α-basic-crystallin expression in basal-like breast cancer and its association with brain metastasis
1025 Background: Basal-like breast cancers are high grade tumors with poor prognosis, having propensity for brain and lung metastasis (Perou et al. Nature 406:747–52, 2000, Cheang et al. Clin Cancer Res 14:1368–76, 2008, Luck et al. Clin Oncol (R Coll Radiol) 20:40–5, 2008). α-basic-crystallin (αBC), a small heat shock protein with anti-apoptotic and oncogenic activity, is expressed in about half of basal-like breast cancers but only 6% of other types (Moyano et al. J Clin Invest 116:261–70, 2006). Here we investigate the association of αBC with sites of distant metastasis in a large cohort of breast cancer patients. Methods: Our cohort consists of 4046 early invasive breast cancers referred to the British Columbia Cancer Agency from 1986 to 1992. Archival paraffin tissue blocks were used to construct tissue microarrays. Breast cancer subtypes were defined using a surrogate of six immunohistochemical markers: ER, PR, HER2, Ki-67, epidermal growth factor receptor and cytokeratin 5/6. αBC immunostaining was scored by pre-established, published criteria. All documented sites of distant metastasis were abstracted by chart review according to predefined categories. The null hypothesis was tested using chi-square and Fisher's Exact tests; all tests were two-sided. Results: Among 3,248 cases with interpretable αBC data, 11% were αBC +. Among patients who developed distant metastatic disease, the 10-yr BCSS survival in αBC+ and - tumors was 12% and 29%. Sites of metastatic disease included: brain (15%), lung (35%), liver (35%) and bone (65%). Brain metastasis was significantly more common among αBC positive tumors (Fisher's Exact test p<10e-8). Basal-like tumors with brain metastasis commonly co-expressed αBC (Chi-square p=0.006). Conclusion: αBC is significantly associated with brain metastasis, particularly among basal breast cancers. These findings suggested that αBC may be involved in tumor cell metastasis and may allow early identification of a subset of patients at particularly high risk of brain metastasis. [Table: see text] No significant financial relationships to disclose.