Using aromatase inhibitors in the neoadjuvant setting: evolution or revolution?

The beneficial androgenic action of steroidal aromatase inactivators in estrogen-dependent breast cancer after failure of nonsteroidal drugs

Direct treatment of ER (+) breast cancer with Formestane diminishes the tumor within weeks. This is unlikely due to lack of estrogens alone. We proposed that it is the negative influence of androgens on the growth of ER(+) breast cancer. We investigated the influence of Formestane and Exemestane and of their major androgenic metabolites 4-hydroxytestosterone and 17-hydroexemestane on the proliferation of MCF-7 cells and ZR-75-1 cells. Inhibitory effects could be prevented by antiandrogens and siRNA. Activation of the AR in MCF-7 and U2-OS cells was tested by reporter gene assays. In vivo androgenicity was evaluated using the Hershberger assay. Influence on the cell cycle was demonstrated by flow-cytometry. Influence of androgens on the activity of CCND1 was demonstrated by Chip-qPCR. Antitumor activity was determined by topical treatment of DMBA tumors. We found that breast cancer cells can metabolize Formestane and Exemestane to androgenic compounds which inhibit proliferation. This can be explained by hindering the accessibility of CCND1 by histone modification. Androgenic metabolites can abolish the growth of DMBA-tumors and prevent the appearance of new tumors. The lack of cross-resistance between steroidal and nonsteroidal aromatase inhibitors is due to inhibitory effects of androgenic steroidal metabolites on the production of cyclin D1. These sterols not only inhibit proliferation of cancer cells but can also stop the growth of DMBA cancers upon direct absorption into the tumor. The quick and considerable effect on ER(+) tumors may open a new avenue for neodjuvant treatment.

Estrogen, progesterone, and HER2/neu receptor discordance between primary and metastatic breast tumours-a review

Discordance in estrogen (ER), progesterone (PR), and HER2/neu status between primary breast tumours and metastatic disease is well recognized. In this review, we highlight how receptor discordance between primary tumours and paired metastasis can help elucidate the mechanism of metastasis but can also effect patient management and the design of future trials. Discordance rates and ranges were available from 47 studies (3384 matched primary and metastatic pairs) reporting ER, PR, and HER2/neu expression for both primary and metastatic sites. Median discordance rates for ER, PR, and HER2/neu were 14 % (range 0-67 %, IQR 9-25 %), 21 % (range 0-62 %, IQR 15-41 %), and 10 % (range 0-44 %, IQR 4-17 %), respectively. Loss of receptor expression was more common (9.17 %) than gain (4.51 %). Discordance rates varied amongst site of metastasis with ER discordance being highest in bone metastases suggesting that discordance is a true biological phenomenon. Discordance rates vary for both the biomarker and the metastatic site. Loss of expression is more common than gain. This can affect patient management as it can lead to a reduction in both the efficacy and availability of potential therapeutic agents. Future studies are recommended to explore both the mechanisms of discordance as well as its impact on patient outcome and management.

Evaluating the feasibility of performing window of opportunity trials in breast cancer

BACKGROUND

The waiting period to surgery represents a valuable "window of opportunity" to evaluate novel therapeutic strategies. Interventional studies performed during this period require significant multidisciplinary collaboration to overcome logistical hurdles. We undertook a one-year prospective window of opportunity study to assess feasibility.

METHODS

Eligible newly diagnosed postmenopausal, estrogen receptor positive breast cancer patients awaiting primary surgery received anastrozole daily until surgery. Feasibility was assessed by (a) the proportion of patients who consented and (b) completed the study. Comparison of pre- and poststudy Ki67 labelling index and cleaved caspase 3 scores (CC3) was performed.

RESULTS

22/131 (16.8%) patients were confirmed eligible and 20/22 (91%) patients completed the study. 19/20 (95%) patients agreed to undergo optional additional tissue biopsies. The mean duration of anastrozole use was 24.7 (15-44) days. There were a statistically significant decline in mean Ki67 indices of 48.8% (p < 0.001) and a trend towards significance in the decline of CC3 (p = 0.17) when comparing pre- with posttreatment values.

CONCLUSION

window of opportunity trials in breast cancer are a feasible way of assessing the biologic efficacy of different therapies in the presurgical setting. The majority of eligible women were willing to participate including undergoing additional tissue biopsies.

Expression and relevance of TRPS-1: a new GATA transcription factor in breast cancer

GATA transcription factor family members have been found to play a critical role in the differentiation of many tissue types. For example, GATA-3 has been found to be highly correlated with estrogen receptor α (ER) expression and is emerging as one of the "master regulators" in breast ductal epithelial cell differentiation. Recently, we discovered another GATA family member highly prevalent in breast cancer called the trichorhinophalangeal syndrome-1 gene (TRPS-1). Using a quantitative immunohistochemistry (qIHC) approach, we found that TRPS-1 was significantly correlated with ER, PR, GATA-3, as well as HER2 expression. However, TRPS-1 was also found to be expressed in a high proportion of ER(-) ductal epithelial breast cancers (BCs), indicating that it may act as a ductal epithelial cell-specific transcription factor regulating cell fate at some point in the epithelial cell differentiation pathway. In keeping with this hypothesis, we found that TRPS-1 protein expression in BC above a certain threshold using qIHC correlated with markedly improved overall survival. Cox proportional hazards analysis found that both TRPS-1 and ER expression above critical threshold equally predicted for improved survival. Thus, TRPS-1 may be a powerful new positive prognostic marker in BC, and further IHC studies, as well as examination of its molecular function in ductal epithelial cell differentiation in the breast, are warranted. In this regard, data on the role of TRPS-1 in the differentiation of cells from mesenchymal precursors in other tissues, such as kidney metanephric mesenchymal cells, columnar chondrocytes, and osteoblasts, in mouse models may be useful. Indeed, these studies have found that TRPS-1 is a critical regulator of mesenchymal-to-epithelial cell transition. In the mammary gland, the restricted expression of TRPS-1 in human, mouse, and rat ductal epithelial cells suggests that it may also play a similar role during ductal luminal progenitor/stem cell differentiation. We present a model of TRPS-1 action in which it may act upstream of GATA-3 and ER on an earlier ductal epithelial progenitor cell or mammary stem cell during mammary gland development and also helps prevent reversion of ER(+) BC cells back into mesenchymal-like cells. This model predicts that BCs with low or no TRPS-1 expression may inherently be much less differentiated and more aggressive tumors with less favorable prognosis.

Constitutively nuclear FOXO3a localization predicts poor survival and promotes Akt phosphorylation in breast cancer

BACKGROUND

The PI3K-Akt signal pathway plays a key role in tumorigenesis and the development of drug-resistance. Cytotoxic chemotherapy resistance is linked to limited therapeutic options and poor prognosis.

METHODOLOGY/PRINCIPAL FINDINGS

Examination of FOXO3a and phosphorylated-Akt (P-Akt) expression in breast cancer tissue microarrays showed nuclear FOXO3a was associated with lymph node positivity (p = 0.052), poor prognosis (p = 0.014), and P-Akt expression in invasive ductal carcinoma. Using tamoxifen and doxorubicin-sensitive and -resistant breast cancer cell lines as models, we found that doxorubicin- but not tamoxifen-resistance is associated with nuclear accumulation of FOXO3a, consistent with the finding that sustained nuclear FOXO3a is associated with poor prognosis. We also established that doxorubicin treatment induces proliferation arrest and FOXO3a nuclear relocation in sensitive breast cancer cells. Induction of FOXO3a activity in doxorubicin-sensitive MCF-7 cells was sufficient to promote Akt phosphorylation and arrest cell proliferation. Conversely, knockdown of endogenous FOXO3a expression reduced PI3K/Akt activity. Using MDA-MB-231 cells, in which FOXO3a activity can be induced by 4-hydroxytamoxifen, we showed that FOXO3a induction up-regulates PI3K-Akt activity and enhanced doxorubicin resistance. However FOXO3a induction has little effect on cell proliferation, indicating that FOXO3a or its downstream activity is deregulated in the cytotoxic drug resistant breast cancer cells. Thus, our results suggest that sustained FOXO3a activation can enhance hyperactivation of the PI3K/Akt pathway.

CONCLUSIONS/SIGNIFICANCE

Together these data suggest that lymph node metastasis and poor survival in invasive ductal breast carcinoma are linked to an uncoupling of the Akt-FOXO3a signaling axis. In these breast cancers activated Akt fails to inactivate and re-localize FOXO3a to the cytoplasm, and nuclear-targeted FOXO3a does not induce cell death or cell cycle arrest. As such, sustained nuclear FOXO3a expression in breast cancer may culminate in cancer progression and the development of an aggressive phenotype similar to that observed in cytotoxic chemotherapy resistant breast cancer cell models.

Role of neo-adjuvant hormonal therapy in the treatment of breast cancer: a review of clinical trials

The clinical benefits of endocrine therapy for patients with hormonosensitive breast cancer are well established. For many years, 5 years of tamoxifen was the gold standard of adjuvant treatment. The recent development of new endocrine agents provides physicians with a more effective therapeutic approach. Nevertheless, the success of neoadjuvant endocrine therapy is much more recent and less reported in the literature. This article reviews the studies published about neoadjuvant endocrine treatment (tamoxifen and aromatase inhibitors). According to the literature, neoadjuvant endocrine therapy seems to be effective. In contrast to neoadjuvant chemotherapy, neoadjuvant endocrine therapy is well tolerated, with very few patients having to discontinue the treatment because of side effects. It does not constitute a standard treatment but could have potential for elderly women with operable, hormonosensitive, well differentiated and slowly progressing (SBR I) tumor or for patients with lobular MSBR 1 carcinoma (low chemosensitivity). The newer generation of aromatase inhibitors (letrozole, anastrozole, exemestane) appears to be more active (in terms of overall response rates and conservative surgery rate) than tamoxifen. Patients with an estrogen receptor Allred score of 6 and over are more likely to respond and gain a clinical benefit. The optimal duration of neoadjuvant therapy has not yet been investigated in detail. These preliminary results should be confirmed by further studies.

Down-regulation of phosphatidylinositol 3'-kinase/AKT/molecular target of rapamycin metabolic pathway by primary letrozole-based therapy in human breast cancer

PURPOSE

The phosphatidylinositol 3'-kinase (PI3K)/AKT/molecular target of rapamycin (mTOR) pathway is involved in the development of tumor resistance to endocrine therapy in breast cancer cell lines and represents an attractive target for pharmacologic intervention. However, the effects of endocrine therapy with aromatase inhibitors on in vivo expression of this signaling cascade, and its relation to tumor response and patient outcome, is unknown.

EXPERIMENTAL DESIGN

PI3K, phospho-AKT (pAKT) and phospho-mTOR were assessed by immunohistochemistry on tumor specimens collected at baseline and after 6 months of treatment in 113 elderly breast cancer patients consecutively enrolled in a randomized phase II trial of primary letrozole therapy and letrozole associated with metronomic cyclophosphamide.

RESULTS

Basal expression of the pathway was not significantly correlated with response or patient outcome. Both letrozole alone and letrozole with cyclophosphamide resulted in a significant reduction of PI3K expression (P = 0.02 and P < 0.005, respectively) and phospho-mTOR expression (P = 0.0001 and P = 0.0001, respectively). pAKT showed no change in the letrozole arm, whereas it was significantly decreased in the letrozole plus cyclophosphamide arm (P < 0.005). pAKT expression reduction was associated with a greater response rate (P = 0.05) and greater reduction in Ki67 expression (P = 0.05). Phospho-mTOR expression reduction was associated with a significantly longer disease-free survival in a multivariate analysis (P = 0.02).

CONCLUSIONS

Letrozole inhibits key molecules in the PI3K pathway that are important targets of new drugs being developed to overcome resistance. Changes in these molecules may have prognostic significance. These results should be taken into account when planning prospective trials testing up-front aromatase inhibitor with drugs targeting the PI3K/AKT/mTOR signaling pathway.

Antitumor effects of doxorubicin followed by zoledronic acid in a mouse model of breast cancer

BACKGROUND

The potent antiresorptive drug zoledronic acid (Zol) enhances the antitumor effects of chemotherapy agents in vitro. We investigated the effects of clinically achievable doses of doxorubicin (Dox) and Zol, given alone, in sequence, and in combination, on the growth of established breast tumors in vivo.

METHODS

Female MF1 nude mice were inoculated subcutaneously with 5 x 10(5) human breast cancer MDA-MB-436 cells that stably expressed green fluorescent protein (ie, MDA-G8 cells). Beginning on day 7 after tumor cell injection, the mice were injected weekly for 6 weeks with saline, Dox (2 mg/kg body weight via intravenous injection), Zol (100 microg/kg body weight via intraperitoneal injection), Dox plus Zol, Zol followed 24 hours later by Dox, or Dox followed 24 hours later by Zol (n = 8-9 mice per group). The effects of treatment on tumor growth were determined by measuring tumor volume; on tumor cell apoptosis and proliferation by immunohistochemistry using antibodies for caspase-3 and Ki-67, respectively; and on bone by microcomputed tomography and bone histomorphometry. All P values are two-sided.

RESULTS

Treatment with Dox or Zol alone or Zol followed 24 hours later by Dox did not statistically significantly decrease final tumor volume compared with saline. Mice treated with Dox plus Zol had statistically significantly smaller final tumor volumes than those treated with Dox alone (mean = 122 mm(3) vs 328 mm(3), difference = 206 mm(3), 95% confidence interval [CI] = 78 to 335 mm(3), P < .001), with Zol alone (122 mm(3) vs 447 mm(3), difference = 325 mm(3), 95% CI = 197 to 454 mm(3), P < .001), or with Zol followed 24 hours later by Dox (122 mm(3) vs 418 mm(3), difference = 296 mm(3), 95% CI = 168 to 426 mm(3), P < .001). Treatment with Dox followed 24 hours later by Zol almost completely abolished tumor growth. Tumors from mice that were treated with Dox followed by Zol had more caspase-3-positive cells than tumors from mice treated with saline (mean number of caspase-3-positive cells per square millimeter: 605.0 vs 82.19, difference = 522.8, 95% CI = 488.2 to 557.4, P < .001), with Zol alone (605.0 vs 98.44, difference = 506.6, 95% CI = 472.0 to 541.2, P < .001), or with Zol followed by Dox (605.0 vs 103.1, difference = 501.9, 95% CI = 467.3 to 536.5, P < .001). The treatment-induced increase in the number of caspase-3-positive cells was mirrored by a decrease in the number of tumor cells positive for the proliferation marker Ki-67. No evidence of bone disease was detected in any of the treatment groups following microcomputed tomography and histological analysis of bone.

CONCLUSION

Sequential treatment with Dox followed by Zol elicited substantial antitumor effects in subcutaneous breast tumors in vivo, in the absence of bone disease.

Treatment of breast cancer in older women

BACKGROUND

Breast carcinoma management in the elderly often differs from the management in younger women and there is considerable controversy about what constitutes appropriate cancer care for older women. This controversy is reflected in the persistence of age-dependent variations in care over time, with older women being less likely to receive definitive care for breast cancer. There has been a significant increase in the last years in the number of studies conducted in older patients with breast cancer. Although available age-specific clinical trials data demonstrate that treatment efficacy is not modified by age, this evidence is limited by the lack of inclusion of substantial numbers of older women, particularly those of advanced age and those with comorbidities.

METHOD

The literature-based evidence of the last 10 years was extensively reviewed on the main issues concerning the treatment of breast cancer in older women.

RESULTS

Surgical treatment in older patients has evolved from avoidance to mastectomy to breast-conserving surgery, similarly to younger patients. Given its negative effect on the quality of life, in the last few years the role of adjuvant radiotherapy has been questioned in elderly patients with breast cancer. Adjuvant chemotherapy benefit in older patients applies mainly to Estrogen-receptor-negative patients, while in Estrogen-receptor-positive patients a major role is played by endocrine treatment. New "elderly-friendly" drugs, that can help clinicians to reduce toxicity, are now available for breast cancer.

Optimal sequence of hormonotherapy in advanced breast cancer

PURPOSE OF REVIEW

Several active, well tolerated hormonal agents have become available in recent years for the treatment of patients with advanced, hormone receptor-positive breast cancer. When used in an appropriate sequential strategy, hormonal therapies offer the opportunity of prolonging disease control and maintaining quality of life. The widening use of aromatase inhibitors in the adjuvant setting, however, means that traditional sequential cascades must be revised. The review describes the most relevant evidence that can contribute to the optimal positioning of each agent in the sequence.

RECENT FINDINGS

Most recent phase II and III trials of hormonal therapy in advanced breast cancer have examined the role of exemestane, letrozole, anastrozole, and fulvestrant in postmenopausal women.

SUMMARY

Partial non-cross resistance between nonsteroidal (letrozole and anastrozole) and steroidal (exemestane) aromatase inhibitors may allow treatment with exemestane after a nonsteroidal aromatase inhibitor and vice versa. The estrogen receptor downregulator fulvestrant is also an option after treatment with aromatase inhibitors. The role of the progestin megestrol acetate and, paradoxically, of tamoxifen in the sequential strategy for advanced breast cancer is less well studied.

Of mice and men: the many guises of estrogens

Models of estrogen insufficiency have revealed new and unexpected roles for estrogens in males as well as females. These models include natural mutations in the aromatase gene in humans, as well as mouse knock-outs of aromatase and the estrogen receptors, and one man with a mutation in the ERa gene. These mutations, both natural and experimental, have revealed that estrogen deficiency results in a spectrum of symptoms. These include loss of fertility and libido in both males and females; loss of bone in both males and females; a cardiovascular and cerebrovascular phenotype; development of a metabolic syndrome in both males and females, with truncal adiposity and male-specific hepatic steatosis. Most of these symptoms can be reversed or attenuated by estradiol therapy. Thus estrogen is involved in the maintenance of general physiological homeostasis in both sexes.

Multicenter phase II trial of neoadjuvant exemestane for postmenopausal patients with hormone receptor-positive, operable breast cancer: Saitama Breast Cancer Clinical Study Group (SBCCSG-03)

This multicenter phase II trial evaluated the efficacy and tolerability of 4 months of neoadjuvant exemestane in 44 postmenopausal patients with estrogen receptor (ER)-positive and/or progesterone receptor-positive, stage II to IIIB breast cancer measuring >or=3 cm. Pathological response was assessed by a central review board using response criteria proposed by the Japanese Breast Cancer Society. Clinical response [complete or partial response (PR)] was assessed by caliper, mammography, or ultrasound. Rates of breast-conserving surgery (BCS) and adverse events were also evaluated. A pathological response was observed in 13 (43%) of 30 patients who underwent surgery at 4 months. Fourteen patients were excluded from the pathological analysis: eight continued exemestane because of PR or stable disease (SD) at 4 months, three underwent chemotherapy because of progressive disease, and three underwent surgery within 2 months because of adverse events. A clinical response was seen in 27 (66%) of 41 evaluable patients. BCS was performed in 27 (90%) of 30 patients who underwent surgery at 4 months. Of the ten patients eligible for mastectomy at baseline, six chose to continue exemestane treatment without surgery because of a PR or SD at 4 months. Adverse events, most of which were grade 1, occurred in <or=10% of patients. These results suggest that neoadjuvant exemestane treatment is effective and well tolerated in postmenopausal women with ER-positive breast cancer. Further studies are required to determine the optimal duration of neoadjuvant treatment and to identify response criteria that can more accurately predict long-term outcomes.

Identifying menopause in breast cancer patients: considerations and implications

The pivotal role for oestrogen in the aetiology and progression of the majority of breast cancers is well established; consequently, endocrine therapy is an important approach in the treatment of this disease for many women. While tamoxifen has been the mainstay of endocrine therapy for breast cancer for over 30 years, we now have a range of therapeutic manipulations, in particular utilising the aromatase inhibitors (AIs) in post-menopausal women. To date each strategy employing an AI, including primary adjuvant monotherapy, switching from tamoxifen after 2-3 years, and extending adjuvant therapy with an AI after 5 years of tamoxifen, has shown superiority compared with tamoxifen alone; however, AI monotherapy is not suitable for pre- or peri-menopausal women, and therefore, an accurate assessment of the menopausal status of each individual patient is essential. Unfortunately, defining post-menopausal status can be fraught with difficulty, especially when cancer therapy is either recently completed (e.g. chemotherapy), or ongoing (e.g. tamoxifen and/or luteinising hormone-releasing hormone analogues). This paper shall review the definition of menopause in breast cancer patients and explore the issues and implications surrounding such a definition with respect to therapy choice for patient and physician alike.

Estrogen receptors evolution in neoadjuvant aromatase inhibitor (AI) therapy for breast cancer in elderly women: stability of hormonal receptor expression during treatment

In France, 20% of breast cancers occur in women over the age of 70 and 10% in women over the age of 80. As these women are not included in screening programs, breast cancer is often diagnosed later, at the stage of a large tumor.

PURPOSE

To analyze clinical response, possibilities of conservative treatment and course of hormonal receptors in patients receiving neoadjuvant aromatase inhibitor (AI) therapy for at least 6 months.

PATIENTS AND METHODS

There were 75 patients, with a mean age of 75 +/- 8 years (range, 58-91 years) received AI for 6 months after the diagnosis of invasive breast cancer with positive hormonal receptors. Clinical and radiologic tumor reduction, the number of conservative treatments and the course of estrogens receptor-labeled cells were determined for each patient.

RESULTS

All but 1 of these patients obtained clinical reduction of their tumor. Of these, 86% patients received conservative treatment. In the majority of patients, estrogen receptor (ER) level did not vary between the initial assay and analysis of the operative specimen.

DISCUSSION AND CONCLUSION

Aromatase inhibitors are effective as neoadjuvant therapy in ER positive elderly patients with large tumors, as is tamoxifen. Changes in hormone receptor expression during treatment do not predict clinical response. In our experience, neoadjuvant AI therapy should be administered for at least 6 months to optimize clinical response before deciding upon surgery. Discrepancy observed in the literature could be explained by the duration of the treatment.

Pre-menopausal breast cancer and aromatase inhibitors: Treating a new generation of women

Aromatase inhibitors have revolutionized the treatment of post-menopausal women with hormone receptor positive breast cancer. However, approximately 22% of all cases of breast cancer in North America are diagnosed in women below the age of 50 and a substantial proportion of these women are pre-menopausal. In the pre-menopausal population with hormone receptor positive disease, research on the use of aromatase inhibitors is only beginning to emerge. In this review, the mechanism of action of aromatase inhibitors and the history of endocrine treatment for pre-menopausal breast cancer is briefly presented. Available research to date regarding efficacy and toxicity of aromatase inhibitors in the treatment of pre-menopausal breast cancer and future research directions are also discussed.

Of mice and men: the evolving phenotype of aromatase deficiency

We are rapidly becoming aware of the importance of estrogen in maintaining virtually all facets of male health. In order for estrogens to be synthesized endogenously, the enzyme responsible for their synthesis from androgens, aromatase, must be functional. The seven known men in whom aromatase is nonfunctional all have a mutation in either exon V or IX of the CYP19 gene, which encodes aromatase. Collectively, these men are reported to have undetectable estrogen; normal to high levels of testosterone and gonadotropins; tall stature with delayed skeletal maturation and epiphyseal closure; osteoporosis; impaired lipid and insulin metabolism; and impaired reproductive function. The aromatase knockout mouse presents with a phenotype that is similar in many aspects and provides a valuable tool with which to examine and manipulate the actions of estrogen. By studying the naturally occurring aromatase-deficient humans, together with studies of the aromatase-knockout mouse, we are expanding our understanding of the essential role of estrogen in male physiology.