Correction
for
Blakely et al., Cancer Res 66 (12) 6421-6431.
Cancer Research 67, 844, January 15, 2007. doi: 10.1158/0008-5472.CAN-67-2-COR2
© 2007 American Association for Cancer Research
Correction: Pregnancy-Induced Protection against Mammary Tumorigenesis
In the article on pregnancy-induced protection against mammary tumorigenesis in the June 15, 2006 issue of Cancer Research (1), the parity status of six of the 43 arrays used to derive the 70-gene expression signature was misclassified through an error in data entry. These arrays represented six of the 14 arrays run for Fischer 344 rats. The remaining 37 arrays for the Lewis, Wistar-Furth, Copenhagen, and Fischer 344 mammary samples were properly classified, as were the independent Lewis rat and FVB mouse samples used to validate the findings. This misclassification both obscured genuine parity-induced changes in the Fischer 344 strain and added biological noise due to genes that were covarying but unrelated to parity. As a consequence, after correcting the parity status for the six Fischer 344 arrays and applying the same analytical criteria described in the article, the authors found that the core parity-induced gene expression signature was reduced from 70 to 47 genes. Similar to the original 70-gene signature, this 47-gene signature is sufficient to distinguish between independent nulliparous and parous samples from all rat and mouse strains analyzed in the article. Corrected versions of Tables 1
and 2
appear below.
Each of the five originally identified functional gene categories (Tgf-ß3, differentiation, immune markers, growth hormone/Igf-1 axis, and extracellular matrix components) are retained within this signature. Genes lost from the original 70-gene signature remain significantly altered in two of the four rat strains and are still plausible candidates for contributing to parity-induced protection against mammary tumorigenesis. Notably, a role for downregulation of Ghr, which is not included in the corrected signature, in parity-induced protection is still supported by the FVB mouse data and the QRT-PCR analysis of independent Lewis rat samples presented in the article. Also consistent with a role for the GH/Igf-1 pathway in parity-induced protection, Igf-1 remains downregulated — and Igfbp5 remains upregulated — on the corrected list of genes.
Overall, despite the reassignment of six samples, the conclusions of the article remain unaltered. Moreover, as a primary goal of the original article was to narrow down the list of genes to those most robustly associated with parity-induced protection, the corrected signature accomplishes this and provides an even smaller overlap of evolutionarily conserved gene expression changes associated with parity-induced protection against mammary tumorigenesis.
References
- Blakely CM, Stoddard AJ, Belka GK, Dugan KD, Notarfrancesco KL, Moody SE, D'Cruz CM, Chodosh LA. Hormone-induced protection against mammary tumorigenesis is conserved in multiple rat strains and identifies a core gene expression signature induced by pregnancy. Cancer Res 2006;66:6421–31.[Abstract/Free Full Text]
