Background:
Misidentification between human cell lines had been a long-standing problem in the community (Ref.1,2). However, there was no high throughput method to eliminate it. As a collaboration work of cell banks around the world, the short tandem repeat (STR) polymorphism analysis was proved to be applicable for detection of misidentified cell lines (Ref.3). In 2004, we introduced the STR polymorphism analysis. After the analysis of all human cell lines in 2004, approximately 10% of human cell lines in our cell bank were detected as misidentified cell lines (Ref.4). These misidentified cell lines were discussed with their depositors and a decision made, based on the depositors’ input, as to how to proceed in each case.
Three cell lines, RBE (RCB1292), SSP-25 (RCB1293) and ETK-1 (RCB1289), were deposited from the same scientist in 1996 as the cell lines derived from intrahepatic cholangiocarcinoma. Following the STR polymorphism analysis in 2004 above, SSP-25 and ETK-1 were shown to be identical. After informing this result to the depositor, the depositor told us to stop the distribution of ETK-1.
Thus, from 2005 we have distributed RBE and SSP-25 as two different cell lines derived from two different patients of intrahepatic cholangiocarcinoma disclosing the results of STR polymorphism analysis of them (Table 1).
Recently, by information received from an outside researcher we noticed the paper reporting establishment of RBE and SSP-25 (Ref.5). In this paper, RBE and SSP-25 were described as the two cell lines which were derived from the same patient of intrahepatic cholangiocarcinoma but were possessing different characteristics.
Taken together, the current SSP-25 which we have distributed from 2005 does not correspond to RBE and is therefore not the cell line published in the paper above (Ref.5). Instead, the current SSP-25 corresponds to ETK-1, which was published in another paper by the same group (Ref.6). In other words, the cell line which should have been retracted in 2004 was SSP-25 but not ETK-1.
Looking at all available data and information, we have decided to continue distribution of both RBE and SSP-25. This decision was made based on the facts that we have provided RBE and SSP-25 to many scientists from 2005 as two different cell lines derived from two different patients and papers by those users have been published.
To ensure that we are fully transparent regarding the origins of RBE and SSP-25, we continue the distribution of these two cell lines disclosing the following information:
“The SSP-25 which we have distributed so far is not the cell line published in the paper (Ref.5). SSP-25 was originally reported to be established from the same donor as RBE, but their STR profiles show that these deposits come from different individuals. Instead, SSP-25 is identical to ETK-1, which was published in another paper by the same group (Ref.6). Authentic stock of SSP-25 is not present for the moment.”
References
1. Cases of mistaken identity. Science 315: 928-931 (2007)
2. Identity crisis. Nature 457: 935-936 (2009)
3. Masters, J.R. et al. Short tandem repeat profiling provides an international reference standard for human cell lines. Proc Natl Acad Sci USA 98: 8012-8017 (2001)
4. Yoshino, K. et al. Essential role for gene profiling analysis in the authentication of human cell lines. Hum Cell 19: 43-48 (2006)
5. Enjoji et.al. Sarcomatous and adenocarcinoma cell lines from the same nodule of cholangiocarcinoma. In vitro Cell. Dev. Biol.-Animal 33: 681-683 (1997)
6. Enjoji et.al. Hepatocytic phenotypes induced in sarcomatous cholangiocarcinoma cells treated with 5-azacytidine. Hepatology 26: 288-294 (1997)