Aim: This work aims to evaluate H3K27me3 expression in luminal-like breast tumors, using immunohistochemistry assay, to assess the prognostic value of this epigenetic alterations in estrogen positive breast cancer (BrC).
Introduction: BrC is the second most incident cancer worldwide. In Portugal, in 2012, BrC was simultaneously the leading cancer in incidence and mortality in women.1 Around 70% of all BrC are hormone-receptor positive, that is the major part of breast tumors is luminal-like.2 H3K27m3 is a gene repression marker3,4 and is associated with gene silencing, playing a crucial role in cell proliferation and differentiation.3 H3K27me3 may have some clinical value in several types of cancer since it can be used as a biomarker. This histone modification has been associated with poor prognosis of some BrC subtypes.5
Methods: It was used a cohort of BrC patients of the Portuguese Oncology Institution of Porto (IPO-Porto), diagnosed between 1994 and 2002. A total of 102 luminal-like tumor cases were assessed by immunohistochemistry, to H3K27me3 expression. To verify the prognostic value of H3K27me3 levels, Cox regression with a log rank test was performed for both disease-specific and disease-free survival.
Results: Through the result analysis, it was established that only tumor grade (p=0.021) was significant associated with disease-specific survival. Nevertheless, both luminal subtype (p=0.016) and H3K27me3 expression (p=0.012) were significantly associated with disease-free survival. Indeed, H3K27me3 high expression is associated with higher recurrence risk, especially in Luminal A.
Conclusion: We could confirm the prognostic value of H3K27me3 expression in luminal A subtype BrC patients. Therefore, higher H3K27me3 expression in luminal A tumors is associated with a greater probability of recurrence.
However, studies in larger cohorts are mandatory to validate its clinical utility.
Acknowledgements: This study was funded by a grant of the Research Centre of Portuguese Oncology Institute of Porto (CI-IPOP-74-2016).
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