Promotores' perspectives on the virtual adaptation of a hereditary breast cancer education program

Breast cancer is the most common cancer in women in the United States (U.S.) and the leading cause of cancer related death among U.S. Hispanics/Latinas (H/Ls). H/Ls have lower rates of screening and longer time to follow up after an abnormal mammogram. We developed a comprehensive community health educator (promotores)-led education and risk identification program for Spanish-speaking H/Ls in California to increase mammography screening, genetic testing, and the understanding of the impact of family history on cancer risk. Due to COVID-19, we adapted the program to a virtual platform. The experience of transforming the program to a virtual platform provided unique opportunities for collaboration between researchers, community partners, and participants. Promotores are major partners in community based participatory research and in the provision of health care services, but their voices are often excluded from scientific reports. This commentary is an effort to provide a platform for promotores to share their experiences and for the readers to understand their approach in bridging the gap between health care services and communities.

Abstract 5237: Regulation of genes located in 6q25 by an Indigenous American genetic variant in breast cancer patients from Peru

Genetic studies in women of Hispanic/Latina origin identified a single nucleotide polymorphism (SNP) in the 6q25 region, rs140068132, that correlates with Indigenous American (IA) ancestry and is protective against BC. The underrepresentation of Latin American populations in public databases has hindered the study of the mechanisms by which this SNP confers a protective effect. We aimed to identify IA germline variants associated with BC risk and to test their association with tumor gene expression in this region.

We performed a case-control fine-mapping analysis in the 6q25 region. BC patients part of the PEGEN-BC Study (N=1809) were included as cases and women from a pregnancy outcomes study in Peru as controls (N=3334). Genome-wide genotype data were available and missing genotypes were imputed using the TOPMED Imputation Server. Logistic regression was used to test the association between each SNP and BC risk. We exome-sequenced 247 breast tumors of PEGEN-BC patients. Tumor subtype was assigned by the pam50 method. We excluded patients diagnosed with stage IV disease, with tumors classified as normal-like or as uncertain, and carriers of the GG genotype for rs140068132, leaving 242 samples. Association between rs140068132 and gene expression of genes in the 6q25 region was tested adjusting by age at diagnosis and IA ancestry.

The strongest signal corresponded to rs140068132 (odds ratio (OR)=0.53, p=1.9e-21). The model adjusted by rs140068132 revealed three additional independent variants that correlate with Indigenous American ancestry: rs184135739 (OR=0.8, p=0.006), rs141057867 (OR=0.87, p=0.006) and rs140125124 (OR=1.23, p=0.015). Gene expression analysis stratified by subtype revealed that among HER2+ tumors (N=63), rs140068132 was associated with ARMT1 (fold change comparing AA to AG (FC)=1.6, p<0.01), CCDC170 (FC=1.8, p<0.01), MTHFD1L (FC=0.7, p<0.01) and RMND1 (FC=1.4, p=0.013). Among Luminal-B (N=68) tumors, there was an association with ARMT1 (FC= 1.9, p=0.001), ESR1 (FC=1.4, p=0.04) and MTHFD1L (FC= 0.8, p=0.02). Only ESR1 was associated with the SNP (FC= 0.5, p= 0.03) among basal tumors (N=56). No association was identified among Luminal-A tumors (N=55). rs141057867 showed evidence of cis-association with CLDN20 (FC=1.4, p=0.014) among HER2+ subtypes and rs184135739 with ZC3H12D (FC=2.1, p=0.02) and SUMO4 (FC=1.8, p=0.023) among Lumina-A tumors.

Two of the three novel IA SNPs are protective against BC and show association with gene expression. The rs140068132-G variant regulates the expression of genes in the 6q25 region in a subtype-specific manner. A possible mechanism explaining the protective effect of the rs140068132 polymorphism might be linked to the lower expression of MTHFD1L among G-allele carriers in some subtypes. This gene is deregulated in cancer and its expression is negatively associated with cancer survival, including BC.

Citation Format: Valentina A. Zavala, Xiaosong Huang, Sandro Casavilca-Zambrano, Jeannie Navarro-Vásquez, Carlos A. Castañeda, Guillermo Valencia, Zaida Morante, Monica Calderon, Julio E. Abugattas, Henry Gómez, Hugo Fuentes, Ruddy Liendo-Picoaga, Jose M. Cotrina, Katia Roque, Jule Vásquez, Luis Mas, Marco Gálvez-Nino, Jovanny Zabaleta, Tatiana Vidaurre, Laura Fejerman. Regulation of genes located in 6q25 by an Indigenous American genetic variant in breast cancer patients from Peru. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5237.

Breast cancer subtype and clinical characteristics in women from Peru

Introduction

Breast cancer is a heterogeneous disease, and the distribution of the different subtypes varies by race/ethnic category in the United States and by country. Established breast cancer-associated factors impact subtype-specific risk; however, these included limited or no representation of Latin American diversity. To address this gap in knowledge, we report a description of demographic, reproductive, and lifestyle breast cancer-associated factors by age at diagnosis and disease subtype for The Peruvian Genetics and Genomics of Breast Cancer (PEGEN-BC) study.

Methods

The PEGEN-BC study is a hospital-based breast cancer cohort that includes 1943 patients diagnosed at the Instituto Nacional de Enfermedades Neoplásicas in Lima, Peru. Demographic and reproductive information, as well as lifestyle exposures, were collected with a questionnaire. Clinical data, including tumor Hormone Receptor (HR) status and Human Epidermal Growth Factor Receptor 2 (HER2) status, were abstracted from electronic medical records. Differences in proportions and mean values were tested using Chi-squared and one-way ANOVA tests, respectively. Multinomial logistic regression models were used for multivariate association analyses.

Results

The distribution of subtypes was 52% HR+HER2-, 19% HR+HER2+, 16% HR-HER2-, and 13% HR-HER2+. Indigenous American (IA) genetic ancestry was higher, and height was lower among individuals with the HR-HER2+ subtype (80% IA vs. 76% overall, p=0.007; 152 cm vs. 153 cm overall, p=0.032, respectively). In multivariate models, IA ancestry was associated with HR-HER2+ subtype (OR=1.38,95%CI=1.06-1.79, p=0.017) and parous women showed increased risk for HR-HER2+ (OR=2.7,95%CI=1.5-4.8, p<0.001) and HR-HER2- tumors (OR=2.4,95%CI=1.5-4.0, p<0.001) compared to nulliparous women. Multiple patient and tumor characteristics differed by age at diagnosis (<50 vs. >=50), including ancestry, region of residence, family history, height, BMI, breastfeeding, parity, and stage at diagnosis (p<0.02 for all variables).

Discussion

The characteristics of the PEGEN-BC study participants do not suggest heterogeneity by tumor subtype except for IA genetic ancestry proportion, which has been previously reported. Differences by age at diagnosis were apparent and concordant with what is known about pre- and post-menopausal-specific disease risk factors. Additional studies in Peru should be developed to further understand the main contributors to the specific age of onset and molecular disease subtypes in this population and develop population-appropriate predictive models for prevention.

Erratum: Cancer screening and breast cancer family history in Spanish-speaking Hispanic/Latina women in California

[This corrects the article DOI: 10.3389/fonc.2022.940162.].

Cancer screening and breast cancer family history in Spanish-speaking Hispanic/Latina women in California

Background

Breast cancer is the most common cancer among women in the U.S. and the leading cause of cancer death among Hispanics/Latinas (H/L). H/L are less likely than Non-H/L White (NHW) women to be diagnosed in the early stages of this disease. Approximately 5-10% of breast cancer can be attributed to inherited genetic mutations in high penetrance genes such as BRCA1/2. Women with pathogenic variants in these genes have a 40-80% lifetime risk of breast cancer. Past studies have shown that genetic counseling can help women and their families make informed decisions about genetic testing and early cancer detection or risk-reduction strategies. However, H/L are 3.9-4.8 times less likely to undergo genetic testing than NHW women. We developed a program to outreach and educate the H/L community about hereditary breast cancer, targeting monolingual Spanish-speaking individuals in California. Through this program, we have assessed cancer screening behavior and identified women who might benefit from genetic counseling in a population that is usually excluded from cancer research and care.

Materials and Methods

The "Tu Historia Cuenta" program is a promotores-based virtual outreach and education program including the cities of San Francisco, Sacramento, and Los Angeles. Participants responded to three surveys: a demographic survey, a breast cancer family history survey, and a feedback survey. Survey responses were described for participants and compared by area where the program took place using chi-square, Fisher exact tests, and t tests. Multinomial logistic regression models were used for multivariate analyses.

Results and Conclusion

We enrolled 1042 women, 892 completed the cancer family history survey and 62 (7%) provided responses compatible with referral to genetic counseling. We identified 272 women (42.8% ages 40 to 74 years) who were due for mammograms, 250 women (24.7% ages 25 to 65 years) due for Papanicolaou test, and 189 women (71.6% ages 50+) due for colorectal cancer screening. These results highlight the need of additional support for programs that spread awareness about cancer risk and facilitate access to resources, specifically within the H/L community.

Association between Ancestry-Specific 6q25 Variants and Breast Cancer Subtypes in Peruvian Women

BACKGROUND

Breast cancer incidence in the United States is lower in Hispanic/Latina (H/L) compared with African American/Black or Non-Hispanic White women. An Indigenous American breast cancer-protective germline variant (rs140068132) has been reported near the estrogen receptor 1 gene. This study tests the association of rs140068132 and other polymorphisms in the 6q25 region with subtype-specific breast cancer risk in H/Ls of high Indigenous American ancestry.

METHODS

Genotypes were obtained for 5,094 Peruvian women with (1,755) and without (3,337) breast cancer. Associations between genotype and overall and subtype-specific risk for the protective variant were tested using logistic regression models and conditional analyses, including other risk-associated polymorphisms in the region.

RESULTS

We replicated the reported association between rs140068132 and breast cancer risk overall [odds ratio (OR), 0.53; 95% confidence interval (CI), 0.47-0.59], as well as the lower odds of developing hormone receptor negative (HR-) versus HR+ disease (OR, 0.77; 95% CI, 0.61-0.97). Models, including HER2, showed further heterogeneity with reduced odds for HR+HER2+ (OR, 0.68; 95% CI, 0.51-0.92), HR-HER2+ (OR, 0.63; 95% CI, 0.44-0.90) and HR-HER2- (OR, 0.77; 95% CI, 0.56-1.05) compared with HR+HER2-. Inclusion of other risk-associated variants did not change these observations.

CONCLUSIONS

The rs140068132 polymorphism is associated with decreased risk of breast cancer in Peruvians and is more protective against HR- and HER2+ diseases independently of other breast cancer-associated variants in the 6q25 region.

IMPACT

These results could inform functional analyses to understand the mechanism by which rs140068132-G reduces risk of breast cancer development in a subtype-specific manner. They also illustrate the importance of including diverse individuals in genetic studies.

Abstract 3683: Identification of optimal set of genetic variants from a previously reported polygenic risk score for breast cancer risk prediction in Latin American women

Around 10% of genetic predisposition for breast cancer is explained by mutations in high/moderate penetrance genes. The remaining proportion is explained by multiple common variants of relatively small effect. A subset of these variants has been identified mostly in Europeans and Asians; and combined into polygenic risk scores (PRS) to predict breast cancer risk. Our aim is to identify a subset of variants to improve breast cancer risk prediction in Hispanics/Latinas (H/Ls).Breast cancer patients were recruited at the Instituto Nacional de Enfermedades Neoplásicas in Peru, to be part of The Peruvian Genetics and Genomics of Breast Cancer Study (PEGEN). Women without a diagnosis of breast cancer from a pregnancy outcomes study conducted in Peru were included as controls. After quality control filters, genome-wide genotypes were available for 1,809 cases and 3,334 controls. Missing genotypes were imputed using the Michigan Imputation Server using individuals from 1000 Genomes Project as reference. Genotypes for 313 previously reported breast cancer associated variants and 2 Latin American specific single nucleotide polymorphisms (SNPs) were extracted from the data, using an imputation r2 filter of 30%. Feature selection techniques were used to identify the best subset of SNPs for breast cancer prediction in Peruvian women. We randomly split the PEGEN data by 4:1 ratio for training/validation and testing. Training/validation data were resampled and split in 3:1 ratio into training and validation sets. SNP ranking and selection were done by bootstrapping results from 100 resampled training and validation sets. PRS were built by adding counts of risk alleles weighted by previously reported beta coefficients. The Area Under the Curve (AUC) was used to estimate the prediction accuracy of subsets of SNPs selected with different techniques. Logistic regression was used to test the association between standardized PRS residuals (after adjustment for genetic ancestry) and breast cancer risk. Of the 315 reported variants, 274 were available from the imputed dataset. The full 274-SNP PRS was associated with an AUC of 0.63 (95%CI=0.59-0.66) in the PEGEN study. Using different feature selection methods, we found subsets of SNPs that were associated with AUC values between 0.65-0.69. The best method (AUC=0.69, 95%CI=0.66-0.72) included a subset of 98 SNPs. Sixty-eight SNPs were selected by all methods, including the protective SNP rs140068132 in the 6q25 region, which is associated with Indigenous American ancestry and the largest contribution to the AUC.We identified a subset of 98 SNPs from a previously identified breast cancer PRS that improves breast cancer risk prediction compared to the full set, in women of high Indigenous American ancestry from Peru. Replication in women from Mexico and Colombia, and H/Ls from the U.S will allow us to confirm these results.

Citation Format: Valentina A. Zavala, Tatiana Vidaurre, Xiaosong Huang, Sandro Casavilca, Jeannie Navarro, Michelle A. Williams, Sixto Sanchez, Elad Ziv, Luis Carvajal-Carmona, Susan L. Neuhausen7, Bizu Gelaye, Laura Fejerman. Identification of optimal set of genetic variants from a previously reported polygenic risk score for breast cancer risk prediction in Latin American women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3683.

Abstract PO-203: Assessment of previously reported polygenic risk score for breast cancer in Peruvian women

Background: Breast cancer is the most common cancer among women worldwide. Mutations in high and moderate penetrance genes account for ~10% of breast cancer cases. The remaining genetic predisposition is explained by multiple common genetic variants of relatively small effect. Genome-wide association studies in individuals of mostly European and Asian genetic ancestry have identified multiple risk-associated loci which can be combined into a polygenic risk score (PRS) to predict breast cancer. Our aim was to assess the association of a 313 polymorphism-PRS score (313-PRS) previously published and breast cancer risk in women of a relatively high proportion of Indigenous American ancestry from Peru. Methods: Breast cancer patients were recruited at the Instituto Nacional de Enfermedades Neoplásicas in Lima, Peru, to be part of The Peruvian Genetics and Genomics of Breast Cancer Study (PEGEN-BC, N=1,755). Women without a diagnosis of breast cancer from a pregnancy outcomes study conducted in Lima, Peru, were included as ‘convenience' controls (N=3,342). Genome-wide genotype data were available for all women and missing genotypes were imputed using the Michigan Imputation Server including individuals from 1000 Genomes Project phase III as the reference panel. The 313 polymorphisms were extracted from the imputed data set for further analysis without imputation-r2 filter. Logistic regression was used to test the association between standardized PRS residuals (after adjustment for genetic ancestry) and breast cancer risk. Results: The 313-PRS was positively associated with breast cancer risk in women from Lima, Peru. (OR lowest decile vs. intermediate deciles=0.56, 95%CI= 0.44-0.71, p= 0.00001; OR highest decile vs. intermediate deciles=1.58, 95%CI=1.27-1.95, p= 0.000035). Analysis stratified by quartiles of Indigenous American ancestry did not show heterogeneity. AUROC curve analysis showed similar estimates for all quartiles of Indigenous American ancestry ranging from 0.59 (Q1-lowest ancestry) to 0.61 (Q4-highest ancestry). Conclusion: We confirmed the association between the previously published 313-PRS and breast cancer risk in highly Indigenous American women from Peru. The magnitude of the association and AUROC curve were not statistically significantly different by quartiles of Indigenous American ancestry. The similarity in the AUROC curve estimates by ancestry in a study where the highest ancestry quartile (Q4) includes women with more than 91% Indigenous American ancestry suggests that PRS developed in mostly European women could be used in Latin American populations of high Indigenous American ancestry.

Citation Format: Valentina A. Zavala, Tatiana Vidaurre, Xiaosong Huang, Sandro Casavilca, Jeannie Navarro, Michelle A. Williams, Sixto E. Sanchez, Bizu Gelaye, Laura Fejerman. Assessment of previously reported polygenic risk score for breast cancer in Peruvian women [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 PO-203.

Cancer health disparities in racial/ethnic minorities in the United States

There are well-established disparities in cancer incidence and outcomes by race/ethnicity that result from the interplay between structural, socioeconomic, socio-environmental, behavioural and biological factors. However, large research studies designed to investigate factors contributing to cancer aetiology and progression have mainly focused on populations of European origin. The limitations in clinicopathological and genetic data, as well as the reduced availability of biospecimens from diverse populations, contribute to the knowledge gap and have the potential to widen cancer health disparities. In this review, we summarise reported disparities and associated factors in the United States of America (USA) for the most common cancers (breast, prostate, lung and colon), and for a subset of other cancers that highlight the complexity of disparities (gastric, liver, pancreas and leukaemia). We focus on populations commonly identified and referred to as racial/ethnic minorities in the USA-African Americans/Blacks, American Indians and Alaska Natives, Asians, Native Hawaiians/other Pacific Islanders and Hispanics/Latinos. We conclude that even though substantial progress has been made in understanding the factors underlying cancer health disparities, marked inequities persist. Additional efforts are needed to include participants from diverse populations in the research of cancer aetiology, biology and treatment. Furthermore, to eliminate cancer health disparities, it will be necessary to facilitate access to, and utilisation of, health services to all individuals, and to address structural inequities, including racism, that disproportionally affect racial/ethnic minorities in the USA.

Abstract C092: Immune characteristics of triple-negative breast cancer (TNBC) in Latin American women from Colombia

Background: Triple-negative breast cancer (TNBC) is an aggressive form of the disease with limited treatment options and poor survival. A series of retrospective studies established the presence of tumor-infiltrating lymphocytes (TILs) in most primary breast cancers, the number of which affect the response rate to chemotherapy in both neoadjuvant and adjuvant treatment contexts. A subset of TNBC is highly immunogenic, and recent studies have shown that understanding the specific immune profiles of tumors has implications both for treatment and prognosis. Most studies have been conducted in samples of women of European origin, and little is known about the immune profile of TNBCs in Hispanic/Latinas. The specific goal of our study was to test the association between immune characteristics of TNBC from Colombian patients and genetic ancestry proportions, to determine if genetic ancestry could be a relevant factor in defining the immune characteristics of TNBC.

Methods: We obtained 41 TNBC tissues through collaboration with the National Cancer Institute in Colombia along with demographic and clinical information. Genetic ancestry was estimated with a panel of 106 ancestry informative markers and the program STRUCTURE. RNA was extracted from FFPE tissues, qualified using Agilent chips, and used for sequencing at the Translational Genomics Core at the Stanley S. Scott Cancer Center. Using the TNBCtype program we confirmed 33 samples as TNBC. The program xCell was used for cell-signature identification based on RNAseq data. We explored associations between genetic ancestry and scores obtained for different immune cell-types and an overall immune score using linear regression. We analyzed the association for the following specific cells: Th1 cells, Th2 cells, Treg, CD4 T cells, CD4 TEM, CD4 memory T cells, CD8 T cells, CD8 TCM, CD8 TEM, CD8 naive T cells, macrophages, macrophages M1, macrophages M2, and mast cells.

Results: The overall immune score was positively associated with the proportion of African ancestry (p=0.049). Interestingly, we observed that Indigenous American ancestry was inversely associated with the Treg cell score while African ancestry was positively associated with it. Levels of these regulatory cells have been correlated with prognosis in ER- and triple-negative disease. We also found that CD4 T cell and CD4 memory T-cell scores were positively associated with African ancestry (P=0.006 and P=0.049 respectively).

Conclusions: Our results suggest that genetic ancestry among Latina women from Colombia is associated with certain immune characteristics of breast cancer. We need to further test these associations in a larger sample to confirm the findings, obtain additional insights, and understand their implications for TNBC treatment and prognosis among Latin American women.

Citation Format: Valentina A. Zavala, Laura C. Carrasquilla, Silvia J. Serrano-Gomez, Maria C. Sanabria-Salas, Melody C. Baddoo, Jone Garai, Jovanny Zabaleta, Laura Fejerman. Immune characteristics of triple-negative breast cancer (TNBC) in Latin American women from Colombia [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C092.

Abstract B080: Assessment of the molecular mechanisms of a protective variant for breast cancer in Latinas

The incidence of breast cancer is lower in women of Latin American origin in the U.S. compared to European American and African American women. Among Latinas, the rs140068132A&gt;G variant, which is common in women with IAA, has been associated to a lower risk of breast cancer. The frequency of the G allele is 0% for non-Latinos while 12% in Latinos, being highest in the Peruvian population (23%). This variant is located on chromosome 6 near the Estrogen Receptor 1 gene (ESR1) and even though experimental evidence suggests that this variant might be functional, the molecular mechanisms that explain its protective effect are unknown. We hypothesize that the rs140068132-G variant decreases ESR1 expression, which affects the expression or function of genes involved in associated pathways. We aim to test the association of the rs140068132 variant and gene expression in breast cancer tumors from patients with high IAA. We collected 47 breast tumors and blood samples from the Instituto Nacional de Enfermedades Neoplásicas in Lima, Peru. These patients were genotyped for IAA estimation and determination of the rs140068132 genotype. Total RNA was extracted from tumor samples and used for a paired-end sequencing (2 × 75bp paired-end,100 million reads per sample) in the Illumina NextSeq500. Differential gene expression between genotypes was performed by DEseq2 R package and statistical significance was determined using FDR&lt;0.05 for samples with at least log2 1.5-fold change. Differentially expressed isoforms were detected by EBseq R package using FDR&lt;0.05. Tumor intrinsic subtypes were obtained using PAM50 as implemented in the genefu R package. The average IAA for the 47 Peruvian patients was 77% (SD=0.17). Twenty-seven patients were homozygous AA, 19 heterozygous AG and 1 GG for the rs140068132 variant. According to PAM50 classification, 10 tumors were Luminal A, 12 Luminal B, 15 HER2+ and 10 Basal. Among luminal tumors there was a suggestive trend towards lower expression of the ESR1 gene in patients carrying the protective allele (p=0.16). Including all subtypes, 27 genes were differentially expressed according to the rs140068132 genotype. Four of these genes are ER dependent or associated with ER status. The expression of the top gene, which is a transcriptional target of ER, is lost in patients with the protective allele. This association is mainly driven by its expression in luminal tumors and remained significant after adjusting for IAA. ESR1 isoforms were not differentially expressed by genotype, however significant differences were detected in the expression of isoforms for 115 genes, of which 18% have been reported to be transcriptional targets of ER or functionally related. Our preliminary results suggest that the rs140068132 variant decreases ER expression and affects the expression of functionally associated genes in luminal tumors. Further allele-specific expression analysis will elucidate if this variant is part of a cis-regulatory module.

Note: This abstract was not presented at the conference.

Citation Format: Valentina A. Zavala, Tatiana Vidaurre, Katie Marker, Sandro Casavilca, Lizeth Tamayo, Carlos Castañeda, Jeannie Vásquez, Fernando Valencia, Zaida Morante, M. Calderon, J. Abugattas, H. Gomez, H. Fuentes, C. Monge-Pimentel, Silvia Neciosup, Jovanny Zabaleta, Laura Fejerman. Assessment of the molecular mechanisms of a protective variant for breast cancer in Latinas [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B080.

Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Is Associated with Indigenous American Ancestry in Latin American Women

Women of Latin American origin in the United States are more likely to be diagnosed with advanced breast cancer and have a higher risk of mortality than non-Hispanic White women. Studies in U.S. Latinas and Latin American women have reported a high incidence of HER2 positive (+) tumors; however, the factors contributing to this observation are unknown. Genome-wide genotype data for 1,312 patients from the Peruvian Genetics and Genomics of Breast Cancer Study (PEGEN-BC) were used to estimate genetic ancestry. We tested the association between HER2 status and genetic ancestry using logistic and multinomial logistic regression models. Findings were replicated in 616 samples from Mexico and Colombia. Average Indigenous American (IA) ancestry differed by subtype. In multivariate models, the odds of having an HER2+ tumor increased by a factor of 1.20 with every 10% increase in IA ancestry proportion (95% CI, 1.07-1.35; P = 0.001). The association between HER2 status and IA ancestry was independently replicated in samples from Mexico and Colombia. Results suggest that the high prevalence of HER2+ tumors in Latinas could be due in part to the presence of population-specific genetic variant(s) affecting HER2 expression in breast cancer. SIGNIFICANCE: The positive association between Indigenous American genetic ancestry and HER2+ breast cancer suggests that the high incidence of HER2+ subtypes in Latinas might be due to population and subtype-specific genetic risk variants.

Genetic Epidemiology of Breast Cancer in Latin America

The last 10 years witnessed an acceleration of our understanding of what genetic factors underpin the risk of breast cancer. Rare high- and moderate-penetrance variants such as those in the BRCA genes account for a small proportion of the familial risk of breast cancer. Low-penetrance alleles are expected to underlie the remaining heritability. By now, there are about 180 genetic polymorphisms that are associated with risk, most of them of modest effect. In combination, they can be used to identify women at the lowest or highest ends of the risk spectrum, which might lead to more efficient cancer prevention strategies. Most of these variants were discovered in populations of European descent. As a result, we might be failing to discover additional polymorphisms that could explain risk in other groups. This review highlights breast cancer genetic epidemiology studies conducted in Latin America, and summarizes the information that they provide, with special attention to similarities and differences with studies in other populations. It includes studies of common variants, as well as moderate- and high-penetrance variants. In addition, it addresses the gaps that need to be bridged in order to better understand breast cancer genetic risk in Latin America.

Abstract 483: BRCA1 protein expression is downregulated by miR-185, miR-93 and miR-107 in breast cancer tumors

BRCA1 is a tumor-suppressor gene whose mutations confer a high risk to breast cancer. Fifty percent of hereditary breast cancer tumors without germline mutation have impaired BRCA1 expression, as well as 30% of sporadic cases. Somatic events that silence BRCA1 expression have been described in breast cancer tumors, such as promoter hypermethylation and BRCA1 gene deletion; however, these mechanisms do not completely explain the loss of BRCA1 expression in breast tumors. Our aim is to identify miRNAs differentially expressed in tumors with negative or moderate BRCA1 protein, which could regulate BRCA1 expression. Total RNA from 50 fresh-frozen breast cancer tumors was isolated and miRNA profiling was performed using miRNA microarrays. Sixteen miRNAs were found exclusively upregulated in BRCA1-negative, and ten in BRCA1-moderate tumors. Among them, in silico analyses predicted eleven miRNAs that could regulate BRCA1 expression. The effect of five of these microRNAs was assessed using a luciferase reporter assay in HEK293T cells, where the complete BRCA1 3'UTR, or a segment of its coding region, was cloned within the 3' end of the Luciferase gene. Cells were co-transfected with each of the selected microRNAs. MiR-185, miR-93 and miR-107 significantly downregulated luciferase activity by binding to the 3'UTR. Also, we transfected these microRNAs into a nontumorigenic breast cell line (MCF10A), where miR-93 diminished endogenous BRCA1 expression in 48%, miR-185 in 39% and miR-107 in 38%, in relation to non-transfected cells. These results strongly support that these microRNAs are potential regulators of BRCA1 expression in breast cancer tumors.

FONDECYT1120200, CONICYT21120269.

Citation Format: Valentina A. Zavala, Patricia Gajardo, Paola Faundez, Carolina Alvarez, Pilar Carvallo. BRCA1 protein expression is downregulated by miR-185, miR-93 and miR-107 in breast cancer tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 483.

New clinical advances in immunotherapy for the treatment of solid tumours

Advances in understanding the mechanisms of cancer cells for evading the immune system surveillance, including how the immune system modulates the phenotype of tumours, have allowed the development of new therapies that benefit from this complex cellular network to specifically target and destroy cancer cells. Immunotherapy researchers have mainly focused on the discovery of tumour antigens that could confer specificity to immune cells to detect and destroy cancer cells, as well as on the mechanisms leading to an improved activation of effector immune cells. The Food and Drug Administration approval in 2010 of ipilumumab for melanoma treatment and of pembrolizumab in 2014, monoclonal antibodies against T-lymphocyte-associated antigen 4 and programmed cell death 1, respectively, are encouraging examples of how research in this area can successfully translate into clinical use with promising results. Currently, several ongoing clinical trials are in progress testing new anti-cancer therapies based on the enhancement of immune cell activity against tumour antigens. Here we discuss the general concepts related to immunotherapy and the recent application to the treatment of cancer with positive results that support their consideration of clinical application to patients.