Our data suggest that elevated PYGO2 expression in primary prostate adenocarcinoma is a potential risk factor for BR.

AimsEstrogen and progesterone hormone receptor (ER and PR) expression in invasive breast cancer predicts response to hormone disruptive therapy. Pygopus2 (hPYGO2) encodes a chromatin remodelling protein important for breast cancer growth and cell cycle progression. The aims of this study were to determine the mechanism of expression of hPYGO2 in breast cancer and to examine how this expression is affected therapeutically.MethodshPYGO2 and ER protein expression was examined in a breast tumour microarray by immunohistochemistry. hPYGO2 RNA and protein expression was examined in ER+ and ER− breast cancer cell lines in the presence of selective estrogen hormone receptor modulator drugs and the specificity protein-1 (SP1) inhibitor, betulinic acid (BA). The effects of these drugs on the ability for ER and SP1 to bind the hPYGO2 promoter and affect cell cycle progression were studied using chromatin immunoprecipitation assays.ResultshPYGO2 was expressed in seven of eight lines and in nuclei of 98% of 65 breast tumours, including 3 Ductal carcinoma in situ and 62 invasive specimens representing ER-negative (22%) and ER-positive (78%) cases. Treatment with either 4-Hydroxytamoxifen (OHT) or fulvestrant reduced hPYGO2 mRNA 10-fold and protein 5–10-fold within 4 h. Promoter analysis indicated an ER/SP1 binding site at nt −225 to −531 of hPYGO2. SP1 RNA interference and BA reduced hPYGO2 protein and RNA expression by fivefold in both ER- and ER+ cells. Further attenuation was achieved by combining BA and 4-OHT resulting in eightfold reduction in cell growth.ConclusionsOur findings reveal a mechanistic link between hormone signalling and the growth transcriptional programme. The activation of its expression by ERα and/or SP1 suggests hPYGO2 as a theranostic target for hormone therapy responsive and refractory breast cancer.

Quality control (QC) for immunohistochemistry (IHC) analysis routinely incorporates archived specimens for on-slide control material. We have assessed the utility of cell-line-derived xenograft (CDX) tumours for QC in breast estrogen receptor (ER) and progesterone receptor (PR) biomarker testing. Immunoblot and IHC analyses were used to select cell lines with different steady-state levels of ER and PR expression. CDX tumours all demonstrated consistent and comparable expression of ER and PR with corresponding cell lines from which they were derived. Three pathologists experienced in breast biomarker reporting scored tumours from different locations on mammary fat pads to determine reproducibility. Tumours from different locations were consistently scored as identical, and the CDX tumours representing different levels of biomarker expression were similar to patient-derived controls. Pathologists could not consistently distinguish CDX tumours from patient-derived controls, suggesting that within the appropriate quality management setting, CDX tumours may serve as control material for reporting purposes.

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Neither shortened nor prolonged fixation affects ER expression, consistent with previous findings. In equivocal Her2-expressing tumours, however, increasing fixation increased the sensitivity of Her2 IHC reporting while not affecting FISH.