2381/32160
Joanna P. Wood
Joanna P.
Wood
Andrew J. O. Smith
Andrew J. O.
Smith
Karen J. Bowman
Karen J.
Bowman
Anne L. Thomas
Anne L.
Thomas
George D. D. Jones
George D. D.
Jones
Comet Assay Measures of DNA Damage as Biomarkers of Irinotecan Response in Colorectal Cancer In Vitro and In Vivo
University of Leicester
2015
Colorectal cancer
Comet assay
DNA damage and repair
Biomarker
Topoisomerase-I inhibitor
2015-05-07 10:13:41
Journal contribution
https://figshare.le.ac.uk/articles/journal_contribution/Comet_Assay_Measures_of_DNA_Damage_as_Biomarkers_of_Irinotecan_Response_in_Colorectal_Cancer_In_Vitro_and_In_Vivo/10144709
The use of irinotecan to treat metastatic colorectal cancer (CRC) is limited by unpredictable
response and variable toxicity, however, no reliable clinical biomarkers are available. Here
we report a study to ascertain whether irinotecan-induced DNA damage measures are
suitable/superior biomarkers of irinotecan effect. CRC-cell lines (HCT-116 & HT-29) were
treated in vitro with irinotecan and peripheral blood lymphocytes (PBL) were isolated from
patients before and after receiving irinotecan-based chemotherapy. Levels of in vitro, in vivo
and ex vivo-induced DNA damage were measured using the Comet assay; correlations
between damage levels with in vitro cell survival and follow-up clinical data were
investigated. Irinotecan-induced DNA damage was detectable in both CRC cell-lines in vitro,
with higher levels of immediate and residual damage noted for the more sensitive HT-29
cells. DNA damage was not detected in vivo but was measurable in PBLs upon mitogenic
stimulation prior to ex vivo SN-38 treatment. Results showed that, following corrections for
experimental error, those patients whose PBLs demonstrated higher levels of DNA damage
following 10 hours of SN-38 exposure ex vivo had significantly longer times to progression
than those with lower damage levels (median 291 versus 173 days, p = 0.014). To conclude,
higher levels of irinotecan-induced initial and residual damage correlated with greater cell
kill in vitro and a better clinical response. Consequently, DNA damage measures may
represent superior biomarkers of irinotecan effect compared to the more often-studied
genetic assays for differential drug metabolism.