Analysis of in vitro chemoresponse assays in endometrioid endometrial adenocarcinoma: an observational ancillary analysis.

BACKGROUND: Chemotherapy plays a role in the treatment of endometrioid endometrial cancer (EEC); however, tumor grade may affect response. Our objective was to evaluate associations between tumor grade and in vitro chemoresponse. METHODS: We conducted an analysis of primary tumor samples from women with EEC undergoing in vitro chemoresponse testing. Results were classified as sensitive (S), intermediate (I), or resistant (R) to each drug tested. Correlations between tumor grade and response were examined. RESULTS: Data was collected from 159 patients: 28 with grade 1 (18%), 52 with grade 2 (32%), and 79 (50%) with grade 3 tumors. Median age of patients was 62 (range 31-92). Most patients were Caucasian (83%) with advanced disease (Stage III: 50.9%; Stage IV: 13.2%). Overall chemoresponse was similar across all grades. Fifty percent, 56 and 51% for grade 1, 2, and 3 tumors, respectively, demonstrated S results to at least 1 agent. There was no association between grade and in vitro response to chemotherapy agents (p > 0.05) except a marginal association between grade and doxorubicin response (p = 0.08). Grade 1 and 2 cancers were more likely to demonstrate R results for doxorubicin compared to grade 3 cancers (G1: 19% vs G2: 25% vs G3: 8%; p = 0.08). In a subset tested for all 7 agents, only one patient tumor was pan-R and 4 were pan-S. CONCLUSIONS: Based on our data, grades 1-3 EEC have similar in vitro chemoresponse. These findings suggest that chemotherapy may be useful in advanced low grade EECs, but further clinical correlation is needed.

Evaluation of in vitro chemoresponse profiles in women with Type I and Type II epithelial ovarian cancers: An observational study ancillary analysis.

OBJECTIVE: Type I epithelial ovarian cancers (EOCs) are reported to be relatively chemoresistant. This study sought to compare pretreatment chemoresponse assays in Type I vs. Type II EOCs. STUDY DESIGN: 383 women with stage III-IV EOC enrolled in an observational study, with known chemoresponse assay results for 7 common therapeutic agents, were included. Type I EOCs were defined as grade 1 serous/endometrioid cancers and all clear cell/mucinous cancers. Type II EOCs were classified as grade 2-3 serous/endometrioid cancers and undifferentiated cancers. Chemotherapy assay responses were classified as sensitive (S), intermediately sensitive (I), or resistant (R). All patients were treated with platinum/taxane therapy following cytoreductive surgery. RESULTS: Thirty (7.8%) tumors were classified as Type I EOC, and 353 (92.2%) as Type II EOC. Type I patients were younger at the time of diagnosis (median age: 57 vs. 62 years, p=0.018) and had longer survival compared to Type II patients (mPFS: 25.8 vs. 16.4 months, HR=1.71, p=0.042). Eighty-six percent of Type I EOC specimens demonstrated a sensitive chemoresponse assay result to at least 1 agent; 35.7% were pan-S to all 7 agents. After adjusting for stage, debulking status, and type of EOC, multi-drug resistance was twice as likely in women with Type I EOC compared to Type II EOC (pan-R, 14.3% vs. 6.8% (p=0.268); pan-S, 35.7% vs. 51.2% (p=0.183)), but did not attain statistical significance. CONCLUSION(S): The majority of women with Type I EOC displayed assay sensitivity to at least one agent. Given the small sample size these findings need to be evaluated further.

Analytical Performance of a 15-Gene Prognostic Assay for Early-Stage Non-Small-Cell Lung Carcinoma Using RNA-Stabilized Tissue.

A 15-gene prognostic signature for early-stage, completely resected, non-small-cell lung carcinoma, (which distinguishes between patients with good and poor prognoses) was clinically validated in prior studies. To achieve operational efficiencies, this study was designed to evaluate the assay's performance in RNA-stabilized tissue as an alternative to the fresh-frozen tissue format originally used to develop the assay. The percent concordance between matched tissue formats was 84% (95% Wilson CI, 70%-92%), a level of agreement comparable to the inherent reproducibility of the assay observed within biological replicates of fresh-frozen tissue. Furthermore, the analytical performance of the assay using the RNA-stabilized tissue format was evaluated. When compared to an accredited reference laboratory, the clinical laboratory achieved a concordance of 94% (95% Wilson CI, 81%-98%), and there was no evidence of bias between the laboratories. The lower limit of quantitation for the target RNA concentration was confirmed to be, at most, 12.5 ng/µL. The assay reportable range defined in terms of risk score units was determined to be -4.295 to 4.210. In a large-scale precision study, the assay showed high reproducibility and repeatability. When subjected to a maximal amount of genomic DNA, a potential contaminant, the assay still produced the expected results. The 15-gene signature was confirmed to produce reliable results and, thus, is suitable for its intended use.

A cost-effectiveness analysis of a chemoresponse assay for treatment of patients with recurrent epithelial ovarian cancer.

OBJECTIVE: Clinical validation of a chemoresponse assay was recently published, demonstrating a significant increase in overall survival in recurrent ovarian cancer patients treated with therapies to which their tumor was sensitive in the assay. The current study investigates the cost effectiveness of using the assay at the time of ovarian cancer recurrence from the payer's perspective. METHODS: Using a Markov state transition model, patient characteristics and survival data from the recent clinical study, the cumulative costs over the study horizon (71 months) for both the baseline (no assay) and intervention (assay consistent, hypothetical) cohorts were evaluated. RESULTS: The assay consistent cohort had an incremental cost effectiveness ratio (ICER) of $6206 per life year saved (LYS), as compared to the baseline cohort. Cost-effectiveness was further demonstrated in platinum-sensitive and platinum-resistant populations treated with assay-sensitive therapies, with ICERs of $2773 per LYS and $2736 per LYS, respectively. CONCLUSIONS: The use of a chemoresponse assay to inform treatment decisions in recurrent ovarian cancer patients has the potential to be cost-effective in both platinum-sensitive and platinum-resistant patients.

A chemoresponse assay for prediction of platinum resistance in primary ovarian cancer.

OBJECTIVE: Recurrence following primary platinum-based chemotherapy remains a challenge in the treatment of patients with advanced-stage epithelial ovarian cancer. This study examines whether a chemoresponse assay can identify patients who are platinum-resistant prior to treatment. STUDY DESIGN: Women (n = 276) with International Federation of Gynecology and Obstetrics stage III-IV ovarian, fallopian, and peritoneal cancer were enrolled in an observational study, and the responsiveness of their tumors was evaluated using a chemoresponse assay. All patients were treated with a platinum/taxane regimen following cytoreductive surgery. Assay responses to carboplatin or paclitaxel were classified as sensitive, intermediate sensitive (IS), or resistant. Association of assay response with progression-free survival (PFS) was analyzed using the Kaplan-Meier method and a Cox regression model. RESULTS: Patients whose tumors were resistant to carboplatin were at increased risk of disease progression compared to those with nonresistant (sensitive + IS) tumors (median PFS: 11.8 vs 16.6 months, respectively, P < .001), and the association was confirmed after adjusting for other clinical factors (hazard ratio, 1.71; 95% confidence interval, 1.12-2.62; P = .013). Association of assay response to paclitaxel with PFS trended in multivariate analysis (hazard ratio, 1.28; 95% confidence interval, 0.84-1.95; P = .245). For tumors resistant to carboplatin, 59% were sensitive or IS to at least 1 other commonly used agent, demonstrating the ability of the assay to inform treatment decisions beyond the standard platinum/taxane regimen. CONCLUSION: Assay resistance to carboplatin is strongly associated with shortened PFS among advanced-stage epithelial ovarian cancer patients treated with carboplatin + paclitaxel therapy, supporting use of this assay to identify patients likely to experience early recurrence on standard platinum-based therapy.

A prospective study evaluating the clinical relevance of a chemoresponse assay for treatment of patients with persistent or recurrent ovarian cancer.

OBJECTIVE: Use of in vitro chemoresponse assays for informing effective treatment selection is a compelling clinical question and a topic of debate among oncologists. A prospective study was conducted evaluating the use of a chemoresponse assay in recurrent ovarian cancer patients. METHODS: Women with persistent or recurrent ovarian cancer were enrolled under an IRB-approved protocol, and fresh tissue samples were collected for chemoresponse testing. Patients were treated with one of 15 protocol-designated treatments empirically selected by the oncologist, blinded to the assay results. Each treatment was classified by the assay as: sensitive (S), intermediate (I), or resistant (R). Patients were prospectively monitored for progression-free survival (PFS) and overall survival (OS). Associations of assay response for the physician-selected treatment with PFS and OS were analyzed. RESULTS: A total of 262 evaluable patients were enrolled. Patients treated with an assay-sensitive regimen demonstrated significantly improved PFS and OS while there was no difference in clinical outcomes between I and R groups. Median PFS was 8.8 months for S vs. 5.9 months for I+R (hazard ratio [HR]=0.67, p=0.009). The association with assay response was consistent in both platinum-sensitive and platinum-resistant tumors (HR: 0.71 vs. 0.66) and was independent of other covariates in multivariate analysis (HR=0.66, p=0.020). A statistically significant14-month improvement in mean OS (37.5 months for S vs. 23.9 months for I+R, HR=0.61, p=0.010) was demonstrated. CONCLUSIONS: This prospective study demonstrated improved PFS and OS for patients with either platinum-sensitive or platinum-resistant recurrent ovarian cancer treated with assay-sensitive agents.

Adaptation of a chemosensitivity assay to accurately assess pemetrexed in ex vivo cultures of lung cancer.

PURPOSE: Pemetrexed is the only FDA approved treatment for mesothelioma and is a second line agent for treatment of non-small cell lung carcinoma (NSCLC). Pemetrexed is inhibited by folate and its analogs, which are components of many culture media, making it challenging to study pemetrexed in vitro. In order to accurately evaluate pemetrexed's effects in vitro, the protocol for a standard chemosensitivity assay, the ChemoFx drug response marker, had to be modified. EXPERIMENTAL DESIGN: Novel rinse and media change steps were assessed and then added to the assay protocol in order to observe pemetrexed activity. The intraday and interday stability of pemetrexed were also established under the adapted protocol. Then, the modified protocol was used to examine pemetrexed in 65 ex vivo lung cancer specimens. RESULTS: Substituting 5% RPMI + EGF for BEGM allowed pemetrexed to exert its anticancer activity in the ChemoFx DRM. ChemoFx classified 6.2% of the lung specimens as responsive, 9.2% as intermediate responsive and 84.6% as non-responsive to pemetrexed. CONCLUSIONS: Adapting the ChemoFx protocol allowed for the accurate evaluation of pemetrexed anticancer activity in ex vivo lung specimens. ChemoFx evaluation may provide an indication of a patient's clinical response to the drug prior to pemetrexed treatment. Having this information when treatment options are being considered could avoid wasted time, unnecessary costs and needless side effects that are the result of an inappropriate chemotherapy regimen.

Cell line derived multi-gene predictor of pathologic response to neoadjuvant chemotherapy in breast cancer: a validation study on US Oncology 02-103 clinical trial.

BACKGROUND: The purpose of this study is to assess the predictive accuracy of a multi-gene predictor of response to docetaxel, 5-fluorouracil, epirubicin and cyclophosphamide combination chemotherapy on gene expression data from patients who received these drugs as neoadjuvant treatment. METHODS: Tumor samples were obtained from patients with stage II-III breast cancer before starting neoadjuvant chemotherapy with four cycles of 5-fluorouracil/epirubicin/cyclophosphamide (FEC) followed by four cycles of docetaxel/capecitabine (TX) on US Oncology clinical trial 02-103. Most patients with HER-2-positive cancer also received trastuzumab (H). The chemotherapy predictor (TFEC-MGP) was developed from publicly available gene expression data of 42 breast cancer cell-lines with corresponding in vitro chemotherapy sensitivity results for the four chemotherapy drugs. No predictor was developed for treatment with trastuzumab. The predictive performance of TFEC-MGP in distinguishing cases with pathologic complete response from those with residual disease was evaluated for the FEC/TX and FEC/TX plus H group separately. The area under the receiver-operating characteristic curve (AU-ROC) was used as the metric of predictive performance. Genomic predictions were performed blinded to clinical outcome. RESULTS: The AU-ROC was 0.70 (95% CI: 0.57-0.82) for the FEC/TX group (n=66) and 0.43 (95% CI: 0.20-0.66) for the FEC/TX plus H group (n=25). Among the patients treated with FEC/TX, the AU-ROC was 0.69 (95% CI: 0.52-0.86) for estrogen receptor (ER)-negative (n=28) and it was 0.59 (95% CI: 0.36-0.82) for ER-positive cancers (n=37). ER status was not reported for one patient. CONCLUSIONS: Our results indicate that the cell line derived 291-probeset genomic predictor of response to FEC/TX combination chemotherapy shows good performance in a blinded validation study, particularly in ER-negative patients.

Distinct genes related to drug response identified in ER positive and ER negative breast cancer cell lines.

Breast cancer patients have different responses to chemotherapeutic treatments. Genes associated with drug response can provide insight to understand the mechanisms of drug resistance, identify promising therapeutic opportunities, and facilitate personalized treatment. Estrogen receptor (ER) positive and ER negative breast cancer have distinct clinical behavior and molecular properties. However, to date, few studies have rigorously assessed drug response genes in them. In this study, our goal was to systematically identify genes associated with multidrug response in ER positive and ER negative breast cancer cell lines. We tested 27 human breast cell lines for response to seven chemotherapeutic agents (cyclophosphamide, docetaxel, doxorubicin, epirubicin, fluorouracil, gemcitabine, and paclitaxel). We integrated publicly available gene expression profiles of these cell lines with their in vitro drug response patterns, then applied meta-analysis to identify genes related to multidrug response in ER positive and ER negative cells separately. One hundred eighty-eight genes were identified as related to multidrug response in ER positive and 32 genes in ER negative breast cell lines. Of these, only three genes (DBI, TOP2A, and PMVK) were common to both cell types. TOP2A was positively associated with drug response, and DBI was negatively associated with drug response. Interestingly, PMVK was positively associated with drug response in ER positive cells and negatively in ER negative cells. Functional analysis showed that while cell cycle affects drug response in both ER positive and negative cells, most biological processes that are involved in drug response are distinct. A number of signaling pathways that are uniquely enriched in ER positive cells have complex cross talk with ER signaling, while in ER negative cells, enriched pathways are related to metabolic functions. Taken together, our analysis indicates that distinct mechanisms are involved in multidrug response in ER positive and ER negative breast cells.

Chemoresponse assay for evaluating response to sunitinib in primary cultures of breast cancer.

PURPOSE: Not all patient tumors respond equally to the same type of therapy. An in vitro chemoresponse assay that can suggest individualized tumor response to therapies, in this case sunitinib, can be a valuable guide for clinical decision-making. RESULTS: The assay was shown to be sensitive and reproducible while differentiating renal cell lines based on sunitinib sensitivity and evaluating vendors' supply of the compound. Of the cultured breast cancer tumor specimens treated with sunitinib, ChemoFx classified 7.6% as responsive (R), 20.5% of specimens as intermediate responsive (IR), and 71.7% as non-responsive (NR). EXPERIMENTAL DESIGN: The ChemoFx(®) drug response marker (DRM) (Precision Therapeutics, Inc.) was carried out on SK-OV-3 cells treated with sunitinib to establish appropriate dose ranges and assay thresholds, and to evaluate vendor supplies of sunitinib. Once reference values were determined, the assay was applied to eight different renal cell lines treated with sunitinib, each of which was subsequently classified into responsive, intermediate responsive, and non-responsive groups. Next, ex vivo tumor samples from 39 clinically diagnosed breast cancer patients were grown in culture and assayed for their response to sunitinib using ChemoFx. CONCLUSIONS: Chemoresponse assay assessment is an effective tool for evaluating sunitinib sensitivity in cultured cell lines as well as ex vivo breast cancer samples. An in vitro assay that may indicate an individual patient's clinical response to a chemotherapeutic agent can be beneficial in time, cost, and clinical outcome when therapeutic options are considered.

An in vitro chemoresponse assay defines a subset of colorectal and lung carcinomas responsive to cetuximab.

Cetuximab is a chimeric monoclonal antibody for the epidermal growth factor receptor (EGFR) that may provide benefit to select cancer patients; however, identification of the characteristics of those patients who may benefit from its use is not complete. The ChemoFx® drug response marker (DRM) is an in vitro assay that can provide drug response data on tumor specimens before any patient treatment is initiated. We determined the feasibility of using the ChemoFx DRM to test tumor samples for sensitivity to cetuximab. We exposed four non-small cell lung carcinoma (NSCLC) cell lines (H358, H520, HCC827, and H1666) to cetuximab and determined their sensitivity using the ChemoFx DRM and, in parallel, EGFR status using immunocytochemistry, Western blotting, and In-Cell Western (TM) analysis. We used the ChemoFx DRM to determine cetuximab sensitivity of primary NSCLC and colorectal tumor samples. The ChemoFx DRM distinguished between cetuximab-sensitive and -resistant cell lines. Cetuximab sensitivity was not dependent on EGFR mutational status; H358 cells were non-responsive to cetuximab yet contain wild-type EGFR, whereas H1666 cells were intermediately responsive to cetuximab and contain wild-type EGFR. HCC827 (EGFR-mutant) cells were intermediately responsive and, as expected, H520 cells (EGFR-null) were non-responsive to cetuximab. ChemoFx-determined cetuximab sensitivity of primary NSCLC and colorectal tumor samples was 9.0% and 7.5%, respectively. Use of the ChemoFx DRM is feasible for determining cetuximab sensitivity. The ChemoFx-determined cetuximab responses of primary NSCLC and colorectal tumor specimens were similar to published response rates of patients to treatment with cetuximab monotherapy.

Analysis of chemotherapeutic response heterogeneity and drug clustering based on mechanism of action using an in vitro assay.

BACKGROUND: Cancer chemotherapeutic treatment is a complex scientific task. The ChemoFx Drug Response Marker (DRM) assists physicians in identifying treatment protocols likely to be effective for specific patients. MATERIALS AND METHODS: The ChemoFx DRM was used to study drug response in vitro. Established human cancer cell lines and primary cultures of patient tumor specimens were challenged with chemotherapeutic agents to observe response of multiple tumor samples and determine whether drugs with similar mechanisms of action elicit similar response. RESULTS: These studies demonstrated heterogeneous response among patient tumor samples and clustering of drug response with similar mechanisms of action. Also highlighted was the reproducibility of ChemoFx DRM and its utility in characterizing tumor response to chemotherapy. CONCLUSION: Heterogeneous drug responses observed in vitro were similar to those observed clinically. Response characteristics were similar for drugs with similar mechanisms of action, suggesting response heterogeneity is determined at a cellular and molecular level.

Differential sensitivity to platinum-based chemotherapy in primary uterine serous papillary carcinoma cell lines with high vs low HER-2/neu expression in vitro.

OBJECTIVE: We sought to identify effective chemotherapy regimens against uterine serous papillary adenocarcinoma (USPC). STUDY DESIGN: Six USPC, half of which overexpress HER-2/neu at 3+ level, were evaluated for growth rate and in vitro sensitivity to 14 single-agent chemotherapies and 5 combinations by ChemoFx (Precision Therapeutics Inc, Pittsburgh, PA). RESULTS: Cell lines overexpressing HER-2/neu showed higher proliferation when compared to low HER-2/neu-expressing cell lines and a lower half maximum inhibitory concentration (IC(50)) when exposed to the majority of single-agent chemotherapies. High HER-2/neu expressors were more sensitive to platinum compounds, manifesting a 5.22-fold decrease in carboplatin-IC(50) (P = .005) and a 5.37-fold decrease in cisplatin-IC(50) (P = .02). When all cell lines were analyzed as a group, chemotherapy agents tested demonstrated lower IC(50) when used in combination than as individual agents. CONCLUSION: USPC overexpressing HER-2/neu display greater in vitro sensitivity to platinum compounds when compared to low HER-2/neu expressors. Higher proliferative capability rather than increased drug resistance may be responsible for the adverse prognosis associated with HER-2/neu overexpression in USPC.

Assessment of erlotinib in chemoresponse assay.

BACKGROUND: There is a need to identify the subset of patients sensitive to epidermal growth factor receptor (EGFR) inhibition prior to using such treatments. MATERIALS AND METHODS: Three non-small cell lung cancer (NSCLC) cell lines (H292, H358, and Calu3) and 34 primary human lung tumor specimens were tested for chemoresponse to erlotinib. RESULTS: The assay distinguished responsiveness to erlotinib among NSCLC cell lines and human lung tumor explants. The H292 cells were responsive, the Calu3 cells were intermediate responsive and the H358 cells were non-responsive. These results were consistent with published tumor growth inhibition by erlotinib in xenografts derived from these cell lines. Out of the 34 patient specimens, 3 (8.8%) were responsive to erlotinib, 7 (20.6%) were intermediate responsive and 24 (70.6%) were non-responsive. CONCLUSION: The in vitro chemoresponse assay profile was similar to that noted for human tumors in clinical trials. Chemoresponse testing may help predict patient response to erlotinib and assist chemotherapy decision-making.

Comparison of angiogenesis-related factor expression in primary tumor cultures under normal and hypoxic growth conditions.

BACKGROUND: A localized hypoxic environment occurs during tumor growth necessitating an angiogenic response or tumor necrosis results. Novel cancer treatment strategies take advantage of tumor-induced vascularisation by combining standard chemotherapeutic agents with angiogenesis-inhibiting agents. This has extended the progression-free interval and prolonged survival in patients with various types of cancer. We postulated that the expression levels of angiogenesis-related proteins from various primary tumor cultures would be greater under hypoxic conditions than under normoxia. METHODS: Fifty cell sources, including both immortalized cell lines and primary carcinoma cells, were incubated under normoxic conditions for 48 hours. Then, cells were either transferred to a hypoxic environment (1% O2) or maintained at normoxic conditions for an additional 48 hours. Cell culture media from both conditions was collected and analyzed via an ELISA-based assay to determine expression levels of 11 angiogenesis-related factors: VEGF, PDGF-AA, PDGF-AA/BB, IL-8, bFGF/FGF-2, EGF, IP-10/CXCL10, Flt-3 ligand, TGF-beta1, TGF-beta2, and TGF-beta3. RESULTS: A linear correlation between normoxic and hypoxic growth conditions exists for expression levels of eight of eleven angiogenesis-related proteins tested including: VEGF, IL-8, PDGF-AA, PDGF-AA/BB, TGF-beta1, TGF-beta2, EGF, and IP-10. For VEGF, the target of current therapies, this correlation between hypoxia and higher cytokine levels was greater in primary breast and lung carcinoma cells than in ovarian carcinoma cells or tumor cell lines. Of interest, patient cell isolates differed in the precise pattern of elevated cytokines. CONCLUSION: As linear correlations exist between expression levels of angiogenic factors under normoxic and hypoxic conditions in vitro, we propose that explanted primary cells may be used to probe the in vivo hypoxic environment. Furthermore, differential expression levels for each sample across all proteins examined suggests it may be possible to build a predictor for angiogenesis-related anticancer agents, as each sample has a unique expression profile. Further studies should be performed to correlate in vitro protein expression levels of angiogenesis-related factors with in vivo patient response.

The ChemoFx assay: an ex vivo chemosensitivity and resistance assay for predicting patient response to cancer chemotherapy.

The ChemoFx Assay is an ex vivo assay designed to predict the sensitivity and resistance of a given patient's solid tumor to a variety of chemotherapy agents. A portion of a patient's solid tumor, as small as a core biopsy, is mechanically disaggregated and established in primary culture where malignant epithelial cells migrate out of tumor explants to form a monolayer. Cultures are verified as epithelial and exposed to increasing doses of selected chemotherapeutic agents. The number of live cells remaining post-treatment is enumerated microscopically using automated cell-counting software. The resultant cell counts in treated wells are compared with those in untreated control wells to generate a dose-response curve for each chemotherapeutic agent tested on a given patient specimen. Features of each dose-response curve are used to score a tumor's response to each ex vivo treatment as "responsive," "intermediate response," or "non-responsive." Collectively, these scores are used to assist an oncologist in making treatment decisions.

Ex vivo enrichment of malignant carcinoma cells in primary culture.

AIMS: Establishing and maintaining human tumours in primary culture can be challenging. In this application, a short-term primary culture process is desired to ensure cells maintained in culture are representative of the in vivo tumour for the purpose of chemoresponse testing. To ensure the appropriate cells are being grown, the cultures must be evaluated for malignancy. The clinical gold standard determination of malignancy is cytological evaluation by a cytopathologist. METHODS: Fifty human tumour specimens (breast, colon, lung, ovary) were established and maintained in primary culture. Cytospins were prepared upon initiation of culture and again at completion of the culture process. Cytospins were stained (Diff-Quik, Papanicolaou) and evaluated by a cytopathologist for the percentage of malignant cells at both times. RESULTS: An increase in the percentage of malignant cells was noted in 86% (43/50) of the cultures evaluated; 8% (4/50) of the cultures maintained the same percentage of malignant cells throughout the culture period, and 6% (3/50) displayed a decrease in malignant cells. On average, the percentage of malignant cells increased by 37% and was not associated with the length of culture (range 5-28 days). CONCLUSIONS: The described primary culture process enriches for malignant cells, which is desirable for further evaluation such as chemoresponse testing.

Difficulty demonstrating estradiol-mediated Erk1/2 phosphorylation in MCF-7 cells.

While some studies report that estradiol (E2) activates extracellular-signal regulated kinase (Erk1/2) in MCF-7 breast cancer cells, others report E2 does not activate this signaling pathway. This study attempted to resolve the conflicting reports by investigating experimental variables that could impact Erk1/2 activation using a high through-put assay that quantitatively assessed Erk1/2 phosphorylation. Variables tested included: cell staging and dosing regimes with and without charcoal-stripped serum, different MCF-7 cell sublines and culture densities and several E2 formulations and solvents. Levels of phosphorylated Erk1/2 were normalized to cellular protein rather than to total Erk1/2 protein because an antibody purported to recognize total Erk1/2 preferentially reacted with non-phosphorylated Erk1/2, potentially exaggerating the apparent level of Erk1/2 activation. Dosing MCF-7 cells with E2 containing small amounts of stripped serum induced Erk1/2 phosphorylation; however, this induction was largely attributed to serum factors. E2 administered in serum-free medium did not significantly alter Erk1/2 phosphorylation under any condition tested; immunocytochemistry corroborated this conclusion. While phosphatase inhibitors generally increased Erk1/2 phosphorylation, they did not impact E2-altered Erk1/2 phosphorylation. It remains important to resolve the basis of conflicting reports regarding E2-induced Erk1/2 activation due to the potential importance of this pathway on breast cancer and other processes.