1alpha(OH)D5 is a good candidate for in vivo chemoprevention studies. It may mediate its action by inducing expression of VDR and of TGF-beta1, as is seen in other systems.

No abstract

We have investigated the role of high-resolution ultrasound (US) in the analysis of sentinel node(s) in melanoma patients in pre-operative staging and follow-up. One hundred and six lymph node basins in 88 melanoma patients undergoing sentinel node biopsy (SNB) were examined: 25 (23.6%) were US positive for metastases and 81 (76.4%) were negative. Subsequent histological analysis of the 81 negative lymph nodes confirmed the absence of metastases in 80 cases (98.8%), whereas, in the 25 US-positive lymph nodes, metastases were found in 16 cases (64%). The follow-up of all patients submitted to SNB in our unit included a US investigation of operated and contralateral nodal basins every 4 months for the first 3 years and then every 6 months. Of a total of 300 patients, four (1.6%) were found to have locoregional nodal disease during follow-up. In three of these four patients, US was crucial in indicating the presence of nodal metastases, which would have gone undetected on physical examination. The result of this study (negative predictive value of 98.7%) introduces the possibility of selecting patients who may avoid an SNB procedure based on the results of pre-operative US examination.

Vitamin D analogs are effective inhibitors of breast cancer cell growth, but many breast cancer cell lines show various degrees of resistance to the growth inhibitory effect of vitamin D. In this study, we investigated the mechanism of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] resistance of the human breast epithelial cell line HBL100, which had been immortalized by Simian virus 40 (SV40) large T antigen. We determined the expression, DNA binding and transactivation activity of vitamin D3 receptor (VDR) in HBL100 and a vitamin D-sensitive ZR75-1 breast cancer cell line. Western blot analysis revealed a comparable expression of VDR gene in both cell lines. However, gel retardation assays demonstrated nuclear proteins from ZR75-1 cells but not from HBL100; cells expressed a 9-fold increase in the binding activity with a vitamin D response element (VDRE). Using a transient transfection assay, we showed that the VDRE was activated by 8-fold in ZR75-1. However, in HBL100 cells there was no activation observed in response to 1,25(OH)2D3. On the other hand, co-transfection of a VDR expression vector could restore 1,25(OH)2D3-induced VDRE transcription in HBL100 cells. Moreover, stable expression of VDR in HBL100 cells resulted in enhanced sensitivity of the cells to the growth inhibitory effect of 1,25(OH)2D3. Since CV-1 cells express very little endogenous VDR, the interactions of VDR and large T antigen were carried out in these cells. By transient co-transfection, we observed that expression of the large T antigen strongly inhibited 1,25(OH)2D3-induced VDRE transcriptional activity in a dose-dependent fashion in CV-1 cells. At 120 ng VDR concentration, the inhibition was completely reversed. Thus the loss of the growth inhibitory effect of vitamin D3 in HBL100 cells may be caused by the expression of the large T antigen in the cells, and provide further evidence that VDR is required for efficient growth inhibition by vitamin D3.