Nucleotide Excision Repair (NER) is a critical pathway involved in breast cancer (BC). We have previously published that a low DNA repair capacity (DRC) is associated with a higher risk of BC in Puerto Rican women. Let-7b belongs to a miRNA family with tumor suppressor activity that targets oncogenes. We isolated miRNAs from plasma of 153 Puerto Rican women with and without BC. DRC was measured in lymphocytes by means of a host cell reactivation assay. These women were divided into four groups according to their DRC level: High (>3.8%) and low (<3.8%). The four groups consisted of BC patients with high (n = 35) and low (n = 43) DRC and controls with high (n = 39) and low (n = 36) DRC. Epidemiologic data were collected at initial BC diagnosis and almost five years after diagnosis. A significant difference in Let-7b expression was found in BC patients with high DRC versus the remaining groups (p < 0.001). Thus, our data reveal a possible role of Let-7b on DRC during breast carcinogenesis. Our study is innovative because it provides the first evidence that Let-7b may play role in DRC regulation (through the NER repair pathway) in BC.

Breast cancer (BC) is the most commonly diagnosed cancer in women worldwide and is the leading cause of death among Hispanic women. Previous studies have shown that women with a low DNA repair capacity (DRC), measured through the nucleotide excision repair (NER) pathway, have an increased BC risk. Moreover, we previously reported an association between DRC levels and the expression of the microRNA (miRNA) let-7b in BC patients. MiRNAs can induce genomic instability by affecting the cell’s DNA damage response while influencing the cancer pathobiology. The aim of this pilot study is to identify plasma miRNAs related to variations in DRC levels in BC cases. Hypothesis. Our hypothesis consists in testing whether DRC levels can be correlated with miRNA expression levels. Methods. Plasma samples were selected from 56 (27 cases and 29 controls) women recruited as part of our BC cohort. DRC values were measured in lymphocytes using the host-cell reactivation assay. The samples were divided into two categories: low (≤3.8%) and high (>3.8%) DRC levels. MiRNAs were extracted to perform an expression profile analysis. Results. Forty miRNAs were identified to be BC-related (p<0.05, MW), while 18 miRNAs were found to be differentially expressed among BC cases and controls with high and low DRC levels (p<0.05, KW). Among these candidates are miR-299-5p, miR-29b-3p, miR-302c-3p, miR-373-3p, miR-636, miR-331-5p, and miR-597-5p. Correlation analyses revealed that 4 miRNAs were negatively correlated within BC cases with low DRC (p<0.05, Spearman’s correlation). Results from multivariate analyses revealed that the clinicopathological characteristics may not have a direct effect on specific miRNA expression. Conclusion. This pilot study provides evidence of four miRNAs that are negatively regulated in BC cases with low DRC levels. Additional studies are needed in order to have a complete framework regarding the overall DRC levels, miRNA expression profiles, and tumor characteristics.

Resveratrol is a (poly)phenol that has been reported to have beneficial properties against several cancers, such as breast cancer (BC). Resveratrol is also known to possess antioxidant capacity and estrogen and antiestrogen‐mimetic activity. BC is a heterogeneous disease in which the behavior and biological characteristics of the tumors can vary; therefore, affecting disease prognosis and treatment selection. Breast tumors can be classified based on three hormonal receptors: estrogen (ER), progesterone (PR), and HER2. Based on their status, four molecular subtypes have been identified: luminal A (ER+, PR+/−, HER2−), luminal B (ER+, PR+/−, HER2+), HER2+ (ER−, PR−, HER2+), and triple‐negative (TN) (ER−, PR−, HER2−).PURPOSESince resveratrol is a (poly)phenol with estrogen mimicking properties and estrogen has been shown to induce DNA damage, the main objective of this study is to assess the DNA damaging and antioxidant potential of resveratrol among the four principal molecular subtypes. Since previous studies from our laboratory show a relationship between ER positivity and DNA repair through the nucleotide excision repair (NER) pathway in BC, we chose to assess DNA damage, through NER pathway, and expression changes in genes related to antioxidant response.METHODSBC cell lines resembling the different molecular subtypes were used to achieve our aim. To assess DNA damaging induction through the NER pathway, the cells were irradiated with ultraviolet C (UVC) light. MCF‐7 (luminal A) cells were cultured and treated with 250 μM resveratrol for 2 hours before and after UVC exposure (20J/m2) and were compared with untreated cells exposed to UVC. After dosing and irradiation DNA damage through the NER pathway was measured using the alkaline comet assay. NFE2L2 expression was measured through RT‐PCR.RESULTSOur results show that both treatments with resveratrol before and after UVC exposure induced DNA damage in MCF‐7 cells. While untreated cells (UVC only) showed a 10.68 ± 3.12%, resveratrol pre‐treated cells had a 29.0 ± 0.88% (p=0.07). MCF‐7 cells treated with resveratrol after UVC exposure had a DNA damage of 65.2 ± 16.57% (p=0.22). Gene expression measurements of NFE2L2 are currently ongoing.CONCLUSIONSAlthough these changes were not statistically significant, they suggest a role of resveratrol in DNA damage induction in MCF‐7 cells upon NER pathway activation. Currently, we are working with the MDA‐MB‐231 (TN), BT‐474 (luminal B), and SK‐BR‐3 (HER2+), to compare the DNA damaging potential of resveratrol among the different molecular BC subtype through the NER pathway. We will also assess protein expression of key NER proteins through western blot.Support or Funding InformationThis study was supported by NIH‐NIGMS #2R25GM096955, #S06GM008239‐20, 9SC1CA182846‐04, #U54CA163068, and G12‐MD007579.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Background: Vitamin D regulates estrogen synthesis among other mechanisms involved in breast cancer (BC) carcinogenesis. An important gap, to our knowledge, is whether blood levels of vitamin D are associated with DNA repair capacity in women with BC. Previously, we reported that a low DNA repair capacity (DRC) is a risk factor for BC and that DRC levels are associated with estrogen receptor (ER) positivity in women with BC. Moreover, we also reported that there is an intrinsic variability in DRC levels among the four principal BC subtypes. Therefore, our aim is to study the link between DRC and plasma vitamin D levels in BC and among BC subtypes. Methods: Treatment-naïve BC cases and controls were selected from our cohort of Hispanic women (n=1,187). DRC was assessed in lymphocytes through the host-cell reactivation assay. Vitamin D was measured using LC/MS/MS. Results: Women with BC (n=91) had higher (+6.6 ng/ml) vitamin D than controls (n=22) (p=0.007). There were significant differences in vitamin D levels (p&lt;0.05) between BC cases with high (≥3.8%) (n=17) and low (&lt;3.8%) (n=74) DRC levels. Vitamin D and DRC were negatively correlated in BC cases (r=-0.2296, p=0.03). When women with BC and low DRC levels (n=56) were stratified into: luminal A (n=17), luminal B (n=11), HER2+ (n=10), and triple-negative (n=18), women with HER2+ and TNBC showed the highest levels of vitamin D (p&lt;0.05). Women with ER- had higher levels (+7.6 ng/ml) of vitamin D than women with ER+ tumors (p=0.005). After finding that plasma vitamin D levels from women with BC and controls were significantly different when stratified by DRC levels and BC subtypes, ROC curves were constructed to examine whether these levels could allow us to discriminate between our four study groups. Significant differences (p=0.0126) were found for cases and controls with low DRC; AUC of 0.7178. When considering all women with BC independently of DRC levels, the AUC was 0.7353 (p=0.0300). Conclusions: This study provides the first evidence of a link between vitamin D and DRC levels in women with BC. We also present data as to how vitamin D varies across four molecular subtypes of BC in Hispanic women. Impact: Our results fills an important gap on the link between plasma vitamin D and DRC levels in women with BC. Funding: This study was supported by grants #S06GM008239-20, 9SC1CA182846-04, and 5SC1CA157250-02, 5U54CA163071-04, 5R25GM096955-08. Citation Format: Carmen Ortiz, Jarline Encarnacion, Ralphdy Vergne, Luis Padilla, Jaime Matta. Plasma vitamin D levels and DNA repair capacity in four molecular subtypes of women with breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1760.

Vitamin D exists as vitamin D2 and D3, which are metabolized to 25-hydroxyvitamin D [25(OH)D], the major circulating vitamin D metabolite. Besides its physiological functions, vitamin D levels have also been studied as a risk factor for several hormonal cancers including breast cancer (BC). Worldwide, BC accounts for nearly a quarter of all cancers in women. Nutritional studies report that vitamin D intake is associated with a lower BC risk. Several discrepancies exist regarding the role of serum vitamin D in BC risk. While some studies report BC risk reduction by vitamin D only in premenopausal, others propose that it only occurs in postmenopausal women. BC tumors may (+) or may not (-) have three hormonal receptors: estrogen (ER), progesterone (PR), and HER2. Based on their status, four principal molecular BC subtypes have been identified: luminal A (ER+/−, PR+/−, HER2-), luminal B (ER+/−, PR+/−, HER2+), HER2+ (ER−, PR−, HER2+), and triple negative (TN) (ER−, PR−, HER2−). If BC is analyzed in terms of molecular subtypes, low vitamin D levels have been associated with aggressive phenotypes and worse prognosis. Vitamin D also influences estrogen synthesis. Since we have previously shown that a low DNA repair capacity (DRC), measured through the nucleotide excision repair pathway, is a risk factor for BC and vitamin D has also been found to affect DNA repair, the focus of this study is to examine the role of plasma vitamin D levels and DRC in BC. The main aim is to elucidate whether there is an association between vitamin D and DRC levels among the four molecular BC subtypes. We hypothesize that a negative correlation between 25(OH)D and DRC levels will be observed among these subtypes. As an initial effort, 47 BC cases and 20 controls without BC were selected from our large BC cohort. DRC was measured in lymphocytes of untreated women using the host cell reactivation assay. Pathology reports were examined to divide BC cases according to their molecular BC subtype: luminal A (n=13), luminal B (n=11), HER2+ (n=10), and TN (n=13). Plasma 25(OH)D levels were measured using the UniCel DxC System at a CLIA-certified lab. Our results show a negative correlation between 25(OH)D and DRC levels (p=0.04). Statistically significant differences were found for vitamin D levels among the different groups (p=0.0019, ANOVA). Moreover, higher 25(OH)D levels (47.97±2.4 ng/mL) were found in ER- BC cases (p=0.03, t-test). When comparing vitamin D levels in BC subtypes, a significant difference was found in HER2+ and TN groups when compared with the control group (p&lt;0.05, Kruskal-Wallis). Based on these preliminary results we conclude that plasma vitamin D levels may be correlated with DRC levels in women with BC. Ongoing studies with a larger sample size are aimed at elucidating more precisely the potential association between vitamin D and DRC in these molecular BC subtypes. Citation Format: Carmen Ortiz, Jarline Encarnación, Ralphdy Vergne, Wanda Vargas, Jaime Matta. Correlation between vitamin D levels and DNA repair capacity in breast cancer patients stratified by molecular subtypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3286. doi:10.1158/1538-7445.AM2017-3286