Tamoxifen in early breast cancer

Mammographic density: a potential monitoring biomarker for adjuvant and preventative breast cancer endocrine therapies

Increased mammographic density (MD) has been shown beyond doubt to be a marker for increased breast cancer risk, though the underpinning pathobiology is yet to be fully elucidated. Estrogenic activity exerts a strong influence over MD, which consequently has been observed to change predictably in response to tamoxifen anti-estrogen therapy, although results for other selective estrogen receptor modulators and aromatase inhibitors are less consistent. In both primary and secondary prevention settings, tamoxifen-associated MD changes correlate with successful modulation of risk or outcome, particularly among pre-menopausal women; an observation that supports the potential use of MD change as a surrogate marker where short-term MD changes reflect longer-term anti-estrogen efficacy. Here we summarize endocrine therapy-induced MD changes and attendant outcomes and discuss both the need for outcome surrogates in such therapy, as well as make a case for MD as such a monitoring marker. We then discuss the process and steps required to validate and introduce MD into practice as a predictor or surrogate for endocrine therapy efficacy in preventive and adjuvant breast cancer treatment settings.

Multi-site clinical evaluation of DW-MRI as a treatment response metric for breast cancer patients undergoing neoadjuvant chemotherapy

PURPOSE

To evaluate diffusion weighted MRI (DW-MR) as a response metric for assessment of neoadjuvant chemotherapy (NAC) in patients with primary breast cancer using prospective multi-center trials which provided MR scans along with clinical outcome information.

MATERIALS AND METHODS

A total of 39 patients with locally advanced breast cancer accrued from three different prospective clinical trials underwent DW-MR examination prior to and at 3-7 days (Hull University), 8-11 days (University of Michigan) and 35 days (NeoCOMICE) post-treatment initiation. Thirteen patients, 12 of which participated in treatment response study, from UM underwent short interval (<1hr) MRI examinations, referred to as "test-retest" for examination of repeatability. To further evaluate stability in ADC measurements, a thermally controlled diffusion phantom was used to assess repeatability of diffusion measurements. MRI sequences included contrast-enhanced T1-weighted, when appropriate, and DW images acquired at b-values of 0 and 800 s/mm2. Histogram analysis and a voxel-based analytical technique, the Parametric Response Map (PRM), were used to derive diffusion response metrics for assessment of treatment response prediction.

RESULTS

Mean tumor apparent diffusion coefficient (ADC) values generated from patient test-retest examinations were found to be very reproducible (|ΔADC|<0.1x10-3mm2/s). This data was used to calculate the 95% CI from the linear fit of tumor voxel ADC pairs of co-registered examinations (±0.45x10-3mm2/s) for PRM analysis of treatment response. Receiver operating characteristic analysis identified the PRM metric to be predictive of outcome at the 8-11 (AUC = 0.964, p = 0.01) and 35 day (AUC = 0.770, p = 0.05) time points (p<.05) while whole-tumor ADC changes where significant at the later 35 day time interval (AUC = 0.825, p = 0.02).

CONCLUSION

This study demonstrates the feasibility of performing a prospective analysis of DW-MRI as a predictive biomarker of NAC in breast cancer patients. In addition, we provide experimental evidence supporting the use of sensitive analytical tools, such as PRM, for evaluating ADC measurements.

The effect of antineoplastic drugs in a male spontaneous mammary tumor model

Male breast cancer is a rare disease. The limited number of clinical cases has led to the primary treatments for men being derived from female breast cancer studies. Here the transgenic strain FVB/N-Tg(MMTV-PyVT)634Mul/J (also known as PyVT) was used as a model system for measuring tumor burden and drug sensitivity of the antineoplastic drugs tamoxifen, cisplatin, and paclitaxel on tumorigenesis at an early stage of mammary carcinoma development in a male mouse model. Cisplatin treatment significantly reduced tumor volume, while paclitaxel and tamoxifen did not attenuate tumor growth. Cisplatin treatment was shown to induce apoptosis, grossly observed by reduced tumor formation, through reduced Bcl-2 and survivin protein expression levels with an increase in caspase 3 expression compared to control tumors. Tamoxifen treatment significantly altered the hormone receptor expression levels of the tumor, while additionally upregulating Bcl-2 and Cyclin D1. This suggests an importance in hormonal signaling in male breast cancer pathogenesis. The results of this study provide valuable information toward the better understanding of male breast cancer and may help guide treatment decisions.

CD36 repression activates a multicellular stromal program shared by high mammographic density and tumor tissues

Although high mammographic density is considered one of the strongest risk factors for invasive breast cancer, the genes involved in modulating this clinical feature are unknown. Tissues of high mammographic density share key histologic features with stromal components within malignant lesions of tumor tissues, specifically low adipocyte and high extracellular matrix (ECM) content. We show that CD36, a transmembrane receptor that coordinately modulates multiple protumorigenic phenotypes, including adipocyte differentiation, angiogenesis, cell-ECM interactions, and immune signaling, is greatly repressed in multiple cell types of disease-free stroma associated with high mammographic density and tumor stroma. Using both in vitro and in vivo assays, we show that CD36 repression is necessary and sufficient to recapitulate the above-mentioned phenotypes observed in high mammographic density and tumor tissues. Consistent with a functional role for this coordinated program in tumorigenesis, we observe that clinical outcomes are strongly associated with CD36 expression.

SIGNIFICANCE

CD36 simultaneously controls adipocyte content and matrix accumulation and is coordinately repressed in multiple cell types within tumor and high mammographic density stroma, suggesting that activation of this stromal program is an early event in tumorigenesis. Levels of CD36 and extent of mammographic density are both modifiable factors that provide potential for intervention.

Magnitude of peroxisome proliferator-activated receptor-gamma activation is associated with important and seemingly opposite biological responses in breast cancer cells

BACKGROUND

The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) has become a potential target for the prevention and treatment of breast cancer. However, recent in vitro and in vivo studies have raised the question of whether activation of PPARgamma leads to the promotion or reduction of tumor formation. Studies using several cancer cell lines, animal models, and a variety of PPARgamma agonists have shown discordant results, including changes in cellular proliferation, differentiation, and apoptosis of cancer cells and tumors.

METHODS

We studied the effects of low-, moderate-, and high-dose treatment of the PPARgamma ligands 15-deoxy-delta1214 prostaglandin J2 (15dPGJ2) and troglitazone (TGZ) on parameters of cell growth, differentiation, and apoptosis in the epithelial breast cancer cell line MDA-MB-231.

RESULTS

The biologic effects of these compounds depend largely on ligand concentration and the degree of PPARgamma activation. For example, low concentrations of 15dPGJ2 (<2.5 microM) and TGZ (<5 microM) increased cellular proliferation, but concentrations of 15dPGJ2 > or = 10 microM and of TGZ at 100 microM blocked cell growth. TGZ (100 microM) slowed cell cycle progression, and 15dPGJ2 (10 microM) caused an S-phase arrest in the cell cycle and induced morphological characteristics consistent with apoptosis. Expression of CD36, a marker of differentiation in these cells, was induced by 2.5 microM 15dPGJ2 or 5 to 100 microM TGZ. However, higher concentrations of 15dPGJ2 did not alter CD36 expression. Transcriptional activation studies demonstrated that 15dPGJ2 is a more potent PPARgamma ligand than TGZ. Regardless of the ligand used, though, low transcriptional activation correlated with an increased cellular proliferation, whereas higher levels of activation correlated with cell cycle arrest and apoptosis.

CONCLUSIONS

PPARgamma activation induces several important and seemingly opposite changes in neoplastic cells, depending on the magnitude of PPARgamma activation. These data may explain, at least in part, some of the discordant results previously reported.