Androgen & vitamin D nuclear receptor expression in archival breast tumour samples

Breast tumour cells have receptors for androgen and vitamin D and their clinical significance is not completely understood. Therefore, the present study was undertaken to analyze androgen and vitamin D receptor levels in human primary infiltrating ductal breast carcinomas (IDC) and benign breast tumour archival samples and to find out their correlation, if any, with the clinical findings.

Paraffin blocks of benign and malignant breast tumours were sectioned, deparaffinized, and nuclei released by pepsin digestion. After antigen retrieval, nuclei were stained with primary antibodies for androgen or vitamin D receptors and secondary fluorescein isothiocyanate (FITC) labeled antibodies and propidium iodide respectively, to quantitative receptor expression and DNA content by flow cytometry.

Androgen receptor positive nuclei ranged from 16-66 per cent in the IDC tumours as compared to 36-67 per cent in the benign tumours. Based on flow cytometric comparison of AR expression in AR positive and negative cell lines established earlier, 24 of 28 tumours from postmenopausal women were AR positive compared to all benign tumours and 32 of 33 tumours from pre-menopausal patients. Vitamin D receptor positive nuclei ranged from 14-89 and 2-75 per cent in IDC and benign tumours, respectively. All pre- or post-menopausal tumours were VDR positive as compared to 10 of 15 benign tumours that were VDR positive. No correlation was seen between nuclear androgen and vitamin D receptor expression of the IDC or benign tumours. There was a positive correlation between per cent of receptor positive nuclei and antigen density as measured by ratio of the mean log fluorescence channel value (MFC). No statistically significant correlation was found between nuclear receptor expression (per cent positive nuclei or antigen density) with that of tumour stage, lymph node status, tumour grade, patient age or menopausal status.

There was no significant correlation between androgen or vitamin D receptor expression and clinical findings. The expression of AR and VDR and the antigen density in the nuclei of the archival breast tumour samples were highly variable because of the tumour heterogeneity. Future studies with fresh biopsy samples of tumour on AR and VDR levels and their up- or down-regulation may be useful while stratifying the patients for hormonal therapy.