Breast cancer (BC) is the most common malignancy among women worldwide. A major advance in the understanding of the genetic etiology of BC was the discovery of BRCA1 and BRCA2 (BRCA1/2) genes, which are considered high-penetrance BC genes. In non-carriers of BRCA1/2 mutations, disease susceptibility may be explained of a small number of mutations in BRCA1/2 and a much higher proportion of mutations in ethnicity-specific moderate- and/or low-penetrance genes. In Central and South American populations, studied have focused on analyzing the distribution and prevalence of BRCA1/2 mutations and other susceptibility genes that are scarce in Latin America as compared to North America, Europe, Australia, and Israel. Thus, the aim of this review is to present the current state of knowledge regarding pathogenic BRCA variants and other BC susceptibility genes. We conducted a comprehensive review of 47 studies from 12 countries in Central and South America published between 2002 and 2017 reporting the prevalence and/or spectrum of mutations and pathogenic variants in BRCA1/2 and other BC susceptibility genes. The studies on BRCA1/2 mutations screened a total of 5956 individuals, and studies on susceptibility genes analyzed a combined sample size of 11,578 individuals. To date, a total of 190 different BRCA1/2 pathogenic mutations in Central and South American populations have been reported in the literature. Pathogenic mutations or variants that increase BC risk have been reported in the following genes or genomic regions: ATM, BARD1, CHECK2, FGFR2, GSTM1, MAP3K1, MTHFR, PALB2, RAD51, TOX3, TP53, XRCC1, and 2q35.

The RAS/RAF/MEK/ERK pathway regulates certain cellular functions, including cell proliferation, differentiation, survival, and apoptosis. Dysregulation of this pathway leads to the occurrence and progression of cancers mainly by somatic mutations. This study aimed to assess if polymorphisms of the RAS/RAF/MEK/ERK pathway are associated with gastric cancer. A case-control study of 242 gastric cancer patients and 242 controls was performed to assess the association of 27 single nucleotide polymorphisms (SNPs) in the RAS/RAF/MEK/ERK pathway genes with gastric cancer. Analyses performed under the additive model (allele) showed four significantly associated SNPs: RAF1 rs3729931 (Odds ratio (OR) = 1.54, 95%, confidence interval (CI): 1.20–1.98, p-value = 7.95 × 10−4), HRAS rs45604736 (OR = 1.60, 95% CI: 1.16–2.22, p-value = 4.68 × 10−3), MAPK1 rs2283792 (OR = 1.45, 95% CI: 1.12–1.87, p-value = 4.91 × 10−3), and MAPK1 rs9610417 (OR = 0.60, 95% CI: 0.42–0.87, p-value = 6.64 × 10−3). Functional annotation suggested that those variants or their proxy variants may have a functional effect. In conclusion, this study suggests that RAF1 rs3729931, HRAS rs45604736, MAPK1 rs2283792, and MAPK1 rs9610417 are associated with gastric cancer.

Transcriptional coactivators play a key role in RNA polymerase II transcription and gene regulation. One of the most important transcriptional coactivators is the Mediator (MED) complex, which is an evolutionary conserved large multiprotein complex. MED transduces the signal between DNA-bound transcriptional activators (gene-specific transcription factors) to the RNA polymerase II transcription machinery to activate transcription. It is known that MED plays an essential role in ER-mediated gene expression mainly through the MED1 subunit, since estrogen receptor (ER) can interact with MED1 by specific protein–protein interactions; therefore, MED1 plays a fundamental role in ER-positive breast cancer (BC) etiology. Additionally, other MED subunits also play a role in BC etiology. On the other hand, microRNAs (miRNAs) are a family of small non-coding RNAs, which can regulate gene expression at the post-transcriptional level by binding in a sequence-specific fashion at the 3′ UTR of the messenger RNA. The miRNAs are also important factors that influence oncogenic signaling in BC by acting as both tumor suppressors and oncogenes. Moreover, miRNAs are involved in endocrine therapy resistance of BC, specifically to tamoxifen, a drug that is used to target ER signaling. In metazoans, very little is known about the transcriptional regulation of miRNA by the MED complex and less about the transcriptional regulation of miRNAs involved in BC initiation and progression. Recently, it has been shown that MED1 is able to regulate the transcription of the ER-dependent miR-191/425 cluster promoting BC cell proliferation and migration. In this review, we will discuss the role of MED1 transcriptional coactivator in the etiology of BC and in endocrine therapy-resistance of BC and also the contribution of other MED subunits to BC development, progression and metastasis. Lastly, we identified miRNAs that potentially can regulate the expression of MED subunits.

Hereditary myopathies are a group of genetically determined muscle disorders comprising more than 300 entities. In Chile, there are no specific registries of the distinct forms of these myopathies. We now report the genetic findings of a series of Chilean patients presenting with limb-girdle muscle weakness of unknown etiology. Eighty-two patients were explored using high-throughput sequencing approaches with neuromuscular gene panels, establishing a definite genetic diagnosis in 49 patients (59.8%) and a highly probable genetic diagnosis in eight additional cases (9.8%). The most frequent causative genes identified were DYSF and CAPN3, accounting for 22% and 8.5% of the cases, respectively, followed by DMD (4.9%) and RYR1 (4.9%). The remaining 17 causative genes were present in one or two cases only. Twelve novel variants were identified. Five patients (6.1%) carried a variant of uncertain significance in genes partially matching the clinical phenotype. Twenty patients (24.4%) did not carry a pathogenic or likely pathogenic variant in the phenotypically related genes, including five patients (6.1%) presenting an autoimmune neuromuscular disorder. The relative frequency of the different forms of myopathy in Chile is like that of other series reported from different regions of the world with perhaps a relatively higher incidence of dysferlinopathy.

Breast cancer (BC) is the most common cancer among women worldwide. BRCA1/2 are responsible for 16–20% of the risk for hereditary BC. Other susceptibility genes have been identified; Fanconi Anemia Complementation Group M (FANCM) being one of these. Two variants in FANCM, rs144567652 and rs147021911, are associated with BC risk. These variants have been described in Finland, Italy, France, Spain, Germany, Australia, the United States, Sweden, Finnish, and the Netherlands, but not in the South American populations. Our study evaluated the association of the SNPs rs144567652 and rs147021911 with BC risk in non-carriers of BRCA1/2 mutations from a South American population. The SNPs were genotyped in 492 BRCA1/2-negative BC cases and 673 controls. Our data do not support an association between FANCM rs147021911 and rs144567652 SNPs and BC risk. Nevertheless, two BC cases, one with a family history of BC and the other with sporadic early-onset BC, were C/T heterozygotes for rs144567652. In conclusion, this is the first study related contribution of FANCM mutations and BC risk in a South American population. Nevertheless, more studies are necessary to evaluate if rs144567652 could be responsible for familial BC in BRCA1/2-negatives and for early-onset non-familial BC in Chilean BC cases.

Breast cancer (BC) is the most common malignant disease in women worldwide. Several studies have reported that microRNA-146a (miR-146a) dysregulation plays a role in multiple cancers, including BC. However, the mechanism underlying this association is controversial, possibly reflecting diverse roles for this miR in different types of cancer. The SNP rs2910164:G>C, located within the miR-146a precursor, has been linked to a BC risk. Our group previously showed a specific association between rs2910164:G>C and an increased BC risk in patients with early-onset sporadic BC. There are no studies in the literature that evaluate the functional consequences of the rs2910164 polymorphism in the BC process. Therefore, the goal of the present study was to evaluate in vitro the effect of the SNP rs2910164:G>C on BC progression in luminal A and triple-negative cell lines. We found that rs2910164:G>C upregulated the expression of two mature miR-146a sequences, 3p and 5p. Furthermore, pre-miR-146a-C enhanced proliferation, migration, and invasion in luminal A and triple-negative breast cells, as well as decreasing cisplatin-induced apoptosis. Interestingly, the pre-miR-146a C allele decreased cisplatin resistance in MCF-7 cells but increased cisplatin resistance in MDA-MB-231 cells. We propose that the rs2910164 C allele promotes miR-146a overexpression, which is causally involved in proliferation, migration, invasion, apoptosis, and cisplatin resistance.