Abstract P4-09-07: ING1 Expression Measured by AQUA can be an Independent Prognostic Marker in Breast Cancer
Authors: Thakur S , Klimowicz A , Pohorelic B , Dean M , Konno M , Bose P , Magliocco A , Riabowol K 
Published: August 2014

Background: Breast cancer accounts for around 45,000 cancer related deaths in North America per year. The high incidence of breast cancer observed in this region is most likely due to the availability of various screening programs used to detect breast cancer, which otherwise may never get diagnosed. There is an inverse relation between the cost of treatment and patient survival as the breast cancer progresses to higher grades. Therefore, screening and diagnosing breast cancers at earlier stages is needed which can improve patient survival.

The INhibitor of Growth (ING) family of tumour suppressor proteins are implicated in diverse cellular processes including chromatin remodelling and apoptosis. ING proteins are stoichiometric members of histone acetyl transferase (HAT) and histone deacetylase (HDAC) complexes. Their expression is downregulated in several cancers, including breast carcinoma. Alternatively, ING function may be compromised by mislocalization to the cytoplasm. However, the association of expression of ING proteins and cancer specific survival has not been studied yet. In this study, we aimed to evaluate the prognostic significance of ING1 in breast cancer.

Patients and Methods: This study included 443 Breast Cancer patients diagnosed in Calgary, Canada from 1985–2000. Clinical data were obtained from the Alberta Cancer Registry and chart review. Tissue microarrays (TMAs) were assembled from triplicate cores of formalin-fixed paraffin-embedded tumour tissue. ING1 protein expression was quantified using fluorescent immunohistochemistry and automated quantitative analysis (AQUA) in normal breast epithelial cells and breast cancer samples. 5 year progression free survival (PFS) was analyzed using Kaplan-Meier plots and Cox proportional hazard modelling.

Results: In our study, we found that ING1 expression is significantly downregulated in the breast cancer patient samples relative to normal breast epithelia. High or low ING1 cytoplasmic/nuclear (C/N) ratio results in poor 5 year PFS. Also, the low tumor/stromal (t/s) ratio of ING1 results in poor prognosis. In univariate analysis, t/s ING1 expression showed a negative correlation with tumor stage [p = 0.008]; tumor grade [p = 0.000]; nodal status [p = 0.000] and 5 year PFS [p = 0.004]. However, no correlation was observed with ER, PR or HER2 status. In multivariate analysis, t/s ING1 proved to be an independent and better prognostic marker [HR 0.582, p = 0.037] than HER2 [HR 2.230, p = 0.057]; Age at diagnosis [HR 2.010, p = 0.205] and tumor size [HR 1.471, p = 0.189].

Discussion and Conclusions: This is the first study to evaluate ING1 expression in breast cancer using the AQUA technique. ING1 expression high or low in the C/N ratio might disrupt the stoichiometry of chromatin-modifying complexes and hamper ING1s extra nuclear functions, leading to poor survival. The significantly improved survival observed in patients with high t/s ING1 expression further strengthens the role of ING1 as a tumor suppressor.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-09-07.