Src Inhibition Blocks c-Myc Translation and Glucose Metabolism to Prevent the Development of Breast Cancer

Preventing breast cancer will require the development of targeted strategies that can effectively block disease progression. Tamoxifen and aromatase inhibitors are effective in addressing estrogen receptor-positive (ER(+)) breast cancer development, but estrogen receptor-negative (ER(-)) breast cancer remains an unmet challenge due to gaps in pathobiologic understanding. In this study, we used reverse-phase protein array to identify activation of Src kinase as an early signaling alteration in premalignant breast lesions of women who did not respond to tamoxifen, a widely used ER antagonist for hormonal therapy of breast cancer. Src kinase blockade with the small-molecule inhibitor saracatinib prevented the disorganized three-dimensional growth of ER(-) mammary epithelial cells in vitro and delayed the development of premalignant lesions and tumors in vivo in mouse models developing HER2(+) and ER(-) mammary tumors, extending tumor-free and overall survival. Mechanistic investigations revealed that Src blockade reduced glucose metabolism as a result of an inhibition in ERK1/2-MNK1-eIF4E-mediated cap-dependent translation of c-Myc and transcription of the glucose transporter GLUT1, thereby limiting energy available for cell growth. Taken together, our results provide a sound rationale to target Src pathways in premalignant breast lesions to limit the development of breast cancers.

Abstract P1-03-01: Evidence for the Warburg effect in mammary atypia from high-risk African American women

Background: Aggressive cancers are known to consume glucose avidly and produce lactic acid (rather than fully metabolize glucose via the Tricarboxylic Acid (TCA) cycle). This shift toward lactate production, even in the presence of adequate oxygen, is termed the Warburg effect. The Warburg effect is thought to be a late event in breast cancer, however, our studies in high-risk women provide evidence that the Warburg effect occurs during cancer initiation. This is an important observation as glucose-signaling can be readily targeted for breast cancer prevention with minimal toxicity. Here we investigated the role of the Warburg effect in breast cancer initiation in young high-risk women.

Methods and Results: Similar to fluorodeoxyglucose, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) is a fluorescent glucose analog that can be used to track glucose uptake and glycolysis. 2-NBDG spectroscopy provides a means to track glucose metabolism in live mammary epithelial cells from high-risk women. We used 2-NBDG spectroscopy to measure glucose uptake in ER− breast cancer and live atypical mammary epithelial cells from high-risk premenopausal women. We observe that both triple-negative breast cancer and a subset of atypia exhibits accumulation of 2-NBDG.

There is growing recognition that phosphoprotein signaling networks (rather than single genes) play a key role in breast cancer initiation and progression. Our team used Reverse Phase Proteomic Microarray (RPPM) profiling to test for activation of phosphoprotein signaling networks in atypical RPFNA cytology from high-risk premenopausal women in our cohort. RPFNA were obtained from two independent sets of 39 and 38 high-risk premenopausal women; 45% of these women were African American. The signaling network most highly expressed in precancerous cells contained activated signaling proteins associated with the Warburg effect (AKT/mTOR/PI3K), insulin signaling (pACC, IRS1) and epithelial to mesenchymal transition (EMT) IL6/Stat3/vimentin.

Conclusions: This is the first evidence that abnormal glucose uptake and the Warburg effect occurs during breast cancer initiation in high-risk premenopausal women. These studies demonstrate our ability to identify abnormal glucose and activated signaling networks associated with the Warbug effect in atypical mammary cells from high-risk women.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-03-01.

Abstract 686: Warburg effect in mammary atypia from high-risk women

Background: Aggressive cancers are known to consume glucose avidly and produce lactic acid (rather than fully metabolize glucose via the Tricarboxylic Acid (TCA) cycle). This shift toward lactate production, even in the presence of adequate oxygen, is termed the Warburg effect. The Warburg effect is thought to be a late event in breast cancer, however, our studies in high-risk women provide evidence that the Warburg effect occurs during cancer initiation. This is an important observation as glucose-signaling can be readily targeted for breast cancer prevention with minimal toxicity. Here we investigated the role of the Warburg effect in breast cancer initiation in young high-risk women. Methods and Results: Similar to fluorodeoxyglucose, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) is a fluorescent glucose analog that can be used to track glucose uptake and glycolysis. 2-NBDG spectroscopy provides a means to track glucose metabolism in live mammary epithelial cells from high-risk women. We used 2-NBDG spectroscopy to measure glucose uptake in ER- breast cancer and live atypical mammary epithelial cells from high-risk premenopausal women. We observe that both triple-negative breast cancer and a subset of atypia exhibits accumulation of 2-NBDG. There is growing recognition that phosphoprotein signaling networks (rather than single genes) play a key role in breast cancer initiation and progression. Our team used Reverse Phase Proteomic Microarray (RPPM) profiling to test for activation of phosphoprotein signaling networks in atypical RPFNA cytology from high-risk premenopausal women in our cohort. RPFNA were obtained from two independent sets of 39 and 38 high-risk premenopausal women; 45% of these women were African American. The signaling network most highly expressed in precancerous cells contained activated signaling proteins associated with the Warburg effect (AKT/mTOR/PI3K), insulin signaling (pACC, IRS1) and epithelial to mesenchymal transition (EMT) IL6/Stat3/vimentin. Conclusions: This is the first evidence that abnormal glucose uptake and the Warburg effect occurs during breast cancer initiation in high-risk premenopausal women. These studies demonstrate our ability to identify abnormal glucose and activated signaling networks associated with the Warbug effect in atypical mammary cells from high-risk women.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 686. doi:1538-7445.AM2012-686

Ductal carcinoma in situ: challenges, opportunities, and uncharted waters

Ductal carcinoma in situ (DCIS) is a heterogeneous group of diseases that differ in biology and clinical behavior. Until 1980, DCIS represented less than 1% of all breast cancer cases. With the increased utilization of mammography, DCIS now accounts for 15% to 25% of newly diagnosed breast cancer cases in the United States. Although our ability to detect DCIS has radically improved, our understanding of the pathophysiology and factors involved in its progression to invasive carcinoma is still poorly defined. In many patients, DCIS will never progress to invasive breast cancer and these women are overtreated. In contrast, some DCIS cases are clinically aggressive and the women may be undertreated. We are able to define some of the predictors of aggressive DCIS compared with DCIS of low malignant potential. However, our ability to risk-stratify DCIS is still in its infancy. Clinical risk factors that predict aggressive disease and increased risk of local recurrence include young age at diagnosis, large lesion size, high nuclear grade, comedo necrosis, and involved margins. Treatment factors such as wider surgical margins and radiation therapy reduce the risk of local recurrence. DCIS represents a key intermediate in the stepwise progression to malignancy, but not all aggressive breast cancers appear to have a DCIS intermediate, notably within triple-negative breast cancer. Ongoing studies of the genetic and epigenetic alterations in precancerous breast lesions (atypia and DCIS) as well as the breast microenvironment are important for developing effective early detection and individualized targeted prevention.

Abstract CN07-03: IL6 and AKT as targets for chemoprevention

Background: Currently we lack adequate prevention strategies for triple-negative breast cancer; progress in designing targeted strategies is limited by a lack of knowledge of the biology of cancer initiation. The origins of triple-negative breast cancer in premenopausal women are poorly understood. Importantly, we do not understand whether the molecular pathways that underlie the aggressive behavior of triple-negative breast cancer can be detected in premalignant breast lesions. Growing evidence indicates that early mammary carcinogenesis is regulated by integrated signaling networks and not by isolated genes. Interleukin-6 (IL6) plays a role in stem cell regeneration, promotes epithelial to mesenchymal transition (EMT), and high IL6 serum levels predict a poor outcome in premenopausal women with triple-negative breast cancer.

Methods and Results: We used Reverse-Phase Protein Microarray (RPPM) profiling to test for activation of phosphoprotein signaling in premalignant Random Periareolar Fine Needle Aspiration (RPFNA) mammary epithelial cytology from 65 high-risk African American women. Unsupervised hierarchical clustering of RPPM proteomic analysis RPFNA aspirates identified three activated ER− signaling pathways including co-activation of Akt/mTOR/PI3K and IL6/pStat3/vimentin. Analysis of interstitial breast tissue demonstrated that high interstitial IL6/VEGF cytokine production predicted high epithelial expression of pStat3/vimentin. Based on these observations we are currently launching a prevention trial to target Akt/mTor using metformin 500 mg bid.

Conclusion: This is the first demonstration that Akt/mTor and IL6/Stat3/vimentin signaling is activated in pre-cancerous mammary epithelial cells from high-risk premenopausal women. Currently we are testing whether trials are on-going to test whether metformin can inhibit activation of mammary epithelial Akt/mTor and perhaps IL6/Stat3/vimentin signaling.

Citation Information: Cancer Prev Res 2011;4(10 Suppl):CN07-03.

Abstract PR2: Warburg effect revisited: Glucose addiction in precancerous mammary epithelial cells in African American women

Background: Only 14% of African American women with triple-negative breast cancers will be alive at one year. Early detection is greatly needed. Here we aimed to investigate whether activation of biologic pathways that predict aggressive triple-negative breast cancers are also activated in atypia in high-risk African American women. Aggressive cancers are known to consume glucose avidly and produce lactic acid (rather than fully metabolize glucose via the Tricarboxylic Acid (TCA) cycle). This shift toward lactate production, even in the presence of adequate oxygen, is termed the Warburg effect. The Warburg effect is thought to be a late event in breast cancer, however, our studies in high-risk African American women provide evidence that the Warburg effect occurs during cancer initiation. This is an important observation as glucose-signaling can be readily targeted for breast cancer prevention with minimal toxicity. Here we investigated the role of the Warburg effect in breast cancer initiation in young high-risk African American women.

Methods and Results: Similar to fluorodeoxyglucose, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) is a fluorescent glucose analog that can be used to track glucose uptake and glycolysis. 2-NBDG spectroscopy provides a means to track glucose metabolism in live mammary epithelial cells from high-risk women. We used 2-NBDG spectroscopy to measure glucose uptake in ER-breast cancer and live atypical mammary epithelial cells from high-risk premenopausal women. We observe that both triple-negative breast cancer and a subset of atypia exhibits accumulation of 2-NBDG.

There is growing recognition that phosphoprotein signaling networks (rather than single genes) play a key role in breast cancer initiation and progression. Our team used Reverse Phase Proteomic Microarray (RPPM) profiling to test for activation of phosphoprotein signaling networks in atypical RPFNA cytology from high-risk premenopausal women in our cohort. RPFNA were obtained from two independent sets of 39 and 38 high-risk premenopausal women; 45% of these women were African American. The signaling network most highly expressed in precancerous cells contained activated signaling proteins associated with the Warburg effect (AKT/mTOR/PI3K), insulin signaling (pACC, IRS1) and epithelial to mesenchymal transition (EMT) IL6/Stat3/vimentin.

Conclusions: This is the first evidence that abnormal glucose uptake and the Warburg effect occurs during breast cancer initiation in high-risk African American premenopausal women. These studies demonstrate our ability to identify abnormal glucose and activated signaling networks associated with the Warburg effect in atypical mammary cells from high-risk African American women and provide an important target for breast cancer early detection and prevention.

Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):PR2.

Abstract B9: Community strategies for investigating the biology of breast and cervical cancer initiation in African-American women

Background: African-American women have the highest overall cancer death rate from breast and cervical cancer and shortest survival of any racial and ethnic group in the United States. These disparities are heightened in the Southern United States. For example, the US breast cancer death rate is 23.0 (per 100,000) for Caucasian women, as compared to 34.3 for African-American women. The North Carolina breast cancer death rate is 27.2 for Caucasian women and 38.0 for African Americans; and in our study area, Durham County, the breast cancer death rate is 27.5 for Caucasians and 42.0 for African-Americans. The causes of these inequalities are complex and interrelated, but arise, at least in part, from disparities in income, education, nutrition, and access to healthcare. For complex historical reasons, African-Americans have had mixed experiences in accessing care and in the quality of care they receive. In addition, distrust has arisen within the African-American community regarding the intents and purposes of health care researchers.

Cutting edge breast imaging technology, prevention, and early detection trials exist at academic that could potentially improve early diagnosis and increase our chance of understanding the complex relationship between disparities, genetics, diet, and the environment in promoting breast cancer. Lack of access, mistrust, and community barriers all play a key role in preventing young African-American women from benefiting from state-of-the-art breast imaging and new strategies for early detection of breast and cervical cancer.

Methods and Results: To address the unacceptably high death rate among young African-American women from breast and cervical cancer, we have used a multi-disciplinary intervention that includes: 1) community Navigators, 2) access to breast and cervical cancer prevention and early detection services through free community clinics, 3) community partnered breast and cervical cancer prevention trials, and 4) opportunities for mentorship and career development. As a result, we have been able to improve access to early detection strategies in a community based setting and have provided mentorship for 27 young Minority scholars to enter medical school and graduate programs. Our community based breast MRI trial for underserved women has performed over 600 breast MRI since 2004. Over 50% of these women entered in this trial are Women-of-Color.

Conclusion: A community based strategy can be highly successful for improving early detection of breast and cervical cancer but only if there is community participation during the initiation of clinical trials and joint community-academic mentorship of young Minority Scholars.

Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):B9.

Metabolic Syndrome and Breast Cancer Risk: Is There a Role for Metformin?

Obesity is one of the most important known preventable causes of cancer, accounting for up to 20% of cancer deaths in women. Obese women have increased risk of dying from breast cancer as well as an increased risk of distant metastasis. Metabolic Syndrome (MetSyn) is a group of metabolic conditions that include 1) abdominal obesity, 2) atherogenic dyslipidemia, 3) elevated blood pressure, and 4) insulin resistance. MetSyn is known to promote the development of cardiovascular disease and diabetes and may be associated with increased breast cancer risk. Emerging evidence supports an association between mammary adipocytes and their secreted adipocytokines and breast cancer initiation and progression. Metformin (1,1-dimethylbiguanide hydrochloride) is a drug used to treat type 2 diabetes and MetSyn. We review the potential association between MetSyn in promoting breast cancer and emerging evidence for the use of metformin in cancer prevention.

Protein microarray analysis of mammary epithelial cells from obese and nonobese women at high risk for breast cancer: feasibility data

BACKGROUND

Obesity is a well-established risk factor for cancer, accounting for up to 20% of cancer deaths in women. Studies of women with breast cancer have shown obesity to be associated with an increased risk of dying from breast cancer and increased risk of developing distant metastasis. While previous studies have focused on differences in circulating hormone levels as a cause for increased breast cancer incidence in postmenopausal women, few studies have focused on potential differences in the protein expression patterns of mammary epithelial cells obtained from obese versus nonobese women.

METHODS

Protein expression was assessed by reverse-phase protein microarray in mammary epithelial cells from 31 random periareolar fine needle aspirations performed on 26 high-risk women.

RESULTS

In this pilot and exploratory study, vimentin (unadjusted P=0.028) expression was significantly different between obese and nonobese women.

CONCLUSIONS

Vimentin is integral both to adipocyte structure and function and to the epithelial-to-mesenchymal transition needed for cancer cell metastasis. Further research is needed to confirm this finding and determine the possible effects of the adipocyte microenvironment on the initiation and progression of breast cancer in high-risk women.

IMPACT

Differential protein expression patterns obtained from a future expanded study may serve to elaborate the underlying pathology of breast cancer initiation and progression in obese women and identify potential biomarkers of response to preventative interventions such as dietary changes and exercise.

Abstract A108: Phosphoprotein network activation during breast cancer initiation

Background: Currently we lack the ability to rapidly test new agents to prevent breast cancer. Targeted agents are in clinical testing for treatment of breast cancer but are not being adequately explored for prevention. This is because, without biomarkers to select women that are most likely to respond and rapidly evaluate response, Phase I/II testing of targeted agents for prevention will be too risky and expensive. Single biomarkers have been traditionally used to evaluate response to chemotherapeutic agents. However, single biomarkers may not be adequate to evaluate the complex phosphorylation network signaling events that occur during breast cancer initiation. Furthermore, emerging evidence suggests that resistance to targeted agents may occur through paradoxical activation of quiescent signaling pathway. As a result, it has become increasingly important to monitoring network signaling in women receiving targeted agents.

Targeted agents that have low-toxicity profiles and have inhibitory activity against breast cancer cell proliferation and/or invasion may show promise as a prevention agent. However, before any given targeted agent could be tested for pilot prevention trials, we first need to identify 1) signaling pathway(s) that are affected by the drug in preclinical models of breast cancer, 2) short-term and long-term consequences of treatment, 3) potential biomarker(s) to closely track response.

Methods and Results: We tested for protein network signaling in cytological specimens in women at high-risk for breast cancer. Our group used reverse-phase protein microarray (RPPM) platform to test for proteomic signatures of short-term risk to breast cancer. RPPM was developed to provide reproducible assessment of 50 phospho-proteins in 5,000 epithelial cells. Initial signature testing was performed in mammary cytology obtained from two groups of 50 high-risk women undergoing Random Periareolar Fine Needle Aspiration (RPFNA). Unsupervised heirachal clustering of RPPM proteomic analysis RPFNA aspirates from high-risk women identified three activated signaling pathways 1) Akt/mTOR/PI3K/cSrc, 2) EGRF/MEK/ERK, and 3) HER2/bcl-2.

Conclusion: Here we demonstrate our ability to identify activated phospho-protein signaling pathways in limited RPFNA cytology. The power of this approach is that we can use a combination of RPPM and RPFNA to track response to any new targeted prevention agents. Importantly, we are able to validate our proteomic signatures in parallel nanobiosensor testing of live atypical RPFNA cytology from women in our high-risk cohort.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):A108.

Breast self-examination: defining a cohort still in need

BACKGROUND

The value of breast self-examination (BSE) to detect early breast cancer is controversial.

METHODS

Within an institutional review board-approved prospective study, 147 high-risk women were enrolled from 2004 to 2007. Yearly clinical examination, BSE teaching, and mammography were performed simultaneously followed by interval breast magnetic resonance imaging (MRI). Women underwent additional BSE teaching at 6 months. Women reporting a mass on BSE underwent clinical evaluation.

RESULTS

Fourteen breast cancers were detected in 12 women. BSE detected 6/14 breast cancers versus 6/14 detected by MRI and 2/14 by mammography. Of 24 masses detected by BSE, 6/24 were malignant. The sensitivity, specificity, and predictive value of BSE to detect breast cancer were 58.3%, 87.4%, and 29.2%, respectively. The sensitivity, specificity, and predictive value of a Breast Image Reporting and Data System (BI-RADS) score of >or=4 on MRI were 66.7%, 88.9%, and 34.8%, respectively.

CONCLUSIONS

BSE detects new breast cancers in high-risk women undergoing screening mammogram, CBE, and yearly breast MRI.

Reproducibility of random periareolar fine needle aspiration in a multi-institutional Cancer and Leukemia Group B (CALGB) cross-sectional study

BACKGROUND

Random periareolar fine needle aspiration (RPFNA) is a research technique developed to assess short-term breast cancer risk in women at increased risk of breast cancer. Although there is increasing acceptance of RPFNA, neither the reproducibility nor the inter-institutional compatibility of RPFNA has been established. To address these key limitations, the Cancer and Leukemia Group B (CALGB) Prevention Group tested the reproducibility of RPFNA in a multi-institutional cross-sectional study.

METHODS

Sixty-three high-risk women from five CALGB institutions (Duke, Ohio State, Roswell Park, Dana Farber, and Vermont) underwent RPFNA from July 1, 2007 to June 30, 2008. Duplicate bilateral RPFNA was performed on each woman by a single investigator on a single day. Masood Cytology Index score was assessed by a single blinded cytopathologist.

RESULTS

There was a high degree of statistical agreement in the Masood Cytology Index scores of duplicate RPFNA samples from the same breast, with a Spearman correlation coefficient of 0.8312 (P < 0.0001). Importantly, although there was agreement in duplicate samples from the same breast, there was lack of agreement between duplicate samples from the opposite breast.

CONCLUSIONS

This multi-institutional study shows that RPFNA is a highly reproducible measure of breast cytology in a cooperative group cross-sectional trial. RPFNA did not show a high degree of agreement between breasts, suggesting that breast cancer risk and progression may occur at different rates in individual breasts from a single woman. These studies provide proof-of-principle for future RPFNA-based cooperative group prevention studies.

CpG island tumor suppressor promoter methylation in non-BRCA-associated early mammary carcinogenesis

BACKGROUND

Only 5% of all breast cancers are the result of BRCA1/2 mutations. Methylation silencing of tumor suppressor genes is well described in sporadic breast cancer; however, its role in familial breast cancer is not known.

METHODS

CpG island promoter methylation was tested in the initial random periareolar fine-needle aspiration sample from 109 asymptomatic women at high risk for breast cancer. Promoter methylation targets included RARB (M3 and M4), ESR1, INK4a/ARF, BRCA1, PRA, PRB, RASSF1A, HIN-1, and CRBP1.

RESULTS

Although the overall frequency of CpG island promoter methylation events increased with age (P<0.0001), no specific methylation event was associated with age. In contrast, CpG island methylation of RARB M4 (P=0.051), INK4a/ARF (P=0.042), HIN-1 (P=0.044), and PRA (P=0.032), as well as the overall frequency of methylation events (P=0.004), was associated with abnormal Masood cytology. The association between promoter methylation and familial breast cancer was tested in 40 unaffected premenopausal women in our cohort who underwent BRCA1/2 mutation testing. Women with BRCA1/2 mutations had a low frequency of CpG island promoter methylation (15 of 15 women had <or=4 methylation events), whereas women without a mutation showed a high frequency of promoter methylation events (24 of 25 women had 5-8 methylation events; P<0.0001). Of women with a BRCA1/2 mutation, none showed methylation of HIN-1 and only 1 of 15 women showed CpG island methylation of RARB M4, INK4a/ARF, or PRB promoters.

CONCLUSIONS

This is the first evidence of CpG island methylation of tumor suppressor gene promoters in non-BRCA1/2 familial breast cancer.

ESR1 promoter hypermethylation does not predict atypia in RPFNA nor persistent atypia after 12 months tamoxifen chemoprevention

PURPOSE

Currently, we lack biomarkers to predict whether high-risk women with mammary atypia will respond to tamoxifen chemoprevention.

EXPERIMENTAL DESIGN

Thirty-four women with cytologic mammary atypia from the Duke University High-Risk clinic were offered tamoxifen chemoprevention. We tested whether ESR1 promoter hypermethylation and/or estrogen receptor (ER) protein expression by immunohistochemistry predicted persistent atypia in 18 women who were treated with tamoxifen for 12 months and in 16 untreated controls.

RESULTS

We observed a statistically significant decrease in the Masood score of women on tamoxifen chemoprevention for 12 months compared with control women. This was a significant interaction effect of time (0, 6, and 12 months) and treatment group (tamoxifen versus control) P = 0.0007. However, neither ESR1 promoter hypermethylation nor low ER expression predicted persistent atypia in Random Periareolar Fine Needle Aspiration after 12 months tamoxifen prevention.

CONCLUSIONS

Results from this single institution pilot study provide evidence that, unlike for invasive breast cancer, ESR1 promoter hypermethylation and/or low ER expression is not a reliable marker of tamoxifen-resistant atypia.