(Mainichi)

Some iPS cells for regenerative medicine, distributed by a stock project at Kyoto University's Center for iPS Cell Research and Application (CiRA), showed cancer-related genetic and chromosomal abnormalities when differentiated to the target cells, several sources close to the project revealed.

Some of the iPS cells, even those produced at the same time, showed various abnormalities while others did not, depending on the research institution they were distributed to, prompting experts to voice concerns over their safety. The CiRA has acknowledged the facts, and the cells that developed abnormalities were not used in patients.

The project stockpiles iPS cells provided by the same suppliers at the same time in a cell line. In clinical research and a trial, iPS cells and differentiated cells go through genome analysis, and are transplanted into mice to check whether they turn cancerous. It is then decided which cell line should be distributed to implementing agencies.

Of the 27 cell lines distributed since August 2015, test results were revealed for four. Of these, abnormalities were found in two cell lines. The two cell lines were distributed in several containers to two research institutions, respectively, and were differentiated to the same target cells at each institution.

For one of the cell lines, one institution found a genetic abnormality in relation to cancer, while the other found a numerical disorder in the chromosome. For the other cell line, one institution found a different genetic abnormality, while the other institution did not find any irregularities. Furthermore, the institution that found the abnormality did not find any problems in the cells kept in a different container.s

Genetic abnormalities included a high-risk abnormality, similar to those found in humans with cancer. When implanted in mice, abnormal tissue growth that cannot be seen with normal cells was confirmed.

"No matter what kind of cell, an error could occur during the process of cultivation and differentiation," said specially appointed professor and manufacturing supervisor Masayoshi Tsukahara of the iPS cell stock project. He explained, "There's no other choice but to conduct careful tests before putting them to use."

Several experts in Japan, however, expressed concerns that safety cannot be ensured if test results vary depending on containers.

Michael Snyder, professor at Stanford University's School of Medicine and the director of the Center for Genomics and Personalized Medicine, pointed to the need to evaluate the matter in an open discussion.

(Japanese original by Momoko Suda, Science & Environment News Department)

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Kyoto Univ.-distributed iPS cells found with abnormalities after differentiation - The Mainichi