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Abstract
Introduction
Gene
expression signatures have been identified for epithelial ovarian
cancer survival (TCGA) and intrinsic subtypes (Tothill et al.). One
obstacle to clinical translation is that these signatures were developed
using frozen tissue, whereas usually only formalin-fixed, paraffin
embedded (FFPE) tissue is available. The aim of this study was to
determine if gene expression signatures can be translated to fixed
archival tissues.
Methods
RNA
extracted from FFPE sections from 240 primary ovarian cancers was
analyzed by DASL on Illumina BeadChip arrays. Concordance of expression
at the individual gene level was assessed by comparing array data from
the same cancers (30 frozen samples analyzed on Affymetrix arrays versus
FFPE DASL).
Results
The
correlation between FFPE and frozen survival signature estimates was
0.774. The TCGA signature using DASL was predictive of survival in 106
advanced stage high grade serous ovarian cancers
(median survival 33 versus 60 months, estimated hazard ratio for death 2.30, P = 0.0007). Similar to Tothill, we found using DASL that most high grade serous ovarian cancers (102/110, 93%) were assigned to subtypes 1, 2, 4 and 5, whereas most endometrioid, clear cell, mucinous and low grade serous cases (39/57, 68%) were assigned to subtypes 3 and 6 (P < 10e-15).
(median survival 33 versus 60 months, estimated hazard ratio for death 2.30, P = 0.0007). Similar to Tothill, we found using DASL that most high grade serous ovarian cancers (102/110, 93%) were assigned to subtypes 1, 2, 4 and 5, whereas most endometrioid, clear cell, mucinous and low grade serous cases (39/57, 68%) were assigned to subtypes 3 and 6 (P < 10e-15).
Conclusions
Although
individual probe estimates of microarrays may be weakly correlated
between FFPE and frozen samples, combinations of probes have robust
ability to predict survival and subtype. This suggests that it may be
possible to use these signatures for prognostic and predictive purposes
as we seek to individualize the treatment of ovarian cancer.
Highlights
►
Gene expression profiles of serous cancer demonstrate biologic and
prognostic heterogeneity that we discerned from archival paraffin
specimens.
► This approach facilitates retrospective and prospective analyses of the disease using more population-based cohorts
► This approach facilitates retrospective and prospective analyses of the disease using more population-based cohorts
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