We suggest that safety checks for cytogenetic normality prior
to stem cell infusion should include both metaphase and interphase
cytogenetic analyses. Stem cells harboring chromosomal
aberrations must be excluded from cell therapy, and integrated
and standardized guidelines to evaluate genomic instability are
essential. For instance, the Food and Drug Administration (FDA)
guidelines for Chemistry, Manufacturing, and Control (CMC) Information
for Human Somatic Cell Therapy Investigational New Drug
68Applications (INDs) does not include protocols for the evaluation
of genomic instability [22]. In Europe, a committee for advanced
therapies presented “Reflection paper on stem cell-based medicinal
products,” which detailed the evaluation of genomic instability
[23]. This reflection paper recommended cytogenetic analysis, as
well as tests for telomerase activity, proliferation, and cellular
senescence, although these analyses were considered optional.
Collectively, accurate guidelines and standardized tests for the
evaluation of genomic instability have not currently been established.
In this study, we tracked cytogenetic heterogeneity using
G-banding and interphase FISH analyses during the cancerous
transformation of MSCs. Heterogeneity among clones with distinct
chromosomal aberrations dynamically changed over time, similar
to what is observed in cancer stem cells. We conclude that to accurately
evaluate of the tumorigenic potential of MSCs, interphase
FISH analyses should be used in combination with conventional
cytogenetics.