Association of TGF-β1 Polymorphisms with Breast Cancer Risk: A Meta-Analysis of Case-Control Studies †

The microRNA Lifecycle in Health and Cancer

MicroRNAs (miRNAs) are small non-coding RNAs of ~22 nucleotides that regulate gene expression at the post-transcriptional level. They can bind to around 60% of all protein-coding genes with an average of 200 targets per miRNA, indicating their important function within physiological and pathological cellular processes. miRNAs can be quickly produced in high amounts through canonical and non-canonical pathways that involve a multitude of steps and proteins. In cancer, miRNA biogenesis, availability and regulation of target expression can be altered to promote tumour progression. This can be due to genetic causes, such as single nucleotide polymorphisms, epigenetic changes, differences in host gene expression, or chromosomal remodelling. Alternatively, post-transcriptional changes in miRNA stability, and defective or absent components and mediators of the miRNA-induced silencing complex can lead to altered miRNA function. This review provides an overview of the current knowledge on the lifecycle of miRNAs in health and cancer. Understanding miRNA function and regulation is fundamental prior to potential future application of miRNAs as cancer biomarkers.

TGF-β at the crossroads of multiple prognosis in breast cancer, and beyond

Transforming growth factor β (TGF-β), a pluripotent cytokine and a multifunctional growth factor has a crucial role in varied biological mechanisms like invasion, migration, epithelial-mesenchymal transition, apoptosis, wound healing, and immunosuppression. Moreover, it also has an imperative role both in normal mammary gland development as well as breast carcinogenesis. TGF-β has shown to have a paradoxical role in breast carcinogenesis, by transitioning from a growth inhibitor to a growth promoter with the disease advancement. The inter-communication and crosstalk of TGF-β with different signaling pathways has strengthened the likelihood to explore it as a comprehensive biomarker. In the last two decades, TGF-β has been studied extensively and has been found to be a promising biomarker for early detection, disease monitoring, treatment selection, and tumor progression making it beneficial for disease management. In this review, we focus on the signaling pathways and biological activities of the TGF-β family in breast cancer pathogenesis and its role as a circulatory and independent biomarker for breast cancer progression and metastasis. Moreover, this review highlights TGF-β as a drug target, and the underlying mechanisms through which it is involved in tumorigenesis that will aid in the development of varied therapies targeting the different stages of breast cancer.

TGFBR1*6A as a modifier of breast cancer risk and progression: advances and future prospects

There is growing evidence that germline mutations in certain genes influence cancer susceptibility, tumor evolution, as well as clinical outcomes. Identification of a disease-causing genetic variant enables testing and diagnosis of at-risk individuals. For breast cancer, several genes such as BRCA1, BRCA2, PALB2, ATM, and CHEK2 act as high- to moderate-penetrance cancer susceptibility genes. Genotyping of these genes informs genetic risk assessment and counseling, as well as treatment and management decisions in the case of high-penetrance genes. TGFBR1*6A (rs11466445) is a common variant of the TGF-β receptor type I (TGFBR1) that has a global minor allelic frequency (MAF) of 0.051 according to the 1000 Genomes Project Consortium. It is emerging as a high frequency, low penetrance tumor susceptibility allele associated with increased cancer risk among several cancer types. The TGFBR1*6A allele has been associated with increased breast cancer risk in women, OR 1.15 (95% CI 1.01–1.31). Functionally, TGFBR1*6A promotes breast cancer cell proliferation, migration, and invasion through the regulation of the ERK pathway and Rho-GTP activation. This review discusses current findings on the genetic, functional, and mechanistic associations between TGFBR1*6A and breast cancer risk and proposes future directions as it relates to genetic association studies and mechanisms of action for tumor growth, metastasis, and immune suppression.