Increased Expression of Inflammatory Genes in Pregnancy-Associated Breast Cancers.
Authors: Asztalos S. , Gann P. , Hayes M. , Nonn L. , Wiley E. , Khan S. , Susnik B. , Diaz L. , Banerji N. , Tonetti D. 
Published: December 2010

Introduction: Epidemiological studies have shown that women of all ages experience a transient increase in the risk of developing breast cancer following pregnancy. Furthermore, breast cancers detected soon after a completed pregnancy (pregnancy-associated breast cancers, or PABCs) have a worse prognosis than those detected at more distant intervals (Schedin 2006). We previously found evidence for increased expression of inflammatory genes in the human breast following pregnancy. (Asztalos et al. 2008). In this study we analyzed the same gene set in human breast cancer tissue, to investigate the role of inflammation in pregnancy associated breast cancers.Patients and Methods: Women ≤ 45 years of age with breast cancer were eligible for the study, and were categorized as either nulliparous, recently pregnant or distantly pregnant. Thirteen nulliparous, 14 recently pregnant (&lt;2 years since pregnancy) and 15 distantly pregnant (5-10 years) patients were identified. Tumor regions were isolated from formalin-fixed paraffin embedded tissues using Laser Capture Microdissection, followed by RNA extraction and cDNA synthesis. Genes of interest were preamplified linearly, followed by real time PCR. We chose 59 genes involved in the processes of inflammation, ECM remodeling and angiogenesis. A small number of breast cancer prognostic genes were also included. Gene expression between groups was compared using either t-test, ANOVA or unsupervised hierarchical clustering.Results: When recent and distant PABCs were combined and compared to the nulliparous group, we observed a number of significantly differentially regulated genes, such as CXCL1, THBS1, ELN, IL11 and MMP3. Upregulation of CXCL1 in the post-pregnant samples is interesting since CXCL1 is an important inflammatory chemokine, with implications in cancer. THBS1, a natural inhibitor of neovascularization and tumorigenesis, was downregulated in the post-pregnancy group. In this early analysis, we did not observe a difference in gene expression between recent and distant pregnancies, possibly due to the limited number of samples. However, immunoglobulin A showed a trend towards upregulation in the recent pregnancy group, suggesting an enhanced state of immune activity in the cancers occurring in the recently pregnant breast. When concerted gene expression was compared by non-supervised hierarchical clustering, we found that PABCs (both recent and distant) had more frequent associations with inflammation associated gene-expression patterns than those of nulliparous patients.Conclusions: This is the first study to address the hypothesis suggesting the role of post-pregnancy events, such as inflammation, ECM remodeling and angiogenesis in the etiology and aggressiveness of PABCs by looking at a set of human breast cancers with known pregnancy history. We show that the cancers of patients detected post-pregnancy are more frequently associated with an inflammation-associated gene expression pattern, than those of nulliparous women. The exact role of inflammation in the aggressiveness of PABCs remains to be further elucidated.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5158.