Research Article

Characteristics and Validation Techniques for PCA-Based Gene-Expression Signatures

Figure 5

Validation plot for Mix-29/29 signature applied to DC dataset. Merging two “good” signatures and applying the resulting signature to a relevant dataset do not mean that the new signature will be valid. The probesets in the Mix-29/29 signature have a coherent expression (a), but the ratio of PC1/PC2 (b) is lower than that in the individual signatures. The uniqueness is also slightly worse (c). That the Mix-29/29 model is not working as expected is clearly seen in the transferability plot (d), where the PCA model for the DC dataset is not related to reference values.
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