Immunohistochemical Study of the BCAR1/p130Cas Protein in Non-Malignant and Malignant Human Breast Tissue

BCAR1/p130Cas is a docking protein involved in intracellular signaling pathways and in vitro resistance of estrogen-dependent breast cancer cells to antiestrogens. The BCAR1/p130Cas protein level in primary breast cancer cytosols was found to correlate with rapid recurrence of disease. A high BCAR1/p130Cas level was also associated with a higher likelihood of resistance to first-line tamoxifen treatment in patients with advanced breast cancer. Using antibodies raised against the rat p130Cas protein, we determined by immunohistochemical methods the BCAR1/p130Cas localization in primary breast carcinomas, in tumors of stromal origin, and in non-neoplastic breast tissues. The BCAR1/p130Cas protein was detected in the cytoplasm of non-malignant and neoplastic epithelial cells and in the vascular compartment of all tissue sections analyzed. Immunohistochemistry demonstrated variable intensity of BCAR1/p130Cas staining and variation in the proportion of BCAR1/p130Cas-positive epithelial tumor cells for the different breast carcinomas. Double immunohistochemical staining for BCAR1/p130Cas and estrogen receptor confirmed coexpression in non-malignant luminal epithelial cells and malignant breast tumor cells. The stromal cells in non-malignant tissues and tumor tissues as well as breast tumors of mesodermal origin did not stain for BCAR1/p130Cas. This immunohistochemical study demonstrates a variable expression of BCAR1/p130Cas in malignant and non-malignant breast epithelial cells, which may be of benefit for diagnostic purposes.

Abstract S4-07: Tamoxifen resistance driven by the DNA cytosine deaminase APOBEC3B in recurrent estrogen receptor positive breast cancer

Recent studies have implicated the DNA cytosine deaminase APOBEC3B as a major source of mutation in breast cancer. APOBEC3B explains a large proportion of both dispersed and clustered cytosine mutations, the latter of which are also called kataegis. APOBEC3B expression levels correlate with poor outcomes for patients with estrogen receptor positive breast cancer. While targeted therapies, such as tamoxifen, are available to treat these tumors, secondary drug resistance often develops. Here we suppressed endogenous APOBEC3B in the estrogen receptor positive breast cell line MCF-7L with shRNA. Lowered levels of APOBEC3B did not affect in vitro growth or sensitivity to estradiol. In a xenograft model of tamoxifen therapy, suppression of APOBEC3B associated with prolonged responses to tamoxifen (p<0.05). Furthermore, APOBEC3B over-expression did not affect in vitro cell growth but accelerated the development of tamoxifen-resistant tumors in vivo. In addition, we studied two separate cohorts of 285 breast cancer patients who received first line treatment with tamoxifen for recurrent disease. High APOBEC3B expression levels measured in the primary tumor associated significantly with unfavorable progression free survival in multivariate analysis that included the traditional predictive factors (age, dominant relapse site, disease-free interval, estrogen receptor and progesterone receptor, and adjuvant chemotherapy; HR=1.67, p=0.0001). The median period of progression free survival was 7.5 months for patients with APOBEC3B high primary tumors and 13.3 months for those with APOBEC3B low tumors (p<0.0.0001). These studies demonstrate that APOBEC3B drives resistance to endocrine treatment with tamoxifen in recurrent disease.

Citation Format: Harris R, Law E, Sieuwerts A, LaPara K, Leonard B, Starrett G, Temiz NA, Sweep F, Span P, Foekens J, Martens J, Yee D. Tamoxifen resistance driven by the DNA cytosine deaminase APOBEC3B in recurrent estrogen receptor positive breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S4-07.

Abstract P3-06-01: Hotspot mutations in PIK3CA are predictive for treatment outcome on aromatase inhibitors but not for tamoxifen

Introduction: PIK3CA is the most frequent (30%) mutated oncogene in breast cancer and may lead to an activation of the PI3K/AKT/mTOR-pathway. Cell lines resistant to tamoxifen have an activated PI3K-pathway. Phase III clinical trials show substantial benefit when mTOR-inhibitors are added to aromatase inhibitor treatment. On the other hand, patients with PIK3CA exon 20 mutation expression signature show better treatment outcome after adjuvant tamoxifen therapy. To address this controversy, we evaluated the PIK3CA mutation status in 1423 primary breast cancer specimens for its relationship with prognosis and treatment outcome after first-line endocrine treatment.

Methods: Hotspot mutations in exon 9 and 20 of PIK3CA were detected by multiplex snapshot analyses. Mutation status in ER-positive tumors was related to metastasis free survival (MFS) in 292 untreated lymph node negative (LNN) patients and time to progression (TTP) in patients with metastatic disease treated with first-line tamoxifen (N = 482) or aromatase inhibitors (AIs; N=103). Whole genome mRNA and miRs expression profiling was performed in the latter patient subset to develop a PIK3CA gene signature in 64 specimens. This was validated in 28 independent ER-positive specimens.

Results: We could evaluate 1371 specimens and detected 437 hotspot mutations for PIK3CA (32%). Mutations in exon 20 were detected in 256 patients (59%), of which 40 cases with a H1047L (16%) and 216 with a H1047R (84%) mutation. Mutations in PIK3CA exon 9 were discovered in 174 patients (41%), with E542K and E545K mutations in 59 (34%) and 105 (60%) cases, respectively, as the most prevalent ones. Finally, 6 patients had PIK3CA double mutations for both exon 9 and 20 and one patient had a E542K and E545K mutation.

Evaluation of the untreated LNN patients for prognosis showed no relationship between MFS and PIK3CA mutations (HR = 1.07 [95% CI: 0.73–1.56]; p = 0.73), neither for exon 9 nor exon 20 compared to wild-type. In the multicenter cohort of 482 patients with advanced disease treated with first-line tamoxifen no link with treatment outcome and PIK3CA mutation status was observed (HR = 1.13 [95% CI: 0.92–1.38]; p = 0.24). However, patients with advanced disease treated with first-line AIs (N = 64) showed a significant longer TTP for patients with a PIK3CA mutation compared to wild-types (HR = 0.46 [95% CI: 0.25–0.87]; p = 0.017).

Expression profiles of mRNAs and miRs were integrated and resulted in signatures for PIK3CA status discovered by pathway (17 genes) and expression analyses (10 genes and 9 miRs). Validation and comparison with published signatures in the 28 independent tumors showed that our 10-genes signature had the highest PIK3CA prediction accuracy (75%), with 60% sensitivity and 78% specificity. Moreover, this signature better associates with TTP (HR = 0.38 [95% CI: 0.20–0.72]; P = 0.003).

Conclusion: Mutations in PIK3CA are not prognostic value in untreated ER-positive LNN patients, not predictive in ER-positive patients with advanced disease treated with first-line tamoxifen therapy, however, are predictive for favourable outcome after first-line AIs. Moreover, we propose an expression signature of 10 genes as a putative biomarker to predict the PI3K status and response to AIs.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-06-01.

Abstract P4-02-16: High miRNA26A1 and Low EZH2 Expression Levels Are Associated with Favorable Outcome to Tamoxifen in Advanced Breast Cancer through Similar Molecular Pathways

Background: We showed that decreased expression levels of EZH2 are associated with a favorable outcome to tamoxifen in advanced breast cancer. Furthermore, EZH2 knockdown in MCF7 cells resulted in estrogen receptor (ER) upregulation and increased sensitivity to anti-estrogens. Recently, EZH2 has been identified as a target of miRNA26A1 and miRNA101.

Objective: To associate miRNA26A1 and miRNA101 expression levels with: A) EZH2 and B) molecular pathways and C) outcome to first-line tamoxifen monotherapy for advanced disease.

Materials & Methods: Expression levels of miRNA26A1, miRNA101, EZH2 and references (miRNA-132 and miRNA-374) were measured using quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) in 235 ER-positive primary breast cancer specimens from patients with advanced disease. The levels of expression were related to clinicopathologic factors and disease outcome. Pathway analysis was performed in a subset of 65 ER-positive tumors with available gene expression microarray data available. Computations were performed with STATA and P-values <0.05 were considered statistically significant.

Results: The miRNA26A1 levels were significantly associated with levels of ER, progesterone (PgR), HER2 and EGFR, whereas miRNA101 levels showed significant relations with PgR expression and menopausal status. The miRNA26A1 and miRNA101 levels showed an inverse relation with EZH2 mRNA levels (Spearman Rank Correlation of -0.21 and -0.15, respectively, P<0.05). As continuous variable in univariate analysis, miRNA26A1 (Hazard Ratio (HR) =0.13, 95 % CI: 0.06-0.28) correlated with Time to Progression (TTP), while miRNA101 did not (HR=0.87, 95% CI: 0.70-1.07). In multivariate analysis including traditional predictive factors, the third with highest miRNA26A1 levels (HR=0.49, 95% CI: 0.34-0.72) alone, or combined with the third with lowest EZH2 levels (HR=0.56, 95% CI: 0.35-0.88) were associated with a favorable TTP independently of traditional factors. Pathway analyses identified 2 overlapping, cell cycle, related pathways with two genes (CCNE1and CDC2) differentially expressed (P<0.05) between tumors with high and low levels of miRNA26A1 and EZH2, respectively. Levels of CCNE1 and CDC2 were tested in the 235 tumors and showed as continuous variables also a significant association with TTP (HR=1.27, 95% CI: 1.12-1.45 and HR=1.53, 95% CI: 0.129-1.81).

Conclusions: The miRNA26A1 and miRNA101 levels have an inverse relation with levels of EZH2, however, only miRNA26A1 has predictive value in advanced breast cancer. Pathways comparison between miRNA26A1 and EZH2 identified 2 overlapping cell cycle related pathways and the genes CCNE1 and CDC2. Low levels of EZH2, CCNE1 and CDC2 and high levels of miRNA26A1 are associated with a favorable outcome to tamoxifen therapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-02-16.

The 76-Gene Signature Defines High-Risk Patients That Benefit from Adjuvant Tamoxifen Therapy

Background: A significant proportion of ER-positive tumors exhibit resistance to endocrine therapy. Clinical studies in LNN/ER+ patients show that the absolute distant disease-free survival benefit of tamoxifen therapy is only about 9%, with a relative benefit of about 30%. These benefits from treatment may, however, differ substantially according to e.g. patient's age and the tumor level of ER and it is therefore of importance to identify biomarkers that allow identification of those breast cancer patients who may actually benefit from adjuvant tamoxifen. This study was to assess the benefit from adjuvant systemic tamoxifen therapy in breast cancer risk groups identified by the previously established prognostic 76-gene signature.Material and Methods: In 300 lymph node-negative (LNN) estrogen receptor-positive (ER+) breast cancer patients (136 treated with adjuvant tamoxifen, 164 having received no systemic adjuvant therapy), distant metastasis-free survival (DMFS) as a function of the 76-gene signature was determined in a multicenter fashion.Results: In 136 tamoxifen-treated patients, the 76-gene signature identified a group of patients with a poor prognosis (hazard ratio (HR), 4.62, P = 0.0248). These patients showed a 12.3% absolute benefit of tamoxifen in 10-year DMFS (HR, 0.52, P = 0.0318) compared with untreated high-risk patients. This represented a 71% increase in relative benefit compared with the 7.2% absolute benefit observed for all 300 patients without using the gene signature. In the low-risk group there was no significant 10-year DMFS benefit of tamoxifen.Discussion: In summary, the 76-gene signature defines high-risk patients who benefit from adjuvant tamoxifen therapy. Although we did not study the value of chemotherapy in this study, low-risk patients identified by the 76-gene signature have a prognosis good enough that chemotherapy would be difficult to justify. The prognosis of these patients is sufficiently good, in fact, that a disease-free benefit for tamoxifen therapy is difficult to prove, though benefits in terms of oco-regional relapse and a reduction in risk for contralateral breast cancer might justify ormonal therapy in these patients.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2021.

Integrated Genomic Profiling of Endocrine Therapy Response in Advanced Breast Cancer

PurposeIn hormone receptor positive breast cancer the response rates for endocrine treatment, i.e. tamoxifen (TAM) or aromatase inhibitors (AIs), are only 50 to 70% in the advanced disease setting. The overall aim of this retrospective study is to identify a molecular signature using integrated genomic profiling to improve prediction of endocrine treatment outcome in the advanced disease setting.ObjectivesA) To compare mRNA expression profiles of TAM- and AI-treated patients and to identify genes and pathways associated with treatment outcome.B) To discover miRNA and mRNA signatures predictive for AI response.Patients and MethodsFresh frozen Estrogen Receptor (ER)-positive primary breast cancer specimens from patients with advanced disease treated with first-line AIs (N=55) or TAM (N=109) were analyzed. Expression profiles of 670 miRNAs and 44K mRNAs were generated using multiplex qRT-PCR and microarrays. Profiles were related to clinical response and time to progression (TTP). Statistical and bio-informatic tools were applied to discover and combine markers into an integrated genomic predictive signature. The nearest centroid prediction method of BRB-ArrayTools (Version3.7.0) was used to assess the predictive value.ResultsThe quality controlled and informative expression profiles of 277 miRNAs and 14112 mRNAs in 50 AI-treated tumors and 10433 mRNAs in 101 TAM-treated tumors were included for further analysis in the discovery phase.Global testing of mRNAs linked to Biocarta pathways demonstrated the involvement of the interferon pathway in endocrine therapy response in both AI- and TAM-treated patients. Using BRB-ArrayTools survival analysis to find genes associated with TTP (P<0.05), we identified 1002 mRNAs in AI-treated and 662 mRNAs in TAM-treated tumors to be significantly related with TTP.The overlap of 40 mRNAs between AI- and TAM-treatment was defined as a mRNA signature for endocrine treatment outcome. In TAM-treated patients this classifier has a 69% accuracy (63% sensitivity, 74% specificity), an odds ratio for clinical benefit of 4.69 (95% CI 1.99-11.05, P<0.001) and a hazard ratio for TTP of 0.17 (95% CI 0.10-0.29, P<0.001). In AI-treated patients, this 40mRNA signature has a performance of 78% accuracy (84% sensitivity, 62% specificity) and significantly predicts clinical benefit (odds ratio = 8.27, 95% CI 2.00-34.3, P=0.004) and TTP (hazard ratio = 0.07, 95% CI 0.02-0.22, P<0.001).After statistical analysis a 16 miRNAs classifier for AI-treatment outcome was identified with a performance of 78% accuracy (89% sensitivity, 46% specificity). This classifier significantly predicts clinical benefit (Odds ratio = 7.07, 95% CI 1.57-31.9, P=0.011) and TTP (hazard ratio = 0.24, 95% CI 0.09-0.61, P=0.003).The genomic mRNA and miRNA signatures are currently integrated and validated in additional samples as well as “in silico” on tumors treated with neo-adjuvant AI (Miller et al, JCO 2009).ConclusionThis is the first study that combines miRNA and mRNA profiling in an attempt to define an integrated genomic signature for endocrine treatment outcome. Additional prospective multicenter studies are needed to confirm the predictive value of this signature.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3029.

Down Regulation of EZH2 Is Associated with ESR1 Upregulation and Response to Endocrine Therapy in Breast Cancer

Background: We have previously identified a gene signature for resistance to first-line tamoxifen therapy in advanced breast cancer. One of these genes is Enhancer of Zeste Homolog 1 (EZH1), a member of the EZH family of which EZH2 has been identified as being prognostic. Both genes are involved in transcriptional control and epigenetic memory maintenance and act as polycomb repressors. The aim of this study is to investigate these genes for their predictive value and, if associated with clinical outcome, to evaluate the functional role in treatment response in vitro.Experimental design: Expression levels of EZH1 and EZH2 expression were measured using quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) in primary breast cancer specimens and related to clinicopathologic factors and disease outcome. Functional studies were done in MCF7, a human estrogen sensitive breast cancer cell line. Expression levels of EZH2 were downregulated with siRNAs, and changes in cell numbers were determined treating with (the anti-estrogen) ICI164.384. In addition, alterations in expression levels of putative downstream genes, including the estrogen receptor (ESR1), were measured.Results: When analysed as continuous variable in univariate analysis, only EZH2 was significantly associated with therapy resistance and a shorter Progression Free Survival (PFS) in 278 patients with advanced disease treated with first-line tamoxifen monotherapy. In univariate analysis the tertile with highest EZH2 levels was associated with clinical benefit (OR=0.48, 95%CI: 0.26-0.89; P=0.02) and with PFS (HR=1.80, 95%CI: 1.32-2.46;P<0.001). In multivariate analysis including traditional predictive factors, highest EZH2 levels were independently related with a shorter PFS (HR=1.58, 95%CI: 1.10-2.26; P=0.01). Despite, EZH2 mRNA levels were not significantly correlated with metastasis free survival (HR=1.14, 95%CI: 0.98-1.32; P=0.10) in 688 lymph node negative patients who did not receive adjuvant systemic therapy.EZH2 silencing in MCF7 caused a significant decrease in cell numbers (38%, range 17-53%, N=3) whereas ICI164.384 treatment resulted in decrease of 25% (range 12-30%, N=3) compared to controls. Combining EZH2 silencing with ICI-treatment reduced cell numbers with 67% (range 54-75%, N=3, P<0.001). Interestingly, downregulation of EZH2 was associated with an almost 2-fold upregulation of ESR1 (N=6, P=0.001). This inverse relation has been confirmed in additional “in silico” analyses.Conclusion: High levels of EZH2 are associated with poor clinical outcome for tamoxifen therapy of advanced breast cancer. EZH2 silencing in MCF7 cells inhibits cell proliferation, it upregulates ESR1 levels and increases sensitivity to ICI164.384. Further validation is needed to confirm that silencing of EZH2 leads to an upregulation of the ESR1 and as a consequence to a better response to anti-estrogens. This finding sheds new light on the involvement of EZH2 in anti-estrogen treatment offering possibilities for novel management strategies.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5131.

Metastatic Outcome of Estrogen Receptor (ER)-Negative Breast Cancer Appears Independent of Both Age-at-Onset and Tumor Proliferative Potential

Breast cancers arising in younger women are associated with worse survival outcome when compared with stage-matched breast cancers diagnosed in older women; to date, however, the poorer outcome of these younger onset breast cancer cases has not been fully explained by prognostic biomarkers or biological mechanisms. Collecting age cohorts of node-negative, estrogen receptor (ER)-positive sporadic breast cancers, we recently showed that younger onset cases can be distinguished from older onset ER-positive cases by expression profiling but not by genomic profiling, revealing a predictive age signature and enrichment of a proliferation gene expression signature (Perou et al., 2000) among younger ER-positive breast cancer cases (Yau et al., 2007). To further explore the impact of age on the outcome and biology of early stage breast cancers stratified by ER status, we pooled outcome and expression microarray data on adjuvant-untreated, node-negative cases obtained from three sources (van de Vijver et al., 2002; Wang et al., 2005; Desmedt et al., 2007). Dichotomized age-at-onset cohorts were defined as either younger (Y) ≤ 39 y or older (O) ≥ 40 y cases. Gene expression data from 447 ER-positive (61 Y, 386 O) and 178 ER-negative (40 Y, 138 O) cases, generated from either of two microarray platforms (Affymetrix, Agilent), were mapped by gene symbol and combined using distance weighted discrimination (DWD), to produce pooled datasets for each ER subtype containing 6209 unique genes. Distant metastasis-free survival (DMFS) was plotted by Kaplan-Meier analysis out to 15 years for 563 of the pooled 624 cases (400 ER-positive: 52 Y and 348 O; 163 ER-negative: 36Y and 137 O), and log rank significance testing was performed. DMFS of all 163 ER-negative cases was significantly worse than that of all 400 ER-positive cases (p = 0.05); and DMFS of all 88 Y cases was significantly worse than that of all 475 O cases (p = 0.02). DMFS of ER-positive Y cases was significantly worse than ER-positive O cases (p = 0.02), but DMFS of ER-negative Y cases was not significantly different than that of ER-negative O cases (p = 0.66). Consistent with our earlier results, expression of a 38-gene proliferation signature was significantly enriched in ER-positive Y cases relative to ER-positive O cases. In contrast, this proliferation signature was not differentially enriched in ER-negative Y cases relative to ER-negative O cases. While high proliferation gene signature expression correlated with worse DMFS in ER-positive Y and O cases, it did not correlate with ER-negative DMFS in either Y or O cohorts. Thus, metastatic outcome analyses indicate that for node-negative breast cancers without systemic treatment, age is a prognostic factor only for ER-positive and not for ER-negative disease. Moreover, gene expression analyses indicate that the better prognosis of ER-positive breast cancers arising after age 39 may be attributed to their lower proliferative potential while the worse DMFS of younger onset ER-positive breast cancers may be attributed to their higher proliferative potential. In contrast, the metastatic outcome of ER-negative breast cancer appears independent of both age-at-onset and tumor proliferative potential.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4051.

Decreased expression of EZH2 is associated with ESR1 upregulation and response to anti-estrogens

Abstract #6127

Background: In prostate and breast cancer high levels of Enhancer of Zeste Homolog 2 (EZH2) are associated with tumor progression. EZH2, a histone H3 methyl transferase, is part of the polycomb complex. Together with histone deacetylases (HDACs) EZH2 regulates “genome wide” gene transcription silencing. The aims of this study are a) to correlate EZH2 expression with endocrine therapy response in patients with recurrent disease treated with first-line tamoxifen monotherapy and b) to determine the role of EZH2 in endocrine therapy response using in vitro cell line models.
 Material and Methods: EZH2 mRNA levels were measured with quantitative real-time PCR (qRT-PCR) in 297 retrospectively collected hormone receptor positive (HR+) primary breast tumor specimens of patients with recurrent disease who did respond (N=110) or were resistant (N=187) to first-line tamoxifen monotherapy. In vitro, EZH2 and estrogen receptor (ESR1) expression was downregulated with siRNAs in the human breast cancer cell line MCF7 and assessed for their sensitivity to the selective estrogen receptor degrader ICI164.384 after 96hrs treatment (N=3). To establish therapy response in vitro, cell number counts were determined. All p-values are two-sided and significant if P<0.05.
 Results: In 297 HR+ breast tumors, EZH2 as continuous variable, associated significantly with poor response (OR= 0.67 [0.49-0.91]; P=0.001) and a shorter progression-free survival (PFS) (HR=1.28 [1.11-1.47], P<0.001). In the multivariate model with traditional predictive factors, the tertile with highest EZH2 levels was independently related with response (OR= 0.50 [0.26-0.98]; P=0.045) and PFS (HR=1.82 [1.33-2.49], P<0.001).
 In vitro, EZH2 downregulation in MCF7 with siRNAs showed a significant decrease in cell number compared to the mock silenced cell line (40%). Moreover, ICI treatment of EZH2 silenced MCF7 cells resulted in a 70% cell number decrease versus 23% decrease in the controls (P<0.001). In addition, EZH2 downregulation is associated with a twofold upregulation with ESR1 (P<0.001). Conversely, silencing of ESR1 in MCF7 resulted did not alter EZH2 levels but, as expected, increases HER2 protein levels.
 Conclusion: In primary breast tumors, high EZH2 mRNA levels are associated with poor outcomes after tamoxifen therapy. These results suggest that EZH2 may identify patients at risk for tamoxifen therapy failure. In vitro studies show that downregulation of EZH2 inhibits cell proliferation and on the other hand results in upregulation of ESR1 levels. The latter may explain the increased sensitivity to ICI164.384 of EZH2 silenced cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6127.

Novel endocrine therapies in breast cancer

Endocrine therapy of breast cancer consists of a variety of both medical and surgical ablative treatment modalities, but ablative therapy is increasingly replaced by medical treatment. Most endocrine therapies have more than one endocrine effect, frequently together with direct growth inhibitory actions via receptors. Endocrine therapy can be effective in all phases of the disease, but curative only in early disease while in advanced cancer it can only prolong survival. In the past decade the number of available endocrine agents has been drastically increased. Novel approaches in the endocrine therapy of breast cancer are application of new antiestrogens, antiprogestins, new potent aromatase inhibitors, analogues of luteinizing hormone-releasing hormone (LHRH-A) and somatostatin, inhibitors of prolactin secretion, vitamin A and D analogues, bisphosphonates, growth factor antagonists, tyrosine protein kinase inhibitors, protease inhibitors, inhibitors of angiogenesis, radiolabeled hormones and monoclonal antibodies. New cell biological factors such as oncogenes and suppressorgenes, secretory proteins and membrane receptors can be used not only as prognostic factors but also for prediction of type of response to endocrine and chemotherapy. Thus, these cell biological parameters can be used to select high and low risk patients, type of systemic treatment, and can also be used as targets for new treatment modalities. Future studies on treatment of all stages of disease will increasingly focus on promising combined treatment modalities.

Cell biological factors associated with the response of breast cancer to systemic treatment

A large number of cell biological parameters are currently available to predict the prognosis of patients with breast cancer, but it is still difficulty accurately to predict the response to treatment. A valuable prognostic factor can be a poor predictive factor for response, and vice versa. High tumor levels of ER, PgR, AR and pS2 predict a relatively good response to endocrine therapy, while EGF-R positively, HER2/neu positivity, aneuploidy, high proliferation indices and possibly high uPA levels indicate a high chance of poor response to endocrine therapy in metastatic breast cancer. With respect to chemotherapy, a high proliferation rate and HER2/neu amplification predict a good response to therapy in metastatic disease, while MDR gene expression and possibly c-myc amplification are related to a worse response. In conclusion, the newer cell biological parameters can be used to select high and low-risk patients, type of systemic treatment, and as targets for new treatment modalities.