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In a previous work, we identified nine founder mutations present in close to 80% of BRCA1 and BRCA2 mutation carriers, and distributed across the country. The presence of founder mutations constitutes a valuable opportunity to develop new strategies for genetic screening. Genetic tests are primarily performed by NGS sequencing, which requires sophisticated and expensive equipment, and it takes 2-3 weeks for the results to be informed to the patient. In addition, genetic tests are not covered by insurance companies in Latin American countries. In this work, we present the standardization and technical validation of a real-time PCR based methodology for allelic discrimination in order to identify the nine Chilean founder mutations in BRCA1 and BRCA2 genes.We designed nine pairs of probes and nine pairs of primers to amplify synchronically nine regions of the BRCA1/BRCA2 genes by real-time PCR, in order to identify the nine founder mutations through allelic discrimination analyses. Technical validation was performed using 90 positive and 90 negative samples for each mutation. The methodology was tested in a second group of 60 patients. Our method correctly classified carriers and non-carriers of one of the nine Chilean founder mutations with a 100% specificity and 100% sensitivity, compared with Sanger sequencing performance.We develop an inexpensive, simple, and fast mutation detection method that could be implemented locally in Hospitals from the Private to Public health system. This methodology may be useful for the screening of BRCA1 and BRCA2 mutations in other populations.

Metastasis, the leading cause of cancer-associated deaths, is promoted by transcription factors SNAIL, SLUG, ZEB1 and TWIST through the activation of epithelial-mesenchymal transition (EMT). MicroRNAs can suppress EMT, emerging as candidate molecular biomarkers and novel therapeutic targets. Herein, we evaluated microRNAs downregulated in breast cancer tissues expressing EMT transcription factors, to find new potential regulators of EMT. MiR-30a, miR-1271, miR-196a, miR-202, miR-210, miR-22, miR-331 and miR-34b were validated. Seven microRNAs downregulated luciferase activity through EMT transcription factors 3’UTR, and all microRNAs decreased cell migration, invasion and/or proliferation. In MDA-MB-231 cells, miR-196a and miR-22 decreased endogenous ZEB1 levels, and miR-30a endogenous CCR7 levels. These results suggest that microRNAs studied are novel regulators of EMT through the control of SNAIL, SLUG, ZEB1 and TWIST. They also regulate the metastatic behavior of cancer cells, and may control the development of lymph node metastasis through the regulation of CCR7.Graphical abstract

BRCA1 has been found to be absent or miss localized in the cytoplasm in a relevant proportion of breast cancer tumors with no germline mutations. BRCA1 main function is in the nucleus, and its interaction with BARD1 is relevant for its nuclear translocation and retention. Our aim was to analyze the sub-cellular localization of BRCA1 and BARD1 in breast cancer tumors, and determine the level of expression of their splice variants BRCA1-Δ11q and BARD1-α and BARD1-β. BRCA1 and BARD1 expressions were performed by immunohistochemistry and immunofluorescence in 103 breast cancer tumors. Colocalization was determined by confocal microscopy. Transcript variants were determined by qRT-PCR. We found BRCA1 localized in the cytoplasm with BARD1 in 51.4 % of tumors. An exclusive nuclear localization of both proteins was observed in 7/103 tumors (6.8 %). Indeed, these tumors displayed an apparent nucleolar colocalization of BARD1 and BRCA1. In relation to splice variants, there is a tendency to an overexpression of BARD1-α mRNA (30 % of tumors) and a decreased expression of BARD1-β (41 %). BRCA1 full-length was downregulated in 63 % of tumors, and 37 % showed BRCA1-Δ11q variant overexpressed. Our findings contribute to a better understanding of the expression and sub-cellular localization of BRCA1 in breast cancer tumors. Interaction of BRCA1 and BARD1 seems to be not affected in 58.2 % of tumors, which showed colocalization of both proteins. The absence of BRCA1 in 41 % of tumors reveals a BRCAness phenotype, constituting an excellent marker for therapy sensitivity, to platinum drugs or PARP inhibitors.

Diverse studies have concluded that Vitamin D plays a main role of in breast cancer risk. The active metabolite of vitamin D, is a pleiotropic hormone that regulates proliferation, survival, and differentiation of many cell types, through its nuclear receptor VDR. Clinical and epidemiological studies have described the association of decreased serum concentrations of 25-hydroxy-vitamin D with a poor prognosis in patients with breast cancer. The metabolism of vitamin D is meticulously regulated through a complex process, involving the vitamin D-activating enzyme CYP27B1, responsible for the final hydroxylation step to form the active metabolite and CYP24A1, the key enzyme in the inactivation of this metabolite. It is also known that VDR is central for vitamin D-mediated transcription regulation. For all these processes it is necessary that vitamin D enters the cell. In the kidney, internalization of the circulating vitamin D is accomplished by megalin, a membrane receptor for vitamin D, which has not been defined in mammary tissue. Until today reports published in relation to the mechanism of vitamin D uptake and its metabolism are scarce in breast cancer tumors. Our aim was to quantify the expression and to determine the localization of: megalin, VDR, CYP27B1 and CYP24A1 enzymes in breast cancer tumor tissues and normal breast tissue. For this purpose, tissue microarrays of formalin-fixed and paraffin-embedded tumor samples and normal breast tissues were analyzed through immunohistochemistry. This study showed that megalin is localized apically in epithelial cells of normal breast tissue, as previously described in the kidney. On the other hand, in breast cancer tumors megalin expression was diminished. Interestingly, we found that megalin had a different localization in two breast cancer tumor subtypes. In luminal breast cancer tumors, megalin was localized mainly in the cellular membrane whereas in triple negative tumors we observed a cytoplasmic localization. For VDR, CYP27B1 and CYP24A1 our results showed that all these proteins are expressed in normal breast tissues. VDR and CYP24A1 have a heterogeneous expression in relation to tumor subtypes and these are highly expressed in all luminal breast cancer tumors, whereas in triple negative breast cancer subtype its expression was low. Our results suggest that exists an alteration in classical metabolic pathway of vitamin D in the tumor subtypes analyzed of breast cancer. With these results we can suggest that in luminal tumors, which have the better prognosis compared with other subtypes, tumor cells still to respond to vitamin D, while in triple negative subtype, the tumor cells reduce their ability to: uptake, catabolize the active metabolite and respond to vitamin D favoring tumor progression. Citation Format: Gabriela Valarezo, Victoria Ortega-Hernández, Gonzalo Escobar-Massú, Wanda Fernández, María Paz Marzolo, Pilar Carvallo. Vitamin D uptake and metabolism in breast cancer tumors: Differential expression of megalin, VDR, CYP27B1 and CYP24A [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 1440.

Breast cancer is the leading cause of cancer death among women worldwide being distant metastases the main cause of disease. Patients with triple negative breast cancer tumors develop distant metastases earlier compared to luminal tumors. Epithelial-mesenchymal transition (EMT) induced by TGFβ signaling pathways, is the main mechanism to promote metastasis through the expression of the transcription factors TWIST, SNAIL, SLUG and ZEB1. Expression of EMT transcription factors has been studied in cancer cell lines however studies in breast cancer tumors with different subtype have not been reported. In addition, the molecular mechanism that induce EMT program is not known yet. In this study we evaluated the expression of the four transcription factors as well as the state of TGFβ/SMAD, ERK/MAPK and PI3K/AKT pathways in breast cancer cell lines HCC1937 (triple negative) and T47D (luminal) after TGFβ treatment. The same analysis was done by immunohistochemistry in 100 breast cancer tumors with different subtype. After TGFβ treatment T47D showed activation of ERK/MAPK and PI3K/AKT pathways and expression of only two transcription factors: SNAIL and SLUG. HCC1937 cells showed activation of TGFβ/SMAD and ERK/MAPK pathways and expression of TWIST, SLUG and ZEB1 but not SNAIL. Similar results were observed in breast cancer tumors, being TGFβ/SMAD pathway active in the majority of triple negative tumors, whereas an active state of PI3K/AKT was observed in luminal tumors. Active ERK/MAPK pathway was observed in both triple negative and luminal tumors. In relation to expression of transcription factors triple negative tumors with an active state of the TGFβ/SMAD pathway showed expression of transcription factors TWIST, SNAIL and SLUG, whereas those tumors with an active state of ERK/MAPK pathway showed only ZEB1 expression. Luminal tumors with an active PI3K/AKT pathway frequently showed ZEB1 expression. Our results showed that expression of a specific EMT transcription factor induced by TGFβ is related to the tumor subtype and depends on the activated signaling pathway. These results suggest different mechanisms of EMT induction by TGFβ in relation to breast cancer tumor subtype. Citation Format: Victoria Ortega-Hernández, Wanda Fernandez, Pilar Carvallo. Alternative activation of TGFβ signaling pathways in breast cancer tumors with different subtype is related to a differential expression of transcription factors that induce EMT [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 2036.

Breast cancer is the leading cause of cancer death among women worldwide, being distant metastases the main cause of death. Epithelial to mesenchymal transition (EMT) has been implicated in promoting cancer invasion and metastasis. This process can be induced by TGFβ through the expression of transcription factors: TWIST, SNAIL, SLUG and ZEB1, which expression may be promoted by different signaling pathways such as SMAD2/SMAD3, PI3K/AKT and ERK/MAPK. The expression of EMT transcription factors has been previously studied in several cancer cell lines, although no studies have been performed in breast cancer tumors. In this study, we analyzed by immunohistochemistry the expression of the four transcription factors, and the signal transduction key proteins p-SMAD2 (ser465/467), p-SMAD2L (ser245/250/,255) and p-AKT (ser473), in 107 breast cancer tumors. We found expression of at least one transcription factor in all triple negative tumors (n=24), while only 70% luminal tumors showed expression of at least one of these proteins. Expression of ZEB1, SNAIL and SLUG was observed in tumors with metastases to lymph node, whereas the majority of tumors expressing TWIST were negative for lymph node status. All triple negative tumors with an active state of the signal transduction pathway TGFβ/SMAD showed expression of at least one transcription factor, whereas 65% of luminal tumors with an active state of the same pathway showed no expression of these transcription factors. Active state of PI3K/AKT pathway was observed only for luminal tumors as it has been described. Sixty-three percent of tumors having this pathway active showed expression of at least one transcription factor. In conclusion we found differential expression of EMT transcription factors in relation to lymph node status and a differential active state of signaling pathways in relation to tumoral subtype of breast cancer tumors. Our results suggest a different mechanism of EMT induction by TGFβ in relation to two tumor’s subtypes and lymph node metastasis. Citation Format: Victoria Ortega-Hernandez, Patricia Gajardo-Meneses, Wanda Fernandez, Pilar Carvallo. Alternated activation of TGFβ pathway and differential expression of epithelial to mesenchymal transition transcription factors in relation to lymph node metastasis in two subtypes of breast cancer tumors [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 864. doi:10.1158/1538-7445.AM2017-864