MCM3 upregulation confers endocrine resistance in breast cancer and is a predictive marker of diminished tamoxifen benefit

Resistance to endocrine therapy in estrogen receptor-positive (ER+) breast cancer is a major clinical problem with poorly understood mechanisms. There is an unmet need for prognostic and predictive biomarkers to allow appropriate therapeutic targeting. We evaluated the mechanism by which minichromosome maintenance protein 3 (MCM3) influences endocrine resistance and its predictive/prognostic potential in ER+ breast cancer. We discovered that ER+ breast cancer cells survive tamoxifen and letrozole treatments through upregulation of minichromosome maintenance proteins (MCMs), including MCM3, which are key molecules in the cell cycle and DNA replication. Lowering MCM3 expression in endocrine-resistant cells restored drug sensitivity and altered phosphorylation of cell cycle regulators, including p53(Ser315,33), CHK1(Ser317), and cdc25b(Ser323), suggesting that the interaction of MCM3 with cell cycle proteins is an important mechanism of overcoming replicative stress and anti-proliferative effects of endocrine treatments. Interestingly, the MCM3 levels did not affect the efficacy of growth inhibitory by CDK4/6 inhibitors. Evaluation of MCM3 levels in primary tumors from four independent cohorts of breast cancer patients receiving adjuvant tamoxifen mono-therapy or no adjuvant treatment, including the Stockholm tamoxifen (STO-3) trial, showed MCM3 to be an independent prognostic marker adding information beyond Ki67. In addition, MCM3 was shown to be a predictive marker of response to endocrine treatment. Our study reveals a coordinated signaling network centered around MCM3 that limits response to endocrine therapy in ER+ breast cancer and identifies MCM3 as a clinically useful prognostic and predictive biomarker that allows personalized treatment of ER+ breast cancer patients.

TIMP-1 and responsiveness to gemcitabine in advanced breast cancer; results from a randomized phase III trial from the Danish breast cancer cooperative group

Background

Tissue inhibitor of metalloproteinases-1 (TIMP-1) has anti-apoptotic functions, which may protect TIMP-1 positive cancer cells from the effects of chemotherapy such as docetaxel and gemcitabine. The purpose of the present study was to evaluate TIMP-1 immunoreactivity as a prognostic and predictive marker in advanced breast cancer patients receiving docetaxel (D) or gemcitabine plus docetaxel (GD).

Methods

Patients with locally advanced or metastatic breast cancer who were assigned to D or GD by participation in a randomized phase III trial were included in the study. Assessment of TIMP-1 status was performed retrospectively on primary tumor whole-tissue sections by immunohistochemistry and tumor samples were considered positive if epithelial breast cancer cells were stained by the anti-TIMP-1 monoclonal antibody VT7. Time to progression (TTP) was the primary endpoint. Overall survival (OS) and response rate (RR) were secondary endpoints. Associations between TIMP-1 status and outcome after chemotherapy were analyzed by Kaplan-Meier estimates and Cox proportional hazards regression models.

Results

TIMP-1 status was available from 264 of 337 patients and 210 (80%) of the tumors were classified as cancer cell TIMP-1 positive. No significant difference for TTP between TIMP-1 positive versus TIMP-1 negative patients was observed in multivariate analysis, and RR did not differ according to TIMP-1 status. However, patients with TIMP-1 positive tumors had a significant reduction in OS events (hazard ratio = 0.71, 95% confidence interval (CI) = 0.52-0.98, P = 0.03). Additionally, a borderline significant interaction for OS was observed between TIMP-1 status and benefit from GD compared to D (P_interaction = 0.06) such that median OS increased by nine months for TIMP-1 negative patients receiving GD.

Conclusions

TIMP-1 status was an independent prognostic factor for OS but not TTP in patients with advanced breast cancer receiving either D or GD. There was no statistically significant interaction between TIMP-1 status and treatment, but a trend towards an incremental OS from the addition of gemcitabine to docetaxel in patients with TIMP-1 negative tumors suggests further investigation.

Association of tissue inhibitor of metalloproteinases-1 and Ki67 in estrogen receptor positive breast cancer

BACKGROUND

The role of tissue inhibitor of metalloproteinases-1 (TIMP-1) in estrogen receptor (ER) positive breast cancer remains to be fully elucidated. We evaluated TIMP-1 as a prognostic marker in patients treated with adjuvant tamoxifen and investigated TIMP-1s association with Ki67 and ER/progesterone receptor (PR)/human epidermal growth factor receptor 2 (HER2) profiles.

MATERIAL AND METHODS

TIMP-1 expression was evaluated by immunohistochemistry (IHC) on formalin fixed paraffin embedded primary tumor tissue in two independent cohorts comprised of 236 and 192 patients, respectively.

RESULTS

No differences in disease free survival (HR 0.98; 95% CI 0.63-1.53; p = 0.92) and overall survival (HR 0.94; 95% CI 0.63-1.43; p = 0.79) were observed according to TIMP-1 status. A significant negative association between TIMP-1 and Ki67 was identified (p = 0.015). TIMP-1 expression did not differ significantly according to ER/PR/HER2 profiles. When analyzed as separate variables PR and HER2 status tended to have a positive but non-significant association with TIMP-1 (PR: p = 0.08; OR 2.54; 95% CI 0.91-7.10, HER2: p = 0.08; OR 0.48; 95% CI 0.21-1.08) whereas ER status was not associated with TIMP-1 expression (p = 0.48; OR 0.68; 95% CI 0.23-1.99).

CONCLUSION

TIMP-1 does not appear to be prognostic in breast cancer patients receiving adjuvant tamoxifen. We identified a negative association between TIMP-1 and Ki67. We did not confirm our previous in vitro findings of a negative association between TIMP-1 and PR.

TIMP-1 Status Measured by Immunohistochemistry in 268 ER Positive Postmenopausal High-Risk Breast Cancer Patients Treated with Adjuvant Tamoxifen: Association to Recurrence Free Survival

Background: A proportion of ER positive breast cancer patients do not benefit from adjuvant tamoxifen treatment. Tamoxifen has been shown to induce apoptosis in human breast cancer cells in vitro and Tissue Inhibitor of Metalloproteinases-1 (TIMP-1) protects cancer cells against apoptosis. We therefore raised the hypothesis that ER positive breast cancer cells with high TIMP-1 immunoreactivity would show reduced benefit to tamoxifen treatment.Material and methods: Tumor tissue from 268 high-risk postmenopausal ER positive breast cancer patients was used for this study. All patients underwent surgery for primary invasive breast cancer. The majority of the patients were lymph node positive: 92% (246/268). Patients were allocated to 1, 2 or 5 years of adjuvant tamoxifen as mono-therapy. Recurrent disease was diagnosed in 33% (89/268) of the patients. Median time to recurrence was 3.1 years and the median time of follow-up was 12.4 years. Archival formalin-fixed and paraffin-embedded primary tumor tissue was used to generate tissue microarrays comprising two, 2 mm cores from each tumor. TIMP-1 immunoreactivity was evaluated using the mouse monoclonal antibody (clone VT7) raised against recombinant human TIMP-1. This antibody exclusively reacts with TIMP-1. A central assessment of TIMP-1 status was performed. Tumors were analysed by bright field microscopy and scored semi-quantitatively as 0 - 3 with regard to the number of stained tumour cells and intensity of the staining. An index combining the number of positive tumor cells and staining intensity was created: low (0-2), median (3-4) and high expression (5-6).Results: IHC was successfully performed in 266 cases. TIMP-1 IHC negative cases were observed in 39% (105/266) of the tumors and 61% (161/266) were TIMP-1 IHC positive. The index combining the number of positive tumor cells and staining intensity showed low expression in 59% (157/266), median expression in 24% (65/266) and high expression in 17% (44/266) of the tumors. TIMP-1 negativity and low TIMP-1 index showed no significant association with tumor grade, tumor size or lymph node status. When performing Kaplan-Meier plots, TIMP-1 expression was not significantly associated with recurrence free survival in univariate analyses (p = 0.1).Conclusion: This study did not confirm our hypothesis that TIMP-1 immunoreactivity in ER positive breast cancer cells are associated with reduced benefit from adjuvant tamoxifen treatment. This is partly in contrast with prior studies on endocrine therapy of metastatic breast cancer (Lipton et al 2008) where high serum TIMP-1 was associated with reduced response to endocrine therapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2025.

Effect of TIMP-1 Overexpression on Endocrine Sensitivity of MCF-7 ER Positive Human Breast Cancer Cells In Vitro

Background: A large proportion of ER-positive breast cancer patients are offered endocrine therapy following surgery for primary breast cancer. However, many of these patients do not benefit from the treatment. Currently, no markers exist to predict whether or not an ER positive breast cancer patient will respond to endocrine therapy. Thus, additional predictive markers need to be identified to ensure a more tailored treatment. In this regard, recent clinical studies have demonstrated that high serum levels of TIMP-1 are associated with a poor response to tamoxifen or letrozole in ER positive patients with metastatic disease (Lipton et al., JCO 2008). The purpose of the present study was to investigate the association between TIMP-1 and endocrine therapy by using an in vitro approach.Tamoxifen has been shown to induce apoptosis in human breast cancer cells in vitro and TIMP-1 has been shown to inhibit drug induced apoptosis.Materials and Methods: We stably transfected the human breast carcinoma cell line MCF-7 S1 with the human TIMP-1 gene and established single cell clones expressing different levels of TIMP-1. The sensitivity of these cells to estradiol, tamoxifen and 4-hydroxy tamoxifen was compared using the crystal violet assay. For the estradiol experiments, cells were grown in RPMI 1640 supplemented with 10% DCC-stripped FCS and without phenol red and for the tamoxifen/4-hydroxy tamoxifen experiments cells were grown in RPMI supplemented with 10% FCS. Cells were grown in their maintenance medium. Experimental media was added at day two, at a cell density of 20-30%, renewed at day five, and cell number determination was performed at day seven., In all experiments the mean value for each treatment was estimated from triplicate or quadruplicate independent wells and expressed in percentage relative to cells treated only with vehicle.Results: TIMP-1 overexpresing cells grew with a distinct morphology with more well circumscribed cells, and adapted faster to stripped serum than wild type and vector control MCF-7 cells. Independent of TIMP-1 production, all cell lines demonstrated estradiol sensitivity and inhibition of growth by either tamoxifen or 4-hydroxy tamoxifen.Conclusions: This in vitro study shows that overexpression of TIMP-1 in MCF-7 cells did not change the sensitivity of endocrine treatment of the cells. This is in contrast to our experiments with the same cells demonstrating decreased sensitivity to chemotherapy of TIMP-1 overexpresing cells. Moreover, our results are in contrast to those published by Lipton et al., JCO 2008, showing that patients with metastatic breast cancer and high serum TIMP-1 levels had a reduced benefit from endocrine therapy. On the other hand, the present results are supported by our recent finding that TIMP-1 cancer cell immunoreactivity is not associated with benefit from adjuvant tamoxifen therapy in ER-positive breast cancer patients (Bjerre et al., 2009)

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2029.