Historical Redlining, Persistent Mortgage Discrimination, and Race in Breast Cancer Outcomes

Importance

Inequities created by historical and contemporary mortgage discriminatory policies have implications for health disparities. The role of persistent mortgage discrimination (PMD) in breast cancer (BC) outcomes has not been studied.

Objective

To estimate the race-specific association of historical redlining (HRL) with the development of BC subtypes and late-stage disease and a novel measure of PMD in BC mortality.

Design, Setting, and Participants

This population-based cohort study used Georgia Cancer Registry data. A total of 1764 non-Hispanic Black and White women with a BC diagnosis and residing in an area graded by the Home Owners' Loan Corporation (HOLC) in Georgia were included. Patients were excluded if they did not have a known subtype or a derived American Joint Committee on Cancer stage or if diagnosed solely by death certificate or autopsy. Participants were diagnosed with a first primary BC between January 1, 2010, to December 31, 2017, and were followed through December 31, 2019. Data were analyzed between May 1, 2022, and August 31, 2023.

Exposures

Scores for HRL were examined dichotomously as less than 2.5 (ie, nonredlined) vs 2.5 or greater (ie, redlined). Contemporary mortgage discrimination (CMD) scores were calculated, and PMD index was created using the combination of HRL and CMD scores.

Main Outcomes and Measures

Estrogen receptor (ER) status, late stage at diagnosis, and BC-specific death.

Results

This study included 1764 women diagnosed with BC within census tracts that were HOLC graded in Georgia. Of these, 856 women (48.5%) were non-Hispanic Black and 908 (51.5%) were non-Hispanic White; 1148 (65.1%) were diagnosed at 55 years or older; 538 (30.5%) resided in tracts with HRL scores less than 2.5; and 1226 (69.5%) resided in tracts with HRL scores 2.5 or greater. Living in HRL areas with HRL scores 2.5 or greater was associated with a 62% increased odds of ER-negative BC among non-Hispanic Black women (odds ratio [OR], 1.62 [95% CI, 1.01-2.60]), a 97% increased odds of late-stage diagnosis among non-Hispanic White women (OR, 1.97 [95% CI, 1.15-3.36]), and a 60% increase in BC mortality overall (hazard ratio, 1.60 [95% CI, 1.17-2.18]). Similarly, PMD was associated with BC mortality among non-Hispanic White women but not among non-Hispanic Black women.

Conclusions and Relevance

The findings of this cohort study suggest that historical racist policies and persistent discrimination have modern-day implications for BC outcomes that differ by race. These findings emphasize the need for a more nuanced investigation of the social and structural drivers of disparate BC outcomes.

Redlining-associated methylation in breast tumors: the impact of contemporary structural racism on the tumor epigenome

Purpose

Place-based measures of structural racism have been associated with breast cancer mortality, which may be driven, in part, by epigenetic perturbations. We examined the association between contemporary redlining, a measure of structural racism at the neighborhood level, and DNA methylation in breast tumor tissue.

Methods

We identified 80 Black and White women diagnosed and treated for a first-primary breast cancer at Emory University Hospitals (2008-2017). Contemporary redlining was derived for census tracts using the Home Mortgage Disclosure Act database. Linear regression models were used to calculate the association between contemporary redlining and methylation in breast tumor tissue. We also examined epigenetic age acceleration for two different metrics, regressing β values for each cytosine-phosphate-guanine dinucleotide (CpG) site on redlining while adjusting for covariates. We employed multivariable Cox-proportional hazards models and 95% confidence intervals (CI) to estimate the association between aberrant methylation and mortality.

Results

Contemporary redlining was associated with 5 CpG sites after adjustment for multiple comparisons (FDR<0.10). All genes were implicated in breast carcinogenesis, including genes related to inflammation, immune function and stress response (ANGPT1, PRG4 and PRG4). Further exploration of the top 25 CpG sites, identified interaction of 2 sites (MRPS28 and cg11092048) by ER status and 1 site (GDP1) was associated with all-cause mortality. Contemporary redlining was associated with epigenetic age acceleration by the Hannum metric (β=5.35; CI 95%=0.30,10.4) and showed positive but non-significant correlation with the other clock.

Conclusion

We identified novel associations between neighborhood contemporary redlining and the breast tumor DNA methylome, suggesting that racist policies leading to inequitable social and environmental exposures, may impact the breast tumor epigenome. Additional research on the potential implications for prognosis is needed.

Abstract PD1-03: Neighborhood deprivation and breast cancer mortality among Black and White women

Background: Neighborhood deprivation is hypothesized as a potential driver of racial disparities in breast cancer mortality. However, research shows that neighborhood deprivation is associated with increased breast cancer mortality among White women, but has little to no association among Black women. No study has previously considered the intersections of race, social cohesion, or urban/rural status in the association between neighborhood deprivation and breast cancer mortality. Methods: Neighborhood deprivation was examined in relation to breast cancer mortality among 31,358 non-Hispanic Black and non-Hispanic White women diagnosed with invasive breast cancer (stage I-IIIA) between 2010-2017, followed through 2019, and identified by the Georgia Cancer Registry. Two composite scores, the Area Deprivation Index (ADI) and neighborhood deprivation index (NDI), were used to characterize neighborhood deprivation. A third composite score, the Yost index, was assessed as a measure of neighborhood socioeconomic status (SES). Each composite score was composed of factors representing six domains: poverty, income, occupation, housing, employment, and education. Data on ADI were obtained from the Neighborhood Atlas and was assessed in deciles. American Community Survey data from 2011-2015 and principal components analysis were used to derive the NDI and Yost index. Both measures were assessed in quartiles. Each composite variable was measured at the block group level and linked to patient data. Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between each composite variable and breast cancer mortality, overall and by race/ethnicity. Intersectionality will be examined by considering the joint effects of race/ethnicity, social cohesion, and urban/rural status. Results: During the 9-year follow-up period, 2,353 (1,347 non-Hispanic White, 1,006 non-Hispanic Black) women died from breast cancer. Regardless of which composite score was assessed, living in the most deprived or lowest SES neighborhoods was associated with an increased risk of breast cancer mortality in models adjusted for age and race (ADI decile 10 vs. 1: HR=1.57, 95% CI 1.26-1.96; NDI quartile 4 vs. 1: HR=1.43, 95% CI 1.26-1.63; Yost index quartile 1 vs 4: HR= 1.34, 95% CI 1.18-1.51). Stratification by race/ethnicity showed associations were slightly stronger among non-Hispanic White women but null among non-Hispanic Black women. Results from analyses examining the joint effects of race/ethnicity, social cohesion, and urban/rural status are forthcoming and will be presented in December. Conclusions: Consistent with previous studies, our study found that living in a deprived neighborhood may increase breast cancer mortality among non-Hispanic White women, but not non-Hispanic Black women. Investigating the association with an intersectionality framework may help identify subgroups of women who are particularly susceptible to the adverse impact of neighborhood deprivation on breast cancer mortality.

Citation Format: Lauren E. Barber, Jasmine M. Miller-Kleinhenz, Maret L. Maliniak, Leah Moubadder, Jeffrey Switchenko, Lauren E. McCullough. Neighborhood deprivation and breast cancer mortality among Black and White women [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD1-03.

Drivers of racial, regional, and socioeconomic disparities in late-stage breast cancer mortality

BACKGROUND

The authors identified tumor, treatment, and patient characteristics that may contribute to differences in breast cancer (BC) mortality by race, rurality, and area-level socioeconomic status (SES) among women diagnosed with stage IIIB-IV BC in Georgia.

METHODS

Using the Georgia Cancer Registry, 3084 patients with stage IIIB-IV primary BC (2013-2017) were identified. Cox proportional hazards regression was used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) comparing mortality among non-Hispanic Black (NHB) versus non-Hispanic White (NHW), residents of rural versus urban neighborhoods, and residents of low- versus high-SES neighborhoods by tumor, treatment, and patient characteristics. The mediating effects of specific characteristics on the association between race and BC mortality were estimated.

RESULTS

Among the study population, 41% were NHB, 21% resided in rural counties, and 72% resided in low SES neighborhoods. The authors observed mortality disparities by race (HR, 1.27; 95% CI, 1.13, 1.41) and rurality (HR, 1.14; 95% CI, 1.00, 1.30), but not by SES (HR, 1.04; 95% CI, 0.91, 1.19). In the stratified analyses, racial disparities were the most pronounced among women with HER2 overexpressing tumors (HR, 2.30; 95% CI, 1.53, 3.45). Residing in a rural county was associated with increased mortality among uninsured women (HR, 2.25; 95% CI, 1.31, 3.86), and the most pronounced SES disparities were among younger women (<40 years: HR, 1.46; 95% CI, 0.88, 2.42).

CONCLUSIONS

There is considerable variation in racial, regional, and socioeconomic disparities in late-stage BC mortality by tumor, treatment, and patient characteristics.

Time to Surgical Treatment and Facility Characteristics as Potential Drivers of Racial Disparities in Breast Cancer Mortality

BACKGROUND

Black women are more likely to die of breast cancer than White women. This study evaluated the contribution of time to primary surgical management and surgical facility characteristics to racial disparities in breast cancer mortality among both Black and White women.

METHODS

The study identified 2224 Black and 3787 White women with a diagnosis with stages I to III breast cancer (2010-2014). Outcomes included time to surgical treatment (> 30 days from diagnosis) and breast cancer mortality. Odds ratios (ORs) and 95% confidence intervals (CIs) associating surgical facility characteristics with surgical delay were computed, and Cox proportional hazards regression was used to compute hazard ratios (HRs) and 95% CIs associating delay and facility characteristics with breast cancer mortality.

RESULTS

Black women were two times more likely to have a surgical delay (OR, 2.15; 95% CI, 1.92-2.41) than White women. Racial disparity in surgical delay was least pronounced among women treated at a non-profit facility (OR, 1.95; 95% CI, 1.70-2.25). The estimated mortality rate for Black women was two times that for White women (HR, 2.00; 95% CI, 1.83-2.46). Racial disparities in breast cancer mortality were least pronounced among women who experienced no surgical delay (HR, 1.81; 95% CI, 1.28-2.56), received surgery at a government facility (HR, 1.31; 95% CI, 0.76-2.27), or underwent treatment at a Commission on Cancer-accredited facility (HR, 1.82; 95% CI, 1.38-2.40).

CONCLUSIONS

Black women were more likely to experience a surgical delay and breast cancer death. Persistent racial disparities in breast cancer mortality were observed across facility characteristics except for government facilities.

Understanding gastrointestinal cancer mortality disparities in a racially and geographically diverse population

BACKGROUND

Gastrointestinal (GI) cancers represent a diverse group of diseases. We assessed differences in geographic and racial disparities in cancer-specific mortality across subtypes, overall and by patient characteristics, in a geographically and racially diverse US population.

METHODS

Clinical, sociodemographic, and treatment characteristics for patients diagnosed during 2009-2014 with colorectal cancer (CRC), pancreatic cancer, hepatocellular carcinoma (HCC), or gastric cancer in Georgia were obtained from the Surveillance, Epidemiology, and End Results Program database. Patients were classified by geography (rural or urban county) and race and followed for cancer-specific death. Multivariable Cox proportional hazards models were used to calculate stratified hazard ratios (HR) and 95% confidence intervals (CIs) for associations between geography or race and cancer-specific mortality.

RESULTS

Overall, 77% of the study population resided in urban counties and 33% were non-Hispanic Black (NHB). For all subtypes, NHB patients were more likely to reside in urban counties than non-Hispanic White patients. Residing in a rural county was associated with an overall increased hazard of cancer-specific mortality for HCC (HR = 1.15, 95% CI = 1.02-1.31), pancreatic (HR = 1.11, 95% CI = 1.03-1.19), and gastric cancer (HR = 1.17, 95% CI = 1.03-1.32) but near-null for CRC. Overall racial disparities were observed for CRC (HR = 1.18, 95% CI = 1.11-1.25) and HCC (HR = 1.12, 95% CI = 1.01-1.24). Geographic disparities were most pronounced among HCC patients receiving surgery. Racial disparities were pronounced among CRC patients receiving any treatment.

CONCLUSION

Geographic disparities were observed for the rarer GI cancer subtypes, and racial disparities were pronounced for CRC. Treatment factors appear to largely drive both disparities.

Abstract PR-03: Neighborhood-level redlining-associated methylation in breast tumors: The impact of structural racism on the tumor epigenome

Background: Structural racism has been associated with breast cancer mortality. Exposure to adverse inequities may drive epigenetic perturbations that affect racial disparities in breast cancer outcomes. This study examined the association between neighborhood-level redlining and DNA methylation in non-Hispanic Black and White women diagnosed with breast cancer. Methods: Genome-wide DNA methylation was measured using the EPIC array in the tumor tissue of 84 women. Linear regression models were used to examine the association between neighborhood-level redlining and methylation, regressing β values for each cytosine-phosphate-guanine dinucleotide (CpG) site on redlining while adjusting for covariates. Redlining was derived for census tracts using the Home Mortgage Disclosure Act database. We used a false discovery rate (FDR) threshold &lt;0.1, and for CpGs below this threshold, we examined interactions with Estrogen Receptor (ER) status. We employed multivariable Cox-proportional hazard models to estimate whether aberrant methylation was associated with all-cause mortality. Results: 36 of the CpG sites were associated with neighborhood-level redlining (FDR&lt;0.1). The majority of genes are implicated in carcinogenesis including genes in immune function (BANP, IGDCC3, GPR15), oncogenic signaling (IGFALS, RNLS, RTP3), and angiogenesis (ANGPT1). Further exploration of these 36 CpG sites revealed no interactions by ER status, no probes were associated with all-cause mortality. Conclusions: We identified novel associations between neighborhood-level redlining and the breast tumor DNA methylome. Our data are the first to show that structural racism impacts the breast tumor epigenome.

Citation Format: Jasmine M Miller-Kleinhenz, Leah Moubadder, Kirsten M. Beyer, Yuhong Zhou, Anne H. Gaglioti, Jazib Gohar, Lindsay J. Collin, Kashari Henry, Karen M. Conneely, Uma Krishnamurti, Olivia D'Angelo, Keerthi Gogineni, Mylin Torres, Sheryl Gabram-Mendola, Lauren E. McCullough. Neighborhood-level redlining-associated methylation in breast tumors: The impact of structural racism on the tumor epigenome [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PR-03.

Racial Disparities in Diagnostic Delay Among Women With Breast Cancer

PURPOSE

Early diagnosis is fundamental to reducing breast cancer (BC) mortality, and understanding potential barriers from initial screening to confirmed diagnosis is essential. The aim of this study was to evaluate patient characteristics that contribute to delay in diagnosis of screen-detected cancers and the contribution of delay to tumor characteristics and BC mortality.

METHODS

Three hundred sixty-two White and 368 Black women were identified who were screened and received subsequent BC diagnoses within Emory Healthcare, a part of Emory University health care system (2010-2014). Multivariable-adjusted logistic regression was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) associating patient characteristics with delay to diagnostic evaluation (≥30 versus <30 days), delay to biopsy (≥15 versus <15 days), and total delay (≥45 versus <45 days). Additionally, the ORs and 95% CIs associating delay with tumor characteristics and BC mortality were computed.

RESULTS

Black women and women diagnosed at later stages, with larger tumor sizes, and with triple-negative tumors were more likely to experience ≥45 days to diagnosis. In multivariable-adjusted models, Black women had at least a two-fold increase in the odds of delay to diagnostic evaluation (OR, 1.98; 95% CI, 1.45-2.71), biopsy delays (OR, 2.41; 95% CI, 1.67-3.41), and total delays ≥45 days (OR, 2.22; 95% CI, 1.63-3.02) compared with White women. A 1.6-fold increased odds of BC mortality was observed among women who experienced total delays ≥45 days compared with women without delays in diagnosis (OR, 1.57, 95% CI, 0.96-2.58).

CONCLUSIONS

The study demonstrated racial disparities in delays in the diagnostic process for screen-detected malignancies. Total delay in diagnosis was associated with an increase in BC mortality.

Neighborhood-Level Redlining and Lending Bias Are Associated with Breast Cancer Mortality in a Large and Diverse Metropolitan Area

BACKGROUND

Structural inequities have important implications for the health of marginalized groups. Neighborhood-level redlining and lending bias represent state-sponsored systems of segregation, potential drivers of adverse health outcomes. We sought to estimate the effect of redlining and lending bias on breast cancer mortality and explore differences by race.

METHODS

Using Georgia Cancer Registry data, we included 4,943 non-Hispanic White (NHW) and 3,580 non-Hispanic Black (NHB) women with a first primary invasive breast cancer diagnosis in metro-Atlanta (2010-2014). Redlining and lending bias were derived for census tracts using the Home Mortgage Disclosure Act database. We calculated hazard ratios and 95% confidence intervals (CI) for the associations of redlining, lending bias on breast cancer mortality and estimated race-stratified associations.

RESULTS

Overall, 20% of NHW and 80% of NHB women lived in redlined census tracts, and 60% of NHW and 26% of NHB women lived in census tracts with pronounced lending bias. Living in redlined census tracts was associated with a nearly 1.60-fold increase in breast cancer mortality (hazard ratio = 1.58; 95% CI, 1.37-1.82) while residing in areas with substantial lending bias reduced the hazard of breast cancer mortality (hazard ratio = 0.86; 95% CI, 0.75-0.99). Among NHB women living in redlined census tracts, we observed a slight increase in breast cancer mortality (hazard ratio = 1.13; 95% CI, 0.90-1.42); among NHW women the association was more pronounced (hazard ratio = 1.39; 95% CI, 1.09-1.78).

CONCLUSIONS

These findings underscore the role of ecologic measures of structural racism on cancer outcomes.

IMPACT

Place-based measures are important contributors to health outcomes, an important unexplored area that offers potential interventions to address disparities.

Abstract PO-168: Association between geography and cause-specific mortality in gastrointestinal cancers in Georgia

Background: Cancers of the gastrointestinal system represent a diverse range of diseases with different etiologies, from screening-detectable colorectal cancer (CRC) to pancreatic cancer, often diagnosed at late stage and highly lethal. While racial disparities have been observed for some of these cancers, the impact of geography is less understood. Georgia is an ideal place to examine disparities in geography because it has a diverse setting and population, with approximately 25% of residents living in a rural area and nearly one-third identifying as non-Hispanic Black (NHB), according to the 2010 decennial census. Methods: We obtained clinical (age at diagnosis, tumor stage, tumor size), sociodemographic (e.g., insurance status, marital status, SES index), and treatment information (e.g., receipt of surgery, lymph node biopsy/removal) on nearly 30,000 NHB and non-Hispanic White (NHW) men and women aged 18 years and older, diagnosed with CRC, hepatocellular carcinoma (HCC), pancreatic cancer or gastric cancer between 2009 and 2014 in Georgia from the population-based Surveillance, Epidemiology, and End Results (SEER) Program.

Patients were classified as residing in a metro or non-metro county at diagnosis according to 2013 rural-urban continuum codes. Multivariable Cox proportional hazards models were used to calculate the hazard ratios (HRs) and corresponding 95% confidence intervals (95% CI) for the association between residing in a non- metro versus metro county and cause-specific mortality, stratified by patient characteristics. Results: Over 75% of the study population resided in a metro county at diagnosis, with the highest proportion among HCC cases (81%) and the lowest proportion among CRC cases (76%). Overall, NHBs were more likely to reside in metro counties (82%) than NHWs (74%). The average length of follow-up varied by cancer site and metro status, ranging from 35 months (CRC in metro areas) to 4 months (pancreatic cancer in non-metro areas). For all cancer sites, patients in metro counties were more likely to be younger, single, have localized disease (except gastric cancer), and receive surgery of the primary site. By comparison, patients in non-metro counties were more likely to be diagnosed at older ages, have Medicaid, and be widowed. Residing in a non-metro county was associated with higher cause- specific mortality among the youngest patients (age 18-49 years) for pancreatic cancer (HR=1.4, 95% CI: 1.1, 1.9) and gastric cancer (HR=1.8, 95% CI: 1.2, 2.6). We also observed a higher hazard of mortality for residing in a non-metro compared to metro county among NHB HCC patients (HR=1.3, 95% CI: 1.0, 1.7) and never married gastric cancer patients (HR=1.5, 95% CI: 1.1, 2.1). Associations among CRC patients were less robust. Conclusion: Our results suggest residing in a non-metro county is associated with higher mortality among some groups diagnosed with rarer gastrointestinal cancers. Geographic differences in access to diagnosis and treatment may contribute to this disparity.

Citation Format: Rebecca Nash, Jasmine M. Miller-Kleinhenz, Maria C. Russell, Lindsay J. Collin, Katherine Ross-Driscoll, Jeffrey M. Switchenko, Lauren E. McCullough. Association between geography and cause-specific mortality in gastrointestinal cancers in Georgia [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-168.

Targeted nanoparticles for image-guided treatment of triple-negative breast cancer: clinical significance and technological advances

Effective treatment of triple-negative breast cancer (TNBC) with its aggressive tumor biology, highly heterogeneous tumor cells, and poor prognosis requires an integrated therapeutic approach that addresses critical issues in cancer therapy. Multifunctional nanoparticles with the abilities of targeted drug delivery and noninvasive imaging for monitoring drug delivery and responses to therapy, such as theranostic nanoparticles, hold great promise toward the development of novel therapeutic approaches for the treatment of TNBC using a single therapeutic platform. The biological and pathological characteristics of TNBC provide insight into several potential molecular targets for current and future nanoparticle-based therapeutics. Extensive tumor stroma, highly proliferative cells, and a high rate of drug resistance are all barriers that must be appropriately addressed in order for these nanotherapeutic platforms to be effective. Utilization of the enhanced permeability and retention effect coupled with active targeting of cell surface receptors expressed by TNBC cells, and tumor-associated endothelial cells, stromal fibroblasts, and macrophages is likely to overcome such barriers to facilitate more effective drug delivery. An in-depth summary of current studies investigating targeted nanoparticles in preclinical TNBC mouse and human xenograft models is presented. This review aims to outline the current status of nanotherapeutic options for TNBC patients, identification of promising molecular targets, challenges associated with the development of targeted nanotherapeutics, the research done by our group as well as by others, and future perspectives on the nanomedicine field and ways to translate current preclinical studies into the clinic.

Abstract B045: uPAR-targeted theranostic nanoparticles effectively decrease expression of IGF-1R and Ki67 in drug-resistant triple-negative breast cancer human xenograft

Background: Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype that affects about 20% of breast cancer patients and has a high incidence in young African American women. Currently the only therapeutic options for TNBC patients is chemotherapy, however, more than 60% of TNBC patients are highly resistant to chemotherapeutic treatment. The development of novel therapeutic approaches is essential to enable treatment of patients with chemo-resistant TNBC.

Our lab focuses on the development of receptor-targeted theranostic nanoparticles. We have developed a class of urokinase plasminogen activator receptor (uPAR) targeted theranostic magnetic iron oxide nanoparticles (IONPs) carrying therapeutic agents that are clinically beneficial to TNBC patients, including DNA damaging agents, such as doxorubicin (Dox) or cisplatin (Cis). We are targeting uPAR because it is highly expressed in malignant cancers including aggressive breast cancer tissues and tumor stromal cells that are enriched in TNBC tissues.

Methods: Tumor fragments from TNBC patients, obtained from a Phase II clinical trial that is ongoing at the Breast Cancer Clinic in the Winship Cancer Institute, were implanted in the mammary fat pad of SCID mice. The tumor xenografts grew to about 1 cm in diameter in 12 to 15 weeks. Tumor fragments were then implanted into the mammary fat pad and passaged through nude mice for testing the therapeutic efficacy of the uPAR-targeted nanoparticle-drugs. Histological analysis of post-chemotherapy TNBC and primary tumor xenograft tissues with or without uPAR-targeted IONP-Dox was conducted using immunohistochemistry and dual immunofluorescence techniques.

Results: We have previously reported that the uPAR-targeted IONP-Dox causes tumor growth inhibition following systemic delivery. Using CD44 and uPAR as biomarkers we also reported histological analysis of post-chemotherapy TNBC and primary tumor xenograft tissues showed high levels of CD44+/CD24- tumor cells and up-regulation of uPAR. Primary TNBC xenografts treated with conventional Dox had increased levels of CD44+/CD24- cells and strong uPAR expression. Conversely, the tumor tissues from the uPAR-targeted IONP-Dox treated group showed decreased levels of CD44+/CD24- and uPAR positive cells.

We have further investigated the biomarkers insulin-like growth factor 1 receptor (IGF-1R) and Ki67. IGF-1R has been shown to be overexpressed in more than 50% of TNBCs and may be associated with the drug-resistant TNBC phenotype, while Ki67 is a conventional biomarker for proliferation. We observed that uPAR-targeted IONP- Dox treatment decreased IGF-1R expression compared to the control group and the group treated with conventional Dox. We also observed that Ki67 expression was decreased in the uPAR-targeted IONP- Dox treatment group compared to control group and the group treated with conventional Dox.

Conclusions: Results of our study demonstrated that uPAR-targeted theranostic IONPs selectively delivers therapeutic payloads of the chemotherapeutic drug Dox to inhibit the growth of uPAR positive tumor cells. It is likely that uPAR expressing tumor cells are an aggressive and potentially drug resistant cell population that overexpress breast cancer stem-like cell biomarker (CD44+/CD24-) as well as up-regulation of a growth factor receptor, IGF-1R. These results support further investigation of theranostic nanoparticles as an approach to overcome drug resistance in TNBC.

Citation Format: Jasmine M. Miller-Kleinhenz, Hongyu Zhou, Weiping Qian, Ruth O'Regan, Amelia Zelnak, Toncred Styblo, Lily Yang. uPAR-targeted theranostic nanoparticles effectively decrease expression of IGF-1R and Ki67 in drug-resistant triple-negative breast cancer human xenograft. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B045.