LincRNAs and snoRNAs in Breast Cancer Cell Metastasis: The Unknown Players

SIMPLE SUMMARY: Recent advances in research have led to earlier diagnosis and more targeted therapies against breast cancer, which has reduced breast cancer related mortality. However, the majority of breast cancer-related deaths are due to metastasis of cancer cells to other sites of the body, a process that has not been fully elucidated. Among the many factors and genes implicated in the regulation of the metastatic process, RNAs that do not code for a specific protein (non-coding RNAs) are emerging as crucial players. This review focuses on the role of long intergenic noncoding RNAs (lincRNAs) and small nucleolar RNAs (snoRNAs) in breast cancer cell metastasis. Both are subclasses of non-coding RNAs that function as regulatory molecules in processes such as cell proliferation, apoptosis, epithelial-to-mesenchymal transition, migration, and invasion, all of which are severely disrupted in aggressive cancer cells that are able to form metastasis in distal sites. In the current review, we identify the most important lincRNAs and snoRNAs that have been recently associated with breast cancer metastasis both through in vitro and in vivo experiments. ABSTRACT: Recent advances in research have led to earlier diagnosis and targeted therapies against breast cancer, which has resulted in reduced breast cancer-related mortality. However, the majority of breast cancer-related deaths are due to metastasis of cancer cells to other organs, a process that has not been fully elucidated. Among the factors and genes implicated in the metastatic process regulation, non-coding RNAs have emerged as crucial players. This review focuses on the role of long intergenic noncoding RNAs (lincRNAs) and small nucleolar RNAs (snoRNAs) in breast cancer cell metastasis. LincRNAs are transcribed between two protein-coding genes and are longer than 200 nucleotides, they do not code for a specific protein but function as regulatory molecules in processes such as cell proliferation, apoptosis, epithelial-to-mesenchymal transition, migration, and invasion while most of them are highly elevated in breast cancer tissues and seem to function as competing endogenous RNAs (ceRNAs) inhibiting relevant miRNAs that specifically target vital metastasis-related genes. Similarly, snoRNAs are 60–300 nucleotides long and are found in the nucleolus being responsible for the post-transcriptional modification of ribosomal and spliceosomal RNAs. Most snoRNAs are hosted inside intron sequences of protein-coding and non-protein-coding genes, and they also regulate metastasis-related genes affecting related cellular properties.