour, the Chair of the Committee on Publication Ethics, told us that in general “there is no numerical value that can easily be applied” as to how much overlap constitutes plagiarism, adding that she cannot comment on specific cases.

The paper’s last author Carlo Croce, a researcher at The Ohio State University (OSU), denies that he plagiarized. To boot, he told us that he’s been cleared of a plagiarism charge (it’s unclear if that relates to this paper or not):

Following an [anonymous] denunciation the University investigated the matter and found that there was no plagiarism whatsoever. Keep in mind that people…reading a paper may get some sentence impressed in their mind and then repeat it in a paper. That has to be avoided, but it might happen. If the paper is completely different, possibly on a different subject, with completely different data it would be very difficult to claim plagiarism.

We were unable to verify the claim that OSU cleared Croce of a plagiarism charge. The Research Integrity Officer at OSU declined to comment on whether Croce had been investigated, citing an OSU policy against disclosing that information.

To shift gears a little here: this is not Croce’s first tangle with notices. He shares two retractions with Alfredo Fusco, a cancer researcher in Italy who has been under criminal investigation for scientific misconduct. And many of Croce’s papers have been flagged on PubPeer by commenters suggesting that there are issues with some of the figures.

One of those papers questioned on PubPeer, “Downregulation of p53-inducible microRNAs 192, 194, and 215 Impairs the p53/MDM2 Autoregulatory Loop in Multiple Myeloma Development,” was corrected earlier last month by Cancer Cell over image problems. Here’s the notice:

During figure preparation for the original article, the image of the western blot showing MDM2 protein expression upon miR-194,192, 215, and scrambled sequence (Scr) treatments in the MM1s cell line was mistakenly replaced in Figure 4A with the image of the western blot showing MDM2 in NCI-H929 cells in the same figure panel. The correct corresponding image of the western blot showing MDM2 protein expression in MM1s is shown below in the corrected Figure 4A.

In addition, because multiple normalizations of the same set of samples were performed due to the use of phospho-antibodies, the authors inadvertently duplicated the Gadph image of MM1s in the total Akt image of NCI-H929 in the same panel. The results were not affected by this duplication. The corresponding total Akt and Gapdh images used for pAkt normalization for both RPMI-8226 and MM1s are now included in the corrected Figure 7A, shown below.

The authors apologize for these errors and any confusion that they may have caused.

The 2010 paper has been cited 197 times.

In 2014, we reported on a letter from OSU to pseudonymous whistleblower Clare Francis saying the university and the U.S. Office of Research Integrity had chosen not to investigate a few of Croce’s papers in response to specific allegations Francis raised in 2013. The reasoning: the manuscripts were not generated at OSU, and no OSU employees had contributed to the figures in question.

Hat tip: David Sanders

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