Use of monoclonal antibody for assessment of estrogen and progesterone receptors in malignant effusions

New insights into estrogenic regulation of O6-methylguanine DNA-methyltransferase (MGMT) in human breast cancer cells: Co-degradation of ER-α and MGMT proteins by fulvestrant or O6-benzylguanine indicates fresh avenues for therapy

Endocrine therapy using estrogen receptor-α (ER-α) antagonists for attenuating horm2one-driven cell proliferation is a major treatment modality for breast cancers. To exploit any DNA repair deficiencies associated with endocrine therapy, we investigated the functional and physical interactions of ER-α with O6-methylguanine DNA methyltransferase (MGMT), a unique DNA repair protein that confers tumor resistance to various anticancer alkylating agents. The ER-α -positive breast cancer cell lines (MCF-7, T47D) and ER- negative cell lines (MDAMB-468, MDAMB-231), and established inhibitors of ER-α and MGMT, namely, ICI-182,780 (Faslodex) and O6-benzylguanine, respectively, were used to study MGMT- ER interactions. The MGMT gene promoter was found to harbor one full and two half estrogen-responsive elements (EREs) and two antioxidant-responsive elements (AREs). MGMT expression was upregulated by estrogen, downregulated by tamoxifen in Western blot and promoter-linked reporter assays. Similarly, both transient and stable transfections of Nrf-2 (nuclear factor-erythroid 2-related factor-2) increased the levels of MGMT protein and activity 3 to 4-fold reflecting novel regulatory nodes for this drug-resistance determinant. Of the different ER-α antagonists tested, the pure anti-estrogen fulvestrant was most potent in inhibiting the MGMT activity in a dose, time and ER-α dependent manner, similar to O6-benzylguanine. Interestingly, fulvestrant exposure led to a degradation of both ER-α and MGMT proteins and O6-benzylguanine also induced a specific loss of ER-α and MGMT proteins in MCF-7 and T47D breast cancer cells with similar kinetics. Immunoprecipitation revealed a specific association of ER-α and MGMT proteins in breast cancer cells. Furthermore, silencing of MGMT gene expression triggered a decrease in the levels of both MGMT and ER-α proteins. The involvement of proteasome in the drug-induced degradation of both proteins was also demonstrated. Fulvestrant enhanced the cytotoxicity of MGMT-targeted alkylating agents, namely, temozolomide and BCNU by 3 to 4-fold in ER-α positive cells, but not in ER-negative cells. We conclude that MGMT and ER-α proteins exist as a complex and are co-targeted for ubiquitin-conjugation and subsequent proteasomal degradation. The findings offer a clear rationale for combining alkylating agents with endocrine therapy.

MGMT inhibition restores ERα functional sensitivity to antiestrogen therapy

Antiestrogen therapy resistance remains a huge stumbling block in the treatment of breast cancer. We have found significant elevation of O(6) methylguanine DNA methyl transferase (MGMT) expression in a small sample of consecutive patients who have failed tamoxifen treatment. Here, we show that tamoxifen resistance is accompanied by upregulation of MGMT. Further we show that administration of the MGMT inhibitor, O(6)-benzylguanine (BG), at nontoxic doses, leads to restoration of a favorable estrogen receptor alpha (ERα) phosphorylation phenotype (high p-ERα Ser167/low p-ERα Ser118), which has been reported to correlate with sensitivity to endocrine therapy and improved survival. We also show BG to be a dual inhibitor of MGMT and ERα. In tamoxifen-resistant breast cancer cells, BG alone or in combination with antiestrogen (tamoxifen [TAM]/ICI 182,780 [fulvestrant, Faslodex]) therapy enhances p53 upregulated modulator of apoptosis (PUMA) expression, cytochrome C release and poly (ADP-ribose) polymerase (PARP) cleavage, all indicative of apoptosis. In addition, BG increases the expression of p21(cip1/waf1). We also show that BG, alone or in combination therapy, curtails the growth of tamoxifen-resistant breast cancer in vitro and in vivo. In tamoxifen-resistant MCF7 breast cancer xenografts, BG alone or in combination treatment causes significant delay in tumor growth. Immunohistochemistry confirms that BG increases p21(cip1/waf1) and p-ERα Ser167 expression and inhibits MGMT, ERα, p-ERα Ser118 and ki-67 expression. Collectively, our results suggest that MGMT inhibition leads to growth inhibition of tamoxifen-resistant breast cancer in vitro and in vivo and resensitizes tamoxifen-resistant breast cancer cells to antiestrogen therapy. These findings suggest that MGMT inhibition may provide a novel therapeutic strategy for overcoming antiestrogen resistance.

Clinically used breast cancer markers such as estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 are unstable throughout tumor progression

PURPOSE To investigate whether hormonal receptors and human epidermal growth factor receptor 2 (HER2) change throughout tumor progression, because this may alter patient management. PATIENTS AND METHODS The study cohort included female patients with breast cancer in the Stockholm health care region who relapsed from January 1, 1997, to December 31, 2007. Either biochemical or immunohistochemical (IHC)/immunocytochemical (ICC) methods were used to determine estrogen receptor (ER), progesterone receptor (PR), and HER2 status, which was then confirmed by fluorescent in situ hybridization for IHC/ICC 2+ and 3+ status. Results ER (459 patients), PR (430 patients), and HER2 (104 patients) from both primary tumor and relapse were assessed, revealing a change in 32.4% (McNemar's test P < .001), 40.7% (P < .001), and 14.5% (P = .44) of patients, respectively. Assessment of ER (119 patients), PR (116 patients), and HER2 (32 patients) with multiple (from two to six) consecutive relapses showed an alteration in 33.6%, 32.0%, and 15.7% of patients, respectively. A statistically significant differential overall survival related to intraindividual ER and PR status in primary tumor and relapse (log-rank P < .001) was noted. In addition, women with ER-positive primary tumors that changed to ER-negative tumors had a significant 48% increased risk of death (hazard ratio, 1.48; 95% CI, 1.08 to 2.05) compared with women with stable ER-positive tumors. CONCLUSION Patients with breast cancer experience altered hormone receptor and HER2 status throughout tumor progression, possibly influenced by adjuvant therapies, which significantly influences survival. Hence, marker investigations at relapse may potentially improve patient management and survival.

How should cancer presenting as a malignant pleural effusion be managed?

The objective of the study was to review the natural history of patients with a malignant pleural effusion but without obvious evidence of a primary, to assess the value of investigations used to look for a primary and to assess the response to palliative chemotherapy. This was done by a retrospective study of patients' notes at the Lung Unit, Royal Marsden Hospital, Sutton, Surrey. Improvement in tumour-related symptoms (and duration) on chemotherapy was assessed by the patient before the first course of chemotherapy and following each course using simple descriptive criteria as follows: (1) complete disappearance of symptoms (CR); (2) good improvement in symptoms (PR); (3) minor or no change in symptoms (NC); (4) worse symptoms (PD). Pleural effusion objective response (and duration) according to Hamed definition: success defined as a continued absence of reaccumulation of pleural fluid on all follow-up radiographs; any reaccumulation was regarded as a treatment failure. Overall survival was measured from the date of histological/cytological diagnosis to death. The study included 42 patients, 27 males and 15 females with a median age of 55 years. A primary was found in 15 patients (36%), and considered to be lung cancer. A total of 11/32 (34%) had a thoracic computed tomography (CT) scan with abnormalities compatible with a diagnosis of lung primary. When thoracic CT scan was negative, fibre optic bronchoscopy was always negative (0/13). Abdominal and pelvic CT scan, abdominal ultrasound, pelvic ultrasound and mammograms failed to reveal the primary. Twenty-three patients underwent local treatment and 37 received systemic chemotherapy. A total of 29/37 (78%) patients achieved symptomatic improvement (median duration, 6 months) and 32/37 (86%) an objective response of their pleural effusion on chemotherapy (median duration, 6 months). The median survival of the whole group was 12 months (3-60+ months). In this series the thoracic CT led to a diagnosis of lung primary in 34% of the cases. Other radiological examinations and bronchoscopy were unhelpful. Chemotherapy achieved symptom relief in 78% of patients.

Prognostic and diagnostic implications of estrogen and progesterone receptor assays in cytology

Scientific evidence suggests that cancer is a consequence of genetic changes that result in uncontrolled cellular growth, tissue invasion, and metastasis. This concept has led to a great deal of excitement in the medical community in the hope that precise identification of genes involved in human cancer could potentially facilitate our understanding of human malignancies. It may also be possible to apply this information directly to different clinical settings. Many technologies are now available which offer opportunities for pathologists to not only expand their diagnostic abilities, but also to assess the prognosis of a given tumor in a specific patient. These include immunocytochemistry, flow cytometry, cell image analysis, and molecular genetic studies. In this review, the role of immunocytochemical hormone receptor assay as an aid in tumor prognosis and in prediction of tumor response to endocrine therapy will be discussed. Emphasis will be placed on the use of hormone receptor assay as an adjunct in diagnostic pathology and in assessment of metastatic tumors of unknown origin. The potential value of assessment of hormone receptors in different cytologic preparations will also be discussed.