Abstract P2-02-10: Circulating level of GP88/Progranulin is associated with clinical outcome and overall survival in stage 4 breast cancer patients

Monitoring of disease status in metastatic breast cancer (MBC) patients is a necessary step for an optimal management of patients during and post-therapy. Imaging technologies are the methods of choice in the standard of care to monitor therapy response and disease status in MBC patients. These methods are expensive, time-consuming and have limited sensitivity for real time monitoring. Measurements of circulating tumor markers CA15-3, CA125 and CEA have contributed, albeit with limitation, minimally invasive methods for MBC disease management. It is our hypothesis that measuring biomarkers involved in tumor biological processes may provide better evaluation of the disease state and thus aid real-time clinical management of MBC patients. Thus, addition of such new circulating disease biomarkers may improve the management of MBC patients. The 88kDa glycoprotein Progranulin (GP88/PGRN) fit these criteria. GP88/PGRN is expressed in tumor tissue and not in normal mammary tissue counterpart and secreted in the circulation of BC patients. Biological studies have established GP88/PGRN as a critical driver of BC cell proliferation, survival, invasiveness and drug resistance. Clinical studies have demonstrated that high tumor GP88/PGRN expression was prognostic for recurrence and that breast cancer patients had a statistically elevated GP88/PGRN serum level compared to healthy individuals. In the present study, we examined whether GP88/PGRN serum levels were elevated in MBC patients and whether GP88/PGRN circulating levels were correlated with patient clinical outcome and overall survival.

Under an IRB approved protocol at the University of Maryland Greenebaum Comprehensive Cancer Center, 101 stage 4 BC patients undergoing standard of care therapy and meeting the inclusion criteria were consented and enrolled. MBC patients' demographics, clinical and disease characteristics and therapies were collected as part of the study. Blood samples were collected from each patient at specific times at follow-up visits during and post-therapy. The prepared serum was stored at -80C until tested for GP88 using a GP88 enzyme linked immunoassay developed in our laboratory.

Statistical analysis using Kaplan-Meier functions established whether there was a correlation between GP88/PGRN serum level and overall survival in MBC patients. MBC patients with distinct survival characteristics (P=0.0002) could be stratified based on their circulating GP88/PGRN levels. Analysis of this association was carried out in MBC patients based on their age, race, tumor characteristics, receptor status and metastatic burden (number and sites of metastasis) and will be reported. We conclude that circulating levels of GP88/PGRN in MBC patients are correlated with overall survival and that monitoring circulating GP88/PGRN levels would provide additional information and valuable insight into real-time MBC disease status.

This work was supported by grant R43 CA 210817-01A1 to GS.

Citation Format: Serrero G, Hawkins D, Hicks D, Rosenblatt P, Tait N, Yue B, Tkaczuk K. Circulating level of GP88/Progranulin is associated with clinical outcome and overall survival in stage 4 breast cancer patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-10.

Abstract P1-03-06: Improvement in risk predictive value of Nottingham prognostic index by determining GP88 tumor tissue expression for estrogen receptor positive breast cancer patients

Background: The Nottingham Prognostic Index (NPI), which includes nodal status, tumor size and histological grade was established to provide predictive value information on post-surgery survival for primary breast cancer patients. Attempts to improve NPI's performance have included addition of other biomarker expression and morphological features such as vascular invasion. In the present study, we investigated whether expression of the autocrine growth and survival factor GP88 (progranulin), known to be overexpressed in breast cancer, whereas it is negative in normal mammary tissue, would improve NPI's predictive value.

Methods: We examined the tumor tissue GP88 expression by immunohistochemistry (IHC) in formalin fixed paraffin embedded tissue sections from 508 cases of estrogen receptor positive (ER+) invasive ductal carcinoma (IDC) with known clinical outcomes (disease-free and overall survivals) and with known NPI. GP88 IHC tumor tissue expression was determined using an anti-GP88 antibody (clone 6B3) developed in our laboratory. GP88 expression was scored (0, 1+, 2+, 3+) by two board certified pathologists and classified into two IHC score groups of GP88 < 3+ (0, 1+, 2+) and GP88 = 3+. The correlation between GP88 scoring, NPI and disease-free (DFS) and overall survival (OS) outcomes was then examined by Kaplan Meier analysis, Cox proportional Hazard (CPH) ratio and Pearson's C2 test.

Results: Kaplan-Meier survival graphs categorized by NPI scores (< 3.4, 3.4-5.4, and >5.4) and by GP88 expression (< 3+ and 3+) showed that for each NPI subgroup, patients with GP88 IHC score of 3+ had a worse disease-free survival (DFS) and overall survival (OS) than patients within the same NPI subgroup with tumors that had GP88 IHC score < 3+. When adjusted for NPI, high GP88 score was highly significantly associated with recurrence with a hazard ratio of 3.30 (95% CI 2.12 to 5.14).

Conclusions: The data suggest that measuring GP88 tumor tissue expression by IHC at time of diagnosis for breast cancer patients with primary ER+ IDC could provide recurrence prediction and survival information complementary to that provided by the determination of NPI alone and thus may be useful for risk management of patients diagnosed with breast cancer.

Citation Format: Serrero G, Hawkins DM, Bejarano PA, Ioffe O, Tkaczuk KR, Elliott RE, Head JF, Phillips J, Godwin AK, Weaver J, Hicks D, Yue B. Improvement in risk predictive value of Nottingham prognostic index by determining GP88 tumor tissue expression for estrogen receptor positive breast cancer patients [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 P1-03-06.

Abstract P1-02-12: Determination of a serum progranulin (GP88/PGRN) level associated with overall survival in metastatic breast cancer patients

Imaging technologies are the methods of choice in the standard of care (SOC) to monitor therapy response in metastatic breast cancer (MBC) patients. However, such methods are expensive and have limited sensitivity to detect disease response in a timely manner. Measurement of the circulating tumor markers such as CA15-3, CA27.29 and CEA has provided additional minimally invasive methods in disease management of MBC patients. While useful, they have limitations in providing clinicians with a reliable insight into real-time disease monitoring. Understanding of real-time biological processes may provide better biomarkers of the disease state and thus aid real-time clinical management of MBC patients by identifying circulating disease associated biomarkers. Thus, addition of such new circulating biomarkers may improve the management of MBC patients. We have characterized a target biomarker that would fit these criteria, the 88kDa glycoprotein Progranulin (GP88). GP88 is expressed in tumor tissue and not in normal mammary tissue counterpart and is secreted in the circulation of BC patients. Biological studies have established GP88 as one of the critical drivers for breast cancer cell proliferation, survival, invasiveness and drug resistance. Clinical studies have demonstrated that elevated GP88 tumor levels were prognostic for recurrence and that breast cancer patients had a statistically elevated GP88 serum level than healthy individuals. Using tissue and serum tests to detect and quantify GP88 could provide an new strategies for identifying patients at high risk of recurrence and monitoring disease progression in BC patients undergoing therapy. In the present study, we examined whether GP88 serum levels were elevated in MBC patients and whether GP88 serum levels were correlated to patient overall survival.

Under an IRB approved protocol, 92 MBC patients that met the inclusion criteria and were undergoing therapy at the UMGCCC Breast Clinic were consented and enrolled. Clinical and disease characteristics along with serum CA15-3 values were collected as part of the study. Serum samples were collected from each patient during therapy and subsequently the patients were monitored. The serum was stored at -80C until tested for GP88 using a GP88 enzyme linked immunoassay developed in our laboratory.

Statistical analysis using Kaplan-Meier functions established whether there was a correlation between GP88 serum level and overall survival in MBC patients. By analyzing the KM plots at different GP88 cut points, we identified two populations with distinct survival characteristics. When examined more thoroughly the difference in overall survival of patients with <60ng/ml and >60ng/ml was statistically significant (P=0.0002). Correlation analysis of serum GP88 and CA15-3 were performed and will be presented.

We conclude that circulating levels of GP88 in MBC patients are correlated with overall survival. It would appear that patients that can be managed to have a GP88 below 60ng/ml will survive longer. Thus measuring circulating GP88 levels would provide additional information to that available in today's SOC for monitoring. This valuable insight into real-time disease status will assist clinicians in patient management.

Citation Format: Serrero G, Hawkins DM, Yue B, Hicks D, Tait N, Tkaczuk KR. Determination of a serum progranulin (GP88/PGRN) level associated with overall survival in metastatic breast cancer patients [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 P1-02-12.

Abstract OT3-03-03: A prospective study of glycoprotein 88 (GP-88) blood test in healthy women undergoing screening for breast cancer (BC) with mammography (MM)

Background: Population based BC screening with XRAY mammography (MM) has been widely accepted as standard of care for women aged 40+ with average risk of developing BC. Sensitivity and specificity of MM is dependent on breast tissue density and up to ∼20% of BC are undetected by MM. The development of a dependable, low cost blood-based BC screening test to increase the sensitivity and specificity of currently existing BC screening methods is needed.

Rationale: GP88 is expressed & secreted by BC cells & is not expressed by normal mammary epithelial cells, 2 retrospective randomized multi-site trials (a training study & a validation study of 300 cases each) demonstrated that elevated GP88 expression in estrogen positive (ER+) invasive BC was statistically correlated with a 4-fold increase in the risk of 5-yr BC recurrence. GP88 was an independent predictor of BC recurrence in multivariate analysis of other factors such as PR expression, tumor size, grade, lymph node status & stage. The quantitative GP88 EIA was developed to determine the amount of GP88 in biological fluids. The blood based EIA assay is highly specific for GP88 & both sensitive & linear over a wide dynamic range, i.e. detection of GP88 concentrations from 0.1 to 20ng/ml. A baseline GP-88 level of28.4 ± 5 ng/ml was established by us for healthy volunteers (HV). In BC pts a statistically significant increase of serum GP88 was observed in early stage pts (40.7 ± 16 ng/ml; p=0.007). Stratification of BC pts according to their clinical outcomes shows that pts having no evidence of disease (NED) have serum GP88 levels within the range of HV. These data suggest that pts with breast tumors express & secrete high levels of GP88.

Objectives: 1. To determine prospectively GP-88 blood levels in HV at average risk of developing BC screened by MM & in women with recently biopsy-confirmed BC. 2. To establish the statistical distribution of GP88 serum levels in subjects by baseline BIRAD classification (1-6). 3. To determine if the initial GP88 level is predictive of change in BIRADS classification from baseline to 12-mos follow-up. 4. To determine if baseline GP88 level is predictive of the appearance of BC at 12 mos follow-up in HV who were cancer-free at study entry.

Inclusion Criteria: Female, aged >=40 yrs old, presenting for screening or diagnostic MM or diagnostic workup and/or biopsy due to abnormal MM <= to 12 wks before study entry.

Study procedures: Serum levels of GP88 in subjects with average BC risk factors will be measured prospectively at baseline; 3-6 mos & 6-12 mos & correlated with BIRADS reading of the screening MM, BIRADS 1-6; GP88 serum level will be correlated with pathologic results of breast biopsies performed on subjects with suspicious BIRADS (4 & 5) MM & final pathologically confirmed diagnosis of breast cancer as BIRADS 6.

Study Progress: The study is ongoing; currently we have 308 subjects enrolled, the total number of subjects will be up to 725 & screened up to 1400. Study is UM IRB approved & is conducted at the University od Maryland Medical Center (UMMC) and UM Baltimore Washington Medical Center (BWMC). Funding is provided by Maryland Industry Partnership Grant (MIPS)& Avon Grant No. 02-2013-018.

Citation Format: Tkaczuk KHR, Campassi C, Kesmodel S, Bellavance E, Rosenblatt P, Nichols E, Feigenberg SJ, Coughlin P, Drogula C, Urban B, Galandak J, Dromi S, Kuo L, Yue B, Hicks D, Serrero G. A prospective study of glycoprotein 88 (GP-88) blood test in healthy women undergoing screening for breast cancer (BC) with mammography (MM). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-03-03.

Abstract P3-05-12: Combination of anti-progranulin (GP88/PGRN) antibody and letrozole inhibits tumor formation of letrozole resistant breast cancer cell lines

The 88 kDa glycoprotein GP88 (Progranulin, PCDGF, acrogranin) is the largest member of the granulin/epithelin family of growth modulators identified as a driver of tumorigenesis. GP88 (PGRN) was also shown to be overexpressed in invasive ductal carcinoma (IDC)whereas it was negative in benign tumors and normal mammry epithelial tissue, thereby establishing GP88 as a therapeutic and diagnostic target in breast cancer (BC). Our laboratory has developed validated tools to measure GP88 in tumor biopsies and biological fluids as well as blocking its action. WE showed that GP88 was secreted and detected in the serum of BC patients at an increased level when compared to healthy subjects. Pathological studies with 530 cases of ER+ IDC with clinical outcomes showed that GP88 tumor expression was an independent prognostic indicator of recurrence in early stage BC patients. Training study followed by an independent validation study demonstrated that high GP88 tissue expression (GP88 3+) was associated with a 4-fold increase in risk of recurrence at 5 years. A neutralizing anti-GP88 antibody AG1 was expressed in a high yield CHO cell line was developed. The present study examined the effect of AG1 in letrozole resistant cell line AGLetR developed by long term selection in letrozole supplemented medium. This cell line showed decreased letrozole responsiveness in vivo and therefore constituted an excellent model for investigating letrozole resistance in vitro as well as in vivo. Here we report the results of studies investigating the effect of various doses of AG1 on LetR tumor development in combination with letrozole for AGLetR. We show that treatment with AG1 (10 mg/kg i.p.) in combination with letrozole was efficient to maintain long term responsiveness and inhibit tumor growth. Letrozole alone (5mg/kg) was unable to inhibit tumor growth and showed a doubling of tumor volume. Interestingly, long term combination treatment lead to tumor regression and inhibited tumor growth.

These data suggest that inhibiting GP88 could provide a novel and alternative therapeutic strategy for patients with resistance to anti-estrogen therapy, being tamoxifen or letrozole.

This works is supported by 2R44CA124179, HHSN 261201200060C, and HHSN2612014400C from NCI.

Citation Format: Serrero G, Dong J, Yue B, Hicks D, Hayashi J. Combination of anti-progranulin (GP88/PGRN) antibody and letrozole inhibits tumor formation of letrozole resistant breast cancer cell lines. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-05-12.

Abstract P5-09-05: Progranulin (GP88) expression and letrozole resistance in breast cancer

The 88 kDa glycoprotein GP88 (Progranulin, PCDGF, acrogranin) is the largest member of the granulin/epithelin family of growth modulators. GP88 was originally characterized in our laboratory through a biological screen to identify drivers of tumorigenesis. Published studies have established that GP88 represents an ideal therapeutic and diagnostic target in breast cancer (BC) leading to the development of validated tools to measure GP88 in tumor biopsies and biological fluids as well as blocking its action. It was shown that: 1) GP88 expression increases with tumorigenesis; 2) in ER+ breast cancer cells, GP88 stimulates proliferation and its overexpression confers estrogen independence and resistance to several anti-estrogens and aromatase inhibitor; 3) inhibition of GP88 expression by antisense transfection inhibited proliferation in vitro and in vivo; 4) In Her-2 overexpressing breast tumors, GP88 stimulated Her-2 phosphorylation and conferred trastuzumab resistance; 5) GP88 is expressed in 80% invasive ductal carcinoma (IDC) and 60% of ductal carcinoma whereas it is negative in lobular carcinoma, benign lesions and normal mammary tissues; 6) GP88 is secreted and can be detected in the serum of BC patients at an increased level when compared to healthy subjects; 7) Pathological studies with 530 cases of ER+ IDC with clinical outcomes showed that GP88 tumor expression was an independent prognostic indicator of recurrence in early stage BC patients. Training study followed by an independent validation study demonstrated that high GP88 tissue expression (GP88 3+) was associated with a 4-fold increase in risk of recurrence at 5 years.

Since GP88 displays not only diagnostic but also therapeutic potentials, we developed a neutralizing anti-GP88 antibody AG1 that inhibited GP88 biological effect (proliferation and migration) in a dose-dependent fashion in vitro. AG1 was expressed in a high yield CHO cell line and formulated. We have shown that in tamoxifen resistant cells, treatment with AG1 would inhibit tumor growth and restore tamoxifen sensitivity. The present study examined the effect of AG1 in letrozole resistant cells. We have developed from a letrozole sensitive cell ER+ BC cell line, a letrozole-resistant cell line by long term selection in letrozole-supplemented medium. This cell line (LetR) shows also decreased letrozole responsiveness in vivo and therefore constitutes an excellent model for investigating letrozole resistance in vivo as well as in vivo. Here we investigated the effect of various doses of AG1 on LetR tumor development alone or in combination with letrozole. Treatment with AG1 (10 mg/kg i.p.) in combination with letrozole was efficient to maintain long term responsiveness to letrozole and inhibited tumor growth. In addition to the mouse xenografts study, an IRB approved clinical study examines changes in GP88 circulating levels in patients with resistance to aromatase inhibitors. Preliminary data will be presented.

In conclusion, inhibiting GP88 could provide a novel and alternative therapeutic strategy for patients with resistance to anti-estrogen therapy, being tamoxifen or letrozole.

This work is supported by 2R44CA124179 and HHSN 261201200060C from NCI and 02- 2013-018 from the Avon Foundation for Women.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-05.

Abstract P2-10-40: Correlation between expression of the prognostic marker Progranulin (GP88) with Oncotype Dx Recurrence Score in estrogen receptor positive breast tumors

Background: GP88 (Progranulin, acrogranin) is an 88kDa glycoprotein overexpressed in breast tumors and involved in their proliferation and survival. Biological studies have shown that GP88 in ER+ breast cancer cells was associated with estrogen independence and resistance to anti-estrogen therapies and aromatase inhibitors. In addition, GP88 stimulated migration, invasion and angiogenesis, hallmarks of metastasis. Pathological studies have demonstrated that GP88 was preferentially expressed in invasive ductal carcinoma while lobular carcinoma was mostly negative. No expression was found in normal mammary tissue. Two retrospective studies totaling 530 cases of ER+ formalin-fixed paraffin-embedded invasive ductal carcinoma (IDC) established that high GP88 expression was associated with a 4-fold increase in risk of recurrence and 2.5-fold increase in death when compared to low GP88 scores. Multivariate analysis showed that GP88 remains a predictor of recurrence even when adjusted for prognostic factors such as tumor size, grade, stage, lymph node status and age. High level of GP88 was also found to be elevated in the serum of breast cancer patients when compared to healthy individuals. Since GP88 tumor tissue expression appears as a prognostic factor for ER+ breast cancer, we proposed to investigate whether GP88 tumor tissue expression would correlated to Oncotype Dx® Recurrence Score which is now for early stage ER+ node negative breast cancer patients.

Methods: Eight five cases from women ages 37–77 with ER+ invasive mammary carcinoma from three different institutions and with an available Oncotype Dx recurrence score were selected with approval from each site's IRB. GP88 expression was determined by immunohistochemistry (IHC) using the anti-human GP88 6B3 monoclonal antibody (A&G) on a Ventana automated staining platform. For all cases examined, GP88 IHC scores (0, 1+, 2+, 3+) were compared to routine clinicopathologic factors (tumor size, grade, and stage), PR, HER2/neu and Ki67 expression (by image analysis) and to their Oncotype DX® recurrence score (Genomic Health). The associations of GP88 with the parameters described above were assessed by t test or ANOVA.

Results: The GP88 tissue expression correlated with Oncotype Dx Recurrence score (p < 0.03) as well as with Ki-67 index (p < 0.004). Age, HER2/neu and PR status did not correlate with GP88 expression. Details of these finding will be presented here.

Conclusion: This study shows that GP88, an important tumor aggressiveness indicator, significantly correlates with Oncotype DX score and confirms that GP88 correlates with other tumor clinicopathologic parameters and prognostic markers. Further studies are underway to determine whether GP88 in combination with routine markers, particularly Ki67, could be used instead of Oncotype DX Assay to predict outcome and provide information for the management of ER+ breast cancer patients.

This study is supported by grant 02–2010-010 from the Avon Foundation for Women.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-40.

P2-12-32: Association between Progranulin (GP88) Expression and Recurrence Risk for Breast Cancer Patients with Estrogen Receptor Positive Invasive Ductal Carcinoma

Purpose: GP88 (progranulin) is a critical player of breast tumorigenesis for estrogen receptor positive (ER+) breast cancer. Pathological studies showed that GP88 was expressed in invasive ductal carcinoma (IDC), but not in normal mammary tissue, benign lesions or lobular carcinoma. The present study examines GP88 prognostic significance in association with recurrence risk for patients with ER+ IDC.

Patients and Methods: Two retrospective multi-site clinical studies examined GP88 expression by immunohistochemistry (IHC) analysis in paraffin-embedded tumor tissues in correlation with patients’ survival outcomes. The training study established a GP88 cut-off value associated with decreased disease-free (DFS) and overall (OS) survivals. The validation study verified the GP88 cut-off value and compared GP88 prognostic information with other prognostic factors in multivariate analysis.

Results: GP88 expression is associated with a statistically significant increase in recurrence risk for ER+ IDC patients. The training study established that GP88 3+ score by IHC analysis was associated with decreased DFS (p=0.0004) and OS (p=0.0036). The independent validation study verified that GP88 3+ score for the high risk group and demonstrated that GP88 3+ score was associated with a 5.9-fold higher hazard of disease recurrence and a 2.5-fold higher mortality hazard compared to patients with tumor GP88<3+. GP88 remained an independent risk predictor after considering age, nodal status, tumor size, tumor grade, progesterone receptor expression, treatment and disease stage.

Conclusion: Our training and validation studies demonstrate that the survival factor GP88 is a prognostic biomarker, predictive of recurrence risk and increased mortality for ER+ IDC patients, independent from other prognostic factors. These results provide support for measuring GP88 tissue expression for newly diagnosed early stage breast cancer patients.

This work was supported by grants R43CA124179, and U01CA113916 from the National Cancer Institute, grants 07-2007-064 and 02-2010-010 from the Avon Foundation for Women.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-32.

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.

GP88 Serum Level Is Increased in Breast Cancer Patients with Disease Progression

GP88 (progranulin) is an 88-kDa glycoprotein autocrine growth factor that plays a critical role in breast tumorigenesis. GP88 is expressed in human BC tumors in a positive correlation with their tumorigenicity. In estrogen receptor positive (ER+) cells, GP88 expression is low and is stimulated by estradiol whereas in ER negative (ER-) cells, it is constitutively overexpressed. In ER+ cells, increased GP88 expression was found to be associated with resistance to anti-estrogen therapy. In Her-2 overexpressing breast tumors, increased GP88 expression was associated with Herceptin resistance. Inhibition of GP88 expression in human breast adenocarcinoma cells resulted in a drastic reduction of tumor incidence and tumor growth in nude mice. Immunohistochemical studies carried out with 206 paraffin-embedded human breast biopsies have shown that GP88 is expressed in invasive ductal carcinomas in correlation with expression of markers of poor prognosis whereas normal tissues and benign breast lesions were negative. Importantly, high GP88 expression in tissue biopsies was accompanied by decreased disease-free and overall survival. Since GP88 contains a signal peptide for secretion, we have shown that GP88 can be found in serum. An IRB approve blood sampling study of 189 patients (Race: Caucasian- 91, African American-92, Asian-6; median age- 51 with a range from 26 to 81) established at the University of Maryland demonstrated that GP88 was measurable in serum and that GP88 serum level was statistically elevated in breast cancer patients when compared to healthy individuals. Median level of GP88 was 40.7 ng/ml (range 6.4-80) in early stage (stage 1 –3) BC pts (p- value = 0.007) and 45.3 ng/ml (range 9.8 to 158.4) in stage 4 metastatic BC patients (p-value= 0.0007). Statistically significant increase in circulating GP88 level was found in early stages as well as in metastatic disease when compared to healthy individuals.Since we have shown that GP88 tissue expression was associated with increased disease recurrence, the present study was focused on examining whether GP88 serum level was also increased in disease progression and could be used to monitor disease recurrence. Our data show that patients with disease recurrence or progression presented a 5 to 10 fold increase in their GP88 serum levels.This study identifies GP88 as a measurable biomarker for recurrence or disease progression not only at the tissue but also at the serum level.This study is supported by grants from MIPS, the Avon Foundation and from the National Cancer Institute.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6040.

Association of serum levels of the growth factor GP88 with disease progression in breast cancer patients

e22021

Background: The autocrine growth factor GP88 is an important player in breast cancer. GP88 is expressed in human BC tumors in correlation with their tumorigenicity. Increased GP88 expression was associated with anti-estrogen therapy resistance in ER+ cells and Herceptin resistance in Her-2 overexpressing breast tumors. Inhibition of GP88 expression inhibited tumor incidence and growth in nude mice. Immunohistochemical studies have shown that GP88 is expressed in invasive ductal carcinomas (IDC) and that high GP88 expression correlated with increased recurrence and mortality. Since GP88 is found in serum, we hypothesized that GP88 was elevated in the sera of breast cancer patients compared to healthy individuals and that GP88 serum level increases with disease progression. Methods: An IRB approved prospective study was established at the University of Maryland Breast Clinic to determine the serum level of GP88 in breast cancer patients (BC pts). Approximately 5 ml of blood was drawn every three months. GP88 serum concentration was determined in triplicate by human GP88 enzyme immunoassay. 190 BC pts were accrued. Sera from healthy volunteers (HV) were obtained to establish GP88 baseline. BC patient characteristics: Caucasian- 91, African American-92, Asian-6; median age, 51 (range 29- 86), stage I - 48, II - 52, III - 26, IV - 63. Results: Median serum GP88 level was 28.7 ng/ml (range 16.6–38.2) in HV, 40.7 ng/ml (range 6.4–100) in early stage (stage 1 -3) BC pts (p- value = 0.007) and 45.3 ng/ml (range 9.8 to 158.4) in stage 4 BC patients (p- value= 0.0007). Statistically significant increase in serum GP88 level was found in early stages as well as in metastatic disease when compared to HV. In addition, patients that were initially diagnosed with early stage disease but recurred showed a 5 to 10 fold increase in their GP88 serum levels. Conclusions: GP88 serum level is significantly higher in the sera of BC than HV subjects. Moreover, GP88 serum level increased in association with disease recurrence and progression. This study identifies GP88 as a measurable biomarker for disease progression not only at the tissue but also at the serum level. These results are also interesting since GP88 is also a therapeutic target of malignant progression of breast carcinoma.

No significant financial relationships to disclose.

Elevated serum levels of the growth factor GP88 are found in breast cancer patients when compared to healthy individuals

Abstract #2006

Background: GP88 is an autocrine growth factor that plays a critical role in breast tumorigenesis. GP88 is expressed in human BC tumors in a positive correlation with their tumorigenicity. Increased GP88 expression is associated with resistance to anti-estrogen therapy in ER + cells and with herceptin resistance in Her-2 overexpressing breast tumors. Inhibition of GP88 expression in human breast adenocarcinoma inhibited tumor incidence and growth in nude mice. Immunohistochemical studies have shown that GP88 was expressed in invasive ductal carcinomas in correlation with the expression of poor prognosis markers whereas normal tissues and benign lesions were negative. High GP88 expression in tumor biopsies was accompanied by decreased disease-free survival. Since GP88 can be secreted, we have hypothesized that GP88 could be secreted in the circulation and found in serum. We examined whether GP88 could be found in the circulation and whether GP88 could be elevated in the sera of breast cancer patients when compared to healthy individuals.
 Methods: An IRB approved blood sampling study was conducted at the University of Maryland Breast Clinic to determine the serum level of GP88 in healthy volunteers (HV) and breast cancer patients (BC pts). Serum GP88 concentration was determined in triplicate by quantitative enzyme immunoassay. 189 BC pts were accrued. In addition, sera from 18 HV were obtained to establish a GP88 baseline in healthy volunteers. BC patient characteristics: Race: Caucasian- 91, African American-92, Asian-6; median age, 51 (range 29-86), stage I – 48, II - 52, III – 26, IV - 63.
 Results: Circulating GP88 was measurable in the serum. Median level of GP88 was 28.7 ng/ml (range 16.6-38.2) in HV; 40.7 ng/ml (range 6.4-100) in early stage (stage 1 –3) BC pts (p- value = 0.007) and 45.3 ng/ml (range 9.8 to 158.4) in stage 4 metastatic BC patients (p-value= 0.0007). Statistically significant increase in circulating GP88 level was found in early stages as well as in metastatic disease. Correlation studies with BC prognostic factors such as stage, tumor size, lymph node involvement, tumor grade and presence of ER and HER-2 will be presented.
 Conclusion: GP88 can be detected in the sera of HV and BC pts. Comparison between the two groups of subjects indicates that GP88 level is significantly higher in the sera of BC pts. These studies are important as they identify as a measurable circulating biomarker GP88 that is also a therapeutic target of malignant transformation or malignant progression of breast carcinoma (BC). Future studies will examine whether there is any correlation between the serum level of GP88 and therapeutic response to systemic therapy in breast cancer patients.
 This study was supported by grant from MIPS, the Avon Foundation and 1R43 CA 124179-01A1 from the National Institutes of Health.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2006.

Tissue expression of the growth factor GP88 is a predictor of recurrence in patients with estrogen receptor positive breast tumors

Abstract #1088

Background
 Our laboratory is working on the characterization of novel breast cancer targets that have therapeutic an/or diagnostic applications. We have previously identified the growth factor GP88 as a significant player of breast tumorigenesis. GP88 is expressed in human breast cancer cells in a positive correlation with tumorigenesis. In estrogen receptor positive breast cancer cells, GP88 mediates estrogen proliferation effect and its increase is associated with resistance to anti-estrogen therapy. Inhibition of GP88 expression in human breast adenocarcinoma lead to inhibition of tumor incidence and tumor growth in nude mice. Pathological studies showed that ductal carcinoma expressed GP88 whereas benign lesions and normal mammary tissue were negative. Based on this evidence, the present study was carried out to investigate whether high GP88 expression in estrogen receptor positive invasive ductal carcinoma is associated with increased recurrence and decreased overall survival.
 Methods
 Under an IRB approved study, 239 archival formalin-fixed, paraffin-embedded estrogen receptor positive invasive ductal carcinoma with a minimum of 4 years follow-up were obtained from three United States tumor banks The clinical data included patients demographics such as age and race, tumor characteristics including tumor size, tumor grade, nodal status, disease stage and receptor status, time and type of first recurrence, time and status of last follow-up. GP88 expression was determined by immunohistochemistry using Oncostain 88TM IHC kit on five-micrometer sections. GP88 expression was scored as: <10% of cells staining – negative, >10% of cells staining – positive with positive staining graded from weak/focal (1+) to moderate/focal or diffuse (2+) to strong/diffuse (3+). The statistical analysis of GP88 expression in all cases was carried out. The Oncostain 88TM test performance was evaluated for its ability to predict disease-free (DFS) and/or overall survivals (OS) using Kaplan Meier curves and the Cox proportional hazards models for quantification of risk.
 Results
 The data show that ER+ cases with high GP88 expression (3+) had a hazard ratio for OS of 2.29 (95% CI, 1.38-3.78; p< 0.0013) and a HR for DFS of 2.88 (95% CI 1.59-5.24; p<0.0005). GP88 3+ remained highly significant for OS and DFS even when the data were adjusted for covariates such as nodal status, disease stage, tumor grade, tumor size, supporting the findings that GP88 brings independent information on the recurrence risk and overall survival of ER+ invasive ductal carcinoma.
 Conclusion
 This study demonstrates for the first time that high GP88 expression (3+) is a predictor of higher recurrence and increased mortality in ER+ IDC. These data provide a novel biomarker tissue assay (Oncostain 88TM) with prognostic significance in breast cancer.
 This study was supported by grant 1R43 CA 124179-01A1 from the National Institutes of Health.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1088.

Circulating levels of the breast cancer growth factor GP88 in the serum of breast cancer (BC) patients

20050

Background: The 88 kDa autocrine growth factor PC-Cell Derived Growth Factor (GP88) plays a critical role in breast tumorigenesis. GP88 expression was low in estrogen receptor positive cells, whereas in ER negative cells, it was constitutively overexpressed. Increased GP88 expression was associated with anti-estrogen therapy resistance in ER+ cells and Herceptin resistance in Her-2 overexpressing breast tumors. Antisense inhibition of GP88 expression in human breast adenocarcinoma lead to inhibition of tumor growth in vivo. Immunohistochemical studies have shown that GP88 was expressed in 80% of invasive ductal carcinomas in correlation with expression of poor prognosis markers whereas normal tissues and benign breast lesions were negative. Since GP88 is secreted by breast cancer cells, we examined whether GP88 was found in the circulation at an elevated level in the sera of breast cancer patients when compared to healthy individuals. Methods: A blood sampling study was conducted to determine the serum level of GP88 in healthy volunteers (HV) and breast cancer patients (BC pts). Ten ml of blood was drawn every three months to obtain serum. GP88 serum concentration was determined in triplicate by quantitative enzyme immunoassay using human GP88 as standard. 126 BC pts were accrued. . In addition, sera from 53 healthy volunteers were obtained to establish a GP88 baseline in HV. BC pts characteristics: race: Caucasian- 61, African American-60, Asian-5; median age: 52.5 (range 26–84), stage I-32, II-34, III-18, IV-42. Results: Circulating GP88 was measurable in the serum. Median level of GP88 was 32.8 ng/ml (range 15.3–42.8) in HV and 43.8 ng/ml (range 15.4–158.4) in BC pts, (p-value = 0.0007). Conclusions: GP88 is measurable in the sera of HV and BC pts. Comparison between the two groups indicates that GP88 level is significantly higher in the sera of BC pts. These studies are important since it identifies GP88 as a measurable biomarker that is also a therapeutic target of malignant transformation or malignant progression of breast carcinoma (BC). Future studies will examine the correlation of GP88 level with BC prognostic factors. Correlation between the serum level of GP88 and therapeutic response to systemic therapy in breast cancer patients will also be assessed.

[Table: see text]

Effect of resveratrol on the expression of autocrine growth modulators in human breast cancer cells

The effect of resveratrol on the growth of human breast cancer cells was examined. Resveratrol inhibited the growth of estrogen receptor-positive MCF-7 cells cultivated in the presence of estradiol in a dose-dependent fashion. At 10(-5) M, resveratrol maximally inhibited the growth stimulatory effect mediated by 10(-9) M estradiol without affecting cell viability. At the molecular level, resveratrol in a dose-dependent fashion antagonized the stimulation by estradiol of an estrogen response element reporter gene construct and of progesterone receptor gene expression in MCF-7 cells. Resveratrol also inhibited the proliferation of the estrogen-receptor negative human breast carcinoma cell line MDA-MB-468. These later data suggest that resveratrol can also inhibit breast cancer cell proliferation by another mechanism besides estrogen receptor antagonism. We show here that resveratrol altered the expression of several autocrine growth modulators and their receptors in MCF-7 cells. Resveratrol at 10(-5) M inhibited the expression of the autocrine growth stimulators transforming growth factor-alpha (TGF-alpha), PC cell-derived growth factor, and insulin-like growth factor I receptor mRNA. In addition, resveratrol significantly elevated the expression of the growth inhibitor TGF-beta2 mRNA without changes in TGF-beta1 and TGF-beta3 expression. These data suggest that resveratrol inhibits proliferation by altering autocrine growth modulator pathways in breast cancer cells.

Mediation of estrogen mitogenic effect in human breast cancer MCF-7 cells by PC-cell-derived growth factor (PCDGF/granulin precursor)

PC-cell-derived growth factor (PCDGF) is an 88-kDa glycoprotein corresponding to the granulin precursor. We have reported that PCDGF was expressed in human breast cancer cells. In estrogen-receptor positive cells, 17-beta-estradiol (E(2)) transcriptionally stimulated PCDGF expression in a dose- and time-dependent fashion. We demonstrate here that PCDGF mediates the mitogenic effect of E(2) in MCF-7 cells. PCDGF substituted for E(2) to stimulate DNA synthesis. The E(2) mitogenic effect was inhibited in a dose-dependent fashion by anti-PCDGF neutralizing antibody. Inhibition of PCDGF expression by antisense transfection also inhibited the E(2) mitogenic effect. In contrast, overexpression of PCDGF in MCF-7 cells resulted in cells that were able to proliferate in the absence of estrogen and were tamoxifen resistant. The PCDGF signaling pathway was examined. Like E(2), PCDGF stimulated mitogen-activated protein kinase activity. PCDGF could substitute for E(2) in stimulating cyclin D1 expression. The cyclin D1 stimulation by E(2) was 50% inhibited by anti-PCDGF antibody. In contrast, PCDGF did not stimulate c-myc expression, another molecular target of E(2). We conclude that autocrine PCDGF mediates the E(2) mitogenic effect via stimulation of cyclin D1. These studies provide information on estrogen action and identify an autocrine molecular target in human breast cancer cells.

Adipose differentiation related protein: expression, purification of recombinant protein in Escherichia coli and characterization of its fatty acid binding properties

Adipose differentiation related protein (ADRP) is a 53 kDa protein encoded by a cDNA originally cloned by differential hybridization from murine adipocytes. ADRP is induced during the early onset of the adipose differentiation program and is expressed at high level in mature adipocytes. We have demonstrated that ADRP stimulated the uptake of fatty acids thereby providing evidence for a functional role of ADRP in lipid metabolism. In the present paper, the murine ADRP has been expressed as a recombinant histidine-tagged protein in Escherichia coli, and purified from expressing cultures in order to examine its biochemical properties. We report here that the purified recombinant ADRP binds fatty acids and exhibits stoichiometric saturable binding of NBD-stearic acid with a K(d)=0.145+/-0.003 microM and a B(max)=0.99+/-0.05. Analysis of fluorescence emission spectra indicates that the polarity of the ADRP binding site is near epsilon approximately 23, close to that observed for fatty acid binding sites in other lipid binding proteins such as the liver fatty acid binding protein. The data presented here provide evidence that isolated ADRP purified in the experimental conditions described here can be used for functional studies.

High density lipoprotein-mediated cholesterol uptake and targeting to lipid droplets in intact L-cell fibroblasts. A single- and multiphoton fluorescence approach

Fluorescent sterols, dehydroergosterol and NBD-cholesterol, were used to examine high density lipoprotein-mediated cholesterol uptake and intracellular targeting in L-cell fibroblasts. The uptake, but not esterification or targeting to lipid droplets, of these sterols differed >100-fold, suggesting significant differences in uptake pathways. NBD-cholesterol uptake kinetics and lipoprotein specificity reflected high density lipoprotein-mediated sterol uptake via the scavenger receptor B1. Fluorescence energy transfer showed an average intermolecular distance of 26 A between the two fluorescent sterols in L-cells. Indirect immunofluorescence revealed that both fluorescent sterols localized to L-cell lipid droplets, the surface of which contained adipose differentiation-related protein. This lipid droplet-specific protein specifically bound NBD-cholesterol with high affinity (K(d) = 2 nM) at a single site. Thus, NBD-cholesterol and dehydroergosterol were useful fluorescent probes of sterol uptake and intracellular sterol targeting. NBD-cholesterol more selectively probed high density lipoprotein-mediated uptake and rapid intracellular targeting of sterol to lipid droplets. Targeting of sterol to lipid droplets was correlated with the presence of adipose differentiation related protein, a lipid droplet-specific protein shown for the first time to bind unesterified sterol with high affinity.

Inhibition of PC cell-derived growth factor (PCDGF, epithelin/granulin precursor) expression by antisense PCDGF cDNA transfection inhibits tumorigenicity of the human breast carcinoma cell line MDA-MB-468

PC-cell derived growth factor (PCDGF) is an 88-kDa growth factor originally purified from the highly tumorigenic teratoma PC cell line and corresponds to the epithelin/granulin precursor. In teratoma cells, PCDGF expression was shown to be essential for tumorigenicity. We have reported that PCDGF was expressed in estrogen receptor-positive (ER(+)) human mammary epithelial cells in an estrogen-dependent fashion. In this study, we have investigated PCDGF expression in human mammary epithelial cell lines ranging from immortalized nontumorigenic cells to ER(+) and ER(-) breast carcinoma cells. Northern and Western blot analyses indicated that PCDGF mRNA and protein expression was low in nontumorigenic cells and increased in human breast carcinomas cell lines in a positive correlation with their tumorigenicity. Treatment of the ER(-) MDA-MB-468 cells with anti-PCDGF neutralizing antibody resulted in a dose-dependent inhibition of their proliferation, suggesting that secreted PCDGF acted as an autocrine growth factor for breast carcinoma cells. We then examined the in vitro and in vivo growth properties of MDA-MB-468 cells, where PCDGF expression had been inhibited by antisense PCDGF cDNA transfection. Inhibition of PCDGF expression resulted in a reduced proliferation rate in vitro and a 60-80% reduction in colony formation. Tumor formation in vivo was dramatically inhibited in antisense cells with a 90% inhibition of tumor incidence and tumor weight. These results demonstrate the importance of PCDGF overexpression for the proliferation and tumorigenicity of ER(-) breast carcinomas and suggest that PCDGF overexpression may play an important role in human breast cancer.

Stimulation of adipose differentiation related protein (ADRP) expression in adipocyte precursors by long-chain fatty acids

Adipose differentiation related protein (ADRP) is a 50-kDa protein expressed in adipocytes and transcriptionally activated when adipocyte precursors differentiate into mature adipocytes. Recent experiments have demonstrated that ADRP is a fatty acid binding protein that specifically facilitates the uptake of long-chain fatty acids. The present investigation provides evidence that ADRP mRNA and protein expression in preadipocytes is stimulated by fatty acids in a time- and dose-dependent fashion. ADRP mRNA expression was maximally stimulated at fatty acid concentrations of or above 10(-5) M. Stimulation of ADRP expression was observed with the nonmetabolizable fatty acid 2-bromopalmitate and with natural fatty acids. Stimulation of ADRP mRNA expression by fatty acids peaked between 5 and 8 hr and decreased by 24 hr. Stimulation of ADRP expression by fatty acids was completely inhibited by treatment with actinomycin D, suggesting that fatty acid stimulates ADRP gene expression at the transcriptional level. Comparison of the effect of several fatty acids with varying carbon chain lengths indicated that long-chain fatty acids were active in stimulating ADRP, whereas short-chain fatty acids such as caproate and 2-bromooctanoate had no effect. The degree of saturation of fatty acids did not influence their ability to stimulate ADRP expression. These studies provide new information on the regulation of ADRP and identify a new target regulated by fatty acids during adipose differentiation.

Insulin but not IGF-I is required for the maintenance of the adipose phenotype in the adipogenic cell line 1246

The mouse adipogenic cell line 1246 which possesses both insulin and insulin-like growth factor I (IGF-I) receptors was used to investigate the role of IGF-I and insulin on the proliferation of adipocyte precursors and their differentiation into mature adipocytes. Results indicate that both insulin and IGF-I stimulate the proliferation of the 1246 adipocyte precursors with IGF-I being slightly more potent than insulin. Dose-response studies indicated that both polypeptides acted at physiological concentrations corresponding to binding to their own receptors. In contrast, comparison of insulin and IGF-I capacity to stimulate terminal adipose differentiation indicated that only insulin was active when added at physiological concentrations. IGF-I could not stimulate adipocyte differentiation except at supraphysiological concentrations (100 ng/ml and above) permitting its binding to the insulin receptors on 1246 cells. Time course study of expression of early and late markers of adipose differentiation indicated that the induction of markers such as adipose differentiation-related protein (ADRP), lipoprotein lipase (LPL) and fatty acid binding protein (FAB) took place even in the absence of insulin. However, the level of early and late differentiation markers decreased to a level below the one found in undifferentiated cells when cells had been maintained in the absence of insulin after differentiation had been initiated. These data indicate that although insulin is not necessary for the early onset of the adipose differentiation program, it is stringently required for the maintenance of the adipocyte phenotype and cannot be substituted by IGF-I.

Multiple forms of p55PIK, a regulatory subunit of phosphoinositide 3-kinase, are generated by alternative initiation of translation

A cDNA encoding p55PIK, one of the regulatory subunits of phosphoinositide (phosphatidylinositol) 3-kinase, was cloned from a cDNA library derived from the mouse mammary epithelial cell line C57MG. The cDNA coding for full-length p55PIK was transiently expressed in COS-7 cells. Western blot analysis of p55PIK expression using a specific antibody against p55PIK revealed that multiple protein products with different molecular masses were detected in COS-7 cell extracts. Experiments presented here demonstrate that multiple forms of p55PIK detected in COS-7 cells were produced by alternative initiation of translation. We also show that at least two in-frame start codons (AUG#2 and AUG#5) in p55PIK mRNA are used in COS-7 cells for the initiation of translation of p55PIK into proteins of 54 kDa and 50 kDa respectively. p55PIK mRNA was also alternatively translated into two proteins in PC cells, a mouse teratoma cell line, indicating that the alternative initiation of translation of p55PIK is not restricted to COS-7 cells. Results from immunoprecipitation and Western blot analysis showed that two forms (54 kDa and 50 kDa protein species) of p55PIK were detected in C57MG cells. Interestingly, when C57MG cells were treated with insulin, only p55PIK, but not p50PIK, bound to insulin receptor substrate-1 protein, providing evidence that different forms of p55PIKs may have specific distinct roles in signal transduction pathways.

Adipose differentiation related protein (ADRP) expressed in transfected COS-7 cells selectively stimulates long chain fatty acid uptake

Adipose differentiation related protein (ADRP) is a 50-kDa novel protein cloned from a mouse 1246 adipocyte cDNA library, rapidly induced during adipocyte differentiation. We have examined ADRP function, and we show here that ADRP facilitates fatty acid uptake in COS cells transfected with ADRP cDNA. We demonstrate that uptake of long chain fatty acids was significantly stimulated in a time-dependent fashion in ADRP-expressing COS-7 cells compared with empty vector-transfected control cells. Oleic acid uptake velocity increased significantly in a dose-dependent manner in ADRP-expressing COS-7 cells compared with control cells. The transport Km was 0.051 microM, and Vmax was 57.97 pmol/10(5) cells/min in ADRP-expressing cells, and Km was 0.093 microM and Vmax was 20.13 pmol/10(5) cells/min in control cells. The oleate uptake measured at 4 degrees C was only 10% that at 37 degrees C. ADRP also stimulated uptake of palmitate and arachidonate but had no effect on uptake of medium chain fatty acid such as octanoic acid and glucose. These data suggest that ADRP specifically enhances uptake of long chain fatty acids by increasing the initial rate of uptake and provide novel information about ADRP function as a saturable transport component for long chain fatty acids.

Resveratrol, a natural product derived from grape, exhibits antiestrogenic activity and inhibits the growth of human breast cancer cells

Resveratrol is a natural phytoalexin compound found in grapes and other food products. In this study, the effect of resveratrol on the growth of human breast cancer cells was examined. Results show that resveratrol inhibits the growth of estrogen receptor(ER)-positive MCF-7 cells in a dose-dependent fashion. Detailed studies with MCF-7 cells demonstrate that resveratrol antagonized the growth-promoting effect of 17-beta-estradiol (E2) in a dose-dependent fashion at both the cellular (cell growth) and the molecular (gene activation) levels. At 5 x 10(-6) M, resveratrol abolished the growth-stimulatory effect mediated by concentrations of E2 up to 10(-9) M. The antiestrogenic effect of resveratrol could be observed at a concentration of 10(-6) M and above. The antiestrogenic effect of resveratrol was also demonstrated at the molecular level. Resveratrol in a dose-dependent fashion antagonized the stimulation by E2 of progesterone receptor gene expression in MCF-7 cells. Moreover, expression of transforming growth factor-alpha and insulin-like growth factor I receptor mRNA was inhibited while the expression of transforming growth factor beta2 mRNA was significantly elevated in MCF-7 cells cultivated in the presence of resveratrol (10(-5) M). In summary, our results show that resveratrol, a partial ER agonist itself, acts as an ER antagonist in the presence of estrogen leading to inhibition of human breast cancer cells.

Stimulation of PC cell-derived growth factor (epithelin/granulin precursor) expression by estradiol in human breast cancer cells

PC cell-derived growth factor (PCDGF) is an 88 kDa glycosylated protein isolated from a highly tumorigenic mouse teratoma derived cell line which is similar to the epithelin/granulin precursor. Using Northern blot and western blot analyses, we detect the expression of PCDGF mRNA and protein in MCF-7 human breast cancer cells. We show that 17-beta-estradiol stimulates PCDGF mRNA and protein expression in a time and dose-dependent manner. The stimulation of PCDGF expression by 17-beta-estradiol was observed as early as 4 hours and reached a maximum at 12 hours. Maximal stimulation of PCDGF mRNA and protein expression by 17-beta-estradiol was observed at a concentration of 10(-8) M. The stimulation of PCDGF expression by 17-beta-estradiol was completely inhibited by treatment with actinomycin D and with the antiestrogen 4-hydroxytamoxifen. The stimulation of PCDGF expression was also demonstrated in another human estrogen-responsive cell line T47D. The results presented here provide evidence of a novel estradiol responsive gene product in human breast cancer cell lines and give information about the hormonal control of epithelin/granulin (PCDGF) expression in these cells.

Inhibition of adipose differentiation by phosphatidylinositol 3-kinase inhibitors

Phosphatidylinositol (PI) 3-kinase plays an important role in various cellular signaling mechanisms in several cell systems. The role of PI 3-kinase in adipose differentiation was investigated. For this purpose, we examined the effect of specific inhibitors of PI 3-kinase on the differentiation of two adipogenic cell lines, 1246 and 3T3-L1. The results show that two structurally different inhibitors of PI 3-kinase, i.e., LY294002 and wortmannin, blocked adipose differentiation in a time and dose-dependent fashion. The results from time- course studies indicated that PI 3-kinase activity is most important in the early phase (day 4 to day 6) of the differentiation program. The effect of PI 3-kinase inhibitor on the expression of the peroxisome proliferator-activated receptor (PPAR) gamma, a master regulator in adipogenesis induced during the differentiation process, was also examined. LY294002 significantly inhibited the induction of PPARgamma mRNA expression. During the initiation phase of adipogenesis (day 4 to day 6), the expression of PPARgamma was induced and LY294002 blocked the increase of expression of PPARgamma mRNA. The inhibition of expression of PPARgamma may provide a molecular mechanism for the action of PI 3-kinase inhibitors on adipose differentiation.

Inhibition of tumorigenicity of the teratoma PC cell line by transfection with antisense cDNA for PC cell-derived growth factor (PCDGF, epithelin/granulin precursor)

The PC cell line is a highly tumorigenic, insulin-independent, teratoma-derived cell line isolated from the nontumorigenic, insulin-dependent 1246 cell line. Studies of the PC cell growth properties have led to the purification of an 88-kDa secreted glycoprotein called PC cell-derived growth factor (PCDGF), which has been shown to stimulate the growth of PC cells as well as 3T3 fibroblasts. Sequencing of PCDGF cDNA demonstrated its identity to the precursor of a family of 6-kDa double-cysteine-rich polypeptides called epithelins or granulins (epithelin/granulin precursor). Since PCDGF was isolated from highly tumorigenic cells, its level of expression was examined in PC cells as well as in nontumorigenic and moderately tumorigenic cells from which PC cells were derived. Northern blot and Western blot analyses indicate that the levels of PCDGF mRNA and protein were very low in the nontumorigenic cells and increased in tumorigenic cell lines in a positive correlation with their tumorigenic properties. Experiments were performed to determine whether the autocrine production of PCDGF was involved in the tumorigenicity of PC cells. For this purpose, we examined the in vivo growth properties in syngeneic C3H mice of PC cells where PCDGF expression had been inhibited by transfection of antisense PCDGF cDNA. The results show that inhibition of PCDGF expression resulted in a dramatic inhibition of tumorigenicity of the transfected cells when compared with empty-vector control cells. These data demonstrate the importance in tumor formation of overexpression of the novel growth factor PCDGF.

cDNA cloning and expression of a novel family of enzymes with calcium-independent phospholipase A2 and lysophospholipase activities

Previous studies have suggested that activation of calcium-independent PLA2 (CaIPLA2) is an early event in cell death after hypoxic injury in proximal tubule cells. An approximately 28-kD CaIPLA2 with preferential activity toward plasmalogen phospholipids has been recently purified from rabbit kidney cortex (D. Portilla and G. Dai, J Biol Chem 271, 15,451-15,457, 1996). Their report describes the cloning of a full-length rat cDNA encoding CaIPLA2, using sequences derived from the purified rabbit kidney cortex enzyme. In addition, cDNA from rabbit kidney that encode the rabbit homologue of the enzyme and a closely related isoform were isolated. The rat cDNA is predicted to encode an approximately 24-kD protein, and each cDNA contains the sequence G-F-S-Q-G, which fits the active site consensus sequence G-X-S-X-G of carboxylesterases. Several lines of evidence (DNA sequence comparison, Southern blot analysis, and examination of the expressed sequence tag database) show that CaIPLA2 enzymes are encoded by a multigene family in rats, mice, rabbits, and humans. Northern analysis of various tissues from the rat indicated that the CaIPLA2 gene is ubiquitously expressed, with highest mRNA abundance observed in the kidney and small intestine. The rat CaIPLA2 cDNA, when expressed in a baculovirus expression system, and the purified rabbit kidney cortex protein exhibit both CaIPLA2 and lysophospholipase activities. The cloned CaIPLA2 cDNA are expected to aid in understanding the role of CaIPLA2 in cell death after hypoxic/ischemic cell injury.

Identification of cell surface binding sites for PC-cell-derived growth factor, PCDGF, (epithelin/granulin precursor) on epithelial cells and fibroblasts

PC cell derived growth factor (PCDGF) is an 88-kDa glycoprotein purified from the culture medium of the highly tumorigenic mouse teratoma-derived cell line PC. PCDGF was shown to stimulate the proliferation of 3T3 fibroblasts and PC cells. Amino acid sequencing of PCDGF indicated its identity to the precursor for the 6-kDa polypeptides epithelins and granulins. In this paper, we investigated the binding of PCDGF to the mink lung epithelial cell line CCL64. Scatchard analysis indicates that 125I-PCDGF binding to CCL64 cells is curvilinear, corresponding to the existence of two classes of binding sites: high affinity binding sites (560 +/- 170 sites/cell) with a Kd1 of 43 +/- 15 pM and low affinity binding sites (16,350 +/- 5900 sites/cell) with a Kd2 of 3.9 +/- 1.9 nM. 125I-PCDGF was chemically crosslinked to cell surface receptors on CCL64 cells with disuccinimidyl suberate. A major crosslinked band of about 190 kDa with radiolabeled PCDGF was detected after SDS-PAGE, suggesting the presence of PCDGF binding sites with molecular weight of about 120 kDa. 125I. PCDGF crosslinking studies indicate the presence of PCDGF binding sites with a molecular weight similar to those of binding sites on CCL64 cells on the surface of two other PCDGF-responsive cell lines, 3T3 fibroblasts and PC cells. These data suggest that the receptors for PCDGF are widely distributed on cells of distinct embryonic origin.

Stimulation of adipose differentiation related protein (ADRP) expression by ibuprofen and indomethacin in adipocyte precursors and in adipocytes

Adipose differentiation related protein (ADRP) is a 50 kDa protein expressed at high level in differentiated adipocytes. ADRP expression is very low in undifferentiated adipocytes and increases rapidly and dramatically as the cells undergo adipose differentiation. In the present study, we demonstrate that ADRP expression at the mRNA and protein level is stimulated in adipocyte precursor cells in a time- and dose-dependent fashion by treatment with cyclooxygenase inhibitors, particularly indomethacin and ibuprofen. Lipoxygenase inhibitors such as AA861 and nordihydroguaiaretic acid were ineffective. Stimulation of ADRP expression was observed with 10(-5) M ibuprofen but maximal stimulation required a concentration of 3 x 10(-4) M. Nuclear run-on experiments indicated that indomethacin or ibuprofen stimulated the transcription of the ADRP gene in undifferentiated adipocytes. In addition to stimulating the induction of ADRP in undifferentiated cells, ibuprofen and indomethacin also stimulated the level of ADRP mRNA and protein in differentiated adipocytes. These experiments provide new information on the regulation of ADRP, an early inducible gene in the adipocyte differentiation programme in adipocyte precursors and in adipocytes and identify a new target for cyclooxygenase inhibitor action during adipocyte differentiation.

Adipose differentiation-related protein is an ubiquitously expressed lipid storage droplet-associated protein

The adipose differentiation-related protein (ADRP) was first characterized as a mRNA induced early during adipocyte differentiation (Jiang, H. P., and G. Serrero. 1992. Proc. Natl. Acad. Sci. USA. 89:7856-7860). The present study demonstrates that ADRP mRNA is expressed in a variety of tissues and cultured cell lines. Immunocytochemical examination revealed that ADRP localizes to neutral lipid storage droplets in cultured murine 3T3-L1 adipocytes, murine MA-10 Leydig cells, Chinese hamster ovary (CHO) fibroblasts, and human HepG2 hepatoma cells; the association of ADRP with lipid droplets was confirmed by subcellular fractionation of MA-10 Leydig cells. In addition to ADRP, steroidogenic cells and adipocytes express the perilipins, a family of lipid droplet-associated proteins that share a highly related sequence domain with ADRP. ADRP and perilipins co-localize on lipid droplets in MA-10 Leydig cells. While ADRP was found on small lipid droplets in 3T3-L1 preadipocytes and early differentiated adipocytes, it was absent in maturing adipocytes. In contrast, perilipins were absent early during differentiation, but were found on small and large lipid droplets at later stages. The transition in surface protein composition of adipocyte lipid droplets from ADRP to perilipins occurred 3 days after the initiation of differentiation when cells displayed co-localizatioin of both proteins on the same lipid droplets. The specific localization of adipose differentiation-related protein to lipid droplets in a wide variety of cells suggests that ADRP plays a role in management of neutral lipid stores.

Prostaglandin F2alpha receptor (FP receptor) agonists are potent adipose differentiation inhibitors for primary culture of adipocyte precursors in defined medium

Prostaglandin F2alpha inhibits adipose differentiation of primary culture of adipocyte precursors and of the adipogenic cell line 1246 in defined medium. In the present paper, we investigated the effect of FP receptor agonists cloprostenol and fluprostenol on the differentiation of newborn rat adipocyte precursors in primary culture. The results show that cloprostenol and fluprostenol are very potent inhibitors of adipose differentiation. Dose response studies indicate that both agonists are more potent than PGF2alpha in inhibiting adipocyte precursors differentiation. 50% inhibition of adipose differentiation was observed at a concentration of 3 x 10(-12) M for cloprostenol and 3 to 10 x 10(-11) M for fluprostenol respectively whereas the PGF2alpha concentration required to elicit the same effect was 10(-8) M. In contrast compounds structurally related to PGE2 such as 17-phenyl trinor PGE2 had no effect on adipose differentiation except when added at a 10,000-fold higher concentration.

Endocrine and paracrine negative regulators of adipose differentiation

Obesity which is characterized by an abnormal adipose tissue development is a first degree public health hazard in industrialized countries. One important aspect in the study of adipose tissue development is to investigate the hormonal control of proliferation and differentiation. Any qualitative or quantitative change in these hormones or their receptors can result in abnormalities in the process of proliferation and/or differentiation possibly leading to obesity. Therefore, it is important to identify these factors and investigate their mechanism of action. We have concentrated our efforts in the study of factors triggering differentiation (positive regulators) and also of factors inhibiting differentiation (negative regulators). The present paper provides evidence of the importance of EGF/TGF-alpha and of PGF2 alpha as differentiation inhibitors for adipocyte precursors in primary culture. Data presented here also demonstrate that TGF-alpha is expressed in adipose tissue and that its expression is specifically stimulated by PGF2 alpha, thus suggesting the existence of an amplification mechanism between two differentiation inhibitors within the adipose tissue. The importance of these two types of differentiation inhibitors in the regulation of adipose tissue development is discussed.

Prostaglandin F2 alpha stimulates transforming growth factor-alpha expression in adipocyte precursors

Transforming growth factor-alpha (TGF alpha) and prostaglandin F2 alpha (PGF2 alpha) are potent inhibitors of adipocyte differentiation. We demonstrate here that TGF alpha messenger RNA (mRNA) is expressed in freshly isolated fat pads and in primary culture of adipocyte precursors cultivated in defined medium before and after differentiation. We show that PGF2 alpha stimulated TGF alpha mRNA expression in a dose-dependent manner. PGF2 alpha also stimulated TGF alpha production in the culture medium of adipocyte precursors in primary culture. PGF2 alpha stimulated TGF alpha mRNA expression in both undifferentiated and differentiated cells. 9 alpha,11 beta-PGF2 alpha, which also inhibited adipose differentiation, stimulated TGF alpha mRNA expression similarly to PGF2 alpha, whereas other PGs had no effect on TGF alpha mRNA expression. The time-course experiment indicates that the stimulation of TGF alpha mRNA expression by PGF2 alpha is observed within 6 h of exposure to PGF2 alpha and is inhibited by treatment of the cells with actinomycin D. The effect of PGF2 alpha on TGF alpha expression did not require activation of protein kinase C and was fully reversible. As both TGF alpha and PGF2 alpha are inhibitors of adipose differentiation, it is suggested that stimulation of TGF alpha expression by PGF2 alpha could represent an amplification mechanism to modulate adipocyte precursor differentiation and adipocyte function within the adipose tissue.

Prostaglandin F2 alpha inhibits epidermal growth factor binding to cellular receptors on adipocyte precursors in primary culture

Prostaglandin F2 alpha (PGF2 alpha) and epidermal growth factor (EGF) are potent differentiation inhibitors of adipocyte precursors in primary culture. We show here that PGF2 alpha specifically inhibited EGF binding to adipocyte precursors in a dose dependent fashion. Scatchard analysis indicates that PGF2 alpha causes a 50% decrease in the number of available EGF cell surface receptors without change in receptor affinity. Comparison of EGF binding at different temperatures and on fixed cells indicates that PGF2 alpha increases internalization of EGF-receptor complexes in adipocyte precursors. Phorbol myristate acetate (PMA) also inhibited EGF binding in adipocyte precursors. PGF2 alpha effect was abolished in cells exposed to prolonged treatment with PMA indicating that PGF2 alpha effect on EGF binding is mediated by protein kinase C. These results would suggest that in adipocyte precursors PGF2 alpha may be the physiological mediator of phorbol ester effect on EGF receptor properties.

Characterization of calcium-independent cytosolic phospholipase A2 activity in the submucosal regions of rat stomach and small intestine

This study was undertaken to compare the calcium-independent phospholipase A2 (PLA2) activities in the cytosols of twelve rat tissues and to determine whether their activities were distinct. 1-O-Alk-1'-enyl-2-[14C]-oleoyl-sn-glycero-3-phosphocholine (PlsC) and 1-O-Alk-1'-enyl-2-[14C]oleoyl-sn-glycero-3-phosphoethanolamine (PlsE) were synthesized and used as substrates, instead of phosphatidyl compounds, to exclude hydrolysis by cytosolic PLA1 activity that could be present in some of the cytosolic preparations. For each tissue, we examined substrate specificity, pH optimum, and effect of adenosine triphosphate (ATP) and ATP analogues. PLA2 activity was detected in eleven out of the twelve issues examined. Based on substrate specificity and pH optimum, cytosolic calcium-independent PLA2 were classified in three groups. The first group, which included PLA2 from small intestine, stomach and spleen, had the highest specific activity with PlsC as substrate (1253, 309 and 75 nmol/mg protein/hour, respectively) and an optimal pH at 6.5. Activity with PlsE as substrate was much lower (20-37%) than with PlsC. The second group of PLA2 activities included the cytosolic activities from thymus, lung, liver and pancreas that showed lower specific activities for both substrates (14-23 nmol/mg protein/hour with PlsC) and had a broader optimal pH range of 6.1 to 7.5. The cytosols from brain, kidney, heart and muscle comprised the third PLA2 group that was found to have a higher specific activity with PlsE (5-20 nmol/mg protein/hour) than PlsC and an optimal pH range from 7.4 to 7.9.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of adipose differentiation by 9 alpha, 11 beta-prostaglandin F2 alpha

Prostaglandin F2 alpha (PGF2 alpha) is a potent adipose differentiation inhibitor for the adipogenic cell line 1246 and for adipocyte precursors in primary culture with an ED50 of 3 x 10(-8) M. In this paper, we examined the effect of several prostaglandins which have structural similarities with PGF2 alpha on the differentiation of 1246 cells and of adipocyte precursors in primary culture. The results show that only 9 alpha,11 beta-PGF2 alpha is as potent as PGF2 alpha to inhibit differentiation of adipocyte precursors in primary culture and of the adipogenic cell line 1246. In the presence of 9 alpha,11 beta-PGF2 alpha, the cells remained fibroblast-like, typical of undifferentiated adipocyte precursors. Triglyceride accumulation and increase of specific activity for glycerol-3-phosphate dehydrogenase were inhibited. In addition, mRNA expression of early markers of differentiation such as lipoprotein lipase (LPL) and fatty acid binding protein (FAB) was decreased. The isomer 9 beta,11 alpha-PGF2 alpha and other PGF2 alpha derivatives were inactive. These results provide new information on the biological activity of 9 alpha,11 beta-PGF2 alpha as an inhibitor of adipose differentiation and about the structural characteristics of prostaglandins required for maintenance of a high adipose differentiation inhibitory effect.

A novel mouse gene highly conserved throughout evolution: regulation in adipocyte differentiation and in tumorigenic cell lines

A cDNA clone referred to as 168 was previously isolated from mouse 1246 adipocytes by differential hybridization on the basis of its down regulation in adipocytes when compared to preadipocytes. 5' RACE was used to obtain a full length clone of 761 bp encoding for a highly basic 25 kD polypeptide that is extremely conserved in several diverse species of eukaryotes. There is a single amino acid substitution at position 202 compared to the human homolog, QM, a putative tumor suppressor. Clone 168 mRNA decreases 80% in rat primary culture of adipocytes compared to preadipocytes and does not decrease when differentiation is blocked by PGF2 alpha or EGF, indicating that the decrease is correlated with expression of the differentiation phenotype. Finally, two 1246 cell line variants that exhibit altered growth and increased tumorigenicity have a similar level of 168 mRNA when compared to the non tumorigenic adipogenic parent cell line.

Structure of the gene encoding mouse adipose differentiation-related protein (ADRP)

Adipose differentiation-related protein (ADRP) is a novel 50-kDa membrane-associated protein whose message levels are induced rapidly and maximally after triggering adipocyte differentiation. The gene encoding mouse ADRP has been isolated and characterized from four overlapping lambda phage clones. The gene spans 14 kb and contains 8 exons and 7 introns. Exons range in size from 50 to 696 bp and intron sizes range from 87 bp to 4.3 kb. Major and minor transcription initiation sites were determined 76 and 78 bp, respectively, upstream of the initiator methionine. A TATTTTA sequence is centered 30 bp upstream of the major transcription start site, and within the 5'-flanking region there are several putative transcription factor binding sites. ADRP has been mapped to chromosome 4, specifically between the b and Ifa loci. A second ADRP-like gene was isolated and partially characterized. This second locus is not expressed in 12 different mouse tissues and shares 87% sequence similarity to ADRP over exon and intron regions analyzed. Finally, this is the first reported genomic structure of ADRP.

Purification of an autocrine growth factor homologous with mouse epithelin precursor from a highly tumorigenic cell line

PC cell line is a highly tumorigenic insulin-independent variant from the teratoma-derived adipogenic cell line 1246. Culture medium of PC cells contains a growth promoting activity for 3T3 cells and producer cells. PC cell-derived growth factor (PCDGF) was purified to homogeneity from PC cell-conditioned medium as an apparent 88-kDa protein by chromatography on heparin-Sepharose, Sephacryl S-200, and phenyl-Sepharose. Digestion with peptide-N-glycosidase F yielded an apparent 68-kDa protein component indicating that PCDGF is a glycoprotein containing about 20 kDa of carbohydrate. Partial sequence from Edman degradation of peptide fragments obtained by digestion of PCDGF with cyanogen bromide and trypsin demonstrates that PCDGF contains regions of sequence identity to that deduced from the granulin or epithelin precursor cDNAs. Granulins are small polypeptides purified from granulocyte extracts with no apparent biological functions. Epithelins are cell growth modulators purified as small molecular mass 6-kDa polypeptides from kidney extracts. The existence of a large molecular mass precursor for granulin or epithelin has been predicted based upon recently cloned cDNAs encoding these biomolecules within a 63.5-kDa protein with putative glycosylation sites. No biological activity has previously been attributed to the precursor. The present results indicate that PCDGF is a potential precursor for epithelin and/or granulin, that this 88-kDa protein is secreted and glycosylated, and that it can function as a mitogen for 3T3 cells as well as an autocrine growth factor for PC cells.

Impaired epidermal growth factor production in genetically obese ob/ob mice

Epidermal growth factor (EGF) is a potent inhibitor of adipose differentiation in vitro and delays adipose tissue development in vivo. Here we show that in the homozygous male obese mice the level of EGF in the submaxillary gland and plasma is significantly lower than in the glands and plasma of age-matched control littermates. This EGF deficiency in ob/ob mice was observed as early as 5 wk of age when obesity had just become apparent and was also found in adult mice. The level of prepro-EGF mRNA expression in the submaxillary gland was also lower in obese mice than in control littermates. However, the level of kidney prepro-EGF mRNA was the same in mice with both phenotypes, suggesting that the regulation of prepro-EGF mRNA expression is different in both tissues. These results indicate that genetic obesity in mice is accompanied by a decrease in the production of EGF.

Nucleotide sequence of the C-terminal region of the mouse epidermal growth factor receptor and expression in teratoma-derived cell lines with increased tumorigenic properties

The isolation of a cDNA corresponding to a portion (amino acid 943 to 1073) of the cytoplasmic domain of the mouse EGF receptor surrounding the auto phosphorylation sites was obtained by using the reverse transcriptase polymerase chain reaction (RT-PCR) approach. Deduced amino acid sequence of mouse EGF receptor (EGFr) shows a 92% and 76% homology to corresponding regions in the human and the chicken EGFr, respectively. This cDNA was used to develop a sensitive RNase protection assay to investigate EGF receptor mRNA expression in mouse C3H teratoma derived cell lines with increased tumorigenic properties which display a progressive decrease of EGF binding and response. The results show that increased tumorigenicity was not accompanied by a change in EGF receptor mRNA expression. Moreover, they indicate that the RNase protection assay developed using the probe described here is a sensitive approach to investigate EGF receptor expression in murine cells.

Fibroblast growth factor inhibits proliferation of a highly tumorigenic insulin-independent teratoma-derived cell line

The present paper examines the effect of basic fibroblast growth factor (bFGF) on the proliferation of teratoma-derived cell lines having increased tumorigenic properties isolated from the non-tumorigenic adipogenic cell line 1246. Although FGF is a mitogen for the non tumorigenic 1246 cells and for the moderately tumorigenic 1246-3A cells derived from the 1246 cells, bFGF inhibits the proliferation and DNA synthesis of the highly tumorigenic PC cells starting at concentration as low as 30 pg/ml. The inhibitory effect of FGF on PC cell growth is irreversible as demonstrated by the inability of the cells to resume proliferation once FGF is removed from the culture medium. Comparison of 125I-bFGF binding to the three cell lines was performed. Based on the Scatchard analysis of the binding data, PC cells display only low affinity class of FGF binding sites whereas 1246 and 1246-3A cells presented also high affinity binding sites. The inhibitory effect of FGF on PC cells did not go through activation of a PKC mediated pathway, which is also known to inhibit PC cell proliferation, since FGF inhibition of PC cell growth was still apparent after PKC down regulation. FGF was still able to transiently stimulate the expression of mRNA for early growth associated genes as demonstrated by c-myc and c-fos expression, although it inhibited cell proliferation on PC cells. Our data demonstrate that the highly tumorigenic teratoma cells acquire an inhibitory response for a factor which is growth stimulatory to non-tumorigenic and moderately tumorigenic cells from which they are derived.

Paracrine regulation of adipose differentiation by arachidonate metabolites: prostaglandin F2 alpha inhibits early and late markers of differentiation in the adipogenic cell line 1246

The effect of arachidonate metabolites on the differentiation of the adipogenic cell line 1246 was investigated. Among the metabolites examined, only prostaglandin F2 alpha (PGF2 alpha) inhibited differentiation in a dose-dependent fashion with an ED50 of 3 x 10(-9) M. PGF2 alpha inhibited the mRNA expression of lipoprotein lipase, clone 154, and fatty acid-binding protein, which are early markers of differentiation, as well as glycerol-3-phosphate dehydrogenase specific activity and triglyceride accumulation, which are late markers of differentiation. Chronic exposure of 1246 cells to PGF2 alpha before and during differentiation indicated that the cells that have just initiated their differentiation program were the most susceptible to the inhibitory effect of PGF2 alpha. Since 1246 cells produce PGs, we determined whether the PG produced by the cells influenced adipose differentiation. Cyclooxygenase inhibitors added to the culture medium stimulated differentiation of 1246 cells up to 18-fold depending on the type and concentration of inhibitor used. In contrast, lipoxygenase inhibitors had no effect. Treatment of 1246 cells with arachidonic acid resulted in a dose-dependent inhibition of cell differentiation. Oleate or linoleate had no effect. These data indicate that PGF2 alpha inhibits early and late events of adipose differentiation and that the endogenous production of PGs (particularly PGF2 alpha) plays an important role as a negative paracrine or autocrine regulatory pathway of adipose differentiation.