Long non-coding RNAs (lncRNAs) signaling in cancer chemoresistance: From prediction to druggability

The acquisition of cancer cell resistance to conventional chemotherapeutics is considered the major driver of treatment failure and disease recurrence in most solid and hematological malignancies. The molecular basis of tumor chemoresistance has been extensively investigated and newly identified gene signatures have eventually paved the way towards the development of novel therapeutic interventions in the era of precision medicine in oncology. Long non-coding RNAs (lncRNAs) are defined as a class of transcripts longer than 200 nucleotides that lack translational activities and are highly abundant across the human genome. LncRNAs show higher tissue and cell subtype specificities than most mRNAs, while their biological relevance has been associated with the regulation of coding gene expression at the epigenetic, transcriptional, and post-transcriptional levels, regulation of DNA replication timing and chromosome stability, as well as aging and disease. Given their specific expression and functional diversities in a variety of human cancers, lncRNAs have currently received extensive attention regarding their implications in the disease pathophysiology and their potential applications as diagnostic/prognostic biomarkers and/or therapeutic targets in cancer. Over the last decade, different lncRNAs were found to play pivotal regulatory roles in drug resistance of certain cancer cell types via mechanisms that include among others, alterations in drug efflux, metabolism and targeting, cell death machinery, DNA damage repair, epithelial to mesenchymal transition (EMT), autophagy and oxidative stress management, as well as modifications in epigenetic regulators, oncogenes, and miRNAs. The present review discusses the current state of knowledge on the emerging research into lncRNAs as drug resistance regulators and predictors in various tumors, emphasizing lncRNA patterns associated with cancer stemness, certain drug classes and common underlying mechanisms of action. The review further reveals cutting edge strategies for lncRNA modulation and the current progress on lncRNA-targeting molecules designed to overcome cancer resistance. Our input is a reference for future research investigations on cancer chemosensitivity and provides new insights into the clinical development of lncRNA-targeted pharmacological interventions.