Tamoxifen increases apoptosis but does not influence markers of proliferation in an MCF-7 xenograft model of breast cancer

Twenty-four nude mice bearing MCF-7 breast cancer cells grown as xenografts and treated with tamoxifen (2.5 mg slow-release pellet) were studied for up to 35 days. Tumour size was measured in 2 dimensions at regular time-intervals and tumours were harvested on each of days 2, 4, 7, 14, 28 and 35 after the start of treatment. Control animals (8) received no treatment and the tumours were harvested after 0 or 35 days. Tumour sections were assessed for prevalence of apoptosis and mitosis and examined immunocytochemically for Ki(67)(MIB-1) and bcl-2 expression. Tumours increased in size during tamoxifen-treatment, but at a significantly slower rate (max. 2.6-fold) than in the untreated control animals; thus tumours not actually regressing may, nevertheless, be responding significantly to tamoxifen. MIB-1 and bcl-2 immunostaining and mitosis failed to show any consistent change over the period of study. Apoptosis, however, increased progressively and significantly to day-28 in tamoxifen-treated tumours, reaching approximately a 5-fold increase over day-0 values, then decreasing again to nearly 3-fold by day-35 (P= 0.0002). The apoptosis: mitosis ratio in treated tumours also increased to approximately 10-fold on day-28 over day-0 values, decreasing to nearly 4-fold by day-35 (P= 0.037). Within the treated group, apoptosis was significantly inversely correlated with both mitosis (R = -0.38, P= 0.03) and expression of bcl-2 (R = -0.48, P= 0.0056) and strongly positively correlated with both time on tamoxifen (R = +0.63, P= 0.0003) and the % inhibition of growth by tamoxifen (R = +0.58,P = 0.0012) in the 28 individual, treated tumours (estimated relative to the mean growth rate in the controls). The apoptosis: mitosis ratio was also inversely correlated with bcl-2 expression (R = -0.56, P= 0.0021) and positively correlated with both time on tamoxifen (R = +0.50, P= 0.0068) and % inhibition of growth (R = +0.56, P= 0.0019). In this hormone-sensitive tumour model for breast cancer, in which tamoxifen caused inhibition rather than regression, it was not possible to detect significant changes in the marker proteins Ki(67)and bcl-2, or in the prevalence of mitosis in relation to treatment; these factors may therefore not be accurate indices of response to tamoxifen in all situations. By contrast, however, tamoxifen induced a significant, early increase in the prevalence of apoptosis associated with inhibition of tumour growth and an inverse relationship in both mitosis and bcl-2 expression, suggesting that apoptosis may be an accurate and sensitive early marker of even a moderate response to tamoxifen.

Whole-body FDG-PET imaging for staging of Hodgkin's disease and lymphoma

Accurate staging of Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL) is important for treatment management. In this study, the utility of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) whole-body PET was evaluated as an imaging modality for initial staging or restaging of 7 HD and 11 NHL patients.

METHODS

Whole-body PET-based staging results were compared to the patient's clinical stage based on conventional staging studies, which included combinations of CT of the chest, abdomen and pelvis, MRI scans, gallium scans, lymphangiograms, staging laparatomies and bone scans.

RESULTS

Accurate staging was performed in 17 of 18 patients using a whole-body PET-based staging algorithm compared to the conventional staging algorithm in 15 of 18 patients. In 5 of 18 patients, whole-body PET-based staging showed additional lesions not detected by conventional staging modalities, whereas conventional staging demonstrated additional lesions in 4 of 18 patients not detected by whole-body PET. The total cost of conventional staging was $66,292 for 16 CT chest scans, 16 CT abdominal/pelvis scans, three limited MRI scans, four bone scans, five gallium scans, two laparotomies and one lymphangiogram. In contrast, scans cost $36,250 for 18 whole-body PET studies and additional selected correlative studies: one plain film radiograph, one limited CT, one bone marrow scan, one upper GI and one endoscopy.

CONCLUSION

A whole-body FDG-PET-based staging algorithm may be an accurate and cost-effective method for staging or restaging HD and NHL.