Concordance between renal tumour biopsy and robotic-assisted partial and radical nephrectomy histology: a 10-year experience

We aimed to assess concordance between renal tumour biopsy (RTB) and surgical pathology from robotic-assisted partial nephrectomy (RAPN) or robotic-assisted radical nephrectomy (RARN). Patients with preoperative RTB undergoing RAPN or RARN for suspected malignancy (9 September 2013-9 September 2023) were enrolled retrospectively from three sites. Patients were excluded if the tumour had prior cryotherapy or if biopsy or nephrectomy histology were unavailable or inconclusive. The primary outcome was concordance with the presence/absence of malignancy. Secondary outcomes were concordance with tumour subtype, World Health Organisation nuclear grade (patients with RTB clear cell or papillary RCC only), false-negative rate, false-positive rate, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). In the enrolment period, 332 and 132 patients underwent RAPN and RARN, respectively. Of these, 160 received preoperative RTB, with nine patients excluded, leaving 151 eligible patients. Median age was 63 years, and 49 (32%) were female. On surgical specimens, 144 patients had malignant histology. RTB was highly concordant with presence/absence of malignancy (147/151, 97%). Concordance with tumour subtype occurred in 141 patients (93%), while concordance with nuclear grade was seen in 42/66 patients (64%, RTB grade missing in 53 patients). False-negative rate, false-positive rate, sensitivity, specificity, PPV, and NPV were 2%, 14%, 98%, 86%, 99%, and 67%, respectively. Limitations include absence of complication data and exclusion of patients biopsied without surgery. In patients undergoing RAPN or RARN, preoperative RTB has high concordance with surgical pathology, both in the presence of malignancy and RCC subtype.

Comparative study between the use of double J ureteric stents vs bander ureteric stents during robotic-assisted radical cystectomy with intra corporeal ileal conduit urinary diversion

Robotic-assisted radical cystectomy (RARC) is fast becoming the standard of care with comparable oncological outcomes to open surgery for patients with muscle-invasive bladder cancer. Ileal conduit is by far the most popular means of urinary diversion following a cystectomy. Use of stents is common practice to reduce uretero-enteric anastomosis-related complications. In the current study, practice was changed from the use of Double J (DJ) stents to bander stent intraoperatively. The potential advantages of using bander stent are avoiding second surgery for stent removal and easier change under local anaesthetic in the interventional radiology department. To compare the incidence of blocked, slipped stents and rate of ureteroileal anastomotic stricture after RARC with intracorporeal ileal conduit between practices of using DJ stents and bander stents. Retrospective analysis of all the patients undergoing Robotic radical cystectomy and intracorporeal ileal conduit between June 2014 and August 2023 was done. Initially, all intracorporeal anastomosis were covered with DJ stents. The practice was changed to cover the anastomosis with bander stent in November 2020. Number of patients needing re-surgery for blocked, slipped stents and ureteroileal anastomotic stricture were analyzed and compared using Chi-square analysis and Fisher's exact test (P < 0.05). A total of 168 patients underwent RARC with intracorporeal ileal conduit between June 2014 and August 2023 of which 128 patents were diverted with DJ stents and 40 with bander stent. The mean age and the patient demographics between the two groups were comparable. Of the 128 patients who were diverted with DJ stents, 6 (4.7%) had blocked stents, 3 (2.3%) had slipped stents, and 3 (2.3%) developed ureteroileal stricture needing readmission and urgent invasive intervention to exchange the stent or nephrostomy tube, whereas only 1 (2.5%) of the 40 patients with bander stent had blocked stent which was changed under local anaesthetic in the interventional radiology suite with no slipped stents reported and 2 (5%) had ureteroileal stricture who needed nephrostomies. Intraoperative ureteric stenting using bander stent has the potential to reduce the incidence of stent-related complications, such as blockage, slippage, and ureteroileal anastomotic stricture, following RARC with intracorporeal ileal conduit urinary diversion. Additionally, managing bander stent-related complications is less invasive with lower rate of readmission postoperatively compared to managing DJ stent-related ones.

Predicted heart mass based on ideal body weight for donor-to-recipient size matching

BACKGROUND

Predicted heart mass (PHM) is a commonly used tool for donor-to-recipient size matching. However, incorporating body weight as part of PHM can be considered problematic given its high variability, and low metabolic nature of fat. We sought to assess whether substituting the actual donor and recipient weight with the ideal body weight (IBW) would affect the association of donor-to-recipient PHM ratio with 1-year and overall survival after heart transplantation.

METHODS

The United Network for Organ Sharing (UNOS) database was queried for adult patients who received a primary heart transplant between January 2000 and September 2021.

RESULTS

Both PHM and ideal PHM (IPHM) ratios were associated with one-year (PHM: p = .003; IPHM: p = .0007) and overall (PHM: p = .02; IPHM: p = .02) survival. In the continuous analysis with restricted cubic splines, both PHM (p = .0003) and IPHM (p = .00001) were associated with relative hazards of death.

CONCLUSION

IPHM is significantly associated with post-transplant survival and may be a useful compliment to PHM.

Insights and Recommendations From Two Urology-Based Educational Interventions: Development of a Urology Teaching Programme and Out-of-Hours Urology Handbook

Exposure and education in urology for medical students (MSs) and junior doctors (JDs) have long been overlooked, resulting in inadequate preparedness for the management of urological cases/patients. This study addresses this deficiency through the implementation of a Urology Teaching Programme (UTP) and the creation of an Out-of-Hours Urology Handbook (OOHUH). The UTP was delivered virtually, targeting senior MSs and JDs, and covered common urological presentations and management pathways from a JD's perspective. The OOHUH aimed to enhance the care provided by general surgery senior house officers (SHOs) at Lister Hospital (Stevenage, UK), offering guidance for nine common urological conditions in emergency and out-of-hours settings. Both initiatives demonstrated significant improvements in knowledge and confidence in urology. The findings underscore the importance of supplementary urology education and suggest strategies for bridging training gaps in medical curricula and clinical practice. Recommendations include tailored induction programs and simulation days for junior doctors, along with the widespread adoption of such educational interventions to enhance patient care and trainee preparedness in urology.

Heart Transplant Volume Associated with Lung Programs and Database Survival Ratings

BACKGROUND

Several factors affect heart (HTx) and lung (LTx) transplant program outcomes. Variability in institutional and community characteristics have been shown to influence survival. At present, currently, half of HTx centers in the United States do not possess a concomitant LTx program. This study sought to better understand the relationship of HTx with and without LTx programs.

METHODS

Nationwide transplant data were collected from the Scientific Registry of Transplant Recipients (SRTR) in August 2020. SRTR star rating ranges from tier 1 (lowest) to tier 5 (highest). HTx volumes and SRTR star ratings for survival were compared between the centers with heart-only (H0) programs and the centers with heart-lung (HL) programs.

RESULTS

SRTR star ratings were available for 117 Transplant centers with one or more HTx reported. The median number of HTx performed over one year was 16 (IQR: 2-29). Number of HL centers (n=67, 57.3%) were comparable to H0 centers (n=50, 42.7%) (p= 0.14). The HTx volume at HL centers [28 (IQR: 17-41)] exceeded HTx volume at H0 centers [13 (IQR: 9-23)], (p <0.01); but were comparable to the LTx volume at HL centers [31 (IQR: 16-46)] (p=0.25). Median HTx 1- year survival rating was 3 (IQR: 2-4) at both H0 and HL centers (p= 0.85). HTx volume and LTx volume were positively associated with respective one-year survival (p< 0.01).

CONCLUSION

While LTx program presence is not directly associated with HTx survival, it has positive association with HTx volume. HTx and LTx volumes are positively associated with one-year survival.

915 An Unusual Case of Breast Tuberculosis: A Case Report

Background

Breast Tuberculosis (TB) is a rare form of extra-pulmonary tuberculosis. It can mimic the presentation of many breast diseases including malignancy. We present a case of breast tuberculosis that had negative cultures from breast tissue while positive on lymph node biopsy.

Case presentation

A 36-year-old Libyan British lady presented to the symptomatic breast clinic with a large left breast mass during the first trimester of her fifth pregnancy. She has received antibiotics to treat mastitis but with no improvement. On Examination she had large left upper quadrant mass with skin tethering as well as palpable left axillary lymph nodes. Ultrasound imaging suggested features suspicious for malignancy and hence core biopsies were obtained which showed chronic inflammatory changes only. Ziehl Neelson stain was negative at this stage. A week later she developed low grade fever as well as signs of infection at biopsy site, this was treated with flucloxacillin, pus aspirated from underlying mass and sent for culture and sensitivity. Unfortunately, this lady travelled to Tunisia after her review and was subsequently diagnosed with breast tuberculosis on cultures from lymph node biopsies. On her return to our clinic, she was on appropriate treatment for TB, she had good response to treatment and follow up ultrasound showed stable residual collection.

Conclusions

This case illustrates the challenges in the diagnosis of breast tuberculosis as it is a rare entity of a disease that remains less prevalent in European countries. In most cases full recovery can be expected with anti- tuberculous treatment.

Artificial intelligence in urological oncology: An update and future applications

There continues to be rapid developments and research in the field of Artificial Intelligence (AI) in Urological Oncology worldwide. In this review we discuss the basics of AI, application of AI per tumour group (Renal, Prostate and Bladder Cancer) and application of AI in Robotic Urological Surgery. We also discuss future applications of AI being developed with the benefits to patients with Urological Oncology.

Review of the evidence for robotic-assisted robotic cystectomy and intra-corporeal urinary diversion in bladder cancer

Radical cystectomy, pelvic lymph node dissection and urinary diversion is the gold-standard treatment for muscle-invasive bladder cancer. The surgery is both complex and highly morbid. Robotic cystectomy is now in its 16^th year with established techniques and sufficient research maturity to enable comparison with its open counterpart. The present review focuses on the current evidence for robotic cystectomy and assesses various metrics including oncological, perioperative, functional, surgeon-specific and cost outcomes. The review also encapsulates the current evidence for intra-corporeal urinary diversion and its current status in the cystectomy arena.

A Retrospective Study of Immunotherapy Treatment with Uro-Vaxom (OM-89®) for Prophylaxis of Recurrent Urinary Tract Infections

OBJECTIVES

To present our experience with the long-term preventive effect of immunotherapy with Uro-Vaxom® on recurrent urinary tract infections (UTI) in adult patients.

MATERIALS AND METHODS

Retrospective analysis of 79 patients with recurrent UTI treated with Uro-Vaxom. Recurrent UTIs were defined as ≥ 2 infections in 6 months or ≥ 3 in 12 months. Patients received a 6 mg Uro-Vaxom capsule daily for 90 days followed by discontinuation for 3 months and then administration for the first 10 days of subsequent months 7, 8 and 9 as a 'booster' regime. The primary outcome measure was the number of UTIs encountered in the 12 months pre-treatment compared to 12 months post-treatment.

RESULTS

There was a significant decrease in the mean number of UTIs in the year following initiation of Uro-Vaxom® compared to the year preceding administration 3.14 versus 1.53 (p < 0.05) respectively.

CONCLUSION

Uro-Vaxom represents a safe and effective treatment option for prophylaxis of recurrent UTIs. In the UK, Uro-Vaxom is currently unlicensed. This study adds to a growing body of evidence in favor of non-antibiotic immune-prophylaxis for recurrent UTI.

The future of robotic surgery

How robotics could help shape the future of surgical care.

Unusual presentation of Henöch-Schonlein purpura

We present a rare case of a 4-year-old boy with newly diagnosed Henöch-Schonlein purpura (HSP) affecting the scrotum and penis. The patient presented to the emergency department with palpable purpura symmetrically distributed over the lower limbs. This was associated with arthritis of the right knee, abdominal pain and scrotal swelling. These symptoms were preceded by an upper respiratory tract infection (URTI). The patient was initially treated with empirical oral antibiotics for epididymitis and was discharged. He subsequently re-presented 12 days later with penile swelling, erythema and tenderness. An ultrasound scan of the penis revealed grossly oedematous subcutaneous tissue with normal penile architecture. His symptoms resolved spontaneously and the patient remains under close follow-up by the paediatric team for further sequelae of HSP.

Abstract P2-09-10: A new oral SERD AZD9496 for treatment of hormone dependent postmenopausal breast cancer

Treatment of hormone sensitive breast tumors with endocrine therapy such as antiestrogens or aromatase inhibitors has improved their clinical outcomes. However, not all tumors respond and the ones that do respond may eventually acquire resistance. One of the proposed mechanisms of resistance to endocrine therapy is overexpression of ERα and cross-talk of ERα with growth factor receptors. Studies including our own have shown that downregulation of ER with pure antiestrogen fulvestrant in combination with AIs may prolong responsiveness of the tumors to endocrine agents. Fulvestrant has been employed as either first or second line treatment for ER positive breast cancers alone or in combination with AIs. Studies have suggested that further escalation of dose may provide further benefit. However, dose escalation of fulvestrant which is administered via intramuscular injection is difficult due to its poor solubility. To overcome this shortcoming of an injectable drug, a novel orally active SERD (selective estrogen receptor downregulator), AZD9496 was developed. In addition to being orally active, AZD9496 is selective for mammary ERα. In the current study, we compared the effect of AZD9496 and fulvestrant on the growth of MCF-7Ca (human estrogen receptor positive MCF-7 cells stably transfected with human placental aromatase gene) xenografts grown in ovariectomized athymic nude mice. Tumors were allowed to form with androstenedione (aromatizable source of estrogen) supplement. When the tumors reached ~250 mm3, mice were grouped such that the mean tumor volumes were not significantly different (p&gt;0.99). Mice bearing xenografts of MCF-7Ca were then treated with fulvestrant (1 mg/d-sc) or AZD9496 (5 mg/kg/d-po), alone or in combination with anastrozole (200μg/d-sc) for 23 weeks. Tumors were measured weekly and growth rate was calculated. AZD9496 was significantly better at inhibiting the growth of tumors compared to control (p&lt;0.001) and anastrozole (p=0.04). AZD9496 was equally effective in inhibiting the growth of MCF-7Ca xenografts as fulvestrant (growth rate, p&gt;0.99 and tumor volume on week 23, p=0.99). In the second study, efficacy of AZD9496 was evaluated on against anastrozole resistant MCF-7Ca xenografts. Tumors were treated with anastrozole (200μg/d) for 13 weeks. During this time, the tumors initially regressed but eventually began to grow and had doubled in volume. At this time-point, they were regrouped to receive second line treatment. Single agent AZD9496 was marginally significant compared to continued anastrozole treatment (p=0.07). Nevertheless, second line treatment with AZD9496 was equally effective as fulvestrant (p=0.36). The combination of anastrozole with AZD9496/fulvestrant was more effective in reducing tumor growth compared to continued anastrozole treatment. Next, we measured the effect of AZD9496 on the mouse uterus. Uterine weight of mice treated with AZD9496 was not significantly different from mice that were treated with androstenedione (p=0.99). These results suggest that AZD9496 was selective for tumor ERα and had no effect on the uterine ERα. These results suggest that AZD9496 may be a better alternative to fulvestrant due to its selectivity for mammary ER and same efficacy as fulvestrant obtained upon oral administration.

Citation Format: Sabnis GJ, Kazi A, Schech A, Yu S, Golubeva O, Weir H, Brodie A. A new oral SERD AZD9496 for treatment of hormone dependent postmenopausal breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-09-10.

Unusual case of respiratory embarrassment secondary to tracheal compression by a dilated oesophagus in a patient with recurrent achalasia

We present the case of a 79-year-old woman with recurrent achalasia following a laparoscopic Heller's cardiomyotomy. The patient presented to the emergency department, with epigastric pain, severe dyspnoea and profound respiratory acidosis. She required intubation and ventilation followed by gastric decompression with nasogastric tube and the administration of intravenous antibiotics for a lower respiratory tract infection. Once stable, she underwent a CT scan revealing a massively dilated oesophagus causing marked tracheal compression. She received a period of continuous positive airway pressure ventilation while on the intensive care unit, for persistent low saturations, however, this was promptly ceased due to exacerbation of gastric dilation and fears over perforation. The patient responded well to conservative measures and was discharged home 18 days later awaiting follow-up with operating consultant surgeon.

Nephroureterectomy for emphysematous pyelonephritis: An aggressive approach is sometimes necessary. A case report and literature review

•

Emphysematous pyelonephritis (EPN) is a life threatening necrotising infection of the renal/perirenal tissue mainly seen in poorly controlled diabetic patients. Urological intervention is required to relieve obstructive uropathy.

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CT has 100% sensitivity and should be the imaging modality of choice for diagnosis, classification and prognostic scoring.

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Percutaneous catheter drainage and medical management have improved survival rates. Overall mortality has dropped from 50% to 18%.

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Septic shock, rising creatinine, thrombocytopaenia, Wan’s type 1 EPN, disturbance of consciousness and bilateral EPN are indicators of poor prognosis.

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Emergency nephrectomy should be reserved for severe EPN.

Introduction

Emphysematous pyelonephritis (EPN) is a life-threatening urological emergency. A high index of suspicion is required for diagnosis as such patients may present to physicians with typical features of pyelonephritis.

Presentation of case

A 67 year old lady presented atypically to the Emergency Department with symptoms of renal colic. The diagnosis of emphysematous pyelonephritis was established on prompt CT scanning. She did not respond to conservative management. Due to acute, critical deterioration, she underwent a radical right nephroureterectomy. The resected kidney involved a long segment of necrotic, gangrenous ureter. The patient had a smooth post-operative recovery and was successfully discharged. She remains well on follow-up after one year.

Discussion

Early radiological diagnosis is imperative for risk stratification of EPN. Current evidence recommends percutaneous catheter drainage with interval nephrectomy as the gold standard treatment. We review the literature for pathophysiology and clinical prognostic factors. This case adds onto the limited evidence base on ureteric involvement in EPN, suggesting a revision of EPN classification.

Conclusion

Further research on ureteric involvement and treatment outcomes in EPN is required. Even in the current era of minimally invasive surgery and renal preservation therapies, early open nephrectomy still has a role in the management of EPN.

The relationship between ambient ultraviolet radiation (UVR) and objectively measured personal UVR exposure dose is modified by season and latitude

Despite the widespread use of ambient ultraviolet radiation (UVR) as a proxy measure of personal exposure to UVR, the relationship between the two is not well-defined.

Abstract OT3-2-11: A phase II study of letrozole and lapatinib followed by an addition of everolimus in postmenopausal women with advanced endocrine resistant breast cancer (BC)

Background: Several preclinical studies demonstrated that crosstalk between growth factor receptor pathways, particularly HER2, and ER signaling confers resistance to endocrine therapy (ET). There are emerging data showing the involvement of immune system and miRNA with endocrine resistance. EGF30008 trial showed a benefit of lapatinib in combination with letrozole, mainly in HER2-positive (HER+) metastatic BC (MBC) while a subset analysis of this trial showed that HER2-negative (HER2-) patients (pts) with acquired endocrine resistance may also benefit from this combination. Our preclinical study suggests that everolimus is synergistic with letrozole and lapatinib.

Trial Design: This is a single arm phase II study for postmenopausal women with hormone receptor-positive MBC progressing after aromatase inhibitor, tamoxifen, or fulvestrant. The total target accrual is 76 pts (38 HER2+ pts and 38 HER- pts). In the first phase of the study, pts will be treated with letrozole and lapatinib (1,500 mg daily). Upon disease progression, pts will enter the second phase where everolimus (5 mg daily) will be added to letrozole and the dose of lapatinib will be reduced to 1,250 mg daily. For correlative studies, peripheral blood samples will be serially collected to evaluate for serum HER2 extracellular domain (ECD), circulating miRNAs, PC cell-derived growth factor (GP88), immune regulatory cells including myeloid-derived suppressor cells, NK cells, and Treg cells. These parameters will be correlated with tumor response. In pts with accessible tumors, optional serial biopsies will be performed at baseline and upon progression in each phase of the study. The tumor tissue will be tested for total HER1, HER2, and HER2 expressions as well as HER2:HER2 homodimers, HER2:HER3 heterodimers, HER1:HER2 heterodimers, p95, and HER3/PI3K (p85 subunit) using VeraTag assay.

Statistical Method: The primary objective is to evaluate the clinical benefit rate (CBR: CR, PR, SD &gt; 24 weeks) of the combination of letrozole and lapatinib as well as the combination of everolimus, letrozole, and lapatinib. This is a three-stage design which is an extension of the Simon's two-stage design. The sample size is based on the assumption that a CBR below 10% (null hypothesis) would indicate ineffective therapy and the statistical power is set at a higher CBR of 30% which we consider is plausible. Therefore, if 0 of the first 10 pts in each cohort have clinical benefit, the study will be closed; otherwise additional 8 pts will be enrolled. If ≤ 1 of the total 18 pts has clinical benefit, the study will be closed; otherwise an additional 9 pts will be enrolled. If ≤ 5 pts have clinical benefit the therapy is considered not promising; and if ≥ 6 pts of the total of 27 have clinical benefit, the therapy is considered worth pursuing. This design has ∼90% probability to accept the therapy for further trials if the true CBR is indeed at least 30% and 10% probability to accept it if the true clinical benefit is indeed below 10%.

To date, there are a total of 6 pts enrolled. Accrual is currently ongoing. Please contact ntait@umm.edu for further information.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-2-11.

Abstract PD5-2: Preclinical assessment of HDAC inhibitor entinostat combined with all trans retinoic acid (ATRA) in aromatase inhibitor resistant breast cancer

Treatment with aromatase inhibitors (AI’s) is highly effective against breast cancer in ER positive postmenopausal women. However, some patients eventually become resistant to AIs. Tumor initiating cells (TIC’s) represent a subpopulation of tumor cells, which show self-renewal capacity. We are focused towards discovering strategies to reduce the growth of breast cancer TICs, which may result in resistance. We have developed a xenograft model that mimics post-menopausal hormone responsive breast cancer. In this model, aromatase transfected human hormone sensitive MCF-7 cells (MCF-7Ca) are inoculated in ovariectomized athymic nude mice and allowed to grow in presence of D4A (aromatizable substrate of estrogen). Results obtained using this model have been confirmed by numerous clinical trials. Using this model, we have established that single agent AI is better than tamoxifen in controlling tumor growth. We also observed that although, AI letrozole provides a longer control over tumor growth, tumors eventually began to grow. In the current study, we investigated the effect of ATRA (All-trans Retinoic acid) (125μg/day, ip) and a histone deacetylase (HDAC) inhibitor entinostat (SNDX- 275) (50μg/day, po) with or without letrozole on letrozole resistant tumors in a xenograft model system. Ovariectomized athymic nude mice bearing xenografts of MCF-7Ca cells, were treated with letrozole till they became resistant (15 weeks). At this time, the mice were grouped to receive ATRA, entinostat plus ATRA or the combination of ATRA plus entinostat plus letrozole till week 23. The mice treated with entinostat plus ATRA letrozole showed a significant decrease in tumor growth rate compared to mice treated with single agents or entinostat plus ATRA (p&lt;0.0001, p = 0.02). On week 20 weeks, 2 mice from each treatment group were euthanized and tumors were harvested. The tumors were digested enzymatically with collagenase and hyaluronidase and freed of debris using centrifugation and filtration. Mammosphere forming ability of TICs in the tumor tissue was measured by seeding 10,000 viable cells from each treated tumors under non-adherent conditions to access the self-renewal capacity. Quantitative PCR analysis of tumors cells showed a significant downregulation of the known TIC molecular markers, BCRP, ALDH, BMI-1 and Nanog compared to letrozole treated tumors. Similar results were also obtained when LTLT-Ca (long term letrozole treated MCF-7Ca) cells treated with ATRA and entinostat in combination with letrozole and then seeded in non-adherent conditions. The combination of ATRA plus ENT plus letrozole significantly (p&lt;0.01) reduced number of mammospheres formed compared to single agents alone. We have shown previously, that LTLT-Ca cells have higher percentage of side population (cells expressing higher level of efflux pumps such as BCRP) compared to MCF-7Ca cells. The treatment of LTLT-Ca cells with the combination of ENT and ATRA with letrozole drastically reduced the percentage of side population. Overall, these studies indicate that the combination of ATRA, entinostat and letrozole is effective in reducing tumor recurrence in letrozole resistant tumors.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD5-2.

Abstract P1-07-01: Histone deacetylase inhibitor entinostat reverses epithelial to mesenchymal transition of breast cancer cells by reversing the repression of E-cadherin

Loss of ERa in breast cancer correlates with poor prognosis, increased recurrence rates and higher incidence of metastasis. In our previous studies, we have shown that histone deacetylase (HDAC) inhibitor entinostat (ENT) can upregulate ERα and aromatase in ER-negative cells and tumors, making them sensitive to aromatase inhibitors (AIs). In the current study, we are showing that ENT can also reverse epithelial to mesenchymal transition (EMT), which is considered to be a first step in the process of metastases formation. EMT is characterized by loss of intracellular adhesion (loss of E-cadherin); loss of epithelial markers such as cytokeratins and upregulation of mesenchymal markers such as vimentin; acquisition of fibroblast-like spindle morphology and increased motility. Various carcinomas undergo varying degrees of EMT and capacity to undergo EMT correlates inversely with levels of E-Cadherin. It is widely accepted that loss of E-cadherin is associated with more invasive phenotype. Epigenetic silencing of E-cadherin has been implicated in metastatic cell lines and invasive breast cancers.

Triple negative breast cancer cells such as MDA-MB-231 and Hs578T show a basal phenotype characterized by loss of E-cadherin expression and higher expression of mesenchymal markers such as N-cadherin, vimentin along with transcriptional repressors such as twist and snail.

In this study, we measured the effect of entinostat on the EMT. When MDA-MB-231 and Hs578T cells were treated with ENT, E-cadherin transcription was increased along with reduction in N-cadherin mRNA expression. Similar results were also seen in tumors of MDA-MB-231 and Hs578T xenografts treated with ENT (for 5 weeks and 2 weeks respectively). A dose dependent increase in E-cadherin was seen along with a dose dependent decrease in N-cadherin mRNA. Although, we did not observe any reduction in vimentin protein, phosphorylation of vimentin was increased and vimentin remodeling was changed as seen by immunofluorescence. We performed chromatin immunoprecipitation (ChIP) assay to measure the activation of E-cadherin promoter. Treatment of MDA-MB-231 and Hs578T cells increased the activation of E-cadherin promoter as seen by increased acetyl histones at the promoter region of E-cadherin. Twist and snail are known repressors of E-cadherin gene and we saw that ENT treatment reduced the association of twist and snail with the E-cadherin promoter. ENT was also able to downregulate twist, which may be responsible for reduced twist association with the E-cadherin promoter.

In summary, these findings suggest that HDAC inhibitor ENT can reverse EMT and may help reduce the formation of metastasis.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-07-01.

PD01-06: Endoxifen Exhibits Potent Anti-Tumor Activity and Regulates Different Genes Than Tamoxifen in an Aromatase Expressing MCF7 Model Resistant to Letrozole

Background: First in human studies of Z-endoxifen hydrochloride (E), the active metabolite of tamoxifen (T), are underway in metastatic breast cancer (BC). Previous data have demonstrated the superiority of aromatase inhibitors (AI's) over T in estrogen receptor (ER) + BC. Using an in vivo aromatase expressing model (MCF7/AC1), we compared the antitumor activity of E with T and Letrozole (L), as well as the antitumor activity and global gene expression changes of E with T in an L-resistant model.

Methods: MCF7/AC1 tumors were stimulated with androstenedione. Once tumor size reached 300 mm3, mice (30/group) were randomly assigned to one of five treatment groups: control (daily, po), T (500 μg/day, sc), endoxifen 25 mg/kg/day p.o.(LDE) endoxifen 75 mg/kg/day p.o. (HDE) or letrozole, 10 μg/day s.c for 4 weeks. Tumors were harvested from control, T, and E groups while the L group continued treatment until the development of resistance defined as an increase in tumor volume of at least 300% from day 1. Mice with L-resistant tumors were randomly assigned to T (n=4) or E (n=5) for 4 weeks and then sacrificed. Gene expression in L-resistant tumors was quantified using Affymetrix U133+2 and changes in gene expression profiles [comparing T and E with L-resistant (n=3)] were analyzed. Genes identified as significantly different were confirmed by real-time RT-PCR assays.

Results: At the 4 week time point, both doses of E and L resulted in greater anti-tumor activity than control (Wilcoxon rank sum test: all p &lt; 0.0001); however, tumor burden did not differ between T and control (p=0.095). HDE resulted in significantly less tumor burden than T (p=0.002) but was similar to L. In mice that continued on L, resistance developed at 24 weeks in 9/25 mice. These mice were randomly assigned to either T (n=4) or E (n=5) for 4 weeks. Tumor volume (expressed as a% of its size prior to randomization) was significantly different comparing E (73.3%; range: 69.3 to 80.75%) versus T (148.39%; range: 114.07 to 165.99%) (Wilcoxon rank sum test p=0.016). Compared to control, microarray studies identified 1518 unique probe sets regulated by E (p&lt;0.001) compared to 441 for T including estrogen-regulated genes such as progesterone receptor (PGR) and amphiregulin (AREG) that were significantly down-regulated in the E group [PGR (−6.2 fold, p=0.000008) and AREG (−3.2 fold, p=.0006) but unchanged or up-regulated in the T group (PGR unchanged and AREG +9.2 fold p=0.00002). These findings were confirmed by RT-PCR.

Conclusions: Using the MCF7/AC1 model previously used to show the superiority of AI's over T, HDE demonstrated similar antitumor activity to L and was superior to T. In cells resistant to L, E was superior to T and gene expression changes demonstrate that E down-regulates while T activates estrogen regulated genes. These findings support the ongoing development of E for the treatment of ER+ BC.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD01-06.

Abstract PD01-05: A Combination of HDAC Inhibitor Entinostat (MS-275), All Trans Retinoic Acid (ATRA) and Chemotherapy Drug(s) Causes Regression of Established Xenografts of Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is a subgroup of breast cancer that rapidly develops resistance to chemotherapy. Currently, TNBC patients are treated with anthracycline and taxane-based regimens. These treatments result in some improvements in the clinical outcomes; however, they are associated with poor prognosis. Also, endocrine therapies are ineffective since the tumors do not express the estrogen receptor. Recent studies have shown that histone deacetylase (HDAC) inhibitors could reverse the epigenetic profile of some genes, including ER, EGFR, and RAR≥2. We have recently shown that treatments that combine the HDAC inhibitor, Entinostat (MS-275), with the aromatase inhibitor, Letrozole, result in regression of xenografts of MDA-MB-231 breast cancer cells. Since RAR≥2 is re-expressed as well, we reasoned that combining epigenetic therapy using MS-275, with differentiation therapy using a RAR≥2 agonist (ATRA) will provide an effective combination of drugs against TNBC. We also examined possible potentiation of anticancer activity of these agents by low nontoxic doses of chemotherapy (doxorubicin and paclitaxel). In vitro, human TNBC cell lines, MDA-MB-231, HCC 1143, SUM159, SUM149 and BT20 responded significantly better to the triple combination compared to the drugs used singly or in combination with MS-275. Upon treatment, re-expression of the silenced RAR≥2 and downstream effectors was observed in the cell lines in vitro and in tumor xenografts of MDA-MB-231 cells. Subcutaneous tumor growth in immunodeficient mice was strongly inhibited (10/14 significant regression) using a combination of MS-275, ATRA and low dose Doxorubicin, compared to the drugs administered singly or in combination with MS-275. No significant weight loss was observed in any of the groups. This combination was then used to treat tumor xenografts of SUM159, another TNBC cell line, and gave a promising result. Furthermore, combination of MS-275, ATRA, and a clinical dose of Paclitaxel can effectively inhibit growth of MDA-MB-231 and SUM159 cells. These results suggest that combination of HDAC inhibitor and RAR≥2 agonist with low dose chemotherapy has the potential to be an effective treatment against TNBC. This study provides encouraging new information for a nontoxic, and novel combination of drugs which could be effective against TNBC.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD01-05.

Abstract P4-03-05: The Warburg Effect and RUNX2-Regulated Metabolic Switching in Breast Cancer: A New Therapeutic Target?

Breast cancer (BC) is the leading cause of cancer deaths among women in North America and Western Europe. Numerous studies have shown that breast tumor progression is associated with a switch from mitochondrial oxidative phosphorylation (OxPhos) to increased utilization of glucose and aerobic glycolysis (Warburg effect). Uncovering underlying mechanisms regulating this progression may lead to innovative approaches for treatment. The RUNX2 DNA-binding transcription factor is expressed in highly aggressive BC and regulates bone metastasis in animal models. We observed increased expression of RUNX2 in primary human ductal carcinoma in situ (DCIS), which correlated with grade and proliferative index (Ki67 staining), decreased estrogen receptor/progesterone receptor expression (ER/PR status), increased glucose uptake values by PET scanning, and increased expression of the glucose transporter, GLUT1. Further, more than 80% (9 out of 11) of triple-negative BC cell lines examined expressed RUNX2. Therefore, to test the hypothesis that RUNX2 may alter the metabolic status of breast cancers and increase their dependence on glycolysis during tumor progression, we have generated a Tet-OFF model system using MCF7 cells with inducible RUNX2 expression. RUNX2-positive MCF7 cells exhibited increased cell death under conditions of glucose depletion or when treated with 2-deoxy-glucose, a competitive inhibitor of hexokinase II. Conversely, RUNX2-positive cells were more resistant to OxPhos inhibitors (rotenone, oligomycin) than RUNX2-negative cells. We also observed higher expression levels of GLUT1 and pAKT in RUNX2-positive MCF7 cells. Hypoxia-inducible factor-α (HIF1α) is a transcription factor that regulates cancer metabolism through its activation of glycolytic genes, while SIRT6, an NAD-dependent deacetylase, is a negative regulator of HIF1α activity. This occurs, in part, via inhibition of HIF1α transcriptional activity. RUNX2-positive or negative cells expressed HIF1α in response to glucose but RUNX2-positive cells exhibited lower SIRT6 expression than RUNX2-negative cells, suggesting that with the loss of SIRT6, HIF1α might be more active in promoting glycolysis in the presence of RUNX2. These results suggest that RUNX2 may have clinical diagnostic value as an indicator of BC metabolic stress and predictor of poor prognosis. Current strategies are utilizing computer-assisted drug design to develop RUNX-specific inhibitors to target BC glycolysis and tumor growth.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-03-05.

Intrauterine growth retardation associated with precocious puberty and sertoli cell hyperplasia

The original description of patients with Russell-Silver syndrome included precocious puberty, the mechanism of which was unclear. We describe a child with a Russell-Silver syndrome-like phenotype who presented with precocious puberty that was associated with hyperplasia of the Sertoli cells. The patient was found to have an immature cryptorchid testicle; hyperplastic Sertoli cells were also aneuploid carrying trisomy 8. This chromosomal abnormality was present in Sertoli cells only and could not be detected in peripheral lymphocytes, tunica vaginalis, or other, normal, testicular tissue. Sertoli cells in culture showed excess aromatization providing an explanation for the rapid advancement of the patient's bone age. We conclude that in a patient with a Russell-Silver syndrome-like phenotype, Sertoli cell hyperplasia was associated with somatic trisomy 8, increased aromatization, and gonadotropin-independent precocious puberty.

The Growth Factor GP88 (Progranulin) Confers Aromatase Inhibitor Resistance to Breast Cancer Cells

The development of aromatase inhibitors has provided novel therapeutic strategies for post-menopausal patients with estrogen receptor positive (ER+) breast tumors. Aromatase inhibitors, such as letrozole, inhibit ER+ breast cancer cell growth by blocking the synthesis of estrogen by the enzyme aromatase in the tumor stroma. However, ER+ breast cancer cases can sometimes fail or cease to benefit from such therapy. Several mechanisms have been proposed for aromatase inhibitor resistance. Here, we investigate the role of the 88 kDa autocrine growth factor PC-Cell Derived Growth Factor, also known as GP88 or progranulin on the acquisition of aromatase inhibitors resistance by ER+ breast cancer cells. GP88 is the largest member of the epithelin-granulin family characterized by a unique cysteine rich motif. GP88 has been shown to play a role in breast tumorigenesis. GP88 expression increased in breast cancer cells in a positive correlation with tumorigenesis whereas inhibition of GP88 expression lead to a 98% reduction in tumor incidence and growth rate in vivo. Pathological studies of paraffin embedded breast cancer biopsies have shown that GP88 is expressed in infiltrating ductal carcinoma (IDC) in correlation with expression of parameters of poor prognosis but was independent from Her-2 expression. Most importantly, increased GP88 expression in ER+ IDC was associated with increased recurrence and decreased overall survival. The present study investigated the effect of GP88 on the proliferation and letrozole responsiveness of ER+ breast cancer cells that express high aromatase activity (MCF-7 CA and MCF-7 AC1 cells). For both cell types, GP88 added exogenously conferred letrozole resistance in a time and dose-dependent fashion. GP88 also stimulated survival and soft agar colony formation of MCF-7-CA and AC1 cells in the presence of letrozole. GP88 overexpressing cells displayed higher basal levels of phosphorylated ERK1/2 and AKT, both known to be activated in GP88 mitogenic signaling pathways. In addition, naturally letrozole resistant breast tumors displayed a 10-fold increase in GP88 expression when compared to letrozole sensitive cells. Treatment of these letrozole resistant cells with GP88 SiRNA lead to a dose dependent inhibition of proliferation and restoration of letrozole sensitivity indicating that GP88 is regulating the ability of the cells to respond to letrozole.These data show the importance of GP88 as a target for the development of diagnostic and therapeutic products for aromatase inhibitor resistant breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4171.

Synthesis and Characterization of Her-2 Targetable N-(2-Hydroxypropyl)methacrylamide Copolymer Conjugates

Background: Current Her-2 overexpressing cancer therapies are limited by rapid drug resistance development from Trastuzumab (TRZ) treatment or low selectivity and non specific side effects of hepatotoxicity with small molecular tyrosine kinase inhibitors such as lapatinib. N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-drug conjugates with tailored side-chain composition have demonstrated their clinical potential as tumor targetable chemotherapeutic delivery systems. The present study evaluates the potential of novel HPMA copolymer-TRZ conjugates to enhance the therapeutic index of Her-2 targeted therapy.Material and Methods: HPMA copolymer-TRZ conjugates were synthesized in two steps. In the first step, an HPMA copolymer precursor containing reactive p-nitrophenyl ester (ONp) side chains was synthesized by free radical precipitation polymerization. In the second step a series of polymer precursors were conjugated to varying amounts of TRZ by aminolysis. The feed ratio of TRZ to HPMA copolymer was calculated based on the number of primary amine groups available on TRZ surface as determined spectrophotometrically using the 2,3,6-Tri-nitrobenzenesulfonic acid (TNBS) assay. The copolymer conjugates were characterized by correlating the feed ratio with the degree of conjugation (TNBS assay) and molecular weight distribution (size exclusion chromatography). The antiproliferative action of HPMA copolymer-TRZ conjugates was evaluated on a Her-2 overexpressing BT474 breast cancer cell line. Cell proliferation was quantified by MTT assay. Activation of Her-2 after treatment with polymer conjugate was measured by western immunoblotting.Results and Discussion: A series of three HPMA copolymer-TRZ conjugates were successfully synthesized and characterized. It was observed that an increase in the feed ratio of HPMA copolymer precursor to TRZ resulted in a corresponding increase in the degree of TRZ conjugation. The size exclusion chromatography profile of the conjugates was also consistent with the degree of conjugation. As HPMA copolymer precursor contents increased, the elution time decreased suggesting an increase in the hydrodynamic volume of conjugates. The growth inhibition effects of all HPMA copolymer-TRZ conjugates were concentration dependant. The half maximal inhibitory concentrations (IC50) of the conjugates with TRZ/HPMA=1/1, 2/1 and 4/1 were 10, 29, and 20 nM respectively, which were comparable to that of free TRZ (8 nM) suggesting that the antibody retained bioactivity against Her-2 overexpressing cancer cells upon conjugation to the polymer. Western immunoblotting showed that polymer conjugated TRZ effectively downregulated activated Her-2 (phospho-Her2) to a greater extent than free TRZ.Conclusion: Here we report for the first time, the successful synthesis, characterization and in vitro evaluation of HPMA copolymer-anti-Her-2 drug (TRZ) conjugates for active targeting to Her-2 overexpressing breast cancer cells. The conjugate compositions were consistent with their molar feed ratios and inhibited model cancer cell growth comparable to the free drug. Preliminary studies indicate improved efficacy of TRZ against Her-2 positive breast cancer cells when administered as polymeric conjugate.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5065.

Complete IGF Signaling Blockade by the Dual-Kinase Inhibitor, BMS-754807, Is Sufficient To Overcome Tamoxifen and Letrozole Resistance In Vitro and In Vivo

Resistance to hormonal therapy is a clinically unmet need in breast cancer. IGF signaling has been identified as a major mechanism of resistance to hormonal therapy in breast cancer. As components of the IGF signaling pathway are expressed in most breast cancers, the development of IGF-1R monoclonal antibody (mAb) and tyrosine kinase inhibitors (TKI) are active areas of clinical investigations. A key distinction between the mAb and TKIs are their differences in their ability to inhibit the Insulin Receptor (InsR). While targeting the InsR with TKIs may have a theoretical liability of hyperglycemia, targeting only the IGF-1R may have the theoretical liability of incompletely blocking IGF signaling. As InsR isoform A expression, which can transduce IGF-II-mediated proliferation, is higher in breast cancers compared to normal breast tissue, we investigated whether IGF-1R or IGF-1R/InsR inhibition was sufficient for overcoming resistance to hormonal therapy. To determine the optimal combination strategies for clinical investigations, we tested the hypothesis that IGF signaling inhibition could overcome primary (or de novo/intrinsic) and secondary (or acquired/selected) resistance to hormonal therapy. For these studies, we used either hormone therapy-naïve or hormone therapy-resistant variants of the breast cancer model, MCF-7/AC-1, which has been engineered to stably express full-length human aromatase. We employed and compared a novel, potent dual kinase inhibitor of the IGF-1R and InsR, BMS-754807, which is currently in early clinical investigations, with the IGF-1R antibody mAb391. BMS-754807 has been shown to induce apoptosis more potently than mAb391 in Rh41 human rhabdomyosarcoma cells. In vitro, BMS-754807 demonstrated profound synergy in combination with tamoxifen and letrozole (median effect combination index &lt;0.1). In vivo, BMS-754807 enhanced the anti-tumor activity of tamoxifen and letrozole in hormone-naïve tumors and induced regression of tumors resistant to tamoxifen or letrozole when combined with letrozole. This activity was not observed with mAb therapy, which resulted in greater up-regulation of InsR-A and erbB receptor expression and activation. This suggested a greater susceptibility to resistance pathways with mAb therapy. Dual IGF-1R/InsR blockade alone or in combination was tolerated by the animals and has no significant change in glucose homeostasis. Gene expression profiling experiments to compare the difference between the effects of tamoxifen in combination with BMS-754807 and with mAb revealed alternative pathway signaling is one of the potential mechanisms of resistance.In summary, combined hormonal therapy with BMS-754807 overcomes primary and secondary resistance to tamoxifen and letrozole and was well tolerated. IGF-1R blockade with a mAb alone is insufficient to overcome resistance and induces InsR over-expression. Thus, IGF signaling through either InsR or IGF-1R may be a major mechanism of resistance to hormonal therapy. These data suggest that blockade of IGF-1 and IGF-II from activation of IGF-1R and InsR, with agents such as BMS-754807 have promise in extending the benefits of hormonal therapy in breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 402.

Expression of ERα and Aromatase in MDA-MB-231 Tumors by HDAC Inhibitor Entinostat Leads to Growth Inhibition by Aromatase Inhibitor Letrozole

The treatment for hormone receptor-positive breast cancer has improved significantly since the development of aromatase inhibitors (AIs). Nevertheless, AIs are ineffective in estrogen receptor-negative (ER-) tumors, which comprise of approximately 25% of breast cancers and tend to be more aggressive. Studies have shown that repression of ER in these hormone receptor-negative tumors may be due to epigenetic modifications. The discovery of recruitment of histone deacetylase enzymes in gene silencing provides a rationale for inhibition of HDAC activity to release transcriptional repression as a potential therapeutic strategy. The objective of the present study was to express ERα and aromatase with HDACI treatment and thereby sensitize tumors to growth inhibition with aromatase inhibitors. In this study we used ER negative, hormone refractory MDA-MB-231 human breast cancer cells. Treatment with HDAC inhibitor entinostat led to upregulation of ERα, aromatase and its activity in a dose dependent manner in cells and xenografts. MDA-MB-231 xenografts were grown in ovariectomized female nude mice. Mice were inoculated with 2.5 X 106 cells per site subcutaneously. When the tumors reached 150 mm3, the mice were grouped into 4 groups (n=10), so that the mean tumor volume was not statistically different across groups (p=0.88). Tumor volumes were measured twice weekly. The mice in the letrozole group had a mean tumor growth rate (β = 0.023 ± 0.014) that was not statistically different (p=0.76) from that of the control group (β = 0.038 ± 0.007). Also, the growth rate of entinostat group (β = 0.034 ± 0.011) was not significantly lower than that of the control (p=0.33). However, the growth rate of entinostat plus letrozole group ((β = -0.003 ± 0.013) was significantly lower than that of the control (p=0.01), entinostat (p=0.03) and letrozole (p=0.049) groups. The combined treatment of entinostat plus letrozole was significantly more effective than either agent alone. In addition, the ability of this combination to inhibit migration in vitro was examined by wound healing assay. The combination of entinostat plus letrozole provides superior inhibition of migration (p&lt;0.001) compared to control, entinostat and letrozole alone. To test the efficacy of this combination in preventing the outgrowth of tumor foci in the lung, mice received an inoculation of 3 X 106 cells intravenously via the tail vein. They were treated three weeks later with entinostat alone, letrozole alone, or the combination. Mice were treated for six weeks, and then euthanized. Treatment with entinostat alone or letrozole was not significantly effective, but the combination resulted in a significantly reduced number of both visible and micrometastases (p=0.03) compared to no treatment (control) and the entinostat alone group. Thus, up-regulation of ERα and aromatase resulted in sensitization of tumors to significant inhibition of growth, cell migration and formation of micro-metastases by the aromatase inhibitor letrozole.Our results provide the basis for possible use of AIs in combination with HDAC inhibitors for the treatment of hormone refractory ERα negative breast cancer. This could open a new avenue for the management of ER- breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 401.

Epidermal growth factor variations in amniotic membrane used for ex vivo tissue constructs

INTRODUCTION

The amniotic membrane (AM) is used for engineering ex vivo tissue constructs used in ocular surface reconstruction. Epidermal growth factor (EGF) content of the AM is believed to play a key role in supporting corneal epithelial cell expansion on AM. This study investigated EGF content in AM in relation to intra- and inter-donor variations and the effect of processing and preservation (handling).

METHODS

Fifteen human AM, both fresh and handled, were analyzed for EGF gene and protein expression by real-time polymerase chain reaction and ELISA, respectively.

RESULTS

EGF gene expression was predominantly seen in the AM epithelium (p<0.01). Similarly, EGF protein too was predominantly seen in the epithelial layer (p<0.01) for fresh and handled samples. EGF protein content varied between membranes (inter-donor) and at different sites within the same membrane (intra-donor). The highest EGF protein concentration was noted in the AM apical and mid-region epithelium. Significant EGF protein loss (p<0.01) was observed after handling.

CONCLUSION

There is a considerable variation in EGF content between and within donors. This is further affected by handling of the AM. Such variations could affect the clinical efficacy of tissue constructs. Current use of AM for ex vivo expansion of epithelial cells is not standardized and remains an area of concern.

History of aromatase: saga of an important biological mediator and therapeutic target

Aromatase is the enzyme that catalyzes the conversion of androgens to estrogens. Initial studies of its enzymatic activity and function took place in an environment focused on estrogen as a component of the birth control pill. At an early stage, investigators recognized that inhibition of this enzyme could have major practical applications for treatment of hormone-dependent breast cancer, alterations of ovarian and endometrial function, and treatment of benign disorders such as gynecomastia. Two general approaches ultimately led to the development of potent and selective aromatase inhibitors. One targeted the enzyme using analogs of natural steroidal substrates to work out the relationships between structure and function. The other approach initially sought to block adrenal function as a treatment for breast cancer but led to the serendipitous finding that a nonsteroidal P450 steroidogenesis inhibitor, aminoglutethimide, served as a potent but nonselective aromatase inhibitor. Proof of the therapeutic concept of aromatase inhibition involved a variety of studies with aminoglutethimide and the selective steroidal inhibitor, formestane. The requirement for even more potent and selective inhibitors led to intensive molecular studies to identify the structure of aromatase, to development of high-sensitivity estrogen assays, and to "mega" clinical trials of the third-generation aromatase inhibitors, letrozole, anastrozole, and exemestane, which are now in clinical use in breast cancer. During these studies, unexpected findings led investigators to appreciate the important role of estrogens in males as well as in females and in multiple organs, particularly the bone and brain. These studies identified the important regulatory properties of aromatase acting in an autocrine, paracrine, intracrine, neurocrine, and juxtacrine fashion and the organ-specific enhancers and promoters controlling its transcription. The saga of these studies of aromatase and the ultimate utilization of inhibitors as highly effective treatments of breast cancer and for use in reproductive disorders serves as the basis for this first Endocrine Reviews history manuscript.

Xenograft models for aromatase inhibitor studies

As several aromatase inhibitors are now available for treating breast cancer, we developed a model system to compare their antitumor efficacy and to explore strategies for their optimal use. Tumors are grown in ovariectomized, immunodeficient mice from MCF-7 human breast cancer cells transfected with the aromatase gene (MCF-7Ca) and can therefore synthesize as well as respond to estrogen. Results from this model have been predictive of clinical outcome. Thus, inhibiting estrogen action and estrogen synthesis by treating mice with the aromatase inhibitor letrozole and the antiestrogen tamoxifen in combination did not result in synergy. Moreover, when tamoxifen treatment was no longer effective, tumor growth was significantly reduced in response to sequential letrozole treatment. However, our findings indicate that letrozole alone was better than all other treatments. Although letrozole resulted in long sustained growth inhibition, tumors eventually grew despite continued treatment. Mechanisms of resistance to letrozole were investigated during the course of treatment. ER was initially upregulated in responding tumors, but subsequently decreased below control levels in tumors no longer responsive to letrozole. Her-2 as well as adapter proteins (p-Shc and Grb-2) and signaling proteins in the MAPK cascade (p-Raf, p-Mekl/2, and p-MAPK), were all increased in letrozole resistant tumors. In LTLT cells, isolated from the letrozole resistant tumors and treated with inhibitors of the MAPKinase pathway, MAPK activity was decreased and ER expression restored to control levels. Inhibitors of EGFR/Her-2 also restored the sensitivity of LTLT cells to letrozole. These results suggest that crosstalk occurs between ER and tyrosine kinase receptor signaling. Therefore, to investigate whether down-regulating ER would prevent activation of MAPK and resistance to letrozole, xenografts were treated with letrozole and faslodex in combination. Her-2 and MAPK were not increased and tumor growth was inhibited throughout 29 weeks of treatment. These results suggest that blocking both ER and growth factor mediated transcription may delay development of resistance to letrozole and maintain its growth inhibition of breast cancer.

Aromatase and breast cancer

Several aromatase inhibitors and also new antiestrogens are now available for treating breast cancer. We have developed a model to compare the antitumor efficacy of these agents and to explore strategies for their optimal use. Results from the model have been predictive of clinical outcome. In this model, tumors are grown in ovariectomized, immunodeficient mice from MCF-7 human breast cancer cells transfected with the aromatase gene (MCF-7Ca). The possibility that blockade of estrogen action and estrogen synthesis may be synergistic was explored by treating mice with the aromatase inhibitor letrozole and the antiestrogen tamoxifen alone and in combination. The results indicated that letrozole alone was better than all other treatments. In addition, when tamoxifen treatment was no longer effective, tumor growth was significantly reduced in mice switched to letrozole treatment. However, tumors ultimately began to grow during continued treatment. To investigate the mechanisms by which tumors eventually adapt and grow during letrozole treatment, we determined the expression of signaling proteins in tumors during the course of letrozole treatment compared to the tumors of control mice. Tumors initially up-regulated the ER while responding to treatment, but subsequently receptor levels decreased in tumors unresponsive to letrozole. Also, Her-2 and adapter proteins (p-Shc and Grb-2) as well as all of the signaling proteins in the MAPK cascade (p-Raf, p-Mekl/2, and p-MAPK), but not in the Pl3/Akt pathway, were increased in tumors no longer responsive to letrozole. To investigate whether sensitivity to letrozole could be regained, cells were isolated from the letrozole resistant tumors (LTLT) and treated with inhibitors of the MAPKinase pathway (PD98059 and UO126). These compounds reduced MAPK activity and increased ER expression. EGFR/Her-2 inhibitors, gefitinib and AEE78S although not effective in the parental MCF-70a cells, restored the sensitivity of LTLT cells to letrozole. In xenografts, beginning treatment with letrozole and faslodex to down regulate the ER prevented increases in Her-2 and activation of MAPK and was highly effective in inhibiting tumor growth throughout 29 weeks of treatment. These results suggest that blocking both ER- and growth factor-mediated transcription may delay development of resistance and maintain growth inhibition of ER+ breast cancer.

Aromatase inhibition and inactivation

Aromatase is the key enzyme in the synthesis of estrogens and mediates the conversion of androstenedione and testosterone to estrone and estradiol. Because of the importance of estrogen in stimulating breast cancers, the inhibition of estrogen synthesis is a logical approach to treatment. Aromatase is an excellent target for inhibition, because it is the last step in steroid biosynthesis, and, therefore, there are no important downstream enzymes to be affected. In addition, although aromatase is a P-450 enzyme and shares common features with other enzymes in this class, such as liver metabolizing enzymes and steroidogenic enzymes, it has unique features in the aromatizing reaction, features that are amenable to the development of selective inhibition. The approach we took to develop the first aromatase inhibitors was to design substrate analogues based on the structure of androstenedione. Some of these inhibitors, such as 4-hydroxyandrostenedione [4-OHA (later known as formestane)], also cause enzyme inactivation. Instead of being released at the end of the reaction, the substrate analogue remains bound. Therefore, the inhibitor is not required to be present at all times to maintain inhibition, and it has high enzyme specificity. Subsequently, other investigators have taken a different approach to developing compounds based on inhibitors of P-450 enzymes. High selectivity has been achieved with some of these reversible inhibitors. We have developed a unique animal model with human tumors to compare the antitumor efficacy of antiestrogens and aromatase inhibitors and to optimize their use in sequence and combination as a guide for future clinical trials.

Aromatase expression in the human male

The role of estrogens produced by the testis may involve negative feedback regulation of androgen biosynthesis. Estrogens are also associated with contractile processes of seminiferous tubules, and might have mitogenic effects on Sertoli and Leydig cells. To investigate the location of aromatase (estrogen synthetase) in the testes, tissue from normal human subjects, aged 3 months to 72 years were studied using immunocytochemistry. In mature testes, aromatase immunostain was always associated with Leydig cells and was absent from Sertoli cells. Aromatase activity ranged from 0.014-0.55 pmol estrogen per mg/h and was significantly correlated with the immunostain intensity (P<0.02). Activity and immunostain intensity did not correlate with increasing age. Rather, the highest levels were measured in four of six testes of men aged 18-20 years, three of whom also had the strongest immunostain in larger and more prominent Leydig cell clusters than those in the other specimens. A low level of aromatase activity but no immunostain was detected in prepubertal testes. However, in several prepubertal patients with Peutz-Jegher's Syndrome (PJS) with bilateral multifocal sex cord tumors and enlarged seminiferous tubules and Sertoli cells, aromatase was expressed in these Sertoli cells, but absent from normal Sertoli and Leydig cells. Increased aromatase expression in these tissues involved activation of upstream regulatory elements of the gonadal P II promoter of P-450(arom). In a prepubertal boy with gynecomastia but without PJS, aromatase excess appeared to be due to increased aromatization in skin fibroblasts and lymphocytes. Several members of the patient's family including his sister also expressed high levels of aromatase. This condition appears to be inherited in an autosomal dominant manner.

The effect of combining aromatase inhibitors with antiestrogens on tumor growth in a nude mouse model for breast cancer

We have previously established a model for postmenopausal, hormone-dependent breast cancer in nude mice which is responsive to both antiestrogens and aromatase inhibitors. In this model, MCF-7 human breast carcinoma cells transfected with the aromatase gene (MCF-7CA) synthesize sufficient estrogen to form tumors in ovariectomized nude mice. In the present study we used this intratumoral aromatase model to investigate the effects on tumor growth of the new nonsteroidal aromatase inhibitors letrozole (CGS 20,267) and anastrozole (ZD 1033) and the antiestrogens tamoxifen (ICI 47,474) and faslodex (ICI 182,780). Furthermore, we determined whether the inhibition of estrogen synthesis together with inhibition of estrogen action would be more effective in controlling breast tumor growth. The results of our studies indicate that the aromatase inhibitors anastrozole and letrozole, as well as the new pure antiestrogen faslodex, have potent antitumor effects in the mouse model. In the treatment of mice with mammary tumors, letrozole was more effective in suppressing tumor growth than anastrozole. This was consistent with the Ki values of these inhibitors against placental aromatase and the IC50 values in cell culture (MCF-7CA), which indicated the greater potency of letrozole as an aromatase inhibitor. Letrozole also had greater antitumor effects than tamoxifen and faslodex. The antitumor effect of letrozole was substantial, making it difficult to detect any additional effect on the tumors when letrozole was combined with the antiestrogens. However, the combined treatment of anastrozole + tamoxifen and anastrozole + faslodex also did not increase efficacy compared to the aromatase inhibitor alone. In addition, combining the two antiestrogens did not suppress tumor growth more effectively than faslodex alone. Our results show that treatment with the combinations of aromatase inhibitors with either tamoxifen or faslodex are not more effective in blocking estrogen stimulation of tumor growth than the aromatase inhibitors alone.

Aromatase inhibitors and their antitumor effects in model systems

The potential of aromatase (estrogen synthetase) within the breast to provide a significant source of estrogen mediating tumor proliferation is suggested by studies reporting 4- to 6-fold higher estrogen levels in tumors than in plasma of postmenopausal patients with breast cancer. Recent studies in our laboratory have identified aromatase and its mRNA in tumor epithelial cells using immunocytochemistry and in situ hybridization. In addition, significant aromatase activity, which was stimulated 7-fold by dexamethasone, was measured in metastatic cells isolated from a breast cancer patient. Increase in proliferation, as measured by proliferating cell nuclear antigen immunostaining in tumor sections and by thymidine incorporation into DNA in response to testosterone, was observed in histocultures of breast cancer samples. This latter effect could be inhibited by 4-hydroxyandrostenedione. These results imply that intratumoral aromatase has functional significance and may be an important target for successful inhibitor treatment of breast cancer patients. To investigate treatment strategies with aromatase inhibitors and antiestrogens, we developed an intratumoral aromatase model to simulate the hormone responsive postmenopausal breast cancer patient. Tumors of estrogen receptor positive human breast carcinoma cells (MCF-7) transfected with the human aromatase gene are grown in ovariectomized nude mice. These cells synthesize sufficient estrogen to stimulate tumor formation. We have utilized this model to investigate the effects on tumor growth of the antiestrogens, tamoxifen and ICI 182780, and the aromatase inhibitors, letrozole and anastrozole (arimidex), alone and in combination. Both the aromatase inhibitors and the antiestrogens were effective in suppressing tumor growth. However, letrozole was significantly more effective than the antiestrogens. When the aromatase inhibitors were combined with the antiestrogen, tamoxifen, tumor growth was suppressed to about the same extent as with the aromatase inhibitors alone. Furthermore, the results do not suggest any benefit from combining tamoxifen with the pure antiestrogen, ICI 182780. Thus sequential use of these agents is likely to be more advantageous to the patient in terms of longer duration of effective treatment.

Inhibition of androgen synthesis in human testicular and prostatic microsomes and in male rats by novel steroidal compounds

The C(17,20)-lyase and 5alpha-reductase are key enzymes in the biosynthesis of androgens. The effects of novel steroidal compounds were evaluated as inhibitors against both human C(17,20)-lyase and 5alpha-reductase in vitro. The concentrations of testosterone (T) and dihydrotestosterone (DHT) in the prostate, testis and serum and changes in the tissue weights were also determined in rats treated with the novel inhibitors. L-12 and L-26 showed potent inhibition of human testicular C(17,20)-lyase with IC50 values of 50 and 25 nM, respectively. L-12, L-38, and I-47 showed moderate inhibition of human testicular C(17,20)-lyase with IC50 values of 75, 108, and 70 nM, respectively similar to ketoconazole (78 nM). Interestingly, L-6, L-26, and L-38 also showed some inhibitory activity against 5alpha-reductase with IC50 values of 75, 125, and 377 nM, respectively. Finasteride, an inhibitor of 5alpha-reductase had an IC50 value of 33 nM. However, ketoconazole did not inhibit 5alpha-reductase nor did finasteride inhibit C(17,20)-lyase. Treatment of normal male rats with several of these novel inhibitors (50 mg/kg x day, s.c., for 14 consecutive days) caused about 45-91% decrease in serum, testicular and prostatic T concentration. Similarly, serum and prostatic DHT concentration were significantly decreased in rats treated with these novel compounds by 50-90% compared with controls. Surgical castration caused almost complete elimination of circulating T and DHT concentration in rat tissues. L-6 and L-12 were the most effective and reduced the wet weight of the prostate by 50%. Although future improvements in their bioavailability are necessary, these novel steroidal compounds show promise as potential agents for reducing T and DHT levels in patients with androgen dependent diseases.

The effect of estrogen on aromatase and vascular endothelial growth factor messenger ribonucleic acid in the normal nonhuman primate mammary gland

In the present study, the baboon was used as a model to investigate the effects of steroid hormones on vascular endothelial growth factor (VEG/PF) and aromatase expression and on proliferation of the normal mammary gland. Immunocytochemistry revealed that both aromatase and VEG/PF were expressed in the epithelial cells of the terminal ductal lobular units. Mammary tissue biopsies were obtained from female baboons during the follicular and luteal phases of the menstrual cycle, 4 weeks after ovariectomy (OVX), and after 2 weeks of treatment with estradiol benzoate (E2B; 500 microg/day, i.m.). Although there was little apparent difference in aromatase messenger ribonucleic acid (mRNA) in tissue from follicular and luteal phases or after ovariectomy, aromatase mRNA was decreased in tissue from ovariectomized (OVX) animals treated for 2 weeks with E2B. Furthermore, aromatase activity in tissue from these animals was markedly reduced compared to activity in tissue from the OVX animals before treatment (P < 0.001). In one animal in which mammary aromatase activity was measured sequentially during the follicular and luteal phases, aromatase activity was increased significantly after OVX and was reduced to the level in the intact animal by subsequent treatment with E2B. This effect on both aromatase activity and mRNA occurred rapidly 2 and 4 h after injection with E2B. In contrast to its effect on aromatase, E2B treatment of OVX animals stimulated VEG/PF mRNA 2 and 4 h after injection. In histoculture of mammary biopsies from these animals in the follicular and luteal phases of the menstrual cycle or after OVX, [3H]thymidine incorporation was increased significantly by incubation with testosterone (T) as well as estrogen (P < 0.01). The effect of T was blocked by aromatase inhibitor, 4-hydroxyandrostenedione, suggesting that the tissue is responsive to E produced by aromatization of T in the tissue. When mammary tissue from OVX animals was cultured with T, there was a significantly greater increase in [3H]thymidine incorporation than in histocultures of tissue from intact animals (P < 0.01). However, in histocultures of tissue from the OVX animals treated with E2B (500 microg) for 2 weeks, [3H]thymidine incorporation was similar to the level in tissue of intact animals incubated with T. No significant changes occurred in [3H]thymidine incorporation with the nonaromatizable androgen dihydrotestosterone or progesterone alone. These findings suggest that estrogens produced locally by aromatization of T have a functional role in mammary tissue. Aromatase expressed in the mammary gland could be important in maintaining local estrogen concentrations, particularly after menopause. Estrogen appears to regulate transcription of both aromatase and VEG/PF in the mammary gland, suggesting a regulatory loop by which local estrogens could stimulate VEG/PF production. Thus, paracrine/autocrine mechanisms that can enhance the proliferation of malignant cells and their metastatic spread already exist before transformation.

Aromatase and its inhibitors

Inhibitors of aromatase (estrogen synthetase) have been developed as treatment for postmenopausal breast cancer. Both steroidal substrate analogs, type I inhibitors, which inactivate the enzyme and non-steroidal competitive reversible, type II inhibitors, are now available. 4-hydroxyandrostenedione (4-OHA), the first selective aromatase inhibitor, has been shown to reduce serum estrogen concentrations and cause complete and partial responses in approximately 25% of patients with hormone responsive disease who have relapsed from previous endocrine treatment. Letrozole (CGS 20, 269) and anastrozole (ZN 1033) have been recently approved for treatment. Both suppress serum estrogen levels to the limit of assay detection. Letrozole has been shown to be significantly superior to megace in overall response rates and time to treatment failure, whereas anastrozole was found to improve survival in comparison to megace. Both were better tolerated than the latter. The potential of aromatase within the breast as a significant source of estrogen mediating tumor proliferation and which might determine the outcome of inhibitor treatment was explored. Using immunocytochemistry and in situ hybridization, aromatase and mRNAarom was detected mainly in the epithelial cells of the terminal ductal lobular units (TDLU) of the normal breast and also in breast tumor epithelial cells as well as some stromal cells. Increase in proliferation, measured by increased thymidine incorporation into DNA and by PCNA immunostaining in response to testosterone was observed in histocultures of breast cancer samples. This effect could be inhibited by 4-OHA and implies that intratumoral aromatase has functional significance. An intratumoral aromatase model in the ovariectomized nude mouse was developed which simulated the hormone responsive postmenopausal breast cancer patient. This model also allows evaluation of the efficacy of aromatase inhibitors and antiestrogens in tumors of estrogen receptor positive, human breast carcinoma cells transfected with the human aromatase gene. Thus, the cells synthesized estrogen which stimulated tumor formation. Both aromatase inhibitors and antiestrogens were effective in suppressing tumor growth in this model. However, letrozole was more effective than tamoxifen. When the aromatase inhibitors were combined with tamoxifen, tumor growth was suppressed to about the same extent as with the aromatase inhibitors alone. Thus, there was no additive or synergistic effects of combining tamoxifen with aromatase inhibitors. This suggests that sequential treatment with these agents is likely to be more beneficial to the patient in terms of longer response to treatment.

Intratumoral aromatase model: the effects of letrozole (CGS 20267)

An intratumoral aromatase model in the ovariectomized nude mouse was developed which simulated the hormone responsive postmenopausal breast cancer patient. MCF-7, human breast cancer cells transfected with the aromatase gene, inoculated into ovariectomized nude mice are able to synthesize sufficient estrogens to enhance cell proliferation and the development of tumors. These tumors are responsive to both antiestrogens and aromatase inhibitors. However, letrozole was found to be more effective than tamoxifen and caused tumor regression, a result not previously noted in nude mice with endocrine treatments. When the aromatase inhibitors were combined with tamoxifen, tumor growth was suppressed to about the same extent as treatment with the aromatase inhibitors alone. Thus, there was no additive or synergistic effects of combining tamoxifen with aromatase inhibitors. These results suggest that letrozole has the potential to be more effective than tamoxifen for achieving greater reduction in estrogenic effects on tumors and uterus in postmenopausal breast cancer patients. In addition, sequential treatment with these agents is likely to be more beneficial to the patient in terms of longer response to treatment.

Aromatase expression in the human breast

The plasma levels of free estradiol are very low in postmenopausal women. However, concentrations of estrogens within breast tissue have been reported to be higher than in plasma and similar to plasma concentrations in premenopausal women. One mechanism by which this may occur is for breast cells to synthesize estrogens themselves and produce high concentrations locally. Thus, tumor aromatase may be a significant source of estrogen which stimulates tumor growth. To address the question of the importance of this pathway, we have investigated the expression of aromatase within the normal breast and breast cancers. Because conventional biochemical assays for measuring aromatase activity require relatively large amounts of tissue, we developed an immunocytochemical method using a monoclonal antibody to determine the expression of aromatase. The method can be applied to sections of tumors embedded in paraffin blocks as routinely prepared for pathology. Since we have previously shown that mRNA for aromatase (P450 arom) and the protein are expressed in the same cells of the human placenta, we used in situ hybridization of sequence specific probes to P450 arom mRNA in breast tissue as one method to verify the specificity of the immunocytochemical detection of the enzyme. Both immunocytochemistry and in situ hybridization identified aromatase enzyme and mRNA expression in the epithelial cells of the terminal ductal lobula units (TDLU) and surrounding stromal cells of the normal human breast, and in the tumor epithelial cells and stromal cells of breast cancers. In addition, evidence for the functional significance of tumor aromatase was indicated by a correlation between aromatase activity and expression of proliferating cell nuclear antigen (PCNA) in the tumor, and by increased thymidine incorporation into DNA in response to testosterone in tumors in histoculture which had high aromatase activity but not in those with low activity. The findings suggests that estrogen produced locally is important in enhancing proliferation of the tumor.

Comparison of biochemical aromatase activity with aromatase immunohistochemistry in human breast carcinomas

The role of intratumoural aromatase in human breast cancer growth remains controversial. At the same time as the use of aromatase inhibitors in the clinical setting continues to increase, so does the need for a tool to predict the likely response to this treatment. Intratumoural aromatase is a candidate predictive marker. The presently accepted 'gold standard' methods of assessment of aromatase activity are biochemical assays. However, these are time-consuming and require relatively large amounts of fresh or frozen tissue which are frequently not available. The development of a reliable immunohistochemical technique for the assessment of intratumoural aromatase which could be applied rapidly to more readily available paraffin-embedded material is therefore highly desirable. Unfortunately aromatase immunohistochemistry is also an area of controversy; some authors describe localisation to the stromal compartment but others to the malignant epithelial cells themselves. The aim of this study was therefore to compare immunohistochemical scores using two different antibodies with biochemical aromatase activity. Taking a group of 29 human breast carcinomas we demonstrated a strong correlation between immunoreactivity with a monoclonal antibody (p = 0.01) but not with a polyclonal (p = 0.16). The monoclonal produced reactivity in both epithelial and stromal cells but the polyclonal in only stromal cells. The implications of these results are discussed together with the need for further studies.